The Temperature Monitoring with Alarm DIY Soldering Kit is a simple comparator with an LM741 operational amplifier. The OPA compares a set voltage value with the voltage provided through a resistor voltage divider, where one of the resistors is a thermistor (temperature-sensitive resistor).
A trimmer potentiometer allows to set the reference voltage.
If the measured temperature is lower than the setpoint, a red status LED will show the device is active and operational. As soon the temperature reaches the setpoint, the NE555 timer IC is triggered to generate a frequency that then is transmitted by the on-board buzzer.
The Temperature Monitoring with Alarm DIY Soldering Kit is an easy-to-assemble beginner’s kit. Start with the lowest profile components, which are the resistors, and finish with the tallest part (5V DC port).
Watch the polarity of the LED (flat side – cathode – is marked on the PCB) and the electrolytic capacitor (plus side – long lead – is marked on the PCB).
Finished module size: 50 x 30 x 15mm
