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Philip Stubbs: Quad-copter Build Log

Planet HantsLUG - Mon, 05/01/2015 - 21:06
Having enjoyed watching a series of videos on YouTube, I have been inspired to have a go at building a quad copter. I hope to include here some notes that will act as a reminder for myself. If anybody else decides to try this, please don't rely on this information alone, but please do your research.

RadioThis seems like a good place to start. If this bit can't be made to work, then nothing has been wasted on motors, batteries ESC's etc.
Rather than build an entire transmitter, an old DigiFleet transmitter will be gutted and used for the housing, control sticks, knobs and switches.
I had been hanging onto this transmitter, thinking that I would use it someday, but in the meantime, the NiCAD cells had spilt their guts and pretty much wrecked the circuit boards inside. So nothing was lost by tossing out the control boards, to make space for an Arduino. At the same time, all the parts were removed to give everything a good clean.
Some parts were ordered from Banggood to get started on the radio. An Arduino Pro Mini to use as the reciever, and Arduino Leonardo for the transmitter, and a couple of NRF24L01 boards for the 2.4GHz radio link.

Connecting Arduino to NRF24L01 BoardsAfter receiving the Arduino boards, the first thing was to load new Blink programs. This confirmed that they worked, and I could program them. The only issue was for some reason the Leonardo will only work as root. When it cam to connecting the the NRF modules to the Arduino, it was again the Leonardo that was proved to be more challenging. In addition to the power lines, the NRF's require five extra connections. Three of those connections are not available on the standard header, but are available on the ICSP header. As the remaining two connections can be assigned to any digital pin, it is possible to have all of the Leornardo's 12 analogue input pins free to use. This would make it possible to connect up all the controls on the radio, if needed.

The diagram below shows how the NRF boards were connected for initial testing.

With this set-up, it has been possible to communicate between the boards from different locations in the house.

SoftwareThe YouTube videos that started this mentioned a specific library for the RF modules. For no good reason, for this test, the Radio Head library has been used.
Learnt so far
  • Getting the radios to work was easy.
  • The Leonardo is not quite as simple to use as the pro-mini. Mainly due to the build in USB has to be handled by the Arduino software in a different way.
  • Choosing the Leonardo for the transmitter will allow me to use all 12 analogue inputs.
  • Just because a NRF24L01 board has a plug for an aerial does not mean that it is the high power version!
Categories: LUG Community Blogs

Meeting at "The Moon Under Water"

Wolverhampton LUG News - Mon, 05/01/2015 - 13:32
Event-Date: Wednesday, 7 January, 2015 - 19:30 to 23:00Body: 53-55 Lichfield St Wolverhampton West Midlands WV1 1EQ Eat, Drink and talk Linux
Categories: LUG Community Blogs

Bring-A-Box / Pub meet, Epsom Downs, 10th Jan 2015

Surrey LUG - Sun, 04/01/2015 - 23:48
Start: 2015-01-10 12:00 End: 2015-01-10 12:00

We have regular sessions on the second Saturday of each month.  To kick off the New Year we're meeting at the Tattenham Corner, Epsom.  A commanding view of Epson Downs, good food (a Beefeater pub), beer and a welcome whether you're a regular Surrey LUG enthusiast or a first-timer.

 

Categories: LUG Community Blogs

Steve Engledow (stilvoid): Keychain and GnuPG >= 2.1

Planet ALUG - Fri, 02/01/2015 - 15:48

A while ago, I started using keychain to manage my ssh and gpg agents. I did this with the following in my .bashrc

# Start ssh-agent eval $(keychain --quiet --eval id_rsa)

Recently, arch updated gpg to version 2.1.1 which, as per the announcement, no longer requires the GPG_AGENT_INFO environment variable.

Unfortunately, tools like keychain don't know about that and still expect it to be set, leading to some annoying breakage.

My fix is a quick and dirty one; I appended the following to .bashrc

export GPG_AGENT_INFO=~/.gnupg/S.gpg-agent:$(pidof gpg-agent):1

:)

Categories: LUG Community Blogs

Steve Engledow (stilvoid): TODO

Planet ALUG - Fri, 02/01/2015 - 12:58

Here's this year's TODO diff as compared with last year.

New Year's Resolutions
  • Read even more (fiction and non-fiction)

  • Write at least one short story

  • Write some more games

  • Go horse riding

  • Learn some more turkish

  • Play a lot more guitar

    I did this but want to do more!

  • Lose at least a stone (in weight, from myself)

    I almost did this and then put it all back on again

  • Try to be less of a pedant (except when it's funny)

  • Try to be more funny ;)

    I'm sure I've achieved these ;)

  • Receive a lot less email

    In particularly, unsubscrive from things I don't read

  • Blog more

    Particularly about technical subjects

  • Write more software

  • Release more software

  • Be a better husband and father

    I think I'm doing alright but I'm sure I can do better

  • Improve or replace the engine I use for my blog

Categories: LUG Community Blogs

Chris Lamb: Goals

Planet ALUG - Thu, 01/01/2015 - 21:36

Dr. Guy Winch:

We used to think that happiness is based on succeeding at our goals, but it turns out not so much.

Most marathon runners, for example — not professionals but the amateur runners — their high for completing the marathon usually disappears even before their nipples stop bleeding.

My point is that the high lasts for a very short amount of time. If you track where people's happiness and satisfaction is, it is in "getting" or in making progress towards our goals. It's a more satisfying, life-affirming, motivating and happy thing than actually reaching them.

So it's a great thing to keep in mind... Health, for example. When you define health as something you want to do, living your life and looking back on the week and saying "That was a healthy week for me: I worked out this number of times, I did this amount of push-ups, I ate reasonably most of the time..." that's very satisfying and that's where you'll feel happy about yourself. And if you're too focused on a scale for some reason, then that's an external thing that you'll hit... and then what?

So it is about creating goals that are longer lasting and really focusing on the journey because that's really where we get our happiness and our satisfaction. Once it's achieved... now what?

Categories: LUG Community Blogs

Chris Lamb: 2014: Selected highlights

Planet ALUG - Wed, 31/12/2014 - 17:23

Previously: 2012 & 2013.


January

Was lent a 15-course baroque lute.

February

Grandpa's funeral. In December he was posthumously awarded the Ushakov Medal (pictured) for his service in the Royal Navy's Arctic Convoys during the Second World War.

March

A lot of triathlon training but also got back into cooking.

April

Returned to the Cambridge Duathlon.

May

Raced 50 and 100 mile cycling time trials & visited the Stratford Olympic pool (pictured).

June

Ironman Austria.

July

Paced my sister at the Downtow-Upflow Half-marathon. Also released the first version of the Strava Enhancement Suite.

August

Visited Cornwall for my cousin's wedding (pictured). Another month for sport including my first ultramarathon and my first sub-20 minute 5k.

September

Entered a London—Oxford—London cycling brevet, my longest single-ride to date (269 km). Also visited the Tour of Britain and the Sri Chomnoy 24-hour endurance race.

October

London—Paris—London cycling tour (588 km).

November

Performed Handel's Messiah in Kettering.

December

Left Thread.com.

Categories: LUG Community Blogs

MJ Ray: GPG Transition Statement

Planet ALUG - Tue, 30/12/2014 - 10:34

Rather late but I guess that just confirms it’s really me, right? The signed text and IDs should be at http://mjr.towers.org.uk/transition-statement.txt

Thank you if you help me out here I’ll resign keys in a while.

Categories: LUG Community Blogs

Steve Kemp: Reducing, or redirecting at least, charitable donations.

Planet HantsLUG - Tue, 30/12/2014 - 00:00

This is the time of year when there are lots of adverts shown on TV solicating donations for charities, which frequently end with the two words "thank you".

I've always felt there were too many charities in the world, and that it was hard to half-heartedly give money to one charity this month, one the next, and still another next year. On that basis I decided long ago to give my money solely to three charities. If I had money that was spare, or I felt generous that month, I would give it to one of "my" charities. Any other appeals I just ignored (with minor exceptions for one-off events like tsunamis, etc).

I won't claim credit for this idea, it came directly from my mom who does the same thing. I've given money to the same three charities for twenty years now. Maybe not thousands, but hopefully enough to be useful. Certainly more than I'd have given if my donation were split between more recipients.

Now I'm changing. As of next year only one charitable organization will get my pennies. The other two haven't done anything bad, wrong, or failed/succeeded (sadly), but it feels better for me to stick to a single recipient.

Happy Christmas.

(Details shouldn't matter, but to answer the obvious question the charity I've kept is the RNLI.)

Categories: LUG Community Blogs

Martin A. Brooks: Elite Dangerous: Tips for explorers

Planet HantsLUG - Sun, 28/12/2014 - 17:45

If you’re not into, or don’t have the equipment to go bounty hunting, exploring in Elite Dangerous can be a lucrative way to make money.  Here are some tips for Commanders wanting to have a go.

You will need a detail scanner which costs CR250,000.  You can explore with just the basic scanner, but it’s much harder.  Assign the scanner to your secondary fire group. It you want to explore deeper space, then you’ll need a fuel scoop, too.   You can get by without a scoop to start with but it means you need to be careful not to stray too far from an inhabited system.  It’s a good idea to keep track of the last inhabited system you were at, if you start to run low on fuel, head back.

Pick a system where there’s no navigation information available, look for the red system information icon in the galaxy map. Systems with an actual name rather than a designation are likely inhabited.

As you jump into the system, whilst still in witchspace, set the throttle to zero. You’re going to arrive very close to the local primary and don’t want to get too hot.  As soon as you exit, press and hold secondary fire to charge the scanner, it takes a few seconds before firing.  The first object you’ll immediately pick up is the star, point the ship at it and hit your “target ahead” key.  You’ll see your ship start scanning it, this takes a little while.  If your detail scanner picks up any other nearby bodies, you’ll get an alert telling you.

Target each unexplored object in turn, working from closest to furthest away.   Anything within 5ls you can scan just by rotating your ship and pointing at it, however at some point you’ll need to start moving around the system.

Be careful near the star, it’s easy to overheat your ship.   If an object is on the other side of the star just point your ship away from the star to get some altitude and, when the heat levels decrease, gradually turn to get the target in your sights.

Learning to jockey the FSD’s autothrottle is essential.  If you keep overshooting objects then you’ll just waste time.  Once the object is in your sights, push the throttle forward until the power line turns blue and leave it there.  Your ship will now automatically accelerate and decelerate for you.  You’ll need to get each object within range to scan, the distance depends on the mass of the object.  Stars can be scanned from a long way out, gas giants from about 100ls, planets from around 20ls or 10ls and rock belts 5ls.

Not all systems contain planets, or they might be out of the range of your detail scanner.  You can try looking round the sky for objects moving relative to the background, I don’t bother and just move on the the next system.

Data you gather can be sold at any station provided you’ve travelled at least 20LY from where you got it.  The least you’ll get is a few hundred credits, however even a single star explored will usually net you around CR1200.   More interesting systems, with high metal content planets, will net you much more.  The highest I’ve seen to date is CR53000.  There seems no point in hoarding the data, the price doesn’t change regardless of distance.

Every so often, seems to be about 1 in 20, you’ll get an interdiction attempt.  It’s up to you whether you fight or flee but if you lose your ship, you will also lose any navigation data you have not sold.  If you get something juicy, it’s probably worth making a deliberate trip to an inhabited system to cash it in.

As you travel around a solar system, you’ll see blips on your scope marked Unidentified Signal Source.  If you investigate these then you may be lucky and it’s free cargo (albeit it will be marked stolen), or it may be dumped toxic waste, or it may be a trap.  The traps are not usually hard to evade if you don’t feel like a fight.  Stolen cargo can be offloaded at the black market, you might have to carry it around for a while before you find one.  I usually limit myself to investigating one USS per system, usually once I’m done with exploring.  If it turns out to be a trap then I just jump to the next system.

 

Categories: LUG Community Blogs

Chris Lamb: find(1), trailing slashes and symbolic links to directories

Planet ALUG - Wed, 24/12/2014 - 23:06

Here's a nice little "gotcha" in find(1).

First, let's create a directory and a symlink to that directory. We'll add an empty file just underneath to illustrate what is going on:

$ mkdir a $ ln -s a b $ touch a/file

If we invoke find with a trailing slash, everything works as expected:

$ find a/ a/ a/file $ find b/ b/ b/file

... but if we omit the trailing slash, find does not traverse the symlink:

$ find a a a/file $ find b b

This implies that any normal-looking invokation of find such as:

find /path/to/dir -name 'somefile.ext' ...

... is subtly buggy as it won't accomodate the sysadmin replacing that path with a symlink.

This is, of course, well-covered in the find(1) manpage (spoiler: the safest option is to specify -H, or simply to append the trailing slash), but I would still class this as a "gotcha" because of the subtle difference between the trailing and non-trailing slash variants.

Putting it another way, it's completely reasonable that find doesn't follow symlinks, but when this behaviour based on the presence of the trailing slash—a usually meaningless syntactic distinction—it crosses the rubicon to being counter-intutive.

Categories: LUG Community Blogs

Chris Lamb: 8:20AM. Sunday, 22 December 2013

Planet ALUG - Wed, 24/12/2014 - 20:39

Running east into the sun, he hadn't seen another human for over half an hour. He navigates Westferry Circus and heads south, cutting from the road through to the riverside pathway. He keeps is breathing steady - no reason to hurry.

The wind catches him from Westminster. It smells slightly salty but it's an ersatz attempt, nowhere near bracing enough to be a real sea breeze.

Pressing on, the vacant citadel of Canary Wharf disappears behind him. But as the peninsula curves around, a man appears in the distance. Even half a mile away he looks out of place, or rather—given the hour—time. He's walking purposefully, but it doesn't feel the kind of route someone would be taking to work. He's not wearing quite enough clothes for the weather either, and homeless people are rarely made to feel welcome in the Docklands. His supermarket denim visibly flaps in the breeze. "Relaxed fit", they call it.

When he gets within earshot the man cocks his head, not expecting to hear the regular cadence of approaching footsteps. He turns slightly to reveal he's cradling a large bottle of Coca-Cola, meekly wrapped in the swathing bands of two anonymously blue corner-shop plastic bags.

The runner eyes the Coke greedily but can quickly see that it has already been opened, tainted. Although only a mouthful or so has gone, a brown froth sloshes against the top of the container. Amateur, he thinks. He'll regret that later.

He looks back up to the man, who is now smiling at him. His left hand bccomes visible as he strides: a four-pack of Carling. The man laughs.

"Oh, you and me mate are worlds apart!" the man shouts.

It's immediately friendly. He starts to raise his Carling as but thinks better of it. It's momentarily awkward.

"Worlds apart mate", the man continues. "Have a good one!"

The runner smiles back.

Only in time, the runner thinks. They both can't stop.

Categories: LUG Community Blogs

Mick Morgan: merry christmas 2014

Planet ALUG - Wed, 24/12/2014 - 18:26

As I have noted before, 24 December is trivia’s birthday. Since my first post dates from 24 December 2006, today is trivia’s eighth birthday. It seems like only yesterday.

I haven’t posted much in the last few months. I have a lot of material I need to cover, and a backlog of articles I want (or at least wanted) to write so I will endeavour to get back into a writing routine as soon as I can. Meanwhile, since it is yet again christmas time, and it’s trivia’s birthday, I couldn’t let today pass unblogged.

Let’s hope 2015 brings all that you wish for.

Best Wishes

Mick

Categories: LUG Community Blogs

Steve Kemp: Switched to using attic for backups

Planet HantsLUG - Fri, 19/12/2014 - 00:00

Even though seeing the word attic reminds me too much of leaking roofs and CVS, I've switched to using the attic backup tool.

I want a simple system which will take incremental backups, perform duplication-elimination (to avoid taking too much space), support encryption, and be fast.

I stopped using backup2l because the .tar.gz files were too annoying, and it was too slow. I started using obnam because I respect Lars and his exceptionally thorough testing-regime, but had to stop using it when things started getting "too slow".

I'll document the usage/installation in the future. For the moment the only annoyance is that it is contained in the Jessie archive, not the Wheezy one. Right now only 2/19 of my hosts are Jessie.

Categories: LUG Community Blogs

Mick Morgan: solidarity with the tor project

Planet ALUG - Sat, 13/12/2014 - 19:16

On Thursday 11 December, Roger Dingledine of the Tor project posted the following email to the “tor-talk” mail list (to which I am subscribed).

I’d like to draw your attention to

https://blog.torproject.org/blog/solidarity-against-online-harassment
https://twitter.com/torproject/status/543154161236586496

One of our colleagues has been the target of a sustained campaign of harassment for the past several months. We have decided to publish this statement to publicly declare our support for her, for every member of our organization, and for every member of our community who experiences this harassment. She is not alone and her experience has catalyzed us to action. This statement is a start.

Roger asked those who deplored on-line harassment (of any person, for any reason) and who supported the Tor project’s action in publicly condemning the harassment of one of the Tor developers to add their name and voice to the blog post.

I am proud to have done so.

Categories: LUG Community Blogs
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