In Which Jarrett Builds

 

That was a long “next month”. A recap is in order. This post chronicles the long descent into complete and utter apathy.

 

In September 2014, I made some sketches for a lamp I wanted to build. The intent was to use the glass plate from a desktop scanner as the light diffuser, and laser etch a fractal pattern onto it to create a frosted effect, instead of being optically clear.

Here is a test piece I did, with a laser cutter and an image found off the internet.

 

 

The results were pretty fantastic. Fine details get lost, because it looks like the mode of operation is the laser heating up enough of the glass to chip off a small chunk before moving on. And so on, for the entire image. It creates great looking, even optical diffusion, though.

 

For another test, I decided to design and build a similar, but smaller lamp. Glass scanner beds are a limited supply. Using a glass tile I found at a craft store, I designed an arm to hold it onto a wall, a few centimetres away from a PCB containing some high power LEDs.

 

 

The initial model and 3D print is shown on my previous post.

Here is the final version, with some corrected measurements and better mounting point.

 

And the PCB arrived shortly after the last post.

 

Oops!

That’s mistake number one. Everything was intended to be clean and white, but I guess I forgot to change the soldermask from the default DirtyPCBs red. It’s not the end of the world. This is a prototype of a prototype, after all.

 

The first board was populated, and then the lamp languished for a year and a half.

 

—

 

Recently, I found it buried in a locker and tried plugging it in for the first time. With no prior consultation to documentation, I tried it on a bench power supply, starting at 5v. Nothing happened, so I turned it up to 10. At 15v, the semiconductor on the board released some smoke and glowed red for a few minutes.

Nope!

 

Back to the docs, I read that I had used an adjustable 5v boost converter, so that solved that.

I soldered up another board (I had two spares of the IC), including the DC barrel jack this time, and plugged it in again. Turns out I had the wrong polarity!

No smoke, but some troubleshooting proved that I had definitely fried the chip.

 

This was pretty much the limit of how much I cared, so I did what anyone would do:

I jumped over the active parts of the circuit with a power resistor, and ran the LEDs directly from a 19v laptop power supply.

 

 

Job done!

Next time I’ll build in some more safety factor.

Additionally, looking at the lamp from the side is really really bright because of the bare 1W LEDs. I kinda planned for this and put some slots in the side of the base for some acrylic sheets, but I’m quite done with this design.