How to Build an IR LED Circuit
In this project, we will show how to connect an IR LED so that it emits infrared light.
This is a very simple project, as all that is needed is to give the IR LED power. Once it gets sufficient power, it will emit its infrared light.
The only parts that are necessary to build this circuit are:
- 3 Volts DC
- 2 Cell AA Battery Holder
- 62Ω Resistor
- IR LED
- Jumper wires/Alligator Clips
The 3VDC which is needed for this circuit can be obtained from 2 AA batteries placed in series. Since most AA batteries provide 1.5 volts of power, 2 cells are sufficient for this project. However, if you have a DC power supply, you can use that also to provide power by adjusting it to give out 3V.
The IR LED needed for this project can be obtained from many different online retailers such as
sparkfun and many others. For this project, we are going to use the one
provided by Sparkfun, the YoungSun LED Model No. YSL-R531FR2C-F1, a 850nm IR LED.
IR LED Circuit
The IR LED circuit we will build is shown below:
All that the LED needs is 1.5VDC dropped across it.
This is the datasheet for the IR LED we are using for this circuit: IR LED Datasheet.
The datasheet specifies that this LED should receive about 1.5VDC of power. This is specified in the forward voltage specification. The forward voltage is the amount of voltage
that should be dropped across the terminals, anode and cathode, of the LED.
The datasheet also specifies that the LED should receive a maximum forward current of 50mA.
This means that no more than 50mA should
flow through the IR LED circuit. Since we want to limit the current flowing through the LED to 50mA, we add a 62Ω resistor to our circuit. Current= voltage/resistance. Therefore, 3V/62Ω= 48mA.
62Ω is the smallest resistance we can provide to the circuit. Any smaller of resistance and we risk the current exceeding the maximum current specification. Exceeding this current rating can
damage or destroy the LED, so this should never be done. If you want to dim the infrared output, however, you can use a greater resistance resistor, such as a 80Ω resistor.
Testing the IR LED
An IR LED is different than a regular LED because it does not emit visible light which we can see. Infrared light is outside the visible spectrum. Therefore, when we provide power to the infrared light, we cannot tell whether it is functioning or not. In order to detect this infrared light which an IR LED gives off, we must use an IR detector circuit to do so. An IR detector circuit is a circuit which can pick up infrared light. Therefore, it will be able to tell whether our IR LED is working or not.
In another project, the IR Detector Circuit, we built a circuit which can detect infrared light emission. See this circuit to be able to
detect this one which we've just built.