evenwicht

Lenovo USB-C PSU for laptops powers a Rasberry Pi, but cannot simply charge bicycle lights. WTF?

https://lemmy.sdf.org/post/52444164

Mar 17 at 10:43amWeb
Show threadThePantser4d ago
The lights most likely do not have the extra circuitry to talk to the charger to negotiate voltages. Since it’s a charger that can change voltage as you stated then the device must be able to say “hey give me 5v”. You will need to use a dumber 5v only charger for those devices.
Show threadevenwicht4d ago
What would be the meaning of a default voltage then? My understanding of USB PD is that 5v is a default, which I took to mean it would deliver 5v in the absence of a handshake.
Show threadNotsosuperfloh4d ago
Most usb- c pd adapters wont put ouz any voltage on their own. the end device must tell the adapter what voltage they want via the cc pins. on the raspberry pi this is done via resistors between cc1 snd cc2 to get 5v. those pins are most likely unpopulated on your bycicle lights, so they get no power.
Show threadbrillotti4d ago
This is correct. I made my own USB C to 30 pin adaptors for old iPods and this is precisely how I had to build them.
Show threadRomkslrqusz4d ago

In addition to what others have said, I would hazard a guess that these bike lights shipped with a charger that uses a 5V brick and a Type A to Type C cable.

With A to C, no negotiation happens - 5V just gets sent.