Buriedcode
Full Member level 6
homemade backlight
Hi,
I've got a few nokia displays, and some generic LCD panels, and I'm thinking about making my own backlight, since buying them is terribly expensive, and its hard to find exact sizes (well, enough to cover the panel, but not too much).
I'm not into EL, or CCFL, just LEDs, these are cheap, available in many colours, easy to drive, and are in many shapes (rectangular, SMD etc..).
The nokia LCD's (3310, 3210, monochrome ones) use LED's on the PCB to backlight (side light), with the plastic keypad frame as a light guide, with a white sticker underneath. This seems to work, but wastes a lot of light (used to light the keypad as well). The leds are not 'under' the LCD, they are facing upward, and the plastic frame covers them, curving at a right angle going under the LCD.
I was thinking of using some clear acrylic as a sort of light guide, but its difficult to polish for reflecting surfaces, for internal reflection, so could I just use some mirror tape, or metal foil? OR would 'white tape' be the best option?
I was hoping that, for side lighting, I could simply mirror three sides of the plastic sheet, and the bottom, then place some sort of diffusing filter over the top, and wack it under my LCD. I could make a small plastic housing for SMD leds that clips on the un-reflected side, and makes sure all light goes into the plastic. Also, maybe 'roughen up' with a file the bottom surface, before putting on the foil, to scatter reflections all around the panel.
Also, the 3310 LCD (without the keypad housing) has a silvery film over the bottom, which lets 'some' light through. I personally think this is a reflector, and I've read that to add a back light, the reflector must be removed, and placed under the backlight (so the BL is sandwiched between LCD and reflector). But why would nokia place the reflector between the BL and LCD? Unless of course its simply a polarizing filter, but its like tarnished silver.
Sorry for the long post, but ANY idea's/experiences with LED backlighting, light guides, diffusuers would be welcome. I find it hard to believe that making an effective cheap BL is so hard.
Thankyou,
BuriedCode.
Hi,
I've got a few nokia displays, and some generic LCD panels, and I'm thinking about making my own backlight, since buying them is terribly expensive, and its hard to find exact sizes (well, enough to cover the panel, but not too much).
I'm not into EL, or CCFL, just LEDs, these are cheap, available in many colours, easy to drive, and are in many shapes (rectangular, SMD etc..).
The nokia LCD's (3310, 3210, monochrome ones) use LED's on the PCB to backlight (side light), with the plastic keypad frame as a light guide, with a white sticker underneath. This seems to work, but wastes a lot of light (used to light the keypad as well). The leds are not 'under' the LCD, they are facing upward, and the plastic frame covers them, curving at a right angle going under the LCD.
I was thinking of using some clear acrylic as a sort of light guide, but its difficult to polish for reflecting surfaces, for internal reflection, so could I just use some mirror tape, or metal foil? OR would 'white tape' be the best option?
I was hoping that, for side lighting, I could simply mirror three sides of the plastic sheet, and the bottom, then place some sort of diffusing filter over the top, and wack it under my LCD. I could make a small plastic housing for SMD leds that clips on the un-reflected side, and makes sure all light goes into the plastic. Also, maybe 'roughen up' with a file the bottom surface, before putting on the foil, to scatter reflections all around the panel.
Also, the 3310 LCD (without the keypad housing) has a silvery film over the bottom, which lets 'some' light through. I personally think this is a reflector, and I've read that to add a back light, the reflector must be removed, and placed under the backlight (so the BL is sandwiched between LCD and reflector). But why would nokia place the reflector between the BL and LCD? Unless of course its simply a polarizing filter, but its like tarnished silver.
Sorry for the long post, but ANY idea's/experiences with LED backlighting, light guides, diffusuers would be welcome. I find it hard to believe that making an effective cheap BL is so hard.
Thankyou,
BuriedCode.