Hi,
I think you are right. Opto-isolators can be as slow as a wet week depending on the model and how you set them up.
I have attached a pic of two very common optocouplers. Note that the phototransistor in one has no external base connection.
Thus the sole way it can turn on is light from the photodiode, thus the photodiode needs to brightly illuminate the phototranistor,
commonly 10mA or more. Typically the time response is slow, 10-20us with these devices and you would struggle to
pass a 100kHz signal through it.
The other optocoupler pictured has an external connection to the base. That is typically biased to about 0.6V such that the
phototransistor is on the threshold of conduction. Thus the light from the photodiode need be very much less intense
to cause the phototransistor to conduct, less than 1mA photodiode current. Response time is likewise much
improved, of the order of 1us.
The extra biasing circuitry, especially being so heat sensitive, means that the biased photocouplers are used only as needed
in comparison to the simpler non-biased optocoupler.
The question is why are you so hung up on optoisolators? Firstly its common for the input of stepper driver to have optocouplers
built in already. There is no need to isolate at the ESS/BoB end and THEN AGAIN at the driver end.
I use:
https://www.homanndesigns.com/index.php?main_page=product_info&cPath=54_22&products_id=59&zenid=n2f38qp4ho6mv9eb9rm7hhp7a0from Homann Designs in Australia, I live in New Zealnd so they are kind of local to me. These are very simple and plain
bi-directional BoBs WITHOUT optoisolators. I've been using them for over five years and have not blown anything
up yet, and I can blow stuff up real easy!
If fact I did a poll a while back:
https://www.machsupport.com/forum/index.php?topic=39723.0Only five people replied, a bit disappointing, but none of those five people (100%) have blown up a PC because they did
not use opto-isolators. I'm not saying you can't blow up a PC but it doesn't happen much either.
The advantage of the Homann BoBs is that without the opto's they are as fast as the TTL buffers used, ie tens of MHz.
The C10 is cheap enough, $23USD and bi-directional. Note it has no bloody opto's . Neither does it have any relays
for the spindle nor a PWM to analog circuit for a VFD, you would have to make and add those as required.
https://cnc4pc.com/c10-bi-directional-parallel-port-interface-card.htmlCraig