Gadget Freak Case #238: Controller Adjusts Garage Lights

April 17, 2013

I installed two sets of fluorescent lights in a two-car garage as part of a renovation project. Because the ceiling has a large opening, I had to arrange the 16-foot-long rows of florescent lights parallel to the garage door opening. This setup blocked light from one row of lights when a door was open and retracted.

As an alternative to a second light switch on the wall for the lights above the door, I created an automatic switch that uses a solid state relay. The relay is housed in a double-depth four-inch octagonal junction box used for house wiring and ceiling lamps. The box attached to the wooden ceiling joist above the obstructed fluorescent lamp fixture. You can find a suitable electrical box at hardware and home improvement stores. This type of box often comes with a mounting bracket that simplifies attachment to a wooden joist.

A standard doorbell or door chime transformer provided 16VAC power for the control circuit, and this type of transformer can attach directly to the metal box. A simple circuit connected to the solid state relay control terminals rectifies the AC control voltage to provide DC to the relay. Observe the polarity of the connections to the + and - terminals on the solid state relay. A magnetic reed switch (SW2) senses when the door is open and causes the relay to turn off the lights over the opened door.

A low-voltage transformer attached to a four-inch octagonal electrical junction box.

This view inside the junction box shows the transformer (right), the solid state relay, and the rectifier diode, resistor, and capacitor attached to the + and - control inputs on the solid state relay.

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