Topic: Using 5V and 12V P.C. fans with FARS.

[sam2004gp]

Would it be possible to just buy a couple more white plastic bowls that match pretty close and remove only the top existing one. That way you butcher only the new ones and don't change any existing ones and anything gows wrong you can go back to original config.? make sense?

Nope, it is the shield that Ambient Sells, the "plates" are not true circles.  They are oval with specific plastic molded in to help the stability of the screws as they pass thru each plate. 

You can see their "non-circular" design best in this photo.

[DanS]

D'oh!!   Man, that's too bad. I know how you must feel. I'd be hesitant cutting into it as well. Have you had it torn apart to see if you could reconfigure the sensor's position and squeeze a fan above it without to much modification?

[sam2004gp]

yep, no additional room.  But the two plates on the bottom have no center hole.  So I am going to remove one, and cut a fan hole in the other.  If I decide it's no good then I will "replace" the hole that I had cut out, and put the two plates back on the bottom.

[Anthony]

Don't know how efficent a fan on the bottom will be?

[JOE]

I've decided to go ahead and get the Davis Daytime FARS setup.  It's not that expensive and I know it will fit.

My setup is not the best siting anyway.  On roof.  About my only choice without moving.

I have my solar panel facing south now.  Would it help to turn it a little more towards the west to maybe keep the fan running a little later in the day?  Or would that hurt the only panel with recharging in the morning hours?

I don't think having a fan driven wind inside is what we want, is it?  Just enough air movement to keep it "fresh".  On a day with much breeze at all, it's not even necessary to have a fan, is  it?

Does anyone know which way the Davis blows?  Up or down?  I am assuming up and drawing air from the bottom, but I haven't verified that.
 

[DanS]

I've decided to go ahead and get the Davis Daytime FARS setup.  It's not that expensive and I know it will fit.

My setup is not the best siting anyway.  On roof.  About my only choice without moving.

I have my solar panel facing south now.  Would it help to turn it a little more towards the west to maybe keep the fan running a little later in the day?  Or would that hurt the only panel with recharging in the morning hours?

I don't think having a fan driven wind inside is what we want, is it?  Just enough air movement to keep it "fresh".  On a day with much breeze at all, it's not even necessary to have a fan, is  it?

Does anyone know which way the Davis blows?  Up or down?  I am assuming up and drawing air from the bottom, but I haven't verified that.
 

Hi Joe, Since your sensor is roof mounted your idea of positioning the solar panel a little more toward the west might be a good idea. This might help counter the heat radiating off the roof from the afternoon sun. You would need it more in the afternoon than in the morning before the roof is heated.
I also agree with your statement   "I don't think having a fan driven wind inside is what we want, is it?  Just enough air movement to keep it "fresh".  On a day with much breeze at all, it's not even necessary to have a fan, is  it?"  Just enough air flow across the sensor to keep it fresh/replaced should do it. Stagnant or uncirculating air may delay accurate temp/humidity readings.
Since I don't have a Davis someone else will have to chime in to answer FARS question but from everything I've seen and from all Weather1967's tests I would imagine Davis puts them on top drawing up and out the top.

[DanS]

Don't know how efficent a fan on the bottom will be?

Anthony, Weather1967 (Dimitris) has ran tests to try that out and got "unstable" results. He says that a fan blowing across the sensor gives inaccurate readings and the best position is at the top blowing out, drawing up across the sensor.

Cheers,
Dan

[mackbig]

Agreed on not blowing accross the sensor, but I dont think top or bottom "sucking" would matter all that much.  Yes warm air rises, but there should not be that much convection going on in there.  The size of the fan relative to the space being "sucked" is not that material.  A little flow is all you need....

From a rain design point of view bottom is easier, and also since the mount for the Ambient shield is on top also easier.  However Jim's design while not using an Ambient shield is pretty cool (see below), I am sure a large white "plate" could be added to the top of the Ambient shield to protect the fan and still allow for top
mounting...

Andrew

ps: anything I can do to make my radiation shield look more ominous, the
better...

Don't know how efficent a fan on the bottom will be?

Anthony, Weather1967 (Dimitris) has ran tests to try that out and got "unstable" results. He says that a fan blowing across the sensor gives inaccurate readings and the best position is at the top blowing out, drawing up across the sensor.

Cheers,
Dan

[DanS]

That does look pretty cool and nicely designed. Can imagine "neighbours" staring at that.
I've been wondering about the bottom mount fan blowing downward/out. I can't imagine where it would draw air more than 1 or 2 plates above because the fresh air would be coming in all around the sides. No suction left to reach up to the top so air up there doesn't move (with no breeze or wind). Where a fan up top would draw out rising air so all air moves.

[tomcj2]

Does anyone know which way the Davis blows?  Up or down?  I am assuming up and drawing air from the bottom, but I haven't verified that.

CORRECT, from the bottom and out the top.

[JOE]

ps: anything I can do to make my radiation shield look more ominous, the
better...

Any way you can rig up some motion sensor LED's or something?  Like only blink when "they" are out and moving?

Maybe a small parabolic audio dish...

[mackbig]

I will guinea pig it.  Worst case I end up with a fillable hole in the bottom.  The sensor pretty much sits on the bottom "plate".   Not hard to test, fire up the fan then get a stogie going, then put it beside the shield at the top and work down, if the smoke moves into the sensor near the top at all, its working....

Andrew

That does look pretty cool and nicely designed. Can imagine "neighbours" staring at that.
I've been wondering about the bottom mount fan blowing downward/out. I can't imagine where it would draw air more than 1 or 2 plates above because the fresh air would be coming in all around the sides. No suction left to reach up to the top so air up there doesn't move (with no breeze or wind). Where a fan up top would draw out rising air so all air moves.

[mackbig]

Once I get 12 volt to it for the fan, the lighting possibilities are endless.  perhaps leds flashing around this sign.... Andrew


ps: is it possible to resize images to make them smaller with the bb IMG tags?

ps: anything I can do to make my radiation shield look more ominous, the
better...

Any way you can rig up some motion sensor LED's or something?  Like only blink when "they" are out and moving?

Maybe a small parabolic audio dish...

[DanS]

I will guinea pig it.  Worst case I end up with a fillable hole in the bottom.  The sensor pretty much sits on the bottom "plate".   Not hard to test, fire up the fan then get a stogie going, then put it beside the shield at the top and work down, if the smoke moves into the sensor near the top at all, its working....

Andrew

Your sensor being mounted near or on the bottom is ideal. I shouldn't have ass u me d it was near the top and a 12v fan should have no problem pulling air down across it being that close. It will still be interesting to hear the results of your "stogie" test if you don't mind posting when finished.