-
After 15+ years, we've made a big change: Android Forums is now Early Bird Club. Learn more here.
Accessories e4g Car Charger Question
- Thread starter darksoul
- Start date
-
- Tags
- samsung epic 4g
Does the phone regard it as a 500mA USB port, or does it recognize it as a high-current charger and charge as quickly as it does with the stock charger? I'm going crazy trying to find a low-profile USB power adapter that properly shorts out the USB data pins so the phone will recognize it as a charger and draw full power.
Yeah. The saddest part of the whole thing is that it's theoretically an official Chinese standard. It's not even hard to implement. From what I've read this afternoon, the main problem is that most of the really cheap chargers from China that say they can do "1 amp" would fry themselves if you tried to actually draw that much current for several hours. And... they know that 99.8% of consumers don't have the slightest idea why some chargers can charge their phone in a couple of hours, while others can barely tread water. So, they omit the connection, knowing that then the phone won't draw more than 500mA, and few users are any wiser.
It's the whole "PMPO-vs-RMS" debacle, except unlike audio amplifiers, there's no common standard for expressing the electrical equivalent of THD, so there's even less to forcibly keep the manufacturers honest. What we desperately need is for someone like Google (simply because phone makers want to sell their own overpriced power supplies that are generally good, but sinfully marked up by retailers and generally impossible to buy online from reputable companies like Amazon) to set some official standards that can't be fudged (say, defining max advertised current as the amount that can be drawn continuously for 60 minutes without the charger's chip exceeding its official operating temperature or blowing its fuse when operated at 30 degrees Celsius and 60% relative humidity), trademark a term like "Empowered USB" to describe a supply that 1) can run at its stated capacity without overheating and 2) will be recognized by devices as a charger instead of a mere 500mA USB port.
It's the whole "PMPO-vs-RMS" debacle, except unlike audio amplifiers, there's no common standard for expressing the electrical equivalent of THD, so there's even less to forcibly keep the manufacturers honest. What we desperately need is for someone like Google (simply because phone makers want to sell their own overpriced power supplies that are generally good, but sinfully marked up by retailers and generally impossible to buy online from reputable companies like Amazon) to set some official standards that can't be fudged (say, defining max advertised current as the amount that can be drawn continuously for 60 minutes without the charger's chip exceeding its official operating temperature or blowing its fuse when operated at 30 degrees Celsius and 60% relative humidity), trademark a term like "Empowered USB" to describe a supply that 1) can run at its stated capacity without overheating and 2) will be recognized by devices as a charger instead of a mere 500mA USB port.
In the chargers that include a charger "base" and a removable usb cable like ours, the shorted or resitance jumping can be done in the carger base so you use a standard cable (as our is) but when connected to the charger it acutally is not just straight through of the six ptential connections.
In other words if the 4 and 5 pin need to be shorted for over 500 ma charge, you can be using a standard cable, but inside the charger those pins are shorted, effectively shorting them at the micro end when on the charger.
I have posted a request to start a pinout thread here if anyone is interested.
it isn't a design flaw in the Epic for it to limit itself to 500 ma if a standard usb is detected. It is intentional and the standard practice for the protection of your pc's 5 volt power rails. Proper conforming USB devices are not supposed to attempt to pull more than 500 ma.
That is why makes of devices that can need more than 500 ma, say for faster charging or use in high demand situation like navigating, make alterations in the wiring of the USB. When the device detects the alterations , it knows it is not connected to a PC, and allows its own charging system to pull more than 500 ma from the power source.
on a standard data usb connections (pins) 4 and 5 pin are discrete, separate electrically. When a high pwoer device such as a smartphone sees that it assumes it maybe connected to a computer and will not ask for more than 500 ma. Bu if they are shorted in the cable (one technique of several), or often in the charger which produces the same affect, the device assumes it is not connected to a computer and asks for >500 ma.
dbpaddler
Android Expert
I understand the concept, but at this stage of the game, there should be a way for the phone to detect the difference in current it's receiving and adjust accordingly without a special cable or charger needed. It's been a while since my 8th grade circuits class, but a computer is only sending out so much current regardless of what a device wants, no? So regardless of the status of the other pinouts it senses the incoming current andd accepts what's coming in. If it senses one amp coming in it can adjust to accept the amperage.
Or am I wrong in assuming power is being pushed from the source and not pulled from the phone? And even if I'm wrong, which is a strong possibility as my geekness doesn't extend to far into circuitry, why is this the first phone for many to exhibit this slow charging behavior?
Or am I wrong in assuming power is being pushed from the source and not pulled from the phone? And even if I'm wrong, which is a strong possibility as my geekness doesn't extend to far into circuitry, why is this the first phone for many to exhibit this slow charging behavior?
db it isn't the first phone. almost all large screen multi-radio (especially wifi and gps) smarptphones are set to
a) pull max 500ma if connected to a computer, or a usb connection that looks like a computer, and
b) pull some amount more if connected to their charger, which they can detect through one out of half a dozen widely used schemes of jumping around the six possible connections on standard usb.
let's number the connections on usb port 1 through 6 (they are not actually numerated that way but it is ok for now.) lets say one and four are dc voltage + and -. let's say 2 and 3 are data channels.
you could short 2 and 3, or 3 and 5, or 4 and 5, or instead of a short, place a resister between them, and set the phone to use that determinant to know it is not hooked to a computer. That is what makers do.
In terms of what the computer sends out, and what it does when demands for more current are made, some computer power supplies can deal with this and others not. that is why you cannot certify a device as USB complaint if it can draw more than 500 ma with standard usb wiring.
Yes your chances of burning out the PC (or a charger) are very low, but makers do not want to mess with standards since that would open them up for all kinds of damages claims.
finally without these specialized jumps your device may try and go into some data transfer mode, which some makers set as default when in the presence of standard usb wiring. If I plug my navigator into my computer with a standard usb, it goes into data transfer mode and will not work as a navigator, if I plug it in with its specialized car or homecharger (it has 4 and 5 shorted) it works as a navigator.
a) pull max 500ma if connected to a computer, or a usb connection that looks like a computer, and
b) pull some amount more if connected to their charger, which they can detect through one out of half a dozen widely used schemes of jumping around the six possible connections on standard usb.
let's number the connections on usb port 1 through 6 (they are not actually numerated that way but it is ok for now.) lets say one and four are dc voltage + and -. let's say 2 and 3 are data channels.
you could short 2 and 3, or 3 and 5, or 4 and 5, or instead of a short, place a resister between them, and set the phone to use that determinant to know it is not hooked to a computer. That is what makers do.
In terms of what the computer sends out, and what it does when demands for more current are made, some computer power supplies can deal with this and others not. that is why you cannot certify a device as USB complaint if it can draw more than 500 ma with standard usb wiring.
Yes your chances of burning out the PC (or a charger) are very low, but makers do not want to mess with standards since that would open them up for all kinds of damages claims.
finally without these specialized jumps your device may try and go into some data transfer mode, which some makers set as default when in the presence of standard usb wiring. If I plug my navigator into my computer with a standard usb, it goes into data transfer mode and will not work as a navigator, if I plug it in with its specialized car or homecharger (it has 4 and 5 shorted) it works as a navigator.