how can I minimize battery usage for door monitor?

Hi,

Any recommendation how to keep to a very minimum usage of battery for an Arduino board that will be powered by battery and monitoring door open/closed status (use of magnetic reed switch for detector & RF transmitter using virtualwire library).

For example: a) should I use polling or interrupt (I assume an interrupt would be better)? b) if using an interrupt what best to do in the main loop? e.g. put a long delay? nothing? c) anything else I should do in the setup() method to help reduce power usage?

Some notes: i) I was assuming I'd use a 9V batery ii) I'm using the "Arduino Pro 328 - 5V/16MHz DEV-09219" http://www.littlebirdelectronics.com/products/Arduino-Pro-328-%252d-5V%7B47%7D16MHz.html. This seemed to be the cheapest board for what I need (?)

thanks

You may want to put your Arduino to sleep and only wake it up when there is something to report.

http://www.arduino.cc/playground/Learning/ArduinoSleepCode

Also, you could look into powering your RF transmitter from an Arduino digital output. Turn off power when sleeping and only power it up when needed.

thanks - I really like the "look into powering your RF transmitter from an Arduino digital output"...great idea