Friday, 24 May 2019

Hackspace Magazine! Keeping track of my articles.

It's been a privilege to write for the Raspberry Pi foundations Hackspace Magazine since last October and I have been meaning to create a post about various articles I have written but never got around to it. So I thought I might create this post with links to all the issues I have article in and a little description of the articles and keep adding to it as (hopefully) the articles keep getting commissioned and published!



Issue 12, Where it all began! I had a "design your own rocket" tutorial in here using the amazing opensource Openrocket design and simulation package.

Issue 14,  An article on Manual Milling machines and beginning machining.

Issue 15, An article on Lathes and their use and a review of a Neke Laser Engraver.

Issue 16, An article on Making a multi headed screwdriver using the lathe and mill and a review of the Eleksmaker Eleksdraw pen plotter.

Issue 17,  Part one of a two part introduction to laying out PCB's for professional fabrication with Kicad.


Issue 18, Big issue for me this one! I had the feature article on Space, featuring lots of maker/amateur satellites, a focus on Libre Space Foundation and a tutorial on setting up a SatNOGS ground station. Also had a tutorial on making a "Slim Jim" antenna and also the second part of the Kicad two part tutorial.

Issue 19, Tutorial on Marking out and Centre punching accurately for metal work and I also wrote the space of the month article on the fabulous Prishtina Hackspace.

Wednesday, 8 May 2019

DIY Screw Switches for Rocketry




In high power rocketry its good practice to have some kind of keyed switch or remove before flight system that isolates the avionics from power. Important as often these systems are connected to small wells filled with explosives that are fired at points in the flight to split airframe sections and deploy recovery parachutes etc. Isolating the system (killing the power) enables the flyer to handle, carry and prepare other aspects of the rocket and only arm the system when necessary.

I've used small 3.5mm stereo jacks and sockets and when the stereo jack is removed 2 pins are connected under a spring steel load to which I have soldered a power cable. I have also experimented with rotary key switches. I have never flown key switches and recently read about some failures using rotary key switches and I've always wondered at what force/speed would it be possible that my clamping stereo jack socket might separate in flight and and kill power?

I then came across the idea of screw switches. A screw switch essentially is a system where a circuit only becomes connected when a screw is tightened. They are often made by hand by epoxying a nut onto a metal bar which is insulated and another metal piece added on top which will be connected when the screw/bolt is tightened. I wanted to try and make one that was accurately repeatable so I could make a multiples but also smaller, tougher and neater.



So I quickly decided on using double sided copper clad fr4 and a PEM nut press fitted to one side. I CNC routed the boards with a hole to receive the PEM nut and 2 holes for M2 mounting bolts. As the M2 mounting bolts would connect the 2 sides of the FR4 I routed a clearance area which generously clears the head of the M2. I fitted a PEM nut (press fit using a 1.5 ton arbour press) to the first prototype and continuity checked that the two sides of the board where still electrically isolated. To make the switching screw I have epoxied another PEM nut onto an M2 bolt and when fully tightened it connects the 2 sides of the board. On the other end of the M2 bolt I made a small punch mark to disrupt the last couple of threads on the bolt which means it cannot be fully unscrewed.

As the device is copper clad I routed the board to have a tab on one end  (at the top of the picture below) onto which power wires can be soldered either side. Therefore when the M2 bolt is fully tightened it connects the wires and allows current to flow.



It then just needs to be mounted in a position inside the rockets electronics bay where its possible to have a small hole in the airframe allowing a small screwdriver to be inserted to open and close the switch. As a mockup I made a small 29mm bulkhead and added a standoff to mount the switch too.
Finally one of the great benefits of a CNC is repeatability, I have now knocked up a few of these and they sit awaiting deployment in upcoming rocket builds.


EDIT!! So some people where asking questions and struggling to see how this worked so I've done a little video explanation and demo! 

DIY Rocketry Screw Switch from concretedog on Vimeo.

Saturday, 23 February 2019

DIY mini vacuum former



I've been meaning to make one of these for years and in amongst everything else I found a bit of time to do it the other week. It's a simple build of a box with a very holey lid - it's ace owning a small CNC as this is precisely the kind of job it's worth its weight in gold for. A quick measure of my cheap shop vacuum nozzle diameter (an Argos special that has lasted years despite abuse) and the CNC cut the side sections to match. I'm experimenting with recycling milk bottles at the moment and using a hand held heat gun. It works well and pulls a strong seal around objects. I fancy trying to make some lightweight small nosecones next to see how they compare in weight to the very thin walled 3d printed ones I have made. 

Tuesday, 12 February 2019

FOSDEM 2019

A snowy welcome on the saturday!



 The huuuge keynote by mad dog. Amazing sight!

I was incredibly lucky to go out to FOSDEM as part of the Libre Space Foundation (LSF) team the other week and despite lots of snow and travel disruption had a great time hanging out and working over in Brussels. It was my first time at FOSDEM and I was blown away by the worlds largest conference. It was fabulous to be able to move around and see and meet the teams behind some of the most prevalent open source software, debian, opensuse, grafana, gitlab, nextcloud and so many more. As currently I am freelancing mainly as a writer I made sure to have a little chat and express my thanks to the Libre Office team, whilst it might not be the most exciting platform in the world it does provide me with the basic tooling to earn my living!


Above, the Gitlab team who have been great supporters of LSF. 

LSF/SatNOGS contributors meet the Grafana team (and inform them of an Influx db bug they found!!)

Going out early the LSF set up camp in a large apartment (The Mansion) and LSF contributors poured in from all over europe staying a while to have meetings, hack on code and discuss development face to face. Its astonishing, humbling and exciting to see these volunteers pour their considerable skills into LSF project. As a more mechanical guy it was hard to follow much of the development but everyone was incredibly kind and patient and willing to teach others. Very affirming. (Although there was some discussion around rocketry hardware which funnily made me boot my tiny laptop to show how my ematch ignitor circuit works!)

Team... looking tired on the Saturday night!



Flying Ryan air means taking the worlds tiniest laptop!


A busy booth


FOSDEM was incredibly busy and I spent some time each day helping on the LSF booth, speaking to a constant flow of people from all over the planet about our missions to democratise space and provide open hardware and software to enable people to get involved. Hopefully it results in more people supporting what we do but also I feel sure that certainly a few more people are interested in moving towards setting up their own SatNOGS groundstations on the global network.

General picture dump..


Loved this!



So many LSF people! All in to see Alex Csete talk about our SDR makerspace project




Wednesday, 23 January 2019

Project Roundup!



Been a while since I posted here so thought I might get the ball rolling again with a little round up of current projects I am tinkering on. Above is a picture of a planned level two rocket build I am starting to work on as it would be great if I could get my L2 certification flight and exam done this year and also pass my RSO (Range Safety Officer) as well. That would mean that it could be possible for me to officiate over other people HPR flights but could also look into the possibility of running a launch event more locally?



I've also on an off since before Xmas been tinkering with some odd parachute designs, first playing with plastic and tape and now moving to making a ripstop nylon version. These hexagonal annular parachutes fly quite well, have low side loading and seem very strong due to the way the shroud lines continue over the canopy. I'm slowly developing more skills and knowledge around recovery/chute making and have a few other projects I want to explore.



I've also been tinkering on and off with a simple GPS tracker design using a NEO6 gps board and  HC12 radios. My current off the shelf GPS tracker (works on mobile network) is too large for a 29mm rocket airframe I am considering and therefore this route gives more options in terms of getting it to fit. The tracker currently spits whole NMEA sentences which are received by another HC12 hooked up to the one note mini laptop and the whole thing acts as a wireless serial bridge. 


Finally been making, machining and tinkering with various things to write some more articles for Hackspace Magazine, I'm really enjoying the writing and hopefully the articles are being well received! I'll post a roundup of articles out so far after the next issue with some of my work is published.




Saturday, 15 December 2018

3d printed lathe carriage lock.





A while back I saw this  lathe accessory on thingiverse and downloaded the files, I printed the bits a few days ago and have been fiddling with it on and off, press fitting captive nuts inside it and tapping sections.

It's a handy little thing for 2 purposes, it has a profile that allows it to be clamped to the lathe ways and also has a clampable hole that accepts something that is 8mm diameter. So it's very handy for holding a dial test indicator (as above) for example to make a very precise last cut or other accurate positional stuff. 

It's also pretty useful with just an 8mm piece of steel bar in it and the bar can be set to a fixed position and it acts as a stop guide for the carriage. Useful for quickly making repeat passes/cuts on a job to the exact same point. I like the idea and it works ok, I might do a redesign at some point as I think making the assembly a bit wider would be useful and would increase its clamping force making it adhere to the ways more securely.

Thursday, 13 December 2018

Scheduling an Observation on SatNOGS

The other week, as part of my presentation at INSPACE 3 I included a few slides about how simple it is to schedule an observation on a satNOGS ground station. If you build and deploy your own  ground station as part of the network you can then schedule any station on the network, but until you do that you can't and that means that this aspect of satNOGS operation remains unseen. I realised at this talk that people might feel that this part of operating a SatNOGS station is complex! Let me reassure you it isn't! All scheduling happens via the satnogs.org website and lets walk through how it works!

So when you log in you get sent to your dashboard  landing on your stations page. Above we see my station number 217. There's some basic info about the station and a map. As a side note if I am here to check a previous observation on my station I can hit the blue "view all" button and it takes me to a list of observations. However we are going to scroll down and set up a new future observation.
So if we scroll down on our station landing page we get to a box which is continually populated with the future passes of satellites above our station. It has on the left the name of the satellite and a meter which tells us the historic success of satNOGS stations being able to get a good observation of the satellite (this gives a kind of health status of the satellite). Next we see the time frame of the pass then some details about the elevation. Finally a small plot of the pass with the centre of the cross hair representing the position of our ground station, basically the satellite will pass from the green end of the line towards the red. The last object on the right is a schedule button to begin to arrange an observation of that satellite on that pass. However lets just quickly have a look at another useful thing!
Back on the left hand side you might notice that each of the satellite names is actually a link. There are so many satellites out there and on the SatNOGS database it's unlikely you will know them all by name! So if you click on the link you get a pop up with an overview of the satellite. For example, above I clicked on the Fox 1B name and it shows me that it is a 1 unit cubesat and that it has a pretty good record of being successfully observed
Next, we have closed that popup, and we have clicked the schedule button to set up a new observation of the Fox 1B satellite. We are sent to this page (above) which has details of the satellite and the pass and also a drop down list of the possible transmitters we can schedule to observe. This is important as some satellites may have numerous types of transmitters or transmission we can try to observe. For example a satellite may have a voice aspect (as in radio operators speaking through the satellite as a kind of satellite repeater) but also might have some data being sent separately as telemetry giving details of the satellites condition. Having made sure to select the transmission we want to observe we then click the green schedule button.

So we now have an upcoming observation setup and we see the observations individual page. This page (unless for some reason we  decide to delete it) will remain as a unique page for this observation. After our station has performed the scheduled observation it should populate with the observation data. So if we come back to this page after the observation we should see an image of the waterfall. 
Like so! Above is an observation page after the observation and we land on the waterfall tab, if we click the audio tab we should be rewarded with an audio file of the observation which we can play in the browser or download.



We can also click through to the data tab, now this may be empty dependant on the type of observation and  if we were looking for data or not,  but if we did receive some data it should be on this tab. 

So above we see some telemetry frame data from the FOX 1 A satellite, for this particular satellite we could copy this data and run it through the free software made available on the satellites mission website and decode what the data means. However for an increasing number of satellites the satNOGS network is set up to decode the data and present it in this tab. This could take different forms but for example if we observe the NOAA satellites we may return to a decoded image in this tab!

So that's it in a nutshell, I mentioned earlier that on the first dashboard landing page we might click the "view all" observations button and that's a handy way to get to all the observations in a list that our station has either completer or has pending.





 I hope that that little walk through is useful and shows just how simple it is to get going once you have your station set up! So join us and you can also get hunting satellites! If you are interested in setting up a satNOGS station there are loads of sources of help, not least the satNOGS area on the libre space foundation community forum.