Anyone use digital signals to connect 7i96 to a VFD?

Hi all,

It's been a while, so I hope you're all well in these crazy times.  I haven't had much time to work on my system, (falling off a ladder and breaking one's arm will do that) so I've been out of touch. I'm not allowed to build the machine, (heavy bits are beyond me still) but I'm currently building the electronics enclosure.. and wiring all the bits inside. It's slow going, but I'm making progress.

Onto my question....

I know most people seem to use the 10V analogue signals to control their VFD from their Mesa card(s) of choice, but I was wondering if anyone has ever used the 24V digital signals?

I have a little 2.2KW Invertek Opti Drive E3, and it seems to have a digital input range of 8-30V or so, so given the Mesa has a 24V I/O... it seems like it might be possible. However, since I can't find anyone who has.... I wonder if it is possible.

If anyone has, I'd like to hear your experiences, considerations, and setup? I just think a higher voltage digital signal might be a little less prone to noise. No aversion to analogue though.

Hope everyone out there is doing ok!

Take care,
Harmo.

I know most people seem to use the 10V analogue signals to control their VFD from their Mesa card(s) of choice, but I was wondering if anyone has ever used the 24V digital signals?

Do you mean the digital inputs like RUN, FORWARD, REVERSE? That is no problem. But for setting the variable speed I don't see how you could use the digital inputs.

Some VFD's have digital inputs that will run the spindle at a preprogrammed speed for each of them, maybe that?
Otherwise,never seen a VFD that can be controlled by 8 to 30V, ever, that just seems wrong.
There are 4 to 20 mA inputs on most of them though, so who knows ...
Maybe that is the input OP is talking about as it would be ok for it to be tolerant to those voltages.

You could use pulse width modulation at a particular voltage to manage the speed. It's how many computers control the CPU fan speed when the temperature rises and drops.

I run Huanyang GT VFD's on both my machines. They have an HDI input for what is said to be speed control using pulse between 0-50KHZ at 9-30v.

I have never used it nor have I seen it used this way but looks to be possible with the right hardware. I'm wondering what you would run the pulse drive with?

@hoffb77 Thanks for the clarification.

So then it would really be limited by the maximum output frequency of the digital outputs of the 7i96. I think 50 kHz may be a bit much but maybe PCW can give you a definitive answer.

A step output should be able to handle the frequency but as far as I'm aware those are all 5V. So you would need to use a reasonably fast optocoupler.

Using a stepgen and a 5-24v level converter ought to work. You can pick up an 80khz for under $20. I think it would be a pretty cool project to tie it all together.

You could use a level translator from a stepgen output to run this
A simple small signal MOSFET (2N7000)  would do but if you
wanted isolation a logic opto-isolator would work (say a TLP104)

Hey everyone,

I love how you all just run with my questions. Thanks everyone.

I'm sorry if the topic seems crazy or frivolous, but with lock down, broken bones, pain meds, and "life getting in the way" of CNC progress... these are the things I like to think about.

What if I could use a digital signal? How would I do that? Would there be any tangible benefit? Has anyone done it and why?

Or maybe I'm just suffering from medication-enhanced cabin fever with the household pets using me as a mecca for body warmth.

Like I said, I'm not averse to analogue control, but I always like to consider alternatives.

Hope you're all well, and thanks for the interesting discussion. If anyone does it, I'd love to read about it.

Harmo.
 

Sorry if that's not what you asked for, but since your vfd has the rs485 port you can control everything with a simple usb-rs485 key. at least I do that.
Mauro