Author Archives: graeme

AM radio, variometer tuned

variometer-tuned AM radio

This was an experiment to see if there was an easy way to avoid having to make a variable capacitor. The previous designs I made using a home-made variable capacitor, although cheap to  make, still needed quite a bit of time and effort. This one was surprisingly easy and works really well. It’s a bit strange having to tune it by swinging the coil around, but one gets used to it.

This design used fixed capacitors in the tuning circuit. Tuning is accomplished by varying the inductance instead. This is accomplished by a variometer – a coil wound in two halves, one inside the other in such a way that the angle between them can be varied.

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A little “hands-on learning” goes a long way

Many students have been here over the years, making various handcraft projects, and I’m always eager to hear feedback about how the experience has influenced their lives or schooling afterwards. Continue reading

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DIY fluxgate magnetometer for experimenters


I don’t think I’ve ever made anything with such an impressive-sounding name before. Doesn’t it sound like something out of a sci-fi movie?

I didn’t make this as a project for my students – it’s a bit advanced. Rather I made it as part of my ongoing quest to record electromagnetic earthquake precursors: one of the ways in which they might be observed is by recording small changes in the Earth’s magnetic field. Thus my interest in magnetometers.

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Simplest Seismometer – Experiments with direct recording through PC sound card

In this post I am not talking about the chopped audio method used in all my previous devices. This one is just straight audio – directly into the PC’s sound card.

Some time ago I had bought into the idea that “you can’t record earthquakes through a PC’s sound card because they don’t respond to low frequencies,” in fact I had repeated it myself. But recently I’ve found that this is not strictly true for all sound cards. Very long period waves from distant quakes will certainly not register much through any sound card, but on some cards, quite good results can be obtained with local quakes and P waves from strong, distant quakes. (The trace in the above photo shows P waves from a 7.3 quake in Japan, a little left of center. Ignore the other stuff to the right of it; that’s “student quakes”.) Continue reading

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Summer 2012

Several classes were run this summer. A few projects were repeated for the new, mostly younger students, while some of our older students made the pendulum seismometer described in this previous post.

This is quite an advanced project. While we did spend some time on theory, such as the differing speeds of P and S waves and how their arrival times allow us to calculate how far away an earthquake was, we didn’t go into much more as it starts to invlove math concepts that are way above their level. However, as they learn more in school, I’m sure they’ll get much more out of it than most, since they will have seen those theories in action in the real world.

Cutting wooden pieces for seismometer base

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Computer Game Addiction and What You Can Do About It

By Graeme Keon

The father’s sentence was abruptly cut off by the boy’s, “Well I don’t care! OK?!!!” shouted in a kind of sulky, “Look what you’ve done to me” tone of voice, then the “BAM!” of the slamming door. Another futile attempt at talking some sense into him was over. The father got a grip on his temper, mulled over some possible disciplinary actions, then finally walked away in a quandary. Coming down heavy on him had never helped in the past – it only seemed to worsen the situation. At least it was quiet – nothing but a few keyboard and mouse clicks from the other side of the door. Continue reading

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Do schools kill creativity?

In one of my favorite on-line videos, Sir Ken Robinson gives a very entertaining talk on education and how it undermines creativity. The case he presents is very much in alignment with the content of the book, Motivation to Learn, especially in regards to a person’s native interests and talents and what miracles can result when these are nurtured in a child. He gives a wonderful example, starting at 15:06 minutes into the video, about Gillian Lynne, whose choreography can be seen in the long-running stage musicals “Cats” and “Phantom of the Opera.” The account of how her talents as a child were recognized and allowed to blossom is a valuable lesson for parents or anybody working with children.

The title of the video is “Ken Robinson says schools kill creativity”. It includes Chinese subtitles.

And another great speech on education was given about 4 years later, in the following video. Continue reading

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Simple AM and Short Wave Radio Projects for Beginners

AM radio with spiral-wound coil and home-made tuning capacitor


The radios described here are a regenerative design utilizing a single JFET and cheap audio amplifier integrated circuit.

(JFET: “Junction Field Effect Transistor”, a small electronic device which can amplify radio signals and is used as the basis for these radios.

Regenerative: employing “regeneration” (feedback), a technique used in simple radio designs to increase the amplification of radio signals.)

Here in Taiwan, there don’t appear to be many people dabbling in radio as a hobby. My recent experiments with simple radios that students might be able to make, have been regarded somewhat like “black magic”. So it hasn’t been too difficult to get students interested in it and a few of them have made the radios described below with very good results. Continue reading

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Cheap seismometer using sound card and Amaseis – now running under Windows

After about a year and a half of messing around, I finally got this very cheap seismometer system working and displaying real-time data under both Windows and Linux (More on how to set up Linux later.) Educationally, it has great potential.

It consists of the sensor and an interface box. This interface is radically different from traditional digitizing methods. The earthquake signal, after being amplified, then modulates a fixed 5 KHz audio tone. That plugs into the microphone socket of a computer running three pieces of software under Windows (XP in the one shown here). They are, 1) the one I put together – “seismochop”, which retrieves the earthquake signal from the audio tone and converts it to serial data, 2) a virtual serial port package called com0com which acts as a relay, and 3) Amaseis – software that records and displays earthquake data. These three can be downloaded free.

This very cheap and rather unusual way to digitize an earthquake signal was inspired by my experience in ham radio, when AM transmitters were common. When I found the same principle (amplitude modulation of a carrier wave, or more correctly here, pulse amplitude modulation) used in “cheapchop“, even including the basic software, I was able to get it working.

Here is a screen shot of a local quake I recorded today. There’s a DOS window I brought to the foreground for the screen shot. That’s seismochop showing the data samples at about 11 samples per second. Continue reading

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“Why don’t they teach kids to be responsible?”

On page 21 of All About Motivation to Learn, the point is made that the current education system contributes to irresponsibility in children. That if they’re allowed no control over their education, if they are not consulted, their thoughts and opinions overruled or ignored, then they will feel no personal responsibility for the result. Much like this learner driver being “pushed out of the driver’s seat.”

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BFO Metal Detector – Student Project

(* BFO: “Beat Frequency Oscillator” a technical term describing the most common operating method used by metal detectors.)

The previous post mentioned the metal detector our students made during the winter vacation.

Following are the technical details:

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Winter 2012 Handcraft Classes

A great activity that will get kids out of the house during vacations (and away from computer games) is hunting for “treasure” with a metal detector. This winter, after some R&D work I finally worked out a design that would be easy enough for youngsters to make and use, but still powerful enough to find small things like coins.

(The technical details of it will be posted soon have been posted in a separate post here.)

Although the electronics work was not totally new to them (these students had made the morse key project earlier) it still required close supervision, so we only ran two small classes of three students each. About fifteen hours were needed to complete the project. Continue reading

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Summer 2011

Several classes were run this summer. Once again we found it very difficult to get the students to go home at the end of the two and a half hour course periods. It seems they just can’t get enough of this! Here is a summary of their activities:

Most of the projects, such as the crane required some woodwork so a lot of sawdust was flying around in the beginning.

The 4 wheel drive car continues to be a popular project and several were made this summer.

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Student Seismology Research Station – Seismometer and Magnetometer Recording Via Computer Sound Card

(Seismology = the study of earthquakes
Seismometer = device for measuring earthquakes
Magnetometer = device for measuring magnetic fields)

One cannot ordinarily record earthquakes via a computer sound card as they don’t respond much to the slow vibrations experienced in earthquakes. (Update: not strictly true. See my latest on this: Simplest Seismometer – Experiments with direct recording through PC sound card) However, with some cheap electronic trickery and clever software, it can be done, and very adequately for the purposes of study. The seismometer above, made by a high school student, in its first night of testing recorded this local 3.8 quake – a magnitude 1 in Taipei:

(click on the pictures for larger versions)

and as a surprise bonus, some filtering of background noise revealed this distant quake as well. It was a 5.9 from 1000 km away in the Philippines.

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Making animated GIF pictures

(Graphics Interchange Format, “GIF” is a computer image format that has become popular on the internet.)

It’s not very difficult to get children interested in computers. (What an understatement.) And if one hopes that their interest can be channeled into something useful, this is a fun way to start. Animated GIFs are a great way to create interesting web pages, blogs email attachments etc., and the ability to create them will be a useful skill in any future internet-related career.  It’s not hard to learn how to make them. I’m describing here how I have made them on the Linux operating system. I use it for two main reasons:

1) It is all freely available software, so one will not be tempted to use pirated software and set a bad example.

2) Children are rarely familiar with it so they will not be distracted by their favorite games, chat programs etc.

These were some of my students’ first attempts.

Jonathan's table tennis player

Lily wagging her tail. Made by Ariel

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