marlin AUTO PID tuning help

so im trying to get my printer to do the auto tune feature... the hot end AT PID runs great... but when i run my AT PID for the bed it starts ok then quits... it then responds with an error, like :::
running the command M303 E-1 C8 S90

ok B:62.96 @:127
ok B:62.96 @:127
PID Autotune failed! timeout
ok T:23.0 /0.0 B:63.1 /0.0 T0:23.0 /0.0 @:0 B@:127


i tried to figure out what the deal was, but to no avail i had to email nophead about it... and no, i wasnt running the PSU he sends in the kit... i had a wintact wp507f12 12v30a PSU... but for some reason it wouldnt start even with the green wire grounded all the time, and when i did start up i only got 8.4 v to the bed... so i ditched it and got a 400w 12v25a PSU, i added the load resistors to the 3.3 and 5v lines, reassembled and viola, i have 12.4 vdc at the ramps board...however when i run the AT PID for the bed im only getting 11.6 - 11.8v ... then the error as above... PID tuning is enabled in the marlin, and everythign seems to be ok other wise... What am i missing? I tried google and youtube for the error but cant find anything...

Edited 1 time(s). Last edit at 01/11/2015 12:12AM by 09zx-6r.

What is the actual voltage across the bed terminals?

What is the resistance of your bed?

If you disable bed PID and set the temperature to 90C, how long does it take to reach it?

Seems like it only gets to 63C in the time allowed, which looks to be 10 minutes: https://github.com/neildarlow/Marlin/blob/Marlin_v1_Mendel90/Marlin/temperature.cpp#L313. It should heat faster than that.

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[www.hydraraptor.blogspot.com]

ok so i ran it again...
PSU is outputting 12.25vdc to ramps board with NO load.. when running heat bed its sending 11.92vdc...
bed resistance is 2.1 ohms...

voltage to bed is 11.76vdc...

i disabled BED PID and re-ran it to 90C thru pronterface... well it didnt work to well... the thermistor read 72 of 90 and it took 15:37 (min:sec) to get there, i would have kept it on but when i put a thermometer on the bed it was 10C higher than the thermistor reading...

my thermistors are epocs 100k and marlin is set to 1... and another thing i noticed, during cooling stage the thermometer is spot on below 50C with the thermistor reading...

either way, its taking way too long... any suggestions?

also, nophead i didnt want to bother you with this and didnt think u would be the guy to respond... youve been bothered by me enough thru gmail (johnathan.09zx6r) but i do appreciate it...

nophead, the PCB for the D-sub connector, has the motor terminals, what phases are the color order? the PCB is black, green, blue, red... but my motor colors are Red,Black (A1A2) Blue, Green (B1B2)... is the order on your PCB in correct sequence or do i need to change it? how do i test the extruder motor?

Edited 4 time(s). Last edit at 01/11/2015 05:01PM by 09zx-6r.

The bed resistance is the problem. The ones we ship are about 1.1 Ohms.

The motors I use have coils labelled AC, BD : black green, red blue so no real correspondence.

As long as one coil is connected across the first two pins and the other across the second two pins the motor will spin. If it goes the wrong way swap either pair.

To test the extruder cold you need to send a G code that disables the cold extrusion prevention. I can't remember off hand but it will be in the manual.

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[www.hydraraptor.blogspot.com]

what type of heat bed do u supply? im using the MK2B prusa bed...

i have a feeling that my power supply isnt enough on the voltage side... im thinking of a dedicated 12v30a supply and not a ATX PSU, or at least the one i have in there...only because when its on and no load the PSU is outputting 12.25 to the ramps board but when loaded with anything on, its 11.7 - 11.9 at the bed, extruder, motors, and when everything is powered on, i get 9.81 vdc output... so regaurdless of the bed resistance, i think the PSU is the issue...its a china cheapy i had layin around...

in addition, what could cause the heatbed to have higher resistance... i went to the reprap wiki and it said it should be 1.1-1.2 ohms... but i have 2.7... how can i reduce it or should i get a new heatbed...
nophead, you sir are a huge help and i appreciate it...

as for the motor wiring, iv made a switcharoo to the colors, red black pairs in the first two terminals, and the blue green in the second terminal set... my motors are paired as red black, and blue green... so i think this should work out ok...

Edited 1 time(s). Last edit at 01/11/2015 08:01PM by 09zx-6r.

FIXED IT,,, WOO HOO GO ME!!!

so the bed was 2.7ohms from pad 1 to pad 2... however, if i tie pad 2 and 3 together and retest, i get 1.6 ohms from pad 1 to pad 2&3...

so i soldered it up, re tested the AT PID, and VIOLA... 12vdc at the bed and reaches 90C in 3:27 (min:sec)... Passed PID autotune...



THANKS NOPHEAD