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Let's suppose there is an LM35 temperature sensor that has a 10mV/°C transfer function. This means that for each 1°C it produces 10mV linearly. Then, we can simulate the sensor using a battery in the beginning. The circuit has a CAS of 0.1V/V to create the desired output (read the same as the input without the mV and in Celsius, e.g., 10mV = 10°C and -1V = -1000mV = -1000°C). I used an INA (Instrumentational Amplifier) to: reduce the loading effect completely from the sensor, balance it easily if necessary, and subtract the output of the PID controller with the output of the sensor; an INA has a very big CMRR to reduce external noise. A PID controller is a type of controller that is the most commonly known controller and most commonly used today. It consists of a sum of a proportional amplifier integrator and a differentiator; it tries to be as precise as possible, similar to the input, by automatically calculating the steady-state error up to 0%. We also have an indicator or an alarm (yellow LED) that turns on if the temperature input is not between 0°C and 100°C (i.e., between 0V and 100mV), and it's off if otherwise. This circuit also has a protection system that can be turned on and off using the SPDT switch, disconnecting the ground off the battery, simulating the sensor from the beginning. One can also manually reset the protection system by pressing the button; it takes about 1ms to reset it (used with 555 IC). The red LED indicates that the system has failed (as if the fuse is not working again). Finally, the green LED indicates that the protection system is ON or OFF, and it's also displayed with a 7-seg display.
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