Dilshan R Jayakody’s Web Log

The BG7TBL FA-5 frequency counter has become recognized as an excellent choice for experimenters and radio enthusiasts, offering high-spec performance comparable to branded units. But it remains remarkably accessible due to its low cost.  FA-5 Frequency counter. The FA-5 has powerful hardware. However, most existing control applications lack a good user experience. Many of them rely on scripting languages, such as Python, while others utilise simple command-line interfaces . These limitations inspired us to create FA-5 VizControl . This native application provides a comprehensive, intuitive, and portable desktop experience for managing the FA-5 . We developed FA-5 VizControl using Lazarus and the FPC ( Free Pascal Compiler ). This choice ensures maximum compatibility and portability. The application functions as a standalone, portable executable on both Linux and Windows operating systems. There is no need for complex installation routines. Users simply download and launch...

This is a simple surge arrester array that I made in my free time. Built using readily available components, the array provides effective shielding against lightning-induced surges and static discharges that can damage sensitive transmitting and receiving systems. The primary goal of this project was to create a robust, low-loss surge protection unit that can handle multiple RF lines simultaneously. By integrating gas-discharge based lightning arresters with a solid grounding infrastructure, the array ensures that transient over-voltages are safely diverted to ground without affecting normal signal transmission.  Installed surge arrester array. The core of this project relies on a few key components: At the heart of the design are eight BL-2000 Lightning Arresters , each incorporating a GDT ( Gas Discharge Tube ). These units are designed to conduct high-voltage transients from the coaxial line directly to ground within microseconds of a surge event. The BL-2000 series is a...

The Arduino Mini Amplifier is a compact audio system that merges vintage analog and modern digital components. It combines a Philips TDA8425 audio processor and an Arduino Nano , supporting Bluetooth and line-in audio, spectrum analysis, stereo modes, and software-controlled tone adjustment. Finished prototype of the Arduino Mini Amplifier. The Arduino Mini Amplifier is organized into six major subsystems: the audio processor, spectrum analyzer, Bluetooth source, power amplifier, control interface, and power management unit. This modular setup allows each part to operate with minimal interference from the others, making designing and PCB routing easier. The system uses separate paths for analog and digital ground signals (these are called GNDA for analog ground and GNDD for digital ground). Their connections are limited to specific points, which helps prevent unwanted electrical noise from the MCU from reaching the analog audio circuits. The audio section is centered on the T...

For some time, hobbyists have relied on dedicated sound generator ICs, such as the UM3561 , UM3562 to build compact alarm and siren circuits. Unfortunately, this device is becoming increasingly difficult to find in the market. The manufacturer of the chip, United Microelectronics Corporation (UMC), is still around. However, they are no longer producing the UM3561 or UM3562. As part of a fun experiment, I decided to design a replacement circuit using only discrete transistors and passive components. This avoids the need for specialized ICs altogether. The result is a simple yet effective transistor-based siren. It can reproduce the familiar rising and falling alarm effects typically associated with police cars, fire trucks, or ambulances. Finished prototype of the electronic siren. The design philosophy behind this project was straightforward: recreate the functionality of the classic two-timer based siren circuit ( NE556 / NE555 pair), but instead of timers or sound generator ICs, u...

Managing liquid levels in tanks is a common challenge across home, agricultural, and industrial automation systems. Whether dealing with a rooftop water tank or a chemical reservoir in a processing plant, maintaining the correct fluid level is crucial to prevent overflow, avoid dry-run damage to pumps, and reduce unnecessary power consumption. To address this challenge, we have designed a compact and reliable electronic limit switch module. This microcontroller based controller automates fluid level regulation with precision and ease. Prototype build of electronic limit switch module. Traditional fluid level control methods often rely on mechanical float switches and simple relay logic. While effective, these methods can suffer from issues such as bounce noise, relay chattering, and wear over time. This module modernizes this process by integrating microcontroller based debounce filtering, hysteresis, and control on/off delays. To perform its operation, the module utilizes two fl...

Ecowitt2APRS is a new open-source Linux service that I have been working on for the past few weeks. This project is designed to seamlessly integrate weather data from Ecowitt compatible professional weather stations into the global Automatic Packet Reporting System Internet Service (APRS-IS) network, transmitting this information in the standardized format of APRS weather packets. APRS, an amateur radio-based system, facilitates real-time tactical digital communications, covering applications such as GPS position reporting and the dissemination of meteorological data. Ecowitt2APRS addresses a specific need within this ecosystem: providing a lightweight and efficient method for weather stations to contribute to this data stream. Live data view from my Ecowitt weather station on aprs.to. The Ecowitt2APRS service is developed as a minimalist daemon for Linux environments. It ingests live weather data from Ecowitt compatible stations, converts it into the required APRS weather pac...

When it comes to automation and control systems, there's often a need for multiple digitally controlled output terminals with high-voltage handling capabilities. Many existing modules are bulky, expensive, or require numerous additional components to function. To address this gap, I've developed a fully open-source, USB-controlled 24-channel high-voltage driver. This device provides precise, flexible control in a compact and user-friendly package. The project is open hardware, released under the CERN-OHL-W license, ensuring transparency from hardware schematics to firmware code. The driver module communicates via USB using a simple virtual COM port, eliminating the need for special drivers and complex setups. Prototype version of the module. At the core of the system are three TPIC6B595 shift registers, each supplying eight open-drain outputs that can handle up to 50V and sink currents of up to 150mA per channel. These registers are daisy-chained to achieve a total of 24 ...