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Smoke detector using endstop circuit.

Posted by GRAYWOLF 
Smoke detector using endstop circuit.
June 06, 2017 01:12PM
I am working on adding a smoke detector that has a single pole double throw relay contact. I also have a machanical endstop without the microswitch with which I can connect the smoke detectors relay to.

My question is this - How would I connect the endstop to ramps 1.4 so that when triggered, ramps would send the same "Kill All" signal as it does with Thermal Runaway?

I'm assuming that I can make some use of the AUX2 pins.

Edited 1 time(s). Last edit at 06/06/2017 01:18PM by GRAYWOLF.
Re: Smoke detector using endstop circuit.
June 06, 2017 03:06PM
The 'kill button' of a graphic display connects a ground (negative) to pin 41. You could piggyback your normally open contact to it with the common to ground

There is surely a way to reasign an endstop to it in firmware (but I don't know how)


Re: Smoke detector using endstop circuit.
June 06, 2017 04:57PM
Here's an idea:

have smoke detector relay connected to GFCI outlet that 3D printer is connected to. When smoke is detected, relay shunts hot to ground (through current limiting resistors) triggering GFCI protection. Simple and independent of 3D circuitry that could be on fire and unable to process relay input in software.
Re: Smoke detector using endstop circuit.
June 07, 2017 06:17AM
Quote
newbob
Here's an idea:

have smoke detector relay connected to GFCI outlet that 3D printer is connected to. When smoke is detected, relay shunts hot to ground (through current limiting resistors) triggering GFCI protection. Simple and independent of 3D circuitry that could be on fire and unable to process relay input in software.

Thats not nice to do a power short, just to do Switch off.
But you are on the right way. Security always has to be Independent from the System to secure. So just use the relay to completely Switch of the Printers power (at the Input of the power supply).
Re: Smoke detector using endstop circuit.
June 07, 2017 07:37AM
Quote
Dancer
Quote
newbob
Here's an idea:

have smoke detector relay connected to GFCI outlet that 3D printer is connected to. When smoke is detected, relay shunts hot to ground (through current limiting resistors) triggering GFCI protection. Simple and independent of 3D circuitry that could be on fire and unable to process relay input in software.

Thats not nice to do a power short, just to do Switch off.
But you are on the right way. Security always has to be Independent from the System to secure. So just use the relay to completely Switch of the Printers power (at the Input of the power supply).

At least in US ground and neutral wires are same gauge (not the feeder wire but that's irrelevant) and connect to the same busbar at the panel. Sending few mA through ground is all it takes, just make sure that current limiting resistors can dissipate the heat (or use neon bulb) and I'd probably add a fuse there just for good measure. GFCI outlets are tried and true, contain manual test buttons and new ones test themselves and lock-out when bad. Plus, your printer is ground fault protected or, if you get AFCI/GFCI combo outlet, you would get arc and ground fault protection at the same time.

Of course I'm open to hear why doing so 'is not nice'.
Re: Smoke detector using endstop circuit.
June 08, 2017 12:46AM
Well, in Europe there are some Areas with ground and neutral connected to the same busbar, but there are much more Areas where there is no direct connection between ground and neutral.
In theese cases, the only connection between those two is some kilometers away at the transformationn Station. Your house has its own grounding to earth and the current you are putting on ground wire really has to go some Kilometers throug natural earth till it gets ist way back to the current circuit.

So there is a metallic wire at your house directly burried in the earth, where it is wet. putting current on it does make an electrolytic cell and over time destroys your ground wire. If this happens, no GFCI will help you anymore, because there won't be any current over the ground wire. --> Ground short on any device to any touchable part means death.

That's why we have to frequently test our GFCI and have a professional measure grounding-resistance every few years. If it gets to high, you have to put a new ground wire into earth. This normaly costs some 1.000 Euros. So better avoid any unnecessary current over ground.

Thats why I would put a relay directly in the mains supply line of the Printer, directly breaking its supply, and not relying on the GFCI

Edited 2 time(s). Last edit at 06/08/2017 12:52AM by Dancer.
Re: Smoke detector using endstop circuit.
June 08, 2017 07:22AM
Tried and tested

[forums.reprap.org]

I'd agree with others who have commented before no fire safety system should be running off the microcontroller which could be in a fault state when you need it to work.


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Re: Smoke detector using endstop circuit.
June 08, 2017 08:19AM
Quote
DjDemonD
Tried and tested

[forums.reprap.org]

I'd agree with others who have commented before no fire safety system should be running off the microcontroller which could be in a fault state when you need it to work.

I like, in this setup, that when the smoke alarm clears (40 sec after smoke clears) power remains off. If I read the schematic correctly - circuit will continue sending power to the printer when it's power is off. I think it would be the best to power smoke detector circuit directly from an AC/DC adapter and send TTL high signal (when power is on) to the printer controller so system knows the protection is on.
Re: Smoke detector using endstop circuit.
June 08, 2017 11:42AM
Quote
DjDemonD
Tried and tested

[forums.reprap.org]

I'd agree with others who have commented before no fire safety system should be running off the microcontroller which could be in a fault state when you need it to work.

Thanks mate, that is the same module I use but I just could not find that diagram, google is being dyslexic for me!
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