Comments on: 555 Timer Basics – Astable Mode http://www.circuitbasics.com/555-timer-basics-astable-mode/ Raspberry Pi, Arduino, and DIY Electronics Projects and Tutorials Sat, 20 Jan 2018 12:10:26 +0000 hourly 1 By: Akash srivastava http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-17231 Sun, 07 Jan 2018 14:37:00 +0000 http://www.circuitbasics.com/?p=166#comment-17231 In my circuit control volt 0- 10 v on pin no 4 (reset pin ) the output is controling. Please explain

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By: :) http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-10201 Sun, 15 Oct 2017 15:29:07 +0000 http://www.circuitbasics.com/?p=166#comment-10201 thank you

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By: Charles http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-5154 Sun, 30 Jul 2017 18:57:35 +0000 http://www.circuitbasics.com/?p=166#comment-5154 Absolutely you turn the LED off longer then it is on. Hook your LED to pins 3 and 8. This will change the formula to:

t(OFF)=(0.69)(R1+R2)(C1) in seconds

t(ON)=(0.69)(R2)(C1) in seconds

It’s called sinking.

For off time change R1
For on time change R2 and/or C1.

Hope this helps someone

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By: Oli http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-3298 Sat, 20 May 2017 16:09:49 +0000 http://www.circuitbasics.com/?p=166#comment-3298 Why does the schematic use a second capacitor for output 5, but a resistance in the video?

Is it possible to offset a very much larger or smaller C1 value with different R1/R2 values, or should C1 be always around 0,1 mF ? Ive seend examples using C1 values ranging from 0,01 mF to 100 mF.

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By: rwad http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-2909 Thu, 04 May 2017 04:07:16 +0000 http://www.circuitbasics.com/?p=166#comment-2909 Does this circuit work? I did exactly the same but mine stays on for one second and doesnt turn back on.

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By: KTR http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-2431 Tue, 04 Apr 2017 12:26:13 +0000 http://www.circuitbasics.com/?p=166#comment-2431 Awsome explenation really

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By: Aparajith Sridharan http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-2218 Mon, 06 Mar 2017 00:48:21 +0000 http://www.circuitbasics.com/?p=166#comment-2218 it is not possible to do that directly on a 555 timer (ON time >= OFF always) . but you can design on time = 60 secs and off time as 10 secs and use a transistor at the output configured to invert then it will work a treat.

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By: Ryan Madden http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-2217 Sun, 05 Mar 2017 22:46:58 +0000 http://www.circuitbasics.com/?p=166#comment-2217 Alright so guys if you invert the led so it goes from pin 3 to positive and crank R1 you will get a longer off time than on. And it will still trigger itself.

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By: Ryan Madden http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-2188 Thu, 02 Mar 2017 02:35:59 +0000 http://www.circuitbasics.com/?p=166#comment-2188 Great resource thank you very much. Could you please do a circuit that has a longer off time than on. Any example of this would be great and I could then work out the values I need from there. My project requires time low for 10 minutes and time high for 30 seconds. I have ready the other comments who ask for this and understand that it may not be possible with one 555 timer, but can it be done with a 556 or 2 555’s? or by inverting the load? I’m still a novice and any help would be appreciated. Cheers

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By: George Birbilis http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-2149 Fri, 24 Feb 2017 09:37:25 +0000 http://www.circuitbasics.com/?p=166#comment-2149 isn’t there some way to negate the logic at the led side?

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By: Circuit Basics http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-2148 Fri, 24 Feb 2017 08:14:15 +0000 http://www.circuitbasics.com/?p=166#comment-2148 Hi Sovatna, this brings up an interesting point – the time off actually can’t be longer than the time on. Looking at the equations for time on and off:

Ton = 0.69 x C1 x (R1 + R2)
Toff = 0.69 x C1 x R2

We can see that the only way to get a Ton smaller than Toff (with C1 and R2 constant) is with a negative R1. Which of course doesn’t exist. Thanks for the question!

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By: sairam tech http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1934 Sun, 04 Dec 2016 06:49:03 +0000 http://www.circuitbasics.com/?p=166#comment-1934 yes definitely

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By: John Zar http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1726 Tue, 04 Oct 2016 10:59:48 +0000 http://www.circuitbasics.com/?p=166#comment-1726 What will happen if I change the power source from 9V to 5V, will it work fine?

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By: George Birbilis http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1690 Mon, 26 Sep 2016 15:59:36 +0000 http://www.circuitbasics.com/?p=166#comment-1690 TH means time the signal stays high
TL means time the signal stays low

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By: Syahmi Shawal http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1689 Mon, 26 Sep 2016 15:39:52 +0000 http://www.circuitbasics.com/?p=166#comment-1689 meaning (TH) and (TL)???

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By: Atef http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1437 Tue, 19 Jul 2016 12:11:08 +0000 http://www.circuitbasics.com/?p=166#comment-1437 Pls, i want to make :
On = (0.1) Off & = (0.05) Off
Frequency = 25 Hz & 50 Hz & 100 Hz & 200 Hz & 500 Hz & 1K Hz & 2k Hz & 4K Hz & 5K Hz & 10K Hz
( 10 steps )

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By: sovatna http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1354 Mon, 27 Jun 2016 15:50:52 +0000 http://www.circuitbasics.com/?p=166#comment-1354 May I know how to blink the led (on) for 10 second and (off) for 60 second as the first question mentioned?

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By: George Birbilis http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1322 Tue, 14 Jun 2016 17:07:23 +0000 http://www.circuitbasics.com/?p=166#comment-1322 Guess you could put multiple in parallel, each with their own resistor (or even with a common one calculated). To avoid burning LEDs try 123D circuits free online from Autodesk, shows you when LED burns

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By: azri http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1321 Tue, 14 Jun 2016 16:34:43 +0000 http://www.circuitbasics.com/?p=166#comment-1321 Can I put more then one led ?

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By: Quang Truong http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-1130 Sun, 03 Apr 2016 15:07:18 +0000 http://www.circuitbasics.com/?p=166#comment-1130 Did you read this part?

t(on)=(0.69)(R1+R2)(C1) in seconds

t(off)=(0.69)(R2)(C1) in seconds

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By: yash http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-844 Wed, 09 Dec 2015 13:03:09 +0000 http://www.circuitbasics.com/?p=166#comment-844 howto make the same circuit for a servo tester?

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By: Mustafa Nafees http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-815 Sun, 29 Nov 2015 22:56:50 +0000 http://www.circuitbasics.com/?p=166#comment-815 555 timer

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By: mohammed ali http://www.circuitbasics.com/555-timer-basics-astable-mode/#comment-741 Mon, 28 Sep 2015 15:46:09 +0000 http://www.circuitbasics.com/?p=166#comment-741 First I want to thank u so much….. and I want the led to be off longer than it’s on….
For example… if the led is on for 10 seconds….. then off for 60 seconds…
Plz can u help me

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