Join devRant
Do all the things like
++ or -- rants, post your own rants, comment on others' rants and build your customized dev avatar
Sign Up
Pipeless API
From the creators of devRant, Pipeless lets you power real-time personalized recommendations and activity feeds using a simple API
Learn More
-
I had a similar problem with long extensions to a keyboard cable (device in a central machine room area, patchable to multiple studios). It manifested itself as irregular data transmission, but the actual problem was low DC voltage - as you highlight here. An adjustable source voltage would be a fine thing in many circumstances, although not likely to be allowable per the USB spec? i have no actual knowledge of the spec and what it says about voltages in detail, e.g. where the spec voltage(s) are determined, power source or device end, under load and not, etc
-
@spongegeoff I think the problem here is that there are devices like USB hubs in between, so any negotiation regarding power has to happen on the level of direct links and not on top of the serial protocol. You can't allow your powerbank and the laptop to agree on 7 volts without the hub getting a say.
I don't know a lot about USB though so this may be an inherently solved problem -
@lorentz yeah, there would have to be some tally back of the destination DC level, but that is unlikely to be compatible with the USB spec as is. I just upped a DC voltage for a specific installation, have no idea how that could ever be implemented for the USB standard. It was a fix for the issue at the time.
-
@spongegeoff I mean, since USB is strictly hierarchical, it's easy to imagine a scenario where each connected node has a high and low voltage signal (maybe a difference from optimal?) which is only reported one link up, and the parent gets to tally the received reports, adjust some internal variable resistors until everyone agrees, and then forward voltage change recommendations upwards. It would add a lot of complexity to the protocol but it would enable a lot of extender abuse that is very unreliable right now.
-
@spongegeoff I'm not sure how you'd get extender cables to report their voltage rating though
-
@impune-pl said it before I did. This is the reason.
-
IIRC this is also in part due to history. because of the transistors involved based on silicon, when creating a stable voltage regulator, it amounts to 5v. Example is the 7805 voltage regulator, which is really cheap to produce.
https://eleccircuit.com/7805-5v-vol...
I humbly request the confirmation from an electronics engineer for this, it's been too long ago for me. -
"Power requirements are a gas, they will expand until occupying the entirety of the acceptable window"
Devices need only 4.3 volts because USB can offer only 5. If USB had been designed to work with 6, companies would make less efficient / cheaper devices that require 5.3 volts.
Same thing with cables, they would simply use cheaper, less efficient cooper and the higher voltage advantages would be lost again.
Good engineering solutions are always on the brink of being screwed over by poor financial decisions. -
@exerceo I might be wrong, but I would still imagine that manufacturing companies would use crappy step-up setups to increase tension in mobiles if it meant that they could use cheaper 5.3v components.
Naturally this is not the case for high-end devices, but cheap is what makes the world go 'round.
The economics of mediocrity are a bitch, and a tricky problem to solve.
From today, this beauty is 'ticking' on my desk :D
Today at school I borrowed an oscilloscope and a few capacitors and used a circuit I made at home to just demo...
My Mini-project for college. Any electronics enthusiasts here?
The default USB voltage hould have been specified to 6 instead of 5 volts.
Six (6) volts would allow for longer cables than five (5) volts do, since the spare voltage compensates for the resistance of cables. This is even more crucial for USB hubs. USB hubs are highly dependable upon these days due to laptop vendors dropping the number of USB ports down to two or even one. I am looking at you, Medion.
If several devices are connected to a USB hub, the voltage can quickly drop below 4.5 volts due to the resistance between the USB hub ports and the computer's USB port, causing some devices to restart themselves even if the computer's USB port is not over capacity. If it were over capacity, it would just regulate down its output voltage to prevent overcurrent.
Lithium-ion batteries need at least 4.3 volts arriving at the battery terminals to fully charge, and mobile devices are typically not equipped with a boost converter. Even if they were, they are rather inefficient, meaning they would produce significant heat and waste a power bank's energy. Other USB devices such as flash drives and peripherals might power off below 4.5 volts. However, 6 volts have solid 1.7 volts of margin to 4.3 volts, more than twice the margin of 0.7 volts that 5 volts have. On the way from the power supply to the end device, the voltage has to pass several barriers which weaken it, including the cable, connector endings, and the end device's internals such as the charging controller.
Sure, there are quick charging standards such as by Qualcomm and MediaTek which support elevating voltages to nine (9), twelve (12), and even twenty (20) volts. However, they require support by both the charger and mobile device. If six (6) volts were the default USB voltage, all devices would have been designed to accept this voltage, and longer cables could have been used anywhere. Obviously, all USB devices should be able to run on five volts as well.
Six volts would have been more stable, flexible, and reliable.
rant
voltage
electronics
power supply
electrical engineering