230VAC to 9VDC rectifier question

Discussion in 'Homework Help' started by keithisdoped, Aug 24, 2011.

  1. keithisdoped

    Thread Starter New Member

    Aug 22, 2011
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    hi geniuses, once again i have a question :D
    Its my first time working with XFormer,
    and as you can see i have designed in my schematics, question is, is it correct?
    i'm using a 1A Fuse , 9V 1A XFormer , 4 x 1N4001 , E-Cap 1mF and 7809 regulating IC..
    do i need the E-Cap?

    second question is because my XFomer has 8 pins how do i wire it in my PCB and do i need a socket for it? and does it have polarity because the one i'm using is a DS2Y-S-DC9V-R but it's hard to find the datasheet and the one i found does not really explain much..

    once again appreciate it!
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    If you want DC then you need a capacitor at the output, yes.

    Googling "DS2Y-S-DC9V-R" brings up a relay. Is this the right part number?
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Are you sure that you have a transformer at all? Looking up "DS2Y-S-DC9V-R" on the Internet, I can only find relays.
    http://datasheet.octopart.com/DS2Y-S-DC9V-R-Panasonic-datasheet-2347.pdf

    Transformers are rarely used with sockets, but relays more often are. You need to be quite sure that you have a properly rated mains transformer before connecting it to the mains, and be certain of the right way to connect it, or else you may have a bad accident.
     
  4. keithisdoped

    Thread Starter New Member

    Aug 22, 2011
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    ahh looks like i got the wrong item lol! errr but will my circuit work? if im getting a 230/9V 1A transformer? i'm from singapore and our mains are delivering 230VAC.. and err praondevou so i need one more 1mF E-Cap after the output of the 7809 IC? i thought the 7809 will deliver me a stable 9V? correct me if im wrong..
     
  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    Yes the transformer 230V/9V should work. Dropout voltage of the regulator is about 2V, DC is higher than the 9V so it should be ok. Make sure you buy a transformer for the current rating you want, otherwise it's output voltage could drop so much, that there is not enough DC at the input of the regulator. DC in needs to be higher than 9V + dropout voltage. You can also buy a transformer with a slightly higher output voltage.

    No, no need for 1000uF after the 7809. You can put however 100nF if you need a better transient response.
    Put 100nF at the input too if the 1000uF is not near the regulator.
     
    Last edited: Aug 24, 2011
  6. keithisdoped

    Thread Starter New Member

    Aug 22, 2011
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    does this look better? and yeah thinking about plugging it into the mains, i am quite worried it might blow up on me... any precautions or extra safety measures i should take? yeah this circuit will be going into a box but apart from that anything i am missing out?
     
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  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The 78xx series of regulators require that an 0.33uF cap be present from the input to GND, and an 0.1uF cap present on the output to GND; otherwise it may oscillate at frequencies in the MHz range - I have seen this happen.

    You can also use larger capacitors, but the small caps must be present, and they must have very short leads.
     
    Georacer and keithisdoped like this.
  8. keithisdoped

    Thread Starter New Member

    Aug 22, 2011
    14
    0
    nice!
    thanks for the info!
     
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