USB current

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
sylus
Posts: 108
Joined: Fri Aug 05, 2016 9:47 pm

USB current

Postby sylus » Mon Aug 15, 2016 1:12 am

Could you tell me what is the current of USB accessories plug on top of printer because i try to use my Ip cam 5v 1.2A and it shuttering.
I try panel USB same issue.
USB current could be set in firmware or it's hardware limitation?

Jetguy
Posts: 3107
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: USB current

Postby Jetguy » Mon Aug 15, 2016 2:56 am

Hardware limitation and BTW, 1.2A is way, way, way out of USB 1.0 and 2.0 spec.
http://www.extremetech.com/computing/11 ... smartphone
"In the USB 1.0 and 2.0 specs, a standard downstream port is capable of delivering up to 500mA (0.5A)"

sylus
Posts: 108
Joined: Fri Aug 05, 2016 9:47 pm

Re: USB current

Postby sylus » Mon Aug 15, 2016 9:10 am

I see but it means that the official camera current is less than 500 ma. .......

Jetguy
Posts: 3107
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: USB current

Postby Jetguy » Mon Aug 15, 2016 1:45 pm

What we know is, your camera didn't work and spec says don't draw more than 500mA.
Personally, I think it's (edited to be PC to novices) bad to put ANY load on the pcDuino knowing that is your print server and the heart of your printer.
Power your camera externally and let the printer be "just" a printer.
Why add something that could damage your printer or cause issues??
Last edited by Jetguy on Tue Aug 16, 2016 11:30 am, edited 1 time in total.

Jetguy
Posts: 3107
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: USB current

Postby Jetguy » Mon Aug 15, 2016 3:10 pm

Again, I get it and blame Raise a little bit for extending the USB cable up as a solution. This is one of the first things I ripped out/removed on my Kickstarter N2. I get it, they needed a fast solution to support the camera they offered. The public demanded it but the reality is, it wasn't exactly top level engineering. It was a last minute add on.

Rather than BS each other, I'm just cutting straight to the facts. I would not load down any USB port on the pcDuino with a 1A or greater load or a combined load greater than that. It doesn't have some huge regulator- and it's taking 24V in and lowering to 5V which is a huge drop in voltage. If you know anything about this level of electronics, you simply would not do what you are trying and even though Raise 3D offered it as a solution, I disabled it on my own machine just to prevent such mistakes. I won't plug anything more than a USB thumb drive into a USB port and if I use a camera, it's externally powered.

Jetguy
Posts: 3107
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: USB current

Postby Jetguy » Mon Aug 15, 2016 3:32 pm

In this thread, I put some decent pictures up of the pcDuino board that the USB cable is power by (just uses one of the inward facing USB ports inside the plastic enclosure). viewtopic.php?f=4&t=613&p=5932&hilit=pcduino#p5932

Based on the inductor sizes and the regulator, thermal considerations and derating, I wouldn't push it. Again, what we know is, 24v from the main PSU comes in over a simple JST-Xh 2 pin connector, probably 22 gauge and is then regulated into 5V and 3.3V used by the processor, LCD, and wifi modules on the board. There is not exactly a ton of over capacity here. The real kicker is that again, if your external load you plugged in causes a problem, well that either affects your ability to print or could even damage the very heart of the printer. Rather than risk that, I would say sound advice to not use the port, regardless of what anyone else tells you "it's OK", because looking at the hardware, I say it's not worth the risk of when it goes wrong.


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