# can you Parallel Voltage Regulators.



## krogerssolar (Jan 8, 2009)

Hi all i've had an idea for powering track side light signals via solar and battery setup but would like to power them from 12volt Regulators in Parallel to cover MA or Amps and to keep the voltage the same when the battery is being charged. my Question is can you Parallel Voltage Regulators together or will they be off by a few volts.


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## JPCaputo (Jul 26, 2009)

You can, all you need is a small resistance inline with each output. Before connecting all the regulators together. 0.1 ohm 1/4 to 1/2 watt resistors will be plenty, 1/2 watt is better.1/4 watt will be close to the limit. I^2*R = watts. 

The purpose of these resistors is to allow for each regulator to output slightly different voltages without overloading the regulator with the highest voltage output since it would be trying to pull up the voltage of the lower regulators. Kinda like the suspension on a loco to accept the imperfections in track.


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## krogerssolar (Jan 8, 2009)

Got it Thanks.


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## Dan Pierce (Jan 2, 2008)

Instead of wiring 3 LM7712 for 3 amps (check specs when buying, some are only 1/2 amp), use the LM350 for 3 amps. It is adjustable, so for lights lower it to 11 volts for dimmer lights and longer life of bulbs. 
There is even a 5 amp version.


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## Greg Elmassian (Jan 3, 2008)

Yeah, but now you have to set a trimpot to set the voltage, and there's another point of failure, or potential problems, or you have to get your resistors right to set the voltage. 

For many people the fixed regulator is better. 

Also, remember that now you need a BIG heat sink if you are dissipating the power for all 3 amps in one heat sink. 

Pros and Cons to each method. 

Regards, Greg


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## Dan Pierce (Jan 2, 2008)

And the LM338 for 5 amps!! Yes , a heat sink and even the 7812's need a heat sink, so be it. that would be 5 lm7812's (assuming 1 amp version, twice as many for the 1/2 amp version) wired up vs a single LM338 and 2 resistors. 
And all regulators mentioned need noise suppression capacitors.


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## Greg Elmassian (Jan 3, 2008)

OK, so now we answered the question literally, what kind of setup do you have that can run several amps? Must be a nice solar panel. 

With most solar installations, efficiency is what the system is all about, therefore passive regulators converting part of your precious electricity into wasted heat is not normally a luxury you can afford. 

What you really would like is a DC to DC inverter with efficiency in the high 90's, so you don't waste anything. 

Usually this is what takes the raw output of the solar panel (where the voltage varies wildly) and converts it into a constant DC of varying amperage, and then into a battery. 

I'd get one of these and you then have higher efficiency, no heat to dissipate, and you have solved your regulation and storage problem in one shot. 

Greg


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## krogerssolar (Jan 8, 2009)

Greg Thanks for your Replay. i Defiantly like your Idea of using a DC to DC inverter i over looked that one guess when you live off grid with DC to AC inverters you over look the other. Thanks


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## Greg Elmassian (Jan 3, 2008)

You might contact Rick at Cordless Rennovations to see if he has such a beastie ... he shows one on his solar car.. 

Greg


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## krogerssolar (Jan 8, 2009)

Thanks Greg im all set on my solar Side just wondered about giving a few circuits a constant 12volt voltage as to not smoke any components i have found a few inverter/converters im looking at. 

Thanks Kevin


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## Greg Elmassian (Jan 3, 2008)

So, on your solar side, what is the voltage you are getting? You must have some regulated supply voltage. Is it AC or DC? 

Just curious, especially from your alias... 

Greg


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## krogerssolar (Jan 8, 2009)

This Projects Voltage its max Open Voltage will be Around 20.0V DC of course during charging/usage it will go down a good bit depending on my Battery demand. I have a Xantrex/Trace Charge Controller C35 ill use to control the charging a bit over kill but it will work i wont be needing the 30 or so amps in capacity and the panels are are 5watt or 10 watt depending on which one's i use. A small setup compared to my main solar array that can produce 1200Watts of power its open current voltage is close to 110V DC its regulated in a Outback Power Systems FM80 Charge Controller down to 12volts then converted from DC to AC to run any AC item i have. I Would love to run from my main system but my run of wire would be to far and there would be a good amount of voltage loss along with this small load it shouldn't be tide to my DC To AC systems DC Voltage.


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