power/barrel connectors

[D Yuniskis]

Hi,

I rescue a fair number of items without their respective
power supplies, wall warts, bricks, "whatever".

Usually, I run things through a little routine:
- select a mating connector from "goody box"
- program power supply for correct polarity/voltage
(set current limit to something "reasonable" -- useful
if the morons who made the device failed to mark the
polarity of the power connection!)
- see if device works
(if not, toss in recycle bin)

At this point, I have a "mating connector" but little
more than that (the connectors are too damn small to
*label* in any meaningful way).

So, I use a drill index to sort out the ID and a dial
caliper to get the OD. This covers most of the variation
among connectors (though some also have extended barrel
lengths :< )

Is there an *easier* way of doing this? Or, some
(bizarre) rule of thumb? E.g., a correspondent
recently made the comment that US devices tend to have
center positive -- which seems pretty common though I
know I have found devices with outer barrel positive...
unfortunately, I can't attest as to whether those were
"foreign" manufacture (ha! damn near EVERYTHING in
the US is made overseas, so... ;-)

Thx,
--don

 

[Rich Webb]

Hi,

I rescue a fair number of items without their respective
power supplies, wall warts, bricks, "whatever".

Usually, I run things through a little routine:
- select a mating connector from "goody box"
- program power supply for correct polarity/voltage
(set current limit to something "reasonable" -- useful
if the morons who made the device failed to mark the
polarity of the power connection!)
- see if device works
(if not, toss in recycle bin)

At this point, I have a "mating connector" but little
more than that (the connectors are too damn small to
*label* in any meaningful way).

So, I use a drill index to sort out the ID and a dial
caliper to get the OD. This covers most of the variation
among connectors (though some also have extended barrel
lengths :< )

Is there an *easier* way of doing this? Or, some
(bizarre) rule of thumb? E.g., a correspondent
recently made the comment that US devices tend to have
center positive -- which seems pretty common though I
know I have found devices with outer barrel positive...
unfortunately, I can't attest as to whether those were
"foreign" manufacture (ha! damn near EVERYTHING in
the US is made overseas, so... ;-)

http://en.wikipedia.org/wiki/Coaxial_power_connector is a good reference
for these buggers. This seems to be one of those areas where standards
were so good, they decided to have several of them!

Center-positive seems like a sensible choice although, as you note, not
all are set up that way. Fortunately it has become more common for
devices to have the little --(.-+ polarity marking, or its inverse.

 

[Grant]

Hi,

I rescue a fair number of items without their respective
power supplies, wall warts, bricks, "whatever".

Usually, I run things through a little routine:
- select a mating connector from "goody box"
- program power supply for correct polarity/voltage
(set current limit to something "reasonable" -- useful
if the morons who made the device failed to mark the
polarity of the power connection!)
- see if device works
(if not, toss in recycle bin)

You don't open them to see what's inside, behind the power connector?

At this point, I have a "mating connector" but little
more than that (the connectors are too damn small to
*label* in any meaningful way).

So, I use a drill index to sort out the ID and a dial
caliper to get the OD. This covers most of the variation
among connectors (though some also have extended barrel
lengths :< )

Sounds good.

Is there an *easier* way of doing this? Or, some
(bizarre) rule of thumb? E.g., a correspondent
recently made the comment that US devices tend to have
center positive -- which seems pretty common though I
know I have found devices with outer barrel positive...
unfortunately, I can't attest as to whether those were
"foreign" manufacture (ha! damn near EVERYTHING in
the US is made overseas, so... ;-)

Can't think of easier, apart from opening up the toys as part of the
investigation.

Worst I've seen is a DC powered device after somebody plugged in an
AC plugpack connector --> Boom! went the DC filter cap, about the same
time as the PCB fuse blew, messy...

Grant.

 

[D Yuniskis]

Hi Rich,

http://en.wikipedia.org/wiki/Coaxial_power_connector is a good reference
for these buggers. This seems to be one of those areas where standards
were so good, they decided to have several of them!

Exactly. "Standards are great! EVERYONE should have one!"
:<

Then there are the "inside out" varieties (Sony is fond of these
but Dell and Toshiba also use them on laptops and LCD monitors)

Center-positive seems like a sensible choice although, as you note, not
all are set up that way. Fortunately it has become more common for
devices to have the little --(.-+ polarity marking, or its inverse.

Yeah, but the morons who thought up the marking scheme also
didn't think it through very well. E.g., '+' and '-' are
usually represented in circles. The connector body is
abstracted as "-(o-".

Now, reduce this to the point where you would typically
*greek* text and the connector legend starts to look like
"-(o)-" (i.e., ink bleed closes the 3/4 circle that
is intended to *almost* surround the center pin's representation.

<frown>

When I REmark these connectors (and wall warts), I use
a circled '-' or a circled '+'. Takes less space than their
silly graphic *and* its unambiguous -- even when scaled!

Unfortunately, the connectors that you can usually buy
often have shorter barrel lengths than the connectors
that are "required" for the device(s) in question. :<
Otherwise, I would just buy one of each and build a custom
"octopus cable" out of them (which would allow me to
label each "tentacle" with a description of the connector
at its tip!).

[I use a bag of "tips" -- like shown in the Wiki page
you referenced -- that I connect to a mating "receptacle"
attached to the programmable power supply. These tips
are almost always "longer" than the "standard" ones you
can purchase!]

 

[D Yuniskis]

Hi Grant,

You don't open them to see what's inside, behind the power connector?

Shirley you jest? :> Too many of these things are snap-together
construction (if not outright solvent weld!). Those few that
are screwed together hide the hardware under labels, rubber feet,
etc. (so accessing them often does cosmetic damage to the device).

If the device is missing voltage/polarity markings and I
can't find it online, I *might* consider surgery -- but
the device would have to be worth the effort (else just
toss it in the recycle bin)

Sounds good.

I think having a selection of each of the mating-mating connectors
(i.e., the connector that exists on the device) mounted on a
labeled piece of phenolic could be a win. Find a tip that
fits the device. Then, see which *labeled* connector on the
"template" similarly fits this mate.

Can't think of easier, apart from opening up the toys as part of the
investigation.

Worst I've seen is a DC powered device after somebody plugged in an
AC plugpack connector --> Boom! went the DC filter cap, about the same
time as the PCB fuse blew, messy...

Yeah, it would be nice if things were all AC. But, I guess they'd
rather put the rectifier and regulator in the wall wart instead of
the "device". :-/

 

[Don Klipstein]

E.g., a correspondent recently made the comment that US devices tend
to have center positive -- which seems pretty common though I know I
have found devices with outer barrel positive... unfortunately, I can't
attest as to whether those were "foreign" manufacture (ha! damn near
EVERYTHING in the US is made overseas, so... ;-)

My experience is that there is no reliable hard-and-fast rule, but
that *almost* everything has center positive, shell negative. With one
major exception that I know of: 9V "stomp box" style musical
instrument effect devices tend to be center negative, shell positive.
Some other wallwart-powered musical instument devices may follow that
alternative convention.

 

[Don Klipstein]

Grant wrote:

Shirley you jest? :> Too many of these things are snap-together
construction (if not outright solvent weld!). Those few that
are screwed together hide the hardware under labels, rubber feet,
etc. (so accessing them often does cosmetic damage to the device).

If the device is missing voltage/polarity markings and I
can't find it online, I *might* consider surgery -- but
the device would have to be worth the effort (else just
toss it in the recycle bin)

What I like to do is "go for it" - take a guess at polarity, usually
center-positive unless the device is of a class and voltage that I know
to usually be center-negative.

If it works - *woohoo!*

If not, reverse polarity and see if I blew it out. If it does not
work at that point, I usually return it to where I got it (usually a
dumpster).

Not that I do a lot of this - when I find time to do electronics
after my non-electronic day job, I mostly nowadays do stuff that I can
get paid for doing. Healthcare coverage inflation and the modern
economy is forcing me to work more and play less. My dumpster diving
for electronic-related devices in recent years is mainly for power
supplies and hardly for prospective loads for them or for devices
likely to go into "The Recycle Bin" or products likely to be favored
to be sources of components likely useful only in "pure science"
"mad-scientist" / curiosity area. I filled my home enough with enough
of that sort of stuff already...

<SNIP from here>

 

[D Yuniskis]

Hi Dave,

I have one handheld radio (Kenwood TH-315A) which uses a NiCd battery
pack (8.4-volt nominal). The drop-in desktop charger has a
center-positive coaxial jack for a 12-volt supply. The radio has a
"DC in" jack which takes the very same plug, so you can run it
directly from the wall wart.

Huh? Ah, OK. The "desktop charger" is a little "base/cradle"
into which the radio can be placed for charging and *that* gets
its power from a wall wart. The wall wart can also be plugged
directly into the radio (eliminating the bulk of the desktop
charger but sacrificing some convenience -- i.e., you can't just
"drop it in")?

The detachable NiCd battery pack has a direct charging input, so you
can top it up without needing the drop-in charger... but this input is
a center-negative (!) jack of a slightly smaller OD.

Ouch! So, there are *three* "equivalent" power connections to
the radio:
- set of "drop in contacts" for the desktop charger
- barrel connector to power radio (also charges battery?)
- different barrel connector on battery pack

I'd have enjoyed the opportunity to be a fly-on-the-wall (possibly
armed with a machine gun) during the engineering meetings which
selected this design. Why, oh why?

Are the needs of the battery pack different from those of the
radio? I.e., I've seen radios that expected a current limited
supply to be connected to the "battery input" connector to
top off the battery -- but a low impedance supply to connect to
the *radio* (to power the radio).

Of course, picking the same connector for both is daft.
(and picking opposite polarities even moreso -- unless
they waste a diode drop in each connector)

 

[D Yuniskis]

Hi Don,

What I like to do is "go for it" - take a guess at polarity, usually
center-positive unless the device is of a class and voltage that I know
to usually be center-negative.

If it works - *woohoo!*

If not, reverse polarity and see if I blew it out. If it does not
work at that point, I usually return it to where I got it (usually a
dumpster).

I try to maximize my chances of getting it right the first
time. Current limiting the supply usually gives me a
second chance if the polarity is unmarked and I get it backwards
(Sony seems to be the biggest culprit, there).

Not that I do a lot of this - when I find time to do electronics
after my non-electronic day job, I mostly nowadays do stuff that I can
get paid for doing. Healthcare coverage inflation and the modern
economy is forcing me to work more and play less. My dumpster diving
for electronic-related devices in recent years is mainly for power
supplies and hardly for prospective loads for them or for devices
likely to go into "The Recycle Bin" or products likely to be favored
to be sources of components likely useful only in "pure science"
"mad-scientist" / curiosity area. I filled my home enough with enough
of that sort of stuff already...

Yup, been there, done that. We've been on a "purge" for
a number of years, now.

I probably rescue 6 laptops a year, dozens of LCD monitors, etc.
Diverting these from landfills (*or* The Recycle Bin) and
getting them back into "circulation" is a small effort on
my part -- yet usually pays big returns when you see someone
who couldn't normally afford such things smile at the "gift".
Or, even folks who *could* afford such toys (it does no one
any good in a landfill; and I suspect the recycled value
has got to be a few percent of it's "working value")

 

[D Yuniskis]

Heck if I know. What I've started doing, is lopping the last
ten inches of cable off a wall-wart supply, and reconnecting
it with a four-position (Molex Minifit latching nylon) connector.
Pin 1 is low-voltage (+) , anything from 0 to 6V; pin 2 is low-v (-);
pin 3 is high-voltage (-) and pin 4 is high-voltage (+).
Usually it's only using two pins, but +5/+12 power for external
disk drives uses all four (#2 and #3 both are grounds).

Ah, OK. You're expecting to deal with more than just
two-conductor barrel connectors. (I think this is a
more "expansive" approach than I've been pursuing)

For AC, connections are at pins 2 and 3 (so the DC targets would
not connect, or just short it rather than get blown up).
So, all my tips are pluggable into all my wall-warts, and if the wall-
wart
has the right rating, and the tip is the right connectivity for the
target, that wall-wart can power that target.

Great! You've obviously thought this through!

And every time I want another unit pressed into service, I either find
a correct wallwart, or connectorize an orphan wallwart appropriately.
The work is never completely done, of course. Little cardboard
string-tags on the tips is the next to-do item.

<frown> I don't see any easy way to label things.
What is particularly annoying is that many tips
*appear* to be color coded. But, there doesn't seem
to be a "standard" that applies, here.

I have dozens of assorted "tips" like the first photo in:

http://en.wikipedia.org/wiki/DC_connector

I have a digitally programmable power supply (i.e., a
keypad and display on the front panel) with the
mating connector wired to its output connection.
So, I can power a device by finding the connector
that "fits", then programming the PS for the
appropriate voltage (I can't do AC wall wart emulation)

Unfortunately, it feels a lot like "having a can full of
random screws" that you dig through in search of the
*right* screw... :<

 

[D Yuniskis]

Hi Joel,

Did you come across this entry? -->
http://en.wikipedia.org/wiki/Coaxial_power_connector
Yes.

It seems like there are color standards... just lots of them -- EIA has
one, Radio Shack has one, etc. So it if effectively useless... (yellow
and black do seem the most common, for whatever reason).

Exactly. The problem with standards is when folks don't
*follow* them. E.g., I came across a set of socket drivers
that seemed to think the role of colors was to make the
driver set more "attractive" :<