SparkFun Forums

[rickblair]

I am using the serial LCD (LCD-09393) on a project and it works perfectly, that is until I switch from USB to external power supply. On USB power everything works as expected. When I change to an external power supply, all other perifrials work, but the LCD won't come on. I have tried with just a bare UNO with only the 5 volt, ground and digital pin 2 connected. Same behavior. USB works great, Power supply does not work.

I have tried 2 different power supplies. 5 volt -2Amp and a 5 volt 10 amp! Same issue.

Everything else gets power from the 5 volt output on the arduino just fine.

I even went so far as to use an external 5 volt supply, but the serial expects the ground for signal and power are the same.

Any insight would be much appreciated.

Thanks

[darrellg]

Are you plugging a 5V power supply into the power jack of the Uno? That jack requires 7-12V to regulate properly.

Also, when you are powering devices from separate supplies, it is expected that the grounds will all be connected to each other.