Weather Station - External

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ISS

This is where the weather data is gathered through a series of instruments, this data is collected in the Integrated Sensor Suite (ISS) before being sent to the Vantage Pro2 console using a 4 core cable connected via an RJ11 plug into the ISS.

The ISS collects data from a Rain sensor which comprises of a calibrated tipping bucket, for every 0.2mm of rain collected, the bucket tips, other sensor are the temperature, humidity, UV and solar, the last two have only recently been fitted, but these will have to be moved as the data from them is wildly inaccurate due to poor placement of the sensors.

The yellow infill is Solar energy received, note the 'trough' is where the house obstructs the sensor as the arcs, before reappearing later in the day, I'm going to put this and the UV sensor above the house ridge line to stop this, keep an eye out for the updated pages where this will be covered. Update - Moved the sensor and what a difference!

 

   
ISS with the cables ready to pass through the cable entry point  where they plug into the board sockets (it does look worse than it actually is)

Rain Collector Filter - Top

The main problems I have are the amount of debris that finds it's way into the rain collector, this then blocks the hole to the tipping buckets, I read about using a sieve to catch this, so that what I have done, the sieve I used was from Sainsbury's (5052767219411 barcode) made from non rusting stainless steel, the size I was looking for was 150mm (6") in diameter to fit neatly within the rain gauge, the only one I could find at the supermarket was a two pack set made up of a 100mm and 150mm, so the wife thought I had treated her to a 100mm sieve, no wonder she looked at me a bit odd :-)

The hardest part was grinding down a smooth finish after I had cut the sieve handle and supporting hook off, no further work was required other than gently placing it within the mouth of the rain collector.

   
Pre sieve destruction 20 minutes later minus a handle & hook All done    

Rain Collector Heater - Top

I thought I would improve the weather station by the addition of a thermostatically controlled heater within the rain collection housing, the idea being that should snow fall, the slightly heated collector would melt the snow and a useful measurement could be gained.. The task was fairly simply once I had obtained all the parts, and eBay was my friend on this one, the total costs came to about £15.00 which is cheaper than buying the Davis heater unit.

The heater is a wire wound 22 Ohm, 25watt resistor, this was affixed to a large heat sink in order to spread the effective area of the component, I used thermally conductive paste to ensure good heat transfer, I also used spacing fiber washers on the mounting angle brackets supporting the heat sink, as I wasn't sure if the plastic base of the rain housing  would stand up to the temperatures that a directly connected heat sink might transfer via the fixings, glad to say it's not melted it's way out yet!

In the loft is a 24v AC power supply to the weather station camera, this has also been used to supply the resistor via a thermostat set to close contacts at 4oC and open at 15oC, this huge offset is unavoidable with a 'cheap & cheerful'  mechanical thermostat, in my application it makes no difference, I suppose I could have used a thermistor sensored unit with a smaller hysteresis, but hey, it's only for melting a bit of snow!

Typical level of snowfall in the Fens

Wire wound resistor mounted on heat sink.  
Thermostat mounted on an offcut of Vero board.  

To keep the heat generated where it was needed, I lined the inside of the rain collector with a reflective insulator (the sort of thing that goes behind radiators to stop heating the wall and reflect it back into the room).

 

Fan Aspirated Radiation Shield (FARS) - Top

Although the weather station is not in the very best place for optimal performance, I thought at least the data that it does gather should be as accurate as I can make it, with this in mind I bought the Davis 7747 Daytime Fan Aspirated Shield Kit from Scientific sales, Lawrenceville, New Jersey, great company to deal with and fast shipping to the UK. The purpose of the FARS is to gently draw air to be sampled past the sensors, rather than rely on static air to be measured within the solar shield, it does make a difference, not a huge difference, but enough to say its accurate.

Even taking into consideration the additional customs charges, I was still quid's in, I can recommend this route to anyone.

As I had a wired Vantage Pro 2 and a 24v supply to the weather camera and rain collector heater, decided to use a voltage regulator to reduce this 1.75v DC and run the FARS 24/7 from this supply, the fan did come with a solar panel which in my case wasn't needed, so I sold it on eBay to pay for the voltage regulator and with what was left over I had fish & chips.  The installation of the fan assembly and shield disks was really straightforward, all the parts and a comprehensive manual was provided in the kit  The recommendation is to take the unit down, which I did, and the strip and build was done in my garage, this also gave me a good opportunity to give the solar shield and the tipping buckets a good clean.

From the forums I saw that one chap had used a wire mesh beneath the fan to stop insects accessing the sensor assemblies should the fan stop rotating, I thought it was a good idea and did the same and bought a small piece of 2mm mesh from eBay and fitted it, after all, it certainly won't do any harm.

Fan in place, direction of rotation  and speed checked.
Velleman voltage regulator, 24v AC in and adjusted to give1.75v DC (bottom scale) out to volt meter. When testing he fan this was found to be the best setting, 2 volts to the fan just made it too fast in my view, 1.75 v was not to low as to stall the motor and gave a reasonable air flow,
The regulator is adjustable by a potentiometer from 1.5 to 35v (24v in my case),I removed the potentiometer and replaced it with a fixed value resistor of 47Ohms as the smallest vibration on the potentiometer would have a significant effect on increasing the output voltage.
Due to the load of the fan, the voltage regulator needs a heat sink as it does get rather warm without one and will shorten the life of the component if not fitted.    
Regulator affixed with double sided tape to the weather stations connection box - Red & Black output to fan, polarity is important to ensure the fan is running in the right direction.    
       
Back together and tested as working, all you can hear from the FARS is a very low hum as the motor is turning.

Tip: When sliding the ISS lid on, make sure the cable from the console outlet is in the groove to the side of the PCB otherwise it may make a bad connection and communications with the display will stop and it's a git to fault find!
   

UV & Solar Sensors - Top

I bought the UV and Solar sensors at the same time as the FARS and from the same company, the sensors need a bracket if they are to be mounted on the weather station, it would be awkward to try the assembly in place in case you drop something, so it does take some disassemble and that why I chose to do it all in one go along with the FARS. The fitting of the sensors was really easy, just three screws which pass through a spring so that the unit can be adjusted using each screw to be level, (on each sensor is a bubble level gauge so you can't go wrong), once fitted they plugged directly into the marked ISS sockets and that was it!

Sensors being fitted to bracket.
   

Installing the Weather Station - Top

I live in a relatively built up area as far as weather stations are concerned, when you read guides on what is optimal, my location falls way short on a few things, like the orientation of the house in relation to the sun, but the choice of no data collection wasn't an option, so I just cracked on.

The only place it could realistically be mounted was behind my garden shed, and these are a few pictures of the installation, my biggest error was getting the UV & Solar sensors as it highlighted was a daft place it was to fit them, the ISS graph shows this.

After locating the best spot for the weather station, I ran in the cables for the ISS from the house (covered here), I drew in 2x Cat5e cables,  1x 8 core telephone cable and 1x 0.75mm cable. An earth cable was also fished down the wall cavity in order to earth the conduit to the aerial amplifier in the loft.

     
Before   Frame being treated Dry cement pre-mix 'tamped' down and watered in    
     
Cables drawn in galvanized conduit   Front of Weather Station Cables contained in conduit to ISS and camera    
 

Installation of Earth Rod for the Weather Station - Top

After a severe electrical storm which left me 'off-air', I thought I'd improve the earthing of my system in a hope of keeping everything at ground potential to reduce future impacts of lightning, the conduit used for the wired station was used as an earth for the television amplifier in the loft, I used a 4' copper rod local to the weather station and used and earth clamp around the conduit and connected the rod to this, from the rod I ran a cable to the external cameras ground point.

In the loft I fitted and earth connection block, from this ran separate 2.5mm2 earth cables to the lightning detectors (Boltek and Blitzortung) and to a copper piping bonding point in the house, only time will tell if this has helped.

     
Hammer to the ready Rod driven 4' into the ground   Leveled up before cementing in place    
         
  All done with access box just visible        

 

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