The circuit is pretty simple, it centers around a 555 timer IC
. The 555 timer is wired up in astable mode
, meaning that it will be outputting a continuous square wave, with a frequency dependent on the resistance between the two pins labelled "POT" in the diagram above. The only extra components needed are a 1kOhm resistor and a 0.01uF capacitor. The circuit is powered by a single 9V battery, connected at the ground and 9V pins. A speaker is connected to the ground and output pin (pin 3) of the 555.
I also included a jumper wire in my circuit, indicated by the two pins labelled "jumper" in the schematic above. A jumper wire is a wire that connects one part of a circuit to another in case it is too difficult to find a path for it on the printed circuit board (PCB). Pins 4, 5, and 8 should all be connected to 9V, but since they are on opposite sides of the 555 timer this was a little tricky. As you can see in fig 2, I already had conductive traces running under the 555 timer, so I had to use a jumper cable to connect pins 4 and 5 to 9V without running into other traces or taking a very long path around the chip (although this might not be a problem with regular copper traces, a long path with conductive paint will add some unnecessary resistance to the circuit).