Transistor Light Switch Kit

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

Activity engagement

45–60 minutes. Explore 5–10 min · Build 15–20 min · Test and discuss 25–30 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
• 2N2222 NPN (5 PCS) — 1 transistor
• Tactile Push Button Switch 12x12x8mm 4-Pin — 1 button
• 1K Ω 1/4 Watts (10 PCS) — 1 resistor
• 10K Ω 1/4 Watts (10 PCS) — 1 resistor
• 5mm LED - Red Color — 1 LED
• 330 Ω 1/4 Watts (10 PCS) — 1 resistor

What you learn

• A transistor can switch a load from a control signal.
• Base current needs a limiting resistor.
• Emitter, base and collector positions depend on the supplied package.

Connection guide

• Use the supplied 2N2222 pinout labels. Emitter → GND; collector → LED cathode.
• LED anode → +5 V through 330 Ohm. Base → +5 V through push button and 1 kOhm.
• Connect 10 kOhm from base to GND so the transistor turns off when the button is released.

Steps to make it

1. Disconnect all power and identify the supplied part labels and pinouts before wiring.
2. Read the transistor package pinout before inserting it into separate breadboard rows.
3. Wire the LED collector branch, then the button/base resistor and pull-down.
4. Inspect the circuit with power off and confirm the LED resistor is present.
5. Apply regulated 5 V; press and release the button ten times and record the LED state.
6. Disconnect power and draw separate control-current and LED-current paths.

Test challenge

Predict what happens when the base signal is absent, then test repeated presses.

Observation task

Input OFF/ON, predicted LED state, observed LED state and transistor pinout sketch.

Expected result

Pressing the button supplies base current and switches the LED on; releasing it switches the LED off.

If it does not work

Wrong transistor pin order is the first check. Never bridge the LED resistor or connect the base directly to +5 V.

Try next

Compare this switching role with a relay, focusing on moving parts and input current.

Use and supervision

Use only the supplied low-voltage DC parts. Disconnect power before rewiring; check polarity and labelled pinouts. No soldering or exposed mains connections. Adult guidance is recommended.

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.