A garage door opener refers to a motorized device, usually electric, which will open a garage door without manual lifting. These days, most doors can be opened via remote control. A few historical facts:
- The electric garage door opener was invented in 1926. The inventor was C. J. Johnson of Indiana.
- They did not become popular until after World War 2.
- Initially, the doors were opened by a switch at the end of the driveway or in the garage.
- The garage door remote control was invented at the same time, independently, by two different people. It was developed from wireless technology first used in the 2nd World War.
- Remote control wireless systems have undergone several generations of change to provide more security and to prevent interference from other wireless systems.
The Electric Opener
The most common opener consists of a power unit, counterbalance springs, a trolley, trolley tracks, a chain, belt, or screw pulling assembly, and a quick-release mechanism allowing the door to be lifted by hand during power failure.. The entire machine hangs above the garage door in spring tension technology.
The power to lift the door comes from stored potential energy in the torsion springs. They are under tension from steel counterbalance cables. The electric opener controls how far the door opens and closes, as well as the force the garage door exerts. In most cases, the garage door opener also holds the door closed in place of a lock. Limit switches on the power unit control the distance the garage door opens and closes once the motor receives a signal from the remote control or wall push button to operate the door.
The Remote Control
The remote control consists of a transmitter and a receiver and managing electronics. The first devices were simple and operated on a single frequency. This created many issues both with interference and with controls operating different doors due to sharing the frequency.
The shared frequency problem was dealt with in a second generation technology. Generally, digital switches were set to match the transmitter/receiver pair. However, since codes were limited in number, they could easily be spoofed by criminals and presented a security problem. Whiles still used in shared-gate communities, these fell out of favor. The third generation devices uses a frequency spectrum range between 100-400 MHz and most of the transmitter/receivers rely on rolling code technology. This is similar to that used on remote automobile lock/unlock mechanisms. The newest controls are similar to third generation controls, but they are limited to a frequency of 315 MHz. The 315 MHz frequency range avoids interference from the Land Mobile Radio System (LMRS) used by the U.S. military.