I am looking to control the speed and direction of an 18V cordless drill I have disassembled. Based on my research so far, it looks like there are a few motor controller boards I could purchase to meet my goal. However, for the sake of cheapness and my own learning, I was wondering if I could control using any of the components already in the drill.
Attached below is a picture of the components. Drill, gearbox, trigger assembly and what I assume is a transistor (my knowledge is lacking).
How would I replicate what the trigger is doing including the direction reversal? Would PWM pin allow replicate the pull trigger? I am not sure what the best way would be to reverse polarity to change directions.
The drill's electronics have been optimised over a long period to do just exactly that job and no other. You are looking at the result of more than 20 years of development on electric drills. The trigger does a whole bunch of clever things just due to its mechanical design, with an absolute minimum number of parts that have to be assembled.
There's really very little that you can salvage out of the drill controller to be used for another purpose.
My choice would be to buy a general purpose Arduino motor driver with an appropriate voltage and current rating. Something like the Sparkfun Monster Moto would be perfect, although a little expensive.
Stopwatch:
Thanks for the data sheet. I am surprised by the 60A rating, because the switch (Jin doing ea 12 z3 12A) is rated for 12 Amps.
A 12A max MOSFET would get red hot at 12A without massive heatsink or water-cooling!
You'd normally never go close to the max current rating except for brief pulses, because the
power dissipation is at its absolute max and the forward voltage will be upto several volts.
The way to choose a MOSFET is by on-resistance. A 10milliohm device at 12A would dissipate 1.44W
when on, which would be good with a smallish heatsink.
Also you should always expect a good safety margin between operating conditions and absolute
maximum ratings. The switch 12A is an operating value, not an absolute maximum.
