LCD replacement  - Page 1
Forum section: electronics / repair

author: Liteace
author_rank: Regular Contributor
timestamp: January 21, 2020, 05:28:54 pm
content: Need some help guy's please, I broke the screen on my gas analyser, this is the screen:MDLS20464DThere is a couple on the internet for sale but they are quite expensive, I have also seen loads of later type LCD's on China sites, for example, thesehttps://www.banggood.com/IIC-I2C-2004-204-20-x-4-Character-LCD-Display-Module-Blue-p-908616.html?rmmds=search&cur_warehouse=CNhttps://www.banggood.com/1Pc-Geekcreit-1602-Character-LCD-Display-Module-Yellow-Backlight-For-Arduino-p-978155.html?rmmds=search&cur_warehouse=CNhttps://www.banggood.com/5V-2004-20X4-204-2004A-LCD-Display-Module-Blue-Screen-For-Arduino-p-915064.html?rmmds=search&cur_warehouse=CNwould any of the above work ?Thanks

author: reboots
author_rank: Regular Contributor
timestamp: January 21, 2020, 07:28:22 pm
content: I believe your display module has a standard HD44780-style parallel interface. Either of your first and third product links should work, although the first one comes with an I2C translator board which you won't need. The second link is to a 2-line display, which is probably not what you want.

author: wraper
author_rank: Unknown
timestamp: January 21, 2020, 07:51:51 pm
content: Quite standard 20x4 LCDhttps://www.ebay.com/itm/20x4-2004-Character-LCD-Display-Module-2004-LCD-Yellow-Blue-Blacklight-HD44780/113712823858?hash=item1a79cffe32:m:mSnlHru07Q7FIWiJESjykPQ

author: wraper
author_rank: Unknown
timestamp: January 21, 2020, 07:55:01 pm
content: Quote from: Liteace on January 21, 2020, 05:28:54 pm1st (if you remove small adapter board) and 3rd should work. Second has only 2*16 character rows instead of 20*4.

author: james_s
author_rank: Super Contributor
timestamp: January 21, 2020, 08:53:15 pm
content: Should be no problem to wire in any 20*4 44780 compatible display you find. The only issue I've ever had is sometimes you need to fiddle with the contrast voltage, if there is not a pot you may need to add one or wire in a resistor but first try just installing a new display and see what happens. While they're not too exciting to look at, I do like these displays because they're so standardized and they're dirt cheap and widely available.

author: Liteace
author_rank: Regular Contributor
timestamp: January 21, 2020, 11:18:27 pm
content: Thanks Guy's, I have ordered the 1st one on the list, it'll see what its like in daylight as its blue, if no good for the price I can order another white/yellowThanks Again

author: TheMG
author_rank: Frequent Contributor
timestamp: January 22, 2020, 02:59:16 am
content: I never particularly liked the blue/white backlit LCDs they've never been particularly great for bright ambient lighting, and the viewing angle of such LCDs is usually not very good.I usually go for the more traditional yellow-green transflective LCD modules. Another bonus of the transflective modules is you can turn off the backlight to save on battery life, and the display is still perfectly readable. The blue LCDs you can not, and must have the backlight on at all times.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 22, 2020, 10:40:42 am
content: You could also try to replaceonly the LCDrather than the entire display module?

author: james_s
author_rank: Super Contributor
timestamp: January 22, 2020, 11:18:37 pm
content: I suppose you could but why? The entire module is so cheap why mess around with trying to find glass that is an exact fit?

author: wraper
author_rank: Unknown
timestamp: January 22, 2020, 11:27:18 pm
content: Quote from: GeorgeOfTheJungle on January 22, 2020, 10:40:42 amAnd where are you are going to find glass part itself? It's not like they are sold separately in retail. Also while there are tons of compatible displays sold, does not mean that glass part is compatible between them.

author: Liteace
author_rank: Regular Contributor
timestamp: February 19, 2020, 09:15:39 pm
content: Screen arrived, stupid me should have taken you Guy;s advise and ordered the normal yellow LCD, the blue, I have to manually switch on the back light but I cant do that till the machine has run through itsa 90 second walm up, in the 90 seconds it gives options that I can only just seeAlso the new screen even when the back light is on its not readable when you look straight at it, you can only see it if you look from an angle as the contrast wont adjustI'll order another yellow screen

author: Gyro
author_rank: Super Contributor
timestamp: February 19, 2020, 10:36:10 pm
content: That's simply the contrast bias level being set too high. You should be able to adjust this - check what is feeding Pin 3 (V0), hopefully it's just a potential divider made up of two resistors which you can tweak. That's assuming that the contrast isn't adjustable in the firmware.

author: Liteace
author_rank: Regular Contributor
timestamp: February 19, 2020, 10:46:49 pm
content: The contrast is adjustable in the setting but it wont adjust with this screen for some strange reason, its got the darker / lighter setting but when I set it to lighter does nothing, when I go back into setting its back to darker setting again

author: Gyro
author_rank: Super Contributor
timestamp: February 19, 2020, 10:50:28 pm
content: Doh, that's a shame. It must have a different bias voltage requirement to the available range. I didn't think that happened these days.

author: Liteace
author_rank: Regular Contributor
timestamp: February 19, 2020, 11:09:17 pm
content: The track between R41 and R42 is the feed for VO pin 3[ Specified attachment is not available ]

author: syau
author_rank: Frequent Contributor
timestamp: February 19, 2020, 11:26:25 pm
content: Just temporary replace the R41 with a 10k variable resistor, adjust it until you get a good contrast. Replace that variable resistor afterward with a new resistor will do.

author: Liteace
author_rank: Regular Contributor
timestamp: February 20, 2020, 07:05:07 pm
content: That little controller board I took of the back of the new screen had some sort of pot, I checked it, soldered it on, adjusted it. took the valve, looked through loads of old stuff, found a resistor with near enough and now got thisAll I have to do now is fine a resistor that firs nice, this on is to bigbeforeafter

author: Gyro
author_rank: Super Contributor
timestamp: February 20, 2020, 07:09:06 pm
content: Good fix.

author: Liteace
author_rank: Regular Contributor
timestamp: February 20, 2020, 07:23:55 pm
content: Ive have ordered another screen, the yellow standard one, this one looks nice, more modern, I would keep it if the back-light switch when I switched on the machine but unfortunately it doesn't, I have to shine a torch on it to see the setting to switch back light on after its 90 sec warm up. I'll use it as is till the other arrivesAnyone know where I can buy these, I dont think they will stand another remove - re-solder

author: james_s
author_rank: Super Contributor
timestamp: February 21, 2020, 01:15:35 am
content: I suppose you could bypass the backlight control so it's always on, or bypass it with a resistor so the settings are dim and bright, although I like the older style greenish yellow displays better anyway.Those look like ordinary 0.1" machined pin headers, I've bought them from ebay sellers in china before.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: February 21, 2020, 03:04:01 am
content: Amazon has those pins.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: February 21, 2020, 06:52:33 am
content: Look for "machined pin header 2.54 mm"