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LM555: Monostable Mode Not Working <60ms

Saad Paya
Prodigy 10 points
Part Number: LM555

I'm using the LM555 in the monostable mode to generate a pulse from 1ms to 1s on the press of a button.For the timing I have a variable 1Meg Resistor and 1uf Cap.

When I try to measure the pulse below 60 ms by setting the variable resistor below ~60k the output pulse still shows 60ms pulse.

I have attached the the circuit and associated waveform for clarification. 

The blue waveform is the trigger, while the purple waveform is the output.

Could you assist me so I can get the full range of pulse widths for my application.

Regards,

Saad

  • 0
    TI__Guru*** 149776 points
    Saad,

    Reduce C5 value to 1nF

    Trigger has a higher priority than threshold. Therefore trigger width must be less than time for C3 to get to 2/3 VCC.

    There is a danger for potentiometer set to minimum. Current through the potentiometer could be very high.
    I suggest adding 1k (or slightly less)