LED blink project

Thread Starter


Joined Nov 8, 2019
I want to build a circuit with 2 LED that blink alternatively with a delay
Like this:
0.25s: LED1 on, LED2 off
0.5s: both LED off
0.25s: LED1 off, LED2 on
0.5s: both LED off
And the cycle repeat.
First, I think I will use 555 timer, but I can't figure out how to make the 0.5s pause.
Do you guy have any idea?

Thread Starter


Joined Nov 8, 2019
This is my first design. I can make the LED 1 and LED 2 blink alternatively. But I don't know how to add the pause time in between.


Joined Mar 22, 2019
I would observe that on the basis of a 0.25 second tic rate your outputs for LED1 and LED2 are as follows:
0 1 0
1 0 0
2 0 0
3 0 1
4 1 1
5 1 1

LED1 is basically a single clock delay of LED2. So concentrate on constructing the LED2 sequence then run that output through a single D flip flop to get the LED1 output. You can use your 555 timer to generate the 0.25 second oscillator that drives the clock input of the flip flop.


Joined Jul 1, 2009
This is a school project- the objective is for you to figure these things out. IN electronics, the most basic way to introduce a delay is using a capacitor and a resistor-- there are formulas to help you figure out the time constant. I recommend learning about capacitors, and picking a specific value, and then learning how to calculate the resistor size, so you get the time delay you want.


Joined Aug 7, 2008
If you can use some discrete parts, C s R s, & diodes ? then a 4 stage 555 ring counter can be made
Each 555 triggers on pulse trailing edge via R/C to next 555 input. Might want to provide a startup reset. Start is taking first stage , pin 2 lo momentarily.
Last edited:


Joined Jul 11, 2016
The direct answer with the circuits had been deleted, because it doesn't allowed in Homework Help forum, if any Helpers provides the direct answer for the TS then he may get ban from this Homework Help forum.
Last edited by a moderator:


Joined Jan 29, 2010
Please bear in mind this Thread is in the Homework Forum and so the help we give should be limited to guidance for the TS, not final solutions.



Joined Aug 23, 2012
use two timers then combine the signals for your led drivers -- as the counters can't be used the most likey option is the other timer being 1-shot retriggerable
the whatsoever transition trigger goes like -- See the Simulation
/¯¯¯¯¯¯¯\_______/ A=Timer 1
/¯¯\____/¯¯\____/ B=Timer 2
/¯¯\____________/ A·B
________/¯¯\_____ A̅·B
Please take a look on #2.
When a member keeps on giving direct answers to the Homework Help section, the moderating staff will start a discussion if a ban from the Homework Help section will be applied to that member.

PLEASE READ - Posting Questions in the Homework Help Forum


Joined Aug 7, 2008
At the bottom of this page find, Similar Threads, short way down to Getting a ball to glow---.
might find something useful, see faulty drawing post #9.