emonGLCD display not working

I have just built a emonGLCD and loaded up the Ardunio software.

I lknow that data is being recieved as the LED's are changing from red to green etc, the backlight is also on, but my screen is totally blank.

Any idea's what could be the problem ?

glyn.hudson's picture

Re: emonGLCD display not working


This issue has been resolved via email. Thanks to gb09566's troubleshooting skills the issue was identified as a GND plate link on one of the pads of C8 on the rear of the board caused by a PCB manufacturing defect. I will be in touch with the manufacturer to try and resolve this issue. Please post if you have had a similar issue.

So far this is the first problem thats been reported in the 30 or so emonGLCD's sold and 10 or so that we have built up ourselves.  

For referance the GLCD voltages as measured on the bottom 20 pins on the GLCD are: 

1= 8.27v       

2= 7.14v       
3= 5.94v      
4= 2.53v        
5= 1.32v       
6= 0 v          
7= 2.35v        
8= 8.47v        
9= 5.76v        
10= 2.58v        
11= 11.1v        
12= 12.53v       
13= 0v              
14= 4.86v          
15= 4.86v           
16= 0.12v           
17= 0.03v                 
18= 3.27v           
19= 3.27v  

20= 0v       

The voltage will obviously change depending on what is displayed on the LCD. The voltages above were measured when displaying a single CT power measurement on the screen. The imporatant thing to note is that only pins 6, 13 and 20 should be 0V. A fault could be present if any of the other pin voltages are measured to be 0V

The GLCD can be tested before soldering by inserting the bottom 20 pins (the top 6 pins are only there for stability) in the board then bending them gently at an angle to make contact when powering up the board. Before doing this upload a a demo sketch, I recomend the JeeLabs GLCDd demo that's included in the GLCD library. All pins must make contact as the board is powerd up. 

AndrewL's picture

Re: emonGLCD display not working

Hi there - I'm having the same issue, 

Leds going on and off, but screen blank?

I have run through the voltages on the pins and they are all close to those above, although 16 seems to be almost zero.


Any tips?






billmeds's picture

Re: emonGLCD display not working

Hi, I'm also having a similar problem. enomGLCD was working perfectly for about 2 weeks with solar PV monitor sketch.

PCB is version 1.4. I have checked that capacitors C13 and C14 are mounted correctly (i.e. opposite to polarity shown on silk screen). I've also checked the LCD pin voltages and they are similar to those above and pins 6, 13 and 20 are the only ones that are 0V. I've also checked all the solder joints on the lcd.

The emonGLCD works briefly when powered up but after a few seconds the display goes blank. The sketch continues to run as the LEDs function normally.

Any suggestions?

Thanks, Bill

Robert Wall's picture

Re: emonGLCD display not working

Have you checked for dry joints? It would be unusual for a dry joint to show up after only 2 weeks, but it's the next thing to check if you haven't done so already. The symptoms are similar to the problem that the reversed capacitors caused, which caused the voltage multiplier to not work properly. And that it works on power-up and then fades is consistent with that.

I assume you're also checked for anything getting hot?

billmeds's picture

Re: emonGLCD display not working

I had checked for dry joints and I had already resoldered the 20 pins of the display, however I discovered that the display would occasionally appear if I put pressure along the bottom edge of the board which lead me to believe there may be a bad connection somewhere. I have resoldered the display pins again, being particularly carefull of the pins between the 2 rows of caps which are difficult to access and the display is working again.

I'm slightly embarrassed that it seems to have turned out to be a bad solder joint as I've been soldering since 1979 although it's been a while since I built up any pcbs. On the other hand it's a much easier fix than trying to get the display out!

Robert Wall's picture

Re: emonGLCD display not working

Don't worry about that - the plated-through holes do suck up quite a bit of solder and do take a bit more heat. And was it lead-free solder?  (I'm dreading my supply of 60-40 running out! I got a 1 lb reel in 1968 and it's looking a bit slim now.) So all's well then.   

billmeds's picture

Re: emonGLCD display not working

Yes, it's been working now for almost 24 hours continuously. Thanks for your help.

It was leaded solder that I bought in about 1980 possibly when I built my ZX80, my real is almost empty too!

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