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REMOTE CONTROL By BOB YOUNG The beginnings of remote control Bob Young has had over thirty years experience as a designer and manufacturer in the field of remote control, particularly radio control. He is the proprietor or Silvertone Electronics, which has been notable for radio control products for many years. In this, his first article in SILICON CHIP, he introduces the subject of radio control. When Leo Simpson approached me to do a monthly column on remote control, I was a little hesitant at first. While I have written quite a lot for radio control model aircraft magazines during my 26 years as a radio control manufacturer, I have never had the chance to discuss all aspects of remote con-. trol, either model, industrial or · commercial. , Not that this presents any real problem, for during those years I have undertaken projects covering :an of those aspects and many more, including some low key military applications. I Perhaps by way of introduction then, a brief description of some of the more interesting projects in remote control I have been involved in would be in order. But first to the name. Originally, or as the Bible puts it, " In the beginning", remote control was generally accomplished by the "wireless" transmission of one or more frequenies in the electromagnetic spectrum. This was the system used by Tesla in his model submarine, the very first R/C [radio control) model, demonstrated in 1896. Tesla used two separate carrier frequencies and an AND gate [another of his inventions). Thus, as a general rule, remote control became "radio control". Technology has rendered this term obsolete with the development of ultrasonic, infrared, laser and long range wire-guided systems, and a host of other mediums of transmission. To further complicate things we now have radio controlled people, as many service vans tell us on their advertising panels: "Radio Controlled, 24 Hour Service". Thus our field of interest is better described as the ''Remote Control of Mechanical Devices" or if a vehicle, the more common "Remotely Piloted Vehicle" or RPV. This now leaves the way open to employ any transmission medium we choose. The early days It appears that Leo remembers me from the early days at Silvertone Electronics. Around 1965 or thereabouts I developed a single channel TX (transmitter) and Rx [receiver) for use in models. This early super-regenerative receiver from Silvertone Electronics was a hybrid unit employing an XFY34 valve and three germanium transistors. 4 SILICON CHIP Before servos became available, model aircraft were controlled by rubber-driven escapements which gave left & right rudder control. This wa:s very popular with radio control modellers of the time and was regarded as state of the art. It had a one valve super-regenerative front end using an XFY 34 to give a bandwidth of 300 to 400kHz. Following the front end were three transistors, the final stage driving a miniature relay, which in turn drove an escapement. The escapement was a rubber band driven actuator which was used to turn the rudder; the only control available. It was operated in sequence: first left, then right. There were no steps in between. If you forgot which you used last, left or right, you just found out the hard way. All this was driven by a 1.5V penlite cell and a 22.5V hearing aid battery supplying the HT (high tension). Oddly enough, these sets were extremely reliable and gave good results in practice. We did some very satisfying flying with them and the only reason we stopped servicing them was that hearing aid technology zoomed ahead and valves and 22.5V batteries became difficult to obtain. Over the years we gradually developed these sets into a fully transistorised unit which was much nicer to handle, with its single 6V battery and no delicate valve filament to worry about. And of course super-regen gave way to superheterodyne. Electrically-driven servo units eventually took over from escapements. This early unit is Japanese made and is big & bulky by modern day standards. Reed units Single channel receivers gradually gave way to tuned reed units. These were a real eye-opener and I tend to feel sorry for any modeller who missed this era. Here we used a bank of 10 or 12 tuned reeds to filter out the audio tone modulation, thus giving true multi-channel operation. Heaven had arrived on Earth at last. These 12 tones had to be tuned inside a full octave to avoid har- Tuned reed units were used to fiter the audio tone modulation on the receiver output to give multi-channel control. This unit employed 10 separate reeds. monies and placed extraordinary demands on the tone generator, for they had a bandwidth measured in just a few Hertz (typically 4-BHz), or as we used to say in those days, a few "cycles per second". If there was any drift in the receiver, it would be all over for the model. Modern solid state oscillators have no problem achieving this degree of stability but in the late 50s it was almost impossible to achieve in a portable unit. The reedbank itself was very cleverly constructed right from the very beginnings and changed little in the 10 or so years they were in commercial production. Practical results were poor though, until Bob Dunham of Orbit in America, produced a toroid stabilised tone generator which revolutionised the sport of radio controlled model aircraft. Reliability became accepted as the norm and the really good flyers produced results which were almost indistinguishable from those seen from modern proportional control units in use today. This was quite a feat, keeping in mind that we only had on or off servos, no proportional. You learned to pulse the controls for half throw. The other major problem and one that still shows up today in modern remote control systems, was the lack of simultaneous control. Modern garage door units, for exOCTOBER 1989 5 This view shows the works of a modern radio-controlled model aircraft. The multi-channel receiver at left drives a number of servo units for full control over throttle, ailerons, flaps, elevators, rudder & nose gear steering. ample, now give up to 10 separate switching channels (in remote control a decoded data stream is called a channel) but not simultaneously. This is no problem when switching on lights but in a model aircraft travelling at 50 metres per second there is no time for queued commands. Also some manoeuvres call for the application of three or more controls simultaneously. Thus a successful remote control system for vehicular work must be capable of simultaneous multi-channel transmission with a response time of less than 100 milliseconds. Modern digital systems can deliver 32 channels very easily in less time than this. Interestingly enough, despite this being faster than the human response time (200 milliseconds), you can still notice the slight lag in control response. For competition flying, 50ms is the absolute maximum cycle time with the typical figure being around 14 to 20ms. To arrive at this modern system was a constant technological battle every inch of the way. I started by producing a super-regen valve/ transistor hybrid unit, using 10 miniature relays and a 22.5V HT 6 SILICON CHIP battery, which had to be large enough to drive the relays. The whole airborne system including batteries came out at about 22 ounces (this was before the days of metrics, remember) and it was big and bulky. To give simultaneous control of two channels, we mixed two tones which halved the power to each reed and made tuning even more difficult. Reed gaps had to be adjusted and in the early days before transistorised amplifiers to drive the servo motors, you had the inductive load of the relay on the reed points which resulted in pitting. The relay contacts had to be adjusted and kept clean as well. No instructors On top of all of this you had to teach yourself to fly. No RCAS (Radio Controlled Aircraft Society of NSW) qualified instructors on flying fields in those days. Ah ... they were the good old days. But we really did enjoy it. The incredible difficulties that each of us faced in bringing home the model intact after a day's flying generated a sense of camaraderie no longer seen these days. And the sense of achievement - it was indescribable. However above all of this the thing that sustained our interest was the constant dream of the big one: simultaneous proportional control. When we got that, we could build scale Spitfires with retracts. To cut a long story short, we did eventually get just that and much, much more but very few of us ever built that scale Spitfire with retracts. Such is the stuff that dreams are made of. My first production proportional set was a fully transistorised, 5-channel PPM (Pulse Position Modulation), superhet unit with an airborne weight of 450 grams (I measured it as 16oz but I've converted it for the benefit of those who have forgotten ounces). I could not believe that I had finally achieved true three dimensional flight with five simultaneous controls and the freedom and accuracy of manoeuvres that accompanied this amazing technological achievement. And it was amazing; make no mistake about it. I still look in wonder at the incredible cleverness of the men who made all of this possible. I dislike intensely the modern jaded consumer who has everything This modern radio-control transmitter uses pulse code modulation (PCM) techniques to provide simultaneous 7-channel control. The aircraft is flown by manipulating two joystick controls on the front panel while optional channel mixing is provided by the front-panel switches. and never stops complaining, or worse still, never stops to consider the magic of it all. They were heady days, for we were blazing trails where no.man had gone before. But the most amazing thing of all, from my point of view as a technician, was the lack of tuning resulting from the use of .Pulse Position Modulation (PPM). It was unbelievable. These days it seems incredible when I look back at just how difficult it all was. When I look at the modern control unit with microprocessor control, inbuilt memory, voltage monitor, liquid crystal display and everything else that opens and shuts, it takes my breath away. It all seems so long ago and I guess it was, for I flew my first R/C model in 1955. Yet even today I have not lost my fascination for the concept of wireless control of model aircraft. To me, it is the ultimate in technological achievements and yet Tesla was sailing his multi-channel radio controlled model submarine long before Marconi ever achieved his reputation. That man was absolutely incredible. But that's another story. Other applications As a result of my experience in radio control, I gradually became interested in the wider applications and thus began to involve myself in industrial and commercial projects. Some of the early ones included radio control of flag poles, the window washing robot for the Sydney Opera House, a full size Volkswagen 1600 TLE, toasters, chairs and so on. You name it, I have done it or at least, thought about doing it. It was all good fun but very dangerous at times. Hanging off a flag pole in a high wind, 22 storeys above the ground is not my idea of the best way to spend an afternoon. Flying military target models, in which people are constantly putting bullets through receivers and batteries and servos, and which results in aircraft digging furrows near where you are standing, is another. Nearly running over a curious policeman with a driverless Volkswagen rates low on the scale also. And of course there was the day we had to test the droparm switch on the Opera House window washing robot, only to see it skid to a stop, totter at the end of the glass roof, and vanish over the edge of a 20 metre drop, nearly taking an apprentice with it. When we peered cautiously over the edge, there was 90 kilograms of robot dangling in space at the end of a rubber hose, with a quick disconnect fitting the only thing between it and oblivion. All of this on a wet, glass roof, pitched at a very unpleasant angle. But all in all, I would have to be listed among those who really did enjoy my work, that is until the economic system fell over in Australia and manufacturing became a dirty word, particularly in consumer electronics. Thus, in keeping with all of the survivors, we fled to the niche market. Here we found much of interest including radio control of military targets, robots for film companies, radio controlled concrete placement booms and so on. So from the occasionally dangerous we now moved into the really scary: machines six storeys high, fullsize pilotless aircraft that fly over the horizon, robots that require 24 channels of simultaneous control to do the job (and operators with only two hands), trolleys weighing 80 tonnes, and much more. New technology Now we began to call upon the very best technology had to supply. The new techniques include pulse code modulation (PCM), microprocessor coding and decoding, input noise algorithms, multiple OCTOBER 1989 7 ' I I This remote-controlled model ship was designed by Nikola Tesla in the mid 1890s and relied on a two-carrier system. Another of his designs was submersible. verification of valid data, stringent fail safe requirements and many, many more safety features. Which leads us nicely into the item at the very heart of R/C applications. That is, just how applicable is R/C and the technology involved, to your application? For example, PCM (Pulse Code Modulation) is ideal for industrial control of machinery but can be too rigid for model aircraft work. This sounds a little confusing so let me explain. When we began flying proportional control in 1964, all of the first generation PPM sets had a built in "fail safe". Thus the incoming pulse train was examined and any spurious pulses a hove a limit previously defined as tolerable resulted in the set being shut down, the servos neutralised and the throttle run back to low. All this sounded highly desirable until the practical results came in. Very quickly fail safe was defined as " That circuit which neutralised the controls on the way to the crash". What the designers had forgotten was that the modern aerobatic model aircraft was doom8 SILICON CHIP ed once the controls were neutralised. Cutting the throttle wa s a very big help however and reduced damage significantly. Second generation systems did away with the failsafe system and relied upon random noise to average out the controls, or even the odd snatch of restored control, to keep the aircraft flying until the interference passed. Sometimes the interference did not pass and you just fought the model all the way to the ground but at least you could fight. Once that failsafe locks out, it' s all over, that is unless the model has good inherent stability. Then you just lost it, for it flew away. I once lost a model in Sydney and had it returned from Leeton (in Victoria) months later. Flying through noise and interference was the system used until recently and served us well for over 20 years, giving excellent reliability in use. Someone then r ediscovered the failsaf e when PCM sets arrived on the market and even now after several years, the correct way to use PCM sets is still causing confusion in the model aircraft field. The big difference between the two systems is that PCM uses microprocessors for encoding/ decoding and the old PPM (Pulse Position Modulation) system uses logic. Thus, you must choose your technology very carefully to suit your application. At least the modern PCM set now gives the option to configure your own fail-safe parameters, even to switching it out completely if desired. The situation in industrial control is quite different. As zero deviation. from the norm is required, any interfe rence can be made to shut down the system immediately until the signal is once again valid. PCM is ideal in this application. Wired controls But is R/C the correct technology for your application? There is nothing cheaper and more reliable than a piece of wire (except perhaps two pieces of wire in parallel) and designers of wire guided missiles realise this only too well. The Argentinian Cruiser " General Belgrano" was reportedly sunk from a range of 45 kilometres by two Mark 24 "Tigerfish" wire guided torpedoes. Now that is a lot of wire but it is one way of ensuring the torpedo is not interfered with on its way to the target. As it turned out the report was incorrect and the torpedo was an old Mark 8 non guided. One interesting sidelight here is that the Tigerfish was thought to be unsuitable for sinking a surface vessel. By introducing a radio link, you increase the complexity and cost and reduce the reliability. There are many ways to make the link continued on page 111 This early single-channel superhet receiver was designed for use with motordriven escapements or could be used to drive a single servo. Notes & Errata Touch Lamp Dimmer, June 1989: As noted in the article, the revised version of the SLB0586 does not require diodes D1 and D2 but they will not affect circuit operation if they are left in. However, now that the revised chip has been released, as SLB0586A, it has been found not to work in the circuit as published. To make it work, two components must be changed. The 680k0 resistor must be swapped for a 0.33µF capacitor while the .0022µF capacitor should be swapped for a 1ookn resistor. These components will fit without any modifications to the PCB pattern being required. If your kit has the original SLB0586 IC, no circuit changes are necessary. Studio Series 32-Band 1/3 Oct- ave Equaliser, March, April 1989: one of the four 220µF electrolytic capacitors shown on the main equaliser in the wiring diagram (Fig.1(b} on page 48 of the April issue} is reversed in polarity. The capacitor in question is connected to pin 4 of IC2. Ultrasonic Car Burglar Alarm, July 1989: the wiring diagram on page 63 shows one side of the siren connected to chassis. It should connect to + 12V, as shown on the circuit on page 61. Garbage Reminder, August 1989: the .047 µF supply bypass capacitor shown between IC6 and IC7 on the wiring diagram of page 50 is shown as 0.1µF on the circuit of page 49. The value is not critical though and either 0.lµF or .047µF is OK. Advertising Index Allied Capacitors .... .... .. .... .... 65 Altronics ...... .. ...... .. ....... 46-49 Arista Electronics ............. .. .. 1 7 Banksia Information Tech ...... 89 Board Solutions .. .... .. ... .......... 9 Dauner Electronics .. .. .. .. . .. ... 1 3 David Reid Electronics ..... 56,57 Dick Smith Electronics ..... 68-73 Electronic Solutions .. ..... . 14, 15 Elmeasco .... ..... .. .. ..... .... .. OBC Geoff Wood Electronics ..... .. IFC Harbuch Electronics .. ... .. ... .. . 94 Hycal Instruments .. .... .. .. ...... 13 Jaycar Electronics .. .. .. .... 36-39 80-83 J.V. Tuners .. ... ............. .. ..... 94 Kepic .... ... .. .... ... .. ........ .. .... . 95 Novocastrian Electronics .... .. 1 9 PC Marketplace ....... .. ..... ..... 31 Pelham .. .. .. .................... .. . 112 Power-Sonic Corp .... .... ..... . IBC Philips Test & Measurement .. 89 RCS Radio ... .... .. ...... .. .. .. ... 102 Rod Irving Electronics .. ... 96,97 WIA .. .. .. .. .... .. .... ............... 103 tell me where I can get one? SILICON CHIP is a great magazine. I like the Vintage Radio section and the Serviceman's Log. What happened to the Technology Letters? (A.R., St George, Qld}. • Tunnel diodes have become very rare. In the 1960s they were regarded as the wonder diode but very largely they look to have been a solution looking for a problem. Their special claim to fame is that they have a "negative resistance" characteristic which enables them to be used as amplifiers or oscillators right up to microwave frequencies. Now, most of the applications for tunnel diodes appear to be fulfilled by more conventional devices such as microwave transistors and Gunn diodes. General Electric was at one time the major manufacturer of tunnel diodes but this is no longer the case. However, we have been in contact with the agents for General Electric, GEC Components, and they have indicated that they may be able to source tunnel diodes, depending on the type number and quantity required. If you want to make further enquiries, you can contact GEC Components by phone on (02} 887 6222 or by fax on (02} 805 0272. Remote Control ctd from page 8 secure and military designers are constantly searching for better ones. Some of the more complex included frequency hopping, chopped chirp, exotic encoding and above all else, making the vehicle as intelligent as possible, so that it can perform its task with as little outside assistance as possible. All of this and more will be discussed in columns to come. There'll be simple explanations covering the installation of the equipment into models, care and feeding of nicads, and the correct use of servo arms, plus the exotic. It should be a lot of fun. See you next month. ~ The Way I See It ctd from page 90 ly turned up in disposals stores for 50c each or three for a dollar! "As far as I could see, the only thing the power transformer did was to operate the pilot light. A single wire ran to the nest of pots and another to the circuit board, PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd , Bexley, NSW 2207. Phone (02) 587 3491 . • Jemal Products, 5 Forge St, Welshpool, WA 6106. Phone (09) 350 5555 . • Marday Services, PO Box Avondale, Auckland, NZ. Phone 88 5730 . 19-189, being soldered, of all things, to the piece of PCB foil spelling out the manufacturer's part number! "What does a friend do in this situation? Does one protest that the $300 miracle healing machine is just a con and refuse to proceed any further with the farce? "Knowing the lady as I did, I replaced the crunched diodes with three new ones and assured her that they were a close equivalent to the originals. And of course, as soon as she turned it on, she noticed the difference!" K.W. observes that "thousands of electronic enthusiasts have pulled apart discarded computer boards. How many can claim that they've actually repaired one?" ~ OCT0BER1989 111