Hi everyone:

I need to have a DC motor driver circuit for my project. The only thing i know is that the output of my microcontroller (PICAXE) is about 5v and some miliamps. Well my motor needs 12v and max current is 3 amps. How can i make this work when microcontroller sends a 5v signal (high) ?

I would really appreciate your help!

 

I suggest you consider PWM control with a logic-level mosfet, such as the IRLZ24 or IRLZ44. Put the mosfet between the negative pole of the motor and ground (i.e., low side). You should have a diode across the motor (reverse biased) and may need capacitors across it is well. Check out any number of PWM designs for that power range. John

 

If the motor needs to turn in both directions, you will need to learn about the "h-bridge." An internet search on that term will yield much explanation and many examples.

 

Here's a good H-Bridge circuit that works well. It uses a MOSFET driver chip:
http://www.robotroom.com/HBridge.html

If the chip gets hot from drawing too much current, you may want to modify the circuit so that the chip drives power MOSFETs (and then connect those FETs to the motor) rather than driving the motor directly.

 

I'm sure you probably considered this option (which many people will disagree with)but you could simple use a relay to control the motor. You didnt say how precise or controllable the motor driver needed to be and the simplest solution is usually the best one.