Saturday, 10 February 2018

22mm Diameter PCB project... NOW OPENSOURCE!

So I posted a while back about how I had used these 22mm pcb's I'd made in prototyping an ematch ignitor system for use in rocketry. Although I made these stackable boards so they would fit inside a popular size of Estes rocket body tube I'm aware that they are quite useful for lots of things. So i've open sourced them so anyone can get some made, or add improve or change them.

There are three boards,an Attiny85 board with some power LED and indicator LED, a SOT89 power supply board which could be built up with either a 3.3v or a 5v supply. Finally there is a "kludge" board which is useful for adding in some thru hole components into the system. Some quick pics here but in the files on Git each board is well documented in a pdf. All the dust components are 0805 so super accessible for hand SMD soldering. :)

Its REALLY easy to get these boards made using these files via the amazing OSHpark basically go over to my repository on Git and on the main repo page click the green download button on the right hand side as seen in this picture.
 When you have the files go to the Oshpark site and click the upload button and browse to the file for each board that ends .kicad_pcb. You'll get a render in your browser whcih should match the pictures in my documentation and then you click order and pay! You should currently be able to get a minimum order of 3 of each of these 3 boards for just less then £10 GBP :)


So I plan to build a small altimeter, maybe a small neo pixel payload for a night launch, I have a tiny OLED I want to play with with an ATTiny85 (not for a rocket!) and maybe some midi stuff.... What are you gonna make?!?! If you do use these please let me know... I would be thrilled to see them out in the wild!

Thursday, 18 January 2018

New Job, Basic Income... my first week.

So I’ve had a change of job and I am now working for a fabulous organisation called Indycube they are a Community Benefit Society and run a network of co-working spaces across the UK. They also have a membership scheme which brings people a host of benefits in a package delivered in partnership with the Community Union.. They are passionate about community and the well being of the self employed and lobby around these themes and the future of work etc.

As part of the job I have some time each week as a basic income allowance where I am paid but am allowed to work on anything I like, which is fantastic. It will enable me to do all kinds of things.. so I wanted to do just a little post about the first thing that I have done with my basic income.

 My two kids went back to school after the Christmas holidays (in which yes I did briefly erect an enormous rocket with lights on) and my son was very excited to come out of school and tell me that his theme of work for the term was “flight” … he then went on to tell me he had told his teachers that his dad builds rockets. I could tell he desperately wanted to take a rocket into school! So I got a message to his teacher and arranged to go in and do a morning of talks to Harri’s entire year group about rockets! I took in the whole fleet and lots of components and made each session as interactive as I could. The kids absolutely loved it and had loads of pictures with the rockets and asked lots of questions. Harri was as proud as punch and it was generally hailed as a success. But it extends beyond that.. whilst there I chatted to the teacher of my daughters class who told me he was trying to set up a code club. He was thrilled that I then grabbed his email and introduced him to the Wales code club coordinator who hopefully can get him access to a wider network/resources but I also introduced him to a local legend I know through my sponsorship/voluntary stuff with North Wales Technology and it looks like I have landed the code club a really experienced volunteer. 

So when I think of all the possible benefits of just this few hours of activity my basic income has enabled (inspired kids, learning about stem/steam subjects, new rocket fans, developing code clubs, people seeing other peoples voluntary work etc) it feels like basic income makes good things happen and is a real part of the future of work and community.

So that was my first week of basic income allowance… I can’t say each week will have as much excitement or impact… but I’ll certainly blooming try.     

Sunday, 14 January 2018

Crossform Parachutes

Ages ago I came across this great video from the UK High Altitude Society 2015 conference about crossform parachutes and their use. Its a fantastic short talk by Ed Moore and explains why the crossform chute is a good choice as it balances the factors of ease of construction and performs well with much less spinning/gliding and coning... the TL;DR is use these and have less area to search or less distance to walk to recovery!

The video of the talk is online and I found that over the last couple of years I've gone back to it and rewritten a load of notes from it which promptly disappear into the piles... so this time I thought I'd type them up, add diagrams and share them. Beyond just sharing notes, Ed's fabulous talk presents the math required to design a crossform chute but he doesn't go through a full example process. I have done this in this document and hopefully included every step of the math! Much of the math can also be applied to other parachute designs. The document is open source and available as a pdf and as a libreoffice odt file on this Git repository

Saturday, 6 January 2018

My Openrocket workshop getting started script now online!

So I've just uploaded my Openrocket walkthru/getting started guide document to git. It's the script that we follow as a part of my rocket design workshops I've run a few times now. I've also shared this document a to a few people directly who have worked through it successfully in about 20 minutes. It takes you through designing and simulating a small model rocket but you'll be able to experiment with your own larger and more amazing designs by the end of it!

Feel free to share far and wide.

Sunday, 31 December 2017

Ematch timed ignitor and 22mm PCB project

22mm_ematch_test_edit from concretedog on Vimeo.

So I've been plugging away on a few projects slowly in the background over the last couple of months one of which is developing a collection of stackable 22mm diameter PCB which are designed to fit inside a common small estes rocket body tube diameter but also could be used for all kinds of rocket or none rocket related projects.

I'll come back to those but breifly wanted to show the video above which is a prototype of an ematch ignition system that I've made using my 22mm boards. At the moment the circuit awaits a defined delay time and then fires a mosfet to send the current to the ematch ignitor. These type of systems are used sometimes in high power rocketry to ignite a small black powder or pyrodex charge to separate 2 sections of a rocket to deploy a parachute for recovery. Sometimes instead of a timer the ignition circuit is linked to an altimeter to deploy the charge and resulting chute at a specific altitude on the way back down.

So back to the 22mm project.. I realised I was at risk of forgetting what little I know about KiCad (my preferred opensource electronics PCB design package) and wanted a project and have though for a while a collection of useful small boards would be worth having. So I've designed two boards so far and had them made by OSHpark which has been a fabulous experience... you don't even have to battle to get your gerber exports sorted for OSHpark as they will work directly from a KiCad PCB file... just upload... check the preview render of the board layers in your browser and if ok... hit order!

So far I have a board for SOT89 power regulators and a board with an Attiny85 and some power indicators and an LED! The next board will be basically a prototyping board (think veroboard in the 22mm form factor) and I have a few ideas beyond that. I am determined to (after the prototyping board is done) to get all the files on github so anyone can order some if they think they might be useful. They stack and have holes for M2 threaded bar which is connected to ground to minimise power wiring.

 Some pics of the boards

Saturday, 30 December 2017

Turning Graphite Nozzles

I've been reading a lot on hybrid rocket engines over the Xmas break and although I am nowhere near ready to actually start building a hybrid engine (apart from that micro hybrid I started YEARS ago maybe!) I wanted to do something practical and decided to turn out a graphite nozzle on the lathe. Mainly to get a feel for how graphite machines ... which the answer is.. astonishingly easily! It cuts very well with little regard for speeds and feeds and responded well to standard HSS tooling. 

Although I am working through the maths in the hybrid book I am looking at, I'm not actually at the point where I have a design. So this nozzle is just made with similar dimensions to a Laval nozzle drawing in the book with a 30 degree angle for the nozzle side and a 45 degree angle for the combustion side. I'm pretty pleased with it as a test piece and its certainly given me a feel as to what is possible in graphite.

Above is the 45 degree side that would face the combustion chamber.

The 30 degree nozzle side and the arbitrary sized throat. 

Tuesday, 5 December 2017

INSPACE TWO 30/11/2017


So yes, last week INSPACE TWO happened, the second event I've organised as part of the INSPACE program and run as a North Wales Tech event with the support and venue of API pontio. This time the theme was earth observation using the open and available Copernicus data returned by the fleet of Sentinel satellites as well as some earth based data collection.

In truth I didn't personally have to do much on the night! I stuck together a quick introductory set of slides about the rationale behind picking this topic for the event and a brief overview of the Copernicus program and the Sentinel fleet. I then handed over to the fantastic Dr Jamie Williams and Anthony and Sebastian from the Aberystwyth based company Environment Systems. They very kindly then took the around 30 delegates through how to use the enterprise and free versions of their API allowing the participants to download data of various types (imaging/radar etc) and import it into the opensource QGIS environment. Massive thanks to the EnvSys team who were fantastic and worked the room well after some excellent presentations and got everyone going with their systems.

Huge thanks also go out to S2 recruitment who again kindly sponsored our pizzas which fuelled the workshop well and by the end of the 3 hours everyone had learnt a lot and managed to download and begin to play with some data... from space... :)

I spent the night floating around and chatting to people and heard a good spread of existing and emerging ideas for use cases for earth observation data both in commercial terms but also definitely spoke to some participants who had found new ideas they could utilise in their academic research.

So finally.. one more thank you to the Envsys team, to API pontio for the venue and equipment, to S2 again and a huge thank you to Carwyn from North Wales tech who puts in a huge amount of work all the time to make the NWT events program as rich and as varied as it is.

Stay tuned for details of INSPACE THREE!