Photodiode controlled bistable mode flip flop 555 timer circuit

Using an old diagram, I made this video on building a breadboard bistable 555 timer circuit. The photodiode videos that follow modify this circuit. Helps me more if you watch the video by clicking this link 555 timer bistable mode flip flop circuit step by step build with diagram and push buttons and subscribe to my YouTube channel while you are there!

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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

Photodiode replacing trigger/set pin

Following video shows how I quickly swap out the mechanical push button switch at the 555 timer’s trigger/set pin with a photodiode. Amount of current that flows through a photodiode depends on how much light is falling on it. Bright enough light, it conducts current similar to a switch that is on. Low enough level of light and little to no current flows through it, similar to an open switch. Click Photodiode replacing push button switch in 555 timer bistable mode flip flop circuit to watch the video directly on YouTube, or watch below. I got the switches from the Elegoo kit and I use the adapter to power all of my breadboard power supplies. The kit has many of the same type of components that I normally use from other kits or have bought individually.

Photodiode replacing reset pin

Finally, I made the following video Photodiode controlling reset pin of 555 timer wired in bistable mode flip flop. I used the photodiode to control the reset pin instead of the trigger pin. The largest difference that this produces from the last circuit, is that while the reset pin gets a low signal (it is active low), the 555 timer holds the output low no matter what signals the trigger or threshold pins may receive.


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