I have a body cam which charges from a usb I currently charge from my PC but I dont know what the output is. The bodycam manual states DC-5V>=500mA I have a charger plug with usb socket but this states 5V: 1.2A. Would the charger plug cook the bodycam or would it be ok to use?
ss snipped-for-privacy@hotmail.com wrote in news:poTRH.44237$ snipped-for-privacy@fx08.ams:
That will be fine, the bodycam is saying that the charger should be able to supply 5V at greater than or equal to 500mA. Your 5V 1.2A charger meets that condition as it can supply 5V greater than 500mA so no problem.
The charger simply outputs a constant 5V and using one capable of supplying a larger current for say a fast charging phone will do no harm.
Thank you.
It should be OK. 500mA is the maximum you can draw from a computer USB2 socket but adapters with USB sockets for charging are often capable of supplying more Usually about 1.5A max). It is the voltage rather than current capability which matters. At 5V the camera will draw what it needs from the adapter up to 500mA. Plugging the camera into a stand alone USB charger will not draw any greater current or overcharge the camera.
USB seems to be a pretty decent way of powering such things. Provided the power supply is adequate. One capable of more current than needed isn't going to matter. Too small would.
There are some USB chargers (the one supplied with my Samsung phone is an example) which can supply *either* 5V or 9V. The latter is how it achieves "fast charging" of the phone. However it requires the device and the charger to negotiate that they support this. Any device which doesn't negotiate it will receive the default 5V at whatever current it needs up to the maximum of the charger which I around 1.5 - 2 A.
No, it'll be fine - it will only draw what it needs to charge itself.
The USB port has a maximum current limit, your USB device has a current limit - the lower of the two decides the charge rate.
OK to use.
500mA load will use 41.6% capacity of charging source (1.2A). Well within bounds.*******
Here are some general data points.
Type Book Rate Typically available Protocol (power src may limit)
USB2 port 5V @ 500mA 5V @ 1100mA None
USB3 port 5V @ 900mA 5V @ 2000mA None
ChargePort 5V @ 2000mA 5V @ 2000mA Informal/Proprietary strap resistors
USB-C Varies/huge Varies/huge
USB2 and USB3 by themselves are pretty simple.
The "computer knows the limit", is the Book Rate column.
There is a fuse in the computer, which provides the "do not cross this line" limitation. That's what the larger number is for.
Usually items (your body cam), try to adhere to the book rate. And then the fuse can implement the intended purpose, which is to prevent stuff from getting burned if there is an electrical fault.
*******Some retail motherboards have USB2 or USB3 ports with some colour around the port, to indicate it has special properties.
This can be the ChargePort.
Apple may have done the first of these, biasing the USB D+ and D- to various voltage values, as a "flag" to other equipment, how much more current could be drawn. This allowed pigs, like maybe an Apple iPad, to charge at 5V @ 2 amps.
*******The USB.org standards body noticed what Apple was doing, and of course, they could not leave this topic untouched. In retaliation, they invented huge tomes of electrical specs, for their own negotiation schemes. There are well over 500 pages of bumpf to shovel through, to learn about the new power schemes (only available on really new equipment).
The end result, is the Power spec and charging spec, allows sending up to 100W (if the device wants it), over a USB-C cabling setup.
Some of these designs, there is a negotiation chip near the connector end. And this carries out a protocol, where the electronics "talk amongst themselves" before allowing current to flow.
For the "human victim", this means learning an inordinate amount of tripe about the topic. I could not explain the options to you, even if I wanted to... They're that bad. Maybe a rich guy could afford to "plug in random crap until something works". This makes it pretty hard to look at Chinese tat on Amazon and say with authority, "yes, one of those is what you want".
Whereas with the old USB details, like your question, we can still offer advice and say "yup, OK".
A guy at Google was trying to help people with these new cables, until one day, a "bad" cable ruined the laptop he used to test the cables :-) Which I consider to be the supreme testament to this topic. If the volunteer-advice-giver gets burned equipment, what are the rest of us supposed to do ?
Thank you, USB.org .
Paul
It would be OK I'd imagine as it would be current limited by something in the charger. So many devices come with no actual power brick these days it would be hard to complain that anything recent should not well just work. Brian
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