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A DIY Homemade
Ignition Coil Driver - A High Voltage Power Supply
One of the simplest ways to make a battery powered High Voltage power supply is to use a common car ignition coil. Ignition coils are a type of induction transformer based on the Tesla Coil invented by Nikola Tesla in 1891. The voltage rise is not given by the turns ratio like in a standard transformer, but is proportional to the rate of change of current in the primary circuit. This means to get a high output voltage you must be able to stop the power flowing into the coil as quickly as possible. In old cars this was simply done mechanically. For use as a HV power supply this needs to happen rapidly over and over. To do this a spacial square wave power supply is uses which switches power on and off to the coil hundreds or thousands of times per second.
WARNING: High Voltage is generated by this device!
Standard ignition coils can be obtained from most car parts stores for around £25. It is not essential to use two 12V batteries like shown in the circuits shown below, but it will allow you to obtain bigger sparks. We have some compact induction coils available for sale for under £20. Click the link to check stock.
This driver circuit is based on the commonly used 2n3055 transistor due to it high power switching capability. While these are cheap and high temperature tolerant, they are susceptible to voltage spikes caused by the inductive nature of the load (ignition coil). Pretty much any power transistor, IGBT or MOSFET can be used in this circuit as long as it is rated for at last 5A and 100V. Ones with higher voltage ratings will be less likely to be damaged by spikes. Further protection methods are outlined lower down this page and in the comments. If you use a MOSFET or IGBT instead of a bipolar transistor like the 2n3055, you should also add a pulldown resistor of about 10k between the base/gate pin and GND.
| TR1 | Ignition Coil |
| T1 | BFY51 Small Transistor |
| T2 | 2n3055 Power Transistors or HV MOSFET or IGBT |
| R1 | 100 Ohm Resistor |
| D1 |
1N4007 will do but preferably a Schottky Diode |
| RC1 | 0.1µF Capacitor + 10K Resistor |
RC1 is used to help suppress high voltage spikes that can destroy the power transistors.
T2 represents two power transistors connected in parallel and mounted on a heatsink.
This next circuit is designed for a higher powered output. Two ignition Coils are connected in parallel but with opposite polarity. This means that the output voltages of each coil are out of phase or opposite to each other (when one is positive, the other is negative). Using this configuration the output is taken from the two coils output terminals, whereas the circuit above uses the output terminal and ground.
These circuits will work great for driving ignition coils for high voltage but they can be susceptible to damage from inductive spikes. When an ignition coil is being driven unloaded (open circuit on the output) there will be significantly increased back emf and risk of damaging the driver circuit. We sell an ignition coil driver module which has built in protection against most spikes that would damage a driver. It also includes an early warning indicator which will show you how severe the back emf is from your load.
Protecting Your Ignition Coil Driver
If you build an ignition coil driver to make high voltage sparks and arcs, you will need some sort of EMI protection for your circuit. Without it, it is very likely you will destroy the transistors or driver ICs.
Snubbers are a tricky subject, but in general they are used to reduce electromagnetic interference (EMI) or voltage spikes. There are many ways to reduce EMI and it can often be useful to use various snubbers in different parts of the circuit. These diagrams represent a few possible ways you can snub EMI in an ignition coil driver. These are known as dissipative snubbers because the excess energy is disspated as heat or light.
The top digram uses a series connected capacitor and resistor. The values used will depend on your drive frequency. (See RC1 at top of this page). Generally speaking, a bigger capacitance and smaller resistance will snub more, but also absorb more drive power thefore reducing efficiency. A compromise must be found that best suits your setup.
The next diagram uses a device known as a MOV (Metal Oxide Varistor). These are semiconductor devices which will only begin conducting when the voltage between its terminals exceeds its rated value. It will stop conducting when the voltage goes low again. In the example shown above, the MOV will short out any spikes coming from the load, but it is also shorting the driver circuits output for the same brief instant. The MOV chosen must be able to dissipate the power ans have a voltage rating that will cause it to activate before the voltage gets too high for the drive circuit.
You can also place a small neon indicator bulb (Ne1)in series with a 1k resistor and place this between the low voltage wires to your ignition coil. This bulb will begin to glow when the back EMF reaches about 100V or more. If you see it glowing, you need a better snubber like RC1 (top diagram) or a MOV (varistor) rated to clamp the voltage below the maximum your components will tolerate.
The information provided here can not be guaranteed as accurate or correct. Always check with an alternate source before following any suggestions made here.
For these circuits we used a simple 555 based squarewave generator circuit. You can see the schematics at the links below.
'Dead bug' Signal Generator
Signal Generator with PWM
The signal generator with PWM is the more stable and versitile of the two.
Thank you for any help
If it is the common cylinder type, there is usually a faint mark by he terminals. Also some have a different sized terminal for positive and negative. The positive terminal is usually the larger one.
If this does not help, try searching the model or type in google
I've built the same ignition coil driver as the one shown above. The one with 4 power transistors and 2 ignition coils. I'm only running at 12V presently and the sparks are not that dramatic. Thin blue ones at about 2cm long. My circuit is drawing about 4.5 amps though.
Is there anything I could do to create longer sparks? Would using a 24V power supply help? I'm trying to build a Jacob's ladder.
Many Thanks
If the pulse width (duty cycle) of frequency is not quite right you can end up drawing lots of power but only getting a tiny output from your coils. The "Signal Generator with PWM" linked above is highly reccomended for this.
24V would help, but you should try to get better output from 12V first.
When you are drawing arcs like in a jacobs ladder the output of the ignition coils is effectivley 'shorted' and will demand a lot of current from the PSU. Keep an eye on the temperature of your transistors when doing this.
We have been working on a new driver circuit recently and it should hopefully be ready in a few days. I'll post a link here when it's ready.
Thanks
You can use a pre built one or there are schematics for 555 based ones here and here. You could also look at the coil driver circuit with the signal generator included
Driving a single common cylinder type ignition coil at optimum frequency/pulse width will typically draw around 5A with a load on its output.
just finished sticking together the 555 Pulse generator and am very happy with it. Now I finally obtained some ignition coils and want to test them right away. When building the Amp above, I got stuck with the RC-Filter. Why is it included in the first shematic, but left out in the second one, but again included in the big supply unit (the one with nine transistors)?? And what kind of ratings do the resistor and cap need?
The RC filter is recommended to reduce the chance of blowing the transistors, but the exact component values will depend on the frequency at which you drive your coils. Higher frequency would need smaller capacitor. The resistor just serves to limit the current.
It works by damping the oscilations in the coils, but it can therfore reduce the efficiency of the system.
If you are only operating your ignition coil driver with a stable load (like a neon light) on its output then you can get away with not using the RC filter. If you want to make sparks, jacobs ladders etc then you will need some sort of protection. I have destroyed a fair few 2n3055 transistors when driving ignition coils without protecive components. I recently added better (but less powerful) version here. you could add more MOSFETs in parralel though to make it tollerate bigger loads.
One way might be to use one ignition coil to charge a capacitor to pulse the primary of a second ignition coil. This way could make very high voltage, but I dont think the insulation in your coil would last very long.
First, I'm proceeding from the assumption that the ignition coil will supply as much current as it can unless there is a load on the output with a resistance that will limit the current to less than what the ignition coil can supply.
I figured that if I connected a resistor in series with an ammeter and the ignition coil, that it would cause a voltage drop proportional to the current flowing through it (according to Ohm's law), but the current flowing through it would be constant regardless of the resistance as long as it wouldn't normally limit current to below the maximum that the ignition coil could supply. If the series resistor actually was limiting current, this could be calculated after the current was measured.
My multimeter can support a maximum of 600V across its leads, and when measuring current on the uA scale, has a measured resistance (by another multimeter) of approximately 110 Ohms. Estimating by the length of the spark gap, the 2 ignition coils that I have connected in anti-parallel are generating approximately 60kV. Since many of the factors here are estimates, I decided to proceed with my calculations from the standpoint that the multimeter could only handle 300V.
From these values, I calculated that a series resistor of approximately 22,000 Ohms would drop sufficient voltage so that the voltage drop across the multimeter would be approximately 300V. Using Ohm's law, this should allow approximately 2.7A to flow through the circuit (max), so assuming that the ignition coil can't supply that much current (which is a very reasonable assumption), it shouldn't limit the current flowing through the multimeter.
When I connected up the circuit, it didn't fry my multimeter (Yay!), and the multimeter measured approximately 8mA rms (although this varied a bit over time by maybe 300uA) from my two ignition coils connected in anti-parallel.
Measuring DC current, the multimeter measured very close to 0uA. This suggests that the ignition coil output has a duty cycle of almost exactly 50%, even though the signal generator that I am using is producing approximately a 75% duty cycle square wave.
I don't have an oscilloscope, so I don't know what the exact waveform is for the output of the ignition coil ... has anyone tested this?
This is a manually drawn image of the scope trace i saw from just detetcting the voltage with a small antenna about 1m away.
Also you might want to take a look at building a large voltage divider to get more accurate measurements than what you could get just with an antenna. I'm going to make one myself if I can get the resistors, but I calculated that a voltage divider that would use .1mA of current and would provide a 100:1 ratio would need over a thousand 400V resistors. I'm trying to see if I can find some cheap resistors rated at more than 400V.
I don't know if you would see the same trace if it were connected by a voltage divider, but it would be good to compaare.
You can make a small jacobs ladder using just a single ignition coil. The size that the arc will expand to is determined by the current flowing in it.
The No. of transistors needed would depend on your coil, but you could probably just use one. Each 2n3055 can handle about 15 Amps if it is kept cool enough. Typical heatsinks for TO-3 cases are quitle large.
Using 2n3055's can be tricky with jacobs ladders. the arcing can cause voltage spikes that exeed the thw 100V maximum of a 2n3055. Make sure you buy a few spare ones if you plan to draw arcs.
The timing capacitor is usually quite small in size. I think a microwave one may be too large but theres no harm in trying it if you allready have one. Almost any capacitor will work, but its capacitance will determine the frequency of the circuit. A larger capacitor will produce lower frequency because it takes longer to charge.
The three legs on the transistor are explained in this link. You will only see 2 pins on an actual 2n3055 because the metal casing is used for the collector (+ve). You can use a 2n3055 datasheet to identify the other pins.
Andrew:
The suggestion on Jan Wagners page is certainly a good idea to help protect the transistors.
The ground terminal could be the battery negative terminal.
The small transistor is only needed when driving lots of 2n3055's in parralel. If you are just using one or two then you can get away with just driving 2n3055's from the 555 output (through a 100 ohm resistor).
Yes, a smaller capacitor would cause higher frequncy pulses in the circuit.
If you want to change the capacitance by connecting capacitors together, connecting them in series will reduce the capacitance.
Your circuit seems fine to me, but I've used that 555 circuit before and wasn't very impressed. It oscilates and you can adjust the frequency ok, but duty cycle control is very limited.
The DIY PWM Signal generator project is far more reliable. The addition of the LM393 comparator allows you to adjust the duty cycle between 0 and 100%.
You could always add this later if you are not satisfied with the performance of your current design.
CesarIII:
You make a good point. As mentioned above, additional components are needed for full control over duty cycle.
John:
It depends on your speaker and PSU. If you are using a 12V batery as your PSU, then each pulse will simply connect 12V directly to your speaker. I tried it with a big 8ohm speaker and it was pretty loud. I was able to tune it to the resonant frequency of my desk, causing everything on it to shake quite violently.
Justin:
Yes, the two resistors with arrows marked 10k, are variable resistors. The range of frequencies you can adjust the circuit over is still determined by your capacitor.
We can switch from 12V to 24V like in a briged audio amplifier, just using 4 transistors and a SG3525 or a 555 and a CD4013. Althoug using 4013 will force the duty cycle to 50% :(
What you think?
The SMPS (Switched Mode Power Supply) method can be a little more tricky with ignition coils. This is because they are effectivley autotransformers but with a very high ratio. The arcing and high voltage present at the output causes broadband RF (Radio Frequency) noise which can interfere with the correct operation of the transistors.
Anyone making this project will probably notice that the pulses to your coil are not always as regular as the signal you are sending to the transistors from the 555. This is not a major problem in this circuit, but if a bridge configuration is used, the transistors can easily be destroyed by a condition known as 'shoot through'. The is where a pair of transistors come on together (when they should not) short circuiting the input power supply through the transistors causing them to overheat.
Sometimes the varistors fail catastrophically, and can thefore take out another component with it.
This happens because some varistors don't recover very fast, so when your transistor switches on power can be shorted through the MOV causing it to blow.
Run it for a few seconds, then switch it off and check to see if your MOV (or anything else) is getting hot.
Make sure when connecting the power, duty cycle is set to low, or zero to avoid surges. Don't turn the duty cycle up too high, it will use loads of power, but reduce the output voltage. 50% is usually suficient.
Most importantly, don't forget, high voltage devices are very dangerous and should be treated with great care and respect. Don't get complacent, always be very very careful.
I was able to obtain an oscilloscope and used it to get a trace from the ignition coil generator that I made using a similar method to what you used, but I attached an antenna to the hv output a well as the oscilloscope. The trace showed something similar to your's, but the apparent resonance was much less damped. The output waveform frequency seemed to be exactly what the input frequency was (about 1kHz) and the resonant frequency was calculated to be at approx. 6.6 kHz. Changing the antenna length on the hv side seemed to change the resonant frequency somewhat, so the antenna's capacitance might actually have something to do with the resonance.
A diode is usually placed in parallel with the transistor like shown in the top schematic on this page.
While this may reduce the risk of blowing a 2n3055, it cannot guarantee full protection. There are many possible reasons for transistor failiures in inverter circuits like these.
Crispy:
Somtimes people place ignition coils in a container filled with oil. This helps prevent arcing from the ignition coils terminals.
There's a huge numer of coil types available, ask at your local auto spares shop to see what's available.
I've built the circuit shown on this page. when i used it worked all right. then some time later(2 weeks) it seemed like the output lost a lot of its power. I used it with a high voltage diode in series with its output to charge capacitors with a spark gap in parallel with them as to charge and discharge with pulses. now to even charge a capacitor i have to arc the high voltage to the capacitors because if i connect the wire to the capacitor the ignition coil loses all its power.
Do you have any ideas on what's going on and how can i fix it?
1. Faulty 2n3055 transistor. These can fail in a wide range of ways. The most common transistor failiures cause it to latch on or off, but somtimes they can be only partially damaged, giving symptoms like you describe.
2. Faulty HV diode. In the same way as above, a diode can be just partially damged.
These sorts of intermittent or partial faults are caused by exessive voltage or current surges in the circuit.
This post may help you find more info.
Please be aware that the output from this terminal is highly dangerous and quite deadly. Even when switched off a capacior inside can retain a lethal amount of energy. Never put your fingers anywhere near the HV output terminal (even if the TV is unplugged). Don't take any risks with these things, they can kill.
I expect that if you were to arc from this output to a small piece of tin, it would begin to melt the tin. The plasma temperature in the arc would be very hot, but it would draw more current from the transformer than it is designed for. The positive HV DC output is only used to create an electrostatic attraction between the moving electrons (cathode rays) and the inner surface of the screen. Making arcs (which is neccesary for the high temperatures) is effectivley a short circuit accros the transformer output.
The transformer will prrobably survive this sort of treatment if it is just intermittent, but if switching transistor is used for controling power to the coil, it will overheat and blow in a relativley short time.
Also the output of the transformer is rectified (converted to DC) by a voltage multiplier. The diodes in this may also be damaged by too much current.
You can limit the current (but thefore the temperature) drawn by your arcs by placing a large resistor in series with the output. If you don't have such a resistor, a length of carbon may suffice.
dose your design handle T waves[rmc]
whats the signal generator
The top diagram which shows RC1 will be more stable, but it can still be blown quite easily when the output is pushed quite high. The 555 timer circuit you used has a very limited range of adjustment for pulse width (duty cycle). It stays around 50%, which is quite high and will create a lot of back EMF spikes.
The PWM signal generator has a fully adjustable duty cycle so you can adjust the power more precisley and keep it below 50%.
Obviously putting less power in, means you get less HV power out of your coil, but there is always a compromise to be made somewhere in electronics design. Running at lower power levels means that components are less likley to be destroyed, but there is still no guarantee. Making High voltage sparks from low voltage DC sources is often problematic.
There are also several other methods for protecting your components from the spikes. Have a look at Andrews posts above. This link discusses various methods for protecting against surges from inductive loads. It's targeted for relay switching but the principles are the same.
All the other components are listed at the top of the page.
If you are wanting to make long sparks, then I would reccomend using a different circuit. The best one would be the Pulse controller.
Can higher current power Mosfets be used in this curcuit?
Is there a limit on the number of Mosfets? Possiblly with a seperate Mosfet board/unit with enough cooling could this control 80A+ electric motor, or course with protection. Mosfet ex: HUF76145P3, High Current MOSFET, N-Channel, Enhancement Mode, 75A, 30V. Ebay of course. Thanks John
The antiparralel inition coil setup actually seems to be more likley to blow transistors when its not loaded. If the output is loaded, then there is usually no problem. The transistors are exposed to HV spikes mostly when the circuit is being used for making sparks.
Higher powered mosfet will work, but mosfets require a higher gate/base voltage to switch them. If your DC source is 12V then this should be no problem. The gate pin of mosfets is like a capaciative load so there should be no problem driving large mosfets. If you are looking to control a motor, then I would recommend this circuit.
Problematic:
100R just means 100 Ohms. The R is often used where the decimal point would be. eg. 2R2 = 2.2 Ohms, 4k7 = 4.7k (4700) Ohms.
The way you have shown VR1 would just give the same resistance all the time. You need to use the centre pin and one outer pin.
Your question regarding the 2n3055 pinout has been answered previously. Check the post dated 3rd December 2006 4:45pm.
I've modified your diagram to show the pinout of the 2n3055. The 2 pins under the 2n3055 are actually offset slightly to one side. It's not clear from that previous datasheet, so try this 2n3055 datasheet. You'll need to scroll down to page 4.
I've not used a multimeter to find the pinout before because I have one of these very handy component analysers. I suppose you could use the diode test mode. You should see a low resistance between base and emmitter if the +ve lead is on the base pin. It shouldn't conduct the other way around, but don't hold me to that, I've not tried it! :)
If the capacitors you placed on the output are not specifically rated for high voltage, then they will certainly get melted.
even if it dosnt i can use it on my ignition coil because the coil would act as a resistor draining power from the capacitor as it cahrges causing a pulse, im not to sure but that is my theory. would this be right or wrong?
I don't understand what you are trying to do with your ignition coil and capacitor. Please explain in more detail if you want more help.
I have a few questions about these ignition coils and drivers in general, and was wondering if anyone here could answer them. First, it is my understanding that the high voltage output of an ignition coil is produced in part by the voltage produced across the inductor as a result of the square wave with the equation (e = L(di/dt)). Is this correct? Also, if this is correct, it seems that a perfect square wave would produce an infinite voltage across the inductor, but this is obviously not true. Why is this? Also, is the peak voltage mathematically predictable or is it entirely due to stray resistance and/or inductance? Also, what kind of voltage could I expect to get out of the ignition coil if I ran it with a sine wave instead of a square wave, using it as a normal autotransformer?
I'm planning on trying to build a HVDC power supply based on ignition coils. Most such designs use a bridge rectifier and a smoothing capacitor. With ignition coils producing very short peak voltages, wouldn't the ripple be significant unless a very large smoothing capacitor was used? And is there any way to decrease/prevent this ripple other than by using such a large capacitor?
Thanks,
Chules
Your question about a true square wave causing the voltage to rise to infinity is a good one. This would be true if it were possible to instantly stop the curent flowing in the inductor, but because of several factors, this can not happen.
The wire that makes the coil obviously has some resistance, but this is not our main concern because we allready know that superconductors having zero resistance are possible. Assuming we have eliminated all resistance from the coil, we are now left with inductance and the self capacitance of the coil. The self capacitance is a product of the seperate coil windings and the voltage difference between them. This capacitance is only very small, but it is plenty enough to prevent the voltage rising to infinity. A capacitor has an associated time constant which means it will take a finite amount of time to charge or discharge. This prevents any instant change of current in the coil and therefore limits the voltage rise produced.
The output votage is calculable, but it can get tricky to account for all the factors, especially when some of the values are not known.
If you use a sine wave then the dI/dt will naturally be smaller and therfore will give a lower output voltage. You would need to se a higher voltage sine wave to get the same output voltage as you would from a low voltage square wave.
With a square wave input the ripple is likley to be significant so a large capacitor is often the only solution. Alternativley combinations of capacitors and inductors can help smoth it out.
If the coil is driven at resonance, the output voltage will be higher and the waveform more sine like.
Thank You,
EE
A snubber circuit of some sort would probably be needed to stop high voltage spikes damaging the ICs. Just placing a capacitor across the coils input terminals would help but it would also reduce the output voltage by a small amount.
The primary capacitor in a TC is essential as its value determines the resonant frequency of the system.
The peak output voltage you can get from a coil is determined by the input voltage and the rate of change of curent (dI/dt). Since the dimmer has total control over dI/dt and the input voltage is always at mains level there is not much you can do.
If a DC output is ok, then you could use the ignition coil to drive a voltage multiplier for increased voltage.
For a saltwater cap the water needs to be saturated with salt (no more will dissolve). Also avoid aluminium as the electodes as the salt water will cause them to oxidise on the surface and give poor conductivity.
You can find the HV caps and RF chokes on eBay.
You seem to be missing the point. People are here and asking questions so they can learn new things. Were you somehow born with the knowledge you have?
artemoonlv:
The 2n3055 needs a resonable current for it to switch. Unlike a MOSFET, these often need more current than an IC (like a 555) can supply.
You will need a circuit designed for higher frequencies if this is what you need.
Our Power Pulse Modulator will drive flyback, ignition coils and almost anything else. The frequency is adjustable so you can set it to whatever works best.
A common signal source is based on a 555 timer like this DIY signal generator.
You can also buy such a circuit with the signal generator, power transistor and added transient protection in our Cyber Circuits shop.
can I use this circuit to drive ignition coil ( with
RC1 and diode for protecting 2n3055 )- to have one battery for oscillator and to have an other for induction coil?
Many Thanks!!!
Increasing the voltage applied to the ignition coil wlll mean that it will draw more current, but it could just be wasted if the core is becomes saturated (can't contain any more magnetic flux).
Using a power pulse modulator set to high frequency and with a smoothing capacitor in parallel with the output will serve as an adjustable switch mode power supply.
You may be able to get single sparks if you can press and release your switch fast enough. It would be pretty easy to burn out your 2n3055's like that though.
venu:
It is totally dependant upon your loads impedance. You can calculate the current using ohms law.
Driving a common cylinder type ignition coil at its resonant frequency from 12V will typicaly draw about 5 amps.
Connecting your capacitors in parallel will not cause problems if they both have a suitable voltage rating.
i got 12 2n3055 transistors on large heatsink. I noticed that they are not equally heating. One is very hot and some are cold or warm. What can I do to fix this?
Many thanks!!!1
Thanks your circiut works perfectly!
The output voltage will depend on the specs for your specific coil. It averages around 20kV
e.g. - Have the HV generator running constantly and switching the HV to multiple spark plugs (according to ignition timing) via some thyristor.
or - Have multiple HV spark generators (one for each set of spark plugs) and turn them on/off according to the ignition timing.
For a 4 cylinder engine - 4 sparks per revolution @ 750(min)/8000(max) RPM -> 3000(min)/32000(max) sparks per minute -> 50(min)/534(max) sparks per second or Hz......
In theory "arc" ignition sounds better than spark ignition......
im interested in musical tesla coils but need some background information first: for a solid state tesla if you use say a simple design like the self resonating flyback could you just add the music input into the feed back wires to switch to the frequency of the musci? thank you for your help.
They have not been designed or tested for use with engines, but the circuit does drive auto ignition coils. Your suggestions seem sound, but I couldn't comment on the effectiveness of an arc ignition compared to a spark ignition.
alan swane,
It may be possible to do it like that but I would excpect a lot of distortion in your input signal caused by the feedback/self resonanting system.
The best way is to drive the HV supply (a flyback or TC) at a set frequency which is high enough to be inaudiable to humans. This signal is then amplitude modulated with the audio signal which you wish to hear.
For example; you have a driver like on this page driving an ignition coil at a set frequency. You would disconnect the signal from the base pin of the 2n3055 (or equivalent) then connect it to the collector of another transistor (such as BFY51). This transistors emitter pin would then go to the base pin of the 2n3055s. You can now add your audio signal to the new transistor. The audio signal would dynamicaly alter the resistance of the transistor so that the power level of the drive frequency becomes proportional to the audio input. Of course there may be a need for a few R's and C's to keep the voltages in your circuit correct. Now any arc could easily be modulated with audio.
this diagram shows how a BFY51 transistor is used like a switch or valve for controling how much of the HF (high frequency) signal is allowed to get to the power transistor.
With 0V placed on the modulation input, the HF signal will be blocked and thefore the power transistor will not switch on. When some voltage is applied to the modulation input, the HF signal can pass through and drive the power transistor. The level of the HF signal reaching the power transistor will be proportional to voltage applied to the modulation input. Therefore if the modulation input voltage is varying with time, the output power of the ignition coil at the HF drive frequency will vary with it.
What second audio input?
Two or more 23055s can be placed in parallel to allow for more current.
I can only guess that one of the wires in your pair is ground, the other will be signal.
Like I already mentioned, I don't think this will work properly with a self resonating design. The frequency generated by the self resonating circuit is equivalent to the HF drive signal, but if you start trying to modulate this the feedback loop will become unstable and therefore cause the drive frequency to change.
I wondering what you think the problem is. I think that I need to switch the TIP3055 with something faster. The TIP only does 3MHZ. I don't have a BFY51. Could I just get a few fast, low current transistors and hook them up in parallel to meet the current requirements? Do you think that a faster switching transistor would solve my problem?
Each transistor will switch at very slightly different times due to manufacturing tolerances. This has two major drawbacks in this application.
1. If the peak current exceeds the capacity of a single transistor, the first one in the array to switch on is likely to get destroyed. With many cycles happening within a second you can blow several transistors quite easily.
You can prevent this from happening by placing a current limiting resistor in series with each transistor. This will protect the transistors but it is not efficient because a lot of heat is generated when the high current flows through a resistor. One reason multiple transistors are used here is to reduce the total 'on resistance' which allows more current to the coil.
2. The output voltage of the coil is proportional to the rate of change of current in the primary coil. With an array of transistors, they are not switching together so this rate of change is reduced slightly. The added junction capacitance also increases the time it takes to switch off.
The TIP3055 does switch off pretty slowly compared to the BFY51 (1us vs 60ns). You probably don't need a preamplifying transistor anyway if you are using just one 2n3055.
To get the full output of your ignition coil you must ensure the transistor is switched fully on before it is switched off, and you must switch it off in the shortest time possible.
In fact, the resonant frequency generally increased with increasing resistance. This seemingly paradoxical behavior is due to the non-linear character of the diode.
Just a small note...
Also don't use your PC or anything expensive as your audio source if you are modulating an ignition coil. There is a high risk that you will damage your source.
Look for info on optoisolators for keeping your audio source electrically isolated from your HV circuit.
Is the output the two output terminals connected or does the spark jump between the coils?
When in parallel the outputs are in phase. This means that the voltage between the two outputs will always be zero. If the outputs are connected together they will operate as a single ignition coil would but with the potential to deliver 2x the current.
What light bulb?
The signal generator can have its own battery or just run from the same source as the coil
The light bulbs electrical connections should be shorted (linked together), then a single wire from this should be connected to the HV output of the ignition coil. This makes the fillament inside the bulb at a high voltage compared to the ground (and surrounding objects). The plasma filaments will reach out for grounded objects placed near to the bulb.
It's best to keep HV wires as short as possible so that energy is not lost to the surrounding air. The best way to connect your bulb is to stick it right onto the output of the ignition coil with some wire or foil inside to make the connection (like this).
And can I do a set up where I have 2 parallel sets of coils hooked up in antiparallel? (4 coils. 2x voltage. 2x current)
Yes you can, if they are all the same model coil.
Yes most npn transistors will work if it has similar current and voltage ratings.
john redcorn,
100 ohms is still ok for 9V.
Bob Dole,
A neon or fluorescent light will glow when connected to the HV output
Is is possible to run the signal generator off of a separate 3v source and run a full 12 through the 2N3055?
Common ground is just a connection between the ground, 0v, or -ve terminals in seperate circuits. e.g. To connect a signal source with a 9V battery to the ignition coil driver a wire is connected between -ve terminal on the 9V battery and the -ve terminal of the 12V battery. This is your common ground. You can then connect the signal output of 1 circuit to the signal input of the other.
Albert
Yes, See above. It should not fry on 11 V. You probably just need to limit the current with a 100 R resistor.
On the connection to the comparator? On the whole circuit?
Can I have a voltage regulator chip on the VCC of the 555?
Or do you mean in series with the ignition coil?
Thanks a lot for your help.
If there is no mains voltage and no HV capacitor on the output, then the electric shock is unlikely to kill directly. It could still make you jump or cause muscle reflex which could indirectly hurt you or someone else.
If all metal parts are insulated and the coil is running at high frequency, then there is little danger from touching the glass.
You still need obvious safety measures like making sure things aren't getting hot or internally arcing.
1) Would it make sense to optically isolate the signal generator section from the power stage (e.g. use the phototransistor of an optoisolator as the first stage of the Darlington pair)? Then if back EMF roasts the optoisolator, it wouldn't affect the comparator and 555.
2) Where would be the best place for a varistor in this circuit? Would it be across the primary terminals of the coil, or between the collector and emitter of the power transistor? I'm thinking the latter option makes more sense, since it would shunt any high-voltage EMF to ground and (hopefully) bypass the power transistor (sparing it from an untimely demise ;^) ).
Thanks in advance,
Dave
ipod playing a constant tone.
it works great!
1) Yes that is a good way to protect your circuit.
2) There are many ways to do this. You could place a mov across your load but this would add capacitance (decreasing dI/dt) and would need to be rated to dissipate a reasonable amount of power. Placing one between c and e of the transistor would also work if it were rated for similar power levels.
You can also place a MOV or zener diode between base and collector so that the transistor automatically switches on if the voltage is high.
john,
Yes, read the information on this page.
maximum operating voltage 275v AC
pulse energy rating 20 joules
peak pulse current 2000amps
device types ve17mo275k, 275A20A, TNR15G431K,INR1D431,TVR14431
$ 1.50 i dont know if this would work or not but a varisitor seems more efficiant for this circuit.
No.
justin,
Wax will help prevent unwanted arcing but don't forget that wax is a hydrocarbon (a fuel) and will burn when soaked into things.
No your varistor will not be adequate. It will only activate at around 275 volts. If you are using a 2n3055, then the max voltage it will take (Vce) is 100V. You need a varistor that will activate just before 100V, or a transistor with a higher Vce (Vds for a MOSFET).
Thanks a lot!
I would guess the 555 is blown. Are you able to verify that it is oscillating?
jason t-bert,
Yes, if the output of your coil is connected to a load there will be much less back EMF produced.
your neon globe design works perfectly in protecting the 555 timer circuit plus rc1. im putting more in parrallel to run my flyback i just wanted to thankyou for all your help, laters
will placing two transformers running on different drivers still inceace voltage if connected or do they have to be connected to the same driver?
Everything else is fine. The 555 is fine. All the transistors are fine. It's just the comparator. Time after time. It's an LM339.
Oh, and I found this circuit works a lot better substituting 2N6547 for the 2N3055.
Separate drivers can be used, but they must share the same input signal so the coils are pulsed at exactly the same time.
DB
You need to adequately control the back e.m.f produced. When you are driving the coil and there is no arc, massive amounts of e.m.f are getting back to your circuit. This is because you are pulsing energy into the coil but not absorbing it on the output, the only place for the energy to go is to reflect back into your circuit. You must absorb this energy before it gets to your 393.
For protecting it, should I employ the snubbers you have?
I am using capacitors and neon.
The neon i'm using is a module with a built in resistor. I think it's 33K. Should I remove this resistors or replace it?
I switched the 339 for a 393. It dies too.
What about using a choke on the wires that go into the coil?
Oh, and it's a bad thing if the arcs come out of the top of the coil and strike the inputs?
Is is bad that corona appears traveling through the alkyd tower thing and into the inputs?
refering to your ignition coil driver at the top would putting a high frequency through the circuit instead of dc affect its operation in a way that it will not switch ? also i plan to use a mosfet but have no clue as to what type i should use or how to identify which pin is which thankyou
p.s i dont think that the 2n3055 would last very long for my plans lol.
How about hooking up a high voltage, high current diode across the + and the collector of the transistor?
Isn't the interference of reverse polarity of the input? Shouldn't that just short out the back EMF?
Yes you could use a high frequency sinal instead of the V+ connection to the coil. The flow of current (for the same voltage) will be significantly reduced though due to the reactance of the coil.
A 2n3055 is not suitable because it has a breakdown voltage of just 100V. IRF70 is a good MOSFET for dealing with switchmode power as it has a breakdown of 400V and a current of 10A. It is also avalanche rated so an over voltage breakdown will not destroy it as long as the current is kept below 10A.
A true SSTC is not a simple thing to make. They are prone to destroying your MOSFETs. Preventing this involves overcoming many technical chalanges which are beyond the scope of this article.
DB,
The 1n4007 is there do do this in both diagrams. Diodes have alimited response time though so it is not always effective. A schottky diode would be better if it had sufficient power ratings as these respond quicker.
The interfernece is not just reverse polarity allthough the initial large spike may be.
thanks again for all your help
Cheers
thanks again for all your help
Simon
ps I am building the second circuit on this page.
Match coils will work better. BC139 should be ok if you have a resistor to limit the current like shown in the diagrams. A larger one might be better though.
Simon Dodd,
The current limiting will just reduce the max voltage you can get. It should still work noticeably. You can put a speaker in place of the coils to test the circuit (it should be pretty loud).
RMC: Im planning on adding audio modulation to my driver, and im just wondering would it be wise to use opto-isolators on the inputs to the audio modulation, would this kill any risk of smoking my laptop/signal generator? Furthermore, for feedback protection across the load would an MOV with a series resistor and series diode (facing -ve to +ve) help eliminate feedback without shorting out the power to the coil? Thanks for your help.
Using 555 pulsed circuit with Mosfet driver IRFP450 and paralleled auto ignition coils, upright oil filled type.
With the circuit tuned well, I can get hot streaming arcs up to 9-10 cm but having problems with arcing from the HV out terminals to the primary coil terminals on top, very bad on one of the coils where there seems to be a small crack in the housing. Since I have the input AC on a Powerstat, I can bring the volatge up slowly to see where the arc begins on the ignition coil out to the screw terminals. Even with some insulation, at full voltage there is some arcing everywhere over the tops of the coils. The two ignition coils I currently have are different brands but similar upright cylindrical, oil filed types. Only a problem when I try to get a long spark. At 1-2 inches there is no problem. I have HV wires soldered to the screw terminals and I tried to insulate the primary terminal with hot glue last night but no go.
Is there anything that can insulate this area to stop the arcing? e.g. Silcone putty, Hot glue, mineral oil emersion (messy) etc??
If not, should I just buy another set of ignition coils on ebay?
There appear to be many kinds of coils and I was told that certain types do not work well with the solid state driver circuits....e.g HEI type shown below.
Which coil will give the best arcs, HV out and durability? Cost no object.
Procomp below has primary and secondary terminal far apart, may reduce arcing??? Not sure what type it is???
Procomp Ignition Coil
ProformHigh Perf 66943C HEI Ignition Coil 50,000 Volts
Crane Cams - GM External Ignition Coil PS-91 Fire Ball
One website said the first coil shown above was no good..." Pro-Comp...Chinese masquerading as Australian, run as fast as you can away from that junk."
Thanks much for any help!
Dan
I'm no expert in ignition coils and have never even seen one like the one in the image (looks cool though). I couldnt really suggest what the best type to use is. Let us know how your project goes.
Thanks.
Your 555's are being destroyed because energy is being reflected back from your ignition coil in the form of high voltage transients. There is some info on how to protect against this in the article and in the comments.
I can't say for sure why your sparks are small, but I would expect the coil to draw more than 3.4A at 15V. It is possible that your PSU is limiting the current too much.
Thanks very much,
Sam.
Placing the diode across the load as you describe will cause the diode to absorb the whole reverse voltage spike which will be large like you say. The RC circuit does work to absorb spikes (the resistor heats up too) but it is going to reduce the possible output voltage of the coil. When your capacitor is charged or there is nothing on the output of the coil there will be more EMF because the energy is reflected back.
Thanks
The brightness (temperature) of a discharge is proportional to the current flowing through it. Creating very high voltage is not necessary and can produce dangerous x-rays when applied to vacuum tubes. It would be more efficient to use a voltage that is just enough to start the discharge and to use as much input current as possible.
Thanks
Ideally the transformer for a multiplier needs to be a proper AC output, the output from an ignition coil does not reveres very much so they are not great for driving a multiplier. A pair of them used and pulsed at opposite times and with opposite voltages would work much better.
What energy X-rays are you trying to produce (100keV, 1MeV ?) I would assume it would be in the lower keV range otherwise you would need a long accelerating tube for the electrons. Is your purpose for X-ray imaging? If so then I guess the high current is important so that a good exposure can be taken before the subject moves and blurs the image. Since this would be a short burst of X-rays the best way to achieve the stable HV and high current from batteries would be to charge a large HV capacitor with the multiplier, this would then need to be dumped into the accelerating tube through a resistor in a controlled way.
newbie, carlo,
Any NPN bipolar transistor rated similar to the BFY51 will be fine. (capable of 1A)
1) What wire gauge size should I be using to connect each component? Is connecting all the components through a bread board OK?
2) You have provided a parts list, but only some have their actual code provided (i understand that each part code will depend on the type of ignition coil used), but is it possible for you to provide me with the list of parts you used, so that i may compare to what i should be using?
I am using the cylinder type bosch ignition coil .
Thank you and any help will be greatly appreciated.
The parts list is all there. The capacitors and resistors do not have codes, you just buy something of the same value.
Thanks!
The current limiting effect of a capacitor can be calculated as follows.
The reactance of the capacitor (measured in ohms) is;
1 / (2*pi*f*C)
pi is 3.142, f is the mains frequency, c is the capacitance.
You then use ohms law to calculate the current that can flow.
Eh?
student,
The output waveform is not square, it looks like this.
Many thanks...
I got my signal generator working, but it doesn't work very well on my igniton coil. I forgot to add a 100 ohm resistor on the output of the 555 timer, so is that my problem?
http://www.rmcybernetics.com/projects/DIY_Devices/homemade_signal_generator2.htm
with this:
http://www.velleman.be/downloads/0/illustrated/illustrated_assembly_manual_k2543.pdf
to create a more powerful (capacitor discharge) pulse?
When using these various circuits to generate a high frequency spark. Would the circuit be cabable of operating in the mHz range typical 0 -5 mHz and if not what would limit this factor.
Thanks
No, not really. What exactly do you want to do?
Tracker,
No. The reactance produced in the coils of the transformer will impede the flow of current more as the frequency increases.
In order to cause significant current flow in the coil at this frequency, the input voltage would need to be much higher. This would need a whole different setup.
Thanks for the reply, what I want to do is to drive a plasma globe at frequencies up to 5 meg so I sumize I would not need the DC side of this etc, is that perhaps something you could organise with your services.
thanks!
A plasma globe needs to be AC. The difficulty in what you want to create is the variability of it. It would be relatively simple to make a circuit which oscillates at a fixed frequency anywhere in that range, but being able to adjust from DC to 5MHz with one HV device would be very tricky and expensive.
Dan,
The capacitor would need to be charged to a higher voltage than the supply for it to give you a better arc.
p.s. this circuit is untested and dangerous!!!
khobby@gmail.com
All help appreciated, great project.
You have mentioned that he coils are orientated so that when one is fully positive, the other is fully negative so there is a larger voltage between the two, this however would involve the output of the coils to be AC.
I'm a bit new to all this, so i'm sure most of what is written herein is wrong, but if does generate am AC output could you please explain how?
Thanks
When the coils are wired in opposition they both output pulses of opposite polarity. So if one outputs +20kV, the other outputs -20kV at the same time. The difference between these voltages is 40kV.
- a 2N3055 is not advisable for an ignition coil due to kick-back voltages (30-3000V) and as you know a 2N3055 can only withstand 50-60V (i think).
i would advise an 2N3773 those can handle 100-160V i think
-also placing a diode over the collector-emitter isn't that goed if you want high voltage peaks
of course it will protect the transistor, but it will filter away that high voltage peak.
- The best method for building an ignition coil driver is
(and im talking out of experience)
a 555-signal driver powerd by a battery or some other low voltage source (note that the voltage must be at least 5V)its also advisable to use a darlington transistor to magnify the signal coming out of the 555.
then as switching transistor a 2N3773 or a robbust MOSFET that can handle some voltage. and over the Transistor/MOSFET, you place an 100V VDR this should protect it from kickback
and at last not least,the current trough the coil. an voltage from 12V to 80V should be enough and a current of maximum 6A or else the oil in the coil wil boil and eventuelly the coil will explode under the pressure.
i find it important to give this information to you becouse ive seen a lot of accidents with those things.
i hoped you learnt from it :-D
I was hoping it could be excited somewhat close to how lasers or flourescent bulbs are excited.
----
And what will be,when you drive your coil with resonant frequency? (i have kV meter (it shows 20kV max) ) Voltage will suddenly rise up?
There will be several resonant modes of a coil. At several frequencies, you will see a distinct rise in output voltage.
My question is, what is the science behind the ability for both the positive end and the negative end to spark to the same ground reference? I would also ask how it is possible for either plug to continue to fire if the other end is actually disconnected from its respective spark plug?
This, of course, is what is happening, generally, with the primary winding in a coil. Once the current stops the field collapses and the energy built up within the secondary windings has to go somewhere. But what has me confused is that this energy can flow without the apparent need for a return path, as in a circuit.
I'm trying to fix a 1999 Chrysler Intrepid (2.7L V6) that my grandfather owns. We're getting a misfire on cylinder #4 (verified by fault codes and other testing). This is a Coil On Plug engine, no plug wires. We tried switching coils but the misfire stays at #4. Also tried new spark plugs. No change.
I checked continuity in the coil driver wire from the #4 cylinder coil connector to the PCM and there is continuity with no resistance. So the coil driver wire seems to be fine.
With the engine running, I am getting a reading of 13.4/13.5 volts on every coil connector (by disconnecting one connector at a time and probing the power feed wire). Here's the interesting part. When I probed the coil driver wire in the same way, I get a reading of -0.06 volts at all the good, proper firing cylinders. On #4 where I'm getting the misfire, I'm reading (+)0.03 volts. And it's a constant reading on all of them, it doesn't fluctuate (as least not on the multimeter display).
Any idea what that means or why the "good" readings are negative voltage (reverse polarity?)? I'm not sure what the specs should be or if I should even being reading the coil driver wire with a voltmeter (multimeter).
Any ideas or explanations would be really appreciated, you guys definitely seem to know what you're talking about.
Thanks!
Both. The spark structure may vary slightly, but ionization will occur on both poles causing a spark to grow from each. When the two sides meet, a conductive channel of air will exist between the electrode allowing more current to flow. This is when you hear the typical 'snap' sound of the spark because the higher current flow super-heats the air causing it to expand rapidly and create pressure (sound) waves.
Alex,
No it wont output a square wave. If you want minimum current from it, you will need to limit the current using a resistor on the output. 5V is not really enough to get a good output from an ignition coil.
This whole line of questions stemmed from this Thread on a Motorcycle Forum I belong to. http://www.nakedgoldwings.com/forum/viewtopic.php?t=11577&sid=ff6c575c05a2220e6433123f1a7eb150
Should you have the patience to look at it, I would be interested in your comments on the veracity of some of the information offered. I am Briang on that site, btw.
Once a charge is built up in a coil and the primary circuit is switched off, what happens to the charge in the secondary winding if there is no path for it to discharge to?
Is the charge ever able to bridge the insulation within the coil to the primary winding to discharge, assuming a sound, unbroken insulation between the windings?
P = V x I
If I is small because the only current is tiny from ionising the air, V must be high to keep P out equal to P in.
If your input voltage/current is within the ratings of the coil it will be fine, but if you exceed these it is possible that the insulation will breakdown just like the air does.
For an electric fence you will be using very low frequency and low duty with a mostly unloaded output. This will give you quite large spikes after each output pulse. A 1n4007 would help, but I would reccomend using a different transistor. A MOSFET like the IRF740 would work well as it can tollerate 4x the voltage of the 2n3055. A MOV rated just below the 400V rating of the MOSFET should be placed in parallel with the diode. If you are using a single supply for the whole circuit, you should also place a MOV rated to keep your PSU voltage low (a 10VAC MOV will be good for a 12VDC supply) between your V+ and Ground to prevent your ICs' from being fried by voltage spikes on the power rails.
i'd like to ask your opinion regarding my final year project. i'm implementing voice recognition in car security system..so,if possible could you provide me the appropriate car ignition circuit..my project accepts voice command as input and processed by PIC microcontroller. the output from the microcontroller will be directed to car ignition circuit for activation..i'm just building the prototype,not the real one..many thanks..
Thanks again for all your help
I am looking to build a very small circuit to allow aftermarket rev counters to read a 12V square wave - effectively a miniture replica of the driver and primary side of an ignition circuit. Such rev counters have a filter circuit on their input to stop the back EFM spike from the '-' terminal of the ignition coil damaging the circuitry. This circuit also prevents them working from a 12V square wave. My plan was to drive a small inductor (about 5mH?) from the 12V square wave via a transistor driver. Hopefully it's '-' terminal will have a big enough back EMF spike to drive the rev counter. I have run in to a problem with the very low coil resistances of small inductors. They will burn out if connected across 12V. If you know of any simple way around this it would be very useful. Thankyou.
Thanks!!
-Der Strom
I would think what you suggest is not safe. The capacitor and the ignition coil are probably not designed for so much current and could heat up and explode.
Thanks again!!
Der Strom
Would it be worth the trouble to guard against back spikes dividing the Voltage by 2 in series like that?
Then Parallel a few series sets for more Current support?
Would there be any problem of noticable propagation of the switching between them that would ruin performance of the spark signal (In other words: If the two transistors don't exactly switch on at the same time)?
i have several aftermarket ignition coils for motorcycle. i want to test which one works gives longer and bigger spark. meaning i want to know which aftermarket coil works best.
do you have a circuit that will provide spark for the ignition coil so that i can determine which one works best?
No, just use a different transistor such as a MOSFET or IGBT. IRF740 is a good example.
richie,
Yes, this pulse width modulator would work great for that.
quel est le schéma de branchement d'un
POWER PULSE MODERATOR PWM-0C10A
avec une bobine de voiture
quel voltage puis je obtenir
10.000v 50.000v
merci et meilleures salutations
do the darlington pair of bfy51 and 2n3055 at 12 vdc input can generate current of 3.5 amps?
English only please.
rahul,
What motor? Use a fuse or a resistor to limit current flow.
*** avec le schéma de " DER STROM ""
quel est le "" hight voltage "" obtenu
*** pour ce schéma peut on utiliser votre module PWM OC10A
*** quelle est la puissance suplémetaire ( en kv) apportée par un deuxième "ignition coil "
si je ne suis pas sur le bon lien ,
(mon anglais a des manques )
indiquer moi le bon
merci et meilleures salutations
*** with the diagram of " DER STROM " " which is the " " hight voltage " " obtained *** for this diagram can one use your module PWM OC10A *** which is the power suplémetaire (in Kv) brought by a second " ignition coil " if I am not on the good bond, (my English has lacks) to indicate to me the good thank you and better greetings.
I translated your post using this page
In future please use this to traslate your mesages.
The translaton is not great so i am not exacly sure what you are asking. You mention a diagram by dr strom, what is the post number of this diagram?
avec le schéma présenté en décembre 2006
quelle tension ( en kilo volts ) obtenez vous
remerciements
I'm controlling the gate to my IRF740 directly with 555 pulsed output, and have my coil between the collector and ground, but I can't get over 400V (I charged a capacitor with it and tested that). I have a small capacitor across the coil inputs and a fast-switching diode antiparallel with the collector and emitter of the MOSFET. I'm guessing dI/dt isn't enough, do I have to sink current from the IRF's gate or something?
Also maybe the diode is not great. if it is too fast, it would stop the dI/dt being fast enough for a HV output.
I'll get a few potentiometers and ditch the diode to figure out what's wrong... I put 10K ohms of resistance between the gate and collector and got rid of the diode and saw no improvement.
A simple test of your mosfet part of the circuit is to tap quickly the gate pin on a 12V source. This should make the ignition coil spark as you release the connection.
I have the gate grounded with 10K ohms, and when I remove gate voltage the ignition coil sparks. However, when I put the pulsed output from the 555 to the gate, I still get next to nothing on the output. I'm using a very low frequency, and I have tried feeding the gate directly from the 555's output, with and without resistance, and I have also tried a small transistor to amplify the pulse, which shouldn't be necessary with a MOSFET... but I don't know what else to do. My setup is like the first image on this page, using a basic 555-timer astable multivibrator.
The MOSFET works, and the pulsed output of the 555 makes an LED flash, so I am really confused as to why this is not working. I've tried replacing the 555 chip, and I get the same result.
Anwers to both yor question are on this page allready.
ScotchTapeLord,
It sems as if there is some problem with the 555 output. Possibly it is not at a good frequency for your coil, or the duty could be wrong. Also it could be that for some reason the 555 does not swith off quickly enough. Are you aple to observe its output on a scope?
Typically a MOSFET needs about 10V to switch fully on, make sure yur 555 is outputting enough voltage.
I have traces of real car primary signals from my oscilloscope (a cheap PC based DSO), which I have compared to the trace I get from my driver circuit, and they are quite different.
There is no noticeable 0V part to the 12V square wave which I am assuming is driving the coils in the car circuit. It looks more like a continuous 12V signal with the expacted back emf spikes of around 300V. I assume it's beneficial in a car maximise the duty cycle of the wave, as the coil takes time to charge, but discharges almost instantly, and that the OV section must be there (otherwise there would be no spark), and that my oscilloscope is too slow to catch it. This seems odd though as it catches the back emf spike well. Do you think this is a reasonable explanation, or is there something happening that I am missing?
Sorry if the question is slightly off topic, but you seem to know far more about how to drive car ignition coils than anyone else I have found. Thanks,
Where are you connecting your scope?
I also have your resistor and capacitor snubber circuit in parallel with the coil in my DIY driver to try to prevent damage to the MOSFET. I'm wondering whether this is affecting the oscilloscope trace? I think I'll try disconnecting them to see if I can get a trace without for comparison.
Also, I had a thought which may be useful for your high voltage experimantal circuits. As well as using car ignition coils, why not use a car ignition driver module too? Most mid 80's to mid 90'd VW's, and many other cars have the ignition driver module as a seperate unit inder the bonnet. Typically they have half as many coil drivers inside as the number of engine cylinders from cars with an even number of cylinders (wasted spark ignition, and are driven by a 12V square wave from the ECU. You can't dismantle them to see what is inside, as they tend to be bespoke chips, but they obviously have all the necessary transient suppression built in, and can be bought for next to nothing from scrap yards or eBay.
It is possible that it is 'freewheeling' too much current. What diode do you use? The RC will only help if it is over voltage which kills your diodes.
Richard Jones,
The connection you describe may give you odd reading because of protective components or reversed diodes in the circuits. Just measure between the coils input pins.
btw great page this is my 3rd driver i try building, the first one was a 555 n it worked on a speaker as a nice signal gen, but never worked on a coil, the second was another type of 555 but just flat out didn't work. i like this one cuz its nice and simple, i just used part of my first driver on the input signal, and bam worked :), thanks for the page
Sincerely,
Der Strom
You would need to use an opto-isolator and make sure the input and output are not connected to the same power supply.
No it is not designed to only spark when you switch the power. You have a problem in your circuit.
Aldrin,
Yes, but the output will be DC and of lower current.
Der strom,
It is not likely to help unless you just make brief pulses at a very low frequency. The flash circuit steps up the voltage, and will release it as a pulse of current. If you are drawing power continually from it, it will just be wasting energy as heat in the electronics.
what do you think might be wrong? where should i start looking? any suggestions or ideas?
thanks:)
Hello. I received an answer to my last message. Large mercy. A message s' is lost. I repeats it. All my excuses if that is doubled bloom. in the diagram presented in top of the page, with two ignition coils and 4 transistors, the generator presents only 3 exits. Which is the connection with a PWM which requires one + - battery and v+, v. Thank you for your answer. Cordially. PS Your site is a mine of information a little hidden
C du BFY51
2 B E
+ batterie B collecteurs 4 2055
Emetteurs 4 2055
- batterie
Helo. I want to connect a PWM to the circuit with 4 transistors and 2 ignition coil.en l' without knowledge in electronics, I studied the diagrams for HHO, the gun, the first diagram of this page. I found a solution! ! shown in my message. I connect L+ connection to resistance (100 r) of the BFY. Thank you to say to me if my idea is good. So not which is the correction. All my thanks. I think my schéma is bad .
ordered a PWM
i'm bulding a spark generator like andrew's design. i need your advice, if i want to measure and control the arcing current,what should i do? is just putting some potentiometer and ammeter?
You control the current by adjusting the setting of the duty (pulse width).
A snubber (RC1) should just be placed in parallel with the load.
atuk,
A potentiometer would likely be destroyed if you put it on the HV output side. If you want to control the output current, you can just control the input current using Pulse Width Modulation.
The output current could be measured by placing an ammeter in series with the output, or by measuring the voltage drop across a small resistor and calculating it using ohms law.
You need to post a circuit diagram otherwise I can't help you.
jango,
I don't understand you.
The reason is due to the way transistors work. The transistor is activated by applying a voltage or current (depending on the type of trnasistor) to the base (or gate) pin. The voltage is applied relative to the emitter (or source) pin.
For example;
Some transistor is rated to switch on when the voltage on the gate pin is 8V. This voltage is measured between the gate and the source pin. When the source (or emmitter) pin is grounded, then the voltage you apply to the gate pin is always relative to ground (0V). If the source pin is connected to the load (ignition coil), which is then connected to ground, then the source pin will be higher than 0V when the transistor is on. If you are only applying 8V to the gate pin (relative to ground) then it wont be enough to switch the transistor properly.
This is epecially problematic with coils becasue the voltage would oscillate and the circuit would be unstable.
the whole thing needs to be transportable by a single person to take it to Uni
Thank You
Colin Cade
You don't need a car battery, you can buy smaller 12V batteries called SLA (Sealed Lead Acid) batteries.
i have been looking at SLA batteries on eBay. Unless you sell these as well?
what sort of AH should I be looking at for reasonable result
sorry, just looked at the spec of your PPM, 10A
Colin
My question is what would be the best way to lower the frequency of the 1mohm pot? I would like to fire about once per second to perhaps 20 times per second. Is this feasible on this board?
If so what would you suggest?
Thanks,
Bing
This looks really interesting!
Recently i have seen some videos on youtube about plasma speakers http://www.youtube.com/watch?v=3AD-deOyljA&feature=channel.
My idea is to use an AVR microcontroller to generate the PWM signal at something like 70 kHz and sample sound with the a/d converter at something like 30-40 kHz. The sampled values would then be used to set the duty cycle of the PWM signal. Do you think this could work with an old car ignition coil to generate sound? It would be really cool.
If i manage to build this i will post the schematics and the source code in case someone is interested.
Thanks!
The attached image has the part of the schematic with the IGBT transistor and an 3d image of the complete board (the kicad-components i made have no 3d footprint). The reason for the "dual" gate connection to the IGBT is that i was not sure if the microcontroller was able to control the igbt, but in the end it was.
I was able to create a tiny arc (3 mm) by adjusting the frequency and duty cycle, and the diode (D1) got quite hot. I removed the diode with hope for a bigger arc, and that broke the igbt in one second. The power supply i used was an old pc psu with 12 amps from the 12v output.
So, before i buy another igbt for 15$, should i replace the diode with a cap and resistor, or should i use some different kind of transistor?
I have a Stihl 2 stroke chainsaw engine and i want to replace the entire ignition circuit as it is badly damaged. Is it possible for me to still use the flywheel mounted in the engine and the transformer in it too but re-winding the transformer so that i have the necessary output voltage to drive this circuit throught the -input signal-? Which at the same time, the output would be connected to the engine's sparkplug.
Thanks!
Is it possible for me to use this circuit as a replacement for an old ignition circuit from an old chainsaw 2 stroke engine? I was thinking of re-winding the high voltage transformer with very little windings so that i get a very small ammount of output voltage and then use that output as the input of this circuit, instead of using a signal generator, in fact the transformer would act as a signal generator.
Then i would connect the high voltage output from the sparkcoil from this circuit to the engine's sparkplug.
The bad thing about this is that i need an external power source, as a battery, to run this ignition system, expecially because there's no return current to the battery. Maybe i should had a dyno to charge the battery at the same time.
Would you mind pointing me a schematic?
[Perhaps stacked in some way?]
-I have had really nice arcs using the IRF740's but I havent managed to get these to live for much more than a minute, yet :-)
How could I do to increase the spark to more than 3 cm
tks
The finished product will be connected to a 30kv TV tripler, to rectify the voltage, and obviously, triple it. So it needs to be an AC signal.
When turned on and fully connected (without the tripler), the 555 timing circuit doesn't work, but when setup in a more classic way, it still does, and once this circuit is disconnected from the timing circuit, the timer starts pulsing again. All the components test good.
Do you have any suggestions of how to achieve what I want to do? Or can you see why my pictured circuit wont work?
I would suggest not using the 2n3055 though. This is an old article and there are much better alternatives available now. You would be better off using a MOSFET or IGBT as you can get ones with a higher voltage rating than the meagre 100V of the 2n3055.
With most ignition coils the HV return is internally connected so you would have no choice, but if possible, you should use the common ground.
Be aware that ignition coils can make a lot of feedback so you should make sure your low voltage electronics are well protected.
Cheers!
I have some questions and hope you can help me:
Rode a circuit with a 555, but only with an astable common, not with PWM and am using a transformer 3A / 24V automotive and coil, but also do a lot of spark off the coil, still had some problems that just exploded ! I wonder:
How many volts can support an automotive coil?
What is the maximum frequency that it can support (I'm using 2kHz)
What would be the reason it blew up, since it does not is not too hot?
I appreciate the help! Hug from Brazil!
Cabral
Would a sine-wave oscillator instead of a square-wave give better efficiency for driving an ignition coil?
The input voltage for most ignition coils 12 - 16V. If they are blowing up, it is most likely due to over heating.
Jim,
I don't know. Look up the part number on-line.
Noah Spurrier,
Yes you can use a TVS.
The driver must be square wave to work properly.
Thank you so much you have a great site!
Jack Hallaran Atlanta, USA
RC1 should be 10W, and 1kV. You can use a variety of values here. I often use a 1kV 220nF capacitor with a 50W 120R resistor. You may have to determine experimentally what values work best at the frequencies and duties you will use.
Dear Sir, i also confused with RC1 capacitor value also. and what type of capacitor is this? metal, polystert? ceramic or what type? as size does matters in module. small parts small module also. thanks
You should use polypropylene or another quality capacitor good for power circuits.
You can replace both transistors with a single IGBT, but you will need at least 10V of signal to switch it well. You should also have a 10k resistor between gate and GND.
The results you get will depend on how quickly your magnetic filed near the sensor is flipping. It would need to be about 50Hz or more.
The output voltage proportional to the rate of change of current at the input. You can vary the fall time, or the pulse width of the drive signal to change the output voltage.
You will certainly need to protect your circuit. Use an RC snubber at least, also a power resistor of a few ohms in series with the coil. You may also need zener diodes and schottky diodes on the power lines.
The OCBI is not complex. Ignition coils make a lot of voltage spikes so your circuit needs to deal with this otherwise it will just fail.
Something like the power pulse controller would work well with an IGBT. We also have similar devices available in the shop.
The values needed for the snubber will depend on the operating frequency, the spec of the coil, and the load on the coil. You will need to detimine what works best for your setup. In the twin coil example you might also need a snubber. It was just left off the diagram for simplicity.
This circuit is really not worth building. As I have stated before, this article is very old and there is a modern alternative available. See power pulse controller.
The power capacity is limited mainly by the chosen transistor. If you need more power than the one shown, simply choose a different transistor. There are some quite powerful IGBTs available these days.
Allthough this circuit works, it is really not good. Paralleling bipolar transistors in this way is not reliable. You can use MOSFETs or IGBTs in parallel and they will be much more effective.
As you are using an OCXI as your drive signal, you can simply connect the SIG output terminal connector to the gates of your array of parallel MOSFETs/IGBTs without the need for the BFY51 preamplifier. You will still need to protect the array from voltage transients though
That transistor looks ok, but please consider my comment in post #4704
You will need to use a much higher value of resistance, and use a several resistors to form a voltage divider to that it will suit your scope.. You should also discharge the spark to ground via the resistor so that your scope has a ground reference.
The spark will also discharge a lot of EMI, so you might want to shield it or at least keep it a reasonable distance away.
The efficiency of the coil does drop off as frequency increases due to losses in the core. Smaller coils usually work better at higher frequencies. The impedance of the coil will also increase with frequency. This means for the same input current at a high frequency, you would need to use a larger input voltage. After about 20kHz you will only get very low current on most ingition coils when using a 12V supply.
It is to do with the first law of thermodynamics (conservation of energy), and the relationship between power, voltage, current, and, resistance (or impedance) as described in ohms law.
When the current switches off, the magnetic field around the coil will collapse. The energy in the field is transferred to the coil as an electric current flowing in the opposite direction to the initial current. Ignoring losses, the power (energy/time) in field will be equivalent to V x I. Since the transistor is now off the resistance of the circuit is very very large. Therefore in order to balance the equation V=IR, V must become very large and I very small.