Spasmodic resets - PSU to blame?

I've been doing a lot of printing lately - none of that 24/7 stuff but several hours per day for a few days.

Other than a Panelolu2, my M90 is pretty standard stuff. I have an RPi powered from the power supply so that I can use the Webcam feature of Octopi but not plugged into the MELZI which carries a USB cable connected to my laptop. All prints are from the SD card.

A week or so ago, when I was out of the room, my printer just stopped mid-print. When I got back, the nozzle was sitting on top of the print, temperatures as indicated on the Panelolu display were set to zero and Pronterface running on the laptop told me that the printer was disconnected. Annoyed and puzzled, I set things going again and all went well.

The same thing happened again a couple of days ago - not a clue why.

Unfortunately it has got a lot worse - these spasmodic resets are now more frequent and for no apparent reason, power just stops and comes back on again - the Panelolu display might flash once or twice indicating an on-off-on-off-on situation.

Investigating further, I checked that all power leads were firm in their respective terminals on the MELZI. I swapped the mains lead just in case there was an intermittent fault there but the problem persisted. I then noticed that I was able to trigger this reset by switching the heat bed on. When the bed comes on, its temperature rises for 10 seconds, maybe more and then everything resets. Sometimes I have to switch the hot end on as well as the bed to get the same effect.

Next, disconnecting the RPi seemed to cure it as I was able to finish three short (<30 minutes) prints but that was only temporary - it's happening again.

My thoughts now are that the PSU is on its way out - does that sound a reasonable assumption given that it cuts out whenever a large current is drawn? Can anybody suggest any more fault finding steps which will enable me to find the problem?

Alan

Edited 1 time(s). Last edit at 11/17/2013 04:59PM by Alzibiff.

Usually power supplies shut down until the power is cycled. They don't normally dip out and recover unless the mains is interrupted.

Does the power definitely dip or is it just the Melzi resetting? Perhaps add an LED to see if it flickers.

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[www.hydraraptor.blogspot.com]

Quote
nophead
Usually power supplies shut down until the power is cycled... .

Thank you but I am not too sure that I understand exactly what you mean. Are you saying that ATX power supplies only go off and come back on again if the mains power has been removed and then reinstated? If so, I think that I have eliminated that scenario by swapping out the mains cable.

Further development ..... last night, I physically removed the Panelolu2 and reflashed the firmware, commenting out the "#define Panelolu" line so that the system didn't wait for handshake signals from the non-existent board. I couldn't use the SD card but managed to set off and complete a 45 minute print via USB.

When I get home from work tonight, I will flash the firmware with the version I was using prior to installing the Panelolu and see how things go from there - back to basics.sort of thing.

By the way the LCD display flashes and with everything going back to the 'just switched' state, I suspect that the MELZI IS resetting . On the assumption that disconnecting the Panelolu2 WILL cure things, (fingers crossed), I am wondering whether the problem has arisen because I always print from SD - how much in and out can the onboard SD socket take before it fails I wonder and is there any alternative?

Alan

Yes in my experience ATX PSUs usually shut down until turned off and back on again if they are faulty, or just fail completely. For example when the capacitors wear out you get excessive ripple on the rails and that causes the over voltage detection to trip and causes a shutdown. To get brief dips in power I think it would take a loose connection on one of the components.

If the SD socket is worn out you could use the one on the Panalolu.

Have you tried loading the SD card from the PI, is it any faster than Windows?

Edited 1 time(s). Last edit at 11/18/2013 05:53AM by nophead.

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[www.hydraraptor.blogspot.com]

Hi Alan

From your post above I assume you are printing from the SD card on the Panelolu2? In the past when I have removed an SD card during a print the G code in the buffer would finish and then the software would hang, but the display would not reset (temperatures would also remain set) that was with an older version of Marlin - I have not tried this for along time, but I don't think a worn SD card slot is the most likely scenario. In the past we did have one Panelolu user who has a poor reset switch connection and a printer vibration issue which cause the hardware to reset at random points. Mendel90s don't vibrate much and the Panelolu2 with IDC connectors is more robust but it is worth checking the physical cabling is secure.

Tony

OK - more to report (but still not solved the problem )
I disconnected the Panelolu2 and flashed my pre-Panelolu2 firmware. Result - pretty much the same as before in that all fine and dandy until I switched on the hot end and the heated bed which is when the printer disconnected from my laptop and temperatures set to 0C - that is, as if everything had been reset. This happened on a couple of occasions although the reset didn't occur as soon as I had switched on the current eating circuits, it took up to a minute or so. At one point, it did not reset until almost ready to print. Conclusion - Panelolu2 not to blame.

Next .... I connected an LED to the +5V and GND lines which I had taken to power my RPi. Set the temperatures, watched the LED glowing brightly. All fine and dandy, no problems ...... until about 50 minutes into a print when the LED started flashing and the printer came to a stop. Does this point to the PSU having problems? I cannot think of anything else to do other than replace the PSU unless anybody else can offer an alternative.

Alan

Edited 3 time(s). Last edit at 11/18/2013 12:50PM by Alzibiff.

I've noticed that during bed heating (less so on the extruder), the LEDs that I have illuminating my print area will flicker. My LEDs are connected to one of my Panelolu FETs, which as far as I know just switches my 12V feed directly from the PSU. I've never thought much about the flickering as the LEDs draw less than 500mA per metre, so my 40cm worth should only draw 200mA. I can't imagine that we're anywhere near the limit of what that PSU can pump out, but is it possible that we're causing enough of a ripple that the Melzi gets upset?

The regulation on the 12V rail is not brilliant on PC power supplies so when the bed switches the voltage might swing by nearly a volt. A bit of ripple won't affect the Melzi though as it would have to drop to about 7V before the 5V rail would be affected.

I would try tapping on the PSU to see if anything is loose. Perhaps the mains switch is dodgy?

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[www.hydraraptor.blogspot.com]