Posituve pulse triggered 555 monostable

[ark5230]

I am trying positive pulse triggered monostable using NE 555 timer IC.
Trigger Pin - 2 triggeres at 1/3 Vcc, can this value be lowered to say 1/4 Vcc or even less.
A link to related issues will also be helpful.

 

[godfreyl]

Connecting a resistor between pin 5 (CTRL) and pin 1 (GND) will reduce the threshold voltage and the trigger voltage. That's what pin 5 is for.

Threshold voltage = voltage on pin 5.
Trigger voltage = half of threshold voltage.

 

[bigdogguru]

You might find the following links of interest:



555 Timer



555 Timer Operating Modes


Reference Attached 555 Timer Appnotes


BigDog

 

[ark5230]

So nice of you both.
Pin pointed answer with all necessary supporting details.
Really it helped me handling this so fast with all clarity.
I am trying to figure out the positive pulse triggering aspect, it can be handled otherwise.
Thanks again, the contribution is really wonderful.
ARK

 

[Audioguru]

A 555 is triggered with a negative-going pulse to its pin 2. Use a transistor or logic inverter to convert your positive pulse to a negative-going pulse.

 

[ark5230]

Thanks Audioguru
The application was such that avoiding additional active components was preferable.
Else this would be implemented.
Also there is possibility of getting the things done in microcontroller firmware.
Thanks a lot for valuable suggestion.