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Solar cell for 12v observatory fan

Nostromo

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Nostromo

Nostromo

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Guys I have an old 80mm 12v PC fan which I'd like to use to pull air into my observatory to keep it as dry as possible in there. Can anyone recommend a solar cell spec I can buy to mount on the side of the observatory to drive this thing? I haven't a clue how to work out how much power iI need. It needs to spin the fan on a cloudy day too if possible.

My plan is to cut a hole in the side, and pop the fan in. I may use more fans if that isn't enough.

I'm after a web link or something and if anyone has electronics knowledge much appreciated...

Many thanks Nick

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Psychobilly

Psychobilly

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The fan should have either a current or power value on it somewhere.

The best way would be to use a solar panel to charge a 12V battery .. if you want the fan to run continuously then the solar panel must put more "power" into the battery during daylight than the fan will take out in the whole day...

There will be inefficiencies to take into account in the equation so I would have thought you would want a solar panel rated 5 or 6 times greater than the fan...

Typically an 80mm fan is 1.5-2W so a 12W panel charging a battery should cope ....

Billy...

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Nostromo

Nostromo

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I'm afraid NASA are a bit high budget Chrs :hello2:

I don't think I need a battery as this fan only needs to run during the day - at night moisture isn't a problem. During the day the mount stays cold for a few hours in the morning and that's when the condensation forms on it... I'll have a dig for a cell which could drive the fan... I don't want to have to play with a battery too... Nick

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Psychobilly

Psychobilly

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I'm afraid NASA are a bit high budget Chrs :hello2:

I don't think I need a battery as this fan only needs to run during the day - at night moisture isn't a problem. During the day the mount stays cold for a few hours in the morning and that's when the condensation forms on it... I'll have a dig for a cell which could drive the fan... I don't want to have to play with a battery too... Nick

In that case your not going to need much at all... a 12V cell producing a couple of watts should be adequate to run the fan...

But in my experience dew forms at night and clears naturally during the day....

Billy...

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Nostromo

Nostromo

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In that case your not going to need much at all... a 12V cell producing a couple of watts should be adequate to run the fan...

But in my experience dew forms at night and clears naturally during the day....

LOL that's what I thought too. Part of my business as kinda based on it :hello2: But strangely enough, this is more like "daytime condensation". It only happens when I've been observing late and it warms up outside. I think what's happening is that during the daytime, the temp increases and so does the moisture level in the air. The metal counterweights and so-on however stay chilled for a couple of hours, because the have high thermal mass, so they get moisture, which then dissapears at about mid day due to natural air circulation inside the POD.

I was considering those solar fans used in boating, but I wanted to see if there was a cheap DIY approach to get started - just to see if pushing air at the whole setup would cool it during the day and keep low moisture inside the dome, by pushing out around the edges past the rollers - there's an air gap there anway. I was thinking if that doesn't work then, there is no point in going to the expense of a boating fan.

The PC fan has a rating of 12v 0.45a and is "DC Brushless" and it's 100mm. So I guess I need a solar cell to go on the POD bay with that rating. This one on Ebay looks OK but it's a trickle charger so not sure if I need to fiddle with it a bit.

Does anyone know if I can just wire the cell up straight the fan or if I need to modify the built in bits inbetween, like fuses and diodes, etc?

Nick

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