A Narrow Scan PIR

The PIR datasheet (and bandpass of the electronics) indicate that the sensor will respond to signals up to about 10 Hz but at reduced sensitivity. Therefore scanning for "Little Monsters" (LMs) is feasible.

The next step is to consider a suitable narrow beam "lens". After much research the lens became a vertical slot. The slot is designed for an apperture of 10 to 15 degrees horizontally and 30 to 40 degrees vertically:

Here is the SE-10 mounted inside the box:

The initial testing worked great:

• The sensor appertured appeared to be about right.
• The sensor did not react to very slow LM movements (i.e. tippy-toe) across the apperture.
• Responded with a dual pulses for slow LM movements entering and leaving the apperture.
• Responded with a single pulse when leaving the apperture for fast movements.

Without a suitable motor base, the sensor moves too much when scanning but it was clear that "fast" scanning works.

AlanX