# Sunlight Activated Switch



## MDShunk (Jan 7, 2007)

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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## paul d. (Jul 13, 2008)

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


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## steelersman (Mar 15, 2009)

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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## Joshua (May 13, 2009)

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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## steelersman (Mar 15, 2009)

Joshua said:


> 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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## Wireless (Jan 22, 2007)

Don't they make photocells that work both ways?


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## Jeff000 (Jun 18, 2008)

almost more need a temp sensor to activate it more then a photocell.
Or a timer in series with the photocell.


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## Noe (Apr 7, 2009)

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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## gilbequick (Oct 6, 2007)

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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## CFL (Jan 28, 2009)

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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## Mike_586 (Mar 24, 2009)

MDShunk said:


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


That would do it. I'd probably use one of the types that has a sliding shade so I could tweak sensitivity.


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## 220/221 (Sep 25, 2007)

Photocell would be dusk to dawn. Light turns it on, not heat.

How about a thermostat?


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## steelersman (Mar 15, 2009)

actually light turns it off.


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## 220/221 (Sep 25, 2007)

You have snatched the pebble from my hand Grasshoppa. It is time for you to leave.


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## s.kelly (Mar 20, 2009)

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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## Joefixit2 (Nov 16, 2007)

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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## Greg (Aug 1, 2007)

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


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## steelersman (Mar 15, 2009)

how about instead of a solar panel heater which uses electricity, you use a solar water heater which uses zero electricity: 

http://www.treehugger.com/files/2007/08/make_a_solar_wa.php


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## polutj (Jun 8, 2009)

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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## manchestersparky (Mar 25, 2007)

Marc gave you the answer in his post- 
A RELAY controlled by the photocell
Sun goes down-photocell powers up the coil on a relay that OPENS a set of contacts. Sun comes up- photocell powers down the coil on the relay and the contacts CLOSE thus your pump turns on


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## Mike_586 (Mar 24, 2009)

manchestersparky said:


> Marc gave you the answer in his post-
> A RELAY controlled by the photocell
> Sun goes down-photocell powers up the coil on a relay that OPENS a set of contacts. Sun comes up- photocell powers down the coil on the relay and the contacts CLOSE thus your pump turns on


I'm just a little shocked at how many guys just aren't understanding what you just said, considering Marc's post (the very first replay) would effectively do exactly what the guy was asking for.


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## steelersman (Mar 15, 2009)

Mike_586 said:


> I'm just a little shocked at how many guys just aren't understanding what you just said, considering Marc's post (the very first replay) would effectively do exactly what the guy was asking for.


I obviously understood.


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## drsparky (Nov 13, 2008)

Here, just install a SLC 500. It will do anything you need.:jester:


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## polutj (Jun 8, 2009)

Again, thanks much for all the replies, and yes, yes, yes, yes the relay idea is this first and most obvious and was my initial approach to the problem. My original post stated:

"I need a simple "Sunlight" activated switch - sounds easy but past designing my own, I can't find one commercially available."

I was simply wondering if there was a "plug-n-play" device out there as it seemed like such a simple and perhaps common need. The market is flooded with night or dark activated switches. If theres a sunlight activated switch out there -- I can't find it and I've looked long and hard. I just thought one of you may have a line on one, and I was figuring for $20 or so I'd be done.

I was and still am "shocked" and I do mean shocked that every solar supply shop I called or emailed or visited on the web had nothing like this and in-fact had one guy say "what a good idea..."

What am I missing here -- doesn’t solar energy come from the sun? Wouldn't there be a need to know when the suns out in terms of operating / controlling solar type devices like circulation pumps....I don't get it...I can’t be the first person looking for something like this commercially available… but in the end yes an array & relay is the way to go and was my original plan...so it looks like I’ll be designing my own! Watch for it in solar shops near you!


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## joe cool (Jun 4, 2009)

Joefixit2 said:


> 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.


I think this is the way to do it. If you could find a way to recalibrate an electric water heater thermostat that would make it so easy. A section of water filled black ABS pipe on the roof would respond to the hottest part of the day. You could play with the thermostat until you got the temperature right.


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## Lancelot (Jan 22, 2012)

Hi
I know this is an old post but did some one find a switch like this which can activate a circulating pump if the sun is out (not a light sensitive switch but a sun ray activated relay)

Regards


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## Chickenhawk (Sep 25, 2020)

polutj said:


> Again, thanks much for all the replies, and yes, yes, yes, yes the relay idea is this first and most obvious and was my initial approach to the problem. My original post stated:
> 
> "I need a simple "Sunlight" activated switch - sounds easy but past designing my own, I can't find one commercially available."
> 
> ...


Did you find a solution to this I would like a similar thing. I can find a relay but need to integrate into 240V preferably with out Licensed electrician requirements. eg relay activated 240 volt switch (portable) 12 Volt Twilight Switch | Jaycar Electronics


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## Wirenuting (Sep 12, 2010)

Chickenhawk said:


> Did you find a solution to this I would like a similar thing. I can find a relay but need to integrate into 240V preferably with out Licensed electrician requirements. eg relay activated 240 volt switch (portable) 12 Volt Twilight Switch | Jaycar Electronics


Head over to the DIY website, you’ll find your answer there.


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