I have used these in many projects and in my experience: they are large but highly controllable in that you can change the dela...  Read More

I have used these in many projects and in my experience: they are large but highly controllable in that you can change the delay timing, the distance sensitivity (up to 30') and the repeatability of the trigger timing.  Read Less

The sr501-series motion detectors are very reliable and a stable pir.

The sr501-series motion detectors are very reliable and a stable pir.  Read Less

All pir's require a few seconds to warm up, so plugging them in usually causes them to trigger.

All pir's require a few seconds to warm up, so plugging them in usually causes them to trigger.  Read Less

I have used smaller pir's and most do work, but i have found that the smaller units have an initial delay before turning on.

I have used smaller pir's and most do work, but i have found that the smaller units have an initial delay before turning on.  Read Less

The sr501's have a quicker response time.

The sr501's have a quicker response time.  Read Less