Heat Sense Alarm Kit

Classes 5-6, typical ages 10–12. Age ranges vary by learner. Guided low-voltage electronics.

Activity engagement

45–65 minutes. Explore 5–10 min · Build 15–20 min · Test and discuss 25–35 min. Estimated time for building, testing and discussion.

What you need

No computer required. An adult helps inspect connections.

Included components

• Small Breadboard / Mini Solderless Board - 400 points — 1 breadboard
• Jumper Wire Combo - Male to Male, Male to Female and Female to Female Breadboard Connecting Wires (10 Qty Each) — 1 set
• Illustrated Activity Guide and Observation Sheets — 1 set
• Fitted Headers and Labelled Connection Leads — 1 set
• 4 CELL AA BATTERY HOLDER WITH SWITCH / COVER — 1 holder
• AA BATTERY — 4 battery (individual units)
• Regulated 5 V Power Supply with Short-Circuit Protection — 1 power supply
• NTC Thermistor Temperature Sensor Module — 1 sensor module
• 5 V Active Buzzer — 1 buzzer
• 5 V Sensor Output Driver with Trigger Selector — 1 interface circuit

What you learn

• Temperature changes the NTC resistance; the comparator switches at its adjusted threshold.
• A comparator turns a changing sensor signal into a digital threshold output.
• A separate output driver keeps the sensor signal separate from its load.

Connection guide

• thermistor sensor VCC/GND → regulated +5 V/GND; its labelled DO output → driver IN.
• Driver VCC/GND → the same supply; use its supplied active-low/high trigger selector to match the module.
• Buzzer positive → driver labelled load +; buzzer negative → driver labelled load −.

Steps to make it

1. Disconnect all power and identify the supplied part labels and pinouts before wiring.
2. Switch the supply off and identify the sensor DO terminal; do not confuse it with AO.
3. Connect the sensor, preassembled labelled driver and output using the connection card.
4. Power on and adjust the sensor sensitivity at the baseline condition until the output is stable.
5. Gently warm the sensor between dry fingertips, then allow it to return toward room temperature.
6. Repeat five controlled trials, changing only one condition, then switch off and dry/clean the sensing surface as appropriate.

Test challenge

Gently warm the sensor between dry fingertips, then allow it to return toward room temperature.

Observation task

Room/warmed/cooling condition, threshold position and alarm state.

Expected result

Temperature changes the NTC resistance; the comparator switches at its adjusted threshold. The driver makes that change visible or audible.

If it does not work

Check the DO pin, shared ground, sensitivity setting and driver trigger selector. A brief sensor pulse gives only a brief output; this is not a latching alarm.

Try next

Discuss the difference between a threshold alarm and a calibrated thermometer.

Use and supervision

Warm the sensor only with dry fingertips. No flame, hot plate or boiling water. Use the supplied 5 V DC power unit and switch off before rewiring.

How this experiment works

Download class activity guide

Cover illustrations show component types. Functional animations explain principles and are not recorded prototype tests. Follow the supplied connection labels and pinouts.