brian-av(at)lloyd.com
Guest
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 Posted: Sun Sep 10, 2006 10:10 am Post subject: Switch contact rattings which is best for this app |
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On Sun, 2006-09-10 at 04:56, FLYaDIVE(at)aol.com wrote:
| Quote: | Silver is the better conductor - But - Oxidized much more.
Gold is obviously slightly less in conductivity (but, you will never know
that) than Silver - But - for the practical, does not oxidize.
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Switches maintain their low on resistance by both mechanical wiping and
by the very tiny arc that occurs on make and break. If you do not pass
any current through a switch, often the mechanical wiping is
insufficient to ensure a low on-resistance. Gold, unlike silver, has the
characteristic that it maintains its low on-resistance regardless of the
current flowing through it. That is why it is used to switch signals
with no appreciable current (like audio signals).
| Quote: | Without getting ridiculous in explaining a switch ... If you Double the
Voltage you Half the current. So a Switch that is rated at 0.4 Amps (at) 28 VDC will
be able to handle 0.8Amps (at) 14 VDC.
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This is 100% false and incorrect. A switch rated at 0.4A is rated at
0.4A regardless of the voltage. The voltage ratings have to do with
reliably breaking the circuit. This also depends on whether you are
breaking a circuit carrying AC or DC. The amp rating also depends on
whether you are switching a resistive load or a lamp load. The low
resistance of a lamp filament causes a high inrush current so you need a
switch that is designed to carry more current so it isn't damaged by the
inrush current.
Barry, I strongly recommend you go back and reread the Aeroelectric
Connection. Bob does an excellent job of covering these things in there.
In a forum such as this, you really need to be sure of your answer
before you post one.
Brian Lloyd
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