Building a 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 about 20 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 commerical 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, a 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). 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. Click Here for technical information on similar switches offered by Jameco Electronics. As you will see, these switches are rated to work down to -40F and provide at least "10,000,000 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" 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.
Operation
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 100F and to 10F so far) and in heavy rain and snow. Yet, if freezing rain is occuring the wind vane will 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) the bolt 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 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.
Update March, 2009: The instrument has been outside for 5 years and is still working. Some switches continue to fail on occasion, but my remedy described above gets them working again. I will likely replace the wooded base, holding the 8 switches, with a plastic disk.
I will update this website if other problems with the instrument arise.
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).
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.
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 the central bolt and held in place with two brass washers and a nut. A black wire is also wrapped around this nut and run along with the cable to the inside of the house to complete the electrical circuit. In retrospect, wrapping the wires around the nut was not a good idea as the connection gets dirty and disrupts the circuit. I should have soldered the wires together.
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 cap rides above the top by just a few millimeters. This also helps keep rain and snow from getting inside in the instrument.
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.
Like many things, my windvane will probably wear out in the years ahead. So, I may construct a new electronic wind vane design using these mechanical "Reed Switches" They are also available at All Electronics (see my links below) and are significantly lower in cost. I don't know how well these particular switches will work and how long they will function. So if you are thinking of making an electronic wind vane, consider experimenting with these switches. Again, they cost rather little.
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, rinsed bleach bottle and affix the tape to the inside cuve 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 and gently heating it in the oven for a short while. This creates a nice 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 10 to 20 degrees of temperature change.
This instrument works rather well for measuring temperatures from about 20F to at least 90F and responds quite quickly to temperature changes. Yet it does suffer from hysteresis. and may lose its calibration over time. This problem may get reduced as the instrument is used over time and is "broken in".
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.
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 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 available at All Electronics. I have tried this motor with a ~9W solar panel and it spins fast. I am also experimenting with a 12V DC motor from American Science & Surplus. The motor is under "Mega Motor Mart", Item #36849. The webpage is here.
(3) A junked fan blade 10 to 12 inches in diameter.
(4) Some scrap wood, plexiglass sheet, styrofoam 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.
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.
If you did not like this website then you certainly won't enjoy my website on making a large homemade telescope
Disclaimer Statement: The information on this website is provided for informational purposes only. The instrument 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.