Simple 555 timer circuit needed.

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Discussion Overview

The discussion revolves around designing a circuit using the LM555 timer, specifically focusing on creating a configuration that requires a switch to be held down for one second before activating the output (pin 3 high). Participants explore potential circuit designs and alternatives, including the use of a dual 555 timer chip.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant seeks a sample circuit for an LM555 timer that activates after a switch is held down for one second.
  • Another participant suggests using a push button on the trigger pin to initiate the timer cycle.
  • A later reply clarifies that the switch needs to be held down for one second before the output goes high.
  • Another participant proposes considering the 556 chip, a dual 555 timer, to potentially trigger one timer from another after a delay if the switch remains depressed.

Areas of Agreement / Disagreement

Participants express varying ideas on how to implement the desired functionality, and no consensus on a specific circuit design has been reached.

Contextual Notes

The discussion does not provide detailed circuit diagrams or specific component values, and assumptions about the circuit's behavior and requirements remain unverified.

Who May Find This Useful

Individuals interested in timer circuits, particularly those looking to implement a delay mechanism using the LM555 or 556 timer chips.

ThisIsMe
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Hi all, great forum here. Hope to learn a lot.

I am looking for a sample LM555 circuit. In simple terms I am looking what I think to be a reverse of the monostable circuits I have seen.

More or less I have a switch that needs to be held down for 1 sec before the circuit is active (pin 3 high on the LM555). Or is there another circuit? I think the 555 would do what I need, just need a sample circuit to bump me in the right direction.

Reseting the circuit I think I can handle, but just need a simple circuit to get me there.

Any help would be greatly appreciated.
 
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You could put a push button on the trigger pin to signal a start of a cycle.
 
triden said:
You could put a push button on the trigger pin to signal a start of a cycle.

That is sort of what I a doing now. The switch needs to be held down for one second and then before pin 3 goes high.

If that makes better sense.
 
You might want to check into the 556 chip. It's a dual 555 timer. See if you can use one to trigger the other after 3 seconds if the switch is still depressed.
 

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