Dust control system auto on/off

I got a Grizzly system to vacuum/manage my dust and it runs great but requires that I turn it on/off manually.

I see that my CNC control box has an accessory power slot that can be activated/de-activated based on CNC commands. Is there a document/guide to hooking my dust system up to that or someone who could instruct me on how to do it?

There are two relays, each one has an input power and output plugin (underneath the control box). So you provide whatever voltage you need to the input, and plug your DC into the output.

You can use the Relay 1 or Relay 2 buttons on the screen to switch them, and M7 or M8 (depending on which relay) in your Gcode to turn it on, and M9 to turn it off. The M30 that comes wih the AVID build will also turn off the relays I believe.

Cool, that’s about what I thought it would be. So I’ve got the purpose of the relay usage and power ports correct then?


Filler for the dumb 20 character minimum.

Bear in mind that the motor driving your dust controller may not enjoy being switched on and off frequently, unless it has a soft-starter.

If you do “long” runs with the CNC, then there is no problem. But it you start and stop it frequently (perhaps every 5-10 minutes or so), you may find that the thermal cutout triggers at annoying times, unless it is also protected by a soft-start circuit.

My plan would be that it’s only an ‘on’ at the start of a cut job and ‘off’ at the end, replacing what I would do myself before I start a job and after it finishes, but I will keep that frequency in mind when planning my projects - thanks for the feedback :slight_smile:

Before you start looking into modifying Post Processors to operate the dust collector via g-code commands, take a look at a g-code file you’ve already used. You might already be set up and ready to go.

I have a similar system that uses a Harbor Freight 2 hp dust collector. Depending on which CAD/CAM software and Post Processor you use, you might not have to make any modifications to your g-code or Post Processor at all. I use Vectric Aspire, and the g-code that is output through the Avid CNC Post Processor already includes an M07 command at the beginning of the g-code file, before the M03 command that turns on the spindle. (M07 turns on Relay 2 in my Avid CNC control box.) The result is the dust collector fires up before the spindle comes on, allowing it to get up to speed while the spindle is coming up to speed.

At the end of the g-code file, the M09 command (which turns off both Relay 1 and Relay 2 in the control box,) is already there, just before the M30 (End of program) command, long after the M05 command that turns off the spindle. The result is the dust collector turns off long after the spindle shuts down and the axes return to the home position, allowing it to clear any chips that might be still in the hose after the cut is complete.

As I said, all of that was already built into the Avid post processor in Vectric Aspire, so I didn’t have to do a thing to make the system work. All I did was plug the dust collector and the power supply cord into the appropriate Relay 2 ports on the control box. It works like a champ.

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I am using the default/shipped-with everything from AvidCNC currently. So vcarve pro and mach4, avid controllers, spindle, etc - which is why I was hoping to find a sanctioned guide of some sort for using the relay power ports.

I think I can probably puzzle it out with the responses here so far that have confirmed the capabilities are there to use :slight_smile:

Just like you, I’m using the default everything from Avid CNC. The only difference is I’m using Aspire, and a different brand of dust collector.

If you go to the Avid CNC Controller Setup Guide and scroll down just a little, you’ll see an explanation of the relay inputs and outputs for both relays.


Basically, you’ll need a power cord with a standard male plug to plug into the wall outlet at one end, and a female C13 type plug at the other end. I needed a 12’ long cord in my case, and ordered one off Amazon. Here’s a (non-affiliate) link to the one I got:


That cord got power into the relay. The other side (Relay Output) is where you just plug the dust collector power cord into the controller box. The power switch on the dust collector is turned ON, and stays that way.

Again, look at any g-code file you’ve already saved. Specifically, look for either an M07 or M08 command. In the pic below, I put a red box around the M07 command that was generated by the Avid CNC post processor. You should have the same thing. That M07 command turns on Relay 2. So, I have my dust collector plugged into Relay 2. (For some reason M08 turns on Relay 1 and M07 turns on Relay 2. Really, Avid? Really?)

If you look down at the bottom of that g-code file, you should see an M09 command. That turns off the power to both relays, turning off the dust collector.

Again, I didn’t set any of this up. That’s how the Avid CNC Post Processor created the g-code “right out of the box.” I spent about 3 days doing research, trying to figure out the best setup for my application, only to find that I didn’t need to do any of that research. Everything was already in place. I just needed to plug it in and try it. (To be fair, I was also waiting on delivery of more parts for the dust collector pipes and hoses, so it wasn’t a total waste of time.)

To manually turn the dust collector on or off, just click the Relay 2 button on the Mach4 screen, and you’re all set.

If you have any questions, feel free to ask. Good luck!

Fantastic, thank you for the detailed information :slight_smile:

What happens if you have a 220volt dust collector? I lost this feature when I upgraded to a larger DC, plus I have two machines, I’d love to sort it out.


Check out the control box setup instructions I linked above. The relays are rated for 250v AC, 15 amps. Having said that, I’d contact Avid support and see what they say. My dust collector is 120v, so it wasn’t an issue for me.

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I had planned to put my dust collector (120V) on one of the CNC controller relays, but then I decided I wanted to place the DC more centralized to other tools and didn’t want to run a long extension cord.

My solution was to buy a wireless switch rated for 120V/15A, capture the RF sent by the wireless remote, analyze and decode it, take relay signal and power from the CNC controller and run it into a microcontroller, spit out the RF signal when it senses a relay signal, turning my dust collector on/off remotely.

After many hours, custom PCBs, and coding - I found I prefer the original remote control! The automatic on/off just didn’t suit my workflow.

But it was a fun project. I hope to share the process one day.

I like that idea. With 2 machines running and 1 DC it is a challenge to have gcode turn it off and on, it would have to be pretty smart to know if one machine finishes and it needs to keep running for the other…