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Motor controller

hanneshdc

Nov 30, 2010
2
Joined
Nov 30, 2010
Messages
2
Hi!

I'm a complete electronics newbie, but I'm really into programming. I want to make a speed controller for a quad rotor helicopter, where a PIC microcontroller is to regulate the speed of each motor induvidually.

I will be using PWM to control each motor's speed. However I need to amplify the signal. The whole circuit including the motors will run at 3.7V, but the PIC controller can only supply (or sink) 25mA from a pin, a far cry from the 1.8A max. of a motor.

I'm assuming all I need is a transistor? But what kind? and do I need any other components in my circuit?

Thanks
 

rob_croxford

Aug 3, 2010
262
Joined
Aug 3, 2010
Messages
262
Yes you will need a FET to act as a switching device. (I advice you use a fet as in simple terms it is triggered by voltage and not current). This Fet should be fine to run from the 25mA (the output from the pic should be sitting at arround 5V) however be sure to choose your fet appropriatly as you want it to turn fully off at 0V.

I would not suggest running the motor directly from the pic... i would use the FET as a switch between say 10V and ground to run your motors and use a resistor to get the appropriat current.

Could you give more information? for instance what is your feedback to the pic?? or are you going to use a Pot etc...

You should not need to amplify the signal as the PWM signal only switches the power on and off. Therefore you will also need constant power to the FET which in turn will act as the switch
 

hanneshdc

Nov 30, 2010
2
Joined
Nov 30, 2010
Messages
2
Thanks for your reply!

It's for a helicopter with 4 rotors, where the pic will take inputs from a radio reciever (already have that working) and from a gyro sensor for stabalisation. I'm also running everything of the same battery which has 3.7V.

I would have no clue how to choose an appropriate FET, is there a way to calculate it?
 
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