PWM / Controlling high number of N20 Mini DC Motors

Status
Not open for further replies.

thebirds

New member
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 mottors, 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; and since the required amperage is low, Teensy should be able to suplly and control the motor directly. However, while attempting to do so, I am unable to run the motors at the (previoulsy 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-Brdige. 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) The Teensy should not be powering the motors. Separate supply is needed to prevent spikes/dropouts on the sensitive power rail.
Motors draw much higher currents at stall (ie from standstill), so budget more like 0.5A to 1A per motor for the motor supply unless
you can guarantee only a fraction are simultaneously active.

PWM control is often done using a decay mode (and has to be if a single switching device is used), which is not linear with PWM
duty-cycle, nor independent of the load - this may make consistent speed control difficult. Synchronous rectification mode is
more linear and robust if you want more solid speed regulation. Either that or active feedback.

2)
3.3V MOSFETs are nearly all surface mount devices. There are however thousands to choose from in SMT, a good electronics
supplier's website is the place to do parametric search for components, or pick your favorite semiconductor manufacturer and
their website will have similar tools and guides to their ranges.
 
Status
Not open for further replies.
Back
Top