PWM/frequency signal as input to Mesa card

I've ordered at set of 24V optocoupler isolation boards from the Aliexpress link below. It's gonna be a month or so before they show up, but when they arrive I'll try the new firmware and see if I can get this working.

 

www.aliexpress.com/item/1005003242672161.html

They are specified to handle a maximum signal frequency of 5KHz so even by Chinese standards they should hopefully be able to handle the 1-2khz rangeI'm planning to use per PCW's advise.

I have a similar inverter. I think we can use the modbus interface.

Is that some hidden feature that needs to be activated?

I can't find anything in the manual regarding modbus.

www.nidec-netherlands.nl/media/2019-freq...ss3-0478-0352-03.pdf

Sorry, my bad . My driver is another series. Your inverter is missing modbus

After running some prolonged milling sessions with my mill I've decided to go a different route here.

I'm going completely replace the VFD, the gigantic 2kw AC spindle motor and the noisy 6 speed transmission.

I'll be replacing the whole setup with a Delta B3 2kw 400v AC servo rated for max 6000 RPM and use a belt drive with 1:1 ratio pulleys to drive the spindle directly.

This should give me plenty of low end torque, a built in encoder and double the max RPM of what I had before at much lower noise level.

But I just realized that the question of how to read the spindle load from the servo drive still remains. The load is available from the Delta servo drive either as an analog signal or via Modbus.

As I'm using a Mesa 7i96S + 7i84 combo I have no analog inputs available and the Modbus capable RS422/485 port is already used for the 7i84.

What's the best way around this?

Do I try to source a Mesa 7i76EU which has a few analog inputs and replace the Mesa 7i96S board?

Can I use the FPGA expansion port in some clever way without adding too many expansion cards?

 

1. get a Mesa THCAD, it can do pretty good analog to digital, should be more than enough for spindle load, but that would also require an encoder input to Mesa 7i96S, in case the spindle is already using it.
That might still be usable if the spindle does not require the index pin as THCAD requires only a single pin.
Or wire the THCAD to the IDC26 connector, might need firmware flashing.
2. Get a LM331 chip, some resistors and capacitors, and build a voltage to frequency converter, 8 pin chip, 1-3$ a piece, info here:
www.ti.com/lit/ds/symlink/lm231.pdf?ts=1...Fwww.google.com%252F
3. same as 2 but get a ready made module, under 10$ usually.