Introduction: Raspberry Pi Camera Mount for the AxiDraw
For about a year now, I am the happy owner and user of the brilliant Axidraw, the modern pen plotter made by Evil Mad Scientist Laboratories. I make plots, based on binary and ternary number systems (if you're interested, check: https://dutchplottr.nl/en/ ).
A pen plotter is mesmerising machine to watch, I have seen many people, completely seized by the movements of this machine. When I finish a new plot, I show it on Instagram and Twitter, most of the time accompanied by a movie. At first they were just little clips, later I made some time-lapses from above and from the side.
At some time I started to use a Raspberry Pi as the dedicated plotter computer. By using that machine I could walk away and do my job while the plotter was doing his. Some plots take several hours.
When I bought a Raspberry Pi, I also purchased a camera that I hadn't used till that time. I experimented with it as as normal video camera and a a streaming device. But then I thought of a different way of using it. Because of the fact that is is such a tiny, very light weight camera (3 grams), it can be positioned everywhere. I imagined that it could also be mounted to the pen holder so that is would take a video from the pen's perspective. At first I tried to tape it, but that didn't work.
So, I had to make a mount.
I have no illusions I could ever win but voting for my entry is very much encouraged.
- Raspberry Pi (all versions work, I use a Raspberry Pi 4): $35-$55
- Axidraw (all versions work, I use a V3 and a V3/A3): $475-$800
- 3D pinter
- Iron wire (2 mm diameter)
- Plastic spacers or something equivalent
- Small files
- Optional: a piece of perspex
Step 1: Designing the Mount
I took a close look at the pen holder and decided to hang it on the side. I first made some calculations to find the perfect angle for the camera. The last adjustments were made using a model in Adobe Illustrator. I exported the file as a SVG to be able to import it in Tinkercad, my 3D design program of choice (the only one I master ;-).
In Tinkercad I built a 3D design of the flat SVG and exported it to a STL file. I printed it and of course it had several flaws. Back to Illustrator and again to Tinkercad (maybe a more advanced 3D design programs is at order). I did this several times and finally I had a design that worked. The only thing I had to do by hand is to widen the crack where it hangs over the pen holder. Our 3D-printer was not exact enough. I used some small files and in a few minutes it fitted snuggly.
You can download the file here and if you want to make amendments or get some inspiration to make a much better one, feel free to do so of course. You can find the Illustrator file and the STL file here. And if you want to tinker with the design in Tinkercad, you can do that here.
Step 2: Finishing the Mount
Now I had to attach the camera to the mount. At first I tried to use some plastic screws. Unfortunately the smallest ones I had were not small enough (M2). So I had to come up with another solution. I searched our warehouse at school and found iron wire that fitted nicely.
I searched and found the mechanical dimensions of the Raspberry Pi camera (see picture) and drilled holes in the mount at the right places. I put the iron wire in. To make it more sturdy, I glued a 4 mm thick piece of laser cut perspex at the back. I used some superglue to put it all together and sanded the perspex down to a few millimeter to make the mount a bit more light weight.
I then modified a few nylon spacers and glued them to the mount. After that I adjusted the wire to have put all four of them in the holes of the cam. The friction is more than enough to hold the camera.
Step 3: Using the Mount
I mounted the the mount and started to record a video (using raspivid on the the Raspberry Pi). I checked the video and was very disappointed. The video was blurry. I checked the specs of the Raspberry Pi camera and found out that the images are sharp from 50 cm to infinity. And that is has a fixed focal length.
That was a setback. I didn't think of that. And that is double stupid because I am after all a physics teacher and I should have thought of this. But! I found out that the camera is hackable! The lens is glued to the body but when you remove the glue, you can rotate the lens and then you can change the distance at which the camera takes sharp images. I had to be careful because the camera is able to produce sharp images at a few centimeters (my distance) but that is the limit of the lens. Rotate it a bit more and the lens falls of.
To loosen the cameras lens turned out to be a tricky business (three dots of glue) but I succeeded. I had to rotate the lens more than 360ᵒ. But then the image was razor sharp.
The videos are very nice and strange. The paper seems to move underneath the pen. I have to make some videos with long pen strokes during which the pen doesn't leave the paper. My plots are through their very nature not like that.
You could use this system to do other interesting things.
- You could make use of the travel to make illusions going from one place to another. So, if you make some images that sync to the cameras frequency, you could make a film.
- You can also make a kind of presentation, like the one fashionable Prezi. Make drawings at different places and design a SVG file to go from one place to another.
I hope you enjoyed this Instructable. I don't think there are very many people that own an Axidraw and make their plots using a Raspberry Pi but maybe, one or two of you will try this out. That would be amazing and I hope if you do, you share your results.
Participated in the
Raspberry Pi Contest 2020