Got a wind speed sensor from Maplin’s Ebay shop for £2.50. Stuck it in a bit of polystyrene and used my computer’s case fans to blow air at it for testing purposes. I imagined there would be a little motor in there, and different (tiny) voltages would determine how fast it was spinning – nope that was wrong. What happens (I imagine with a magnet and reed switch, as I’ve found some use that) is that every half a revolution, it makes (or breaks, can’t remember) the circuit, so I just plugged this straight onto my breadboard where I had been testing push-to-make buttons with Python, Pi GPIO and interrupts (really easy to do, and eats 90% less CPU than just having the script whirl round in a while True: loop).
After a bit of maths to convert the RPM to mph (basically speed = distance/time, and time = 1/frequency(rpm)) I started to get some realistic values. Also after some research, most desk fans blow air at about 4mph if you are a foot or two away from it, so used one to test my results were feasible.
Next I got a bit of wood, drilled some holes in the end of it so the wind speed sensor and its wire could be secured, and stuck it out the window.
In other news, I was in some credits!
Some of the footage taken by me of the Aberystwyth storms made it into the programme “The Storm That Stole Christmas” on Channel 4 (27th Feb, 9pm), so I was listed in the credits!