Sunday, 19 March 2017

Rapid prototyping

 Another piece of making for College of Wizardry. I was asked if I could make some badges from the logo on the IC website.

This neatly demonstrates how good a 3D printer is for 'rapid prototyping' even with a simple thing like this.

The first step was to take the source logo and put some spacing between the various element with a bitmap editor. This was so they would come out as separate objects once traced.

Then I used Inkscape to trace it into a series of paths. There are several ways to do it but I got the best results from choosing to trace on two different levels of brightness then selected the resulting objects one by one and tidied up/removed them manually.

Do not underestimate how long this takes, I spent something like four hours doing this. Then I turned this into an OpenScad file using an export filter I found on Thingiverse.

With an OpenScad file I was then free to hack the design around, altering which bits got printed or not, relative heights and so on. This is where the fast prototyping came in, as I could print it quickly and have a look at the result as a physical object. Although with hand editing of the OpenScad file it was still a slow process.

Eventually we settled on just the lion's head part of the logo and played with the size a bit.

Even with a decent looking design, it was still always going to look a bit plastic, but a quick dab of coloured varnish sorted them out. I wiped it off the highlights to create some basic shading and bring through the base colour. Then it was a case of sticking badge pins on the back of each one with hot glue and they're done.

The design process took a while but then I could batch produce them easily. So we ended up with one each for most of one of the player factions, limited only by running out of filament after one of the print runs went bad. Which still happens very occasionally, my 3D printer is definitely an enthusiast/hobby device rather than a consumer item.

Saturday, 18 March 2017

Kiosk setup on a Raspberry Pi running Jessie and the Pixel Desktop

I've started playing around with embedding a Pi with a little 2.4" screen into a prop and I've noticed all the howtos for this kind of thing are old and don't apply circa March 2017.

Now we have the Pixel desktop it's very similar but you need to edit the following file...


#@lxpanel --profile LXDE-pi
@pcmanfm --desktop --profile LXDE-pi
#@xscreensaver -no-splash
@xset s off
@xset -dpms
@xset s noblank
@chromium-browser --kiosk --incognito

Make it look like this by commenting out the lines for lxpanel and xscreensaver then add an entry to start Chromium at the end opening whatever page you'd like Chromium to start with.


Thursday, 16 March 2017

Magic Wand

Elina is off to the very high profile LARP College of Wizardry at the end of March and there's been a lot of gathering of costume and props for it. She suggested a wand with a bare LED that lights with a push / push switch but I decided to have a go at adding some more interactivity to it.

What's ensued is a lengthy exercise in making a prop from scratch using my 3D printer and trying to do as little hand crafting as possible, apart from final finishing. This is to keep it compact and fit all the components, especially the batteries and wiring, into as small a space as I can.

It's nothing spectacular on the tech front, an Arduino Nano, GY-521 6DOF accelerometer breakout board and 21 Neopixels. On that front it's very much blinkenlights project:101.

The entire thing ended up being scaled around getting four alkaline cells in the body and being able to print this on my printer which has a build volume of 20x20x20. In principle I could have done something with a single 18650 Li-ion cell but these are very chunky and a step-up PSU to drive the Neopixels would be a pain as they're hungry beasts that need 5V. Smaller cylindrical Li-ion cells seem to be unusual and I like the idea of easily swapped disposable cells.

The obvious starting point is making the shaft the place to hold the cells but AAs are too chunky and AAA cells make for a very long thin wand so I settled on N cells. These are easily available and a good compromise on size that matches up with the space I needed for the Neopixels in the tip. This has meant the wand ended up about 35cm long in total, pretty much exactly what I wanted from it. It's still a little chunky but short of swapping to alternative lighting, maybe the 3030 rather than 5050 Neopixels this is about as small as I can get it.

The Neopixels are beautifully bright, so much so that the translucent 'natural' PLA I used to print the tip doesn't really manage to diffuse them very well but as it's going to do very occasional effects I'm not worried about this.

I've used the accelerometer to do very basic gesture detection. Once the wand is awake, holding it level and twisting it changes the colours. Raise it up and you get a flame-like flickering up the tip, swipe it down and the effect rushes forwards and fades out. Leave it pointing down and it goes to sleep.

For finishing I hacked at the printed article with a Dremel, sandpaper and knife then covered it with some coloured varnish. The result is pretty wood-like from a distance.

She's off to the event soon, let's see how well it is received. I've done a very basic demo video of the working code, but given it's easy to reprogram and I'm barely using the features of the gyro I reckon there's scope to improve on this significantly.