astable multivibrator (ic 555)

[aniket433]

monostable multivibrator (ic 555)

is it possible to use monostable multivibrator (ic 555) to generate 120 seconds pulse...?

 

[not-a-moderator]

Yes it is possible, altough your 120 seconds won't be extremely accurate. You can expect to end up with about +-10% tolerance on your timing.

https://www.electronics-tutorials.ws/waveforms/555_timer.html

 

[aniket433]

Yes it is possible, altough your 120 seconds won't be extremely accurate. You can expect to end up with about +-10% tolerance on your timing.

https://www.electronics-tutorials.ws/waveforms/555_timer.html

i got the ic M74HC123 which gives a pulse up to 60 sec. it consists 2 of monostable multivibrator...
is that mean single multivibrator gives 60 sec pulse ? or both the multivibrators combinedly gives up to 60 sec pulse..
datasheet is given below
https://html.alldatasheet.com/html-pdf/23042/STMICROELECTRONICS/M74HC123/1622/1/M74HC123.html

 

[not-a-moderator]

A single multivibrator gives a 60 sec pulse if the values of Rx and Cx are set correctly.
The limits for Cx and Rx is:
Cx:
no limit
Rx:
Vcc < 3.0V 5 kohm to 1 Megohm
Vcc > 3.0V 1 kohm to 1 Megohm

In the case where Rx · Cx are large
enough and the discharge time of the capacitor
and the delay time in the I.C. can be ignored, the
width of the output pulse tw (out) is as follows :
tW(OUT) = 0.45 Cx · Rx

The Maximum allowable values of Cx and Rx are a function of leakage of capacitor Cx, the leakage of device and leakage due to the board
layout and surface resistance. Susceptibility to externally induced noise may occur for Rx > 1 Megohm