Looking for advice as to how to integrate a relay into my MPCNC system that could automatically be turned on or off at the completion of a job.
Similar to how a 3D printer turns off the fan at the end of the printing process.
I know there is a fan output on the RAMBo board and I was thinking of using that.
I am also unsure how and where to add the code to toggle the fan output on the RAMBo board from EstlCAM.
Thanks
Tom
In EstlCAM, go to Setup/CNC Programs. Select the “Texts” tab. “Program Start” and “Program End” are where you can add g-code commands that get added to each g-code file exported. As for controlling the fan pins, you can use an M106 (set fan speed) and M107 (fan off) to control the pin. I use this technique to control an IOT relay to turn my router on and off.
Note that on the Rambo board, the three default fan pins are 12V. If you need to a 5V pin instead, it is an easy firmware change. So what do you want to control with your fan pins?
Thank you very much Robert for the help, it is greatly appreciated.
I want to control a relay/contactor that will in turn shut down my router (RotoZip tool) and turn off my vacuum system.
I do a lot of my cutting while I am at my desk in the next room to my shop and when I hear the vacuum and the router shut down I will know the job is done.
Thanks again
As far as the relay, I will be using a multi pole 12vdc cube relay, so the 12vdc off the RAMBo fan output should be ok
You really should not do that. Fires are very possible in cnc machines.
Just out of curiosity, can I ask why it would be recommended not to do this ?
The draw for the cube relay will be about that of a fan, the cube relay will drive a contactor that is rated for more than twice the current of the vacuum cleaner and the RotoZip tool.
The RAMBo board is in a fan cooled enclosure.
If the concern is that I am not near the CNC machine, it is in the adjacent room from my desk, maybe 10’ away.
I really don’t think people stand over the machine 100% of the time and watch it, but then again I’m probably incorrect.
This is my concern. It takes just a moment for some bad CAM or an overheated driver to drive the bit and collet right into the work. Then a few dozen seconds later, it will be a fire and if you’re not standing right over it, it will keep going until it runs out of fuel.
Yes, they do. If not that, they stay in the room doing other activities, but within eyesight.
I leave my printer running while I leave the house or sleep. I pause my cnc when I go pee. It just is much more dangerous. It isn’t a matter of if, but when.
I’ll agree with you regarding the CNC and staying close, but I will disagree with you regarding the printer (if a 3D printer). I see more possible fires with a 3D printer due to the current being drawn for the heat bed and hot end. I feel this is much more dangerous than the CNC.
I am running dual end stops and homing for the Z axis
My other question is where would I tie it in on the Rambo board ?
As per the notes in the dual end stop setup guide, the headres normally used for the fans are not to be used on the full Rambo board
If you take a look at this image, you can see the three pairs of fan pins. I used Fan 2. You have to specify Fan 2 in your g-code.
I’m in a similar situation to yours [Tom] in that I spend a lot of time in a room adjacent to my MPCNC but still within easy hearing distance. I have no hard data, but antidotal info indicates it is uncommon for these rigs to start a fire. The problem is that if it does happen, it can be catastrophic. I don’t want my hobby to cause my family a great deal of pain. And unlike a 3D printer, when an MPCNC starts a fire, there is typically a lot of combustible material around.
To mitigate the problem, I added the following to my system:
I can atest to the fire hazard being very real!
I, like you thought it wasn’t a big deal. i keep my printer running overnight all the time!
Then i went to get something to drink in the house while the cnc was running in the garage.
I came back to a smouldering dremel. the collet had come loose and bore itself in the table.
the smell of the burning dremel was very bad throughout the garage and luckeliy i was relatively on time.
But i learned my lessen then and there.
Don’t leave your CNC out of sight and keep the panic button in reach!
Note that the issue is not electrical in nature, but mechanical. Aside from the mains power in to your controllers transformer, and whatever your spindle is using, I doubt there’s enough juice in most rigs to do much damage fast enough to be a horrifically awful proposition. It’s the bit and collet spinning at tens of thousands of rpm. Ever tried to start a campfire using a fire bow? Now imagine you’re doing it with a length of tool steel, at 20-30k RPM, without ever slowing down, and completely surrounded by intentionally dried wood, and probably a fair amount of sawdust, chips, and other kindling.
IMHO, this is the only subject “we” come close to really berating people about (unless you get into dry rub vs wet rub in the smoked meats thread, but that’s on you…) Safety is not something to be taken lightly. And it’s one thing if you were doing something stupid that could get you hurt, but if you’re endangering your family… Maybe a different hobby? Full-contact quilting, Marquis of Tuckenbury rules, perhaps? 
I’m not going to keep at you about this. Everyone needs to spend their own risks to match their own values. I am also not an actuary and I don’t have the numbers to say for sure.
But… I do want to point out the ways a CNC is more dangerous than a 3D printer. The 3D printer is intentionally heating to a higher temperature than the CNC. But it is heating a small amount of metal to a temperature underneath the smoke point of the plastic. Most of the materials around it are not flammable. It has a temperature gauge to close the loop and turn off the heat at a set temperature. There are software checks to try to ensure that the heater and the thermistor are working (and people get upset when those checks are turned off, naturally). The total wattage of a standard 3D printer while heating up is less than 200W, and that drops a lot when the bed reaches temperature.
The CNC on the other hand, has a 600w spindle. It has no temperature sensors. It does not turn off when reaching speed. It is operating in a piece of plywood, and the table is probably made out of wood.
My personal experience with this went like this. I was in the garage, cutting something out of 3/4" ply. I was cleaning up the garage, with my hearing protection on. I had just ordered a smoke alarm, which I know don’t work great in a garage situation, but I thought it might be cheap insurance. I was on the step ladder, installing the smoke alarm when I smelled smoke. I looked over and my Z has skipped steps and the collet was on the wood. The bit that was sticking out was all cutter, so it was still cutting, but the collet was rubbing against the top surface, which was covered with dust. I had the vac on and I could smell the smoke and it was getting worse. But it was not out of hand. I turned it off and it cooled right off. If I had been in the other room, looking at a web cam, I would not have known anything until it was literally in flames, and at that point, I would have to be watching it much more intensely than I was in the garage. The smoke alarm never went off.
I really don’t want to hear about another MPCNC burning down. That video is awful, but it was at least in a dirt floor barn. If this had been in a finished shop, it might have taken out a lot more. Or if it was against a wall in a garage, it might have even taken a life. That scares me enough to preach in the forums about not leaving your machine alone. I am not responsible for you or your choices, but I will speak up to make sure it isn’t just naivety causing people to take unnecessary risks. If you know the facts and think that wheeling the machine outside, or putting a webcam on it, or being only one room away mitigates the risk enough for you, then that’s your responsibility. I won’t agree with you though.
“Extinguisher Ball is made with human, pets and environmental friendly materials.”
WTF!? 
Extinguisher Ball is people!
Soilent green 
Jeff, I now understand your point an will take your advice and I thank you for this information.
I just never though of it that way.
Thanks again for all the help and advice everyone, it is greatly appreciated.
I think one watching of the video gives us all a good idea on what could happen.
Anyone who has run any of these machines for more than an hour has had an instance where something didn’t go exactly right. A bit slipping in the collet, a programming error that sent one or more axis out of anticipated range, or any of a thousand things that could and do go wrong.
But since these little “goofs” happen while we were right there, there is no serious repercussion, the machine gets shut down quickly, the problem fixed, possibly a little swearing about wasted material, but usually that is the extent of it, and we go on our happy way, perhaps muttering, “I won’t do that again”.
I think again, of all of my mishaps, and think more about what COULD have happened, had I not been very, very close by.
As always,
On my machine I found I had to add a delay after the router was powered on to allow it to spin up to speed before it started cutting.
I use G04 P3 (for a 3 second delay)
I read that the dwell time is in milliseconds but for some reason that command for me is in seconds. I’m using GRBL FWIW.
I do think there are ways of making a cnc safe for another room. Infrared cams, enclosures with smoke alarms that have failsafe relays, closed loop steppers to prevent missed steps (like what happened to jeff). I have worked in industrial hvac equipment (basicly giant gas burners with fans) and have seen the immense amount of money, effort and regulations that go into making them safe. Like most things in life it is about acceptable risk. But like others I agree that simply listening for the machine to stop is not enough for me, and I would not allow any of my friends or family to operate a machine that way… I wonder if anyone has tried putting a fire sprinkler system into their mpcnc setup 
Edit: maybe we can modify the spindle speed control pid to have a CT current sensor and monitor for prolonged gross changes in current consumption and rpm speed?
