Temperature Range Indicator Using a Window Comparator

The goal of this experiment is to make a temperature range indicator using a window comparator. This kind of equipment is usually used in processing and manufacturing engineering, usually in places where thermometers cannot be suitably used. They alert you when there is a transition in temperature using LED lights which light when a certain range is reached. We can use them for quality assurance and maintenance work.

-12V battery clip

-LM339(2)

-1N914(2)

-thermistor 33k

-LED: any three colors

-Capacitors: 10u, 100u(3)

-Resistors: 33k, 20k(3), 1.2k, 1k

-connecting wires

-breadboard

-In this particular experiment, we are going to use a thermistor with measures 33k-ohms at standard room temperature (68F) and varies about to about 3570 ohms over a range of 10F

-Using a 12 volt supply, the thermistor voltage will be 6 volts in the center of the range.

-As the temperature increases, the total resistance decreases and this affects the inputs and outputs on the pins of the LM339 triggering the LED's when a certain range is reached

-different temperature ranges vary the voltage across the thermistor which results in the voltage being on the upper limit or lower limit and this will cause a LED to turn on showing if it is over temperature, lower temperature, or medium temperature.