EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Drjaymz on December 06, 2024, 12:28:50 pm
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I bought some EL paper from eBay which comes with a cheapy EL driver, so cheap you can hear it singing away and something like 4khz.
What I didn't expect was that when I came out of my dark shed the frequency of that singing changes. I covered it up and it goes back. I went to my desk lamp and sure enough the freqency of the circuit changes when light falls on the EL strip. I was not expecting that.
I haven't mangled the driver yet, but its probably a self-resonant super cheapy thing, I think it produces AC. so just a couple of transistors and maybe a transformer or something even more crude.
I googled it and didn't find much. I would image some property of the material changes with light exposure. Its unlikely to be temperature because its instant, capacitance or resistance maybe.
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Ok, because I'm meant to be working I don't have all my kit with me, but I have got a chinese component tester. I checked and the frequency reduces when its light.
It thinks the panel is a capacitor with an ESR of 17R.
In the Dark it thinks its 11nF
In the Light it thinks its 22nF
So its a light sensitive capacitor - thats pretty groovy, its not a slight effect either, it doubles its capacitance.
I did open the driver and its a centre tap inductor (looks like mini transformer) there are two SMD transistors and a 5pin package which might be a double fet or diode jobby, not sure its so small I cannot see a thing, but I imagine its a push pull oscilator thing.
So I didn't know that and I guess if I searched properly I'd probably find it mentioned online somewhere.
I'm going to guess there is a photodialetric effect? Never heard of it.