DIY Weather instruments


Bill's Homemade Weather

Instruments and Solar Projects 


This webpage provides information on how to make an inexpensive electronic windvane that displays the outside wind direction on a display indoors.   It is made from easy to find parts. If you are resourceful, it can be constructed at a price far far below what you would pay for one commercially made.  I also provide instructions on making a simple, low cost thermometer, RH sensor, ceilometer, and solar panel.
Homemade Wind Vane - Introduction

Observing the weather can be lots of fun and educational. There are all kinds of weather instruments available to collect weather data, but unfortunately they can be quite expensive.  Rather than pay hundreds of dollars for a windvane that provides an indoor display of the wind direction, I decided to build one instead.   It would have a resolution of 22.5 degrees of azimuth and designed to last for years in the open environment.  

The heart of the weathervane design I provide here is the magnetic switch. These switches come in different sizes and are commonly found in burglar alarm systems and even some commercial electronic wind vanes.  When a small magnet passes over the switch, the switch closes.  This closed switch can be used to turn on a small light bulb or Light Emitting Diode (LED).  What I did was attach the magnet to a shaft that has a wind vane on top.  When wind rotates the shaft and the magnet swings over 1 of 8 switches placed on points of the compass, one or two Light Emitting Diodes (LED) mounted in a small box inside my house lights up and tells me which way the wind is blowing.

Putting it all together

I completed my weathervane in February, 2004, and it's still working. Here are the parts I obtained to build the electronic weathervane :

(1) Eight "press fit" Magnetic Switches (shaped like small cans) available at all All Electronics (see my Links below) or Here at Electronics Goldmine.  I have opened up one of them to see how they work and they are  mechanical  "reed-type" switches packed into the can and sealed with epoxy.  These switches are rated to work down to at least -40F and provide millions of operations before wearing out.
(2) Eight light emitting diodes or LED's, available at All Electronics or most electronic supply stores.
(3) Small electric switch to shut the circuit off
(4) Some 8 strand cable and another length of insulated single strand wire to connect the windvane to the display
(5) Battery holder for two AA batteries.
(6) Plastic or wood box to house the LEDS and battery
(7) Plastic cylinder 2.5 inches wide (to house the switches and shaft), available at a plumbing supply store
(8) Plastic bottle cap about 1 1/2 inches in diameter
(9) Plugs made of plastic or wood for both ends of the cylinder.  I used a hole saw bit on my drill to make these.
(10) Five to 6 inch long, 1/4" bolt -Galvanized or brass
(11) Assortment of galvanized or brass bolts and washers for holding the vane to the shaft
(12) Small 3/4" length of ~1/4" ID pipe (acts as a bearing for the shaft as it exits the top of the cover)
(13) Six inch section of 1/2 inch aluminum pipe or sturdy plastic to make the windvane
(14) Small section of light weight plastic or metal sheeting to make the windvane

Using the diagrams and photos below, you can see how I put all these parts together.

Once you get the magnetic switches and LED's, don't run off just yet to get the other parts and start construction.  My design works, but after giving it some thought, you may come up with a design that is simpler, more weatherproof, and uses even fewer parts. And if you can find junk scrap parts, hardware, wire, etc, around your home (I like it when folks recycle!) you could build this weathervane for less than $30.  The key is designing the instrument so that the shaft rotates with the least friction and the magnet, switches, and circuit connections are protected from the environment (i.e., rain, snow, sunshine, etc, etc). Also, be careful not to apply too much voltage as I have found that the switches will stick open or closed.  Once you have the unit built, install it so that it is perfectly level and use a compass to orient it to true North. Also try to locate it away from trees or other obstructions.


The windvane and switches have been working well since February, 2004.  The switches respond to changes in wind direction very quickly even in extreme weather conditions.  The instrument has functioned over a wide range of temperatures (between 105F and to 0F so far) and in heavy rain and snow.  Yet, if freezing rain is occuring the wind vane may get frozen in place until the ice melts. 

Two or three of the switches fail occasionally and then start working again.  I am not sure why.  I think many times it is from too low a voltage or current in the circuit. The two AA batteries I use may be just enough for the circuit to work and when they drop just a little in performance a switch will not work.  Often when I pass an additional 1.5V through the switch circuit for a few minutes it works fine again. Another method I use to get the switch to work again is to simply replace the batteries with new ones.

On two occasions none of the switches would work.  At first I thought the switches got too hot in the Summer sun or the indoor display on the windowsill got too hot in the afternoon sun and either the LED's or batteries stopped working because of the heat.  But I now think that the wires wrapped around (not soldered) a metal washer in the base of the instrument get oxidized or dirty and the circuit fails. I then have to clean the wires with sandpaper to get the circuit working again. So if you make this circuit yourself, I recommend soldering all outside connections..

If it is humid, condensation sometimes occurs on the shaft near the bearing where it later freezes, keeping the windvane from moving. To help keep this from occuring, I spray a little light oil (WD-40) on the bearing.

Using a block of plywood to mount the switches was not a good idea.  I checked the instrument in March, 2007, and the plywood is slowly coming apart even though it does not get wet when it's raining or snowing. A block of plastic should have been used instead. I also checked the switches and the epoxy seems to have failed on one of them, allowing me to easily pull apart the switch and see how it works. Inside the can it's a reed switch.  I slid the switch back into the plastic can and it still works okay.

In April, 2009, I took the instrument down to replace the decaying wooden base, solder all outside wire connections, and give it a fresh coat of black paint.  See below for more information. Soldering the connections seems to have solved the circuit problems noted above. And as of February, 2014, 10 years later, the instrument still works.  The only other component that has failed is the plastic bottle cap cover.  In early 2014, it shattered while I was raising the shaft for lubrication with oil.  It was easily replaced with a new one.

Lastly, when installing the instrument on your roof  or elsewhere high above the ground, please be careful!  If you don't like heights, then get someone else to install your windvane.  Also please make sure it is properly grounded for protection against lightning (see my link below).
Schematic and Photos

Homemade weather vane
Homemade electronic wind vane
Above is a schematic diagram of the windvane, without the protective cover over the magnet and switches.  Only 1 of the 8 magnetic switches are shown.  One lead from each of the switches are all soldered together to one length of wire.  This wire and the 8 remaining wires (9 total) from the switches are strung down the side of the house and into an indoor display of 8 LED's positioned in a circle inside a box.
Here is the weathervane base  (~2 1/2 inches wide) showing the placement of the 8 magnetic switches.  The switches are placed in a circle about 1 to 2 mm apart.  This way when the magnet passes over between two switches, two LED's on the indoor display will light up and  provide better wind direction resolution (i.e., NNE, SSE, NNW, etc., etc.,). Also note the phillips head bolt in the center.  A drop of oil is placed in the "X" shaped head and the vane shaft (I sawed off  the top of the shaft bolt and filed it to a nice point) pivots on this.  Lastly, I used 3/4 inch thick oak plywood for the base, but a block of plastic would have been better and more weatherproof.
Here is the bottom of the windvane with the base removed. The white circle is the magnet inserted into a piece of balsa wood that was painted black.  Two bolts hold the wood piece to the shaft.  Note how the wood piece is aligned parallel to the wind vane. The base of the shaft was filed down to a nice point so that it would pivot easily in the phillips head bolt. The base of the magnet rides about 5 mm above the switches.  If you build this instrument, you may have to adjust this height based on the spacing you have between the switches (see the previous photo).

If you look deep inside, you can see where the shaft exits the top of the cover (PVC pipe fitting). The top of the cover was cut from a 1/2 inch thick piece of sheet plastic that fit snugly into the top of the PVC fitting. I then sealed the joint with silcone glue. Next, I hammered a small piece of brass pipe into the hole to act as a bearing for the shaft and the shaft fits nicely (not too tight) through it. I periodically lubricate this bearing with light oil
Here is the base of the instrument attached to the PVC pipe cover.  It's held in place with two small brass screws.

A total of 16 wires (2 per switch) come out from the base.  Eight are soldered to the cable (wrapped in tape), while the other eight are wrapped around a metal washer held in place with a central bolt and two brass washers and a nut. A black wire is also wrapped around the washer and run along with the cable to the inside of the house to complete the electrical circuit. In retrospect, wrapping the wires around a washer was not a good idea as the connection gets oxidized/dirty and disrupts the circuit. As I note later on below, I should have soldered the wires together.
This next photo shows the assembled windvane as it appears after being outside in the elements for well over a year.  Using a "U "bolt, the instrument is attached to a boom that is attached to a vertical pole on the roof of my house.

I used a white covering to help keep the switches cool in the Summer months.  To keep preciptation from getting inside the cover through the shaft hole,  I drilled a hole into a plastic salad dressing cap and placed it on the shaft. I later painted this cap black.  The wind vane  was then place over the cap and the two were bolted together.  I used plenty of silicone glue to seal the bolt on top of the shaft and all around it. The base of the cap rides just a few mm above the top of the cover The instrument as shown is waterproof, but I have noticed condensation build-up on the inside of the cover and along the shaft.  Yet, it has not effected the performance of the instrument.

The wind vane itself is made from a lightweight sheet of plastic (looks like cardboard) and aluminum pipe sealed shut at both ends.  I added a bolt at the forward end of the pipe to help balance the vane.  I painted it black to help melt any ice build-up on it when the sun is shining during the winter.

25 feet of cable connect the wind vane to the indoor display and two AA batteries (3V) is sufficient to light up the LED's.  If you use a longer length of cable, you made need to use additional batteries.


The next photo shows the top of the instrument with the vane lifted up so that you can see the shaft and bearing (This is what I do when I periodically apply oil to the shaft).  The bearing was hammered into the plastic top so that about 1/4 inch of it remained above the top.  This keeps rain water and snow melt from getting inside.  As noted earlier, the bottle cap rides above the top by just a few millimeters.  This also helps keep rain and snow from getting inside in the instrument. 


Here is the inside display showing two LED's illuminated, which indicates the wind blowing from the west-northwest.  Because the switches in the base are close together, the magnet will fire off  two lights as it passes over between two switches. This doubles the resolution of the wind measurement.  To make this work correctly you may need to rotate the switches a bit after they have been inserted in the block base. 

A total of nine wires enter underneath a window using using a small piece of  ribbon cable and are conneted to a 9 point terminal in the back of the display to complete the circuit.  In the upper left of the diplay is a small switch to turn off/on the LED's.  Also behind the display I bolted a battery holder for 2 AA batteries.
By April, 2009, the wooden base was in poor shape and a number of the switches failed to work (owing to oxidation of the wire connections at the base of the instrument).   So I decided to remove the entire unit (windvane and display) and refurbish it.  Above is a photo showing the decayed wooden base and the back of the display showing how the wires are connected to the box.
Here is the new plastic base with the switches installed.  I used a hole saw to create it.  One wire from each switch (including the black wire)  is soldered to a wire loop in the center. In the past they were simply wrapped around a thin metal washer.  Over time oxidation occured and the circuits began to fail more often.
Here is the top side of the new base beside the old wooden one.  The new plastic base should hold up much better to the outside weather conditions. 

Building a Homemade "Biplastic" Thermometer

There are many types of thermometers -- liquid in glass, bimetal, and an assortment of electronic-based sensors. In late 1970s, I was trying to make a homemade thermometer based on the bimetal concept of measuring temperature, but was having troubles joining two strips of different metals together.  In 1981, I wondered if two different kinds of plastic joined together would work the same way.  After giving it some thought and tinkering around,  I made a "biplastic" thermometer from a strip taken from a discarded plastic bleach bottle and an equal  length of "strapping" tape.  Just like two different kinds of metal,  the plastic strip and tape have different rates of expansion/contraction with changes in temperature.  And when they are fastened together the resulting strip deforms as the temperature changes.  

Putting it all together

The cost to make this simple homemade biplastic thermometer is just a few pennies.  Here is what I use to make this homemade thermometer:

(1) Strip of plastic from a bleach bottle,  2 to 4 inches long and as wide as the strip of strapping tape that will be used
(2) Length of strapping tape the same length and width as the plastic strip
(3) A cocktail straw
(4) Small block of wood 1/2" by 1/2" by 2"
(5) Small, stiff sheet of white cardboard
(6) A few thumbtacks

First, I cut out the plastic strip from a clean and well rinsed bleach bottle and affix the tape to the inside curve of the plastic strip.  Note: If you make the curve of the plastic into a tight semicircle before affixing the tape, the deformation (i.e., sensitivity)  of the strip will be much greater with temperature changes.  I have done this by wrapping the plastic strip around a piece of metal pipe, holding it in place with a hose clamp or something similar, and heating it in boiling water or in an oven at 250F for a short while.  This melts the plastic and creates a tight plastic curve for me to attach the tape.

Next, I tape or glue a cocktail straw to one end of the plastic strip.  Using a thumbtack, I then affix the sensor to a small block of wood.   Finally, the block of wood is tacked to a small sheet of cardboard.  See the diagram below for more information.  Once completed, I test the instrument by simply breathing on it.  My warm breath makes the cocktail straw move significantly downward.

Calibration and Operation

To calibrate my homemade thermometer I use another commerical thermometer placed near my instrument.  Using a pen, I note the temperature and write its value on the cardboard sheet adjacent to the cocktail straw pointer.  I repeat this for every 5 to 10 degrees of temperature change.

The instrument works rather well for measuring temperatures from about 5F to at least  90F.  Compared to other temperature sensors, this thermometer has considerable mass, slowing it's response time to changing temperatures.  Accuracy can be as good as about +/- 2F around 65F and is lower (about +/- 3F ) near 10F.  The sensor can suffer suffer from hysteresis. and may lose its calibration over time.   These problems are reduced as the instrument is used over time and re-calibrated as necessary.  

I have found that bleach bottle plastic and strapping tape works best, but try different types of plastics and tapes.  Also experiment with different shapes of the plastic strip.  Remember, the tighter you make the curve of the plastic, the more the cocktail straw will move for a given temperature change.  
Homemade thermometer

Here is the homemade thermometer outside where the temperature was marked at 23F.  Click the image for a larger view.

Here is the homemade thermometer inside the home where the temperature was 67F.  Because the plastic was shaped into a tight circle, the pen arm moved downward over 2 1/2 inches over a 44 degree temperature change. Click the image for a larger view. I have taken this thermometer several times from a warm room to 10F outside and back inside again and it maintains it's calibration.  The sensor shown here is over two years old and over this time the sensor has possibly been "broken in", improving it's accuracy.

Homemade Electronic Relative Humidity (RH) Sensor
Experimenting with "Wire Glue"  can be quite interesting.  The glue is water-based and contains very tiny carbon particle ("nano-carbon").  It's cheap and conducts electricity nicely when dry. I have been looking into ways in which this material can be used for making electronic weather sensors. So far, I have made a simple and rather crude electronic relative humidity sensor, but it is very inexpensive and easy to make. Here's how:
(1) Cut out a small ~1 cm X 0.5 cm X 0.5 cm cube from a piece of styrofoam. Experiment with different shapes and non-conducting materials.  Stick a short length of thin wire on each end and secure with glue if necessary.
(2) Mix a small amount of wire glue with Elmers glue in a ~1:1 ratio.  I am experimenting with different ratios and other wood glues for better results   
(3) Paint this mixture on the styrofoam cube and let dry.  See the photo below.
The humidity sensor will have a room room temperature/RH resistance anywhere from 10K to 500K Ohms, depending on how it was made.   Moisture in the air will be absorbed by the glue and I think this increases the spacing between the carbon particles and hence the electrical resistance of the sensor.  In moist (100% RH) conditions, the sensor resistance can rise to over 1 mega Ohm.  You can see this by hooking up the sensor to an Ohm meter and then breathing on the sensor.  The RH sensor has a rather slow response time, but eventually diffuses the water molecules and the resistance will drop back down.  Hysteresis is a problem and I am working to lessen it.  The sensor may also be sensitive to temperature changes as well.  I have also noticed that the resistance gradually increases over time even though the RH has remained the same.

make Humidity sensor

Here are two electrical relative humidity sensors being tested.  The long thin one was made with a strip of balsa wood and coated with a mix of wire glue and Titebond III wood glue.  The second sensor used the same coating, but I used a small piece of styrofoam.  This particular sensor had a resistance of about 12K ohms with the room relative humidity around 50%. Over time (months) the resistance gradually increased. 
Homemade DIY Ceilometer
Years ago I built a homemade ceilometer that measures the altitude of cloud bases at night.  I built the instrument using a Edmund Scientific 18 inch parabolic reflector and a 300 watt clear (not frosted) incandesent bulb. The mirror comes with a central hole to mount the bulb and has a focal length of 4.5 inches.  The filament in the bulb was positioned to be at the reflector focal point.  This way, a beam of light is projected.  At nightfall, the mirror was then aimed at a 90 degree angle and a patch of light would be seen at the bases of clouds up to about 4,000 feet.  To measure the height,  I made a simple clinometer from a protractor, straw (site tube), and weighted string.  I would then walk a known distance (at least 300 feet) from the vertical light beam and measure the angle from the ground to the patch of light on the cloud.  See the diagram below.
Homemade ceilometer
Using simple trigonometry,  I could then measure the height of the cloud base above the ground.  I have to say that it was a lot of fun. 
If you build this device, please do not aim it at flying aircraft and shut the light off if aircraft approach.  Check local laws/restrictions to see if you can operate a ceilometer of my design in your area.  
I strongly recommend wearing safety goggles when using this instrument.  If rain starts falling, the raindrops hitting the hot light bulb might cause it to break or shatter. 

Building a Homemade Solar Powered Fan

This project is not a weather instrument, but with energy prices on the rise you may find it a helpful if you own a house with poor attic circulation.  Having good cirulation in your attic helps to cut utility bills and makes roofing shingles last longer   Yet, buying and installing an attic fan is costly.  Even solar powered attic fans that are easy to install cost hundreds of dollars.

I am building a homemade solar powered attic fan that should cost around $100, which is far below what a commercially made one costs.  The fan will be mounted in one of the gable vents in my attic with the solar panels installed on the roof.   Here are the parts I have found so far:

(1) 48 0.5V  by 1 Amp (or similar)  solar cells available at Electronics Goldmine (see the link below). Each cell is 4.5 by 1.5 inches in size and I got 36 for $1.99 each and another 12 later on for $2.49 each. Two sets of 24 cells will be soldered together in series.  These two sets of cells will then be connected in parallel to produce a ~20 by 20 inch panel with an output of about 12 volts and 2 amps (or 24 watts) of power, open circuit.   Also try Surplus Shed (see link below) or Ebay as they sometimes sell low-cost solar panels or cells.

(2) A cheap DC motor that operates from 12 to 48 volts and can spin a fan blade at least 8 inches in diameter 
(3) A junked fan blade 10 to 12 inches in diameter.  

(4) Some scrap wood, plexiglass sheet,  and hardware to build a frame for the solar cells and a simple frame to hold the fan up to the attic gable vent.

I have soldered the cells together and they are VERY fragile! If you purchase the cells I used, the front sides may be difficult for you to solder.  So, if you are not good at soldering (like me) get some practice in before soldering solar cells together and try different wire than what I used.  Below are photos of the the project to date.  I will post more as things progress.

This solar powered fan could also be used to ventilate a small telescope observatory or greenhouse.  If you are interested in trying to build you own solar fan, purchase the motor first  and do some experimenting with a DC power source and  a junk fan blade to see if it generates enough circulation for your needs.  If it does, then go buy or build solar panels with the proper wattage.  The solar panel could also be configured to charge a car battery.
Here is a close up of two of the 48 solar cells soldered together.  I used insulated multistrand wire to solder the cells in series. I should have tried other wire, but this was the best I had.  Soldering the font side of the cells as shown here was very difficult.  I used 60/40 solder, a 25 watt soldering iron,  and prepped the metal band on the cell by lightly scratching it with a razor blade.  Yet, I had a very difficult time getting the solder to stick or the solder joint would later fail. 



This photo shows the backside of the cells soldered together in series.  Soldering this side was much easier. I did not have to scratch this side before soldering.  Note the chip in the cell, second from the left.  All the cells are sold with minor chips.  They don't seem to affect their performance.

All Electronics: Supplier of all kinds of electronic parts and equipment.

Electronics Goldmine: Another supplier of low cost electronic parts, with a good selection of solar cells that could be soldered to together to make a low cost solar panel.

BG Micro Yet another supplier of cheap electronic parts.

When installing anything on your roof, make sure it is properly grounded to protect you and your home from lightning.

Surplus Shed. All kinds of interesting stuff at low prices.

American Science & Surplus. Another source of interesting stuff.

My Other Websites 
A description of how I built a large homemade Dobsonian telescope 

My recipe for hot sauce  Making your own hot sauce is easy and tastes great.
Webpage Author: H. William James.  All images and text are copyrighted.  2004 - 2015

About the Author: "H. William James" is a professional scientist with over 30 years of experience. For nearly 40 years he has enjoyed spending his spare time designing and building scientific instrumentation and other mechanical or electrical devices.

Disclaimer Statement: The information on this website is provided  for informational purposes only. The instruments and devices described by the author function as described, but your results may vary.  The author disclaims any liability for any damages, injuries, or any other losses of any kind you may incur.