Remote Controlled Voltage Source

Discussion in 'The Projects Forum' started by supertux1, Jul 3, 2008.

  1. supertux1

    Thread Starter New Member

    Jul 3, 2008
    Hi All!

    I have a project which requires me to remotely adjust a voltage from 0 to 10V. There are some special considerations which require it not to be radio frequency control or a long wire. I'm thinking IR. (Read on...)

    The device that is to be controlled is a regenerative DC motor drive board that varies the motor speed based upon a voltage at a pair of terminals.
    I currently use a potentiometer as a voltage divider for this, but I don't want to be anywhere near the thing when its operating.

    That motor turns a massive 12" diameter 3/4" thick Garrolite disc in an asynchronous rotary spark gap for my 6" 3.5kW Tesla Coil.

    I want to build a remote control for it so I can adjust the speed of the motor (spark gap break-rate) while the coil is running.

    I was thinking of using the LM2907 F-V converter IC to turn IR light pulses into a voltage for the motor controller. For a transmitter, I was thinking
    of using a plain 555.

    In my junk box I have most of these parts, including one of those Radio Shack IR receiver modules. It requires a carrier of 40kHz, which might be a good idea considering there may be a lot of IR interference from the sparks and other sources. (Massive EMF....)

    So I was thinking two 555's or a 556 with one half dedicated to producing the carrier for the detector module and the other the frequency modulation. And lots of really big bright IR LED's.

    Sound good? Does anyone have any good 555/556 examples for lightwave IR remote control?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    I've done that with a pair of 2907's to adjust a supply floating at about 5 KV, with optoisolators to keep voltage off the lines. You probably don't want wires running from your Tesla coil...

    Think of grabbing a bit of optical fiber for the voltage break. No background sparks to worry about. Convert the control voltage to a frequency, run it through the fiber, and convert back to a voltage.
  3. Externet

    AAC Fanatic!

    Nov 29, 2005
    Hi super.
    I would direct my thinking towards two photocells/photoreceivers, one to gradually increase the voltage and another gradually decreasing it.
    A laser pointer aimed to them and a radiocontrol servomotor turning a potentiometer may work, by one photocell/phototransistor to drive it forward and the other reverse. The potentiometer fed by 10V and its wiper being your variable output.
    You can be as far as needed but aim well !

    If you want it simpler, a nylon fishing line can move a sprung linear potentiometer too.
    Last edited: Jul 3, 2008