How to Make a Burglar Alarm Circuit for Your Home Security?

These days home security systems are given great importance everywhere. However these security automation systems are very expensive to implement. Here I will help you to make a simple IR security system by your own using an Infrared-photodiode pair.

Earlier we had already published another intruder alarm circuit diagram which was based on LASER and LDR. However it has a probability that the thief might see the LASER beam and avoid theft alarm easily. This simple circuit will give you an insight into how do burglar alarms work.

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IR Transmitter and Receiver Circuit for Best Remote Control System

A remote control system for appliances makes our life smarter and easier. The wireless remote control circuit may be based on IR waves or RF waves, IR being cheaper. An IR emitter circuit is based on TSOP at the receiver section. Each TSOP operates at a particular frequency which depends on a number present on it. So each TSOP requires specific remote controller for its operation. There comes the importance of IR universal remote control which can be used to operate all normal hobby circuits.

Here the basic principle of operation is Frequency Shift Keying (FSK). It enables to generate variable frequency so that it can detect different TSOPs.We are using two 555 timers here, both operating in astable mode which then drives the IR led.

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Simple Continuity Tester Circuit Using 555 Timer

Normally we use continuity testing to check if a circuit, PCB or cable is continuous or not. It also helps us to check if a bulb is burnt out or not. Simply we can do the test by using a battery and a led or buzzer, but they are not precise or accurate.

Usually we use a continuity test multimeter which is little bit costly and bulky too. Also these give a positive indication even when there is 100 ohms of resistance between the probes.

So how to make a continuity tester which has no such kind of drawbacks. This circuit is built around a common 555 chip wired in astable mode. The continuity test circuit can precisely judge continuity as that low 6 to 8 ohms(which can be set by using the preset). Speaker is used to indicate the continuity.

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Simple 555 Timer AM Transmitter Schematic for Science Fair Project

We have published so many FM transmitter circuits at CircuitsGallery, so this time I am going to introduce a simple AM transmitter circuit based on 555 timer. Firstly let us have a look at what is Amplitude Modulation. AM is a modulation technique where the amplitude of carrier varies according to the input message signal. AM has been a widely used modulation technique due to its longer range but has the disadvantage of lesser noise immunity. It is commonly used in walkie talkie applications.

Here 555 multivibrator generates a frequency of AM range so you can receive the transmitted audio signal in the AM radio receiver. This simple AM transmitter is suitable for school projects.

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Simple Emergency Light Circuit with Automatic Charger

Some of our readers requested for Emergency circuit with charge controller. Here I'm presenting  such kind of a circuit diagram with automatic charging.

It is very easy to implement on your home and work areas.Our circuit is capable of turns on the light automatically when power failure occurs and turn off if main supply is return.

LEDs are used as emergency light bulbs in this system, The important specialty of this Emergency circuit is an automatic charge controller which recharge the battery if the voltage is below the threshold level and cut off the charging supply to the battery, if the voltage reach at the pre-set level, two LEDs are used to indicates the of presents of main power and activation of charger.

This circuit mainly focus to lead acid battery life, in this circuit design we limit the maximum charging voltage is 13.8V as per lead acid battery manufacturers.

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How to Make a Simple Boost Converter with 555 Timer?

We may come across many circumstances where we need 12V from a 5V (as from USB ports which only provide 5V), but it may not be sufficient to drive all the circuits. To face such situations we are introducing a dc to dc boost converter circuit which can generate 12 volt from 5 volt. Today boost converter applications are used in different devices like dc dc power supply, dc-dc converter module, isolated dc dc converter etc. The main component used for this circuit is a 555 timer IC operating in astable mode. It generates a square pulse which is then given to a simple transistor inverter to get inverted outputs. These two outputs will drive a voltage pump which increases the voltage level by series addition. However this 555 timer boost converter has a disadvantage of low output current so it can’t drive high current devices. To get more current you have to use a step up converter circuit that we will introduce later.

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Automatic Rain Sensing Wiper System using 555 Timer

Have you seen Audi, Lexus or Ford rain sensing wipers and wondered how they work in these vehicles? They are handled by sensors at the center of the windscreen which detects rain water and turns on the wiper motor. Here is the working of rain sensitive wipers with circuit schematic. The main component of this circuit is a 555 timer IC that works in monostable mode. Two metal sheets fixed at a small distance apart are used as rain detector sensors. From the working of a monostable 555 timer, a negative voltage on the trigger pin will cause a high output. So when it rains, trigger pin gets a negative voltage. Output of one shot 555 (monostable) is connected to a relay through a transistor. The transistor acts as a switch for the relay to turn ON the wiper motor during rain.

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555 Touch Sensor

How to make a touch sensor? Here is a simple DIY touch sensor circuit diagram using 555 timer monostable mode. Touch switch is only a conducting metal sheet that acts as touch sensor. The 555 touch switch is not a touch capacitive sensor; it is only a metal touch sensor button. Using this you can turn on and off devices by single touch. Here we are using a JK flip flop IC 7476 that is connected as T-flip flop. The output of T-flip flop is connected to the base of transistor to turn ON the relay so as to control high current electrical devices such as fan, motor, lamps etc.

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12v Battery Charger Circuit with Auto Cut off

This is a simple DIY charge controller schematic posted in response to a request by one of our readers on our facebook page. The main component of this auto battery charger circuit is a 555 timer which compares the voltage in the battery. It turns ON the charger if the battery voltage is below the variable preset voltage (12 volt chosen here) and turns OFF the charger if the voltage reaches 13.8 volt. The battery charging voltage of the charger can be varied by adjusting the variable resistor and maximum charging is limited by a 13.8V zener diode on the fifth terminal of 555 IC.

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PWM LED Dimmer/ Brightness Control by 555 Timer With Video Simulation

How to change the brightness of a LED? Whether led lights are dimmable? Is it possible to adjust the brightness of LEDs? LED is basically a diode, when the forward voltage exceeds 0.7 volt, it starts to glow, and if the forward voltage is less than 0.7 volt, it will be in the OFF state. What happens if we are providing a high voltage to the LED so as to increase the brightness?

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555 timer monostable calculator for monostable multivibrator

Few days back, here on CG we introduced an astable frequency calculator tool and the response we got from that motivated us to present a similar one for monostable too. Monostable multivibrator is a triggerable pulse generator which produces a single pulse upon receiving a trigger. Previously we have published a wonderful article describing the working of monostable multivibrator with animation. I recommend you to read that for better understanding.

Once we trigger the 555 timer one shot circuit, the output goes to high and stays there  for some time (T=1.1 R C) and then returns back to ground level. The capacitor and resistor form a time constant RC for the circuit. As the name indicates it has only one stable state (at ground potential) and the unstable state is called quasi stable state.

Monostable calculator is intended to give duration of the pulse (delay) for the one shot timer 555. The duration of stable state or the pulse width is determined by the control capacitor and resistor. I hope this 555 timer calc will surely make designing easier for you.

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Electronic mosquito insect repellent circuit using 555 IC

Mosquitoes are one of the most irritating bugs and they spread many diseases. Wide varieties of mosquito repellents are available. Here we are talking about a method which would most likely drive away the mosquitoes with the help of certain frequency generators. Researchers have found that insects are typically allergenic to a specific spectrum of frequency range called the ultrasound frequency.

This is a simple circuit of ultrasonic mosquito (insect) repeller for insect control based on the theory that insects like mosquito can be repelled by using sound frequencies in the ultrasonic (above 20 KHz) range. This insect repellent frequency is farther than the hearing range of humans, but can cause a lot of nervousness to the insects and also to animals like dogs and cats. Bug control is easy with this best insect repellent.

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555 Timer Astable calculator for Astable Multivibrator Designing

We know that astable multivibrator is simply an oscillator circuit that produces continuous pulses without the help of any external triggering. The oscillation frequency and time period can be manually controlled through simple modification of resistors and capacitors i.e. by changing the values of R1, R2 and C1. You can use a 555 timer astable calculator tool to make your designing easier.

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555 timer IC Inverter circuit schematic 12V to 220V

This article explains What is inverter? And how can you construct your own simple low cost 12V to 220V inverter circuit. An inverter is nothing but a DC to AC converter. Inverters are very useful electronics products for compensating emergency power failure, as it performs DC to AC conversion.

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AC can’t be stored for future use but DC can be stored for future use in a battery. The stored DC can be converted back to AC by using power inverters.

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555 timer IC audio amplifier circuit schematics

Here we are going to discuss about a simple timer IC 555 project. The 555 timer IC can be used as an audio amplifier with astable multivibrator configuration. It functions as to carry out pulse width modulation (PWM) of audio signal. Current(I) capacity of 555 timer amplifier is 200mA which is sufficient to drive a small speaker. This simple 555 IC based amplifier circuit is a good substitute for conventional low power amplifiers. The low frequency audio signal is applied to the control voltage pin (5th pin) of 555 for pulse width modulation (PWM) generation. For beginners who want to know 'what is PWM?', read simple PWM modulation concept.

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Monostable 555 Multivibrator Working Principle and Circuit diagram with Animation

Monostable 555 timer multivibrator circuit (one shot monostable multivibrator) is a retriggerable mono shot pulse generator. The name ‘Mono stable’ indicates that it has only one stable state. The unstable state is called ‘Quasi stable state’. The duration of stable state or the pulse width is determined by the charging time constant of the RC network. We can transfer the multivibrator from stable state to quasi stable state by using  push button trigger switch. The animated (simulated) working of the mono stable 555 multivibrator is shown in this article. You can use our monostable 555 timer calculator tool to find the duration of pulse(width) easily.

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Astable Multivibrator using NE 555 timer IC -Circuit diagram and working

Astable Multivibrator can be designed by using 555 timer IC, Op Amps and also using transistors. The 555 IC provide accurate time delay from mille seconds to hours.

The frequency of oscillation can be controlled manually by simple modification.

555 is suitable for circuit designers with a relatively stable, cheap, and user-friendly integrated circuit for both monostable and astable applications.

The 555 timer IC was first introduced around 1971 by the Signetics Corporation as the SE555/NE555.

This is a simple 555 timer circuit project. Astable Multivibrator is simply an oscillator circuit that produces continuous pulses. The frequency can be controlled by changing the values of R1, R2 and C1.

You can construct astable multivibrator using transistors also, but the 555 circuit is comparatively simple.
Read Also: 555 Timer Astable calculator

Components

1. NE 555 or SE 555
2. Resistor (1MΩx2, 1KΩ)
3. Capacitors (0.01Fµ, 1Fµ)
4. LED

Circuit Diagram of Astable Multivibrator

Output Waveform of Astable Multivibrator

Design of Astable Multivibrator

Capacitor charges through R₁ and R₂ there for charging time is given by

T_charge=0.69(R₁+R₂)C₁,

during this time the output is High, so

T_charge=0.69(R₁+R₂)C₁=1.38 sec

Capacitor discharges through R₂ only there for discharging time is given by

T_discharge=0.69 R₂ C1,

during this time the output is Low, so

 T_discharge=T_off =0.69 R₂ C₁=0.69 sec

 Time Period=T_on+T_off=2.07sec

 Frequency of oscillation=0.483Hz

Duty Cycle is calculated by the following manner

Working of Astable Multivibrator

• Consider the flip flop is initially cleared, when the power is switched on, then the output of inverter will be HIGH.

• Now the capacitor C1 starts charging through R1 and R2. (Discharge transistor Q1 is OFF).

• When the capacitor voltage exceeds 2/3 Vcc, the upper comparator output will be High, it Reset the control flip flop.

• So the Q output of control flip flop will be LOW and Q’ will be High. So the final output from Inverter is LOW.

• At the same time, the discharge transistor Q1 turns ON and the capacitor starts discharge through R2.

• When the capacitor voltage less than 1/3 Vcc, the lower comparator output will be high, then the control flip flop get set to High. (Q=1, Q’=0, Final output=1).

• Now the discharge transistor Q1 if OFF and then capacitor starts charging. This process continues.

• The LED connected at the output will glows according to the output status.

• 4th pin is Reset pin, a Low voltage at this pin resets the IC. The Low signal is applied to the base terminal of reset transistor Q2. Then it turns ON followed by Discharge capacitor Q1 and capacitor discharges. See the images below.

Working Principle 555 timer IC with Images

555 Timer internal diagram after triggering (Capacitor charging)
Now let’s see the different process taking place while you are triggering a 555 timer IC.

• Voltage at the pin 2 goes below 1/3 Vcc.

• Lower comparator switches to high state (1).

• Controls flip flop sets and Q’ output (inverted output of flip flop) goes to low state (0).

• Final output (Not gate) goes to High state (1)

555 IC Internal diagram while discharging

• Voltage at pin 6 goes above 2/3Vcc Upper comparator switches to high state (1).

• Control flip flop resets and Q’ (inverted output of flip flop) output of goes high state (1).

• Discharge capacitor turns ON and capacitor discharging occurs (Q2 short circuit both end of the capacitor).

• Final output (Not gate) goes to Low state (0).

555 Timer internal diagram while reset

• Applying + ve voltage at reset pin (4) Discharge transistor Q1 turns on.

• It short circuits both end of capacitors. Voltage at pin 2 goes below 1/3 Vcc.

• Control flip flops sets and final output goes Zero.

555 timer pin out

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Clap Switch Circuit using NE555 timer IC

Here is one of the interesting 555 timer circuits to trick your friends while studying electronics in schools. Clap switch circuit is the local name of sound controlled flip flops. This sound controlled light can also be used as sound detection sensors. Flip flops are single bit storage elements. NE555 timer IC is the important part of this circuit. Here NE555 is configured in monostable multivibrator mode and is connected to the clock input of a 7474 D flip flop. The flip flop is connected to work in 'Toggle' mode. The relay circuit is energized by a 7474 flip flop. You can connect any electrical/electronic device at the output instead of the electrical bulb used here. Below is the electronic circuit diagram and working of the clap light switch.

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Remote Control Light Circuit Diagram Using 555 Timer

You may wonder if it is possible to control a light using a remote controller. In this article CircuitsGallery presenting an interesting DIY circuit that helps you to turn ON and OFF a lamp with a remote controller.

Here we have made use TSOP, an IR receiver, which detects the IR rays from the remote. NE555 is the next important part which produces a clock pulse for toggling the D flip flop.

The relay helps to connect any electrical devises to the circuit and you can control any electrical equipment not only a light.

You must need regulated power supply of 5 volt to do this circuit because TSOP require 5v. Its voltage should not exceed 5V.

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