Heating and Cooling time problem (LM555)

Discussion in 'Homework Help' started by pigpig1985, Mar 25, 2010.

  1. pigpig1985

    Thread Starter New Member

    Mar 24, 2010
    1
    0
    I would like to use a press button to generate an instant signal, and then timer start to count and the heater will heat for 5 seconds. Within this 5 seconds, whatever I press button how many time or press down for long time, the timer will not be disturbed.
    After 5 second, there are 10 seconds cooling times. Within this 10 seconds, whatever I press button how many time or press down for long time, the heater and timer will not have any response.
    After 10 seconds, the system can be active again.

    If I press down for very long time, the heat will heat 5 seconds then cooling 10 seconds periodically.

    In fact, my final goal is replace the press button by a light sensor to turn on the system. Therefore, I need the cooling time to protect the heat over heat when the sensor is accidently covered.
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Two 555s, one for the initial time. The second is also a monostable, but it disables the first (an inverter will be needed). Since you want the 1st timer to restart if the button is still pressed you may also want to use the power pin (pin 8) along with the reset ping (pin4).
     
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