diodes are current hungry devices and can pull a lot of current and burn themself, due to which they cannot be connected directly to the power supply or battery and require a driver circuit. The driver circuit limits the current goes in the diode and also increase the life of the laser diode as compare to the other current limiting procedures.
The laser diode driver circuit shown here is very easy to build and using very few components. The heart of the circuit is a LM317 IC that is used here as a current limiter. The circuit is using a 200 ohms variable resistor or pot to adjust the output current. A laser diode also get damaged on accidental reverse connection of the battery, therefore a 1N4007 diode is used to save the laser diode from this problem. The 10uF electrolytic capacitor is used to smooth the output of LM317 IC.
A laser diode is a sensitive device due to which it is important to take care of it when connecting in the circuit. It is better to first disconnect the power supply or battery from the driver circuit and short the pins of the 10uF capacitor before connecting the laser diode with the circuit. A switch can also be added between the supply and circuit.
A laser diode driver circuit is a very important device to operate a laser diode because a laser diode is a current operated device. You can also drive a laser diode with a resistor but it is not a good way and it mostly hearts the diode. One can not operate these diodes without the driver circuit because the laser
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