LCD causing havoc...

hi,
i am working on aproject with arduino uno smd ,and a simple 16x2 lcd.
when i upload the hello world program of arduino examples the lcd only works well when connected to the 5V pin of the arduino and not with an external 5V supply.

can anyone help me out with this prob as i cannot use the 5V pin of my arduino.....i have to plugin a ethernet shield with it....

thnx

What about the ground? Do you use the same ground for arduino and LCD?

This is a wild guess, but seems to be a kind of semi-standard answer to most questions like that... electrical noise from the wall-wart?

(Sits back to see if the gurus think so or not :wink: )

see if i use both the 5V and gnd pin of the arduino it works well, arduino is connected to laptop via usb cable....

ashrey:
see if i use both the 5V and gnd pin of the arduino it works well, arduino is connected to laptop via usb cable....

Yes, but the ground of the external supply must be connected to the Arduino ground.