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.
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 →
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.
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 →
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.
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 →
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 →
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 →
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 →
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.”
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.
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 →
Sodium Acetate: a chemical compound made by combining acetic acid and sodium bicarbonate, or simply just plain old vinegar and baking soda. It is used as a flavouring ingredient in snack foods and in hand warmers. Chemical formula: CH3COONa.
This is our second attempt at experimenting with sodium acetate (also known as “hot ice”). The aim was to create a tower using a solution of sodium acetate and water. It was a success!
Disclaimer: Kids’ Resource Center or the person who posted this video are not responsible for any harm or injury caused in using the information contained in this video. Use the information at your own risk.
I made this video to show how an elevator affects the magnetometer trace. This is something, for those using a magnetometer to detect earthquake precurors, to be aware of. Notice the characteristic of the trace. Not to be mistaken as an earthquake precursor.
(Editor’s note: Simon is using the magnetometer described in this post. He lives on the 7th floor and sees very little traffic noise on his daily recordings, but at certain times of day he had been plagued by some very regular signals, always about the same size. In this video he shows how he finally tracked down where they’re coming from.)