slightly OT, need some electronic circuit help

Michael Torrie torriem at
Sun Oct 7 17:52:09 MDT 2012

On 10/07/2012 12:32 AM, Ryan Byrd wrote:
>> However it does not specify what sort of op amps to use.  I am unsure
>> how to translate the schematic into a working circuit with real parts.
>> Also I don't know how to choose the resistor values.
> this page:
> has a similar "Rotary Position Closed-Loop Servo System" circuit:
> except this time there are resistor values.
> the op amp shown is powered by +/- 15 volt which makes me think it's a
> generic 741, something like:

Any ideas on how to get negative volts?  I have only one power source...
12V positive.  One method is to double the voltage with some circuit,
then divide it and use the middle as the ground.  Another method might
be to divide the 12V and then use the +/- 6V output to run a set of
relays to switch 12V power directly into the motor.

Bear in the mind the motor uses anywhere from 1 to 10 amps perhaps,
depending on load.

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