Is USB current @ 3A safe to use? - Electronic Circuits Projects Diagrams Free

ahdai · 22nd June 2008, 12:28 AM

I plan to make a regulated 5v 3A max power supply and will attach 4 female USB bracket to it. I understand that the current draw will be determined by the load. In my case it will be my PDA and MP3 players.

I have not seen a USB power supply that high current like mine selling anywhere. Do you guys think it is safe for my USB gadgets?

Mikebits · 22nd June 2008, 12:35 AM

Not a chance.
USB in a NutShell - Chapter 2 - Hardware
USB.org - Documents

ParkingLotLust · 22nd June 2008, 01:13 AM

Mike, maybe he means he's going to build a USB charger - just a 5v supply connected to a few USB plugs, to charge things like MP3 Players and whatnot.

If he means that he's going to pull 3A from a USB port then youre right, there's no chance.

ahdai · 22nd June 2008, 01:23 AM

The links you provided are talking about official USB specifications. The 500ma was fixed to protect the PCB and circuit on the motherboard from burning up.(thin copper lines and wires can't take the current)

If you do a simple search, there are tons of different adapters that offers 5v @ 1000ma. What i am trying to do is 3 times as much current.

Anyone else care to say something?

ahdai · 22nd June 2008, 01:25 AM

Yes, i am making a USB charger that can offer up to 3A max. Just wondering if it will be safe?

crutschow · 22nd June 2008, 02:50 AM

Quote:

Originally Posted by ahdai

Yes, i am making a USB charger that can offer up to 3A max. Just wondering if it will be safe?

As long as you plug in USB devices that are designed to be powered by the USB port, I don't see a problem.

Someone Electro · 23rd June 2008, 07:54 PM

Yeah 3A will power 4 devices without a problem. Because no device is allowed to draw more than 500mA.

Mikebits · 23rd June 2008, 09:33 PM

Sorry, I misunderstood. I was thinking that you wanted to draw 3 amps from your USB.
So what you are saying is that you have a 3A supply and want to use it to power your USB devices. That should work with plenty to spare.

Sceadwian · 24th June 2008, 02:35 AM

Make sure you run heavy +VCC and GND wires to each connector, and preferably separate ones to each. Ideally you'd want to use separate +5 regulators to keep noise from transferring, but if these are just for charging and not for communication it's not needed, just make sure the regulator can handle +/- 1 amp current swings and still maintain regulation. You can always use large output capacitors to help buffer the regulator's input and output.

ahdai · 24th June 2008, 09:01 AM

Thanks everyone for the feedback. I have done it and my PDA charges damn fast now. Forgot to mention that it is powered by solar energy. Now i can charge every USB device i have without a PC.

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22nd June 2008, 12:28 AM	(permalink)
ahdai	Is USB current @ 3A safe to use? I plan to make a regulated 5v 3A max power supply and will attach 4 female USB bracket to it. I understand that the current draw will be determined by the load. In my case it will be my PDA and MP3 players. I have not seen a USB power supply that high current like mine selling anywhere. Do you guys think it is safe for my USB gadgets?

22nd June 2008, 12:35 AM	(permalink)
Mikebits	Not a chance. USB in a NutShell - Chapter 2 - Hardware USB.org - Documents

22nd June 2008, 01:13 AM	(permalink)
ParkingLotLust	Mike, maybe he means he's going to build a USB charger - just a 5v supply connected to a few USB plugs, to charge things like MP3 Players and whatnot. If he means that he's going to pull 3A from a USB port then youre right, there's no chance.

22nd June 2008, 01:23 AM	(permalink)
ahdai	The links you provided are talking about official USB specifications. The 500ma was fixed to protect the PCB and circuit on the motherboard from burning up.(thin copper lines and wires can't take the current) If you do a simple search, there are tons of different adapters that offers 5v @ 1000ma. What i am trying to do is 3 times as much current. Anyone else care to say something?

22nd June 2008, 01:25 AM	(permalink)
ahdai	Yes, i am making a USB charger that can offer up to 3A max. Just wondering if it will be safe?

23rd June 2008, 07:54 PM	(permalink)
Someone Electro	Yeah 3A will power 4 devices without a problem. Because no device is allowed to draw more than 500mA. __________________ Il give you shocking experience.

23rd June 2008, 09:33 PM	(permalink)
Mikebits	Sorry, I misunderstood. I was thinking that you wanted to draw 3 amps from your USB. So what you are saying is that you have a 3A supply and want to use it to power your USB devices. That should work with plenty to spare.

24th June 2008, 02:35 AM	(permalink)
Sceadwian	Make sure you run heavy +VCC and GND wires to each connector, and preferably separate ones to each. Ideally you'd want to use separate +5 regulators to keep noise from transferring, but if these are just for charging and not for communication it's not needed, just make sure the regulator can handle +/- 1 amp current swings and still maintain regulation. You can always use large output capacitors to help buffer the regulator's input and output. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

24th June 2008, 09:01 AM	(permalink)
ahdai	Thanks everyone for the feedback. I have done it and my PDA charges damn fast now. Forgot to mention that it is powered by solar energy. Now i can charge every USB device i have without a PC.