Help，Can ordinary LEDs replace thin-film LEDs? - Page 1
Forum section: electronics / repair

author: daisizhou
author_rank: Super Contributor
timestamp: August 17, 2024, 03:45:43 am
content: This is a ventilator.It is no longer used on patients.I usually use it to learn and practice the operation of the ventilator.Due to the long time，Aging of the digital luminous film of the main display.I unpacked it,Found that there are 5 HV6506PJ drivers,I guess 4 HV6506PJs should be used for the step display, and 1 HV6506PJ should be used for the 2 8-bit digital tubes in the center.https://www.scribd.com/document/249426163/Manual-e100m-Serman-Rev-d-2202104 pagesI hope to fix it cheaply.The original factory has stopped after-sales maintenance.My plan is to use ordinary LEDs (chips) to replace each film, then make a PCB, install the LEDs on the PCB, and use them to replace the original display. The center will use the most easily available 8-bit digital tube to replace the original display.I don't know if my idea is feasible.If you have a better idea, I look forward to your help, thank you

author: daisizhou
author_rank: Super Contributor
timestamp: August 17, 2024, 08:13:07 am
content: I don't know if this connection is possible, it looks like HVout and BPout are high voltages, I don't know if it's possible to connect a light-emitting LED here

author: MathWizard
author_rank: Super Contributor
timestamp: August 17, 2024, 06:34:09 pm
content: IDK the circuit, but for the chip it says it's 'a low-voltage serial to high-voltage parallel converter'. The output voltage is upto 80V in this datasheet. Yeah so that be a huge amount to drop just with resistors to some single LED. IDK about chip LED's or how many LED's could be put in series. If the HV was only 15V, then you could probably use some logic IC like a level-shifter to get back to the 5 or 12V you might have wanted to use for regular LED's. Any idea if the chip's have a problem?IDK about digital luminous film, what about getting more of that?

author: daisizhou
author_rank: Super Contributor
timestamp: August 17, 2024, 10:26:15 pm
content: Quote from: MathWizard on August 17, 2024, 06:34:09 pmThis is the first time I have come across this type of display.It looks like a monochrome LCD screen, but on top of a plastic film.In the picture below, you can vaguely see that only part of the LCD display is normal.This means the chip is functioning normally.There is a 3-core flat wire in the lower right corner. I guess it may be connected to high voltage, similar to the backlight.

author: oPossum
author_rank: Super Contributor
timestamp: August 17, 2024, 11:27:48 pm
content: May be an EL displayhttps://en.wikipedia.org/wiki/Electroluminescent_displayCheck the high voltage power supply. Should be about 100 volts. The display itself may be in serviceable condition.

author: daisizhou
author_rank: Super Contributor
timestamp: August 17, 2024, 11:51:58 pm
content: Quote from: oPossum on August 17, 2024, 11:27:48 pmIt seems that the LCD display is almost incomplete.Do you mean only repairing the high-voltage backlight power supply part?

author: oPossum
author_rank: Super Contributor
timestamp: August 17, 2024, 11:57:03 pm
content: I think the entire display is EL. Not an EL backlight behind a LCD. The high voltage drivers would not be needed for a LCD, but are needed and often used with EL displays.

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 12:14:52 am
content: Ok, if it's an EL display, can I change it to LED or other easier to implement methods?Due to their age, many plastic films or coatings have aged or been damaged, resulting in incomplete displays

author: Haenk
author_rank: Super Contributor
timestamp: August 18, 2024, 08:33:37 am
content: Quote from: daisizhou on August 18, 2024, 12:14:52 am"easier" seems impossible - you would need to a) create a whole new segmented display and b) maybe create a new driver circuit.If you really need to have this running again, ignore the round segments and just create something for the 7-segments. Maybe use a LCD, and keep the original driver chip, just dropping the voltage might work (due to the little current required by LCD).I assume this was a custom EL display, money obviously didn't matter. And the EL foils do fail, a lot. However, if all segments do no not work anymore, it might be the power supply after all - did you peek around checking voltages?

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 08:57:01 am
content: My initial plan was to replace each LCD progress bar with a glowing LED as shown in the following picture,The middle two use ready-made 8-bit digital display tubes.Now it seems that my plan will fail because EL's electrical performance is almost completely different from LED's.I didn't check the high voltage part because the wiring connecting the high voltage has cracked and some conductive layers have started to peel off

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 18, 2024, 10:08:59 am
content: Do you really want to solder and place over 140 LEDs there?If yes, I´d try to find out if you can modify the supply voltages of the high voltage driver ICs to LED compatible levels.

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 10:14:23 am
content: If placing LEDs is feasible I will proceed with the plan.I don't know if the electrical performance of EL is compatible if I change it to LED, because I am not familiar with EL components.www.scribd.com/document/249426163/Manual-e100m-Serman-Rev-d-2202Page 104 has the schematic diagram of the display partthanks

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 18, 2024, 10:23:45 am
content: I can't download the manual (registration required) but as I had a quick look over the datasheet pages, I wonder if it´s possible to reduce "V_pp" to let´s say 5V and connect LEDs to the outputs.The max current of 0.5mA is not very much, but may be sufficient for a bright display. You could test it with a few wired LEDs that get patched to the headers.

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 10:34:10 am
content: Schematic downloaded. Attached.

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 10:46:49 am
content: with...

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 10:52:36 am
content: Quote from: Phil1977 on August 18, 2024, 10:23:45 amDo you want me to connect and test as shown below?

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 10:53:29 am
content: I appreciate your help, thanks

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 18, 2024, 10:56:23 am
content: I you could lift up pin 7 of IC U7, then you would disable the step-up-converter of the EL-driver and the output voltage VD should be slightly below 5V.The EL-driver-ICs supply AC to the segments, but it seems it´s just the VD-voltage switched on/off. I can't see any reason this would harm the LEDs.Does anyone see a reason not to try it? I hope the OP is aware that placing and routing >140LEDs according to a given schematics is quite a lot of workQuoteNo, don't connect the LED directly to the VD-supply of the device. I´d reduce the VD from 50V to 5V and then connect a few test LEDs to the outputs of the driver IC instead of the EL-display.Sorry some edit was flawed. Now quotes and content should be okay again.

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 11:02:44 am
content: I think everyone is mistaken.From the video of it working below, I believe it is an LCD.And HV6506PJ is an LCD driver.I think it needs to be replaced by a shift register with a 32-pin output.

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 11:07:59 am
content: Quote from: Phil1977 on August 18, 2024, 10:56:23 am

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 11:09:57 am
content: The datasheet for the HV6506PJ lists the high voltage supply current as 0.5 mA, which would be difficult to drive LEDs.

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 18, 2024, 11:18:06 am
content: 0.5mA can be sufficient for non-multiplexed an efficient LEDs.But you should definitely first clarify if it´s a LC- or EL-Display. If it´s LCD then current will be far too low.

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 11:28:37 am
content: Quote from: Phil1977 on August 18, 2024, 11:18:06 amIt looks like an LCD display.I usually see glass LCD,This is the first time I have seen this kind of soft plastic film.Due to the long time of use, the display effect is very bad.Is there a better and more feasible upgrade solution?

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 11:36:51 am
content: It would be possible to make a custom board that would allow LEDs to be mounted to replace the LCD.Can be connected with FFC cable.VD power supply should be low voltage.or can make a cheap FPC board with JLC.

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 12:08:55 pm
content: Quote from: squadchannel on August 18, 2024, 11:36:51 amBut I don't know how to connect the LED to HV6506PJ, because HV6506PJ was originally connected to the LCD.

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 02:07:08 pm
content: For now, remove Q1 and Q2 in the schematic and connect a low voltage source to the VD pin. 3.3-5V is about right.Connect the anode of the LED to one of the SEGs in the schematic and the cathode to GND. Attach a limiting resistor in series to keep the current below 0.5mA.The cathode of the LED should be connected to the BP of the HV6506, but I do not know how the BP is controlled.You can either connect it to the BP or to GND, whichever is better.If this were an LCD, it would need a bias circuit to operate at about 1/3 bias, but no such thing seems to exist, rather it is an odd display, like an EL, that uses high voltage.I once saw a video of an electric curtain used for house windows and doors. I believe it was one of those things that would be translucent when turned on, and transparent when turned off.Maybe that is it. I believe it used high voltage as well.

author: tooki
author_rank: Super Contributor
timestamp: August 18, 2024, 02:17:06 pm
content: Quote from: Phil1977 on August 18, 2024, 11:18:06 amFYI, in English we never say "LC-Display".We say either "LCD" or "LCD display", or the full "liquid crystal display". (Any examples you may find are invariably from non-native speakers.)

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 18, 2024, 02:59:12 pm
content: Quote from: tooki on August 18, 2024, 02:17:06 pmIn Germany we have too many pedants who teach you "A LCD display is a liquid crystal display display"... But thanks for the hint!

author: tooki
author_rank: Super Contributor
timestamp: August 18, 2024, 03:30:15 pm
content: Quote from: Phil1977 on August 18, 2024, 02:59:12 pmHeheheh. We occasionally get that in English regarding "PIN number", "HIV virus", "ATM machine", etc.[off-topic]The one that REALLY irks me in German is "ISB-Nummer" (for ISBN, which is "International Standard Book Number"), because it violates the internal hierarchy of that compound noun. Indeed, it ignores the fact that compound nouns have internal hierarchies, and are not flat lists of constituent words!If you diagram it, the "head" of the compound is "Number". That compounds to(Book+Number), and that in turn is compounded to "Standard Book Number" (the originally British predecessor to the ISBN),(Standard+(Book+Number)). And when that standard was adopted by ISO and extended to an international standard, it became(International+(Standard+(Book+Number))).So when German says "ISB-Nummer", it's violating the hierarchy by pulling out an element from the innermost set, creating a new hierarchy that makes no sense:((Internationales+(Standard+Buch))+Nummer). There is such thing as a "Standardbuch" (=Standardwerk), but that actually changes the meaning entirely, to a number specific to international definitive books...But alas, Duden or whatever decided that ISB-Nummer is what is officially correct, so we live with it...[/off-topic]

author: daisizhou
author_rank: Super Contributor
timestamp: August 18, 2024, 11:06:39 pm
content: Quote from: squadchannel on August 18, 2024, 02:07:08 pmI drew a simple schematic, is this what you mean?

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 19, 2024, 04:37:55 am
content: If it was me, I'd snoop the Data(pin 27), Latch(pin 23), Clock(pin 25), of U2 (HV6506) and feed this to a MCU connected to an ordinary LCD/OLED raster display and interpret & display the data with my own code. That would avoid wiring all those LEDs, etc.

author: daisizhou
author_rank: Super Contributor
timestamp: August 19, 2024, 05:01:14 am
content: Quote from: Kim Christensen on August 19, 2024, 04:37:55 amGood idea, your suggestion reminds me of the GC9A01 I once had, which is a 1.28-inch TFT screenI measured the actual size and the circular hole diameter is 70 mm.If you have a suitable screen please let me know, thanks

author: Koray
author_rank: Regular Contributor
timestamp: August 21, 2024, 08:12:42 am
content: High voltage driver and the grayscale in video and the plastic film substrate sounds like e-ink display to me.K.Edit: Nope, it is an LCD display with an EL backscreen illumination. Apparently the one in the video does not have the EL working.

author: daisizhou
author_rank: Super Contributor
timestamp: August 21, 2024, 08:20:18 am
content: Yes, it looks like it is low voltage.I'm looking for a suitable LCD screen to replace it