Technical Meeting Feedback.

At the January ASTRO Technical Meeting, there were many things demonstrated and talked about. You may ask, does any of this stuff have a practical application? The answer is YES!

Ken brought along a magnetic field detector that he designed and constructed to find electrical cables underground. I had need to locate my neighbours underground power in the last few weeks and so asked Ken if I could borrow his unit. This device relies on current flowing through the cable being detected and so I went searching while they were cooking dinner on the electric stove. The strength of the field is displayed on a meter and almost straight away I obtained a reading. I then followed the path of the cable from start to finish by sweeping the pickup to and fro across the cable. One thing I found interesting was that as the thermostat on the cooker operated, I could see the strength of the reading rise or fall, depending whether it was turning the element on or off. On digging (very carefully) above where the cable was detected I did find it exactly where Ken's device indicated it should be.

Ken also demonstrated a servo unit that he had built. It looks like a similar device may soon find it's way into the self leaning/steering  motor bike/car that was demonstrated at the March ASTRO meeting.

The Fischer and Paykel motor that I demonstrated certainly created a lot of interest as it is such a perfect design to be used as a low speed generator. Also because the coils are so accessable and easily changed for configuration etc it makes a really good choice for Adams type motor experiments. Bob has already found himself one and is at present removing it from the machine.

I think that this demonstrates the usefulness of these meetings as both the hardware and information shared can help other experimenters. So bring along your experiments and devices, finished or not and share your expertise with others. Please don't leave it up to the same people each meeting. Remember, those who bring hardware along get to talk about the subject that interests them  while the "bring nothingers" don't.                                            ............................Bruce

MARCH TECHNICAL GROUP MEETING

Lionel brought along his Adams type motor.

Peter with one of his high power magnets.

The March Technical Group Meeting began at 8.05pm with 16 people present. First up I presented the fuel mixture meter that was featured in the article in the last ASTRO newsletter. Next, Peter showed a gas charging unit that he rescued from the rubbish a couple of years ago. He intends to do some experiments with it in the near future. Peter also brought along a magnetic brake from a lift which could be useful for anyone doing magnetic experiments. He demonstrated how it had different effects on various sizes and shapes of steel. The meeting then drifted somehow onto a discussion on deionised / distilled / Ecovortec water.

Randal brought along a car and a truck generator which he had modified to become rotary converters. The output was wired to two sliprings fitted to the shaft on the front of the generators. Input is 12 or 24 volts and the output is a pure sinewave at 50Hz. The frequency is dependent on rotational speed which for a two pole generator is 3000rpm. A transformer can be wired to the output and so any voltage can be produced, even 240 volts. The estimated efficiency is around 60%. Randal pointed out that during his experiments he removed the voltage feeding the field coils, wired a diode across them and found that the generator still had an output. However he also pointed out that even with this effect there was definitely no over unity happening in the generator.

Lionel brought along his Adams type motor / generator which he had modified since the last meeting. He had changed the magnet arrangement so that when the power pulse is on, the coil repels the magnet and when the pulse is turned off, the back emf causes the next magnet to be attracted into the coil. He now has electronic switching of the pulse and has also experimented with capacitors across the coil to try and achieve some sort of resonance. The value of the capacitor has been in the range of 4.7uF to 10uF depending on the coil windings. By adjusting the timing of the pulse, Lionel found that the current dipped from 1 amp down to 0.45 amps while on 24 volts at a speed of 975 rpm.

Resulting from this demonstration was some feedback from Ken on the choice of FETs in this type of circuit with the main point being that you should use a lower voltage rated FET to get a lower RDS (resistance from the drain source) and thus have less heat wasted in the circuit. The other point that was made was that when using transformer laminations, make sure that they are not shorting out between each other by cleaning up any burrs caused by cutting them and making sure they are insulated from each other.

Ken was the last member to bring along hardware which consisted of a box full of electronic bits which will one day soon be an extremely efficient 12 volt to 36 volt voltage converter. Efficiency should be >90% due partly to the switching resistance of the five FETs in the circuit being under 5 milli-ohms. The converter will run at 20Khz and have a switching time of 30 nanoseconds. The heart of the unit is a powdered iron core that the inductor is wound on. Ken is expecting to have the unit completed by the next meeting and will bring it along to show it running. The converter's eventual use will for use in an electric bike.

We all adjourned to the Kitchen for supper but as it was early, it was decided that it would be interesting for Matthew to give some more insights into his discoveries into number sequences and the meaning of life. After the meeting I was lucky enough to score a short ride in Randal's electric car. The performance was impressive and was comparable to your average four cylinder up to the speed limit of 60Kmh which makes it an ideal vehicle for commuting around the city and suburbs. One thing that Randal demonstrated to me was how well the vehicle rolls once the power is off with no petrol engine to slow it down.

So all in all it was another successful meeting with the last two stragglers leaving the carpark at 12.15am. (I should know, I was one of them!

...Bruce

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Flying Pig Mail Box I have a rather unusual request from a pensioner, it seems she has a mailbox shaped like a flying pig! The pig is repeatedly getting vandalised, do we have any members with the required skills and time that could help with a pig/mailbax alarm, if so please speak to Ken or Andrew S.

No Peters page this month.

Philip James describing his brilliant steering/balance system.

DISCLAIMER:  All information given in this newsletter is for educational purposes only.  No claims are made on or for the validity or correctness of the material provided.  ASTRO S.A. Incorporated accepts no responsibility for any mishaps or accidents incurred by any persons utilising this information.