emonGLCD characters barely visible

I got to step 21 in the emonGLCD build guide but the characters are barely visible. I'm guessing that is not a good sign?

The test sketch prints temperature and flashes the LEDs like it's supposed to. 

I had only made the voltage check in step 16 using the FTDI programming cable (and got 3.3v). I have just checked and when using the mini USB plug I get 0 v between the GND and VCC pads on the RFM12B socket.

I'm guessing the easy thing to do would be to order a new kit?


glyn.hudson's picture

Re: emonGLCD characters barely visible

Could you post up a photo of what you can see on the display and a photo of the board? It sounds like it's almost working. Are you using this GLCD library? https://github.com/jcw/glcdlib

trendt's picture

Re: emonGLCD characters barely visible

The characters are so hard to differentiate that I can't capture them in a photo. If I tilt the display and look at it from an angle I can see the temperature and the other information in the test sketch printed on the display. I'm using the GLCD library. 

Could this have something to do with the fact that I'm getting 0v between the GND and VCC pads on the RFM12B socket using USB? Still getting 3.3v using the FTDI programming cable.

Can I somehow verify that the display is getting sufficient power? 


glyn.hudson's picture

Re: emonGLCD characters barely visible

You could measure the voltages of the row of pins at the bottom of the board. The voltages should be something like this. They won't be exactly the same values since the display will be displaying different things but if you measure pins to be 0V when they should measure a higher voltage then this could be a cause for concern. But the fact the LCD is displaying stuff indicates that the problem might lay with the LCD not the PCB. 

You don't need to use the USB, you can power the unit from an FTDI for testing, make sure it a 5V FTDI cable. 

It will be tricky for you to hold all the LCD pins in contact and measure the voltages, you might need an extra pair of hands! I think for the LCD to be initialized all pins will need to be in contact on power up. If the LCD does not get initialized I don't think the correct voltages will be on the pins anyway. 

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                

Double check all the capacitors along the bottom have been soldered in correctly (correct value and orientation). These capacitor create a voltage multiplier circuit to power the LCD. 

If your still having trouble maybe the best thing is to send the whole unit back to us, we can then determine if the problem is with LCD for the PCB and replace the offending item or you.

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