BY MICHAEL SIMPSON
rain gauge or another anemometer.
One of the most difficult aspects
of making an anemometer is the construction of the cup and hub assembly. If they are not perfectly balanced,
the anemometer may not operate
properly or even worse, fly apart at
high speeds. A company called
ForceField has solved this problem for
us. They offer a molded plastic cup
and hub assembly for around $20.
As shown in Figure 2, the assembly has a very small pre-drilled hole in
the center, so all we need to do is
enlarge it to the correct size and it will
always be dead center.
Our homemade anemometer will
feature this assembly. We will build a
small ball bearing mount to attach the
assembly and a couple of magnets
and a reed sensor. Don’t panic; the
reed sensor is nothing more than the
small glass reed removed from a reed
relay that you can purchase from your
To interface this anemometer, we
will use a small, 1-Wire board available
from a company called Hobby Boards.
You will be hearing more about
Hobby Boards later in this article, as
well as throughout the series.
The dual counter shown in Figure
3 is a very small board that measures
about 3/4” x 1”. It has a small battery
that will allow the onboard DS2423 to
retain its counts for years.
shows the basic
hookup for connecting a reed to the
counter. The cool
thing about the
onboard DS2423 is
that it has built-in
denounce so you
don’t have to worry
about any additionally
circuitry. Notice that
we are only using half
of the counter so later
we can connect some
other sensor like a
Features of the Homemade
• This is the most sensitive anemometer out of the three. I ran several tests
outside, and on very calm days this
was the only anemometer turning.
The cup assembly has the lowest mass
so it takes much less air flow to get it
going and it also tended to track the
variations in winds much better than
■ FIGURE 2
• This device is very resistant to water
damage due to its simple design.
• Since you are building the unit, it
will be very easy to repair or replace
Take a counter reading, wait
1.5 seconds, then take another. Subtract
the first from the second and multiply
by . 88.
• This anemometer has the smallest
footprint and weighs the least of all
three, so the weather pole used can
be quite small.
Homemade Anemometer Assembly
Before you proceed, please read
through all the instructions. You will
need the following tools to complete
• It’s not restricted to 1-Wire. You can
use several interface options.
• Drill — This can be any kind of drill.
You will also need 1/8” and 5/16” drill
I ran tests up to 50 MPH with
my car, so this anemometer should
hold up nicely under most weather
conditions. This anemometer uses the
• Pliers — You will need these to tighten the lock nut.
• Screwdriver — You will need this to
tighten the machine screw.
MPH = counts over 1.5 second
time period . 88
• Soldering Iron — This is needed for
■ FIGURE 3
■ SCHEMATIC 1
February 2007 35