About sandy

Designer and builder of Polargraph machines, software etc.

The majestic Lunargraph!

Posted on November 22, 2012 by sandy

Extremely impressed by this installation, just gawk:

Lunar Trails from Seb Lee-Delisle on Vimeo.

Organised by the inimitable Seb Lee-Delisle for the Dublin Science Gallery, this is a high quality polargraph-style machine that plots the paths, in real time, of the lunar landers as controlled on the nearby full-size arcade cabinet!

This is a cracking piece of work, a beautiful, exciting collision of engineering and programming – thanks to Seb for showing us what can be done with some string and pens! I would really love to see some more stuff about the wonderful mechanical solutions that his mechanical engineer Paul Strotten came up with to realise this installation.

Lunar Trails Flickr gallery

Should’ve checked those wires

Posted on November 18, 2012 by sandy

Well, it was going to happen sooner or later – I didn’t check the PCB design properly before sending it off to have it made, so the SD card doesn’t work on any of the batch of PCBs I’ve just received. OOPS.

Fortunately, the repair isn’t too much of a problem.

But that’s a bit embarrassing isn’t it. You know I’m the kind of person who lectures others about why it’s worth spending a little extra time checking things too.

So anyway, any Polarshield-based products you buy for the foreseeable future will have this ugly little hack on it. It’ll get neater over time, and have a bit of tape on top so should be robust. I’m publishing it here and have fixed the eagle PCB files for in the future.

Driving PolargraphSD wirelessly

Posted on October 24, 2012 by sandy

I’m finally on top of assembly so can pause for breath. Thank you to the folks who are still waiting, your machines will be coming to you in the next week or two (at the most).

I wanted to let people know that there’s a couple of neat features in the Polarshield, the first of which is an XBee-shaped socket that can take a wireless transceiver.

It’s as easy as that. There’s a weak line in the case that can be cut away if you wanted to do this. This is a great way of simplifying installation of a polargraph machine in a particular space. I used a wireless connection just like this in the Spectrum Arts machine so that I could do the machine setup / calibration manually and do any little pen tests I wanted to make sure ink was flowing, then draw from SD. There I used XBees, here I’m using XRF modules (and a Bee Adapter for the PC end).

One foible I came across with my XRFs (maybe I was being dumb) is that I couldn’t get my PC to talk to the PC-side XRF any faster than 9600 baud. Which is unfortunate because the default rate that the polargraph controller speaks at is 57600 baud, so I added a property to the controller that changes that rate. If you need to use it, you’ll have to edit the properties file – there isn’t a visible control for it in the application itself.

But once that’s done, it just works as a serial cable replacement: Great! It doesn’t work for reprogramming the arduino firmware yet – I tried to get that working but never did, so you still need to use a USB cable for that.

A wireless module is not supplied as part of any kit – I decided these are still too expensive, and a little too far outside my expertise to start troubleshooting, but the socket is there for those who would like it.

Polargraphs and Malthusian Paradox

Posted on October 18, 2012 by sandy

The Malthusian Paradox is an ARG, or rather “An immersive transmedia narrative experience, played out online and in real life” that is currently is running in Nottingham – have a look here http://malthusianparadox.com/?p=208.

The project uses a couple of Polargraph machines, along with Adam Sporne’s exciting Drawnomic machine in it to reveal, slowly some clues – I’m excited to see how it turns out!

Motors ho!

Posted on October 6, 2012 by sandy

Good news: Motors are here at last. First couple of orders will be heading out the door this weekend. Thank you to all the folk who have been waiting so patiently – I appreciate your understanding.

In the absence of other news: New brackets

Posted on September 17, 2012 by sandy

I’m still waiting for motors, but in the mean time I have been busily printing cases and soldering polarshields. An hour and a half now – now bad.

Here’s some new Polargraph motor brackets I’ve had made. These have a couple of little improvements over the old designs that make them a little neater to install. Cable management really:

But the other feature is that they can also be installed upside down, with the motor hanging rather than being lifted – this should make cables even tidier. Harder to mount and unmount however.

Sorry for the continued wait folks, and thank you for your patience.

A weekend of fixes

Posted on September 2, 2012 by sandy

Hello, please find enclosed a few fixes, an improvement, and a new feature.

Fixed:

Controller – Pulling a selection area that overhangs the bottom of an image would cause an unhandled exception. Fixed by mending the Rectangle.surrounds(..) method. Off by one, tsk.
Controller – Changing to another serial port would always set the baud rate to 57600, regardless of what was set in the properties file.
polargraph_server_mega – Rolled mbcook’s pbm format fixes into the mega branch. I’d forgotten that I had to do that. Also rejigged it a little, but cosmetic.

An improvement:

polargraph_server_* – All firmwares have had their straight line (C17) commands improved. The last version was ok, but seemed to work much better on polarshields than on the adafruit shield, because of a poorly scaling acceleration algorithm. It was pretty pausey. I have pinched the acceleration algorithm from Mike McCauley’s Accelstepper library, and that works much, much better. I even half understand it.

And a feature in a pear tree:

Vector art that has been created from an automatic bitmap tracing process tends to be made up of loads of tiny lines. When processed through the controller and quantised to the grid of the machine, they often end up on top of each other, and duplicate points are just slow.

So I’ve added this new slider, which is essentially a ~~low~~high-pass filter that filters out lines below a certain length. It re-samples longer lines, and discards entirely lines that are shorter than the threshold. See these two vector previews:

The left-hand figure has only duplicate points filtered out, this brings it down from around 15,000 commands to 11,700. Quite a few of those are still just single points – just dots.

The right-hand figure has the shortest vector filter bumped way up, and only has 300 commands.

The drawing wasn’t very good because my pen was running out and it was a bit fast, but you get the point. Smaller filter values will result in more fidelity, while bigger values will have a more dramatic effect.

Polargraph v1.2.4. Code in the repo as usual, and compiled and bundled up in a zip.

PolargraphSD updates

Posted on August 25, 2012 by sandy

Thank you to all the people who have terrified me by ordering PolargraphSD machines and vitamin kits. I have been gently buying up all the bits I still need, and have most things en route except for a critical component – motors. Turns out the factory has a summer holiday and shuts down for a month! So motors won’t be arriving until the end of the first week in September (a fortnight from now). Hopefully other stuff will be here by then, so most of the slow work will have been done and it won’t take long to assemble and test and pack.

I’m going to take a couple more orders before suspending – really a dozen or so is the most I’m comfortable owing folk, so there’ll be a pause while I figure out a smarter way of doing it.

Buying a Polarshield on its own

After talking with new forum member ITVirtuoso, I figured I should offer a polarshield-only pack. This would be either 1) PCB plus components to solder yourself or 2) PCB with all essential components soldered.

This is a little trickier than it might otherwise be because it’s an SMT design (0805 sized components), and a lot of folk aren’t quite comfortable doing surface mount stuff. But if I do only the SMT stuff, then it’s not quite complete enough to actually test. So actually 1) could be very cheap, and 2) could be comparatively expensive, considering what you’re getting, which would be a board full of connectors and resistors (pretty much). Don’t really know how much demand there’d be for either, so let me know if either appeal. How much fear does SMT hold these days?

Full colour drawings

The same new user as above has just started with his machine, and has already got some very impressive results – jumping right in with a full colour, four-layer CMYK drawing that looks pretty great to me, go and have a look!

Polargraphs from Manchester Maker Faire on Wired blog

My two partners in crime Stuart Childs (he of the DRBO) and Matt Venn (he of the energy monitor and the two-wire pen-lift mechanism) have been evangelising with their own polargraph-compatible machines around and about this year, and were at the Manchester Mini Maker Faire last month to great effect.

Wired’s Geekmom covered it and has positive things to say. Thanks to Stuart for pointing this out, and for both of them for being such enthusiastic supporters.

DRBO – A new drawbot kit

Posted on August 23, 2012 by sandy

The best thing about being involved in a project like Polargraph, is that you meet like-minded people. Stuart Childs is one of these people, and a good guy to know. He is one of the guys behind FriiSpray (which is another art/tech crossover project), amongst other things. He has put together a very neat new drawbot kit called the DRBO. It comes complete with arduino uno and motorshield, motors and all the bits you need, and is made of fragrant lasercut mdf. I got a kit of the hardware bits off him to try out.

As you see, it is adorable when small, but the most best thing about it is that the top bit, the drawing surface bit is pretty sacrificial, if you unbolt it, then you’ve got a good little unit that contains the motors, bobbins and microcontroller, and all you need is a couple of nails banged into a wall to hook the threads over, and you’ve got a machine as big as you want. The threads can just run down to the DRBO on the floor. No messing about with long wires or some such.

Now, when I’ve tried such shenanigans in the past, it’s never been quite as straightforward as that, but in principle at least, this is very handy. There’s a very good case for keeping the motors close to the drivers, and it’s so much neater if nothing else.

The build is easy and it’s an example of good design for lasercutting. It’s all push-out and bolt-together, well-labelled, and there’s even a little circle of sandpaper stuck on to take off the burrs, and a couple of wrenches that have enough life in them to tighten up all the nuts and bolts that you might want more than finger-tight. That’s a really nice touch. My favourite bit is that there are counter-sunk bolts at certain points on the surface, and Stuart supplies these dinky little magnetic buttons to hold the paper on! Brilliant!

The box for the microcontroller is big enough to fit an arduino mega in it, for those who mate megas with adafruit shields.

I did take other pics, but none of them are quite as good as the ones on the DRBO site. It’s also dead cheap, considering this is basically a full arduino+stepper motors dev kit, PSU, microcontroller, motorshield, motors, servo, fitments, the lot.