Using 12v System to Directly Power Computers and other DC Eq.

Does anyone have a recommendation or experience with a setup for powering non-marine DC-powered devices (computers, the obvious example) from the 12v system? Hopefully this is a dumb question and that will be pointed out to me.

Since so many products are DC (but call for varying voltage levels and are designed to rely on specific AC adaptors in home applications) it seems that it would be efficient to power these directly from the 12v source. How have people dealt with the range of output voltages that would seem to be required? A panel full of auto-cigarette-lighter-adapters doesn't seem too clever. What is a practical means for having a variable-voltage DC output or, alternatively, is there a simple device that can be placed between each device and the 12v source to supply proper voltage/current to that device?

Thinking of desktop computer equipment, is there a practical means to supply 5v power directly to the components?

Thanks for any input

-JPC

 

Well, laptop computers can require anything from 12 to 19 V; other electronics all have their own requirements too. DC-DC converters could do this, but that gets pricey, especially when you add the circuitry to clean up the output. Simple resistive voltage dividers can give you <12 V power from a 12 V source, but that's not very efficient.
Computer equipment can be really sensitive to fluctuations and surges in the supply voltage. A computer's power supply is filtered against noise and fluctuation, as well as supplying very stable 12, 5, 3.3 and sometimes 2.5 V power to the components. You'd have to duplicate all of this functionality.
Seeing as most components are designed for standard voltages- 120 VAC, 240 VAC or 12 VDC- it seems to me that the usual system of sticking with these standards is probably easiest.

 

Better than a potential divider is a variable voltage regulator (or several in parallel if you need the current handling).

Desktop computers are a bit simpler, though. You can get a module from http://www.logicsupply.com/index.php/cPath/40_65

Do remember though, Salt-water is the enemy of electronics.

Tim B.

 

Some devices have more than one internal power supply levels and they have to be kept isolated (require galvanic isolation). It will be difficult to operate these devices from a single DC source. A/C to D/C conversion is pretty efficient and simple.

 

12V power supplies for computers

This used to be a little difficult, but lately there is so much demand for vehicle-based PC's that there are a lot of available power supplies that are 12VDC (or up to +36VDC or so) IN and ATX or other PC standard power OUT.
Some of them , for small single-board X86 - Win-XP type computers are not much bigger than your thumb! Let me get a few references... (digs thru bookmarks....)

One for $50
http://www.aerial.net/shop/product_info.php?currency=USD&products_id=171
Another: 200 Watt, multiple output
http://www.mini-box.com/PW-200M-DC-DC-power-supply?sc=8&category=13

A nice motherboard about $150, which I think I'll use:
http://www.via.com.tw/en/products/mainboards/motherboards.jsp?motherboard_id=202

Most of this technology comes from the Car-PC guys putting GPS and MP3 in their Camaro etc etc..

This stuff is great for those of us who can't decide if we're a computer nerd, boatbuilder fanatic or TIG Pilot...

 

Almost everybody uses a lap top for Cmap navigation driven from nmea 0183 GPS.

You WILL be able to get a correct fitting to drive your lap top from a cigar lighter socket.

I would add that you might want to think carefully on the battery supply ie what battery bank you use. For instance if you have a dedicated engine start ,that would be good as you would take the power source from another--house bank say. Otherwise you will get some shut downs when you hit the starter.

Incidentaly I take off power for all my instruments from the house batteries--simple for the reason that I might want to see the depth or my position with out switching on main engine starts.

 

Reboot on engine start???

Jack, a couple of interesting things here:

One advantage to using a separate computer rather than a laptop is that the laptop can be very easily damaged, especially with salt spray possibilities.. Also, the cost can be much less for the same capabilities... but more work to 'install'! Also the possible interfaces and options are much greater.

The better 12V vehicle power supplies for PCs will not shut the PC down when starting a car, on the same battery. But I personally agree that on anything other than a small boat, there should be a separate starting battery that is disconnected from the onboard systems when engine starting.

 

DC to DC converters?

Several firms, like Vicor, make a solid state DC to DC converter . http://www.vicr.com/products/dc-dc/converters/dc-dc_converters/
http://www.vicr.com/products/dc-dc/converters/mxmnmc/
http://www.wallindustries.com/productcart/pc/viewCat_P.asp?idCategory=89
http://www.power-one.com/products/dcdc_overview.html

Vicor's mega-mod Jr converters can provide solid clean DC at different voltage levels from the input.

Having used them for a decade to run PLC's, PC's and RF modems in remote locations where all the power was 12 VDC; I'm sure these converters will deliver reliable power at the exact output levels specified.

They're not inexpensive but they're reliable stepping DC voltage UP -OR DOWN.

They work as a defacto filter for noise and input spikes or fluctuations too, since the clipping tolerance @ the output is so tight; you end up with excellent quality DC output in addition to the level step changes.

Using these converters you can provide super 'clean' power of the exact voltage level needed for any DC powered device. Often, when you take apart PC or comm equipment OEM power supplies you'll find that the primary power output is converted down (an up) by just these exact components; even the brands linked here.

Cheers,
kmorin

 

Vehicle DC chargers/power supplies are readily available. The intermediate black box functions as a power filter also, protecting against spikes and such.
Here's one that fits different devices by changing the plug tip. Only need one charger, charge up to 3 different devices at once.

http://www.igo.com/product.asp?sku=2366908

I agree with the advice to install an isolator and have separate batteries for engine starting and for everything else. I did that with every boat I owned, anchored out for days at a time, ran various electrical goodies according to whim or need, but always had a fully charged bank to start engines.

 

A cheap and simple option to me seems to be a power inverter – just plug that into e-bay (pardon the pun ). It converts from 12V to mains power so my computer can be recharged, or run directly from, a mains source.

 

(Low)- Powering a computer onboard

I've been looking at this for a while. The power budget for running a moderately capable X86 computer that is optimized for low power seems to be about 20 watts (25 if you're playing an MP3 or watching a DVD). See http://www.epiacenter.com/powersim/powersim_v2/epiasimulator_v2.htm
for some possibilities.. I'm thinking I'll probably run a VIA MII 6000E.

Some expensive (About $4200) commercial Boat Computers like SeaPC http://www.seapc.se/items/luna.html use a board like this. For power, they say:"The average power consumption is 30 W or 2.5 amps on a 12 v system."

I think it's hard to get a Laptop that is running thru an inverter supplying 12V to 120/220 down to that power. Can someone who's doing this measure the current at 12V on such a configuration, for a 600 Mhz or more machine running WIN-XP or Linux, with the screen active??

One problem is that there are two active power-converters in the system (not counting what the PC is doing internally) that each have a less-than perfect efficiency..

Those making a passage under sail care about this more than weekend sailors...

 

I measured current some time ago at 12 volts:

No-load 0.9A
Laptop 6A
Acorn A7000 2.6A (search the web if you're wondering what this is)

as I remember a desktop machine was about 12A

Except for the laptop, these do not include the current drawn by the monitor.

The big problem is not actually supplying power. It's cooling the CPU in a manner that prevents corrosion to the motherboard.

Tim B.

 

Cooling in Corrosive Environment

That problem is addressed pretty nicely by the lower-power VIA chipsets and the Eden processor, which allows an 800 MHz machine with fast memory and built-in graphics that support DVD playback, with NO FAN. See the Mini-ITX motherboards at:
http://www.via.com.tw/en/products/mainboards/motherboards.jsp?motherboard_id=202
A quote is: "The VIA EPIA MII is available with the fanless VIA Eden™ ESP processor for ultra low power, quiet or silent system designs". This 17x17Cm motherboard is used in a few different $2000 - $4000 "Boat Computers". But it costs about $160 for the system board with processor (soldered..NOT socketed).

So that's where I'm headed right now....

 

For really low power applications I like to use low power PC/104+ processor boards such as AMPs Micro886ULP http://www.ampltd.com/prod/u886.html which is a low power Pentium III class PC/104+ processor. To run off DC power, I add a PC/104 power supply such as http://www.tri-m.com/products/engineering/#power . The PC/104 power supplies have a wide input voltage, for example the HE104 has an input voltage of 6 - 40VDC. Most of these power supplies provide power to the PC/104 stack through the ISA and PCI bus connectors so there is no wiring required between the power supply and the cards. If you plan to use the PC for a navigation system then you will need more storage space than is economically feasible with flash, so you can add a 2.5" hard drive with a PC/104 Hard Drive Mounting Board http://www.diamondsystems.com/products/hddmount . The PC/104 cards stack together like a sandwich and then you can seal the stack in an enclosure of the correct length such as the CT104 http://www.tri-m.com/products/engineering/ct104.html . They have standard end caps that handle most requirements http://engineering.tri-m.com/products/enclosures/CT-stdendcap.htm . For boat applications with a hard drive I don't trust the rubber grommet shock isolators so I replace then with wire rope isolators such as http://www.isotechoem.com/pdf/WireRope.pdf . I use the "VEHICULAR / Rough Terrain (Off-Highway) / 20Hz Vertical" table on page 21 or 25 to guide the selection and give a 20 Hz natural frequency. To deal with salt air corrosion I like to mount the PC/104 stack in a sealed enclosure. With the ultra-low power processor you are supposed to be able to run it without a fan, but I usually put a stirring fan inside the enclosure to prevent hot spots. I like the Parvus Thermocool PC/104 because it is thermostatically controlled http://www.parvus.com/support/SupportPage.aspx?ProductID=55 which saves a little power when the fan isn't required, but also helps to keep heat in in low temperature operation.

If power and corrosion are less critical and you want a turn-key solution, then I like the Stealth Computers fan-less Little PC http://www.stealthcomputer.com/littlepc_fanless_p4.htm . Use the shock isolators mentioned above and you're ready to go. I can provide a picture of a Little PC installed on Shock Isolators for a 45 knot boat application (next time I take my camera to the boat).

BTW: My favorite GPS/compass is the Crescent Vector OEM started kit because in addition to accurate position it provides heading to true North to within 0.2 degrees at a rate up to 20 Hz. The accuracy and stability is excellect for driving an autopilot and you don't need to worry about declination, but that probably another thread.

 

A few more options here for the technically inclined, if you want to run stuff like computers etc. directly on DC without an inverter.
For those with a bit of electrical knowledge and who like building their own stuff, I highly recommend Vicor's DC/DC converters as the starting point for your system. They're simple, reliable solid-state devices and are very efficient; they have a huge selection of input and output voltages available, http://www.vicr.com/products/dc-dc/converters/ . If you run a 24 V or 48 V battery bank, it's not hard to wire up their converters to give you anywhere from 2 to 48 VDC, and the output is clean enough to run even the most sensitive electronics. We've had very good luck with these in solar cars, running with wildly fluctuating input voltages and at insane temperatures; the converters don't flinch one bit.
The same company also makes a range of ready-to-run power supplies for all manner of DC/DC applications, http://www.vicr.com/products/configurable/ . It shouldn't be too hard to find something there that would suit whatever you need to run.