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A very basic dusk sensor supplied with a bulkhead light from a prominent UK trade supplier (Toolstation).  It is so minimalist that it has slight stability issues at the transition from on to off.

https://youtu.be/-I-XQdFWmIQ

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Very minimalist dusk sensor with flicker issue

Dave sent this for our exploration. It's a dusk sensor that was built into a wall mounting bulkhead light, but the very minimist circuitry means that at the transition from day to dusk (and dawn) the light will flicker. This module was probably intended for tungsten bulbs, but has survived the transition to LED versions. The stability issue is purely down to the simplicity of the circuitry and the lack of significant hysteresis at the switching point. There's a high probability that it's sensitive to light leakage from the bulb it's controlling. Given that it seems to switch near the zero crossing point, it shouldn't harm most lamps, but it's still not an ideal way to control them. The fix is to swap it out for a three wire version that has a permanent supply so it can use more sophisticated circuitry. If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty. #ElectronicsCreators

Comments

Mike Page

I did a skiplight design back in 2004 which used a photodiode for dusk sensing. And yes - it is totally necessary to include some hysteresis to avoid chatter. It also helps to mitigate feedback from the light being controlled to the light sensor. Otherwise congratulations you just built an optical oscillator!

Anonymous

Instead of adding a light to indicate when that test unit is on I’d just replace the switch with one with built in light, I always put switches with built in 230v illumination in everything I build so I at least know if the thing has 230v when I suspect a bad PSU for example.