dc plug sizes on power adapters

[Furkin]

Hi,

I have a couple of power adapters. I thought they had 2.1mm dc plugs (or maybe 2.5) dia.

I have measured them on a micrometre but they are actually 3.3 & 3.7.

Are these dc plug measurements supposed to be accurate,,,,,,, or are 2.1/2.5 ones always bigger than ‘sold as’ ?

The 5.5 ones measure accurately.

Seems a silly question, but I need to be sure as I need to sell a couple, and want to have it right.

cheers

 

[flameport]

There are lots of sizes, many of which are very similar.
https://en.wikipedia.org/wiki/Coaxial_power_connector

 

[AdrianUK]

the 2.1 or 2.5mm relates to the diameter of the male pin which fits inside the inner sleeve of the socket.... not the outer diameter of the whole thing

 

[Furkin]

Ah,,,,, thanks for that. I forgot to add the micrometre shots, but now, I can see it wouldn't help - but I'll add them anyway, to help my quest, and any other readers.

 

[SimonH2]

I usually determine centre pin size by careful use of appropriate sized drill shanks - and the outer with callipers (what you've shown is't a micrometer). That's fine when looking at the plug, working out the corresponding sized for the socket part is a lot harder.
There are many combinations of inner and outer sizes - with a few manufacturers apparently subscribing to the "standards are great, we should have some of our own" approach to interoperability

 

[Furkin]

Thanks Simon,
I don't know why I put micrometre - I don't even have one !
Good tip about pin size. I'll check everything in the house now I know.
cheers all

 

[SimonH2]

Just to add - some manufacturers even change the connector between different units of the same thing.
A few years ago at work we had a customer with a failed network switch. Netgear replaced the switch under warranty - but then when I went on-site to fit the replacement, the power supply connector had changed. Of course, they don't ship a replacement power supply when shipping the different unit - so a further delay and a further trip to the customer's site to fit the replacement switch and the power supply Netgear sent.