MONK MAKES MNK00085 Slider for Micro Bit Instructions
- June 6, 2024
- MONK MAKES
Table of Contents
Instructions:
SLIDER
FOR MICRO:BIT
V1A
INTRODUCTION
The MonkMakes Slider for micro: bit allows you to interact with your micro:
bit by sliding a control left and right.
The board uses a 10kΩ linear variable resistor (pot) to output a voltage
between 0 and 3V that can be measured in your micro: bit programs using one of
the micro:bit
connections as an analogue input.
PARTS
Please note that a BBC micro: bit is NOT included in this kit.
Before you do anything else, check that your kit includes the following items:
Slider for micro:bit| 
---|---
Set of alligator clip leads (5 leads)| 
GETTING STARTED
About Alligator Clips
When using the alligator clips to connect your micro: bit to the MonkMakes
Slider for micro: bit board, you have to be a bit careful how you connect the
clips at the micro: bit end. The best way is to connect the clips vertically
as shown below.
Connecting the alligator clips like this prevents any accidental connections between the large connectors with the holes in and the much smaller connectors (gold lines in the photo above)
Connect the micro: bit to the Slider for micro: bit
Use three of the alligator clip leads to connect your micro: bit and Slider
for micro: bit together.
Its a good idea to use the red lead for 3V, black for GND and a different
color to connect the output of the Slider for micro:bit to your BBC micro:bit.
You can use P0,
P1 or P2 of your micro: bit, but for the example programs here, it is assumed
that you have connected it to P2 as shown above.
THE VARIABLE RESISTOR
The main component of the Slider for micro: bit is a sliding variable resistor
(also often called a potentiometer or just pot). The other components on the
board are designed to protect your micro: bit against accidental damage should
you connect things the wrong way around and the amber power LED that show that
the Slider for micro: bit is powered.
Here’s the schematic diagram of a variable resistor and micro: bit working
together.
The variable resistor is actually a resistive track, across which the micro: bit supplies a voltage of 0V at one end (the left) and 3V at the other (right). When you move the slider left and right you are moving a sliding electrical contact along the track. When the slider is at its leftmost position, the voltage at the slider will have a voltage of 0V and when its at the rightmost position the slider will have a voltage of 3V. When its in the middle position, this voltage will be half way between 0 and 3V in other words 1.5V. Note that the actual voltage will probably be less than 3V if you are powering the micro: bit from batteries.
The slider voltage is measured by the micro: bit using P2 (or whichever pin
you decide to use) as an analog input.
The three connections 0, 1 and 2 can all be used as analog inputs. In Block
code, you do this using the analog read pin block. This block measures the
voltage at the connector specified but rather than return the actual voltage
in Volts, it returns a number between 0 and 1023.
When the slider is in its leftmost position, the reading will be 0 and when
rightmost the reading will be 1023. Note that in practice the maximum value
will be around 1013 rather than 1024 because of extra circuitry built into the
Slider for micro: bit that protects the micro: bit.
This example will display the reading when button A is pressed. Load it onto
your micro: bit (see the link) and try moving the slider to various positions
and then press button A and see what the reading is.
Click on this link and then Download the program onto your micro: bit:
https://makecode.microbit.org/_5x9RyqRKyTwL
If you are using Python, the following program does the same as the blocks
code above. You can download all the Python example code for this kit at
https://github.com/monkmakes/mb_slider. The program is called
analog_reading.py.
For more information on using MicroPython on your micro: bit, see the Section
MicroPython with Mu, later in these instructions.
Here are some more programs for you to test out the slider.
PROGRAM 1. SLIDER NUMBER
This program displays a single digit between 0 and 9 depending on the position of the slider. To try it out using Block code, visit this webpage in your browser. https://makecode.microbit.org/_C9mFbkMwu7iw
Click on the Download link at the bottom of the window and copy the HEX file
onto your micro: bit. Once flashing is complete, you should see that the
micro: bit’s display shows a number. When you slide the Slider back and forth
you should see the number change from 0 (left) to 9 (right).
By dividing the analogue reading by 110, the maximum reading of 1023 becomes 9
(actually 9.3) but we use the round block to round this down to 9.
Here is the MicroPython version of this program. The program is called
slider_number.py.
PROGRAM 2. SLIDER BAR GRAPH
This example uses the Blockcode plot bar graph of block to display a bar graph that responds to the slider position.
Here’s a link for the code: https://makecode.microbit.org/_HYtds3Yg9J32
Notice how the range of the plot bar graph of block is set to 0 to 1023. Move
the slider about to change the display.
The Python version of this is a little different because MicroPython for the
micro: bit does not include an equivalent of the plot bar graph of block and
so we have to write our own. This is contained in the bargraph function that
expects a number between 0 and 5 as its parameter and then displays 0 to 5
lines of LEDs. You will find the code in
slider_bar_graph.py.
PROGRAM 3. SNAKE
This example uses the Slider to make a wiggly snake animation when you move
the slider. This is a little difficult to describe, so perhaps just try it
out: https://makecode.microbit.org/_hgvDyoM2KVEP
The code uses an array to keep track of the dot position on each row. The
forever block first shuffles all the dot positions up one place using a for
loop.
It then clears the display and then sets the position of the bottom-most dot
to be determined by the slider position. It then draws all the dots. The pause
block just slow things down.
Here is the MicroPython code which follows exactly the same pattern. You will
find it in the file slider_snake.py
PROGRAM 4. MU PLOTTER
This final program is only available for MicroPython using Mu because it uses
Mu’s Plotter facility to plot values sent out from the micro:bit to your
computer over USB.
Load the program onto your micro:bit (called mu_plotter.py) and then click on
the Plotter button in the tool bar. Now when you move the slider about you
will see the values change in the plot.
Here’s the code:
The data has to be sent as a Python tuple, even though it only has one value.
That’s why there are extra () and a comma in the line highlighted above.
MICROPYTHON WITH MU
The code for this kit is available both as Block code and as MicroPython. If
you would like to run the MicroPython versions of the programs rather than the
Block code, then you can download all the programs from Github here:
https://github.com/monkmakes/mb_slider
Click on the green Code button and select the option Download ZIP. Extract the
ZIP archive and you will find a directory containing the python programs for
all the projects.
You can then use the Mu editor (https://codewith.mu/) to Load the downloaded
programs and then Flash them onto your micro: bit.
The MicroPython versions of the programs are modelled closely on their Block
equivalents and should be easy to follow.
TROUBLESHOOTING
Problem: I am moving the slider, but the reading is not changing.
Solution: Make sure that the analog read pin block has the same pin
selected as is physically connected to the Slider for micro:bit’s output.
Problem: The amber power LED on the Slider for micro:bit is not lit.
Solution: Make sure that your micro:bit itself is receiving power and
that the GND and 3V connections of the micro:bit are connected to the GND and
3V connectors of the Slider.
Problem: How can I connect more than one Slider for micro:bit to my
micro: bit?
Solution: You can use any of the micro:bit’s pins to read analog values,
so to use a second micro:bit you just need to supply it with power and connect
its output to an otherwise unused pin as shown below.
Note that you will need some more alligator leads.
LEARNING
micro: bit Programming
If you want to learn more about programming the micro: bit in MicroPython,
then you should consider buying Simon Monk’s book ‘Programming micro:bit:
Getting Started with MicroPython’, which is available from all major book
sellers.
For some interesting project ideas, you might also like micro:bit for the Mad
Scientist from NoStarch Press.
You can find out more about books by Simon Monk (the designer of this kit) at:
http://simonmonk.org or follow him on Twitter where he is @simonmonk2
MONKMAKES
For more information on this kit, the product’s home page is here:
https://monkmakes.com/mb_slider
As well as this kit, MonkMakes makes all sorts of kits and gadgets to help
with your maker projects. Find out more, as well as where to buy here:
https://monkmakes.com you can also follow MonkMakes on Twitter @monkmakes.
From left to right: Electronics Starter Kit for micro: bit, Power for micro: bit (AC adapter not included) and 7 Segment for micro: bit.
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