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Tengentially, a question: USB PD iis supposed to allow you to use USB-c for up to 240w, but I start feeling uncomfortable at way lower wattages. The connector j

by bjoli 3y ago

Tengentially, a question: USB PD iis supposed to allow you to use USB-c for up to 240w, but I start feeling uncomfortable at way lower wattages. The connector just seems too small and flimsy. The wires are fine, so much I understand, but is it really sensible?

lxgr 3y ago
240W are reached using higher voltages (48V@5A), not higher currents, compared to 100W (20W@5A). The only real concern is arcing while making or breaking a connection, and the 48V mode has special provisions to avoid that, including the cable having to have provisions to make the the control pins are disconnected before the power pins to give the power supply time to lower the voltage.
- jackvalentine 3y ago
  I know very little about USB-C or PD. Two of my laptops give me a physical 'buzz' sensation when charging via USB-C. Is this because they're not grounded? Should I be worried about the issue at higher wattages?
  - lxgr 3y ago
    Most USB-C (and other laptop chargers, for that matter) are of the double-insulated/"Class 2" variety. This means that they're galvanically separated from the primary circuit and not grounded to a protective earth conductor. For EMI reasons, there needs to be a connection (via a very small capacitor) to the primary side. This creates a measurable, and as you've noticed sometimes even physically detectable, voltage leak from the primary side, but is completely harmless since it can't actually sustain any meaningful current. More details here: https://electronics.stackexchange.com/a/216967/23924 https://electronics.stackexchange.com/a/216967/23924 If it really bothers you, you can get a three-prong USB-C power adapter. These can just ground the EMI to protective earth, and you won't feel anything. You can convert most Apple laptop power supplies into one by using a properly grounded cable, for example; they have a grounding connector (which is not connected to anything using the regular duck head adapters, though – hence the phenomenon of "buzzing MacBooks"). The phenomenon of being able to sense it using your fingers is called "electrovibration" and is actually quite fascinating. There's research into being able to use it as a form of haptic UI feedback!
    - rubatuga 3y ago
      If you want a three-prong USB-C power adapter, options include Apple, Dell and HP.
      - jackvalentine 3y ago
        Found this one just before - https://satechi.net/products/6-port-gan-charger https://satechi.net/products/6-port-gan-charger

by bjoli 3y ago

lxgr 3y ago

240W are reached using higher voltages (48V@5A), not higher currents, compared to 100W (20W@5A). The only real concern is arcing while making or breaking a connection, and the 48V mode has special provisions to avoid that, including the cable having to have provisions to make the the control pins are disconnected before the power pins to give the power supply time to lower the voltage.

jackvalentine 3y ago
I know very little about USB-C or PD. Two of my laptops give me a physical 'buzz' sensation when charging via USB-C. Is this because they're not grounded? Should I be worried about the issue at higher wattages?
- lxgr 3y ago
  Most USB-C (and other laptop chargers, for that matter) are of the double-insulated/"Class 2" variety. This means that they're galvanically separated from the primary circuit and not grounded to a protective earth conductor. For EMI reasons, there needs to be a connection (via a very small capacitor) to the primary side. This creates a measurable, and as you've noticed sometimes even physically detectable, voltage leak from the primary side, but is completely harmless since it can't actually sustain any meaningful current. More details here: https://electronics.stackexchange.com/a/216967/23924 https://electronics.stackexchange.com/a/216967/23924 If it really bothers you, you can get a three-prong USB-C power adapter. These can just ground the EMI to protective earth, and you won't feel anything. You can convert most Apple laptop power supplies into one by using a properly grounded cable, for example; they have a grounding connector (which is not connected to anything using the regular duck head adapters, though – hence the phenomenon of "buzzing MacBooks"). The phenomenon of being able to sense it using your fingers is called "electrovibration" and is actually quite fascinating. There's research into being able to use it as a form of haptic UI feedback!
  - rubatuga 3y ago
    If you want a three-prong USB-C power adapter, options include Apple, Dell and HP.
    - jackvalentine 3y ago
      Found this one just before - https://satechi.net/products/6-port-gan-charger https://satechi.net/products/6-port-gan-charger