Anyone know the maximum voltage that can be safely fed in via the USB connection? Mostly interested in Uno and Nano.
Thank you
Alan
I think the USB spec says 5.25V
AWOL:
I think the USB spec says 5.25V
That sounds like the maximum a USB will put out. Is that the same as how much the Arduinio will tolerate... or is it 6v, 7v, 10v... on the USB power pins.... without a) blowing up or b) affecting its life expectancy?
That sounds like the maximum a USB will put out
That's right - any more than that, and it isn't USB, QED.
The power isn't coming from a USB source. It has a USB plug on the end though.
The power isn't coming from a USB source. It has a USB plug on the end though.
So, it isn't a USB connection.
Have a look at the schematic - see how much protection there is between USBVCC and the porcessor.
AWOL:
The power isn't coming from a USB source. It has a USB plug on the end though.
So, it isn't a USB connection.
Have a look at the schematic - see how much protection there is between USBVCC and the porcessor.
I looked at the schematic and my electronics knowledge doesn't extend to working this out from it.
Can anyone just tell me the voltage?
Cheers Alan
See reply #1.
The most you could apply to the processor is 5.5V, so 5.25V gives you a little margin.
You'll need regulated 5V. It should be able to supply minimum 500mA for full current load (per port).
From here, it says "When operating at a full unit load, a minimum VBUS of 4.75 V is specified with a maximum of 5.25V".
3V to 5.6
some laptop have a higher AMP and always there is a spark logo on the port, its the better port if you want use it for the arduino
i don't think there is a usb charger higher than 5.6 !!
I have a USB plug used for supplying power to things... no data pins connected.
I also have USB sockets for receiving this power, again with no data pins connected.
Sometimes 6v and sometimes 9v. I was hoping that the Arduino wouldn't bust apart if I plugged 6v or even 9v into the USB port power pins just as if I was powering via Vin.
oh ok,
Sometimes 6v and sometimes 9v !!
use the arduino power jack and you will be safe XD
i burn arduino uno days ago, i used solar cell charger 9V, connect it to the usb port,
but i am not sure is that from the voltage or AMPs
so just try XD
USB power goes thru 500mA PTC (fuse) then direct to 5V power line.
Don't drive it with more than 5.5V.
6V and above you exceed the uC Absolute Max voltage.
For 7.5V & higher, use the barrel jack.
Under 7.5V, the reverse polarity diode knocks down the voltage to point where the regulator maybe not have enough voltage to regulate any more.
My Nano is going inside a project box so was looking for a sneaky way to use my existing power supply options and minimise making more holes and sockets to get power in for when its not connected to a PC... which is most of the time.
cut the usb wire, solder it to power jack and that's it
i think its more easy to open a hole than cutting a square in the box
http://absba8.absba.org/teamwork10/Hardware%20UUpdate/03/03.jpg
This is what I ended up doing...
A 2" x 3" x 1" project box, a 2.1mm power socket fitted and connected to the input of a USB car charger. The charger was stripped out and fitted inside the box as well connected to the input socket. I chose a charger from three different ones I took apart. This one had a much more sophisticated circuit based on a chip (whose ID I've forgotten 
but allows 6v - 40v input, resistors, inductor, capacitor and a nice little LED and capabe of delivering upto 1.5 amps - so plenty in reserve) over a very simple one with one voltage regulator chip, one resistor, one tiny capacitor and an LED.
Power comes out on the USB micro that is attached to the USB charger.
Also, I added a 9v battery insure the project box connected to the input jack in such a way that it is powering the USB charger only when a plug is NOT in the socket. So this doesn't power all the time there is no external plug I have also added a small slide switch.
I can plug my unstabilised wall power supply into the socket, a 6V upwards battery pack or use the internal battery.
It is also possible to switch the internal 9v on and unplug the external supply without causing the Nano to reboot. If I'm fast I can also plug the external supply in without it rebooting. That's the larger capacitor keeping things running while the switch is made.
All this came from the parts bin so I'm very happy 
with my standalone Nano 'power pack' which can be reused with other projects and with adaptors powers my Unos, Megas and home built Arduinos using a standard USB Serial in adapator, and is robust enough to be handled (no more breadboard wobbles).