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Motion Detector light problem?


Well-Known Member
I am having a crazy problem that makes no sense to me yet. When I test a motion detector light inside the work shop they work good but when I put it outside I get different results. In the work shop I am using 100 watt incandescent light bulbs but outside I only have the LED light connected to the motion detector. Sensitivity is set at maximum range.

When I test motion detector inside the work shop light works good at 40 ft. When I open the big 10 foot roll up doors motion detectors work good when I walk across the driveway 80 ft away at night using 1 incandescent bulbs. When motion detector it mounts on the wall about 8 ft up motion detector will NOT come on until I walk up to it 20 ft from the detector?

LED light is 7800 lumens rated 80 watts. 1 incandescent light bulb is rated 100 watts. Amps are very nearly the same. What the heck is the problem?

LED light has a built in LDR sun light detector that should not be a problem after dark. If light coming ON was a problem for LDR then light would come ON then go OFF.

Maybe I need to test motion detector with a 60 watt incandescent bulb to see if lower amp load is a problem?

Maybe the empty motion detector light socket needs a 100 watt incandescent light bulb to make motion detector work correctly?????

Light will not come on when I drive me SUV up the driveway after dark. I have swapped out the motion detector 2 times with other good working motion detector I still get same results. Timer switch is set on 5 minutes.

I have another motion detector I can swap out to see what happens.

I almost forgot to mention, if LED light comes ON then goes OFF it will not come ON again until light has been OFF for 30 seconds.



Well-Known Member
Most Helpful Member
Maybe the empty motion detector light socket needs a 100 watt incandescent light bulb to make motion detector work correctly?
Some motion detectors switch the light on/off with an electromagnetic relay; others have a solid-state switching device (triac). The latter may not play happily with LED lights whereas the former should work with incandescent or LED lights.


Well-Known Member
Most Helpful Member
If it's a two-wire unit, it's drawing power through the lamp while the lamp is off.

A filament lamp at low current will drop very little voltage; a LED lamp may drop quite a high voltage before any significant current passes through it, depending on the design.

In other words the detector electronics don't have enough power.

Three-wire types have a permanent supply plus a switched output, so don't have that type of problem.

You may be able to work around it by providing a bypass to the lamp, something like a 0.1uF cap and 100 Ohm resistor in series - the same as a "snubber" circuit. That will pass a small current without causing an overload.


Well-Known Member
A 100 watt incandescent light bulb in the empty light socket solved the problem. It is interesting when I walk in front of the motion detector the incandescent bulb comes on first then 2 seconds later the LED light comes on. Tonight when it is dark I will test it with a 60w & 40w & 25w light bulb to see if it works correctly. I don't want to waste anymore electricity than I need too for this to work.

The motion detector is now timing the correct time. With switch set on 1 minutes it was timing about 20 seconds then light turned off early. With switch set for 5 minutes it was timing about 2 minutes then light went off. The incandescent bulb is now making the motion detector time for a full 5 minutes before turning off with switch set to time for 5 minutes.

Tomorrow I will neaten up this messy circuit & cut off all the extra wire. The 100w bulb is directly over the LDR I had to duct tape a penny over the LDR to keep the LED light on. If the incandescent bulb comes on in the rain glass will crack so it needs a different bulb or rain protection. I will figure that out tomorrow.


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