USB "charger doctor" (volt+current display)

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Chloe
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hank wrote:
So which seller has the good soldering job/more recent version?

Well these things can vary but I got mine from Ebay seller estore2009.

fran82
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Thanks for the photos, videos and comments!

I will tell you guys which version is the one that DX sells…. in 2 weeks :_(

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spaceboy
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What do you guys use this for?

fran82
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I will use it to check the voltage drop of the usb 5v when charging/using high powered devices and measuring the current they draw when charging/using…. also checking the quality of the ps

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Werner
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Mine arrived just right now. Sadly I have just loaded all devices to 100%…

But it seems to work, soldering is okay, the shunt is soldered in a bit angled but I see there no problem.

Neat little device.

fran82
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Werner, what do you wanted to say with “Sadly I have just loaded all devices to 100%…”??

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spaceboy
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I think he is saying he cannot test any chargers just now.

gadabout
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spaceboy wrote:
What do you guys use this for?

Among other things, I plan to use it to test / check the output on some small solar panels.

I'm interested to see just how big an efficiency drop I get with changing alignment and levels of light.

Buwuve
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fran82 wrote:
Werner, what do you wanted to say with "Sadly I have just loaded all devices to 100%…"??

 

I think, all his batteries are charged up to 4,2V and he hasn't any other at the moment. Now he has to use a flashlight to get a battery, which must be charged again. The sun will be down here in Germany in maybe an hour Smile

Light up the darkness.

Chloe
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spaceboy wrote:
What do you guys use this for?

It’s handy to measure current draw from USB power sources without having to make something from spare parts and DMM.

Woody
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[quote=Chloe] Well these things can vary but I got mine from Ebay seller estore2009. [/quote=Chloe]

I ordered one from there too – arrived this morning, which is pretty quick considering non-tracked China(?) Post. Neat little tool – thanks for the link Chloe.

fartybum
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Been waiting 33 days for mine, contacted the seller yesterday, he said wait a bit longer Sad , I’ll be claiming when it gets to 40 days.

Chloe
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Woody wrote:
I ordered one from there too – arrived this morning, which is pretty quick considering non-tracked China(?) Post. Neat little tool – thanks for the link Chloe.

Things seem to be getting to me quicker by China Post lately. How is yours? Does it look like the same revision or more like HKJ’s example?

Woody
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Chloe wrote:
Woody wrote:
I ordered one from there too – arrived this morning, which is pretty quick considering non-tracked China(?) Post. Neat little tool – thanks for the link Chloe.

Things seem to be getting to me quicker by China Post lately. How is yours? Does it look like the same revision or more like HKJ’s example?

I haven’t taken it out of the plastic casing, but it looks similar to your picture. It says “CHARGER Doctor” and “3.5V- 7.0V, 0A-3A” on front. Reads 5.06v from my laptop. Only took 11 days to get here – pretty good.

leaftye
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Woody][quote=Chloe] Well these things can vary but I got mine from Ebay seller "estore2009":<a href="http://stores.ebay.com/estore2099">http://stores.ebay.com/estore2099</a>. [/quote=Chloe wrote:
I ordered one from there too - arrived this morning, which is pretty quick considering non-tracked China(?) Post. Neat little tool - thanks for the link Chloe.

I just ordered.  How long did it takes your tester to arrive from this seller?

The low mode should be lower.

Woody
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Mine was ordered 29th August; sent next day, arrived in UK 10th September.

leaftye
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Thanks Woody.  Two weeks sounds good to me.  Hopefully I'm as lucky.

UPDATE: An hour and ten minutes have passed and it's now marked as shipped.

The low mode should be lower.

gadabout
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Mine arrived a couple of days ago.

Unfortunately I didn't realise the display only shows 2 decimal places. Not a problem for most users I imagine, but not quite what I need to check the output from my small solar panels in less than full sun!

Does anyone know of one of these that resolves down to 1mA?

 

Mind you it has been very interesting comparing actual output of various plug packs and battery boxes against their labelled ratings.  Seems there is a whole system of "Chinese mA" I wasn't aware of previously!  Laughing

leaftye
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You could use this and check more easily with your multimeter.  I'd put type A connectors on both ends though.

https://www.tindie.com/products/FriedCircuits/usb-tester/

 

The low mode should be lower.

gadabout
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Thanks leaftye

A little more DIY than the current one but could be workable if I can't find a self-contained all-in-one unit. Smile

Bookmarked!

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leaftye wrote:

You could use this and check more easily with your multimeter.  I'd put type A connectors on both ends though.

https://www.tindie.com/products/FriedCircuits/usb-tester/

 

But you will probably loose more voltage on this one. The "Doctor" has a 0.05ohm resistor to measure the current across, with wiring to the DMM and the resistance in the DMM, you can very easily get above that.

The voltage drop is not really interesting, as long as you are only measuring a few milliampere, but if you use the same setup to measure 500mA or more it will affect the result.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

bguy
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I ordered mine off eBay on 8/15, and got it yesterday. Seller was onzway2010, and cost $2.83 shipped. I have a bunch of multimeters, but this is cheap small and easy.

The main reason I got mine was to check the cheap USB chargers that say they put out higher current. We all know how accurate the specifications are for cheap Chinese products. I have a few to test, one of them is this one:
http://dx.com/p/215107

So far I tested my OEM Galaxy S4 AC charger, I got 1.3 amps. I also tested the S4 on my computer’s USB port, and it’s at 0.32 amps.

I also tested my mouse that has some lights on it. With all of them off it uses 0.04A, and with all of them on, 0.11A.

I do wish it had 3 significant digits, but 10ma resolution will be good enough for the price I paid. I also wish it had a button to switch between V and A. Most of the time I only want amps.

leaftye
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I ordered mine to test out solar chargers.  I'll be reviewing one soon, and it'd be nice to have an easy way to determine the output.

The low mode should be lower.

gadabout
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leaftye wrote:

I ordered mine to test out solar chargers.  I'll be reviewing one soon, and it'd be nice to have an easy way to determine the output.

As long as you test in bright sunshine you will probably be OK.

The past couple of days here (since I got my parcel) as luck would have it has been mostly overcast. 

I thought solar panels were supposed to generate close to their rated voltage even in poor conditions, but giving very low currents.  Now I'm not so sure if this is correct.

These meters only read from 3V upwards and when testing on some of my small panels with 5V USB output, I couldn't seem to get any display at all.   Perhaps it depends on the load I apply.

Also, quick heads-up - the display is very, very dim when trying to view it outdoors.  You might need to use an extension cable and put the meter in box of some kind or shroud it in your palm in order to be able to read it.

spaceboy
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Mine arrived today.

Been using it on my Samsung Galaxy Note 2 charger:

5.25V and 1.60A when Note 2 is switched off. Nearing full capacity it has dropped to 0.3A, voltage varies between about 5.25V and 5.30V

Now dropped to 0.25A…

biggulp
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I bought one too but have no way to know how accurate it is. How do you measure the accuracy of it?

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biggulp wrote:
I bought one too but have no way to know how accurate it is. How do you measure the accuracy of it?

Depends on how accurately you want to measure the accuracy. Wink

Generally you will need some known reference to test it against, but if you don’t have a good understanding of measurement chances are you will do some part of the measurement wrong, or introduce errors.

Don’t worry about it, might be a good way to go.

Still a bit dim

Werner
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Like I said it measures with a resistor so it may change thechargingprocess on some devices…so watch out the current with device in between could be lower than without…

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Nothing is going to directly use the “about” 5v from the USB to charge a battery, so a 0.125v drop should make no difference other than “maybe” a couple percent less max current draw, nothing anyone would notice, or most could likely measure.

Most meters use a shunt, a very small resistor placed in series, then measure the voltage drop and calculate the current flow from that, so nothing unusual about the method.

Still a bit dim

HKJ
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Danglerb wrote:
Nothing is going to directly use the "about" 5v from the USB to charge a battery, so a 0.125v drop should make no difference other than "maybe" a couple percent less max current draw, nothing anyone would notice, or most could likely measure.

UNI-T UT61E has a drop of up to 1.1 volt when measuring mA, I would say that is significant.

Danglerb wrote:
Most meters use a shunt, a very small resistor placed in series, then measure the voltage drop and calculate the current flow from that, so nothing unusual about the method.

The shunt resistor is not that small in all meters, especially on the mA and uA range it will be larger and a drop of 0.5 volt is not uncommon when close to maximum current in a range.

On top of that you have to add the loss in connections and cables, this is insignificant at a few mA, but at higher currents it will be significant.

For people that know their DMM and what they do, it is easy to work around some of these voltage drops (One way is to buy the uCurrent adapter from EEVBlog).

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

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