---+!! Ondio Backlight Mod (preliminary article, to be completed) <img src="%ATTACHURLPATH%/backlight.jpg" alt="backlight.jpg" width="400" height="586" /> %TOC% ---++ Let There Be Light! The Ondio is internally prepared for an EL display backlight, but on the units we've seen this is not equipped. We don't know why, either it was creating interference, or hard to get, or Archos *just saved on the components. The strange thing is that Archos even changed the driver chip when Sipex moved out of the EL market, so they actively maintained the feature. The Archos software is driving the backlight port pin, Rockbox had to learn it. Personally, I miss the backlight and decided to mod my unit by equipping the missing parts. Making a more simple LED backlight was no real option, there is not enough space behind the display. ---++ EL lighting EL stands for electroluminescence. The effect is that certain phosphors are glowing when exposed to an alternating electric field. An EL foil contains such a substance between 2 electrodes. It takes a high AC voltage to excite it, but little current. Typically, about 200V with 200 Hz. A specialized inverter chip (with a coil) is used to generate such from standard DC supply. The good thing about EL lighting is the completely even lighting of the area, and that the foil can be cut into almost arbitrary shape, as long as you don't cut away the connector electrodes. The downside (compared to LED lighting) is a certain wear of the phosphor, it is not suitable for continuous operation. The brightness is noticeably going down in the range of 1000 hours. But for our backlight this should be sufficient. The power consumption is comparable to LEDs. ---++ Material The closest match to the size we need I could find is here:<br> http://www.myplace.nu/mp3/backlight.htm There is also a link to a small swedish web shop where it can be ordered. It comes with a little inverter assembly, but unfortunately not the chip we need. However, the simple way would be to just wire it somehow, there is space e.g. between the main and the tuner board. I went for the more aesthetic solution, wanted the original assembly. However, I took the inductor and the capacitors from the kit, although no perfect match. For the required circuit, see the EL driver datasheets in the DataSheets section. *Still too big: original and trimmed foil, with the inverter from the kit:* <br /> <img src="%ATTACHURLPATH%/foil.jpg" alt="foil.jpg" width="800" height="574" /> *Bill of material:* <br> EL foil in suitable size<br> Sipex SP4403 or NPC SM8141BV, depending on your model, below for SM8141B<br> 470uH SMT inductor<br> 100V SMT diode<br> 100V 100nF SMT capacitor<br> 200kOhm SMT resistor<br> 10kOhm SMT resistor<br> 10-100nF SMT capacitor<br> ---++ Assembly It requires SMT soldering equipment and skills, a very limiting factor, besides the required components. *The missing parts are back:* <br /> <img src="%ATTACHURLPATH%/pcb.jpg" alt="pcb.jpg" width="400" height="531" /> *The look with the foil and LCD sandwich:* <br /> <img src="%ATTACHURLPATH%/lcd.jpg" alt="lcd.jpg" width="600" height="631" /> --- *Other modded devices* Here's mine showing that Rockbox can also handle the backlight:<br /> <br /> <img src="%ATTACHURLPATH%/Backlight-Logo.jpg" alt="Backlight-Logo.jpg" width='400' height='325' /> Many thanks to JoergHohensohn who provided the material and to JensArnold who actually did the mod. :)
r11 - 02 Mar 2007 - 00:09:16 -
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