Monday, 12 September 2016

Don't scream at your hard disks - 2016 version

Brendan Gregg while an engineer at Sun Microsystems in 2008 posted a YouTube video showing that shouting at hard disks could cause faults.

This past weekend ING Romania tested their datacentre's fire suppression system and according to the Motherboard the gas released with a 130dB+ noise that fatally damaged enough of their hard disks to knock out the datacentre. It seems their monitoring hardware's range topped out at 130dB. Ouch! They had swap over to their DR site and have still to determine the extent of the damage.

For comparison 130dB would be felt standing 15.24m (50ft) away from a military jet aircraft take-off with afterburner on an aircraft carrier.

Saturday, 16 July 2016

Black Cat Electronics -- Smith

Cat attention input error with resulting keyboard buffer overflow and sharp-claw priority hardware interrupt.

Apply cuddles to continue or any other action to encounter the glacial stare of disdain. Any attempt at rebooting will not offer a safe-mode option.



Cat, King of the large ape servants, Destroyer of worlds, Annihilator of scratch-blocks, Ribbon affectionardo, Aquaphobic and Laptop heatsink.


Monday, 27 June 2016

Hamerkop Lunchtime

I photographed this hamerkop (Scopus umbretta) eating what I think is a guttural toad (Amietophrynus gutturalis) at the Durban Botanical Gardens' lake. Hamerkop is Afrikaans for hammer (hamer) head (kop) which is quite appropriate.

It had already stabbed the toad with its beak to kill it a couple minutes before and was throwing it in the air to align it with its beak so as to swallow it. It had tried quite a few times already so this wasn't as lucky a photo as you might think, although this was the occasion it got it right. It lowered the toad into the water each time again before trying again which accounts for the water spray off the toad.

When I was a teenager and at school my mother found a hammerkop eating my goldfish as she was walking through the garden on her way to work in the school's tuck-shop. She chased it away but it just landed on the roof and waited. So my mother got an umbrella hoping to use it as a scarecrow, but the hammerkop didn't think much of it and landed right next to the umbrella and she had to leave. I think I lost 72 goldfish. 

I learned much later to stop keeping goldfish and rather to stock fast breeding small fish I didn't care much about. Then you can rather enjoy the wildlife that come to eat the fish than trying to work against them.

My neighbour who gave me the advice also gave me the fish by scooping a bucket-load out of his pond. The fish were black and slim so they stood a decent chance of hiding in my pond which was very deep with lots of plants. The most interesting outcome was that fishing spiders started living in the foliage in the pond.

It is quite a big bird at around 50cm tall and obviously isn't shy about stabbing things, but this didn't stop my daft 9 month old cat from trying to stalk one on an open lawn while the bird was next to my fishpond. The bird wasn't even bothered with me standing fairly close by. The hamerkop turned its head to focus on the leopard crawling cat and stood there for a while as if it couldn't believe it, then walked away while looking at the cat, flying off after a bit when the cat didn't give up.

We often had hadeda ibis (Bostrychia hagedash) in our garden which are a bit bigger than a hamerkop and have equally stabby beaks. They use them to punch into the ground and grab earthworms and insects. Our cat totally ignored them so I wonder if he had become older and wiser, that they were too big or that they were rarely alone put him off.

Wednesday, 22 June 2016

Bar-throated Apalis

I can highly recommend it as a place to visit & stay, although you should have a car with high ground clearance.

I used to drive there in a VW Golf -- the original box-shaped one, very, very slowly with one wheel in the middle of the road and the other on the side of the road to avoid for the deep ruts. On one occasion going home from the lodge on the mountain top, after perhaps a 40 minute crawl, I reached the tarred main road which has a 100kph speed limit and accelerated. My wife shouted at me to not drive so fast ... I was only doing 60!

There is another lodge in the forest which has 4 (5?) rivers to cross. My golf happily splashed across all of them except the last one on the return journey. It always hit a rock with the underside, I could never find the rock and it never hurt the car. :-)

My next car had high ground clearance and I drove the route normally at a reasonable speed, but the first salesman lost the deal because he insisted I needed a 4x4 :-) I guess he never saw the Top Gear episode where the backup car, an old VW Beetle made it right across Botswana.

Monday, 20 June 2016

African Spoonbill in Flight

An African spoonbill (Platalea alba) in flight over the Durban Botanical Gardens.

They are commonly seen around the lake there as are:
The last three are commonly seen at the lake, while the previous ones are probably always there as they breed in the gardens. Kingfishers can be seen at the lake diving for prey, but I only saw them occasionally.

There a lot of other birds to be seen in the Garden in general and I can highly recommend it as a place to visit. 

Thick-billed weavers (Amblyospiza albifrons) used to be common as they bred in the reeds on the sides of the lake but the Garden cleared the reeds a few years ago and I haven't seen them there since. There also used to be a lot more Sacred Ibis but they pruned the trees they favored for nest building.

Monday, 13 June 2016

Spur-winged goose

I photographed this spur-winged goose (Plectropterus gambensis) having a bath in the Durban Botanical Garden's lake. They are related to geese but despite their common name they have enough anatomical differences that they are in their own sub-family Plectropterinae.

Sunday, 12 June 2016

Pink-Backed Pelican Fun

In South Africa Pink-backed Pelicans (Pelecanus rufescens) are only found in Kwazulu-Natal. One of the easiest places to see them is at the lake in Durban's Botanical Gardens where they roost at night in the trees around the uphill side of the lake. This is one of only three breeding colonies of this pelican species in South Africa.

The lake is also home to African Helmeted Turtles / Marsh Terrapins (Pelomedusa subrufa). I had previously seen Sacred Ibis walk up to a turtle on land and bang its shell with its beak for a bit while the turtle waited for the indignity to stop tucked away in its shell, before marching onward.

While watching the pelicans one weekend, one of them started playing with a object, throwing it up into the air and then catching it with its beak. As the object went up it would spiral around making a Catherine Wheel of water while the pelican would paddle into place to catch it.

I couldn't make out what the toy was but it was about the size of a turtle. The pelican played around for a few minutes allowing me to get some fantastic photos, but while worrying about the poor little airborne creature.

When I got home and looked at the photos it happily turned out that the object was actually the old seed cup from a Sacred Lotus flower (Nelumbo nucifera) which grow on the one side of the lake.

I was lucky to have this photo and 7 others chosen in a bird photography competition held by Birdlife KwaZulu-Natal to form part of the 30 to be displayed in an exhibition at the Durban Natural History Museum in October 2010. 

Turtle, Terrapin or Tortoise?

While reading up on the turtles/terrapins for this post I found that the turtle versus terrapin versus tortoise common name usage is far more unusual than I had thought. I had often called these turtles with someone correcting me to terrapin, although as you can see from the common names of this particular species both terms have been used. As an example of the strangeness, seemingly in Australia where there are no indigenous land-dwelling tortoises, all the freshwater turtles are called tortoises.

Tuesday, 1 March 2016

Raspberry Pi 3 Model B

The Raspberry Pi 3 Model B was officially announced yesterday, which is either the foundation's fourth or first birthday depending on how you view the 29th of February :-)

The most significant changes are:
  1. Integrated 802.11 b/g/n Wireless LAN
  2. Integrated Bluetooth 4.1 Classic & Low Energy.
  3. 1.2Ghz 64-bit ARMv8
The CPU has moved from 32-bit to 64-bit but it will use a 32-bit Raspbian version while they investigate whether there is any value in moving to 64-bit mode.

It will require a 2.5A power supply.


Pied starling

A pied starling (Spreo bicolor) also photographed, like most of the previous bird posts, in the West Coast National Park.

Monday, 29 February 2016

Purple-crested Turaco (Lourie)

While growing up I never saw louries (turacos) in our garden, but over time the bird populations changed and for about the last ten years I lived there Purple-crested Turacos (Tauraco porphyreolophus) often visited our garden.  I saw two together fairly often so there was at least a pair of them.

Their call is an unmistakable repeated kok-kok-kok sound which my wife describes as laughing. They are shy and fly from tree-to-tree, hopping between the branches, mostly hidden in the foliage. When they fly their crimson red flight feathers are dazzling.

With their loud call you are left in no doubt about where they are. However trying to see them for a good photograph with hopefully all of the bird and not in dark shade drove me crazy. I finally got some decent pictures when one stayed out in the open on an old avocado pear tree for a moment, rather than buried in our enormous Forest Natal Mahogany Tree (Trichilia dregeana).

Friday, 26 February 2016

Helmeted Guineafowl

Helmeted Guineafowls (Numida meleagris) are common in South Africa, this particular one photographed, like the previous few posts, in the West Coast National Park. I love their spotty plumage.

Origin of the names


The origin of the name guineafowl and it's species name meleagris is interesting.

The guineafowl was domesticated in classical times in Greece and were called melanargis meaning black & silver which was corrupted to meleagris.

They were distributed throughout the Roman Empire as were the Moroccan Guineafowl subspecies (N. m. sabyi). The Romans also called the former species meleagris and the latter the numidian fowl or hen. N. m sabyi has possibly been extinct since the 1950s.

Both disappeared from Europe after the Roman Empire declined. Guineafowls were rediscovered by the Portuguese explorers on the west coast of Africa in the late 16th century which is where they get their modern common name guineafowl

The naming of the wild turkey from North America (Meleagris gallopavo) intertwined with the guineafowl (Numida meleagris) but from what I've read it seems rather murky with multiple theories.

They both share the word meleagris, one as its genus the other as its species. The guneafowl obviously had that name first, but the puzzle is why did the turkey get it too. One theory is that they appeared in the European market at around the same time with resulting confusion.

While the scientific name link is obvious, the common name turkey doesn't escape either.

One theory is that merchants from the Ottoman Empire traded in guineafowl and that the birds got a nickname of turkey. Settlers in North America saw what seemed to be similar birds and then called them turkeys. Another theory is that merchants from the East also sold turkeys later... A further theory on Wikipedia is that they were named turkeys just because it was an exotic place like Guinea which seems unlikely, but I suppose weirder name choices have been made with less basis.


Turkey name theories:
  1. The flight of the turkey, The Economist, 20th December 2014
  2. Guinea Fowl, Roy Crawford in Poultry Breeding and Genetics Elsevier, Amsterdam, 1990
  4. Helmeted Guineafowls, Wikipedia
  5. Wild Turkey, Wikipedia
  1. Guinea Fowl, Roy Crawford in Poultry Breeding and Genetics Elsevier, Amsterdam, 1990
  2. Extinct Birds, Julian P. Hume, Michael Walters, 19 Feb 2012
  3. Helmeted Guineafowls, Wikipedia
  4. BirdLife International, Helmeted Guineafowl Numida meleagris

Yellow Bishop

Here is another bird photographed in the West Coast National Park in South Africa. It is a Yellow Bishop (Euplectes capensis) which is a species of weaver (Ploceidae).

Thursday, 25 February 2016


A Bokmakierie (Telophorus zeylonus) in the West Coast National Park with an insect. Bokmakieries are a species of bushshrike endemic to Southern Africa.

The West Coast National Park is a very beautiful nature reserve about an hour's drive from Cape Town. It borders Langabaan Lagoon on the one side and the Atlantic Ocean on the other. The best time to visit is in August or September when the flowers are in full bloom and the private land north of the reserve is opened for visitors.

Praying Mantis

This impressive praying mantis was hanging onto the top of a window-frame. I'm not sure what it is but it looks like one of the African Stick Mantis species (Hoplocorypha)

There are more than 200 species of mantis in sub-Saharan Africa.

Sunday, 14 February 2016

Common Hairtail Butterfly

I photographed this Common Hairtail butterfly (Anthene definita definita) drinking water and minerals from the mud on a farm road in the Karkloof Mountains. Its wingspan is between 25-28mm.

A good tip I learn't when I was a kid photographing my dog was to always photograph animals at their level -- even if that sometimes means lying down in the mud in a tractor rut, or in the case of my dog being pounced upon and having my face licked.

Saturday, 13 February 2016

Phantom Flutterer

The Phantom Flutterer (Rhyothemis semihyalina) is a very beautiful dragonfly that occurs throughout Africa, the Indian Ocean islands, part of the Middle-East and part of southern Asia.

The iridescent purple is fantastic - the close-up photograph beneath this one shows it better although a photo doesn't do it enough justice. I've rarely seen this dragonfly but I was lucky enough to photograph this one right next to my front door. I can sprint for a camera quite fast!

Friday, 12 February 2016

Gaudy Commodore Butterfly

This is a Gaudy Commodore butterfly (Precis octavia sesamus) in its winter form photographed in my garden. Its summer form is red with black markings.

It's a large butterfly that I've always found hard to photograph as it's quite skittish (well at least around me!) unless you come across it early in the morning while it's still cold outside.

Thursday, 11 February 2016

GPO No. 309 Telephone (Siemens)

My wife has a British GPO No. 309 telephone manufactured by Siemens in the UK that was used in South Africa.

The 300 series telephones were manufactured between 1937 and 1959 for the British GPO although production seems to have continued longer for UK associated markets such as South Africa, Australia, etc...

 It still works fine except for the obsolete pulse dialing. The only repairs I needed to make was to heat shrink over where the fabric cable had frayed back from the handset and the wall socket end. I was interested in putting a pulse to tone dialing converter in it but my wife preferred it to remain unchanged and used for receiving calls and most certainly hearing them!

The phone has three distinct parts from bottom to top: A heavy ballasted base plate, a bell-set and the actual phone.

Phone -- Dial and Handset


The pulse dial mechanism is in the top-center in the photo above. After the dial is turned it is returned to its resting position by a spring at a constant rate regulated by a centrifugal governor device. It is the horizontal device near the top of the picture with a circular brass housing on the right-hand side. It has a worm-gear rod that goes to the left and engages with the gear that is visible there.

The leaf spring contacts produce the pulses by disconnecting the direct current of the line briefly between one and ten times. The voltage on the line is negative in relation to ground to help prevent corrosion. 

The leaf springs parallel and nearest to the terminal block at the bottom are for disconnecting the line when the handset is on-hook. There is a vertical metal spike that is just visible above the contacts which drives down between them when the hook is depressed to disconnect them.

I think the large electronic part on the right-hand side is an inductor.



The bell-set is in the rectangular box and is wired to the phone above it by an external cable. This was required as it separates off the phone into a stand-alone unit with the intention that people might like to have it located somewhere else, like a hallway, so that it could be heard throughout the house. It is very loud so unsurprisingly from what I've read it seems most people just wanted it connected together.

The bell-set has two different sized bells struck by a ball-shaped hammer in-between them, driven by an electromagnet. This gives it a beautiful two-tone ring that sounds much better than the vintage-phone ringtones on smartphones ...  more menacing ... like if you don't answer it will rip your face off, but in a beautiful way.

The white block at the bottom of the bell-set photo is a capacitor. It blocks the direct current and allows through the alternating current of the ringing signal sent by the exchange.

Ballast Plate

The very heavy ballast plate beneath the already heavy bell-set seems overkill so I would guess it might have been attached directly to the lighter phone when the bell-set was elsewhere. On the ballast plate there is a wiring and parts diagram:

The handset has an interesting old moving iron speaker. The cover unscrews to reveal a metal disc which can be slid carefully off horizontally. It is held in place by permanent magnets underneath it and driven by a solenoid. 




Microphone Housing


The microphone's cover also unscrews to reveal a microphone unit that is simply resting on spring contacts and so will just drop out. It also contains the screw terminals for the handsets wiring.

If you ever come across an old telephone like this for sale I would strongly suggest buying it. If nothing else it could be converted into a fantastic alarm clock! Perhaps you could set the time using the dial and turn off the alarm by raising and lowering the handset?

Friday, 5 February 2016

Moss under a Microscope

Moss from a path in my garden under a microscope with grains of fine sand. This photo was taken with a USB microscope I bought from Adafruit that I used to inspect circuit boards.

My father has now adopted it as it turns out it is brilliant for looking at postage stamps for the little differences that philatelists need to spot. All his friends at his stamp club have been buying USB microscopes since he showed them. Better to look at a nice large screen than squint through a magnifying glass...

A circuit board using the same microscope at a lower magnification:

Thursday, 14 January 2016

DIN to RCA Converter and Switch Box

My father-in-law has a 1968 B&O Beomaster 1400 Stereo receiver which has beautiful sound.

Being from an era when there were no CD players and the myriad of other equipment we now attach to receivers it only has two 5-pin DIN socket inputs, one for phono and the other for a tape deck / aux. For years he swapped a DIN to RCA cable between his CD player and tape deck to cope with the one DIN line-level input.

At about the same time his CRT TV and turntable broke, the new TV adding an extra input (awful internal speakers) and both replacements with RCA connections. He shopped around for a solution but no store had anything helpful.

So I made a box with:

    3 RCA inputs switched to a single DIN output
    A direct RCA to DIN connection for the turntable.

The plastic enclosure is coated on the inside with RF/EMI shielding.

I used a nice selection switch which has a grub screw to hold it in place.

The underside has stick-on rubber feet.

Saturday, 9 January 2016

Recycled Door and Mirror

A neighbor replaced a meranti (Genus Shorea) door which had partially decayed and he gave it to me. After leaning against a wall outside for a few years I sawed off the rotten bits and made this mirror from some of it.

The thick base and uprights are from one of the sides of the door and the edges of the mirror from a couple of the slats. The mirror glass was also recycled having previously been stuck directly on a wall.

The mirror hinges were surprisingly hard to get. We eventually found them at a huge hardware & timber store, no thanks to any of the store assistants who had never heard of such a thing.

Friday, 8 January 2016

Small Problem

A friend's iPhone cable was working intermittently and he asked me to take a look. The broken wire was hanging on for dear life by a speck of insulation. So tiny.

It was a bit of a challenge to add the heat-shrink with such little space and not have it shrink while soldering so close. Forceps come in handy as a heat-sink. I'm sure that's why they were invented, or at least that's the excuse I used to buy it. I'm sure two would be better...

I didn't need an excuse to own a shifting spanner and a set-square, but they make nice heat-sinks too in a pinch.

One happy friend.

Thursday, 7 January 2016

New Legs

For years a broken chair made from Imbuia sat in my workshop waiting for a use. My wife gave me a mirror whose plastic base had broken to fix and an interesting match was made. 

Spot the Culprit

My wife's sewing machine emitted the magic smoke with a nice bang. Spotting the culprit wasn't exactly hard. Quite impressive, split open underneath too. Fixed it with a salvaged X2 0.1μF part.

Warning: Be aware that X & Y safety rated capacitors operate at mains voltage. These caps are designed to fail open for safety.