Garage Doors & Openers

A garage door opener is a motorized device that opens and closes garage doors. Most are controlled by switches on the garage wall, as well as by remote controls carried in the garage owner's cars. more...

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Technology

The current garage door opener market offers a variety of transmission technologies. They use *frequency spectrum ranges between 300-400 MHz and most of the transmitter/receivers rely on hopping or rolling code technology. This approach prevents perpetrators from recording a code and replaying it to open a garage door. Since the signal is supposed to be significantly different from that of any other garage door remote control, manufacturers claim it is impossible for someone other than the owner of the remote to open the garage. When the transmitter sends a code, it generates a new code using an encoder. The receiver, after receiving a correct code, uses the same encoder with the same original seed to generate a new code that it will accept in the future. Because there is a high probability that someone might accidentally push the open button while not in range and desynchronize the code, the transmitter and receiver generate look-a-head codes ahead of time.

There have been different modes of mechanical drive over the years as well. A common misconception is that the door opener lifts the door directly, however, most of the lifting is done by the counterbalance system using either torsion springs or linear expansion springs. There are also several clever counterweight systems. All of these systems allow the door to be moved with much less force and allows the door to come to rest in partially open positions.

The most common style of operator for residential use is the trolley operator. The motor hangs near the center of the ceiling and a rail guides the trolley across the ceiling to the top of the doorway. The trolley is attached to the door arm that is then attached to the top of the door. When the trolley traverses the rail the door opens and closes.

Another style of operator is the jackshaft that works with a torsional spring counterbalance system. Instead of attaching to the door, it attaches to the spring shaft. Rotation of the shaft still allows the springs to do most of the lifting while adding the extra force to move the door. The major advantage is that this operator resides to the side of the door and does not require a rail. The trolley style operator often is encumbered with obstacles (beams, pipes, etc) or it becomes an obstruction itself. Jackshaft operators are not as popular due to the inherent safety issues. It is very difficult for the machine to sense when the door is crushing someone.

There are several ways to make the trolley move across the rail. Older systems include a rotating rail with a wheeled trolley that used the rotary motion of the rail (pole) to force the trolley across the distance. It was called a monkey on a pole. It was too dangerous, but it did inspire the screw drive system.

Read more at Wikipedia.org