A Semitone Crystal board with descriptions.
The Semitone Crystal has been the first lighting controller (“dimmer”) model in the Semitone series. It is based on the Atmel AVR® microcontroller architecture, features 3 LED's as mode indicators and infrared remote receiver as the primary user interface.
The Crystal is an easy to build, easy to use one-channel lighting controller. It's fine for stand-alone high-voltage halogen lamps (resistive loads only!). It supports up to 10 presets which hold brightness and - optionally - fade delay values per entry.
The Crystal is a fading dimmer, which means that all brightness changes are done by fading. Whether you are loading a preset brightness or toggling standby mode; the controller always fades smoothly from one brightness to another. Of course, the fade delay can be adjusted. The Semitone Crystal offers fade delays from 10ms until over 7 minutes for a full-stroke fading process.
User and machine interfaces
Interface for RC5 capable remote controls (any available universal remote should support this protocol). It offers the complete functionality for these functions:
- load/store brightness,
- adjust brightness,
- mode selection,
You can connect one button to toggle standby mode.
For feedback, modes and states are indicated by 3 LED's.
Dedicated UART protocol
(For communication over RS232, an additional level converter is required, such as the MAX232.)
The UART offers direct access to the internally stored data, which is:
- fade delay,
- target brightness (for fading),
- preset values,
GNU/Linux frontends for command line and for GTK are available. The UART protocol specification can be found in the documentation packages on the Sourceforge Project Site.
Due to the small microcontroller, this device can only be programmed in assembler for our purpose. Unfortunately, the Flash ROM is now full, so we cannot add more features.
GSemitone, a Gtk2 control application for the Crystal.
- GSemitone: Gtk2 frontend, fully supports the Semitone Crystal
- dim: command line interface for the Semitone Crystal
You are invited to write applications for other toolkits or operating systems. The dedicated communication protocol specification is publicly available (see the documentation packages).
(as of firmware version 0.3.1)
- 256 dimming steps
- internal linearization
- fade speed from 10 ms until 436 s for full-stroke
- 10 brightness and fade speed preset memories
- power-up settings memory
- RC5 IR remote control support, IR setup procedure
- UART support (protocol R1)
- external standby push-button support
All relevant information can be found in the Releases section, including board layout, firmware source code, and documentation.
There is an official single-sided board layout, included in the hardware package.