My first laser project

[ctbram]

This is my first laser project.

We were throwing away some old dvd reader/writers where I work so I pulled them apart and grabbed the laser diode and some other bits.

I bought a 5mW laser module with focusable line prism from DX.com for $3.99. I tossed the line prism so I had a focused dot or if I flip the lens around it seems that I get a collumated beam that can still be adjusted. I still have some questions on the lens but I'll post those with pictures in a follow on post.

I did some research on laser safety and then on driver circuits and then watched some youtube stuff and then read some more on laser safety (this is fun and all but I don't wish to go blind).

Armed with all the knowledge I needed to get started, and feeling relatively confident that I would not end up blind, I raided the electronics supply at the university that I work at and assembled a current limiting Daedal Laser circuit to drive the laser diode I harvested from the dvd drive (see the attached image of the proto-board circuit, the DDL circuit diagram, and the laser module that I purchased from DX.com.

The photo also has the Infra-Red diode from the DVD which looks almost exactly like the LD. I determined which was which after building the DDL circuit and simply testing both and very low power to determine which was which.

I then pushed out the 5mW LD from the laser module and pressed in the LD from the DVD drive.

There are a couple minor divergences from the DDL circuit diagram.

1. In place of the LM317T I used an LM117T which according to the data sheets is functionally the same.
2. In place of the 100 Ohm pot I inserted a 100 Ohm resister for testing and safety. With this resistor the output of the laser should by around 13mW.
3. Later I put a 18 Ohm resistor and have been testing at around 68mW (only pointing at diffuse surfaces) mostly fiddling with the lens which I will discuss in a follow on post.
4. Until I get safety glasses I do not intend to drive the LD any higher. The maximum theoretical output should be around 313 mW at 250mA.
5. The bread board also has a momentary contact push button switch and yellow LED ciruit to turn on the circuit and indicate it's active. You can see these in my original hand drawn circuit diagram.

I'll post some shots of the beam and further development notes as I go forward. Deciding on safty glasses. I'd like to get two piar as what fun is it if can't share the experience with a friend without blinding them!

On that note if anyone would care to chime in on decent protective glasses that won't break my bank account i'd be greatful.

 

[ctbram]

I am guessing this question has been asked before but is there a way to measure the power output of the laser diode in the circuit above?

I cranked it up full today (theoretically it should have been 250mA and 313mW). I could burn black electricians tape if I used the focused beam but it seemed very weak compared to the videos I have seen where they were popping balloons from 6 meters away and with a collumated but fairly large diameter beam.

With mine I have to flip the lens and place an object at the focal point of the beam about 3 inches from the lens and even then it just barely produces smoke.

All the video's I watch of supposed 650nm 300mw laser seem far more effective and do not have to be at a specific focal distance from the lens??