USB V, I and mAhr meter

On Thu, 19 Feb 2015 20:25:16 +0000 (GMT), Dave Liquorice wrote in :

What's the purpose of the second port (uUSB?) next to the cable inlet? Can you log info from there? ("you can easily scan it") Or indeed from the main cable? Does it also pass through power? ("Can get power from the male connector and Micro USB port")

We used to have Japenglish in our documentation, now we have Chinenglish... :-/

Thanks.

Haven't figured that out and not had time to plug it into a host to see if it has any USB smarts inside, I doubt it has as it doesn't need any. A logging output would be nice but it's not mentioned. I suspect it's an alternative uUSB "standard" power input to use instead of the Type A "male"(*).

Er yes, that's the purpose of it to show the volts and current flowing on the bus. The mAh reading with 10 memories I can imagine being useful for those designing USB powered devices intending to run them from batteries.

Or bung it in your phone/table USB charging lead and see how much current it's taking (thus how fast the charge will be) and how much energy has been transfered.

(*) How you can sex a USB connector where the mating conductors just slide against each other I'm not sure.

Chinglish, actually.

I think you misread, my question was a follow-on from the first; does the secondary port have any power capability? I understand that the documentaion is limited. In any event the device is cheap enough that I might get one to investigate why my Nexus 7 (2013) does not charge well from my office PC.

Thanks.

Like you say cheap enough, but I bought one of the "Charge Doctor" to see why my Qi charger didn't work when used from *some* USB cigar lighters, it didn't help becuse the charger wouldn't work from *any* USB outlets with the Charge Doctor in series ...

Maybe the LCD vs LED display will reduce the current draw enough to help.

It's a power input for sure, so the unit can measure the performance of hardwired uUSB "standard" chargers/PSU's. Just used it between a Pi and power source: PSU > (Type A - uUSB) > Meter > (Type A - uUSB)

Limited as in none supplied with the unit. Bunging the model number KCX-017 into google is far more productive. Still chinglish. B-)

It has no USB smarts as expected. Plugged into linux box lights up, indicates voltage and zero current, nothing new in dmesg, plug memory stick into it, it now shows 0.06 A and dmesg shows the memory stick.

I don't think I've ever seen a host USB or simple power source port that isn't Type A. So you'd plug into the Type A outlet with a Type A to uUSB (or what ever the Nexus 7 uses) lead.

At least it has confirmed why the USB HDD and Pi on the same 2.1 A USB power supply weren't happy. 2.1 A is probably enough current, just, but the voltage sags due to cable length. The Pi doesn't mind but the HDD does. Now is there a fig 8 mains input twin Type A outlet

That'll be because your office PC is an SDP and capable of at 500mA supply. My Nexus 7(2012) takes a long, long time to charge from such a socket. Surprisingly when connected to 2A DCP it charges in about 1/4 of the time.

Here is an image of the PCB and chips. Not sure it will help much. I can't make out the part numbers, but someone else might.

The large part seems to be an HT1621B which is just the LCD driver chip. I can't begin to make out the part number of what is likely to be the CPU to the left.

number

Much better images here:

The other large chip is a PIC16F1933.

Like with sex, one of the things has to go inside the other. Do you need me to draw a picture?

---druck

just

You are missing the point that it is the mating conductive parts of each circuit that determines the sex. In a USB connector the mating conductors only slide against each other, one does not penetrate the other.

The body shells do fit one in the other but that does not determine the sex of the connecter. There are connectors out there where the male or female connection parts can be fitted into either body shell part. Or are even designed such that the connector with pins fits over the matching connector with holes, take a look at cable mounted XLRs joining together. Then look at panel mounted and a cable connector, the sex could be considered to swap if you just used bodyshell.

Andy Burns submitted this idea :

can't see the LED display drawing that much current that it matters, maybe 50mA - ish.

It alternates its display between current and voltage.

But that's 10% of what a "standard"(*) USB port can deliver. Enough such that your measuring kit can have significant effect.

The ones I saw had two line displays.

(*) The wonderful things about standards is that there are so many to choose from.

So in reply to an example where the charge doctor did matter, you say it shouldn't matter? The Qi charger needs a 2A supply and is picky about cables too.

Doesn't the shield count as a conductor?

Dave Liquorice formulated on Monday :

From a 500mA source it would make a small difference. From a 2amp USB source where the item itself max's out at 1amp, it would make no difference at all.

This might be of help in purchasing decisions:

As the load resistor is .05R, that 2A should be dropping just 0.1V.