Retronics, a pseudonymous classic radio collector, confronted a problem when restoring a Tandberg Sølvsuper 4 radio. The radio’s entrance panel makes use of a Magic Eye, a now not manufactured part. Retronics developed a contemporary Digital 6U5 Magic Eye alternative utilizing a round IPS show, STM32 microcontroller, and two PCBs to deal with the restoration neighborhood’s wants.
Magic Eye Tubes are vacuum tubes that visually point out a sign’s energy. Classic radios use them to assist customers tune into particular frequencies by visualizing the energy of a sign. Since these tubes are now not manufactured, there’s a dwindling provide of used components out there.
Importing firmware to Digital 6U5 (📷: Retronics)
The DIY Digital 6U5 Magic Eye alternative has two printed circuit boards. A base PCB plugs into the socket meant for the unique 6U5 tube. Its major perform is to get the automated acquire management (AGC) voltage from the radio and cross it to a microcontroller (MCU) board. The MCU board interfaces with the show and, because the title implies, accommodates an STM32F103CBT microcontroller and an analog conditioning circuit.
Authentic 6U5 (left), Digital 6U5 (proper) (📷: retronics)
The radio’s AGC sign is proportional to its energy. Sadly, its voltage vary is from 0 to -22 volts. A conditioning circuit based mostly round a Microchip MCP6001 op-amp converts the sign into a variety appropriate for the MCU.
Retronics acquired a purposeful 6U5 for comparability. After a meticulous course of revealed that the 6U5 doesn’t have a linear or logarithmic response, Retronics devised an algorithm approximating the unique. The result’s a totally purposeful drop-in alternative “tube.” The STM32 microcontroller runs code written across the Arduino framework. Retronics developed the challenge in VSCode utilizing PlatformIO.
All the parts for the DIY Digital 6U5 Magic Eye alternative are housed inside a 3D-printed enclosure. For these excited by replicating this challenge, the KiCad design recordsdata, 3D fashions, and Arduino code can be found for obtain from the Digital 6U5 GitHub repository. For detailed info on the design and implementation, try this weblog submit.