Clean Dual polarity Regulated 15/-15,+5 Volt Power Supply Project

Discussion in 'The Projects Forum' started by farhan89, Nov 6, 2010.

  1. farhan89

    Thread Starter Member

    Feb 13, 2010
    34
    0
    Hello Guyz!

    I have built this Dual Polarity Regulated 15/-15,+5 Volt Power Supply by my self,

    There is no +5v Ckt in the Schematic , i have installed that by my self

    http://img109.imageshack.us/img109/9129/061120101365.jpg
    http://img44.imageshack.us/img44/7646/061120101366.jpg
    http://img683.imageshack.us/img683/328/061120101367.jpg
    http://img696.imageshack.us/img696/4664/061120101368.jpg


    Where there are some big soldering i because of some faulty IC's and wrong connections,

    I have also 1 Question , how to know max Amperes this power supply can give?

    Also Comment on it's build :)


    Will make New 1 with high amperes sooon.............
     
  2. mpearson

    New Member

    Nov 6, 2010
    1
    0
    The max current output is determined by the rating of your weakest component. For example: if your transformer is rated for 2A, but your regulators can only handle 1A, you have a 1A power supply. The rating of the regulators is also dependent on how well you can dissipate heat (heat sinking).
     
  3. farhan89

    Thread Starter Member

    Feb 13, 2010
    34
    0
    ^^^
    Thanks for guiding!
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I do not see a fuse on the primary side of your transformer. Do you have one? The line (hot) side should be fused, before it gets to the switch.

    It looks like you used electrical tape on the 120v jack connections? That is not good at all; the adhesive on electrical tape will eventually get "gummy" and the tape will fall off. You should use heat shrink tubing instead; two layers.

    You did not use the ground lug on the 120v jack connector. You should connect it to the transformer's case; that way if the primary winding shorts, it will blow the fuse (that you need to install if you have not done so yet). The secondary side should also be connected to the ground lug; that way if the transformer shorts from primary to secondary, the ground will protect you.
     
  5. farhan89

    Thread Starter Member

    Feb 13, 2010
    34
    0
    WOW! V.Imp points


    Since it was my first project so i didn't realise those points, In my next project i will consider these points
     
  6. Rbeckett

    Member

    Sep 3, 2010
    205
    32
    Have a look at the Elenco XP-720K schematic. It can be downloaded online and is exactly what you describe. I built one from the kit and it performs flawlessly with very good regulation and almost zero voltage creap. Their circuit drawing is almost exactly what you have drawn, with minor variation in smoothing caps and rectifier diodes. The max available amperage for that PS is 5A on the 5V, and 1A on the variable volts and those are limited by the 7805, LM317 and LM337's capabilities.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I just spent 10 minutes writing another reply, hit my NumLock key by mistake, and found myself on my home page moments later, my efforts having gone to the bit bucket. :rolleyes:

    In your 1st pic, there appears to be an indicator lamp in the upper left corner. Insulate at least one of the leads using heat shrink tubing, or they will short.

    Your wiring is running everywhere in curlicues. Use zip-ties to make a nice, neat compact bundle. Keep the 120v wiring separate from the secondary side wiring. Otherwise, that jumble of wires will cut down the airflow in the enclosure.

    Heat sinks on the regulators are very small; they won't help a lot. They need to be much larger.

    The fan is rather far from the heat sinks. Use PVC pipe or other inexpensive material to make a duct, directing air right at the heat sinks.

    Next project, use 120v fans instead of 12v fans that are powered by the secondary side; you're stealing power from what your supply could otherwise output.

    I don't see any way for air to get out of your enclosure. You need to have holes for the hot air to exit, at least as much surface area as the inlet for the fan; preferably more.

    Linear supplies generate lots of heat; most of it in the regulators. Even really large heat sinks aren't enough under many circumstances. Keep in mind that P=EI, or Power in Watts = Voltage x Current. If your unregulated side is 22v and you are putting out 15v at 0.5a, then power dissipated in the regulator is (22-15)*.5 = 7*.5 = 3.5 Watts. The greater the voltage differential across the regulator, the worse the power dissipation problem becomes.
     
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