Charging dictation machine from USB mains charger

[nospam]

then all you've seen is non-compliant junk.

a compliant usb port will only source 500ma *after* a negotiation.

in the event a device tries to draw more, the user is alerted, and without the need to reboot:

only if you want to fry stuff.

the spec *is* reality, with billions of compliant devices out there.

anyone who has a usb keyboard that has a usb port for a mouse or trackpad (which is nearly all usb keyboards) 'uses that shit'.

people with laptops also use bus-powered hubs, usually for another flash drive or some other low power accessory.

not everything requires 500ma.

a real engineer designs products that comply with the relevant specs.

if they don't, the products won't interoperate with the rest of the world and the so called engineer will likely be looking for alternate employment rather quickly.

another number you pulled out of your ass.

those logos are there for a reason and anyone who ignores compliance logos of any kind has only themselves to blame when problems happen.

go buy something without a underwriters lab (ul) logo on it. make sure your fire insurance and life insurance is up to date.

[nospam]

call it firmware then. it's still 'software'.

[Carlos E. R.]

You wrote on another post:

Dumb Devices Detecting USB Power Availability If a device doesn't talk USB it can only assume 100mA is available from a standard USB connection, or by detecting the D+ and D- pins are shorted together it can assume 500mA is available as the charger must be a USB Dedicated Charging Port (DCP).

_DUMB_ means no software, and it can source 500 mA.

You wrote it... :-)

[nospam]

not all chargers are dumb. many have firmware and 'talk usb'.

[Piet]

If that would be the case and it would rely on the 500mA max of a USB port, then it would be incompatible with the AC 514 that Olympus lists as an accessory...

-p

[Carlos E. R.]

I doubt that "many" in the sentence. I see no purpose to "talk usb" on

500 mA devices.

And if there are other spec tricks for 1A or 2A devices, same thing goes. I think that (some) 2A devices do talk. Mine doesn't because at least my phone doesn't charge at 2A on it. Or they talk different dialect.

[Andy Burns]

For charger-only devices (excluding type C), the "talking" is reduced to various combinations of resistors across the pins.

[Carlos E. R.]

LOL :-)

Yes, there are dialects: Apple, Chinese, European...

[whisky-dave]

And daleks come from Skaro.... which is relivant if listening to a boring lecture on differnt dialects, your mind tends to drift into reality ;-)

[pamela]

I hadn't seen that accessory. Thanks for mentioning it. Olympus can be a bit proprietary but I'll assume it doesn't use non-standard signalling like Apple does on its chargers.

[Rob Morley]

I wonder if part of the confusion in this discussion is the failure to differentiate between "charger" and "power supply". A power supply is intended to supply a fixed voltage (within tolerance) up to the limit of its output. A charger is intended to provide the appropriate voltage/current according to the state of charge of the cells it is attached to; typically it supplies constant current (by controlling the applied voltage) up to a certain cell voltage, then constant voltage until current drops to full charge level or a timer shuts it off. All "USB charger" wall warts are actually USB PSUs, as the USB spec requires them to supply constant voltage throughout, while the attached device is responsible for managing its cells (or management/protection is built into each cell).

[nospam]

doubt all you want. nearly all chargers are 1a or greater, so they

*must* have some sort of firmware, even if it's a state machine.

only very old chargers are 500ma, or cheap shit which wouldn't be compliant anyway.

there aren't other tricks. sourcing more than 500ma requires conforming to the charging spec.

[nospam]

where did you get that idea?? apple does not use non-standard signaling on its chargers. they are fully usb compliant.

[Piet]

There isn't really.

There isn't for 1A devices. There is for 2A devices: they must comply with fast/quick charging:

For non-compliant devices the charger will give 1A max. Which, on second thought, would imply that Pamela could charge her digital dictator from a 2A charger.

Either your phone doesn't comply with the fast/quick charge standard, or you have to enable fast/quick charging. Check if your phone is on the compliant device list:

-p

[Andy Burns]

Let's face it, pamela isn't going to accept anything less than a guarantee signed in blood by the person who designed the recorder, they they will personally buy her a new one if a 2A charger kills it.

[woo]

Mac keyboard shift key not working?

[pamela]

Gulp!

[pamela]

Got to be as ultra-cautious as you say. I've already damaged two ?100+ Olympus voice recorders most probably by the way they were charged through a USB port.

The advice I've been getting in this discussion veered one way and then another. In one inspired moment afew days ago, I was persuaded by an interesting post (moments before someone immediately contradicted it) to just try the mains charger on my recorder. I'm happy to report that all seems well.

Thanks to all who helped.

I would have dismissed the assembled throng in this thread but you guys seem to be having such a good time discussing and arguing about it that I don't have the heart to spoil the fun. Carry on fellas. Don't mind me. :-)

[Andy Burns]

USB is largely for consumer devices, consumers see USB plug, see USB socket and (rightly) think that belongs in there; it's up to the designers to ensure that it works, or that at worst it does no harm, USB wouldn't have lasted long if it was otherwise.

[nospam]

probably not.

as it should be.