Other Question to the electronic engineers

[Deleted member 103]

Hi guys,

I use an Arduino Nano USB-powered and 9V battery.
The standard circuit of Arduino is so that is always uses the input with the higher voltage.
I want to but that Arduino 9V battery only be used when there is no voltage on the USB port is available.

Know someone how I can do that?
Perhaps a simple circuit?

 

[Deleted member 103]

Hi Filippo
You are using an operational amplifier IC but refering to it as solid-state relay. The IC LM358 is an op amp while the number in the red arrow in post# 18 is refering it as CPC2317N which is a relay.

In the Fritzing circuit I have the LM358 because have not found a template for the CPC2317N.

 

[Deleted member 103]

Finally it worked.
I have used this here and now works as intended.