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NEW: Motor Controller for Propeller Platform — Parallax Forums

NEW: Motor Controller for Propeller Platform

Nick McClickNick McClick Posts: 1,003
edited 2010-01-28 17:17 in Propeller 1
I've been working on a doggy door for a while - while the software is straightforward, finding a suitable motor controller has been more difficult.

The problem is:
  • A lot of the inexpensive motor controllers are too meager to control anything but the most dinky motors. ladyada's Arduino shield only does 600mA continuous, 1.1A peak.
  • The beefier controllers either:
    • are really expensive (Pololu's DMC 01 can do 13 amps, but it's $100), or
    • only control a single motor, or
    • have complicated control schemes
So I've been on the lookout for a medium power, inexpensive, and easy to control circuit - I was flipping through starlino's website and I spotted exactly what I was looking for. He calls the circuit the 'OctoDriver', it combines 2 h-bridges to provide 8 amps peak, 4 amps continuous to each motor and with 4 chips, you can control 2 motors. I asked him if I could put it on a PCB, and he thought it was a great idea. I couldn't think of a better name, so I call my version "The OctoDriver".
4306347372_62abcfecae.jpg

You can find out more, pick it up, download files, etc, on the project page. I also did a pretty detailed howto. And like all the other Prop Platform Modules I've done, layout files are available under the MIT license.

What do you think?

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Comments

  • Bill HenningBill Henning Posts: 6,445
    edited 2010-01-27 22:40
    Nice work Nick!

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  • John AbshierJohn Abshier Posts: 1,116
    edited 2010-01-27 23:06
    For you truth table, if EN is low the driver is coasting not braking. To break you need EN high and both A's high or both low.

    John Abshier
  • Nick McClickNick McClick Posts: 1,003
    edited 2010-01-27 23:46
    @Bill - thanks! It was a lot of fun to put it together.

    @John - thanks for the catch! I've fixed it on the project page and howto.

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  • RsadeikaRsadeika Posts: 3,845
    edited 2010-01-28 13:43
    @Nick, you had ask me a question in the other thread, the answer would be more appropriate here. For an entry level motor control board, it is sufficient. For a board that would be of use in robotics projects, it is way under utilized. As a minimum, screw down terminal for the unused pins, remembering that most sensors, I believe have three wires, one of which is a ground wire. Since you are dealing with batteries, in my case I use 6V 8-10AH, you really want to know the charge state of the battery, in a lot of cases you end up using more than one battery. You really need something that would give a visual (battery state), and some data, that your robot program can deal with. The ADC that I had mentioned would be used for some sensors, and probably a voltage divider setup for the battery.

    I did not look at the schematic of the board, but you should make sure that the Propeller pins are completely isolated from a power surge, and maybe a fuse would be appropriate to make sure, if something goes wrong. These are just a few things that I could think of for your platform.

    For a real robotics platform, I am starting to think that maybe the Propeller Platform Module (PPM), and the shields may not be the way to go. You can add shields, up or down, to a finite limit, which makes the whole thing look, and function in an awkward manner. For expansion purposes, you really do not have an easy way of adding another PPM, and that is probably what would have to happen as the robot has to use more and more sensors.

    I did not want to do a review of the PPM, as it pertains to robotics, IMO, but I hope that you use the critique in a positive way. In general, there is a lack of good quality robotics boards that are cheap, and reliable. I think that a localized cluster of Propellers would probably be a good solution, but, at the moment, there is that lack of boards, and support material. I am NOT an EE, so, I have some severe limitations as to would I could accomplish, form a PCB perspective.

    Ray
  • Nick McClickNick McClick Posts: 1,003
    edited 2010-01-28 17:17
    @Rsadeika - is it your thinking that you're limited to one module on top of the Propeller Platform, and one module underneath?

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