Hi, Captain Arghuino here!

The goal of this fun Instructable is to teach kids how transistors work. It demonstrates how a transistor can amplify a small current.

We will be using a fun comic format to make it easier to understand. It is an excerpt of the Island of PodPi, a monthly comic series to teach kids Electronics and JavaScript on Arduino. Let's make a High-Five Sensor that will light up an LED when two people high-five each other. This project only requires the following parts.

For this experiment you will need:

1 mini breadboard (we use an Arduino mini prototype shield)
1 NPN Transistor (BC548, 2N3904, etc.)
1 LED
1 330 Ohms resistor
1 4K7 Ohms resistor
a 4.5V-9V power source

You can order your components today for $5.50 using this link.

Step 1: Information About NPN Transistors

Transistors are the miniature brain cells of today's digital devices, like computers, phones and more. They were invented more than a half a century ago. A transistor has two different jobs:

As a switch, a transistor can allow a current to flow through it or act as an insulator and not allow any current flow. This is used in computers and all digital devices.
As an amplifier, a transistor can amplify a tiny current flowing through its base to allow a much larger current to flow through its collector and emitter. This is mainly used in analog devices and this particular DIY sensor.

There are two types of transistors: NPN and PNP. In this lesson, we will only use the NPN type. There are many different types and you need to pay attention to their pins (B, C and E). Each type may have different pinouts. To know more about the type of transistor you are using, simply access the datasheet by looking it up on google.com. For this example we are using the 2N3904 transistor.

Download the high-resolution picture.

Step 2: The Sensor

The sensor works by having a tiny current flow through the base. By having one person hold the 5V and one person hold the base, when the two persons touch each other with a High-Five for example, a tiny current is allowed to flow through their bodies from the 5V all the way to the base of the transistor. The transistor then amplifies the current between its collector an emitter and thus powers the LED.

Step 3: Setting Up the Circuit

Setup the circuit as shown in the cartoons.

Place the transistor with the flat side facing the right
Add an LED across the middle of the breadboard and have the short lead (cathode) be on the same row as the Collector of the transistor.
Add a resistor from the other side of the LED (anode) and connect one side to the power supply (5V).
Add a wire between the Emitter of transistor and the ground (GND)
Connect a wire to the Base of the transistor (middle pin) and give it someone to hold (make sure to touch the metal inside the wire).
Connect a wire to the 5V supply and hold the other end (make sure to touch the metal inside the wire)

Step 4: Let's Try It!

There you go! Now high-five your partner and you will have the LED light up every time you touch each other.

You can get the parts for this project for FREE (just pay shipping and handling) at: https://shop.podpi.com/collections/components/products/high-five-sensor-kit

This project is part of the PodPi Volume 7 on transistors. The Island of PodPi is the first comic book series to teach kids electronics and JavaScript programming. Every month a new volume is published covering a different topic from the resistor to the world of IoT. Find out more at http://www.podpi.com

Captain Arghuino