DIY Laser cut Shortwave UV Light

UV lights are an important tool with a ton of uses including florescent minerals and exposure of photo sensitive materials. Short wave UV lights can be rather costly. The most popular brand is Way Too Cool who makes a quality and durable light, but they can be a bit costly. I wanted to see if it is possible to make a cheaper alternative for one of these lights. After perusing eBay for a shortwave UV lamp, I came across an entire kit that included 2 shortwave lamps and a DC driver for around $25, which was exactly what I was looking for to make. All it needed was power and a case.

Case

My initial instinct was to use a plastic project box, but I then remembered that we are not cavemen, we have technology. I drew up an extremely simple box design and laser cut it out of 1/8″ birch plywood.

All the parts laid out

When designing the bottom plate the lamps sit against, the reflector was a concern. Light is emitted around the entire circumference of the lamp, so I didn’t want the lamp simply recessed inside of a box, as a ton of light would be lost. I began playing with the idea of a complex curved reflector, but in the end I simply added a reflective Mylar material to the bottom panel, and have the sides extend downward to shield light from going sideways and allow the light to be set down.

Bulbs in the case

Electronics

I wanted the light to be as portable as possible, so the battery had to built in. The driver included with the 254nm lamps required 12v, and drew just over 3 watts at that voltage. My initial plan was to make a 3 or 4 cell lithium pack with 18650 cells, but this would require a BMS board. The issue with most of the cheap BMS systems for under $8 is that they aren’t reliable, and people report they don’t actually balance the batteries. I don’t want to take any risks on this, or spend more than $20 on a power supply for this light.

In the end I decided on using a single 18650 cell to power the driver. There is a cheap protection circuit to prevent over discharge of the battery and a DC-DC converter to step the batteries voltage to 12v. The charging is handled by a cheap USB charging module. Power to this module is provided from a dc barrel jack on the lid of a box. The voltage in from the jack runs through a 5v linear regulator so that voltages other than 5v can be used to charge the battery. This is not the most elegant or efficient solution in any way, shape, or form, however, it is cheap and gets the job done. If I was making more than one of these lights I would design a custom PCB to integrate all the electronics into a single board.

Finding a battery to suit this application was rather difficult. I was looking for a high capacity cell with low drain, but most of the cells out there are designed with super high C values for electronic cigarettes. I ended up choosing the LG MJ1. This cell has a capacity of 3500 mAh and a C value of just 10A. They can be found online for just under $4 per cell. A single cell should have enough power to run the light for about 3 hours. There is still plenty of room in the case, and it can easily hold 4-5 cells, but I’m not sure why you would need 15 hours of run time on a light like this.

Picasso level diagram

The electronics were soldered together then heat shrunk to prevent shorts. Everything is held in place with hot glue. Again, if I was making more than one, a custom PCB screwed to the case would be a much better solution.

Cost

UV-Kit$31.97
LG MJ1 Battery$4.00
Lithium Protection Circuit$0.60
Lithium Charge Circuit $0.50
DC-DC Step Up
$1.10
Linear Regulator$1.00
Switch$0.75
Barrel Jack$0.50
Plywood$2.50
Handle$2.00
Total$44.92

My light was much cheaper than most shortwave light out there, although it is only 3 watts. If I was to make another, I would buy just the lamps and build the driver circuit myself. This would drive the cost down quite a bit as germicidal lamps a pretty cheap on eBay.

Conclusion

I’m super happy with the results. If were were to do this again, I would add screws to hold the case together rather than glue, a custom PCB, a UV pass filter, and higher wattage lamps.

Adventures in Making a DIY Supreme Lighter

Supreme is a street wear brand that makes little to no sense to me. They give people the illusion that they are buying something exclusive, and it works really well. They slap their name on just about anything, and sell it for 10x what the product would normally retail for. For example, a brand new red Zippo lighter can be purchased online for under $13 shipped, while Supreme branded Zippos sell for upwards of $100 on Ebay. This begs the question, how hard would it be to for us to add that white text ourselves?

I started out by replicating both sides of the lighter in CorelDraw. The font in the supreme logo is Futura Bold Italic. Recreating the graphic was extremely simple. I used the crop tool in Corel to crop the r in both text boxes to split the logo in two, and that was about it.

The next step was to test the sizing and alignment on the lighter. To do this, I put a piece of tape over the lighter, and ran the laser at a low power setting that was just powerful enough to leave a mark on the tape. We can use this non-permanent marking to see the size and position of the graphic on the lighter. Once we have a product we are happy with, we can cover the lighter in tape, and raster our graphic on full power, removing both the masking tape and the red powder coat. After the powder coat is burned away by the laser, a sticky residue is left behind, however, it is easy to remove with isopropyl alcohol and cotton swabs, exposing the brass

Laser marking tape to check position

Spray Paint

I now had a very high quality stencil on the lighter, and it was time to add the white. My first idea was to use white spray paint.

Masked and painted
Spray Paint Lighter

The result looks decent. It looks real, and would make a great display piece, but the white paint isn’t durable enough to withstand daily use. After just a few days, the paint began to wear off. We need a more durable coating to hold up to the wear and tear.

Powder Coating

Powder coating adds a strong and durable plastic coating on metal parts. It is applied with a specialized gun that charges the particles of the powder electrically and they stick to the part. Then, the part is then put in an oven and allowed to cure.

The process for powder coating is extremely similar to that of the spray paint lighter except for the masking tape. Standard blue painters tape will not withstand the curing temperatures upwards of 350 degrees Fahrenheit. Instead, a specialty masking tape for powder coating is used. This was rastered away on the laser and I was left with an extremely similar scenario to that of the painted lighter. An Eastwood Powder Coating Gun was used with gloss white powder to coat the lighter

After the coat had been applied and baked, it was time to remove the mask. My initial reaction was not good. The lines were far from crisp, and powder coat was bleeding over onto the red. I initially wrote powder coating off as a failure, but after playing with it a bit, the coat had not stuck to the red powder coat below it, and the white was easily removed from the red with Scotch-Brite.

Before Scotch-Brite, lines not clean
After cleaning it up

I am quite happy with the lighter, It looks great, and has a long-lasting durable logo on it. It would be hard for someone to identify this as a fake. How could anyone fake something like this anyway??? Its not like somebody used a laser engraver to etch away high temperature masking tape and powder coated it themselves, right?

Improving Upon the Sparrows Hall Pass

The Sparrows Hall Pass is a handy credit card sized tool used for opening doors by manipulating the latch. In my wallet, I carried the Hall Pass as well as a Schlage and Kwikset key depth gauges. The key gauges seemed unnecessarily large, and it looked like I could combine these three tools without severely reducing the structure of the ‘Hall Pass’

The 3 pieces of steel the new design combines

I started by drawing the original design in SolidWorks, then added the stepped key gauge. Minor design changes were made after a few cardboard prototypes were made and tested, but after that it was off to be lasercut. I had ten of these cut out of .035″ Stainless Steel for $62 from a seller on Ebay.

Final Design

When I received the parts, they were blank. To label the key types and depths, I laser engraved them. Our laser is only 45 watts, and is not powerful enough to etch steel on its own, so we use a product called CerMark. CerMark paints onto the steel and is allowed to dry. The design is then engraved to the part, and the excess CerMark is rinsed off. The result is a dark and durable etch on the steel.

Finished Product

Overall, I am very pleased with the results I received. Having a single tool to carry around is significantly easier than having 3 bulky pieces of steel. If I were to make another version, I would add a hexagonal hole large enough to accept a standard screwdriver bit somewhere on the part so it can be used as a pocket screwdriver.