By T.K. Hareendran

International Electronic Design Freelancer • Technical Author • Hardware βeta Tester • Product Reviewer
Articles Written 466

TL431 & Li-Ion Battery

TL431 is a cheap ‘n’ cheerful yet reliable programmable precision shunt regulator chip available in 3-pin TO-92 package. This monolithic IC voltage reference operates as a low temperature coefficient zener which is programmable from Vref […]

USB OTG Power Guard

As you may well know, you can borrow USB standard 5 volt dc supply from any smartphone equipped with USB on-the-go (USB OTG) port. USB OTG is a hardware (and software) standard that allows you […]

Universal 2S Li-Ion/LiPo Charger Module

This is a simple and 100% safe universal linear charger module for 2S Lithium-Ion (Li-Ion) and Lithium-Polymer (LiPo) batteries with the recommended constant-current/constant-voltage (CC/CV) charging algorithm. Initially charging takes place in the current mode and […]

Little Rescue Light

During an unexpected blackout in particular, a simple light source can be a handy aid. With only two transistors, one photo resistor, and a few other components you can build an automatic emergency light. Here’s […]

Simple Wireless Door Bell

Here’s an interesting circuit of a wireless door bell/buzzer for electronics students and hobbyists. The circuit is a short-range radio-frequency (RF) tone generator realized with the help of a cheap 433MHz RF transmitter & receiver […]

Tiny Tone Decoder Module

I’d made a number of tone decoder projects with the unique NE567 PLL tone decoder chip in 1990s, and most were published in Elektor Electronics (UK), Silicon Chip (AU) and Electronics For You (IN) magazines. […]

Portable Snake Repeller

Afraid of snakes? Don’t worry, here is a portable electronic snake repeller solution to keep all poisonous snakes out of your surroundings. All you need is to simply put the device on the bare floor/soil […]

Little Melody Maker

Here is a simple do it yourself project of a little melody maker useful for all those hobbyists interested in making electronic toys or fancy gizmos for their kids. For extreme simplicity and flexibility, the […]

Poor man’s USB Rubber Ducky

I believe most readers are familiar with Hak5’s USB Rubbery Ducky. Well, simply it is a $45 key stroke injection tool, masked as a generic usb flash drive, widely used to hack unlocked computers. Computers […]