While much harder to find than the ubiquitous 9, 15, or 25 pin D there
is a variation with a couple fat pins for high current or coax plus
sometimes some control pins. I didn't find them in Digi-Key but did find
them in Allied's latest catalog. In the shell of a 15 pin (normal
density) there's two power pins and 5 signal pins. Power pins are
available with current ratings of 10, 20, and 40 amps. Surely the
voltage drop of the 40 amp lines (hooked to number 8 wire) would be low.
Plugs and receptacles without pins are under $5 each, and the pins are
under $3 each in small quantities. So a mated pair with pins would run
about $22. It costs more to ship small quantities of Mate-N-Lok shells
and pins than to pay for them. A significant contrast. Amp series 3
circular plastic connectors with pins rated for 25 amps might make an
intermediate compromise though over $600 each for crimp tools is a
definite drawback.
The trouble with paralleling pins as that the resistance of the pin is
not that consistent to cause perfect current sharing. So that its most
likely that one pin will carry more than the rest until it burns open
then the others will take over. Multiple pins will probably give good
reliability but not necessarily as small a voltage drop as one good fat
pin... And not all D type connectors are made like Cannon connectors.
Many of the least expensive have tin plated stamped contacts with far
less metal than the machined and gold plated Cannon that rated the
rating of 5 amps per pin. These stamped tin things are probably really
only good for a couple amps per pin, and then only if you aren't picky
about voltage drop. There is a world of difference between connectors
made by Amphenol and Cannon and connectors carried by RS and All... and
made into cables for $3 in China. Fortunately most computer signal
applications can tolerate a volt drop (or more on RS-232 except from a
laptop) so the excess drops in these cheap connectors and cables don't
cause us to notice.
How about a pendant cable, say 12 gauge black/red low voltage zip cord,
with a male insulated spade lug on the positive and a female on the
negative. That would prevent wrong polarity connections and with the
heavy duty spades required to fit the 12 gauge wire, the connections
would be more reliable than a round overloaded molex type pin.
73, Jerry, K0CQ
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