# Anemometer

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Take a Mathmos wind light (from Think Geek) and modify it to read wind speed (using a voltmeter).

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## Step 1: Take the Thing Apart

Remove the one screw and gently separate the plastic case into its two pieces.

## Step 2: Remove the Guts

Carefully remove the generator and LED's from the plastic case (they just slide out). The wire from the generator is extremely small and could easily be broken.

## Step 3: Add a Wire to One of the LED's

Solder a wire wrap wire to one leg of an LED.

## Step 4: Attach Wire to the Other LED Leg

Solder a wire wrap wire to the other leg of the LED.

## Step 5: Put the Unit Back Together

Place the generator back into the plastic case. Carefully attach the other half of the plastic case and fasten with the screw.

## Step 6: Connect to Voltmeter

Attach the two wires to a voltmeter. Set the voltmeter on a low AC voltage scale. 2.5 volts equals about 15 mph. You will not get much higher than 2.5 volts unless you clip the "heads" off the LED's (then you would lose the pretty lights).

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## 6 Discussions

Take it out on a ride with your car on a day with no wind. You will know the speed of the wind because the speedometer on your car will tell you.

You need a "known" anemometer to measure wind speed (I have a cheesy little plastic thing with bouncing plastic balls inside). Set them both in front of a powerful fan and note the voltage at a measured wind speed. This voltage flattens out when the LED's start to light up, because the current draw increases quickly when the LED's come into play. If you want to take this beyond about 15 mph, I would suggest clipping the LED's and placing some load across the generator output (try 1 K ohm to start). That should keep the generator from spinning to wildly at higher wind velocity. I live in a hurricane area (took a lot of damage from Hurricane Charley in 04), so a rough reading of wind speeds would be interesting. I really don't want to cut the blue LED's--it looks cool at night. I guess I'll have to buy another one to go any farther with the anemometer concept.

I reckon you could mod this so the wind speed could be read on something, instead of reading the amount of volts and converting it into speed. Im pretty stupid with electronics though so yeah...

2 replies

I did a search, because I am interested in the same thing. The cheapest voltage data logger I could find was \$75. It is a USB data logger (EL-USB-3) from Lascar (http://www.microdaq.com/lascar/usb/el-usb-3.php).

I guess nobody has done an Instructable on to create one from scratch, but I'll do some more searching.