Electronic Finish Line - Make your own

CooksProjects Monday, 4/12/2021

Chaos Canyon (of YouTube DSPN fame) has recommended that I post here about a Race Start timer and speed measuring device for Hot Wheels style diecast cars I have made.  I initally made it for my children and to clearly show the winner when we raced Hot Wheels cars down track placed on the stairs!

It uses an Arduino microprocessor, some basic electronic components and perspex for the casing.  It should cost less than $30; much less if you shop around for the components.

Infrared light is used to detect the cars crossing the unit.  As there are no moving parts, not only is the accuracy of the measurement maximised but also no damage is caused to the car by impact to flaps (unless it comes off the track and hits the box).  The unit is self-contained and easily transportable as well.  All that is needed is a USB power supply, or a laptop if you want to record the extra data.  Make this device and there is no longer any doubt on which car won a race.

My Race Timer design can start a race, measure the time taken from lights out to complete the circuit and show the winning car, along with the speed difference to an accuracy of 1 millisecond or 1/1000th (0.001) of a second (Formula 1 accuarcy).  With some software tweaks (included in download), you can have a dual function unit that can be a Race Timer and also become a speed trap which measures the speed of each car as it passes through the gate.  Using this optimised fimware, the theoretical maximum detectable speed of a car is 288Km/h!  This information is immediately displayed on the onboard LCD display and the data can be sent to a computer via the USB link for use in a Redline Derby!

You can see a short demo of the unit on my YouTube channel, CooksProjects.


The race timer starts with a grand prix style audible start sound and flashing light sequence.  As the first car passes the sensors, the winning car's lane LED is turned on.   Using the onboard LCD display, the winning race time and time difference between the winning and losing car is displayed in thousandths of a second.  After a short delay, the individual car’s actual speed is shown (Km/h), followed by the scale speed of each car (based on Hot Wheels scale of 1:64).  The timer then resets for another race with the race start sound and lights sequence.  If the second car does not pass the sensors within 10s of the first car passing the sensors, a crash is assumed for the second car and the winning lanes times and speeds are displayed before resetting for another race.  The theoretical maximum speed the unit can measure as a Race Timer is 144Km/h with a time accuracy of up to 2ms (based on Arduino Uno).

Data can be transmitted to a computer via the serial interface to reveal more detailed information, including actual times in milliseconds.  This could be used as a record in a Grand Prix style event or for comparing different cars characteristics.

Further development of the software has resulted in a dual function unit that is capable of continuously recording the speed of multiple cars passing the sensors or the race timer mode as above. The main difference when operating in the speed sensing mode is that the speed of the last car in that lane is displayed continuosuly until the next car traverses the sensors and it's speed is displayed.  This data can be sent to a connected computer as well.  The device will continue detecting cars and displaying the speed until power is removed.  The theoretical maximum speed the unit hardware can measure in this mode is 288Km/h due to the faster, optimised firmware detecting loop. 

A detailed instruction booklet providing technical drawings of the casing, more detailed instructions and hints on how to build this project as well as the limited release source code for the dual function Race Timer and Speed Measurer functions is available for a small fee:
Get the booklet and software at Cook's Projects shop 
(The design dimensions are based on normal orange track and cars less than 60mm high.  The booklet assumes a basic knowledge of electronics and the Arduino IDE.)

If you have any suggestions for improving the functionality of the unit, or adding additional features that may be of benefit to the more decerning racer, please let me know!  Add your comments here or on our YouTube channel.  To get notification when the other products we have in development go live, don't forget to subscribe to our YouTube channel. 

I hope that this project inspires someone to make up the Race Timer.  Please post your results on the CooksProjects YouTube channel or website (soon to be developed - links will go on CooksProjects Channel first).

Now there can be no doubt on which car is the fastest! 

A more detailed video on how to make the Timer is at:

How to Make a Race Timer/Speed Measurer for Hot Wheels style cars

You can also see us using the design as a Speed Measure in this video (2:40 into video):



View member profile
Chaos_Canyon 4/12/21

Brilliant. Thanks for posting. 

to join the conversation or sign-up now