5V Out Pin Gives More Than 5V


I am trying to power an SD card shield, pitot tube and a 10dof IMU with an Arduino. Unfortunately, the Arduino only has one 5V pin so it is powering both the pitot tube and the IMU. When I power the Arduino with my computer's usb port everything works, but it breaks down when I go to power it with a 9V battery.

The 5V out pin gives more than 5V (~7.6V measured with multimeter) when powered by the 9V battery. When powered by the computer it gives about 4.5V. This is messing with the pitot tube because it is purely analog. My question: is this a problem with the power source, or is it possible that I am overloading my Arduino and it just can't keep up with the current draw? What tests can I run to troubleshoot this?

Thanks for your help!

If the 5v pin gives more than 5v I suspect something is broken.

How much current are your peripherals drawing from it?

The PP3 type of 9v battery is generally useless for an Arduino because it can't supply enough current - but that should not explain your high voltage.

Are you sure you are not reading the voltage on the Vin pin ?


Use a multimeter to check there is not a short circuit between Vin and +5V pins, since that
is strongly suggested by the observations. BTW you may well have a dead board since 7.6V is
above the absolute maximum supply voltage for the ATmega chip, which is 6.0V


Thanks for your replies. I will be checking the current and for a short later today. Is there a power source that you can recommend over a 9V battery?


The perfect power source depends on what is already available in the rest of your system. A 7.2V lithium would be good but there's no point adding a special battery just for the Arduino if you already have a different battery.

A good DC-DC buck or boost converter is essential for most other voltages. While the Arduino can run off 12V, the internal regulator can't supply much power out to connected devices with a 12V input.