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555 timer tester is a simple circuit that serves to test the condition of IC 555. 555 timer circuit tester, in principle, start the timer 555 in astable multivibrator mode. As an indicator of the status of the timer 555 good condition or damaged to use 2 pieces LED which will light up in a blink alternately when the timer 555 in good condition. And only one will turn on or off all the timer 555 when the condition is broken. 555 timer circuit tester is powered using 9 Volt DC voltage source. Complete circuit tester 555 as follows.   How to use 555 timer tester is in conjuction with IC 555 to test the existing IC socket according to the order button. Then activate the power switch to begin testing the 555 timer ic. Then live we observe the LED indicators 2 before, whether flashing alternately (good) or not blink or even die all (timer 555 damaged). source:link

Burglar alarm circuit or Theft alarm circuits are available in several forms. The above circuit was one of that kind using timer IC 555 as the main component. The circuit is very easy to construct and the cost of this circuit is also very less. So we can implement this circuit by our own and install this circuit in our home so that you can improve your knowledge and it also adds protection to your home. Using IC 555 Burglar Alarm Circuit Diagram The working of this circuit is very easy to understand.In the above circuit IC 555 was used as a Astable multivibrator.The Astable multivibrator puts out a continuous stream of rectangular pulses having a specified frequency. Thus by using the Astable multivibrator we can produce continuous frequency which was given as input to the speaker which makes an alarm sound in case of any disturbance in its trip wire. Pin diagram of IC 555 was given below for your better understanding. Now we can see how we can change the Astable Multivibrator to a ala...

The 555 astable multivibrator can be used as a free running ramp generator. when the frequency determining network Ra and Rb in the 555 astable multivibrator is replaced by a Current mirror. Figure shows the circuit diagram for free running ramp generator. Read More.....

This circuit is very handy as a timer circuit for a lamp, for lighting a staircase, for example, but can also be used as indicator for the front doorbell. A significant advantage of this circuit is that the circuit draws almost no current when in the inactive state. The circuit is activated with push button (S1), after which IC5 (a 555 timer IC) starts to count down the set time. During this  time the triac continues to conduct and the lamp is turned on. The ‘on’ time of the  lamp is on is determined by the combination of R1 and C2 and can be changed as  required by your application or personal  preference. R2 and C3 have been added because the  555 expects a ‘negative’ pulse at its trigger  input. When the power supply is turned on,  C3 holds the TR input of the 555 Low for a short time, which triggers the timer IC. Circuit diagram : Lighting Governor Circuit Diagram Depending on the exact type (brand) of  555, the value of C4 (330 nF) may have to be changed to ensure a high enou...

This electronic circuit is a very nice and simple alarm circuit that is based on the 555 timer integrated circuit. This alarm circuit can be used with many types of sensors like : light or temperature sensors. As you can see below some types of sensors that can be connected at this type of alarm circuit ( darkness , light , cold and heat sensor ). If the sensor detects that the temperature or light is outside of the desired range the alarm will be activated .By turning the  potentiometer from the base of Q1  you will modify the sensibility of the sensor . When the alarm is activated the Q2 transistor acts as an audio amplifier and speaker driver for the 16 ohms speaker . This alarm circuit require a 12 volts DC power supply circuit .

For a lower parts count than the 2 transistor multivibrators, 2 LED s can be alternately flashed with a 555 integrated circuit configured as shown in Schematic 2.  I chose the combination of a 2K2 and a 47K resistor to determine the oscillation frequency along with the 10 uF capacitor connected to pins 2 and 6. You can practically change the (R Speed) 47K value to between 10K and 100K or more. Greater resistance = lower speed. You may also wish to connect up a 100K or so potentiometer instead of the 47K resistor for a variable speed version. Additionally, the 10 uF capacitor value can be changed. Feel free to experiment. Although, alternately flashing LED s  is great for the beginner to electronics, the basic one ON, one OFF circuit gets boring quickly. In the next section, we will try to improve the look and try to approximate a flash like a police car (within limits).

A very simple electronic key code lock circuit that require few external components can be constructed using this schematic diagram . This electronic key code lock circuit is based on a common 555 timer circuit and some other common components . This low cost key code circuit use six switches that needs to be pressed to open the lock, but only two switches at a time. In many other , more expensive electronic circuits the key code is formed by pressing some switches one by one , not like in this case two switches . If you don’t like to press two switches in the same time you can eliminate one switch , but in that case the code can be more easy to guess by someone ells .Thus a total of three sets of switches have to be pressed in a particular sequence. (Of these three sets, one set is repeated.) An essential property of this electronic code lock is that it works in monostable mode, i.e. once triggered, the output becomes high and remains so for a period of time, governed by the timing c...

Emergency Lamp With 555 is one solution for lighting during power outages. With Emergency Lamp Series 555 uses a 12VDC voltage source that can be supplied from the 12V battery. Emergency Lamp 555 Series With these very simple and easy to make because all the components easily available in the market. Emergency Lamp Series With this 555 can turn on the light 5W-10W. The circuit is built with an astable multivibrator with the IC 555 that is used to mendrive transformer through Q1. For more details can be viewed directly from the series Emergency Lamp With 555 follows. Emergency Lamp Using TLC555 Working frequency range of 555 Emergency Lamp With this set of configurations R1, R2 and C2. T1 in series Emergency Lamp With 10V 500mA 555 is a transformer. Secondary part (0-10V) is connected to the Q1 to be given the signal from the multivibrator. Then the primary (0-220V) is connected to the lamp.

This electronic circuit is a very nice and simple alarm circuit that is based on the 555 timer integrated circuit. This alarm circuit can be used with many types of sensors like : light or temperature sensors. As you can see below some types of sensors that can be connected at this type of alarm circuit ( darkness , light , cold and heat sensor ). If the sensor detects that the temperature or light is outside of the desired range the alarm will be activated .By turning the  potentiometer from the base of Q1  you will modify the sensibility of the sensor . When the alarm is activated the Q2 transistor acts as an audio amplifier and speaker driver for the 16 ohms speaker . Dual Sensor 555 Timer Alarm Circuit Diagram This alarm circuit require a 12 volts DC power supply circuit .