LCD Loses its Mind

I have this happen on my Printrbot every once in a while. Not entirely sure what causes the spaz out, but it's never effected a print in progress. Once the print is done, I disconnect the printer from the software, turn the printer off and on again, and the problem is solved. Temporarily.

Maybe a power supply dropout / lack of filtering issue. I notice the extruder LEDs are flickering with the heater current as well. Fortunately it doesn't seem like a chronic issue on my gMax, it's only happened once so far.

If that is indeed the case, you could put a relatively large Electrolytic Cap across the 12v inputs from the power supply to the RAMPS board. I would keep that as a last resort though.

Thanks, Ray, I do have 38 years' experience as an electronics engineer I'd probably try some decoupling up on the LCD first to solve that issue, but it doesn't happen too often (twice now).

Hey Julia,
That's always a difficult thing to gauge, especially when not face to face, in conversation. I'm a hardware designer specializing in electronics and C.A.D.
Good call on localizing the cap to the problem area as a first resort.


Have you found a way to make the forums email when a new/ reply post is made?

Yes, there's a preference somewhere in User Control Panel for automatically subscribing to any thread you post to. You can also manually subscribe to any thread you want; there's a button/link thingie in each topic.

Here it is:

Wonderful, thanks for that.

Hi guys.

I've been meaning to make a post specifically to this problem. I have noticed this 'garbled' text comes up every now and then. It specifically comes up when I have a static charge and I touch anything metal on the printer. This means if its either very dry in our workshop or I have a lot of static charge and I adjust the z-axis couplers, touch the LCD screen bolts or touch the metal frame. Because of this i think it is some sort of grounding issue which may involve the LCD screen.

The good news is (thanks to a great backer who we will call MW) we have a solution. If you see this garbled text during a print 90% of the time you can remove the SD card, reinsert it and the text is back to normal. This also works when you find your print stops for no reason and either says 'waiting for user input' or says nothing. I have found this is not a result of the 70cm ribbon cable as sone sources have suggested.

Hope this helps.

I witnessed it happen yesterday coinciding exactly with a rapid stepper move, leading me to think (despite Gordon's comment about it not being related to the ribbon) that it could be due to capacitive/inductive coupling of stepper motor EMI into the ribbon. The ribbons run in close proximity to a lot of cables carrying high current pulses with (presumably) fast risetimes, and I don't think any of the cables are shielded. I've not noticed any correlation to my touching the printer and transferring static charge, and I'm very aware when that happens since I work around electronics all the time.

Since I'm now running the machine from a PC it's less of an issue that when I was running from the LCD alone, but it's still pretty annoying.

Very interesting. I'm not pretending to be an electrical engineer rather an architect with an electrical fascination and interest. We can send you shorted ribbon cable (i think they are 35mm) to see if this resolves the issues. We have also been looking into good-quality shielded ribbon cable which has come at an extremely high price so far (over $20 per cable) which does not seem like a viable solution at this point.

Shielding the stepper cables is probably a more viable solution than shielding the ribbons. A quick sanity check would be to remove the LCD and physically separate the ribbons from as much other wiring as possible and see if the problem occurs.

The stepper cables actually are shielded. They are USB cable which come in 500ft spools. We do all the crimping here on-site so I don't think they are the problem. The endstop wire is actually headphone wire which again doesn't seem to cause interference due to its proximity and current.

We've found the problem to be something with the LCD SD card slot due to the fix with removign the card. Any other ideas?

OK, cool that the stepper cables are shielded. I'll take a look at the LCD board when I get a chance. There are no decoupling caps visible on the back side, but I haven't taken it apart yet.

I agree that it could be the caps. I believe this is the board if it helps http://reprap.org/wiki/RAMPS_1.3/1.4_GA ... with_Panel

I want to touch base on Gordon's post at the bottom of the first page. I've had this happen at work with the Printrbot Plus and we never use an SD card, so that happened while it was running over USB.

If it is true that inserting an SD card solves the problem, perhaps we need to find the area in the firmware that is run when a card is inserted and set that up to be activated somehow, perhaps a separate reset button just for this, or have that run every time the knob is actuated.

I'd prefer that software explanation than the alternative, which is that the hardware of the card is somehow exposed to ESD, which doesn't seem feasible.

Today I moved the LCD module and its cables away from the printer and its cables. All day long I tried to make it malfunction, by touching the printer after walking across carpet, by slinging the X and Y axis drives around, etc. Until a moment ago I couldn't get it to spazz out - it seemed much more robust and I thought I'd identified the problem as cable noise pickup, but then one last time I touched the printer frame after walking on carpet, and - bingo! So it's looking like ESD. Or maybe cable noise pickup and ESD susceptibility?

Messing with the SD card is cause of the garbled text for me.