Solar system questions...

To the smartest board on the planet....

I may have mentioned that I'm putting up a greenhouse in my backyard- which is now done.  In that greenhouse, I'm going to have 2 different solar powered systems.

One is easy, it will operate 24/7, so it will have a solar panel, a 12V battery, a load (which is on a timer), and a charge controller looking over the whole system.

The second one should be easy, but looking into it- not so much.  It does not need to run 24/7- and I really only want to run it when the sun is out.  In theory, it could be as easy as a panel and the load, and nothing else.  But the load is pair of small electric motors, and when the voltage gets too low- they start having issues.  Plus, it's really only wanted to run when there is full enough sun, anyway.  So it needs some kind of controller to make sure it's being loaded at a minimum voltage supplied by the solar panel. Say 12V.  Output regulated to 12-14 V.  When looking for solar voltage regulators, I get a bunch of solar charge controllers- but all of them require a battery to run.  Which I really don't want to put in this system.  I'm trying to find a simple voltage regulator that won't output anything until I get to a specific input, which I can't seem to find.  My google power isn't good enough to exclude all of the battery systems out there.

Would a simple car voltage regulator work?  Or do they require batteries, too?  If they would work, what would be a simple one?

Thanks.

Looks like you need this:

https://www.amazon.com/Electronics-Salon-Voltage-Disconnect-Protect-Prolong/dp/B018TK5WIM
 

Edit: Mind you this is not a regulator, just a low-voltage cutoff, so if your system is capable of producing too much voltage for the load device, this board wouldn't protect the load from that.

I wonder if a disconnect like this would work: https://www.amazon.com/Electronics-Salon-Voltage-Disconnect-Protect-Prolong/dp/B018TK5WIM

Yes it says "battery" on the input, but really any voltage below the target voltage should - in theory - cause it to disconnect the load. It's also cheap at $17. You'd need to encase it somehow to protect it from moisture in the greenhouse.

Edit: Gameboy - does that mean we're great minds?

Should the fans be triggered by the sun or by interior temperature?

I've got a very simple system in my shed that's a panel, a controller, an old car battery (PC680 that doesn't want to start cars anymore) and a motion-sensitive LED light. I could try to disconnect the battery to see if the system still works when there's sun out.

But I think what you want is something much simpler, basically just a voltage regulator. A smart guy could probably build one out of a dollar's worth of parts. Leave solar out of it, you just have a variable voltage input that you want to turn into a consistent voltage. Let me ping a buddy.

In reply to Keith Tanner :

It's not a fan system.  It's a pump system used to occasionally move some fluid.  I don't want it to run 24/7, and only running it when the sun is strong enough is fine.  

The cooling fan thing may come later....

But, yes, all I need is a voltage regulator that does not need a battery to operate.  Which I have no idea how to make.

In reply to GameboyRMH :

In reply to dculberson :

That should work.  The high end voltage should not be a problem, as the pumps are rated to a high voltage, and the power needed is pretty well matched with the targeted 10W panel.

You can't just drop hints and not tell us. What fluid? What's going on? Curiosity!

I built a voltage regulator for my Land Rover a decade ago. It fit into a little tin for mints. Voltage regulators are really simple.

How many amps on the pumps?

Do you want to do any soldering or just plug in a magic box?

Hmm... use an inverter with a timer controlling a 120V pump?

Last year, I experimented with feeding my plants compost and work tea.  Worked really well.  This time, I want to automate that better.

So the idea is to have a bin set up for each.  Each will have an almost 5W pump, which will pump liquid over the bin.  At the same time, it will pump a little of that directly into a water reservoir that is used to supply water to my containers.  (and some water will go back from the reservoir to each container, too- circulating the water).  

It's kind of a hybrid of various hydroponics and self watering bins that includes the compost/worm tea.  And what makes it really cool- instead of using off the shelf fertilizers, I'm making my own.  

It does work out to be pretty organic, but I'm looking to have as cheap a system as possible.  Given last season's results, I'm pretty excited about next year.

This is just for the circulating part.

As for your second question, I can do soldering, but if a magic box is cheap enough....   Last year, I lost on an arduino experiment (I didn't have the patience to figure out why someone else's working code would not run)

Ian F said:

Hmm... use an inverter with a timer controlling a 120V pump?

That's a good question- and the answer is that I don't want to run power out to the greenhouse.  At least permanently.

Based on the thread title, I just dropped in ready to note that I'd have kept Pluto, but carry on.

How about just using one of those VW battery solar chargers mentioned in the long-term parking thread? They're about the right size for 5W. I don't know what their power output is, but it would be easy enough to measure.

https://www.ebay.com/itm/VW-Solar-Panel-Battery-Maintainer-Charger-OBD2-Plug-OEM-1C0915687D/182895819321

Smart friend says you're going to have a big inrush current, so you probably do want a battery in the system to supply that. Really, the easy option is just a battery and a charge controller that manages the load.

You've got everything you need on the other system already, there's no reason for a second one. Run a separate timer for the other load and let the charger controller turn the pumps on and off with the sun. It's not really a problem at all.

Zener diode may get what you want

In reply to Keith Tanner :

Again, I don't want it running 24/7, and the required battery to maintain that operation.  All the solar charge controllers that I can find require a battery.  For this system, it would need something like a 20Ahr battery.  PLUS the charge controller (and a larger solar panel).  Just getting the voltage limiter is one of those two items.

I would think that this does what you want..

Instructables link.

I'd combine the two systems. Use batteries to buffer and to provide a more constant voltage. Just use a solar eye from a outdoor light and use it to open a relay when it gets dark out to control the pumps.

alfadriver said:

In reply to Keith Tanner :

Again, I don't want it running 24/7, and the required battery to maintain that operation.  All the solar charge controllers that I can find require a battery.  For this system, it would need something like a 20Ahr battery.  PLUS the charge controller (and a larger solar panel).  Just getting the voltage limiter is one of those two items.

You don't need it running 24/7. Most solar charge controllers that control the load have different settings. You can have them run the load only when the sun is out. Since they're only running when the sun is out and only pulling 10w, the battery is mostly there to feed the other system via a timer. We don't know anything about the other system - solar panel size or load or battery - so it's hard to put numbers to it. But adding this system on doesn't put any load on the battery other than a bit of extra juice for that surge when the pumps start.

But if you don't want to do that, your loads are so low that a simple voltage regulator and low voltage cutoff is easy. Get the voltage regulator from NAPA and wire this in for your cutoff: https://www.ebay.com/i/282635450992?chn=ps&dispctrl=1

RossD said:

I'd combine the two systems. Use batteries to buffer and to provide a more constant voltage. Just use a solar eye from a outdoor light and use it to open a relay when it gets dark out to control the pumps.

Not a bad idea, but I'd have to figure out how to wire that in- especially since most outdoor light systems turn on when it gets dark.  Which is backwards of what I'd like to do.

A 'normally open' (NO) relay compared to a 'normally closed' (NC) relay. Some relays have both.

The switch on the right would be the 'eye' load wire. Of course you would need to find a 12v one...

Then the 'pole' would be from the battery and the NC to the pumps.

In reply to RossD :

This might be handy- http://www.instructables.com/id/Light-activated-switch/ as the relay output isn't specified- so I can make it close when lit enough.  And the light amount to turn it on is variable.

Hmmmm... disappointed.

I came here to see a question about ring around Uranus.

Can you use a thermostat?  It seems like you only need this to run when the sun is out.  Can you setup a thermostat that would get direct sunlight and therefore raise the temp?

wvumtnbkr said:

Can you use a thermostat?  It seems like you only need this to run when the sun is out.  Can you setup a thermostat that would get direct sunlight and therefore raise the temp?

 

 

I think light would be a better trigger than temp.   In the middle of summer, the nighttime temps will higher than spring day temps when it also needs to run.

alfadriver said:

Ian F said:

Hmm... use an inverter with a timer controlling a 120V pump?

That's a good question- and the answer is that I don't want to run power out to the greenhouse.  At least permanently.

That's not what I said.

Battery -> inverter -> time clock -> pump.