Lesson 7: Transistor Pushbutton (Preview)

Materials Needed

1 LED
1 10k Ω Resistor
1 330 Ω Resistor
1 Pushbutton
1 NPN2222 Transistor
4 AA Batteries
1 Battery Holder (4 AA batteries)
1 Mini Breadboard
1 Jumper Cable

In this lesson, you will be making a circuit using both a pushbutton and a transistor.   Please note that the video for this lesson will be posted at a later date. 

A transistor is a switch that is activates or deactivates the circuit based on the current flow to its base pin.  We will use the pushbutton to control the flow of current to the transistor but ultimately the transistor is the switch that controls the flow to the LED.  While you have built a similar circuit using a simple switch, we will build upon this concept as the circuits become more complex.  

Diagram 1: NPN Transistor

Instructions

First, assemble the pushbutton with its button caps, if you have not done so already.

Then position Pushbutton #1 pin into E2 and E4 and G2 and G4.

Next, place Transistor #1 in the following position: collector pin in I9, base pin I10 and emitter pin I11.

Now , place 10k Ω resistor with one pin in J4 and the other end in J10.  This is inline with the base pin of Transistor #1.  Place the 330 Ω resistor in H11 (inline with the emitter pin)and H16.

Insert the LED leads in G16 and G17 (Longer leg – Anode in G16; Cathode in G17)

Next place a jumper wire in C2 and F9 (inline with the collector pins).

Now, assemble the battery pack with the 4 AA batteries and place the ground wire (black) in F17 and the red wire (positive) in A2.

Now see what happens when you press the pushbutton.

Breadboard Diagram 2: