These light sensor switches seem to be very common on eBay, so I bought one to check it out. I wouldn’t recommend these for switching high inrush loads like a metal halide light, but they look quite acceptable for low power LED lamps. The units are rated at 10A, but I’d advise against using them anywhere near that rating.
The simple capacitive dropper circuit is not rated to supply the relay’s full current continuously, so the voltage rail drops to about 6V when the relay has pulled in. This is actually a good thing, since it won’t harm the power supply and it reduces the dissipation in the relay’s coil. When the voltage rail is pulled down by the energised relay, all the voltage divider reference voltages drop to match, so it doesn’t really affect circuit stability, although it does explain the shorter turn off delay.
Probably points of failure are the relay contacts if used with a high inrush or operational load, possible water ingress, although it does seem to be designed to shed water in a controlled manner and the inevitable degradation of the dropper capacitor which will finally result in the relay not pulling in properly.
Here’s a link to Andrew’s website where he’s selling the Quicktest units.
Here’s a link to a general search on eBay com for the dusk sensors.
110V version –
220V version –
12V DC version –
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