emonGLCD Display Problem

Submitted by Tony Antique on Tue, 15/12/2015 - 14:42

I have just assembled a emonGLCD following the very good detailed instruction.

I am running the test sketch (https://github.com/openenergymonitor/EmonGLCD/tree/master/tester).

Unfortunately I have no display. However everything else seems to be working.

LED s cycle red / green.
Back light is lit up.
Serial monitor lists temp, light, and the switches are active.
Voltages seems OK
RFM module works (as tested with another sketch)

Are there any other tests that may help me diagnose my problem?

Thanks, Tony.

Re: emonGLCD Display Problem

Submitted by Robert Wall on Tue, 15/12/2015 - 22:00.

Have you soldered in the display, or are you testing it wedged in place?

Re: emonGLCD Display Problem

Submitted by glyn.hudson on Wed, 16/12/2015 - 00:57.

Can you post a photo of the assembled PCB so we can check the component placement and orientation of capacitors etc.

Re: emonGLCD Display Problem

Submitted by Tony Antique on Wed, 16/12/2015 - 16:05.

I attach three photos - the display is soldered in position.

Re: emonGLCD Display Problem

Submitted by Robert Wall on Wed, 16/12/2015 - 16:57.

When you say "Voltages seems OK", are you referring to the main supply rails or the GLCD pins?

Here are the approximate GLCD pin voltages. Particularly important is the voltage multiplier - pins 9 - 12.

1 - 8.53
2 - 7.34
3 - 6.09
4 - 2.48
5 - 1.24
7 - 1.63
8 - 7.07
9 - 4.44
10 - 1.65
11 - 9.68
12 - 10.96
14 - 3.27
15 - 3.27

I presume you checked for solder whiskers etc before you added the display. (That's one reason for testing the display before you solder it, as it's nigh on impossible to rectify a fault after the display is soldered in.)

Re: emonGLCD Display Problem

Submitted by Tony Antique on Thu, 17/12/2015 - 19:03.

I checked the 5 volt , bottom left corner of the board and the 3.3 v at various marked points.

The GLCD pin volts are approx as follows:-

1 - 0.01

2 - 0.04

3 - 0.03

4 - 0.00

5 - 0.01

6 - 0.00

7 - 0.07

8 - 0.48

9 - 0.53

10 - 0.29

11 - 0.34

12 - 1.04

13 - 0.00

14 - 3.30

15 - 3.30

16 - 0.01

17 - 0.01

18 - 3.30

19 - 3.28

20 - 0.00

Something wrong, but what?

Re: emonGLCD Display Problem

Submitted by Robert Wall on Fri, 18/12/2015 - 00:11.

The 3.3 V supplies are intact on 14 & 15, GND is correct on 6, 13 & 20, 16 - 19 are data.

Pin 4 being 0.00 is worrying, is that ceramic capacitor (C11) good or is it shorted? All those ceramics (C8 - C12) are to GND, so check their insulation (go from the LCD pins to PWR-. I see megohms from pin to GND on all).

Re: emonGLCD Display Problem

Submitted by Tony Antique on Fri, 18/12/2015 - 11:31.

Robert thank you very much for your help.

All the ceramics (C8 - C12) look good.

They all measure either 20M+ or 0 ohms from -ve ( pin 20).

Re: emonGLCD Display Problem

Submitted by Robert Wall on Fri, 18/12/2015 - 14:20.

I can't spot an obvious assembly mistake, and given that the processor itself is working and the peripherals work, it's beginning to look like the display itself is faulty.

Just before we give up, can you check the 4 electrolytics, observing polarity. I see the capacitor charging, and then megohms again.

If you see the same, it looks as if the voltage multiplier inside the display isn't working (it should give you something approaching 12 V on pin 12) and I think it's time to email the shop and remind them of this thread.

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