Picture of Arduino Skateboard Speedometer

Using an Arduino, it is easy to make a speedometer/tachometer for virtually any man-powered vehicle. I made one for my skateboard that used a small magnet to count revolutions and utilized an LCD display screen.  This Instructable will show you how you can do the same step by step. 

You will need a few things before we get started. 

1) A man-powered vehicle (I will be using a skateboard)
2) An Arduino
3) A plastic Arduino protective box (pictured)
4) A small magnet (mine is 1/4 inch in diameter and about 0.2 inches tall)
5) A magnetic relay switch
6) A 9V battery and an adapter that connects this battery to the Arduino plug (pictured above plugged into an Arduino)
7) A small LCD screen (16 x 2 character display)
8) 10K and 47 Ohm resistors
9) Wires
10) A soldering iron and solder
11) Gorilla glue, super glue, crazy glue, or some adhesive of the sort
12) 10K Potentiometer

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Step 1: Putting the Magnet on the Wheel

The first thing I did was embed the small magnet in my rubber skateboard wheel. I drilled a small hole (1/4" diameter to fit the magnet snugly) on the inside of one of my back wheels toward the edge of the wheel. I then dropped some gorilla glue in this hole and fit the magnet in it so about half of the magnet's height was imbedded in the wheel and half was sticking out of the wheel. Later this magnet will allow the magnetic relay switch to count the wheel's revolutions when the relay switch is near the spinning magnet.  
leonardor (author) 1 year ago
Hey guys,
Sorry I was really slow on getting the arduino code back up. I've re-uploaded a pdf with the code, so everything should be good now. Enjoy!
dannyboy079 months ago
heyy leonardor I'm still trying, what brand type 16x2 lcd did you use, I'd appreciate it if you commented on my email thanks a lot :)
michmag9 months ago
can some one please help me find the relay switch he is using! please thank you
leonardor (author)  michmag9 months ago
Here's another:
leonardor (author)  michmag9 months ago
Look for reed switches or hall effect sensors. Here's an example:,or.r_cp.r_qf.&bvm=bv.57752919,d.cGU,pv.xjs.s.en_US.JVi-ZN0rCA0.O&biw=1371&bih=745&tch=1&ech=1&psi=dm2hUtv4DYn2oATs9ICwCw.1386311030542.3&ei=g22hUqSHK5DroATb6oDABQ&ved=0CMECEKYrMAs
dannyboy079 months ago
hey leonardor I'm trying to do it, I connected everything I used your pdf arduino code and my lcd display turns on but it doesn't show mph or anything do u have any idea what could be the problem?
leonardor (author)  dannyboy079 months ago
The lines
towards the bottom of the code are the ones that dictate what the LCD should display. More generally, the bottom of the code after
void LCDPrint ()
is the part of the code that you should look at. Make sure you have this part exactly as written. Also make sure you haven't accidentally commented out any lines of code. But if your code is identical to the pdf file, then I'm not exactly sure what the problem could other than a wiring problem. Sorry I can't be of more help
ипънев9 months ago
Hey guys,
How i can convert RPS to M/S & MPH to KMH?
it isn't that hard al you have to do is rpm*(circumference of your wheel in cm)*(60 min/hr)*(1/100000 miles/inches)=speed in KMH
and change everey MPH to KMH in the code and why change RPS?
Neil.r1 year ago
Hi link for code (word file) is not working. Can you fix it? Thanks!
You mentioned a 10K Potentiometer. I didnt see it anywhere in the write up, what did you use it for? And can you please re post that word doc. It is blocked by admin.
almogu1 year ago
hello, I love, but does not work the link to doc to download the code. I would like to try. thanks
Risso1 year ago
link for skateboard speedometer code.doc is down ... please re-up
Ronni5301 year ago
Hello I wanted to download the word file containing the code for this project. The link is not working. Can you please fix it. Thank you.
Richard.s1 year ago
I am unable to access the code file shown here.

Can you provide an alternate source to obtain a copy?

hey urs was the easiest and the cheapest speedometer...and can u mail me the picture of the magnet and the relay attached to the wheel so that i can attach it to my cycle compared to it ........please mail it to me as fast as u can..u can mail me at or or reply to me as fast as u can.please please PLEASEE

Thank you!
Please, for your own sake, do NOT post your email address in public comments! It will attract spammers. Instead, send a personal message to the creator of the instructable.
painfulfart2 years ago
how do you test for sens value and milisegundos value? thanks.. also could someone explain why use a analog input not a digital input since its counting on (1023) and off(0) values?
bbsux2 years ago
Hall effect sensors always "seem" to be better until you look at all the supporting hardware you'll need to setup to make sure they get a clean digital signal. Trust me its not as easy as it sounds.
idoha2 years ago
I think you mean Arduino LONGBOARD Speedometer. Anywho, this is an awesome project, and I love skate/longboard mods. I did notice though, that the box is kinda bulky, and seeing you're only using 1input and 6 outputs, maybe switch out that uno for a pro mini:

Not as easy to code, but I think worth it for your project.
nerd74732 years ago
where did you get the plastic case for the arduino?
leonardor (author)  nerd74732 years ago
You can find them right here...
I agree with Technochicken. A few thousand clicks and it is done for. Plus, it would probably miss a few clicks at high speeds...

However, a reed switch will give you easier coding.

Very cool.
ben_k2 years ago
Good project. Rater than using a mechanical relay (was it a reed switch?), it might be more reliable and longer lasting to use a solid state Hall Effect sensor, which does not rely on moving mechanical contacts to sense the magnetic field.