Estop and IOT relay

Is there a way for the E stop to shut off the IOT relay controls?

For example if the coolant loop is used to control and IOT relay and gsenser has active M8 command, the IOT relay will continue to power the switched (normal off) outlets as long as M9 isn’t sent.

It seems the e stop just stops the stepper motors?

Is there a way to change this so the e stop will stop the IOT relay signal as well? Or even just sent an M9 command when the stop is pushed?

What machine do you have?

oh yeah guess that could be helpful :slight_smile:

Mk2 48x30

Doesn’t the estop cut power to the longboard?

No it cuts power to the steppers from what I am experiencing.

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So it stays connected to your computer when the estop is pressed? I don’t have a LongMill, but I thought the estop cut power to the long board?
How do you have your iot relay connected?

Correct it stays connected and the .nc program keeps running on gsender display

The steppers cut out so the machine stops moving and has lost position the instant the stop is hit.

I have the IOT wires to the coolant loop as suggested on the article. + coolant to + on IOT relay and ~ coolant on long board to - IOT.

M8 turns relay on to engage the plugs and M9 cuts it off.

But hitting stop doesn’t send an M9 or turn off the longboard just kills the steppers

Check the estop is wired to the longboard correctly. When the estop is pressed it should cut all power to the board.

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Again, I don’t have a LongMill, but that doesn’t sound right.
Where is the estop connected?

It’s connected to the connector on the top surface of the long board per the instructions. I can send a picture when I’m home.

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Hey @Jstirrat,

I can provide a bit more clarity on the E-stop, but not sure I can help with your actual question.

The LongBoard receives power to its ‘brain’ using the USB connection cable. When you hit the E-stop, the power to your motors is cut, but if you flip over the board, you will see a small blue light on the board is still powered. This is the USB cable still providing power to your ‘brain’.

To improve reliability, the new SuperLongBoard’s ‘brain’ now receives its power from the power brick. This means the ON/OFF switch controls the power, which means E-stops on both boards still works to immediately stop the motors in the case of an emergency.

You may be able to create a macro to assist, but I’m not sure it can be tied into an E-stop press.


Thanks . So sounds like what I’m experiencing is expected behaviour. the estop kills the steppers but not the microcontroller therefore the coolant loop stays active despite the steppers loosing power. I imagine if I unplugged the power brick that I’d still be able to connect then from what you are saying.

I saw on the super long board one of the benefits was

“Safe E-stop depowers motors and disables accessories”

So I presume that implies the longboard does not do that.

I can think of a number of ways to get an E stop in the router circuit including a 120v estop in line with the power bar, or the router. I could go low voltage and estop the coolant command but if they’ll relay has a hiccup the router could stay powered. But this will mean 2 separate “stops” which seems suboptimal if there is a problem. Might be the best I can do.

I can’t have the shop vac, router, and long mill all on the same circuit. I have multiple available but killing power to them all via a central stop is tricky…


Here’s the post that I had seen.

Well, if it doesn’t cut power, it’s not really an E-stop. I can’t really think of a use for just cutting power to the steppers.
I’d remove the big button, check it’s specs, and repurpose as a true estop.
Many CNC controllers isolate the 5v line from USB from the MCU. I’m sure that’s what the SLB does, but I’m really surprised by the current estop function. You’d be better off wiring it in as a feedhold (that’s what I do on my Shapeoko).

Yeah the LongBoard uses the E-stop essentially as an On/Off switch, but since the Arduino receives power over USB from the computer, that in turn provides power to all other 5V IO. This means the E-stop can only really disable power to the motors and 12V out.

This is still plenty useful as an E-stop since it halts all machine movement through a hard electric cutoff to the motors rather than relying on Pausing from the firmware, so it’s technically the safest and most reliable solution. Though obviously it has some drawbacks, all of which I aimed to address with the SLB (and I think we did!)

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Thanks Chris,

So if the estop kills the 12v power I guess I could put a relay using the 12v power as the switch and the 5v coolant loop (12V on closes the circuit, 12V off opens it) and then the estop would interrupt the power on the relay which would shut off the IOT relay.

Any suggestions on a relay that would do that within the specs of the machine?

What are you switching with the IOT?
Doesn’t the Stop button do what you need?

I’m glad they’re improving this on the SLB.
That said, after running all types of hobby level CNCs, I’ve never been in a true Emergency Stop situation. I still have a way to cut power to everything, though.

It is switching the router off. Want one button to cease all electronics and don’t want to have to get myself near the router or find a switch on a power bar if there is a problem.

I work in healthcare and have seen my share of power tool injuries. No need to get closer than you need or delay shutting equipment off.


I wouldn’t be able to provide any specific relay recommendations, but any that could take 12v input and handle 5V output should do you well. I’m pretty certain it would accomplish exactly the behaviour you’re looking for

I use both Gsender and USG with the Longboard controller. Also have a Logitech game controller connected and have the following buttons set for Start, Pause and Stopping the machine.

Blue (Start), Green (Pause), Red (STOP) and Yellow (Z-Safe Height). The E-STOP Power Button has to be connected for the Longboards main power. I never really use it in an emergency (there if needed) but instead just hit the Red Stop Button on the game controller which immediately shuts down everything.

The Longboard stays powered up and all axes can still be moved afterwards. I run an M3 and M8 command in the Gcode file and have things set to wait a few seconds for the spindle to spool up before the job starts. You could also use the Program Events to insert Gcode commands. If you need to pause or emergency stop the machine it’s just a matter of pushing the Green or Red buttons. Has worked well for me so far doing it this way.

I’ve been using an SSR relay that’s connected to the Longboards coolant input . . . vacuum connected to this in my case. Was using an IOT on one of my other machines but for whatever reason it was picking up some kind of interference from the spindle motor I think causing the machine to shut down. Replaced it with an SSR and problem went away.


Do you have the link to the ssr relay?