Wiring A Relay for a Router-based CNC Machine

[DurhamDev]

Hi all,

I built myself a 4x8 CNC router, based upon the BuildYourCNC.com "GreenBull" design, and it works great. A few months ago, I took it upon myself to try and build a relay to turn the router on and off when running jobs, but this seemed to cause me no end of issue.

Presently, I turn on my router, turn on my vacuum system, and then run my program. Once complete, I will reverse this process, and shut everything down. I'm usually in another room when the program completes, so I've got it set to send me an email when complete. In all honesty, the perfect solution would be for the machine to shut itself down when it's all finished, and that's why I've been researching the relay idea.

Based upon the instructions and wiring diagrams I found here (link: Tom Benedict Builds a Relay Box for His Taig CNC Mill), I created the appropriate relay system, and it sort of works. By "sort of", I mean when I run the program, the router starts up and spins, but this is where I have the issue. The router doesn't seem to have enough power to keep running, so it's speed either cycles up and down, or in the case of a different router (which, admittedly, had a 'ramp up to full speed on startup' mode as a selling feature), would only hum and not spin up at all. From my understanding, the relays should not do anything more than signal the power when to flow, and when not to flow. They shouldn't impede it in any way, should they?

I am planning on upgrading to a VFD and spindle in the near future, and was also hoping to figure this out prior to connecting it, as I don't want to cause any issues to the additional electronics upon connection.

If anyone could give me some advice on what to look for, I would sincerely appreciate it.

Thank you!

Rick

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[Al_The_Man]

What type of controller is it? It should be possible to use a contactor that would have to be manually retained by P.B. until the machine booted up.
BTW, if using a VFD, an output on the VFD can be utilized to pick up a vacuum or cooling pump etc, whenever the program runs the spindle.
Al.

[DurhamDev]

What type of controller is it?

The relay was purchased from BuildYourCNC.com, and information on it is here: https://buildyourcnc.com/Item/electr...breakout-relay

It should be possible to use a contactor that would have to be manually retained by P.B. until the machine booted up.

I'm sorry, but I don't know what you mean. (I'm not familiar with what 'manually retained by P.B.', sorry!) Could you please explain.

BTW, if using a VFD, an output on the VFD can be utilized to pick up a vacuum or cooling pump etc, whenever the program runs the spindle.

Are you saying that once I upgrade to the VFD, that it will have the ability to trigger the spindle as well as the vacuum, without the need for this relay solution? (If so, and I can't figure this one out, then this is definitely great news!)

I appreciate the help, Al. Thank you.

[coherent]

All the DC side of the SSR does is use the low voltage from your breakout board or controller to pull the contacts and open and close the high voltage AC side of your SSR. Your main power in normally comes from a 120 or 240 outlet, through your SSR and to your plug/receptacle that your router, spindle or vacuum etc is plugged in to. Other than being on or off it should have nothing to do with the actual voltage from your mains...through the SSR.. to your router. A PWM or VFD setup is needed for speed control. If your router/spindle was pulling more power than the SSR is rated for that could be an issue but in my experience it would just fry the SSR, not cause speed fluctuations. Check your Solid State Relay type and power specs/ratings. May be just a bad relay thats not opening/closing the contacts completely?

If it's rated for the amperage/wattage, you should be able to turn on/off both a router and a vacuum without issues.

[Al_The_Man]

I thought the object was to shut the whole machine down, but if just the Vacuum then the majority of VFD's have configurable outputs either a relay contact or a open collector transistor that can be used to pick up a suitable relay.
In this case you can set the output to come on when NOT at zero speed, IOW any time the spindle starts, the relay picks up, and shuts off at zero rpm.
Another option parameter is to pick up when At Speed, again when the spindle has reached the programmed rpm.
I used the feature once to pick up the spindle brake when the spindle had stopped.
Al.

[DurhamDev]

I thought the object was to shut the whole machine down, but if just the Vacuum then the majority of VFD's have configurable outputs either a relay contact or a open collector transistor that can be used to pick up a suitable relay.

My purpose is to turn on the router when the program runs, and off when it's complete. Right now, the router doesn't spin up fully when running from the relay. (It works perfectly fine when I plug it in directly to the wall and power it on/off from the switch.) It sounds like I may have an issue with my relay, so I'll delve into it a bit more. Perhaps it's not suitable for this purpose.

In this case you can set the output to come on when NOT at zero speed, IOW any time the spindle starts, the relay picks up, and shuts off at zero rpm. Another option parameter is to pick up when At Speed, again when the spindle has reached the programmed rpm.

I will investigate this. I don't presently have a spindle, but obviously when I do, I'll have a LOT more questions.

Thanks!

[Al_The_Man]

With a VFD you do not start it by applying the main power, it is done with a small contact closure input, it has main power at all times, unless E-stop etc..
The controller has to issue a M3 or M4 (FWD/REV) and M5 for spindle stop to close one of these contacts or inputs..
Al.

[john-100]

Hi Rick

I have just looked at Tom's wiring diagram :-



and noticed an error with the wiring to the fuse holder

to avoid a shock hazard the live (hot) supply should go to the terminal at rear of the holder
the tag at the side should go to the relays

if some one removed a good fuse with the power on
you could touch the fuse when its in contact with connection that goes to the tag at the side of the fuse holder



John

[DurhamDev]

I have just looked at Tom's wiring diagram and noticed an error with the wiring to the fuse holder. To avoid a shock hazard the live (hot) supply should go to the terminal at rear of the holder. The tag at the side should go to the relays. If someone removed a good fuse with the power on, they could touch the fuse when it's in contact with connection that goes to the tag at the side of the fuse holder.

I would NEVER have figured this out on my own. (No matter how many times I accidentally shocked myself.)

Thanks for this information!!!

Rick

[Al_The_Man]

Here is a link from a while ago for spindle control from the parallel port, using a 2n7000 and a SSR. After post #7
http://www.cnczone.com/forums/genera...64477-cnc.html
Al.