GRBL controller versions, documentation

Alright, I SWEAR I looked in the wiki first…

Is there any documented list of the various revisions to the S3 GRBL control board, what changed in each version and maybe even a boardmap or pinout of each?

I’m looking to add spindle on/off control via relay to my S3 and router, but most of the discussion I’ve found is around older or unspecified board versions - some say it can be done, others not, and there is rarely a version mentioned.


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That’s one of the topics I’ve always been a bit hazy about. AIUI, whether or no it can be done depends on whether there’s a pin for it on the board — the Carbide Motion boards use the same board for the Shapeoko as the Nomads, so have the circuitry, but there isn’t a connector on them — you have to solder onto the pads.

For an SO3, just let us know which relay you purchased and its wiring requirements and your board revision and we’ll send you back an annotated diagram w/ instructions on how to connect it to your board.

For the record, the (incomplete) page on the wiki would be but I haven’t figured out a way to phrase the above for that which doesn’t make me feel like an idiot and worry about the sort of e-mails we’ll get. I’m pretty sure the IOT relay has been the most popular.

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I’ll crack it open today and get my controller version. I just need to know which pads and I can back engineer it from there.

I’ve had good luck with this relay for some other projects: I’m using that to control a 1.5HP induction motor in my shop today and it’s been excellent, though does need a bit of active cooling at that current.

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v2.4d according to the silkscreening on my board. That enough info to know which pins will get a +V when grbl gets a spindle-on command?

send an e-mail w/ that information in to and we’ll have someone look it up (sorry meant to specify that) — while there is some further information on the wiki (specifically and the surrounding which links to: ) another source for information would be the Sparkfun Stepoko board on GitHub.

Done and Done. Would it be good/advisable if I made a write up on what I did, following reply to said email? Not sure how closely guarded the pinout of the CM boards are…

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I think your documenting how you implemented this for your specific board would be a very good thing, and I’d love to have it written up well enough on the wiki that I could duplicate it for my setup. (just barely was fast enough to avoid a bad crash using my Shapeoko today when I failed to switch on the router when I should have)

Will do. I made some good progress tonight, stymied by the bad emr relay that I was testing with. Spiffy SSR on the way though, I’ll do a write-up on Wednesday (give or take).