Motion Sensor Controlled Vending Machines
Introduction
Vending machines operate 24 hours per day, seven days a week using large amounts of energy throughout those hours of operation. In addition to consuming 2,500 to 4,400 kilowatt-hours (kWh) of energy per year, they add to cooling loads in the spaces they occupy. At average electricity costs of about US$0.08/kWh, annual operating costs can range from $200 to $350.
New, efficient vending machines are available that can greatly reduce operating costs through the use of motion sensors. These sensors allow the machines to function only when a person is present in front of the sensor. The compressors run only enough to maintain a suitable temperature throughout the workday, but the lights and other components remain off in order to minimize overall energy consumption.
The Technology
Passive Infrared Sensors
Most vending machine sensors use a type of technology known as passive infrared sensors (PIR), which unlike optical sensors that use an LED transmitted and infrared receiver, emits nothing. Rather than radiating, the PIR responds to infrared energy being emitted by any nearby objects. Any object with a temperature above zero degrees Celsius emits infrared energy, through black-body radiation.