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Problems selecting a PCB Transformer

Discussion in 'Datasheets, Manuals or Parts' started by NewcastleSAR, Jan 1, 2007.

  1. NewcastleSAR

    NewcastleSAR New Member

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    Cheers Nigel..

    Many thanks for your help. :)

    Declan

     
  2. Hero999

    Hero999 Banned

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    Now this is confusing.

    There are two different projects here.

    Which one are you refering to?

    If it's the first one "Darkroom Timer 1 6V.pdf", then I stick so what I've said.

    If it's the second one "DarkroomTimer Schematic.pdf" then you're right, I have made a mistake, that tiny 1.5VA transformer just won't do.

    However I do feel that 1A is still a bit overkill, those LEDs will only take 7*18.6mA = 131mA (they're multiplexed aren't they?) and I can't see the rest of the circuit using much; maybe the whole thing will use 200mA maxumum.

    15V isn't needed a 12V will do.

    What's the point of the opto-isolator? The relay should provide all the isolation you need.

    Why bother with a separate 12V supply? You can get 5V relays you know.

    NewcastleSAR,
    Which project do you want to build, the first of the second?
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Assuming the figures are correct, 200mA from the 22V after rectification, is still 4.4W.
     
  4. dave

    Dave New Member

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  5. NewcastleSAR

    NewcastleSAR New Member

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    Hi Hero999

    At present, I'm haven't decided which of the circuits I am going to build although I am leaning towards the 2nd circuit titled the 'DarkroomTimer Schematic.pdf'.

    As both used transformers, my questions were related to assistance in attempting to understanding and select the correct type of transformer from RS Components.

    Looking at both circuits in a simplistic manner for my brain, I see what you are saying in relation to the 12V section. Is there any particular reason why I couldn't use the PSU Section of the 6V Circuit (adjusting Transformer to suit) and also integrating the Solid State Relay S201S01 (superseded by S201S05) into circuit 2 ('DarkroomTimer Schematic.pdf') thus doing away with the 12V section?

    Declan
     
    Last edited: Jan 4, 2007
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Seeing as you're having to ask for advise on a transformer, I don't suggest you attempt redesigning the circuits!.
     
  7. NewcastleSAR

    NewcastleSAR New Member

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    Hi Nigel..

    Yes, I understand what you are saying and wouldn't attempt to even consider redesigning the circuit but in terms of understanding concepts, would what I said work?

    Declan
     
    Last edited: Jan 4, 2007
  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Yes, the principle is OK.
     
  9. NewcastleSAR

    NewcastleSAR New Member

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    Cheers for that Nigel..

    This discussion has been very enlightening. I'm going to talk to the School's Technology Teacher to get further advice from him. I did electronics years ago but to be honest, the amount of maths in it put me off and being at a young age, that wasn't hard.

    Now as I approach 40, I think I would be in a better 'educational state of mind' to learn.

    Many thanks

    Declan :)
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Good luck! - it's EXCEEDINGLY rare to find one who knows anything about Electronics - it's usually taught by a teacher who attended a short course (1 day or something!).
     
  11. Hero999

    Hero999 Banned

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    But I suggested a 12V transformer.


    So I'd recommend a 12V 300mA transformer.

    That's true, I knew more than my technology at the age of 12.

    I have a feeling that these circuits were designed by a PIC expert rather than an electronics expert.
     
  12. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It's hardly a big deal fitting a 1A transformer! - it will run cooler for a start!, and it's likely the designer had a transformer available.
     
  13. Hero999

    Hero999 Banned

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    I was thinking more about the use of a separate 12V power supply and an optoisolator as well as a relay.
     

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