Cumulus Support

Hi all,
I am trying to build my own weather station and I am having lots of problems with the wind vane.

I am currently trying the reed switch method and would like to ask a few questions.

Which is the best way to orient the reed switches to the magnetic. ie do the metallic strips of the reeds need to be above/below each other or do they need to be side by side or at 45 deg etc.

I have been trying for approx a 2 weeks to work this out but keep struggling. First my magnet was to weak, so I brought another but this was way to strong as the all the reeds connected when the magnet was within 15cm so I am now buting another magnet and then I also tried different orientations but keep gettign different results.

Thanks
STG

The photos here and here and maybe most clear in this post
suggest that in one design of weather station, the direction of movement of the magnet is such that it passes over the thin edges of the reeds one after other. Put another way, the magnet and reed move in same direction.
The photos do not show the orientation of the magnet with regard to its poles, and that is likely to be more crucial than movement direction.

But that is just my interpretation of a few photos in the forum, it is too many years since I last fitted a reed switch for me to remember the orientation experiments I did.
There may be advice in technical specifications online about your particular reed switch.

Hi,

The lines of the actuating magnet field need to run along the length of the Reeds, so it doesn't matter if the reeds face each other "sideways" or "one above the other". This magnetic field turns the two reeds into "bar" magnets and since they are offset end to end, a North Pole faces a South Pole and opposites attract!

The field lines outside of the body of a (permanent) bar magnet (e.g. made from iron or ceramic materials) run from the pole near one end to the pole at the other, approximately parallel to its axis. Therefore the "best" (most sensitive) way to activate a reed switch is to place a permanent bar magnet beside it (i.e. with their axes parallel to each other). However, IIRC Fine Offset actually arranged their magnets at right angles, but with one end of it and the reed switch close together, thus using the "radial" component of the magnetic field, where it exits at one end of the magnet.

Modern Neodymium magnets are often disc-shaped, with N and S poles on opposite faces, so they can be considered as a very "short" circular bar, but still with a very high field strength, so may need to be positioned some distance away from the reed switch. The field strength tends to reduce by the "inverse square law" of distance (i.e. 25% field strength if the spacing is doubled).

Cheers, Alan.

Modified my Fine offset wind vane as per the picture. The magnet is a Neodymium magnet from amazon and on the other side of it I put a couple of dabs of super glue. I now get all 16 weather points registering and it doesn't seem to "helicopter" as much but time will tell.


Sorry I don't have a display of before the update.


(The picture is not of the unit I am using as I forgot to snap it before installation. I created this from another vane to show the magnet and balancing blue tack!!)