This is a brief test of NVE Corps. AAH002-02E magnetic sensor. This is a high sensitivity, single axis version intended to sense the Earth's magnetic field (among other things). It has an operable range of 0.3 - 3.0 Oersted field strength (the Earth's field strength is around 0.5 Oe). In this test, a small screw driver is magnetized and brought near the sensor to see what sort of output it would provide after going through an amplifier with a gain of approx. 10. The output is sensitive to the orientation of the magnetic field; varying with the cosine of the angle between the sensor and the field. There are other versions of the technology that are more suited to angular measurement, but this one seemed the easiest to handle for initial testing.
A test to see if the speed data available on a web page matches the actual speed of the turbine. It seems to be fairly close, but there is a lot of variability in the wind and filtering/lag in the web page presentation so the results are inconclusive. Please note that this web site is not up anymore since I took down the wind turbine.
A project to provide wind speed data to the internet. An Arduino is used to measure the wind speed. It communicates via USB cable with a Raspberry Pi to provide the current data on demand. The Raspberry Pi inserts the data into a web page. This may not be the most elegant solution, but for the moment it is what I could get working. The Raspberry Pi is running Apache to serve the web pages which are written in HTML and Php. Python is used to communicate with the Arduino. The web page can be seen at winddata.noip.me provided it is up and running. It is still a work in progress. My hope is to interface the Arduino with a current controller for the VAWT 035 wind turbine to provide data on its performance as well. Note: this video is from April of 2014. The web server is no longer in use.
A way to measure RPM by simulating an LM2907 is demonstrated using an Arduino and Adafruit 16x2 LCD display. This technique uses one digital pin and one timer. The timer generates an interrupt every 4 ms. The interrupt routine checks for a change on the input pin. If there is a change, a constant value is added to an accumulator or "bucket." In either case, pin change or not, the accumulator is multiplied by a value less than one. The value in the accumulator represents the RPM of the rotor generating the signals. The advantages of this technique include: regularly spaced interrupts, no division operations that could result in a divide by zero error, no timing problems with RPMs near zero, provides a cap on the maximum RPM, and no subtraction operation that could result in a negative value. It appears to be a robust way to measure RPM. It is best to use signals with approximately 50% duty cycle. Variations in the duty cycle might cause problems if used to measure frequencies near the theoretical maximum.
I'm working on a circuit to control the current coming from a wind turbine to help it run at its optimum speed. One task for this controller is to measure input current. It could be done with a series resistor and a high side current monitor or a hall effect device, but I wanted to try it with a current transformer since I hadn't used one before and I wanted to see how it worked. This video shows the signal coming from a current transformer and some modifications to the basic circuit to get the desired waveform. Please note that according to the literature I read if your current is always positive as in this case the current must periodically go to zero to let the core "reset." (the term the author of the paper I referenced used) I added a diode that was not present in the literature because it seemed to be a good addition for circuit protection. (Note: I am not experienced in working with these transformers)
A detailed look at an RPM sensor for a wind turbine using an LM2907 and one of the phases from the alternator. The output is a voltage that when sampled by a 10 bit A/D converter will yield 1 ADC count per RPM. The frequency response is low (about 1/2 second time constant), but the turbine RPM should not be changing too rapidly anyway. Calculations are shown at the end of the video.