Hoping someone can help me…I am making a 3d printer setup on my CNC machine frame. Got everything mounted, gonna use ramps 1.4 and a mega. I got an mk7 extruder setup, and I am ready to start wiring everything up, or so I thought…
The extruder has 2 thick, extra insulated wires, and 2 thin white wires that look almost translucent where they go into the extruder piece. Admittedly the extruder came assembled, so I have a few questions.
Can I wire this directly to the ramps board?
If so which set of wires is the thermistor?
Does polarity matter on either, and if so how to tell positive from negative if they are the same colors?
I found a doc somewhere that implied I needed some sort of intermediary safety board and a thermostat, so not sure if I need to order more parts. If I do need more parts can someone clue me in on what I’m missing?
Thinner wires are the thermister. I don’t think polarity matters, but you’ll notice when your temperature is negative if it does. Or it might not be negative, but it’ll drop when you’re heating it. You’ll need to know the thermister type for firmware configuration. The thicker wires attach directly to the ramps board too.
I would at a guess say the thin wires are the thermistor and the thicker ones are to the heater cartridge/resistor they are wired directly to the ramps board and the polarity does not matter… there is a wiring diagram on wiki…
Polarity doesn’t matter. Thick wire is the heater, thin wire is the thermistor.
Ramps has ports for both.
Make sure you use the voltage the heater is rated for.
Get a smoke alarm and have it in the room the printer is in. The Ramps board handles the temperature control, no external board should be required.
There isn’t a good safety device for these other than buying high quality components, a smoke alarm, and not letting it run unattended.
The thin wires are the thermistor, it’s non-polar, and it should be plugged into whatever is labeled as your hot end’s thermistor.
The thick wires are the heater cartridge. They’re also non-polar. You should be able to wire them directly to your board, to whatever is labeled “hot end heater”, and that’s the component some people may be mentioning as something to run through a “safety board” (which is probably a solid state relay).
That shouldn’t be necessary for your hot end, however. High power heated beds should be run through an SSR, but your electronics should handle the hot end’s heater directly.
It does indeed look like there’s a relay on there, but it appears its mechanical. I guess maybe its recommended but not absolutely needed? It looks like it would probably be a pretty easy board to make, my biggest concern was that I didn’t order a thermostat/thermocouple because everything I read prior only mentioned the thermistor and hotend which I got a pretty good deal on(hopefully its decent quality).
You don’t want a mechanical relay for this kind of temperature control, the frequent on/off switching will kill it very fast. SSRs are made for that kind of thing while mechanical relays aren’t.
