[NLRS] Power Poles

[John P. Toscano]

Dr. Gerald N. Johnson, electrical engineer wrote:

> Now using the powerpole family depending on color codes seems to me to
> be leading to disaster. In the near dark, or illuminated by a
> monochromatic light source (single color LED or low pressure sodium
> vapor street light) the colors may be easily mixed (or used by the
> partially or fully color blind). Can that box made for 5 volts handle
> +28? Probably not. If it could it would be running off 28 volts! Unless
> you shuffle the stacks of power pole you will have interchangeable
> connections based only on color. Suppose you have a helper setting up
> the rover, who thinks your set of colors are because you couldn't find
> all to match and plugs at random. The power poles will accept the wrong
> load, though the load may not survive the wrong voltage.

You DON'T have to rely on color coding with the Power Pole connectors to 
get it right.  You could easily make all of your power connections with 
4 connectors, perhaps Black, Red, Yellow, Orange, and define a standard 
order in which they would be arranged (perhaps BLK=Ground, RED=+12, 
ORG=+24, YEL=+48 in order from left to right), or perhaps
    BLK  RED
    ORG  YEL
if you preferred, since the Power Poles can be stacked either 
horizontally or vertically.  They even make special "polarizing" pieces 
that are longer or shorter than the regular ones, so that the cable 
can't easily be plugged in "off by one position".

Granted, some idiot (or unsuspecting "helper") might come along with a 
two-connector Power Pole and connect it wrong to your 4-conductor 
harness, but no system is foolproof, given the ingenuity of fools.

I am all in favor of making it DIFFICULT to plug things in the wrong 
way, but even in my notorious klutziness, there are limits as to how far 
I will inconvenience myself to force myself to get it right.  YMMV.

In my own case, I use the standard BLK and RED arrangement for +13.8 VDC 
power, and am planning to use GRN and BLU for PTT-IN and PTT-OUT when I 
get around to rebuilding my transverter interfaces and IF switching 
system.  (The switchbox, to select the proper transverter, uses PTT-IN 
to get the PTT signal in from the microphone PTT or footswitch, sends it 
through the selected switch position to the proper transverter 
interface's PTT-IN, which goes to a sequencer.  The sequencer has 
PTT-OUT signals to the T/R relay, preamp (if present), PA (if present), 
transverter, and back down to the radio.  The PTT-OUT from interface 
back to switchbox is then sent back to the IF radio, to actually key its 
transmitter.)  I plan to use a square arrangement of plugs, and Anderson 
makes a 4-conductor holder that mounts nicely on a panel.

I am planning on using BLK, RED, and ORG for some new gear being 
integrated (slowly) into my home and rover systems that require +27.6 
(or around +24).  In other words, on the pieces that require 24-28 VDC, 
there would be a RED connector in the middle of a 3-piece Power Pole 
stack, even if the equipment didn't need any +12, only +24.  Sure, it 
"wastes" one red connector shell, but that shell doesn't need a contact 
if there's no +12V requirement, and so the expense is pretty small.  I 
consider it pretty cheap insurance, for the reasons that Jerry cites.

Supply    Cable   PP      PP     Cable
GND -------------[BLK]  [BLK]------------------GND
+13.8v ----------[RED]  [RED]  (n/c)                 equipment
+27.6v ----------[ORG]  [ORG]---------------+27.6v

Now, I would trust *myself* to only plug a 4-connector harness into a 
4-connector harness, and a 3-connector harness into a 3-connector 
harness, and a 2-connector harness into a 2-connector harness.  I 
probably would *NOT* trust a stranger to help me do that, but at least 
I'd trust myself.  Probably because *I* know how much time and money I 
spent on all of it to get it put together and working.  So I don't feel 
the need to make everything with 5 or 6 connectors, when only certain 
pieces of gear will use certain lines.  But for my systems, the bottom 
line will be, if the two halves don't have the same number of poles in 
the same horizontal/vertical arrangement, DON'T TRY TO PLUG THEM 
TOGETHER!  I think that's safe enough for me.  On the other hand, if 
your connector is compact enough to have 5 or 6 or 8 contacts on every 
one, like the connectors cited by Jerry, by all means pick a wiring 
arrangment and use that connector for everything, connecting only the 
contacts you need.

Food for thought:  How many pieces of gear do you have that run on 13.8 
VDC, and would tolerate a few tenths of a volt less than that for 
operating voltage?  Now ask yourself:  Does EVERY ONE OF THEM have a 
diode in series with the 13.8V input to prevent the thing from blowing 
up if plugged in backwards?  Why NOT?  Why are they not built that way 
at the factory?  Why did you not add the diode yourself?  Very cheap 
insurance.  And for the items that draw too much current, or that can't 
tolerate the voltage drop of one diode, why isn't there a reverse-biased 
diode in series with a fast-blow fuse across the power supply input? 
This causes no voltage drop and the diode only conducts when the 
equipment is connected backwards, and only until the fuse blows.  Still 
very cheap insurance.  Obviously, this doesn't help with getting the 
proper voltages on the proper wires (other than a plus-vs-minus 
problem), but my point is that there are a lot of things we could do to 
our equipment to protect it from the inevitable human failure, and we 
don't always take advantage of those either.


Method 1:  Diode passes full current draw of equipment, and drops the 
source voltage slightly.  If reverse-connected, NOTHING happens (the 
equipment does not turn on, nothing is damaged, virtually no current is 
drawn from the supply).

                  |\ |
+13.8v supply ---| >|----- equipment +13.8v input
                  |/ |

GND ---------------------- equipment GND



Method 2: Fuse must be large enough to pass full current draw of the 
equipment with a modest margin.  Diode will only conduct if power is 
connected backwards, and only until the fuse blows.  No voltage drop to 
the equipment, but a blown fuse if connected backwards.  Diode could be 
rated for lower current than the equipent and fuse, since it only 
conducts for a very short time, but I'd want it to be at least close.

                     FUSE
+13.8v supply ------o~~o------- equipment +13.8v input
                           |
                          ---
                           ^
                          / \
                          ---
                           |
GND --------------------------- equipment GND

(Pardon the crude ASCII graphics.  You need to used a fixed-width font 
for them to make any sense.)

73 de W0JT