Minimally Burning Laser with Easy Power Supply

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I made (assembled?) a 100mW laser and have made some cuts and burns with it. It is minimal, which means slow and small and it only cuts black,matte surfaces. I bought the laser module off the internet (and ultimately from hong kong) for $70. The 'making' end mainly involve scavenging a lens and contriving a power supply. The only really novel contribution, on my part, is the power supply. Insist and I'll get pictures. It has been a year since I went through all this, so apologies. I also got safety goggles. These have an OD (optical density) of 4 and, obviously, filter light at the correct wavelength (650 nm in this case). In the interest of safety I also always point it down, and never at anything reflective, especially not near metal or glass (which can send beams, still strong enough to cause damage, in effectively nonpredictable directions). Despite the word towards safety, the below-elaborated healthy attitude towards trial, error and more error may make some people feel uncomfortable. Well. I'm still here.

Here are the specs:

  • Wavelength : 650nm RED
  • Output power (mW) @ 25C : 100mW
  • Operating Current (mA) : 185ma
  • Operating Voltage : 3.0 - 5.0V DC
  • Operation Mode : CW
  • Modulation Mode: Analog or TTL > 10khz
  • Beam Divergence > 0.4 mrad
  • Output Power Stability < 1.0%

The important bits are the wavelength (match it to your goggles), power (minimum that burns is 80, I hear. I went for 100) and the operating voltage (3-5 volts).

Out of the box, it doesn't focus light enough to burn or cut anything. I taped a focusing lens on. (Folly! beg. of end.)

The power supply is due to much guidance and inspiration from my old roommate. At first I just cut off a stretch of USB cable from an old mouse and twisted the wires to the output of the laser, ignoring the third wire. (Which wire is the 'third' wire? Uhh, I just tried it). The USB standard supplies, uhh, I forget, well, I think 5 volts. Definitely somewhere between 3 and 5 vols. So with just that I was already rolling. But I wanted portability.

A 9 volt battery supplies, as advertised, 9 volts. If you take the bottom off many such batteries (not all) you will clearly see 6 AAA batteries folded up but attached in series (where a single AAA battery supplies 9/6=1.5 volts). In these batteries, you can use two twisty ties and electrical tape to rewire a 9 volt battery to supply 4.5 volts. Just change the 6 in series to two parallel series of three. This supplied me 4.5 volts, and it worked fine. Of course, the batteries that aren't made of 6 AAA batteries are instead filled with battery acid, the consistency of clay. I don't know how to keep from making that mistake again. But the stuff isn't too nasty, I just felt bad disposing of it.

Details. So, I got a nine-volt battery made of 6 AAA units in series. I took off the bottom, so the contacts were exposed. With the 9V on its side, you will see three columns of two AA batteries. I snipped the little strip of foil that connects the two batteries in the middle column. Than I grabbed a twisty tie and took a little bit of the plastic/paper off of each end to give the 'wire' two ends. Take off just enough to connect the AAA's contact with one of the 9 volt contacts on the other end, and no more. If you take off more than that, and the metal of the twisty touchs the 9V casing, you will complete a circuit with the battery's case and it will start to get warm, then hot. That provides a handy indication that you are doing something wrong and should try again. Well; it provides a handy indication that you are doing something wrong.

Connect one end of the twisty tie to one of the newly snipped AAA ends. Solder 'em if you've got 'em, but I just sort of winged it, wrapping the snipped foil around the twisty with pliers. Take the other end and attach it to either the positive or the negative contact of the 9-volt's business end. Which? Well the internal AAAs aren't very well labeled, since they were never meant to see light, so just wing it. Attach the AAA to whichever 9V contact doesn't make the battery hot. With the other twisty, attach the other AAA butt to the other 9V contact.

If my attempts at description haven't made it obvious, I don't know much about electronics; only enough to get into trouble.

Afterwards, e-tape the ass-end of the 9V casing shut and tape the twisties firm to the 9V casing and you have a 4.5 volt power supply for the laser. To attach it, you can just twist the wires around each 9V contact. But to be classy, since 9 volt batteries connect very nicely to each other (WHY?), I dismantled a second 9V battery for just the contacts (a.k.a business end), and attached the laser's wires to it to create a plug for the 4.5V power supply. Then lots more tape. Plugging the battery into the the laser's new plug makes it shine. Glory be.

So, what could be more foolish than playing with very dangerous lights and opening batteries with pocket knives? Burning yourself a tattoo. I cut a spiral, in Jan or Feb '08. Believe it or not, all this effort was towards the goal of providing myself a compelling means to promote personal mindfulness. I wanted something small, personal, and homemade but visible enough close up to encourage me to not get stuck in my head. Since then, I have also come to appreciate the (superficially?) oxy/moronic ring to high-tech-Buddhist-laser-tattoos. In the end, it didn't entirely work. I was hoping the effort and pain and visual salience would provide strong enough holds to attach real personal meaning. It turns out that to give the burn the meaning I intended, takes continuous time and attention. No shortcuts to mindfulness, and I am still in the process of giving the burn meaning.

On the subject of attention, I deferred posting this project because I didn't want much. Bragging about your neat things is awfully contrary to cultivating self awareness. On the other hand, many reasons conspired to provide compelling reasons to publish.

  • value of sharing ideas on the internet
  • preventing exclusion-via-patent (am I helping to do that by publishing this?)
  • the initial failure of the mindfulness-promoting aspect of the design
  • and the potential to inspire others to create.

It took about 2 months to mostly heal and about 6 months before it wasn't slightly more red than the surrounding skin. After a year (now) it had healed almost completely, so I tried it again last week (Folly!). I'm applying some natural compounds described elsewhere in this blog (the walnut ink) to both stain the new burn and compromise the ability of my body to heal itself. I'll share if that works. I saw some internet-meme-inspired burns on MAKE a few months later (April?) and a tattoo artist using a laser to cut leather furniture (he was close. But damn, it had to have crossed his mind to do humans. I think he is just keeping it on the DL.). All those cuts are much more geometrical, having been made with computer-controlled lasers. For the most part, you can only get access to these with very close connections to well-funded shops in well-funded universities .

Well, I hope this is valuable to someone. Please don't irreparably damage yourself in any unintended manner.

(Update Beg. of March: yeah, pretty faint. It won't the next butterfly tattoo anytime soon.)

1) BATTERIES -- If you'd like to avoid the mess of battery surgery, you can grab a three-battery AAA holder here: or at Radio Shack (or wire two together in parallel if you need the amp-hours). You can also use electrical tape to make a nice bundle of as many as you like (in multiples of three, with the appropriate number positive-up and positive-down, then solder bell wire across the ends to create the series-parallel battery pack you want. When you wear down the pack, you have to do it again, so it's better to buy the holders. If you want the 9v connectors, you can buy those as well, wired or solderable. If you want both the 9v connectors and form factor, then what you're doing is the way to go. If you don't need portability you can also buy a Radio Shack 4.5 VDC power supply here:
2) EXCLUSION BY PATENT -- I discussed this with a patent attorney at work after designing, building and shipping to a supplier a gaging system for measuring a tricky common mechanical feature on certain electronic assemblies. I worried about buying my gage design back from the supplier if they filed. The attorney's comment was this: that to be patentable, the object must be 'not in common use for the intended purpose,' and that publication of the idea _may_ tend to indicate that. He also said our company only patented marketable items, and wouldn't search and file if we don't intend to manufacture and sell gages, which we don't.
David. 08:57, 29 March 2009 (EDT)