Re: "Barrel" connectors

On 6/16/25 9:15 AM, Don Y wrote:

On 6/16/2025 8:59 AM, legg wrote:

They're not infinitely variable.

 No, but there are a score or more different configurations
(neglecting length variations).  And, many of them are
"close enough" that you can get the wrong plug to mate
and still not make electrical contact.
 [And, the mechanical aspects still won't address V, A,
polarity, AC/DC, etc.]
 

Some info on the web wikimedia barrel connectors.
>
Here's a spreadsheet with ID, OD and center pin diameters,
along with mfr ident and typical use (user beware):
>
https://ve3ute.ca/query/IEC_EIJ_DIN_Barrel_Connector.zip
>
Center-pin equipped parts expect resistively programmed
info for correct function a la USB-C. Some expect to be
output-voltage-adjusted by the same means.

 I thought the "three-pin" variants talked to an I2C-sortof
device *in* the brick to identify the actual device?

Some Dell notebook power supplies have used that approach.
The barrel consists of two concentric cyclinders with the outer being the negative connection and the inner one being the positive supply. The pin directly connects to a OneWire Dallas Semi/Maxim memory that has the power supply ID.
The computer can then interrogate the power supply to determine current capability and that it is a genuine Dell supply.
My first exposure to one resulted in me destroying the supply!
There was no protection for the memory device and I accidentally shorted the centre pin to the inner barrel when attempting to measure the voltage output.
The 19V from the supply destroyed the OneWire memory. Whenever the PSU was plugged into the computer it would not identify it as a Dell supply and would not charge the battery and would only run at reduced speed.
It is not obvious that the outer barrel and inner barrel are not the same connection.
Be careful with Dell supplies. Modern ones may be different this is from ~15 years ago

Note that current ratings assume correct mating and may
not be guaranteed by various mfrs or vendors.
>
Labelling the installed connector can be useful if your
memory doesn't serve you well.

 Once you have the mating wall-wart/brick, you typically
care little about the actual connector being used.
It's not like you're going to plug something ELSE into
that port.