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| Eggbot |
There is something quietly
radical about the Junkbot idea. It started not with a lesson plan or a product
brief, but with a question: what can you actually make with the stuff lying
around? Over nearly a decade of exploration, educator and maker Scott Turner
refined a simple concept — a vibrating robot built from a drinks can, a small
motor, and a handful of pens — into something that touches on environmental
science, engineering, and computing all at once.
This post is for the makers who
like to build first and ask questions later, for parents who want to spark
something in a curious kid on a weekend, and for educators looking to point
people toward genuinely interesting projects. We are going to look at how you
build one, and then think about where the idea can go next.
Why junk?
The word “junk” is doing
important work here. When a project starts with recycled materials — a crushed
can rescued from the bin, pens past their prime — it immediately lowers the
stakes. There is no expensive kit to worry about, nothing precious to break.
That psychological shift matters enormously, especially for younger makers who
are still learning to be comfortable with failure.
“The
best STEM projects are the ones where the first attempt doesn’t work, and that
feels interesting rather than discouraging.”
Junkbots also embed an
environmental message naturally — without it needing to be laboured. Reusing a
drinks can is just part of the build. The conversation about materials, waste,
and resourcefulness happens because it is baked into the process.
The core build: a vibrating vibrobot
The basic Junkbot is a vibrobot
— a robot that moves by vibrating. Fit an unbalanced weight to a small motor,
power it up, and the vibration propels the whole thing along a smooth surface.
It is simple physics, but watching it actually move for the first time never
gets old.
The Crumble controller from
Redfern Electronics is an excellent fit for this project. It is inexpensive,
has its own beginner-friendly block-based programming environment, and
crucially — it has motor drivers built in, so you do not need extra components
to control a motor. That keeps the wiring manageable and the whole build
accessible.
The Crumble Junkbot — step by step
What you will need:
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Drinks can: The body — any standard aluminium
can.
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3 pens (with lids): These form the tripod legs.
Ballpoints, felt tips — anything goes.
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Small DC motor: A cheap hobby motor is fine.
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Unbalancing weight: A broken toy propeller, a
blob of misshapen Blu-Tack, or even a clothes peg.
•
Crumble controller: From Redfern Electronics —
includes built-in motor drivers.
•
Battery pack: To power the controller and motor.
•
Crocodile clips: Or loops of wire if you do not
have clips.
•
USB cable: To connect the Crumble to a computer
for programming.
Steps:
1.
Build the body: Tape the three pens onto the
side of the drinks can, evenly spaced to form a stable tripod. The can sits on
the pens — these are your legs. Then attach the motor to the can with tape,
making sure the axle can spin freely. Fix your unbalancing weight to the motor
axle. The more off-centre it is, the more the bot will vibrate.
2.
Wire it up: Using crocodile clips (easiest) or
loops of wire, connect the battery pack to the Crumble controller’s power
terminals. Connect the motor to the motor output on the Crumble. Plug a USB
cable from the Crumble into your computer. That is the entire wiring job.
3.
Install the software: Download and install the
free Crumble software from redfernelectronics.co.uk. It is a block-based visual
environment — drag blocks to build your program, just like Scratch.
4.
Write your first program: Start simple: drive
the motor forward at, say, 75% power, wait a second, then drive it backward at
the same power, and repeat. You may need to experiment with percentage values —
different motors and different unbalancing weights produce different behaviours.
That experimentation is the point.
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| Example code |
5.
Let it loose: Place the bot on a smooth surface
— a kitchen worktop or a wooden floor works well. Hit run and watch what
happens. It will probably not do exactly what you expected. That is a feature,
not a bug.
The Junk-Eggbot: a more ambitious variation
The Junk-Eggbot is a more
involved sibling project. An Eggbot is a machine that can draw on curved
surfaces like eggs or ping-pong balls by rotating the object on one axis while
moving a pen on another. Building a junk version with the Crumble controller is
a considerably more involved challenge — but it is a great escalation point
once the basic vibrobot is feeling comfortable.
It introduces the idea of
coordinated multi-motor control, pen servo mechanics, and the satisfaction of a
machine that produces something visually interesting. Think of it as a natural
second chapter for anyone who gets hooked on the first build.
What this teaches — without you having to say so
The Junkbot is not obviously a
lesson. It is a build. But it quietly covers a remarkable amount of ground:
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Physics: vibration, mass distribution, friction
— all visible and tangible.
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Engineering design: making decisions under
constraint, iterating when something does not work.
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Electronics basics: circuits, polarity,
connecting components safely.
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Programming concepts: loops, sequence, variables
(those motor percentages) — in a context where the output is a physical thing
moving in the world.
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Materials thinking: what can a drinks can do?
What about a clothes peg on a motor axle?
The key is that none of
these are announced. They emerge from trying to make the thing work. They are not very controllable but that randomness has his own charm.
Where to go from here
Upgrade paths and ideas worth exploring
The vibrobot is a gateway. Once
it is moving, the natural question is: can I control it better? Scott Turner
has explored exactly this — connecting both Raspberry Pis and BBC micro:bits to
junkbot builds to add remote control and more sophisticated programming. The
Crumble is an ideal stepping stone to those platforms.
Some directions worth
considering:
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Add a second motor to enable some steering.
• Use the Crumble’s ability to connect to Sparkles (its LED component) to add light.
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Experiment with new junk chassis: a plastic bottle, a
cardboard tube, a tin can of a different size.
For parents, the weekend build
is the point. Do not worry about the curriculum — just build it, see what
breaks, fix it, and build it again slightly differently. The learning is in the
iteration.
For makers, the interesting
question is what other junk could serve as a robot body. The structural
challenge of making a new chassis stable enough to actually move is its own
design puzzle.
Original projects by Scott Turner.
Crumble controller by Redfern Electronics. The Crumble software is available
free at redfernelectronics.co.uk. The original Junkbot blog post can be found
at robotsandphysicalcomputing.blogspot.com
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