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LCD flickering like crazy, any idea why?

Posted by vetteguy112233 
LCD flickering like crazy, any idea why?
November 10, 2013 04:51PM
Makerfarm I3, 8" Ramps 1.4......

My LCD screen is flickering and it's driving me crazy. I've tried 2 different power supplies, the second one had the 2, 4pin connectors and is rated to 20A on the 12v rail. My first one only had 1, 4pin connector, so I had to use one of the other power wires, but either way the LCD flickers with both power supplies.

I've contacted Colin and he said he doesn't know what the problem is.

Edited 1 time(s). Last edit at 11/10/2013 04:51PM by vetteguy112233.
Re: LCD flickering like crazy, any idea why?
November 10, 2013 06:03PM
Is it just the backlight coming and going or does the screen go nuts? If it's the screen then a few things to check:

1) Make sure the cables are all intact. Ribbon cable is easier to damage than you might think.
2) Check the solder joints on the board between the Ramps and the cables.
3) Same with the solder joints on the Ramps and on the Mega.

If it's just the backlight (text stays ok) then check:

1) Solder joints on the contrast adjust pot and the pot it's self (adjust it a little and see what happens)
2) The connector between the LCD and the main board

I'd bet 3" of slightly used filament that it's a dirty spot on the pot. smileys with beer. If the LCD module looses power even for a second the text goes nuts. Same is true if you spark it (it's low humidity ESD season again ..).
Re: LCD flickering like crazy, any idea why?
November 12, 2013 09:00AM
Try adding a fan to the ramps maybe your arduino is overheating and is resetting
Re: LCD flickering like crazy, any idea why?
November 12, 2013 09:16AM
If the Arduino is dying, the info on the screen will get messed up. If it's just flicker (no garbage) then it's in the lighting or contrast circuits on the display.
Re: LCD flickering like crazy, any idea why?
November 12, 2013 12:03PM
I have flicker on my LCD screen that definitely corresponds with whether the hotend is receiving power or not. I strongly suspect the voltage on my RAMPS board isn't as confined as it should be. It hasn't seemed to effect the printing process at all, though. Is this what you're seeing?
Re: LCD flickering like crazy, any idea why?
November 12, 2013 03:15PM
The LCD *should* be getting power from the +5V line. That line normally comes from the regulator on the Mega board. If the 5V regulator is dropping enough to impact the LCD that's not a good thing. The regulator should be OK to +7V on it's input. It's input is the +12 line to your hot end. If it's getting to +7 there is something very wrong with you power supply or your board.
Re: LCD flickering like crazy, any idea why?
November 12, 2013 06:23PM
Uncle Bob, I can't disagree with any of that. Let's open this can of worms for a moment, which you're welcome to close again by ignoring it or polite request.

I'm running off a 420W Antec Earthwatts power supply, and a line from its 5V rail is definitely what is powering the LCD. (ATX 5V --> ramps aux pin --> mega board) I've completely removed the RAMPS D1 diode that would have otherwise been providing the power, and I didn't do so neatly. (I've totally replaced D2, which I fried while checking voltages uncautiosly.) I've got a thread on here somewhere discussing my issues, including false indications of *hotend* MINTEMP when starting the *heated bed*, unless the hotend is already reading about 25C or so. My RAMPS board, I suspect, has always been a little flighty, and I look forward to starting with something new for this next one. This PC power supply might not be particularly well suited for this job, either.

If any of this sounds like a known issue, I'd be happy to listen with the emotional detachment I now consider mandatory for this particular issue. confused smileyangry smileycool smiley

(Sorry to hijack this, vetteguy. Jump back in here and I promise to do what I can to help.)
Re: LCD flickering like crazy, any idea why?
November 12, 2013 06:33PM
Ok, so that's a bit of a non-standard setup on a Ramps. In your case either the connection to the +5 is *slightly* flaky or the same is true of the ground return. Since it flickers with the hot end power, I'd bet on the ground return in your case. With your setup (unlike the standard Ramps) the ground drop back to the supply will get directly into your +5. With a standard Ramps, the +5 is regulated to the local ground and it does not vary if the ground back to the supply moves a bit.
Re: LCD flickering like crazy, any idea why?
November 12, 2013 07:59PM
Thanks, Uncle. I can't confirm or deny what you're saying, but it sounds like a good explanation. Back when I still had my D1, I could only get my LCD to work if I also had the Arduino powered via USB (which defeats the purpose.) I was getting too low voltage out that way otherwise. Given what I learned checking pins, I suspect that I have a short somewhere. It seems like it might be in the PCB, as odd as that sounds. I sure can't find anything in the nearby solder joints.

Rather than ramble on like a crazyperson, I think I'll see if I can make the whole thing moot with a new RAMPS. Troubleshooting this old one is no longer as much fun as it used to be.
Re: LCD flickering like crazy, any idea why?
November 13, 2013 04:42AM
Bum pcb's are a possibility. Ramps boards without the stepper drivers are pretty low cost. I keep a couple spares around. They take a while to cheap ship from far far away. Having one to swap in and out makes troubleshooting a lot easier.

As I've mentioned a number of times, I'd dump the PC power supply on most of these printers. An industrial 12V 30A supply is pretty cheap ($44 or less). They are much better suited to this sort of application.
Re: LCD flickering like crazy, any idea why?
November 13, 2013 09:03AM
Quote
uncle_bob
I'd dump the PC power supply on most of these printers. An industrial 12V 30A supply is pretty cheap ($44 or less).

Yup, and I'm gonna. In fact, I'm going to give 24V a whirl, but that's a discussion for numerous other threads. I made the choice to go with the power supply when my objective was to minimize cost. In retrospect, that decision cost me a lot more in time than it saved in money, but I learned a lot in the process. I wouldn't recommend the ATX route to anyone but the most price sensitive who already have a suitable one on hand.
Re: LCD flickering like crazy, any idea why?
November 13, 2013 09:48AM
If you do decide to go to 24V, be very carefull. The supply of 24V heater cartridges for hot ends seems to be pretty limited at the moment. That may be due to a production problem with them. Also figure out what the plan will be for fan power and your Mega. A 12V / 24V hybrid system may be the best answer. Low power 12V industrial supplies are dirt cheap (like $10 to $15 for 1 to 4 amps).
Re: LCD flickering like crazy, any idea why?
November 13, 2013 03:58PM
I have noticed that when I turn on my hotend that tends to stop the flickering, but I've also noticed that it returns at random times. Lately I've noticed it flickering even more during actual printing. My LCD screen isn't messed up at all, I can always read everything.
Re: LCD flickering like crazy, any idea why?
November 13, 2013 05:07PM
I'm assuming you haven't modified anything, so the printer and wiring configuration is stock. If so, your LCD runs off of the +5 from the Mega board regulator. Power goes from the mega to the Ramps, from the Ramps to the LCD adapter board. From the adapter to the ribbon cables. Cables to LCD board. LCD board to display. Somewhere in that set of "stuff" is a broken or loose connection. It could be a broken wire, a bad solder joint, a bum connector, or a defect inside the LCD display.

Simple (because I don't have to do all the work) way to check it - grab a DVM and start monitoring +5 to ground along the path. At some point you will find the +5 bouncing around. What ever is between that point and the regulator is suspect.
Re: LCD flickering like crazy, any idea why?
November 13, 2013 05:16PM
Your prefered maker shop may be out but there are plenty of quality 24v heater cartridges in the channel at the manufacturer/distributor level. A 24v psu is a definite advantage for bed heating. High end builds are migrating to 24v and I'd reckon we'll see more support for 24 volt boards that can power the AtMega.
Re: LCD flickering like crazy, any idea why?
November 13, 2013 06:31PM
I've looked at a couple of places for the 24V units and they all seemed to be out of them. Maybe nobody was buying them. I agree that 24V is a nice way to go for a couple of reasons, it's just got a couple of things you need to carefully work out. It would be nice if a 7808 dropped onto the Ramps board more easily.
Re: LCD flickering like crazy, any idea why?
November 14, 2013 10:58AM
I also just noticed that the motor underneath/at the back of my print bed is making a weird high pitched noise that perfectly matches the flicker of the LCD screen during warm up. I noticed this when I first turned on the printer, at some point it releases control of the motors and you can move them manually, but while it still had control of the motors it was making that noise.
Re: LCD flickering like crazy, any idea why?
November 14, 2013 01:31PM
What vetteguy is describing is *exactly* like what I experience in my everyday operation of my printer, with the exception that it doesn't really bother me.

That said, if I remember to check the voltages, I'll let you know what I learn.

FWIW, I think the stepper noise is a symptom unrelated to the cause.
Re: LCD flickering like crazy, any idea why?
November 14, 2013 02:08PM
Karmavore, thanks for the info. The only reason it bothers me is because I'm worried either I've hooked something up incorrectly or my power supply isn't doing it's job. This is my second power supply with the same results.

My previous power supply didn't have the extra 4 pin connector, so I used a regular connector. This newer power supply did have the extra 4 pin power connector, so I used the black and yellow from it to go into the other side of the ramps board.
Re: LCD flickering like crazy, any idea why?
November 14, 2013 02:24PM
My LCD does not flicker at all under any operating conditions.
Re: LCD flickering like crazy, any idea why?
November 14, 2013 08:29PM
Quote
vetteguy112233
The only reason it bothers me is because I'm worried either I've hooked something up incorrectly or my power supply isn't doing it's job.

Yup, I went through this phase, and I was right to be worried. Not everything was right with my ramps board, and it was (afaik) delivered to me not right. The LCD, for instance, would not work because a non-zero but insufficient voltage was making it to the LCD. And I've found voltage on a pin where it definitely should not be. I didn't get the LCD functional until I removed D1 and powered the Arduino from my ATX supply's 5V rail. Everything I currently need to work works now. And for what it's worth, my flicker is a just subtle change in brightness.

So don't think of my post as me telling you that everything's ok. It's more like the guy in the support group who is proudly leading a functional life despite his affliction.

That said, I'm replacing my board. $20 to avoid a weekend's frustration is a no-brainer, and then I'll have a board to take greater risks with.
Re: LCD flickering like crazy, any idea why?
November 15, 2013 06:54PM
Which one is D1, I'll check to see if I have voltage there as well.
Re: LCD flickering like crazy, any idea why?
November 15, 2013 07:17PM
D1 is the diode that connects the +12V rail to the input of the 5V regulator on the Mega board. If it's missing you don't have a Mega running unless you either have another +5 supply or a computer hooked in. On some boards it comes loose and you have to solder it in. It's a 1A diode so it will handle a lot more current than the poor little regulator on the Mega board.
Re: LCD flickering like crazy, any idea why?
November 17, 2013 10:12AM
Uncle bob, where is the contrast adjustment? is it the little hole under the control knob for the LCD or is it on the RAMPS board?
Re: LCD flickering like crazy, any idea why?
November 17, 2013 10:16AM
If you have a contrast adjust it's going to be on the LCD end of things. It should be a little pot. On most of them it's around back somewhere and not on the face side of the assembly. You know you have the right thing when the display goes from all black(isn) to all white(isn) as you rotate the pot.
Re: LCD flickering like crazy, any idea why?
November 17, 2013 10:27AM
It was worth a shot, I found it on the back side of the LCD and adjusted it many times back and forth to see if that would stop the flickering, but that didn't change anything other than the contrast of the screen.
Re: LCD flickering like crazy, any idea why?
November 18, 2013 08:01AM
If you spun it a couple times that will wipe off what ever crud might be there. It's a simple enough thing to check. As a bonus, you now can set the contrast to be optimum for your normal viewing angle.

I'd clip lead the DVM onto the +5 and ground on the display board. Watch the +5 and see what it's doing when you see the filcker. The DVM may not be fast enough to catch every burp, but it shouuld show something.
Re: LCD flickering like crazy, any idea why?
March 15, 2014 08:51PM
I had similar symptoms about a week after installing a Raspberry Pi running OctoPrint. I'm theorizing that the WebCam and other power draw was forced to come from the printer because the PC was not meeting the needed amperage. This must have put stress on the hardware because I never had trouble running straight from the SD card before. I also noticed that pulling out the SD card had an effect on the flickering as well. As I fix, I bought an approved powered USB hub from the Raspberry Pi project site and made sure that everything was hooked in through that powered hub. This got rid of the flickering and made the system run great. I hope this helps...
Re: LCD flickering like crazy, any idea why?
November 03, 2016 09:35AM
I have a very simple solution. If you are using octoprint or some other usb and are powering ramps 1.4 via 12v then open up your usb data cable and cut the vcc +5v red wire. this will clear everything up as the usb device controlling your machine will no longer draw power from your ramps board. A diode would probably also help, but cutting the +5v only works just fine.
Re: LCD flickering like crazy, any idea why?
October 18, 2017 06:53AM
+1 for edgeconsults solution

With one caveat - While 99.9% of USB cables have internal wires coloured Black, white, green, red, and there is a colour coding standard where Red = 5V...

DON'T ASSUME that this colour code has been respected inside a random sealed-plug USB cable from Far, Far Away...

I spent a frustrating time debugging an implementation, where the USB cable had 5v=black!!!

The USB cable was otherwise perfectly well made, had I not cut it I would never have known. I have since checked and found a lot of my similar short cheap blue cables that come with Arduino clones have similarly random internal wiring. I am always amazed at how reasonable quality items can be for such low prices, just don't expect standards to be followed anywhere they are not plainly visible!
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