Wall Adapter inquiry

Hello every one.Please i have 2 questions about wall adapters 1-Is it suitable to use a Wall Adapter 12Vdc (1A) with (Arduino uno+It's ethernet shield) or i will face a problem with the wall adapter's ampere . 2-I want to make my system(that will work on a wall adapter ) working even the Electricity Power is cut.I think about a wall adapter with a backup battery but can i find something like that for the arduino or i should look for another solution. Many thanks.

Too much current won't hurt, too much voltage will. A "12V" wall-wart might give 20V without load if its unregulated - its important to know if the supply is regulated (much prefered).

The higher the current at 5V you want to use with your circuit the more important it is to keep the power supply low voltage (the regulator on board turns excess voltage into heat proportional to total current). A good quality 5V regulated supply can go directly to the 5V pin, a regulated supply from 7V up goes to Vin and uses the on-board regulator.

One way: Have the wall adapter go thru a diode to the Barrel Jack connector, and have your lower voltage battery go thru a diode to the barrel jack connecter. When the wall adapter voltage goes away the battery will kick in.

MarkT:
Too much current won’t hurt, too much voltage will. A “12V” wall-wart might give 20V without load if its unregulated - its important to know if the supply is regulated (much prefered).

The higher the current at 5V you want to use with your circuit the more important it is to keep the power supply low voltage (the regulator on board turns excess voltage into heat proportional to total current). A good quality 5V regulated supply can go directly to the 5V pin, a regulated supply from 7V up goes to Vin and uses the on-board regulator.

Thank you.but if use a regulated Wall Adapter 12Vdc (1A) with the (uno+ethernet shield) 24/7 will it harm any thing or i should get a lower voltage due to the working period.

CrossRoads: One way: Have the wall adapter go thru a diode to the Barrel Jack connector, and have your lower voltage battery go thru a diode to the barrel jack connecter. When the wall adapter voltage goes away the battery will kick in.

Thanks but i want to know do you mean that the same the Barrel Jack connector will be connected with the wall adapter and the battery and it will choose the power source automatically.

For the battery backup you might want to think about something like the SparkFun LiPower shield.

https://www.sparkfun.com/products/10711

It's a Lithium Ion / Lithium Polymer battery charge controller for the Arduino, so you can power your system of nice high power Lithium batteries and safely manage the charging of them.

You will need a regulated 5V power supply for it though, so in stead of a 12V wall wart, you might want to think about a 5V phone charger instead.

This is what I was referring to. No battery charging.
When Vdc is higher than Vbatt, the battery diode is “reverse biased” and current from the battery does not flow.
When Vbatt is higher than Vds, than the battery current flows into the Arduino.
I recommend a diode with Low Vforward, such as a 0.3V shottky diode.

Many Thanks CrossRoads and majenko .

No problem.