I use sunset to automate some inside lights. Lattitude is about 54 degres. I noticed that in summer it doesn’t get dark until a good 40 mins until after sunset. To be honest in the middle summer twilight doesn’t really turn to night. In the winter its dark much closer to sunset.
So I have built this light sensor.
I had an old outdoor temp and humidity sensor that I bought >15 years ago that the NTC temp sensor had rusted off(it worked by 433mhz). It could measure between -31C and 70C. I replaced the sensor with an LDR and I needed to add about 8K resistor in series with it to get a decent light detetion range.
I replaced the 2xAA cells with a TP4056(with a 10K resistor to reduce the charge current given the tiny solar panel). I attached a 350mAh cell I found in a vape I found in the hedge around my garden. I attached a 30x90mm 5 Volt solar panel and housed it all in a IP67 (100x68x50mm) case.
I took the chance that it would be 4.2V tolerant. I didn’t have a 3.3 LDO to hand.
There has been no sunshine in past few days but it get’s to about 99% at 9am.
So far it looks like I would like inside lights to come on when light outside is at about 90%.
I pick up the signal on my RTL-SDR dongle.