So here’s yet another approach: use a small PIR module, like the tiny “arduino” ones I use at Randall. This thing has a 1k Ω resistor on the output, and we can already trigger repeats & duration, so it’s essentially mirroring what a 555 timer would do and at the same time it would only blink the LED when presence is detected in the garage.

That would save on the battery by not blinking it when there’s no one around.

The sensor still needs to be powered.

Links from when I used that kind of sensor at Randall:

Sensor is a HC-SR501. Datasheet link via Aliexpress.

• The SR501 uses a 7133 voltage regulator. We can feed it with the 5V from the AIU’s 7805.
• The BISS001 drives the OUT pin directly via a 1kΩ resistor.

Main component is a BISS0001, datasheet link from Ladyada.

Of note:

• Input voltage: 5-20 V; and on another page it says 4.5-20 V..
• Power consumption: 65 mA.
• Quiescent current: < 50 uA.
• Output TTL 3.3 V.
• Jumper L = single trigger, H = repeat trigger.
• Pot on the jumper side = sensitivity.
• Pot farther from the jumper = time delay (5-300 s).
• Must be mounted horizontal for a variation left/right (e.g. pins at top or bottom).

One thing I had noticed at Randall is that these do not work when powered by 3 V. The unit “blinks” the output repeatedly. My guess is it fails to initialize (they go through a 1-min stabilization phase when first powered).

In my case, that means I need a 3-AA battery holder instead of my current 2-AA battery holder. It does work well with a 3-AAA holder.

On the output side, I got the illumination I want using a 1k Ω resistor on the output and a green LED. Red one was a bit weak for the value, although I could remove the extra 1kΩ.

I installed that and it works nicely as I want.

Update: I got about 1-2 years out of 3 AAA batteries powering this with moderate daily usage.