Sunday, April 12, 2009

Adventures in Backlighting Part 1

My K5m needs a new backlight.  Has for some time, actually... and, unfortunately, most of the places that were carrying them a few years ago seem to have disappeared.  So I figured I'd try a DIY approach.  

I know from having tested it previously, using a battery-powered inverter and a length of EL wire, that both the backlight itself and the inverter are bad.  I ordered a sheet of EL material and connectors from's small-quantity online store, along with some connectors.  It's a cut-to-size sheet, so I can cut it to fit into the space inside the K5m's LCD display.  For the inverter, I ordered a Hantronix HVI-5E from Mouser; it appears to be about the same shape and size as the existing one, and should be easy to retrofit.  The inverter's output is spec'ed as 90V at 400 Hz.  

First, I set it all up on my workbench:

I'm using the power supply from one of the function blocks of the Discombobulator to power this experiment.  The inverter is shown plugged into the experimenter socket in the center of the picture.  It takes +5V DC.  The EL sheet is the foil-colored panel to the right (this picture shows the reverse side).  Here's a close-up of the connection:

Here's the front side.  It's only pink when it is not powered; it is supposed to light up white.

Unfortunately I haven't gotten it to work yet.  Every time I connect the sheet, the power supply shuts down.  It also does that if I try to probe the inverter output with the scope.  If I just hold the probe close to the connector, I can see the AC waveform on the scope and it looks good, but the moment the scope probe touches the conductor, no more power.  Haven't figured that out yet; I don't know if it's overloading the +5, or if the inverter does something nasty that tricks the protection circuit.  I guess I'll need to try a different supply.  

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