Problem Power Arduino Uno: Drop in Vin when 5V output connected to BackLight LCD

Hello everybody,

This is my first post in the forum, I hope that I am following properly the rules.

I am powering my Arduino Uno with an external power source at 9 V using the Vin input. Then I am using the 5 V output to power the Blacklight LEDs for an standard LCD. The problem that I have is that when the Backlight is connected, suddenly the Power Source supply drops from 9V to 5V.

Nothing else is connected to the Arduino, just the Power on Vin, GND and the backlight for the LCD.

Any idea about what can be happening?

Thanks a lot.

The backlight is drawing more current than your 9V source can supply. Is it a PP3 9V battery?

Do you use a resistor for that (led) backlight ?

Hey guys,

Sorry all of you for not answering some month ago. It was my first post on the forum, and since short after writing I found the problem, I completely forgot to answer you again, I am terribly sorry. Today, looking old messages I noticed that.

Just for the record, the problem with my LCD with simpler than that. I had bought the LCD in the local hobbyshop, and they didn't give me any documentation, so I found one schematic on the internet that I thought it was the right one, however it had the pin number changed, so I wasn't powering the back light properly.