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Range And Oven Electronic Controls

How Does an Electronic Control Work on Ranges and Wall Ovens

Electronic controls are used today in place of thermostats because they are less expensive to manufacture. In addition to that, an electronic control actually has more control over the baking and broil process then older thermostats. Because thermostats are mechanical and use a gas that expands to operate a diaphragm that opens and closes switch contacts, they tend to develop wear after a few years. This usually results in erratic temperature control for the oven.

Electronic controls are matched to an oven sensor thermistor. This oven sensor or thermistor is in the oven cavity and is connected to the electronic control with two wires. A thermistor is a temperature sensitive resistor, where the resistance to the flow of electrons changes as its temperature changes. Generally speaking an oven sensor, or thermistor, will increase in resistance as the temperature in the oven cavity goes up. The electronic control sends out a small amount of electrons to the oven sensor, and compares that to the amount of electrons that return. An algorithm within the logic of the electronic control interprets the resistance of the sensor and displays that as the oven temperature on the oven control display. Furthermore, that calculation is used to send out a small electrical current to relays that close switch contacts for bake and broil.

The relays used by range electronic controls are usually mounted on the back of the electronic control board. However on some model ranges and wall ovens there is a separate board with the relays attached. Either way the function is the same. The relays are normally open switch contacts, held closed by an electromagnetic field when voltage is applied to the coil within the relay. A small current sent from the electronic control energizes the coil creating an electromagnetic field, pulling a plunger that closes the switch contacts within the relay. Once the range or wall oven comes up to temperature, the electronic control stops sending that small voltage to the relay coil, and the relay drops off opening the contacts in the circuit. The electronic control continues to monitor the resistance of the sensor. When the oven cavity starts to cool down, the resistance in the sensor changes, causing the electronic control to send that small coil voltage back to the relay closing the contacts again.

What makes electronic controls used in ranges and wall ovens better for baking is that they can cycle the broil element on and off in bake to provide better baking. In addition to that an electronic control may be designed to energize the coil to the broil element to help bring the oven up to temperature faster in bake. This is especially true if a range or wall oven has the fast preheat option.