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Potentiometers in a circuit

  1. Mar 17, 2013 #1
    If I add a potentiometer to my circuit will I be able to control the brightness of the LED with the meter?
     
  2. jcsd
  3. Mar 17, 2013 #2
    potentiometers are nothing more than variable resistors .so by adjusting it you either increase or decrease both the voltage/current as voltage is relative to current.and vice versa.
    Now usually potentiometers are with low wattage so they cannot manage large currents or they will overheat and damage.In the case of a single or multiple led's that is not the problem as led draws few miliamps an average of 20mA I guess.
    Yes if you have a let's say 9v battery you can put a potentiometer in series with the Led but be careful as led's have a current limiting resistor.It would be better to use the resistor in series with the pot and the battery.Without the resistor you could accidentally or on purpose turn it to very few ohms resistance and the current through the led would be too high and it would burn down your led (destroy it )
     
  4. Mar 17, 2013 #3

    sophiecentaur

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    A fixed series resistor of about 300Ohms would ensure that the LED doesn't get overloaded. (The LED will take up about 1.5V of the supply volts and that leaves 7.5V from your 9V battery. 7.5V across 300Ohms will give you 25mA when your variable resistor is at zero - safe.
     
  5. Mar 17, 2013 #4

    davenn

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    The only way you are going to effectively adjust a LED brightness is to use a PWM ( Pulse Width Modulation) circuit

    There's numerous circuits available online using NE555 timers and a small handful of other components to do this :)

    Dave
     
  6. Mar 18, 2013 #5

    Bobbywhy

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  7. Mar 18, 2013 #6

    sophiecentaur

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    It's all a matter of the level of expertise, surely. PWM could be beyond the experience of someone who has just done Ohm's law but trying to use a variable resistor will show them the shortcomings of the method.
     
  8. Mar 18, 2013 #7

    davenn

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    yup, they will learn how quickly you can pop LED's ;)

    D
     
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