Hi to everyone,

Thanks for simming the circuit Torben, the infor about the peaks and such is nice to know.

As for Sarma's suggestion about just giving up and buying new LCDs, well I got the displays cheap and because my means are limited I usually have to work with what I have to hand. I know in an ideal world none of us would have to make do, but sadly I am still looking for that utopian bliss

Also Audio Guru suggests that an Oscillioscope would be better to measure the output, but sadly a scope is not yet on my agenda due to limitations of cash, but I live in hope, and considered making one of the simpler PIC based PC scopes? Thoughts?

Anyway I wondered if there was a different way of measuring the output, no doubt someone knows of a fiendish method that doesn't involve a scope?

Further to Torbens suggestion that the circuit is overkill, I was wondering if simply putting the output of a 555 astable circuit running at the required frequency through a small audio output type transformer could be possible, again I am thinking this simply because I have some of them to hand, and from the specs on the backlight it seems that very little actual current would be drawn.

Which brings me to one final question - would I need to limit the current to the EL as is required when using LEDs or is the EL somehow self regulating?

Thanks for all the suggestions and help guys, keep it coming please.

Al

Originally Posted by bigal_scorpio

Hi to everyone,

Thanks for simming the circuit Torben, the infor about the peaks and such is nice to know.

No problem.

Further to Torbens suggestion that the circuit is overkill, I was wondering if simply putting the output of a 555 astable circuit running at the required frequency through a small audio output type transformer could be possible, again I am thinking this simply because I have some of them to hand, and from the specs on the backlight it seems that very little actual current would be drawn.

It's possible, at least mathematically. There are simple circuits like this one. I played around with it for a while in LTSpice and came up with this:

Try whatever transistors you can--I'd start with TIP41 and TIP42; I just used the ones listed because I had models for them.

[Edit: just to clarify: that's not my circuit; I just modified Tony van Roon's to do what I wanted.]

Another note: I find that the sim hits around 400Hz output with the pot's wiper at around 0.75 (turned three-quarters up).

Which brings me to one final question - would I need to limit the current to the EL as is required when using LEDs or is the EL somehow self regulating?

Thanks for all the suggestions and help guys, keep it coming please.

Al

I don't know the answer to that question. The circuit I posted delivers about 20mA into a 5kOhm load, but I don't know what kind of load the EL presents. The datasheet for the EL panel doesn't show any current limiting on the example schematic, but that doesn't mean that the driver chip used doesn't limit the current.


Torben

Hi Torben,

Just about to start building your circuit when I noticed something iffy. Are C3 and L2 doing anything? There is a link that bypasses them, is this intentional?

I must admit to being a bit lacking in knowledge about inductors so if the bypass is intentional please let me know.

Thanks again.....Al

Hi Torben,

Thanks mate, I'll get building and good luck with the ballgame

BTW just had an idea about testing the output on the other circuit I made, wondered if I could try a Neon lamp (from an old lighted switch) across the output, but I didn't get a flicker!

Al

Originally Posted by Torben

The bypass is just to get the darn thing working in LTSpice. Myself, I'd try it just leaving bypass out to start with.

LTSpice is probably simulating it right. Q2 should have it's emitter and collector lead swapped and R4 should be a jumper. Then you can take out the bypass.

Originally Posted by bigal_scorpio

Hi Torben,

Thanks mate, I'll get building and good luck with the ballgame

BTW just had an idea about testing the output on the other circuit I made, wondered if I could try a Neon lamp (from an old lighted switch) across the output, but I didn't get a flicker!

Al

Hi Bigal please see whether the document in the link below could be of some help for the EL backlit inverters.

http://stekinc.thomasnet.com/Asset/I...IMP803-pdf.pdf
If so, most probably the inverter element used in an old calculator with vacuum tube display (green) would perhaps be suitable instead of re-designing one.

Here's a really simple to build L/C meter
http://ironbark.bendigo.latrobe.edu.au/~rice/lc/index2.html