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I want to drive a DC motor (linear actuator) rated at 12V with a 24V DC supply. Will using a driver IC that does current regulation (e.g. MP6515) be enough, or would I need additional measures in place? All other components would be properly sized (capacitors, etc.)

DC Motor Overvoltage Operation suggests that using 24V instead of 12V would be ok from an insulation perspective, and I know stepper motors in 3D-printer stepper motors are regularly run at voltages much higher than rated. I'm just unsure if I miss anything that would be different for DC motors.

I don't aim at getting more power or torque, I just want to use existing motors with another power supply needed for different reasons.

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  • \$\begingroup\$ Exactly which "DC motor (linear actuator) rated at 12V" do you have? \$\endgroup\$ Commented Aug 12, 2021 at 1:35
  • \$\begingroup\$ Hi @BruceAbbott, Its a cheap chinese one of course :) js-tgz-u2 12V 50mm 6mm/sec 1500N. There are some others as well, which I cannot get the exact specs of right now. \$\endgroup\$
    – TobiM
    Commented Aug 13, 2021 at 20:33

2 Answers 2

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Depending on cable capacitance, the driver losses may cause an increase in temperature rise with twice the supply voltage, so heatsinking may need attention.

Otherwise, the current in the outputs are limited using a constant off-time control circuitry of 16 us typ.

Thus, depending on the actuator dI/dt=V/L on-time with this hysteresis, will promote a PWM astable activity.

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  • \$\begingroup\$ Hard working man! :) In supplement to Tony's, besides the mechanical and electrical issues; The control, if you (@TobiM) have any, will likely need to be tuned for the "loop gain" change. First, limit the output, not to overdrive or to burn the coil, and then get into the tuning. \$\endgroup\$
    – jay
    Commented Aug 11, 2021 at 16:48
  • \$\begingroup\$ To clarify: I do not desire to control the motor other than forward, backward, stop. What I'm reading from "will promote a PWM astable activity" is: might work, but no guarantees? \$\endgroup\$
    – TobiM
    Commented Aug 11, 2021 at 16:59
  • \$\begingroup\$ It is a stable operation but the "astable" varies in frequency slightly as well as duty cycle with changes in On time. \$\endgroup\$ Commented Aug 11, 2021 at 17:09
  • \$\begingroup\$ Sorry, please bear with me: english is not my native language and all EE is self-taught. I understand, if I were to drive the MP6515 with PWM, the final output might be unpredictabe. But will this be of any concern if I only drive it forward, backward, stop? Or do you refer to the duty cycle/on time the driver will implicitly generate to limit the current? \$\endgroup\$
    – TobiM
    Commented Aug 11, 2021 at 17:28
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    \$\begingroup\$ Tobi, you do not need to control it with PWM, that is internally controlled with load by the IC \$\endgroup\$ Commented Aug 11, 2021 at 17:44
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The controller you have chosen to run a brush-style motor uses PWM only for limiting current rather than voltage. Applying a higher-than-rated voltage to a brush-style motor may cause it to draw excessive current, even when lightly loaded. In your case, the motor might spin up until it reaches the current limit, where it would remain regardless of load. Unfortunately, when the motor is lightly loaded, the power is not going to your load so it goes into heat in the motor.

I suggest choosing a controller that provides a speed control-type (voltage) PWM along with the current limit. If you hard-limit the voltage PWM to 50%, you should be fine.

Good luck!

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  • \$\begingroup\$ Thank you for mentioning this. At 12V the actuators draw around 1A, so I guess at 24V I would make the limit at 0.5A. Either way that would be around 12W, and there possibly wont't ever be really light load. Plus, they will only run for about 10-15 seconds in my application, with several minutes at least to cool down. A problem might be, that I want to use the load sensing to simulate end stops. This works perfectly for 12v actuator at 12V supply. Guess I will have to test with 24V. Does not seem as it would immediately explode though :) \$\endgroup\$
    – TobiM
    Commented Aug 13, 2021 at 21:18

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