How to Build an RFID Race Timing System

If you're the kind of hands-on race director who doesn't shy away from a challenge, you may have considered building your own RFID race timing system.

Building a race timing system from off-the-shelf components is a lot easier than you think. And it can give you great control over your timing costs as well as provide a stepping stone into race timing.

In the rest of this article you'll find everything you need to start your race timing career, from understanding your options and choosing the right tools for the job to thinking through common race timing challenges and sorting out your backup procedures.

Starting at ground level...

How does RFID work?

RFID (short for Radio- Frequency IDentification) uses radio technology to identify and track objects through the use of radio tags.

The basics of an RFID tracking system go something like this:

1. Pick an object you want to track (e.g. a runner)
2. Take an RFID tag and program on it information about the object you want to track (e.g. the runner's bib number)
3. Attach the tag to the object you want to track
4. Use an RFID reader to scan the tag and read back the information you have programmed on it

RFID technology was originally developed for industrial applications, where it was used to provide easy tracking of objects as they moved through warehouses and manufacturing plants. It was during the 90s that RFID was first adapted for use in mass-participation sports.

The very first RFID race timing systems were like any other new technology: very expensive and - let's face it - quite rubbish. But progress has been swift and RFID has come a very very long way.

Today RFID timing is considered the golden standard for race timing and can be relied on to provide near-100% accurate results for even the largest races. And it has become affordable enough to bring it within reach of most every race out there.

The different types of RFID

There are many different types of RFID frequencies and technologies in use commercially, and not all are suitable for race timing.

Low Frequency (LF)

Low frequency RFID uses frequencies in the 125-134kHz range to identify tags in close proximity (usually less than 10 centimeters) to the tag reader. LF RFID can only handle low read rates, making it unsuitable for most race timing setups. It’s widely used in industrial applications and pet IDs, where scanning rates are low and objects are scanned through contact or with the use of handheld RFID readers.

High Frequency (HF)

High frequency RFID uses frequencies in the MHz range. HF has a longer range that its LF counterpart (typically up to a meter or so), can handle a higher read rate and be used to transmit larger data payloads. However, this is still not enough for most race timing applications.

Ultra-High Frequency (UHF)

Ultra-high frequencies are the most widely adopted in race chip timing systems. UHF RFID systems use frequencies in the 860-960 MHz range and can be used to detect as many as 1,000+ tags per second as far as 10-15 meters from the reader, making them ideal for wide and busy finish lines where several tagged participants may be crossing in a short space of time.

Two RFID tags by Smartrac: the very popular UHF DogBone Monza R6 for use on race bibs (left), and an NFC Circus tag that can be read by smartphones (right)

NFC vs RFID

Although technically a subset of RFID, NFC technology (short for Near Field Communication) deserves special mention among RFID technologies.

NFC sits in the LF/HF part of the RFID spectrum and has been increasingly adopted for timing and runner identification in trail and ultra races. Part of the reason why is the low cost of wearable NFC tags (these tags use similar NFC chips to the one you’ll find in your contactless credit card), but also the in-built NFC functionality available in Android smartphones, which essentially can turn any Android phone into a NFC tag reader.

Essential components of an RFID race timing system

Building your own RFID race timing system may seem daunting, but there really are only a few core pieces of equipment you’ll ever need.

You can build a system capable of timing even the largest of races with just a few thousand dollars - or less, if you shop around for second-hand components. Here's what you will need:

RFID tags

RFID tags are worn or carried by participants and are used to identify each one uniquely at timing points. Tags are made up of two components: 1) an RFID chip which is programmed with information about the carrier of the tag, e.g. their bib number, 2) an antenna which enables the connection with the RFID reader.

RFID tags, like the super popular Smartrac DogBone, can be attached on participants' bibs, worn on the shoe or, for bulkier active tags, strapped around the ankle. All of these can be equally effective, but some make better choices than others depending on the type of event you are timing and the antenna setup you plan to use. We'll take a closer look at the different choices for RFID tags later in the article.

RFID tag readers

The tag reader is the “brain” of the chip timing system - and the most expensive item on your shopping list. It uses radio antennas to detect RFID tags, decode the information stored on them (processing and combining multiple readings where necessary) and transmit that information to the race timing software.

The Impinj Speedway 420 4-antenna RFID reader

RFID readers can be handheld, mountable or desktop and vary significantly in cost depending on the number of antennas they can accommodate (usually 2, 4 or 8), their read rate, connectivity options (Ethernet, Bluetooth, Wi-Fi) and other specifications.

Both the Impinj Speedway 420 and Zebra FX9600 (formerly Motorola) are very popular choices of race timing readers in the $1,000 - $2,000 range. They both have 4 antenna ports and with the right antenna setup will give you all the power you need to time any race, however large.

RFID antennas

The job of antennas in an RFID timing system is to detect RFID tags and transmit data from the tags to the tag reader. Most antennas are passive, that is, they not only connect to the RFID reader but are also powered by it. There are three types of RFID antennas commonly used in race timing systems:

Mat antennas

Mat antennas have been used in race timing systems since forever and are the antenna of choice for major marathons and very large events. Mat antennas are placed across the finish, start or intermediate timing line. The mat or plastic cover shields the antenna coils underneath which create an upwards radio field facing incoming tags. Mat antennas work great with both shoe tags and bib tags and are usually foldable and can be extended to any width by connecting multiple antennas together.

Examples of RFID antennas: foldable mat antenna (left), upright panel antennas (center) and a pair of aerial/overhead antennas (right)

Panel antennas

Panel antennas are upright antennas usually positioned in pairs facing each other at either side of the timing line. They create a fairly narrow wedge-shaped field and are oriented slightly outwards facing incoming tags just as they cross the timing line.

Panel antennas are by far the most versatile type of RFID antenna. They can be used in all types of events and are the top choice for high-speed events, like sportives and road cycling events, where even the lowest-profile ground antennas can be dangerous to participants.

Overhead antennas

Overhead or aerial antennas can be used in conjunction with side antennas on the top of finish-line gantries to add a radio "curtain" to the side antennas’ radio "wall". They're typically used to beef up read rates in high-speed races, like road cycling and motorsport events.

Race timing software

Making sense of RFID data captured by the reader and translating that into neat race times is the job of specialized race timing software.

The important thing to keep in mind when buying timing software is that not all software will work with every RFID reader out there. Most software will work either with a dedicated hardware setup or a select list of readers, usually from the bigger manufacturers like Impinj, Zebra, Alien etc.

If you feel adventurous and would consider developing your own race timing software, make sure to check whether the manufacturer of the RFID reader of your choice offers a software development kit (SDK) to help streamline the process.

Miscellaneous components

Mounting accessories

Most RFID antennas on the market come without any mounting kits, which is something you'd need to buy separately to set up your antennas the way and in the direction you want them.

Tripods are particularly good for that job and you you can buy fairly inexpensive professional tripods from Amazon. Then on top of that, you may or may not need to buy a mounting kit to securely attach the antenna to the tripod. Something like this, which works really well with the MTI antennas we discussed earlier:

Mounting kit for an RFID panel antenna

If $30-$40 for one of these is too much (you'll need one of these for each of your antennas), then you can look at cheaper fixed mounting brackets from pretty much any hardware store.

Cables

Last but not least in your RFID timing system build, you’ll need cables to connect your antennas to your reader (and your reader to your laptop, but those are fairly standard Ethernet cables).

The importance of picking quality cables is easy to overlook. Seeing as you’ll be likely operating outdoors and moving things around, you should consider investing in durable, insulated cables that can withstand whatever the weather may throw at you.

Getting the length of your cables rights is also important. You'd think that the longer the cable the better, but, unfortunately, there are reasons why you want to avoid overly long cables:

1. They're more difficult to transport and more prone to causing accidents at busy timing points
2. UHF cables suffer from loss of signal with length, so buying longer cables means having to invest in more expensive low-loss cables

So, when it comes to cable length, give yourself a bit of slack to work with, but don't go too long.

Popular add-ons for RFID race timing systems

While not essential, there are a few more items you could add to your DIY chip timing system to extend its functionality. Below we list some of the more popular race timing add-ons.

Results Kiosk

A results kiosk usually takes the form of a touchscreen box with a ticker tape printer on the side where participants can walk up to and look up their finish times after the race. Results kiosks are becoming very popular with racers and would be a good investment to make for any aspiring race timer.

Cameras

Everybody loves a race-day photo, right?

Thankfully, with RFID you don't need a photographer standing by. You can set up a camera that can be connected to your timing software and triggered whenever a participant crosses the finish for that perfect finish line snap. Photos can be tagged and time-stamped automatically, saving you the hassle of having to sort photos after the race.

LED display screens

Similar to the kiosk, LED display screens can provide a convenient way for participants and spectators to view race results as they come in. These are less interactive than results kiosks, but can cut back on lines for results, thus providing a good solution for larger races.

Types of RFID Tags

When it comes to RFID tags, and depending on your hardware setup (particularly your choice of antennas) and type of event, you will have a choice between different types of tags that vary in cost, reusability and performance. So it's worth spending a bit more time understanding your options.

Disposable vs reusable tags

One of the more important choices you’ll need to make is whether you go with disposable or reusable tags.

There’s three things to consider there:

1. Tag durability
2. Logistics, particularly in collecting and re-programming reusable tags
3. Cost

Reusable tags can be re-programmed for repeat use, which means you will pay the - typically higher - cost of a reusable tag once and be able to use the tags again and again. In contrast, disposable tags, which are cheaper to manufacture, will be distributed to participants or be embedded in a bib never to be used again.

In terms of logistics, throwing a tag away is a lot easier than collecting it. Factor this in in your decision, as having to collect tags at the finish may lead to congestion at your finish area if note managed properly.

Also, keep in mind that disposable tags, being rather flimsy, may not be suitable for use in multi-discipline events or harsher conditions. So for those types of races your choices may be limited to the more expensive reusable options.

Passive vs active tags

Another thing to think about is whether you'll be using passive or active RFID tags. Your choice of passive vs active is an important one as it's going to affect every other aspect of your system, from your RFID reader to your antennas.

Active tags use an internal power source built into the tag to transmit data to the RFID reader without having to rely on the reader’s power. The built-in power source makes active tags more versatile than passive tags but shifts a lot of the heavy lifting from the reader to the tag.

Because in active systems the detection and transmission rests on the tags, active systems can be more accurate and be used to transmit data over longer distances. Also, since the reader doesn't have to do all that much, active tag readers can be much smaller, allowing for the addition of multiple intermediate timing points at a lower cost. All this makes active tags a good choice for multisport and high-speed races.

That said, active tags will be a poor choice for the majority of races. Here's why:

• Cost: active tags are considerably more expensive than passive tags, often costing $20 or more for a single tag
• Bulkiness: active tags are also a lot larger than passive tags, making them more awkward to use by participants
• Maintenance: not only do active tags need to be reused, they also need to be frequently recharged to keep them functional, making maintenance of your RFID tag inventory a bit of a headache

Passive tags are a lot simpler. They do not have a built-in power source and can weigh as little as 1g. As a result, they can be placed almost anywhere (these are the tags covered by a layer of foam you find fixed at the back of race bibs).

Stark contrast: two RFID tags by German manufacturer RACE RESULT, a reusable active tag to be worn with a strap (left) vs a disposable passive tag with protective foam attached at the back of a race bib (right)

Passive tags are also a lot cheaper than active tags and can also be reprogrammed for reuse, although they are so cheap that the hassle of collecting them at the end of a race often doesn’t justify the trouble. Depending on the size of the order, prices for passive tags can start from as little as $0.10 per tag.

For the overwhelming majority of races, where tough or muddy terrain is not an issue, passive tags will be the obvious choice. Unless stated explicitly, everything we discuss here will be based on passive RFID systems, which are the most common and most suitable for the majority of events.

How to encode RFID tags

Before we wrap up our discussion on RFID tags, it’s worth briefly discussing an important part of the race timing process: encoding RFID tags.

When you purchase your tags, each tag will come with a unique code, called EPC for Electronic Product Code. Think of the EPC as the tag’s serial number - it provides a unique ID for each tag. This is the number an RFID reader will read from the tag and send to the timing software by default.

In order to keep track of the tag each participant is carrying, so you can provide meaningful results, you have three options:

1. If you're buying your tags from a third-party provider, ask them to encode the EPC with each participant's race number (you will need to provide a list of race numbers). Most tag providers, particularly those providing tags attached to bibs, will be able to do provide the tags pre-programmed with each participant's race number.
2. If you are buying tags in bulk that have not been assigned to a race yet (or if you're reusing tags from a previous race), you can choose to encode race numbers on the EPC of each tag yourself in a process that is kind of like the reverse of tag reading (more on this below).
3. You can always leave your RFID tags with their original random EPCs, so long as you keep on your timing software or on a spreadsheet a 1-to-1 map of EPC-to-race-number. That way you can turn the EPC-based results your reader will return to a race-number results by matching race numbers to EPC numbers.

If you choose to go with option 2 above - which is a bit of a hassle for larger races - this is how you can manually encode your tags using your RFID reader and timing software:

1. Bring the tag you want to program within range of your RFID reader (make sure there are no other tags nearby)
2. Program the race number you want to assign to the tag on your timing software (most software provide this functionality)
3. Let the reader stamp the race number data to the tag. The tag should now bleep back the race number you encoded.

Cost of a basic RFID race timing system

So how much does it cost to build a basic RFID race timing system?

Well, let's see. For the core system with a single reader and 4 antennas you will need:

• 1 x 4-port RFID reader
• 4 x UHF RFID antennas with tripods and mounting brackets
• 4 x cables

Which, at the time of writing this, equates to $1,585 (Impinj R420 reader) + 4 x $129 (pannel antennas) + 4 x $49 (tripods) + 4 x $15 (pole mount brackets) + 4 x $100 (average cost for your cables, based on a combination of lengths) ~ $2,750 .

Then on top of that, you'll need a laptop running your timing software (there's free software you can use, but it's probably worth investing on a paid software) and, of course, RFID tags, which depending on how many you buy and whether you want to integrate them on bibs etc will vary in cost between $0.10/tag to $0.50/tag (assuming you choose to use passive disposable tags, which is what most events these days do).

Development kits

RFID development kits (like this one from Impinj) are a popular way to get started building your RFID timing system from the ground up. These kits include the bare minimum of components you will need to develop your competence using RFID hardware and ship with components you can reuse to build your larger RFID system.

Timing a race

So far, we have discussed the ins and outs of a basic RFID chip timing system and its components: what you will need and what it will cost.

In the rest of this section and this article, we'll look at some common considerations (and limitations) when using the sort of hardware setup we've discussed above to time races in the real world. Sometimes you'll need more than a single system to accurately time a race. Other times you can get by with a single system.

Here’s some things to think about:

Point-to-point vs out-and-back vs looped races

Even for a simple 5K race, the configuration of your timing system will vary depending on the course.

Out-and-back courses are the easiest to time, since the start and finish happen at the same place. You can simply set up your antennas and reader at the start, record your participants’ start times and finish times and subtract the two to obtain each participant’s net race time.

Looped races are a bit more complicated, because there can be multiple crossings of the start/finish/lap point. If, for whatever reason, the system misses a crossing, things can get a bit confusing. But with a bit of common sense and some post-race cleanup of your data, you should still be able to provide accurate results.

Point-to-point races is where things get trickier. Here, the start and finish can be separated by anything from a few meters to several kilometers. So you're left with a few alternatives:

1. Time the start and move your equipment to the finish. Sounds straightforward but every professional timer would advise against it - all kinds of things can go wrong and you could end up missing finish times.
2. Use two timing systems, one at the start, the other at the finish. This is the best choice, but of course it doubles your hardware and manpower requirements.
3. Set up your equipment at the finish and record finish times only.

Option 3 is what a lot of smaller races will choose to do. Which introduces the next dilemma….

Chip time vs gun time

With a single timing system set at the finish line, you can only hope to be able to publish so-called "gun time" results.

Gun time is the official time by which competitions are measured. Named after the time the race gun goes off (real or figurative), signifying the start of the race, gun time results base the race time of each participant on a common start:

Gun time = Time at which a participant crosses the finish - Time when race starts

Gun time is fair, in the sense that it provides a common start time for the race, but since not all participants can be at the front of the pack for the start of the race, it will tend to overestimate the race time for participants starting further back in the field.

Chip time , on the other hand, (also known as net time) is a lot more representative of a participant's actual race time, as it takes into account the actual time a participant crosses the start line:

Chip time = Time at which a participant crosses the finish - Time at which a participant crosses the start

Chip time will always be lower than the officially published gun time and much more useful for most participants in a race. However, keeping track of start line crossing times requires a start line timing system. Which may mean having to use two systems (one at the start, one at the finish) for point-to-point races.

Using a backup system

Regardless of what system you choose to use and how you set it up, there is a strong possibility your tag read rate will be below 100%.

Dealing with missed times is part and parcel of operating a chip timing system. And most race timers deal with it by using a backup system for recording finish times.

There are a number of approaches in use as backup for chip timing systems:

• Fully manual backup: This is usually done by two people. One of them uses a stopwatch to record people's finish times, the other recording their race numbers. When the two are matched up, a backup list of finish times emerges. Here's the process discussed in a bit more detail by a parkrun race director.
• Race timing apps: Perhaps the most common backup these days comes in the shape of race timing apps. These apps load your start list and allow you to either punch in or tap in race numbers of people as they cross the finish line. The times are automatically recorded by the app and can be exported or emailed to you.
• Manual backup systems in timing software: Most chip timing software come with functionality similar to that of race timing apps, so you can use the same software running your main chip timing system to capture crossing times manually, as backup.
• Cameras: One of the simpler backup systems is using a cheap camera recording at the finish line. Since camera video is time-stamped, you can use the footage to pick out missed finish times.

The whole point of a backup system is to provide peace of mind. So do choose one, but don't go overboard - if properly set up, your main chip timing system will be doing 99%+ of the work.

So there you have it...

...Building a DIY chip timing system from the ground up.

Got questions? Come join Race Timing Hub, our Facebook group dedicated to building, testing and deploying RFID timing systems for races.