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Old 05-05-2006, 16:19   #31

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Originally Posted by Pblais

Pure sine wave power is better for computers - period. I used to work with computers in a van that had two installed with some other equipment. The non sine wave power we started with was breaking computers left and right and then we went with pure sine wave power and the repairs were cut to almost nothing.

Most inexpensive inverters generate square waves. And while that alone is not the serious pronblme the trouble comes from the fact that the poor inverter square wave transitions always tend to shoot high and low. So on the scope it is not just a sharp square edge at the square points. Instead you see spikes at the leading edge of the top of the square wave.

This means you are getting radical spikes in voltages constantly. Pure sine wave power is much better for sensitive electronics. Stepping DC voltage is more efficent than converting DC to AC then back to DC. You'll use a lot less actual battery power going DC to DC. Yoiu can get good power supplies made for automotive use and just skip the inverter (at least for the computer) completly.

For a laptop you can find sources on the internet for about $50 or so. Adding 12 volt automotive sockets is a pretty easy project you can do yourself.

Paul, this is one instance where I disagree with you. I think it's the only one I've ever come across.

Running a laptop on a square-ish wave inverter is no problem at all for the computer. It's not efficient, but I do it for the sake of convenience. The square-ish wave from the inexpensive inverter goes to the laptop's *external* power supply, which then supplies a steady DC voltage to the computer. This DC voltage isn't going to be affected much by what's upstream of the power supply. I read a constant and true 24VDC coming into my laptop running on the cheapest of the cheap inverters. I also have a high power WiFi setup running off the same inverter. All function extremely well with no voltage fluctuations at the DC input to the equipment.

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Old 05-05-2006, 17:46   #32
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Well square waves alone would not be a problem if the spikes on the transitions were not so large. You just don't get one without the other. Thats based on running $200,000 of high tech gear on poor inverters for days on end in three vehicles driving around town. The difference was dramatic when it was switched out for pure sine AC power We needed about 2 KVa of power so that is less than 10 times a PC. We saw it partly becasue we ran so long and used so much power. I sure hiope most folks don't cruise with a 2 KVa 120 volt load.

What you can see is not a picture of what is the reality of of what goes on. Sure the voltage is going to read steady, but you can't see it without a scope. I can't say it does not work as you know it does work. But it costs you almost double converting twice DC / AC then DC again plus it hammers away at your power supply. That means more battery bank load and you can't get around it. The power transformers are geting beat up all the time. If they go bad they take the meat of the equipment with it. Poof!

What you read is the the average you don't read the spikes as they come in under the radar. Not in a big way but like someone jabbing you in the ribs every split second and the heat in your PC adapter is the wasted heat.

For $50 you can buy a DC to DC converter that will plug direct to the motherboard. It's the same cost as an AC power supply (and smaller). This isn't an expensive solution. I do belive pure sine power is better for electronics if you want to go with AC power as the source. Lots of things are not easily converted to a DC source and you buy off the shelf and use the inverter.

With a laptop it's too easy not to just get a 12 volt adapter. For a desktop you need a different power supply. Maybe not so easy for some folks to install but it's not as hard and some of the other simple things you do on board.

Paul Blais
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37 15.7 N 76 28.9 W
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Old 06-05-2006, 13:31   #33
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For a desktop you need a different power supply.
Not true - see my earlier post. But this is a large current drain. If going the PC route, with todays high power components, it doesnt matter if you are using a pure syne wave transformer or a dc/dc converter, you will still use too much power!

If you want to go this route, then the only sensible method is to create a proper 12v PC brick, where the box is used as the heat sink, and there are no fans - hence considerable reduction in power requirement.
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Old 13-05-2006, 11:55   #34
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We have 2 laptops on board. We have found the outlets from Dell and HP and for 1,600 US (total) we had the latest and greatest with the exception of a larger hard drive. That was the only difference. besdie, you don't really need the absolutely most powerful machine.

Our logic was we could afford to replace PC every couple of years with the factory outlet refurb machines. Our machines new from the Dell & HP were around 3,000 apeice.

Next time we will install a 12 volt desktop and an external antenna. We have found many places in the Caribe where free wireless could be had while sitting on the boat. The notebook cards or internals did have the power. We use a Linksys exteranl USB wifi. But next paycheck we will go with a remote mounted high gain antenna and external modem.

Many wifi systems are offered for free or we have be able to hijack unprotected sites of which there has been a ton.

We will always carry a laptop for portabilty.

One recommedation is to get the car converter instead of inverting and then converting the 12 volt dc to 110 and then to what ever the pc uses. the HP uses 19 volts. This is a huge waste of house amps and makes you dependent upon the invertor. If the invertor fails no laptop.

just something to think about.
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Old 13-05-2006, 16:06   #35

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The Toughbooks are probably the only "hardened" computer form a large commercial vendor. Pricey, but if you look into the design they have done things like use shock mounts on the drives--which ordinary laptops just don't do. That difference could prevent you from losing data, or losing a drive, or needing to reinstall software, on a day pounding through a chop.
Or, you could save a lot of money using a cheaper laptop with a shock-mount, a foam pad under it, etc. It won't be easy to find one that is spray-resistant, etc. the same way though, but that's a question of how careful you can be with it, versus your budget.
Putting a conformal coating on computer boards is not as simple as it might sound. Once you coat them, you change the electrical characteristics of everything (mainly capacitance, I'm told) and that can affect how it will operate, if it will still operate. And it will affect heat transfer, etc. If you can afford to toss the computer out if it doesn't work--go for it.
But I don't think a desktop has any place aboard the boat, given today's laptop prices AND the ability to pull it off the boat, either to use a shore connection, or secure the laptop off the boat, etc. Among other things the whole laptop--even the processor, if you've bought one with a "mobile" type--is designed to use less power, and that's a good thing on a boat. With low end desktops taking 200W and many selling with 350-400W suppies, versus laptops that run on 40-75W, there's a tremendous power consumption difference. And that's without the power consumption of the desktops' additional display.

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