I enjoy DIY, but to keep things simple I purchased an anemometer cupset (3 cups). I feel that a magnetic reed switch would get "bounce" at higher speeds and I was thinking of a disk with a slot, and sensing with an LED/photoresistor pair. Would the photoresistor be fast enough? Or would I need something like a phototransistor?
Are there even better ways while keeping with the KISS (Keep it simple stupid) principle?
Also, how do I convert rotation pulses into MPH?
Note: I live in Florida and as long as my tower (20 feet tall) stands, I might be recording hurricane force winds.

  • \$\begingroup\$ Budget for KISS? \$\endgroup\$ – jonk Oct 9 '18 at 19:09
  • \$\begingroup\$ Maybe around $20.00. \$\endgroup\$ – Gary Stenzel Oct 9 '18 at 19:13
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    \$\begingroup\$ Simply debounce the reed switch in software. Or if you like you can use a hall sensor. Conversion of measurements is off-topic here, converting pulse interval to tangential velocity of the cups is simple math, but the conversion of cup velocity to wind speed is much more complex and must be determined for a given design. \$\endgroup\$ – Chris Stratton Oct 9 '18 at 19:16
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    \$\begingroup\$ To calibrate for MPH, you can take it out in car, maybe in parking lot on non-windy day. Then hold it out of window (will need helper obviously!) and correlate speed of rotation with speed of car. Roughly wind speed that anemometer experiences will be close to speed of car. \$\endgroup\$ – mj6174 Oct 9 '18 at 19:19
  • \$\begingroup\$ @ChrisStratton, I forgot about hall sensors. If I remember correctly, it would be fast enough even in high winds. \$\endgroup\$ – Gary Stenzel Oct 9 '18 at 19:29

Keeping optical components clean will be difficult on your 20ft tower, so I think a magnetic switch is the way to go. A solid-state Hall effect switch like this will be cheap and reliable: https://www.mouser.com/ProductDetail/Diodes-Incorporated/AH3362Q-P-B?qs=sGAEpiMZZMvhQj7WZhFIALYUm%252b6RWDedmaZuFNup%252bZqbCHvIWSV%2fzw%3d%3d

A solid-state Hall effect switch like that is the standard for this purpose (used in motor encoders, etc). It's more reliable than a reed switch over time, and has built-in hysteresis so you won't need to worry about switch bounce.

Use a microcontroller to get pulses per second. (In the code, you would actually measure "seconds between pulses" or, to reduce noise, "seconds between 4 pulses", and take 1/that.) You can calibrate against a commercial anemometer, or hold your anemometer far out the window of a car driving at a known speed.

  • \$\begingroup\$ This sounds like a solid idea, thanks for taking the time to help me! \$\endgroup\$ – Gary Stenzel Oct 10 '18 at 2:01
  • \$\begingroup\$ I do have two unused Arduinos, but I need to learn how to program them. This old dog still wants to learn some new tricks. \$\endgroup\$ – Gary Stenzel Oct 10 '18 at 12:54

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