A pressure pad is a pressure-sensitive surface that creates a circuit and causes some action to occur when pressed. This technology was very common as a means of automatic door opening before motion-sensing technology dropped in price. In most cases, the pad is comprised of two disconnected parts. The electrical system flows through the inner area, but has a break in the circuit directly under the pad. When the pad is pressed, the outer section connects with the inside section and the circuit completes for a few seconds. This triggers an immediate response in a larger connected device.
Pressure pad technology was an early means of automating tasks. Since the pad relies on a simple circuit with a mechanical activation, it was very easy and inexpensive to produce. All a person had to do was push on a pressure area and a task would happen. This task could be anything from opening a door to turning on a machine to activating a light.
The technology really came into prominence at grocery and department stores. The pressure pad looked like a large rubber rectangle on either side of the door. When a person approached the door, it would open automatically. This was an important step in retail store automation, as the store no longer needed to monitor the door to help people carrying armloads of goods in and out.
Some pressure pads work on an on or off principle. When pressed, it sends a signal to a connected device; this changes its state to the next one in its operating routine. For instance, a pad connected to a light would turn it on when pressed. The next press would turn the light off, and then the next would turn it back on, and so forth.
Other pads work on a circuit completion principle. These pads create a state in the connected device that only exists when the circuit is complete. This is the common method used by automatic doors. As long as something is pushing the pad, the circuit remains complete and the door remains open. As soon as the circuit is broken, the door closes.
The last type of pressure pad works on a combination of these two principles. These create a state when pressed, but a different state when held. Some light switches use this method; a pressure pad will turn a light on and off when quickly pressed. If the top part is pressed and held, the light will become brighter—if the bottom part is held, the light will go dim. When the pad is released, the light stays at the current level.