Hey!
First of all, I'm an electric skateboarder and sometimes we rent a karting track and have some freeriding and some time trials, unfortunately we have to time this by hand and is not really precise at all so we had the idea to make a timing system.

The idea is: Mostly we have about 30 people attending and 10 people on track during the time trials, so it has to time 10 people and when their lap is done it has to upload the time to a webserver with the name of the rider and his time. Our budget is around 300€ I think. We only have to time the time trials which is 2 laps per person.

I thought of doing this by arduino and maybe an ultrasonic sensor to start the lap, but I'm not sure how we would time each rider by that, so im not sure about that. If anyone could help out it would be super awesome!

 

Interesting problem. In track and field, the timing of individual lanes is usually done with a camera, which gets expensive. For skateboards, is it OK to place a low profile strip across the track at the finish line? For example, something which can sense pressure at each lane from the leading wheels? In your sport, what is considered crossing the finish line?

 

Interesting problem. In track and field, the timing of individual lanes is usually done with a camera, which gets expensive. For skateboards, is it OK to place a low profile strip across the track at the finish line? For example, something which can sense pressure at each lane from the leading wheels? In your sport, what is considered crossing the finish line?

How thin is that strip?
Crossing the finish line will be with the front wheels, same for the start

 

Is each skater required to stay in a specific lane during the time trial?
A threshold type Hall effect device at the lane end/start boundary could possibly be triggered by a magnet glued to the individual skateboard, interacting with a timing circuit ... This approach, if practical, would not be overly costly.

 

Is each skater required to stay in a specific lane during the time trial?
A threshold type Hall effect device at the lane end/start boundary could possibly be triggered by a magnet glued to the individual skateboard, interacting with a timing circuit ... This approach, if practical, would not be overly costly.

There's a small delay before we let someone go. for example: person 1 can go, and 10 seconds later person 2 can go etc etc
But there's no specific lane

 

With the Hall effect device approach, the main requirement would be that the individual racer remain in one individual lane from start to finish. This rule provides for a standard distance that different timing intervals can be compared to.
... There would be one or two logic type considerations to account for timer start, stop, and first or second lap, but not anything too complex.
... If there are no lanes, then maybe a trigger pad could be marked with stain, paint or tape ... A Hall device, about the size of a small coin, would have to be embedded in the track ... This would not be difficult with a wood surface .... Epoxy might be used to smooth over the top surface.

 

I dont think it's really practical if we have to stay in one lane

 

... So maybe just try to hit the timer trigger at the end.

 

How thin is that strip?
Crossing the finish line will be with the front wheels, same for the start

Some strips can be quite thin. Some work on resistance, some on capacitance, some cause an air pressure pulse. Here is an example. I think the challenge is to make connection with each strip in a lane in a practical way. Something like thin wires going across the track to a box. Anyway, here is an example. https://www.adafruit.com/product/1071

The cable going to the edge could be "twisted pair ribbon cable". Again, fairly thin. https://en.wikipedia.org/wiki/Ribbon_cable

Attach it all to the track with wide tape.

 

I'll look into that! But how would it be possible to identify a rider?

 

I'll look into that! But how would it be possible to identify a rider?

Automatically identify the riders is a whole other thing. For that, the skateboard needs some sort of ID. Can you attach something to the bottom of the skateboard? Like a small box with double sticky tape? Article on RFID timing of sporting events: https://en.wikipedia.org/wiki/Transponder_timing

Perhaps something like these commercial systems can be hacked together. https://rfidtiming.com