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Bench power supplies! [help!]

Discussion in 'General Electronics Discussion' started by The.Pisces, Dec 19, 2015.

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  1. The.Pisces

    The.Pisces

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    Dec 19, 2015
    Hello everyone, I am currently trying to find a good power supply for my electronic projects. However, I am very confused on where to go, should i go with building one (If it's worth it) or buying one (which is expensive in my country). Moreover, What's the difference between the switched mode power supplies and the normal ones that use the LM-series voltage regulators. If I was to build one what should i choose to make sure i get a good efficiency. edit: Should i go for those chips ( i've seen some instructables on those chips that help make the power supply better?)
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    hi there
    welcome

    switchmode PSU's (SMPS's) are physically much lighter, often much smaller and much more efficient than linear PSU's for any given current rating

    yes, you could build a linear PSU, but unless you are already well skilled in electronics
    and working with mains power, DONT do it -- buy one instead
    you should be able to get a reasonable variable voltage SMPS for ~ 0 - 30V and up to 5A for around 50 - 150 GBP


    Dave
     
  3. duke37

    duke37

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    Jan 9, 2011
    It all depends on what you want to do. To drive a powerful transmitter you should go for a comercial 13.8V, 30A supply.
    To test small circuits, a PP3 9V battery is best.
    Operational amplifiers often use +12 to 15V/ -12 to 15V
    Other circuits work on 5V or even less.

    Switch mode power supplies can be 'dirty' and cause interference to radio circuits. Linear power supplies using regulators are cleaner but are not so efficient so can get hot.

    Why do you need a good efficiency if taking power from the mains. Anything you are likely to make probably will not run a lot and mains power is cheap and keeps your tootsys warm.

    An old computer power supply can give all the voltages you are likely to need. These are switch mode with added linear regulators.

    And welcome to EP
     
  4. The.Pisces

    The.Pisces

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    Dec 19, 2015
    I'd like to go with building one however, where should I start if I am going with a linear voltage regulated power supply. By the way if I am going with that, which voltage regulator will make the efficiency a little better? I can't help my self but to build one (it's like something is itching me to building something in the holiday ). And if I will build it I'll try to post some kind of guide to building it.
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    unless we know with doubt that you are experienced working with mains voltages
    we would be reluctant to advise you, and suggest instead that you find some one in your area
    that can mentor you in person .... don't want you killing yourself or others


    Dave
     
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  6. Martaine2005

    Martaine2005

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    May 12, 2015
    Personally, I'd go with Duke37's idea of an ATX computer power supply.
    It doesn't sound like you have any experience with mains voltages.
    They are very efficient and safe.

    Martin
     
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  7. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Hello. First tell us how much money you have to spend. What current are you thinking your circuits would draw? A safer option would be to buy a wall wart or some other cheap PSU, say 12 Volts and build your own adjustable regulator. This way you are only dealing with 12 Volts and not 240.
    Adam
     
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  8. The.Pisces

    The.Pisces

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    Dec 19, 2015
    How about using a ready to use 24v power supply (used for LED strips) and continue building from there like adding a dc to dc buck converter then using a potentiometer to vary the current and voltages. I'd like to atleast learn something while building or what's the use. By the way touching the grills of a 24v powe supply can kill you if i'm correct??. Can buck converters interfere with radio's and that kind of stuff?
     
  9. Martaine2005

    Martaine2005

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    The point is to keep you and everybody safe!
    You have not answered any questions about voltages or current.

    Martin
     
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  10. The.Pisces

    The.Pisces

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    Dec 19, 2015
    The power supply should range from 1.5v to 30v however the maximum i will use is 24v, and the current should range from 2-4 ampere.
     
  11. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    I agree its so rewarding building your own circuit. I never heard of anyone getting a serious shock from 24 Volts. Just dont put your tongue across the terminals. The power supplies for LEDs are normally constant current. Not saying you cant use them just might be better to use a bog standard PSU. SMPS regulators if designed correctly should not be an issue with radio, however they can introduce noise into a circuit unless good filtering is added. A small inductor and output capacitor is sometimes all thats needed.
    Adam
     
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  12. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Thank you Darling.
     
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  13. Martaine2005

    Martaine2005

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    Your welcome honey bun!!
     
  14. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Thats going to be one hell of a PSU at 24 Volts and 4 Amps. Thats going to need a very large heat sink.
    Adam
     
  15. Martaine2005

    Martaine2005

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    This may be of use to you.
    A very knowledgeable young man has 'modded' his own computer power supply.
    If you like it, you can call him... @Supercap2F
    He incorporated a micro controller too.

    Martin
     
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  16. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    That will be Dan then better known around here as @Supercap2F
     
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  17. Martaine2005

    Martaine2005

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    Yes, good ole (young) Dan..
    If the OP is into programming? Could be right up his street!

    Martin
     
    Arouse1973 likes this.
  18. Supercap2F

    Supercap2F

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    Mar 22, 2014
  19. BobK

    BobK

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    Any linear regulator going down from Vin to Vout will waste exactly the same amount of power. The formula is

    Pwaste = (Vin - Vout) * Iout

    You can save a little by using a low dropout regulator, which will allow you have a smaller Vin, but if you are going up to 30V anyway, but normally use 12V, the difference would be small.

    Normal regulator: Vin = 32V
    Low dropout regulator: Vin = 30.5V

    If regulating down to 15V at 4A

    Normal regulator wastes (32 - 15) * 4 = 68W
    Low dropout regulator wastes (30.5 - 15) * 4 = 62W

    Note that either of these will need an enormous heat sink.

    I think shooting for 4A is unrealistic.

    Bob
     
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