electricallight-fixture
I am planning on installing some LED light strips in a closet full of shelves. I am using an A/C adapter (wall wart, brick, what have you) connected to the strip, which plugs into an outlet. I plan to have the outlet controlled by a light switch to provide on/off to the light strip.
Is it possible to use a motion sensor as the light switch?
Or, is there an easier way to get the LED lights to turn on automatically?
Assuming you're talking about motion sensors like this:
Switches like that need power. They can work by trickling current through incandescents if hooked up like a normal single-throw switch (in series with feed going to lights). If the switch has 4 wires (hot, return, switched, and ground) then you can hook them all up and it will power itself using it's own hot + return. In that case, it shouldn't have to trickle power through the light's circuit, and fluorescents should be able to turn off.
The basic problem is that the occupancy switch that you chose to purchase is one designed to be able to work in series with the load attached to it. If the attached load is too small (too low of wattage) the switch assembly does not get enough power to operate correctly. For the particular model you have this is on the order of 40 to 50 watts of minimum load. From a technical standpoint it kind of sucks that they work this way BUT they are designed to work in place of a simple light switch that is in in series with its load.
Your Radio Shack relay does not come close to representing a 40-50W load on the switch so the only other way is to add some additional load in series with the switch (i.e. equivalently in parallel with the relay coil). As you have come to see this is not a very satisfactory solution and some other scheme needs to be found.
The best situation in this case is to acquire the alternate type of occupancy switch as mentioned in that thread that you linked. That type of switch has a live AC lead and neutral AC lead connected to it to power the switch unit irrespective of the size of the load. A separate output connection goes off to the load you are trying to switch. This type of switch may take a little re-wiring in your garage but that should be easier than trying to wire in the kludged extra load that the current switch requires. If you choose to deploy this improved version of the switch you will be able to remove the Radio Shack relay from the installation.
To make yourself feel better about the fact that you now have an extra occupancy switch you could pick a room in your house that has a tendency to get its light left on accidentally and install the extra unit in place of its light switch. Maybe this is a bathroom the kids use or a far closet that does not get used often.
BTW
It looks like Leviton now has a whole slew of different model occupancy switches that are also designed for single pole switch replacement but have removed the minimum load requirements. These do not require a neutral wire connection but do require a GND wire connection.
Best Answer
Yes. You can buy standalone sensors designed to switch lights on and off. There are both plug-in switches and ones that you hard-wire to your light fitting.
It depends. You could use a microswitch on the closet door.