Archive of the former Yahoo!Groups mailing list: 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...