LCD backlight control with BJT

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hi all,

i'm new arduino , research online found out pin on lcd screen used backlight control.

i want control backlight depending on values obtained ldr. have managed ldr working , reading values well. furthermore, researching found cannot directly connect arduino pin on lcd. need bjt.

could please guide me how can decided bjt can used purpose? possible suggestion bjt?

many thanks


 

 

1. have check (datasheet of lcd), max current flowing through backlight. determine how current bjt has handle (there operating range).
backlight current assumption: 50ma. (recommendation: don't go max! (mightbe on 120ma !).

2. voltage won't issue if power 5 .. 12v.

3. have decide, if go npn or pnp, depending on how switch transistor. if go high activate backlight, npn bjt do.

4. there dozens if not hundreds of npn's out, match requirements.
taking above said consideration, go e.g. bc547 or equivalent.

(max ec voltage = 45v, max current = 100ma).

look @ link, find more information.


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