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First Project - Led Power Question

Discussion in 'LEDs and Optoelectronics' started by sergio1, Jul 8, 2013.

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  1. sergio1


    Jul 8, 2013
    Hey guys I’m brand new to electronics and I’m embarking on my first project. I was hoping someone with more experience can clear a few things up for me.
    My goal is to decode the IR messages from a remote.
    I have 2 leds a detector and a transmitter:
    The detector has a forward voltage of 1.2 at 1mA I’m using an Arduino as my power source with 4.7V out. I’m familiar with ohms law but how can I bring both the voltage and the current to 1.2volts at 1mA?
    Also, what are some good ways to learn the math behind electronics? Any books?
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Firstly, whilst a LED can be used as a photodetector, there are specific devices made to do this.

    A detector is not typically used with a high forward current like you suggest. It is normally used like a (very) small solar panel. The very tiny currents generated are amplified and detected.

    There is a sticky with reviews of some books in another section. Let me look it up for you.

    Here it is:
  3. Nemo


    Jul 9, 2013
    You should think of the IR Detector as a transistor, were the cathode is the Collector, the Anode is the Emitter and the Light it receives is the Base.

    What this means is that you supply the cathode with a voltage and connect the anode to your load. When the detector sees IR light, it allows the voltage to flow to your load.

    In the Below circuit you are a battery, an IR detector, a LED and a Switch. When the switch is closed "AND" the IR detector receives IR light, the circuit will complete and the LED will light up.

    Forward voltage as the amount your voltage you supply the IR detector will drop. So in the above circuit, if I have a 5 volt battery and I am using your detector with a 1.2v FV at 1ma. I will see 3.8v from it when it is detecting IR.

    We can also multiply 1.2v with .001 amp = .0012W, this tells us that the IR detector will use .0012 watts of power.

    I hope this helps.
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