PWM / Controlling high number of N20 Mini DC Motors / 3.3V MOSFET

Other Hardware Motors, Mechanics, Power and CNC
1

Hi there,

I'm attempting to fine tune the control of a high number (16) N20 DC motors (ref product) rated for 6V. In my application I do not need neither a high torque nor a high precision/reliability of the motors, but I need them to be silent, thus I'm running them at a lower voltage to reduce the audible noise.

Tested, so far so good.

With a table power supply, I am able to run them at the desired speed/noise/consistency at about 1.5V. At this voltage, the motors consume only about 0.1a.

Two questions:

  • In theory, I should be able to output 1.5V using a PWM pin with my Teensy 3.6 (Arduino-compatible board whose operational voltage is 3.3V); and since the required amperage is low, Teensy should be able to supply and control the motor directly. However, while attempting to do so, I am unable to run the motors at the (previously tested) 1.5V; instead, they make a high pitch noise and do not run - as if, the Teensy wasn't able to supply enough current. But the motors do need a lower current than the 0.25a that teensy can supply. Does anyone have an explanation for this?

  • In case the above indeed is impossible: I'd control them with an H-Bridge. Would anyone have a good recommendation for a logic level MOSFET whose gate operates at 3.3V and thus would work good with Teensy? I'm coming from the 5V Arduino Uno world, thus the ones I've in hands are no good for it... - For now, it be good to get my hands at a couple of THT ones; but the end application will be SMD in a custom made PCB.

Thanks!

1 Like
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Are you trying to run the motor direct from a PWM pin? Read the specification again. Teensy digital/PWM pins can only supply 25mA max. An N20 needs a lot more than that, particularly on startup.

Why do you need an H-bridge if you're only running the motors in one direction?

Steve

3

Hi Steve,

Thanks for the reply!

You are right, I've misinterpreted the specs of Teensy. All good, option 1 is out.

I do need to control the motor both ways; thus, the H-Bridge. As a matter of fact I'm also measuring the amount of current drawn by the motor with a sensor in-between the GND drain to detect the stall - it works very well too.

I really would appreciate a recommendation for MOSFETs that could interface with Teensy at 3.3v.

Thanks!

4

Nevermind, I will go with a DRV8838 as it is my safest choice atm and time is ticking. Thanks anyways!

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