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Thread: A3982 Driver Design

  1. #1
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    Default A3982 Driver Design

    Hello Folks.
    I am working on a simple motor driver based on Allegro's A3982 Driver http://www.allegromicro.com/en/Produ..._Numbers/3982/

    Eventually I would like to release the schematics and board layout upon the community, but in order to get there, I need to actually get the board working.

    For some reason I am reading a constant voltage (the bridge voltage) on all of the H-Bridge outputs. I am wondering if anybody here sees what the problem is, As it is completely eluding me.

    So, without further adieu here are some images of the board layout and the schematic. I would appreciate any feedback you guys can give.

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    Attached Thumbnails Attached Thumbnails A3982 Driver Design-a3982-driver-schematic-pdf   A3982 Driver Design-a3982-driver-schematic-png   A3982 Driver Design-a3982-driver-board-png  
    Last edited by bkinman; 10-07-2008 at 11:40 PM.


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    I just realized. This schematic is not quite up to date. The potentiometer should be replaced with a 10k resistor. Currently the driver is maxed out at 2A.





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    Quote Originally Posted by bkinman View Post
    For some reason I am reading a constant voltage (the bridge voltage) on all of the H-Bridge outputs. I am wondering if anybody here sees what the problem is, As it is completely eluding me.
    Hi.....i am facing the same problem with the IC.....it shows constant voltage when connected to the motor....but shows proper switching when no load is connected to it.....you found the solution to your problem?
    I hope you wont mind posting your findings.....



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    I will post my findings when i figure it out.



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    Well my circuit for the IC is same as your's with a few minor differences.
    There's no resistor in series with the POT.
    No resistance connected with the ROSC pin, its tied directly to VDD.
    SENSE resistors are of 1ohms/2W.

    Rest is all the same but I have two ICs on board controlled by Mega128. One IC works fine but the other one works like yours! Even after replacing the faulty 3982, result is the same.

    I'll post the schematics and the layout......



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    So, I now have a new version of this board. I have removed the potentiometer to control output current in favor of a voltage divider. Also, i have chaged the regulator over to a SOIC package.

    This driver seems to work pretty well, although I'm a bit disconcerted by the speeds at which I am able to step. It seems that i can only step at 2kHz. I will try playing around with the voltage and the fixed-off time to see if I cant more angular velocity out of her.... I am sort of shooting for 4kHz in full-step mode (perhaps this is a pipe dream?)

    In any case, enjoy the pics. If you are interested in the schematic PM me and I will hook you up. I've switched on over to OrCad for this version.

    Here are the pics and a video.
    "http://www.youtube.com/watch?v=RTEwpUSghU4"]video.

    Attached Thumbnails Attached Thumbnails A3982 Driver Design-3154380855_2c79db3dd7-jpg   A3982 Driver Design-3154378199_21da100dde-jpg  


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    Hey there. I dunno if you solved your problem already but I just stumbled across this thread and its dated back to 08 so It may be dead so excuse me if I'm reviving it again... I took a look at your schematic and noticed that all your caps that are on the IC itself are all polarized. I don't know if it is related to your slow stepping speeds and/or your low voltage readings from the H-Bridge but my suggestinon is (If you haven't already) to try to swap all the Polarized capacitors to non-polarized standard ceramic ones and see if that'll work. I did my fair share of research on it. I'm making a driver myself using the A3982.
    That's where I'd start... BTW where did you get those A3982, seems like every one has it as a non stock item with a 5 month lead time :s Its kinda saddening... Any other places you might suggest?



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    Try contacting the Allegro people directly. I got mine long time back, probably these days they don't produce these ICs in large quantities.



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    Good time! Tell me, have the same situation with constant voltage at the output. Throw chip?

    thanks in advance
    Andrew



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    Quote Originally Posted by bkinman View Post
    Hello Folks.
    I am reading a constant voltage (the bridge voltage) on all of the H-Bridge outputs.
    The same problem



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    Default Re: A3982 Driver Design

    Hello, just stumbled on this thread, although quite old : I' m strugging with the same problem of constant voltage on output:
    could you please tell me if the problem was a fried A3982 or some kind of board bug ?
    TIA and best regards ,
    Giancarlo



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