I need a switch, controller, etc to activate a pump/circuit only when the sun is shining

treed678

Did lots of searching yesterday but came up empty handed. I can't be the only person who's needed this. Hopefully a less than $20 part, unless it's built into an [inexpensive] charge controller. I'm afraid direct panel, with wide volt/amp output ranges, to pump may damage the pump. Pump will be 12V from 3 to 6 amps.

If I use a programmable timer that the PV output may be low at times, depleting batteries, say if it's mostly cloudy. Obviously I could make the pump times shorter than total daylight hours if I can't find the part I need as a last resort, not ideal.

I insist on a controller because the pump may not be able to handle the wide range of inherent PV voltage/amperage, and as small a battery as possible to minimize maintenance costs. The battery will basically be a cache, and the PV will provide most of the energy.

This setup worked great when I used temp differential controllers for water heating (only heated when collector was hotter than storage tank temp = sun nearly always out), but this is for a pool and temperature is irrelevant. Hopefully there is a delay of some type (many have them - e.g. landscape lights) built in so the pump doesn't switch on/off too frequently.

EDIT: Obviously there are COUNTLESS "dusk to dawn" light controllers, etc. What I need is dawn to dusk, the opposite basically. That search turned up surprisingly few options.

Suggestions?

Cariboocoot

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

Voltage controlled switch maybe? Not exactly a $20 part though: http://www.solar-electric.com/inverters-controllers-accessories/chco/volcon.html

Charge controller with LOAD terminals that has built-in LVD? Again not $20 but it is a whole controller: http://www.solar-electric.com/inverters-controllers-accessories/chco/mochco/stpwmchco/ss-10l.html

With either you can disconnect the load based on Voltage being too low. For an actual "sun sensor" you'd need to rig something like a relay driven by PV that would only close contacts to the load when the PV put out sufficient current, indicating you have enough sun for the pump. Once again not $20 and you'd have to experiment a bit to get the output current and relay matched. It should be separate from the charging PV.

treed678

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

Option 2 is worth considering. Temperature compensation and 4 stage charging are nice options for this price. Also, the disconnect voltage is fairly high, which is exactly what's needed.

I wondered about a 1-2 watt panel wired directly to a 12V relay = activating the pump circuit. Might cook the relay coil though, huh? lol

Those dusk to dawn switches are so inexpensive, <$10 usually. I hate to spend a lot for the opposite purpose. Seems like there should be something simple without much expense.

EDIT: The first link will be useful for future diversion load configurations. I've been meaning to explore that option more.

Cariboocoot

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

I wondered about a 1-2 watt panel wired directly to a 12V relay = activating the pump circuit. Might cook the relay coil though, huh? lol

No, because panels are a current source and a relay is a (relatively) fixed resistance. Panels will only produce current as to the load on them, so adjusting the resistance upwards reduces the current. It takes more power to activate a relay than to hold it, which is good for engaging but not so good for disengaging.

But you might have to sort through a lot of relay specifications before finding one with suitable ratings both for coil activation and contact load. There's thousands of relays out there.

ZoNiE

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

Option 2 is worth considering. Temperature compensation and 4 stage charging are nice options for this price. Also, the disconnect voltage is fairly high, which is exactly what's needed.

I wondered about a 1-2 watt panel wired directly to a 12V relay = activating the pump circuit. Might cook the relay coil though, huh? lol

Those dusk to dawn switches are so inexpensive, <$10 usually. I hate to spend a lot for the opposite purpose. Seems like there should be something simple without much expense.



EDIT: The first link will be useful for future diversion load configurations. I've been meaning to explore that option more.

Buy a relay with a 110V coil that the dusk-dawn controller can actuate and use the normally closed contacts. Relay will turn on when the sun goes down and open contact to the motor, shutting it off.

Granger, McMaster, Local electrical supply, etc...

Photowhit

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

You could have a dusk to dawn switch run a NC relay, might be interesting figuring how much to limit the light to it so it only runs in bright light.

I believe there are dawn to dusk switches, I recall looking for one in the past.

Photowhit

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

Okay, since it looked like I copied ZoNie's response, I did a quick search, here's a web site dedicated to dawn to dusk switches, I'd guess for fountains, be careful, they only require 1 foot candle to activate, so your next stop might be for some neutral density filters!

bill von novak

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

I need a switch, controller, etc to activate a pump/circuit only when the sun is shining

Easiest is a 6V panel (you can get them from Radio Shack for ~$10) and a matching relay. Both should be under $20. Relays have a fair amount of hysteresis so they won't be chattering too much, but obviously you aren't going to get features like short-cycle prevention or LVD.

vtmaps

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

I'm afraid direct panel, with wide volt/amp output ranges, to pump may damage the pump. Pump will be 12V from 3 to 6 amps.

Do you need to pump when there is not enough light to power the pump? In other words, do you intend to have batteries?

If you don't need batteries, what you want is a linear current booster. That will prevent damage to the pump and give you longer hours of pumping each day.

--vtMaps

zoneblue

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

Or a purpose built solar direct pump?

vtmaps wrote: »

Do you need to pump when there is not enough light to power the pump? In other words, do you intend to have batteries?

If you don't need batteries, what you want is a linear current booster. That will prevent damage to the pump and give you longer hours of pumping each day.

--vtMaps

treed678

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

You guys are awesome... I love this forum.

The idea of "reverse relaying" a dusk to dawn controller is genius. The 6v panel -> matching relay also seems good.

Maybe I could buy just a single inexpensive solar light to use as the controller. I'd have to make sure it compatible with the coil I use, or v.v. Or maybe that's a bad idea; thinking they're only 3-5 volts or so. I could just buy a slightly more expensive d2d controller dedicated for the purpose. Wouldn't cost much more and should be easy to find one that could meet voltage and amperage specs for a common 12V relay.

This is ideally a shoestring budget project, so I'm trying hard to keep costs down. Linear current boosters are pretty pricey ($150-ish, right?); I can do ...planning on... small batt & CC for less. The pump and PV ($250-300?) will eat most of the customer's small budget, so anywhere I can save (but not go too cheap/junk) is good. Finding a reliable, relatively high volume DC pump in this price range is very challenging. That's my next focus. Adjusting the photosensor for the right amount of light might also be tricky.

BB.

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

Depending on the battery chosen and how it is treated (watered, charge levels, etc.)--You might be looking at as little as 3-5 year battery life.

With a LCB--You buy it once for the next 10+ years. Not bad on "big picture" costs. Plus no charge controller, no maintenance (other than pump), and perhaps a smaller solar array (more efficient than battery based system).

-Bill

bill von novak

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

Adjusting the photosensor for the right amount of light might also be tricky.

That's a big advantage to using an actual (small) solar panel. If it's generating enough power to pull in a relay coil, the main panel is generating as well.

vtmaps

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

Linear current boosters are pretty pricey ($150-ish, right?); I can do ...planning on... small batt & CC for less.
<snip>
Adjusting the photosensor for the right amount of light might also be tricky.

The CC, battery, photosensor, and relay might cost just a bit less than the LCB, but there is something to be said for keeping it simple. The LCB will be more efficient (no CC or battery losses), and there is less to go wrong... no battery to kill if the photosensor is not set properly or the relay sticks in the wrong position.

--vtMaps

mike95490

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

..Those dusk to dawn switches are so inexpensive, <$10 usually. I hate to spend a lot for the opposite purpose. Seems like there should be something simple without much expense....

Try a relay and use the NO contacts instead of the NC (or whatever works) ?

treed678

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

Haven't used a LCB yet, but I'll take a closer look into them. Was a little concerned about their reliability (vs price). Not really an issue?

I figured with a $30 AGM or so, it wouldn't be terribly expensive to replace every now and then. With a good CC and properly adjusted photosensor or switch, the battery should rarely drop very low in charge. It would be subject to 90-95F ambient though, so that would hurt some.

EDIT: guess I could also get this experimental system setup, use a battery & CC in the mean time (already have them), and wait to decide on the LCB. That's probably what I'll do. I do need to commit to an automated switching circuit now though because we're trying to schedule testing for this weekend.

...and thanks again for the awesome feedback!

BB.

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

A LCB is probably very similar to a dumb MPPT charge controller. No display, no fancy battery charging functions or programmable set points.

-Bill

treed678

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

So... I went ahead and bought a LCB. See, some folks do listen to advice online.

I've only seen one in action, a well pump. I want to give the client the option to spend a little more for something with no battery to worry about. Plus I won't have to worry about more parts, mounting, & wiring for daytime/sun activation. The LCD eliminates 3+ components and will hopefully add durability.

I did find a day operational photo sensitive switch on ebay. $12 I think. Would have also needed a relay though because it only supported 30 watts. Didn't look for higher output models.

The other option seemed good too - 6V panel to matched relay. I'll have to try that at some point. Still requires a battery and CC, but it's less complex and probably more durable than what I was looking at, a photo sensitive switch.

Cariboocoot

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

There are some differences in operation between the various solutions suggested.

The LCB will operate the pump whenever the panels are capable of supplying sufficient power. This is apparently the goal.

The daylight trigger will attempt to operate the pump whenever there is daylight, which is not necessarily the same as sufficient power to operate the the pump.

The direct-drive relay will operate the pump whenever there is sufficient power from the panels, providing the relay panel is "in sync" with the pump panels.

The Voltage controlled switch or LOAD connection on a charge controller will allow the pump to operate whenever there is sufficient power in the battery. This has the advantage of allowing a certain amount of nighttime use, which may be desirable.

When choosing the solution it helps to know these things and which advantages/disadvantages have the most effect on the desired operation.

treed678

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

Well said, Cariboocoot.

Daytime running was basically the goal, and ok/ideal really in this situation. Night time option would be nice, but I always like to avoid storage and additional output requirements when possible.

One thing I wanted to ask about LCB's, if you or someone else can chime in, is can two matched pumps be run in parallel on them? It seems like this should be okay in theory, but I don't know much about them, other than their basic purpose/function. Just wanted to have some idea before I wired up and had a potential problem.

Cariboocoot

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

treed678 wrote: »

Well said, Cariboocoot.

Daytime running was basically the goal, and ok/ideal really in this situation. Night time option would be nice, but I always like to avoid storage and additional output requirements when possible.

One thing I wanted to ask about LCB's, if you or someone else can chime in, is can two matched pumps be run in parallel on them? It seems like this should be okay in theory, but I don't know much about them, other than their basic purpose/function. Just wanted to have some idea before I wired up and had a potential problem.

If you mean two pumps off one LCB it's a matter of load. As long as it can take the load, it's fine. That includes both pumps running at the same time as opposed to just one or the other running. It shouldn't actually matter that the pumps match either. In fact eve if they do their current requirements will vary depending on how hard each one is working.

treed678

Re: I need a switch, controller, etc to activate a pump/circuit only when the sun is shi

That's excellent news. I just assumed ...knowing I could buy two LCB's and sell the larger one I purchased if necessary, but obviously hoped I wouldn't have to. I'm glad you confirmed that. Keeps cost lower too.