[Fall ’09] Pew Pew: 405nm 100mw Handheld Laser

[Description]:

This project is aimed at creating a handheld laser out of a laser diode, specifically a 405nm 100mw diode.

[Processes Applied]:

• Precision Soldering
• Circuitry (Including understanding the importance of grounding)
• Optics

[Summary]:

Note: This project was completed fall 2009 (sophomore year) so some of the details might be slight off, and I’m not sure the exact setup of the driving circuit.

The objective of this project was to create a handheld 405nm (“blue”) laser pointer from basic parts. The main problem with this is 405nm laser diodes cost upwards of $100 or more. But if you’re willing to take a small risk you can buy diodes on eBay from Chinese sellers for ~$5 a diode with +$10 shipping. Downside, they are not a company which you can return items to if it turns out to be faulty, and the wait time is 2-3 weeks for shipping. So with this in mind I ended up buying 5 diodes, mainly because of the high chance of destroying the diode from a random static discharge because of the diodes sensitivity.

What spawned from this worrying and caution was the idea; GROUND EVERYTHING! But the funny thing that happened was the electronics club’s grounding wristband had disappeared into the vast beyond. So I had to create a grounding platform and all from scrap lying around the club. The way I achieved the grounding was by using a piece from a computer case as my working space. The Soldering mount and iron also had to be grounded as well; any static charge must not be allowed to touch the leads. So I ended up putting a screwdriver into the ground port of a three pronged power strip that was plugged into the wall (at first it might look dangerous, but the ground is a zero potential). After that I attached multiple alligator clips to it and also some wire. Last but not least I stripped a wire on both ends and wrapped it around my wrist and the ground to act as a simple grounding wristband.

It was a simple solution to an important problem, but I encountered some problems once I had myself grounded. I could not reach half the tools I needed, so I had to get Mr. Kouttron to assist me. I had to first wire some thin gauge wire to the leads of diodes. This proved extremely tedious since our equipment was general use and our soldering tips were not in good condition. Once I had wired what I thought the positive and negative leads of the 3 leads, I tested it out with the labs power supply which I set to the minimum lazing power requirements specified for this diode. At first I was unable to get it to laze, so I then soldered the odd contact to either the positive or negative (I can’t be sure it was so long ago) which solved the issue. Ultimately I believe that the third pin might have been used for modulating the signal of the laser.

Next I mounted the diode into a case with a cheap focusing lens, which can be manually focused for the distance you are trying to reach. I chose this type of setup so that if I wanted to shine the laser further I could have the focal point change to make a small focal point at any distance. Once I had the diode mounted correctly, I wanted to next determine a power supply and a trigger which I needed to be sturdy and not easily pressed, so that it would not be triggered accidentally. I was toying with the idea of a key locked button so that to use the laser you would need to have the key inserted and put into the firing position and then you would have to pull the trigger. But I was unable to find one to my liking at the local electronics store Trojan Electronics.

I ended up getting a slide switch that will only stay in the on position as long as you were pulling it. This trigger I had wired into my driving circuit which was a simple 3 component circuit which consisted of a resistor, and two components I cannot specify currently because I do not remember exactly what I used and I do not want to remove the tape they are located behind (there are many variations that can be found on the internet for this circuit). I then mounted these different components together on an AA battery holder. The final setup is pictured (in the picture section), the laser setup still runs after a (+3 years {updated}) years of being used and carried in my pocket or bag… still going strong!

[Project Photos]: