Thermocouple Faults to 2000

[wilriker]

@dc42 said in Thermocouple Faults to 2000:

Safety, in case a fault develops inside the PSU. ATX PC PSUs always have this connection internally.

OK, I can see that.
But there comes one question instantly to my mind: if I connect negative output to mains ground as shown in your picture wouldn't those ~12-15A needed to heat up the bed also take this route? I ask because I have my PSU connected to mains with a standard PC power cable that has 3x0.75mm² inside. One for L, N and PE. That would mean a single 0.75mm² would then have to take up to 15A of current. That seems like a good idea to start a fire to me.

So what am I missing?

[Billsrf]

@phaedrux , LOL, Thank you!!!

[dc42]

@wilriker said in Thermocouple Faults to 2000:

@dc42 said in Thermocouple Faults to 2000:

Safety, in case a fault develops inside the PSU. ATX PC PSUs always have this connection internally.

OK, I can see that.
But there comes one question instantly to my mind: if I connect negative output to mains ground as shown in your picture wouldn't those ~12-15A needed to heat up the bed also take this route? I ask because I have my PSU connected to mains with a standard PC power cable that has 3x0.75mm² inside. One for L, N and PE. That would mean a single 0.75mm² would then have to take up to 15A of current. That seems like a good idea to start a fire to me.

So what am I missing?

The current will only go down the mains ground wire if the negative wire from the PSU to the Duet breaks and there is another path from mains ground to the Duet ground such as a USB cable.

[wilriker]

@dc42 said in Thermocouple Faults to 2000:

The current will only go down the mains ground wire if the negative wire from the PSU to the Duet breaks and there is another path from mains ground to the Duet ground such as a USB cable.

OK, I have no USB connection to the Duet and my connection PSU<->Duet is redundant with 2x2.5mm² for GND and Vin each (so a total of 4 wires). Also these wires are not moving so it is rather unlikely that this connection will break (but unlikely does not mean impossible).

I still don't understand why only in your described case the current will go to protective earth (not sure how it is done in the UK but in Germany this is different from the Neutral wire) because - with the exception of the rather small wire gauge - this is supposed to have a very low impedance so that current can take this route for safety reasons.
But then again electricity sometimes does things I don't understand and I am nowhere near to be an electrician so I gonna trust you here and create this connection.

[Billsrf]

Thank you both!!! I was "code" blind and completely over looked the (-) in front of my Z-probe home number.

[Billsrf]

Everything is working as it supposed to except 1 issue. When I do home all, it comes to the middle probes down to 5mm then raises up to 10mm on the DWC screen. I load a file and it crashes into the bed... I'm not under standing how this happens. Once again I think I am missing the obvious here.1_1533928385714_homez.g 0_1533928385713_homeall.g

[Phaedrux]

@billsrf In the files you posted you're still using negative absolute values to move to the center of the bed. So I'm surprised it is going to the middle of the bed as you say.

G90                       ; absolute positioning
G1 X-530 Y-560 F6000      ; go to first bed probe point and home Z
G30                       ; home Z by probing the bed

It would help to see your M558 and G31 commands from config.g to know how your probe is being configured.

[Billsrf]

Sorry, sent the wrong files! Here they are. Thanks for the help.2_1534017286697_Duet Config g.txt 1_1534017286697_Home All.txt 0_1534017286695_Home z.txt

[Phaedrux]

I think your issue may be your G31 command in config.g

G31 P500 X570 Y575 Z5

The X and Y values should be the distance between the probe and the nozzle tip in millimeters.

[Billsrf]

@phaedrux I'm confused! What does the XY value have to do with the nozzle going straight down in to the bed on Z axis?

[Billsrf]

Here is where my probe is zeroing to. When I start a print, it dives 5mm as it should. Then it dives another 5mm crashing into the table. This is where the problem is at. why is it diving twice?

[Billsrf]

Got it!!! Missed a crucial step during the Zero height setup.

[Phaedrux]

@billsrf said in Thermocouple Faults to 2000:

@phaedrux I'm confused! What does the XY value have to do with the nozzle going straight down in to the bed on Z axis?

It may not have anything to do with your current issue but it may cause further issues down the line. Such a large offset could cause your printer to think it is printing half a meter off your build surface when it probes at the edge. Generally the probe is as close to the nozzle as possible. I doubt it is half a meter, but I don't know your printer.

Glad you got it sorted out though.