I hit the dumpster again and pulled out (after much digging and transferring) about fifty Sharp brand 3.6" QVGA TFT LCDs with touchscreens attached. I looked up the info through Google and found they use LEDs for the backlight. Seven white ones, specifically. Tearing a broken one open, I found The LEDs are on a tape about 1/8" wide and wired in series. The spec sheet says they are meant to be driven with about 28VDC. That's not easy to get out of a DC to DC converter. Most don't do that kind of step-up.
What isn't difficult is the task of getting the proper brightness out of the assembly. I used a 12VDC adapter to drive four LEDs initially and found they were decently bright. Hard to look at, at least. Then I remembered the spec of 28VDC and realized I was supposed to be driving three with the adapter I had. Well, I did that and saw dots for about six hours. Each one, spaced the way they are, is more powerful than the same length of a standard CCFL. Giggity.
The small modules mounted to the wider circuit boards are decent, but may be too big without dremel work. The upside to those units is the fact that they are wired in parallel, allowing for easier integration with the 5VDC drive the inverter normally uses. I have a switching converter that will drop 5VDC to the 4VDC I need.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment