Ghurd could you design a low voltage dropout switch to save our batteries?

[Steadfast]

I want to run AC power from my otherpowered inverter out to my coop which is charged by solar and wind.

Lets assume I turn on my chicken coop, to run some small fans during the heat of the day...
I go to work...
and the day becomes overcaste, contrary to the "sunny  Forcast" that day.... 

Is there some sort of switch that will automatically shut off the power coming out of my inverter before my batteries get overdrawn by the fans in the coop? 

I wonder if Ghurd could design such a low voltage dropout (LVD) switch. 

That can be manually dialed down to shut off at a certain a voltage level, via a "trim Pot",
much like Ghurd's load dump switch which has a "trim Pot" and can be manually dialed to turn on the load dump when the batteries hit any high point (like it did when I manually dialed it's trim Pot down to 12.5V to test the switch and then dialed it back up to 14.25V),  but works backwards.

Hey Glenn it appears there is some money to be made here...
from me...
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[Steadfast]

My cobra inverter puts out an alarm when the batteries hit 55%.
(I know this because I was there when it happened) "hey, whats that sound?"

I just want it to shut off instead of just making the alarm buzz...

I wonder how that can be done.
It is obvious that a switch of some sort is being automatically thrown to make the alarm sound,
why can't that switch be modified to turn the thing off...?
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[DamonHD]

Ghurd's gizmo already CAN be adjusted to be used as an LVD as I understand it.

The issue is more to do with confusing the voltage levels and behaviour you want from a dump-load vs LVD.

Rgds

Damon

[Steadfast]

Ghurd's gizmo already CAN be adjusted to be used as an LVD as I understand it.

The issue is more to do with confusing the voltage levels and behaviour you want from a dump-load vs LVD.

Rgds

Damon

The issue is may very well be more to do with confusing the voltage levels...

But unlike a load dump switch which fit in between the batteries and load dump...
This hypothetical LVD switch would fit into the circuit which goes between the batteries and the inverter, to shut it off.

You see,
Glenn already makes a trim pot dialible control switch which turns something on... (a load dump)
how hard would it be for Glenn to make a trim pot dialible control switch which turns something off???  (an inverter)

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Come on Glenn... go for it... take my money!
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[ghurd]

The Ghurd controller can be assembled for LVD.  There are extra resistors in the kit just for that purpose.

For you, the main issue is the inverter and AC loads...

(FYI- usually DC powered fans are far more efficient)

The controller is designed to power/LVD DC loads mostly.  I am sure there are a lot of 'tweaks' for AC loads, but they leave the inverter On wasting power for no reason.

In modest inverter systems, often the inverter has a rocker On/Off switch.
Not many amps go through that switch (often ~100ma).  The switch is connected to the hard to make (AKA: expensive) circuits that control the power.

The solution I came up with is to use the existing circuits in the inverter.
A small efficient relay in parallel with the inverter switch basically circumvents the switch.
Meaning if the LVD says the battery SoC is OK, then the inverter is On.

Can also put the relay in series with the inverter switch, etc.

Any relay powered by a fet must have a Schottky diode reverse paralleled with the relay coil to protect the fet.

Here is an example.
A couple low power lights, and an inverter...
The inverter has a rocker switch.  It is shown removed from the inverter housing to clarify the mechanical wire connections.
Basically, the relay becomes the inverter's On/Off switch, and it is operated by the ghurd controller assembled to an LVD format.



The inverter / relay switch concept was layed out quite well by 'Speo'.  He used an inverter, relay and remote control (instead of LVD) to operate AC loads.
Where he wanted a remote control, you want LVD.  The relay concept is the same.
And Speo takes great photos.
http://www.fieldlines.com/index.php?topic=129565.0

Those setups avoid dealing with high volts (120VAC), or high amps (12V amps is >12X what the 120V AC amps are),
and avoids dealing with the expensive components that already are into many inveters.
Plus it is simple.
I like cheap and simple, when it works.   
G-

[Steadfast]

This is my inverter model:





Check THIS out...  That USB port is only for output... no programming...
BUT look at that "REMOTE" port... hmmmmm..... 




And here is the remote $30 on cobra's site, I betcha I can get it for less on Amazon:


Soooooooo,
What do ya say that I buy a remote switch, have it delivered to your house Glenn,
You make me a cut off switch, hook it up to the remote and mail it to me?

BTW:
This is what the manual says abot the units "Under Power" auto cut off:

Low Voltage Protection –
If the DC input voltage drops below
the alarm threshold of 10.5V the
meter will flash as shown to
indicate Low Voltage Protection,
but the unit will continue to
operate. If the input voltage drops
to 10.0V or less, the inverter will
shut down to protect itself, the
meter will continue to flash as
shown, and an alarm will sound.
To restore normal operation, return
the DC input voltage to at least
12V. The inverter will automatically
return to normal operation.

Input Voltage
The inverter will operate from input voltage ranging
from 10 volts to 15 volts. Optimum performance will
occur when the voltage is between 12 volts and 14 volts.
If the voltage drops below 10.5V+/-0.3V, an audible low
battery warning will sound. The inverter will shut down if
the input voltage drops below 9.5V+/-0.3V. This protects
the battery from being over-discharged. It will restart
when the input voltage exceeds 12V+/-0.3V.

Here is another interesting question:
Does "+/-0.3V" suggest that there maybe a "trim pot" inside the inverter???
If there is a "Trim Pot" in there perhaps turning the shut down upto 11.75V solves all my problems
El-Free-bo.
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[Bruce S]

SF;
The -/+ is for variations of internal ICs ALL of the inverters that I've open up did not have a "trim" pot to adjust.
That "wired" remote probably has a couple wires in it that when pushed flips a "on/off" circuit much like the newer computers don't really have a push button that goes directly to the power supply and mother board.
 Can you get a schematic for your inverter? or possibly for the remote? that would make life a ton easier for finding where to contacts are being made.
Bruce S

[Steadfast]

you are right Bruce: 

I spoke to Brian the tech manager at cobra...
he said there is no trim pot in there for that...

I told him
"Dude, that sucks, a cut off at 10.5V is Terrible Bad.
A cut off that low is around a 20% battery charge and will simply KILL our batteries. 
who came up with that stupid number?"

I explained what I am hoping Glenn can do and asked him for the technical breakdown of their remote switch, which I hope Glenn can modify with a LVD switch.

ah yes... here it is...
I had a heck of a time trying to modify a pdf file so I just snapped a phot of my screen:

[OperaHouse]

Of the inverters I have seen, the switch powers the electronics and also happens to be where they  sample the voltage.  If you wire a diode in series with the switch. that will raise the voltage at which the inverter shuts off by about .6 volts or double that with two.  A 1-2A diode should be sufficient.  Put another switch to short the diodes out when it is an absolute must to run the inverter.

I doubt whether this will work in your case.  Designers generaly do not put battery voltage with the possibility of a lot of current on a "phone plug."  And  as indicated,  that is a momentary switch that may be operating an internal relay.

[Steadfast]

Soooo, Glenn...

I am hooking up may chicken coop this Saturday...

Do you need me to buy that remote from Cobra to work with your LVD switch or do you have an even more clever device planned?

Do you want me to have the remote from Cobra mailed to your home so you can combine the two together before you mail them to me?

How much do I need to pay you through Paypal?

Check your PM for my phone number.

[Steadfast]

[DamonHD]

Well done on your solar fans.  That's a good match of demand to having the energy available, and a lot less demanding than heating!

Rgds

Damon

[Steadfast]

Solar Powering the Chicken Coop:

The plans:


First Bury the electric line from power plant to coop. (AC travels better than DC) I used a tiller to loosen up the ground. And laid out my 50ft pvc incased 12awg wire.


Next, Dig out the 18" trench, bury the pvc sheathed wire, star covering it up.


Yeah, this digging thing, SUCKS Big Time!
I discovered that ditch diggers are REAL MEN... Unlike me... but that's fine by me too.
If "being a Man" must involve ditch digging, I want to be a kept wife.


As I was hooking up the electrical outlet boxes in the chicken coop shed, I noticed I had spectators.

[OperaHouse]

I was just thinking how an autonimous chicken coop controller is just about identical to the UNO chest fridge control.  Turn on fan at a certain temp till things cool down, if battery gets low stop till it charges up a little, and if things ge really hot run the battery down a little lower.... battery vs dead chickens decision.

[Bruce S]

OH;
I've been kinda watching the UNO posts and I'm a little curious. These programmings look a lot like the old if-then statements we used to do on NAND gate stuff.
Is this how you approach the programming or ?
Bruce S
SF sorry for the hijack, I'll nuke this post if you want me to.

[Steadfast]

Until Ghurd finishes my controller,
the way i am working it is this:

If forcaste says is going to be a "Clear Sunny Day" ALL DAY...
that morning I turn on the coop...  by the time I get home I can turn off the coop.

Otherwise, if the forcasst is overcast or raining, I leave the coop off
and let the load dump do its thing if it needs too...

BTW: I left the coop off today, because it was suppose to be overcaste...but it is sunny and clear...
So, my chickens get no fans today while my load dump just runs and runs...
wasting all that free power.

Can you just hear my chickens imploring for either Accurate Forcasts or for Ghurd to hurry up...?
.
Imagine how things will get when the wind actually starts blowing my turbine around come fall?
.

[Steadfast]

Hey there ghurd...

Please, Let me know when you have time to work on my switch again,
and how soon you expect to finish it.

[OperaHouse]

I have been thinking about that problem for a while and if you do get it, what problems does it reallu resolve?   Turn it on in the morning and it operates for hours before you need it just wasting battery power.  Then late afternoon when it really is needed it shuts off. And then predicting the weather.  I did that with my old fridge control.  It wouldn't be too sunny si I would load up the fridge with soft drinks thinking I would get a few minutes between timed cycles.  Then I would get bright sun and a hot restart with the inverter shutting off.  Now with the smarts of the UNO it handles every situation.  It's nice not having to think about it anymore.

Still, if you are set on a hardwired solution the following is a simple manual start circuit that will act like a pushbutton to turn it off at a set low voltage.  It uses a single LM431 Amplified Zener that can be found in most old computer power supplies.  NOTE: There is an error in the schematic made when I coppied it.  The bottom of LED1 goes to the bottom of the relay not the 10uF capacitor.   The voltage divider should be about 2.5V for the LM431 sense pin at the voltage you want it to drop out at.   At nominal voltage LED1 will be on.  Turnj on the inverter and then press PB.  Relay K1 will engage.   LED2 is optional to show the relay is powered.  When the set low voltage is reached relay K1 will drop out.  The relay contact then applies power to K2.  The 2200uF capacitor acts as a low resistance initially causing the K2 relay contacts to close untill the capacitor charges up. That should be a second or so.  A capacitance as low as 470uF may work depending on the relay.  Look for those small 1.2 inch cube ones.  The 4.7K resistor drains off the capaqcitor charge when power is removed.  Again, this is a one shot drop out that must be manually restarted.

[synovialbasher]

A couple of thoughts:

I'm not sure how much electricity you're making exactly, but why don't you use the fans in conjunction with a resistive load as your dump load, and then just run the fans when you need to whenever it's not dumping. Under normal conditions, the only time the system would be dumping is on a sunny (aka hot) day, probably during the peak of the day (my system finishes recharging by about 1 pm) and that's pretty much it. Controlled, too.

Also, I would suggest getting a load controller. The Xantrex C12 might work for you. If you need more than 12 amps, use a C35. I have both and they work great (however, I use them for charge control instead of load).

[OperaHouse]

That prior suggestion leads towards maybe the best solution.  When I first read your thread I thought using an inverter was not the best way to go.  Fractional HP AC induction motors are notorious for being very inefficient, way under 50%.  Then you added to that was the push button on/off.  I would go with a DC motor and skip the problems of the inverter.  You could use a conventional fan thermostat that turns on above a certain temp and then use a GHURD type shunt controller that is on over a set voltage.   Then the fan only comes on when it is hot and sunny.   One source of a DC fan would be the electric fans for car radiators from a Junkyard.  I have been using computer fans.  I bought a bunch of these new cheap well under a buck.  Old computer power supplies have them and they  generally draw from .1 to .15A each.  I have built several of these with scrap lumber left over from doing the interior trim od windows.  A chop saw and staple gun put them together quick.  This one my wife uses in the kitchen window when doing dishes.  A panel of 16 of them would move a lot of air.

[ghurd]

OK, well, I'm not comfortable with a "simple" solution to that type of inverter power switch.
Simple, to me, is with simple parts... and not too many of them... and no parts with more than 4 legs!

The inverter switch needs to trigger on rise... and fall.
Easy enough with the ghurd controller output going to 2 circuits.
Each of those needs a timing circuit (8 legs!).
Then what happens if something skips a beat?  The inverter is On when it should be Off.  So it needs a circuit to compare the ghurd controller output to the inverter output.  And a circuit to 'fix' a skipped beat senario, probably with a timer circuit too.
And sometimes the inverter will be On when there is no reason for it to be On.
This is getting pretty complicated for something 'simple'.

Be a lot simpler (and Cheaper) to get yourself a used Vector inverter with a rocker switch on the front.

Could even add a few cheap and common parts to only allow the inverter to turn On when the fans actually needed to be running.

And OH's statements about AC fans is next.
Can get an old treadmill motor of the type that is usless for a windmill, put a 20" box fan blade on it, power it with DC, and move a boatload of air for 2~3W (less than that Cobra inverter wastes doing nothing but being On?).
This one is 317ma at 13V, IIRC, and will operate well at far less power than that.

Also, I would suggest getting a load controller. The Xantrex C12 might work for you. If you need more than 12 amps, use a C35.

That's what we are talking about, except can do more than 12A with a ghurd controller, for under $20!

G-

[Steadfast]

Glenn, I would still prefer you build my switch. Yes, - still need one pretty badly. Can you call me and let me know if and when you will have the time to work on this?
BTW I can mail the inverter to you if you need it to rewire to by pass the switch entirely.

[Steadfast]

to match the inverter I already have I would have in a "vector", it would run me $300...
just to aquire a stupid rocker switch... YIKES... not an good idea...

Surely there MUST be another way...

[ghurd]

to match the inverter I already have I would have in a "vector", it would run me $300...
just to aquire a stupid rocker switch... YIKES... not an good idea...

Surely there MUST be another way...

A decent 300W or 400W inverter?
Couple 40W fans and 13W CGLs?  And the fans should be changed to DC anyway (could run them from an old switching laptop 120VAC to 12~19VDC brick, so no need to bury a DC wire).

Not sure whats in the coop that would need 2500W.  Maybe a good idea to save the 2500W inverter for other loads.  An inverter that big with loads that small tends to be quite inefficient.

I'll try to email more info tonight.
G-

[Steadfast]

Hey Glenn,
I really would like a switch that works with my present Inverter.

I can send you MONEY to help out, if you can find the time to start devising a solution.
even if that solution involves a robot finger to push the stupid button.

[OperaHouse]

I think he is being too polite.  This is a lot of work for a one of that doesn't have future uses. 

Anyway have a chicken story.........
A man bought a farm and for years his crops failed.  He tried everything.  One day he was in his local farm store and related the story to the owner.  The owner knew the history of the farm and that it had poor soil.  Everyone had failed.  Trying to be helpful he said....."Have you tried baby chicks?"    The farmer said no and the store owner sold him two dozen.

Next week the farmer came in and bought another two dozen.

The following week the farmer came in and bought another two dozen.  The store owner sensed the farmer must be finally succeeding and said.    "You must be doing pretty well with those chicks".   " No" the farmer said. " I must be planting them too deep or too far apart"

The store owner didn't want to get into a discussion and told the farmer he should write the local agracultural extension and tell them the same story.  He did and a week later he got a reply.

SEND SOIL SAMPLE.

[Steadfast]

..

[Steadfast]

WOW...what a bone-headed farmer... 
but then he was the guy who also got scammed into buying the land to begin with.

I guess P.T. Barnum was right...

as for the Government Response:
A TYPICAL  BUREAUCRATIC  REACTION 

[Steadfast]

a friend of mine read this string and sent me this possible solution.
What do you folks think about this device?


$94.08

Crydom's LVD series of DC output low voltage disconnect solid state switches is designed to disconnect 12 or 24 volt battery systems from their loads when the battery voltage falls below a pre-selected DC voltage. The LVD will also automatically reconnect the load circuit once the battery voltage returns to a normal value after charging. The LVD series is offered in a rugged, industry standard encapsulated panel mount package with screw terminals.

The Crydom LVD series requires no operator interface to interrupt or reconnect the battery circuit. Featuring all solid state construction with a low Rds on resistance FET outputs rated at 40, 60, 80 or 100 amps maximum, the LVD series is available with six different threshold voltages to choose from. The LVD series is RoHS & China RoHS compliant.

The Link:
http://www.google.com/url?sa=t&rct=j&q=low%20voltage%20shut%20off&source=web&cd=1&cad=rja&sqi=2&ved=0CDgQFjAA&url=http%3A%2F%2Fwww.digikey.com%2Fus%2Fen%2Fph%2Fcrydom%2FLVD-DC-solid-state-switches.html%3FWT.z_Tab_Cat%3DFeatured%2520Products&ei=a3hTUPfTCMr20gGa1oHgCw&usg=AFQjCNGadXEn2WXNFVv23AhQ1Fqe9SWLOA

Perhaps I could put inside the Chicken Coop, into the circuit just before my main power light switch?  and then just leave the Main Power light switch "On" when I want my power to the coop to cycle on and off??

here again is a video of the power set up inside the coop:

[ghurd]

Several issues.

"Perhaps I could put inside the Chicken Coop, into the circuit just before my main power light switch?"
The thing controls DC, and all the power in the coop is AC, right?

Your next question will be about putting it in the DC line to the inverter.
When it says 40A, it means 40A on something like that.
Thats about 500W, or about 10% of the inverter's surge rating.

and,
If the inverter is On when disconnected from the battery, the big cap bank drains to 0V.
When that SSR decides to start conducting, the cap current surge will be huge.
That makes a $100 "Poof!"


Really, how many watts does the coop need?
I have a bunch of (pre-Schneider takeover) 300W PortaWattz inverters that have rocker switches, new but had the power wires cut off.
A little relay.
A ghurd kit.
The whole schebang would be considerably less than $100.
G-

[gww]

G, Steadfast
I just bought a crydom ssr for 16 bucks including shiping off e-bay.  It is 4-32 volts by 600v-25 amp.   My intention is to go from the aux port of an mx60 charge controller "12v" to turn on a 220 volt 2000 watt hot water heater through an inverter.  I want to do this based on battery voltage.  Why couldn't steadfast run his fans the same way using a ghurd cc to control the voltage kick on and off base on battery voltage with the ssr ac voltage kicking on after the inverter.  This would require the inverter to always be on but should only run the fans at the hot part of the day when the batts are full and when it is probly hottest.  The wires from the ssr to the fan might be long but could be small.  I like it if what I say is pointed out as crazy "if it is" so I can pull back and not have wrong ideals floating around in my head.
Thanks
gww

[Mary B]

The problem with the current inverter is it needs a momentary close to active on/off. Buy a cheap 100 watt inverter to run the fan and use a ghurd kit. I could build the circuit but I see no profit potential so why take the time?

[gww]

Steadfast
MaryAlana seams to be saying the same thing as glen and this ends up being a switch. Ghurd contoller,  300 watt inverter with rocker switch.  What do you think?
gww