nuckolls.bob(at)aeroelect
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 Posted: Tue Dec 02, 2008 5:12 am Post subject: Pressure switch failures |
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At 10:46 AM 12/2/2008 +0100, you wrote:
| Quote: | Hi Bob,
I just read your article on the subject and maybe found reason why my retract gear pressure switches go kaput after brief service.. could it be due to spikes from their intermittent duty relays (sold from Lancair parts provider) which probably don't have internal diode (how can I check?).
Now my question: if I want to try an external spike catching diode, what are its requested specs?
Better, can you suggest a model? |
It's unlikely that your contactors came with
diodes installed. I used to sell an intermittent
duty contactor that did feature built in spike
suppression but it was only one of dozens of
similar parts by the same company that did not
have diodes installed.
I like the 3 amp rated devices like 1N5400
series. Exact voltage or current rating is
not critical. These devices have relatively
robust lead wires and housings. See:
http://www.radioshack.com/product/index.jsp?productId 62578
Can you share the part numbers and/or specifications
for the pressure switches? It may be that your system
would benefit from addition of solid-state buffers
between the switches and contactors. Those intermittent
duty contactors take 4-5 amps to close and might be
tough on the switches whether or not spike suppressors
are installed on the contactors. Also, if you have a
failed pressure switch you could send me, it would
be useful to do a tear-down inspection and see if we
can learn more about the failure mode.
But in any case, addition of the diodes on the
contactor coils is not a bad thing to do and may
well take care of most of your problems.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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