
Show HN: BrachioGraph, an easy-to-build pen-plotter, driven by Python - DanieleProcida
https://www.brachiograph.art
======
DanieleProcida
Full details of the project, including all the code and documentation, are
posted at [https://www.brachiograph.art](https://www.brachiograph.art).

This is my attempt to do something with the Raspberry Pis and cheap servo
motors I've had hanging around that's both genuinely interesting and also as
simple and cheap as possible. Robotics isn't my subject, but I wanted to make
something.

The total cost of hardware (excluding the clothes-peg, pencil and things you
will find in a kitchen drawer) is €14. You could build the whole thing in
about an hour, it's a fun thing to do with a child, and they love the fact
that it's made from household materials.

One thing I like about it is that it's all 'wrong' \- you are not supposed to
use servos or electronics like this, and it's not what a 'real' engineer would
do - but it still works well enough to be fun.

The cost and simplicity are really important because this project has come
with me to events like PyCon Africa
([http://pycon.africa](http://pycon.africa)) and PyCon Namibia
([https://na.pycon.org](https://na.pycon.org)) where not everyone has easy
access to labs and hack-spaces and electronic hobby shops, and many people
have to learn and experiment on much smaller budgets.

There's some custom Python code:
[https://github.com/evildmp/BrachioGraph](https://github.com/evildmp/BrachioGraph)
and contributions and issue reports are welcomed. And it's on Twitter:
[https://twitter.com/BrachioGraph](https://twitter.com/BrachioGraph).

If you build one yourself, please send me a picture!

~~~
ChuckMcM
This would be a better link to have the article reference.

~~~
dang
Ok, we've changed the link from
[https://vimeo.com/372867891](https://vimeo.com/372867891).

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powerbroker
I'm a big fan of ink, since it gives better contrast. Can the python software
be adapted to not drag across freshly drawn lines? Are there pens that work
better in that context? I've got some parts laying around and I just might
build this. Plus, it will make my brother-in-law sad that he spent > $100 for
some kind of plotter he uses on a whiteboard.

~~~
DanieleProcida
It works fine with every kind of drawing implement I have tried:

* pencil * charcoal * ball-point (needs additional weight on the pen) * roller-ball * felt-tip * fibre-tip

It draws so slowly that there's no issue about waiting for the ink to dry.

But what I like best is soft pencil on slightly textured paper.

Daniele

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yorwba
Previous discussion about the documentation for this project:
[https://news.ycombinator.com/item?id=21281525](https://news.ycombinator.com/item?id=21281525)

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geokon
What are the "standard" algorithms for vectorizing bitmap lines?

I'd had a little art project where I wanted to draw lines on the wall and then
have them captured by a camera and vectorised .. preferrably "minimized" to be
as few vectors as possible. I couldn't really design an algorithm that was
satisfactory and I didn't wanna just hack it with some heuristics

I see they're doing it here with an edge detector - anyone have any insight
how it's done? Is this a solved problem in computer science?

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apankrat
A link to the project page with HowTos won't hurt -
[https://www.brachiograph.art/](https://www.brachiograph.art/)

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jascii
Cool project!

Feature-creep: I can't help wondering if there would be ways to improve the
precision enough to make for instance PCB's without increasing the
complexity/cost to much..

~~~
DanieleProcida
Not with these servos or this mechanical arrangement, that's for sure. But,
it's very interesting to think of ways to improve the precision of imprecise
hardware, using only software.

~~~
mmastrac
Could be really interesting to add cheap cameras and OpenCV to this concept!

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jmpman
Fantastic. Thanks. This will be my next project.

