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CFAH2004A Backlight


New member
Hi. I use 20x4 LCD with PIC16F877A and i need to dimming the backlight by microcontroller minimun two step, one at maximun light and one regulated for the night.

Anyone have make one circuit like this?

Backlight parameters: V=3.5V and I=60mA

(sorry for my language!)

Many thanks, Tony

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CF Tech

One easy way is to use a port of the PIC as a PWM (perhaps 100-Hz nominal). Run that port through a 1K resistor to the gate of a FET (IRLML2502, for instance). Connect the source of the FET to ground. Connect the drain of the FET to the backlight's "K" terminal. Connect the "A" terminal of the backlight through a current limiting resistor (Rlimit) to Vcc.

If Vcc is 5v, Vled is 3.5v and Iled is 60mA then Rlimit is 25 ohms.