Lap Counters

04.12.2009 12:56



Lap Counters



The race control counters and timer I built for the  BSCRA track in 1993


Updated March 2004 - part numbers for alternative components added
Updated December 2005 - alternative counters and more on computerised systems
Updated March 2008 &  December 2007 - various minor changes


Lap Counters

ACCURATE lap recording is essential for any serious racing. It saves a lot of trouble if the counters are accurate AND everybody believes they are accurate! Automatic counters can be expected to count the number of times a car passes the counter section in a lane. Counters cannot tell which car is passing the counter strip so the race controller may need to amend the scores if the competitors cannot contrive to go through the counter section in their own lanes. The number of clubs who have had trouble getting their lap counters to work properly, it's not so easy as some people think.

Some makers of home sets have counters specially to suit their track. This article doesn't attempt to cover these systems. I don't know of anybody who has tried adapting these for scratch built tracks - if you know anybody who has made this work successfully why not e-mail me ( ) and I'll add the information to this page / or links to your page.

The TRACK CONSTRUCTION Part 3  described where to put the counting strip on the circuit. But what do you put there?

I could jump straight in and describe the high tech. computer solution, but first lets look at the other options (ancient and modern). Who knows, perhaps a little more understanding of how they work may help a club to get several more years service out of their old counter system and save some money desperately needed to pay the rent!

Hand Counting

Why not appoint one person to count each lane? As we can assume nearly all slot racers have the intellectual capacity to count up to 35 (or whatever) this should be an accurate system. Unfortunately counting laps by hand ranks with counting sheep as an insomnia cure, so people's concentration soon wanders and counting becomes inaccurate. Add to this the need for extra people to stand there and count sheep err I mean laps and it is clear that hand counting is OK as a last resort to complete a meeting when the proper counters break down, but is not a sensible option under other circumstances.

Simple Automatic Counting

The simplest system that can work reliably, and the method that was used by most clubs from the 1960’s is an electro-mechanical counter and a capacitor. Years ago these counter mechanisms were much more widely available at low cost (often as Post Office surplus). If you can find some for few pounds - great!    When I originally wrote these articles, electromechanical counters were realtively easy to find, these days they are becoming  hard to find and expensive - a cheaper and more readily available solution is to adapt an electronic pedometer - click for more info.    Diagram P shows the circuit. 

The counter mechanism counts one when power is applied and then removed from the terminals. These counter mechanisms work with an electromagnet pulling in an iron lever which operates a series of wheels by gears, ratchets etc. All this mechanical stuff does not operate instantaneously. Typically they need a pulse of 1/50 second or more to operate once, and could count twice in 1/10 second. How long is a car on the counter strip? Well if pickup is a bit intermittent it can easily be less than 1/50 second, and sometimes it will give 2 or more pulses inside 1/10 second. This is why just connecting the counter mechanism to the counter strip is not likely to work reliably. The capacitor allows the counter to react to shorter pulses, and won’t allow a second count in the next few moments, so it can provide a reliable counting system. These did need some playing with to work properly, missing laps was dealt with by a larger capacitor or a higher voltage. Double counting was dealt with by a larger capacitor. Typically people used run the counter mechanism at a bit above its rated voltage, and capacitor values of 500µF. Incidentally, diagram P shows one lane, everything except the power supply is needed on each lane (the power supply is common to all the lanes).This circuit only works with the track wired with one polarity. If your track polarity can be reversed an isolated strip is needed both sides of the slot as shown in diagram Q below. Connect one counter wires to each side.

This simple counter works best with a dead section counter strip. Diagram Q shows how more detail of how a dead section is built into the track. They are usually 10-20 cm. (4-8 inches) long. I’ve shown isolated sections of braid both sides of the slot, this gives flexibility for different counter circuits to be fitted in future. Most circuits use one side as the isolated dead section, and the other connected to the appropriate power equally well on braided or tapped tracks.

There is no power to the car on a dead section. If a car does stop on the dead section, somebody will have to push it. Under normal racing conditions cars will coast across the dead bit with no noticeable change in speed. Its usually only when drivers are trying to stop on the start line before a race that you notice the dead section.


Split Tape Counter Strips

"Split tape" counter strips get round the need for a dead section, by providing a half width tape carrying the power, and an isolated half width (see the right hand half of diagram R). When the cars braid bridges the two half widths of tape it completes the circuit and operates the counters. This tends to give a worse pulse than a dead section, (A dead section removes the power from the motor so the guide is pressed down into the slot, and a split tape depends on a wider contact). This sort of counter strip is not used with braided tracks - try cutting a piece of braid to half width and you end up with a pile of separate short bits of wire!


Transistorised Lap Counters

There are relatively simple transistorised circuits that can make the simple counter mechanisms described above work a lot better. This sort of circuit is usually needed to make split tape counters work reliably and is used to overcome problems with dead section counters. There are lots of circuits that could be used, I’ll outline one sort of circuit - mainly for the benefit of readers who understand a bit about these sorts of circuits (I’m not going to attempt a how it works from square 1 type explanation). Variations on the circuit in diagram R have been used on half a dozen different club tracks in the South West, and always seem to work well.

Essentially the circuit replaces the large capacitor in the simple circuit above with a smaller capacitor and a transistor to amplify the effect on the counter mechanism. The small capacitor can charge very quickly without big sparks etc. and the transistor allows a long enough delay so the counter has time to operate and doesn’t double count.

The lap counters only need a low current power supply. The exact values depend on the counter mechanisms you can obtain. Typical 12 volt counters have 500ohm coils so a 15 volt supply would do fine and it would need to be able to supply at least 120 milliamps for a 4 lane track. A 10µF capacitor will usually give about the right delay (a smaller capacitor will shorten the delay time) - a cheap 50 v electrolytic will do fine. Typical components are resistor R 3.3Kohms, the transistor is a BC338 ( BC337, BC183L, BC184L, BC547, BC548, BC549 or BC550 would do equally well) and the diodes 1N4001 (1N4002, 1N4003, 1N4004,  1N4005, 1N4006 or 1N4007 would do equally well). The cost will largely depend on the cost of the counter mechanism - the power supply should only cost a few pounds and the rest of the components should be well under a pound per lane.

This sort of circuit could be adapted to use LCD counter modules in place of electro mechanical counters. (I haven’t built counters using these so I am not certain of the exact component vales) These modules are available from various electronics suppliers at about £10 each, they do the same job as electro mechanical counters, but they do it electronically rather than with magnets, gears etc. Alternatively you could adapt an electronic pedometer However, there is no need to replace electo-mechanical counters that are working reliably - I know of one club that are still getting satisfactory service from counter mechanisms that have been in use since 1968 (and they did work better once the original big capacitor was replace with a transistorised circuit in 1978).

This split tape circuit only works with the track wired with one polarity. If your track polarity can be reversed the isolated strip version needed. This works with either polarity, but needs the gap between isolated section and the powered section needs to be small enough so that the car's  pick up braid will bridge the gap. This might sound a bit dubious, but in fact works entirely reliably even with Scalextric, Ninco etc. cars (which in standard form have a very small pick up area, so are the most severe test of this type of circuit).

Optical Detectors

Clubs with the benefit of a member with the necessary electronic knowledge often used a light beam to operate the counters. The counter mechanism itself was often the sort of electro-mechanical counter used in the simple lap counter. I won’t attempt to describe the circuits to connect the two (see *). Some clubs used photocells in the bottom of the slot with a light shinning from above. More common is a single slotted package containing both the light source and detector (see Diagram S). 

These systems can work well. There are occasional problems with muck in the slot blocking the light path (the cure is obvious once you figure out what has happened). Its important to get the depth right - the guides on Scalextric type cars are not as deep as the Starburst, Cahoza or Jet Flag guides BSCRA racers are used to. One advantage of optical detectors is that there is no dead section of tape. A potential difficulty is noise pickup causing false counting - well sorted systems are immune to this problem, but some clubs resident electronics experts have spent months trying to sort out this sort of problem.

This type of detector is isolated from the track wiring, so works equally well with either  track polarity.

*The optical sensor by itself won't do anything! The important bit is the circuit joining the detector to the computer or counter mechanism. If you have a club member with the necessary electronic knowledge to design and build this - great.  If not you'd be better off with a simpler system.

Computerised Race Control Systems

The lap counters described above do just that - count laps. Its up to the race controller with pen and paper to write out the heats, record the scores, add up the results and arrange them in order. The races have to be timed or the power turned off after a fixed number of laps - another job for the race controller with the aid of a stop watch or an automatic timer. A computer race control system will do all these jobs as well as count laps. A race control system consists of a standard computer (invariably an "IBM compatible" PC) and race control package (some software plus some hardware to connect the computer to the track.)

Which Package?

Which is the best package to buy? To give a proper answer to that I would have to have run race meetings with all the packages available. There are lots of packages available in America, most of which have not been tried in this country. Its a good idea to look at suppliers demo discs or web site to get a clearer idea of all the facilities they offer. Although the basic use of such systems can be picked up quickly, it takes some time to become an expert user. Advice from an experienced user of a race control package can be invaluable, so its not a good idea to be the only UK user of a package. So what packages are successfully used in the UK?

SLOTMASTER was written for British club racing, (My experience is using it on the BSCRA Nationals track,  Bournemouth SRS and Tomacher raceway. It is used for club racing and BOC meetings at a number of other tracks.) It runs on Windows, runs on a 386 or better PC and will support 2 to 8 lanes. It has facilities to work out parts of a lap automatically (so there is no need to find out which hundredth the car stopped on) and will time to 1/1000 sec (if you run it on a 66 MHz 486 or better PC). The under £100 entry level system  lacks the power switching, the higher spec versions with full facilities work through a card plugged into one of the expansion slots in the PC. 

AUTO TRACK was originally written for American raceways. It runs on DOS and will support 8 lanes and is particularly suited to segmented racing, it will also time individual laps to 1/1000 sec. It was used for the last two ISRA World Championships run it the UK, and is also used on the Pinewood 6 lane track. You can order your Steve Ogilvie track with Auto Track.

I'm always happy to update this page with systems that I've seen working well. No doubt there are some good systems out there that I haven't seen. However, some manufacturer's claims are, shall we say,  a little optimistic - so I'll need to see something working well before I'll add it to this web site.  If you know all about some other good packages, why not e-mail me (  ).   

Do you need a dead section, split tape or optical detector for a computerized system? The suppliers of race control packages will tell you what their system needs. Choose your race control package first, then sort out a suitable detector. Will it work with reversed polarity? Again the answer is check with the supplier. 

What PC?

No doubt some of the more experienced web surfers who read this page will be far more knowledgeable on this topic than I am - but for the rest of us.........................Isn’t a computer expensive? - Well it depends what you call expensive. A bottom of the range new computer will set you back over £400, but this is way in excess of the spec. needed to run even the best current lap counter packages. Where as the latest computer games or the latest office automation "bloatware" continually depend on ever higher spec PC hardware, the writers of lap counter packages know most slot racers prefer the low cost of relatively out of date hardware. As home computer enthusiasts and companies are frequently needing to upgrade their PCs to run the latest packages, there are plenty of "previously enjoyed" (or possibly "previously cursed" at work) PCs available for not much money - several places advertise old Pentium PCs for around £50 - and these are entirely adequate for lap counting purposes. It is not uncommon for superseded computers to be scrapped, so if you are in the right place at the right time, the previous owners may be happy to give them away rather than put them a skip.

Any cautionary notes on buying second-hand PCs? Firstly find out what spec your chosen race control package needs, and make sure  you buy something adequate.  If you buy from a reputable trader, you should get a few weeks warranty, so check it out as soon as possible.  If buying privately, check it works before you buy - you wouldn’t buy a second had car without a test drive! People are usually just selling hardware which is obsolete for their purposes, but there might be a few bits of duff hardware mixed in (duff hard drives, duff monitors and connectors with bent pins are the most likely problems).   Obviously if it's free just say thank you - unless it's obviously trashed it's worth a try!

If it comes with an obsolete operating system (Windows 95 or the even older DOS and Windows 3.1) leave well alone - upgrading to later versions of Windows (e.g. 98, ME or XP) can slow old computers to a halt and fill up too much space on their small hard discs.  Lastly - but very important - the lap counter package will probably have a printed circuit card that plugs into one of the expansion slots inside the computer - make sure your computer will take the necessary card. (The cards are pretty standard so this shouldn’t be a problem with a desk top but check before you buy just in case.)

Its worth thinking about security - a computer is the sort of thing that may attracts theft - and in reality there's not much else in the average club rooms that's anything like as worth steeling (unless you leave the club funds lying around in cash). So think about making your club room secure before you get a computer - the risk is not just the nicked computer but the amount of other damage from a break in. Desktop computers don’t travel well, so its not really practical to take it home each week. Laptop PCs travel better, however I don’t know of any system that runs on one, and these generally lack expansion slots so there are difficulties in getting a system to work on a laptop.

There is much more that could be said about computerized race control systems, but I think I better leave that for another time. The next in this series of articles will look at wiring up your track.

Chris Frost


Copyright © 1999, 2000 and 2001 C.Frost with minor updates in 2002 - 2007      All rights reserved

 No liability is accepted for the information on this site or any use to which it may be put.