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DC Motor drive

Discussion in 'Sensors and Actuators' started by colum, Sep 30, 2013.

  1. colum


    Jul 25, 2013
    Im new at this so I hope I don't make the attachments too large or small. I built this circuit and it seems to work for a small DC motor but I need to drive a motor that takes 1 to 6 amps at 27v DC

    problems--DC volts shoots up to 40v from27v when Mtr turned on

    Pontentiometer---Overheats and smokes

    3055 did not get hot but died, 3ohms at all terminals

    I probably need a blocking diode somewhere to prevent spikes or feedback
    I would like to know how to upgrade circuit to one able to handle a heavier load

    I appreciate you reading this ...Thanks....colum

    Attached Files:

  2. Fish4Fun

    Fish4Fun So long, and Thanks for all the Fish!

    Aug 27, 2013

    You should look into PWM and h-bridges, but even then 6A @ 27V is fairly hefty (162W), this is an awful lot for a first go at a power circuit!

    You might notice the schematic has the output limited by a 1A fuse. That is a clue.

    Using a transistor as a current limit in linear mode has serious heat/efficiency issues. That said, designing a switch mode power supply capable of 6A into an inductive load also has issues, especially if it is unfamiliar ground. I would suggest you find an existing PWM DC speed controller. I have not priced any in quite some time, but I would expect you should be able to find something that will work under $200, perhaps way under if there are any in the RC model hobby or some other mass-market usage.

  3. colum


    Jul 25, 2013
    Thanks for your advice Fish. I had forgotten about PWM drives and I can use 411 type transistors which I have used in PWM drives before but for much smaller mtrs anyway its a hobby and I have parts to burn up...Thanks...colum
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