Dilshan R Jayakody’s Web Log

This post is about experimental USB to 3.3V/5V serial TTL adapter which we build recently to work with both 5V and 3.3V MCUs. This project is mainly based on CH340G seral-USB chip. CH340G is cheap and commonly available serial-USB convert IC and now it's commonly found on Chinese versions of Arduino development boards. FTDI's FT232 is another possible alternative for this kind of project, but we drop it because of its famous device driver base chip locking issues . Also, compare with FT232, CH340G is cheap, commonly available and simple to construct with a minimum number of components. In this module, we incorporate a 5V/3.3V voltage selector switch to avoid interface matching issues due to different voltage levels of mainboard/MCU and serial TTL adapter. A prototype version of CH340 USB to serial adapter. In prototyping stages, we use CH340G with breadboard by using SO-16 to DIP16 adapter and supplied PCB is also based on using the same adapter. Except for CH340G ...

HAKKO 907 is popular and commonly available soldering iron in the electronics field. To drive those soldering irons user needs to have HAKKO or any other compatible soldering station. The biggest problems with those soldering stations are there higher price tags and limited availability in the local market. Because of those problems, we decided to create our own soldering station, and for that, we choose " Chinese " version of HAKKO 907 soldering handle. Now Chinese versions of 907 compatible irons are available on eBay for less than 5USD. As per our observations, those Chinese versions of soldering irons look and perform almost similar to genuine HAKKO 907 iron(s). To keep it simple we choose LM358 dual operational amplifier IC to monitor the 907's thermocouple and drive the TRIAC. The entire control circuit of this soldering station is powered by single rail 5V DC power supply. To drive both handle and station we use 12V-0-12V 8A step-down transformer. Interna...

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...

In the last few days, we are looking for some simple FM radio receiver to integrate into one of our ongoing projects. For that, we try several FM radio receiver ICs including TDA7000, CD2003/TA2003/TA8164, CXA1019, and KA22429. Out of all those chips we select CD2003 (or TA2003/TA8164) based receiver for our project because of its simplicity and outstanding performance. Except to CD2003, Sony CXA1019 also perform well but we drop it because of its higher component count. We design our receiver based on Toshiba TA2003 datasheet and later we try TA8164 and CD2003 with the same circuit. Either CD2003 or TA8164 can directly replace TA2003 IC, and as per our observations, TA8164 gives excellent results out of those 3 chips. A prototype version of CD2003 FM radio receiver The PCB design and schematic which we used in our prototype project are available to download at google drive (including pin-outs of crystal filters and inductors ). Except for CD2003 IC, this receiver consist...