Hey bertn, there's no difference between the sensor you used (that you call NO) and the one you linked to (the one you call NC). Both are E3S-G30E4, which are chinese knock off of Omron E3S-G3E4 (you can check the datasheet here: https://downloads.omron.eu/IAB/Prod...els/E3S-G/E036/E036-E1-02+E3S-G+Datasheet.pdf), and there's no NC in photosensors like you can have relays that are normally open or close. You can either get an NPN version which will sink current (it's the one you got with suffix -E4) or a PNP version that will source current (suffix -B4). You can use an NPN to source current too but it's only like 2-3mA, which is not enough to energize the coil of a relay (it's enough for a semiconductor). You can also switch between light-ON and dark-ON by switching polarity on the brown and blue wires. The guy on ebay is probably just trying to grab a few extra bucks by selling the same thing. It's typical of those knock-off, they exagerate the specs to make their stuff look better (both input voltages and sink current are all over the place if you look at ebay sellers, real values are 12-24VDC and 80mA).
In order to do what you want to do in this diagram you'd need a PNP sensor and the circuit would need to be a bit different. You could get a PNP, but there's no chinese knock-off and the real omron are kind of expensive (~50$). The way you made it with 2 relays is the right way.
Nowaday you'd use darlingtons (something like DS2003), SS relays or plain transistors instead of magnetic relays, cause they have much longer life and cost less during mass production (which is obviously not a concern here
). If you use the tiny relays in your first picture, make sure you place a diod on the coil (something like 1N4007) so current spikes don't destroy it too quickly.
Do you use the screw on the left to adjust the height of the sensor?
In order to do what you want to do in this diagram you'd need a PNP sensor and the circuit would need to be a bit different. You could get a PNP, but there's no chinese knock-off and the real omron are kind of expensive (~50$). The way you made it with 2 relays is the right way.
Nowaday you'd use darlingtons (something like DS2003), SS relays or plain transistors instead of magnetic relays, cause they have much longer life and cost less during mass production (which is obviously not a concern here
). If you use the tiny relays in your first picture, make sure you place a diod on the coil (something like 1N4007) so current spikes don't destroy it too quickly. Do you use the screw on the left to adjust the height of the sensor?
