how to get exactly 2 clock cycle from 555 timer upon push button is pressed.

Hi all,

Firstly, i am new to this forum. Kindly forgive me if i am posting this in wrong thread or if anybody has already asked and answered.

Currently i am trying to work on my digital circuit project. In my circuit i have 555 timer, and some other basic digital ic chips, eg gates, shift register, counter, and comparator. What i would like to achieve is that, when i press a push button, i would like my leds to be light up for exactly 2 clock cycle from my 555 timer.

Kindly direct me where should i start. Thanks a lot indeed.

A 555 has no concept of clock cycle count (it is a 1-bit device ; ) so you need to implement a counter and a state machine. Your task is still a bit vague; for example, what should occur if you keep the push-button pressed for longer than 2 clock cycles? And would the push-button need to instantly light the LED, or wait for the next clock pulse?
If you didn't want to implement the generic solution (a state machine) which could handle any number of pulses, then you could use a basic circuit of a binary counter, and bit1 (the second bit) would be a divide-by-2 effectively, i.e. it will go high for 2 clock cycles, and low for 2 clock cycles. You could engineer a circuit to keep the counter permanently in the reset state until a push-button is pressed. You could use a count of (say) 3 to reset the counter circuit again. The count of 3 could be identified by ANDing bit0 and bit1 of the counter. Anyway, it's just an idea..

learner1986 said:

Hi all,

Firstly, i am new to this forum. Kindly forgive me if i am posting this in wrong thread or if anybody has already asked and answered.

Currently i am trying to work on my digital circuit project. In my circuit i have 555 timer, and some other basic digital ic chips, eg gates, shift register, counter, and comparator. What i would like to achieve is that, when i press a push button, i would like my leds to be light up for exactly 2 clock cycle from my 555 timer.

Kindly direct me where should i start. Thanks a lot indeed.

Click to expand...

This is a perfect job for a small microcontroller (eg. PICAXE-08). The question is, can you use one?
:wink:
IanP

https://www.technologystudent.com/pics/outin1.htm

learner1986 said:

Hi all,

Firstly, i am new to this forum. Kindly forgive me if i am posting this in wrong thread or if anybody has already asked and answered.

Currently i am trying to work on my digital circuit project. In my circuit i have 555 timer, and some other basic digital ic chips, eg gates, shift register, counter, and comparator. What i would like to achieve is that, when i press a push button, i would like my leds to be light up for exactly 2 clock cycle from my 555 timer.

Kindly direct me where should i start. Thanks a lot indeed.

Click to expand...

Let's just say, only when i press my push button, i want my counter to start counting (74LS191). How do i connect it. Thank you.