Skip to main content


Showing posts from 2019

Replacement motor driver for mini drills

In my workshop, I got a couple of INGCO power tools. INGCO is a Chinese power tool manufacturer, and this brand is quite popular in Sri Lanka. Out of those tools I frequently used INGCO MG1502.2 mini drill. I purchased this drill three years back and mainly use for engraving and for precision drilling.

A few days ago while I'm using this drill, it suddenly stopped. As a first thing, I checked brushes and mains-lead. After a few minutes of inspections, I found out that both brushes and mains lead are in perfect order. To further examine I decided to open the drill.

The internal layout of this drill is quite simple. It mainly consists of an AC motor and electronic speed controller circuit. After a few checkups, I determined that the electronic speed controller is dead. In speed controller board I notice some unknown microcontroller, 74HC595 shift register, and Z0409MF TRIAC. As like many Chinese products here also they erased the IC number and other markings of the MCU. After exam…

Programmable light controller

The main objective of this project is to design a maintenance free and low-cost light which automatically turns on and off at the predetermined time of the day.

To meet the above requirement I designed this controller using ATmega8 MCU and DS1307 RTC. The driver stage of this light controller is intended to work with commonly available 7W LED modules.

The core component of this programmable light is ATmega8 low power CMOS microcontroller. The main reason to select this microcontroller is it’s lower cost and higher availability. Except for the above two reasons this microcontroller also bundled with a rich set of peripherals which including 23 GPIOs, 3 independent timers, Two-wire serial interface, EEPROM, etc.

Apart from ATmega8 microcontroller, this system uses DS1307 real time clock to maintain system time. Like ATmega8, DS1307 is also a very popular RTC in the market.

This controller is designed to work with a 24V DC power supply. The main reason to select 24V is that most of the…

Lightning arrester installation

Recently I build my new house near Maharagama town. While building this house I allocate space for my antennas and observation equipment. Before installing antennas, I decided to install a lightning rod into the house. The main reason to install a lightning rod is because of the height of the building. It nearly 48 feet (approximately 15m) high, and located in open space, because of those reasons there is a very high probability to hit lightning into my antennas and other equipment.

At the time of this writing, in here in Sri Lanka mainly two types of lightning arrestor systems are in use. The first type is a conventional lightning rod. This type of lightning rod is very common in Sri Lanka and it made with copper rods. The second type is ESE (Early Streamer Emission) type lighting arrestor. This ESE type is now getting popular in here and I saw it in a couple of new buildings. As I noticed most of the lightning arrestor installation companies are now moving into this ESE type soluti…

TCS230 based Bluetooth color picker

This is TCS230 based Bluetooth color picker prototype which we build to test the concept. In here the idea is to extract color from any physical object and transfer it to PC / mobile. To test this concept, we use low-cost TCS230 color sensor.

TCS230 is programmable color light-to-frequency convert IC. This chip produces square wave output with frequency directly proportional to the light intensity. To drive this sensor and capture its output we used PIC16F628A microcontroller. The processed output is then transferred to the host using the HC-05 Bluetooth SPP (Serial Port Protocol) module.

In PC we wrote small Python script to display captured value and color in a Window.

In this design, we drive the TCS230 sensor with 20% frequency scaling. The entire circuit is built using commonly available modules and components. For the color sensor, we use the 8-pin TCS230 sensor module which is commonly found in eBay and other online electronic component stores. This module comes with 4 white LEDs…

13.8V 5A Power Supply

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.

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.

Simple I2S stereo decoder with amplifier

In this project, we build a simple I2S stereo decoder with an amplifier. To decode I2S data we use Princeton TechnologiesPT8211 16bit DAC. KA2206 audio power amplifier is used as the driver stage of this system.

Structure of this I2S 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.