pamela wrote: [...]
Why? You say the device can be charged from a 500mA USB-2 port. So why, if - as you say - you're concerned about frying stuff, don't you get a 1A charger or even less than that?
1A chargers are readily available and something in the order of 600 - 900mA shouldn't be hard to find either. [...]
something can still be fried from a 500ma port and if the charger is compliant, it won't draw more than what it needs anyway.
Yes, I think by now nearly everbody is aware of that. But we're running around in circles.
pamela (the OP) is concerned that she might fry the device, device battery, etc.. As we all know, that *should* not happen if the device complies with the relevant USB standards, but it *could* happen if de device is non-compliant. Nobody - except for the manufacturer/designer of the device - can know/tell for sure [1] whether or not the device is compliant. As has been mentioned, a USB 'label' on the device, box, in the manual, is just that, a label, it's no guarantee that the device really *is* compliant.
I think that, after some 60 responses, this horse is quite dead. Let's have some mercy.
[1] FSV of "sure".
correct.
not correct. the manufacturer want to differentiate itself from the other noncompliant crap and does so by using the usb logo.
nothing is 100%, but reputable companies will not risk using the usb logo without proper authorization from the usb consortium. they have
*way* too much to lose.
Every port I've seen will allow 500mA without any communication. It will also shut off until reboot if that current is exceeded.
Yes it does, no need to f*ck about with electronics, just treat it as a power source.
The spec means nothing, I prefer reality.
Who uses that shit?
I know what I see, you're working from paperwork. Try the real world. It seems you're a theoretical scientist and I'm a real world engineer.
99% of people don't look or care for silly little logos.
If I was certain my recorder and PC were up to spec I wouldn't ask the question. My query is what's the likelihood that there has been some skimping in my case.
Maybe because Pamela does have a 2A USB charger? Why buy another charger if you have one already?
USB ports aren't necessarily powered with the PC off. Why switch on a PC just to charge a USB device if you have a USB charger?
If a 2A charger can fry the device, so can a 1A charger.
But let's look at the device itself. Apparently it's an Olympus LS-P1. According to Olympus it contains one 750 mAh rechargable AAA battery. According to Olympus it is an "Advanced Linear PCM recorder" with "internal charging". It's priced at about EUR 135.
That's the sort of device I'd expect to have well-designed active circuitry for the "internal charging", limiting the current and voltage to the battery according to its level of charge, drawing just the current from the source to accomplish that, irrespective of what the source can deliver. And indeed "official" charger is the "AC 514", rated at 1A or twice what a USB port can deliver, apparently without frying the device. So clearly the device was not designed to only draw power from a PC USB port.
Having said that, is the chance of frying the device with a 2A charger zero? Not necessarily. Personally I wouldn't take the risk, if only because such a charger wouldn't buy me anything, and certainly not faster charging than with a 1A charger (which she may have already: a charger of a smartphone). I expect the battery's charging current would be limited to 1C, or 750mA, less than even the "official" 1A charger can deliver.
-p
Hmm. Looking again at the (original USB2) spec I see that it's a bit more strongly worded than I recalled ...
The spec (Sec 7.2.1) contains the words:
Systems that obtain operating power externally, either AC or DC, must supply at least five load units to each port. Such ports are called high-power ports. So, in fact, every mains-powered desktop PC is *required* to provide 5 "load units" (500mA) on each USB port.
That doesn't eliminate the requirement for a USB device to negotiate before drawing more than 100mA, as low-power USB hosts may not support more than one "load unit".
I can see nothing that requires the host to limit the current availability before or after negotiation of high-power use ... just the sentence:
It is the responsibility of software to ensure adequate power is available before allowing devices to consume high-power. So it looks as though it's perfectly valid and in-spec for a high-power host to make all five "load units" worth of current available at all times, but a device is not allowed to make use of more than one without negotiation. The host must not accept the negotiation unless it actually has the power available.
.. which is what I said PC motherboards typically do.
Please point me to the relevant bit of the USB2 spec, if I've missed something.
if its not up to spec, then you're on borrowed time no matter what you do.
That's exactly my need.
Sad to say, the two recording devices were earlier generation Olympus voice recorders. The cause is inconclusve but I asked the original question because I didn't want my new LS-P1 to go the same way as the other two.
In addition, the LS-P1 charges whilst plugged into the USB port. That's a relatively new feature in voice recorders. In the past I would take out the AAA cell and recharge it and then return it.
This new recorder is designed to record from the PC USB port when connected for file transfer. That further led me to think that the LS-P1 is designed only for charging from a PC.
1C is a bit too high for my liking. I had assumed the recording device took the max current it could from a USB 2.0 port but posters here have advised (with some diagreement) that it is not so simple.
the charge current is determined by the circuitry in the recorder,
*not* the charger.
the device will use as much as it's designed to use, up to the maximum available from the port.
actually it's very simple.
I mean that a 1C rate of charge is a bit too fast for NiMH for my liking (irrespective of the type of charger).
There is another spec for "usb chargers". They don't have "software".
the charger isn't going to charge at 1c unless it was designed to do so, in which case it isn't an issue. plenty of nimh chargers charge at
1c (or more) and then taper off as the battery gets full.the point is that the device will draw only what it needs.
Maybe you miss my point. I wrote that
"a 1C rate of charge is a bit too fast for NiMH for my liking (irrespective of the type of charger)".
I would balk at a faster charge rate and I think other people would too. My comment has nothing to do with USB PC charging and when Piet wrote about it he was referring to a mains USB charger.
and you miss my point, which is you aren't going to get 1c simply by plugging a device into a port that can source 1a or more.
a charger has to be designed for 1c (many are) and they work perfectly fine. however, those are not usb powered.
a mains usb charger more than likely is capable of 1c, possibly even more.
a usb charger almost certainly is *not* designed for 1c and will not charge anywhere close to that.
I think I fully get your point. I just wonder why you raise it at all because it's not what I was talking about in my post:
MID:
Are you sure?
Even if what you write is correct, it doesn't have much to do with my comment that I think 1C charging for an NIMH cell is a bit fast for my liking.
quite sure, given that i own three aa/aaa chargers capable of charge currents as high as 2000mah, which for a small cell, is well above 1c. it plugs into the wall via a 12v power adapter.
chargers for drones, rc cars, etc, can go even higher, but that's a more specialized use case where rapid charging is very important.
that's fine, you don't have to like it, but it's safe and not at all unusual.
it also doesn't matter since a pocket recorder is not going to charge at 1c.
Get a "USB Doctor" to check the current/voltage that it's actually drawing? You could make a break-out cable to use a multimeter, but the USB gadgets are so cheap and convenient it's hardly worth it. A test load is a handy accessory too, so you can check voltage regulation at high current drain.
correct.
an example is a bus-powered hub, often found in a keyboard.
obviously it needs to be able to source the power if it's going to grant a request for it.
most are compliant, but unfortunately not all. cheap crap often isn't.
here's a summary: A USB device is permitted to draw up to 100mA (1 unit load) for USB2.0, and up to 150mA for USB3.0. It may do this prior to any USB communication, so this is the current limit a USB device may draw if using a USB connector to provide the charger input without a USB interface to request a higher current from the USB hub (which it may or may not be granted depending on the hub). ... Standard Downstream Port (SDP) A standard USB port. Supplies 100mA before negotiation and up to 500mA after negotiation of power availability (150mA and 900mA for USB3) ... 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).
note that a usb dedicated charging port is a usb charger, not a usb port on a computer. it would be very stupid to have a usb port on a computer that did not transfer any data.
for the gory details, the latest usb spec is here:
and the relevant bits:
11.4.1.1.1 Over-current Protection The host and all self-powered hubs must implement over-current protection for safety reasons, and the hub must have a way to detect the over-current condition and report it to the USB software. Should the aggregate current drawn by a gang of downstream facing ports exceed a preset value, the over-current protection circuit removes or reduces power from all affected downstream facing ports. The over-current condition is reported through the hub to the Host Controller, as described in Section 10.13.5. The preset value cannot exceed 5.0 A and must be sufficiently higher than the maximum allowable port current or time delayed such that transient currents (e.g., during power up or dynamic attach or reconfiguration) do not trip the over-current protector. If an over-current condition occurs on any port, subsequent operation of the USB is not guaranteed, and once the condition is removed, it may be necessary to reinitialize the bus as would be done upon power-up. The over-current limiting mechanism must be resettable without user mechanical intervention. 11.4.1.2 Low-power Bus-powered Devices A low-power device is one that draws up to one unit load from the USB cable when operational. Figure 11-2 shows a typical bus-powered, low-power device, such as a mouse. Low-power regulation can be integrated into the device silicon. Low-power devices must be capable of operating with input VBUS voltages as low as 4.00 V, measured at the plug end of the cable. 11.4.1.3 High-power Bus-powered Devices A device is defined as being high-power if, when fully powered, it draws over one but no more than six unit loads from the USB cable. A high-power device requires staged switching of power. It must first come up in a reduced power state of less than one unit load. At bus enumeration time, its total power requirements are obtained and compared against the available power budget. If sufficient power exists, the remainder of the device may be powered on. High-power devices shall be capable of operating with an input voltage as low as 4.00 V. They must also be capable of operating at full power (up to six unit loads) with an input voltage of 4.00 V measured at the device side of the B-series receptacle.HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.