YOU CAN BUILD A DRAWING ROBOT OUT OF TWO STICKS AND A PENCIL FOR ABOUT 14 EUROS
A drawing robot made from two sticks, three cheap servos, and a Raspberry Pi Zero that plots sketchy line art for about fourteen euros.
RoboticsDisplays
- difficulty
- ●●○○○
- time
- an evening
- license
- MIT
- repo
- repo ACTIVE749 stars
●●○○○ · an evening · MIT · 749 stars · repo ACTIVE
WHAT YOU’LL NEED
- Electronic parts — full list with part numbers in the repo BOM
- Dev board / microcontroller — runs the project firmware
- Soldering kit + basic tools — one-time buy, serves every future build
Partner
COMPAREE VERDICT
BrachioGraph is a pen plotter designed to be built in about an hour from parts you can find in a drawer or buy for under twenty euros. The mechanics are deliberately minimal: two wooden sticks or lolly sticks for the arms, three SG90 hobby servos, a pen, and some glue. A Raspberry Pi Zero runs the Python software that converts a photo into a line drawing and then sends servo commands to plot it. The draw is not precision — the cheap servos and the rigid stick geometry mean the lines come out loose and sketchy, which is exactly the aesthetic the project leans into. The documentation is thorough and honest: it walks you through assembly, wiring, calibration, and troubleshooting, and it explicitly says the calibration step is fiddly because the servos are inconsistent. The most likely failure is skipping calibration and wondering why the output is worse than the examples — the servos need individual tuning. This is not a plotter for technical drawings; it is a plotter for portrait sketches and wobbly art that looks hand-drawn because it almost is. If you want a weekend project that produces something genuinely charming and costs less than a movie ticket, this is it. If you need repeatable accuracy, you are looking at the wrong machine.
IN THE REPO
NOT IN THE REPO
- —Complete Python software and detailed documentation in the repository.
- —Bill of materials is embedded in the tutorial pages, not a separate file.
- —No CAD files because the mechanical structure is two sticks and glue — dimensions are specified in the docs.
- —MIT licence permits commercial use.
- —The €14 figure is the project's own estimate and assumes you already have a Raspberry Pi Zero and jumper wires.
- —Calibration is manual and essential — the repository includes a whole page on it because the cheap servos drift.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
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Gallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the 'Get started' page in the documentation to understand the build and what you need.(This page lists the parts and walks through assembly with photos.)
- 2.Order three SG90 servos and prepare two sticks — lolly sticks or wooden coffee stirrers work.(The project recommends 10 cm sticks; exact length matters less than making both arms the same.)
- 3.Set up the Raspberry Pi with Raspberry Pi OS and install the BrachioGraph Python library.(Installation is a single pip command once the Pi is running.)
- 4.Assemble the plotter following the build instructions, then work through the calibration page.(Calibration is manual and essential — the servos are cheap and inconsistent.)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
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KNOWN ISSUES
- The €14 cost estimate assumes you already have a Raspberry Pi Zero, jumper wires, and a power supply — if you are starting from scratch, the real cost is closer to €30-40.
- Skipping calibration is the single biggest mistake — the servos drift and the geometry is never perfect, so you have to tune each servo's range or the drawings will be worse than the examples.
- SG90 servos vary wildly between suppliers — some batches are smoother than others, and there is no way to tell before you buy them.
- The sticks must be rigid — flexible sticks or uneven glue joints will make the pen wander even more than the servos already cause.
- The plotting software is Python and runs on the Pi itself, so you need SSH or a monitor to interact with it — there is no standalone app or web interface.
- The sketchy line quality is inherent to the design — if you want plotter-grade precision, you need a different machine with stepper motors and linear rails.
Can I use a different Raspberry Pi model?
Yes — the software runs on any Pi, but the Zero is recommended because it is cheap and low-power. A Pi 4 will work but is overkill.
Do I need a specific brand of servo?
No, but the project is designed around SG90 servos because they are cheap and widely available. Other 9g servos will work, but you will need to recalibrate.
Can I plot on something other than paper?
Yes, as long as the surface is flat and the pen can write on it — card, wood, and fabric all work if the pen is right.
How do I improve the line quality?
Better servos and stiffer arms will help, but the sketchy quality is part of the design — if you want clean lines, you need a different plotter architecture.
Is there a way to plot without a Pi?
Not with this software — the BrachioGraph library is Python and expects to run on a Pi. You could port the code to Arduino, but that is a different project.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
The project says the whole build takes about an hour and costs around fourteen euros — assuming you already have a Pi Zero. What would you plot first if you built one this weekend?
Daniele Procida
Daniele Procida is a developer and technical writer who built BrachioGraph as a teaching project to demonstrate cheap robotics and accessible documentation. The project started as a workshop exercise and grew into a widely used open-source plotter design.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM11d ago
Practical notes from our verification: the repository has not moved and the documentation is hosted on Read the Docs, not in the repo itself, so the getting-started link goes to brachiograph.readthedocs.io. There is no official video — the tutorials are text and images — but the documentation is unusually thorough for a hardware project and includes a whole troubleshooting section. The €14 cost is real if you already have a Pi Zero and jumper wires, but if you are starting from scratch, the Pi alone will push the total closer to €30-40. The single biggest surprise: calibration is not optional and it is not quick — expect to spend as much time tuning the servos as you did building the thing, because the cheap SG90s are inconsistent and the software has to compensate.