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12V DC to Variable DC, Off-the-shelf solutions?
#1
I've seen repeated sage advice that whenever possible, 12VDC should be used instead an inverter to power items that require DC anyway, usually through an AC adapter or power supply.

I've been sorting through some of the devices and gadgets I have.  It seems that a single point, or multi-point power source with variable voltage and current output similar to a bench power supply would be a better solution than having a separate DC-DC adapter for each device.  Having an electronic background, I can envision how something would be put together but I don't like to reinvent the wheel.

Does anyone know of such a device that already exists?  Essentially a bench power supply that runs off 12V DC instead of 120V AC.  Thinking aloud, if a bench power supply is transforming to 12V and rectifying it to half-wave DC, simply bypassing this part would have the same effect, but having the ability to step-up to higher voltages would be needed for many devices.  Off the top of my head, I'd probably pick a limit of 30V max, though I can't see any particular need for this higher voltage yet.

Thoughts?  I'm just brainstorming on this one, so anything reasonably related counts.
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#2
Ah....a magic box!

Look for one on Amazon, they have everything!  Tongue

Seriously....it's easy to take the AC waveform above and below the supply voltage, but I think a VARIABLE DC to DC converter would have some odd problems crossing above and below the input voltage, having to switch from buck to boost or boost to buck as it crosses the input voltage. Maybe a dual converter, with one set of outputs for step-up, and one set for step down.

They do make variable converters, we know that, that operate in EITHER step-up or step-down mode.

They also make DC/DC converters with multiple pre-set values for voltages, like 3.3v, 5v, 12v, etc. 

I think the solution might be to start with a higher input voltage, say, 24 volts, and then all needed voltages should be under that value, say, 5v, 12v, and 19v, for example. That way, the output voltage does not have to 'cross' the input voltage as the output is varied.

There is a simple, low-tech way to do that: a high wattage wire-wound variable potentiometer, but the regulation and efficiency would be low...not suitable for a laptop, but maybe ok for LED lights or roof fans.   

As a practical, easy, efficient, solution, it would seem to me that each DC device should really have its own DC/DC converter or supply.
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#3
How many amps? There are hundreds/thousands of these converters with many different specs.
https://www.google.com/search?client=fir...GGo_9-e-NM

Only things I can think of that might need over 12 volts would be a laptop or cordless tools and I wouldn't want to charge either from a PS. 12v chargers are available for the computers (less than $20 for my HP), might need an inverter to charge the tools with factory charger. I couldn't find a 'car' charger for my Bosch tools.

Guy
"We're all bozos on the bus, so might as well sit back and enjoy the ride."

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#4
I use separate devices.  For the 5 volt USB phones I use the USB outlets on my solar charge controller and inverter.  For the 9 volt radio I have an adjustable buck converter adjusted to 9 volts.  For the ancient 12 volt Asus netbook computer I use a parallel pair of 378R12 low drop out linear 12 volt regulator chips.  The Asus shuts down if you give it less than about 11.5 or more than about 12.8.  If I need a computer with a newer browser with the newer encryption I have a 10.1 inch Windows 7 netbook powered the usual way with a 120 volt inverter powering the original 120 to 19 power supply.  I use it 10 minutes per month with one credit card web page.  For times when I have 120 volt plug in available I have a 13.8 volt power supply that could be hacked but isn't to be adjustable.  It is 20 amp.  

A single adjustable supply would limit you to one thing at a time and it introduces the possibility of breaking a device with the wrong voltage.  That's something I would do.
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frater secessus (12-29-2017)
#5
Looking good so far. I'm thinking pretty low power stuff, less than 2A around 5V sort of thing.

I'm finding quite a bit with the added vocabulary to search with, like this one on eBay:
http://r.ebay.com/Iht1Rs

Not expensive either. I'm not sure about the quality of the output, but for the price it would be worth some experimenting.
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#6
I didn't see a power rating on that converter, just voltage. Maybe I missed it.

Guy
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#7
(12-28-2017, 02:17 PM)WanderingCanuck Wrote: Looking good so far.  I'm thinking pretty low power stuff, less than 2A around 5V sort of thing.

I'm finding quite a bit with the added vocabulary to search with, like this one on eBay:
http://r.ebay.com/Iht1Rs

Not expensive either.  I'm not sure about the quality of the output, but for the price it would be worth some experimenting.

Having enough info for an answer - getting closer .
Now with low power 5v at 2amp , find a good bench supply - typically these are for electronics repair bench , and are higher quality , not all of them the China stuff is reducing many peoples understanding of quality .
In electronics repair , most have a bunch of different power supplies , some can have 2 -3 voltages running simultaneously .
I keep one that goes to 60vdc , this is to cover working on telecom stuff , a lot of that uses 48vdc .
Then you have to choose switching or liner .
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#8
I don't know what different devices you are wanting to power at different voltages.  

In my case there is only 3 different DC voltages and then the 120VAC stuff.  The three DC voltages I use are 5VDC, 12VDC and 19.5VDC.  I have several Blue Seas 12VDC to 5VDC USB outlets scattered about.  They are all 2.4 amps per outlet (4.8 for a dual).  I use these for phones, tablets and hotspots.  The 19.5VDC is a plugin adapter (12V to 19.5V) for my laptop.  My desktop and TV's run off 12VDC natively as well as a crock pot.  I have 12VDC outlets sprinkled around in the places needed.  I have a small inverter and a generator for those items that cannot be run natively from 12VDC.  Much easier and not much of a chance of mucking things up. YMMV
Brian

2000 Roadtrek 200 Versatile "The Beast" (it has been tamed hopefully)  I feed it and it doesn't bite me.
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#9
(12-28-2017, 04:40 PM)John TF Wrote: Having enough info for an answer - getting closer .
Now with low power 5v at 2amp , find a good bench supply - typically these are for electronics repair bench , and are higher quality , not all of them the China stuff is reducing many peoples understanding of quality.

For the bench power supplies you're talking about, are you able to run them directly from 12V or have you modified them?  Or perhaps you run off an inverter?

My question is rather vague, I know, but right now I'm trying to get an idea of the scope of the problem and what's available.  This will enable me to make better decisions as to which devices to include or exclude in my plans, and options on how to power them.

It's a long shot, but are there any readily available solutions that provide some sort of "handshaking" and adjust the supply voltage accordingly when plugged in?  Maybe it's overkill, but just imagine not having to keep track of the correct power adapter for every stupid little electronic gizmo that you own.  You just have a few generic ones and they all have the same plug, but when you plug it in it "magically" supplies the right voltage and maybe some current limiting if needed.  A year or two from now I'll see such a thing on the market, patented of course...
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#10
(12-28-2017, 05:17 PM)B and C Wrote: I don't know what different devices you are wanting to power at different voltages.  

In my case there is only 3 different DC voltages and then the 120VAC stuff.  The three DC voltages I use are 5VDC, 12VDC and 19.5VDC.  I have several Blue Seas 12VDC to 5VDC USB outlets scattered about.  They are all 2.4 amps per outlet (4.8 for a dual).  I use these for phones, tablets and hotspots.  The 19.5VDC is a plugin adapter (12V to 19.5V) for my laptop.  My desktop and TV's run off 12VDC natively as well as a crock pot.  I have 12VDC outlets sprinkled around in the places needed.  I have a small inverter and a generator for those items that cannot be run natively from 12VDC.  Much easier and not much of a chance of mucking things up.  YMMV

Your list is similar so far to the DC devices I'd want to power, though mine includes some other things to charge like hair clippers (4.5V/1A), a VHF radio (6V/0.5A), maybe a wireless router (9V/0.6A), and perhaps a few more.

What do you still run off the inverter?
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