N00B: Which sensor?

Soon I will be the proud owner of a new Arduino Diecimila.

I would like to use my Arduino to make a Bike Computer for my trainer in my basement.

I realize it is a little large for this task, but I am an avid cyclist and I thought this might be a good starter project. I would output the data via the USB and display it on my PC screen.

My question is what sensor would I need to attach to the Arduino to sense the wheel turning. I know I need a magnet, but what do they call that sensor that senses the magnet passing it?

One thought I had is I could just take the wire from an old bike computer I may be able to find.


The solid-state way is to use a “hall-effect” sensor.


or you could use a reed switch (sometimes called a reed relay) which is also triggered by a magnet.

Thanks so much for the suggestions! I really do appreciate it.

A reed switch is probably what bike computers already use, correct?

Thats my guess, but it could be a hall effect sensor as well

Doesn’t magnetic sensors have high inertia? If yes, the wheel turn cannot be sense if turning (running) at high speeds. In this case, a light sensor (IR, LDR, etc…) wouldn’t be better? I’m asking, because I’m not sure too…

I am thinking what I need is indeed a Hall Effect Sensor

Wiki - Cyclocomputer.

Now I just have to find to purchase one. Any ideas? :slight_smile:

hall effect is the way to go…

  • light sensor: too susceptible to ambient light conditions
  • reed switch: slow response for high RPM’s


Thanks for all of the help! :slight_smile:

My Arduino shipped yesterday so I am hoping to have it by Thurs/Fri.

I’ll be keeping track of my project HERE.

I got one other person interested in the Arduino as well. He ordered 2 last week and is designing a Lap Counting System for R/C Truck racing.

Nice. Soon we Arduinos will rule the universe :slight_smile:

Nice. Soon we Arduinos will rule the universe :slight_smile:

personally I hope they use a bigger processor than an Arduino to run the universe. :slight_smile:

But what if I could fit the entire self-replication code in a single Arudino sketch and it could reproduce itself? Couldn’t we take over the universe that way? :slight_smile: