current consumption in sleep mode

I am using arduino uno for rfid communication and most of the time it is in sleep mode and then it wakes for a moment and check any active card is there and sleeps but in sleep power down mode some of its pins are a high level and they are consuming a lot of current even when the arduino is sleeping.How pins are high even in sleep mode ?

The chip can sleep like a bird - it doesn't let go of the perch when it sleeps. One of the worst offenders for power consumption is actually floating inputs - all un-used inputs must be tied high or low, such as with the internal pullup.

The Uno is not a good choice for low power. There are a lot of peripherals, such as the USB interface, which cannot be turned off. Look at using an Arduino Pro Mini as the final destination of your project. You will need a USB interface to program the Pro Mini, but it's possible to do this with an Uno.

Thats useful to know, thanks Morgan.

Wouldnt it be a better option to set the ports as outputs and write them low as part of the sleep routine?

It's all been answered here: http://www.gammon.com.au/power

thanks, its all working but I don’t know why the during sleep my pins are at high level even I have set the pin to low level before sleep.I am using the pin for spi communication with mfrc522 reader.

kumarsu86:
thanks, its all working but I don’t know why the during sleep my pins are at high level even I have set the pin to low level before sleep.

This would be in your undisclosed code, would it?

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kumarsu86: thanks, its all working but I don't know why the during sleep my pins are at high level even I have set the pin to low level before sleep.I am using the pin for spi communication with mfrc522 reader.

The SPI library will be controlling the pins. Since we havent seen your code, Im going to take a guess its the serial clock pin thats staying high?

try sticking the following in right before you write the pins low:

SPI.end()

and of course when you wakeup again, you'll need SPI.begin()