Delay On and Delay Off

Thread Starter

MrsssSu

Joined Sep 28, 2021
190
Hi all :),
The circuit on the left is a delay off circuit using NE 555 whereas The circuit on the right is delay on circuit. For hobby purpose, lets consider this scenerio. When light is off, the led will turn off after a 3 seconds delay whereas when the light is turn back on, the led will turn on after a 3 seconds delay also. I searched the web for the schematic but cant find it. So, I am deciding to combine the 2 circuit below (delay on & off) to achieve my goal? Is this how we are suppose to do it by combining both :) ? LT spice file is attached.

Thank you all for reading





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crutschow

Joined Mar 14, 2008
29,777
Wow sir, I have been searching the web for like 2 hours and couldn't find any. I believe your schematic is the first one to be out in the web haha . Thank you for sharing your knowledge:)
You're welcome.
As a hobby, I've generated quite a few variations of 555 circuits, and one did what you wanted, with a little tweaking to get the desired delay times.

555 circuits are relatively easy to understand, once you know the basics of the 555 operation.
 

LowQCab

Joined Nov 6, 2012
2,041
when the light is turn back on,
What is the Voltage powering the "light" ?
Is the "light" connected to the same Power-Supply as the LED ?
What is the purpose of the Delay ?
Does the Delay need to be adjustable ?, or fixed at exactly 3-seconds to "On", and 3-seconds to "Off" ?
What is the Maximum-Current-Rating of your LED ?
Does the LED need to operate at it's Maximum-Current, or lower, ( to save Battery-Power ).
What is the Forward-Voltage of your LED ?
Is your real-world Power-Supply Regulated at ~10-Volts ? or is it Battery-Powered ?
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Thread Starter

MrsssSu

Joined Sep 28, 2021
190
Here's a single 555 circuit that provides both an ON and OFF delay:
Is that what you want?

View attachment 264624
Hi sir, I have decided to put the circuit to the test on breadboard. However, I do not have a big capacitor (C1) that is 62uF. I only have a 4.7uF maximum. Are there any other parameter that can be adjusted so that it does not utilize too big capactitor to produce the delay :) Thank you:)
 

crutschow

Joined Mar 14, 2008
29,777
You could try it with the 4.7µF capacitor and larger resistors for R2, R3, R4, & R5 (below), but the high resistor values could give flaky results in a real circuit.

Is it that difficult to buy a larger capacitor?

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sghioto

Joined Dec 31, 2017
3,271
When light is off, the led will turn off after a 3 seconds delay whereas when the light is turn back on, the led will turn on after a 3 seconds delay also.
I don't understand this statement. What do you mean when the "light is OFF"? The V2 pulse, power V1 and/or V3? Is there suppose to be a photocell in the circuit?
 
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