Seiko L2432 2x24 LCD

[Robert Hedan]

Hi,

This post is two-fold:

First, does anyone know where I can find the pinout for this LCD?
Second, any suggestions for a circuit to power the EL backlight?

I've searched a lot on this subject and I have to admit I'm quite lost. The datasheet for this LCD is quite vague, it just mentions 5V for the EL and that it is Model 5A, whatever that is. The most data I found is here:
**broken link removed**

They mention where to buy inverters, but don't offer any help in building one. I've read many posts on Aaron's Forum on this subject and couldn't find exactly what I was looking for (that's how I followed Audioguru here, assuming he is the same person).

Any help in saving this heap of LCDs would be greatly apppreciated. I think it's obvious now why they were such a good deal on EBay when I bought them over 1 year ago (been looking on and off for information since). I can program PICs and have MOSFETs on hand.

Robert

 

[spuffock]

Uses HD44780. That says it all, its a standard interface. Use the data for anyone elses 16*2 lcd display, the only difference is the number of characters it will show.
As for the el backlight, try around 100v, 5 to 10 khz. 555, mosfet, ferrite transformer.

 

[Robert Hedan]

D'uh, I just noticed the pin numbers on the PCB until this morning. I didn't know they were a standard pinout for HD44780 though, thanks.

For the EL inverter circuit, is it possible to power it using 5V? Or must I absolutely need mains power? You wouldn't happen to have a link to a schematic for that would you? I know the parts, but I have no idea how to wire them up, especially the 555.

Is it possible to substitute the 555 with a PIC and PWM? I can easily adjust PWM with 2 buttons and observe the results, but I have no experience using a 555.

One last thing, I've never used EL, only LED backlights. What must I keep an eye out for? Is there something I can check to know if I'm pushing the unit too hard, or not enough? Am I forced to rely on my eye to know if it is 'ok'?

Robert

 

[mister_e]

Hey Robert, you're everywhere

TOKO do some EL driver chips. Look at TK659xx family. Some are available from digikey. OR you have some already made solution like JKL components NDL-204 & PALs.

Supertex do some too... **broken link removed**

 

[philba]

you will often find inverters in scanners and you will often find scanners for free (perfectly good older ones). I've salvaged several...

 

[Robert Hedan]

Hi Steve!

Dedicated chips are nice, but I'd like to make my own inverter as a learning experience. This circuit is for personal use only so it doesn't have to be neat and tidy like my main project. I've seen all sorts of schematics for inverters, but many had faults or just looked 'weird' (from not so reliable sites).

And that's why I'm asking here if someone has a link to a decent EL inverter schematic for this LCD.

Robert

 

[Robert Hedan]

Hi again,

I've completed my first attempt at an EL inverter, not very impressive results. The backlight barely glows. Here is a schematic of my circuit:
**broken link removed**

Any suggestions on what to adjust to increase brightness?

Robert

 

[Robert Hedan]

I did more testing this morning, I found it strange that the IC would output a different Hz than specified in the datasheet. Sure enough, my first reading was wrong, I had to have the LCD connected to get a correct reading; I now have 0.255KHz which is just about right for a 250Hz IC.

I also checked the current; 0.35mA, so that isn't really an issue.

I had selected the TK6591x series of chips by placing my multimeter directly on the EL terminals and getting a reading of 5nF. Now I'm starting to wonder if that may have been an error, maybe the EL lamp is really more than that and requires something more powerful than a TK65913 (small lamp size), maybe something like the TK65923 (medium lamp size).

Robert

 

[mister_e]

i think TK65913 would be enough for 8X2 lcd if they exist with EL backlight. TK65923 or bigger will probably solve the problem.

If i compare those EL i have in stock here against LED, it seems LED backlight are a bit more 'bright' than other EL ones... but most EL i have are overstock and surplus ones... so not a good ref point... at least to me

 

[Robert Hedan]

Steve, I'm used to backlighting, this is BARELY glowing, just enough to say that it works and that's it.

I put in an order with DigiKey this morning, I hope to have a TK65923 and 47nF cap tomorrow morning.

Robert

 

[philba]

el brightness is a function of both voltage level and frequency. can you kick the frequency up to like 2Khz?

 

[mister_e]

Philba got a point on that one.. i guess i should read your posts and link better at once...
**broken link removed**

They suggest 400HZ... DOH!

The NDL-204 i use currently work between 450-500 Hz... i have and use those TK65919, TK65929 and TK65939 in stock here... 400Hz unfortunately they don't have them @ digikey now...

 

[Robert Hedan]

Steve, that site also suggested using domestic power to test the EL lamp. Isn't that in the 50-60Hz range?

So that's what I did and the EL came on at about the same brightness as with my inverter. I'm kinda surprised that the EL would work about the same with both 50-60Hz and 255Hz, I expected a big difference (like not work at all).

Robert

 

[philba]

My experience has been in driving el-wire (cool stuff in itself). the typical inverter there is a lot higher than 400 hz. I've seen a couple of documents with charts showing brightness vs frequency and brightness vs voltage. It runs in my mind that the sweet spot for el-wire is like 2Khz and 150 vac. but, the higher the brighness, the shorter the lifespan. I took a quick look for the links to the docs but didn't see them. I really need to clean up my bookmarks.

by the way, to significantly increase the life of the backlight, I would use a transistor to switch on the inverter. press any button on your device and turn on the bl. after a few minute time-out, turn it off.

 

[Robert Hedan]

These LCDs will be used exclusively for testing and really insignificant projects. I use quality LCDs with LED backlighting for all 'good' projects.

Robert