Safety Control in Appliance Doors

The white industry of refrigerators, freezers, microwave ovens, stoves, etc. requires safety elements that detect the status (open/closed) of the appliance doors. 

These door sensors are designed in many sizes and shapes, depending upon the specific application. Many are custom-built. Generally, both a reed switch and a magnet are used, and in many cases, added circuitry is built into a PCB for smart sensoring. If the sensor is not activated after a specified period of time, an alarm will sound, alerting that the door is ajar. In the case of a freezer, several hundred dollars worth of frozen meat and other food can be saved from spoilage if an open door is detected. 

The reed sensor is usually mounted in the chassis of the appliance and the permanent magnet is placed in the doorframe. Thus, when the door is closed, the magnets position is above or parallel to the sensor. When someone opens the door, the circuit is broken. 

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