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Forgive me as I am a ME major trying to wire up a home project (I want the light to turn on when my garage door is fully open, not partially open.) All my components are rated to work at 12V for simplicity, and I tested each one individually. The LED turns on when connected to 12V. The relay works when I trigger it using jumper wires. And the LED on the prox sensor turns on when it is placed against metal. However, when I wire my circuit up like my drawing, it does not work as intended (illuminate green LED when proximity sensor is triggered.) Instead the LED on the prox sensor stays off permanently, until I disconnect the black wire from the prox sensor from the 85 pin of the relay. Does anything look wrong about this circuit?

Relay is Picker PC782-1C-12S-D-X

Prox. Sensor is OMCH SC-3020A

Green LED is AUXMOTEC Green Led Driving Hunting Lights from Amazon

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    \$\begingroup\$ Do you have a datasheet for the prox sensor? Is it capable of driving a relay? \$\endgroup\$
    – Finbarr
    Jan 27, 2022 at 1:34
  • \$\begingroup\$ Why do you need a relay with 30A contacts to drive an LED? It may well be possible to drive the LED directly from the proximity sensor and do away with the relay entirely. As Finbarr says, can you please post a data sheet for the sensor, I couldn't find one with a quick search. \$\endgroup\$ Jan 27, 2022 at 1:45
  • \$\begingroup\$ I thought it was good practice to not drive the load with a prox. sensor and use a relay instead. I wanted mirco relays so they just ended up being 30A. I cannot find a datasheet, there is just the pic on the side of the prox sensor. I got it on amazon amazon.com/uxcell-Detecting-Distance-Inductive-Proximity/dp/… \$\endgroup\$
    – user242506
    Jan 27, 2022 at 1:54
  • \$\begingroup\$ Without a data sheet we're all guessing. Is the output active high or active low? What does the sensor output show with a meter when its LED is off and when it's on? \$\endgroup\$
    – Finbarr
    Jan 27, 2022 at 10:27
  • \$\begingroup\$ If I just put 12V to the brown wire and blue goes to ground, between the black and blue I get 5.67V until I put something metallic against the sensor, then I get 7.71V between the black and blue (and the prox led light on). \$\endgroup\$
    – user242506
    Jan 27, 2022 at 19:33

2 Answers 2

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In your drawing you show the blue to ground and the black to the relay. In the pictures you linked it appears to show them the other way around, black to ground and blue as the output.
It also looks like it is switching positive, not ground, so the relay would need to go between blue and ground. Last, check if it is normally open or closed. There is a review on your link saying they are normally closed, which may not be what you want. If it's normally closed, the relay will be on when the sensor is off.

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  • \$\begingroup\$ If I just put 12V to the brown wire and black goes to ground the LED light on the prox sensor stays on forever, no matter if i put something metallic to it or not. \$\endgroup\$
    – user242506
    Jan 27, 2022 at 19:44
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The relay is wrongly wired.

Terminal 86 of the relay is to be connected to the sensor output and terminal 85 to common.

Here's the correct schematic.

enter image description here

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