Replacing small DC motor with stepper or servo - where to start?
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  1. #1
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    Default Replacing small DC motor with stepper or servo - where to start?

    I operate a working tugboat with a 1950s era searchlight. Tilt and pan movement is via two 115VDC 1/20hp motors, controlled via a crude mechanical "joystick". The OEM motors are failing due to age (OEM replacements are Permanent Magnet) plus the ability to accurately spot the beam is difficult because of "full-on/full-off" nature of switch. Best I can tell, the joystick simply reverses the polarity of the 115VDC supplied to the motor armature.
    searchlight-motor-2.jpgsearchlight-motor-1.jpg

    Replacement of existing DC motors with steppers or servos and a simple controller with joystick seems a logical approach but I know nothing about where to start looking for and matching best components. I DO NOT need position control but would like to have the ability to jog or control the speed of the motors in each direction, presumably by how far the joystick is moved. I would also consider using existing motors if I could control motor speed as well as direction thru joystick.

    Any recommendations on best place to look for matching/purchasing components?

    I have the ability to machine adapters or mounts from the existing foot mounted motors to face mounts typical of small steppers or servos. 12VDC and 120VAC is readily available for power.
    TIA,
    Jim

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    Hey there I tin the concept is sound and will work well. Forgive if sound condescending but I am not sure what your tech skills are like. You can purchase some pretty servos at a decent price from hobby places.
    Some times you can find a deal a receiver and cheapy radio. This way you would not have to run wires. I hope I helped cause the question was a bit ambiguous to me.

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    Conversion to steppers can be done, though it is not that simple as you need stepper drivers, power supply, pulse source and other stuff. And if you running the steppers just as motors without feedback or program, those do not differ much in operation from gear motors. 24V DC small gear motors are simple and inexpensive as are speed controllers for those.

    Below are some random examples of the stuff you can get. Depending on the motor controller, you might need as well a 24V power supply. Those are inexpensive as well/



    High Torque 24V DC DC Worm Geared Motor With Gear Reducer Turbo Motor 27RPM | eBay

    https://www.amazon.com/uniquegoods-W...=fsclp_pl_dp_8

    https://www.amazon.com/Baomain-Joyst...VQZRD1XK0GCYK4

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    I think you should stay with DC motors and simply use a modern 4 quadrant controller like a KBMG 212D along with a 2 axis analog pot joystick. I have used a number of them with a joystick and the performance is almost servo at a fraction of the price and complexity. I think you'd be very happy with the results. They would work with your existing motors so you could easily test it before replacing motors.

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    Thanks for the replies.
    garylucas - Your advice makes total sense and I will pursue that approach.
    Thanks again.

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    Not sure if you are programming it or not, but I've always found NEMA stepper motors to be reliable and good value for money.
    0.3A-2.0A drivers are used for a NEMA 14 or a NEMA 17 stepper motors.
    1.5A-4.5A drivers are generally used with a NEMA 23 stepper motors.

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    I agree with Gary, no need for steppers or servos in this application. DC motors with a proportional speed control joystick are what you want!


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