As the name suggests a garage door opener is a device that is used to open and close garage doors. Generally the models are remote controlled.
The initial garage door openers consisted of an actuator that could open or close the door. This actuator was controlled by a remote. The remote used was very simple and consisted of a transmitter and on the actuator side consisted of a receiver and associated electronics. The receiver would function for a change in amplitude. However they had a major draw back namely security. Anybody with a transmitter could open or close the garage door. There were many incidents of garage opening by neighbors accidentally when they were trying to open their own garages. The next change came with dip switches. These dip switches could use a total of 256 combinations. This was sufficient to overcome the problem of accidental opening of others garages, however the security issue was still not solved. Anybody with a radio frequency recorder could record the frequency when somebody opened his garage door and later used that frequency to open the garage.
Present day technology has overcome the security concern to a large extent by use of rolling frequency or sometimes called hopping code technology. In this every time a new frequency is used to open and close the door.
The mechanical part of the garage door opener is pretty simple. Mainly three types are used: chain drives, screw drives and belt drives. Chain drives are noisy but are the cheapest. Screw drives have a lead screw and nut system to open and close the door. They are a bit costly. The latest models use plastic liner on the tracks to reduce noise and increase the operation speed. Belt drives are the quietest and are comparatively costly. The mechanism also consists of a main spring that is the most important element of the system. Usually two types of springs are used linear expansion and torsional springs.
In the market two types of garage door openers are available namely jackshaft type and trolley type. Even though the jackshaft type occupies less space, the trolley type is more popular. This is because of safety; in the jackshaft type it is difficult to sense when a person or a pet is being crushed under the door.
Some modern systems have auto reverse in case of obstruction like a pet or a vehicle. The remotes generally operate up to a range of 150 feet. Also most systems have keypads that are installed outside the garage and can be used if the remote goes dead.
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