VFD Speed control.

I designed a board with this goal in mind. Its Eagle files are here:

https://github.com/eras/TinyG-VFDController

HOWEVER, I failed :-). It appears my circuit for controlling the analog input of the VFD doesn’t carry enough current, so the effect the RPM output has on the analog input of the VFD is a bit lame – I was never able to reach the full speed of the spindle with this. I used 100kHz as the PWM frequency.

But at least the spindle on/off function works, which is quite convenient. I hope also that the vacuum cleaner relay control works, but I’ve considered adding a few small resistors in series to the transistor array relay pins. In any case, using the transistor array instead of separate transistors was a revelation to me, the first revision of this board has quite a bit more components..

If someone better designing analog circuits wants to lend a hand, please do :-).

I’ve also considered the option of passing the PWM signal as-is to the VFD (via a transistor) and use its filtering mechanism to make it analog, but I haven’t looked into if it would have potential to work.

I am only commenting on this because of the time it took to figure everything out. You need to convert pwm to 0-10vdc look on eBay $7 board. Next you have to do a logic level conversion to feed the the board with a 5volt pwm signal. Use a 2N7000 transistor and two 10k resistors the circuit isn’t to hard to find or build. Use the 5v output and digital ground from the vfd along with the 3.3v, pwm, and ground connections from the tinyg. Connect the grounds together and use the “high level” pwm signal along with the ground to feed the pwm+/- connections on the board. The board I used needs 24v to power it, use the 24v output from vfd along with the analog ground connection. Connect the 0-10v output+/- from the board to the analog input and analog ground on the vfd. **Important set up the vfd to run on external control pd002 and 0-10v pd070** once you set external control you have use the board to turn it on. The For pin on the vfd has to be grounded to turn on the spindle, I used a pc817 optocoupler, use the spon pin and ground from tinyg (add a resistor) connect to pins 1 and 2 on the chip. Pins 3 and 4 are to sink the 24v vfd forward pin to ground (add a resistor). Read up on optocoupler/isolators for the circuit. This will give you m3 and m5 control. Now you need configure tinyg for pwm I just used 2khz and full scale rpm 0-24k and full scale phase 0-1. Make sure you do a reset for the settings to keep. Power everything up and send an m3 command followed by s12000 adjust the conversion board resistor for app. 5v out or app. 12000 rpm on the vfd display. Play with the strings until you get as close as you can. If you want to use reverse then read up on circuits, I am pretty sure you have to leave the For pin high and ground the Rev pin. Switching directions means you have to use the sdir pin from the tinyg to send the spon signal do the Rev pin on the vfd. Good luck