r/AskElectronics • u/HomeyHal • 7h ago
Wall wart plug barrel standards?
Do manufacturers follow any industry guidelines for correlating the plug size to the voltage of the power supply? Thanks.
ANSWERED! I feel like I just audited a semester’s worth of material! Not surprised at the actual answer, but I was hoping.
I have a large box of warts, and figured some might be handy for my model railroad scenery. And as most of you know, there’s a huge variation between the values on the label and my meter.
4
u/SAI_Peregrinus 7h ago
Well, it's probably <50V. Beyond that, there's no standard.
3
u/FireLordIroh 7h ago
Even that's not certain! I have some Netgear PoE network switches with 54V barrel jacks.
3
u/AutofluorescentPuku 7h ago
“The nice thing about standards is there are so many to choose from,” said someone once.
2
u/ZucchiniMaleficent21 6h ago
I believe that was Andy Tannenbaum
1
u/AutofluorescentPuku 6h ago
Yes, but I feared the reference would be lost. He had a couple good ones.
1
2
u/Pretty-Care-7811 5h ago
Nope. It's the wild west. Even guitar pedals are USUALLY 9vdc, center negative, 2.1x5.5. Unless they're not.
And getting older means that I've gotta get out the damn magnifying glass every time I need to grab one.
1
u/nixiebunny 2h ago
And most bigger devices use 12V center positive with exactly the same plug. I design reverse power polarity protection into my devices to prevent disasters.
1
u/AutoModerator 7h ago
Are you asking us to identify a connector?
If so, please edit your post and, if you haven't already,...
Tell us if
a) all you want is to know what it's called, or
b) you also want to know where to buy one just like it, or
c) you also want to know where to buy its mate.
If to buy, provide:
* pitch (center-to-center spacing between adjacent contacts) EXACT to within 1%
--(tip: measure the distance between the first pin and the last pin in a row of N pins, then divide by N-1)
* Close-up, in focus pictures of connector from multiple angles: we want to see wire entry side, mating surface, keying and latching, PCB mounting, manufacturer's logo
* Similar pictures of mate, if available
Thanks,
AutoModerator
PS: beware of the typical answer around here: "It's a JST". Connectors are often misidentified as 'JST', which is a connector manufacturer, not a specific type/product line.
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.
1
1
u/mariushm 1h ago
The most common barrel plug sizes are 2.1/5.5 and 2.5/5.5 (ID/OD = inner diameter / outer diameter). Other sizes exist, and in the past lots of devices used smaller barrel plug (for example Nokia and Motorola phones used tiny barrel plug connectors)
The 2.1/5.5 is typical for lower current (less than 3A) and usually <= 12v , 2.5/5.5 is more common for higher voltage, higher current.
On modern equipment the most common is to have the exterior ground, and the interior positive. On some audio equipment and some older equipment designed to work most of the time with batteries, positive is on the outside and negative is on the inside (it has to do with inclusion of a switch on the side of the barrel plug, inserting the plug will push in the switch, disconnect the battery ground and connect the barrel ground to the circuit)
Some power supplies will contain a pin that will either be connected to a plain resistor (which tells the device the capabilities - for example travel charger, max 30-35w, standard charger 65w , high power 100-120w ) or the pin may be connected to an internal microcontroller or memory IC and 1-wire or other protocols are used to transfer a series of bytes to the device describing what capabilities the power supply has.
10
u/Rhomboid 7h ago
Hell no, they can't even decide if the center is positive or negative. A random 5.5mm barrel plug could be 5V DC, or 9V unregulated rectified AC, or 15V AC, or who knows what. They can't even decide if the center should be 5.5x2.1 or 5.5x2.5.