WXforum.net
Weather Station Hardware => Ambient Weather and Ecowitt and other Fine Offset clones => Topic started by: raedh on September 12, 2012, 04:03:55 AM
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I plan to add two fans to stevenson screen to shield WS-2080 sensor and without adding standard or SRSLx100 shield , is there a guideline how to position fans ( I got to muffin fans )
(https://wto2vq.blu.livefilestore.com/y1pqUMIMQtt3EVZ5BWyKbY9olS8I1syVe7JqJ5mVdDLTqFAmUs_7nX2F_-6MrBxaEirdQiNwGCv5fFX2Shu94N3zHiT_XTRzgOE/IMG_1689.JPG?psid=1)
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Actually a properly constructed Stevenson screen in a ideal location wouldn't benefit from using fans, or doesn't require fans. The temp sensor location inside is just as important. I have a feeling that even if you add 10 fans you are not going to remove the problem, just going to blow it around.
Could you make a small garden or plant area up there that you could mount that in/on ? I think I can feel the heat radiating off those tiles from here. :-)
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](*,) I thought that adding fans will solve this problem, I will make a plan to do what you suggest because i think it is the solution what ever i did , and I'm convinced that rooftops is bad location to mount weather stations
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I'm planning now to make a wood container to grow grassy stuff so I can mount the station on top of , and wondering what might be suggested for container dimenssions that can help reduce ground heat radiations
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How much room do you have to use? Maybe some photos of the roof area you can use may help.
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i will use this area by build a wood container with a recommended dimessions ,and i dont know if i can mount the station on top of any avaiable plastic containers , what do you advice,
(https://wtoa1a.blu.livefilestore.com/y1pbrXbZ2E_8z5a9QHB7aaxmihraJope8i9sqaJjJtXLHqtC23Z3LyqRbPICj7UEBxWQuiRyx8zg3QwE2-SJbnWKYNsY9YwVkwH/DSC03407.JPG?psid=1)
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raedh
Because your stevenson screen it have small dimension ,and it do not have double louvers.It necessary to put one fan 8 x 8 cm over a plastic tube ,and inside the plastic tube is the thermo/hygro sensor.
I had many times experiments for this problem,and i solved with this way
You can see what i mean inside at this page
http://users.otenet.gr/~meteo/project_stevenson-screen-box.html
Another two photos
http://i62.servimg.com/u/f62/11/22/64/62/fan110.jpg
http://i62.servimg.com/u/f62/11/22/64/62/fan210.jpg
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will try this out today I'm already have these requirements and see the minimum for today , and very helpfull and great job what you did
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Dimitris, your idea is great and is perfect when the screen is mounted where it should be. However, as you can see in the pictures, his is mounted on a roof over floor tiles that radiate the daytime heat. Any type of screen, aspirated or not, is just blowing this tile heat around and not protecting the sensors from it. He needs a shield like you suggest but needs to remove the heat surface below it too. ;)
Dan
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DanS, you're right I added two fans (but without platic Tube) and it did a reverse job I got hight temperature in the night and nothing changed in daytime, but i will try the plastic tube
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What's over the wall on the left side in the picture? Are there any walls around your roof area that look down to the open ground area?
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Hi Dimitris! Good to see you here again! :)
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Dimitris, your idea is great and is perfect when the screen is mounted where it should be. However, as you can see in the pictures, his is mounted on a roof over floor tiles that radiate the daytime heat. Any type of screen, aspirated or not, is just blowing this tile heat around and not protecting the sensors from it. He needs a shield like you suggest but needs to remove the heat surface below it too. ;)
Dan
Hi Dan
I agree
Stevenson screen must is 1,5 - 2 meters over the ground ,but if raedh he put it on the roof 2 meters over at a corner of the roof,not center the roof ,i beleive if he make some mods at top the stevenson screen with Insulated material
http://i27.servimg.com/u/f27/11/22/64/62/klovos13.jpg
Do not have high temperature problem
All this i had saw about 4 years ago when i experimented a long time with this problems,because the sun is very hard and here like Chiang mai :-)
Thank you Greg (Slow Modem)
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Thanks all for your kind help and suggestion, weather1967 I will do what you suggest and monitor a week trend min, max, and during the daytime
Thanks All
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With the sensor in the plastic tube you will see differents raedh
The plastic tube work like a protect to sensor,and do not enclaved warm air,because the fan take all the warm air and go above it on the top.
But you will put the fan like photo,and for better put a aluminium tape all arount a plastic tube .The fan sucks air from the side of sensor out-temp -hum,and air flow go above on the roof
Of cοurse you must have the Stevenson screen at correct place,as i said before
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I was asking what's over the other side of the wall(s) thinking of some arrangement that places the sensor more out in the open, away from the roof, like this.
(http://i588.photobucket.com/albums/ss324/DanS_photo_09/thermoShield_zpsc75dc313.jpg)
Maybe even include a modified Stevenson screen over this to help keep the sun off it.
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Hi DanS, the wall that looks to open area is the right side (west side) and currently it is mounted in that side but 70 cm above the ground and still making a base to the box with hieght 2m ,
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I just wait till this moment to show my problem more clearly , first this is the WU link so i describe what happened,
http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=
the maximum for today 28.3 which extactly as forecasted (29) and even lower , but if see you our nigths are calm and temperature inside the stevenson screen keep warm , if you can read the history the temperature from 19:00 till 21:22 around 23.6 which totally wrong, i Just take off the senors with standard shield outside the box over a small container it dropped to 23.1 then dropped to 22.8 , i dont know if this normal that temperature inside the box always higher than outside and it is the correct and I dont know when winter come this problem ends
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I just wait till this moment to show my problem more clearly , first this is the WU link so i describe what happened,
http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=
the maximum for today 28.3 which extactly as forecasted (29) and even lower , but if see you our nigths are calm and temperature inside the stevenson screen keep warm , if you can read the history the temperature from 19:00 till 21:22 around 23.6 which totally wrong, i Just take off the senors with standard shield outside the box over a small container it dropped to 23.1 then dropped to 22.8 , i dont know if this normal that temperature inside the box always higher than outside and it is the correct and I dont know when winter come this problem ends
Raedh Do you put the stevenson screen 2 meters above your roof ?
Do you make holes down side at your stevenson screen ?
http://i42.servimg.com/u/f42/11/22/64/62/clovos11.jpg
Do you build the PVC tube fan ?
For correct results the fan must work and the night with half turns ,you can make it with drop low voltage 6 volt (but it need electronic circuit if you use solar pannel with battery for the night) except if you have AC/DC adaptor 3-4,5-6-7.5-9-12 DC volt in your house and the night you change the voltage at 6 volt manual.
Something like this
http://xafareast.en.alibaba.com/product/203420105-200220293/AC_DC_ADAPTOR.html
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Today i did a proof of cocept of gather from DanS and weather1967 suggestion, I mounted the box to most open area side, then raised it 1.5 m above ground the highest I got i ran the fan with 6v in the night the result was like WOW for me it just read 0.2 higher than nearest official weather station which is a big difference from yesterday it was 1.4 , tomorrow i will do the final mounting and modifications to box (hole, the PVC tube and 2m above ground) and monitor it the comng days \:D/, and big thanks to Dans and weather1967
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Raedh
We wait the final result,and photos from the point your roof stevenson screen,and the inside part =D>
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Hi all,
I have a question just before I finish the screen modifications, is it correct to open screen door that facing north at night where I see cooler tempareture at nights
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Yes, with the screen in it's mounted location the access door should be on the north side (living in the northern hemisphere). This keeps the sunshine out while you have it open to work inside it. When you aren't working with it then the door remains closed day and night. If the construction is right then it shouldn't make any difference with the internal temperature of the screen whether the door is open or closed.
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usually what is the spacing between louvers that allow air to circulate freely and also I used what we call it here "WhiteWood"
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I've done all mods of weather1967 suggestions and i post photos tonight, but when operate on 12v i'm getting very cool temperatures :lol:
so i'm now running the fan on lowest voltage :grin:
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weather1967 : With the sensor in the plastic tube you will see differents raedh
for now either without running the fan I;m getting a good readings the expected max for today is 29 , for now am getting 28.5 , waiting night readings :grin:
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the modfications, the best i can do #-o
(http://im26.gulfup.com/Gs161.jpg)
(http://im26.gulfup.com/nRyD2.jpg)
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Νice job :-)
Raedhl The fan sucks air from the side of sensor out-temp -hum,and air flow go above on the roof,do not put air over the sensor ,i think but i am not sure your fan put air over the sensor
And the distance bettwen the above side at out remote sensor with the under side at fan it is 1-2 cm.
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oh! do you mean i have to flip the fan to other side to it suck the air out of tube and distance between fan and sensor is 1-2 cm? so what am doing i worng now
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oh! do you mean i have to flip the fan to other side to it suck the air out of tube and distance between fan and sensor is 1-2 cm? so what am doing i worng now
Yes Raedh you must turn the fan from the other side to suck the air out of the tube,and the distance down side fan with up side sensor is 1-2 cm
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done :grin:,
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done :grin:,
You make measurements day and night ,and tell us the results =D>
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should I keep it the same when winter arrives , because our winter is cold and we have snow event in many times
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That's a topic that some folks may disagree with but I say yes, keep it running year round. The air you draw in and across the sensor is what you want to read no matter what temperature it is. The fan won't make it any colder. If the fan is off with no air flowing then stagnant/still air readings can differ slightly from the outside ambient temperatures.
My feeling about an enclosed temp/hygro sensor.
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do I need to run with lowest voltage ?
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Probably a good idea to run a low voltage to extend the life of the fan. All you really need is a slow steady flow of fresh outside air to pass over the sensor. Higher power that blasts the air in won't gain you anything but having to clean the sensor and fan blades more often. ;)
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should I keep it the same when winter arrives , because our winter is cold and we have snow event in many times
Yes you keep and the winter,it is necessary ,one example the cold nights with no cloud in the sky ,and no wind ,there is temperature inversion the cold air it will enclave in the tube and the temp sensor it show lowest temperature for the correct,for this reason it is necessary to work the fan with half speed at 6 volt ,for unenclave the colder air where it have enclave it the tube,and the temps it will increase.
If there are not temperature inversion the winter night you will see ,if you have open the fan ,and when closed the fan you do not see any differents at temperatures.
Where are you come from ?
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Jordan-Amman, I'd really like to know the purpose of running the fan with 6v instead of 12v
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Amman you say? Some of the best Shawarma's in the world there! Almost everyday for lunch while I was working there. Couldn't get enough. :-P
edit: oooops, don't want to steer this thread off course but my stomach started growling when I saw Amman. Back to Stevenson fan now.
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Jordan-Amman, I'd really like to know the purpose of running the fan with 6v instead of 12v
The day we want the foul power for this use 12 volt,the night it do not necessary the foul power air blow for this use 6 volt.
Dans he wrote correct why we use 6 volt at night
Probably a good idea to run a low voltage to extend the life of the fan. All you really need is a slow steady flow of fresh outside air to pass over the sensor. Higher power that blasts the air in won't gain you anything but having to clean the sensor and fan blades more often. ;)
Ps : Dan and here to Greece we have nice foods :lol:
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Jordan-Amman, I'd really like to know the purpose of running the fan with 6v instead of 12v
The day we want the foul power for this use 12 volt,the night it do not necessary the foul power air blow for this use 6 volt.
If you're handy with a soldering iron this would be easy to make (and cheap) to control 12v in the day and 6v in the night for the fan.
p.s. Dimitris, Ive heard a lot of good things about the food in Greece from former colleagues. Unfortunately that is one of the countries I haven't visited. :-)
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You're all welcome here guys feel it as your second country , for now am running the fan with 6v all day and night that because the daytime we have here where I live a steady breaze 17-25 km/ hr so since made the modification I'm getting good readings . And much thanks to weather1967 and DanS
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Ι added the numbers at electronic components Dan electronic circuit
I added a diode 1N4001 at relay for protection
The resistor 82 οhm - 1 watt it decrease the voltage at 6 volts
Relay 12 volts
Transistor 2N2222
Variable resistor 0-100 Kohm (it needed for to tuning exactly at point to darkness to open)
Photoresistor 2O kohm
Resistor 10K between base transistor and photodiode
Dan i hope some day you come at Athens,and we meeting for Greek food :-)
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Sounds good Dimitris and thanks! (thanks also for the 1n4001 addition. I have a bad habit of forgetting those in the drawings #-o). :-)
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You're all welcome here guys feel it as your second country , for now am running the fan with 6v all day and night that because the daytime we have here where I live a steady breaze 17-25 km/ hr so since made the modification I'm getting good readings . And much thanks to weather1967 and DanS
My pleasure Raedhl,i see from WU two days after you will have thunderstorm there,the fan you can have at 6 volt if you have clouds all day,but 3-4 October i see sun and max temps 31-28 ,this days you must have fan at 12 volt.
http://www.wunderground.com/weather-forecast/JD/Amman.html
Sounds good Dimitris and thanks! (thanks also for the 1n4001 addition. I have a bad habit of forgetting those in the drawings #-o). :-)
No problem Dan,nice to talk with you.
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yes that's why for now its running on 6v as you suggested and readings are better than ambient SRSLX100 reading
, thanks again weather1967, it is a good fealing when you the station give a good and stable readings :grin: