# First Project - Led Power Question

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

1. ### sergio1

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0
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*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,838
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: https://www.electronicspoint.com/book-reviews-t251799.html

3. ### Nemo

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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.

http://imgur.com/2VBMI4Z

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.