Dilshan R Jayakody’s Web Log

13.8V power supplies are commonly used in amateur radio experiments. Most of the portable amateur radio transceivers are designed to work with a 13.8V power source. We mainly build this power supply unit to power some of our amateur radio circuits and modules. This design is based on the popular LM338 5A voltage regulator. We choose this regulator because of to it’s higher current rating, short-circuit protection feature and higher availability. The prototype version of 13.8V - 5A power supply unit. Apart from that, we include MC3423 based crowbar sensing circuit to preventing an over-voltage condition of a power supply unit. We design this circuit by using commonly available 18V×2 (5A) + 12V (1A) transformer. This transformer is available in the market because it’s commonly used with some AF power amplifier systems/kits. We use its 12V terminal to drive 120mm - 12V cooling fan.

In this project, we build a simple I 2 S stereo decoder with an amplifier. To decode I 2 S data we use Princeton Technologies PT8211 16bit DAC. KA2206 audio power amplifier is used as the driver stage of this system. The prototype version of I2S stereo decoder Structure of this I 2 S amplifier is self-explanatory from the schematic. We select PT8211 and KA2206 combination due to lower cost and availability. Unfortunately, PT8211 DIP package is not available in the local market and we use SO package in our prototype. We design PCB for the DIP packages, and therefore we solder PT8211 SO package to PCB using " SO8 to DIP8 " converter. We design this system to work with 9V DC power source but at the prototyping stages, we noticed that it works well with lower DC voltage such as 5V. For the output use any 8Ω or 4Ω (5W or higher rated) full range speaker pair. We test this with 8Ω 8W oval speakers which are commonly found on televisions.

We initially developed this USB atmospheric pressure monitor to study some operating characteristics of Bosch BMP180 sensor . BMP180 is a low-cost sensor for measuring barometric pressure and temperature. According to the datasheet this sensor can use to measure pressure ranging between 300hPa to 1100hPa . This sensor is introduced a couple of years back but still, it is popular due to lower cost and simplicity of its interface. BMP180 based sensor module We did this unit to test the BMP180 sensor more accurately and to study its behaviors. This unit is based on PIC18F2550 microcontroller and the main reason to select this MCU is because of its built-in USB 2.0 interface. BMP180 sensor monitor application To display sensor calibration data and it’s readings we did small windows application. This application display and plot temperature and pressure readings captured from the BMP180 sensor. This unit is programmed to work as a USB HID device and no special device drive...

This is a real-time clock based automatic LED lamp which we originally designed to use as a night light. This lamp can be programmed to turn on and off at the specific time of the day. For example, it can program to turn on at 6 PM on each day and to turn off at 4 AM the next day. The core component of this project is PIC16F883 MCU and its firmware is developed using MikroC Pro for PIC . We select this MCU because of its 7 KB flash memory, I 2 C, UART, E 2 PROM and built-in 8-bit and 16-bit timers. In this system, we use DS1307 RTC because of its availability in the market and lower external component count. A prototype version of RTC Lamp This lamp is designed to work with commonly available 7W LED panels. In our prototype design, we use 7W 24V warm-white LED module to test this system. To drive other LED modules change the value of the R5 resistor of the current limiter circuit. This system is designed to program using the RS232 serial port. A user can modify system time,...

HC-06 is a quite popular slave mode Bluetooth module designed for wireless serial communication. This module can pair with PC, mobile phone or with any master mode Bluetooth peripheral. HC-06 Bluetooth module This simple .net framework based application can use to modify the following parameters of the HC-06 Bluetooth module: Bluetooth display name Pair password BAUD rate Parity check type HC-06 Bluetooth module programmer This application communicates with the HC-06 module through COM port. To emulate the COM port using any Windows compatible USB to Serial converter . While at the testing we try the following modules with this application: FTDI FT232 USB to Serial module CH340 USB to Serial module CP2102 USB to Serial module This application is developed using .net framework 4.5 and Visual Studio 2012. All source code and compiled binaries are available to download at https://github.com/dilshan/hc6-config . This application and its source code are distrib...

Recently I checked Windows 10 IoT core on Raspberry Pi 3 B+ board. While flashing this operating system using Windows 10 IoT dashboard I got " Failed to write provisioning file to the microsd card " error. I tried several options in dashboard UI but I got this error continuously. After some google search, I found a forum in Microsoft MSDN saying that this issue happens due to poor or slow speed SD cards. The SD card which I used previously is Kingston 16GB class 4 SDHC memory card . Later by following the site, I flash this image into new class 10 SD cards and SDXC cards but repeatedly I got this same errors. After a couple of hours of digging I fix this issue by following the steps below: Open Windows 10 IoT core dashboard and try to install the OS image.  If you got " Failed to write provisioning file to the microsd card " error, close the Windows 10 IoT core dashboard . Open C:\Users\USER-NAME\AppData\Local\Temp\RPi2\msi\msicontent\Microsoft IoT\FFU\R...

This is 8 channel CMOS logic probe and pulsar which is useful when designing, testing and faultfinding in digital circuits. This circuit is designed using commonly available CMOS logic ICs which including a couple of 4069 hex inverters and 4040 binary counter. A prototype version of 8 channel logic probe and pulsar The logic probe of this system is based on 4069 hex inverters and it indicates logic high and low states with 2 LEDs. Logic pulsar of this circuit is capable to generate 12 frequencies and highest frequency it can generate is 420kHz.  This pulsar generates a square wave with 50% duty cycle and it's average rise time is 16µS. Both schematic and PCB design of this logic probe and pulsar are available to download at google drive . In this schematic, all LED-L connections should connect to the anode of LEDs and cathode should be connected to the VSS terminal of J31 ( LED-L-H ) connector. All LED-H connections should connect to the cathode of LEDs and anode must...