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Old 06-26-2014, 10:52 AM   #61
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OK, my question above might have been answered here, as I highlighted the appropriate sentences. The defective cable I got might have bad connection for the D+ or D- lines, and the phone could not sense the 200-ohm resistor inside the charger cube.

USB data transfer is sophisticated, but a simple and inexpensive charger should not need fancy hardware/software, and this arrangement is smart. I stopped looking at USB specs a long time ago, so was not aware of this 2007 revision.

The USB Battery Charging Specification Revision 1.1 (released in 2007) defines new types of USB ports, charging ports. As compared to standard downstream ports, where a portable device can only draw more than 100 mA current after digital negotiation with the host or hub, charging ports can supply currents between 500 mA and 1.5 A without digital negotiation. A charging port supplies up to 500 mA at 5 V, up to the rated current at 3.6 V or more, and drop its output voltage if the portable device attempts to draw more than the rated current. The charger port may shut down if the load is too high.

Two types of charging ports exist: charging downstream ports (CDP), supporting data transfers as well, and dedicated charging ports (DCP), without data support. A portable device can recognize the type of USB port; on a dedicated charging port, the D+ and D− pins are shorted with a resistance not exceeding 200 ohms, while charging downstream ports provide additional detection logic so their presence can be determined by attached devices.
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Old 06-26-2014, 11:02 AM   #62
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Harder to explain to a layman is an electric field propagating in a vacuum. Actually that is hard to explain to a EE student.
I had to learn that proof many moons ago as part of my EE degree as I majored in transmission theory. The professor filled up several blackboards with the proof. Of course I instantly forgot it the day after the exam. In practice you had to know Maxwell's equations, not how to derive them.
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Old 06-26-2014, 11:19 AM   #63
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Most likely, the iPad charging starts up and tries to draw 2A. This exceeds the capacity of the little charger, which shuts down to save itself. The "negotiation" for a lower charging current has to be by design, and obviously is not built-in.

I bought a long 12' USB cord to charge my iPhone. It apparently had a miswiring, and when plugged into the phone caused it to announce "Charging is not supported with this accessory".

I thought it was nice that the phone could detect the malfunction but I did not know by what mechanism. Usually when a cable is broken, nothing would happen. I meant to trace the cable to know more, but have not gotten around to it. The USB standard has only 4 wires, but the tiny connector at the phone end has 30 contacts, and this does not make it easy.
It is not likely to be the wiring. I had a charger/FM transmitter for ipod touch which worked fine. Then when upgraded past ios5, it gave the notice of not charging with this device.

Read some complaints to apple, they denied the software angle of not recognizing "unapproved" charging devices. Nonethless the general consensus is that apple is being rotten about third party devices. There may be some workarounds, I just don't feel like drinking anymore apple coolaid. When the ipod touch dies, so will apple company in my mind.

Edit add: Dell seems to do the same with laptops. In the third wire to the laptop is one wire info from the charger regarding currenet cpability and Dell authentication. If not present it will not charege the laptop. There seems to be a workaround in the Bios settings of the laptop.
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Old 06-26-2014, 11:26 AM   #64
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So, I pulled out my DVM, and started probing while the defective-USB-cable-for-the-iPhone puzzle is still on my mind.

I still cannot probe the 30-pin end of the cable, so decided to deduce my theory of bad D+ or D- connection by probing the charge cube instead.

Nope, no 200-Ohm resistor between D+ and D-! Hmm...

Back to the USB specs link provided by misanman...

Ah hah, here it is.
Before the battery charging specification was defined, there was no standardized way for the portable device to inquire how much current was available. For example, Apple's iPod and iPhone chargers indicate the available current by voltages on the D− and D+ lines. When D+ = D− = 2.0 V, the device may pull up to 500 mA. When D+ = 2.0 V and D− = 2.8 V, the device may pull up to 1 A of current. When D+ = 2.8 V and D− = 2.0 V, the device may pull up to 2 A of current.

ALL RIGHT! Out comes the DVM, and what do you know!!!

I measured that 2.8V on the D- and 2.0V on the D+ lines of my eBay-special $0.99 charge cube. That means 1A max according to the Wiki article. Note that the data lines are not really used in a charger because there's no data transfer, and Apple has been using them in a non-standard way to signal current capacity of the charger.

Mistery solved... I only had an iPhone recently, and that was my 1st ever Apple product, so did not know about this rigamarole about non-standard USB chargers.
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Old 06-26-2014, 11:40 AM   #65
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It is not likely to be the wiring. I had a charger/FM transmitter for ipod touch which worked fine. Then when upgraded past ios5, it gave the notice of not charging with this device...
It involves hardware in the charger, but of course also software inside the iSomething. So, you are also correct.

My bad cable has bad data line connections, which should be unused with a charger. However, Apple uses them for their software to sense a non-standard way of identifying the charger capacity. See my posts above.

Apple's method is not much of a secret, being so simple. The Chinese are designing to that specs, and selling an 1A charger like mine for $0.99 on eBay.


PS. I forgot to mention that I knew that the cable was bad because that charger worked with another cable. What stumped me was that I could not understand how a bad D+ or D- would matter (the simple charger couldn't possible be that smart nor need to send any data). And if Vcc or GND line was broken, the phone would not even know if it was plugged to the charger.
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Old 06-26-2014, 12:36 PM   #66
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Harder to explain to a layman is an electric field propagating in a vacuum. Actually that is hard to explain to a EE student.
For a long time, up till the 19th century, even scientists could not accept that anything could be transmitted without a media. So, they filled space with aether, or ether, because vacuum could not possibly transmit light.

See: Aether theories - Wikipedia.
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Old 06-26-2014, 01:06 PM   #67
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I don't know the exact $/kWh, but it's around $0.10 in NC. A little over 1000 kWh and the bill was a little over $100.

At $.10/kWh, I know a lightbulb, computer, or TV that uses 100 W will cost $0.01 per hour or $.24/day if left on continuously. I've also figured out a rule of thumb. At my cost ($.10/kWh), wasting 1 watt hour (1/1000 of a kWh) costs about $1 per year.

In other words, leaving a charger plugged in year round that consumes 1 W continuously whether it's charging or not will cost $1 over the course of a year. Leaving a TV that consumes 300 W turned on 8 hours per day will waste $100 of electricity per year (roughly).

My desktop computer with dual monitors and an old quad core (Q6600) processor and a low end graphics card uses 100-150 watts depending on CPU load. I hit the power button to hibernate it when not in use, and the monitors go to sleep instantly and consume under 1 W when passive. Otherwise I would waste $100/yr by leaving the thing on 24-7.
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Old 06-26-2014, 01:09 PM   #68
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Just mention electrons and a thread starts drawing in nerds like you couldn't believe...
Resistance is futile!
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Old 06-26-2014, 01:17 PM   #69
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Yes, drawn in like moths to a flame.
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Old 06-26-2014, 01:26 PM   #70
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I had to learn that proof many moons ago as part of my EE degree as I majored in transmission theory. The professor filled up several blackboards with the proof. Of course I instantly forgot it the day after the exam. In practice you had to know Maxwell's equations, not how to derive them.
Maxwell's equations sort of fail for wireless transmission at very low power levels (single photons for example).

You have to go into QED

It is enough though in most cases to just understand that the changing electric field produces a changing magnetic field which in turn produces a changing electric field and they surf each other on a boogie board through free space.
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Old 06-26-2014, 01:40 PM   #71
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Maxwell's equations sort of fail for wireless transmission at very low power levels (single photons for example).
Photons are cheap, why be so stingy?

"Send one photon if they come by land, two if they come by sea"

How do I send just one photon, and how do you detect just one?

If I miss catching that single photon, darn, SOL!!!
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Old 06-26-2014, 03:56 PM   #72
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To be honest, I don't understand my bill. It is very complicated, and has a comparison rate, like .10 per kWh.

This page gets updated with costs by state, so probably more useful to those who need the average cost of a kWh.

EIA - Electricity Data
In my state, the price to compare reflects only the cost to generate a KW of electricity. It doesn't include transmission costs, taxes, fixed account costs, and a half dozen or so other items. My last bill had a cost to compare of .073 but my true, all in cost was more like .12 per KW

I can select my power generation provider, but the other costs I've no choice over. The cost to compare is to only aid in the selection and comparison of the power generation provider only.
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Old 06-26-2014, 04:33 PM   #73
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It is enough though in most cases to just understand that the changing electric field produces a changing magnetic field which in turn produces a changing electric field and they surf each other on a boogie board through free space.
Another great analogy

I remember being amazed when I heard that photons had mass. I didn't even realize they were Catholic.
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Old 06-26-2014, 04:57 PM   #74
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I remember being amazed when I heard that photons had mass. I didn't even realize they were Catholic.
<rimshot!>
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Old 06-26-2014, 05:10 PM   #75
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In my state, the price to compare reflects only the cost to generate a KW of electricity. It doesn't include transmission costs, taxes, fixed account costs, and a half dozen or so other items. My last bill had a cost to compare of .073 but my true, all in cost was more like .12 per KW

I can select my power generation provider, but the other costs I've no choice over. The cost to compare is to only aid in the selection and comparison of the power generation provider only.
Agreed. I use the cost from the website I linked in previous post, which is approximately 15 cents.
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Old 06-26-2014, 08:11 PM   #76
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I used 386 kW this past month ending last week which came out to 13.5 cents. Total bill including taxes was $60. This was $10 lower than last year despite a 10% rate increase. My new metal roof is supposed to help lower this cost, but I also bought a small window AC unit for bedroom and shut off house AC at night. I love my bedroom in the mid 60s for good sleeping. Now I sleep great and don't have to cool entire house to get to this level. Come next month I should see even more savings.


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Old 06-27-2014, 08:56 AM   #77
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To OP. If you are retired, you should go back to work.


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Old 06-27-2014, 10:15 AM   #78
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Look at his screenname. My guess is that imoldernu (I am older than you) is about 80 yrs old.

I am 20 years younger, and I am not going back to work, let alone an 80-yr old.
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Old 06-27-2014, 10:20 AM   #79
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Yes, however, those questions display a curiosity of a young engineer.
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Old 06-27-2014, 10:24 AM   #80
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imoldernu is not an engineer, hence he asked for help.

Intellectual curiosity keeps one young.
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