555 Timer Bistable Mode Tinkercad

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gaur23

Joined Nov 25, 2023
1
I am trying to simulate 555 timer in bistable mode. I am following this tutorial

As per the video the default condition is that pin 3 (Out) should be low as pin 2 is high.
Once the button is pressed then pin 2 becomes low and pin 3 is high.

I can see this behavior in real breadboard circuit but I don't understand why it does not work in tinkercad.
555 Timer Bistable Mode.png
 

dl324

Joined Mar 30, 2015
16,691
Welcome to AAC!
I can see this behavior in real breadboard circuit but I don't understand why it does not work in tinkercad.
You have trigger wired to 5V. When you press the switch, you're shorting the power supply.

I didn't watch the video, but it seems to me that you should have trigger and threshold connected. When trigger is at/below VCC/3, the output will be HIGH. When threshold is at/above 2/3 VCC, the threshold comparator will reset the internal flip flop and the output will be LOW. The trigger input alone can't reset the output LOW.

From Signetics (I added pin numbers and GND):
555BlockWithPinNumbers.jpg

Post a schematic in the future so we can see the intended functionality.

EDIT: Had nothing better to do, so I watched the video. Skipped the part where she was explaining how the timer worked and only had to watch about 30 seconds to see that you didn't implement what she described in the simulation.

With reset floating, the timer won't function.
 
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dl324

Joined Mar 30, 2015
16,691
This is what I think you were supposed to do:
1700970724006.png
S1 and S2 are momentary switches. Pressing and releasing S1 will set the RS flip flop and turn the LED on. Pressing and releasing S2 will reset the RS flip flop and turn the LED off.

I thought you were holding the switch to turn the LED on and releasing to turn it off...
 

crutschow

Joined Mar 14, 2008
34,048
Do you want the bistable circuit to work with one or two push-buttons, as it can be made to work either way?

Below is an example of a single PB circuit, where the 555 changes state for every push of the button:
The circuit is insensitive to the length of the PB press or normal contact bounce.


1701102243416.png
 
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