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Universal Timer

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  • MultiMedia SRL
    Universal Timer Parts C1: (determined value) R1: 1K R2: (determined value) IC1: 555 timer IC SW1: Normally Open Pushbutton Explanation This circuit is a very
    Message 1 of 1 , Jan 9, 2003
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      Universal Timer

      Universal Timer

       

      Parts
      C1: (determined value)
      R1: 1K
      R2: (determined value)
      IC1: 555 timer IC
      SW1: Normally Open Pushbutton

      Explanation
      This circuit is a very basic but accurate timing circuit using a 555 timer IC and a few other parts.
      It works by discharging a capacitor and then charging it via a resistor. Firstly a low signal is passed to the trigger (2). This activates the discharge pin (7) which discharges the capacitor. When the threshhold pin (6) of the 555 detects the voltage in the capacitor drop to 1/3 vcc, it drives the output pin (3) high. When the capacitor charges to 2/3 vcc, the output pin is driven to low.
      A formular is used to determine the values of the capacitor / resistor circuit.
      T=1.1RC
      Where T is the time in microseconds, R is component R2 and C is component C1
      Very acurate timing is achived with this very simple circuit ranging from a few microseconds to hours.

      Applications
      Any everyday noncrucial timing application. e.g. egg timer, cooking timer, headlight cutout ect ect.

      Tests
      This circuit's timing is independent of the supply voltage but the voltage must not vary. It will operate from 2.5 to 15 volts, draws only a few milliamps and will drive anything up to 200mA from its output.

       

      http://www.crosswinds.net/~staticwire/start.html

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