300 articles written by T.K. Hareendran

Author: T.K. Hareendran

About: Internationally Certified Freelance Technical Author/Circuit Designer Electronics Engineering Technologist Founder & Promoter of TechNode» PROTOLABZ – An Open Source Hardware R&D Lab Tel: +91 (0) 9447712139 Email:


Arduino Nano Sensor Interface

T.K. Hareendran - 02/21/2018

The nano sensor interface presented below is a microcontroller-based universal sensor interface with a power-saver mechanism. The idea, [...]


T.K. Hareendran - 02/14/2018

It is very easy to build an "SMS-controlled relay" with the help of a cheap GSM modem module [...]

Portable Air-Cooling Fan/Blower for Hobby Workbench

T.K. Hareendran - 02/09/2018

Here is a true recycling project — turning a laptop’s internal CPU cooling fan into a general-purpose portable [...]

How to Play with SIM800L — Part 2/2

T.K. Hareendran - 01/16/2018

Because the SIM800L module is very flexible, a great GSM project design can be relatively simple. But there [...]

AC Power Flasher

T.K. Hareendran - 01/09/2018

AC Power Flasher Design The design presented here is an AC power flasher that provides flexible control of [...]

How To Play with SIM800L: Part 1

T.K. Hareendran - 12/14/2017

Intro to the SIM800L If you are looking for a compact GSM/GPRS module, you can get the SIM800L [...]

Building a Smart Master/Slave Switch

T.K. Hareendran - 12/06/2017

Here is an inexpensive and easy-to-build master/slave switch for integration into powerstrips for the automatic switching of “slaves” [...]

Wi-Fi Witty Primer

T.K. Hareendran - 11/28/2017

This is just an introduction to Wi-Fi Witty (also known as Wi-Fi Witty Cloud Development Board/ESP Witty) — [...]

Visualizing Data with Arduino

T.K. Hareendran - 11/14/2017

I like to visualize things, so I decided to prepare this simple tutorial to help you better understand [...]

How to Use Switch Mode Power Supplies to Power Your IoT Design

T.K. Hareendran - 11/07/2017

An effective and long-lasting power supply is the backbone of any IoT device. Switch-mode power supplies (SMPSs) are [...]