Spindle and Vacuum control - together?

I’ve been using the iOT relay for over a year now to control my router and my shop vac for dust collection. It’s been phenomenal and hooks up to the PWM and GND pins on the board. With this, I set all of my spindle speeds in Carbide Create to 10,000 rpm to ensure that the relay gets the full 5v so that it works every time.

Now I’m working on a water cooled spindle upgrade. I’ll be using the same PWM and GND pins to control my VFD for spindle control, now setting the spindle speeds according to what I’m cutting, not maxed out every time.

How can I still use the iOT relay for dust collection control? There is a 5v terminal on my HY VFD, but I don’t know if that is digitally switched or if it’s always on. Is there another way to hook this up so that my iOT will still get the M3 and M5 commands?

There are various, not very helpfully documented, output modes on the HY VFD that could allow you to get a logic trigger out when the spindle is running, there’s a copy of the manual here.

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I suppose your IoT relay’s input activation threshold can’t be adjusted?

I don’t believe there are any adjustments on it. I’m also not positive yet that the lowest spindle speed isn’t enough to switch it on anyways. But I recall reading somewhere before I bought it that it was important to set the speed in Carbide Motion to 10,000 or so to ensure that full voltage gets applied.

More precisely: the PWM voltage is managed by GRBL based on the $30 parameter (max spindle speed), which happens to be set to 1000 when you initialize the machine using Carbide Motion (I just checked in Carbide Motion 513). This means that GRBL will take the M3 RPM value and adjust it so that 1000RPM grants 5V. Therefore since any workable RPM value should be greater than 1000, you should always get 5V when using Carbide Motion settings. Now, this is irrelevant for people who use a router, but when using a VFD&spindle, you need to set your $30 parameter to the max speed of your spindle, usually 24000, otherwise you won’t get the proper speed (i.e. if you leave $30 to 1000, any value in the G-code will spin the spindle at the max 24000RPM)

If you have the name/reference of your IoT relay we could have a look (just in case, before diving in the muddy waters of HY VFD poor documentation)

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Yes, changing the $30 parameter is on my to do list. That’s part of the thought process that has me here.

I went ahead and did some deep diving into the very poorly written manual and some other forums found via Google that put me on the right track. Fwiw, I have the HY02D223B and I can’t find this specific manual online, so I took a picture of the page I’m referencing. I think I have this problem sorted out (I won’t know for sure until I get to test it), but I made this diagram for anyone else in my situation and also for me in a week or so when I start wiring this up.

But before I begin, the IoT relay has no adjustments, but can accept a trigger input of 12-120VAC or 3.3-48VDC. I certainly did not realize this before.

As an explanation to the poorly written manual, FA/FB/FC is a pass through relay. You provide the power, it provides the switch. This incorrectly translates as a switched 3A/250V output depending on which page of the manual you’re on.

So I’ve decided to redirect 24VDC to the input (FB) and then tap my IoT between the Normally Open Output (FC) and Ground (DCM). When parameter PD052 is set to “01” this relay (FA/FB/FC) is activated when the spindle is in a “Run” state; sending trigger voltage to the IoT, therefore I should have dust collection anytime the spindle is running.

And as a side note, I’ve ordered another IoT that I will wire in parallel (not pictured) using the 24VDC before it goes into the FA/FB/FC relay. This one will operate my CW-3000 chiller so that anytime the VFD is powered on, so will the CW-3000. I’ll leave the VFD on for a few minutes or longer as needed after long cuts so that the CW-3000 has time to slowly cool the spindle closer to ambient.


Sounds like a good plan, thanks for sharing!
Gotta love the “Brkaing” typo in that figure.

n.b. : the only online version of the manual I ever found is this one, and it covers a range of HY models including 223B. You also get the thrill of accessing a russian site to download a PDF with instructions to setup Chinese spindle, which is called “living on the edge” :slight_smile:


Yeah, I think I’ll avoid that option… I’m a submariner, and I don’t need NCIS questioning my internet activity… lol

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You don’t want to meet Leroy Jethro Gibbs?


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I had to Google that reference…

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