Doing better next time:
In the year or two since I finished the Mark 3.5, I’ve had time to give it a good workout and to have a think about what worked, what didn’t, and how to do it better.
Month: November 2011
The Mitochondrion 3.5 – An Excessive Glowstaff (7 of 8)
Debugging:
You wire it all up. You plug it in. You turn it on… and nothing happens.
Debugging Picaxe code and general swearing about unreliability
The Mitochondrion 3.5 – An Excessive Glowstaff (6 of 8)
Tips for making circuit boards – (tiny, dense, double-sided boards in your kitchen):
Like a fool, I tried to pack far too much into far too small a space. Hence the PCBs had to be equally dense and tiny. But then again, fitting electronics into a 25 mm tube is never going to be easy.
The Mitochondrion 3.5 – An Excessive Glowstaff (5 of 8)
Sensors:
Pic by Marla at Kiwiburn 2009
I don’t like dumb objects. I don’t like noticeable user interfaces. I want shiny things that just do what I want, without me telling them what I want. And anyway, given that any physical connections to the outside world will have to come out through the tiny, busy ends, then it’s not like I can cover this staff with buttons unless I want to drill holes in the polycarbonate tube, making horrible stress concentrators and greatly reducing the toughness of the tube. Hence I wanted to squeeze a whole bunch of sensors into the Mark 3.5.
The Mitochondrion 3.5 – An Excessive Glowstaff (4 of 8)
Power and output:
Photo by Loki Gash for Filament Magazine
LEDs
For the purposes of shiny toys, LEDs come in two kinds: bright ones and painfully bright ones. The painful ones draw 350 mAmps or more, need fancy constant-current power supplies for each LED and will melt without proper heatsinking. I went for the bright ones that draw 20 mAmps each and only need a resistor to protect them.
I chose the Piranha-style square LEDs, for the brightness and broad spread of the beams (like these ones from Sparkfun. I thought about going for smaller, surface-mountable ones, but chose the through-hole LEDs for shock resistance.
Never again.
Dry ice, address space mangling, and the persistent headache of batteries
The Mitochondrion 3.5 – An Excessive Glowstaff (3 of 8)
Picaxe Microcontroller:
Photo by Loki Gash for Filament Magazine
Knowing nothing about microcontrollers, I chose something easy to start, the Picaxe family. The learning curve is easy, it’s designed for schools. Of course, something this simple is going to have limitations and by the end of two years of development, I’ve bumped up against most of them, but I wouldn’t have done this differently.
The Mitochondrion 3.5 – An Excessive Glowstaff (2 of 8)
Physical structure and layout:
Photo by Loki Gash for Filament Magazine
Layout, tubing, stiffness, keeping the insides inside, and shock resistance
The Mitochondrion 3.5 – An Excessive Glowstaff (1 of 8)
Vidcap by Craig Bellhouse
Firespinning is fun, but I thought to myself:
1) It’s been done
2) This is the Twenty-First Century and we have semiconductors
3) This is the Twenty-First Century and burning fossil fuels for gratuitous reasons is just so Twentieth
So a plan formed in my head to make a glow staff. Now, coz I’m stupid an overachiever, I decided to make one with bells on. A glow staff that pushed the boundaries, a glow staff like no other. The only limits are technology, time and money. The technology I can handle, and I don’t have kids or a TV, so time and money are no problem.
There was a slight drawback, in that I hadn’t done any electronics since school and wasn’t entirely sure what a microcontroller was or where to get one. I’d never designed a digital circuit or etched a circuit board, but hey, it can’t be that hard, right?
Several years later, the Mark 3.5 is quite shiny. Forty RGB LEDs, all individually addressable, over a hundred patterns, and bright enough to hurt*. So at long last and before I get too carried away with the Mark 4, it’s time to write down and share what I’ve learnt, both about glowstaffs and electronics. This writeup is an attempt to help other people avoid making the same mistakes as me. And there were a lot of mistakes.
The writeup is going to look like this, one per weekday, until we’re done:
- Physical structure and layout
- Picaxe microcontroller
- LEDs and drivers and power and batteries
- Sensors – this really didn’t work
- Making PCBs
- Debugging & Reliability
- Doing it better next time
* – Mostly the Mitochondrion hurts other people, coz when I’m spinning it, I can’t see anyone or anything else.
Repairing a thirty-year old workcentre with 3D printed stainless steel
For those of you who are not Antipodean, the Triton workcentre is an Australian icon. How many other power tools have an owners’ club? Each one mounts a circular saw onto a carriage, mounts that carriage onto a table, and lets you cut wood across and along. In 1975, that was all any man needed to feel fulfilled.
The classic workcentre is the Mark 3, from 1984. The Mark 3 brought along a major step forward for the Triton world, the bright orange paint that they still use today. My Mark 3, like all good tools, came from the in-laws. It’s covered in shavings, a bit rusty, and does the bloody job.