Adjustable Timer Circuits Using IC 555

A timer is a device which produces a delay period after which an external connected electrical load is triggered. The produced time delay is normally adjustable and the user has the freedom to set the time period as desired. There are many ways of making simple timer circuits using different ICs and discrete components; here we discuss one such circuit using the ubiquitous IC 555.

The IC 555 is a pretty common electronic part among the electronic enthusiasts and is also very popular due to the involved simple configurations and low component count.

The two popular multivibrator modes of operation that’s associated with this IC are the astable mode, and the monostable mode. Both of these are useful configurations and have plenty of different applications.

For the present adjustable IC 555 timer circuit design we incorporate the second mode of operation, which is the monostable mode.

In this mode of operation the IC is configured to receive a trigger externally, so that it’s output changes state, meaning if with reference to the ground if the output of the IC is zero, then it would become positive as soon as the trigger (momentary) is received at its input terminal.

This change in its output is sustained for a certain period if time, depending upon the external time determining components. Normally the time determining components are in the form of a resistor and a capacitor which together determine or fix the time period for which the IC output would hold its “high” position.

By changing either the value of the capacitor or the resistor, the timing can be altered as desired. The above time fixing components are termed as the RC component.

Please connect the buzzer or the load between pin#3 and ground, and not between pin#3 and positive as incorrectly shown in the above diagram.

 


The 555 IC timer circuit above shows a very straightforward design where the IC 555 forms the central controlling part of the circuit. As discussed in the above section, the IC is in its standard monostable mode.

Pin #2 receives the external timing trigger from a push-to-ON switch. Once this switch is pushed, the circuit pulls its output to a positive potential   and holds it until the predetermined time delay lapses.

The entire circuit can be built over a small piece of general PCB and housed inside a neat looking plastic enclosure along with the battery.

The output may be ideally connected to a buzzer for receiving the warning alarm after the set time lapses.

Parts List

R1, R4 = 4K7,
R2 = 10K,
R3 = 1M pot,
C1 = 0.47uF,
C2 = 1000uF/25V,
C3 = 0.01uF,
IC1 = 555,
Bz1 = Piezo Buzzer,
Push Button = push to ON switch

A circuit design requested by Mr.Bourgeoisie:




Please connect the buzzer or the load between pin#3 and ground, and not between pin#3 and positive as incorrectly shown in the above diagram.


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109 comments

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Anonymous
January 20, 2012 at 5:04 AM delete

Hi sir, very useful article. Question from me can this circuit control the ac synch motor?. I try to find a circuit that can be use to control ac synch motor direction forward and reverse with time period. please guide me? my email asnf.adsblogger@gmail.com

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January 20, 2012 at 9:00 AM delete

Hi,

No I'm sorry this circuit is not intended for controlling motor rotations.

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Bourgeoisie
March 7, 2012 at 6:35 AM delete

Hey Swagatam,

I want to build a power outage & resumption alarm circuit with the IC 555 that would sound for a given period of time and then goes off on its own. Any suggestions?

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March 7, 2012 at 11:35 AM delete

Hey Bourgeoisie,

The circuit looks a bit complex because it requires triggering during both the occasions.
I'm trying to figure it out, will post it here when I finish designing it.

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Bourgeoisie
March 7, 2012 at 4:26 PM delete

Hey swagatam,

Thank you so much.

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Bourgeoisie
March 7, 2012 at 10:47 PM delete

hey swagatam,

This is what i've been able to come up with so far, my only problem is getting it to sound for a specific amount of time before going off.

http://dl.dropbox.com/u/60538760/schematic.JPG

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March 8, 2012 at 9:06 AM delete

Bourgeoisie, just add a 1000uF/25V capacitor in series between the N/O, N/C relay contacts and the positives of the IC 555. It means the current from the relay should pass through the 1000uF capacitor for reaching the pin 4/8 of the relevant 555 ICs. The positive of the capacitors will go to the relay contacts while the negative will go toward the ICs.
Also make sure that you add a 220K resistor across each of the capacitors.

Regards.

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Bourgeoisie
March 8, 2012 at 8:56 PM delete

Hey Swagatam,

Thanks a lot!, i'll try that and get back to you.

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Bourgeoisie
March 9, 2012 at 7:49 AM delete

Hey Swagatam,

Very cool solution, i tried it out and it worked; but i have a few challenges & questions.

*The way i understand the solution to be is that, the capacitors charge up and become open circuits(D.C voltage) and the 220K resistors don't allow sufficient current to get to the IC.(Please clarify this)
->But if the relay latch goes from NC->NO->NC(power loss and resumption within a short period), the alarm dosen't go off, because the 220K resistor dosen't bleed the capacitor fast enough i guess. When i used 470ohms, the response was faster. So so i go with 470ohms and 1000V? or do you have a more efficient solution.
->Do the values of the capacitor and resistor form the time constant(RC)? and how do i set the alarm sound time?

Thanks.

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March 9, 2012 at 9:29 AM delete

Hey Bourgeoisie,

The earlier solution was not so good, I have designed another circuit which is perfectly suited for the purpose.
I have posted the circuit above, however you will have to connect a buzzer at the output, a speaker will not sound as the IC is not configured as an oscillator.
R3, C1 may be adjusted for getting the desired ON time delay.
Please check it how it works.

Regards.

Regards.

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Bourgeoisie
March 10, 2012 at 4:43 AM delete

Hey Swagatam,


Thanks for the circuit, but when i put it together it dint work. I connected the positive 12V D.C supply to the top left 0.1microFarad capacitor and a 240 ohm buzzer to the pin #3 output. Please help, i cant seem to figure out what i'm doing wrong.

Thanks.

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March 10, 2012 at 9:32 AM delete

Hey Bourgeoisie,

Check the circuit separately first.
Power the circuit and then momentarily short the C1 points manually.
The buzzer should sound and remain ON for sometime and then switch OFf.
I think you will have to increase the value of C1 to make it function properly.

Regards.

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Bourgeosie
March 11, 2012 at 6:22 AM delete

Hey Swagatam,

The voltage at the positive and pin #3 in the circuit are the same, and no current flows through the buzzer, but when i connected the buzzer to pin #3 and ground, the buzzer came on but dint go off after the (R3C1) set time. How do i then go about it?

Regards.

Regards.

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March 11, 2012 at 9:16 AM delete

Hey Bourgeoisie,

I have updated the above circuit, please check it.
This time it should definitely work because I've tested this circuit.

Regards.

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March 11, 2012 at 9:17 AM delete

Resistor values are not critical, you may select any nearby values.

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March 11, 2012 at 8:50 PM delete

The positive of the circuit can be connected to the relay contact along with the transistor base....

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Bourgeoisie
March 12, 2012 at 7:48 AM delete

Hey swagatam,

Thanks for checking it out, i'd implement it and get beck to you soonest.

Regards.

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March 12, 2012 at 9:03 AM delete

Hey Bourgeoisie,

Connect the buzzer across pin3 and ground....

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Bourgeoisie
March 15, 2012 at 1:38 PM delete

Hey Swagatam,

Just to be clear, is the 10k resistor connected to the 1000microFarad capcitor only or is it connected to the 1000microFarad and the line going to pin #2?Secondly,the 1000microFarad capacitor and which of the resistors form the external timing components?

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March 15, 2012 at 1:52 PM delete

The 10K connects to 1000uF (pin #6 and 7) and not to pin #2.

The 1M pot, 10K and the 1000uF cap form the timing components.

Are you having problems? This circuit should work without fail.

Regards.

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Anonymous
January 15, 2013 at 12:24 PM delete

Hi, I have a problem in using PNP transistor, using a 555 IC powered by 12v i connected 2.7k resistor at pin 3 and connected the other end to Base of PNP (557( and connected 12v to emitter and connected the collector to a relay and grounded the other end of the relay and also connected a diode on the two pins of relay. though the IC 555 is working properly and pin 3 goes to ) after the set time the PNP transistor is not working. i also tried BD140. can you help

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January 16, 2013 at 10:56 AM delete

connect an LED in series with the BC557 base resistor (pin#3), it will give you an clear indication of all the functioning. If the LED responds, but the transistor does not respond would mean either the transistor is faulty, wrongly connected.

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Anonymous
January 16, 2013 at 12:31 PM delete

Yes, i had connected an LED to the ground through a 2.7k resistor to indicate output of pin 3, it is working fine. BC557 pin out, flat side facing our face, pin1-E emitter, pin2-B Base, pin3-C, Collector.

should i need to connect a resistor from +volt to Emitter as pullup resistor?.

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January 16, 2013 at 8:31 PM delete

what is pin1? right side or left side pin?

facing the print toward us, and the pins downward, the right pin is the emitter, left is the collector and the center is the base.

no pull up resistor is required, 555 can supply as high as 200mA...

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Anonymous
January 18, 2013 at 12:31 PM delete

OK Sir, i shall try and get back with the results

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Anonymous
January 18, 2013 at 3:35 PM delete

Swagath Sir, Can you give circuit for switching LED Light using BD140 when power is off

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January 19, 2013 at 9:31 AM delete

Please check the first circuit in the following link:

http://homemadecircuitsandschematics.blogspot.in/2011/12/how-to-make-efficient-led-emergency.html

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Anonymous
January 19, 2013 at 2:39 PM delete

thanks, i have one more request, NPN transistors are easy to configure in a circuit, however PNP is difficult, can you help in understanding them better

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January 19, 2013 at 5:40 PM delete

I have explained it here, please refer this article:

http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-understand-and-use-transistors.html

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Anonymous
January 21, 2013 at 2:52 PM delete

Thank you sir, it was very useful

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Anonymous
February 1, 2013 at 11:28 PM delete

Hello mate,
Could you tell me a rough aproximation of the maximum delay this circuit can offer? Which set up should i use to achive it
Thank You!

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February 2, 2013 at 8:04 PM delete

Hi,

Technically you can get infinite range of delay from this circuit, but the circuit starts drifting and doesn't give accurate timing with ranges beyond 2 hour.

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February 22, 2013 at 11:35 AM delete

hai swagatam i want timer circuit without trigging it ,i want to give supply 12 v through another low voltage cutoff circuit relay ,so that if it receives 12 volt supply it should delay on in 15 seconds so that it can reduce unnecessary cutoff of sudden voltage fluctuations .

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February 22, 2013 at 1:21 PM delete

HiSiva,

You may refer to the diagram given in the following article:

http://homemadecircuitsandschematics.blogspot.in/2012/12/thermostat-delay-relay-timer-circuit.html

Eliminate the D2, R6, C3 wiring, and use 12V DC supply in place of 24V AC.
Also make the relay a 12V type.

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Anonymous
February 27, 2013 at 7:25 PM delete

Hi Swagatam, i wanted to try out the design above. but is it possible to hv 2 switches on the circuit? i wanted to make the circuit works by either push on both switches or either one of them. another ques is, hw am I going to select the correct resistor & capacitor to determine the time I want? for eg: 15 mins, 30 mins, 60 mins & 120 mins. Lastly, will the buzzer kept on beeping when the time is up until we switch it off? thx

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February 27, 2013 at 8:34 PM delete

I did not understand your requirement,

You want two switches for the same actions?? you may just connect another switch parallel to the shown one.

Timing can be set by adjusting the values of R3 and C2

yes once the time lapses, the buzzer would keep buzzing until the power is switched off or the push button is reset

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Anonymous
March 1, 2013 at 7:16 PM delete

one problem sir, hw long can does circuit last? possible for a month? if no, any other suggestion to do a timer circuit which cn last tat long? tq

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March 2, 2013 at 7:58 PM delete

you may try the following circuit it would give you a months delay period...

http://homemadecircuitsandschematics.blogspot.in/2012/04/how-to-make-long-duration-timer-circuit.html

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Anonymous
March 5, 2013 at 8:12 PM delete

sorry, not going to use 2 switches anymore. Hmm, is there any formula to find out the time interval? and does 555 produces accurate timing?

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March 6, 2013 at 3:06 PM delete

You can use an online 555 calculator, just fill the given slots and get the required results.

for smaller time periods it gives reasonably accurate timings, but for longer duration it tends to drift away a lot....

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April 11, 2013 at 10:24 PM delete

Hi Swagatam,

I need a timer circuit for my pc fan... ! with 5 min interval,
ie: The fan should turn on automatically after 5min and should stay on for another 5min and again should turn off after that..

on time : 5min
off time : 5min

12v dc fan..


please help me to find a circuit with 555 or cd4060.

thanks

Regards,

Bibin edmond

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April 12, 2013 at 8:07 AM delete

Hi Bibin,

Make the IC555 section given in this diagram, ignore rest of the stages on the left.

http://3.bp.blogspot.com/-Fw_H-NFkFZc/UUQsOXNMhOI/AAAAAAAADlQ/BvMO_t8b-bo/s1600/drl%20day%20time%20running%20light%20circuit.png

for 5 minutes you will have to dimension the capacitor to a bigger value.

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April 12, 2013 at 12:11 PM delete

Ok.. thanks swagatam, let me try... !

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May 26, 2013 at 10:41 PM delete

hey sir, i am designing a water level detector circuit. when the water level reaches to the max, i want a buzzer to turn on ONLY once for like a second and it will stop a motor. can this be done using this circuit? if yes please explain. if no please give some hints. thanks in advance

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May 27, 2013 at 2:06 PM delete

you may try the following circuit:

http://homemadecircuitsandschematics.blogspot.in/2012/04/cheap-semi-automatic-tank-water-over.html

Connect a buzzer with a 1uF series capacitor and connect it across T1/T2 collector and positive.

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Anonymous
May 30, 2013 at 12:07 PM delete

good day mr. swagatam. can you please help us construct a timing circuit which is an output of a logic circuit. we want it to have 3 different time duration outputs. hope you can help us. thanks.

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May 30, 2013 at 8:27 PM delete

Please provide an elaborate explanation of the requirement so that it becomes easier for me to design the circuit.

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June 7, 2013 at 1:18 PM delete

I came across your website searching for a solution to my problem.
Hopefully you can give some insights on how to do this.

I am doing a mod for the multi effects Zoom G3X.
Basically converting some of the buttons into external foot switches.

I got a situation where to trigger a function I must do the following
- Hold down a button then press another button to trigger the feature.

When I tried it with a 3PDT switch it is very inconsistent due to both circuits are triggered simultaneously using a single switch.

Current situation
1) Press the 3PDT switch
2) Circuit A is connected
3) Circuit B is connected at the same time.

This results in very inconsistent behavior as circuit A need to be closed first before circuit B,

I need a way to introduce some delay
1) Press the switch
2) Circuit A is connected
3) Circuit B is connected 100ms later.

Can you please help on how to achieve this as simple as possible?
Timing is not critical
There is no load on the circuit just a simple switch.

Thanks in advance

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June 8, 2013 at 2:00 PM delete

Use a transistor/relay driver stage for circuit B, as shown in this link:

http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-make-relay-driver-stage-in.html

connect a 100uF/25V across transistor base and ground, connect the circuitB via the relay contacts.

the circuit A may be directly wired with the relevant supply

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Anonymous
June 11, 2013 at 4:14 AM delete

Please sir, can i create a circuit that will take 30 seconds to switch On an electric motor with Ic 555

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June 11, 2013 at 10:09 AM delete

you can try it with a 4060 IC circuit, it will do the job.

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June 17, 2013 at 6:45 AM delete

Thanks a lot for your input.
I will try it out.

Thanks

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June 20, 2013 at 5:20 PM delete

please can you show me a circuit using discrete components and the calculations involved

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June 21, 2013 at 12:15 PM delete

you can try the second circuit given in the following link:

http://homemadecircuitsandschematics.blogspot.in/2012/05/simple-delay-timer-circuits-explained.html

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July 12, 2013 at 1:02 PM delete

Hi swagatam ,I wanted to construct a circuit which uses a small voltage of less than one volt to control a relay of 12 v.how can I go about?

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July 12, 2013 at 4:52 PM delete

Hi Ben,

You can try a relay driver circuit as shown here:

http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-make-relay-driver-stage-in.html

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Anonymous
July 13, 2013 at 11:01 AM delete

Hello swagatam, I am trying to think of a circuit were it has a constant 12~14v supply but a timed output to between the hours of 6 in the morning til 6 at night and to be repeated everyday.the output is to latch a twelve volt relay. Any ideas would b grateful as a I am struggling as a beginner. Thanks

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July 14, 2013 at 10:04 AM delete

You can try this circuit:

http://homemadecircuitsandschematics.blogspot.in/2013/07/simple-triac-timer-circuit.html

You will have to remove D2 and replace the triac with a transistor/relay driver stage, after that the variable may be set for achieving the required timing.

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September 1, 2013 at 12:50 AM delete

Hello sir, I have formed this circuit in multisim 12.o. i have the muscle stimulator as the other circuit. can this muscle stimulator be the trigger?? if i put these two circuits on 1 board in multisim, will the result show??

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September 1, 2013 at 12:54 AM delete

Hello sir. I just wanna ask if i put this circuit and a muscle stimulator circuit as the trigger in multisim 12.0, will the result show, like the buzzer would buzz? or it should be done physically to know the results??

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September 2, 2013 at 10:17 AM delete

Hello Jaejjii,

I don't think the simulator would be able to simulate your muscle simulator response along with the above circuit....so I think you should test the configuration practically.

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October 29, 2013 at 3:02 AM delete

hello sir...fist of all thank u for running such a nice blog...sir i want to make a three light running chaser to be worked on ac lights...and want to keep interval switching time 1 minute...pls pls help me sir....thanxx

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October 29, 2013 at 12:51 PM delete

Helo Nitin,

I have explained it in your previous comment with a link....for 1 minute interval you just need to adjust the pots carefully for the required timing.

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Anonymous
November 3, 2013 at 1:53 PM delete

Hi sir

Thanks for the circuit. Can u help me sir? I intended to build a circuit that power ON a hair dryer for 2-10 minutes when switch is closed and power OFF after that period. In between, if I want to OFF the working hair dryer within that period, I intended to put RESET button so. So basically I am trying to make an automatic shut off relay timer with reset button. Can u suggest me any circuit? Thank u in advance :)

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November 4, 2013 at 11:26 AM delete

You can try the second circuit given in the above article, do the following modifications in it:

Remove the buzzer, and put a relay across pin3 and ground.

Remove the transistor and replace the position with a 0.22uF capacitor, also put a 1M resistor in parallel with the above cap.
The timing can be set by adjusting the shown preset.

Whenever power is switched ON, the relay will hold and then deactivate after the delay period has lapsed.

The reay contacts may be wired up with the hair dryer.

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November 9, 2013 at 12:35 PM delete

Hi Swagatam

Would you please tell me the functions of D1, D2 and R1? I have just blew a 555 without them.

What would be the configuration for a positive triggering signal?

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November 9, 2013 at 2:37 PM delete

Hi Abu-Hafss,

R1/R2 are for discharging C1 so that it becomes ready for the next input pulse

D1/D2 are not crucial and may be removed, these are for restricting the entry of high frequency disturbance at pin2 and for eliminating false response by the IC.

There's no way you can blow this IC, unless you short circuit the output for too long or reverse the supply polarity.....

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Anonymous
December 21, 2013 at 11:57 AM delete

great guru am here again the last time i told you that i need a circuit that can close a relay for 8sec and delay it for 1hourand should continue like that for 12hours and stop, you told me to check one of the post you made which i did but to tell you the truth am having difficulties with the designing and time is not really on my side for my project in school. please can you help me design this circuit please i really need your help on this to finish my project please this my email xdungs@gmail.com

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December 22, 2013 at 11:05 AM delete

You will have to construct it first and then check it as per the given instructions, that's all. If you face problems while troubleshooting I'll help you.

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January 27, 2014 at 1:09 AM delete

Hi Swagatam

I am really exhausted, I admit, I have failed. Please help me.

I need two monostable 555 timers configured such that:

1) when switched on, ONLY the first timer should be triggered automatically
2) after completing its preset time the 1st timer triggers the 2nd timer
3) after completing its preset time the 2nd timer triggers the 1st timer
4) hence the cycle repeats indefinitely

Just let me know how to connect the pin #2 of both timers.

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January 27, 2014 at 4:14 PM delete

Hi Abu-Hafss,

I'll do it for for but in return you will have to explain the circuit in your own words, ...agreed?

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January 27, 2014 at 6:03 PM delete

Okay..................
Actually, I had made the circuit; and as per my usual practice I simulated in 2 different softwares. One worked perfectly, but the second one (LTSpice from Linear Technology) did not accepted. And I mostly rely on LTSpice, which I consider to be much accurate.

Here is my circuit https://dl.dropboxusercontent.com/u/20969135/555%20mono-2.gif

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January 27, 2014 at 9:21 PM delete

Hi Abu-Hafss,

The trigger inputs are not configured correctly in your circuit according to me, I'll try to update the correct one soon.

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January 27, 2014 at 9:30 PM delete

Hi Abu-Hafss,
Please refer to the "sequential timer" section in the following pdf link:

http://www.ti.com/lit/ds/slfs022h/slfs022h.pdf

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February 4, 2014 at 1:24 AM delete

Hi Swagatam

The link shows monostable timer with manual triggering whereas, I was talking about automatic triggering at power-up.

If for example we have 3 sequential timers:

a) Only the first timer should start at power-on.
b) The first timer should trigger the second.
c) The second should trigger the third.
d) The third should re-trigger the first one.

My problems is how to restrict the 1st timer to be triggered automatically at power-up?

According to my observations, sometimes 1st timer gets triggered, sometimes 2nd, sometimes 3rd, sometimes all three and some times none.

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February 4, 2014 at 12:06 PM delete

Hi Abu-Hafss,

Replace the switch "S" with a 1uF capacitor and also connect a 10k resistor across the positive and pin2 of this IC, now the circuit becomes an automatic sequential timer as soon as it's powered up.
The circuit will always start from IC1 when switched ON as per my simulation, just try it.

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June 1, 2014 at 1:29 PM delete

Good afternoon sir,
Would U kindly mention the value of D1 & D2.
Wheather a 6v relay will work instead of a buzzer?
Inform the caution to be taken for 6v supply instead of 9v d.c.
Thanks ................
k.kausik

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June 2, 2014 at 9:41 AM delete

Kaushik, D1, D2 are 1N4148 diodes

6V relay can be used but the supply should be also at 6V

the same circuit can be used for 6V operation also, no changes would be required.

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June 3, 2014 at 8:26 PM delete

Good evening sir,
Wishing you a hearty thanks for your kind reply.......
A request ;
A search option & "go to top" is needed on your web page....... So many useful circuits ...a huge no of posts & comments.....
With regards,
K.Kausik

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June 4, 2014 at 10:27 AM delete

Thank you Kaushik,

Your suggestion is very good.

If it's possible to include this feature in my blog template, I will make sure it gets implemented soon.

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June 4, 2014 at 10:28 AM delete

....by the way the search option is already there at the left top of sidebar.

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June 7, 2014 at 8:47 AM delete

sir, can i use the same circuit above using a 12volts power supply? or do i have to modify some of the parts?

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June 7, 2014 at 5:19 PM delete

Jomel, 12V can be also used for the same circuit, no changes would be required

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June 7, 2014 at 9:16 PM delete

Hey Swagatam,

I like ur circuit and i am new to electrical world.
So i want to know that if i have an input of 220 volt ac , what value of resistance i must have to add do that i get output of 9 volt ac

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June 8, 2014 at 11:43 AM delete

Thanks Vipin,

If you are referring to the above circuit, for a 220V operation you can use a 12V AC/DC adapter for it.....12V would also work for the above circuits.

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June 10, 2014 at 7:39 AM delete

sir,i'm planning the same circuit above to control a motor of 12v, 8 amps for a certain time duration,i attached a tip3055 transistor in series with a 1M resistor to the output in place of the buzzer, will that work?

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June 10, 2014 at 4:32 PM delete

Jomel, you will need to do it via a TIP122 transistor.

connect the base of TIP122 to pin3 of the IC via a 1k resistor.

connect the emitter of TIP122 to the base of TIP3055

connect the emitter of TIP3055 to ground.

join the collector of both transistors and connect it to the negative of the motor, and connect the positive of the motor to positive of the supply.

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June 10, 2014 at 10:27 PM delete

Hi Swagatam

TIP122 is a darlington pair, so shouldn't it be replaced with TIP31?

Otherwise, what would this configuration be called i.e. 3 transistors connected in series with common collector?

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June 11, 2014 at 12:09 PM delete

Hi Abu-Hafss,

Here we are looking for a guaranteed and an optimal switching conditions for the 2N3055 since the source current is very low in mA.

Therefore a Darlington is a better choice since it would ensure the full dose of current for the 2N3055 producing an optimal switch-ON for the load

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June 11, 2014 at 12:39 PM delete

OK,thank you sir,i will try and see what will happen

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June 11, 2014 at 1:02 PM delete

Sir,may i ask what is the reason behind the additional transistor tip122?

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June 12, 2014 at 10:03 AM delete

Jomel, for 8amp collector load, the base of 2N3055 would require around 200mA current, TIP122 is used for optimally satisfying this amount of current to the base of 2N3055

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June 14, 2014 at 7:14 AM delete

Good morning sir,
My android mob. is the only way to connect with Net. It's quite tough to search any particular ckt. Plz. Help!!
I need to convert 12v a.c to 12v d.c
A tr. manufacturer told that when a bridge rectifier is added with the out put of 12v d.c it increases the voltage upto 3v. Is it true? Then what should I do....
1)A tr. of 9v d.c out put...
2)any ckt. that provides 12v a.c to 12v d.c using a tr.
Please guide.
With regards, k.kausik

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June 14, 2014 at 11:24 AM delete

Hi Kaushik,

yes that's right. in fact with a filter cap it could rise upto 16V

you can use a 7812 IC for restricting the voltage to 12V or add 4 to 5 rectifier diodes in series with the positive for the same.

the diodes could 1N4007 or 1N5402 depending upon the output current specs

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August 9, 2014 at 4:30 PM delete

I want to make a circuit which work's like I have 9 25 watt clf bulbs and I want to do that when I switch off the first CLF then after each 5 minutes the remaining light would switch off regularly like each should go off after 5 minutes of other means that in 45 minutes all 9 lights go off respectively.So in this case would the last circuit among the drawing's will work or not.Please help me ?

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August 10, 2014 at 4:57 PM delete

I'll try to design it soon and post it in this blog.

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August 22, 2014 at 4:48 PM delete

Hello Swagatam i wanna ON my Banner Light with 555 Timer IC for particular hours like 6-8 Hours and then i wanna off it automatically. Is it possible? Please help me regarding this. it will be helpful for me.

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August 22, 2014 at 7:39 PM delete

Hello Nipun, a 555 IC circuit may not be suitable for acquiring such long delays due to its inefficiency, a 4060 IC is recommended for this as explained in the following article:

http://homemadecircuitsandschematics.blogspot.in/2013/07/simple-triac-timer-circuit.html

try the second one for your application

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August 30, 2014 at 12:07 AM delete

how to increase time duration of this timer? like 4 hours timer

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September 29, 2015 at 7:28 PM delete

Hello.
If I changed the voltage to 15V, will the values of other components change? If yes, then what will be their new values?

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September 30, 2015 at 7:33 PM delete

Hello, nothing will need to be changed for 15V, however at 15V the IC can get a bit warm so it's not recommended.

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November 27, 2015 at 8:42 PM delete

Hello Swagatam, I would like to know if an IRS2453 can be driven by an external oscilator, like UC3845. I want to use this circuit to drive a H bridge in a welding inverter.

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November 28, 2015 at 4:21 PM delete

Hello Alexandru, According to me it does not include this feature, it can be programmed only through the specified Rt/Ct network....

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December 16, 2015 at 4:25 AM delete

hello sir,

i want to make a bathroom light timer switch with IC555, but i want to add a warning alarm sound before the lights goes off when the time limit is reached, can you help me?

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December 16, 2015 at 7:22 PM delete

Hello Enrico, I can certainly help you, please let me know what type of buzzer and lamp do you intend to use in this application.

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December 16, 2015 at 7:50 PM delete

buzzer is DC type and lamp is fluorescent type...what im trying to do is to make it give a warning sound(somewhere about 15 seconds) before the timer switch the lamp off.

the timer is adjustable from 1-10 minutes

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