So, recently I’ve decided I wanted to start making my own little electronics projects. I’ve got a few in mind, but the first one I wanted to do was the Optical Theremin.
I have wanted an optical theremin for quite some time (rough guess would be 5 years), but the prices on them aren’t cheap (the built kits I’ve seen go for around $100), so I figured I’d see if I could dig up schematics and make my own.
To my delight, I found the RS Optical Theremin. It generates a square wave, and the tone will vary depending on the amount of light that the photo-transistors are receiving. Most of the parts for this project will be available at Radio Shack.
I quickly breadboarded-up the schematic on the website, and thoroughly loved the sounds I was getting. However, I wasn’t planning on leaving it as is, so I made a few modifications.
First, I added a power LED and power switch. The LED was handy, so I could tell if the thing was on or not.
Second, I added a volume knob.
Third, I added a killswitch pushbutton, so I could do DJ-like tap-scratching.
Fourth, I added a 1/4″ jack so I could run this to an amp or my sound card.
Lastly, I added a combo 500k potentiometer and SPDT switch. The switch activates the Killswitch, so I can either have the unit in “Tap” mode or in full-open mode (no cutting out). The 500k pot acts as a pitch ceiling. I was really liking the super low pitch square waves I was getting with very little light, so I wanted to be able to control the range on the output pitch. I hooked up a 1Meg Ohm pot and found out the 500k was the sweet zone to get the lowest of the low square waves.
Here’s a schematic I drew up, including the parts I’ve added (click image for closer view).
Next step will be transferring this to a circuit board.