External Power Arduino

It has been much discussion around the power supply voltage of the transformer for Arduino, but nowhere is it discussed the current power supply must provide this. So I would please ask in this topic to summarize the desirable characteristics of an external power supply (transformer) ideal for powering our arduino one, thanks.

I feel that this is a bit of a general question that can be answered in a million ways.

The only good answer imho is : check the specs of the arduino in question and adjust the power source to your needs. If the power source is within specs and the form factor suits your needs; your in business.

BTW a transformer alone is not enough, you will need a diode bridge, voltage controller and some capacitors...

Just my two cents :-)

Why you need a bridge of diodes, capacitors, voltage regulator and some ... ?

You are mentioning a transformer and that component typicaly supplies a AC voltage. The arduino need DC voltage to function.

I suggest you look into the basics of this before you use you arduino, if you get it wrong, you can fry it.

BTW, there are a lot of power supplies out there that can connect directly to an arduino without any alteration.