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Alarms, control, timers electronic circuits

Timers, alarms, detectors and other sensor based circuit diagrams

4 channel infrared remote relays

4 Channel Infrared (IR) Remote is a simple kit using the famous HT12A and HT12D encoder / decoder chips from Holtek... [read]

5 to 30 Minute Timer

A switched timer for intervals of 5 to 30 minutes incremented in 5 minute steps.... [read]

5 Zone Alarm System

This is a complete alarm system with 5 independent zones suitable for a small office or home environment.... [read]

8 Channel software controlled fanbus with PWM

This article is about a software controlled, parallel port-interfacing 8-channel Pulse-Width-Modulated fan controller.... [read]

AC Current Monitor

This circuit was designed on request, to remotely monitor when a couple of electric heaters have been left on.... [read]

Astable Multivibrator

Astable Multivibrator... [read]

Auto Heat Limiter for Soldering Iron

Usually a soldering iron takes a couple of minutes to get adequately heated up to melt the solder, after which the heat generated is much above the requirement... [read]

Automatic Fan Controller

Automatic Fan Controller ... [read]

Bedside Lamp Timer

The purpose of this circuit is that of power a lamp or other apparatus for a given time (30 minutes in this case), and then to turn it off.... [read]

Car Alarm and Immobilizer

This circuit features exit and entry delays, an instant alarm zone, an intermittent siren output and automatic reset. By adding external relays you can immobilize... [read]

Dark Activated Switch

This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an... [read]

Dark Sensitive Switch

Dark Sensitive Switch is a simple project which operates a relay when the light falling on the LDR goes below a set point.... [read]

Dark-activated LED or Lamp Flasher

Dark-activated LED or Lamp Flasher... [read]

DC Motor Control Circuit

Circuit for managing DC motor.... [read]

DC Motor Reversing

A DC motor reversing circuit using non latching push button switches. Relays control forward, stop and reverse action, and the motor cannot be switched from... [read]

DC Motor Reversing Circuit

Reverse rotation of DC electric motor. ... [read]

DC servo motor driver

DC Servo Motor Driver kit, designed using MC33030 IC, is the fastest and low cost way of getting your DC Servo Motor up and running.... [read]

Dual Relay Driver Board

Dual Channel Relay Board is a simple and convenient way to interface 2 relays for switching application in your project.... [read]

Electronic Keypad

Secure any electronic device using this electronic keypad. Circuit is relatively simple and it's built with 4081 CMOS quad 2 input "AND" gate... [read]


Temperature based fan control. Very useful if you want to have quiet cooling while the device is not at full power.... [read]

Frost Alarm

A simple thermistor triggered cold switch with adjustable threshold.... [read]

Garage - Shed Alarm

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays. It's designed to be used with the usual types of... [read]

High current bipolar stepper motor controller

High Current Bipolar Stepper Motor Controller kit is based on chopper drive. Chopper drive is a method of providing a constant current source to a device.... [read]

Hot Water Level Indicator

A simple device to indicate various levels of hot water in a tank.... [read]

Infa-Red Remote Control

This remote transmits a tone using an infa-red LED. This tone is decoded by the receiver. Since the receiver only switches when it hears the tone, there are... [read]

Infra Red Switch

This is a single channel (on / off) universal switch that may be used with any Infra Red remote control using 36-38kHz... [read]

IR Remote Volume Controller

IR Remote Volume Controller circuit diagram... [read]

Jogging Timer

This circuit was developed since a number of visitors of this website requested a timer capable of emitting a beep after one, two, three minutes and so on,... [read]

Mini Metronome

Mini Metronome circuit diagram... [read]

Multi Rocket Launcher

Simple circuit for rocket model starter.... [read]

On-Off Temperature Control

This circuit controls a load (in this case a dc brushless fan) based on a temperature compared with a setpoint.... [read]

On-Off Temperature Control

On-Off Temperature Control device circuit diagram. It's useful for turning on and off devices by high or low temperature.... [read]

Periodic Timer

A switched timer with equal make and equal space periods timing adjustable from over 6 minutes to 38 minutes.... [read]

Photo Timer Circuit

Time is set by potentiometer R2 which provides a range or 1 sec. To 100 seconds with timing capacitor C1 of 100uF. The output at pin 3 is normally low and... [read]

Plants Watering Watcher

This circuit is intended to signal when a plant is needing water. A LED illuminates at maximum brightness when the ground in the flower-pot is too dry: it... [read]

Precision Metronome and Pitch generator

CMos IC1 and IC2B quad AND gate form a 2.4576 MHz crystal oscillator plus a 2400 times divider.... [read]

Proximity sensor

This circuit takes the guesswork out of proximity detection by inducing eddy currents in a living being, whether animal or human. May serve as alarm or some... [read]

Pulse Width Modulation DC Motor Control

Often, people attempt to control DC motors with a variable resistor or variable resistor connected to a transistor. While the latter approach works well, it... [read]

PWM Motor-Light Controller

Pulse width modulation controller for regulating motor speed ... [read]

Rain Detector

This circuit uses a sensor made of a small piece of etched PC board and a simple SCR circuit to detect rain and sound a buzzer.... [read]

Simple DC motor PWM speed control

When the potentiomenter is all up, the Rcharge resistance is 1,0 Kohm (the diode prevents the capacitor to charge through the second potentiometer section... [read]

Simple optical switch

The 555 is proved to be the most versatile and ubiquitous IC all over the world.This is a possible use: simple inverting schmitt trigger.... [read]

Single Zone CMOS Alarm

This circuit features automatic Exit/Entry delays, timed Bell Cut-off and System Reset. It has provision for normally open and normally closed switches and... [read]

Solid state relay switch

Solid State Relay Switch is a simple kit which will help you control (ON / OFF) a single high power circuit from a low power drive.... [read]

Stepper motor controller

This project allows you to control the speed, direc-tion, and step size of a unipolar four-phase step-per motor. The controller is capable of handling motor... [read]

Stepper Motor Controller

The circuit is very simple and inexpensive. This is good thing because most commercial stepper motor controller ICs are quite expensive. This circuit is built... [read]

Tan Timer

This timer was deliberately designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight.... [read]

Temperature-controlled Fan

This circuit adopt a rather old design technique as its purpose is to vary the speed of a fan related to temperature with a minimum parts counting and avoiding... [read]

The Relay Sub Board

The board is now designed so that it may be cut in two to make two separate boards, each with four relays. This should be more than adequate for most purposes.... [read]

Time Delay Relay

A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit... [read]

Time Delay Relay II

When activated by pressing a button, this time delay relay will activate a load after a specified amount of time. This time is adjustable to whatever you want... [read]

Timed Beeper

This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question,... [read]

Touch Activated Light

The circuits below light a 20 watt lamp when the contacts are touched and the skin resistance is about 2 Megs or less. The circuit on the left uses a power... [read]

Unipolar Stepper Motor Controller

circuit diagram for controller for stepper motor.... [read]

Voltage Controlled Switch using 555 Timer

Voltage Controlled Switch with popular 555 timer circuit used in a novel way.... [read]