Project - Motion Control Light for Bathroom

[kdarling]

So, my wife and daughter really hate the old metal vent light on/off pushbutton high up in the middle of the bathroom on my '94. Worse, younger kids can't even reach up to turn it on!

THE IDEA

My first thought was to put a light switch down by the outside door handle. I even bought some 12v remote control keyfob switches, thinking I'd hack one of them into a regular wall switch. But it just seemed like a clumsy solution, and worse, the fobs used batteries.

So at the same time, I ordered several 12V PIR (Passive Infra-Red) sensors off eBay from China, wondering how well they worked and how big they really were. Two versions just had motion detect, one also had a light sensor so you could set it to not come on if there was enough light. (I had planned to use that for both the interior main lights, and for the outside porch light.)

REMOVING THE LIGHT

To install it, I first removed the two screws holding on the plastic light cover. Then the large trim surround's four screws. (Naturally I also used this opportunity to paint the old yellowed trim a nice light beige.) And finally the two screws holding the light & switch assembly to the fan brace. Now the assembly hung awkwardly down from the ceiling about a half foot.

My plan was to wire in the sensor after the switch (so it became the master control, in case I didn't want the light to come on at all for some reason), and then the four lamps would power from the sensor's relay. It would require some snipping and crimping, all above my head.

At the point I realized it would be a LOT easier to do this if I simply removed the entire light assembly. So I snipped the two power wires coming in from the roof, and the two wires going up to the fan. I later made all of the wires very easy to put back together, by crimping quick connect plugs to them.

FITTING AND TESTING THE SENSOR

Since the sensor had the wire screw junctions on its side, I wanted to hide it under the plastic light cover, with just the sensor ball lens poking through. The two models (of the three I got) that would fit were:

eBay motion sensors

motion-detect0.jpg (17.3 KiB) Viewed 2788 times

The first one, the slimmest and without light detection (figured it wasn't needed in the bath, since I always wanted the light to come on) was the black one. Last night I wired it up, and even drilled a matching hole for the sensor ball:

Without and with light cover

But -- when I tested it using a Radio Shack instant adapter 12v plug, it just stayed on and never turned off, even if covered. Durn! And I had drilled the hole for it too. Test rig below:

Testing the sensor

So I ended up having to fall back on the larger white sensor, which worked perfectly right off the bat. I did have to bend down the light reflector inside a bit to make room, and also make the hole larger since now the ball had to be in the middle. Still looks good, though, since this sensor had a nice white decorative top.

RE-INSTALLATION AND CONCLUSION

Putting it all back was a piece of cake with the connectors I had put on the wires. Just plugged in the house power and the fan, and put back 8 screws. Testing, the switch works wonderfully!

Now you simply open the bathroom door a couple of inches, and the lights automatically come on. As long as you move once in a while, the lights stay on. After you leave and shut the door, they automatically go back out after the no-motion time delay you set with a screwdriver (I dialed it for a 30 second delay, but you could go up to about 5 minutes or more if you wanted, or down to about 15 seconds.)

Without a doubt, this is one of the more useful mods I've done. It feels luxurious to have the lights come on automatically before you even get inside the bathroom door, without having to fumble for the overhead light switch. Not to mention not having to worry about running down the batteries because someone accidentally left the light on, unnoticed behind a closed door.

TOOLS: phillips to remove vent, wire snipper/crimper, tiny flat blade to adjust light/timer trim pots, hole saw and/or Dremel.

PARTS: sensor ($6), quick connects ($2.50), butt connectors ($2), wire tap (optional), wire, spray paint (optional). Oh, and if I had been smarter, I'd have gotten in some LED bulbs to replace the old ones at the same time.

[Blue~Go]

Slick! Thanks for posting up the detailed photos and part information. Should make it relatively easy for the next Chinooker who wants to do it.

BTW, it looks like maybe your vent has a solid metal cover? If so, and if you prefer, I think you might be able to get a translucent white one. I say that because that's what's on the later vents of the same type (my rig, for example). Light comes in very nicely, but no-one can see through it. It is more vulnerable to branches and that sort of thing, if that's a concern. I like the daytime light.

(Of course it's possible a later/white cover won't fit, but the basic design sure looks similar.)

[Scott]

Nice one! Thanks a lot for posting this.

I really like the cheap electronic gadgets you can find on Ebay nowadays, but I’ve been burned a few times on things that are DOA or do not function as advertised, and I always discover this AFTER I’ve designed a project around one of those devices.

Glad to see you found a winner. I can think of a lot of uses for those.

[kdarling]

BTW, it looks like maybe your vent has a solid metal cover?

That's just the bedspread that the assembly was laying on when I took the photo

Btw, here's the before and after wiring diagram, to show how simple it was. This is the view after you remove the vent switch/light assembly and lay it down with the lights facing up. The bottom is nearest the door.

Cut the wires from the switch box going to each bulb, then tie all the bulbs together to the sensor output, and power the sensor from one of the switch's original bulb wires.

Motion Detect Wiring

Of course, if you didn't want the switch to power the sensor as I did, you could go even simpler and wire the sensor in parallel instead (so that EITHER the switch or sensor provides power to the lights). Then you'd only need the +/- power wires to the sensor, and have the output tap into any bulb wire (since they must all be tied together back at the switch output hidden inside the switch box). But then you couldn't turn force the light off except by cutting all house power.

Kevin