Month: October 2009

Vinyl cut PCB resist

Vinyl cut PCB resist

Recently, we are working in class on a variation of the Rock and Roll Speakers from Fashioning Technology. Rather than using perfboard for the circuit, we’ll be burning our own circuit board. The chips are through hole LM386’s, but I don’t think it is realistic to have the students drill 8 aligned holes on the circuit board. There is an excellent primer on printed circuit board etching in MAKE, Volume 02. After thinking this through a bit, I came up with an idea to turn the through-hole component into a smd component. The technique is a bit like the design of the Broadcast Your Podcast FM transmitter circuit, which just has you solder the components together in pools of solder on chips of board.

When the chips finally arrived from Electronic Goldmine, I looked up the datasheet for the LM386 to get the measurements. In Open Office Draw, I drew out a design that would match up with the pins. With the help of Pat, who is doing an independent study on CNC tools this year, I sent the file to the machine with the vinyl cutter. He cut the file, then we weeded it to see if it matched the chip. The file matched the pin locations of the chip, so we made a few more iterations to get the process down and the layout right. When we got it right, we cut three copies of the file for boardmaking.

The Mummy’s “Book of The Dead” prop

The Mummy’s “Book of The Dead” prop

We recently had a question from a reader about this prop. “Connie” wrote in wanting to know how to replicate the mechanism that, in the movie, is used to unlock The Book’s cover. Never having seen The Mummy, I went into research mode and enqueued it from Netflix. Then I watched it. Big mistake.

But, you know, to each his or her own. And “The Book of the Dead,” with its ornate clasps and intricate star-shaped key, is admittedly an awesome prop. The scene Connie is referring to, I believe, occurs at almost exactly one hour into the “Deluxe Edition” cut of the film, and shows the intrepid but remarkably foolish archeologists inserting the aforementioned star-shaped key into a correspondingly star-shaped opening in the book’s cover, turning it, and thereby releasing the spring-loaded cover clasps and, with them, all manner of unpleasant whatnot.

So I started Googling around, looking for dweebs enthusiasts that might have already built such a thing. And while I did not find any working mechanical replicas of the prop, I did discover the remarkably beautiful static replica shown in the photo at the top of this post by Jeff Stelter of Stelter Creative Woodworks.