Hello all,

I have a question about how much current the Arduino can supply through it's 5V pin. I read somewhere that it can supply something like 300 mA. However hooking up a LCD Backlight display between the 5V and GND makes the voltage of the power supply go way down, which means it draws way too much current I guess. The Backlight normally takes around 120 mA so it should be fine really.

The strange thing is, this only happens when I have the backlight connected on power up of the power supply. When I hook up the backlight display later, when it's already on, everything is fine.

I don't have a short circuit in my LCD steering, because I got the same results with a resistor. I can connect a resistor of 100, 150 ohms and it does the same. Current should be 33 mA - 50 mA which is way below the 300 mA mentioned on other places. A 10k resistor does work.

Furthermore I keep having problems with connecting to the board with bluetooth. I can connect for like 5 seconds or a little longer and it just disconnects. I know the problem isn't the bluetooth dongle, since I already replaced this one. Anyone any ideas? It seems to get worse the longer the board is turned on. I thought it could maybe a heat issue, but there isn't any compontent that feels warm really.

Maybe somebody recognizes these symptoms and can tell me what's going on. I thought maybe my board is fried, but the microcontroller itself seems to be running fine. The last program I loaded into it can drive a LCD display and works. Putting a new program is a challenge and can't be done. The connection just terminates like mentioned before.

Hope someone can help me and tell me what to do. If it's indeed fried I need a new one and I realy don't know how I did that, if it is. Maybe somebody has some tips on how to test the board.

Kind regards, Bluesplayer89

The power supply on the bluetooth board is designed to be very efficient at running the board from a battery but it can't provide that much current.

The problem you see at power-up is the power supply trying to protect itself from the surge in power caused by the backlighing.

If the power is not stable you'll have issues with the bluetooth connection.

The connection issue is also very much dependent from the code you're running on the processor.