AVR-Chat

--- In AVR-Chat@yahoogroups.com, jay marante <jaythesis@y...> wrote:
> i have a 4x20 character LCD with 16 pinouts. ... It's pretty 
> obvious that pins15 and 16 are for the backlight. i don't know 
which is for the VCC and GND...

Pin 16 is most likely ground and pin 15 is typically a variable 
voltage to adjust the intensity of the backlight (0V darkest, 5V 
brightest).

Your circuit would probably work.  You could also feed pin 15 from 
the wiper of a pot to allow adjustment of the backlight when it's 
switched on by the transistor.

i have a 4x20 character LCD with 16 pinouts. well, i already have the pinouts for pins 1 - 14. its pretty obvious that pins15 and 16 are for the backlight. i don't know which is for the VCC and GND, and how i should connect them. but i alreay have the switching circuit for backlight to turn it on and off. its just composed of a trasistor.
 
                   VCC (5V)
                        |_____
                        _____    >   TO LCD
                        |
                       <     Resistor (470 ohm)
                        >
                        |
                       /
to MCU --v^v^---|                      the transistor used is 2N2222A (NPN) 
               R     \
                       |
                       |
                    GND
 
is that circuit alright?
 
TIA.
 
-jay


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At 08:01 PM 10/04/04 -0700, you wrote:
> Resistor (470 ohm)

This is probably too high. Check the data sheet it should show
the value for the series backlighting resistor and it may be
as low as 15 (one five) Ohms. Also you may get a better result
by using a small fet (2N7000??) for the switch instead of a transistor.
The VCC or anode is usually shown as "A" and the cathode or
Gnd is marked as "K"

Regards

John Samperi

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