I fitted a PIR sensor at my parents' to turn the bathroom light on and off automatically last week but the lights are very dim. On inspection, there is only half of the potential difference across the bulbs and I have no idea why. I'm fairly electrically literate but I am at my limit here so hopefully one of you folks can give me some pointers.
Previously, when the lights were operated by a simple switch, the live was switched and the neutrals were connected in the loft above.
According to the wiring instructions for the PIR sensor, the live and neutrals should be a constant supply to the sensor, with a third feed that becomes live when the circuit closes (when someone enters the room). I have drawn a circuit diagram to illustrate how the circuit looked on the old setup (which worked the lights at full brightness/full 230V potential difference [I live in the UK]), and now, at 115V.
Before on the right, now on the left. Note that the bulbs are wired in parallel both before and after (I drew them wrong). This to me would be the first thing that looks amiss, however this was the case before and they worked just fine. The 3 feeds coming into the junction box are go off to different parts of the house's lighting main, unrelated to these lights.
I grabbed a voltmeter and took some readings across some noteworthy points in the circuit:
At the PIR sensor, the potential difference between the live and neutral terminals is 230V, as expected.
When the PIR sensor is closed (on), the potential difference between the output (A) terminal and neutral is 110V, not expected, should be 230V.
This issue is happening before we even get to the bulbs (which are 11.4V LEDs on transformers, I expect there are also bridge rectifiers built into the transformer modules), so the issue must be with my wiring, but I can't see anything untoward.
Any and all suggestions gladly received! TIA
Best Answer
You have your transformers in series they should be in parallel, sorry I could not keep reading and all the comments. With the transformers in series the output voltage will be 1/2 . Connect the transformers in parallel and your voltage will double. I don’t think your before drawing was accurate. I have seen this done many times by new DIY folks trying to add lights.