3D modeling amplifier electronics laser cutting

The Darth Vader chest box is almost finished


The last month I’ve been working on my Darth Vader chest box. I’ve designed and built my own circuit with the Holtek HT8950A voice modulator, I create a laser cut case and designed 3D printed parts for the chest box. Since I had to learn a lot of new techniques, e.g laser cutting and 3D printing, this is by no means an easy project for me. With the project in it’s final stages now some design problems turn up that need fixing.

Soldering the board.

This week I soldered the components to the board. First I soldered the voice changer components and made sure this part of the circuit is working. Next I soldered the amplifier. I tested the total circuit and it worked the first time which is always a joyful moment. I find the Adafruit perma-protoboard very easy to work with since I’m able to copy the layout from the breadboard. Next I grouped all the buttons that operate the HT8950A on a board and soldered them to a piece perfboard. The buttons on the perfboard fit nicely into the laser cut side panel that I already made. Operating the chest box is easy with this (a major issue with my previous chest box).

Soldered perma-protoboard and breadboard side-by-side.
Close-up of the soldered board with the HT8950A voice changer chip on the right and the LM386 amplifier on the left.
Operating the voice changer with this panel should be easy.

Design issues

Last week I made 3D printed parts for the front of the chest box. Unfortunately I found that these parts didn’t look good with the laser cut box. The plastic parts just didn’t do justice to the laser cut plywood. I therefore decided to laser cut all the parts that sit on the from of the box with I think is aesthetically more pleasing.

Another problem arose with the female audio jack connector that I need to plug in the microphone. The thread of this 3.5mm connector just isn’t long enough to be fitted onto the 6mm thick plywood. I designed a container to solve this. The audio connector fits into this container and the container is screwed to the case. Hopefully this container solves the problem.

Container for the audio jack connector created with Openscad. The container, screwed to the chest box, will keep the audio connector tightly to it’s place.

Yet unsolved problems

  • I need to attach a nylon belt to the chest box. I’m thinking about popper snap fasteners attached to the belt to open or close the belt.
  • The HT8950A works fine with a proper audio signal as input but the microphone that I have, a small electret microphone, doesn’t give any audible output (except for noise). I assume that the signal is to weak and therefore needs amplification.
3D modeling

Designing parts for the Darth Vader chest box with OpenSCAD


A new year, a new beginning. Last year I took a fair interest in technologies like laser cutting and 3D printing but I still relied on my old 20th century skills for my projects. I must admit that the investment in time to master these new technologies was holding me back to advance in both laser cutting and 3D printing. In the very last month of 2015 I took the decision to produce a case with a laser cutter. It was a revelation. A job that would normally take me a day or so was done in a matter of minutes with a precision that I can never achieve with the old saw and chisel. From that point on I decided to invest heavily, in both time and money, in these new technologies.


First I learned to work with Inkscape, a free 2D vector drawing program for laser cutting. I discovered that it is a good tool for illustration (e.g for web design) too. Next I needed a 3D design tool to create parts with a 3D printer. I looked at different programs such as Sketchup, 123D Design but I increasing dislike the proprietary character of these programs. Echoing the words of Richard Stallmann “the proprietary program is a system of unjust power”. On the non-proprietary side there is FreeCAD and Blender but I found the learning curve of these programs too steep. Then I discovered OpenSCAD when reading an article on Hackaday. It’s a free (as in free beer and free speech) program running on Windows, Linux and OSX that has a great community. Instead of using a point and click interface the user has to script his models with a descriptive programming language. This seems strange and cumbersome at first but it actually works for me. I found it very easy to get into. OpenSCAD is very lightweight. Other CAD programs tend to be a burden on a PC but OpenSCAD runs even on low spec machines. Because of the script that OpenSCAD uses it is very apparent what is in the 3D model and what the dimensions are. The comparison with HTML comes to mind. Therefore it is possible for anyone else to see how a model is made, learn from it and make changes to it.

Combined elements of the front of the Darth Vader chest box made in OpenScad. Still needs some work.

Parts for the voice changer

The Darth Vader chest box has a very distinctive look with lots of distinctive buttons and other parts (see images below). I modelled these parts with OpenSCAD beginning with the simple buttons working my way up via the coin slots to the complex rods. I’m satisfied with the result thus far. Next I’ll 3D print the parts and glue them to the plywood chest box I made earlier.

Probably the most simple parts of the chest box are the buttons at the bottom of the box. Modelled in OpenSCAD.
Coin slot type of parts for the Darth Vader chest box.
Rods for the Darth Vader chest box.