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Old 16-12-2008, 05:05   #16
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As Maren mentioned, I use the XO computer as my navigation computer. I have it wired directly to the boat's 12V and it uses .5 AMP. On it I run SeaClear under wine on Ubuntu Linux. The XO is mounted on a swing arm over the navigation table and it uses a wireless keyboard and mouse. I have AIS connected to it and it works great.

The XO is very rugged little computer and the screen is viewable in sunlight. The Linux operating system, all the programs and over a 1000 charts (from Toronto to Pananma) are stored on a 8 Gig SD card.

As a backup computer I use an HP laptop running XP which uses around 3 AMPs.
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Old 16-12-2008, 09:28   #17
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Excellent thread! I do enjoy learning via this forum.

However I have a number of questions...

I use a compaq Presario C700 on board, although to date only when I can connect to 110AC shore power.

It would seem from some posts, that I can connect direct to the computer from the boat's 12v supply (not using the brick) without a problem. Some of the posts however warn that this is only to be attempted with some surge protector... others with the battery removed.

It would seem that there are a number of possibilities... all of which will work. Would it be possible for one of you to list for a non expert the various possibilities and components needed for the following....

Basic safe workable system ?
Suggested system?
Very Best system?

Note: Here in Venezuela obtaining components is very difficult. The postal system is a black hole

Finally, I have tried to access the web,but my knowledge of the subject defeats me so it would be extremely helpful if when listing suggested components one could briefly explain what it does.

Many thanks in anticipation

Regards

Alan
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Old 16-12-2008, 12:12   #18
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Originally Posted by anglooff View Post

It would seem that there are a number of possibilities... all of which will work. Would it be possible for one of you to list for a non expert the various possibilities and components needed for the following....

Basic safe workable system ?
Suggested system?
Very Best system?
Alan
Basic safe workable system ?
1.Use a smallish inverter (modified sine wave ok, but sine wave safer). Plug your 110 brick into the inverter and power the computer.
2.Buy a special 12v brick. It looks like a 110v brick but plugs into a cig lighter socket (check the cig lighter wiring is ok with 6A or so most are). These 12v bricks are made by some manufacturers specifically for there computer or there are after market generic 12v bricks that will power most laptops.
In my experience 2. is more efficient. However the power savings are not enormous and an inverter can be used for powering some other 110v appliances, but a 12V brick will only power the laptop.

Suggested system?
If you donít have a good knowledge of electronics I would suggest staying with the above 1 or 2.

Very Best system?
The greatest efficiency is to feed 12V into the computer directly
3. Via the normal power socket.
4. Via the battery connections

3 and 4 are less safe. I would argue 4 is theoretically more efficient and safer, because more filtering can be added to the circuit and the voltage is identical to what the computer normally gets from this source, but to the best of my knowledge 4 has not been done and there are potential problems such as how the laptop communicates with the battery to measure number of cycles etc. 3 has at least been done successfully by one member at least.
Hope this helps.
If you are keen to try 2 I will try and find a 12V brick that would be OK for your laptop, but it would probably need to be sent by mail.
1 is easier as small inverters are reasonably easy to buy and I suspect you could get one locally.
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Old 16-12-2008, 14:22   #19
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If you go to Tom's Hardware site http://www.tomshardware.com, they have quite a few articles about the actual power draw a computer has (both laptop and desktop). The Atom, which is a low power CPU, is saddled with an older chipset that sucks down the power. Lowest power at idle is about 20 W.
The Intel Atom is a class of CPU's with several levels of power consuption. The first mini-itx board using these cpu's was the D945GCLF made by Intel. These are pretty inexpensive as mini-itx boards go, around $70. The low price was the result of using a desktop chipset, the 945GC, and the Atom 230 which has a TDP of 4 watts. This is the combination that "Tom's Hardware" was reviewing.

The current crop of "Netbooks" use the Atom N270 at about 2 watts TDP and the more expensive but less power hungry mobile chipset, the 945GSE. I don't know what the TDP of the 945GSE is but I expect it is less than half of the 945GC.

One of the first mini-itx boards using the N270 and 945GSE will be the MSI's IM-945GSE-A. This should be available from US distributors in 2-3 weeks and should be a great board for boaters with 6 com ports and 6 USB ports.

If you are building a mini-itx system, Mini-Box is a good source of wide input DC/DC ATX power supplies. If you want run your laptop from your boats 12 volt system I think you should use a DC/DC regulator that will hold the voltage to your computer within a couple percent of the laptops nominal voltage. There are regulators for most brands of laptops made by companies like Lind or PowerStream . Carnetix also makes some Dc/Dc regulators that can be usefull to cruisers.

Bob Stewart
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Old 16-12-2008, 14:39   #20
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I presume as you didn’t understand the reference to the dummy battery you actually mean feeding the 12v via the normal power in socket. It is interesting, and useful to know this works. I would be a little concerned that feeding 12V into an input designed for (16 to 18v or as in my case 20V) would lead to some long term reliability problems due to some of the components carrying 1.5 times the current, but if I now understand your post correctly you have found this reliable.
Yes I meant straight into the power socket on the notebook and have found it reliable, as have quite a number of others who I have shared experiences of on this (but the notebook must be, of course, one that uses a circa 12v battery - will be written on the battery).

I haven't noticed any abnormal heat issues (I have watched for this) and would doubt that the notebook would draw any more current on 12v compared to its normal 18+v. That as the input impedance of the power socket is unlikely to change just because a lower voltage is used and because (putting aside the battery charging) everything inside the notebook operates at less than 12v and one could be quite confident that the voltage regulators providing those lower voltages would run cooler.

I take the battery out because it obviously won't charge and will discharge itself. However, if it was left in I suspect there would not be a problem due to a higher charge current eventuating and in the end all Li-Ion battery packs are internally regulated during charging to avoid the risk of Li precipitation.

As a general rule for DC electronics if one applies a higher than designed voltage they will lose reliability of components or smoke, but if a lower than designed voltage is applied the worst that will happen is that they just won't function. A simple example, as batteries drop voltage at the end of their discharge an electronic item will just stop functioning, it will not start smoking, there is no protection needed for this to be so.

Another example is the CPU in a computer, probably one of the most voltage sensitive components in them. If the voltage to it is increased it will soon fry (as overclockers know). If the voltage is reduced it will just start making errors and eventually just stop operating until the correct voltage is restored.

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On a separate issue I understand you don’t feel A DC to DC converter to be more efficient than an AC to DC converter run from a small inverter. With both my computer and my wife’s computer this is not the case in practice. We save about 25% running the DC to DC converter. My inverter is not large at 600W.
I hope I didn't say that . No I was just referring to the often claimed advantage of the DC to DC step up converters that they convert direct from DC to DC so they must be more efficient. The claim as to there being direct conversion is incorrect as they in fact chop the input DC up into AC (similarly to as an inverter does) and then convert that back to the desired DC voltage. So it does DC->AC, AC->DC just as if one uses an inverter with the notebooks AC power supply one has Inverter{DC->AC}, Power Supply(AC->DC}. I think (hope ) I said that the only likely advantage is one of scale ie one of these DC-DC step up power supplies designed to provide 80W or whatever is going to be more efficient than using a bigger inverter at low current and the notebook's AC power supply even though the stages gone through in getting from 12v to the 18+v are the same with either. That is what you found and what I expect.

Which leads on to the mention by another poster that there is no need to use 12v direct as the DC to DC step up boxes are readily available. Generally I agree with that but the step up boxes in chopping up the DC to AC are very noisy at RF (as are some inverters) and so are very prone to interfering with SSB radio if one has one aboard (and maybe interfere with other things too). All that I have used have required the leads to be wound through ferrites but still a low level of RF leakage from the box itself which may be problematical if trying to recieve low signal strength weather faxes or, if a radio amateur, low signal strength digital such as RTTY, PSK31, etc, or SSTV or even telephony. Also, in my experience they can be unreliable so even if one uses one it may be nice to have a cable made up to operate the notebook direct off 12v just in case.

For spike/surge protection one can get spike/surge protectors from automotive electrical outlets and can just be mounted in the boat's DC panel. The boat builder who built our boat just put one in as a matter of course without me asking - don't know if it does any good or even has been necessary though, but maybe provides some insurance.
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Old 16-12-2008, 15:44   #21
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Christian, there's nothing "new" in low power computing. You choose how big a screen you want, how much CPU power you want, and that's about it, the rest is fixed. The only real difference you can make is to buy a SSD (solid state hard drive, which uses memory chips instead of a rotating plattter) which saves power--but can add $500-1000 to your price. And watch DVDs from the hard drive, not the DVD, which sucks more power to spin. SSDs aren't new, they've just dropped in price this year.

A laptop "built for Vista" can also use less power than an older design built for XP, since the Vista OS allows the hardware to power down in a more granular fashion, literally powering down EVERY subsystem that is not in use.

But for powermising? You're going to be looking at those 9-10" "netbooks" like the eeePC, and anything more that you want, burns more watts.
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Old 17-12-2008, 07:59   #22
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'New' generation

HelloSailor, you may be unaware of a recent generation of micro computers which focus on minimal power use and no moving parts for robustness, and minimal cost. Almost all of these fully-functional computers cost less than $500. (In comparison, my pre-inflation $500 TI scientific calculator seems particularly disappointing.)
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Old 17-12-2008, 08:17   #23
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Amgine, I think that depends on what you consider "micro" and "power". Ignoring the ultra-low-power (but performance limited) computers in the kind being distributed to 3rd world kids, and ignoring the more powerful but still limited machines like the "netbook" 9-10" notebooks commonly selling for $400-600 today, what else is there?

What can compete with the same cpu power, the same ability to run a non-Linux OS, a 13"-15" or larger color display, use 3-4GB of RAM for multitasking, and generally compete on level ground with a commodity-grade laptop?

AFAIK the new low-power CPUs are all wonderful--but they are not competing in the same class of machines. I could say that my PDA outperforms my original PCs in many ways, oncluding low power consumption. But--that doesn't mean it competes with my laptop. Except for the "fits in my pocket and sips power" category.<G>

If all I used it for was navigation charts and sight reductions, and a few other time-and-speeed type calculations, my PDA would still beat the laptop, sure. But overall? Low power CPUs are still low power (consumption and performance) CPUs, AFAIK. They're getting better--but they're still "different".
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Old 17-12-2008, 10:32   #24
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Well...

You're right, using Windows or Mac OS would result in a dead slow box. But you know, I have sailboat, and the motor in it is sized to do the job asked of it. It moves the boat. It doesn't let me wake board, it desn't have muffler poppers or flames shooting out of the carb; it's just an auxiliary marine motor.

The varied OSes on the tiny boxes (and yes, there's a stripped-down version of Windows available) are similarly specialized, and only have the power to do one or two things at a time, and not very complex things at that. The nav software is more than I would expect them to be able to do - but we have one proof of concept using a native Windows navigation software in the fattest (iow slowest) standard distribution of Linux I know.

So, in my opinion, I think your argument is disproven. But I think this thread was specifically about low-power limited machines used for navigation aboard.
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