Problem: With the huge range of USB chargers available and their various power ratings, how do you know which is the best one for your device? How do you know your charger is really fast-charging your device? How do you know which chargers are compatible?
I was wondering how to measure USB charging current. I thought of splicing a multimeter into a USB cable, or getting a clamp ammeter. But I wasn’t confident of my skills in electronics. I couldn’t find any such devices online. I considered asking someone on the Dope to make one for me.
Well, I just found one: PortPilot, a crowdfunding campaign on Indiegogo. About the size of a large USB memory stick, with 1 male and 1 female USB port. It comes in 2 versions, the normal version has LEDs showing the type of charger and charging current as 0.5, 1, 1.5 or 2A. The pro version has a backlit dot-matrix LCD showing voltage and current (to 0.01V and 0.01A, apparently).
This sounds awesome! In case anybody else is wondering about these things as well.
For something like a charger, wouldn’t the relevant units be watts, in which case, don’t you need the charger to under a load to measure that accurately? Then I think you measure the voltage times the amperage. For car battery chargers I’ve seen that as RMS. I assume that this is the same. But I just looked up what setting that would be on a multimeter and it seems that most use an average. So I’m not sure how simple this really is.
Yes. Is there any risk to putting a multimeter in a USB cable, or is that something you’d do without batting an eye? Chargers go up to 3A and that seems like a lot for those pointy leads.
Typically a multimeter will have two amp scales one for mA and the other a 10A scale with a fuse.
Problem is many users don’t know to switch the leads and either get the wrong reading or wind up blowing the 10A fuse.
Interesting. The Kickstarter one appears to be:
[ul]
[li]Better funded (>1000%) - maybe Kickstarter is more popular than Indiegogo[/li][li]Cheaper[/li][li]Uses LEDs to indicate current, like the non-pro version of PortPilot[/li][li]Supports data transfer[/li][li]Comes with cables containing circuitry to tell the device this is a fast-charging port - like the iHustler (http://www.chaosoul.com/showpro.asp?id=564&lb=43)[/li][/ul]
So, the PortPilot Pro has these advantages over a multimeter:
[ul]
[li]Measures current and voltage simultaneously[/li][li]Measures total energy passed[/li][li]Identifies charger type[/li][li]Emulate another charger type[/li][li]Can be used as a programmable fuse[/li][li]Connect and disconnect via software[/li][li]Blocks data transfer - which is supposed to be a security feature, but I’m not too worried about this[/li][/ul]
With all the various USB wall warts, outlets and whatever I would be interested in how clean is the DC voltage. In other words how much AC ripple is there.
Is this mostly for phones? Because AFAIK most devices don’t care, as they’re all 5V, as long as the adapter’s amps are >= what the device requires. This was explained to me once upon a time. But I believe some phones bitch at you, but I don’t know if there’s any performance hit.
All I know is that the Kindle takes forever with 200mA, and goes fast with 2000+mA (now can someone tell me where I put that damn charger!?)
Some chargers fool your iPad into thinking they’re capable of 2A, but only deliver 500mA. You can’t tell unless you time your iPad’s charging. I want to make sure I’m getting what I paid for, and which is the fastest way to charge.
You probably don’t need this because you have a better multimeter, maybe an oscilloscope, and you know what “22 kΩ pullup” means. This must seem like a toy to you.
It’s more for power hungry devices, where the current can vary by 4 times depending on the charger. This may or may not also be related to the woman who may or may not have been killed by her charging iPhone 4/5.