nuckolls.bob(at)cox.net
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 Posted: Thu Oct 02, 2008 7:59 am Post subject: D-Sub Connector Follow-up |
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Hi Bob
Would this be 4A per wire? I'd feel very nervous about putting that amount
of current through an itty-bitty pin.
See:
http://aeroelectric.com/Mfgr_Data/Connectors/Positronic/HDC_Series.pdf
Note contact current rating of 7.5A. In aircraft wire
bundles this assumes a 20AWG wire. Of course, this
drops to what ever the smaller wire is de-rated to
for bundling . . . 5A in the case of 22AWG.
Conservative designers will look at total connector
current density and de-rate further if most or all
of the pins are continuously loaded to max rated.
The open barrel d-sub pins are generally rated the same electrically
but they're much more process sensitive to the installation of
single pins by the neophyte technician using tools like:
http://aeroelectric.com/Pictures/Tools/Crimp_Tools/bct-1.jpg
http://aeroelectric.com/Pictures/Tools/Crimp_Tools/obc-1.jpg
The machined pins are essentially mil-spec and installed
with either an inexpensive ratchet-handled 4-quadrant
crimp tool like . . .
http://aeroelectric.com/Pictures/Tools/Crimp_Tools/rct-3.jpg
or the super-cool, $high$ tool like . . .
http://aeroelectric.com/Pictures/Tools/Crimp_Tools/4-Quad/Daniels_4-Quad_1.jpg
http://aeroelectric.com/Pictures/Tools/Crimp_Tools/4-Quad/Daniels_4-Quad_2.jpg
http://aeroelectric.com/Pictures/Tools/Crimp_Tools/4-Quad/Daniels_4-Quad_3.jpg
All of which produce a consistent installation of a
machined pin.
Although here on the southern tip of the dark continent, we don't get the
machined pins,
only the useless pressed ones...
Steinair, and B&C both stock them.
If think it's fine, then I'll believe you - I've just spent big bucks on
this (see attached pic) military style breakout plug, which is rated at 5A
per pin. 
Then the $time$ invested to swap horses right now
is probably not a good investment. For others watching
this thread, know that it is possible and practical to
achieve nearly full-mil-spec connections in your small
wires using the really good pins and anybody's removable-pin
d-sub shells.
Know too that if you need to run more than 5-7 amps
though any one wire, you CAN parallel pins if you
include a 12" or so total length of 22AWG wire for
ballasting-resistance in series with each pin
(10-20 milliohms). This mall resistance washes
out pin-to-pin variables that make short-wire
paralleling risky. See:
http://www.aeroelectric.com/Pictures/Connectors/D-Subminature/Paralleled_D-Sub_Pins.jpg
I used this technique in a mil-qualified super-sonic
target
http://aeroelectric.com/Pictures/Misc/GQM_1st_Ops_Flight.jpg
power distribution controller . . .
http://aeroelectric.com/Pictures/Misc/GQM_Power_Dist.jpg
to switch 20+ amp battery feeders. I de-rated to 3A
per pin, had 12" 22AWG wire in series with each of
7 paralleled pins to effect a high current feeder
through the d-sub. It passed all the qualification tests.
Bottom line is that the lowly D-Sub is an exceedingly
good value if you can exploit the simple-ideas behind
its design and applications.
Here's the tool/locator reference chart for those
of you who prowl about the hall of the auctions:
http://aeroelectric.com/Pictures/Tools/Crimp_Tools/4-Quad/Tool-Locater_Cross_Reference.jpg
Note that there's a super-pin for D-subs that handles
a single 18AWG wire or two 22AWG wires. This pin's crimp
is at the back of a long pin where the wire grip resides
outside the connector shell.
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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