I have a PIR sensor/switch with the below wiring diagram. The way my lights were configured is that the load (LED light with transformer) is on the wire, so I only have two wires available instead of three.

What can I do?


  • 1
    \$\begingroup\$ I’m voting to close this question because it isn’t about electronic design. Try on diy.stackexchange.com \$\endgroup\$
    – DoxyLover
    Jan 7 at 11:00
  • \$\begingroup\$ You might be surprised but addressing a current limitation of current circuit is more about design than many other questions around here. Nobody should assume that design applies only to new things that materialize out of thin air, everything we do is built on to of previous work. \$\endgroup\$
    – sorin
    Jan 7 at 11:11
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    \$\begingroup\$ @sorin No, this is just a "how do I use my product I bought" question. You don't need an elecrical engineer to solve this. You need to call an electrician to rewire your house to be compatible with the sensor you bought. Or buy another sensor that is compatible with existing wiring. It might still be a good idea to let an electrician do the sensor install, in some jurisdictions it is illegal for you to work on household wiring. Unless you are a licensed electrician. \$\endgroup\$
    – Justme
    Jan 7 at 12:06

1 Answer 1


What can I do?

Very little. You've bought the wrong switch.

A switch designed for inline operation would have to steal some power from the line while on.

enter image description here

Figure 1. Phase-angle control of load voltage / current using a TRIAC device. Image source: LEDnique.com.

While the load is off there is voltage across the switching circuit and this can be used to charge up the control circuit of the switching device. While the load is switched off full mains voltage is available to the switching device as neutral is effectively supplied via the load.


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