Dilshan R Jayakody’s Web Log

This is a simple electronic project which we implemented for some local event to guide audience automatically with some prerecorded voice messages. The core component of this unit is ISD1820PY voice record/playback chip which is manufactured by Nuvoton Technologies . Except for ISD1820PY, this unit use commonly available low power LASER and LDR assembly to detect people. To drive the loudspeaker we use popular LM386 audio power amplifier. Thanks to ISD1820PY and LM386 this system can be implemented on a breadboard or on stripboard with a minimum number of external components. This circuit is designed to drive using 6V or 9V DC battery but it can also drive with 6V or 9V DC regulated power supply. To get 3.3V we use an LD1117V33 voltage regulator, but this can also be replaced with some commonly available 3.3V regulators such as LD33V, MC33269-3.3, etc. For the speaker, we use 4-inch 8Ω full-range speaker. A prototype version of electronic voice messenger. This unit can be u...

74181 is 4-bit arithmetic and logic unit introduced by Texas Instruments in March 1970 and it is known for being the first ALU in a single package. This chip is no longer in manufacturing but still, it is quite popular in CA ( computer architecture ) courses in many colleges. To test the behavior of this 4-bit ALU we decided to construct it on Altera MAX II CPLD. For this project, we choose EPM240T100C5 CPLD and logic design is implemented using Altera Quartus II . For logic design, we refer to Fairchild Semiconductor’s DM74LS181 datasheet. This setup is tested on basic EPM240 series development board with some mechanical switches and couple of LEDs. 74181 4-bit ALU test setup with the EPM240T100C5 development board. There are several test circuits available for 74181 ALU and our test setup is partially based on Electronics for Your (EFY) 1997 article. In another test setup, we use HEF4040 to drive, A and B operands of this ALU. The test setup attached to this article is t...

AN6877 is linear AF level meter IC produced by Panasonic and it is commonly found on much audio equipment. This chip is no longer manufactured by Panasonic and finding replacement chip for AN6877 is also quite difficult. The circuit described in this article is designed to replace AN6877 base LED drivers and it is based on commonly available components. This replacement LED driver is designed using 10, MMBT3904/2N3904 transistors and it can easily modify to get the necessary number of outputs. During the prototyping stages, we test this driver with a minimum of 7 LEDs (AN6877 configuration) and up to 12 LEDs. This LED driver is designed to work with 9V to 12V DC power source. With 7 LEDs and 9V power source, this module can directly replace AN6877 base LED driver modules. Schematic and PCB design related to this LED driver is available at google drive .

ZFM-20 is an optical fingerprint sensor module series developed by Zhiantec . Resolution of these fingerprint modules are 256×288 pixels and depending on the module it can be accessible over UART or USB interfaces. Other than capturing fingerprints this module has inbuilt DSP to process and verify captured fingerprints. This ZFM-20 fingerprint library is developed to capture and retrieve fingerprint images from the above sensor module. The main purpose of this library is to use ZFM-20 sensor with PC as a low-cost fingerprint capture unit and because of that, in-module fingerprint processing and verification functions are not implemented in this library. ZFM-20 fingerprint sensor test setup with CH340G serial to USB converter. ZFM20-LIB is x86 native shared library and it's implemented using Lazarus / FPC . This library is developed to use with most of the programming languages which including C , C++ , Delphi , FPC , Microsoft .net framework based languages, etc. Objec...

This is a single chip dynamic microphone preamplifier which is design to drive using commonly available 12V single rail power supplies. Preamplifier in this article is built around popular NE5532 dual low noise operational amplifier IC and this preamplifier is specifically constructed to drive professional 600Ω dynamic microphones. Internal view of a dynamic microphone preamplifier prototype. This preamplifier consists of two amplifier stages and the initial amplifier is designed to get 36dB gain and final preamplifier is used to get 16dB of gain. Preamplifier gain controller is placed in between those two amplifiers and this separation allows reducing clipping in the output waveform. In prototyping stages, we test this preamplifier with few 600Ω dynamic microphones with a TDA2050 power amplifier . According to our observations, this unit produces excellent output with all of these microphones. To get professional results to use this preamplifier with 12V battery or with regu...

The phantom power supply is widely used in the audio industry to power the active microphones over single audio cable. Most of the phantom power supplies deliver 48V DC over the balanced audio link and power supply unit described in this article is also based on the same technique. The phantom power supply in this article is based on TL783 high voltage regulator IC and 230V - 50V step down transformer. Like most of the phantom power supplies, this power supply is also design to connect in between an active microphone and audio mixer devices. PCB of 48V Phantom power supply. Schematic of this power supply unit is self-explanatory and PCB design is also based on commonly available through-hole components. For the step-down transformer, we use commonly available 230V - 25V-0-25V 1.5A transformer. During the construction, we recommended using shorter wires between PCB and XLR sockets to reduce the noise. PCB and schematic of this power supply unit are available to download at...

Resistor box is a quite useful instrument in analog electronic based design and prototyping tasks. It can easily build with few sets of resistors and with a couple of rotary switches. This quick post is about resistor box which we construct recently using 5W wire-wound power resistors. For this resistor box, we use five, single pole 12 position rotary switches and 50 wire-wound resistors. It gives 5 dials to controls 10Ω, 100Ω, 1KΩ, 10KΩ and 100KΩ steps. Final view of homebrew resistor box. Internal view and high-resolution photographs of this resistor box are available at my Flickr page . Schematic of the resistor box is available here .