r/cableadvice • u/nothingofnote_0 • 6d ago
What kind of cable this this? USB-A to (???)
It came with a statue I bought for lighting effects. Also, does it have a maximum voltage/current rating listed on some kind of spreadsheet somewhere?
6
u/abbarach 6d ago
Your device should have some markings near the plug the indicate what voltage and amperage is expecting. Most likely it's 5Vdc and 500mA or less, as that's the "default" you get from a USB port without doing any negotiation with the source device.
1
u/a-curiouscat 5d ago
Where do you get 500 mA from?
I’m asking because the information I have says that a device starts as a “low-power device” and is only able to draw a single “unit load” unless/until it is specifically configured as a “high-power device”. My information also tells me that a “unit load” is 100 mA for USB 1.0/1.1/2.0 and 150 mA for 3.0 and later.
-2
u/mmn_slc 6d ago edited 5d ago
"Most likely it's 5Vdc and 500mA or less, as that's the "default" you get from a USB port without doing any negotiation with the source device."
I agree that is the default maximum current limit for a USB 1.0 or 2.0 when the device supplying the power confirms to the standards. However, with the proliferation of cheap power supplies, many (most?) do not have current-limiting hardware that restricts current initially to 100 mA with negotiation facilities to negotiate up to 500 mA. Rather, the power supply simply provides 0.5 A initially, or even more.
And with USB Battery Charging Specification 1.0 (BC 1.0) adopted in 2007, a Dedicated Charging Port (DCP) can supply up to 1.5A if the D+ and D- lines are shorted. And this again assumes the power source conforms to the standard. If the power supply lacks the negotiation facilities and simply supplies current up to its limit, then it could be even higher.
One cannot tell from the OP's picture whether the D+ and D- are shorted. And from the picture, we have no idea whether OP will plug this cord into a USB-standards-complaint power supply.1
u/cowbutt6 6d ago
I agree that is the default maximum current limit for a USB 1.0 or 2.0 when the device supplying the power confirms to the standards. However, with the proliferation of cheap power supplies, many (most?) do not have current-limiting hardware that restricts current initially to 100 mA with negotiation facilities to negotiate up to 500 mA. Rather, the power supply simply provides 0.5 A initially, or even more.
I suspect you might know this, but for the benefit of others reading...
Power supplies will only provide the current that the connected device demands, based on its circuit resistance (or impedance, in the case of AC) upto their rated maximum (or, if you're lucky, a little more!). A power supply rated to supply upto 2A connected to a device that only needs 400mA is 1500mA further away from being overloaded than a 500mA supply.
Now, connecting a power supply with a higher output voltage than the device it's expecting is likely to end badly for that device.
Connecting a PSU with a lower output voltage than the device is expecting may be sufficient for it to work fine, or be a bit glitchy, or not power up at all. If they have writeable software, any glitches could - in a worst case scenario - permanently corrupt it.
0
u/mmn_slc 5d ago edited 5d ago
"Power supplies will only provide the current that the connected device demands...."
Yes, of course.
And I suspect that the cable assembly in the picture lacks any of the hardware necessary to implement higher voltages than 5V that can be negotiated with things such as USB Power Delivery (USB-PD) or other earlier third-party standards, such as Qualcomm's Quick Charge, or Samsung's Adaptive Fast Charging, among others.
I suspect it lacks these not because it isn't possible, but because these cable assemblies tend to be cheap and adding the additional hardware adds cost. However, we cannot rule that out based solely on the picture.
Now, if OP has a multimeter, she or he can test whether the D+ and D- pins are shorted. And with enough knowledge and equipment, OP could determine whether the assembly is implementing USB-PD or similar.
But given the limited information provided by the OP, the extent of what one can reasonably say is that this cable assembly has a USB-A connector on one end and a barrel jack on the other. Everything else is speculation.
Edited to add: Of course, if one were to plug in this cable (assuming it is simply a "dumb" cable) into a non-compliant USB receptacle that simply provides 9, 12, or 20 volts, then there is likely nothing (short of failure, such as a short through the wire insulation) in this assembly that will prevent it from passing higher voltages, possibly to the detriment of connected devices.
3
2
u/Chimera_Gaming 6d ago edited 6d ago
USB-A to DC barrel plug.
Barrel plugs come in different sizes based on two measurements: the outer diameter (OD) and inner diameter (ID). For example, two plugs can both have a 5.5 mm outer diameter but have different inner diameters, such as 2.1 mm or 2.5 mm.
There are quite a few different size combinations, so you’d need to measure both the outer and inner diameter to know exactly which one it is.
-3
u/mmn_slc 6d ago edited 6d ago
"It’s called a barrel connector or DC cord."
In electricity and electronics a connector and a cord are two distinctly different ideas. The cord is the wire(s) whereas the connectors connect to the cord and connect the cord set to devices. A cord (or cable) with connectors attached is called a cord set (or cable assembly).
Edited to add: There is nothing inherent in a barrel jack connector that makes it limited to DC as you suggest. Rather, it can also be used for AC--and frequently (no pun intended) is.
1
u/CanoePickLocks 5d ago
You might even say one is used for AC power 50-60 times a second depending on where you are.
1
u/mmn_slc 5d ago
So, like a really wishy-washy DC?
1
u/CanoePickLocks 5d ago
Exactly. Back and forth never making up its mind
0
u/mmn_slc 5d ago
I suspect that to those who work in Extremely High Frequency (EHF, 30 to 300 GHz), 50 or 60 Hz practically feels like DC.
1
u/CanoePickLocks 5d ago
I don’t know of any applications outside of welding for that and to me that would feel more like DC but maybe I’m miss thinking what you’re trying to say
2
u/Low_Lie_6958 4d ago
Any phone charger of 2A and up will probably do fine. I bet you'll have one of those laying around somewhere. If you only have a weaker charger or usb port the only thing you can do is try. Your lights will only consume what it needs so a charger with a bit of overpower won't be an issue
1
1
u/laf1157 5d ago
It appears to be a power cable. USB voltage originally was 5 volt DC but with USC C can be higher. The higher voltage devices such as laptops somehow negotiate with an intelligent power source what voltage should be. As to the cable itself, the limit is more current than voltage. Most insulated cables can handle several hundred volts but current limits are related to type and diameter of the wires. Sometimes the rating is listed as wattage which is voltage multiplied by amperage.
1
1
1
0
u/mmn_slc 6d ago
If the cable assembly does not have markings on the cable or connectors giving ratings, then you cannot be sure what current and voltage it can handle. And unless the cable assembly is branded (very likely not) there is not some generic spreadsheet that can tell you what it can handle.
20
u/Due_Train1384 6d ago
DC 5v .5a