mm-hist.htm; updated: 01 January 2007
History of the MicroMag System
Since the beginning of my modeling career I was interested in smaller
models, the biggest internal combustion motor I flew was a 1.5 cc Webra Record
diesel, the others were the 0.8 cc Webra Piccolo diesel and the Cox PeeWee 020.
I started competition flying with some A-1 gliders but mainly in Coupe d' Hiver
rubber. In this class I became twice the national champion. Both classes are
the smaller version of the World Championship classes A-2 and
When I started RC flight money was a bit of a problem, so I tried to build some gear of my own. Not too successful at that moment but I made some flights with the illustrious galloping ghost system. This is basically a single channel system where the transmitted tone is pulsed. Right-left control is achieved by changing the on-off ratio, where e.g. right can be on and left is off. Changing the pulse frequency could be used to control up-down. The
The magic of the Galloping Ghost system was that it worked! And it was
lighter than any other 'multi' radio system at the time. But, the control was
far from subtle. The single channel variant was used by several suppliers in
the 60's like
A photo of Bentert's receiver and actuator as published in Aeromodeller March 1964
This inspired me to make one myself my actuator weighting
In 1972 Dieter Engels published the do-it-yourself PicoProp system in the German Magazine 'Modell'. This was a single channel analogue proportional radio with a special transmitter and a feedback servo. He integrated the good but simple radio and the servo electronics on one PCboard, where also the clever servo mechanics made from a Swiss TO5 motor with 1:141 reduction box and the remains of a carefully disassembled potentiometer. This complete unit weighed about
I made this system and flew it in my first R/C electric flights in 1974.
The PicoProp single channel board with gearhead for the servo.
It is a pity that I don't have the system itself anymore or even a photo
of mine. The model, with the fuselage rebuild is still flying, now with a
Speed-300 and a 3:1 reduction driving a 6 x 5.5 Graupner speed prop. The model
The Sub Mini as it still flies now.
Around 1985 I started again with the LM1875, an IC from National
Semiconductor meant for toy R/C. It had an AM superhet radio with decoder for 2
channels and circuitry to adopt two extra switched channels. Super for
lightweight R/C at the time, I thought. I designed very nice receivers for this
IC that worked but not very well. Some small commercial receivers have been
made with it but none were a real success as far as I know. The Rx was
In 1994 Herbert Hoger published a small FM receiver of
The LM1875, the Herbert Hoger receiver and my version with servo electronics
I build it and was not entirely satisfied. The Rx had no IF filtering at
all and a ceramic discriminator, a combination that is not good in blocking
interference. Also the IC for the Rx was rather big as it was intended for
double conversion and only a small of the IC part was used. In that time I came
into contact with Wijnand de Joode a very good FreeFlight indoor scale builder
and flyer. His dream was to build and fly Peanut scale models (
An action photo of the FIKE-E in
flight, Me at the controls and Wijnand de Joode on my right.
The Fike is a very fine flyer, although it doesn't have any dihedral the model turns with grace.
I started to design my own Rx along the Motorola Mc3361. I found some very small ceramic IF filters and LC discriminator filter. This Rx with the servo electronics was a direct success. All parts were carefully picked for low voltage performance as the weight of the batteries was (and still is) the remaining barrier for smaller and lighter planes.
Two sides of the first generation of the MicroMag receiver together with the current version.
The first plane was a PonyMax build by Wijnand de Joode. It is a Czech
homebuilt with simple lines and good proportions,
The Pony Max, build by Wijnand de Joode, flown by Rick Ruijsink
This power combination is still used in the majority of my models. Its
first flight was at the 1996 fair in Sinsheim, where the European Slow flight
really took off. Walter Scholl flew his superb
Rainer Mugrauer flying between the legs of nine tables
There was so much interest in the radio that I was forced to plan production. That proved to be more time consuming than I expected. The design work on servo's and radio seemed relatively easy, now all the difficult parts were working properly. One of the problems that I encountered with the first hand made pre-production models was one of compatibility. All the electronics except the speedcontroller were integrated on one PC board, which meant that the channel allocation was fixed. As Graupner/JR always has throttle on channel #1 and e.g. Futaba always on # 3, it would have been required to make two versions. With the fixed crystals this would explode the number of variants that I and/or a dealer would need to satisfy his customers. I also had one client for whom I made the Futaba version and when he moved to Graupner I had to change his receiver back. The other snag was that the neutral timing of the channels had to be adjusted by hand through the placement of individually picked SMD resistors, as the non-computer transmitters have a trim range that cannot cope with the tolerance in the normal timing resistor-capacitor. A few of the pre-production radio's went to the R/C CO2 guru in the USA Henry Pasquet.
Henry Pasquet with a handful of CO2 models.
His positive and critical comments were very welcome, he brought me in contact with Bob Selman, an enthusiastic indoor flyer who is a talented, professional microprocessor programmer.
Bob Selman with his Daisy
We discussed the problems (I don't like the euphemism 'challenges') and Bob promised me we could solve them and he was right. It took some time but it was worth the time. We could, after a lot of bench and later flight tests (one at midnight under the light of a street lantern) realize all the goals.
The original Daisy.....
...... as a testbed for the microprocessor development.
Furthermore one 8 pin IC did replace: one 14 pin, one 16 pin IC, four
transistors, two capacitors and ten resistors. The old receiver was 15 x
The new MicroMag reciever and speedcontroller from both sides on my fingers.
The servo's were improved by using custom made neodym magnets and
specially orthocyclic would coils. This winding technique ensures the optimum
hexagonal wire packaging. This yields the highest magnetic field for a given
mass of copper. The amount of copper in relation to the mass of the magnet was optimized
as well. Two sizes of magnetic actuators are now in production. The small one
Two small and two 'big' actuators mounted on a small balsa tray
An integration of the speedcontroller and the Rx has been considered and
tried, but sensitivity to interference increases, and the 'heavy' motor wires
will be longer, in fact increasing the weight. Also the flexibility for the
producer, dealer and buyer/user is degraded, so this idea was abandoned.
A separate small speedcontroller that is able to handle 1.5 amp was designed. Part of its intelligence is built into the receiver, so these two go together. You cannot use this controller with a normal receiver, you cannot use the MicroMag receiver with a normal speedcontroller. You can use the MicroMag receiver without speedcontroller in a CO2 model or a glider.
Update 01 January 2007
Some years after the introduction of the MicroMag system other suppliers came with their own systems based on magnetic actuators. To name a few http://www.jmp-solutions.com, http://www.microinvent.com, and http://www.microplanesolution.com/index.htm for 27 to 72 MHz systems for use with conventional transmitters. Or on http://www.plantraco.com/hobbies/product_butterfly.html you will find a system on 900 MHz. The ultimate light system based on 27 th 72 MHZ AM transmitters cn be found at http://microflierradio.com.
MicroMag is not available anymore. We are currently considering a new generation of micro radio control systems.
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