Anemometer

Adafruit Ethernet, Motor, Proto, Wave, Datalogger, GPS Shields - etc!

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
actom
 
Posts: 24
Joined: Thu Apr 23, 2015 3:24 am

Anemometer

Post by actom »

Hi,

I have an anemometer (#1733), fona shield (#2468) and solar panel (#1525).

The idea is to plug the components together to an Uno and then program the fona to send me a text message when the windspeed rises above a threshold value.

First up, I don't understand why the anemometer needs a power source. I (incorrectly) assumed that the anemometer would provide a voltage signal using a rotating magnetic field. Why do I have to provide a power source? Since this project was intended to be remotely located (hence the solar panel for the uno/fona combination) how do I provide power to the anemometer? How much power is required?
Also, there is no information on the adafruit website that I could find that gives me the data I need to convert a voltage to a windspeed. Does anyone know of this please?

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Anemometer

Post by adafruit_support_mike »

actom wrote:Why do I have to provide a power source?
In a self-powered anemometer, the rotor would have to drive some kind of generator. There are two major problems with that.

First, generators aren't very efficient at low speeds. They're reasonably linear once you get to 100-200 RPM, but when you get down to 20 RPM it's hard to tell there's any signal.

Second, power isn't free. You have to apply force to a generator's shaft to make it produce current. Looking at it from the other direction, the wind sees the generator pushing back to prevent the rotor from moving. You'll need a certain amount of wind to make the rotor turn at all.

An externally powered sensor doesn't have those problems. If you just stick a wire out from the side that interrupts a photosensor, the output will be proportional to the rotation speed no matter how fast (or slow) the rotor turns. And since a powered sensor doesn't have to steal energy from the rotor to work, the only thing preventing the rotor from turning at low speeds is the friction of the bearings.
actom wrote:Since this project was intended to be remotely located (hence the solar panel for the uno/fona combination) how do I provide power to the anemometer? How much power is required?
It uses about 10mA. A solar panel and a small 12v storage battery should keep it running for a long time.
actom wrote:Also, there is no information on the adafruit website that I could find that gives me the data I need to convert a voltage to a windspeed. Does anyone know of this please?
From the product page:
The voltage will range from 0.4V (0 m/s wind) up to 2.0V (for 32.4m/s wind speed).

User avatar
actom
 
Posts: 24
Joined: Thu Apr 23, 2015 3:24 am

Re: Anemometer

Post by actom »

Mike,

Thank you for your reply.

Is it possible to take an output from the Uno rather than carry another battery for the anemometer?

I thought I could hook up the solar panel to your solar charger (#390) and a 3.7V/2500mAH (#328) and run everything from this. Will there be enough power?

I also see from another post reference to a voltage reference breakout (#2200). What is the purpose of this board?

User avatar
actom
 
Posts: 24
Joined: Thu Apr 23, 2015 3:24 am

Re: Anemometer

Post by actom »

Please excuse my confusion.

I am trying to power a fona shield (#2468) from a solar panel when possible and a Lipo battery at other times.

I assumed (probably incorrectly) that a solar lipo charger (#390) would do the trick. Simply plug the solar panel into the DC jack of the #390, a lipo battery into the batt terminal and the fona into the load terminal.
In this configuration, whilst in bright sunlight and the battery charging away, the fona shuts down. When I place the solar panel in the shade the fona powers up. So it appears that the fona is quite happy to run from a discharging battery and not from a charging one. This is the exact opposite of what I am trying to achieve!!! The fona needs to be on all the time powered from either the sun or the battery.
The CHRG/RUN switch on the fona is set RUN since in CHRG the shield shuts down.

What am I doing wrong? Do I have the correct components for the task?

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Anemometer

Post by adafruit_support_mike »

actom wrote:Is it possible to take an output from the Uno rather than carry another battery for the anemometer?
The anemometer wants at least 7v of supply voltage, so the 5v from an Arduino wouldn't work. If you have a 7v to 12v supply you can run both the anemometer and the Arduino (through its DC barrel jack) from that.
actom wrote:I thought I could hook up the solar panel to your solar charger (#390) and a 3.7V/2500mAH (#328) and run everything from this. Will there be enough power?
You'd need something like a PowerBoost to turn the 3.7v in the LiPo to 5v an Arduino can use, and would still need a way to get a supply rail in the 7v-12v range for the anemometer.
actom wrote:I also see from another post reference to a voltage reference breakout (#2200). What is the purpose of this board?
If you want to measure the anemometer's output with a microcontroller, you'll need an ADC. The ADC's output will only be as good as its voltage reference though. The LM4040 breakout has a precision 2.048v reference which is just the right range for the anomometer's 0.4v to 2.0v output range.
actom wrote:I assumed (probably incorrectly) that a solar lipo charger (#390) would do the trick. Simply plug the solar panel into the DC jack of the #390, a lipo battery into the batt terminal and the fona into the load terminal.
In this case, you don't want to use the LOAD output. Just connect the Solar Charger's BAT/GND pins to the FONA's LiPo jack.

User avatar
actom
 
Posts: 24
Joined: Thu Apr 23, 2015 3:24 am

Re: Anemometer

Post by actom »

Mike,

"In this case, you don't want to use the LOAD output. Just connect the Solar Charger's BAT/GND pins to the FONA's LiPo jack."

Wouldn't this just power the uno/fona from the solar panel? How do I hook up a battery to run the thing when the sun is down?

User avatar
actom
 
Posts: 24
Joined: Thu Apr 23, 2015 3:24 am

Re: Anemometer

Post by actom »

Mike,

I've wired up as I think you suggested.

Does this mean that the Uno/Fona will now be powered from the Lipo at night, whilst the battery will be charged AND the Uno/Fona will be powered from the Lipo/Solar power during the day?
Attachments
Wiring.JPG
Wiring.JPG (120.53 KiB) Viewed 478 times

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Anemometer

Post by adafruit_support_mike »

That's correct.

User avatar
actom
 
Posts: 24
Joined: Thu Apr 23, 2015 3:24 am

Re: Anemometer

Post by actom »

Brilliant! That's the hardware sorted, now for the software...!

User avatar
actom
 
Posts: 24
Joined: Thu Apr 23, 2015 3:24 am

Re: Anemometer

Post by actom »

Mike,

Another question please.

I see that I can increase the charge current by soldering a resistor in parallel to the one over the PROG terminal. What wattage resistor should I use to get the current up to 1000 mA. I have some tiny resistors but they are only 1/8W.

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Anemometer

Post by adafruit_support_mike »

The charge current is 1A * 1k / RPROG.

The PCB already has a 2k resistor, so the current is 1A * 1/2 = 500mA.

To get 1A you'd need a total resistance of 1k, which you can get by adding another 2k resistor in parallel with the one that's already there.

The current through the resistors will only be a couple of milliamps.. low enough that you don't have to care about their power rating.

Locked
Please be positive and constructive with your questions and comments.

Return to “Arduino Shields from Adafruit”