Features
How the AMB Autocount System works

Getting Counted with the AMB System

Hands up those of you who have heard of Alfonsus Maria Bervoets?  OK, what about Pieter Bervoets? Serpent Cars? Result! Pieter IS Serpent Cars, Alfonsus (Fons) is his brother and if you check out Fons’s initials you get AMB. Serpent were one of the very first RC car manufacturers in the 1970’s and after a disputed result of a World Championship (manual counting in those days) Pieter suggested to his kid brother, who was looking for a University electronics project, that an autocount system for RC cars would be a good idea.  Fons took up the challenge with his friend Frans Hin.  Together they produced the AMB Autocount System in 1980.  In 1983 the AMB8300 system was released and there are still some of them in use today. My club bought one in 1987 and it transformed our race meetings.  We didn’t need to chain someone to the computer all day to press buttons.  We could run meetings when we wanted to, not when someone’s wife/girlfriend could be persuaded to endure a day of purgatory.

Since 1983 AMB has branched out into full sized motorsport, karting, moto-cross, cycling, athletics, in fact just about any sport where times and finishing order are important.  When you watch sports events and see a computer or watch manufacturer’s name claiming credit for the timing, there will almost certainly be an AMB Transponder and Decoder in use. All that from RC Cars!

So much for history.  How does it work?

It is a very simple idea with a very robust implementation.  A small module (Transponder) is fitted to the vehicle.  It sends out a signal.  This signal is picked up by a wire loop, under or sometimes over the track and this sent to a decoder.  The decoder works out the number of the module that sent the signal and records the precise time the signal was received.  It sends a message containing this information to a computer.  That is ALL it does.  The program in the computer does all the fancy stuff to work out race order, individual laps times, overall qualifying etc.  It could do exactly the same thing if someone pressed a key for each car.  The big deal about the AMB system is

  1. No one needs to press any keys.
  2. It is far more accurate than eye to hand response times.

The  AMB systems of the 1980’s (AMB8300/8800) could identify up to 10 cars and in the 1990’s (AMB System 20) up to 20 cars.  Towards the end of the 1990s AMB stated looking at a technology that would allow far more cars to be separately identified.  The earlier AMB systems worked on the principle that every transponder was on a different frequency.  The channels could not be too close together, so there was a limit to the number that could be used.  This is a problem that is not confined to Autocount systems.  The solution that is used is to use a single frequency and send a unique digital code in bursts (300 per second for the AMBrc system).  Up to 9 million different codes can be used.  This is more than enough for every vehicle to have its own unique number.  Thus AMB have Personal Transponders.  When you buy one the number is unique to you.  AMB introduced digital technology for full sized motorsport before RC, so the technology is well established.

The earlier AMB systems for R/C had rechargeable transponders that were fitted to the cars before the race and then usually removed after the race for someone else to use.  The new RC system also has rechargeable transponders, the same size and weight as AMB20 Transponders but red rather than black.  These are charged in the same charger rack as the older ones, to upgrade from AMB20 all you need to replace are the Decoder and Transponders, the Charger and Loop are compatible.  The Personal Transponder (PT) is the big attraction of the AMBrc System.  If you have one you can literally fit and forget.  Just stick the numbers on your car and go out and race.  The advantage to the club is that they don’t have to remember to charge up the rack and no one is going to leave with the club’s transponder in their car!  Don’t laugh, this happens and the Club doesn’t always get their transponder back! Most clubs who have upgraded their AMB20 system to AMBrc have bought rechargeable transponders, sometimes only one set of 1-10 instead of 2 sets, but there are quite a few clubs who use only Personal Transponders.  For a new club the financial outlay is much lower.  Another option is for the club to buy Personal Transponders and provide them to the drivers on a rental basis.

Fitting a Rechargeable Transponder.

The usual place to fit these is in the bodyshell.  The post has a hole for a large R clip to secure it.  The optimum angle is for the post to point up or down.  Slightly off the perpendicular is OK, so a shallow angled windscreen is a popular place.  The signal is very directional and if you mount it with the pin facing forwards, backwards or sideways, very little signal will get to the loop, and you will miss laps.  The reason the signal is directional is so the car counts when it passes over the loop, not when it is nearby.

Fitting a Personal Transponder

The personal transponder gets power from the radio in your car.  It does not need much, less than 10 milliamps. It is not going to shorten your run time.  A fully charged set of 2400Ma cells would keep a PT going for the better part of 2 weeks.  The PT comes with a plug that will connect to your radio receiver.  Just plug into a spare channel or the battery channel if you have an electronic speed controller.  If the PT is getting power, it has a small LED that will light up.  When you connect the PT, make sure the connector is plugged in the right way round.  It won’t get damaged if it is the wrong way round and the LED might light up, but you won’t get good counts.  If you are connecting to the battery socket and the LED is not lighting up, your receiver may not be supplying power to that socket.  Some receivers have a diode that prevents power getting out of the battery socket, only allowing power to come in.  In this case if you don’t have a spare channel, you need to connect both the PT and a servo/esc to a single socket.  You can get a Y lead from your local model shop to do just this.  It has a single plug, to connect to the receiver and 2 sockets, one for the servo/esc and one for the PT.

Once the power issues have been settled, how do you fit it to the car?  If the loop is under the track, the lower the better.  Remember the signal is directional; don’t fit the PT on its side.  You can either use double sided “servo” tape or secure it using screws.  If it’s a nitro car I suggest using the screws.  Nitro can “dissolve” the glue on the tape.  If you don’t need the screw lugs and they are stopping you fitting the PT where you want to, you can easily remove them with a knife.  The PT comes with fitting instructions in English, German, French, Spanish, Italian, Japanese and of course Dutch.

A common place to mount the transponder is over the steering servo.  I’ve done this on lots of cars and never had any interference problems.  As with all electrics, keep the wiring neat, avoid tangles and coils.  Zig-zag the wires and secure with a tie wrap.  If the chassis on your car is metal or carbon fibre, this will absorb the signal from the PT.  Mount the PT where it can “see” the track, near the side of the chassis and high enough up to “see” over the edge.  Once you have fitted it, ask the timekeeper to tell you how strong the signal is. They will be able to tell you this from the Race Program transponder signal display.

The benefits of a Personal Transponder

The biggest benefit of a PT is that it is always there for you!  When its time to race, you just race.  No danger of putting the wrong rechargeable transponder in, forgetting to return it, being held up because the previous user has not returned it, or it falling off when you were on for FTQ.  Don’t forget to put your car through technical inspection though!  Because it is always in, you get timed whenever your car is on the track and the loop is “live”.  Some clubs will run “open practice” while booking in.  The bbkRC Race Software can even book you in while you on the track.  You’ll have to go to race control and pay of course.  If the timekeeper is feeling generous he might even turn the printer on so you can see your practice times.  Even if he doesn’t, the computer can announce your fastest lap.  I’ve included the practice sheet from one of the competitors of the Scottish Indoor GP.  Notice that it includes a set up sheet.  I’ve disguised the name to protect the innocent, not that he needed any protection!

If you have a Nitro car, the LED on the PT is an indicator that the electrics are switched on!

The number of PTs used in RC Cars in the UK and Worldwide is growing all the time. In 2004  the UK RC Boat racers started using them.

  
October 2004

Copyright bbk Software Ltd 2004

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