Need Help with LCD backlight.

1

1010

New member
I have JHD12864A 64x128 graphic LCD module. I did't find a good datasheet of this product in the web:mad: .

I want to try out the backlight ckt. does anyone know how much current and voltage does this module takes for backlight?

how to select the resistor value for the backlight without the datasheet?:confused:
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Last edited:
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cosmicvoid

Master
According to the datasheet here: http://www.itron.com.cn/PDF_file/JHD12864A.pdf the forward voltage of the LED backlight is 4.2 volts. No current spec is given. Try different resistors, with a 5 volt supply, starting with 100 ohm, and working downward (or use a 100 ohm 2 watt potentiometer), until the voltage across the LED terminals comes up to 4.2 volts. Do not use less than 4 ohms, which would allow 200 mA, which is probably more than the LED is rated for.

I would guess the current rating might be around 100 mA, which would require an 8 ohm .25 watt resistor. I saw some specs (elsewhere) for two different types of backlight: a 'side' light, rated for 83 mA max, and a 'bottom' light, rated for 192 mA max. So you might modify my advice according to which type yours is.
 
1

1010

New member
cosmicvoid said:
According to the datasheet here: http://www.itron.com.cn/PDF_file/JHD12864A.pdf the forward voltage of the LED backlight is 4.2 volts. No current spec is given. Try different resistors, with a 5 volt supply, starting with 100 ohm, and working downward (or use a 100 ohm 2 watt potentiometer), until the voltage across the LED terminals comes up to 4.2 volts. Do not use less than 4 ohms, which would allow 200 mA, which is probably more than the LED is rated for.

I would guess the current rating might be around 100 mA, which would require an 8 ohm .25 watt resistor. I saw some specs (elsewhere) for two different types of backlight: a 'side' light, rated for 83 mA max, and a 'bottom' light, rated for 192 mA max. So you might modify my advice according to which type yours is.
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Thanks for your suggestion. I tired and it got worked at 20 ohm.
 
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