WHYTRICITY

It seems like everything that's wireless these days is called wi-something, including witricity. If I understand right, this stands for “wireless electricity”, which means wireless power transfer. Designers everywhere, from MIT to Intel, are busily devising methods to eliminate separate power cables for individual devices.

This makes me wonder: why wi?

In the first place, each of these cables is usually connected to a transformer in an AC adapter. Transformers are not exactly leading-edge technology. The earliest descriptions date back to Faraday in the early decades of the 19th century. If we look more closely at how a transformer works, we usually see a primary winding and a secondary winding fitted on a magnetic core. That’s wireless power transfer.

Now let's look at all the modern approaches to obtaining wireless power transfer. Basically, they all amount to reworking the transformer principle, with a primary coil and secondary coil coupled by magnetic induction. The only difference is that people are experimenting with different frequencies and using resonant coils. The last part also sounds a bit familiar – isn’t that how radio broadcasting works, with electromagnetic waves? And let's not forget Tesla, whose enormous Wardenclyffe project was intended to provide wireless power transmission.

So we already have wireless power, but it’s not enough to meet our needs, and furthermore it’s not very efficient. This brings me to my question for you this week: do you see a future for wireless power, or should we start thinking about new forms of power distribution, and what would they be?

WH

your view/repsons:

....I think the future will bring systems that will draw energy from solar, vibrations and energy from air - the last with a chemical reaction. Think of a accumulator where free air can flow feeding into a chemical reaction.

Ron Wesselman

ON and OFF

Do you think Edison used a switch in his experiments? And if so, what did it look like? My guess is that he used a toggle switch – the old-fashioned kind with a big handle, mounted on a sturdy wooden board to keep all the components in place. For some time now, I’ve been toying with the idea of writing a series of articles or a small book on switches and clever ways to turn devices on and off. Everything from simple switches to light switches, low-voltage and high-voltage switches, transistors as switches, switching equipment partially off in the standby state, mercury switches (now forbidden) for detecting motion, and how you can use physical phenomena such as speech, pressure, motion, height differences, water, light, fire, and so on to activate a switch.

I’m writing this during the Elektor presence at the ESC show in Boston. There we meet a lot of good folks, and they visit our booth to show us all sorts of things. Consider the man in the photo: while watching a screen from the corner of his eye, he operates a computer with his voice. He’s called “Golden I.” Naturally, when you’re having a conversation you have to be careful to avoid the voice commands you use to control the computer. Terms such as open, close, file, mail, and so on can confuse the computer and disturb the conversation, or cause the wearer to glance nervously into the little screen. Actually, this is also a sort of switch – I wonder what would happen if you suddenly called out ‘ON’ or ‘OFF’ while standing next to this man? Would his eyes go into standby, or does he also have a screensaver? For his sake, I hope not.

If you know an interesting way to turn something on or off (people, animals, cars, radios, TVs, etc.), you’re more than welcome to send your ideas to theelectronicball@elektor.com.

Wisse Hettinga

Readers respons:

.....

http://robotics.me.es.osaka-u.ac.jp/~taniguti/index-eng.html

This researcher works on ways to control systems with facial expressions. He and his colleagues have developed a way to control an MP3 player with chewing movements and a second system that uses the temple muscles. This last one attracted quite some interest in 2008 on the internet under the name Kome-Kami switch.

A news item in French can be found here: http://www.elektor.fr/nouvelles/telecommande-par-clignements-des-yeux.600651.lynkx

Clemens - Elektor France

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Hi,

I reflashed a router to a linux server. He is doing my webserver, mails, back-up server tetc.

He knows

- the time (from the internet)

- day and night to switch on the lights

See the developments http://edimax.geens.nl/001.hardware/020.Patches/111.lichtschakelaar/

P.v.Geens (Holland)

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I would think that if Edison used a switch in his experiments and/or apparatus, it would have been a knife switch. In the early part of the century when Edison done most of his work, the knife switch was the most popular type available to both the experimenter and to industry. Therefore, it stands to reason that Edison too would have used this type of switch.

This is my opinion based on my knowledge of Edison's work, and the state of the art of electrical apparatus of the day. If you find that this isn't the case, I will apologize and stand corrected.

Regards,

Jim

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Dear Wisse,

Many people overlook diodes as switches. They can be very useful when you want to switch many analog signals at once, as in changing bands in a shortwave radio or changing modes in a transceiver. I've attached an article I found describing diodes as switches.

Best Regards,

Dave Bailey
Technical Support Engineer

IAR Systems Inc.
2 Mount Royal
Marlborough, MA 01752

(article can be dispatched on demand - thanks, WH)

THE IT GUYS AT AU BON PAIN

In general IT departments don't have very good reputation; when you need them thei're not there and when you don't need them they doing upgrading and copying stuff keeping you from working.

Not with Darrel (r) and George (l): they are always there! They run a kind of DIY IT department in a Au bon Pain, just opposite the big Christian Science Church on Massachusetts Ave, Boston. Darrel knows everything about notebooks - he's got a dozen I think - he tears them all down to the real bits and puts them back together and repairs them. George is the expert in asking how you're doing and giving you permission to leave - don't forget to ask.

George and Darrel are more the hub of a small community of people that like to see each other every morning, checking everything is OK. They have questions on websites, computers, mails, the weather forecast etc. and is an nice example of how IT can bring together people.

Straight down the road is the Hynes Convention centre. The home base for the ESC show. That also draws a crowd. Students and professionals on electronics gather discussing the latest and greatest on embedded electronics. Lots of them also visited the Elektor booth to pick up the latest issue.

The visitors on the ESC and the early-morning-I-first-need-a-coffee-DIY-IT-department from George and Darrel were excellent!

WH

THE ELECTRONIC BALL QUESTIONS

Remember we asked you all how to calculate the resistance of a ball made out of resistors? Please find Ron Badmans updated answers. Unfortunately there are more illustration then room on the blog. I'm sure that if you leave a comment for Ron he will be happy to provide you all the illustrations and details.

WH

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Hi Guys,

I have a solution to your resistor ball problem:

I flattened the ball, drew the schematic and loaded it into LTSpice circuit simulator, running on a laptop. I added a 1000 volt battery to the schematic and connected it to two diametrically opposite points. I ran the simulator in DC mode, and it produced a list of all the nodes with their voltages, and all the components (battery and resistors) with the currents through them. Knowing the applied voltage and the battery current, I calculated the resistance for question one.

I repeated this with modified diagrams, to obtain the answers to questions two and three.

Results: I calculated Q1 answer as 1000Volts/0.00647059Amps = 1,545,454 ohms, which agrees with your answer of 1.545 Megohm.

I calculated Q2 answer as 1000/0.0015412 = 648,845 ohms, which agrees with your answer of 0.65 Megohm.

I calculated Q3 answer as 1000/0.00149481 = 668,9891 ohms, which agrees with your answer of 0.67 Megohm.

I think I could claim to have a greater accuracy than other solutions.

I attach the following files:

(1) Three asc files, one for each question, (these are LTSpice simulator files) just in case you have a PC with LTSpice or a compatible circuit simulator, and are able to run them.

(2) Three schematic diagram (pdf) files, one for each question. These are essentially the same except for the measurement connection points.

(3) Three “Results” files (jpg), being a small portion of the simulator dc mode readouts. The only results of importance here are the very last entry, "I(V1)" on each sheet, which is the battery current. The applied voltage is 1000 volts, so the resistance is obtained from these two figures.

(4) A plot (pdf) of the “Transient” simulation for Q1 only. This is not necessary for the solution, but it does give an answer without any manual calculation. In this simulation, LTSpice plots the applied voltage and the battery current; it also calculates and plots the resistance. So you get three lines on the graph, blue for the voltage with a scale second from the left, green for current with a scale on the right, and red for resistance, with a scale on the far left. And as you can see, the resistance is midway between 1.54545 Megohm and 1.54546 Megohm, confirming the manual calculation. (Being dc, the graph doesn’t look much, but it also works for ac and transients.)

Regards

Ron Badman (ZL1AI)

THE SEDUCTIONS OF ELECTRONICS

...and this is how a dimmer looks designed by Gerrit Reimann (Germany).

WH

THE SEDUCTIONS OF ELECTRONICS

Marc von Vahl (Germany) has framed and backlighted some nice PCB designs. Have a look WH

Some precisations about the "gold number"

PHI in electronics is still triggering a lot of people. Please find Rafaels precisations on the 'Gold Number'

WH

Salutations!

First I have to note that Phi is not the "Golden ratio", as you stated in your article. Exactly it is the "Gold-number", or "Number of Phydias", as it is present in the architecture of the Parthenon, in Athens.

Well, exactly "Phi" is the limit in the ratio of two consecutive numbers in the series of Fibonacci. It is a perfect "irrational" number, and as for "Pi" or "e", it only can be defined by a relation in a series of numbers. In this case it also represents the solution for the "Aurea proportio" in the division of a segment. It seems you think that Phi was firstly defined by Pacioli. In fact it was discussed by Euclid in his "Elements", as you can read in the following articles.
http://en.wikipedia.org/wiki/Euclid
http://www.pauloporta.com/Fotografia/Artigos/epropaurea1.htm

When you consider the ratio between three segments which satisfy that L=a+b, while L/a=a/b, the calculation brings us the formula X²-x-1=0, whose solution is x=(1+5^1/2)/2; but also x=(1-5^1/2)/2. As the second solution is not a real number, then we use the first for the operation in the physical world, and we call it "The Golden number".

Well, the fact is that the Fibonacci series is present in a lot of events, in the nature. It is the factor for the growth of a specimen, for the "Harmonische" (tempered) scale of music, for the aesthetic look of a sculpture... But you also find it in our own body. It is the ratio between the facial segments, between the length of the members... Considering this, and as electronics is only a matter of nature, it is normal than you'll find "Phi" in several effects. For example, this is the ratio in the growth of a Larsen signal, or the dumping factor in a natural attenuation. Actually, whenever you have any event where several (more than three) values of the same magnitude vary in the time, or in a ratio of parameters, in a re-entrant manner, you'll meet the Fibonacci series, hence, the Golden number in the progression.

As you can check, the value is not steady till you consider larger numbers in the series. For instance, as the series is caused by he addition of the precedent pair, the ratio between 2 and 1, 3 and 2, 5 and 3, 8 and 5, is far away from Phi. This is the cause that normal observations don't consider the fact, as the values are limited to a few observations, and the Maxwell theory provides an exact answer to the continuous environment (in the linear equations domain). But really the matter is that Phi and the Fractal geometry have a lot in common; thus, the "Golden ratio" is a simple approximation to the phenomena of "fractal growth".

Then don't ask for "applications" where "phi" is of use; better if you ask for the contrary, which phenomena don't fit the theory. Or if you like, ask for examples of how it is observable in the electronic field.

For instance, whenever you have to compute the impedance values for an attenuator, and you need match commercial values, sure than Fibonacci will come in your help.

Best regards
R. de Miguel