USB sync/charge cable warning

12-31-04, 02:59 PM

I know we have discused this before BUT I have some new information. If all you want is the warning skip the next paragraph.

I have found that the +5v from USB and the +5.4v from the wall plug DO come into the axim x50 from differant pins. When looking at the cable (not the axim) with the pins down the +5v is I think the 3rd over from the left on the second set of pins and the +5.4v is the rightmost pin or close to it. (hard to give exact pins without taking it apart). I figured this out using a Dell USB sync cable and a multimeter. As long as there is nothing between the two ends of the cable you just check the resistance between the pins on each end of the cable if the resistance is low such as 3 ohms then they are continuous through the cable.

What this means to you. Most of the direct sync cables and sync/charge cables made by third partys have the +5v from the USB port running to your +5.4v on the axim. While this will not damage the axim (it may damage the computer but should not). It is not correct and at the least these companys should be putting a switch on the cable so you can select where the power goes if it goes to the +5v pin or the +5.4v pin.

When the power runs to the +5v pin the system knows not to charge unless its turned off then to only charge at 500mA which is the max a USB port is able to put out under USB specs. When attached directly to a computer normally what will happen is you try to draw too much current and the port turns off. Some cheap hubs don't have this limit and will supply the extra current and normally is not a problem either.

This is why some people have problems with these cables and others do not. Some computers can handle it or don't have current limiters in place. Others are able to stay under 500mA by not having a dead battry or other high current items running.

About the switch I brought up earlier. If a switch is on the cable you can have the power go to the +5v pin to charge a dead battery then when its charged you can flip the switch to have the power go to the +5.4v pin so you can maintain the battery while using the axim or do a light charge while connected to the computer. This way it can charge and sync at the same time when possible and when its not possible just charge.

EDIT: So in the end if it syncs and charges AT THE SAME TIME through only USB then I would not buy it unless it had a switch you know the device that will be supplying the power can handle large loads. (which most of the wall chargers etc can not do)

JakeRich · 01-01-05, 12:27 PM

Kenban, how do you know there is a separate 5.4v pin? The USB cable won't show the additional connection because it will always connect to the 5V pin (assuming you are right). How did you detect that 5.4 v goes somewhere else? Did you test on the external power adapter? You could multimeter that to see what pin the center conductor was attached to. Did you do that?

If the external power connector goes to the 5.4v input, then trying to use a 5v cigarette lighter adapter is also going to lead to problems. The "blinking" phenomenon reported by some folks may be exacerbated by starting with only 5v on the 5.4v pin.

01-01-05, 12:51 PM

I actually did end up hooking the cable up to a USB power supply and tried it with and without the wall plug attached. The power clearly seems to only go to two pins one has 5v on it and the other 5.4v (which are the power outputs of the USB supply and the wall plug.

Originally I just checked the resistance between the ends of the cable to find where the pins went which if there are chips of some sort in between I would have not been able to trace the wires that way.

Although I do want to say the information about where the power goes on the 3rd party cables IS a guess on my part I don't have any of them. BUT if the cables charge while the unit is on based on what I found about where the power goes it makes sense that they are running the power to the normal power in pin. People who hook these cables up to power supplys that can supply large currents (1 amp or more) have seen no problems at all. The people who are having the problems are hooking them straight up to a computers USB ports (I have read about some labtops having problems with the current) or the versa charger which based on an earlier boxwave post someone found it shows that it can also only supply 500mA. In the past I have found that while during normal use thats enough to run the handheld its very possible to use more then 500mA without even charging the battery.

Really I am making more a few more quesses then I like to but its not like Dell is going to answer a question about the adaptor on the axim or internal workings of the axim. If someone has some more information I would love to hear it. I really do like getting proved wrong :)

JakeRich · 01-01-05, 01:24 PM

Good stuff, Kenban! Thanks for the answers. I suspect you are correct in the assessment. It makes sense, given how it seems to function. I suspect the sync/charge cables are going to be problematic no matter what they try to do. About the only way to avoid problems is to use the 5v input and tell folks to shut off the X50 to charge it.

01-01-05, 01:33 PM

Originally Posted by JakeRich

Good stuff, Kenban! Thanks for the answers. I suspect you are correct in the assessment. It makes sense, given how it seems to function. I suspect the sync/charge cables are going to be problematic no matter what they try to do. About the only way to avoid problems is to use the 5v input and tell folks to shut off the X50 to charge it.

I still like my idea of the switch :) but how do you try to explain when to have it flipped one way or the other to a normal user?

systemghost · 01-02-05, 03:13 AM

could you not combine a couple of micro leds with the switch...green the switch is in the correct position, red it is not...or why not automatic switching...then t'is one less thing for me to learn/remember...

JakeRich · 01-05-05, 12:51 PM

I just made this thread "sticky." Enough folks are going to want to know about this situation, at least until the cable makers sort it out.

fishfuzz · 01-05-05, 07:01 PM

Perhaps we should create a list of what is working/not working.

For me, I'm using the DirectSync cable from Boxwave. It works on my laptop (hp pavilion ze4101), PC (Dell Dimension and home built), and my Arkon mount. I am able to use the device while charging (and the device does show that it is charging properly).

It does not work with the VersaCharger from Boxwave (at this time), but that issue has been attributed to the charger, not the cable.

JakeRich · 01-05-05, 08:12 PM

Originally Posted by fishfuzz

Perhaps we should create a list of what is working/not working.

For me, I'm using the DirectSync cable from Boxwave. It works on my laptop (hp pavilion ze4101), PC (Dell Dimension and home built), and my Arkon mount. I am able to use the device while charging (and the device does show that it is charging properly).

It does not work with the VersaCharger from Boxwave (at this time), but that issue has been attributed to the charger, not the cable.

No, no reason to list stuff. It's not stuff that works, it all depends on the starting battery condition and how the USB port power is sent to the pins in the Axim. There are thousands of combinations and even if your combo works for you, there is no guarantee that if you started with a lower battery level it would continue to work. In fact, at this point it is not possible to define "work." Is work:

1. I can sync and charge from a USB port only,
2. I can sync OR charge from a USB port only, but not at the same time,
3. I can sync and charge from a USB port only if I have an external power supply to charge with, or
4. I can sync and charge from a USB port with a car charger?

Now add to each of those definitions battery levels, e.g,

1.a) I can sync and charge from a USB port only if the battery is at least 90% when I start, but not lower.
1.b) I can sync and charge from a USB port only if the battery is at least 80% when I start, but not lower.
etc, etc, etc.

Bottom line, the Ax takes a LOT of power, so syncing and charging at the same time is probably NOT possible with just USB power UNLESS you have a pretty full battery, no matter the equipment.

Tuba · 01-07-05, 02:13 AM

Bottom line - If I use the Gomadic Dell Axim x50/x50v Power Sync Charging USB Cable what is the worst that can happen?
(a) fry my PC
(b) fry my Axim x50v
(c) sync but not charge
(d) charge but not sync OR
(e) create a worm hole in the space time continuum that zaps my Axim back into an iPAQ 3650

I'm hoping/guessing the answer is (c) and it will depend on the current charge in the battery and the quality of my USB port.

fishfuzz · 01-07-05, 10:56 AM

Regardless of what battery level that I've had (and it's been as high as 100% to as low as 24%), I've been able to both sync & charge with the items listed above.

So it is important to get qualitative information (ie a list of what works, and what doesn't). Would you rather I start my own thread or use the existing discussion?

fishfuzz · 01-07-05, 11:01 AM

1. I can sync and charge from a USB port
This I would consider "working" as long as it has no regard for the battery level.

4. I can sync and charge from a USB port with a car charger?
Where would you sync to in this case? The car? *wink*

Now add to each of those definitions battery levels, e.g,
If the battery level makes a difference, then in my book, it's not working.

JakeRich · 01-07-05, 01:24 PM

Originally Posted by fishfuzz

1. I can sync and charge from a USB port
This I would consider "working" as long as it has no regard for the battery level.

4. I can sync and charge from a USB port with a car charger?
Where would you sync to in this case? The car? *wink*

Now add to each of those definitions battery levels, e.g,
If the battery level makes a difference, then in my book, it's not working.

1. But experience says the battery level is a factor in the power draw, so all answers will regard the battery level.
4. Laptop? I have one, use it in the car all the time. Come out of a meeting, fire up the laptop, sync the data I got in the meeting to the laptop. All on car power.

01-07-05, 02:51 PM

Originally Posted by JakeRich

1. But experience says the battery level is a factor in the power draw, so all answers will regard the battery level.

Guys to help answer this question I am going to pull my multimeter out of the closet that can attach to the computer and check the actual current during charging. I will do this with the axim off and the battery discharged to the point of the axim turning off. One thing a lot of people seem to forget though is there are two differant batterys a 1100mAh and a 2200mAh. I would not be surprised if the 2200 requires a larger current during charging but we will find out.

The first tests will be done using the original voltage of the power adapter which is 5.4v. I will try to do 5v tests sometime later. The tests will take several hours each plus I will have to do some setup work getting a power cable together as I don't have the correct adapters sitting around so it might be a few days before I can post the results from even the first test. FYI I am planning on doing the tests on the 2200mAh battery first because I believe its going to have a higher charge current so I want to show worst case first.

I will also try to do some current tests on what it takes with differant settings to get some solid answers on how much current you need.

Also someone asked about what can go wrong. I do want to say that computer motherboards were not designed to be used in this way and most have protection to prevent you from doing damage by pulling too much current. Chances are you would not do any damage to your computer and before something would happen the port should turn itself off. BUT it is possible although I have never heard of it happening. In the end if I was to be using one of these cables to charge I would use one of those power adapters or use a hub because those are cheap to replace.

Tuba · 01-07-05, 04:49 PM

Thanks for answering my question and for taking the time to test this out. It is appreciated!

FYI, I plugged my Axim (1100 battery) into the USB cradle without the power supply. It synchronized successfully.

The power went down from 75% to 74% while it was on (backlight off).

Then I powered off the Axim and left it plugged in. After a few minutes, the power was up to 84%. The USB cradle charged it up 10%

I assume the USB sync and charge cables will work the same as the USB cradle without the power cord. So I am now going to order the Gomadic cables.

At home I’ll use cradle and power supply. At work I’ll use the Gomadic Sync and Charge. This will also let me keep the PDA in my Vaja case while synching. Not worried about frying this comp b/c it is my work's computer. :)