craig bastin wrote:
>
> for those of you up to the electrics stage, i found these
>
> http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2592
>
> they look like they might be a good replacement for circuit breakers
It appears to me that these are PTC-resistors. Downside of these things
are that they will never really cut the power, but remain in such a
state that the heat development is just enough to increase the
resistance enough to remain in some sort of balance. Another problem is
their relatively high resistance. You will loose some voltage over these
things, depending on the amount of current you are asking. Near their
cut-off current, the voltage drop is sufficient to convert some of the
energy into heat, it is the heat which will increase resistance even
further, and that is why there is some limit in the amount of current
you can ask from it.
With other words: These things have no clear on-off states, but
everything in between instead. Depending on your purpose, this is
allowable, or it is not.
It might be an option to power non-trivial small devices through them
(like a GPS) where the current remains significant below the cut-off
current, but I would not use them for, let's say, the fuel pumps, the
flaps, or the radio. In general, all equipment with changing current
demands and higher current demands are unsuitable.
Oh, and you can't instantly reset them. They need to cool down first
after they "tripped". Not bad for your GPS (unless you are in the middel
of an GPS-IFR-approach), but not so smart for the fuel-pumps, flaps, etc.
Actually, I would stay away from them.
Just my 2 cents.
--
Frans Veldman
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