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Reducing amps in a circuit without change in the voltage

Discussion in 'General Electronics Discussion' started by Karthik rajagopal, May 9, 2016.

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  1. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    I have a 12 v DCadapter with a current rating of 1A and I need to lower the ampere for my circuit without any change in the voltage. Please help me in solving this issue.
     
  2. BobK

    BobK

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    Jan 5, 2010
    No you don't. If the circuit requires less than 1A at 12V that is what it will draw. The Amp ratting of a power supply is the max that it can deliver.

    That is why you can plug a 100W light bulb (about 1A) into the same socket as you can plug a 1500W heater (about 13A) into the same socket in your home. The light bulb does not blow up because the socket can provide 15 or 20A.

    Bob
     
  3. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    Thank you Bob for clearing my doubt. Thanks a lot.
     
  4. cjdelphi

    cjdelphi

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    Oct 26, 2011
    Well... it depends on the circuit
     
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  5. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Correct but not the complete picture. On an unregulated supply rated at 12 V at 1 Amp, if you draw less current the output voltage will be higher. It may not be enough to make a difference, but just be aware of the possibility.
    Regulated supplies you are fine, The voltage does not change at lower currents.
    How do you tell the difference if you do not have a meter? Switching regulated supplies are a lot lighter than unregulated supplies. It has to do with the size of the transformer inside. Unregulated supplies tend to be cube shape and heavy. Switching regulated supplies may be thinner and lighter.
     
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  6. BobK

    BobK

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    True enough, but that kind of supply is pretty much a thing of the past. Most are now switch mode and regulated.

    Bob
     
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  7. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Generally true but we don't know what kind he has.
     
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  8. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    I think I have a regulated power supply. But how to find it out using a DMM?
     
  9. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    But on the adaptor it is give that the current rating is from 100mA to 1000mA. What does that mean?
     
  10. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    Bob what do u mean by a switch mode regulated power supply? Please explain it to me.
     
  11. davenn

    davenn Moderator

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    Sep 5, 2009
    show us a photo of the label on the adaptor
    clear enough that we can read it
     
  12. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Non-switching types are just a transformer, rectifier and maybe a capacitor. 60 Hz transformers are relatively massive and cubical in dimension. Switching regulators change the line voltage to a high voltage DC, chop it up at a high frequency then it goes through a high frequency transformer that is small and light, then rectifier and capacitor. Switching stuff is more complicated but much more efficient and thin due to the board in side. "100 mA to 1,000 mA" pretty much says switching.
    Non-switching 12 V, rated at 1 Amp, will have an output of 12 V at a load of 1 Amp. At 100 mA or no load it may be 18 V out. If you measure the output with a meter and it actually reads the rated voltage with no load it is switching.
    Or if you could just give us a part number we could look up???
     
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  13. davenn

    davenn Moderator

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    not sure how you figure that one ??

    lets wait till he fulfils my image request before confusing him more ;)
     
  14. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    "+12 V DC, 100 mA to 1 Amp" says the voltage stays steady over a broad current range, suggesting a switching regulator. A part number would help confirm or deny this. I haven't seen many wall warts with a linear regulator inside.
     
  15. davenn

    davenn Moderator

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    Sep 5, 2009
    Really ???

    have seem many 100's of them .... extremely common


    Dave
     
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  16. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Our experiences certainly differ.
     
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  17. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    Thank for the reply. I get a constant voltage of 12v in the output when it is not connected to load. And as you said it must be a switching one. I will send the picture of that adapter
     
  18. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    DSC_0002.JPG
     
  19. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    IMG_20160511_204432_816.jpg I have also connected a DC to DC buck converter to vary my voltage from 0.2 v to 11.3 v. Will that affect amps? It is lm2596.
     
  20. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    And guys I had also created another thread . if u guys haven't noticed it , I think there is a leakage of AC current in my transformer. Because when I connect my positive terminal of my LEDs (strip) to the adapter and stand on the ground holding the negative terminal of the LED I can see the LEDs glowing . but it is not so bright. And when I stand on a plastic chair the light goes off. Can anyone analysis the problem and help me. Bcoz I am going to use it with my circuits with microcontrollers.
     
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