Laser Cutter Hidden in a Flip Top Lighter

There may be times when a fuse needs to be lit or something cut at a distance, a laser is a good way to do it but it needs to be disguised as something more everyday....like a flip top petrol lighter..... it would be more covert without the engraving but as I am not spying at the moment I don't think it will matter too much :)

A word of warning! Lasers are not toys and need to be used with care, lasers should always be used with safety goggles designed for the wavelength being used. Always be aware of others around you when using a laser, eyes are not replaceable!

The laser diode used here was the best available when 007 was a boy, much more powerful ones are available now so do your own research to find what you need..... This setup will light stuff easily enough but is weak by modern standards.

Step 1: General Arrangement

This build, though not complex is very fiddly to do as there is not much room to fit everything in, but if you want to have a go here is the information you will need.
This is the General arrangement that I worked from.

List of parts:

Flip-top lighter of your choice (I used a Star lighter from ebay).

Blu-ray laser diode (PHR 803T)

Aixiz module (front end and lens only, Outside diameter turned down to 10mm).

Small block of aluminium (heatsink/optics holder).

Driver (I used the low range Rkcstr driver, google is your friend).

Push button (I took one from a broken DX green laser)

Batteries (GP 10A [9v 38ma/hr]).

Vero board.

Small pieces of scrap brass sheet, for contacts and springs.

Small piece of plastic for mounting driver and insulating battery contacts.

Various colour insulated single strand copper wire.

Step 2: Heatsink Laser Diode Mount

The width of the lighter dictates the size of this assembly the drawing shows basic dimensions The hole is tapped m3 dia.

Once the parts are made the laser diode needs to be pressed into the module.:

Step 3: Wre Up Laser

Solder a pair of wires to the LD (solder the neg pin and the case pin to the same wire to make the laser negative earth) Solder as low down the pins as possible and trim the ends off, you need to save space to clear the lid.
The laser module and heatsink are glued together with 2 part epoxy. Once ahesive is set you will need to trial fit the module into the lighter. I have encapsulated the back of the LD to protect it from damage to the solder joints.

Step 4: Modify Lighter Insert

To do this you will need to remove the flint spring, wadding, wick and striker wheel. Then cut out the front of the windbreak to clear the lens.

While you are at it remove the flint tube, this is easily done by puting the end of a soldering iron into the hole, at the top, when the glue melts push the tube through. Enlarge the wick hole to allow the wiring through. (plastic insulator shown described later)
Fit the laser heatsink and check that the lid will open and close without hitting anything, this just requires you to use a file to take corners off where needed.

Step 5: Bits and Pieces

A plastic insulator and a piece of veroboard are required that will fit comfortably into the lighter insert.
Push the plastic insulator into place and scribe the shape of the hole onto it. Remove the insulator, lay the veroboard on top then drill through the four holes, keeping them within the circle.

Earth return straps need to be made from bits of brass sheet and assembled as shown, .

These are bent up and stuck to the insulator with 2 part epoxy, at a later part of the build these will be bent at the ends and the excess cut off, they will stop the assembly from being pushed too far into the lighter.

At some stage you will need to set up the driver circuit to the desired output, as the adjustor will be hidden once the driver is installed, I connected it up to 9v and dummy load to set it too 110ma. Information on using dummy loads can be found here:
http://www.rog8811.com/laserdriver.htm

Step 6: Wiring It Up Part One

It may be worth noting at this point that the batteries are only 38ma/hr, using them in parallel will give around 120ma, they will not last long, but long enough to be usable. You could adapt this for a lava drive which will make better use of the batteries, I had a Rkcstr so I used it.

Cut a piece of 8mm X 0.5mm brass 25mm long, file a corner off and solder a piece of wire to one end as shown.
The Rkcstr drive can now be attached to the insulator with a dab of glue, place it with solder pads for the laser diode upermost and toward the wires.

Bend 3 wires as shown, trim them to length and solder to correct pads on the driver. Push loops into the remaing holes in the insulator and glue in place. The wires will be perfectly positioned to pass through the drilled out holes in the veroboard.

Connect the wires as shown, leave 4 long ends sticking up, these will be trimmed later.

Step 7: Final Fitting of Insert

I had to rethink the original plan for the negative contacts to the batteries, I was going to put springs in the bottom of the outer case. The problem with this method is that the inner case is held in place by friction, with the springs between the case and the batteries there would be a danger that the inner would be gradually pushed up and may jam the lid.

To keep the correct fit of the inner case a 7mm X 1mm slot needs to be filed in each side then the additional brass parts, shown earlier, are shaped, soldered in place and fitted.

Step 8: Wiring It Up Part Two

Now would be a good time to trim the wires to length, strip the insulation and tin the ends. this is done by inserting the assembly fully, passing the wires through the veroboard. Cut the wires 4mm above the veroboard, strip insulation to top surface of the board.

The wires nearest the edge are soldered to the push button.The other 2 to the LD, be sure to get the polarity correct.