Power resets during boot - redux

It’s definitely a restart because the hunt cycle starts over again after the power cycle.

It’s also not a flicker, the entire unit shuts down momentarily, including the fans, which you can clearly hear at the 17-18s (in the video above).

Just as a data point, I powered her on just now (been off since yesterday afternoon) and it went thru the normal startup without issue. The “clunk” that occurs after the hunt cycle is pretty loud, as heard in this video at ~31s, that’s the moment that the button lights briefly, after which the carriage moves (right after I quit recording):

The clunk is probably the sound of the X and Y motors being energised after receiving a motion plan. No idea why that causes a reset as being constant current they don’t really cause a power surge like a DC motor does.

Agreed, but look at the original video carefully, when the clunk occurs is exactly when the power goes out, and the head moves slightly. It didn’t move in the second, normal startup video.

Was the difference the fact the head was in the correct place in the second video, so didn’t need to move at that point?

Not sure what “correct place” is and how you would tell - it was where it was parked from the last cut before it was turned off.

I think the first stage of homing is to get the logo dead centre under the camera.

Yeah, but there are an extra few seconds after that clunk before the head moves over to the camera.

I just went back and looked, and in the original video, the head moved both times, when the power went off and when it didn’t. Not sure that’s relevant.

Just turned her off and back on, and the “reset” occurred again. Now, thinking thru the possible “update” process, it could have downloaded what was needed after my first power on earlier (it was left on for a while), but then applied it, hence the reset, the second time just now…

That’s not how the process works. It will apply any downloaded update immediately if the device is not in update lock. It only goes into update lock while it is running a job it received from the cloud.

That being said, the last firmware update was over a month ago (1/9/2018), so it is doubtful your machine just received it.

This problem (and that is exactly what it is, a problem - not “perfectly normal operation” ((though, flaky operation is becoming perfectly normal for Glowforge)) ) seems to possibly be firmware related, given the large number of people reporting it.

At least I hope it is a firmware problem, and not a sign of a larger looming hardware issue.

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… and just for kicks, I turned it on again just now (it had been off since my last post ) - reset occurred again, this time without a “clunk”, and the head did not move.

FWIW, I’m an EE and CS major, have had electronics as a hobby for over 40 years, and built several gadgets with a mix of hardware, electronics, and software. This appears to be acting like an overcurrent situation, and as the load from the head motion motors should be minimal, the only other thing I can think of is the coolant pump - which is most likely a simple DC motor?

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That was my first thought, too. The head stepper, lights, fans, coolant pump, and termoelectric cooler (Pro only) are all driven by the 12 VDC supply. The X/Y steppers are driven by a separate 40 VDC supply.

I’ll have to go back and look at my notes, but I don’t recall there being any monitoring of the 12V or 40V supply conditions. There are supervisory devices on the various sources for the control board that are tied directly to the micro’s reset.

The power supply is an interesting design. It uses a first stage regulator to provide 12VDC which runs to a separate DC-DC converter board that outputs the 3.3VDC, 40VDC and HV sources. In theory, if there is an overload on the 12VDC line, it could drop the other source voltages which would trigger a supervisory reset.

I haven’t been tracking it that closely, so I am not sure if this issue is only occurring on Pro models. Is your unit a Pro?

I don’t have a Pro, so I don’t know where in the cycle the thermoelectric cooler powers up, but that could suck up most of the 12 VDC power budget. My knowledge on those devices is limited, so I can’t speculate.

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Really? That is crazy. Normally practice would be to make a 340V rail with a power factor convertor and have one or more down converters off that. It would be very inefficient to run everything off 12V and step it up unless you want to run from a car battery. The reason being losses in rectifiers, etc, are proportional to current squared, not voltage, so driving the whole machine from 12V means a very high current and lots of power loss.

TECs use a lot of power. I have a 40mm one that takes 30A at 15V to give a temperature difference of 10C with 250W of heat going through it. I don’t think the GF one has anything like that ability but I think that is about the right size for a 45W tube.

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I admittedly spent little time on the power supply (cursory at best), and a full examination would likely bear out that your hunch on its operation is more accurate.

The spec plate on the power supply states the 12VDC is good for 32A.


Mine is a pro.

I have a 4-channel digital 'scope, if anyone knew where I could stick it… :smiley:

I highly discourage you from attempting to do anything like that with your Glowforge, ever.

For purely educational purposes, what you’re looking for can be found here.


To add a data point, my GF is continue to do this reset on every power on, and it’s been a few weeks. Then it continues to boot and operate properly. So it’s not a firmware update, and it’s not an intermittent problem, neither of which would repeat every time, but exactly once. I’m stumped. But I hope GF has an idea what’s going on.

Just popping in to say that I have passed this to the team for investigation.

Thanks, Rita. I haven’t used my machine in a few days, but when I turned her on for the first time earlier today, she did NOT reset.

I did, however, have the lid open, which dims the LEDs (negligible) but also prevent certain startup calibration actions, and when it got to the point where the usual “clunk” occurs, it didn’t happen, and power remained on. I’ll try again in the AM even if I don’t have anything to print, with the lid open again.

There was a firmware update released on Feb 26th. They may have addressed this issue.


Ah, but I thought that a reset during startup was expected for an update, so shouldn’t it have done it anyway?

Anyhow, I just fired her up with the lid open again, no reset. I noted that the magic button flash that normally happens around the time of the “clunk” occurred after I closed the lid and the gantry movement started. I need to watch closely next time to see if it flashes when the pump starts up.

It is, but it happens fairly quickly after boot, and not during any of the motion cycles.

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