Dilshan R Jayakody’s Web Log

TFA9842AJ is quiet old 7.5W audio power amplifier introduced by NXP . This amplifier IC is no longer produced by NXP, but still, it's available to purchase in many places, which including eBay , AliExpress , Amazon , etc. NXP TFA9842AJ Power amplifier IC. I tested a couple of TFA9842AJ based amplifiers in the last couple of years. The main reason I liked TFA9842AJ is its simple, clean design, wide operating voltage, and high-quality bass-rich audio output. Thanks to it's built-in DC volume control circuit this audio amplifier can easily interface with MCU. In this article, we provide a generic TFA9842AJ module which works with most of Arduino boards, MCUs and SOCs. Schematic of the TFA9842AJ module. As illustrated above, this system consists of LM321 operational amplifier and TFA9842AJ IC. To support both 5V and 3.3V logic inputs we introduce logical level selection jumper ( J2 ) into this design. To control the volume PWM input must apply to the J1 . In this...

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. PCB of the programmable light controller. 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 supp...

TEA5767 is electronically tuned FM stereo radio receiver comes from NXP for low voltage applications. TEA5767 based radio modules are now common in the field and this project is based on Samsung TT-502 radio module . The main objective of this project is to design low-cost FM tuner based on this TT-502 / TEA5767 module and commonly available electronic components. In this receiver the main controller is ATmega8 MCU, except to that TDA2822 is used as AF power amplifier, PT2257 is used to control the volume. In this given design MCU, PT2257 and TEA5767 radio module are set to work with a 3.3V power source. The LD33V voltage regulator is used to obtain 3.3V from the supply voltage. To control the receiver, MCU provides five push buttons. Those can be used to control volume, perform an automatic scan and manual tuning. The final version of TEA5767 based FM radio receiver. The firmware of this receiver is developed using MikroC for AVR and it is available to download with proje...

Smart Audio Box (SAB) is microprocessor controlled audio switch and amplifier system, which is specifically design for audio composers and for audio engineers. SAB consist of 4 high impedance stereo inputs and two output modes. One output mode can drive stereo headphone/earphone and other output mode can drive pair of 8W speakers. In prototyping stages we identify those modes as " Personal Mode " (headphone output) and " Audience Mode " (power amplifier output). Another main feature of this system is its programmable 16 step attenuation controller. This attenuation controller helps to control the audio output level of each output-mode. Prototyping version of Smart Audio Box The main component of SAB system is ATmega8 MCU, other than that headphone amplifier is design around NJM4556 high current operational amplifier and power amplifier is based on TDA1521A. To operate, this system requires 2 power sources. Microcontroller, ADC interfaces and CMOS logic-s...

These days many verities of alarm systems are available in the market. Some of them get triggered through touch and some type where a wire needs to broken to get triggered.  Both of these types of alarms have some limitations and problems. Wire based alarms are easily avoidable, noticeable and need some regular maintenance. Touch type alarms often pickup RF waves and get activated (because of that it need some controlled environment to function properly). In this project we design and develop LASER based burglar alarm system. Instead of wire(s) this system use LASER light wave and it can effective for more than 50m. Core features of this alarm system are: High audio output power (Max. 3W PMPO) Master light override switch Inbuilt alarm test functionality Memorized power state Quick response time (aprox. 10ms ~ 30ms) Support for wide input voltage range (15V – 25V DC) Easy to build and calibrate Compact size (aprox. 130 × 200 × 60mm) This alarm system is specifically ...