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I am using a TEMT6000 LDR and a PIR to turn on outdoor lighting, well that's the plan. The LDR and PIR are in the same housing, and after some searching on forums, I found that I can combine the V-wires and G-wires from the PIR and LDR. So my wiring to the board is 2x signal, V and G.

If I don't combine them I need two extra wires. However, I am not really sure this is 'allowed' and/or will mess up my signals? So that would be the first question...

The second one has to do with the LDR reading: Prior to combining the V and G wires as mentioned in the first question, I had the sensors on a breadboard. The reading from the LDR (in low lights?) seems to be pretty unstable, ranging from 0-50 with only light noise from outside. I tried to overcome that by measuring at two intervals of 10 seconds, store these values and divide them by two to get a more balanced reading. Theory was fine but when both measurements are 0, the lights go on... the next reading, 5 seconds later, one of them is 50 and the average is 25... so lights are out again. Is there a way to get a more precise reading from the LDR?

Thanks!

Edit: In the sensor housing, 2 meters away from the board I have the LDR and PIR connected like this:

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ Edit your post to add your circuit diagram and links to datasheet. Maybe you could add more details to your first question too, I have no idea what wires you are talking about. \$\endgroup\$
    – user1850479
    Commented Jan 21, 2022 at 20:51
  • \$\begingroup\$ What made you think you could share a switched output with an analog output? i.sstatic.net/2KTe3.png \$\endgroup\$
    – D.A.S.
    Commented Jan 21, 2022 at 21:15
  • \$\begingroup\$ To be honest, I searched for wiring sensors over a longer distance and a discussion about combining V and G in sensors came up where someone shared the V and G lines like I did now. Your question kinda answers mine; it should not be done and each need their own power and ground,so six wires?! \$\endgroup\$
    – snewpers
    Commented Jan 21, 2022 at 21:27
  • \$\begingroup\$ It's fine to distribute power and ground to the two components from the same power source. Very unlikely to be a problem. The only caution there is if the PIR sensor draws enough power to introduce sag or noise into your power line, that will bleed through into the TEMT6000 circuit. \$\endgroup\$
    – vicatcu
    Commented Jan 21, 2022 at 22:19
  • \$\begingroup\$ tonystewardEE75, vicatcu -thanks for your replies. Much appreciated. I think I should not combine the power and ground lines if there is a chance of interference then. \$\endgroup\$
    – snewpers
    Commented Jan 21, 2022 at 22:56

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