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Discussion Starter · #1 ·
Hey Folks, here's an interesting question I hope someone can answer/point me to a solution. I need a simple "Sunlight" activated switch - sounds easy but past designing my own, I can't find one commercially available.

Here’s the application, I’ve got a simple solar-panel heater for my backyard pool and when the sun’s out shining bright I want the circulation pump to turn on and when the sun is not out turn off!

Sounds like a pretty simple idea and I’m sure I’m not the first person looking for something like this. I’ve tried pool supply shops solar supply shops no one’s got anything like this – in fact a guy at a solar supply shop said, “that’s a good idea” what’s up with that? Can this really be that unquie?

I’m thinking it should be as simple as a go-between device, ya know, plug the pump in one side point it to the sun and plug the other side into the GFI – suns out pumps on clouds cover sun or nighttime pumps off? Any help greatly appreciated . . .
 

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Why not use a photocell to run a DPDT relay? That would more or less make the photocell output reverse acting.
 

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i'm wonderin if an electrician could charge more $$ for a " solar activiated switch " instead of a photo cell. :whistling2: ????
 

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What Mark said is the only thing I could think of. Shouldn't be too hard to do. Get a 120 volt relay coil and wire the photo cell to the coil and the pump circuit through a set of normally closed contacts.
 

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I think a photocell and relay would work, at least at determining if the sun was out...however, it sounds like you want it to only be active when the sun is most intense?
 

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I think a photocell and relay would work, at least at determining if the sun was out...however, it sounds like you want it to only be active when the sun is most intense?
yeah photocells would only turn it off at night. If he wants it too be that sensitive then I have no solution for that one.
 

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Partially shading P-cell should make it less sensitive to sunlight thus only activating in only intense sun. I am wondering if a thermo-switch on the heater would be a better solution though.
 

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The photocell would be a fun project, but for ease of use I'd just throw a timer on it. You know when the sun is going to be strong and close to when it's not. With a photocell it'll be on ALL day until it gets dark out. Easy and cheap.

Set it something like from 9am-4pm.
 

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The pump should always run x amount of hours per day (I think 8 hours). I wouldn't worry about how sunny it is , just make sure you time it to run in the hottest part of the day. Make sure you keep a blanket on the pool.
 

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I vote for the temp sensitive option... seems like I have seen some commercial water heating systems that do it that way.
 

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What about a water temperature thermostat? Then the warm water from the heater would circulate into the pool and the cold incoming water would stop the pump until it becomes warmed.

You could use a thermopile bulb inserted into the incoming pipe to activate a millivolt stat, which would close a relay to start the pump. Or something like that.
 

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For the OP's question I would use a time clock.
 

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Discussion Starter · #20 ·
Thanks every one for the ideas and all are good. I’m still a bit shocked that a devise like this is not off-the-shelf (or close) given the simplicity of the application and wide use possibilities. Could be a commercial opportunity!
 
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