# Anemometer Wind Speed Control

#### kris.92

Joined Nov 26, 2012
11
I have been assigned a project to use an anemometer to measure wind speed obviously, but if the speed exceeds a certain rated speed the circuit should turn on an LED. I have just considered having the the anemometer attached to the shaft of a generator and have an LED just connected in series with generator. Thinking that I would have an LED rated for a certain voltage so it wouldn't turn on until that voltage is induced by the generator, but I feel as though that is too simple or if it would work. I am not looking to cheat I would just like some input and ideas on what you may have in mind. And it is an analog circuit.

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#### BillB3857

Joined Feb 28, 2009
2,543
Are you aware of any devices that only conduct after a certain voltage is reached?

#### kris.92

Joined Nov 26, 2012
11
something like a zener diode I was thinking but i am not completely sure how they work.

#### kris.92

Joined Nov 26, 2012
11
So I have come up that the zener diode in reverse bias will break down at a rather high voltage depending on the diode obviously. But, once a diode hits its break down voltage doesn't it essential burn out?

#### BillB3857

Joined Feb 28, 2009
2,543
Did you read the article in the link I posted in #4 above? If you did, I would suggest reading it again to get a better understanding of a Zener. You are on the right track, but need to fill in some details. Info available in the link.

#### kris.92

Joined Nov 26, 2012
11
K I realise I am probably missing something here but I have just wired a simple circuit on my bread board with a resistor in series with a zener diode and an LED and the LED does not light up until about 12 volts is applied to the circuit. So to me that seems kind of like a voltage switch.

#### kris.92

Joined Nov 26, 2012
11
Using a 100 ohm resistor.

#### BillB3857

Joined Feb 28, 2009
2,543
If you read the link, you will know that the zener diode starts to conduct when the reverse voltage reaches/exceeds the zener voltage. Do you know the part number of the diode you used. If so, google it and it will tell you the nominal breakdown voltage. Now, back to your project.... How can you use that concept to cause the LED to light if the wind speed is greater than a certain amount?

Have a look here..... http://electroschematics.com/5816/led-volt-meter/

#### kris.92

Joined Nov 26, 2012
11
I was just thinking that the faster the the anemometer spun the faster the generator would spin inducing a larger voltage. Once or if that induced voltage reached the breakdown voltage of the diode it would be able to conduct and then turn on the LED.

#### BillB3857

Joined Feb 28, 2009
2,543
Right! Now all you need to figure out is what voltage out of the generator represents a given speed. (When I was a kid (many years ago) we held our "windmill generator" out of a car window while our buddy drove at various speeds. That way we could calibrate our system.) My guess is that your generator will not produce the voltage you want at the speed you want the LED to trigger on. If you're lucky, it will be higher. Then what will you need to do?

#### kris.92

Joined Nov 26, 2012
11
I would imagin a resistor before the diode would solve the issue I think.

#### BillB3857

Joined Feb 28, 2009
2,543
You might want to re-think that one a little. What course are you taking and how far along in it are you. That info will help me to help me to help you find the answers.

#### kris.92

Joined Nov 26, 2012
11
sorry I miss read what you wrote before. I guess if the voltage is too low to break down the diode I could just slip in an amplifier.

#### BillB3857

Joined Feb 28, 2009
2,543
What kind of voltage do you expect from your generator?

#### kris.92

Joined Nov 26, 2012
11
I really have no idea. Its just a design and hypothetical so, I could make it whatever voltage I want.

#### BillB3857

Joined Feb 28, 2009
2,543
Sounds like you are on the right track. The zener concept is one that would work as long as the voltage levels from the generator were high enough to break the zener over and power the LED. No external power (other than the generator) needed. Now that you are talking amplifiers, you are adding power supplies. What component can you think of that could possibly monitor the voltage from the generator and sense when a certain level was reached or exceeded?

#### thatoneguy

Joined Feb 19, 2009
6,359
Most commercial spinning anemometers (speed + direction of wind) have a tiny magnet in the hub, which passes a hall effect sensor or a coil in the body. The supporting electronics then count pulses per second to calculate the wind speed.

The key is keeping the moving rotor as light as possible, and having the correct geometry blades on it. This geometry is slightly different than one used for power generation or fans, as they have a different attack angle for more "bite" into the air.

Anemometer vanes need to spin with a very low mass with a very low friction/low drag hub, trying to accomplish that while driving a load is counter-productive. Though it can be done with a modified fan blade, the results won't be as linear or accurate as you'd like.

If direction of wind isn't needed, the thermal anemometer in the circuits above is a reliable and accurate version as well.