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To create your simple AI exercise timer, 
you’ll train a machine learning (or ML) model. 

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This model will recognise when you’re 
exercising and when you’re not exercising.

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You’ll then combine the model with some 
ready-made code for an exercise timer...

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before downloading it to your 
micro:bit and using it in real life.

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Click ‘Open in micro:bit CreateAI’ to launch the project. 

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The project comes with 3 samples 
of movement data for exercising

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and 3 samples of movement 
data for not exercising.

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You’ll need to add more samples by 
recording your own movement data.

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micro:bit CreateAI collects movement 
data samples using the accelerometer  

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(or movement sensor) on the micro:bit.
You will wear a micro:bit and battery  

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pack on your wrist or ankle, so that you can move 
freely to record your own movement data samples. 

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To get started, you need to set 
up the data collection micro:bit. 

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Connect the wrist-worn micro:bit to CreateAI. 
If your computer has Bluetooth enabled then you  

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will just need 1 micro:bit and a USB data lead.
If you don’t have a Bluetooth connection,  

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you’ll be prompted to use 2 micro:bits.
The second micro:bit will remain connected  

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to the USB cable and act as a radio 
link to the data collection micro:bit.

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Follow the instructions on screen to connect.

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 Once your data collection micro:bit is connected

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you’ll see the lines on the live graph 
change as you move your micro:bit about.


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You’re now ready to add your 
own movement data samples.


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As this project already includes some 
data samples, we suggest you just add  

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1 more sample for each action for now, and spend 
more time collecting and analysing data later.

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Decide what ‘exercising’ 
action you are going to do. 

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This could be running, walking briskly, 
jumping, boxing, dancing, or any other exercise. 

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Make sure the micro:bit is attached to 
the wrist or ankle that will be moving. 

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To add data to a specific action, 
select it by clicking on it. 

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You will get a 3 second countdown 
before a 1 second recording starts. 

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Click record and start moving right away 
to ensure you get a clean data sample. 

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A clean sample is one where you 
are moving for the entire sample,  

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you don’t start late or finish moving early.
Next try adding an extra data sample  

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to the ‘not exercising’ data set.
Select it by clicking on the action,  

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then stay still, or only move very 
slightly as you record the sample. 

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You’ll notice that the x,y,z 
lines change places depending  

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on the angle at which you hold your micro:bit.

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The project doesn’t have a lot of data right now, 

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but we have enough to train our own 
machine learning model using CreateAI. 

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So click ‘Train’ to use the 
current data to build an ML model.

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The tool now builds a mathematical 
model that should recognise different  

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actions when you move your micro:bit.
As soon as the model has been trained,  

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you’ll see the Testing model page.
Your data collection micro:bit can now  

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be used to test how well the model is working.
It should still be connected to the tool,  

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and you’ll see that as you move it, CreateAI 
is estimating what action you are doing. 

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Try out different levels of exercising or 
not exercising to see both the estimated  

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action and the certainty bar graph change.
The % on the certainty bar graph shows how  

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confident the model is that 
you are doing each action.

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You may notice your model is not estimating 
some actions accurately, or maybe it is  

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working well for one action but not the other,
so after exploring how it is currently working,  

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it’s a good idea to click on ‘Edit 
data samples’ and improve your model.

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Machine learning models usually work best with 
more data, so record some extra samples for each  

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of the actions, or focus on collecting more data 
for the action that was problematic in testing.

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You can record 1 sample at a time or 
you can record 10 samples in sequence.

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Clean data samples also 
help an ML model work better 

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so interrogate your data set and identify any 
data samples that could confuse the model. 

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You can delete these by pressing x.
Once you’ve added more data and checked  

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your data set, click Train model 
again to use your amended data set. 

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Then test the model again on 
the ‘Testing model’ page.

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Once you’re happy with how 
the ML model is behaving,  

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you can use it with the ready-made project code. 

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Click on 'Edit in MakeCode' to see the code blocks 
in a special version of Microsoft MakeCode.

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You can always return to CreateAI using 
the arrow in the top left of the screen. 

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These code blocks use the model you 
have created within an exercise timer.

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The code uses two variables to keep track 
of how long you've been exercising and how  

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long you've not been exercising.
When the program first runs it sets  

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these timer variables to 0.
The 'on ML start' blocks are  

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triggered when the ML model decides you have 
started either exercising or not exercising. 

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They show different icons on the 
micro:bit's LED display depending  

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on the action it has estimated you are doing.
The 'on ML stop' blocks are triggered when the  

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ML model decides you have finished an action, 
in this case exercising or not exercising. 

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Code inside each block clears the screen and 
adds the duration of the action that has just  

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finished to the variable storing 
the total times for each action.

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The ML model works with the code to allow you 
to view the total time spent on each action. 

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Press button A to see the total time you have 
been exercising and press button B to see the  

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total time you have been inactive.
The timer counts in milliseconds,  

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thousandths of a second, so the number shown 
is divided by 1000 to show a time in seconds.

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To make your simple AI exercise 
timer run on your micro:bit, you  

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just need to download this code to a micro:bit.
If you don’t have another micro:bit available,  

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simply replace the code currently on the data 
collection micro:bit with the project code.


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Now test the project out in real life. 
Do the correct icons display  

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when you are exercising or not?
You can test if the timer code is working  

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well with the model in 3 easy steps:
Press the reset button. 

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Exercise for 30 seconds.
Then press button A.

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You should see the number 30 
scroll across your display.

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You’re now ready to connect to CreateAI, 
collect your own data, use it to train,  

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test & improve a machine learning model.
And you can then combine this model with  

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the ready-made code and try 
it out on your own micro:bit.