Heater bed always on?

daftscience · Post by **daftscience** » Mon Mar 25, 2013 4:56 am

So I just finished a print and noticed my heater bed didn't shut off. And, I can't shut it off. Rebooted, reloaded firmware, unplugged everything (except for power) and the red LED on the board is always on. Anyone else run into this?

Tom

mhackney · Post by **mhackney** » Mon Mar 25, 2013 9:15 am

What does your thermistor say? Is the bed heating up? Maybe you have the LED installed backwards.

daftscience · Post by **daftscience** » Mon Mar 25, 2013 9:44 am

Yeah, It's legit on... Heats up and the thermistor is reporting the correct temp. both rambo LED and onyx led are on. But it won't shut off when I tell it to, restart the electronics and even pull the thermistors (I thought that would definitely shut it off.)

The only time the led on the rambo goes out is if i DC the onyx... but I don't know if that is normal (If the bed temp is set and there is no hotbed attached should that LED be on?) I'm thinking the output might be acting up?

FWIW, I did make sure to really double check when I masked the hotbed for the heat dissipator. However, I noticed I was getting static build up and got a few good zaps when I went to remove pieces. That problem went away a while ago, and this one just started today (many hours of printing in between) Did you know if that's an issue? I've thought about grounding the aluminum plate but haven't.

dbarrans · Post by **dbarrans** » Mon Mar 25, 2013 10:47 am

LED installed backwards? That doesn't make sense. It's a diode. It only works one direction. If its power is reversed, it will stay unlit.

- dan

cambo3d · Post by **cambo3d** » Mon Mar 25, 2013 11:20 am

daftscience wrote:So I just finished a print and noticed my heater bed didn't shut off. And, I can't shut it off. Rebooted, reloaded firmware, unplugged everything (except for power) and the red LED on the board is always on. Anyone else run into this?

Tom

can you post a picture of your wiring at the board

mhackney · Post by **mhackney** » Mon Mar 25, 2013 11:32 am

I have not observed static build up when printing. It might depend on substrate (glass, tape, hairspray, etc), material and temp & humidity among other factors though.

So, to be clear, was the heat bed working properly before and now all of a sudden is staying on?

Oddly, the red heat LED on the RAMBo should light even if the Onyx is disconnected. Not sure why yours goes out.

When you say it is always on, is it heating out of control or staying at a fixed temperature you specify?

daftscience · Post by **daftscience** » Mon Mar 25, 2013 12:08 pm

mhackney wrote:I have not observed static build up when printing. It might depend on substrate (glass, tape, hairspray, etc), material and temp & humidity among other factors though.

So, to be clear, was the heat bed working properly before and now all of a sudden is staying on?

Oddly, the red heat LED on the RAMBo should light even if the Onyx is disconnected. Not sure why yours goes out.

When you say it is always on, is it heating out of control or staying at a fixed temperature you specify?

Correct, it was working perfectly fine. I can't think of any change I have made that would cause a difference. I logged about 15+ hours of printing with no issue using your plate.

I thought that the led used to stay on when the plate was disconnected... Soo that makes this issue seem much more confusing.

Luckily it can never heat out of control... I assume if I had enough power it would go well above 120. If I set the temp to 70 it stay's on regardless of being above 70.

mhackney · Post by **mhackney** » Mon Mar 25, 2013 12:13 pm

Ok, so it sounds like your thermistor is reading the temp correctly too. And I assume the hot end is working properly?

Did you make any changes to pins.h in the past week?

daftscience · Post by **daftscience** » Mon Mar 25, 2013 12:44 pm

Yup, hot-end is working properly, and no changes to firmware. That's actually re-uploaded directly from a clean copy of polygonhell's repetier. What's getting me is that the led goes out I unplug it. :/ I'm printing right now and watching it very very closely. When it's done I'll try uploading the merlin firmware and see what happens there.

The LED labeled Heat 1 is lit too. The spot to the right of the fan plug.

daftscience · Post by **daftscience** » Wed Mar 27, 2013 4:16 am

Alright so here is a little update. I measured the resistance between the heater bed and terminals and I was getting somewhere along the lines of 500ohm between them. So I'm leaning towards a partial? or weak short? if that's a thing. It would also explain how it randomly start's behaving.

I've pulled the heater plate and put extra kapton tape around where the terminals are soldered. I also tripple checked for any scratches on the heater bed and vias that might be causing shorts (I don't see any).

I think the short might be caused by the screws... I'll keep investigating.

mhackney · Post by **mhackney** » Wed Mar 27, 2013 8:25 am

One suggestion is to hook up the Onyx and do not attache it to the base and do not put anything on it (glass/aluminum plae, etc). Then test it. If it is a short from stress or an external jump, that would be eliminated. Carefully check the traces on the Onyx too to make sure they are not pulled up, etc.

daftscience · Post by **daftscience** » Wed Mar 27, 2013 9:55 am

The measurements were from touching the aluminum plate to the terminals on the onyx. Right now I'm trying to solve another issue all together :/ AHHHH lol. http://forum.seemecnc.com/viewtopic.php?f=54&t=1426

If I still have the issue after that I will definitely try your suggestion.

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