Subject Engineering Electrical Engineering


Design a circuit to automatically turn on a heater or air conditioner in response to a change in temperature.
This circuit should use a thermistor (a temperature-sensitive resistor), an op-amp circuit, a battery, a relay for switching on a plug-in heater or air conditioner, and any additional components required to make it work correctly.
Your target application might be for a small heater, window A/C, etc.
These are just suggestions; be creative, and be specific in describing your design requirements.
For the thermistor you choose, estimate hot resistance and cold resistance from the datasheet using realistic temperatures.
Analyze circuit operation in both hot and cold conditions for the Circuit Analysis portion of your report.

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Design Challenge and Target Application
A thermistor circuit can be used to sense temperature. Used in conjunction with a relay and circuit that can detect a decrease in the thermistor’s resistance, a circuit can activate a heater to compensate for a temperature fallen below a specified threshold. One such example are hot tubs, which require the temperature to be at a certain level for the user. This temperature range can be anywhere from 35-40◦C. The thermistor circuit senses when the actual temperature drop below the desired temperature and activates a standard water heater to heat the water, which is being injected into the hot tub. From this scenario, the actual temperature would need to be represented electrically in the circuit and compared to the actual temperature, which would also need to be electrically measured by the circuit....

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