Controlling LCD power

Using Arduino Displays
1

Howdy!
So I'm try to control the turning on and off of an LCD using an IR remote. I first tried to put the 5v through a transistor and using a digital pin to enable the screen, but this failed. Tried to run the LCD GND through the transistor, fail.

I tried the same with a 4N28 optocoupler and if I run the 5v through it, it barely powers the LCD. If I run the GND through it I get absolutely nothing going to the LCD. I believe running the GND would be the proper way to do it.

Any suggestions as to what I am doing wrong? Many thanks!

(cut down diagram to simplify, can provide full sketch if it would be helpful)

2

So I'm try to control the turning on and off of an LCD using an IR remote.

Why? Are you trying to save power or would simply blanking the message achieve what you want?

Don

3

To save power. So the main function is to be a camera dolly. Im using the IR and LCD to set a heap of values before pressing "run" which could run for 1-3hrs. I want to knock off the LCD just before that point.

4

To save power.

You might want to look at this thread --> http://arduino.cc/forum/index.php/topic,161077.0.html for some ideas. You may find that just turning off the backlight will save enough to satisfy your needs.

I first tried to put the 5v through a transistor and using a digital pin to enable the screen, but this failed.

It shouldn't have failed if you did it correctly. You want to use your digital pin to control a PNP transistor as a 'high side switch'. When I did a Google search for 'PNP high side search' I got lots of answers. You would substitute your LCD power pin (usually pin 2) and/or your backlight pin (usually pin 15) for the top part of the 'load' and the LCD GND (pins 1 and/or 16) for the bottom part.

Don

5