Dilshan R Jayakody’s Web Log

I recently had the opportunity to work on another Pioneer PL-250 turntable. The previous owner was having an issue with the platter moving back and forth without continuously rotating, which can be a frustrating problem to deal with.  After a quick inspection, I found that the issue was caused by some faulty electrolytic capacitors (3 × 470µF) near PA2005 and a bad bridge rectifier. These components were preventing the platter from spinning smoothly in the right direction. Fortunately, I had the necessary replacement parts on hand, so I quickly swapped out the bad components. Once the new capacitors and rectifier were in place, I gave the turntable a full service to ensure that everything was working as it should. After completing the repairs and maintenance, I tested the turntable and was pleased to see that it was now spinning smoothly and continuously in the correct direction.

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...

Star test is the most recommended method to test and collimate telescopes . To do a " star test " we need to aim and track telescope with real star and most of the times this is quite difficult to do because of the fast movement of stars and bad sky conditions. Another problem with the real star is air turbulence and some times this effect may lead to false conclusions. However artificial star is an excellent alternative for " real star test " and in this post, we introduce easy to build "artificial star unit" to test and collimate telescopes. This unit is based on commonly available electronic components and it can operate with a 9V battery. At the time of writing this unit can build around LKR 1000.00 (Approximately 7.00 - 8.00 USD). In this given design, we use NE555 timer IC to generate PWM output to LED and this allows us to control the intensity of the artificial star. In our prototype we use high-bright 3mm white LED as our light source. Apa...

UC3844 is a popular current mode controller which is commonly found on DC-to-DC converter circuits and switch mode power supplies. This motor speed controller is also based on UC3844 and it is specifically designed to drive 20V - 24V DC motors. In this given configuration UC3844 produces (approx.) 50kHz to 240kHz PWM output and this range can be adjusted by changing the value of C2 timing capacitor. As per the datasheet, UC3844 is capable to produce PWM output frequency up to 1MHz. This circuit is quite sensitive to the noises, and to get the accurate output to construct this circuit on PCB. As per our observations, long wires on the oscillator circuit may change the stability of the output signal. According to the ON semiconductors , UC3844 has now discontinued product but it is still commonly available in the market for less than Rs. 40.00 (LKR). For this circuit either DIP (UC3844N) or SMD (UC3844D1) version of UC3844 can be used but the PCB design available with this arti...

This is an easy to build " high-bright LED" night light, which I was design and developed in weekend to replace my existing 5W ( filament base) night lamp.  This circuit is mainly based around TL494 PWM driver IC and LM350 - 3A adjustable voltage regulator. The LED used in this project is 9V - 10W high bright LED and this given design is capable to drive maximum of six, 10W LEDs. Microscopic view of 10W High Bright LED with controlled input This unit is design to work with 12V to 30V DC power supply and it can withstand for voltage fluctuation around 12V to 35V. The schematic of this unit is available at upvater.com under the terms of CERN OSH 1.1 License .

Nichrome-Wire Cutter is an essential tool for model aircraft constructions. We mainly use Nichrome-Wire Cutters to fabricate model aircraft wing assemblies, other than that Nichrom-Wire Cutters are used to cut wax, polystyrene materials and other similar kind of materials. In this project we construct electronically Controlled Nichrome-Wire Cutter. The main feature of this cutter is its (non mechanical) variable temperature controller. The temperature of the Nichrome-Wire is controlled using TL494 PWM controller. In this design TL494 is oscillated with fixed frequency and only varying factor is its duty cycle, in this given design R2 is used to control the duty cycle of the frequency. Duty cycle variation with R2 potentiometer This Nichrome-Wire Cutter requires 8V to 20V – 3A DC power source and 16.5V – 3A is recommended supply for this system. When constructing this system makes sure to solder and connect all the components properly, improper connections may cause oscillatio...

In this project we design 2 channel D.C motor controller with pulse width modulation (PWM) based speed and direction control. This module is mainly design to drive 14.4V to 18V electric D.C motors. This motor controller is design to work with 18V - 1.5A D.C power source and it can be directly interface with general microprocessor / microcontroller system (without using any voltage level shifters). While at the prototyping stages we successfully couple this module with several NIDEC D.C fans and blowers which include D1751M24B7AP, E1331K12B7AZ-00, DME37KA, CF24DM506, etc. Control interface for this module is easy to use and at the designing stages we interface it with PIC16F887 and Atmega64 MCUs. Control interface of this module is consisting with 3 inputs (please refer the J3 in the circuit diagram) and using these inputs user may be able to select the motor, apply the brakes and also change the rotational directions of the motor(s). When constructing the circuit it is recommend...