Design problem

Discussion in 'The Projects Forum' started by Bazzer Englander, Jun 4, 2012.

  1. Bazzer Englander

    Thread Starter New Member

    Apr 18, 2011
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    People, I need help with a circuit board, I have this device which has been designed by an electronics engineer to an idea of mine, I have had twenty-thirty of these built and sent out, I've had 15% returned mainly through component failure ie, relay or transformer faults, and now when I,m on the point of getting publicity to start things moving I have an earth fault indicating although there isn't a fault, and the chap who did the design has gone on a bender & I can't get hold of him. I've tried to find the fault to no avail,(I should point out that I'm not an electronics engineer) I've cross checked the circuit against the diagram but I think the diagram is not the right one, I have a parts list which again is not 100% correct, the one I've put together shows the same fault. Before I go too far,ie pictures ect,is anyone able to help.

    Many thanks,
    Barry BazzerEnglander.
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Post schematic (or part of it), PCB layout, pictures and a description of what the circuit is supposed to do.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,145
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    Classic. One of those "contingencies" they don't teach you about in school.

    Anyway, as noted, no one can say much without seeing things. The more detail you can offer, the more you'll get back.
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    first off it seems you have a major configuration control problem. You don't have a good idea of what you are building. This is a common failing of drunkards and fools. I also struggle at it and make commonly make mistakes even though I try not to do this.

    Do you have a unit that works? Start there, compare every part on it with a kit of unbuilt parts and the bill of materials you have. Job one is to re-create (or simply create) what parts are used in this.

    You may have the same problem with the schematic and the assembly drawings. They may be incorrect or incomplete. You need to be able to depend on these 100%

    It is not the worst idea to bring "fresh eyes" into this job.
     
  5. absf

    Senior Member

    Dec 29, 2010
    1,493
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    Are all of these 20-30 cards sent to different customers or just one customer and are they used in different environments? What kind of failures were on the relays? Burnt contacts or burnt coils or not operating? Transformers? Overheat or opened coils on primaries or secondaries? Are they under-rated parts?

    Of course a picture worths a thousand words.... A partial schematic or a photo or parts used would give more clues for people here to analyse.

    Allen
     
  6. Bazzer Englander

    Thread Starter New Member

    Apr 18, 2011
    18
    2
    I can't find how to download pictures to this site to enable me to better inform you, I also posted a continued thread yesterday but cant see where it is on the forum, I did it as a quick reply & it has disappeared into the ethos.
    There dos'nt seem to be an icon of some one sitting and crying into his hands, so this will have to do, "WHaaaaaaaaaaaaaaaaa"

    Bazzer
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    When making post, you need to click Go advanced, then below the window is Manage attachements, so click that and upload all you got.
    Although I am not sure if newbies are allowed to upload, so you might try imageshack, dropbox, or something similar.
     
  8. Bazzer Englander

    Thread Starter New Member

    Apr 18, 2011
    18
    2
    I can't down load diagrams or pictures,I have to wait till my son in law comes home from holidays, Thats sad isn't it.
    The idea of the circuit is to identify if a power supply is wirerd correctly ie the polarity is correct, It's mainly for the carravaning & boating leisure people, In europe its amazing how many sites are wirerd wrong, this Polarity switch reconises the polarity and if it is wrong reverses it in millisecons. It has three LEDs green red & orange, If the green led is on the polarity is correct, If the red & green are on it means the polarity is reversed but has been rectified by the switch ie the live & neutral come in reversed but go out the correct way round, If the orange light is on it means an earth fault. Since starting this thread I've found that damp was causing the orange to stay on,after heating with a hot air gun all worked again except I get a faint red with the green, one thing I have seen on the circuit diagram is one of the transistors is not the correct way round & wondered if that would have a bearing on the operation of the Power changer,The transistor is a 2N7000, Thats all I've got.

    Bazzer.
     
  9. #12

    Expert

    Nov 30, 2010
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    Wait for son-in-law. Without drawings or pix, it is all guessing.
     
  10. BillB3857

    Senior Member

    Feb 28, 2009
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  11. WBahn

    Moderator

    Mar 31, 2012
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  12. WBahn

    Moderator

    Mar 31, 2012
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    To find your long-legged-blond post, just click on your username in the upper left corner of any post you've made and choose "Find all posts by Username".
     
  13. Bazzer Englander

    Thread Starter New Member

    Apr 18, 2011
    18
    2
    No, What my switch does is to recognise whether the polarity is the correct way round & if it isnt automatically reverse it, It will also act like the tester that you've listed inso mutch as it will tell you of an earth fault as well as indicating whether or not the incomming power is reversed but has been rectified.

    Bazzer
     
  14. WBahn

    Moderator

    Mar 31, 2012
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    So how can you determine if the neutral and the safety ground wires are reversed?
     
  15. Bazzer Englander

    Thread Starter New Member

    Apr 18, 2011
    18
    2
    It will show a orange led for earth fault.

    Bazzer
     
  16. WBahn

    Moderator

    Mar 31, 2012
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    I didn't ask how it will indicate the problem. By what means will it detect this particular problem?
     
  17. Bazzer Englander

    Thread Starter New Member

    Apr 18, 2011
    18
    2
    Ah! You'll have to ask the chap who designed the circuit board,See my original thread, HE's gone on a bender.

    Bazzer.
     
  18. WBahn

    Moderator

    Mar 31, 2012
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    Ah. I see. As I think someone else pointed out, that is definitely something you are going to have to address is such a way that you end up with solid documentation, not only of the widget that gets built, but how and why that widget works.
     
  19. MMcLaren

    Well-Known Member

    Feb 14, 2010
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    I don't understand. Is this AC power or AC rectified DC power? What are you talking about, please?
     
  20. WBahn

    Moderator

    Mar 31, 2012
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    I think he is using the term "rectified" to mean "corrected". His box uses relays to swap the lines if it detects they are wired backwards.
     
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