Dilshan R Jayakody’s Web Log

This is contactless DTMF ( Dual Tone - Multi Frequency ) switch to control 16 channel relay boards. This module can turn ON/OFF relays based on DTMF singles which captured from its microphones. This project is building using 4 commonly available ICs which including TL084, TL081, CM8870, and 74LS154. TL084 is used as microphone preamplifier and LPF. TL081 act as combiner and CM8870 is used to decode the DTMF inputs. 74LS154, the demultiplexer is used as line selector. In this circuit TL084 and TL081 and replace with any compatible operational amplifier IC. During our prototyping, we replace TL084 with LM324, TL074, and TL081 with TL071 and got identical results. For the microphones, it is highly recommended to use omnidirectional condenser microphones. In our tests, we get good results when both the microphones are in the 90⁰ plane. This circuit is design to work with single rail 5V DC power source and its output terminal ( SV1 ) is compatible with most of the 16 channel relay bo...

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 a quick post about EAGLE parts list generation script which I was written to replace existing " part2html.ulp ". This script generates a more organized and detailed BOM HTML file and it can directly replace " part2html.ulp ". This script is tested with EAGLE 6.6.0, but it can also work with older versions of EAGLE software. This script is available to download at http://github.com/dilshan/bom-gen with usage details.

FlashProg is USB base flash memory programmer to work with 3.3V serial flash memory devices. This programmer is specifically design to read, program and configure 25x series, serial flash memory devices which are commonly used to store BIOS in PC mainboards. Originally we design this project to read and program BIOS of Foxconn G31MXP mainboard. Our version of G31MXP contains Macronix MX25L8005 8M-Bit serial flash memory and we use this programmer to load some of our custom BIOS to this serial memory. MX25L8005 SPI flash memory on Foxconn G31MXP mainboard FlashProg programmer is built around Atmel ATmega8A microcontroller with standard through-hole type components and it support for both 32 bit and 64 bit Windows and Linux operating systems. All the compiled binaries for both the platforms are available at project home page at flashprog.sourceforge.net . This programmer use very few components and it can be easily constructed on breadboard or on PCB. Both EAGLE and PDF...