Instructables

Arduino Wind Chill Machine

Problem: So I’ve been taking walks with my dog, Marcus and my Arduino pedometer.
  http://www.instructables.com/id/Arduino-Pedometer/
Out here in the high desert in January, it gets cold and a little wind creates a cold wind chill factor. I’m a LAZY OLD GEEK and would like to know what the wind chill factor is.

Solution: I’ve always wanted to build a weather station so I decided to make an Arduino wind anemometer to measures wind speed and a thermometer. An instrument that measures wind speed is called an anemometer. Then the Arduino can calculate wind chill.

Wikipedia Definition: Wind chill (often popularly called the wind chill factor) is the felt air temperature on exposed skin due to wind. It measures the effect of wind on air temperature.

LAZY OLD GEEK ‘facts’: Any object, e.g., a car is not affected by wind chill. If the temperature is 10F, it doesn’t matter if the wind chill is 10F or -40F. Wind chill is the apparent temperature felt by humans and animals. Or I should say some animals. My dog, Marcus has a nice fur coat and is part husky. He doesn’t feel it. He doesn’t care if it’s -40F wind chill and seems to prefer it. Now, I, on the other hand won’t venture out if the wind chill is -40F. But if it’s -10F, I might wear my full face mask (see picture) and venture out. I don’t like to wear it because it’s uncomfortable after a while so it’s helpful to know what the wind chill is.

So that’s not a great reason to build a wind chill machine but I’ve always wanted a weather station and this is a good starting point. My weather station is designed for the U.S., so I use Fahrenheit and MPH.

Attention Readers: If you want to duplicate this project, you will need a laptop with a USB port and a motor vehicle to calibrate the wind speed. Another problem is finding the cups for the anemometer. Many Instructables readers seem to be good at improvising. Aluminum is preferred but plastic should work also. For the innovative readers, I’ve provided some hardware and software tips on how to design your own anemometer. For example, the software could be adapted to an LED or LCD display for a standalone instrument.
 
 
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kentek2 months ago

LZ,

How did you test the SS461C? Is it possible to attach to Arduino and pass a magnet by the chip to get some sort of reading?

msuzuki777 (author)  kentek2 months ago

Yes, it is. What I did was hook it up to 5V as shown in the schematic. Then I put a DMM on the output pin and watched the voltage. I passed a magnet close to the SS416C and the voltage dropped to around zero. Then I flipped the magnet over and passed it near the sensor and the voltage went back to 5V.

You can also do this with the Arduino but you'd have to write a sketch to display the output.

LOG

espdp22 months ago

Very nice project! Just to be funny, and since you are the Lazy Old Geek, have you looked into acquiring a "Weather Rock" or the newer model "Weather Cat"? If I were to replicate this project, it would involve a dozen trips to the hardware store and 10x the money I really needed to spend. A weather rock will save you all that trouble. Cheers! :D

msuzuki777 (author)  espdp22 months ago

I'd never heard of Weather Rock. I like it. I couldn't find Weather Cat but maybe that's cause I'm a dog person.

I like the Weather Rock as it is scalable and portable so I could take it on dog walks. And it's so versatile, like tornado and earthquake warning.

LOG

espdp2 msuzuki7772 months ago
You can hang the Weather Cat outside your window or from a clothesline by its tail, so it's more convenient. ;-)
msuzuki777 (author)  espdp22 months ago

Ah, makes sense.

LOG

kentek2 months ago

LZ,

Do you have a more complete version of the "sketch' you used with anemometer?

I'm totally new to programing.

kentek2 months ago

If you want to get real accuracy in your anemometer read this and plug in all the data:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC338673...

The math is mind numbing. In a nut shell I doubt that there is even 5% difference.

If I see small dogs and toupees flying by and my wind cups are a blur i will assume that the wind is blowing really really hard.

ken

msuzuki777 (author)  kentek2 months ago

You are right about the math but for me, also the physics terminology. So all I care about is if it's too cold for me to take my dog out for a walk and what I should wear. That has so many other subjective factors involved that wind speed is a minor factor.

By the way, I changed my temperature sensor to a DS18B20 as it seems to be calibrated over a wider range. Of course, right now I have three outdoor temperature sensors and they often vary 5-10 degrees.

LOG

kentek msuzuki7772 months ago
I trust they are all oral. :-)

Just made big change to my wind cups mount. I post photo when more complete.
kaw
kentek2 months ago

M---777

Greetings,

I'm working on building a anemometer much like the one you have built. The SS461C- DAMN it's small!

I'm thinking of isolating it in a piece of plastic tubing. At issue is how did you protect the leads from breaking?

msuzuki777 (author)  kentek2 months ago

You are right, they're really small. I don't remember how I did it but I think I used some electrical tape to insulate between leads and heat shrink tubing over the whole assembly. The leads are pretty firmly attached but if you're concerned, you could use hot glue or even epoxy, which I think is what most semiconductors use in their packaging.

LOG

kentek2 months ago

What do you think about this idea:

I'm concerned about bearing friction in light wind. I am considering using an old computer fan brushless motor as the bearing system. It is almost frictionless after you get is past the very slight mag force.

I will probably remove the fan blades and mount some sort of plastic connector with super glue to accept the shaft to my wind prop. Key will be getting mount centered.

BTW: I bought a wind cup unit from a commercial marine parts department for $10. It already has the magnet mounted.

msuzuki777 (author)  kentek2 months ago

Sounds like a good idea. But I agree you may have problems getting it centered and balanced.

Good luck.

rob00862 months ago
Ok, I can see if the winds are light it might be difficult but in regard to the friction if the motor you could use a small motor lets say out of a cd or DVD drive? Just thoughts here.
msuzuki777 (author)  rob00862 months ago

I think cd/dvd motors are brushless. Apparently they have magnets in them so turning them with the wind should generate some voltage but I suspect it would be AC. It might be possible to make it work but it's beyond my expertise.

LOG

rob00862 months ago
I'm a newbie to Arduino but have always had an interest in electronics. Maybe this is a really dumb question but couldn't you also use a motor and measure the volts it generates and convert that into mph or in my case km/hr? Just working on my own weather station and am looking for ideas for an anemometer.

Thanks.
msuzuki777 (author)  rob00862 months ago

A DC motor might work but I have my doubts. Two concerns I have is that you might need fairly large cups to overcome the friction of the motor. And it would be hard to measure small voltages when the wind is light.

LOG

kentek2 months ago

Saved my frail by finding the Honeywell SS461C. I was toying with using discarded motor which added all kinds of new problems.

You've done a really good job of describing all steps in this project.

Thanks,

Ken Wood

msuzuki777 (author)  kentek2 months ago

Thanks,

LOG

FtForger1 year ago
Thanks for the instructable. I'm working on a similar project, but instead of hall effect switches I'm using a home made optical encoder for the interrupt pulses, and my anemometer cups are bring printed on a makerbot by a friend. I'm going to have two 'wheels' one above the other, offest by 1/6th of a rotation and separated vertically by about 1.5 cup diameters. For the wind vane I'm also using a binary optical encoder to get 16 positions. For the wind vane I'm using the bearing from an old hard drive head assembly. The head assembly itself is going to support the bearing. and the anemometer bearing is the spindle bearing from the same HD.
apalacios22 years ago
Nice anemometer!
The way-too-high or -low temp readings you're getting might be from the sensor exposing to direct sunlight or too much wind. I've made dozens of thermometers using the LM35 series of Temperature sensors by National and I've noticed when the sun shines on the sensor, no matter how cold the air is, the reading goes up abnormally high. The same when the wind blows over the sensor. I've had readings of 50°C in a fresh (16°C) morning when the sun rises and reaches the sensor. Heat reflection also gives these readings. I had a sensor 2 yards from a sun-bathed wall and the thermometer went up to 36°C in a 20°C day. Sometimes the error is corrected encapsulating the sensor in white heat-shrink tubing. Maybe painting the sensor white works too.
Nice anemometer indeed!
msuzuki777 (author)  apalacios22 years ago
Thanks. I've actually added two features to my weather station:
http://www.instructables.com/id/Arduino-Weather-Station-Part2/
http://www.instructables.com/id/Arduino-Weather-Station-Part3-Rain/

I don't think my readings are related to sun or wind. The ones I've noticed are just one sample where the one before and after seem to be okay so I suspect that it's either an intermittent connection or glitches in the serial communications. However since they don't happen very often and it's just for my personal use, I pretty much ignore them.

I usually leave it running 24/7. Occasionally, the Arduino stops communicating all together and I have to reset it.
And once, I had to replace the Atmega chip. I'm fairly certain it was lightning.

LOG
ChrysN3 years ago
Cool project!
msuzuki777 (author)  ChrysN3 years ago
Thanks, I enjoyed making it.

Lazy Old Geek
rimar20003 years ago
¡Good work!

Here in Argentina the summer has been a little hot. 43º of thermic sensation in my zone, that is not one of the hotter. And the meteorological service threaten us with more heat during frebruary!
msuzuki777 (author)  rimar20003 years ago
Sorry, my response is so slow. My ISP won't connect to Instructables.com so I'm can't connect unless I use my cousins.

There's actually another thing called heat index which is the counter part of wind chill. I was thinking about adding that feature but our summers are pretty dry so don't know if it would be worth it.

Lazy Old Geek
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