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I am trying to create a small motor driver for a DC motor, 9 V - 12 V. Max current and stall current I do not know, but I am using the stock motor of a Blade CP Helicopter. I just want to know if I am using parts that will work and what parts I should replace. The FET i am using is a 22N50 N-channel FET. Any advice or things I should look out for?

Motor will be only going one direction and will be controlled from a 3 V - 5 V PWM

Yes, I know about the diode across the motor which is a 1N4000.

The schematic: enter image description here

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  • Do you have the motor part number? – tyblu Dec 7 '10 at 8:33
  • its a 370 Motor, i looked for more info but not too much on it – jsolarski Dec 7 '10 at 8:50
  • well the design works, but i dont know the limitations or what could fail. youtube.com/watch?v=fGv7ZcKn0Z0 tested with 5v through the motor, 5 volts on gate – jsolarski Dec 8 '10 at 9:54
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A quick search on the 'net' gives the following

Model: R370

Round type diameter: 24.4 x 30.8 (L)

Voltage (V): 6.0 No load current 0.03 A; speed 4,950 rpm Max efficiency current 0.19 A; speed 4,280 rpm; torque 19 gcm Max output current 0.625 A; speed 2,475 rpm; torque 170 gcm Stall current 1.22 A; torque 140 gcm

Voltage (V): 31.0 No load current 0.035 A; speed 11,140 rpm Max efficiency current 0.2 A; speed 9,530 rpm; torque 43 gcm Max output current 0.63 A; speed 5,570 rpm; torque 149 gcm Stall current 1.22 A; torque 298 gcm

  • This sounds like a possible for your motor...

If the motor you have is about this size (24.4mm Dia x 30.8mm L), then its stall current will be about the same.

And for your FET - a max current around 22A peak around 80A

This FET should easy handle the stall current for your motor.

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  • I think that answers my question about the schematic, thanks! I am going to have to email the manufacture for the exacts, about the motor, but it looks pretty close to the r370. – jsolarski Dec 13 '10 at 2:28
  • 370 is a standard size of 'toy' motor - it appeared in radio controlled cars in about the late 1970's - there were a couple of motors that were used - the big one was the 540 can size. - the main difference between the motors was how the coils inside were wound. For racing cars a thicker wire would be used that would take a lot more current, but the downside was the batteries would run down quicker... (And everything would have to take a lot higher current) – Wonko The Sane Dec 13 '10 at 22:28
  • As you motor is from a model helicopter, the motor is a more standard design - and won't have specs much off the ones quoted for the R370 - I would say a max stall current of no more than 5 Amps... – Wonko The Sane Dec 13 '10 at 22:31
  • You could test the stall current by just connecting the motor across a supply with a meter and stall it - but only for less than 2 seconds... – Wonko The Sane Dec 13 '10 at 22:32
  • Your design for a motor controller is simple, it seems to work and should be capable of handling the stall current from your motor. :-) – Wonko The Sane Dec 13 '10 at 22:33

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