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HB-25 Question — Parallax Forums

HB-25 Question

NWCCTVNWCCTV Posts: 3,629
edited 2010-05-04 05:11 in BASIC Stamp
I have 2 Ea. 12 volt motors. Is it going to be an issue connecting them both to one HB-25? I know they will not run at full speed, but can only afford 1 HB-25 for now. Also, Do I use the battery negative side on the HB-25 to ground the motors?

Post Edited (NWCCTV) : 5/4/2010 4:30:12 AM GMT

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2010-05-04 04:29
    One HB-25 can control one motor. If you want to control two motors, you will need two HB-25s. The only way you could control two motors would be to use a DPDT relay to connect one motor at a time to the HB-25. The relay would have to have contacts that could handle the load and you'd need some kind of power transistor to activate the relay. You'd also have to be careful to turn off the HB-25 before you switched motors by sending it an invalid control pulse.

    You might consider building two H-bridges or buying a pair of ready-made H-bridges rather than an HB-25 if you can't afford two of them.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2010-05-04 04:43
    All the specs on the HB-25 and the example program says it can control 2 motors, and the Schematic has connections for M1 and M2.

    http://www.parallax.com/Portals/0/Downloads/docs/prod/motors/HB-25MotorController-V1.2.pdf
  • WildatheartWildatheart Posts: 195
    edited 2010-05-04 04:52
    NWCCTV, please reread those specs. They actually say...

     2 operation modes: control 1 or 2 HB-25’s independently from a single I/O line

    That's 2 HB's, not 2 motors.

    What happens with the back EMF when the motors are suddenly reversed?

    I'm sure Parallax would't recommend it. They didn't recommend 2 HB-25's to drive one .8 HP motor - even though the the combined output of 2 HB-25's equaled the current requirements of the .8 HP motor (50 Amps).

    Post Edited (Wildatheart) : 5/4/2010 5:03:37 AM GMT
  • NWCCTVNWCCTV Posts: 3,629
    edited 2010-05-04 05:02
    I think I got confused because of this statement in the specs:Modes: Single/Dual Motor Control
  • WildatheartWildatheart Posts: 195
    edited 2010-05-04 05:06
    M1 and M2 refer to the +/- motor leads.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2010-05-04 05:11
    Yea, I got that now. I am checking to see if they can add one more to my order or if I have to pay to ship the second one. I misunderstood because the spec shows Single/Dual motor control, so that kind of threw me off.
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