In this post I’m sharing a tutorial on how to make a simple synthesizer which react to moisture and touch from human body. Originally, this synthesizer is based on quad oscillator using 4093, squarenoise~ module which I used for a workshop on Ho Chi Minh City, Vietnam. This module is quite simple and only using several electronic components which makes it suitable for beginners or as an introduction to DIY electronics. See the video above to see how it sounds and interacts.
Like I said before, the synhesizer are quite simple as shown on the schematic above. VCC is where you connect the 9V+ and GND is, well, GND!. Padout + is where the + of your sound out, pad touch is where you interact with the circuit with your finger or moisture. Note that this circuit are using your body and / or moist as a resistance, it won’t produce any sounds until it is triggered.
The board layout is also pretty simple. The touch pads is where you interact with your fingers. You can also put the pads on the soil for example, to know the moisture level of the soil. Pay attention to the red line, it is a jumper wire which I would recommend you to solder it first before you assemble anything else. I put it bellow the IC so it is hidden from the design. As for the capacitor value, you can use pretty much any value or type. The higher capacitor value, the lower frequency the oscillator will produce. Try to combine different value of capacitor to get the sound that you like. The example above are using 100nf and 2.2uF capacitors. Feel free to experiment ^^.
This is the board print if you want to etch your own board. the size of the board is 10 x 4 cm. Pay attention that this board is designed for you to solder the components on the etched side, not from the blank side. Reverse horizontally the design if you want to put the component from the back of the etched side. A little on how it looks like with the component attached bellow:
EagleCAD (v. 5.x) files: