The F.A.T. Manual
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Scratch Markup Language Fader Hack middle pins are for the channels. Use a volt meter to determine which pin is power and which pin is ground. Plug ground into one of the ground pins on the Arduino and the two center pins from the fader through a voltage divider and into two analog pins on the Arduino. We used A0 and A1. You do not need to hook anything up to the 10V power pin on the mixer. Got it?
Here is a list of items you should have to do this: - Vestax PMC-07 Pro mixer (Any VCA mixer will do, just drop the voltage to 5V or less.) - Four 100 kilohm resistors - An Arduino - A proper Y cable for the PMC-07 Pro - The Arduino sketch we made available here: github.com/scratchml. Build your Y cable. Make a couple voltage dividers. Hook it up like the picture above and BLAMO! Step-by-step instructions are available on Instructables: www.instructables.com/id/Scratch-Markup-Language-VCA-Fader-Hack/.
Notes [1] Cf. www.adafruit.com/products/50. [2] “a voltage divider (also known as a potential divider) is a linear circuit that produces an output voltage (Vout) that is a fraction of its input voltage (Vin). Voltage division refers to the partitioning of a voltage among the components of the divider.� From Wikipedia, http://en.wikipedia.org/wiki/Voltage_divider.