MOTM

Finally, after all the orders for effects and household chores were
completed, I got back to the ribbon controller project.  When I said
the electronics would be "simple as dirt", that could also be read as
"light on functionality".  This is fine for my purposes, all I wanted
was a smooth 0-5 vdc output.  

The ribbons (there's two elements on my controller) are each connected
across a differential amp-1/2 of a TL072-and the "wiper" (the copper
tape) is connected to the negative supply.  In the case of my device,
power comes from a pair of 9volt batteries.  The inputs of the op-amps
each have a 10K resistor to the element.  The feedback and ground
reference (to the positive supply) resistors are 100K trimpots. 
Naturally, the power supply pins are decoupled with electrolytics-10uf
in my case.

Four resistors, four trimpots, two caps and one TL072.  Not too
shabby!    This arrangement allows for a wide voltage output, from
negative rail to positive rail voltages at the output, if so desired.
 In other words you can have the output range from -5 volts to +5
volts to control most MOTM inputs.

One inherent problem with my battery-powered system is as the
batteries fade, my range narrows.  Tough!  If the diff amp is powered
by the MOTM supply, this won't be a problem, though the voltage may
drift with temperature and load.  Again, too bad!  

Lastly, now that the system is in use, my grandson told me "it's too
big!"  Well...next project-the dual joystick modulator/voltage
controller!  Anyone care to see that?

Chub-guided by kids and cats...