Wednesday, 17 April 2013

Sensor lights

One of the problems we came up with in the one-year evaluation was the light in the under-floor store room.
We put a regular ceiling light with a sensor on it, and the problem is that you have to crawl into the middle of the room for it to switch on, since the ceiling is only about 1.4 metres high so the cone of the sensor's sensitivity doesn't spread very wide. My idea of a solution was to move it closer to the door, which should be relatively straightforward.
Their first suggestion was just to put a light switch on it. Since this is a fluorescent tube and it's in a store room, where it could be left on for a day or two, this seems a pretty good place for a sensor.
That night when I put the kids to bed, I noticed that the light was still on in the machine room, where we had been during the visit. This is one of the few places we have a light switch and if the door had been closed, it would have been on for the rest of the month, until next time to clean the filters.
Another option is fitting an external sensor to the light, to switch it on. A further complication with the room is that it has two entrances, around 3 metres apart, so it would be tricky to get one sensor sensing activity in both places. There are sensors for yard lights that react to movement up to 10 metres away, so this should be possible.
The sensor itself sticks down in the middle of the light, which is round with a round fluorescent tube inside. It's not designed to be adjusted, as are most of the other sensors I bought, but I do have a screwdriver.
I was sure to switch off the lights at the breaker when I was doing this. Any kids reading, get a grown-up to help you do this as you might fall off the stool trying to reach the master switches.
The sensor assembly could easily be disassembled from the bracket and the wire was stiff enough to hold it pointing in any direction, so the first thing I tried was putting the plastic cover over it, to see if the sensor could see through it.
At first this seemed successful. After I put the breaker back on, with the lighting-up duration set to the minimum of 5 seconds, when the kids went in from the kitchen the light went on, then they waited for it to go off and went in from the living room and it went on, then they didn't move and it went on again, then they got as far away from the room as possible and it went on again, then again just after it switched off 5 seconds later. Then again, and again regardless of any human activity.
I guessed that the lights were heating up the inside of the cover when they were on, then the parts inside the cover would cool rapidly, which the sensor registered as a movement of heat, therefore switching it off again. So I took the cover off, and it seems to be better. I toyed with making a bigger hole in the cover, but for the moment it's just there with the cover off, working relatively well.