WindPOV Weather Station

A wind turbine powered weather station displaying temperature, humidity and wind speed by persistence of vision using 8 white LEDs along a wing tip. The turbine blades were cut from a length of 4 inch PVC pipe.

A 12v stepper motor salvaged from a floppy drive is used as the generator. The stepper body is mounted to the turbine, the shaft is held stationary. This allows the for the omission of slip rings to transfer power to the persistence of vision display. The controller, sensors and display system are mounted to the motor and rotate along with the turbine blades.

The 4 phase AC from the stepper is rectified with 8 schottky diodes and shunted to 36 volts by three 1 watt 12 volt zener diodes in series. The shunt serves two purposes, to prevent the DC input voltage from exceeding the switch mode buck regulator maximum input, and to provide electrical braking to the turbine in the event of high wind speeds. The resulting input voltage is switched down to 3.5 volts by way of a TPS5420 buck converter.

The MCU controlling the common anode POV display is an AtMega88, chosen for it’s ability to operate at up to 10Mhz from 3.5 volts. The temperature and humidity are sensed with an SHT21 via I2C and absolute position by a hall sensor salvaged from a floppy drive. The hall sensor allows for positioning the POV display as well as calculating rotational speed. A resistive divider was added to sense the voltage generated by the stepper.

The cut in speed appears to be around 100 RPM as the SMPS requires at least 5.5 volts to start up. At 1500 RPM the open circuit voltage of the stepper is just over 60 volts.

The latest version (filmed Mar 03/12), using the same PCB but with a larger wingspan, a bigger stepper motor and 5mm red LEDs is now online at: http://krazatchu.ca/2012/03/02/hackaday-windpov-project/

Testing video in front of box fan, displaying name, not so interesting:

9 Responses to “WindPOV Weather Station

  • So does the fact that the temperature sensor is spinning affect the readings? Although the speed of spin is related to wind speed, since it is moving perpendicular to the wind it seems like this might introduce additional/different wind-chill effects?

  • I couldn’t guess one way or the other…
    The humidity/temperature sensor chip uses an internal heater when measuring the humidity, which when run constantly causes a small increase in the temperature reading.
    The wind over the chip is probably removing this heat faster than it would normally dissipate.

    Michael

  • Impressive project!

  • Impressive. I’ve never seen it done w/ out slip rings could you take pictures explaining your technique? Email/post would be great if not a link to similiar designs.

    good work!

  • Steve,
    I’ve just added a picture to the post about the latest version here:
    http://n0m1.com/2012/03/02/hackaday-windpov-project/
    Michael

  • Windchill will have absolutely no effect here. The air temperature is still the same, windchill applies because the moving air has the ability to remove heat faster than non-moving air. Thus a day with a windchill of -40 degrees feels the same as a day with no wind at -40 degrees as far as heat removal, but the actual outside temperature is not changed by the windchill.

  • what kind of Schottky diodes used as rectifiers you? you could provide me with the technical parameters

  • I believe the Schottky diodes I used were SS18, which are spec’d at 1 amp and 80 volts. The first stepper I used had an open circuit voltage of 60 volts, but with a moderate load and the 36v zener clamp it never gets over 36 volts.
    Michael

  • thanks a lot, I’m in love when I saw this project. now I want to try making one equal to this!

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