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R/C Car ESC & BOE — Parallax Forums

R/C Car ESC & BOE

ScopeScope Posts: 417
edited 2010-03-02 17:34 in Robotics
Hello Folks,

After you wonderful people helped me figure out how to control my r/c servos, I started thinking about other r/c controls.

I'd like to be able to control my r/c ESC's using my Board of Education & BASIC Stamp 2.

Is this possible &/or feasible?

Thanks,

Scope

Comments

  • Roy ElthamRoy Eltham Posts: 3,000
    edited 2010-03-01 03:20
    Most R/C ESC's work just like servos. You should be able to control them via the connector that would normally plug into your reciever unit using the same code that controls a servo.

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  • ScopeScope Posts: 417
    edited 2010-03-01 03:21
    Thanks - so, 750 would be "neutral" and then play with it until blah, blah, blah . . . ? . . .
  • Roy ElthamRoy Eltham Posts: 3,000
    edited 2010-03-01 03:39
    It depends on the ECS as to which values are what. If it's got forward and reverse then it'll usually be similar if not identical values to a typical servo. If it's just one direction (typically found in airplane speed controls) then it might have neurtral at one end and full on at the other instead of neurtral in the middle. My experience is with R/C car speed controls that have forward and reverse and work exactly like a normal servo. In any case it should be easy to hook it up and test. [noparse]:)[/noparse]

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  • Roy ElthamRoy Eltham Posts: 3,000
    edited 2010-03-01 03:48
    Something very important I forgot to mention!

    Many ESC's have power on the red/black wires of the 3 pin connector that goes to the reciever, you DO NOT want that power to feed into the BOE, you just want the signal line. I hope you haven't tried anythign yet and damaged something [noparse]:([/noparse]

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  • ScopeScope Posts: 417
    edited 2010-03-01 13:11
    Not yet - thanks very much.

    I've allocated time resources for testing procedures this evening. Results are scheduled to be provided here accordingly.

    Thanks again.

    [noparse]:)[/noparse]
  • Rick BrooksRick Brooks Posts: 67
    edited 2010-03-01 15:18
    Scope,

    R/C car ESCs have a safety feature that prevents the car from going from full forward to full reverse. Normally, if the car is moving forward and you send it a reverse pulse width, it just brakes to a stop. I tried to get it to reliable go into reverse for a week and gave up. I assume that the motors must be motionless and the control at neutral before reverse can be engaged.

    My solution was to replace the ESC with one made for robotic uses. Parallax sells one that may meet your requirements.

    Rick Brooks
  • Spiral_72Spiral_72 Posts: 791
    edited 2010-03-01 17:31
    Also many ESC will not initialize without first sending a "stick low" or neutral signal...... for safety reasons. You don't want to accidentally have the stick full throttle when you plug in the battery.

    So if it doesn't work, perhaps you haven't sent it the command it's waiting for yet. As mentioned it might be 750, maybe 0, maybe something else.

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  • ScopeScope Posts: 417
    edited 2010-03-01 21:35
    Rick Brooks said...
    My solution was to replace the ESC with one made for robotic uses. Parallax sells one that may meet your requirements.

    I didn't know Parallax sold them - problem solved. Are you referring to the HB-25 motor controller? If so, I have two of them but I thought these were for something else.

    Thanks
  • W9GFOW9GFO Posts: 4,010
    edited 2010-03-01 22:54
    Scope said...
    I didn't know Parallax sold them - problem solved. Are you referring to the HB-25 motor controller? If so, I have two of them but I thought these were for something else.

    If you are replacing a brushless ESC, to drive a brushless motor (it has three power wires) then the HB-25 would not work.

    Rich H

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    The Simple Servo Tester, a kit from Gadget Gangster.
  • ScopeScope Posts: 417
    edited 2010-03-01 22:57
    Thanks Rich

    No, I have all types of motors around here - brushed & brushless.

    I looked up "motor controller" at the Parallax home page and several items popped up - I think I should read through them and try to figure out what looks like a good fit for what I'm trying to do.

    Thanks again,

    Scope
    [noparse]:)[/noparse]
  • Rick BrooksRick Brooks Posts: 67
    edited 2010-03-01 23:21
    Scope,

    I was referring to the HB-25. If your application is less than 16.0 volts and 25 amps continuous, then it should work fine. My application exceeded both limits, so I had to go with another solution.

    If the original ESC doesn't work out, having a couple alternatives to play with is a definite plus.

    Rick Brooks
  • ScopeScope Posts: 417
    edited 2010-03-01 23:40
    Holy Cow!!! This is SO cool! For some reason I didn't realize the HB-25's would work with r/c brush motors! I have many of these hanging around my shop.

    But how I can obtain brushless motor control via my Board of Education & BASIC Stamp 2 - does Parallax have a brushless motor control also?

    And . . . (sorry) . . . my 2 cell lipo's shouldn't drop below 3V per cell - is there something I can do to prevent this from happening? As is, my r/c car ESC's have automatic voltage shutdown, rated at 3V per cell but I wasn't aware of the HB-25 motor control having this same functionality. Isn't it true that lipo's will/could get damaged if their voltage drops below 3V per cell?

    Thanks
  • Roy ElthamRoy Eltham Posts: 3,000
    edited 2010-03-02 00:10
    You can get lipo battery monitor devices that will sound an alarm or flash a led when the batteries are low.
    Here's some links:
    http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=9744&Product_Name=Hobby_King_Voltage_&_Temperature_Monitor_2-6S_(0-150C)
    http://www.rc-flysoft.com/Manuals/LMonMan_01en.pdf

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  • ScopeScope Posts: 417
    edited 2010-03-02 00:33
    Awesome - thanks
  • Spiral_72Spiral_72 Posts: 791
    edited 2010-03-02 17:34
    I can testify about the Lipo cells dropping below 3V..... Ruined a perfectly good pack [noparse]:([/noparse]

    The RC stuff has built in voltage monitoring..... Especially the aircraft components where Lipo's are the standard.

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