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Old Aug 08, 2014, 04:26 PM
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AtomicFlyer's Avatar
United States, NM, Los Alamos
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Watt's Up watt meter display contrast issue

Hey guys. I bought this Watt's Up watt meter about 5 years ago. It works fine but about 6 months ago the display started to become unreadable because of the contrast.

I emailed the manufacturer to ask about a solution but I never got a reply. It's out of warranty so I opened it up to see if there was a potentiometer to adjust the contrast. There aren't any pots. So I was wondering if anyone knows which resistor controls contrast.

I found one other post with the same issue but that meter was new and the guy was able to return it.

Thanks in advance.

Marc
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Old Aug 08, 2014, 04:32 PM
AndyKunz's Avatar
Illinois
Joined Sep 2001
23,504 Posts
Show the rest of the board. You're showing the wrong end of the board.

Andy
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Old Aug 08, 2014, 04:36 PM
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ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
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usually a pair of resistors as a voltage divider on pin3....but that doesn't really look like a contrast issue to me.

if you do have to replace it then 2x16 displays are easy and cheap to find and most have the same pinout...find the data sheet for yours and then look around for one that matches pin wise and layout wise.
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Old Aug 08, 2014, 05:02 PM
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United States, NM, Los Alamos
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Originally Posted by AndyKunz View Post
Show the rest of the board. You're showing the wrong end of the board.

Andy
Andy,
I've attached a photo of the main board. The display board is soldered to the main board using a .1" pitch pin header. I haven't desoldered the display pcb from the main board, but there are 5 resistors on the display board also. I'm now suspecting one of those may control contrast.

Quote:
Originally Posted by ZAGNUT View Post
usually a pair of resistors as a voltage divider on pin3....but that doesn't really look like a contrast issue to me.

if you do have to replace it then 2x16 displays are easy and cheap to find and most have the same pinout...find the data sheet for yours and then look around for one that matches pin wise and layout wise.
Zagnut,
I removed the LCD display and there is a number printed on it. But I couldn't get a hit when I searched google for it. A photo is attached.

Thanks,
Marc
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Old Aug 08, 2014, 05:32 PM
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Tel Aviv, Israel
Joined Jul 2004
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that "display pcb" is an integral part of the LCD module, part number and manufacturer will be on the back of it.

if there is any space between the boards i would cut the pins to free the display and then just desolder each pin individually.
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Old Aug 08, 2014, 06:50 PM
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AtomicFlyer's Avatar
United States, NM, Los Alamos
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Quote:
Originally Posted by ZAGNUT View Post
that "display pcb" is an integral part of the LCD module, part number and manufacturer will be on the back of it.

if there is any space between the boards i would cut the pins to free the display and then just desolder each pin individually.
Zagnut,
Thanks for the tips. I cut the pins and the LCD module is a Xiamen Ocular GDM 1602H. I've attached the data sheet in case anyone else is ever looking for it.

You are exactly right. Pin 3 is used to supply a voltage for contrast adjust. There is a trace from pin 3 to R15 on the main board so I think it's using R15 and R16 as the voltage divider.

Thanks for your help.

Marc
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Old Aug 08, 2014, 07:52 PM
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Tel Aviv, Israel
Joined Jul 2004
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that's the smaller standard size, bit harder to find than the slightly larger module but still tons out there. if the contrast adjustment doesn't work then a new one might be $5-$10, maybe even cheaper on ebay?

whatever you get just make sure the pinout is the same, some manufacturers run the pins in the opposite direction and one even reverses the ground and +V. also don't be tempted to get a backlit one unless you have lots of spare room in the case as they are usually much thicker.

have fun!
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Old Aug 08, 2014, 08:51 PM
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AtomicFlyer's Avatar
United States, NM, Los Alamos
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Quote:
Originally Posted by ZAGNUT View Post
that's the smaller standard size, bit harder to find than the slightly larger module but still tons out there. if the contrast adjustment doesn't work then a new one might be $5-$10, maybe even cheaper on ebay?

whatever you get just make sure the pinout is the same, some manufacturers run the pins in the opposite direction and one even reverses the ground and +V. also don't be tempted to get a backlit one unless you have lots of spare room in the case as they are usually much thicker.

have fun!
If I don't mind waiting to have it shipped from Hong Kong to the USA, I can get one for under $4 on eBay. This has been a fun learning experience. Thanks for your guidance.

Marc
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Old Aug 12, 2014, 05:14 PM
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Germany
Joined Mar 2012
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How do you open up the Watts Up?
I tried to pry it open with a knife but that didnt work. On the manufacturers website they sell just the case as a spare, and they mention glueing it together.
Good to see that the lcd can be replaced
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Old Aug 12, 2014, 08:44 PM
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United States, NM, Los Alamos
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Originally Posted by cyklopz View Post
How do you open up the Watts Up?
I tried to pry it open with a knife but that didnt work. On the manufacturers website they sell just the case as a spare, and they mention glueing it together.
Good to see that the lcd can be replaced
I used a cutting disc on a rotary tool. I cut right at the seam.

Marc
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Old Aug 20, 2014, 11:06 AM
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Hi Marc,
Thanks for the photos showing the internals of the Watts Up meter. I'm thinking of building an energy meter based on the same basic design layout. From what is shown it looks like the black wire (negative) passes current through a .001 ohm current sampling resistor. The photos don't show where the red wire goes, but my guess is it just passes across the board without connecting to anything. Is this correct?

Thx,

Dick
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Old Aug 20, 2014, 09:31 PM
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United States, NM, Los Alamos
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Quote:
Originally Posted by rivers View Post
Hi Marc,
Thanks for the photos showing the internals of the Watts Up meter. I'm thinking of building an energy meter based on the same basic design layout. From what is shown it looks like the black wire (negative) passes current through a .001 ohm current sampling resistor. The photos don't show where the red wire goes, but my guess is it just passes across the board without connecting to anything. Is this correct?

Thx,

Dick
Hi Dick,
I was going to repair my Watts Up meter but I ended up just buying this GT Power meter for $20 on eBay.

I did completely disassemble my Watts Up meter but it's at the dump now. I'm pretty sure the red wire has to land on the board somewhere because otherwise you wouldn't have a reference potential to power the electronics.

Good luck with your project.

Marc
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Old Aug 21, 2014, 03:21 AM
supreme being of leisure
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Tel Aviv, Israel
Joined Jul 2004
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Quote:
Originally Posted by rivers View Post
Hi Marc,
Thanks for the photos showing the internals of the Watts Up meter. I'm thinking of building an energy meter based on the same basic design layout. From what is shown it looks like the black wire (negative) passes current through a .001 ohm current sampling resistor. The photos don't show where the red wire goes, but my guess is it just passes across the board without connecting to anything. Is this correct?

Thx,

Dick
this might help with your project:
http://www.bhabbott.net.nz/wattmeter.html
Bruce Abbott is also a member here.
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Old Aug 26, 2014, 01:24 PM
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Julez's Avatar
Germany
Joined Dec 2003
5,299 Posts
I had the same issue once the other way, it was too faint to read on hot days.

First, you should have a look at the rubber connector strips, which sit between the glass screen and the contacts on the PCB. Clean those carefully with alcohol on both the glass- and the PCB-side, and reassemble the display correctly.

If this should not solve your issue, you have to change the contrast voltage. The pins with positive voltage and ground as well as the contrast pin have been identified as I understand. Connecting the contrast pin via a 5-10k poti with positive will change the contrast in one direction, maybe darker, maybe lighter, I forgot. Connecting the contrast pin to ground will change the contrast the other way. Alternatively, you can try changing the resistors on the voltage devider already present.
I was able to correct the contrast on mine using this mod.
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