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Old 07-01-2010, 06:03   #61
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A small chart plotter has a teenie screen which is usually mounted to a bulkhead 3 feet away. If anything that makes me want to go with a laptop more.
Most chart plotter can be bracket mounted just under the nose if required, Geonav used to make one with VGA output to an external screen.

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maybe I will get a 12v aa recharger to cut down on the waste.
When you become more confident try to experiment with an unregulated 40W solar panel if you do get some sun your side of the world and also use aa similar to Sanyo ENELOOP they keep their charge much longer than traditional NiMH.

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Yah, but here Stateside you won't find many shunts for $6.50
But now Hellosailor get me worried, no shunts for $6.50, may be no sun for 10 hrs, may be no AA either?
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Old 07-01-2010, 11:37   #62
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chala, life in the States is very different from Oz. No 'roos in the streets, but cars are attacked by killer DEER by the hundred thousand every year. No penalty for failing to vote. Or for voting after death, either. All sorts of shockers. :-)
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Old 07-01-2010, 19:20   #63
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you'd want to buy a dedicated 50W inverter for the laptop, because using a 100W or (heaven help you) 400W inverter with only a 40W load on it, is terribly inefficient
egh, what , hellosailor, explain hows its "terribly inefficent", make it good as i,m an elctronics engineer that used to design high powered invertors.

also you commented in a further post that invertors use "ring transformers" !! do you mean torodial transformers, if so your way off here , most modern high frequency switching invertors dont use transformers in this way, they dont often provide isolation for example.
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Old 07-01-2010, 19:31   #64
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Does it matter what kind of transformers they are using? And how do you figure that transformers don't provide isolation, when they create total physical isolation of their input/output sections?

I don't think I suggested any explanation of why invertors are inefficient at low power loads, but every spec sheet I've seen has shown they have much higher losses when they are run under 80-90% of their rated output. If you can point me to the online spec sheet for any of the ones you've designed, I'd love to learn that there's one with 90% efficiency with loads under 20% of full rated output. Or anything similar to that.
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Old 07-01-2010, 20:37   #65
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lets not get into the technicalities of isolating convertors and non-isolating convertors but they exist. think inductor technology rather then transformer technology.

as to efficiences, good invertor design can generate about 95% especially with high dc input voltages ie 48+, very good ones cab get a bit higher. most efficiency fall offs are due to invertor power consumption becoming a larger percentage os the total consumed power and bad designs cab be really bad, but this tends to happen when the load power approaches the internal power comsumption, ie hence 50 percent, but with modern designs that can be kept quite low, there are design tricks too that can reduce the consumption. typically the curve can be flattened

sure you dont want to run a 10 watt load into a 2000w invertor but certainly at down too 30% or even 20% it still can maintain efficiencies at over 80%. equally constant high loading , especially for the cheap types that exist at the 100 to 250 w market can lead to premature failure
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Old 08-01-2010, 11:38   #66
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What is a transformer? An inductor with at least two sets of windings.

So I don't understand, are you saying there are designs that use a simple inductor, with only one winding, one "wire" that has just two ends, instead of a transformer of any kind? Doing what, pumping itself the same way that one might pump a capacitor's voltage?
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Old 10-01-2010, 08:26   #67
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chala, life in the States is very different from Oz. No 'roos in the streets, but cars are attacked by killer DEER by the hundred thousand every year. No penalty for failing to vote. Or for voting after death, either. All sorts of shockers. :-)
I seems to realize, can they swim (the DEER) may be this is why people go sailing. No DONKEYS vote either, you must have honest politicians then.
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Old 10-01-2010, 11:08   #68
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An Auto-Transformer has a single coil, and at least 3 Taps (connections).
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