Skip to main content


Virtual electronic finderscope for the Stellarium

StarPointer is a virtual electronic finderscope for astronomical telescopes. This device works with Stellarium and helps the observer identify objects in the sky.  Prototype version of the StarPointer sensor kit. This unit can be attached to the telescope without modifications and connects with the computer through the USB port. The StarPointer uses a few onboard sensors to determine its angle and position. After obtaining that information, the unit calculates the RA (right ascension ) and DEC (declination) coordinates of the telescope and transfers those details to the Stellarium. The StarPointer builds around the STM32F103C8 microcontroller, ADXL345 3-axis accelerometer , and HMC5883L 3-axis magnetometer . This unit communicates with the PC using the inbuilt USB peripheral of the STM32F103C8 microcontroller. The firmware of the StarPointer is developed using the LibOpenCM3 library and built using GNU ARM Embedded Toolchain . This unit can attach to any astronomical telescope or bi
Recent posts

Portable Image File (PIF) library for Lazarus and Delphi

Portable Image File (PIF) is an embedded-systems friendly, bitmap-like image format with ease of use and small size. This image format develops by the gfcwfzkm ( aka Pascal ) for low-end embedded systems. The file format and PIF's original implementation are available at . In this project, I developed an open-source library for the above file format to get used in Lazarus and Delphi programming languages.  This PIF library supports Windows and Linux operating systems, including Raspberry Pi OS . Sample application in Linux environment. The library is available at .  The library methods are self-explanatory, and sample projects are available for Lazarus and Delphi . For example, the following code block demonstrates opening the Portable Image File and displaying it on the TImage . var pifObj: TPortableImageFile; begin pifObj := TPortableImageFile.Create('sample-image.pif'

Experimental narrowband FM receiver for 2-meter band

This project is about MC3362 and ADF4351 based modularized, 2-meter narrow band FM receiver. In this design, the receiver splits into three modules as RF preamplifier, MC3362 tuner, and ADF4351 oscillator. The RF preamplifier builts around BF900 dual-gate MOSFET. The tuner stage builts using the popular MC3362 , low power narrowband FM receiver IC. For the oscillator, we use the ADF4351 DDS RF signal generator module. The core component of this receiver is MC3362 IC. This IC was designed by Motorola and is no longer in production, but this IC is still available to purchase in many online stores . The chip we used in this receiver was purchased from a local electronic component store for LKR 75 (USD 0.2). The RF preamplifier used in this receiver extracts from the N.Ganesan's (VU3GEK) LRR200, 2-meter band FM receiver project . Prototype version of the RF preamplifier. In this prototype, the above preamplifier was built as a module using a Manhattan construction technique. Th

Wireless Call Bell

This project is about a wireless musical call bell, which I designed to meet some of my friend's requirements. This circuit design uses only the 4000 series CMOS logical ICs, NE555 , UM66 , and TDA7233 audio amplifier IC. For the remote control, we use a 433MHz 4-channel remote control module . This circuit is designed to work continuously with a low-power external 5V power supply. Prototype version of wireless call bell. The PCB in this call bell is designed as a single-sided PCB. The dimension of the PCB is 82mm × 50mm.  All the components in this circuit are commonly available through-hole-type components. The whole assembly process of this musical call bell is shown in the video attached to this document. The RF remote control module we use in this project consists of a remote control decoder and encoding IC. In our version, the transmitter (key fob) has a PT2262 encoder, and the receiver has a PT2272 decoder IC. In the prototype build, the receiver and transmitter are confi

Infrared remote control clone utility

IR Clone is an open-source IR remote control analyzer tool. This utility can analyze any IR remote control that modulates the IR signal with a 38kHz carrier signal. This utility has an option to store and retrieve up to 16 IR signals. In addition, it has PC software to analyze and edit captured IR signals. The hardware component of this analyzer is built around the STM8S003F3 MCU. It has 24LC32 EEPROM installed to store the captured IR signals. This unit is designed to operate with a 5V to 9V DC power source or a 3V battery.  Finished prototype of the IR Clone module Operating modes such as capture or replay can be changed using an onboard jumper on the PCB. These operating modes can change at any time without restarting the unit. In addition to the IR clone PCB, the only external component needed to operate this system is a 4×4 matrix keypad . Most of the generally available 4×4 keypads can directly couple with this system. The dimensions of the IR Clone PCB are 41.2mm × 32.1mm, a

TPA3001D1 Power Amplifier

Recently we looked for a replacement class-D power amplifier to replace my old TDA2030 power amplifier build . While searching for a suitable power amplifier IC, we found TPA3001D1 from the local market. This IC is a slightly older 20W Class-D power amplifier manufactured by Texas Instruments . At the time of this writing, it is priced at LKR 180 (0.89 USD) in the local market and is still available at all major electronics stores (including online stores ). Prototype version of TPA3001D1 power amplifier. To minimize assembling difficulties, we used through-hole-type components in this PCB. The only SMD component in this PCB is the TPA3001D1 IC. We installed the power amplifier IC on the bottom of the PCB because then it would receive good airflow. The table below lists all the components required for this project. Designator Quantity Value C1 , C8 , C13 , C14 , C15 , C16  6  1µF/25V C17  1  10µF/25V C2 , C3

STM8S005C6T6 Ethernet development board

In this project, we built an STM8S005C6T6 based Ethernet development board for our IoT experiments. This development board consists of ENC28J60 , 10BASE-T stand-alone Ethernet controller, CH340G , USB serial interface, 2 LED indicators, and passive buzzer unit. The firmware framework for this development board has been developed using SDCC . To enable IPv4 support, we convert the EtherCard driver, which is available for the Arduino platform. The current version of this driver supports all other EtherCard functions except TCP support. Finished STM8S005C6T6 IoT development board. In the given design, the SPI terminals of the MCU are connected to the ENC28J60 Ethernet controller. All SPI terminals, such as MISO / PC7 , MOSI / PC6 , and SCK / PC5 , are connected directly to the Ethernet controller. In addition, the PC4 terminal of the MCU is used as ENC28J60, CHIP-SELECT .  The CH340G USB serial interface is connected to the UART2 terminals of the MCU. In STM8S005C6T6, the UART2