Dilshan R Jayakody’s Web Log

In this project, we extend the shortwave superheterodyne receiver we developed a few years ago . Like the previous design, this receiver operates on the traditional superheterodyne principle.  In this upgrade, we enhanced the local oscillator with Si5351 clock generator module and Arduino control circuit. Compared to the old design, this new receiver uses an improved version of an intermediate frequency amplifier with 3 I.F transformers. In this new design, we divide this receiver into several blocks, which include, mixer with a detector, a local oscillator, and an I.F amplifier. The I.F amplifier builds into one PCB. The filter stage, mixer, and detector stages place in another PCB. Prototype version of 455kHz I.F amplifier. In this prototype build, the Si5351 clock generator drives using an Arduino Uno board. With the given sketch, the user can tune and switch the shortwave meter bands using a rotary encoder. The supplied sketch support clock generation from 5205kHz (tuner frequ

This active subwoofer filter system provides the frequencies required to run the subwoofer within its limits. The purpose of this unit is to prevent the subwoofer speaker or circuit from overloading at unsupported frequencies. This approach can ensure the safety of the subwoofer speaker or driver circuit. This system consists of TL074 based active lowpass filter, highpass filter, and preamplifier stage. The lowpass filter is in 880Hz cutoff frequency. Highpass filter cutoff frequency can select from the rotary switch. In this given design, the highpass cutting frequencies are at 80Hz, 115Hz, 150Hz, and 180Hz.  Use the calculator application shown here to use this system for frequencies other than those mentioned above.  Finished prototype of an active subwoofer filter circuit. In this circuit, both lowpass filter and high pass filter uses a 3-pole Butterworth filter configuration. Here all the filter component values are calculated using the calculator application mentioned above.

The QN8035 is a stereo FM radio receiver launched by the Quintic Corporation . Compared to other popular digital FM tuners ( RDA5807 , TEA5767 , etc.), this tuner does not seem to be as popular among the DIY community. As we have seen, the biggest problem with this IC is the lack of information. During our initial search, we came across some details about this IC. Much of that information was confined to a product datasheet and a few undocumented GIT repositories. Based on the information we found on the internet, we concluded that Quintic was no longer in business. According to the NXP website , it stated that Quintic Corporation was acquired by NXP in 2015.  Although the Quintic is no longer in business, the QN8035 IC can still be purchase at a low price from online stores. In addition, we found several FM radio kits manufactured using this IC in online stores. Due to the lack of information, I decided to explore this IC to understand its functionality and limitations. In this

These days good quality oscilloscope is not an expensive instrument and, we can see it in most workbenches. With the advancement of oscilloscopes, simple testing tools such as logic probes are not as popular these days. However, if the oscilloscope or logic analyzer was out of reach, the logic probe is a handy instrument to check digital circuits.  Also, in some cases, a logic probe is an easy option to check the functionality of low-speed logic circuits because it provides a real-time visual indication of the logic state without adjustments or calibrations. Prototype version of the logic probe. The logic probe design described in this post uses common and inexpensive ICs, including the popular NE555 timer and LM393 low voltage comparator IC. At the time of this writing, both ICs were prevalent in the market and cost less than LKR50 (US$ 0.25). This circuit design using SMD components to minimize the board size. The dimensions of the soldered PCB are around 70mm × 14mm × 6.6mm, and

CLI, also known as Caller ID and calling number delivery ( CND ), is a service offered by the telephone service provider to customers to obtain the calling party number and date/time of the call. The service activation and information format of CLI are different from telephone network operator to operator. CLI display unit - minimum test setup In this project, we will create a small Caller ID decoder using Arduino UNO and a custom-made HT9032D module. The core component of the project is the HT9032D, which can decode incoming call ID data over a telephone connection. This IC supports Bell 202 FSK and ITU-T version 2.3 CLI protocol specifications. The HT9032D module we created here base on the application example given in the IC datasheet . In addition to decoding CLI data, this module also can detect ring signal rises over the phone line. Assembled HT9032D module The Arduino UNO is used to process the decoded CLI data stream and manipulate the LCD. In an idle state, the decoder a