Arduino Ground Pin Limits

[ddileona]

Hi all,

I have an Arduino Leonardo that is currently communicating with two sensors. The first sensor is a turbidity sensor that runs off the 5V pin of the Arduino. The second sensor is a water level sensor that runs off a 9V wall adapter. Both are grounded to the Arduino ground pins. 

I need to add a third sensor for temperature and will have an input voltage of 3 - 5.5V. I have two questions:

1) Can I connect all three of these things to the Arduino ground? I want to say yes, but I also don't want to fry my board.

2) The temperature sensor needs 3V-5.5V.  Can I also connect it to the 5V pin or will that cause problems?

Thanks!

[DVDdoug]

That should be no problem.   There is a limit to how much total current the Atmel chip can source/sink, but that ground current isn't going through the chip.

2) The temperature sensor needs 3V-5.5V.  Can I also connect it to the 5V pin or will that cause problems?

If it doesn't need too much current you'll be OK.   The on-board voltage regulator has a current limit, but that limit depends on the applied voltage and the ambient temperature.... and I don't know how to determine the actual limits.