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HB-25 equivalent at 24v? — Parallax Forums

HB-25 equivalent at 24v?

Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
edited 2012-12-20 04:57 in Robotics
It appears that 24v motors are out of range for HB-25

Does anyone know of a 24v equivalent?


Jeff

Comments

  • W9GFOW9GFO Posts: 4,010
    edited 2012-12-12 16:46
    You can of course use the HB-25 with a 24V motor at reduced speed, if you supply it with 12V.

    Dimension Engineering makes a series of motor controllers that can handle 24V.

    There is also the TI Jaguar Controller - only $60 now!
  • ercoerco Posts: 20,255
    edited 2012-12-13 10:45
    Jeepers Jeff, I bet I know the 24V motors you mean! :) You def want, 24 or more volts, they're pretty slow at 12V

    Yes, getting a 24V or higher drop-in for the HB-25 might be tough. For use with those motors, I have one of these $4 L298N-based controllers (2 ch, 35V, 2A peak) but haven't tried it yet. Of course it wants PWM input, not servo commands. Hope to try over Christmas break, will report back.

    http://www.ebay.com/itm/110942422752
  • vanmunchvanmunch Posts: 568
    edited 2012-12-15 20:12
    Hey Jeff,

    I second Dimension Engineering. I've used their Sabertooth 60X2 for a robot that weighs ~500lbs without any sort of trouble.

    Dave
  • ercoerco Posts: 20,255
    edited 2012-12-15 21:45
    That Sabertooth is quite a controller for 25/50 amp robots. The little 24V motors I think Jeff is using have a stall current of just 1 amp, so the Sabertooth may be overkill :).
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-12-16 19:42
    I'm trying to push two 24v motors from a dead stop with weight of around 400lb. (occupant and machine)

    The amps at start are expected to be high.

    Jeff
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-12-16 20:21
    erco wrote: »
    Jeepers Jeff, I bet I know the 24V motors you mean! :) You def want, 24 or more volts, they're pretty slow at 12V

    Yes, getting a 24V or higher drop-in for the HB-25 might be tough. For use with those motors, I have one of these $4 L298N-based controllers (2 ch, 35V, 2A peak) but haven't tried it yet. Of course it wants PWM input, not servo commands. Hope to try over Christmas break, will report back.

    http://www.ebay.com/itm/110942422752

    That's a great price on the L298N boards. I'm pretty sure that's about how much I spent for just the L298N chips plus the diodes.

    My Rover 5 Mecanum robot uses L298N controllers. I think they work fine but Gordon doesn't like the L289 for motor control. I think he said something about too much of a voltage drop? I intend to investigate this. I may use one of Pololu's H-bridge boards.

    Speaking of Pololu, they have a board that can handle 24V. It's on sale right now for $36.
  • ercoerco Posts: 20,255
    edited 2012-12-16 21:51
    Duane Degn wrote: »
    I think they work fine but Gordon doesn't like the L289 for motor control. I think he said something about too much of a voltage drop? I intend to investigate this.

    Percentage-wise, losing 2 volts is less significant at higher voltages. At low voltages, zero voltage drop relays come on strong!
  • P!-RoP!-Ro Posts: 1,189
    edited 2012-12-19 21:56
    I've used relays to control the direction and a high-power transistor to control the speed before. This can also reduce the voltage drop as well as the power loss with the current only passing through one transistor. If built right it will also be near impossible to create a short like a half bridge circuit can if used incorrectly. Of course, with relays, there is a higher chance for mechanical failure however.
  • agfaagfa Posts: 295
    edited 2012-12-20 04:57
    Oldbitcollector (Jeff) wrote: »

    The amps at start are expected to be high.

    You would want to find out the stall current before choosing the controller.

    agfa
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