1.5v DC motor with 3.3v controller

hi,


i used guide hook 1.5v dc motor. difference use 3.3v controller instead of 5v.

everything works fine, not sure understand how control voltage pwm. if use 3.3/255 = 0.013, 1.5 volts should reached when set pwm pin 115, motor's performance have not reached max there , feels quite weak.

if turn pin (which shouldn't), motor can spin faster.
if measure voltage across motor, when running, voltage never exceeds 1.5, no matter how high set pwm pin.


my question is: how reach maximum performance without risking destroying either motor or controller?

i'm going guess 3.3v power supply isn't "holding-up" under load.    check that.  you'll need "bigger" power supply or different voltage regulator.   

if you're using on-board 3.3v regulator, motor rated 1/2 amp , that's (depending on how voltage dropping across regulator).   if regulator hot touch, that's bad sign.

quote

if measure voltage across motor, when running, voltage never exceeds 1.5, no matter how high set pwm pin

you can't reliably measure pwm average digital multimeter.*   but, can (briefly) write digital high (or 100% pwm) see get.   (an analog meter movement give average reading.)

quote

if use 3.3/255 = 0.013, 1.5 volts should reached when set pwm pin 115,

once working can boost bit if need to.   you'll fraction of volt drop across transistor , although didn't see maximum voltage rating motor, there graph goes 1.8v.



* p.s.
you can check meter:
disconnect motor there's (almost) no load.
write high or 100% pwm , read meter.
write 50% pwm can read again.

...if it's stable , close half of dc reading can  use meter read pwm.   you can try 10% & 90% see if readings linear.

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