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DC Motor

AImanAIman Posts: 531
edited 2007-01-25 21:52 in Robotics
So I have some motors that are less then 5 VDC and can hook them into my stamp (BS2). They are standard motors not steppers, but there is a problem because triggering a pin doesn't turn the motor on, and when a jumper is run from VSS and VDD the motor won't turn off regardless of if the pin is hooked into the bread board or not.

Suggestions?

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Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2007-01-02 17:35
    A BS2 pin will only source or sink about 25 mA, which is usually WAY less than a motor requires. So, you need a suitable driver transistor or Darlington Array IC which can provide sufficient current for the motor. I believe "What's A Microcontroller" will have examples, as do the Nuts&Volts articles on the Parallax website.

    Note if you "run a jumper from Vss to Vdd" you'll short out the BS2's power supply, with sparks and heat and melting of wires. So I assume that's not what you're really doing...
  • AImanAIman Posts: 531
    edited 2007-01-02 17:56
    The VSS and VDD go to the motor not each other.

    I looked through several books, Whats·A Microcontroller, the Boe Bot and Toddler books and couldn't find anything on motors. I found lots on servos, but nothing userfull on normal DC motors. Nuts and Volts had some articles on motors but I didn't find any explaining how to hook up motors - especially not normal DC motors. There are a few articles on running an H bridge or a moffet but nothing on hooking a stamp into a DC motor - at least not that I have seen.

    The motor works fine if the stamp isn't hooked in, when the stamp gets hooked in the motor either won't start or won't shut off.

    So far I can use the BOE power supply for the motor, so the stamp shouldn't have a problem with a simple high low command. And boy does that motor hum off 5 VDC.

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  • Bruce BatesBruce Bates Posts: 3,045
    edited 2007-01-02 18:47
    agfa -

    You said:

    "Sparks, heat, and melting wires. Thats what I live for. "

    You ought to get a job in a foundry that recycles copper wire!

    Regards,

    Bruce Bates

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  • allanlane5allanlane5 Posts: 3,815
    edited 2007-01-02 20:39
    The reason "H-Bridge" is mentioned so often with a 'normal' electric motor is that an "H-Bridge" allows you to reverse the motor. If all you want to do is make the motor go forward, a simple 2n2222 transistor based circuit (like you would use for a relay) can be used for that purpose.
  • AImanAIman Posts: 531
    edited 2007-01-03 14:40
    AGFA,

    I take it you haven't been around steel mills - espically melt shops. There is nothing calm and organized about them when white or red hot metal misses a spool during wire making or a ladel coming out of an oven brakes open and dumps molten metal on the floor.

    I have a close relative that has worked in mills for years and ran a melt shop for awhile. When liquid metal hits the floor soot goes everywhere and people scatter like scared rabbits. His face was black like burnt wood by the time he got out the day a ladel broke.

    ... Something about an emergency evac siren sounding that makes people move quickly... Its actually amazing how rapidly liquid nitrogen can be released.

    In fact one day a high pressure machine malfunctioned of operator error. They found the capsule about a mile away, lost the end of the building and the 2 workers were killed - one DOI and the other DOA.

    For that matter when I drove flat bed we were prohibited from bring plastic into certain·buildings of steel mills·and weren't allowed to have plastic outside the tractor because of problems with accidental mixing of metal and plastic. Even plastic bottles from softdrinks were strictly prohibited, and I do mean strictly.

    Anyway, back to topic.

    I have some NPN and PNP stuff from Radio Schack that might work. If memory serves I have a 2n2222 and will give it a shot. Combined with Chris's diagrams things should work much better.
  • AImanAIman Posts: 531
    edited 2007-01-03 18:28
    Oh, I know you were being funny. It wasn't taken any other way, just pointing out·that if you want·lots of sparks, smoke and explosions steel mills can meet your fill.

    ...·you can always drive tankers of jet fuel.· [noparse]:)[/noparse]



    I will post what happens with the 2n2222.
  • AImanAIman Posts: 531
    edited 2007-01-09 18:07
    No change with the results.
  • AImanAIman Posts: 531
    edited 2007-01-15 15:30
    Let's try this.

    What EXACTLY are the parts I need to get from Parallax to make these ciruits work?

    It is possible the stuff I have isn't quite right because it came from Radio Shack.
  • AImanAIman Posts: 531
    edited 2007-01-17 16:59
    I can get my motors to run but still need to debug. The Arobot from Arrick Robotics has a diagram of its hook up from the BS2 to a DC drive motor.
  • AImanAIman Posts: 531
    edited 2007-01-25 18:56
    So if I get the Mosfet from Parallax, is it the 60 volt one that they sell?

    If I understand correctly then all I have to do is hook in the Mosfet into the diagram as indicated above and it should work. Is this correct?

    Also - I am a bit confused, I didn't realize Parallax sold an Hbridge. Whats the link?
  • Joe &quot;Bot&quot; RedJoe &quot;Bot&quot; Red Posts: 81
    edited 2007-01-25 21:52
    http://www.parallax.com/html_pages/products/motorcontrol/motor_control.asp
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