Comment by Eisenstein | Hacker News Reader

Comment by Eisenstein | Hacker News Reader

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Don't use magnetic USB adapters. They run a decent risk of frying your device. The USB-C spec was not designed to have the connection broken in that way. You will have no issues 99% of the time, but you will eventually have that time when your device gets fried. It takes a very precise design and a lot of clever engineering to have a high-current power connector with tiny pins be able to break without having the ground be the last connection to be broken.

It is also easy for the magnetic connector to short the power into a data line, and because it doesn't connect in the proper pin order and has no 'mid-plate' it has no mitigation against arcing. See this picture:

* https://imgur.com/a/bMvYtfy

Notice how some pins are longer than others? They are designed that way so that they connect first and disconnect last, so that ground is always established before and after other pins connect. This prevents connecting and disconnecting a cable from frying your electronics.

"The mid-plate shall be connected to the PCB ground with at least two grounding points. The mid-plate shall be designed such that plug pins A4, A5, A6, A7, A8, A9, and B4, B5, B6, B7, B8, B9 do not short to ground during the connector mating process with an effective 6.2 mm receptacle shell implementation." [1]

[0] USB Type-C Spec R2.2 - October 2022, Figure 3-13, Page 65.

[1] USB Type-C Spec R2.2 - October 2022, Section 3.2.1 Interface Definition, Page 43.

* https://www.usb.org/document-library/usb-type-cr-cable-and-c...

Thanks for the heads up. This is a useful warning, as the magnetic adapters seem attractive, but they are not worth it if they risk frying your device.

They're worth it if the risk is small and the device is relatively cheap and low power (5v charging). I'm not going to use these on my MacBook or phone with fast charging but I'll use them on my gamepad and headphones no problem. And I use them for charging only, not data.

I fried a hub, a wall charger, and the USB ports on my monitor before I identified my magnetic USB-C connector as the problem.

A power-only (2 wire) magnetic USB-C cable will be as safe as prior generation magnetic USB cables (it won't be more likely to damage your device)

I’m comfortable using the round two pin charging ones for things that only use the port for charging, not data, like mice, headphones, radios and speakers.

The data ones are almost universally sketchy, as they expose pins (and sensitive internal circuitry) that should absolutely be kept away from the outside world.

There is an emerging range that reduce the exposure somewhat, but I’m still wary.

Sure, it will be safe because it won't be able to go above 5V 3.0A (15W) at absolute max since it won't be negotiating PD. Most likely it won't have the proper termination resistors on the CC line and will get a whopping 900mA@5V = 4.5W

* https://i.imgur.com/n3IjcQE.png

I encourage everyone to actually read the USB 3.2/C/PD spec sheets.

15W (and even 4.5W) sound like enough for charging stuff like controllers, headphones and whatever other small battery-powered devices one has. (Also, do devices like that actually respect that 900mA thing, assuming they're capable of pulling that much power?)

Aside from that: It's obviously not enough for a laptop, but what other devices do you really need that much more for in your day-to-day life? I think I haven't used a USB charger capable of outputting more than 10W in a while (aside from my Nintendo Switch and its charging brick, but because of the dock it wouldn't make much sense to use a magnet adapter anyway). At home, there's always a charger nearby, and when I leave the house my phone usually has enough power anyways, or the trip is long enough for me to throw a powerbank in my backpack no matter how full the phone battery is.

And if you end up in a situation where you really need to quick-charge something, there's nothing stopping you from just taking the plug out for a short while.

The thing is that USB-C was designed to be the universal connector, for both high and low power devices, for charging and data. Should there be a qualification: 'use the specification and standards violating magnetic adapters IF your device is X and not Y or else your macbook might get toasted and btw your warranty is now void for using it.'

Or, just 'don't use shady spec violating components that don't exist in spec for good reasons'?

> Also, do devices like that actually respect that 900mA thing, assuming they're capable of pulling that much power?

USB-C will not 'give it' power unless it conforms to certain parameters like having a resistor on the CC line. This is the reason that crappy devices which merely changed the physical ports from micro-USB to USB-C and come with a USB-C (device end) to USB-A (charge end) will not charge with a USB-C to USB-C cable. The device never got updated to request the power and the USB-C port on the charger just ignores it.

Among the neurotic optimizations I’ve made to my cable setup - retracting USB-C cables and normal cables of any length, adapters for any and all devices I own - I have avoided magnetic adapters for the above reasons.

How did you make retracting cables?

You just buy them. I wouldn't trust them for high-power or high-drain devices, personally, but you can just search amazon and see what they have.

As the other poster said, I just buy them, but I’m in Japan and also pick up these cable organizers for the cost of an American candy bar (¥190): https://www.amazon.com/MUJI-Cable-Smart-Phone-Stand/dp/B097R...

I stopped using magnetic USB adapters when I noticed some sort of interference from them was causing other USB devices from being properly connected. Windows wouldn't recognize or detect the devices.

It could've also been the USB hub I was using, but the problem disappeared once I changed the USB cable with magnetic adapters to a cable with ordinary connectors.

I use some magnetic tips, but only for all my non-USB-C.

Almost everything I have now uses USB-C. The few micro USB and Lightning devices hanging around don’t have the same high current concerns.

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