Slot Car Lap Timer

Ive recently got into the hobby of slot cars. I want to use an arduino to get the lap times and determine who is winning, then send the data to an application on the pc. I've never used and arduino or a product like it so I'm not sure where to start. I would like to keep the project under $50. After researching a bit I've determined that there are two options: IR or Sound Detection. I need it to be able to determine the deference between the cars if there are two of them going by at the same time. I want to use the bare essentials for this project, so I don't want a kit. I was looking at the arduino micro controller but I wasn't sure if it would be sufficient for this project. My second choice was the uno. Which one should I get and which method should I use. This is the ir sensor idea I was going to use IR Tutorial and the sound sensor tutorial I was going to use Sound Tutorial. Again, I need accuracy, so if someone could tell me which is more accurate. Thanks!

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There have been other forum inquiries on your very subject.

Tom... :slight_smile:

My bad. I should have done that first. I thought it would of been a much rarer subject. Thanks

Is there any chance of getting one of these installed under the track in each lane so the car's flap thingy that goes in the slot (I'm sure it has a nice name :slight_smile: ) breaks the beam?

After searching the forums it seems that reed sensors is the best way to go. The cars use magnets to move so when they pass over the reed sensor it will go off and mark the time. I still have a few questions that were not answered in my search. Will the microcontroller handle 4 reed sensors? Is there any other components I would need? Are there cases for the microcontroller? I can’t seem to find any. Again thanks for all the help.

I'd go for an Uno during prototyping, because they have all the pins nicely accessible. Then replace that with a more suitable (smaller) board or module in production, and keep the Uno for the next project.

You need a digital pin for each sensor, so 4 is no problem at all.

This example shows how to count push buttons, which is no different from what you plan to do with a reed switch. (Ignore the part where it counts in 4's, that was a secondary purpose of the example.) (Note: when you read that example you'll see they use a resistor to ground for each pin. It's more common to use a resisitor to 5V, and indeed Arduini have a built-in resistor which can be enabled for that purpose, using pinMode(num, INPUT_PULLUP).It reverses the logic though, ie a closed button or reed switch is now a LOW not a HIGH, but that's easy to take care of in code.)

The bulit-in millis() function counts time in milliseconds from Arduino startup or reset. So record the millis() time when the race starts, and then every time you increment a lane lap count, record the new time and thereby know the lap times.

Thank you guys for the help. I have a a couple more questions. Along with the hall sensors will the uno support one of these NeoPixel Strips. My goal is to use the neopixel strip to count down the start of the race and via the hall sensor determine if anyone passed the start before it went green therefore disqualifying him. The programming wont be a problem because Im a programmer, but I need to know if there will be enough power to run all this. Thanks again.

In your last two comments you went from "reed" to "hall" sensors. I'd suggest sticking with the hall sensors, and let us know what ones you are planning on purchasing so we (the forum) can verify that they're an appropriate choice.

A neopixel strip and the lap sensors will be no problem for an Uno.

I just bought the uno, 2 hall sensors (will upgrade to four later) and I bought the neo pixels led strip here If you could tell me what else I would need I would appreciate it (eg. resistors). Thanks