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### Topic: Controling 12V DC motor with an arduino (Read 3855 times)previous topic - next topic

#### Coisoecenas

##### Nov 16, 2012, 05:34 pm
Hi.
I need to control 2 x 12V DC motor from a wheelchair. I dont have access to the datasheet of these motors, so I dont know what is the maximum output current. So my problem is that I cant design my control circuit if I dont know the max current that can flow into my circuit or it can broke.
Does anybody know how to mesure/calculate the max current from each motor and is there any component that I can use to control these motors from a PWM signal.

Thanks.

#### dc42

#1
##### Nov 16, 2012, 10:01 pm
Use a multimeter to measure the resistance of each motor. From that you can work out the stall current @ 12V. Use the lowest of several readings, rotating the motor a little between readings, because the brushes may make intermittent contact at the low current supplied by the multimeter.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### Coisoecenas

#2
##### Nov 16, 2012, 11:24 pm
Tks for the repply. Just another question. For the max current how can I get it? Ohm law? I=motor resistance/12V? And about the controller? Any opinion?

#### dc42

#3
##### Nov 17, 2012, 07:49 am

Tks for the repply. Just another question. For the max current how can I get it? Ohm law? I=motor resistance/12V? And about the controller? Any opinion?

Yes, Ohm's Law:

I_stall = 12/motor_resistance

For the controller, if you want to run each motor in both directions, you need one H-bridge per motor. Check out the motor drivers at pololu.com. If you want to run the motors in one direction only, it's simpler - you need a suitable power mosfet and schottky diode for each motor.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### Coisoecenas

#4
##### Nov 17, 2012, 02:10 pm
What do you mean by stall current (max current???).  Do you think that a breadboard can take this amount of current? Or if not what is the maximum current that can flow trough a breadboard?
Tks.

#### dc42

#5
##### Nov 17, 2012, 02:33 pm
No, a breadboard definitely cannot carry the stall current of a wheelchair motor. However, most motor drivers have screw terminals for connecting the motor and motor supply, so there is no need to involve the breadboard in this part of the wiring even if you don't want to solder the connections.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### Coisoecenas

#6
##### Nov 18, 2012, 05:41 pm
So, I must use a motor driver (h-bridge) like this,

http://www.digikey.pt/product-detail/en/L9958SBTR/497-11667-1-ND/2746896

or something like that, but they all have pins. So I need a breadboard to make the conections between the motor driver, the battery, the arduino. But if the breadboard can't take the amount of current that flow trough the motor driver, how I'm I suposed to make the connections?

Tks for the help.

#7