Classroom Lesson Plan for the BBC Microbit
Teaching Potential Dividers with the BBC Microbit and Physbit
In this post, we have provided a complete classroom lesson plan, to aid in the teaching of a potential divider circuit, using the BBC Micro:bit and the Phys:bit board.
The Phys:bit is an addon system which allows included prewired plugin modules to easily connect to the BBC Micro:bit for teaching various concepts about electricity and electronics.
If you wish to print out this lesson plan, we have a downloadable PDF available here:
from microbit import *
quantum = 200
pic05 = Image("99000:99000:99000:99000:99000")
pic14 = Image("00000:99000:99000:99000:99099")
pic23 = Image("00000:00000:99000:99099:99099")
pic32 = Image("00000:00000:00099:99099:99099")
pic41 = Image("00000:00099:00099:00099:99099")
pic50 = Image("00099:00099:00099:00099:00099")
while True:
voltage = pin1.read_analog()
if voltage <= quantum:
display.show(pic05)
pin2.write_digital(0)
elif quantum < voltage and voltage <= 2*quantum:
display.show(pic14)
pin2.write_digital(0)
elif 2*quantum < voltage and voltage <= 3*quantum:
display.show(pic23)
pin2.write_digital(0)
elif 3*quantum < voltage and voltage <= 4*quantum:
display.show(pic32)
pin2.write_digital(0)
elif 4*quantum < voltage and voltage <= 5*quantum:
display.show(pic41)
pin2.write_digital(1)
else:
display.show(pic50)
pin2.write_digital(1)
Potential Divider Circuit and Electricity
Background
A potential divider circuit has multiple uses in electronics. For example, it can divide a larger input voltage to a smaller output voltage for use in a circuit. A potential divider can also use a variable resistance sensor to identify an event when something has become wet, or hot, etc. There are many such sensors that can be used for a variety of purposes, e.g. safety systems, automated systems, alarms, etc.
The word ‘potential’ is used because voltage is defined as the ‘potential difference between 2 points.’ We can get into this later but think of the potential difference between the +ve and -ve terminals of a battery.
Study Material
- Pre-programmed Micro:Bit
- Battery
- Phys:Bit Carrier board
- Phys:Bit Potential divider test board
- Test lead and resistor
Basic Use
- Connect the circuit as shown opposite.
- The test lead is connected to the central (Green) connector.
- The resistor from the test lead is connected to the Ground (Black) connector.
- To select each test Press B on the Micro:Bit.
- To move back by one test Press A.
Start-up
- Switch on the Micro:Bit and an ‘Introduction Message’ is displayed.
- Press B to move to Test 1.
Test 1: Check the Board is Working
- A Zero will be displayed on the Micro:Bit.
- Connect the test lead to test points P0 to P5 shown below.
- If the test is working, then you will see a number (0 to 5) shown on the Micro:Bit display corresponding to each test point.
- Once you have confirmed the board is working, Press B to move to Test 2.
Is the equipment working? | YES / NO |
Test 2: Potential Difference
- For Test 2 you will see a bar on the left and right side of the display that shows the relative voltages V2 and V1. The bar height (0 to 5) represents the voltage level.
- Connect the test lead to test points P0 to P5 and record how the bar height for V2 and V1 varies from 0 to 5 for each test point.
Test Point | V2 bar height (left hand) | V1 bar height (right hand) | |
P0 | 0 1 2 3 4 5 | 0 1 2 3 4 5 | |
P1 | 0 1 2 3 4 5 | 0 1 2 3 4 5 | |
P2 | 0 1 2 3 4 5 | 0 1 2 3 4 5 | |
P3 | 0 1 2 3 4 5 | 0 1 2 3 4 5 | |
P4 | 0 1 2 3 4 5 | 0 1 2 3 4 5 | |
P5 | 0 1 2 3 4 5 | 0 1 2 3 4 5 |
Circle the number for each bar reading (V2 and V1) for test points P0 to P5.
Test 2 Observations
Describe how V2 and V1 change relative to one another for the different test points?
Test 2 Conclusions
Explain as best as possible why the voltages V2 and V1 are changing as observed?
Once you have finished Test 2, then Press B to move to Test 3.
Test 3: Voltage Measurements
- For Test 3 connect the test lead to test points P0 to P5 and you will see a different voltage number (V) on the Micro:Bit for each test point.
- Record the voltage V for each test point in the table below.
Test Point | P5 | P4 | P3 | P2 | P1 | P0 |
V (Volts) | ||||||
R (Ω) | 50 kΩ | 40 kΩ | 30 kΩ | 20 kΩ | 10 kΩ | 0 kΩ |
Resistors | R5+R4+R3 +R2+R1 | R4+R3+R2 +R1 | R3+R2+R1 | R2+R1 | R1 | — |
Test 3 Results Analysis
Plot Voltage versus Resistance in the Graph below and draw a straight line through the data.
Test 3 Conclusions
Can you explain why there is a straight line through the data in the Voltage versus Resistance graph? (Hint: Ohm’s law)
Once you have finished Test 3, then you are complete, or Press A to redo any work above.