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Current Limiting Circuit

Discussion in 'General Electronics Discussion' started by kevilay, May 2, 2012.

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  1. kevilay


    May 2, 2012
    Hey guys, Im trying to build a power supply for my guitar pedals. Its going to run several pedals. What I would like to have is a few current limiting circuits in it. Here is how its going to work. I am planning on running it off a 24v 2A supply. I would like to have several 9V (approx 10) outputs, and 1 12v,15v, and 18v output. I was planning on using these regulators I have which are limited at 100mA which is enough for 1 guitar pedal. How could I make a current limiting circuit that will work for this, with an LED to show if their trying to draw to much. Is there a way to avoid making a limiter for each of the 10 9v outputs. Voltage drop could also be a concert.

    Any help is appreciated.
  2. gorgon


    Jun 6, 2011
    If your regulators is limiting to 100mA they should do the job themselves. What type are they? If they are linear regulators 24 to 9 volt gives a big power loss and heat in the regulator, 1.5W at 100mA. If that is acceptable, no problem.

    TOK ;)
  3. kevilay


    May 2, 2012
    Oh the regulators limit the current themselves. So if something needs to run at 120mA and im using a 9v 100mA regulator it will only alow 100mA out. I just want to make sure it wont burn out.

    Is it possible to have an LED to show if its trying to pull more then 100mA. Keep in mind it would have to be cost effect as there would be many of them.

  4. Wabajig


    Apr 14, 2012
    Put a 22 ohm/1/2 watt resistor in series with each output and an LED in parallel with the resistor. Make sure your voltage out is correct and your device is hooked up for a load. You could experiment with the exact value with a pot in the circuit, use a 1K ohm pot configured like a rheostat. Slowly turn the rheostat from 0 ohms until LED is barely lit. Then measure the voltage to your device to make sure it is maintained at 9V, 12V, etc. Now if the device begins to draw more juice than normal, it will get brighter. Also the LED goes in one way to light it up. One note though if your supply shorts, then your LED is toast. Good Luck, John
    Last edited: May 2, 2012
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Ensure that your regulators are rated for a higher current than your load. I would tend to recommend using 1A regulators in this case. It is not because of the current required, but because you're asking them to dissipate over a Watt. The 100mA regulators in their small packages will be stretched enormously trying to do this.
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