Author Topic: Davis VP2 Anemometer Reed Switch Replacement  (Read 376 times)

MervynG

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Davis VP2 Anemometer Reed Switch Replacement
« on: September 24, 2017, 11:35:48 AM »
Having done this twice in the last 8 years and not found detail on how to do it, I thought it might be of interest. New anemometer c£$170 v reed switch a few pence/cents. Do check you have a reed switch fault (permanently closed or open) before embarking on this.

Order some reed switches before you start. They are of the normally open type. I use either  REED SWITCH, 20W -  KSK-1A35-1520 part SW02761  from CPC or part SW923 from Brimal in UK. They're both 220V 20W and only max 10.5mm. The length is critical as the gap in the 'jaws' of the PCB is very small. Reed switches are very fragile but, fortunately, also very cheap. So order 10 in case you break a few. Have a read of this to better understand the challenge you face: https://standexelectronics.com/wp-content/uploads/Precautions_for_Reed_Switch1.pdf

Just in case, I also replaced the tiny 47Ω chip resistors with metal film ones.

You'll need pliers, screwdrivers, soldering iron with small tip, solder, craft knife, an ohmmeter, a magnet, a compass and shrink wrap. A jeweller's eyeglass or a magnifying glass might help too.

I have some images of the process but will try and describe it such that you don't need them. In any case http://www.lexingtonwx.com/anemometer/ has some good ones.

1/ Remove anemometer from whatever pole it is on.

2/ Carefully detach the cable from the pole attaching plastic semi-circle by wiggling it carefully free of the lugs.

3/ Using the appropriate Allen (hex) key, remove both the vane and the cups from the anemometer module.

4/ Remove the small screw which attaches the anemometer module to the upper part of the bent aluminium pole.

5/ Carefully pull the module away from the pole at the same time feeding the freed cable into the lower end to allow this to happen.

6/ Remove the nut and castellated washer from the vane end of the module. This will leave the vane potentiometer threaded shaft protruding through the centre of a small plastic disc recessed into the module. This disc needs to be removed and is held in place by a having had a few dabs of heat applied to its perimeter to melt it and thus 'glue' it to the module body.

7/ Using a small bladed craft knife gently cut around the perimeter of the plastic disc inside the module to release it from the module body.

8/ Gently tap or tease the plastic disc from the module body. Pull the Davis vane potentiometer from the module feeding cable into the module side as required.

9/ The reed switch is soldered onto a PCB. When you look into the cups end of the module you will see 4 legs of a plastic 'cross' and between two of the legs is the reed switch. The PCB is shaped like an upper case T. The reed switch sits across the top of the T. But it is inset in a recess in the top of the T which is about 11-12mm wide. On manufacture, the PCB was inserted tail first into the module until all that was left was the reed switch between two legs of the black plastic cross.  Thus the tail of the T is  out of sight in the module body. The plastic cross is NOT removable but the PCB is. It is only held in place by friction. So using a long thin screwdriver inserted in the vane end of the module aiming towards the gap between the appropriate two legs (the two where the reed switch sits) you can press on the end of the tail of the PCB and, surprise, surprise, the PCB with reed switch attached will simply slide out of the cups end of the module. If there isn't enough slack wire cut it. You can always join some later.

10/ Now for the real fun. Firstly, I unsoldered and removed the reed switch. Then I unsoldered the wires which connected the PCB to the vane potentiometer noting which was red and which was black.Then I dabbed solder on to the chip resistors to short them out (you can miss this if you are not going to replace them). I then soldered a 47Ω metal film resistor to each of the PCB tail end contacts and re-soldered the red and black wires to the other end of the appropriate resistor. I used shrink wrap to insulate the joins. Then, following the advice in the pdf above, I very gently soldered a new reed switch into the recess in the top of the PCB T. The orientation may be important and you can check this both visually and with a magnet and an ohmmeter.

11/ When you think you've succeeded without damaging the new reed switch (the glass envelope is the issue) , put an ohmmeter across the red and black wires and, moving a magnet to and from the end of the PCB T check the reed switch is working. It should be normally open (∞Ω [max] with no magnet and closed (0Ω) when the magnet approaches.

12/ Ever so gently insert the resistors and PCB back into position and reverse the disassembly. When you put the plastic disc back into the vane end recess, gently dab your soldering iron to re-melt it to the sides in a couple of spots. You don't have to be over zealous because: a) you might need to do this again and b) it is sits positioned down when working and c) the vane potentiometer is quite a nice friction fit and unlikely to fall out vertically upwards.

13/ When you re-attach the unit to the pole you will have to re-orientate it with a compass.


Voilà, anemometer fixed!

Felix

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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #1 on: September 24, 2017, 02:30:01 PM »
I also have found that the Davis anemometer is an early failure point of the overall system. And since mine is quite a pain to get to (and naturally it only fails during bad weather), I'm going to replace it next time with an R.M. Young instrument or maybe a Darrera ultrasonic if I can get over the sticker shock.


https://www.darrera.com/en/detalle-producto.php?d=1&id=229

openvista

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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #2 on: September 24, 2017, 05:10:45 PM »
I've already replaced my bearing once (VP2 new in 2013, bearing replaced in 2016) and fear I'll have to do it again soon. As you say, it will happen during the worst time. Bet on it!

My worry with this Darrera unit you linked to is that it would get plugged with snow and/or ice in northerly climates. No heater.
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Felix

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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #3 on: September 24, 2017, 10:36:38 PM »

My worry with this Darrera unit you linked to is that it would get plugged with snow and/or ice in northerly climates. No heater.


It has to be ordered direct from the company in Spain and is available with a heater according to a fellow on the Wx Forum.


He said the step-down transformer provided for the international market is 220/110V AC to 12V DC.


https://www.darrera.com/en/detalle-producto.php?d=1&id=299


The brochure on a similar unit not designed to replace the VP2 anemometer: "The optional heater is activated automatically at temperatures around 4°C, preventing the accumulation of ice and snow on the transducers and allowing precise measurements at low temperatures or during and after a snowfall."




elagache

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Thank you and UltraSonic (?) (Re: Davis VP2 Anemometer Reed Switch Replacement)
« Reply #4 on: September 24, 2017, 10:53:10 PM »
Dear MervynG, Felix, openvista, and WeatherCat station caregivers,

Hey before getting this thread completely distracted . . . . .

Thank you
MervynG for your helpful explanation!

Unfortunately, it does sound like delicate surgery.  I'm not sure how many of us are up to this sort of electronics repair.  Still, at least we have the option!  ThU32:-)

Now onto Ultrasonic upgrades for the Davis VP-2.  So what is the price exactly for the Darrera unit?  Is this one of those items that if you have to ask how much it costs you can't afford it?  ???

In the meantime, while I was trying to find the price I stumbled onto another Ultrasonic upgrade:

https://www.scientificsales.com/ProductDetails.asp?ProductCode=6400

Does anybody know anything about this product?  I can't even find a manufacturer.

Who thought owning a personal weather station could become so complicated! . . . .  :o

Cheers, Edouard  [cheers1]

mcrossley

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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #5 on: September 25, 2017, 07:28:21 PM »
Good guide, be aware that the Davis units have used a Hall effect sensor for some time in place of the reed switch. Whether this proves to be more reliable.......

I had to replace the reed switch in the rain tipper, it was the weekend and I wanted it back in service asap - I stripped out the reed from an old burglar alarm window contact switch - it still working about a year later!
Mark

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Any idea when Davis switched to Hall effect? (Re: Davis VP2 Anemometer)
« Reply #6 on: September 25, 2017, 10:59:58 PM »
Dear Mark and WeatherCat station caregivers,

Good guide, be aware that the Davis units have used a Hall effect sensor for some time in place of the reed switch. Whether this proves to be more reliable.......

Mark do you have any idea when Davis made the switch?  I'm curious to know if my anemometer has the Hall effect sensor or not.  I bought it in 2009.

I had to replace the reed switch in the rain tipper, it was the weekend and I wanted it back in service asap - I stripped out the reed from an old burglar alarm window contact switch - it still working about a year later!

Congratulations!  Thus far, my 8 year old station is working perfectly.  Of course the California weather conditions probably contribute to that.  We are also in a wind-sheltered location, so the anemometer doesn't get too much of a workout.

Cheers, Edouard

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Re: Any idea when Davis switched to Hall effect? (Re: Davis VP2 Anemometer)
« Reply #7 on: September 25, 2017, 11:31:28 PM »
Mark do you have any idea when Davis made the switch?  I'm curious to know if my anemometer has the Hall effect sensor or not.  I bought it in 2009.
Note sure exactly when, but the new version can be identified most easily by the brass tip on pointer of the wind vane- there are other more subtle changes as well.
Mark

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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #8 on: September 26, 2017, 01:16:16 AM »
I bought one of the new anemometers two years ago. Still running, but two years isn't much to go on.
Blick


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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #9 on: September 26, 2017, 04:34:46 AM »
I also have found that the Davis anemometer is an early failure point of the overall system. And since mine is quite a pain to get to (and naturally it only fails during bad weather), I'm going to replace it next time with an R.M. Young instrument or maybe a Darrera ultrasonic if I can get over the sticker shock.


https://www.darrera.com/en/detalle-producto.php?d=1&id=229

I had to replace mine once, and the system worked for another 10 years.    I guess luck of the draw
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MervynG

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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #10 on: September 26, 2017, 06:13:49 PM »
Hi Everyone

Thanks for the replies. Its fiddly not difficult and I have this 'condition' where I have to try and repair everything. Drives my wife mad. Anyway 10 reed switches cost so little it has to be worth a go and, if it doesn't work, well you've lost only pence and an hour of your time, and if it does you'll have saved loads.  I suspect most of my issue is insect ingress. I will no longer attach the pole to an apple tree!!! They were in places I didn't even know existed!

Edouard the anemometer you refer to is made by a French Company LCJ Capteurs. You can find them here:  http://www.lcjcapteurs.com/products/anemometres-terrestres-fr/   I do not know anything about them or it.

elagache

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French product is interesting! (Re: Reed Switch Replacement)
« Reply #11 on: September 26, 2017, 10:37:29 PM »
Dear MervynG and WeatherCat station caregivers,

I suspect most of my issue is insect ingress. I will no longer attach the pole to an apple tree!!! They were in places I didn't even know existed!

Yes indeed, bugs are a description as well as a name.  My station is mounted on the south side of the house.  It is quite hot there and there is absolutely nothing for them to eat.  That reduces some of the interest, but the spiders continue to try anyway.

Edouard the anemometer you refer to is made by a French Company LCJ Capteurs. You can find them here:  http://www.lcjcapteurs.com/products/anemometres-terrestres-fr/   I do not know anything about them or it.

This is a more interesting product than it first appears.  First you can get the website in English which definitely helps in making sense of it:

http://www.lcjcapteurs.com/product/self-powered-ultrasonic-wind-sensor/?lang=en

There is also a brochure that is also available in English.

http://www.lcjcapteurs.com/wp-content/uploads/2017/06/LCJ_Capteurs_Products_guide_Terre_ENG_WEB2_140617.pdf

This device has a huge advantage over the Spanish model because it is solar-powered.  You don't need to run a power supply to it at all.  The only downside is that it can only measure wind speeds from 1 to 40 m/s  (89.5 mph).  The mechanical Davis sensor is rated from 2 to 150 mph with the large cups or 3 to 175 mph with the small cups.  Of course if you actually measured wind at even 89.5 mph - would you still have a house (or a Davis console) to observe it with? 

The current price is around $700.  So that's still a serious obstacle.

Still, something to think about!

Cheers, Edouard

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Re: Davis VP2 Anemometer Reed Switch Replacement
« Reply #12 on: September 26, 2017, 11:41:17 PM »
Interesting replacement ideas. Won't work in cold climates. -15°C (5°F) is the low end of its operating range. Too bad, because this is good solution for high mounted anemometers like mine.
Blick