Fire Sensor Alarm School Project Kit with Thermistor

A thermistor's resistance drops as it warms up, and this circuit uses that shift to trip a buzzer once the temperature climbs high enough. Hold something warm near the sensor and the alarm goes off.

What's included

• Thermistor and transistor
• Buzzer
• 2 x AA battery case
• Assembly diagram guide

What's not included

• Model and backing board
• Batteries
• Tools and glue

This one covers Electrical Systems and Control in CAPS Technology, Grade 9. Pay attention to the transistor when you build it: the pack notes it has to go in with the rounded side facing the right way, or the circuit won't work.

Note: test it with warm air, not a flame.