I am looking for some tiny wind speed/direction sensor with a lower power consumption for a scientific experiment. Any suggestions?
I contacted with vaavud.com about wiring up their sensor with Arduino, however they preferred to use it with a smart phone. Any other sensors alike?
Hello, you can get inexpensive sensors on eBay which could be used with low power circuits.
I am developing a low power weather station. At the moment it consumes around 15mA, but I have some ideas to reduce this to less than 1mA.
Depending on the required sensitivity and precision, another approach comes into mind, inspired by old windmills. Two wind wheels, mounted at 90° orientation, may be sufficient to detect the wind speed and direction. Or 3 off by 120°. The wheels can drive small (model construction) motors, acting as voltage generators, for least (zero) power consumption. Or the traditional approach with rotary encoders or light barriers.
For power reduction any light barriers, as used in rotary encoders, can be turned on during measurement of the wind speed only, and cut off in between.
Wind direction is harder, as long as incremental encoders are used, which can not be turned off without losing the angle information. Here absolute encoders may help, but their resolution may not be very high at affordable price. Here a magnetometer may help, which measures the orientation of a permanent magnet bound to (turned by) a direction sensor.
Yet another approach may use a vertical rod of some shape (balloon?), stuck e.g. into a weak spiral spring, and tilted by the wind into any direction. The tilt direction and degree can be measured by an accelerometer (2-9 DOF), attached to the rod. This looks to me like the simplest solution, achievable precision has to be explored. Eventually two springs can be used, a very weak one for low wind speed, and a stronger one that becomes active only at higher deflection of the rod.
@DrDiettrich The DOF idea sounds great. It can be used both in monitoring wind direction and wind speed. One thing bothers me is that how to prevent the twisted wires since these sensors will be mounted on a spinning object. I also attached some pictures from opening up the device from Vaavud.com. It seems it uses the concept you mentioned. I wish I can just get the readings out on Arduino, because it is the right size not to be noticed by human or animals.
@PaulRB Very nice design. Do you put your device into deep sleep mode? What is the data recording interval?
Thanks. Your comments help a lot.
In img 9712 you can see the light barrier (black U shaped), that separates the rotating slits from the stationary circuit.
There is some interesting reading on types of anemometers here Some of the cup style ones I have seen just use a small permanent magnet motor as the sensor which does not require any power at all since it generates it's own. It was interesting to note that one type of the cup anemometer has a "tag" on one of the cups which causes it to slow down when that is into the wind and by looking at the changes in rotational speed during the rotation, they can determine wind direction. No idea how accurate that is, but it sounds interesting.
The weather station updates the database on the web server every 15 mins. But it cannot go into deep sleep between these times, like my indoor temp/humidity sensors do, because the wind speed, direction and rain sensors need to be constantly monitored otherwise events would be missed. So the ESP chip goes into modem sleep instead, hence the 15mA consumption, where the CPU remains active but the WiFi modem powers down.
I hope to use an attiny84/85 to monitor the sensors so that the ESP chip can go into deep sleep. Communication between the two chips is preventing me from doing this at the moment. I want to use i2c to connect them together but I have not been able to make this work reliably so far.
Thanks PaulBB, gpsmikey, and DrDiettrich. Your ideas and input help a lot.
@gpsmikey I think that the device from Vaavud.com also use the same way to determine wind direction.
@PaulRB I use the Electron board from Particle. It communicates based on 3G signal so it can be installed in a remote area.
I use one of these, without the direction indicator: http://www.ebay.com/itm/Met-One-Wind-Speed-and-Direction-Sensor-C034b-Anemometer-/291753447220?hash=item43eddc4f34:g:0scAAOSwE6VXJsnz
I got it cheap at a swap meet. It uses a reed switch. I programmed a NANO to use interrupts caused by the reed switch. The device needs a 1 MPH wind to begin turning and about 0.8MPH to continue turning.
Saw over 50MPH yesterday during a dust devil passing by.