It turns out my Pi2 problems were yet another dying power supply.
I can easily splice the old power cord onto a new wallwart, but wonder if it's possible to use a USB C adapter that might remain useful after the Pi2 is obsolete.
AIUI USB C power supplies can deliver up to 20 volts after negotiating with the load. Less clear is how the negotiating is done and what happens if a C power supply is connected to a Pi2 which can't negotiate.
Anybody tried it?
Thanks for reading,
bob prohaska
Bob,
I've been going for power supplies which say they are 5V, such as the official RPi-4 USB-C ones. No mention there of having the higher-voltage options. Beware of xPhone "compatible" ones.
A USB charger is not intended to run 24/365. Depending on how much you run your Pi2, you may find you're better off with a proper power supply.
David
Can you point out to sources for this statement, please? Why shouldn't a charger run 24/7? I am now testing one Orange Pi with Vivanco usb charger and I was just wondering if it is OK to use the charger 24/7. It is one that provides 12W and the machine runs presumable on 1/3 of it.
thanks
yes they are.
usb chargers are proper, except perhaps noname junk that's best avoided.
There are actually three classes of 'PSU's, all designed for different use cases:
1) *battery charger*, which is designed for intermittent use, typically it is only in use for a small fraction of its duty cycle. That's because its job is to top off the battery it's attached to and then set its 'charge complete' indicator and shut down. It is NOT designed for continuous operation. 2) *PSU*, USB or not. These are designed to run 24/7, but offer no protection against mains failure 3) 'uninterruptable power supply', which is designed to keep its load powered regardless of interruptions of its power source, though the length of time it can provide power will be specified. Longer costs more. It pays to think about which of those classes you actually want before installing anything: picking the wrong type for your application is likely to be unsatisfactory. And be careful to over-specify rather then under- specify your power source as well as considering its use case because that will extend its life.Spot on. There's a fourth case too: the 'piece of crap'. Avoid at all costs.
The USB-C power interface is a total can of worms IMHO, it is far, far too complex and the chances of buying a supply that implements it completely or properly are minimal.
Anything that uses much more than the extra current available at 5 volts probably needs to be specific to the device manufacturer to be safe.
Just get the effing official power supply already. Maybe it's $2 more but that is definitely worth it.
what about the micro-USB?
Also what about using only the +5V and negative (red/black) - what kind of negotiations are you talking about?!
The chip makers are all over this - there will undoubtedly be a few bad ones but they should fall out of use pretty quickly or get fixed. WiFi and Bluetooth are *way* more complex but all a manufacturer has to do to get it right is use a decent chip.
The 'old' micro-USB is fairly straightforward, usually. I think there are some possible extras but basically the only real 'extra' is the availability of more current from some PSUs.
On USB-C the source and client can 'negotiate' all sorts of changes to the basic 5 volt supply, it can be negotiated up to 12 volts or even
20 volts. The 'negotiation' comprises signals on the other pins of the connector so (as far as I understand it) if you only connect to the 0v and +ve supply pins you should only ever get 5 volts.
Many of these can negotiate with the device they are charging to supply a higher voltage / current.
They are supposed to deliver a fixed voltage. No negotiation. The device determines how much current it will pull at any moment, up to a PSU specific maximum current.
Latest USB PD spec allows 48V @ 5A
Nice cheap, warm cables.
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