A light timer is designed to automatically turn lights on or off at certain set times, without the need for someone to manually flip a switch. There are several circumstances whereby automatic timers can be very handy. You can use simple light timers to turn outdoor lights, strobe lights and decorative lights on and off at certain times. More complex timers are suited to switching on and off grow lights or other light series that do not need to be on for long periods of time.
One of the most common timer circuits is the 555 timer IC, or integrated circuit, commonly known as a chip. The 555 timer IC is useful for quick-flashing projects and long-lasting LED lights that need to turn quickly on and off. It's also useful for dimming lights. Because of the relatively simple circuitry of the 555 timer, someone with the necessary electronics experience can solder it together at home.
Key to the operation of a light timer is the oscillator, which vibrates when it encounters an electrical current. The vibrations keep track of time and shut off lights at the right times. In addition to oscillators, these timers also have capacitors, which store electrical charge and pass it along only as needed. Resistors, which modulate current, are also important parts of timer circuits, as are basic components like stamped circuit boards. With these components you can build your own basic light timer.
When customizing a light timer, it is best to find a diagram for the sort of circuit you want to build and then follow it. For example, time delay circuits are much more complex than basic 555 timers designed to create a strobe effect. You'll find a number of different diagrams for circuit setups, depending on functions, online. Search through timer circuit options on websites like Cogeco for reliable diagrams.
If you want a long time delay for grow lights, it may be easier to buy a time circuit and wire it into your light system yourself. These timers plug into wall outlets and automatically control incoming current to turn lights on and off according to dials set by the user. You may be able to wire in dials to an existing electrical system yourself as well.