Scratch like alternative to finish line

riditz Friday, 6/30/2023

I've been looking for something to track race times at my track for some time. Unfortunately, the fabulous finish lines on the market are very expensive for me.

Luckily thanks to this program called Scratch, which I have been using for a few days, I have managed to program a timer that when it starts, when a traffic light is displayed, gives us the acoustic and visual signal that we activate the exit door manually, Then, when the car passes the finish line, it is detected by a webcam that acts as a motion sensor in a specific area (finish line) that stops the clock.

I did some quick tests and in principle it is functional although I have to adjust some things to get the best precision.
I have not had more time to continue with the project, I will upload some photos and videos when I can.

I forgot to mention that what was necessary for this project was a laptop, the Scratch program and a webcam connected to the PC.

Greetings and excuse my English from Google


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dr_dodge 6/30/23

that is very interesting

wonder if a rasperry pie would run it?

wonder if it will trigger from a gopro?

very cool, thanks for sharing that!

keep us posted


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redlinederby 6/30/23
Site manager

Scratch should run fine on a Pi and has GPIO ability as well so you could probably code and wire it up to do all sort of things. 

I think Scratch supports Arduino boards too so lots of fun possibilities if you got the gear. 

I've just built a new start gate and race timer with a much morre effeicient code and setup than my first one. It is now all controlled from one arduino Uno and displays times to 4 decimal places. Minimal wiring (compared to my first one) and the components all up cost me about $40-$50NZD, can't remember as I bought some parts last year. It has flashing yellow lights then on green the gate drops (servo activated pins) and the timer starts. It is tripped by IR breakbeam sensors at teh finish line and displays the time as soon as it's tripped. Then when you want to go again, press the start button and it resets everything automatically. Very easy really, but the wires can still look a bit intimidating even though it is pretty straight forward.

  • I ain't scared — dr_dodge
  • Similar to how mine works mate...programed to flash 5 times and then the gate drops and timer starts at the same time. Can also reset the timer from the start and finish line....I like your idea of having more than one time recorded.. My new track will have a few more Lcd screens around the place.. — Thunder_Valley_Raceway
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riditz 7/2/23

After manufacturing a provisional support for the camera, we continued with the tests and after several adjustments I have achieved a good result, although it could be improved.
Here are some photos and videos of the project.

The next thing will be to make a solid and permanent structure to house the camera and a covering of the entire structure, to hide the camera and in turn to avoid shadows when passing near the camera

  • thats cool, what is the camera? — dr_dodge
  • Camera= webcam, sorry my translate google — riditz
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riditz 7/11/23

After several tests and adjustments, I managed to detect the car perfectly, but after several individual races, I was able to realize a failure or inconvenience, when the start of the cars was manually activated after the sound to start the chrono, it depends on my timing to make a start at the same time as the time trial, so I can't really measure the individual times well.

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Deedose 7/11/23

For better accuracy, you could try making something like this :In orange is the exit door. When you want to start the race, lower the door as fast as possible, and make it press on the keyboard of your computer. Then, change your programm to make it start the timer.

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redlinederby 7/11/23
Site manager

I've seen a lot of kits and homebrew use a snap switch thing. Similar to what Dee suggests but instead of it just hitting a keyboard or some other button, it's a more rigid switch that clicks and is quick.

And then the leads from the switch go into the controller board or Pi or whatever and trigger the things to start.

One of these:

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riditz 7/14/23

Thank you very much everyone for the help, I think that in the end I will have to do exactly what I was avoiding, which was to get an Arduino and electronic components and build my own finish line.

Whatever I do I will inform you.


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