Inside the Pushbutton

Let’s take a look inside the pushbutton to better understand how and why it changes the circuit when you press it.  In this activity, you will:

• Measure continuity between various combinations of the pushbutton’s pins while it is pressed and not pressed.
• Look inside the pushbutton to see how pressing it makes the electrical connections change.
• Examine the functions of the resistors in the pushbutton circuit.

Parts

In this activity, you will connect new parts, as well as make use of parts from a previous activity.

Parts You Will Connect in This activity:

(1) Resistor – 220 Ω  (red-red-brown-gold)
(1) Resistor – 10 kΩ  (brown-black-orange-gold)
(1) Jumper wire – black
(1) Pushbutton

Setup from Previous Activity:

You will be using the alligator clip leads again in this activity.  The 3 LED circuits are not used in this activity, but will be used again in the next one.

Circuit

Remember from the Parts list in the Build & Test a Pushbutton activity’s Parts section that it has a pin map with pins 1, 2, 3, and 4?  Since you will be probing various pairs of those pins with the micro:bit continuity tester, here it is again for reference.

• Disconnect the USB cable.
• Add a pushbutton to the breadboard’s right terminal strip.  It’s pins should go into rows 19 and 21.  
• Like in the previous activity, make sure the:
  • Pushbutton’s pins stick out of the left/right sides of the button body
  • Pushbutton’s pins sink all the way into the sockets
  • Pushbutton bridges the valley that runs down the middle of the right terminal strip
• Connect the red alligator clip lead from the 3-pin header at P2 to the same row as the pushbutton’s pin 4.  As shown, it’s connected to (j, 19), but any unoccupied socket in that row-of-five would be fine.
• Connect the black alligator clip lead from the 3-pin header at P0 to the same row as the pushbutton’s pin 3.  As shown, it’s connected to (j, 21), but again, any unoccupied socket in that row-of-five would be fine.
• Reconnect the USB cable.