Basic 555 timer bistable flip flop mode circuits

The 555 timer can be used as a flip flop while it is wired up in the bistable mode. Bistable means that the output is stable while it is off until it is forced to turn on via a low pulse to the trigger. And then while the output is on, it stays on, until it is forced off via a low pulse to the reset. Bistable mode can also be thought of as a schmitt trigger.

Photodiode controlled bistable mode flip flop 555 timer circuit page

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Video below: 555 timer bistable mode push button controlled flip flop circuit build and explained Click here to watch directly on YouTube!

555 timer bistable mode push button controlled flip flop circuit diagram by electronzap electronzapdotcom
555 timer bistable mode push button controlled flip flop circuit diagram by electronzap electronzapdotcom

 

  • Grounding the trigger sets the output high (on).
  • Threshold is held at ground (0V) so that it has no chance to reach 2/3Vcc, which would end up automatically shutting setting the output low (off).
  • Grounding the reset set the output low (off).

Bonus video: 555 timer output used to control NPN BJT transistor switch in order to provide more power (voltage and or current) than 555 timer can provide.

 

Bonus bistable 555 timer video using light dependent resistors (photoresistors) to trigger and reset 555 timer.

555 timer internal voltage divider explained with demonstration for beginner learning electronics Click here to watch directly on YouTube!

555 timer light dependent resistor LDR voltage divider high low LED beginner learning electronics video below. Click here to watch directly on YouTube!

Gathering info from unusual polarity indicator LEDs at 555 timer output when inputs are floating Click here to watch directly on YouTube

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