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Help me build a battery charger?

Discussion in 'Power Electronics' started by NateNewThread, Sep 17, 2012.

  1. NateNewThread

    NateNewThread

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    Sep 17, 2012
    Hi All,

    So, the charger I need is discontinued so I have to make one myself. This is probably a pretty easy task for someone that knows about electrical engineering but I am pretty bad with this stuff. I found out that the end that plugs into the device is a coaxial plug made by a company called Radiall which I ordered for 4$ dollars. I also know all the output requirements for the charger end which I will post below. I have a multimeter but by no means am I an expert in using it so please, no jargon. I'll pretty much need baby steps with this process.

    Thanks,
    Nate
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    This is not a charger but a simple "wall wart". It is rated for an output of 7V / 800mA
    Since mains voltage is involved I discourage you from building a new one yourself. Just buy an off the shelf power supply with similar ratings (don't worry if the output current is more then 800mA, only it be not less). Cut off the low voltage plug from the new supply and replace by the plug from the old supply. Observe the polarity!
     
  3. NateNewThread

    NateNewThread

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    Sep 17, 2012
    So I can pretty much just buy an AC adapter and cut off the end and fit my new end on? As long as it has similar output ratings?
     
  4. NateNewThread

    NateNewThread

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    Sep 17, 2012
    Would this work?
     

    Attached Files:

  5. BobK

    BobK

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    Jan 5, 2010
    No, you need one with a 7V output.

    Bob
     
  6. NateNewThread

    NateNewThread

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    Sep 17, 2012
    So this will work?
     

    Attached Files:

  7. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    That one should be suitable.
     
  8. NateNewThread

    NateNewThread

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    Sep 17, 2012
    Thanks Harald

    Another noob questions coming right up.

    I know I should expect two thin wires when I cut the charger cable to splice in the Radiall connector, but how will it wire into the Radiall connector? There MIGHT BE two tabs for them to wire into, but I highly doubt it. I don't really know how to wire coax type fittings,

    Thanks
     
  9. BobK

    BobK

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    Don't remove the coax cable from the connector, cut it, then splce the two wires to the shield and center wire. Do check the polarity though. Most likely the shield will be negative and the inner wire positive, but do make sure of this.

    Bob
     
  10. NateNewThread

    NateNewThread

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    Sep 17, 2012
    Remember, the pictures I took are from my friends cable which I am trying to duplicate using a spare charger (with similar output/input specs) and a coax connector that I ordered from the manufacturer. So wiring straight into the connector will be necessary.
     
  11. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    You will have to jury-rig that. Either use a piece of coax cable as an intermediate (similar to Bob's suggestion) or wrap one wire around the isolation to imitate the coax shield. This is only second best, however.
     
  12. NateNewThread

    NateNewThread

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    Sep 17, 2012
    Ok so I think my question was answered but to clarify let me summarize. When I cut the charger wire I'm going to see 2 small wires, one positive and one negative (the charger I am buying does not have a ground wire). I connect the positive wire to the "center wire" and I connect the negative wire to the "shield". Then its good to go?
     
  13. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    That's quite common, but by no menas a standard. It depends on how the original charger was wired. Usually you'll find a symbolic representation of "+" and "-" on the device into which the cable is plugged.
    Without that information you will have to try and hopefully be lucky. Use crocodile clips to try the right connection before ssoldering it in place.
     
  14. donkey

    donkey

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    Feb 26, 2011
    could he simply grab an LED and resistor plug it up to a connector to see which is positive or negative? or a multimeter might be useful too (I got an elcheapo for $10au)
     
  15. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    As long as the old charger still spits out some juice,: yes.
    As it seems thst his old charger is defunct: no.
     
  16. donkey

    donkey

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    Feb 26, 2011
    I meant to test which is pos and which is negative on his friends good charger that he is trying to replicate.
     
  17. NateNewThread

    NateNewThread

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    Sep 17, 2012
    So what you're saying is to plug my friends charger into the wall and use my multimeter to confirm positive and negative leads on the coax end?

    I just received the Radiall Coax connector and it raised more questions. I know the tiny pin sits inside the coax connector and obviously has to be soldered to one of the charger wires, but the shield? Well I'm still unsure where it sits and how its wired. There's no place where it sits firmly and makes sense to me that you would attach a wire to it someway :confused:
     

    Attached Files:

  18. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Exactly!

    Find out how the connector is wired on the working charger. COnnect the wires from the new charger accordingly to the new plug. You can possibly open the connector on the working charger to find out how it's done there.
     
  19. NateNewThread

    NateNewThread

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    Sep 17, 2012
    I've found a company that stocks the charger so I will be sending this project straight to hell!

    Thanks anyways people.
     
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