Help with laser diode circuit.

[milan.rajik]

This is not related to laser but to laser diode driving circuit.

This page contains a LM317 based Laser diode driving circuit.

https://www.electro-tech-online.com/threads/dvd-burner-laser-pinout-question.121946/

The input V to LM317 is 7.2V and hence I cannot use this circuit. I am making a battery operated Laser device. My Laser diode V rating is 2.2V and I can only use a 2.7V 1500 mAh Li-Ion battery used in mobiles. Please tell me how can I modify the LM317 circuit so that it powers the 2.2V Laser diode.

I am trying to make a vibration sensor. There will be a laser diode and a laser photo detector. Laser light will be falling on detector. The laser diode will me mounted in such a way that it can oscillate lake a fan when there is a motion. When this happens light will be interrupted to detector and this is used for sensing. I am making a optical vibration sensor. I can't use other types (mechanical contact) vibration sensors. I am using 1 mW laser diode.

 

[ArticCynda]

Use a shunt register in the feedback loop to turn it into a constant current source.

 

[milan.rajik]

A circuit would be helpful. Sorry, I mentioned bat V as 2.7V. It is 3.7V 1500 mAh. My system is battery powered. The laser diode will be mounted on a spring. Wen there is vibration the diode will vibrate and light falling on detector will interrupt and this triggers the INTx pin of PIC32MX.

Just a resistor, a 10 mfd 6.3V and a 1N4007 all in parallel to to diode ? A resistor to drop 3.7V to 2.2V ?