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Permanent Magnet DC (PMDC) Motor Controller

  • I assembled a PMDC (permanent magnet DC) Motor Controller for use with my variable speed mini lathe.

    Forum member "Minder" was extremely helpful with this. Although it's a simple circuit, it can still be confusing for those of us who aren't very experienced with building electronics.

    The motor is a 110 VDC (Volt DC) permanent magnet motor, and rated to 250 watts. This should work for any 110-volt DC motor, however, if you adjust the TRIAC and Rectifier to the appropriate amperage.

    The original controller is about USD$150 to replace and comes with overload protection, but you can put this controller together for about $15 in a pinch.

    Sometimes poverty, not necessity, is the mother of invention :)

    You will need:
    - TRIAC (I used Q4008L4 [8-amps 400-volts] but you can use whatever can handle your motor's power)
    - DIAC (I used NTE6408 but again, others will work)
    - Resistors (3.3k ohm resistor, 15k ohm resistor, 100 ohm resistor)
    - Potentiometer (Pot) 250k ohm
    - Capacitors (I used three 0.15uf 200-volt capacitors... schematic calls for 0.1uf)
    - Bridge rectifier (I used KBPC806 [8-amp 600-volt] but any appropriately sized rectifier will work)


    What it looks like wired up:
    motor controller unlabeled.jpg

    Lines showing the connections on the underside of the board:
    motor controller.jpg
jilfe, Minder and Ian like this.
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