Electro-ramblings

Following my trials and tribulations with seemingly-simple push button bistables, Mike M contacted me with some simpler ideas to the same end.

The application demands that two selectable leds to replace one, with any added circuit drawing power from across the driven led.

I had to take a calculator apart this weekend, and inside I found a glass-package diode and an led with no light path to the outside world.

Initial debugging complete, I knocked up a pcb in the kitchen.

I used CadSoft's wonderful free Eagle layout editor to design the board.

I think I have got to the bottom of the 74HC74 hysteresis mystery

The one that meant my LED-controlling bistable switch was not switching properly.

That push button bistable I have still yet to get going is part of an attempt to replace an led in an existing lamp with a choice of two.

I thought I would reveal the rest of my circuit for scrutiny.  

The idea is that the whole circuit connects directly into the lamp instead of the existing led, stealing a few microamps to run itself.

The development 'lab' has moved to the kitchen table as the workshop is so cold that there is liquid nitrogen sloshing around on the floor.

And as well as my 'scope, Dr Frustration appears to be in the house.

For two evenings I have been trying to fault-find a breadboard circuit with only four components that is so trivial I almost didn't try it.

And am not even sure I am at the bottom of it yet.

In mindlessly browsing Wikipedia after my last blog on metrology, I came across something that I am hoping is true

In this article on English units of measure, it claims that the length of a barley seed - a barleycorn - was once the standard from which English measurement was derived, and that it is still in use.

I take my hat off to those who have to measure to extreme accuracies.

I came across slightly long winded but interesting paper on a US website that shows just what a bugger it is.

Got stuck on a train in the snow a week or so ago

The driver was great.

He told us exactly what the problem was, and exactly what he was going to do about it, and then he did it.

The problem was that the live rail was icy and the pick-up could not get enough power.

Those clever robot designers at Boston Dynamics in the US, together with Sandia Labs, have created a shoe box-sized vehicle that can jump over obstacles 7m high.

For military use, and intended to be finished this year, the Precision Urban Hopper can jump over or on to as many as 30 obstacles that are 40-60 times its own height.

Early last year I took a look at a Cree led - Ledil lens combination and mentioned that it looked like a good basis for a caving lamp.

I also said that I would hesitate to make such a lamp in view of the consequences should it break deep underground.

At the time, a real caver responded
 - a caver who makes caving lights, no less.

Arduino is intriguing.

It is a simple cheap development system, including microcontroller hardware, for developing processor-based control systems.

I have never used such a thing, for my imagination ends at BASIC and assembler coding, but it looks likes with Arduino you could string a programme together pretty quickly without having to learn how which bits in the ADC do what (said Alice bitterly).

And I had such a struggle when the CEO of drum-less drum kit company MidiSticks pointed me at this gorgeous miniature digital scope - for about £50.

Sent in by a reader, there is a marvelous internal combustion engine to be seen over on TechEBlog.

http://www.techeblog.com/index.php/tech-gadget/mechanic-builds-smallest-inline-4-engine-ever

Claimed to be the smallest in-line four yet, it sounds delightful.

'Alice'

Respond below, or to alice@electronicsweekly.

Way back in November last year I was looking for a mosfet driver that would drive a top p-fet and a bottom n-fet so that I could run a half-bridge at 100% duty cycle.

Despite helpful replies from both Jeremy and Yilcan Guzelgunler, I got nowhere.

And so, heroically, gave up.

Call me boring, but I quite like packaging.

I neither like or dislike the idea of wireless charging, providing it does not fill up my house with strong magnetic or electric fields.

However, I don't like misleading comparisons.

Given that survival requires nibbling a hole in rock, what kind of teeth do you need?

Quite complex and innovative teeth, it turns out.

Sea urchins hide in DIY limestone holes.

They have five teeth which, like those of rats, grow throughout the animals' life.

In the same way that Harry Beck's 1931 Tube map simplified navigating the London Underground, the Lawrence Livermore National Laboratory has just released a rather interesting chart that summarises US energy consumption.

When I used to go backpacking, I would put all sorts of cloths in my rucksack.

There would be at least: a towel, a flannel, something to wipe mud off the groundsheet, and something to wash up with. 

Over the years, I just managed to cut down the towel size to save space.

But since a foray into the kitchen department of a supermarket, I have reduced the camping cloth count to one.

I actually went and visited by Isambard Kingdom Brunel's Royal Albert Bridge, mentioned in another blog, that carries the main railway between Devon and Cornwall.

Even to an untrained eye like mine, the mechanics look fairly straight forward, except for the diagonal beams from the chains to the main deck, and the curiously complex joints.

I almost could not believe my ears last night.

Good old Radio 4 provided me with another revelation.

Apparently, about a third of the world's languages have no concept of left and right.

I use my DAB radio every day.

And I just bought another one, for my workshop.

So I must be a fan. 

Or at least not a detractor.

I like bridges.

For example, between junctions 11 (A320) and 12 (M3) on the M25 is a brutal-looking cable stay bridge that carries the Chertsey to Virginia Water railway.

It is a magnificent thing, all concrete and steel. 

It looks like the one that got out of the civil engineers design office before the architectural consultant could stop it. 

I can imagine the instruction: "Sod what it looks like, just make it STRONG".

Every time I see these things I am impressed with the elegance of the idea.

A friend of mine was having a car flat battery problem.

It turned out to be the car radio which, when 'off', drew 186mA.

That's 2W!

I don't understand quantum entanglement - Einstein's 'spooky action at a distance' - but I am amazed by it and for no particular reason am pleased that it seems to exist.

I though it was restricted to photon and sub-atomic stuff, but it appears that a mechanical version is also possible.

For example, the UK is largely stable geologically, and not very steep.

This contrasts with New Zealand which is both steep, and a bit lively on the tectonic front.

Cycling around that fine country a while ago, I got invited in for a coffee by a retired guy who turned out to be: a, very interesting and; b, mostly mad.

Several years ago, I used to go to visit Staines in Middlesex (or not in Middlesex - depending on whether you are a Post Office or County Boundary pedant).

Once there, I used to get involved with repairing things and frequently had to buy odds and sods locally.

There were diy sheds in the area, but the local independent diy shop was so good that I seldom even bothered to try the big chain stores.

Each time, they were in pairs, one on either side of a path in the mountains.

My guess is that they detect the passage of people along the path, possibly by microwave.

But the answer could be much simpler.

Does anyone know for sure what they are, what they do, and how they work?

'Alice'

Respond below, or to alice@electronicsweekly.com

I was pondering the failure of my car roof light to operate, wondering if newer cars had gone beyond the corrosion-prone two-pieces-of-metal-and-a-bit-of-plastic door switch.

When reed switches came to mind.

For the uninitiated, these consist of two flat flexible magnetic wires - reeds - held parallel and overlapping in a sealed glass tube.

Some motorcycles have digital gear indicators, some of which work by grounding one of five contacts depending on what gear you are in - plus one for neutral.

For the record, others use a potentiometer, and some after-market versions calculate the gear after measuring engine revs and wheel speed.

I was googling gear indicators and came across this circuit to interface such switches to a seven segment display. 

It is classical digital approach to the problem, with three logic chips and a regulator.

They are made of not-particularly-stretchy plastic - polyethylene I think - and are blown up hard enough to make a noise a bit like a drum - a thankfully quiet drum - when you hit them.

The valve is simply some more of the skin material formed into a tube and stuffed inside one end. The only closing force appears to come from internal air pressure.

There was a drawback to thoroughly removing the nasty old glass insulation from my loft and replacing it with nice safe polyester fluff.

Rodents have moved in.

It may just be a coincidence, but when I took out the mineral wool there were only a couple of birds nests in the loft and not a sign of a mouse.

Now I hear little feet scurrying around at night, and things are starting to get chewed.

Now it turns out they can be a little bit compound, and incorporate reflective focussing.

I am a Radio 4 fan, and once again it has come up trumps.

On More or Less - a programme about numbers - it drew my attention to a book on sustainable energy by David MacKay, a Cambridge professor who said he wanted to get to the bottom of the world's energy balance, and did, and he wrote it all down.

The book is called 'Sustainable Energy - without the hot air', and can be bought in paper form or, most generously on the part of MacKay, downloaded for free as a .pdf.

This is one of two 5MW deep water wind turbines constructed by Talisman Energy (UK)

I was playing I Spy the other night and failed to guess that A stood for Air.

I protested that you can't see air.

But it was pointed out that heat haze and twinkling stars are a result of refractive index variations, so therefore you can see air.

Which got me pondering, as G for Glass is probably legitimate in I Spy.

So now I can cannot decide, in any scientifically defendable way, whether A for Air is cheating or not.

Or maybe I am not supposed to take I Spy so seriously.

'Alice' - a pedant who suffers in a world of inexactitude

Reply below, or to alice@electronicsweekly.com

Turns out that Her Majesty's subjects have broken yet another land speed record - this time the wind powered one - in a rather nice looking vehicle.

From the press release:

On the morning of March 26th, on the dry Lake Ivanpah, the Ecotricity Greenbird driven by British engineer, Richard Jenkins smashed the world land speed record for wind powered vehicles.

The Greenbird clocked 126.1 mph (202.9 km/h), eclipsing the old, American held, record of 116 mph , set by Bob Schumacher in the Iron Duck in March 1999 at the same location.

It also looks like the same team is going to try it on ice.

Good luck gentlefolk

'Alice'

Ps, there is a bit more information here.

Respond below, or to alice@electronicsweekly.com

The first thing I learned was that there is so much more to the job than I thought there would be, so hats off to anyone who gives up their time, usually for free, to do this stuff.

The second thing I learned was that everyone who had already had a go at officiating has stories of school events where angry parents have marched up to them to either argue about, or even corrupt, a judgement.

GOCE is an unusual satellite - the one that was launched recently to measure gravity accurately.

Most unusually, it is an aerodynamic satellite because it flies low at 250km altitude where there are still a few air molecules.

 PICTURE - GOCE is 5m long, weighs 1,100kg, and its chassis is carbon fibre

Its solar cells are stuck on the outside like old-style satellites rather that being on steerable wings, both because drag is less this way, and it can't afford to be vibrated by steering motors.

In fact, it can't afford to be vibrated by anything.

 I came across the LTM8020 dc-dc buck converter and thought it would be ideal for charging the Mark V bike light Li-ion battery.

But when evidence for it was first claimed, no one could repeat the results and the overall effect was worse that a damp squib.
It made scientists look a bit mad.

PICTURE - The US Navy says these three tracks are evidence of cold fusion

Occasionally, the workshop RCD used to trip and I could never find out what was causing it.

In my defence, I did look over the whole lot and made sure there was no water in anything, and everything looked sensible.

It only ever happened after a couple of hours of use, and when workshop heater was set to 2kW.

So for want of something more intelligent to do, I blamed the RCD which is of the plug-in type and which naturally runs fairly warm.

I was trawling the archive of Electronics Weekly, and came across an article from November 16th 1996.

It describes the invention of two famous analogue chips - the 741 and the 555.

Just in case you are interested, as it doesn't seem to be available from the website, I have included the full text below.

Enjoy

'Alice'

Last year around this time, Silicon Labs introduced C8051F9xx - a microcontroller family capable of operation down to 0.9V, and up to 3.6V.

The core does not actually run at 0.9V, there is an in-built boost converter.

Atmel has gone one better, or maybe just 0.2 better, and come up with an MPU that works down to 0.7V.

Inspired by comments made on one of the Electronics Weekly blogs, I thought I would have a go at estimating which led-collimators combination would not dazzle on-comers if used in a vehicle headlight.

A dazzle-free beam must be possible, because the IQ Fly pictured here can do it.

Now, I have to admit that I am winging the calculations here - so any corrections or refutations to the following are welcome.

To be fair, I cannot say I know as much about photons as an earth worm because I have no idea how much worms know about quantum physics.

So instead I will say I know almost nothing about photons*.

This has not stopped me being puzzled by this article

Electronics Weekly sometimes requests device samples.

It is not that the team doesn't believe the specifications we are sent every day, it is just that it can be tricky to put 77dBA or 33 lm into perspective.

The specifications are on the respective web sites, but what are the devices actually like?

So when an engineer friend of mine was mulling over options for a five minute delay circuit, I chipped in that I thought the 4060 14-stage ripple counter and oscillator should be able to do it.

If the designer of the first watch had had access to digital technology, I am fairly sure he or she would have gone straight to digits.

And those with too much money buy mechanical watches.

It impresses me that firms still design mechanical watches - and it pleases me that those that buy them support a thriving and innovative niche engineering industry.

So if you have lots of money, please buy an expensive mechanical watch.  

They were spotted on many houses on the Canary Island of La Palma, all pointing east - possibly towards the larger island of Tenerife - and mostly pointing slightly upwards.

'Alice'

Respond below, or to alice@electronicsweekly.com

 

Eventually the whole thing will be linked up by a microcontroller, but as I have yet to finish testing a surprisingly large amount of code - I finally rewrote the whole thing using a state-machine rather than the rat's nest of flags that graced the MkII.

So I need a nice simple hardware controller to road test the analogue bits now.

The criteria for input and output of the mystery box are:

I want to drive power led from a Li-ion cell.

I have a few specific requirements.

One is that the driver must tolerate a second current source feeding the led, and only supply current when the other source is under 250mA.

It should also not be blown up by this second feed.

And it should shut down to a few µA when switched off.

There do seem to be a few chips that can do this lot, but I thought I would try a home brew version.

There are an awful lot of Li-ion charging chips out there, and you would have thought there was one for every eventuality.

But it turns out there isn't.

For example, there is a sort of no-designer's-land between 6.5V where linear Li-ion chargers top out - although Linear's LTC1734 works up to 8V - and around 12V where switching chargers start. 

And even without an input voltage restriction, what if you don't want to charge the thing at less than 4.2V?

For some foolish reason I automatically assume that precision was invented recently.

I am not quite sure exactly what year I think people started quantifying in parts-per-million.

But I am sure that I am wrong.

For example, I was wandering around the York National Railway Museum a year or so ago when I came across an unexpected treat....

• 22" 1280x1024 or 24" 1680x1050?
• Twisted nematic, in-plane switched, or some other technology?
• A brand or a cheapie?
• HD-ready just in case I ever watch DVDs?

I travelled on Eurostar from St Pancras Station for the first time, and I am impressed, and also slightly disappointed.

I used to leave from Waterloo, and it was always a bit of an embarrassment when returning from Paris or Brussels as the mighty train dropped from 180mph in continental Europe to about 20mph as it bumped and clattered across Kent and crept into London.

Incidentally, I am told that the power electronics in Eurostar has its roots in the UK's Advanced Passenger Train - That ill-fated train which ultimately failed because the ultra-light drive mechanics that allowed it to run fast on standard rails was a technological step too far for its gearbox oil and drive shafts.

Allegedly, the APT had another successful spin-off - its tilting mechanism may be the one used in the Alstom-built Pendolinos that ply the West Coast mainline.

If anyone can confirm or disprove the above 'facts', I would be interested.  

In a break from working out how to stabilise mountain sides, Imperial College London was recently called in to rescue Henry Moore's Arch - a not unpleasant six metre tall stone sculpture that was taken down from a London park in 1996 because it was on the verge of falling down.

Despite its ultra-modern image, Imperial still has wonderful big materials testing machines lurking in its basements, and a startling amount of expertise in things rock.

It found that the sculpture's unusual shape combined with the poor location of the joints between its seven pieces, and the use of travertine which is a brittle stone, conspired to make it unstable.

The generators in Freeplay radios have moved on a great deal from the original Trevor Bayliss design, and look quite superb.

I noticed this when squinting through the blue tinted plastic of a Freeplay EyeMax (pictured). [Recently featured in a Gadget Freak competition, btw - Ed.]

Bayliss' original leap of imagination was that a modern wind-up radio was possible, and he followed this up by developing one - coming up with a design that stored power in a spring.

The spring unwound through a set of gears that spun a small DC motor operating as a generator.

Effectively a Mark II, the next version was a better shape to grip when winding, and added a rather neat power-saving touch - a transistor shorted out the motor when its reservoir capacitor was full - which almost stopped the motor and effectively froze the spring until power was next needed.

Like many people last year, I had a slug infestation.

Now, I claim not to be a cruel person, but the little buggers were eating just about everything in the garden and I wanted them dead.

As I am not keen on the lingering death induced by slug pellets, or their effect on the food chain, an electronic slug-o-cutor had to be the answer.

I couldn't buy one, so one had to be invented.

At this point, don't get too excited, because I never did build anything for it seems that digging over most of the plot in preparation for laying a lawn also kills slugs.

But I enjoyed the design challenge, and this was my thinking.

Years of experience, and quite probably many tragedies, have made the UK wiring regulations what they are - good, sensible rules - albeit written in a somewhat impenetrable form.

For all the right reasons, no power sockets or wall-mounted switches are allowed in bathrooms, and light fittings near the bath, shower and hand basin must be special water resisting types.

However, what I find a little nuts is that there seem to be no special rules for the room immediately under the bathroom - normally the kitchen.

There are times when you read an article and realise the author has got right down to the bottom of the subject.

One such encyclopaedic treatise I came across a few years ago was a Linear Technology application note: 'Ultracompact LCD Backlight Inverters - A Svelte Beast Cuts High Voltage Down to Size' by Jim Williams.

I had never even heard of piezoelectric transformers when I started reading it, but by the end I could see their potential and knew exactly how I would try driving one if I ever had to feed a compact fluorescent lamp.

Jim Williams seems to have a knack of writing thorough applications notes - which I first came across in an old lab copy of a Linear Tech app note book.

Given the problem:

How do you pump water into a boiler using only steam pressure from that boiler?

I would come up with some sort of piston-based steam engine connected to a piston-based water pump.

Which identifies me as a thermodynamic dunce - as a much cleverer no-moving-parts answer was invented 150 years ago; which I came across in a book on steam engine technology.

Basic thermodynamic theory flourished in the mid-19th century, which puzzled me until Richard Wilson, editor of Electronics Weekly, explained it thus: "Because they had big brains and nothing else to think about."

I once saw an artic fox in Norway.

The beautiful fluffy white creature trotted up and sat down only a few metres away, not at all fussed by a couple of cyclists sitting eating sandwiches.

Only I didn't get a photo because my camera had run out of film.

So when I bought a digital camera, I bought one that took easily available AA cells so that I could not run out of film or batteries.

And that worked well for a long time, until I wanted a camera with more than a 3x zoom.

Generally I am amazed at how good stuff is.

For example, this weekend I spent a couple of hours fixing up a friend's cheap bicycle. It must have cost under £200, had been left out in the rain, and wasn't working too well. With a few careful squirts of oil, and a bit of spanner work, it was a proper bike.

Not a thoroughbred, but a vastly better bike than one you would have bought 20 years ago for a similar inflation-adjusted sum.

Webinars are a bit of a lottery, but I came across an excellent one from National Semiconductor.

It is about white power LEDs, and includes a fair amount of detail on colour rendering.

Most of the information is generic, although Lumileds - a sponsor of the webinar - is the only LED maker featured.

I particularly liked the bit explaining why green leaves look grey when illuminated by 'white' light made using a balance of red, green and blue LEDs.

You can get a bit blasé about achievements at the various Fraunhofer Institutes in Germany. They are always doing clever things - take a look the ethylene sensor here: Infra-red sensor tunes fruit ripening

But its Institute for Chemical Technology has excelled itself by proving that explosive blasting in miniature can be used to make tools for hologram production.

I have seen explosive forming before - as a way of forcing aluminium sheet into moulds - but nothing with resolution "in the two-figure nanometre range" that Fraunhofer is claiming.

It was a wistful day in the home workshop yesterday when I got down to the last bit of solder on the only reel I have ever owned.

I have always enjoyed making things, and this particular reel was given to me by my uncle years and years ago when I was a young teenager itching to try electronics.

The last few centimetres went soldering a diode into the wiring loom of my motorbike, which is fitting because on motorbikes is how I remember my uncle.

Now I have a dilemma.

Arthur C Clarke died this morning.

Apart from the science fiction, he should be remembered for the article he wrote describing his idea for a global communication system based on three satellites in fixed positions spaced evenly around the globe.

In this, so one of the editors of Wireless World told me, he described the necessary technology so thoroughly that the article was used years later to defeat an attempt to patent geostationary satellites in the US.

'Alice'

(Pictured: Geostationary communication satellite Galaxy 15 from US firm Orbital. With a launch mass of 1.7tonnes, it is designed to operate for 15 years.)

Civil engineers that I know are inclined to get a bit grumpy about architects, on account of their artistic flair getting in the way of actually designing buildings that work.

But it looks like one talented architectural student has learned his lesson in practicality early, and will probably check with the engineers before he releases any real designs.

US Virginia Tech student Clay Moulton designed the stunning Gravia concept - a gravity-powered floor lamp.

The 1.2m tall device runs somewhat like a grandfather clock, with just over 20kg of brass weights that descend slowly - in this case running a generator.

Occasionally I get that I-wish-I'd-thought-of-that feeling.

And these cunning little tins produce exactly that.

The lid is firmly attached until by pressing the centre of the lid, the lid suddenly snaps down.
It moves a millimetre or so and, by distortions in the metal I never expect to understand, the clips around the edge spring apart allowing the lid to be lifted away.

I was speaking to someone from a big heritage organisation the other day, and learned that there is a hunt for ways to cut the power consumption of chandeliers.

These, apparently, were usually designed specifically for incandescent bulbs, or have been converted to them from either candles or gas.

At 10 lm/W, incandescent bulbs are not very power efficient, but they weigh very little and most importantly their optical output allows the chandelier to sparkle.

LED and compact fluorescent bulb replacements have been tried, but they failed the all-important sparkle test.

Coulombs I can do.

They quantify charge and are proportional to the number of electrons shifted, and not too difficult to visualise as electrons are real little round things.

In a circuit they are being pushed up a gradient against their natural tendency to stay still, if you get my meaning.

Coulombs get an outing in CΔV=IT, that particularly handy formula for sizing reservoir and de-coupling capacitors.