Controlling Vex 393s

[slijin]

Does anyone know how the vex 393s can be powered/controlled without the vex-made speed controller? Or if even poossible, whether they can be directly powered with the signal and ground of a 5v GPIO?

We want to use them as servo substitutes for a newbie project but we're a little tight on money.

Thanks!

[Mark McLeod]

There's not enough power from the GPIO or Relay signal lines to power that motor.
Some of the DSC power pins can power it, but you'd need some type of 5v/7v relay to turn it on/off.

[Phyrxes]

Running a 393 off the DSC requires the placement of a jumper to provide power over the PWM and you still need the vex motor controller in line with the motor.

Question,

Am I correct in assuming a regular 3 wire "old" VEX motor would work fine in this situation?

[Mark McLeod]

Am I correct in assuming a regular 3 wire "old" VEX motor would work fine in this situation?
Yes, they can be run off the PWM outputs, as can any continuous rotation servo. No problem.
I suppose this is a matter of using what they have laying around already to keep expenses non-existent.

[slijin]

I was specifically hoping to power it by paralleling 5V lines from the Teensy (http://www.pjrc.com/store/teensypp_pins.html), a microcontroller that uses the Arduino language. Unfortunately, I hadn't actually checked any specs before asking, but seeing the specs on the motors now (7.2V, 4.8A stall), I'm rather reluctant to even try that theory out.

In any case, for curiosity's sake, how would the 393 be controlled by toggling a 7.2V power supply? Would it be the same type of pulse modulation used on regular motors, or does its construction require a different type of signal?

[Mark McLeod]

It has a standard motor inside, so the same sort of on/off pulse modulation for a duty cycle is used to vary the speed.