If I use 12v, the motor burns, 8v it takes longer to burn and 5v is not enough, will PWM save me?

Here's the deal: I'm working on a project that uses 2 motors (PS2 controller vibrating motor, without the counterweight), I assume these are 5v dc motors, right?

Both rotate the same axis (1 is not enough due to the pressure that is being put on it, a spring mechanism stuff)
With 12v it runs like a dream, till they burn! and from what I observed, always 1 motor hits higher temperature than the other, is there a problem with that?

Then I dropped it to 5v with diodes and the motors didnt have the strenght to start spinning, so I raised to 8v and they spin, not very smoothly (is that spell right?), but you know, they work, but still they're overheating!

If I used PWM to control both of the motors, would it work and not burn'em?

Thanks and sorry for the long and confusing text.

sort by: active | newest | oldest
6 years ago
They aren't designed to be very powerful. They run on 5v, and if you give them more than 5v, they will draw more power at a fixed internal resistance (which goes down with heat), but they won't have a stronger magnetic field to do that work against (to have more torque) and they will get hot. The motors are not perfectly efficient, say 50% at nominal voltage, that will drop to significantly less % when you overvolt them. They'll run faster but wear out much much sooner.

The only way to multiply the strength is using pulleys or gears -- or get bigger motors. PWM is a method to REDUCE the average current flow by starting and stopping it. When tuned properly, 10v at 50% duty cycle should act like 5v at full duty cycle (not accounting for the efficiency drop). It may give you the boost you need, but remember you're dealing with aveage current, so its exactly the same.
Kokkan (author)  frollard6 years ago
Do you have any other idea to break the inertia?
6 years ago
break the inertia? What exactly are you doing with the motors?
Kokkan (author)  frollard6 years ago
When I use higher voltage (7v) it starts spinning right away, when I lower the voltage (5~6v) they need a little help from my finger to star
6 years ago
Those motors are designed to run a relatively big weight vibrating - a balanced platform should be a no-brainer.

Could you confirm your 5v source can supply enough current?
Kokkan (author)  frollard6 years ago
I'm using a 12v battery, 1.3 AH.
And 10 diodes to drop it from 12v to 5v
6 years ago
put both motors in series (+ to -)...and run them both directly from the 12v at 6v each. Your diodes are dropping the voltage but probably don't let enough current through.
Kokkan (author)  frollard6 years ago
Same situation. What if I use a PWM to raise the voltage so both motors start spinning, and then decrease it? a pwm can do that right?
6 years ago
no.

pulse WIDTH modulation turns it on and off...it doesn't change the effective voltage. It changes the % of time the power is applied, not the amplitude (voltage) of the power.

Does your design spin freely if you barely touch it? maybe you need to redesign your mount as its too difficult to turn. Those motors should be able to work wonders at 5 volts.
Kokkan (author)  frollard6 years ago
Not as freely as it should be I guess, imma redesign it, thanks for your help and patience! x)
lemonie6 years ago

A PWM can still burn things. You need to put less power through them - and that means you really need a bigger motor(s).

L