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How to Design a High-Pass and Low Pass Filter Circuits Quickly

In this post we learn how to design audio filter circuits such as high pass filter and low pass filter circuits effortlessly without going through the hassles of complex simulation and calculations. The presented designs will enable creating filter circuits only for the desired specific frequency bands and block all other unwanted frequencies. What’s High … Read moreHow to Design a High-Pass and Low Pass Filter Circuits Quickly

Passive Infrared (PIR) Motion Sensor Circuit

PIR with delay ON alarm

The post discuses the pinout details of the standard passive infrared (PIR) sensor RE200B and also explains how to make a motion detector circuit using a single transistor and relay, which can detect the IR radiation from human body and activate the attached relay. What is a PIR PIR is the acronym for Passive Infra … Read morePassive Infrared (PIR) Motion Sensor Circuit

Password Based AC Mains ON/OFF Switch

In this post we are going to construct a password based mains ON/OFF switch circuit, which can turn ON and OFF the AC mains supply, only when correct password is entered. This prevents the danger of electrocution of the technician who might be currently working with the high voltage lines and equipment. Password Protection for … Read morePassword Based AC Mains ON/OFF Switch

Mains High Low Voltage Protection Circuit with Delay Monitor

The post explains an upgraded version of my previous mains 220V/120V high-low voltage cut off protection circuit which now includes a delayed restoration of power for the load with 3 LED power status indicators. The idea was requested by one of the dedicated members of this website. Circuit Objectives and Requirements I just followed you’re … Read moreMains High Low Voltage Protection Circuit with Delay Monitor

Password Security Lock Circuit Using 4×4 Keypad and Arduino

In this post we are going to construct a password security lock circuit, which can be accessed by a 6-digit password. To be more precise it is alpha numeric password.   Hardware for this Project We are going to utilize 4×4 keypad, which consists of 0 to 9 decimal values, two special character ‘#’ and … Read morePassword Security Lock Circuit Using 4×4 Keypad and Arduino

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