A Tiny Homemade
Square Wave Signal Generator ('Dead Bug' Style)
This page shows you how to make a super simple square wave signal generator. The circuit below uses a 555 timer chip, a capacitor, and some resistors to generate a variable frequency, variable pulse width square wave. The term 'dead bug' refers to the way that the finished circuit resembles a dead insect. This is because the solder connections are made directly to the components and there are legs sticking out making it look much more messy than the diagram below.
This is a very basic circuit and therefore does not produce an ideal square wave over the full frequency range. The pulse width or duty cycle can only be varied by a small amount, and doing so also effects the frequency output.
If you want to try a more advanced and more accurate version see the DIY Signal Generator II
This diagram shows how the circuit can be wired without the need for any circuit board. A 14 pin IC socket is used to hold the main circuit so the 555 chip and the two pots can be simply plugged in. The total parts list is shown below.
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The diagram represents a view from below and is not to scale. The circuit may be a little tricky to solder, but its about as simple as you can get for a signal generator.
The value of the capacitor C1 will determine the range of frequencies produced. Somewhere around 0.1 to 0.01 microfarads should be adequate for mid range audio frequencies.