Servo Control Voltage

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Euticus
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Servo Control Voltage

Post by Euticus » Fri Sep 05, 2003 1:10 pm

Does the control voltage on a servo have to be at the same level as the motor voltage? I am planning to use several different micros to provide the PWM signal for the servos-one micro is 5 volts the other is 3.3. The servo will have it's own supply at 6 volts or more. (I do not want to run the servo motor at 5 volts.) I have never seen this question addressed anywhere.

bwts
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Re: Servo Control Voltage

Post by bwts » Mon Sep 08, 2003 10:10 am

In theory I guess not. U could wire the pot in the servo upto any circuitry U desired although this would mean opening up the servo 2 fiddle with the wiring. It all depends on how sophisticated Ur servo is. Some have position control circuitry on board some dont.<p>B)
"Nothing is true, all is permitted" - Hassan i Sabbah

happy
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Re: Servo Control Voltage

Post by happy » Wed Sep 10, 2003 10:06 pm

Suggest you use a 1N914 diode in series with the control line. Cathode pointing to the higher voltage device(servo). Weak pullup to the 6V between the diode and the servo. Drive the PWM like an open-collector/open-drain.<p>Ooops. Just checked my diodes are not 1N914, as they don't work. Somehow I had put 3.6V zeners in there, accidentally. I suspect schottky diodes may work, as they have low forward voltage drops.<p>[ September 21, 2003: Message edited by: HAPPY ]</p>

Megadan
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Re: Servo Control Voltage

Post by Megadan » Mon Sep 29, 2003 7:03 pm

Most of the newest Futaba R/C receivers generate a 3.3v control signal, while shunting the raw Rx battery voltage to the power lead of the servo. The idea of using a diode inline is good, as long as the 0.6v ding doesn't keep the servo from working. On a recent 14 servo signal reprocessor, I used some special latches designed for disparate voltages.<p>Dan
Dan Danknick

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