T³: Hot Wheels Speed Trap

Adding a chronograph to a Hot Wheels track to measure the speed of passing toy cars.

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At the ISTE 2016 conference, one educator told me that he planned to make a timer for Hot Wheels tracks using an Arduino with his class (I apologize, as I do not remember who it was! If you are reading this, please leave a comment so I can give you full credit).

I thought it was a really great classroom project idea, so I wanted to share. Instead of a timer, I constructed a chronograph using the SparkFun Inventor's Kit and an extra photocell. Here's a video showing the project in action:

I would be remiss if I did not post full instructions for building the project. Good news, everyone! They can be found on InventorSpace.

CChronograph for Hot Wheels

Click the photo to see how to make your own Speed Trap

I was honestly surprised to find that Hot Wheels still makes track sets. The particular one I used in the video can be found at Target.

What other nostalgic toys would you want to hack?

Comments 11 comments

  • Member #482404 / about 8 years ago * / 2

    Decided to upgrade the 'box' and designed a better speedtrap that can be 3D printed to help hold the track and the leds/photocells more consistently. Check it out on Thingiverse: http://www.thingiverse.com/thing:1916428

    • Sweet! Thanks for sharing. This looks like it'll hold together a lot better than the cardboard box :)

  • Inquisitor / about 2 years ago / 1

    Here is a webserver based version that is smaller and cheaper to make since it doesn't use a display. Use any smart phone, laptop or big-screen TV to display results! Arduino Project Hub

  • -------------------- Tech Support Tips/Troubleshooting/Common Issues --------------------

    This project has been moved to Workbench Education. You can find it here => [ https://edu.workbencheducation.com/cwists/preview/11064x ].

  • Mr. Ben / about 8 years ago / 1

    Great post!! BTW, what is the Trim Pot used for here? Is it to control the LCD brightness?

  • Sembazuru / about 8 years ago / 1

    One thing that I noticed in the video was the track jumping as a result of the centrifugal effect created when the car was going through the loop. Did you have any problems with false triggering by the track jumping up and crossing the trigger gates?

    • We didn't have any problems with false triggering, but the car was wasting a lot of energy to raise the track off the ground. After we taped the loop down, we saw the speeds through the gate increase by ~1 m/s.

  • xsk8rat / about 8 years ago * / 1

    Hi Shawn, If you're not hearing a sonic boom from the hot wheels car, please check the units. Video shows 577.59 m/s in first frame and Speed of sound is 343 m/s - or did I mess that up? Otherwise it's lovely! Thanks, Mark

    • Thanks, Mark! The units are correct. The car isn't actually registering at 577.59 m/s, that's a "bad" state that occurs whenever both sensors are covered in shadow, which happened when we were shooting photos/video. In the video (~1:50 mark), the car registers 2-4 m/s, which is more accurate.

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