Marketed on ebay as 'alien' displays.
I fancy ordering a couple of these and seeing if I can make something interesting.
From what I can tell they are electroluminescent and require 200v ac at 400hz.
Theres a warning that dc will wreck the display, I was wondering whether I could run the displays from an ac squarewave or if the displays are so peculier that they need a sinewave or maybe a triangle.
Has any of you guys played with these?
I couldn't find those displays on eBay. Maybe it has to do with what country I'm in? Got a link?
Many years ago I had some EL strips that worked nicely with a sine wave (directly connected to the 60Hz A.C. mains actually). Never tried a square wave. And I don't know much about the more modern EL displays. SO I went looking around the Web this evening.
I found this chip that is specifically for driving EL devices. The output is a rather trashy looking square wave sorta thing - look on Page 4 of the data sheet. Also take note of the fact that it is true A.C. that swings to both sides of ground - not just D.C. turning on and off.
Square wave quickly damages anything that is electroluminescent. At DC they will not produce light at all, since they are capacitors. They require very clean sine wave. At 50 Hz they are less bright than at 200 or 400 Hz, but last longer. And they require current limiting resistors if power source has low internal resistance. This resistor will not greatly reduce brightness, but will protect the power source in case of short inside electroluminescent device. I use an electroluminescent backlight unit from Motorola MPX-220's external monochrome display in conjunction with 330 KOhm resistor at 220 V, 50 Hz, and it works fine.
The best solution for controlling of segmented electroluminescent displays is using relays. That's exactly how such displays were controlled in Apollo (which participated in Soyuz-Apollo project).
Ty, interesting devices, and they save a lot of hassle with special components, unfortunatekly none of my suppliers list them, maybe the manufacturer would supply samples.
Dekatron, excellent webpage, and that has given me some ideas, I could use a centretapped small mains transformer and a couple of components to create a simple blocking oscillatoe, last time I tried that I got a few hundred hz, and the waveform isnt going to be much diffo from the manufacturers suggested circuit.
Using thyristors or triacs to switch the segments is a more elegant way than relay contacts, however I liked the mention in the russian data about opto-resistors, I've never seen such a thing, but I could make something with a led/norp12 ldr and a bit of black tubing, 8 of them, one per segment isnt ridiculous, using a pic I could synchronise them to the ac making multiplexing possible.
The Russians seems to drive these with small transformers pulsed by transistors to get the necessary 220V AC or by 220V AC directly from the mains plug and then using thyristors or triacs to switch them on and off.