How to connect two circuits with an electronic switch?

Discussion in 'The Projects Forum' started by PaulInGermany, Feb 23, 2012.

  1. PaulInGermany

    Thread Starter New Member

    Feb 23, 2012
    3
    0
    Hi folks,

    I'm a tinkerer with no formal training, just a couple books under my belt, and could use some advice.

    I have two separate circuits that I need to "join." The first accepts an audio signal with a max in of 5.6v peak. The second circuit is a simple LED flasher based on the Fairchild 5646, runs on 5.5 volts.

    I need to join these two so that when the audio circuit is getting a signal, the forward voltage is stopped to the LED flasher circuit. And when the audio stops, the flasher circuit resumes its flashing state.

    I'm confident there's a simple way to do this, but it's beyond my limited knowledge. Any advice or pointers would be very much appreciated.

    Thank you!
     
  2. #12

    Expert

    Nov 30, 2010
    16,343
    6,827
    It is impossible to guess how to do this without any drawings of the circuits.
    The "Go Advanced" button leads to "manage attachments" so you can upload drawings. .png format is best.
     
  3. PaulInGermany

    Thread Starter New Member

    Feb 23, 2012
    3
    0
    Thanks, #12. Yes, my tinker status is showing.

    Here are the two circuits I'd like to join. What I'd like to accomplish is when circuit 1 gets an audio signal, circuit 2 disables. When that audio signal halts, circuit 2 gets power again.

    Again, advice is very much appreciated.
     
    Last edited: Feb 24, 2012
  4. #12

    Expert

    Nov 30, 2010
    16,343
    6,827
    When the transistor saturates, the capacitor is discharged through a diode. The RC product sets the refill time. The Zener is 5 volts, assuming the blinker chip operates from 5 volts. You could use a diode to the +5V supply to limit the ctrl pin voltage, but I'm afraid there isn't enough current load on the 5 volt supply to use the waste current.

    This circuit will swing the ctrl pin from +1V to +5V. If the +1V is too high, you can put a diode in series with the ctrl pin (positive facing to the right) to waste .6 volts and make the ctrl voltage swing from .4V to 4.4V. You will need a resistor to ground at the ctrl pin if you add that diode.

    So...here's the principle. You can work out the values.
     
    PaulInGermany likes this.
  5. PaulInGermany

    Thread Starter New Member

    Feb 23, 2012
    3
    0
    Thanks very much, #12. I appreciateit!
     
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