Author Topic: USB leads for bench PSU?  (Read 240 times)

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Offline Technomancer

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USB leads for bench PSU?
« on: May 08, 2020, 11:16:05 pm »
I am looking to do some work on small devices that are powered/charged over USB ports. Is there a cable kit available to go from banana plugs to USB (USB C, micro USB, etc.) or do people usually just buy the banana plugs, get a USB cable to cut the end off of, and make their own?
It feels like this should be something easy to come by but I was either using the wrong search terms or am woefully ignorant of how something like that actually works, hence no one selling such a thing. Any information would be appreciated.
 

Offline Brumby

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Re: USB leads for bench PSU?
« Reply #1 on: May 08, 2020, 11:50:03 pm »
You could try searching on "USB breakout".  This will get you a number of items that have a USB socket and solder pins ready to do what you describe.

BUT - Be careful when working with USB power.  It is not always a simple matter of joining wires to a supply.  Look up USB Power Delivery for a bit of a head spin.
 

Offline JxR

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Re: USB leads for bench PSU?
« Reply #2 on: May 08, 2020, 11:57:46 pm »
There is wonky stuff like this all over ebay, Amazon, alliexpress:
[attach=1]

As to the scarcity of such cables...I would guess it is due to the fact that they are not very useful.  If it is something you really need, I would just make your own.  It is not uncommon for some devices to require some kind of communication/hand-shake between itself and it's charger.  Your power supply cannot provide that hand-shake.

I think I was able to make a cable that could charge my phone a couple years ago.  It required putting a 1k/10k resistor across the D+/D- lines.  But all your really looking at is the charge current of the device with such a cable.  You would need to open it up and replace the battery with your power supply if you were interested in something like the sleep/idle current.

In the end, it really just depends on what you are trying to accomplish/measure.
« Last Edit: May 09, 2020, 12:08:53 am by JxR »
 

Offline Technomancer

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Re: USB leads for bench PSU?
« Reply #3 on: May 09, 2020, 12:18:49 am »
Thanks for the info. What I am looking to do is repair things like Blue tooth headphones that have a USB charging port and handheld game consoles with internal batteries that are charged over USB or some proprietary connector. It makes sense that I would hook the PSU up in place of the battery to test the unit but then how do people typically test the charging circuit? Given the issues with the handshake I assume you just have to trust that your charger is working correctly and hook a meter up between the charger and the device to get a reading there.
« Last Edit: May 09, 2020, 12:23:16 am by Technomancer »
 

Offline JxR

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Re: USB leads for bench PSU?
« Reply #4 on: May 09, 2020, 12:32:09 am »
Thanks for the info. What I am looking to do is repair things like Blue tooth headphones that have a USB charging port and handheld game consoles with internal batteries that are charged over USB or some proprietary connector. It makes sense that I would hook the PSU up in place of the battery to test the unit but then how do people typically test the charging circuit? Given the issues with the handshake I assume you just have to trust that your charger is working correctly and hook a meter up between the charger and the device to get a reading there.

You could just measure the current between the battery and the charger by breaking one of the connections and routing it through your meter.  As to the "handshake" part, you may not know until you try, certainly not everything is setup like that.  Just wanted to point out that sometimes there is more to the charger than just providing it an alternative voltage source like your power supply.
 

Offline JxR

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Re: USB leads for bench PSU?
« Reply #5 on: May 09, 2020, 12:51:28 am »
Have you seen these types of things before?  I've never used one so I can't vouch for them, but seems pretty useful for a quick insight into power consumption/charging before you even have to open the device:

https://www.amazon.com/Eversame-Multimeter-Voltmeter-Indicator-DC3-6-30V/dp/B07JYVPLLJ/ref=sr_1_3?dchild=1&keywords=USB+Tester&qid=1588985338&s=hi&sr=1-3

There are tons of them in different flavors, so I would look around if it looks useful.
 

Offline Technomancer

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Re: USB leads for bench PSU?
« Reply #6 on: May 09, 2020, 12:57:08 am »
I was actually just looking at that same model on Amazon. I think I am going to have to pick one of those up to make things a bit easier. Thanks!
 


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