Circuit for flashing led for 10 seconds after pressing a button using 555 timer

Thread Starter

GreenBird

Joined Dec 20, 2021
8
Hi, I need suggestion / circuit diagram for flashing led for 10 seconds when i press a button and release it. I thing using 555 timer IC, it can be done.
Kindly respond to this thread, Thanks.
 

sghioto

Joined Dec 31, 2017
5,376
Use two 555 timers or one 556. First timer is set up as a 10 second one shot that activates the second timer which flashes the LED at the rate you require.
Oh yeah forgot to ask, Is this homework?
 
Last edited:

dl324

Joined Mar 30, 2015
16,839
Welcome to AAC!

These modes of operation are described in detail in the datasheet. Do you want to try to do it yourself?
 

eetech00

Joined Jun 8, 2013
3,856
Here is an example. The Astable Ton is about 0.5 seconds. See below.
If the LED stays on (in your circuit) it might be because the Astable frequency is to fast.

1640034450528.png
 

crutschow

Joined Mar 14, 2008
34,280
Below is the LTspice simulation of a circuit that should do what you want using one CD4093 quad Schmitt-trigger NAND-gate package, and a transistor to drive the LED.

Closing PB1 to ground (green trace) starts the pulses.
U1a generates the Gate signal ON time period (red trace).
U1b is configured as a relaxation oscillator (yellow trace).
U1c is used as an inverter.
I(D1) is the LED current (blue trace)

R3 & D2 set the initial voltage at RC to about 1/2Vdd, otherwise the first pulse would be about 2.5 times longer than the rest.
R4C1 determine the ON time, and R2C2 determine the pulse frequency.

Edit: Added U1d to form a latch that keeps the Gate signal high until the last pulse is complete, which avoids the possibility of otherwise truncating it.

1640067218710.png
 
Last edited:

Thread Starter

GreenBird

Joined Dec 20, 2021
8
Below is the LTspice simulation of a circuit that should do what you want using one CD4093 quad Schmitt-trigger NAND-gate package, and a transistor to drive the LED.

Closing PB1 to ground (red trace) starts the pulses.
U1a generates the Gate signal ON time period (blue trace).
U1b is configured as a relaxation oscillator (green trace).
U1c is used as an inverter.
I(D1) is the LED current (yellow trace)

R3 & D2 set the initial voltage at RC to about 1/2Vdd, otherwise the first pulse would be about 2.5 times longer than the rest.
R4C1 determine the ON time, and R2C2 determine the pulse frequency.

View attachment 255703
Thanks a lot
 

Rich2

Joined Mar 3, 2014
254
You can make a short timer with a capacitor and single transistor, you could then use this to power a flashing type LED. I made a 13 second timer like this last year.
 
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