Instructables
Picture of Scantron Music Box
Playing with music is always fun. Inspired by Mike Nathan's Punch tape musical synthesis, I designed a 13-tone programmable scantron music box using VCO XR2209 and some other components. 

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Step 1:

Circuit description:
Lots of people use 555 timer to make musical synthesis. I want to try something different. The XR-2209 is a monolithic voltage-controlled oscillator that can generate simultaneous triangle and square wave outputs over a frequency range of 0.01Hz to 1MHz. Its frequency is determined by resistor R1 to R13 and capacitor C1 (see schematic .f=1/ RC). By varying the value of R1/R13, we can get 13 different tones. I use 13 sets of reflective sensor QRD1114 and mosfet 2N7000 to turn on/off R1/R13.  The reflective sensor QRD1114 consists of an infrared emitting diode and an NPN silicon phototransistor. When a white paper is placed on the top of the sensor, the phototransistor output moves from a high voltage state to a low voltage state, and the mosfet will be turned off. By placing a scantron on the top of the sensors, only one mosfet will be turned on each time. The mosfet will be on/off when the scantron is moving.
 
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This is brilliant. However, one consideration. If you added either a second paper guide at the bottom of your machine, or parallel guides on the sides, you'd have a much smoother machine.
This is brilliant. However, one consideration. If you added either a second paper guide at the bottom of your machine, or parallel guides on the sides, you'd have a much smoother machine.
this is so cool I love how you were able to do this all with out a microcontroller!
rimar20001 year ago
WOW, this is very nice! You could make any melody with it.

I suggest you to add a new sample, that have a very known melody instead of a simple scale. It would be far more shocking to hear, looking while the paper goes through the groove. If done, please PM me.