LaCrosse 23xx Wind Sensor Modification

This page describes how to modify the wind sensor of a La Crosse WS2300
Weather Station.
The modification was done based on hints I have received
both from La Crosse, Richard Huntington (New Zealand) and my own
experiments.
Many trials have been made and this modification is the only one
that has worked for me so far.

The La Crosse WS2300 (and WS2305, WS2310) have a problem with the wind
sensor. If the cable between wind sensor and outdoor temperature/humidity sensor
is exposed to electromagnetic interference the wind sensor reading often becomes
25.5 m/s or 91.8 km/h.

The impedance level between the wind sensor and the temperature/humidity
sensor is kept pretty high to save battery power. Obviously the design is not as
robust as it could have been. But there is a reasonably easy modification that
can be done without being very technically skilled.

The modification requires the following tools

  • Side-cutting nippers
  • Tool for modular connector 6P4C (same as used for telephones)
  • Soldering iron and solder
  • Some thin copper wire or strong sewing thread
  • Screwdrivers: Pozidrive 0, Philips 0

The following material is needed

  • Category 5 Shielded Twisted Pair (STP) network cable
  • Some isolation tape or heat shrink tube

The category 5 STP cable is assumed to have 4 twisted pairs colours,
blue/blue-white, brown/brown-white, yellow/yellow-white and
green/green-white.
If the cable you use has different colours you will have
to convert the colours. You could probably use normal shielded cable with 3
wires, but the STP cable is easy to get in a computer store and the wire gauge
will fit the modular 6P4C connector perfectly. The STP cable I have used has a
metal foil shield and an additional thin shield wire that runs along the metal
foil.

The modification is in essence replacing the unshielded and untwisted cable
between wind sensor and outdoor temperature/humidity sensor by a shielded cable
and additionally take advantage of the twisted pairs and pair the 3 signal/power
wires with a ground wire for additional noise immunity.

We start at the end of the outdoor temperature/humidity sensor.

Step 1.

Remove the outside isolation. Remove roughly 40-50 mm.

Step 2.

Assuming that your shield both has metal foil and a thin ground
wire bundle remove the metal foil. If you only have the metal foil you will have
to somehow connect a short wire to this shield.
Cut off the green/green-white
twisted pair.
The other 3 pairs are untwisted and the white pairs are cut to
a length of round 20 mm. Also the shield wire is cut to 20 mm.

Step 3.

Remove the isolation from the 3 short wires.
Additionally take the green-white wire you just cut off and remove the isolation from the tip in
one end.

Step 4.

Time to use the soldering iron.
First put some solder on all 4
wires and the ground wire.
We are now going to solder all 5 wires together.
It is almost impossible to hold 5 wires together at the same time.
With a
small copper wire or sewing thread make a small simple knot like shown.

Step 5.

 

Tie the 4 wires together with the copper wire so that all 4 tips
touch each other.

Step 6.

 

You can now easily heat the wires holding the soldering iron in
one hand and holding the 5th small loose wire in the other hand. Because you
already have put solder on the tip of all wires it is a simple matter of heating
up the solder so it all melts together.

Step 7.

 

You can now remove the copper wire and put some isolation tape or
heat shrink tube round the solder joint to isolate it.

Step 8.

 

We now need to put the 4 wires into the modular 6P4C connector (6
positions/4 contacts – also known as RJ11). The connector is the same as you use
for all sorts of telephone equipment. You can also use a 6P6C (6 positions/6
contacts) but then you have to take care to put the wires in the 4 center
pins.
Place the 4 wires as shown. The 6P4C is shown from where the cable goes
in and the lock pin down.
From left to right: Ground (white), orange, brown
and blue.

Step 9.

 

Carefully press the four wires all the way in maintaining the
right sequence.
With a special tool made for modular (RJ) connectors press
the connector pins in. If you do not have such a tool then you must go out and
either borrow or buy it. If you are smart you buy one that also fits the 8P8C
(RJ45) type. Then you can make your own computer network cables for ethernet. It
takes only a few cables and the cost of the tool is saved. You do not need to
invest in an expensive model since you will only be using it rarely. They all do
the job satisfactory. The expensive professional types are just nice to use and
last longer.
Since the outside isolation of the cable is not inside the
connector the strain relief is not ideal. The wires are only held by the
contacts, so it may be a good idea to support the cable with a tie wrap or
similar when you plug finally plug it into the outdoor temperature/humidity
sensor.

Step 10.

 

Now we need to modify the wind sensor end. This is a bit more
difficult. There is the nice way and there is the easier and faster way. I chose
the nice but difficult way. Richard Huntington (New Zealand) used the simpler
and easier way and both ways are confirmed to be working. I would recommend the
easier way unless you are used to soldering on PCBs. I will show both
methods.
First the difficult way:
Take the wind sensor apart. You will
need to remove the wind mill. It is held by one small screw. When this screw is
removed you can pull off the mill.
Then you open the wind sensor housing.
This is done by removing the 3 visible screws.
Carefully take the housing
apart. Try and get familiar with how the wire is routed. The picture above shown
how it looks like before the modification. I forgot to take a picture
after.
You now remove the existing 4 wire cable by unsoldering it from the
PCB.
Remove the old solder and put a little fresh solder on each of the 4
pads. Not too much.
You now prepare the other end of the STP cable the same
way you did in steps 1 to 7. You may want to make the wires a little bit longer
so that the grounding connection is done right where the cable enters the wind
sensor housing. I do not recommend trying to solder 3 wires and a shield to one
pad on the PCB. Join them in one connection point and then route one single wire
to the ground pad on the PCB.
Make sure to put the new cable through the wind
sensor holder before putting it into the wind sensor housing. Otherwise you have
to pull maybe 10 m of thick STP cable through the holder afterwards.
Now it
is time to put it all back together again.

OK here comes the easier method.

Step 11.

 

Remove the wind sensor holder or bracket (the thing on the right)
from the sensor.
Cut the wire approx as shown. Close enough to the wind
sensor to make sure that the connection point is inside the plastic tube of the
holder. And far enough to make sure that you can cut away an extra piece if it
does not work out for you the first time.

Step 12.

 

Again make the same preparation of the STP cable as you did in
the other end.
Remove the foil.
Remove the unused green/green-white
pair.
Join all the white wires and the ground shield in one solder joint
using a small copper wire to hold them together while you solder.
One
difference is that this time you cut all wires to the same length.
The wire
from the wind sensor also needs to be un-isolated.
For all wires add some
solder to each tip using the soldering iron and some fresh solder (never used
the old solder that has been on the tip for minutes).
If you isolate each
wire connection with heat shrink tubes NOW it the time to add them to the 4
wires PLUS the thicker piece on the cable as well. You know you hate yourself
when you forget and have to do it all over again. If you use isolation tape you
can wrap it around after you have soldered.
Carefully solder the 4 wires
together making sure you get a good connection. By adding solder to the tip of
all the wires before you join them it is very easy to put them together with one
hand and holding the soldering iron with the other hand. You will normally not
need to add more solder. If you do not pre-solder the wire ends you will need a
third hand to hold and apply the solder.

Step 13.

 

When the soldering is done you can remove the copper wire you
used to hold the ground wires together.
Now isolate each wire with tape or
heat shrink tubes. Make sure that the wires are isolated from each
other.
Then add some isolation round the entire cable to prevent humidity
from getting into the cable.

Step 14.

 

Push the holder into the wind sensor housing again.

You are done. All that is left is testing it. If it does not work I bet you
have mirrored the wires. If you have done it wrong inside the wind sensor you
must open it again and correct it. The ground must be connected to the shield
and the ground pairs for the shielding to work. If you mirrored at the modular
connector then you can just cut the connector off and put another the right
way.

I have used round 11 m of wire but it should work maybe up to 30 m of
wire.
Before I made the modification, I saw the 25.5 m/s reading 2-10 times
per day. Sometimes even more. If I used a radio link instead of cable connection
I would get the false reading 1-3 times pr day. This is simply due to the fact
that the wind sensor is read less often when using radio link.
As I write
this I have not seen one single 25.5 m/s reading for more than 3 days (update:
Dec 2004 – and also after more than one year) and I run with the wire link. I am
now much more happy with my weather station since the max wind speed and min
wind chill data can now be used.

Good luck.

Kenneth Lavrsen

2003 October 24.

Original document was published here: http://www.lavrsen.dk/sources/weather/windmod.htm