The white LED’s have finally arrived. Let’s see if it’s possible to use them for illuminating the TFT screen.
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To get the illumination as uniform as possible, I decided to use one LED per cm resulting in a total of 21 pieces. A narrow (5mm) strip of an OHP film serves as a carrier for the LED’s. I put a small resistor (100 Ohm) close to every LED to have the same current going through all of them. At 5V, the measured total current is about 350mA, so the current through each LED is about 17mA. So the voltage drop in the LED is about 3.3V. Of the total power of 1.8W, about 30% are lost in the resistors while the rest goes into the LED’s.
The result is not bad; the screen is slightly brighter at the top near the LED’s, but for a first try, it’s working fine!
