T i m wrote:

The bit of very clear blister pack seemed to have quite an impact so
I'll run some tests and compare. ;-)

What are your objectives, for this overly scientific sensor ?

I have a sensor which mounts on the carriage lamp out front
of the house. It costs about as much as a light switch at
the hardware store.

Photocell sensor. Mine is brick-shaped, with the CdS sensor
mounted on the side of it.

https://images-na.ssl-images-amazon...._QL70_ML2_.jpg

"Time Delay Function : Accurately judges natural light,
won't be triggered due to occasional light such as
car headlights, lightning or other temporary light.

It's suitable for parking lot, street lighting,
outdoor lighting, factory, indoor lighting"

(Example of a CdS sensor as a component...

https://media.digikey.com/photos/Adv..._PDV-P5001.jpg )

The thing has at least three wires, and there's probably
a Triac in there doing the appliance switching.

And their claim in that description is accurate. I've
never seen a false trigger on the thing. A car can drive
by, the light stays on. It's not a motion sensor. The light
it controls, is not some kind of strobe show, like all the
neighbours lights. Mine failed at some point, I bought a
new one and fitted the sensor to the pipe-with-a-hole it
mounts inside. And it's been running for probably 20 years
at this point.

Now, the Triac part is no good for your purposes. But
as far as the sensor function is concerned, it accurately
detects dusk. The light will come on whenever there is a
"complete solar eclipse". Any condition which is sufficiently
dark and sustained long enough, will switch it on. And I
don't go out and "clean the sensor face" - there is no
maintenance whatsoever.

It was cheap, and surprisingly fit for purpose (shocker!).
At the price, I was expecting Magic Smoke or Quibbles.

Paul