Sunday, July 24, 2016

IC 555 TIMER

The 555 timer IC was introduced in the year 1970 by Signetic Corporation and gave the name SE/NE 555 timer. It is basically a  monolithic timing circuit that produces accurate and highly stable time delays or oscillation. When compared to the applications of an op-amp in the same areas, the 555IC is also equally reliable and is cheap in cost. Apart from its applications as a monostable multivibrator and astable multivibrator, a 555 timer can also be used in dc-dc converters, digital logic probes, waveform generators, analog frequency meters and tachometers, temperature measurement and control devices, voltage regulators etc. The timer IC is setup to work in either of the two modes – one-shot or monostabl or as a free-running or astable multivibrator.The SE 555 can be used for temperature ranges between – 55°C to 125° . The NE 555 can be used for a temperature range between 0° to 70°C.













555 circuit  

Function of different Pins:

1.      Ground: This pin is used to provide a zero voltage rail to the Integrated circuit to divide the supply potential between the three resistors shown in the diagram.

2.      Trigger: As we can see that the voltage at the non-inverting end of the comparator is Vin/3, so if the trigger input is used to set the output of the F/F to ‘high’ state by applying a voltage equal to or less than Vin/3 or any negative pulse, as the voltage at the non-inverting end of the comparator is Vin/3.

 3.      Output: It is the output pin of the IC, connected to the Q’ (Q-bar) of the F/F with an inverter in between as show in the figure.

 4.      Reset: This pin is used to reset the output of the F/F regardless of the initial condition of the F/F and also it is an active low Pin so it connected to ‘high’ state to avoid any noise interference, unless a reset operation is required. So most of the time it is connected to the Supply voltage as shown in the figure.

5.      Control Voltage: As we can see that the pin 5 is connected to the inverting input having a voltage level of (2/3) Vin. It is used to override the inverting voltage to change the width of the output signal irrespective of the RC timing network.

6.     Threshold: The pin is connected to the non-inverting input of the first comparator. The output of the comparator will be high when the threshold voltage will be more than (2/3) Vin thus resetting the output (Q) of the F/F from ‘high’ to ‘low’.

7.      Discharge: This pin is used to discharge the timing capacitors (capacitors involved in the external circuit to make the IC behave as a square wave generator) to ground when the output of Pin 3 is switched to ‘low’.

8.      Supply: This pin is used to provide the IC with the supply voltage for the functioning and carrying of the different operations to be fulfilled with the 555 timer.




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13 comments:

  1. Anonymous25 July 2016 at 20:14

    If I buy a 555 timer, how can I know if my 555 timer is working?

    ReplyDelete
  2. Arczed26 July 2016 at 22:12

    To easily test if the 555 timer is working, you may need a 555 timer tester. When you have a good 555 under test, the hi and lo leds are flashing steadily. If you have a defective 555 you may get both leds off, one or both on steady, or one or both on faintly. In all these case the 555 is defective or if you do not have the 555 timer tester, you will need to make a simple circuit with an LED as an indicator. You may see this link "http://www.electronicshub.org/how-555-timer-ic-testing-circuit-works/". After trying, you will already know whether the 555 timer IC you bought is working or not.

    ReplyDelete
  3. John Aldrin Mantes27 July 2016 at 00:34

    What is a comparator? Can you give examples of non-inverting inputs? Thank you in advance. :)

    ReplyDelete
    Replies
    1. Arczed27 July 2016 at 18:34

      A comparator is a device that compares two voltages or currents and outputs a digital signal indicating which is larger. It has two analog input terminals V +, and V −, and one binary digital output V o.

      Delete
    2. Arczed27 July 2016 at 18:41

      Since it is an IC, the non-inverting input of this IC cannot be changed so there are no other examples of non-inverting inputs that can be replaced to it. There may be other example of non-inverting input on other components but for this IC, it is constant :)

      Delete
  4. Unknown27 July 2016 at 17:24

    As you stated, this 555 timer is an oscillator. what are the advantages of this 555 timer from my crystal oscillator?

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    Replies
    1. Arczed27 July 2016 at 18:50

      I'm not so certain if the 555 timer can be used specifically to Crystal Oscillator but some of it's advantages are the following:

      - a steady clock/trigger to keep time in a circuit (astable mode)
      - time delay for an incoming signal (monostable mode)
      - very basic storage of input data/management of two button control system (bistable mode) :)

      Delete
  5. Anonymous31 July 2016 at 03:55

    maam are we going to be able to use all the components on our future activities??

    ReplyDelete
    Replies
    1. Arczed31 July 2016 at 21:32

      Hi Phbrth! Do you mean if you are going to use this 555 timer? Yes! You are going to encounter it probably not this semester but in the next semesters. I hope this blog helps you in advance. :)

      Delete
  6. Unknown6 August 2016 at 06:16

    maam what is the commonly use IC?

    -lacar

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    Replies
    1. Arczed6 August 2016 at 06:39

      Hi Lacar! I cannot really tell whether what is the most commonly used IC because it depends upon the usage on where and what circuit or thing you are going to make. But the 555 timer IC is commonly used in circuits which needs a timer. :)

      Delete
  7. Unknown6 August 2016 at 06:18

    This comment has been removed by the author.

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