Mechanical timers can turn lights on and off in your home as a security feature when you're not home, alert you when something you're cooking is done or can activate aquarium lights or other electrical items when needed. You can choose between programmable digital timers or inexpensive mechanical timers that work using a 24-hour dial. Mechanical timers require you to set them manually via segments, pins or trippers; they don't require backup batteries.

Food Timers

Mechanical food or kitchen timers generally use a 60-minute clock. To operate them, twist the dial clockwise to the desired setting such as 45 minutes. The timer ticks like a clock during the countdown until it reaches the zero setting on the dial. When it reaches the off point, it dings or rings to let you know the time you set has passed.

Analog Timers

Analog timers have a 24-hour dial that mechanically advances as time passes. When the dial reaches a pin or tripper, the light comes on and stays on until the timer advances to the next trip or pin position on the dial.

The dial has numbers that correspond with a clock and hash marks between them for the half hour position. Most 24-hour timers have 48 positions, one at the clock hour and one at the half hour.

Step 1

Move the button on the side of the timer to the position for timer. Depending on the model you have, it may indicate "T" for timer, "Auto" or have some other designation identified in the instructions. Each timer is slightly different, but most come with an override that permits the electrical current to bypass the timer so that you can operate the light manually when you don't want the timer to control it.

Step 2

Insert the timer into the outlet, aligning the three prongs on the back of it with the outlet. Plug in your light, aquarium or other electrical item you want to control into the plug socket of the timer, usually found on the bottom, side or front of the timer.

Step 3

Rotate the dial clockwise so that the dial's number aligns with the current time on the clock and the position on the dial that says Time Now, Time of Day or Current Time, depending on the model you have.

Step 4

Position the first pin to the time you want the electrical item to come off, setting the second pin to the time you want it to turn off. For example, if you want the timer to turn a light on at 7 p.m., set the first pin at that position on the dial and the second at 11:00 p.m. if that is when you want it to shut off. For timers with 24 hour clocks, you would set the first pin at 1900 and the second pin at 2300. Pins are set by toggling them off or on, or in or out.

Step 5

Test the timer by manually advancing it to the On pin to see if the light you plugged into it comes on. Advance it to the Off position to verify the light turns off. Reset the timer to the current time after testing.

Vacation Timers

If you picked up a vacation timer, you cannot set them. They come equipped preset to turn lights on and off at random times to make it appear as if you are home when you're away. The on and off pins or trips are molded onto these mechanical timers; many vacation timers have seven-day, random on and off settings that repeat after seven days have passed.

Segment Timers

Segment timers work the same as pin timers, only you must raise the segments where you want the electrical item on. Simply push up on these segments -- each segment usually represents a half hour -- so that they raise above the timer's face. For example if you want the light to come on at 7 p.m. and off at 11 p.m., as per the previous example, lift eight segments beginning at 7 p.m. and ending at 11:00 p.m. Some segment timers require you to push the segment down and out instead of up.

Vertical Dial Timers

Vertical dial timers have small pins you pull out at the On and Off positions on the vertical dial. The pins are built into the dial itself. Follow the steps for the analog timer, pulling the pins out at the location you want to turn the item on and off.

Timer Trippers

The pins or trippers on the timer include physical trippers you insert at certain locations on the dial or small arrow-type pins you move into the appropriate on and off positions. Green pins represent the time-on position, while the red arrow-type pins represent the time-off position.

Auto Overrides

Newer mechanical timers have a switch that allows you to turn the timer On, Off, or set it to Auto or Timer. Depending on the model of timer you have, when the switch is set to the Timer or Auto position, electricity flows through the timer to the light and turns it on and off at the times you set it. When the timer is toggled to the Off position, the timer or the electrical device won't operate. In the On position, this generally means you can operate the electrical device manually without the timer interfering with the current to the device. Some timers have a switch you toggle between two positions: Timer On or Outlet On.