Open EternityForest opened 1 year ago
mortenmoulder
commented
11 months ago Adding my two cents here. While I agree that backfeed is an issue, having the option to power external devices right from the VBUS pin is a major advantage. If I had to change anything, I would probably add a 0 ohm resistor as a bridge to a diode, that could be broken/removed to allow power both ways. However that would work out.
EternityForest
commented
11 months ago Why not just a single diode, so that power can go from USB to VBus, but not from VBus back to USB?
One could just add an external diode if they had a local supply they wanted to prevent backfeed into, but an external diode can't prevent VBUS to USB flow, while still allowing VBUS to power the onboard 3.3v regulator.
On Mon, Nov 20, 2023, 4:49 PM Morten Møller @.***> wrote:
Adding my two cents here. While I agree that backfeed is an issue, having the option to power external devices right from the VBUS pin is a major advantage. If I had to change anything, I would probably add a 0 ohm resistor as a bridge to a diode, that could be broken/removed to allow power both ways. However that would work out.
— Reply to this email directly, view it on GitHub https://github.com/wemos/docs/issues/55#issuecomment-1819987915, or unsubscribe https://github.com/notifications/unsubscribe-auth/AAFZCH6DAB3G7FBGWN6XHULYFPUARAVCNFSM6AAAAAA4CIJIZSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQMJZHE4DOOJRGU . You are receiving this because you authored the thread.Message ID: @.***>
Right now, connecting external power to the VBus pin would put 5v on the USB-C connector, which could cause a problem if an external USB supply is connected at the same time.
If there was a diode there, then a shield board could have external power without risk of backfeeding a computer, and battery backups could be done without a second connector, with a bit of voltage sense logic.