16. Science

I am exploring a role for the micro:bit in Science teaching. The best science teaching incorporates an investigative approach and the mico:bit has enormous potential to support this heuristic approach.

Possible science investigations (as these are piloted with my science classes the findings will be documented on this website):

  • thermal insulation - the relationship between thickness of insulation and rate of cooling
  • investigating the latent heat of change of state
  • fitness investigation
  • measuring distance
  • measuring the speed of sound
  • the relationship between light intensity and the rate of photosynthesis
  • the relationship between force and acceleration
  • the magnetic field surrounding a bar magnet or wire carrying an electric current.
  • measuring reaction rate
  • measuring soil moisture
  • pollution control


Science Scope - This site outlines a few ideas for using the micro:bit to teach classic science classes:

Data Logging - This document describes different methods using micro:bits to collect and record data for science experiments.


Successfully piloted projects outlined on this website:

  • Soil moisture sensor
  • Potential divider circuit
  • How clean is my pond (pollution control)
  • Fitness investigation
  • Measuring distance
  • Measuring the speed of sound
  • Energy transfer (radio waves)
  • Electrical circuits (burglar alarm)

Soil moisture sensor

The simple soil moisture sensor (shown below) can be used with the micro:bit to estimate the amount of moisture content in soil and display it on the LED matrix screen. The sensor works by measuring a voltage related to the conductance of the soil and using it to estimate the amount of moisture in the soil.

A watering alarm system can be programmed to sound an alarm when plants are in need of watering.

A BBC micro:bit Water sensor can be purchased for under £6.00.

Potential divider circuit

The variable resistor in the circuit diagram can be replaced by a wide range of sensors if they operate by changing their resistance (see the LDR in the picture to the right).

When using sensors that function by changing their resistance they must be arranged as a potential divider. A fixed resistor (R1) is connected, with the sensor, to a common pin (pin 1 or pin 2) on the micro:bit.

The resistance of R1 needs to be similar to the range of resistances produced by the sensor.

How clean is my pond?

Particles suspended in the water reduce the water clarity. Water clarity is very important in keeping a pond healthy. Clear water allows light to reach pond plants. Pollution can be harmful to fish and other pond animals.

Aim

To have a quantitative method of monitoring the water clarity of a garden pond.

Method

Using a standard light source, a standard quantity of water, we will use a micro:bit to quantify the light level falling on a LDR.

This will give a value for the pollution level of our pond water.

After testing the electronics, the threshold pollution level for turning on the filter pump has been set to 500.

This 'default' setting will vary according to the light intensity of the LED, the value of the fixed resistor, the resistance of the LDR, the size of water sample and the clarity requirements for the pond.

Algorithm

When button A is pressed the LED lights up.

The analogue value of the LDR is read and this is stored in a variable.

The LED is turned off.

The pollution value stored in the variable is compared with the default value.

if the value measured is greater than the default, then display the message 'Filter ON' else display the message 'Filter OFF'

End


The apparatus

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Outline lesson plan - follow this link to find out how we used the apparatus in the children's science lessons.

Watch a short video.


Fitness investigation

Introductory video

Walking is an excellent form of exercise that most people can take part in. The average person walks 3000-4000 steps per day. The National Health Service in the UK has set a challenge for each person to walk 10,000 steps per day. This can be counted using a step counter or stepometer.

With thanks to the BBC micro:bit website

When children are studying the cardiovascular system in science or health related fitness in PE they find it interesting to investigate the effect of exercise on their heart rate by carrying out and compare this with other children.

The children will need to standardise the exercise they carry out to be able to make comparisons. This is where the micro:bit comes in.

Once programmed as a stepometer, the.


Measuring distance

Is it possible to measure distance using a micro:bit connected to a HC-SR04 ultrasonic sonar sensor?

Follow this link for wiring information

The sensor needs a voltage of 4.5 to 5V. I found the easiest setup was to use Kitronic motor board connected to a 4.5V power supply to feed the micro:bit and the sensor as I already have a set of these.

The script below was used to give a value for the actual distance being measured. The boards have terminals connected to pin0 and pin1.

A simple calibration calculation was required as the value from the sensor did not match the actual distance. This makes for an excellent teaching opportunity. We are so used to connecting digital meters and expecting them to produce an accurate measurement without considering how the value is obtained and the calibration algorithm required to convert analogue data into a 'real world' quantity.


From experimentation your pupils should be able to determine and apply this calibration algorithm after a number of tests using a known distance. By dividing the actual distance by the value from the sensor, in my case, a conversion factor of x 1.54 was determined. See the results table below.

It is likely that the children will experience some variation so they should make a number of measurements and calculate the average.

Once my pupils applied the conversion factor they could obtain extremely accurate distance measurements up to a maximum of about 3 metres (about the limit of the sensor).

Measuring the speed of sound

The traditionaI way of doing this by experimentation is the 'clap echo' experiment which, with practice, can produce surprisingly good results.

It occurred to me that if we can use a micro:bit connected to a HC-SR04 sensor to measure distance, we should be able to obtain values for the speed of sound over known distances using the pulse time. I recommend doing this after your pupils have used the HC-SR04 sensor to measure distance (see above).

Having worked out a conversion formula based on the known speed of sound in air (343m/s). I gave my pupils a spreadsheet with the formula already entered into the speed column.

=SUM(B42/C42)*13000

They were then given a micro:bit and HC-SR04 sensor, a tape measure, a board held in a stand and clamp as a reflector. For each distance used I instructed my pupils to take at least three readings for the pulseTime and enter the average to the spreadsheet.

An important concept in experimental science is the reliability of the data produced and the need to reduce or eliminate experimental error.

It was up to the pupils to work out how best to conduct the experiment.

Measuring acceleration

Investigating the relationship between force, mass and acceleration.

The traditional method of measuring acceleration is to use a pair of light gates linked to a timer (or for that matter, a micro:bit). The two light gates can be replaced by a micro:bit and an android phone with the Bitty Data Logger app installed.

From the Bitty Software site....

http://www.bittysoftware.com/downloads.html#data_logger

download the file....

micro:bit hex file - no pairing required

then drag and drop the file onto the micro:bit.

In the experiment, the trolley was accelerated using the built in spring. The spring has three different force settings. The acceleration for each setting was measured using the Bitty Data Logging software. The acceleration in g was converted to m/s/s and then plotted against the force in Newtons.

The diagram above shows the data from the experiment and illustrates a directly proportional relationship between the force and resultant acceleration.

To convert acceleration in g to acceleration in m/s/s you can use the Endmemo converter - follow the link below.

http://www.endmemo.com/sconvert/m_s2g.php

Energy transfer - Radio

These lessons are designed to demonstrate the transfer of energy wirelessly via radio waves using a pair of micro:bits to create a remote controlled device.

The fact that most children now talk about ‘having Wi-Fi’ instead of ‘having Internet access’, clearly indicates the importance to the children of radio waves as used by WLAN (wireless local area networks). Radio as a form of energy transfer is largely hidden yet it plays a vital part in all our lives as a mechanism to access the Internet.

Challenge

To create an electronic device that depends on the transmission of energy (between a hand held transmitter and a receiver) in the form of radio waves.

The challenge for the children is to create a system that can be used to turn the lights in a bedroom on and off without having to get out of bed.


I used this as a chance to test the MI power boards (from Kitronik) as the small 'coin' cell makes them much more portable.

The link works well over a short distance - 4-5 metres. It is possible to set the radio to work at higher power but this is at the expense of battery life.

The children will need a pair of micro:bits and a bright LED wired with a current limiting resistor and two leads with a crocodile clip at each end to connect the LED to the micro:bit.

N.B. Don't for get to switch them off as radio - even when set to low power, runs the little battery down very quickly.

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Lesson outlines


Click the link below to watch a demo.

Electrical circuits

We teach simple circuits in a fairly traditional way at Key Stage 2 and Key Stage 3.

This burglar alarm project is designed to reinforce and build on my pupil's knowledge of circuit electricity and introduce them to simple electronics.


Alarm specification

The burglar alarm must be triggered by two or three different sensing components (twpes of switch).

If just one of the inputs is triggered by a burglar, the alarm must sound and continue to sound until it has been reset by the homeowner entering a pin number (A+B).


Sensing circuit

This is a parallel circuit, each sensor (switch) is on a separate branch of the circuit. The logic is that only one switch, switch 1 or switch 2 or switch 3, needs to be closed to make a connection between pin 0 and 3V.

Alarm circuit

To help the children to understand the alarm circuit I tell the children that the micro:bit acts like a 3 volt battery. GND is acting as the negative terminal and pin 2 as the positive terminal.

Lesson outlines

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