With the help of this DC drill speed controller circuit you can control the number of revolutions of your drilling machine. A mini-drill machine is always needed in drilling the printed circuit board. It is usually powered by batteries that limit the capacity of the drill. Using a power supply adaptor with a speed regulator like the one featured here can certainly improve the performance of the drill.
Schematic of the Mini Drill Speed Control Circuit
The speed regulator can maintain the speed of the drill no matter what load is encountered by the drill. Potentiometer P2 controls the speed of the mini-drill. P1 sets the maximum voltage allowed by the mini-drill. After you finish construct this mini drill revolution regulator measure the output voltage. First rotate P2 to the right completely, P1 to the maximum. Now the measured voltage must be 20% less than the maximum allowed motor voltage. If it isn’t then R1 must be lowered or increased.