Build a Coin-Activated Light & Sound Circuit – The Perfect First Sensing Project

Every part needed, pre-tested for compatibility, with an AI build companion trained on this exact project. Shipped from Bengaluru in 3-5 days.

Drop a coin through a tube and watch an LED flash as a buzzer beeps — this kit transforms a simple action into a real electronic count. Young builders learn how invisible infrared light detects an object and triggers a circuit, the very first step into the world of sensors and automation. It's a hands-on introduction to how machines “see” objects, just like the ticket counters and vending machines we encounter every day.

What You'll Build

Your child will assemble a coin-activated counter on a breadboard. Every time a coin passes through the 15cm PVC tube, it breaks the IR beam between an LED and photodiode, making a transistor switch on a bright indicator LED and a piezo buzzer. The result is a working gadget that counts play coins, tokens, or even small buttons — giving an immediate sense of achievement and sparking curiosity about circuit design.

What You'll Learn

• How an IR LED and photodiode pair creates an invisible detection beam
• Using a BC547 transistor as an electronic switch triggered by light
• Breadboard wiring without soldering — perfect for small fingers
• Connecting a buzzer and LED to create a visual and audible output

Kit Contents

Why Buy This Kit Instead of Sourcing Parts Separately

Who This Kit Is For

Designed for young learners in India's early STEM ecosystem: CBSE Class 1-2 students exploring their first science project, ATL Tinkering Lab initiations, and curious 6-8-year-olds at home. The large, plug-and-play breadboard and pre-cut wires make it suitable for small hands. No reading of complex schematics required — just follow the picture-based guide and let the AI companion handle troubleshooting.

Built and Backed by Compoden

Every Compoden kit ships with an AI build companion trained on this exact project — accessible via a QR code on the box, with WhatsApp and email backup. We've spent 10 years building projects for makers, schools, and institutions across India. If a part fails because of a manufacturing defect, replace it free within 7 days.