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Project Notes

#692 Push-button Latch

Testing a simple push-button latched switch circuit for on/off control using the 555 timer.

Build

Here’s a quick demo..

clip

Notes

This is a simple latching circuit for push-button on/off control using the 555 timer.

How it works:

  • by default:
    • the push-button is not pressed
    • the R1/R2 voltage divider pulls the 555 threshold and trigger pins to the mid-level
    • thus neither THRESHOLD(reset) or TRIGGER(set) inputs to the 555 are enabled and
    • the 555 output state is unchanged
  • when the push-button is pressed:
    • if the current output is LOW,
      • the R1/R2 voltage divider mid-point will be pulled LOW
      • TRIGGER(set) falls bellow the 1/3 set-point, causing the 555 to set and output to go HIGH
      • the capacitor C1 holds the button input LOW for long enough for the button to be released
    • if the current output is HIGH,
      • the R1/R2 voltage divider mid-point will be pulled HIGH
      • THRESHOLD(reset) rises above the 2/3 set-point, causing the 555 to reset and output to go LOW
      • the capacitor C1 holds the button input high for long enough for the button to be released

Circuit Design

bb

schematic

Testing on a breadbord:

Latch_bb_build

Protoboard Build

Transfering the design to a small protoboard so that it can be used as a latched switch input.

protoboard_build

Credits and References

About LEAP#692 555 Timer
Project Source on GitHub Project Gallery Return to the LEAP Catalog

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LEAP is just my personal collection of projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

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