My Role in Robocon part 2

Basically, what I am involved in the team is programming the traveler.
I am using PIC Basic pro to do write the program. Besides I am also the key person in designing external circuit for motors, sensors, switches and relays.

I have learnt a lot on how to get external signals from PIC board. How not to use voltage regulator, servo system and I am working on doing PWM is possible.
We are using power window to do the arm swinging. However, the swing is too fast for 12v supply to power window. Now I have 3 solutions. The goal is achieve slow swinging to the limit.

Solution 1: supply lower voltage across power window.
This can be done by using lower voltage battery. –However, lower voltage battery may not produce enough power for power window due to lower current supply.
Second idea is use voltage regulator.-The risk for this is although voltage step down but Power window motor still keep on absorb high current. When high current go across regulator, it burns…

Third idea is use resistance to cut down the voltage. At first I use rheostat. It works for 3 seconds but after that smoke comes out. Ouch!!
Solution 2: use relays to switch in few times.
The arm will swing like stepper motor. A full done is like 8 small degree revolutions. This is a successful one but relay are not making for fast switching….so I am risking the sticking relays happening.

Solution 3: PWM with external board and without using relays.
I think this can be done and I roughly know the schematic diagram. I need rheostat(maybe) and NPN transistor . I have one experiment with bread board and it works.

HOW a PWM works- Prof Horizon teach me before how this stuff works.

Let me take an analogy, it is basically like switching off and on a ceiling fan. When you on the fan, it get 12v supply, if you off the you got 0 v. If you on 5 secs , off 5 secs continuously through, you will get 50% duty cycle, so its like playing with the pulse width.
Use a transistor (MJE 3055T) as switch. High port(as you like) to give out signal from PIC/ICD to act as switch on off action. Then the motor will move in depend on your on off frequency.