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Step 2: About the Circuit

Picture of About the Circuit

At first glance, the circuit might look a little complicated but it's really pretty simple. The best way to make this synth is in stages which is how I will explain each step in making the circuit. You'll also notice that I have included 2 schmatics, the 2nd one includes a amp module and volume pot. It's not necessary to add this but it will dramatically increase the volume. However, I did add an output socket so you can just plug it into a portable speaker to increase the colume. If you also download Fritzing you can play around with the schematics yourself.

I'll go through what each 555 timer does and will try to explain some of the features and how the synth works.

555 Timer 1 & 2

1. Both 1 & 2 timers are basically a flashing LED circuits. To be able to control the speed of the LED on each 555 IC, there are 2 different capacitor values. These are connected to a SPDT switch which allows you to change the speed of the LED's

2. Also connected to each IC is a 10K pot. This also allows you to control the speed of the LED's.


1. IC timers 1 & 2 are also connected to a vacrol. Inside the vactrol is an LED and a Light dependant resistor (LDR). There is a pot connected to each which controls the brightness of the LED's which changes the pitch and tone

2. Check out the next step on what a vacrol is.

555 Timer 3

1. Lastly, IC 3 generates different sounds depending on the brightness of light. There is also a pot that controls pitch.

2. IC 3 is connected to IC's 1 and 2 via 2 vactrols. When you connect the LED's to the LDR's (which is what a vacrol is) you have a fizzle loop synth!

So to summarise - LED's blink at different rates and brightness's which create rhythms and beats controlled by various pots and switches.