Yes it can be done

Jan Panteltje · 2015-06-13T13:19:27+00:00

The question if using cheap ebay acoustic distance meter modules _can_ be used to do wind speed and direction measurements needed to be answered. In a first test the pulse changes were too small to see with 50 Hz repetition frequency using my finger and mains frequency as trigger. Well, if all else fails use differential mode. So I used 2 of these distance sensors, removed the TX side piezo, (remember that one on the MAX232), and put them apart facing in opposite directions. Then took the good old 74HCT86 XOR gate, to see the difference (differential remember) in pulse length between forward direction (wind) and opposite direction (wind). This is without wind, on the good 'ol analog scope: I moved the sensors so the pulse was smallest, the second pulse is the one we want. And this is with wind made by a PC fan on 11.4 V: Note the second pulse again!! Eureka! QED So from this follows that by using 4 cheap ebay distance sensors and 2$ for a HCT7486 xor gate plus 4046 [1] I used as pulse generator to trigger the things, here a detail of the 4046 generator: as you can see I Xperimented with some cap values and settled on 100 k 100 nF as the ebay modules cannot be triggered faster (something to do with the speed of sound perhaps) one can make a decent wind meter for a few dollars or GreeceFree? euros. Anyways, you all know those sjips, xor, PLL, so no need to draw the circuit diagram . Just follow the grey wires in the pictjures... :-) My tronics for today, need coffee. [1] do not gimme that 555 jive, yes that would work too, but I have none, I stocked up on loads of 4046, it is still the most universal sjip I have come across. Yes maybe you could use the xor in it, saves a sjip, that was actually the original plan, but forgot about it, wanted only to see the diff, but then still needed more trigger speed, so had to wire it in anyways.

Yes it can be done

Jun 13, 2015 22 Replies

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Phil Hobbs 11 years ago

Sure, that will work. The sum of all the frequencies will give you the sound speed, and there'll be one extra measurement for a sanity check.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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Pomegranate Bastard 11 years ago

That looks good. What would the pivot be, gimbals or something? If the wind shield was oil filled it would act as a damper. For a boat you could mount the whole thin in gimbals to keep it vertical. If the wind shield was magnetic it would act like a compass and correct for heading. You'd need slip rings or a wireless connection for that though.

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John S 11 years ago

Hey, Jan - Thanks for the info on these modules. Too cheap to pass up so I got 4 of them. Easy to play with and work quite well.

Cheers.

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