TI-H: Indiglo (and other EL) backlighting
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TI-H: Indiglo (and other EL) backlighting
Okay, this is for everybody who is guessing at just what it takes to
make Indiglo glo. Having recently purchased an LCD module with
electroluminescent (EL, aka Indiglo) backlighting, I have a good idea of
how it works. Here goes:
The EL panel itself is very thin, approximately 1 mm. It's got two
terminals coming out one end, where the supply voltage is connected. EL
panels run on AC. That means that a DC source (batteries) isn't going to
work. They also need a fairly high voltage, say about 120-130v.
According to my spec sheet on the EL backlight, the light output is
directly related to the AC voltage and the frequency of the AC voltage.
My graph goes from 0-150v on the x and 0-200 cd/m² (brightness-the '²'
is a squared symbol) on the y-axis. At 50Hz/150v, the output would be
about 20 cd/m². However, at 1kHz/150v, the output is near 250 cd/m²-a
pretty good glow. But at 1kHz/40v, the brightness is only 30 cd/m².
Now, to run the EL panel in an environment where you've only got DC
source (like the TI), you'll need to use an inverter to make AC. You
could use some transistors, capacitors, resistors, a transformer, and
the like to accomplish this. Or, you could just buy an inverter. I chose
to just buy one. It is made by NEC and cost me about $10. Their price is
related to how much current they can produce-a larger EL panel will draw
more current; its inverter will be more expensive. The inverter package
is about 1x.5x.75 inches, with 3 pins sticking out the bottom. I
seriously doubt it would be possible to fit an inverter inside the TI,
however, it shouldn't be too difficult to install a jack or other
connector to pass the DC out to supply the inverter, and the AC back
into the TI to power the EL panel.
While I'm at it, what is the cost and the lighted area (size) of the EL
panels you folks have been finding at stores?
--
Greg Hill
http://braves.bhs.davis.k12.ut.us/
mailto:ghill@lab.tech.bhs.davis.k12.ut.us
mailto:greg_hill@email.state.ut.us
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