Hi, I have a Porter Cable Variable speed router model 890 and would like to know if I can use Mach3 to control the speed of the router. I would probably have to bypass the electronic circuitry inside the router. I have a C3 board to control a DC motor. What I would need to use Mach3 as a speed controller.

If it is not possible, could I remove and replace the potentiometer inside the router and place it in a more suitable place.

Thanks for any advice, Jeff

You need to consult the documentation that came with the router (if any) - and find out if the router is made to take any external control.

Mach 3 can put out two types of control to your spindle. One is step and direction pulses, exactly like an axis motor. The other is a PWM signal (Pulse Wave Modulation).

The PWM signal will probably be the one.
PWM is a square wave signal at a regular frequency, a proportion of the signal "on" and the other proportion is "off", the proportions being equal to the speed you want. This varies as you select the speed using the S function on Mach 3 e.g. if the max speed of your spindle is 4000 rpm, then 2000 rpm would be a 50/50 signal, 1000 a 25/75 signal etc.

Your router electronics may be able to take this directly.

If it cannot, then there are several boards on the market, Digispeed being one of them, that convert this  to a voltage to control your machine. This may be a direct replacement for your potentiometer - in that Digispeed has an input from the computer at one side, then completely electrically isolated at the other side are three wires from the object to be controlled - one wire + voltage, one 0 volts and the return wire gives out the appropriate voltage (between the 0v and + volts) from Digispeed to control your machine speed.

As far as moving your potentiometer - yes this is easily possible - BUT one word of warning, you must check the voltage across the potentiometer so you know what you are playing with. Hopefull this would be low - say 0 to 12 volts. If it is up near the mains voltage be VERY careful, and make sure all your leads are WELL insulated and anything metal you mount your pot on is earthed.

Even is it is low voltage, also check the potential between an earth point and the pot to see that it is truely at (say) 12 volts, and not 12 volts difference between 220 and 232 volts.

Having said all that yes - what you are suggesting is quite simple.

Hi, thanks for the reply.

I have a Digi Speed PWM board on hand so will try to see if I can use it. (Model DC-03 with voltage converter -  0 to 10 volts)

I've been working with electronic for 20 years now. I will try to find info about the Porter Cable circuitry or will open the case to see how it works.

You probably know more than me them !!