Very Easy Cadence Meter for Your Bike <$12

Cadence is the speed at which the pedals turn, measured in Revolutions Per Minute.
Inexperienced riders tend to pedal too slow which will put stress on their knees.

I always wanted to know how fast I was pedaling but I didn't
want to spend a lot of money to do it. Most experienced riders
have a Cadence of 70 to 90 RPM's. When I started using the meter
I found 60-80 to be my norm, but since then I moved up into the
70-90 range without realizing it.

Here is my solution for less then $12 and super easy to do.

Step 1: $10 Cycle Computer

I bought this at Walmart, but many other
stores carry them. They are very accurate
and simple to use. They also turn on
automatically when the magnet passes
the sensor.

It will also record your maximum and
average Cadence plus the number of
times the crank turned. It will also
keep track of the time you are actually
pedaling. When compared with the time
on the speedometer it will tell you
how much coasting you did.

The only drawback is the meter only
reads to 99.9, but you can set it to read
1/2 and remember to double the reading.

Step 2: Computer and Harness

Here's what you get.

1. Computer
2. Computer harness with bracket
and sensor.
3. Wheel magnet and zip ties which I
didn't use because I like the black
ties.

Step 3: One Dollar Magnets

I picked these up at a Dollar store.
You can use about anything, just
check that they are fairly strong.

Phil B found 1/2 inch ceramic magnets
at Radio Shack for $1.99

Step 4: Remove Magnets

I lucked out finding a pack of
5 which you use all of them on
a road bike.

On a Mountain bike you can use
4 due to the difference in the
crank.

I removed the magnets by cutting
around the outside of the magnet
with a knife. Be careful, you
don't want to pry on the magnet
and break it.

Step 5: Place Magnets

Place the magnets on your smallest
chain ring.

I used 5 so the spacing was even
around the crank.

You can use 4 on a Mountain bike.

If the magnets are fairly strong they
will stay put, but they did move when
they were hit with the hose. Be careful not
to get water in the BB when you wash your bike.

If you have aluminum chain rings and bolts you
will have to glue them on. I used rubber
cement on mine anyways.

Step 6: Mount Sensor

Mount the Sensor on the front down
tube as shown. Let a space about
3 mm from the magnet with the end
of the sensor about 1/2 way over
the center of the magnet.

Don't mount the computer bracket to
the handlebar yet, that way you see the
readout easier.

Set the computer by instruction manual
using 3333 as the wheel size and
the speed reading to KM not Miles.

You can check the pickup by rotating the
crank backwards with the kickstand up
and the bike leaning against something.

Once you are happy with the pickup you
can mount the computer to the handlebar.

Step 7: Sensor Position

Here is a second view of the sensor.

Step 8: Computer Set Up

This is the set up for this computer.

Hold left and right buttons down at the same time to reset,
the whole display will flash then go to the wheel size.

It will show 2124 the default setting with the 4 flashing.
Change the 4 to a 3 by pressing the right button.
Once it is at 3 press the left button to move the
cursor over to the next number and set it to 3.
Repeat until the number is 3333

It will then go to the KM/Miles mode.
Since it comes up as KM first just press the
left button to set it as that. The right button
will switch it back and forth between the two.

You set the time by holding the left button down for
about 4 sec when the display is showing the time.
You can select 12 or 24 hr mode then you
will set the time, hours and minutes.

If You you mess up just reset by holding both buttons for
a few seconds and start over.

How it works.

Say you want it to read 60KM at 60 RPM's
60km is 1km per minute or 1000 meters.
1000 meters is 1000/60 or 16.666 meters per sec.
Since there are 5 magnets for each rotation 16.666/5
is 3.333 meters per 1/5 second or 3333 MM.

Each time a magnet passes the sensor it is recording
as if it is moving 3.333 meters.

Mountain bikes or comfort bikes with 4 magnets.

16.666/4 would be a setting of 4166

The reason you need this many magnets is that the max
wheel size you can input on this computer is 5999.

I hardly ever have a Cadence above 90 so the 99 limit is
fine for me. You can cut the number in half and
remember to double the readout if you like. That will
set the top limit to 199.8 RPM's

To check your work go to this site and print out
a gear ratio chart using your tire size, front
chain ring, rear cassette size and the cadence
you want. You can cut it out and tape it
on your bike if you like.
http://www.sheldonbrown.com/gears/

Hope you enjoy this project as much as I do.