Author Topic: Add Fan to stevenson screen  (Read 15737 times)

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Offline raedh

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Add Fan to stevenson screen
« on: September 12, 2012, 04:03:55 AM »
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 )


Offline DanS

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Re: Add Fan to stevenson screen
« Reply #1 on: September 12, 2012, 05:52:48 AM »
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. :-)

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #2 on: September 12, 2012, 06:30:13 AM »
 ](*,) 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

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #3 on: September 19, 2012, 07:22:20 AM »
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

Offline DanS

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Re: Add Fan to stevenson screen
« Reply #4 on: September 19, 2012, 07:46:30 AM »
How much room do you have to use?  Maybe some photos of the roof area you can use may help.

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #5 on: September 19, 2012, 07:57:31 AM »
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,




Offline weather1967

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Re: Add Fan to stevenson screen
« Reply #6 on: September 19, 2012, 08:05:03 AM »
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
 
« Last Edit: September 19, 2012, 08:23:11 AM by weather1967 »
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Offline raedh

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Re: Add Fan to stevenson screen
« Reply #7 on: September 19, 2012, 08:17:34 AM »
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
« Last Edit: September 19, 2012, 08:19:55 AM by raedh »

Offline DanS

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Re: Add Fan to stevenson screen
« Reply #8 on: September 19, 2012, 08:18:17 AM »
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
« Last Edit: September 19, 2012, 08:20:24 AM by DanS »

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #9 on: September 19, 2012, 08:28:35 AM »
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

Offline DanS

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Re: Add Fan to stevenson screen
« Reply #10 on: September 19, 2012, 08:31:43 AM »
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?

Offline SlowModem

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Re: Add Fan to stevenson screen
« Reply #11 on: September 19, 2012, 08:40:01 AM »
Hi Dimitris!  Good to see you here again!  :)
Greg Whitehead
Ten Mile, TN USA

Offline weather1967

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Re: Add Fan to stevenson screen
« Reply #12 on: September 19, 2012, 08:44:29 AM »
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)



« Last Edit: September 19, 2012, 08:48:19 AM by weather1967 »
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Offline raedh

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Re: Add Fan to stevenson screen
« Reply #13 on: September 19, 2012, 08:55:51 AM »
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

Offline weather1967

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Re: Add Fan to stevenson screen
« Reply #14 on: September 19, 2012, 09:00:17 AM »
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
« Last Edit: September 19, 2012, 09:10:27 AM by weather1967 »
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Offline DanS

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Re: Add Fan to stevenson screen
« Reply #15 on: September 19, 2012, 09:33:17 AM »

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.



Maybe even include a modified Stevenson screen over this to help keep the sun off it.

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #16 on: September 20, 2012, 01:42:48 AM »
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 ,

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #17 on: September 20, 2012, 02:46:26 PM »
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

Offline weather1967

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Re: Add Fan to stevenson screen
« Reply #18 on: September 20, 2012, 05:32:49 PM »
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
 
« Last Edit: September 20, 2012, 05:38:50 PM by weather1967 »
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Offline raedh

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Re: Add Fan to stevenson screen
« Reply #19 on: September 21, 2012, 05:44:01 PM »
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

Offline weather1967

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Re: Add Fan to stevenson screen
« Reply #20 on: September 22, 2012, 12:20:29 AM »
Raedh
We wait the final result,and photos from the point your roof stevenson screen,and the inside part   =D>
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Offline raedh

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Re: Add Fan to stevenson screen
« Reply #21 on: September 24, 2012, 12:45:29 PM »
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

Offline DanS

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Re: Add Fan to stevenson screen
« Reply #22 on: September 24, 2012, 07:18:52 PM »
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.
« Last Edit: September 24, 2012, 07:21:51 PM by DanS »

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #23 on: September 25, 2012, 01:38:41 AM »
usually what is the spacing between louvers that allow air to circulate freely  and also I used what we call it here "WhiteWood"
« Last Edit: September 27, 2012, 01:54:42 AM by raedh »

Offline raedh

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Re: Add Fan to stevenson screen
« Reply #24 on: September 26, 2012, 05:54:07 AM »
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: