Battery life on wireless PIR

[greg.g...@gmail.com]

According to the wirless project for the passive infra red motion sensors you reccomend either 4x aa or a single 9v battery for the PIR sensor ,..

Any idea of expected battery life with these 2 options ?

[Gadjet Nut]

Battery life calcs are not a perfect science as there are so many variables. The SR501 uses 40 uA when no motion is detected and 140uA when motion is detected. So let's go with worst case where the sensor is placed in an area that has constant motion.

4xAA batteries = 4000mah
4000/0.14=28571 hours (1190 days)

9V battery = 250mah
250/0.14=1785 (74 days)

I normally go with 75% of what the calculation comes to.

[greg.g...@gmail.com]

Thanks I'll test and provide feedback ..4x AA sounds like the obvious way to go