Advice for combined sensor and end stop wiring.

fcwilt

While it may be too late for your printer it is a better option to use NC switches.

Frederick

dc42

@exerqtor said in Advice for combined sensor and end stop wiring.:

So i was just woundering if it dosn't matter what pin i on the Duet i snag the VSSA from? It's only going to supply two thermistors so i guess it won't matter much?

Yes you can share the VSSA connection between multiple thermistorss.

Fans, hotend and hotend heater share the same VIN (running VIN fans obviously) can't se any issue in that?

Yes, that's OK. Onviusly you need to take the VIN from a connector that can supply the total current - so not a fan connector.

The other thing is that the X and Y endstops both live on one of the Y carriages (corexy machine) and are simple micro switches(NO), so i was wondering if i could just use a common ground source for the two and save a wire there?

Yes. As already mentioned, NC switches are preferred.

The last thing is that it's going to use a klicky probe (also a NO microswitch) for bed leveling, and i was wondering if the best way to wire that up is just by using the "Z_PROBE_IN" and "GND" on the Z probe header, in that case how should it be defined in the M558?

Yes, and again a NC microswitch is preferred. Configure it using P8 in the M558 command.

Exerqtor

@fcwilt

Nothings carved in stone yet, but why would NC be better?

alankilian

@exerqtor said in Advice for combined sensor and end stop wiring.:

@fcwilt

Nothings carved in stone yet, but why would NC be better?

If a wire falls off a NC switch or you have an intermittent connection it will trigger early which will stop movement safely.

If those things happen on a NO switch, it will fail to trigger when homing and you will crash your mechanics.

If you have electrically-induced noise on the endstop wires caused by stepper motor wires or a heated bed, it <may> cause the endstop to accidentally trigger. NC switches are more immune to that kind of noise.

Exerqtor

@alankilian

Okey that's fair

Exerqtor

Now that i've got everything wired i have some issues when it comes to configuring / getting the thermistor to work. It's a "CMFB103F3950FANT" thermistor connected to pin35 on the expansion header and to the VSSA pin on for the E1 temp input.

I've configrued the sensor like this:

M308 S5 P"e2temp" Y"thermistor" T10000 B3950 A"Chamber"

But when i send M308 S5 i get the following:
"Sensor 5 (Chamber Temp) type Thermistor using pin (e2temp,duex.e2temp,exp.thermistor3,exp.35) reading 2000.0, last error: short-circuit in sensor, T:10000.0 B:3950.0 C:0.00e+0 R:4700.0 L:0 H:0"

I've checked the wiring all the way down to the board and it's ok. And between the leads on the board end i meassure 10,2K ish ohm at room temp so the thermistor seems to be working fine?

T3P3Tony

@exerqtor if you are plugging directly into the expansion header then you are missing the pull up to ADVREF (pin 41 on the expansion header. You can use a 4k7 0.1% resistor (as used on the other Duet 2 thermistors) or a 2k2 0.1% resistor (as used in the newer Duex5s). set the R parameter in the M308 command to match the pullup you use (4700 is the default).

Exerqtor

@t3p3tony

AHA! Well that explains why i couldn't get it to work! I moved it to "e1temp" instead then since i'm not using that input atm (haven't got any of those resistors at hand).

BUT as a follow up question, if i want to change it to sensor "S4" instead of "S5", should i send

M308 S5 P"nil"

to free up the pin? Or is it some other way of doing that?

T3P3Tony

@exerqtor you no longer need to free up pins in the way you mention unless you have already allocated them to something else (for example in test). As long as you so not allocate S5 to anything in config.g or other macros (or manually during testing) then it wont be allocated. The allocations don't survive a reboot, rather they are restored from config.g.

so just changing this line in config.g should do the trick:

M308 S4 P"e1temp" Y"thermistor" T10000 B3950 A"Chamber"

Exerqtor

@t3p3tony

The "problem" is that I had allready assigned "e1temp" tro S5, so i had to do " M308 S5 P"nil" " first, but now it works.

Thanks again