Timers
A timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Timers can be mechanical, electromechanical, digital, or even software, since most computers have clocks. more...
 Home
Advertising
Badges/ Patches
Bottles/ Pots
Breweriana
Cigarette/ Tea/ Gum Cards
Clocks
Decorative Ornaments/ Plates
Disneyana
Ethnographic
Fantasy/ Myth/ Magic
Flags
Household
Jukeboxes
Keyrings
Kitchenalia
 Baskets
Bread Bins
Bread Boards
Butter Pats
Butter/ Cheese Dishes
Cookware
Egg Cups
Fridge Magnets
Grinders
Jelly Moulds
Knives/ Forks/ Spoons
Mugs
Napkin Rings
Nut Crackers
Other Kitchenalia
Pie Funnels
Rolling Pins
Salt & Pepper Pots
Scales
Serving Trays
Sieves & Strainers
Small Appliances
Storage Jars/ Containers
Sugar Bowls
Tableware
Teapots/ Kettles
Timers
Toast Racks
Tupperware
Knives/ Swords
Masonic
Memorabilia
Metalware
Militaria
Moneyboxes/ Piggy Banks
Paper & Ephemera
Pens & Writing Equipment
Phone Cards
Photographic Images
Radio/ Television/ Telephony
Religion/ Spirituality
Rocks/ Fossils/ Minerals
Royalty
Science Fiction
Scientific
Sewing/ Fabric/ Textiles
Theatre/ Opera/ Ballet
Tobacciana/ Smoking
Tools & Hardware
Trading Cards/ CCG
Mechanical timers
Early mechanical timers used typical clockwork mechanisms, such as an escapement and spring to regulate their speed. Inaccurate, cheap mechanisms use a flat beater that spins against air resistance. Mechanical egg-timers are usually of this type.
More accurate mechanisms resemble small alarm clocks. The chief advantage of these is that they require no battery, and can be stored for long periods of time. The most widely-known application is to control explosives.
Electromechanical timers
Electromechanical timers have two common types. A thermal type has a metal finger made of two metals with different rates of thermal expansion (steel and bronze are common). An electric current flows through this finger, and heats it. One side expands less than the other, and an electrical contact on the end of the finger moves away from an electrical switch contact, or makes a contact (both types exist). The most common use of this type is now in the "flasher" units that flash turn signals in automobiles, or sometimes in Christmas lights.
Another type of electromechanical timer (a cam timer) uses a small synchronous AC motor turning a cam against a comb of switch contacts. The AC motor is turned at an accurate rate by the alternating current, which power companies carefully regulate. Gears slow this motor down to the desired rate, and turn the cam. The most common application of this timer now is in washers, driers and dishwashers. This type of timer often has a friction clutch between the gear train and the cam, so that the cam can be turned to reset the time.
Electromechanical timers survive in these applications because mechanical switch contacts are still less expensive than the semiconductor devices needed to control powerful lights, motors and heaters.
In the past these electromechanical timers were often combined with electrical relays to create electro-mechanical controllers. Electromechanical timers reached a high state of development in the 1950s and 60s because of their extensive use in aerospace and weapons systems. Programmable electromechanical timers controlled launch sequence events in early rockets and ballistic missiles.
Digital Timers
Digital timers can achieve higher precision than mechanical timers because they are quartz clocks with special electronics. Integrated circuits have made digital logic so inexpensive that an electronic digital timer is now less expensive than many mechanical and electromechanical timers. Individual timers are implemented as a simple single-chip computer system, similar to a watch. Watch technology is used in these devices.
Read more at Wikipedia.org
|
Contact
