Keep It Simple (Stupid) DIY Rocket Altimeter SD Datalogger project

Been working on this little project, a while back I prototyped a diy altimeter using an arduino pro mini (8mhz 3.3v) and a BMP180 barometric pressure and temperature sensor. I have now replicated the working breadboard prototype and made this tiny point to point/deadbug style version. 

The reason I have aimed to build it as small as possible is that I wanted the altimeter to fit inside the payload section of this small "Star Stryker" Estes Rocket kit I built a while back. This rocket payload section probably represents the smallest payload capable rocket on the market so the design will therefore theoretically fit into any payload section.

Weight wise it is 6.5g without the battery and currently 13.7g with a battery.. however the 200ma lipo could be replaced with something smaller (it was just what I had lying around!)

The device is activated by the switch that means that the payload section must have an access hole/port to enable the switch to be toggled with a tool.. but this is ok as the BMP180 sensor needs the payload section to be vented anyway to equalise the pressure and take an accurate reading. One slight addition I am going to make is to attach a larger LED to the pro mini. This LED will be lit on boot and will remain lit during a delayed setup part of the code (10 seconds or whatever is needed) to allow time for the operator to return to the launch controller. Then, when the LED is off, the main loop of the program is initiated writing data to the sd card at 20hz

The code currently is a bit shabby (I am no great coder!) and is just a mashup of  SD library and a BMP180 library sketches.. it's crude but it works! I'm going to work on the code with a good friend in the new year and when we have it polished (possibly dumping data to a .csv file for quick plotting) I'll opensource the project in case it's useful to others! 

OpenRocket and rocketry CNC workflow...

I've been playing with OpenRocket for a while now, essentially this little free java application allows you to design rockets and simulate their performance with an extensive database of rocket engines built in. It calculates both centre of gravity and centre of pressure and uses the Barrowman equations to calculate the stability (or lack of) in your design and has lots of aerodynamics code built in calculating drag coefficients etc. Being able to simulate launches and recovery is excellent and allows you to both optimise your design in terms of feasible altitude but also can allow you to fly within the limits of a particular altitude ceiling. Simulation also is important when you get up to qualifying certification flights for high power rocketry as your rocket needs to perform similarly in real life to what you have submitted in simulation data.

So all of this was exciting as I start to design my first scratch built rocket attempt, however an added excellent bonus is that Openrocket exports it's simulation data into a PDF document which I hadn't done until recently as I wanted to printout some data. The export function also will print out various other useful items from your design including fin templates and centring rings (rings that hold the inner engine tubes to the outer airframe tube) as PDF is a vector format it is readily accepted into most CAD/CAM environments and therefore it is a trivial matter to create tool paths to cut fins and rings etc on my CNC router. Slick!

Soundlab, heart and soul at NESTA HQ

 

With the echoes of Electric Fire's "Do your own thing" still earworming away I sit reflecting on a great event I was lucky to be part of last week at Nesta HQ in London. Soundlab, as part of Heart and Soul, has been exploring in partnership with music tech companies, NESTA and Goldsmiths uni how music technology can be more accessible and how barriers to expression can be reduced.

I am linked into this via the mightly Ashley Elsdon from Palmsounds, Ash worked tirelessly on this event getting companies and developers to give their time (and app codes!) to attend these events and display their tech.

So many great things stand out about this event, the first section of the day was for NESTA staff and from chatting to them they seemed to be really excited to see the reality of a project that they fund and work on. Director of NESTA's Digital arts and media Tim Plyming summed it up astonishingly well when he described not having got on well  with music education and feeling excluded from it..yet within the first 10 minutes of the first Soundlab event he attended he  created more music than he had in his life previously.

I could write pages about the thoughts that these events bring to the surface around accessible innovation, creative process, gestural and physical performance interfaces etc, but rather I will cut to my overriding memory/thought of this event... It is AMAZING and incredibly uplifting to be part of an event where such joyous noise and music are made so readily. It's mindblowing to see people who possibly would be considered by others as "non verbal" and poor communicators..with the right barriers reduced, be up on stage commanding an audience with deep rich emotional performances... that I still hum days later.... I await  Electric Fire's first EP/album keenly. Huge props to Ash, Justin, Mark and all the Heart and Soul team.

Picture dump.... :)

A little light prototyping

 Spent a bit of time today making this light prototype out of some MDF I CNC'd and some yellow LEDS (next revision will be white but I bought a 1000 cheap yellow LED's some years back so they get used first!). It was quite a challenge to solder so I'll tweak the CAD to make the pocket a bit larger to give me a bit more room to work in. I have a few ideas for different sizes of these... Firstly the internal diameter of this one matches the spindle currently on the CNC so I hope to have a snazzy spindle light that I'll probably attach with some small neomydium magnets in the back of the case. Another size I'll make for the manual mill spindle and I fancy making one that could fit to my DIY helping hand accessory for use in combination  with a lens. They also could make a nice light to mount on a camera to take macro shots.

Getting into rocketry

rocket launch keychain camera from concretedog on Vimeo.

So I've been getting into model rocketry, I got bought a starter set as a gift some time ago and finally got the 2 rockets built over the summer, I've launched them a couple of times but yesterday was the first time I did some video, both from the ground and also attaching a cheap keychain camera to a rocket. The above is the result. (And yes.. forgot to set the camera date and time so appear to have launched over 150yrs in the future!)

My lad looking very pleased with the larger estes amazon rocket

So... I have plans! I have a larger kit that will step me up to use the highest over the counter rocket motors available and then after that i'm going to look into getting certified to fly high power rockets. I'm looking to diy as much as possible so have been playing with designing rockets in virtualisation using the amazing free design and simulation package OPENROCKET .. I've also got into sewing lightweight ripstop nylon to make parachutes! I'm learning a lot about sewing and am aiming to make some cross form parachutes after reading some chute theory and running some math. I've also built a little prototype jig assemble that has worked well to enable fixing fins at exactly 90degrees from any given centreline of a circular tube.. I'm going to build a better version at some point and post again.

Derby Mini Maker Faire

 

So, I had the pleasure of helping out at derby Mini Maker faire at Derby Silk Mill museum the other weekend. Here is a photo dump of my shots of the day.. not very good but gives and air of this excellent event. Massive props and respect to Dominic, Hannah, Chris, Andrea and the rest of the team.

The hands of a crewer who has been rigging big steel burny sculptures!

They doubled the size of the show this year with the use of a huge tent...

One of the museum spaces

Maker briefing number 1

BUNNIES!

I spent a fair bit of time co-hosting the make a keyring workshop, casting polymorph!

Super nice laser sticks..

Pattern printing rolling pins

the mighty ragworm

Supervised this brilliant marble run activity a fair bit

BIG ENGINE and paper aeroplane challenge in this room

Shonkbot workshop

HUUUUUGE CNC router!

Smaller CNC but scratchibuilt.. (great cheap spigndle tip from the builder!)

I got to put this massive head on this with the sculptor Johnnie White... Brilliant work

Cast ice gearwheel form the drive system of the burning sculpture

Bubbles....