Ask Electronics

3290 readers

1 users here now

For questions about component-level electronic circuits, tools and equipment.

Rules

1: Be nice.

2: Be on-topic (eg: Electronic, not electrical).

3: No commercial stuff, buying, selling or valuations.

4: Be safe.

founded 1 year ago

MODERATORS

DavideAndrea@discuss.tchncs.de

linker3000@discuss.tchncs.de

What’s the easiest way to pull ~30mA from a USB 3 port without getting a warning from Windows? (lemmy.world)

submitted 2 weeks ago by ch00f@lemmy.world to c/askelectronics@discuss.tchncs.de

11 comments fedilink hide all child comments

Back in my day, you could usually sip a few mA from a USB2 port without any trouble.

When I try that now, Windows pops up with a “device not recognized” error. I know you can draw up to 150mA before enumeration, but it looks like after some time, Windows will complain that you haven’t enumerated yet.

Is there an easy way to keep from getting this error without having to actually make the device smart?

I’m hoping for something dumb along the lines of USB-PD but facing the other direction. For the record, it has to work on a USB-A port, so USB-C hacks won’t work.

top 11 comments

sorted by: hot top controversial new old

[–] carzian@lemmy.ml 7 points 2 weeks ago

Buy the 5 dollariest arduino?

[–] zurohki@aussie.zone 7 points 2 weeks ago (1 children)

One of the QC 2.0 type-A trigger boards?

https://www.aliexpress.com/item/1005006449224730.html

A picture of a PCB with a USB port, voltage selector and DC output

[–] ch00f@lemmy.world 3 points 2 weeks ago (1 children)

I think that’s a Qualcomm proprietary thing that isn’t supported by standard USB downward facing ports.

[–] zurohki@aussie.zone 4 points 2 weeks ago

QC 2.0 is proprietary but it would probably still be identified as a device on a standard USB port. For $2 it's probably worth giving one a try, anyway.

[–] Darkassassin07@lemmy.ca 4 points 2 weeks ago (1 children)

Do you get the same issue if you short the data lines? That's usually the indication (to devices) that the port is for charging only; not sure how thats received in the reverse direction.

[–] zurohki@aussie.zone 3 points 2 weeks ago (1 children)

Looking at the PD spec I got the impression devices are supposed to pull the D+ pin up to a certain voltage, but I got lost partway through.

OP asked for the easiest way and deciphering the spec docs probably isn't it.

[–] Darkassassin07@lemmy.ca 3 points 2 weeks ago* (last edited 2 weeks ago)

For power delivery, ie requesting power outside the typical 5v 3a max; yes.

The charger shorting them together usually indicates to the device, it's fixed at 5v 3a.

I think the device shorting them will indicate to the charger/port that you're only requesting power @ 5v 3a max; but I haven't dived into the spec.

I'd give that a try and dig further if it doesn't work.

[–] Gurfaild@feddit.org 3 points 2 weeks ago

If the computer has a PS/2 port that you aren't using, you could probably power the device by plugging it into a passive USB adapter like the ones that came with older keyboards and mice.

[–] linearchaos@lemmy.world 3 points 2 weeks ago

I probably just run a tap off of a thumb drive.

[–] n3m37h@sh.itjust.works 2 points 2 weeks ago

Mobo not have internal USB headers?