My
experiences with construction of the DIY
Anemometer. 
Directory
WHY
BUILD
AN ANEMOMETER?
My desire to have an anemometer comes from sailing
for a hobby.
Some idea of what the wind is doing, is useful
when deciding if the day is going to be a good sailing day or a great
sailing
day. Although my home made weathervane may suggest that there is
some
wind, it gives no accurate indication of direction or strength.
I searched the web for a more scientific device.
Derek Weston's Rotorvane
DIY anemometer web page was the best
one
I
found.
It looked like a good project that combined my interests
and
produced a practical and useful device.
It is a very clever piece of electronics but not complicated
to build.
I was pleasantly surprised by the simplicity and accuracy of Derek's instructions. The anemometer can be made quite easily without sophisticated tools, providing care is taken. The most sophisticated piece of equipment I used for the construction of the anemometer, was an old electric hand drill with a drill stand.
A great deal of assistance was given to me by Derek,
who was very helpful whenever I had queries about the unit.
He
took a personal interest in helping me to research and repair
faults
when my device did not work first time. I owe him a great debt of
gratitude
for the pride I have in my device.
Encouragement and guidance also from Jeff
Northcott,
a friend with a lot of electronic expertise and patience, who
ensured
that the electronics were easily put together, tested and errors (due
to
my clumsiness) were quickly sorted out . He has a comprehensive weather
station at his home in Christchurch.
Some of the parts that I used for this project, differ from
those
in the parts list. In this page I shall describe how I went about
building
my anemometer and the alterations I made to suit the parts I could get
my hands on.
Further down, you will see how I modified the design of the Sensor
PCB and how I made up a completely new display unit using 5mm LEDs .
This information may help those who wish build one and want to add
a personal
touch to their device.
Any tips or advice that I can offer relating to my personal experiences, are hilighted in green.
BEARING AND SHAFT:
I made the shaft from a piece of 8mm brass rod. It was
all that
I had available that could be used to fit the inside diameter of the
bearing,
so it had to be turned down to size.
I used my electric drill clamped in a vice as a lathe and used
a
medium file.
About 15mm of the shaft was clamped into the drill
chuck,
then the rest of the 60mm shaft was filed down to the same
size as the bearing's inside diameter. This allowed the shaft to fit
quite
snugly into the bearing and come to rest against the un-filed end.
A lot of care was taken when the size was almost
right, to be sure that not too much of the shaft was filed away.
The job was completed with fine abrasive paper to get a firm, but
not tight fit.
A 6mm length of the shaft was left at this size to fit
the
bearing onto, then I continued filing the length of the shaft
until
it was 3.2mm diameter.
Testing the uniformity of the length of
the shaft was achieved with a piece of scrap metal drilled to 3.5
mm. More filing wherever the shaft would not fit through the hole, soon
had the shaft at an even diameter.
Once the shaft was a uniform size, I continued filing, checking the diameter in the same manner, with another piece of drilled scrap metal until the desired size of 3.2mm was reached. Fine abrasive paper was used at the last, to make the shaft smooth.
This process was done in two stages, filed to
3.5mm then 3.2mm, because I did not want to "over file" and make
the shaft too thin.
It takes a long while to file an 8mm shaft down
to 3.2mm and I did not want to have to begin the job all over again.
A small engineers lathe would do a better job much quicker, but as I
did not have one but i did have loads of time, this is the method I
used. The results are much the same i guess.
Once this stage was complete, the
shaft was reversed in the drill. A 1mm wide flange was left at
8mm
diameter and the rest of the shaft was also filed to a size of 3.2mm.
The
flange prevents the shaft from going right through the bearing
and
allows the bearing to support the shaft when it is vertical.
Threads were then cut onto both ends of
the shaft.
The short top end of the shaft needed to
be just long enough to take the spider, the weather shield plus a
securing
nut and washer. The surplus length was trimmed and filed once the
length
was determined after initial assembly.
A taper was filed onto the 6mm length to make fitting the bearing a bit
easier.
I kept some of the brass filings and mixed them with resin when it came time to balance the cups after the tag was connected. Brass filings are heavier than resin, so much less of the balancing compound was necessary.
I used a 4.5mm diameter stainless steel set screw for the thrust
bearing.
This was drilled with a 2.5mm bit to a depth of about 2mm at one end
and
acts as a socket for the chamfer I filed onto the bottom end of
the shaft. A spot
of light grease at final assembly placed into the socket lubricates the
shaft, while one drop of diesel was used to lubricate the top end
bearing.
SPIDER ASSEMBLY
Construction of the spider was reasonably straight forward as per the
plans.
I used a piece of 1.5mm thick switch board,
discarded
by a local electrician. It is very similar to PCB without the
copper
cladding and was easy to work, using a fine toothed saw and a file.
I made up a jig using plywood to carefully clamp the table
tennis
ball halves in exactly the right place when securing them to the
spider.
Instead of holding the spider down with tape, I found that by using a
screw
with a large flat head, better security was possible for the spider
while
the glue set. It was a simple job to accurately clamp the spider with
the
screw, keeping it vertical with the "free" arms over the edge of
a smooth block of wood. I used two pieces of fine wire to
secure
each cup to the spider rather than only one as described in the
construction
notes. This aided their security but did not adversely add weight to
the
spider.
By assembling one cup at a time and allowing time for the glue to set,
this part of the construction took about a week.
I used epoxy resin as used in boat
building
to secure the cups to the spider, rather than two part glue bought in
tubes.
Because the resin takes a while to go off (set)
I placed cling film on the board first, so that nothing could stick to
it or my building jig.
The spider ends and the cups were lightly
sanded where they made contact, to improve adhesion with the resin.
SENSOR BOARD
The sensor board instructions specified the use of vero board
but I do not like using it other than for experimenting.
With only 7 components to place, I believed I could make up a
reasonably
"professional" looking PCB by following the schematic drawing.
I
made my sensor board from a piece of PCB measuring 50mm x 22mm.
While this circuit board looks quite different to the ones now supplied
in the kit, it operates in identical fashion .
The appearance and physical layout of the components on the PCB is not critical I believe, but the electronic connection of the components, is. There may be many ways that the board could be laid out and still operate successfully.
It would have been easier to use the PCB now supplied, but when I built mine, the PCB option was not available in the kit and I was pleased to have had the challenge.
DISPLAY CASE
Preparing the display case was quite straight
forward
although it took a lot of time.
I used a plastic jiffy box from a local commercial electrical
supply store. The appearance of the box I used, makes it look a bit
"industrial",
but for my prototype it is satisfactory.
It measures 105mm x 75mm x 60mm deep which allows ample room to house
a 9v battery for power back up.
I was a bit concerned that an old drill stand and hand drill may not be up to the challenge of precision drilling the 42 holes for the LED's so I had some practice with odd bits of scrap before I drilled the display case lid.
I also did not down load the Rotorvane template for the display
front
panel. I did not trust my PC to down load the template to the correct
scale,
so I made my own. Even though it took longer, I was pleased with the
outcome.
I began by drawing on a sheet of paper, vertical and horizontal
center grid lines, then with a compass I drew two circles of the
required
diameter for the readouts at centers to suit the PCB.
Using a protractor, I marked off the circles in 15 degree
increments,
ensuring that on the speed scale, the top (two) LED's were 7.5 degrees
either side of the vertical line. This allows them to align with
the PCB spacing and made the display symmetrical in its
appearance.
I then penciled vertical and horizontal center lines onto
the display case lid . Using paper glue, I glued the template
onto
the display case lid, taking care to align the grid lines on both
the plastic lid and the paper, without ripping or distorting the
template.
The next step once the glue was dry, (a day or so later) was to prick through the paper with a pin to mark the exact hole centers. the "prickings" were carefully inspected once completed to check their precise spacing, then they were drilled with a 1mm drill and inspected again for accuracy.
Extreme care in this process was most important as any flaws would be forever visible once construction was complete, or another lid would have to be obtained and the process repeated.
After the holes had been drilled it was a simple job to dampen the paper and remove it from the display case, then remove any rough edges round the drilled holes using a countersink bit. BY HAND.
My first attempt at tidying up in this manner ended with a rather ugly large hole. Fortunately it was on one of my practice pieces of scrap. A good lesson learned.
The 9mm hole for the "max. gust" button was also marked in a similar manner and drilled last
Deciding first how the display was to be mounted, determined where
the
cable connections would go.
Holes were drilled in one end of the display case for the
power
socket, the on/off switch and a mono 3.5mm socket for the sensor cable.
The data cable connector was fitted to the side of the display case
that
would be the bottom once it was mounted on a wall.
DISPLAY PCB
Assembly of the display PCB was very simple and straight forward. I
made a minor alteration to the display, to suit parts that I
could
get locally, plus a modification to how power is supplied.
I substituted green 3mm LED's for the red ones shown. I feel they are easier on the eye.
Power is supplied by a 9v plug pack from the mains and the
addition
of a back up 9v dry cell with a power diode so that in the event of a
power
cut, there is no interruption to the device's operation. This idea was
borrowed from Helge Rustad's weather
station
project. The diode is just visible in the lower left, soldered onto the
switch below the supply socket. Above that is the 3.5mm mono socket for
the sensor's input.
I found that it is very important to carefully
inspect all solder joints using a magnifying glass, then run through
the
checking process to test each LED Before the PIC is installed. A
fault in my soldering was not evident until I tried to calibrate the
device.
Considerable frustration came about because
although
I thought I had checked all my solder joints several times, two tracks
had made contact which prevented the device from working the
first
time I powered it up.
CALIBRATION
A calm day is very important for accurate
calibration.
Road tests even in slight cross winds after initial
calibration,
showed marked errors in both speed and direction sensing
For the test, I made up an adapter to power the unit through the
cigarette
lighter plug from the car's 12v battery.
Using the on/off switch made it easier to follow the
calibration
procedure.
I chose a top end scale of 51 knots, each LED representing a
3 knot speed difference.
Calibration speed was 30 knots which equates to 55.56 km/hr, so once
my assistant (wife) had mastered the speed control, the rest was easy.
We were fortunate to have the use of a car with a digital speedometer which made keeping to an exact speed much easier. After a few dummy runs along a quiet stretch of straight road, the test was completed in about 15 minutes.
INSTALLATION
The sensor sits on top of a 1.5m high aluminum pole mounted
on the center of my house roof. 3 stays prevent any movement in
strong
winds.
The display case is screwed to the underside of a shelf in our
dining
room. The sensor cable runs almost straight down from the apex of the
roof,
through the ceiling, to the display unit. The cable is about 6m long.
A mains power socket near the shelf allows the plug pack supply cable
to also neatly lead to the display unit .
My PC is some distance away, making it a difficult
job to connect the anemometer to the PC, but not impossible.
OPERATION
The unit has operated since July 2001 without fault or the need
for maintainence other than re-lubricating the bearing, about
once a year. I reset it almost every day but no
records
have
been kept so far as I use it as a realtime display only.
EXPERIMENTS
I was so pleased with the results of this project, that I decided to
make a second sensor with shorter spider arms. I was able to source all
the parts locally but I found that it is most
important
to obtain the IR. LED and Photo transistor as specified in the kit
as
generic ones available at "corner stores" just do not cope with the
faster
switching times required. They gave faulty readings.
After some thought about the size of the sensor housing, I
decided
on another sensor board design. I drew another layout for a circular
PCB
board like a large washer with the center cut out to allow room for the
nut that secured the bearing housing.
By making the sensor board circular, It fitted nicely into the top
of
the sensor housing so I was also able to make the housing much
more
compact. I figured I could shorten the shaft quite a bit to
reduce
the possibility of shaft wobble, so long as the chopper disc did
not touch the tops of any of the components, then make the sensor
housing length to suit.
The diameter of the PCV tube caps used for the sensor housing was also
reduced
slightly, as it was not necessary to make allowance for clearance
between the disc and the flat PCB.
The photo transistor in my 2nd prototype, stands well clear of the
PCB
and has its head bent down to align it with the IR. LED.
I may have to solder a reinforcing stand off
for the Photo transistor if it is effected by vibration but it has
shown no signs of failing yet.
The photo transistor is at the top left of this photo, partly obscuring the 180R resister and IR LED.
My intention was to be able to monitor the wind with the anemometer sensor permanently installed on my house and have another portable unit that I can use on site at Yacht regattas or any other location I desire.
The length of the spider arms effects calibration markedly, so the display needs to be matched to a single sensor unit or the display needs to be re-calibrated for each sensor.
For this experiment I also made my own chopper disc from a 50mm x 50mm
piece of alloy plate 1.5mm thick.
I used a similar technique that I used for drilling the display case
LED holes.
On a piece of paper I marked out the center hole and then used a
compass
to accurately mark the gap spacing copied from the original chopper
disc.
When these had been marked out carefully, the paper was glued
to the alloy plate and the gap locations were pricked through with a
sharp
object, checked for precision then drilled 1mm first then 5.5mm. This
gave
a satisfactory gap for the photo transistor to see the IR. LED. Once
the
4 sensor holes and the center hole were drilled, the disc was cut out
and
filed carefully down to size and polished.
ENLARGED DISPLAY
Then
I decided that the display in my house could do with being a bit
larger to make the display easier to read at a distance. This could
easily
be done I figured, by fitting 5mm LED's instead of the 3mm ones
specified,
but the layout of the PCB made it difficult to prevent the LED legs
from
shorting together when bent to let the LED's to fit the holes.
My DIY spirit led me to etch a larger scale board, copying the
copper track layout from the original and completely re-drawing the
board.
The diameters of the enlarged displays are 60mm, almost twice the
original
size.
This second unit was built using all locally sourced components
except for the coded PIC 16F84 chip. I carefully borrowed the chip from
the smaller display for the test and the larger one also works as it
should,
(with the sensor it was calibrated to).
The completed large display.
To ensure that the LED s were placed right way round, the PCB was
marked with a small black line where the flat side of the LEDs would
sit. Just visible in the picture.
The new case is constructed from pieces of wood 12mm thick. The case outside dimensions measure 160mm x 115mm x 45mm .
The aluminum strip screwed to the top of the display case allows it to be fixed to the underside of a shelf.
There are no mounting screws for the PCB and face plate. Both the
PCB
and the face plate slide into grooves cut into the display case frame.
The face plate groove is 6mm from the front of the case, while the
PCB sits 15mm behind the face plate.
One end of the case is glued and screwed to the sides (top &
bottom)
while the other end has screws only and no glue holding it together.
This
allows it to be unscrewed so that the PCB and face plate can be slid
into
the grooves before the end is screwed into place, holding it all firm.
All the LED's were placed into the PCB but not soldered until the board and face plate were fitted into the display case. This allowed the height of the LED's to be adjusted to a suitable height through the face plate.
Because the LED's are partially recessed below the surface of the face panel, I found it necessary to place a short length of tubing over each LED. This prevents them from giving a false reading by appearing to be lit by the light from adjacent LED's.
The Max. gust button has been mounted on the back cover along with the input sockets, power switch and the DP9 socket.
To increase the holding power of the screws being fixed into the end grains of the case, holes were drilled into the rear of the case top and bottom. Small wooden dowels were hammered in to these holes to allow the screws to "bite" into the them when the end caps were screwed into place. The dowels are hidden by the back cover when the display unit is fully assembled.
THE BEAUFORT SCALE.
Until not so long ago, all marine wind strengths were assessed using
the scale devised in 1808, by Admiral Sir Francis Beaufort of the
Royal Navy.
The scale is still in use today in some places although generally
marine
wind strenghts are now reported in Knots only.
It should be noted, that these are mean wind speeds in the open sea.
There will often be occasional stronger gusts.
Beaufort
Force
Description
Knots
Sea conditions
0
Calm
0
Sea like a mirror
1
Light
air
1-3
Scale like ripples without crests
2
Light
breeze
4-6
Small wavelets with crests that do not break
3
Gentle
breeze
7-10
Large wavelets. Crests begin to break
4
Moderate breeze
11-16
Small waves some with whitecaps breaking
5
Fresh
breeze
17-21
Moderate waves, many whitecaps, some spray
6
Strong
breeze
22-27
Large waves with white foam crests.Spray blowing from crests
7
Near
gale
28-33
Sea heaps up white foamblown in streaks
8
Gale
34-40
Moderately high waves, crests breakwith foam blown in streaks
9
Strong
Gale
41-47
High waves. Dense streaks of foam. Wave tops tumble
10
Storm
48-55
Very high waves, overhanging crests. Sea white very dense foam
11
Violent
storm
56-63
Exceptionally high waves. Air filed with foam and spray, the sea
12
Hurricane
61-64
becoming completely white with driving spray. Poor visibility
1. Some artwork is necessary for the front panel of my display, which I will soon complete but until then some simple pencil digits have been scribed on the face of the panel.
2. I have down-loaded the software for the anemometer, so the next logical step is to begin recording the information being collected.
3. Now that I have the basics for a weather station, I may add other features such as temperature and rainfall sensing at some time.
4. I use an aneroid barometer, which as a sailor I worship every day, so an electronic version is a definite possibility for studying the weather on a regular basis.