Can't find direct replacement for 7 segment display; need advice - Page 1
Forum section: electronics / repair

author: HooRide
author_rank: Regular Contributor
timestamp: April 18, 2015, 06:21:30 am
content: Several segments have gone out on the display of my fridge and the manufacturer wants $200 for the module with display.I've found the data sheet for the LED Display and it uses, from what I've found, a very unusual pinout (page 3 of the attached data sheet).I've not been able to get any response for Foryard.Anyone have any sources for this part or any ideas on retrofitting a more common display?

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 18, 2015, 06:47:48 am
content: Oh I hate them. Seen that before. Sure it's designed to keep pin count down on whatever controller they use.Past looking through aliexpress, which yields nothing quite the same, it looks mostly common anode. Might be a 'creative soldering' job I.e. wire up a standard common anode display with that pin arrangement. You can get away with bending the pins flat on the new display and carefully soldering some wires to the back. Bit fugly but I'll work.

author: kripton2035
author_rank: Super Contributor
timestamp: April 18, 2015, 07:09:37 am
content: are you sure it's the display that is faulty ?on my samsung fridge, there are missing segments toobut in fact it's the wires that goes from the top of the fridge to the display on the door that are badly connectedand quite impossible to change without changing the whole door ...

author: HooRide
author_rank: Regular Contributor
timestamp: April 18, 2015, 07:19:54 am
content: I'll make a table and figure out what would happen if I use a common anode display, I think it may make it impossible to make certain characters.I'm positive it's the LED display. I've desoldered the display and tried powering it manually and measured for voltage on the PCB.

author: sleemanj
author_rank: Super Contributor
timestamp: April 18, 2015, 09:49:25 am
content: Micro with sufficient I/O, scan the driven lines from the fridge, determine which segment then drive a more normal 7-seg display, repeat as fast as you can.

author: amyk
author_rank: Super Contributor
timestamp: April 18, 2015, 02:44:23 pm
content: Also available here:http://www.snowdragonledhk.com/new-two-digit-40.htm("two digits 0.40" single color 8 pin")http://www.betlux.com/led/0.40-inch-double-seven-segment-led-display-BL-D40G-21,BL-D40H-21.htmApparently known as G/H multiplex:http://www.oasistek.com.tw/en/pdf_download.php?file=TOD-3203HMR-N.pdf

author: HooRide
author_rank: Regular Contributor
timestamp: April 19, 2015, 06:02:48 am
content: Quote from: sleemanj on April 18, 2015, 09:49:25 amI was thinking that originally, if I can't source the parts below, I will probably go this route. A friend suggested a CPLD if I choose that route.Quote from: amyk on April 18, 2015, 02:44:23 pmThank you! My chances of sourcing one of these seems much greater. I hope to report some good news soon.

author: Stonent
author_rank: Super Contributor
timestamp: April 19, 2015, 06:54:12 pm
content: Here's some likely information on how they're driving it.http://elect.wikispaces.com/8+pin+2+digit+seven+segment+display+driverI like the idea overall. Half of the pins are quadrant select and the other half are segment enable.I think the traditional way is 2 digit selects that are the common pin to the digit and then a segment select pin which would yield 10 pins.I might not have thought of doing it the way they did. I might have done it with tying all the pins together on a common anode and common cathode display. Then drive it by alternating + and - , but that would have yielded 9 pins total.I suppose if you mixed the two, you could gain another free pin.Or drive even 4 digits off 8 pins.By the way, I used a special CAD program called Stonent-CAD to design it. The best part is you can install it on your computer with this command!copy mspaint.exe Stonent-CAD.exe

author: codeboy2k
author_rank: Super Contributor
timestamp: April 19, 2015, 08:53:11 pm
content: That's a great idea, Stonent!I like this G/H arrangement actually. I've only ever used the standard 10-pin common anode/common cathode arrangement. From looking at the datasheets of these G/H multiplex displays, some of them are 8 pins on one side, some are 4 on top, 4 on the bottom. But they only need 8-bits from a single I/O port. What makes the G/H display interesting to me, as opposed to the common anode/cathode displays is that you can build your PCB with 8 holes at the top and 8 holes at the bottom and wire them so that the 8 i/o's go the bottom row, then crossover to go to the top row of 8. Now you can support all of 2-digit pinouts from multiple suppliers, and even the anode/cathode arrangement doesn't matter.This way, you can source whatever is available from multiple suppliers and get anything that works; you just load a different firmware, or load the same firmware and use configuration bits in the eeprom (if you had one), or use 0-ohms resistors as configuration bits if you have spare I/Os for it.

author: Stonent
author_rank: Super Contributor
timestamp: April 19, 2015, 10:33:38 pm
content: Well the way I came up with is not nearly as efficient as charlieplexing, but it doesn't require the use of 3 logic states.To start I'm about 1/2 as efficient, but as we progress to 52 pins used, I'm only about 14 percent as efficient.

author: amyk
author_rank: Super Contributor
timestamp: April 20, 2015, 01:51:48 pm
content: Each digit has 8 segments so 2 digits = 16 segments, perfect for a 4x4 matrix. That's probably how this multiplex was invented.

author: jimyy1979
author_rank: Newbie
timestamp: May 23, 2015, 02:24:34 pm
content: Quote from: HooRide on April 18, 2015, 06:21:30 am================================you can try using multimeter to identifying function of each pin.Same thing happened to me once?when i use led productswww.ledlightmake.com?.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 23, 2015, 02:41:34 pm
content: Another option would be to make a small PCB with a few SMD LEDs per segment.

author: markoCS
author_rank: Newbie
timestamp: November 15, 2017, 07:14:05 am
content: Have you manage to found these segments? If yes, please share. I'm having exactly the same problem. Thx!

author: amyk
author_rank: Super Contributor
timestamp: November 15, 2017, 11:52:06 am
content: Look at the links I posted...