Basic speed control question...

You need to have a D/A converter, the spindle drive will require a 10 volt dc speed reference.

Regards Daveb

Lucas.

If you have a max spindle speed of 2000 rpm when the d/a is outputting

Basically its a bcd to analog converter usally 12 or 16 bit's so when a command of 1500 rpm is entered is converted to bcd and the result analog volatge is outpit

Regardsr

Daveb

In Mach3, a pulsetrain is output that simulates a 0-10V analog output

The DC spindle amp looks at the RPM of the motor as an incoming voltage signal from a tach and it looks at the incoming RPM commanded by the controller, also a voltage signal. The motor tachometer might be five volts per thousand RPM (they vary) and the incoming speed control signal is usually a scale from one to ten volts to go from minimum to maximum. The amp has adjustment pots for all these signals.

Hobby CNC DC servo drives use step and direction and could be used to control a DC spindle (if you replaced the tach feedback with an encoder) except they lack the necessary power for a spindle. You would need a card that converts the step and direction pulses from the PC into a zero to ten volt signal to control an amp. A word of caution, I think the signal is relative to the amp ground, not the machine ground. There may be a potential difference enough to zap something if not done correctly.

Very interesting, all of these answers. I had never thought of that before. I had actually thought of using a small DC motor to obtain a voltage (a crude tach), also, it seems it would take less time to obtain a reading this way. Now I just have to figure how to output a