Hi,
Starting to build a weather station and found this anemometer for cheap at a yard sale.
How can I get a reading from this with the Arduino?
It has 2 wires coming out the bottom.
Is it as easy as hooking one wire to ground and one to a pin for reading?
Thanks.
Is it as easy as hooking one wire to ground and one to a pin for reading?
LOW when the encoder is not switched on. LOW when it is switched on. Hardly seems useful.
Now if, on the other hand, you connected one side to +V, and the other to a pin with a pull-up resistor, you'd get alternating HIGH and LOW readings. If that pin were an interrupt pin, and an ISR was registered, the ISR would fire every time there was a pulse.
If there's only two wires coming out, there may be just a brush inside that makes contact once per revolution. You can check this by taking a voltmeter, hold the probes on each wire, and spin the anemometer. If at some point the voltmeter drops to no resistance then that's probably what it is.
If so, apply a voltage to one wire and tie the other wire to an input on the Arduino.
If at some point the voltmeter drops to no resistance then that's probably what it is.
Did you mean ohmmeter?
you connected one side to +V, and the other to a pin with a pull-up resistor, you'd get alternating HIGH and LOW readings.
OK. Let's give that a go.
Or did you mean tie one to ground, and the other to a pin with pullup enabled?
Did you mean ohmmeter?
Yeah. Apparently not enough coffee this morning.
Thanks, I'll try hooking it up when I get home.
So if all I will get is a HIGH reading, then a LOW reading, how do you translate that into wind speed? How would you measure how quickly it is changing?
I made a home made meter last year. Used a bicycle speedometer to record the revs.
The variables that affect the speed your meter runs include the cup size, arm length, turning resistance, etc.
Only ways to calibrate it would be to have a reliable meter next to it and change your variables ( eg. 3 revs per second = 10km/hr ) or do like I did and get the wife to drive down the road at various speeds while you hold it out the window and note the revs at various speeds.
You'll need a windless day to do this, and a very patient wife. Windless days usually easy to find.
Thanks for the laugh DaveO.
My wife is patient, but not the best assistant. She get's bored easily with my projects.
I do have a bike speedometer though. I'll give that idea a try. Maybe with a friend instead of my wife.
Ok, here is what I get so far. I cannot easily connect this to my bike computer, an old Trek Fusion C.
I have hooked one wire to ground and another to analog pin 5 through a 470k resistor.
I tried lower resistors, but got too much noise. Still, when it is not moving a get some low numbers like 3, 5 or 7.
With the anemometer moving at a slow constant speed due to a fan I get the following numbers. I realize this is not actual wind speed yet, but needed to call it something. I see a pattern emerging, 3 zeros followed by 2 or 3 numbers.
Wind speed = 0
Wind speed = 0
Wind speed = 0
Wind speed = 14
Wind speed = 45
Wind speed = 28
Wind speed = 0
Wind speed = 0
Wind speed = 0
Wind speed = 22
Wind speed = 53
Wind speed = 0
Wind speed = 0
Wind speed = 0
Wind speed = 13
Wind speed = 46
Wind speed = 28
Wind speed = 0
Wind speed = 0
Wind speed = 0
Wind speed = 8
Wind speed = 54
Wind speed = 34
How do I translate this into wind speed or am I going about this all wrong?
Do I what DaveO suggested and take this into a car and stick it out the window, then note how fast I am going and the numbers I receive? Thanks for putting up with my questions.
Thanks.
Pauly:
How do I translate this into wind speed or am I going about this all wrong?
Do I what DaveO suggested and take this into a car and stick it out the window, then note how fast I am going and the numbers I receive?
Yes, you stick it out the window.
You'll need 2 assistants. One to drive the car, and one with a camera recording the strange nutter driving down the road with a wind gauge sticking out his car.
You'll need a windless day to do this, and a very patient wife. Windless days usually easy to find.
I have hooked one wire to ground and another to analog pin 5 through a 470k resistor.
Try hooking one to +5v, and the other to a digital input with a pull-down resistor.
Try hooking one to +5v, and the other to a digital input with a pull-down resistor.
When I do that, all I get is 1's, no variation between 1 an 0, just 1's.
You've also tried connecting one to ground, and the other to the Arduino with a pull-up resistor?
If you connect an ohmmeter to the wires and spin the anemometer, does the resistance change as you spin it? Also what value does it give?
Connecting it to a ohmmeter I get .40 when it is not moving and numbers ranging from -12 to 12 or 13 when moving.
So far I get the best results leaving 1 wire to ground and one through a resistor to pin 5. Then I get a series of zeros, followed by numbers like 20, 27, 24 that increase the faster it is spinning followed by a set of zeros, then more numbers.
When hooking it up to digital I get all 1's if one wire is connected to +V and all 0's when connected to ground when it is spinning.
Connecting it to analog pin 5 and +V all I get is 1023.
Thanks.
if you strip the gauge down ( should be possible for bearing maintenance ) can you identify the sensor being used ?
A search for the datasheet of the sensor would tell us exactly what it gives and how it operates.
If you really want to dig into the details on this type of anemometer: http://www.nrgsystems.com/FileLibrary/d460250d29fb4acfa4142a93496e2f9b/Ewea-99.results40.pdf
For the nrgsystems.com #40 (which my kid designs loggers for) the transfer function is:
0.764m/s2 ·F[Hz] or in English .764 Meters per second per Hz of signal.
Your unit could have a factor of 2 or .5 of this depending on configuration...
Thanks for the advice guys. I tried opening it already with no luck. I will try and put some WD40 on it and see if that let's me get inside to see what the sensor is.
I'll also check out the details Terry.