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MAX POWER FROM USB
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

MAX POWER FROM USB

by mindwave65 on Fri Aug 23, 2019 12:11 pm

Team,

I have a feeling this is a simple answer, but I cant find it anywhere, not so I can understand it anyway.

I THOUGHT I read somewhere, in the past few weeks, that there was a maximum AMOUNT OF POWER that could be transferred through USB.

Now, maybe the reason Im having a tough time finding the answer is, I am NOT talking about plugging a device into a USB port on a PC or RPI.

Im referring to powering a device through a USB connection on one end and a barrel jack on the other.

Here's the deal: Almost everywhere you turn nowadays stuff is powered through USB, look at it, the RPI4 is exponentially more powerful than my FIRST PC (VIC 20) and the PSU for that was like 2x the size of the entire RPI.

So Im making some stuff, and I have a screen that SAYS 12v 500mA

I have battery making parts all over my workdesk . Im not kidding I have Lipos, and 18650's rechargeable AAA's and some I don't even recognize.

BUT My memory blows, no really, hold a mic up to my head you can hear it whistle through my ears, its amazing

and I could almost swear that I recently read and article stating that USB connectors (or was it battery paks USING USB connectors?) could only output a certain amount of power, I even MARKED the article and emailed it to myself.....and now I cant find it

please someone help an older guy out?

mindwave65
 
Posts: 23
Joined: Thu Aug 08, 2019 9:37 am

Re: MAX POWER FROM USB

by adafruit_support_bill on Fri Aug 23, 2019 12:44 pm

USB started out as a communications bus for things like keyboards and mice. Power was a secondary concern. Early versions specified that ports could provide up to 500mA at 5v and cables had to support at least that.

When it evolved into a charging standard for phones, there were variations on the standard (both official and unofficial) that allowed dedicated chargers to supply more than the standard 500mA at 5v.

Now the standard has further evolved to address power as one of the primary functions of the bus. And the rules get more complicated. The full specifications can be found at the usb.org site:
https://www.usb.org/usb-charger-pd

And there is a nice practical summary of it here: https://www.extremetech.com/computing/1 ... smartphone

adafruit_support_bill
 
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Joined: Sat Feb 07, 2009 10:11 am

Re: MAX POWER FROM USB

by mindwave65 on Fri Aug 23, 2019 3:14 pm

Bill,

thanks for that. I read extreametech almost every day and never thought to search there.

Thanks again!

J

mindwave65
 
Posts: 23
Joined: Thu Aug 08, 2019 9:37 am

Please be positive and constructive with your questions and comments.