PIn-out for power cable

Discussion in 'Technical Support' started by movrshakr, Oct 7, 2013.

  1. movrshakr

    movrshakr

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    While on a trip, the power/traffic receiver cable for my 540XXL failed--the center pin of the cigarette lighter plug was gone, nowhere to be found.

    I purchased a replacement power-only cable from a Radio Shack because I REALLY needed the GPS to get around. But there are two deficiencies...
    a. It is power only--no traffic receiver
    b. The right angle plug on the cord at the device is much too large and extends below the envelope of the display.

    what I would like to do is cut off the cigarette power supply off the new cable and put it on the original cable, but I need to know the wiring connections.

    First, is this possible? I am assuming there are only positive and negative 5v wires coming out. Are there more than that? And how do I tell which to solder to get polarity right?

    Thanks
     
    movrshakr, Oct 7, 2013
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  2. movrshakr

    Arno Moderator

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    I would suggest you open the adapters and only replace the pin and spring, providing the plastic keeping the pin flange inside the housing is not broken off. Be extra careful using a sharp utility knife.
    Before gluing the halves together test its functionality by using a heavy duty elastic around it.
    Come to think of it the rubber band is good for at least 18 months. Don't ask me how I know.

    TT_USB_CLA.jpg
     
    Arno, Oct 7, 2013
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  3. movrshakr

    movrshakr

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    That sound interesting. From where would I get the pin and spring to install?

    In case this does not work out (not being able to obtain the parts or the retention lip being broken), I'd still like the original answers about what are the wires and defining which is which.
     
    movrshakr, Oct 7, 2013
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  4. movrshakr

    Arno Moderator

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    Frome here:
    I know nothing about the antenna egg or connections within the plug. Maybe canderson can tell you more.

    The picture came about because the poor quality plastic material holding the leaf springs broke away.
     
    Arno, Oct 7, 2013
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  5. movrshakr

    movrshakr

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    I don't understand. Do you mean go back to Radio Shack, and they will have the center pin and spring parts for sale to fit the TomTom cable plug?

    I was assuming that the individual parts for various cigarette lighter plugs would not be interchangeable even though form, fit, and function of different ones would be the same.
     
    movrshakr, Oct 7, 2013
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  6. movrshakr

    Arno Moderator

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    No, you said you had bought a cable already.

    In order to solder the wires from the TT antenna cable to the Radio Shack adapter you should open both adapters anyway to see their wiring.

    Are you sure the Radio Shack version has the same protection built into the plug as TomTom's.
     
    Arno, Oct 7, 2013
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  7. movrshakr

    movrshakr

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    Oh, as I indicated about differences in parts for different plugs, it never occurred to me that the pin and spring from the new one would fit into the TT one. I'll have to look (not at them right now).
    No way to know, but it is marketed as a replacement, albeit a general purpose one.

    Oh, since you have (had?) the plug open, does it have two wires for output or more?
     
    movrshakr, Oct 8, 2013
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  8. movrshakr

    Arno Moderator

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    Good question, but I sent the one in the picture to canderson over a year ago.
    To add insult to injury, that was not from an antenna cable.
    Only subsequently did dhn lent me his combo antenna cable.
     
    Arno, Oct 8, 2013
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  9. movrshakr

    movrshakr

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    Ah, so unless the pin and spring from the new one will fit in the TT one, then I am back to my original questions of "pinouts."
     
    movrshakr, Oct 8, 2013
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  10. movrshakr

    canderson Moderator

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    Yes .. do be careful. You certainly don't want to be dumping 12V into your TomTom. That's a certain means of letting the smoke out - and we all know it's smoke that makes these things operate. So please let me confirm that when you say "I purchased a replacement power-only cable from a Radio Shack", we are talking about a device that provides 5V (not 12V). AFAIK, they sell both car chargers and USB-A (charger end) to USB-miniB (540 end) cables separately, but not as an assembly.

    As I understand it, your charger tip is gone, and it's one of the cables that includes the traffic 'egg' on the cable. Understand first that the TomTom cig lighter adapter does 12V to 5V conversion. So to use any standard USB 5V cig lighter adapter, you'd have to connect a new USB-A connector to your existing TomTom cable after cutting it from the original cig lighter adapter.

    All of this assumes that you can't find a compatible tip for your existing cig lighter adapter.

    If that's the case, then as I understand it, what you will be needing to know is where to attach the wires from a cut end of your TomTom traffic cable to a USB-A connector? So that you can use a standard USB A style cig lighter adapter such as you have (I think) already purchased)?
     
    canderson, Oct 8, 2013
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  11. movrshakr

    movrshakr

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    canderson, ah, rest assured on the power specs. Actually, I am a former electrical engineer that designed systems for use at Cape Canaveral. The new replacement cable from Radio Shack (RS) was inspected before purchase to be sure it was 5v and sufficient current capacity.

    "...charger tip is gone, and it's one of the cables that includes the traffic 'egg' on the cable."
    Yes, if you mean "charger tip" being the + center pin in the large cig power adapter end--not the end at the GPS.

    "So to use any standard USB 5V cig lighter adapter, you'd have to connect a new USB-A connector to your existing TomTom cable after cutting it from the original cig lighter adapter."
    Not what is under discussion at all. I bought a new cable from radio shack. It has proper output from the lighter plug(adapter). The two problems are:
    a. New cable has no traffic receiver.
    b. New cable tip at GPS is too large (sticks down below the envelope of the 540XXL).

    My idea was to move back to the original cable which has the receiver and proper GPS USB plug connector by:
    Cutting off the power cig adapter from the RS cable.
    Cutting off the power cig adapter from the TT cable.
    Put the new RS adapter onto the TT cable, soldering wires properly, and shrink wrap insulate the join point.

    I need to know how to match up the wires out of the cig power adapter to the cable wires that run to the GPS connector. If the wires are **RELIABLY** color coded in the standard TT cable, which color is positive? Or, which pin at the GPS connector needs to be the 5v+ and I can meter that back to the cut end and connect it to the positive 5v out of the RS cig power plug. I know what I am doing electrically, but don't know what is usually called the "pinouts" (specification of what 'signal' is on what pin).
     
    Last edited: Oct 8, 2013
    movrshakr, Oct 8, 2013
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  12. movrshakr

    canderson Moderator

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    So the cable you bought from Radio shack has the wire integrated and terminates in a USB miniB connection? I don't see how you'll use any part of that to solve your immediate problem, which brings us to your ideas on actually solving it...

    You plan to splice the old cable to the new integrated adapter/cable -- is that right? Rather than trust TT to be consistent, there's a better approach that will probably have occurred to you as an electrical engineer.

    You need to go ahead and cut the old adapter off the cable and count wires. Leave yourself just enough wire on the adapter end so that you can strip a bit off of each wire and do this quick check...

    Just ohm out the outer ring (spring) from the adapter to each of the wire stubs you left for the measurement and you'll find the ground. The other will be the +5V. Here's hoping you have only two wires, because then you're done.

    HOWEVER ... some units came with cigarette lighter adapters that included a 3rd 'remote sense' wire. It's used for determining the voltage drop across the main power wires in the presence of varying amounts of current. That wire will be white. In the event that you run across it, ignore it altogether (just tape it off). I could never understand why they couldn't just use decent gauge wire to begin with and not worry about it, especially since the +5 gets regulated to 3.3V internally, but ...
     
    canderson, Oct 8, 2013
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  13. movrshakr

    Andy_P Moderator

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    Unless of course the replacement unit (the Radio Shack one) ALSO expects a sense wire. If that's the case, then taping off that wire would do exactly the same damage as when it breaks in an original charger... i.e. ramp the output volts up to 12V. Boom!

    Basically, the correct approach all comes down to comparing the innards of both chargers, and working out which wire does which, rather than trying to find a colour code for the wires (which may not be consistent anyway...)
     
    Andy_P, Oct 8, 2013
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  14. movrshakr

    movrshakr

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    And last two are excellent discussions/analysis.

    "You plan to splice the old cable to the new integrated adapter/cable -- is that right?"
    Yes.

    Your description of metering the adapter plug wires to the plug contacts is simple and obvious. I was more concerned about getting those connected to the right wire headed to the mini USB--the other direction. Of course, once I know the wire color going to the adapter +, that will be the same color the other direction (duh), unless the Chinese used all black wire for everything--unlikely.

    The sense (regulation) wire would complicate things for sure. However, the adapter is a 5v output (nominal), so I don't know how high it would be designed to go to compensate for wire drop in such a case.
     
    movrshakr, Oct 8, 2013
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  15. movrshakr

    movrshakr

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    Adding to the previous...does anyone have the pin-out for the connector on the TT devices, and specifically, the 540XXL?
     
    movrshakr, Oct 8, 2013
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  16. movrshakr

    Andy_P Moderator

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    Andy_P, Oct 9, 2013
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  17. movrshakr

    movrshakr

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    Yeah, I know the standard USB pinouts are available as you link to, but I would not ASSUME that TomTom followed that.

    Questions arise such as, are they sending the traffic receiver data into the device on the same pins that are used for data Tx Rx transfer when computer connected? Well, maybe. Did they put power on the standard pins? Maybe. Probably. I wouldn't want to proceed on an assumption they did the right thing
     
    movrshakr, Oct 9, 2013
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  18. movrshakr

    canderson Moderator

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    Since the TomTom can pull down wildly different amounts of current depending upon mode (esp during charging), they'll take their own 5V "nominal" output and monitor it at the device end with the remote sense wire, and tweak the supply output as needed to hold the 5V. Note: This practice was common on certain previous models of which we are certain. I don't know about the 540, which is why I'm posting this as a warning such that when you cut the cable, you'll be looking for it.

    Whether the 540 was considered a device that needed this treatment, or for that matter, any device that uses this new 'egg' RDS-TMC traffic device, I don't know because they're scarce as hen's teeth at this point, and we've been unwilling to open one up! That's why I recommended finding the ground, and if there's only one other wire, you have your answer .. but if there are three, that this IS the remote sense wire and it needs to just be taped off since your RS adapter isn't going to have that ability nor any place to connect that wire.
     
    Last edited: Oct 9, 2013
    canderson, Oct 9, 2013
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  19. movrshakr

    movrshakr

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    Took a close look at the original TT cable, and there 'appears' to be only two conductors coming out of the power plug. The wire is flat with bulged edges as if that is where the wires are. I have not done any cutting or disassembly yet.

    If this holds true, there will be no sense/feedback wire and it will all be easier.

    EDIT: see video linked below. My conclusion in this post was wrong. One side of the bulged cable out of the power plug is the antenna, and the other side contains both power wires.
     
    Last edited: Oct 13, 2013
    movrshakr, Oct 13, 2013
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  20. movrshakr

    canderson Moderator

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    Excellent news. I thought that the sense wires were dropped for this newer one piece/one connection style RDS cable, but as I say, I haven't had a bad one in hand to open up, and didn't want to open my only good one!
     
    canderson, Oct 13, 2013
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