Request test jig suggestion for microUSB phone charging current

How would you make a test jig out of a spare USB cable?
For $1.99, I bought at Frys today, this 6-foot USB-A to microB USB male-to-male cable.
http://farm3.staticflickr.com/2894/11739074746_d8ebbfe363_o.jpg
http://farm4.staticflickr.com/3770/11738580543_301162631e_o.jpg
If I cut the cable in half, and isolate the wires, how would you recommend I set it up so that it could become a test jig (to see how much charging current a device actually draws)?
Have you done this before and have advice for how to make that jig?
Specifically, how would you fasten the bare wires, which I presume are very very thin, and therefore fragile?
Also, we'd need a way to insert the ammeter inline to measure current.
Any test jig ideas I can benefit from?
NOTE: This is an offshoot of the USB charger thread, where we determined that a 3.1 Amp dual-USB charger that is 10 Watts is very different than the same spec at 15 Watts.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
: How would you make a test jig out of a spare USB cable? : : For $1.99, I bought at Frys today, this 6-foot USB-A to microB USB : male-to-male cable. :
http://farm3.staticflickr.com/2894/11739074746_d8ebbfe363_o.jpg
:
http://farm4.staticflickr.com/3770/11738580543_301162631e_o.jpg
: : If I cut the cable in half, and isolate the wires, how would you : recommend I set it up so that it could become a test jig : (to see how much charging current a device actually draws)? : : Have you done this before and have advice for how to make that jig? : : Specifically, how would you fasten the bare wires, which I presume : are very very thin, and therefore fragile? : : Also, we'd need a way to insert the ammeter inline to measure : current. : : Any test jig ideas I can benefit from? : : NOTE: This is an offshoot of the USB charger thread, where we : determined that a 3.1 Amp dual-USB charger that is 10 Watts : is very different than the same spec at 15 Watts.
Look on eBay "NEW Universal portable USB power mobile mini Current voltage tester Detector "
Colin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 1/3/2014 2:09 PM, Colin Horsley wrote:

or <http://dx.com/p/usb-av-usb-power-current-voltage-tester-translucent-blue-silver-235090
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 1/3/2014 3:09 PM, sms wrote:

Cool...I was ready to order one until I saw that the data doesn't pass thru. WTF? The connectors are almost touching, why no data? Kinda hard to measure the drain of a disk drive in action when it won't come out of sleep.
Why would you not connect the data unless there were problems?
Anybody bridged the data? Results?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Here's an interesting thing, I've been thinking of getting one: https://www.tindie.com/products/FriedCircuits/usb-tester/
Especially recently as my main phone seems to take a fairly long time to charge sometimes. Doesn't seem to be a specific charger that has problems either.
Basically this USB Tester is just a conveniently shaped PCB with USB connectors and some holes where you can very conveniently attach a multimeter to measure current (or voltage). Data lines pass through and they can also be probed easily.
There's a bundle with a little microcontroller based multimeter too.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 04/01/14 06:09, Colin Horsley wrote:

...or here: http://tinyurl.com/lmvbyl9
About 5 US$ with free shipping to USA.
Werner
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Alexander Y. Sure has written on 1/4/2014 11:21 AM:

Per piece. They sell lots at about $5/piece!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 04 Jan 2014 09:09:54 +1100, Colin Horsley wrote:

Hi Colin, That works, but I was just going to slice a cable in half, and then attach the inner wires to a series of screws.
What I'm thinking is to screw two row of (five?) brass screws into a piece of wood, and then attaching the cable wires to each row.
Then I can either jump the distance with a copper wire, or with the meter leads.
But before I build the test jig, someone might suggest a better platform out of parts commonly found in the garage or shop.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 1/3/2014 4:24 PM, Danny D'Amico wrote:

That works if you never want any data thru it. Better would be to cut the power wire and run that thru a meter. Get out your ohms law calculator and verify that your meter resistance won't defeat you.
Leave all the high speed data wires and ground alone.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 4 Jan 2014 00:24:58 +0000 (UTC), Danny D'Amico
wrote:

voltage tester

attach

Oh lordy. For more than nominal charge currents (or standard supported currents) the thing is "negotiated" with the source device. Get yourself a copy of the Standard, 3.1 is current, older versions can be found.
Start here:
http://www.usb.org/developers/docs/
?-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
josephkk wrote:

Hmm, Jig? Don'have a bread board?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Followups set to sci.electronics.repair .

With a sharp knife, remove 2 inches (50 mm) or so of the outer insulation of the cable, in the middle of the cable. Try hard not to nick the insulation on the four individual wires inside the cable, but if you do, it's not a total disaster.
Next, try to identify the two data wires and the two power wires. Often the data wires will be twisted; the power wires may or may not be. The power wires will also often be one or two wire gauges thicker than the data wires, but not always, and this is kind of hard to tell. The power wires *might* be red and black, but don't count on this.
Pick what you think is one of the power wires and cut it, right in the middle of the stripped part. Strip the cut wire ends 1/4" (6 mm) or so. Get your multimeter and test between all four contacts on the big (PC) end of the cable, and the stripped wire that comes from that connector. It may help to use a paper clip or other small piece of solid wire to touch the contacts in the USB connector if the multimeter probe won't fit.
If the stripped wire is continuous with only one of the two outside contacts in the USB plug, you did indeed cut one of the power wires.
If the stripped wire is continuous with only one of the two inside contacts (it doesn't matter which one), you picked a data wire; solder the stripped ends back together, insulate with a small amount of tape (electrical tape is ideal, Scotch tape will work fine for this), and pick another wire.
If the stripped wire is continuous with more than one contact, then you probably nicked the insulation on more than one wire when you were initially stripping the cable - find the places that are touching and separate them, and maybe insulate the bare spots individually with tape.
Once you have figured out that you did indeed cut the power wire, you can figure out how to hook the power wire up to your multimeter. Your meter may have come with alligator clips that go on the probe ends; if you have those, use them. What I use for things like this, because I already own some, are clip leads - short stranded wires with alligator clips on each end. Rat Shock 278-1157 or 278-1156 are typical; Fry's probably has a better price on similar products. http://www.radioshack.com/product/index.jsp?productId 62661 http://www.radioshack.com/product/index.jsp?productId 62660
If you have alligator clips that fit your meter probes, put them on the probes. If you have a digital meter, clip one probe to one stripped wire and the other probe to the other one - it does not matter which way around the red and black wires are. If you get the probes "backwards", you will get exactly the same current reading, just with a minus sign in front of it. If you have an analog meter, you have to get the probes the right way around, but IIRC you have a digital one.
If you have clip leads, clip a red clip lead to the red probe of your meter and to one of the stripped wire ends. Clip a black clip lead to the black probe of your meter and to the other stripped wire again. As above, if you have a digital meter, it does not matter which way around the red and black wires are.
Next, figure out how to make your multimeter measure current. With the meters most people have, you need to rotate a dial to an "A DC" range, and move the red meter lead over to a different jack on the meter. Do whatever you need to for your particular meter.
Plug the mini-USB end into your peripheral (external hard drive or whatever). Put the peripheral somewhere close to the meter, so you can watch it and the meter at the same time. While watching both the peripheral and the meter, plug the PC end of the USB cable into the PC.
If all is well, the peripheral should come on (hard drive spins up / LED comes on / whatever), and the meter should show some amount of current. If nothing is happening, or if you smell smoke, unplug the USB cable from the PC immediately and investigate. If the peripheral draws "too much" current, the PC may shut down that particular USB port; this isn't permanent, but sometimes it takes a reboot to re-enable the port.
Don't be surprised if the current jumps around some as the device operates. Even "simple" stuff like keyboards will draw slightly different amounts of current when you are typing vs not, or when (say) the Caps Lock LED is on, or whatever. If your meter has a "max hold" or "peak hold" function, that can be useful to capture the highest current reading the meter sees. Some peripherals will have a current rating printed on them, but this is usually the maximum current it will ever draw - it won't usually draw that much continuously.
When you are done measuring current with your multimeter, disconnect the leads from the circuit, and *IMMEDIATELY* move the red lead back over to its regular socket - don't wait until later to move it back. The reason is that in the amps range, the meter is nearly a dead short. It's *easy* to measure current and then try to measure voltage without moving the lead back, and blow the fuse in the meter. I've watched it being done and I've even done it myself.
Standard disclaimers apply: I don't get money or other consideration from any companies mentioned.
Matt Roberds
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.