Power Supply Issue with UNO R3

Projects General Guidance
1

I am creating a Game Show Buzzer similar to the one found at ProjectNotions - projectnotions.com - Quiz Game Controller

I am using my computer and the USB connection to run and test the system. I want to use a 12 volt switching power supply for my project. When I attach the +12 to Vin and - to GND. I get 4.92 volts output on the UNO board.

The problem is when I get it hooked up and throw the switch the lights go crazy without any of the buttons being pressed. Could this be ripple and noise from the power supply?

I have also tried using the Japan Jack using a plug-in wall adapter that outputs 12 volts. The center barrel connection is +. It doesn't work either... I get the same results.

Any ideas?????

2

Where are you measuring the 4.92 volts?

Post a link to the datasheet for the 12v power supply.

And please confirm - are you saying that everything works properly when the Uno is powered from the USB connection?

...R