Arduino Based Weather Station

[Gina]

Here's an updated cross-section of the wind vane hub.

[Gina]

Except that it's not right - I'll do another.  Meanwhile here's the hub which should be to scale.

[Gina]

Black ABS 1.75mm filament has arrived so I can print the encoder wheel.

[JLR domotique]

I try to use the Ds2450, but with a resolutoin, greater than 0.1 Volts and pfference 0.001 volts.
is it possible with the Ds2450 ???

[Gina]

Not sure now - I suggest looking at the datasheet.

[Gina]

I'm now considering having the wind instruments and my all sky camera on the same mast from an idea by angryowl.  Probably have the ASC on the main mast and the wind instruments out on a boom to one side.

Edited December 1, 2017 by Gina

[Stub Mandrel]

Where are you putting the strings and brass?

[Gina]

Hadn't thought of that

[Gina]

I've been working on the ASC but feel like a rest from that so now looking at the weather station again.  The anemometer is finished as shown in the photo below where it's sitting on my desk lamp/magnifier.  A lot of the wind vane part is finished but I shall be changing the design of the mounting.  The anemometer will still be mounted on top of the wind vane damping plate.

[Gina]

The current design for the wind vane part looks like this but I shall need to alter the mounting to fit it on an arm coming out from the main mast.  The top is an aluminium saucepan lid which provides damping for the wind vane in conjunction with a supermagnet attached to the rotating part (grey block on left).  The direction is sensed by four slot type optical sensors on the fixed part with an interrupter plate on the rotating part.  The current mounting arrangement is to fit on the top of a hollow mast (aluminium tube) so that needs changing to a side mounting.

[Gina]

This was the original arrangement with wind and light measuring instruments on the top of the mast with the Arduino in the observatory and using "1-wire" to connect to the sensors.  All this was before the Raspberry Pi came to my attention (maybe even before it came out).  With that and now with at least one of the 1-wire device being discontinued I am having second thoughts.  The RPi 3 has Wi-Fi and WLAN communication of the data back to my indoor computer is a definite possibility.  I am already doing that with my ASC so why not the weather station too?  That means just a power cable going up the mast.

[Gina]

One idea :-

[Gina]

Another :-

[Gina]

Think I prefer the first - simpler.

[Gina]

I have an aluminium pipe about 2" diameter or a bit smaller and 5m long.  That's a good start, already twice the height of the observatory.  My original wind instruments are on a pole about 6m high consisting of an iron water pipe then (I think) 28mm copper plumbing pipe which has bent in the storms.  Aluminium is much stiffer and stronger.  The Met Office recommended height for wind measurement is 10m but I don't think that's necessary for amateur meteorology.  I'm not even sure it needs 6m but I can extend the 5m pipe with some smaller pipe (like I'm using for the ASC) to fit inside.  So I think I have the main mast covered.

The next thing is the arm to take the weather station stuff.  I think that wants to be aluminium too.  I have a choice of tube, channel or extrusion left over from making my 3D printers.  The extrusion is heavier so I'll probably rule that out.  The problem is attaching it to the mast.  It needs some kind of strong bracket but attaching to round tube is not so easy.  I guess I could use aluminium plates either side bolted through.  There is both weight and windage of the weather station parts to consider.  I know I do lots with 3D printed plastic but in this case I don't think it would be strong enough.

[Gina]

Been for a walk up the hill and been thinking...  Since the wind vane is not going on the top of a mast the bearing(s) can be much smaller and therefore produce less drag so the whole thing could be smaller - more like the commercial units.  Instead of the large saucepan lid I could use a simple aluminium disc (which I think I already have) and the magnet could be smaller and lighter and still produce enough damping force.  I have a number of the rare earth magnets of various sizes.  The whole vane assembly could probably be one (or maybe two) 3D printed parts.

[Gina]

New wind vane design.

[Gina]

Hmm...  The cylindrical magnets (15mm diameter and 7mm thick with countersunk hole) I was hoping to use don't seem to produce much drag but a bar shaped one (42mm x 9mm x 7mm) produces quite a lot.  This is a bit less easy to mount but It could be held with a suitably shaped 3D printed housing.  The main point though is that it's heavier and probably too much to balance the plastic wind vane.  I could make the vane itself out of thin aluminium though which would be heavier than the thicker plastic.  I have plenty of thin aluminium sheet.  Some experimenting needed

Edited December 2, 2017 by Gina

[Gina]

This would be the new wind vane print with slot to take the vane and cavity to take the magnet.  Top view.  The encoder rings could be added on top of the centre circle.  Or alternatively the encoder unit could go above the aluminium disc.  I shall probably use threaded rod as the axle.

[Gina]

Side view of wind vane unit (or part of it) showing the vane holder, axle and ball bearing fitted into the aluminium disc.  The encoder disc can be attached to the axle above the aluminium disc inside a 3D printed casing.

[Gina]

Aluminium wind vane added.

[Gina]

I reckon that with the smaller and lighter weather station parts I might be able to get away with a 3D printed arm.  Probably add a web up to the ASC casing to strengthen the mast attachment.  I haven't shown the anemometer, which will be attached to the top of the casing.  The hollow base of the anemometer will cover the top bearing for the wind vane.

[Gina]

This design would be better.

[Gina]

Here's the basics of a combined casing and arm.  The raised part in the middle takes the wind vane top bearing and a hole through the arm is for the wires.

Edited December 2, 2017 by Gina

[Gina]

Only problem with printing this is the size   Currently my largest 3D printer is the Titan which has a 300mm square print bed though when I've finished my Giant printer that will have a 400mm square print bed.  This item will just about fit in the Giant printer bed.  With the Titan I would have to print it in two parts - the casing and the arm and glue the two parts together (not really a problem).  Here are two screenshots of SketchUp with squares representing the print bed sizes.

Edited December 2, 2017 by Gina