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Hacker Public Radio

Your ideas, projects, opinions - podcasted.

New episodes Monday through Friday.

Correspondent

MrX


Host ID: 201

email: mrxathpr.nospam@nospam.gmail.com
episodes: 8

hpr1563 :: Starting Programs at boot on the Raspberry Pi

Released on 2014-07-30 under a CC-BY-SA license.

How I start programs at boot on my Raspberry Pi. Below is a copy of the /etc/rc.local file I use on my raspberry pi.

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi

################## Added by MrX 28/12/12, ############################################################
#  V1, 21/03/14, titied up script, added explination, run didiwiki and got detached screen working at boot

# items are run in a subshell enclosing command in ( and )
# the commands are terminted with a & to run as background task
# by default programs are run as root if this is not required "su" is used to switch user to pi
# becuse each program is run as a subsheel they all run in parallel this is why the sleep
# command is needed, each sleep command must be longer than the sum of the sleeps before
# which ensures the commands are run in sequence and not together
# exit 0 was from the original file to ensure the file exited with status 0
# if the script doesn't exit with status 0 then the pi will not fully boot


# At boot fources audio aoutput to headphones socket (Analogue output)
# from magpie magazine pdf, issue 3 page 4
(sleep 1; /usr/bin/amixer cset numid=3 1) &


# At boot run the command didiwiki as user pi, listening on IP 192.168.1.13 port 8000
(sleep 3; su pi -c "/usr/bin/didiwiki -l 192.168.1.13 -p 8000") &


# run a detached screen session at boot
(sleep 6; su pi -c "cd /home/pi ; /usr/bin/screen -dmS pi-debian -c /home/pi/.screenrc.multiwin") &

exit 0

hpr1496 :: wiki on the raspberry pi

Released on 2014-04-28 under a CC-BY-SA license.

My experience of playing with wiki software on the raspberry pi, I forgot to mention I run the standard rasbian distribution on my pi if you run something else your mileage may vary.

When I listened to the show I noticed a few mistakes, there may be others as the show was pulled together rather hastily

1. The raspberry pi has either 256 or 512 MB of memory Not KB's oops

2. You can automatically create pages using camel-case words they don't need to start with the word wiki so in my example the page WikiNotes could just as easily be called GuffNotes. This is because at first I didnt appreciate the meaning of the word camelcase, you learn something new every day!

3. Wikidot still provides a free account, oops again!

wikidot

dokuwiki

didiwiki

sed man page

some sed tutorial and examples


hpr1478 :: Batteries Part 2

Released on 2014-04-02 under a CC-BY-SA license.

A show about batteries - Part 2

My Slow Battery Charger Hahnel Powerstation TC Max, provides gentle overnight trickle charging

Powerbase battery electric drill, had difficult finding a good link to an example of the drill. It came with a selection of drill bits, sockets and two double ended screwdriver bits.

Cannon A80 digital Camera

A picture of my trusty Philips 5890 Shaver

Garmin Streetpilot i3 GPS Navigation System

Sansa Clip+


hpr1398 :: Batteries Part 1

Released on 2013-12-11 under a CC-BY-SA license.

A show about batteries - Part 1

I can't take the credit for all this detailed information in my podcast, I found this fantastic website many years ago while investigating why the battery in my expensive razor prematurely failed. I tried to hunt for the site but couldn't find it. I wrote up all my notes from memory and recorded the show. It wasn't until I started working on part 2 of my batteries show that I stumbled across this long forgotten site - at least I think it's the same one as it talks about the memory effect on satellites and doctor's pagers so I guess it must be the same one. I'm indeed delighted to find it still exists, and I may very well read it again from top to bottom. It looks like it's been updated a little too. Well done ka7oei a fantastic resource right enough.

Site title: "About NiMH and NiCd cells and batteries (And a little about LiIons, too...)" http://www.ka7oei.com/nicds.html

A picture of my trusty Philips 5890 Shaver http://urun.gittigidiyor.com/kozmetik-kisisel-bakim/philips-philishave-5890-tras-makinasi-77027302

Memory effect http://en.wikipedia.org/wiki/Memory_effect

Doctor's pager http://en.wikipedia.org/wiki/Pager

Sansa Clip http://en.wikipedia.org/wiki/Sansa_Clip#Sansa_Clip

Two Possible Chargers (For use in the UK)

I found it very difficult to find a slow trickle charger, here are two possibilities, you may need to settle for a fast charger as the slow ones now seem to be like hen's teeth, (VERY HARD TO GET).

This is perhaps a little slow with a charge current of only 150ma, would take about 17Hrs to charge 2100 mAh batteries.

http://www.amazon.co.uk/Lloytron-B046-Battery-Charger-batteries/dp/B0035SLPVW/ref=sr_1_12?ie=UTF8&qid=1381055732&sr=8-12&keywords=aa+charger

The charger I use is made by the same company as this although mine is a different model. My model charges at 200ma, and takes about 13 Hrs to charge a 2100 mAh battery. I can't tell what charge current this charger deliveries, but suspect it's a simple slow charger, probably old stock, as I said slow chargers are getting like hen's teeth.

http://www.ebay.co.uk/itm/Hahnel-Powerstation-TC-Action-Charger-with-2-x-2000mAh-Batteries-/321240775553?pt=UK_ConsumerElectronics_Batteries_SM&hash=item4acb713b81


hpr1348 :: Fuse

Released on 2013-10-02 under a CC-BY-SA license.

A show about a 2nd world war fuse that had been in the family for many years, it originally belonged to my grandfather

Here is a link to the British Ordnance Collectors Network forums, which has a picture of a collection of German bomb fuses, the one my grandfather had looked identical to the one on the extreme left hand side of the picture entitled "25A". http://www.bocn.co.uk/vbforum/threads/4700-My-German-Bomb-Fuses


hpr1047 :: Soldering Part 2: An audio demonstration of soldering

Released on 2012-08-07 under a CC-BY-SA license.

Here is a list of useful links to go along with my 2nd episode in soldering

A very detailed page on the art of soldering, lots of good tips hear if you want further reading http://talkingelectronics.com/FreeProjects/5-Projects/Page13.html

Bottle of flux like the type I used at work http://moonflygirl.blogspot.co.uk/2011/03/needle-bottle-for-liquid-flux.html

Tin of flux like the one used at work http://www.teyaa.com/mini-pd10-box-of-tin-soldering-flux-yellow-p-123922.html

Perf board or strip board, I accidentally called it bread board which is something completely different http://uk.rs-online.com/web/p/prototype-development-boards/0434217/

Wikipedia entry for Perf Board or Strip Board http://en.wikipedia.org/wiki/Stripboard

Bread board is used for quick lash ups where soldering is not required as you just push the components into the holes on the board http://www.circuitboards1.com/category/breadboard/


hpr1037 :: Soldering Part 1

Released on 2012-07-24 under a CC-BY-SA license.

A show about the tools needed for soldering

Example of a battery powered soldering iron (similar to the on I had) http://www.iso-tip.com/wp-content/uploads/2011/04/7700IsoTipQuickChargeWeb2-4.jpg

Weller soldering gun kit similar to the one I owned http://www.tooled-up.com/Product.asp?PID=12425

Portalsol Iron (My gas powered soldering Iron) http://in.rsdelivers.com/product/portasol/10181060/miniature-gas-soldering-iron-60w-171mm-l/0600234.aspx

Antex iron, with soldering stand and sponge (The one I fitted I diode to) http://en.wikipedia.org/wiki/File:SolderStation.JPG

Weller magnostatic work station (Similar to the one I used in the early part of my career) http://tehnikservice.net/2010/03/27/temperature-led-for-weller-wtcps/

A modern Weller magnostatic work station http://www.eham.net/reviews/detail/4478

An example of my Weller temperature controlled iron, mine is almost as scabby as this one! http://www.bmius.com/p-7802-weller-ec2002a-soldering-station-ec-2000-power-unit.aspx

An example of a soldering sponge http://www.maplin.co.uk/replacement-sponge-4078

An example of a dry joint http://www.fordwiki.co.uk/index.php?title=File:CrctCrck-2.jpg

Wiki entry on Heatshrink sleeving http://en.wikipedia.org/wiki/Heatshrink

small jewelers screwdrivers I own http://www.amazon.co.uk/Rolson-Tools-28289-piece-Screwdriver/dp/B000WDXMBY/ref=sr_1_9?ie=UTF8&qid=1336310437&sr=8-9


hpr0911 :: Hobbies

Released on 2012-01-29 under a CC-BY-SA license.

A show about the hobbies I've had over the years

The Secret Life of machines videos by Tim Hunkin, originally broadcasted in the UK in around 1980 http://www.exploratorium.edu/ronh/SLOM/

Ohms Law http://people.usd.edu/~schieber/psyc770/resistors/ohms4beginner.html

Information about the thermionic valve http://en.wikipedia.org/wiki/Vacuum_tube

Calculating Wavelength http://www.ewart.org.uk/physics/index.php?l=44

Small Yaseu FT 817, Multi Mode Hf, VHF and UHF transceiver http://www.g4ilo.com/ft817.html 19:00

Base Station Kenwood TS 940S, Multi Mode Hf Transceiver http://www.universal-radio.com/catalog/hamhf/ts940s.html 19:00

Amiga 500 Computer http://www.obsoletecomputermuseum.org/amiga500/

Beginning Ubuntu Linux from novice to professional http://www.amazon.com/Beginning-Ubuntu-Linux-Novice-Professional/dp/1590596277

Linux Pocket guide http://www.amazon.com/Linux-Pocket-Guide-Daniel-Barrett/dp/0596006284/ref=sr_1_1?s=books&ie=UTF8&qid=1327077298&sr=1-1

Wicked cool shell scripts http://nostarch.com/wcss.htm

Raspberry PI, micro Computer for $35 http://www.raspberrypi.org


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