Seeking Spindle Relay Advice

Greetings All,

I am building out a new CNC router that utilizes the STB4100 USB Motion Control board with Mach3.
I now have all 4 steppers wired, working and verified as well as the Estop, Home, Probe and limit switches.

To keep the initial build cost down I am foregoing an inverter/spindle setup and simply allowing Mach3 to operate the Output pin to power my hand router.
Because the STB4100 has no built in relays, and because I can't find any specs on the output port current capabilities,
I have been worried about frying the board if I use the wrong type of relay.
Maybe I am just overthinking this and all relays are going to have the proper resistance to keep current draw low.
As long as I stick to a 24V DC relay.

I would love to hear from anyone who also used the STB4100 and a simple relay to power out a hand router.

My BOB: https://www.amazon.com/dp/B07KYM15PC

Relays I have been considering: https://www.amazon.com/HiLetgo-Chann.../dp/B00LW2GW7U

My router is spec'd at a 2.4A draw. So these 10A ones should hold the load without issue. One thing that was confusing was that these relays appear to require both a 24V power and a 24V signal pin. Maybe simply jumpering the two would suffice.

I also considered trying this: https://www.amazon.com/LIVISN-Contac.../dp/B0829LP662

If I am right about the signal pin, then that would alleviate that issue. But this list a coil current of 60mA where the first one lists 5mA.

Any advice would be appreciated.

Thanks

Quote:

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Originally Posted by Malachite

One thing that was confusing was that these relays appear to require both a 24V power and a 24V signal pin. Maybe simply jumpering the two would suffice.

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Jumpering "Power" and "Signal" would work, but then all the current for the relay coil will come from your BOB output (which may or may not be strong enough). Your best bet is to use the relay as intended: connect the "24V Power" pin to your +24V power supply, and the "IN" pin to your BOB output.

Quote:

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Originally Posted by CitizenOfDreams

Jumpering "Power" and "Signal" would work, but then all the current for the relay coil will come from your BOB output (which may or may not be strong enough). Your best bet is to use the relay as intended: connect the "24V Power" pin to your +24V power supply, and the "IN" pin to your BOB output.

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Yeah, after sleeping on it I decided it was best to not try and take any shortcuts. I don't think these relay boards pull enough power to matter either way. but the last thing I want is a 'hiccup' in the power circuit stalling a stepper in the middle of a cut project. I am also debating on either getting a higher wattage PS or separating them out and getting a separate 32V one for the drivers and using the 24V one for the BOB and my Relay Board.


After digging a little further on the Zon, I also wised up and decided to just get a board that was more designed for this type of project as opposed to trying to hack something together. Same overall type as the one I posted in the links above but a 4 relay version. I wound up picking up this little thing: https://www.amazon.com/gp/product/B00LW2G7V6

This gives me four relays in one package so I can hook up O1 - O4 to a single relay device that uses just one power wire. It was only $7 so I figured it was better than a single or double relay board for the same price. And I can grow in the future if I want to try and add additional options.

I just finished connecting the basics and the relays throw properly as I toggle M3/M4/M5 and M7/M8/M9. I am getting ready to connect the spindle to verify that it truly can handle the current load.

As a side note, one reason I decided to try it the right way, was because I tried to hack together something else and accidentally connected a 24VAC relay to my 24VDC BOB. Yup. O2 is now permanently locked high. I picked up a new board for the finished project and I am using the blown board to finish verifying the basic wiring integrity.

Powered everything up and it all appears to work fine. M3/M5 cycled the relay which powered on the spindle/Router without any issues. So all of my electronics are now verified. Now off to start finalizing the design of the router bed and gantry.

Solid state relays are a better choice; better isolation/less EMI and a simple two-wire low draw (25ma max, typ <10) trigger (e.g. https://www.amazon.com/SSR-25DA-3-32.../dp/B08GPJ1V2J). All the relays you linked to will draw somewhere in the ball of 60ma, the 5ma on the first link is just the trigger current (sans coil). The easiest way to separately power the coil and trigger (and fully isolate the trigger circuit from the coil circuit) is to get a relay that has a JVCC terminal, but those are typically IN low. The relay you purchased can work with a high or low isolated trigger (no jumpers, COM and IN to trigger, DC +/- to power the coil). More info @ https://dalrun.com/Workshop/CNC/#6416

The I/O of the board appears to be common 4 pin optos, I would second looking at a SSR with triac output, if this is a common AC router.

Thanks for the input. Yes, this is, as of this moment anyway, going to be just a simple common AC powered hand router. Fairly low power and spec'd at only 2.4 amps. I might in the future look to upgrade to an actual inverter and water cooled spindle if the hobby becomes something I stick with. The BoB supports the option. I really like the look of that solid state relay you linked. To be honest I didn't even think about those. If I switch to a real palm router that pulls 6-7 amps I would feel much better using those than the 10A rated ones I picked up. So I might have to give that some serious consideration. From memory I think that most of the software I have played with so far allows me to switch the output pins between high and low. So I should be able to make those work either way I think. I will have to research that some more. So maybe those other ones you mentioned would also work. That cheap board I did pick up has jumpers so that you can switch whether it throws on Hi or Lo. I like having the option of the three extra relays but honestly I don't see me using them for anything. Most software I have used only activates them for cooling pumps. So I may never use them anyway. But again thanks for that advice. It was definitely one I overlooked.