USB Power Delivery: Plugging into the Benefits • Hacker News Board

Re: USB Power Delivery: Plugging into the Benefits

#121

Post by smallmancontrov » Mon, Jun 15, 2026, 5:07 PM UTC

Havoc wrote: post #112

smallmancontrov wrote: post #12

Speaking of which, does anyone know a line of PD Decoy modules to convert barrel jacks to USB-C without the atrocious behavior of "oh, the charger doesn't have 12V, here's 9V have fun!" that the early ones all did? Ideally I'd like a little red light to come on or something, but I'd settle for not silently browning out the device.

Don’t think you’ll find it cause it’s not an issue with the decoy - that’s the expected behaviour. 12v isn’t mandatory. Which is insane but here we are. On the plus side some of the bottom tier anker chargers will do 12v. Plus I think the very new PPS ones should too

Transistors exist. Load switches exist. Looking at Digikey, the expensive ones cost $1 in quantity. I'd pay considerably more than $1 per unit to have this feature that I consider necessary for a minimum viable adapter. Based on these comments, though, TAM is probably tiny.

Re: USB Power Delivery: Plugging into the Benefits

#122

Post by theragra » Mon, Jun 15, 2026, 5:10 PM UTC

jeffbee wrote: post #69

Animats wrote: post #11

240 watts over a USB-C connector? What next, USB toasters and coffee pots?

You joke, but this is enough to make recharging an e-bike practical. E.g. https://amplerbikes.com/pages/nova

This is my dream. To reverse engineer my bikes charger and create an USB pd to take with me on a self-sustained trips.

Re: USB Power Delivery: Plugging into the Benefits

#123

Post by Havoc » Mon, Jun 15, 2026, 5:14 PM UTC

smallmancontrov wrote: post #121

Havoc wrote: post #112

Earlier quoted context omitted.

Don’t think you’ll find it cause it’s not an issue with the decoy - that’s the expected behaviour. 12v isn’t mandatory. Which is insane but here we are. On the plus side some of the bottom tier anker chargers will do 12v. Plus I think the very new PPS ones should too

Transistors exist. Load switches exist. Looking at Digikey, the expensive ones cost $1 in quantity. I'd pay considerably more than $1 per unit to have this feature that I consider necessary for a minimum viable adapter. Based on these comments, though, TAM is probably tiny.

Think with these low end decoy triggers you’re lucky if it implements standard never mind the optional parts.

You could always request a non optional feature and convert it up/down yourself

Re: USB Power Delivery: Plugging into the Benefits

#124

Post by smallmancontrov » Mon, Jun 15, 2026, 6:08 PM UTC

Havoc wrote: post #123

smallmancontrov wrote: post #121

Earlier quoted context omitted.

Transistors exist. Load switches exist. Looking at Digikey, the expensive ones cost $1 in quantity. I'd pay considerably more than $1 per unit to have this feature that I consider necessary for a minimum viable adapter. Based on these comments, though, TAM is probably tiny.

Think with these low end decoy triggers you’re lucky if it implements standard never mind the optional parts. You could always request a non optional feature and convert it up/down yourself

Yes, this is one of those "I can't believe I'm considering making it" things. I might actually go forward if I had the slightest confidence I could sell it and amortize my time, but looking at the comments here, who not only didn't understand the problem but didn't understand the problem after having it explained to them -- TAM is tiny, it'll never amortize. Sometimes you just have to scratch an itch, though.

Re: USB Power Delivery: Plugging into the Benefits

#125

Post by v1ne » Mon, Jun 15, 2026, 7:32 PM UTC

sysguest wrote: post #101

security-wise, usb-c is the worst scenario device I've ever seen -- unless you're Apple, you can't make a security-boundary without infringing patent US11205021B2 for laptops, a bad-actor usb-c cable/charger can do so much more, unless your laptop has AI that can distinguish "is this signal really coming from monitor/keyboard/etc ?" I'd rather have plain-old DC adapters (or usbc to dc)

"USB data blocker" on AliExpress yields you very small adapters that enable you to run USB-PD, but block the data lines.

Re: USB Power Delivery: Plugging into the Benefits

#126

Post by [deleted] » Tue, Jun 16, 2026, 3:18 PM UTC

myself248 wrote: post #106

wpm wrote: post #94

Earlier quoted context omitted.

If the board had unpopulated 0802 pads, I absolutely would be.

Yeah, it's a significantly trickier proposition when the pads aren't there. The contacts are in the connector, you just need to bring them out and get the resistor on them, which is frankly a pain I shouldn't have to endure when USB-C has been out for 12 years. None of this is rocket science, the manufacturers just aren't feeling the pain.

[deleted]

Re: USB Power Delivery: Plugging into the Benefits

#127

Post by SAI_Peregrinus » Wed, Jun 17, 2026, 1:37 PM UTC

exmadscientist wrote: post #89

ssl-3 wrote: post #84

Earlier quoted context omitted.

That's close, but it's not quite complete. There seems to be lots of confusion here, and that's natural: It is confusing. For just-getting-power from a USB A port into a USB C peripheral: There are supposed to be 2 resistors in the peripheral device [always], and also 1 resistor within the cable for USB-to-legacy cables[1]. That's 3 resistors, total, to get a relatively dumb USB-C equipped peripheral device to reliab…

My point, which matches what you've written out in more detail, is that there's supposed to be stuff (resistors) in the cable, stuff which is often not there. There are plenty of these abhorrent cables in the wild. And when you come across one, things get weird, because some sources and sinks deviate from the standard in ways that make them work with these bad cables. Others don't do that. (I believe there were a lot…

Resistors don't go in the cable. They go in the device. They indicate that the device can't negotiate voltages above 5V, so just send 5V.

USB-A has no ability to provide voltages other than 5V, so there's no need for indicating it's the max.

Not all chargers have USB-A ports. Many laptops don't have USB-A ports, so if you want to charge a noncompliant device from a laptop it won't work. Or a laptop charger, which is dedicated USB-C.