Planet Arduino

[Fearless Night]’s optical theremin project takes advantage of the kind of highly-integrated parts that are available to the modern hacker and hobbyist in all the right ways. The result is a compact instrument with software that can be modified using the Arduino IDE to take it places the original Theremin design could never go.

The design is based on a ‘Blue Pill’ STM32 MCU development board and two Avago APDS-9960 gesture sensor breakout boards, along with a few other supporting components. Where the original Theremin sensed hand proximity using two antenna-like capacitive sensors to control note frequency and volume, this design relies on two optical sensors to do the same job.

[Fearless Night] provides downloads for the schematic, code, parts list, and even 3D models for the enclosure. PCB files are also included for a convenient assembly, but since the component count is fairly low, a patient hacker should be able to get away with soldering it up by hand without much trouble.

This project creates the audio using the STM32’s Direct Digital Synthesis (DDS) capability and a simple low-pass filter, and has several ways to fine-tune the output. What’s DDS? Our own Elliot Williams explains it in terms of audio output for microcontrollers, and if you’d like a more comprehensive overview, Bil Herd will happily tell you all about it.

[W8BH] attended a talk by another ham, [W8TEE] that showed a microcontroller sending and receiving Morse code. He decided to build his own, and documented his results in an 8 part tutorial. He’s using the Blue Pill board and the resulting device sends code with paddles, sends canned text, provides an LCD with a rotary knob menu interface, and even has an SD card for data storage.

All the code is on GitHub. If you are interested in Morse code or in learning how to write a pretty substantial application using the Blue Pill and the Arduino IDE (or any other similar processor), this is a great exposition that is also a practical tool.

[W8BH] takes good advantage of breakout boards with things such as the displays and jacks on them. Of course, you don’t absolutely have to use those, but it does make life easier. You can see [W8TEE’s] version posted in an online forum.

The parts of the tutorial all build on each other, so you start out simple and get deeper and deeper. The tutorials are PDF files, but they are well organized and easy to read.

We’ve done our tutorials and videos on the Blue Pill. If you don’t want to rely on the Arduino IDE, there are ways around that, too.

Blue Pill header pic: Popolon [CC BY-SA 4.0]

We missed [iliasam’s] laser text projector when it first appeared, perhaps because the original article was in Russian. However, he recently reposted in English and it really caught our eye. You can see a short video of it in operation, below.

The projector uses raster scanning where the beam goes over each spot in a grid pattern. The design uses one laser from a cheap laser pointer and a salvaged mirror module from an old laser printer. The laser pointer diode turned out to be a bit weak, so a DVD laser was eventually put into service. A DVD motor also provides the vertical scan which is just a slight wobble of a mirror. A Blue Pill CPU provides all the smarts. You can find the code on GitHub.

The projector is fairly limited in size with a maximum resolution of 32×14. Some displays use a vector scheme that draws with the laser. This is brighter and more capable, but also more difficult to arrange since the laser has to move rapidly in a complex motion. The raster scanning is much easier to accomplish.

A light sensor tells the CPU when the laser is about to start hitting the vertical scan mirror. Obviously, there are other ways you could arrange for the mirrors to move, but the logic would be the same.

We’ve seen [illiasam] has a lot of interest in lasers. He’s hacked rangefinders and even 3D scanners that we’ve looked at before.