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Sabertooth 2x25 Voltage Question — Parallax Forums

Sabertooth 2x25 Voltage Question

bluegizmo83bluegizmo83 Posts: 3
edited 2011-11-03 17:29 in General Discussion
I need to run a few small DC motors off my Sabertooth 2x25 motor controller but I'm having some issues... The motors I want to run are rated for 3v-5v but the sabertooth has a minimum voltage of 6v. How can I go about using these motors? Is it possible to put 12v in to the Sabertooth and then install a voltage regulator between the sabertooth and the two motor wires to drop the voltage to 3v-5v? Is there another easier way of doing this besides buying a smaller motor controller? Will the Sabertooth 2x25 function with only a 5v input instead of the recommended 6v minimum?

Comments

  • BitsBits Posts: 414
    edited 2011-11-02 08:35
    I would run the motors close to 6V but control them at a slower speed. I don't think the extra voltage would hurt the motors but in the long term who knows. I also don't know what type of motor it is or what type of load you will be placing on the motors.

    I don't think a voltage regulator will help unless the current is very low on the motors.

    *I bet you can run the device on 5 volts, sure would help to have a schematic.
  • $WMc%$WMc% Posts: 1,884
    edited 2011-11-02 10:02
    I wouldn't go below the 6volt min. The regulator needs to keep 5volts out for the TTL micro thats controlling the H-Bridge. The voltage regulator needs at least 6volts in to do this.
    '
    You could experiment with a 6volt lamp reading the voltage out at different duty%s on the motor out leads. 0 to 100%
    '
    Blowing a cheap lamp would be better than blowing a motor for the test.
  • kwinnkwinn Posts: 8,697
    edited 2011-11-02 12:07
    You might consider using 1 or 2 pairs of diodes to reduce the 6V output to approximately 5.3 or 4.6 volts as per the diagram. They would of course have to be rated to handle the motor current.
  • bluegizmo83bluegizmo83 Posts: 3
    edited 2011-11-02 14:43
    Thanks for the replies everyone. The motors are small, they are drive wheels on a small 4wd robot chassis (weights less than 1lb and is only about 10" long and 5" wide) and there are two motors, each rated for a stall of 1.6A and unloaded current of 240ma.
  • AleAle Posts: 2,363
    edited 2011-11-03 08:17
    Which micro are you using for the H-Bridge ? some work well at 4.5V... others go down to 2.7 (for instance attiny/atmegas) no idea about the sx though.
  • bluegizmo83bluegizmo83 Posts: 3
    edited 2011-11-03 17:29
    Ale wrote: »
    Which micro are you using for the H-Bridge ? some work well at 4.5V... others go down to 2.7 (for instance attiny/atmegas) no idea about the sx though.

    I'm really not sure which micro it has... Its a Sabertooth 2x25 motor controller, but I don't think I've ever seen what processor it uses. I think I'm just going to hook up 12v to the Sabertooth and just run the duty cycle at 0%-50% which should keep it below 6v at the motor. I'm gonna be controller the Sabertooth via an RC Receiver and Transmitter so I can easily set my transmitter to Dual Rate and have it max out at 50% output when the stick is moved 100%
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