triac timer circuit - Simple Triac Timer Circuit

Simple Triac Timer Circuit

Here's a simple triac timer circuit which can be used for switching ON a particular device after a predetermined time, set through the given pot or the variable resistor.

The shown circuit diagram of a simple triac timer can be understood by referring to the following explanation:

How the Circuit Works

The left hand side section comprising the IC 4060 becomes the basic delay generator stage. As we all know, the IC 4060 is an extremely versatile time delay generator chip which has a built in oscillator for the required fundamental timing clocks.

The components connected at the pin#9,10 and 11 form the time delay determining parts of the IC.

Precisely, the resistor at pin#10 and the capacitor at pin#9 are responsible for fixing the delay period and may be adjusted for acquiring the required predetermined switching output.

This IC has 10 discrete outputs which produce delays or oscillation periods which are twice to the previous pinout in the order.

Here pin#3 produces the largest delay, followed by pin#2 and then pin#1 and so on as per the specified pinout order. So suppose pin#3 produces delay interval of 1 minute, then pin#2 would produce the same at an interval of 30 seconds, pin#1 at 15 seconds and so on.

Since pin#3 is specified with the highest time interval, we use this pinout as the output.

Therefore suppose we set the RC at pin#9 and 10 with a maximum delay of 2 hours, pin#3 would be assigned to generate alternately changing ON/OFF pulses, having equal delay intervals of 2 hours, meaning initially the output would be OFF for 2 hours, then ON for next 2 hours and so on as long as its powered.

The above explains the IC 4060 configuration, now let's learn about the triac configuration.

As we can see, the output pin#3 is directly connected to the gate of the triac, while the triac A1 and A2 are terminated with the load and the other specified parameters.

When power is first switched ON, C3 at pin#12 of the IC4060 makes sure that the timing count initiates right from zero by resetting pin#12 with a short pulse.

The output pin#3 now initiates with a logic zero output while the IC internal timer starts counting.

Due to the logic zero, the triac stays switched OFF initially along with the load.

Once the predetermined delay interval lapses, pin#3 instantly becomes high, triggering the triac and the load.

The diode connected across pin#3 and pin#11 plays an important function of latching the IC counting process.

If this diode is removed, the counting process will continue and after 2 hours the triac will be again become switched OFF, and this procedure will go on repeating every after 2 hours.

The diode shuts off this operation, and lathes the IC to the ON position permanently.

The above situation provides us with another interesting application of the proposed circuit, by removing the diode we can convert the above circuit into an AC lamp flasher circuit, the flashing rate being set by the RC components.

Also note that irrespective of the RC parts you have the option of selecting/connecting the remaining outputs of the IC with the triac gate for getting a diverse range of time delays.

Circuit Schematic for Delay ON Timer


triac timer circuit 1 - Simple Triac Timer Circuit


The above triac controlled timer circuit becomes suitable for applications which requires a delay switch ON.

For applications which require a delay switch OFF meaning in cases where a load needs to be switched off after a predetermined time interval, the above circuit can be modified as given below:

Circuit Schematic for Delay OFF Timer


simple triac circuit 1 - Simple Triac Timer Circuit


Parts list for the above simple triac timer circuit

R1 = 2M2
R3 = 100K
R2, R4, R6 = 1K
R5 = 1M
C1 = 1uF/25V (must be non-polar, use more in parallel for higher delays)
C3 = 0.1uF disc
C2 = 100uF/25V
C4 = 0.33uF/400V
Z1 = 15V 1watt zener
Tr1 = BT136
T1 = BC547
D1, D2 = 1N4007
P1 = 1M pot

146 thoughts on “Simple Triac Timer Circuit

  1. Have questions? Please feel free to post them through comments! Comments will be moderated and solved ASAP.
  2. Hallo Mr. Swagatam

    I have build a dark sensor to switch on the CFL lamp 220 volt. I just build one with a simple SCR sensor. But if the LDR is getting dark or getting bright, the CFL got flicked for several time. so I have an idea to make a delayed switch on. So if LDR getting dark the lamp is not ON immediately, but the lamp is ON for several minutes after ldr getting dark and vice versa if LDR getting bright.

    would you have a suggestion about it ?


  3. thanks for ur suggestion Mr. Swagatam…

    Using ne555 is my next plan for applying this feature. But I doubt :
    1. can the IC ne555 be supplied with transformatorless power suply ?
    2. can the IC ne555 drive the SCR gate for subtituting mechanical relay ?
    3. can I replace the capasitor c1 with larger to make a delayed switching…?

    so I want to try to make it…

    thank a lot

  4. Hi just a few questions, would this work with a DC input? also if I wanted a 12 hour interval how would I achieve this? And if I wanted to replace triac with a transistor to switch a relay what,would I need? Also if the input voltage was to fluctuate between 6 and 14v DC could I use a DC to DC convertor and if so what would u recommend? Your help would be appreciated, thanks

    • Yes it will work with a DC adapter also.

      you can use a standard transistor/relay driver stage in place of the triac.

      the voltage should be a fixed type around 12V or at the selected relay voltage, if it's fluctuating too widely then I am afraid the relay will not respond at the lower voltages, using a converter will make the circuit very complicated.

      you will have to adjust the RC components for setting the preferred time interval.

  5. If the voltage was to stay between 11 and 14 volts when the voltage fluctuates would this change the time interval? Thanks for your reply

  6. hello sir Swagatam Majumdar. my name is miguel from Argentina. please i need a timer circuit 15 hours .. after 15 hours off a relay … please help me? thank you very much. I also want to tell you that your web site is great

    ATTN: Miguel.

    • Hello Miguel,

      you can use the above circuit,just replace the triac with a transistor/relay stage.

      You can power it with a 12v ac/dc adapter instead of the transfomerless power supply.

  7. This circuit will not work as shown. The cathode of zener diode Z1 should be connected to C4/D1 junction, not to D1/C2 junction.

  8. Yes I understand why you need a zener diode, however the problem is C4 which is used as a capacitive dropper to provide a DC supply for the circuit. For C4 to work as a dropper using capacitive reactance it has to operate on AC but in the circuit it is connected in series with a rectifier diode D1. This means C4 will simply charge up as soon as the circuit is energised and will not work as a capacitive dropper. That is why Z1 cathode needs to be connected to C4/D1 junction so that C4 will see AC.

    • During negative cycles C4 would get discharged through R5 and the cycle would continue, I would like to check it practically and then I'll put my comment back here.

      Putting the zener immediately after C4 is not a bad idea but in the above condition also the circuit should work..let me check it.

  9. You're welcome. During negative half cycles current flows back through C4 via Z1 which becomes forward biased and operates like a normal rectifier diode with typically 0.6 volts forward voltage drop. D1 is necessary to prevent this 0.6 volts appearing as negative voltage across C2 and the main circuit. If you Google 'transformerless power supply' you will see several half-wave circuits which are the same as your modified circuit diagram. The rest of the circuit is very novel and I may have some uses for it. Regards Richard

    • Hi, i want to make this circuit with BTA41/600 please tell me what modifications are needed as this triac needs at least 50ma to trigger, will 4060 pin 3 be able to provide enough juice?

    • Hi, 4060 will not produce more than 15mA, so you may have to employ a transistor stage for switching ON the triac….you can try the second circuit which is designed as a delay-OFF timer

    • Hi!
      Thanks for quick reply, i need circuit with delay switch ON, can you please guide me transistor BC547 pinout accordingly

    • In the last diagram, introduce another BJT stage in between R4 and the base of the existing BC547, in the following manner.

      disconnect R4 from the existing transistor's base.

      Take another BC547, connect its base to R4, emitter to ground, connect a 10K resistor from its collector to positive.
      Now connect the base of the previous transistor with the collector of this new transistor….that's all.

    • Hi
      I made the circuit as guided by you, i replaced 10k resister with 1k on second transistor as with 10k it flickers badly.
      now the problem is its not getting reset instantly as when i turn off and immediately turn on the circuit it gets on without any delay, the main point to design this circuit is to protect refrigerant compressor from main supply kicking in and out as it needs some time to restart.
      also i used ic pin 1 instead of 3 and p1 i replaced it with 33k resistance and I'm getting delay around 2 minutes 20 seconds which solves my purpose but it varies 20 – 30 seconds.
      One more thing i noticed is I'm getting 220v AC/DC output instead of pure AC, is it safe to connect Refrigerant compressor to this circuit? Is there any way we can convert it back to AC.
      I know relay would be simplest solution but i prefer triac to avoid sparks generated in relays.

    • Hi, with 10K it should not flicker because the first transistor is supposed work require very little current for turning off the triac driver transistor.

      anyway, if it's working for you, it's fine!
      using pin#3 will allow 3 times more delay than pin#1.

      if you connect the load with the triac as shown in the diagram, then the load will get a pure AC, and no DC, because the triac is connected only with the AC, and there cannot be any DC here.

      I hope you have included C3 in the design and the 100K at pin#12, these are for ensuring a reset action each time power is switched OFF.

      Try increasing the value of C3 to 1uF, and check the response

    • Hi, I have replaced C3 to 1uF and it solved the delay problem.
      If i check voltage without load then it AC and no DC but if i check with load connected (60 Watts bulb) then meter reads AC/DC
      Please help

    • A digital meter will always show some DC content in AC, and vice versa,
      which is nothing to worry about…the thing to note is that the triac's MT1 and MT2 are connected with the mains AC so the load will get only mains AC unless the triac faulty…

    • Sir I need a circuit in which i can operate a 12 volt dc relay . On switching the relay should remain ON for 5 seconds and after 5 seconds the relay should go OFF for 5 seconds and after 5 seconds it should turn on for for 5 seconds again.his cycle should continue untill supply to the circuit is disconnected.

    • you can try the 4060 timer circuit that's given in the above article, replace the triac with a transistor/relay driver stage and adjust the pot for getting the desired timing
      use a 12V adapter to power the circuit.

  10. Thank you sir . That's one I was really looking for. I made it successfully and working well. Can any thing be connected to this circuit to protect it? Kindly let me know what are the main point which we should note down from a transistor data sheet regarding any transisor. Thank you.

    • Hi Mujahid,

      In transistor datasheet you should only look for the maximum breakdown voltage that it can handle across its collector/emitter and also the breakdown current across these terminals

  11. Sir I would like to know a few questions
    can we use all or some of the outputs of the above explained ic at the same time?
    Can a relay be directly connected to an ic without any transisor. Thanks a lot

    • Yes you can use any desired number of outputs simultaneously, but they should never be interconnected directly.
      Relay cannot be used directly with CMOS devices since their output have very low current, not specified for driving loads like relay etc.

  12. A circuit needs 12 volt and 20mA. Will this effect the circuit if it is connected to a 12 volt 200Amp battery? What happens if the required volt remains the same and amperes are increased to the circuit?

  13. Sir I want to know a very important point is it possible to power the above circuit with both mains and a battery as well in a way in which the battery should not charged with the mains supply.actually I need to power the circuit when mains is unavailable.the battery should remain safe from charging.thank you

    • Do you need a timer circuit or just a mains changeover relay for switching the battery ON/OFF?

      If your need is a timer circuit then you can use the above circuit with both mains and battery also.

      Preferably use a 12V DC adapter for mains operation of the circuit instead of the capacitive power supply.

  14. Let me explain my question in a better way.I need a timer circuit only not any changeover I want to operate the above circuit with both mains(using an adaptor)and a battery simultaneously. My purpose of using two different supplies simultaneously is to operate the circuit even when the mains is unavailable. In case of the unavailability of mains the battery will operate the circuit but the problem is to keep the battery safe from charging of mains supply. Can I use a diode in battery supply?

    • OK, yes you can operate the timer circuit through mains and 12V battery as well, for preventing the battery from receiving the 12V DC from the adapter you can use a blocking diode as correctly suggested by you.

  15. "The higher the capacitance the higher voltage drops."Sir is my understanding about voltage dropper capacitor( capacitor used in place of a transformer to drop voltage) is correct or not?

  16. That.s very kind of you. Actually sir I don.t know much about electronics but this is your help that I.'ve made a mobile operated relay circuit that.s a bit different from yours. And there.s one to operate the generator automatic start and shut down. That.s all great. I read your blogs regularly. Sir I!ve difficulty in understanding the terminology of electronics.would you help me.

  17. Dear sir my question is regarding one of your explained circuit that is proximity circuit. If an IR led and BP104 and a npn transistor and a relay is configured in such a way when the beam of IR led is reflected and falls on photo diode and it triggers the transistor and the transistor gets saturated thus operating the relay for the time as long as the reflected beam falls on photo diode. I mean to know that with these few components it possible to make a simple proximity circuit. Thank you.

  18. A photo diode or a photo transistor is triggered by infrared light only or they can be triggered by any light like sun light or any other bulb. Please explain about photo transistor and photo diode. Thank you

    • it can be triggered by any light source that's why we use a pulsed light while using it as a detector in a circuit, the receiver responds only when the PD receives the pulsed signal from the specified transmitter and other light sources are ignored

  19. Sir can you help me in making a proximity circuit for water tape I need a simple circuit. I tried to make it with the help of infrared receiver found in a computer mouse but it.s not responding well as I need it.

  20. Sir if i want to stop the ic after specific number of ON and OFF cycle then what i should do? I need only 3 cycles. I have made this circuit when three cycles complete I cut this circuit with a timer circuit via a relay. Now I don.t want to use the relay.tell me an easy way to use the above circuit for specific number of ON AND OFF cycle.

  21. Sir in above ckt calculated timing is much varig from practically gatting.
    When triac is on voltage at IC is 11 volt and when it gets off voltage at ic becomes 6 to 7 volt. As transistor makes the collector ground at which we connect vcc through 1 k resister,
    Voltage gets drop.

  22. Sir I made a circuit consisting of ic 4017 and ic 555 its working well as all output at ic 4017 work in sequence but the problem is that when the circuit is switched on every time the sequence does not start from pin 3. While I want the sequence to start from pin 3 whenever the circuit is switched on. How is it possible? Please help.

  23. Sir is it possible if I use two or more ICs 4017 when 1st IC completes its sequential output it should stop completely and the SECOND IC(4017) should start its sequential output and when SECOND IC completes its sequential output it should stop completely then 3rd IC (4017) should start its sequential output and when 3rd ic has completed its sequential output it should stop completely and this cycle should start from the first ic and so on.

  24. Sir I read the post( 18 led chaser circuit) thoroughly you recommended but I couldn't understand how the first ic sequence remains off untill the second ic has completed its output. I want to understand it and connect more ics so it would be very kind of you to explain it further.

  25. Actually sir I want to know the magic of diodes IN4148 in 18 led chaser circuit you have configured. It seems interesting to know. I tried to understand but in vain.please help me I want to connect more 4017 ICs.

    • Dear Mujahid,

      Varistors are always connected parallel to the mains input supply terminals of the circuit which needs protection, PTCs also are wired identically, not sure though, I'll try to present a post explaining these components soon.

  26. Dear Swagatam,

    Hope you're fine.
    I'm trying to build an egg incubator and i'd like to incorpoprate your simple triac timer switch into it. However, the triac circuit did not the input voltage. is it 110v or 220v? i need a 220v circuit. Please advise. I'm sorry for being naive about this.
    Thank you for being patient in answering the questions being asked by the readers. i also learn from them. Keep up the good works Sir! Hats off!



  27. Dear Swagatam,

    Kindly indicate the polarity in every electrolytic capacitor in the simple triac timer circuit. I cannot proceed further to the condtruction of the said project. Please.



  28. Therefore c1(1uf/25v) is a mylar. Can i just simply use .68uf(volt please) in replacement for the 1uf/25v? What do you mean use 'it in parallel?' and what is the value of the p1?

    • yes you can….first insert any random value like 220K, and check after how many minutes the pin3 becomes high….once you get the result you can simply calculate other resistor values for any other desired timing through cross multiplication.

    • C1 can be of any value, but it needs to be strictly non-polar…you can use many 0.68uF capacitors in parallel if non-polar 1uF is difficult to obtain.

      higher values will give higher timing periods

  29. I'm sorry but i'm confused on your statement on what is the value of c1. Once and for all please kindly specify the value and/or rating of it? You said 50v would be enough for C1, at 1uf? What polarity should be connected to ic4060?

    • the voltage rating needs to be twice that of the supply volatge, as a rule of thumb…higher voltage rating will not do any harm.

      when it's non-polar, there's no restriction to polarity, it can be connected anyway round.

  30. In your reply last Sept.20, you said 50v is enough for c1 (in the parts list it is 25v. i doesn't matter anyway,right?). My question is: what polarity of c1 should be connected to pin 9 of ic4060?

  31. Sorry i'm a little confuse. Once and for all. Let me rephrase my question. What should i use for c1? a. 2-.68uf/50v mylar in parallel, or b. 1uf/50v?, what polarity of this capacitor should be connected to pin 9 of ic4060?

  32. Can I able to set 10s delay by using this ic 4060. In our college we did amicrocontroller based automatic bell one day we face a problem that relay stay in Nc position due to this bell rang for long period of time until we turned on the supply. In order over come this we have planned to add some extra time ic that even if the relay fails to operate the bell should be turn off after the 10s time delay. Can I use this circuit for it

  33. Hello,
    I made the circuit (the second one with transistor). Did actually somebody made and test this circuit? Without transistor the circuit works great, but with transistor I can not get the result. It only switch the load (40W lamp) on and after while when it should go off nothing happen. Even on pin 3 on IC there is no rising voltage. Have someone a solution? I have only one change T1 is BC183C and not BC547. Thank you for answer. Regards Kitchi

    • both the circuits should work equally well.

      BC183 is OK and can be used.

      connect a LED in series with the emitter of the transistor or in series its base…when this light up, the triac must go OFF, and vice versa,

      this LED will indicate whether or not your transistor is switching correctly.

      If the LED is not responding ON/OFF or if its permanently ON or OFF would indicate a faulty transistor or wrongly connected transistor..or a faulty IC

    • Hello, suddenly it works. Maybe there was a poor contact. Only one question more. When powering on and the load is on the load (light bulb 20W) is flickering for a 5-10 seconds and volt-meter also is showing ups and downs of the voltage on bulb (very quickly like 2 ups and downs per second) and after 10 seconds bulb is on normally like it should be-no flickering. Could it be defect triac (it is brand new) or voltage at the gate is not ok at startup? Kind regards Kitchi

    • try increasing the value of C2 to may be a 1000uF/25V…this will most probably solve the flickering issue….if that doesn't help increase the value of C4 to 0.47uF/400V

    • Hello. It takes some time sorry, Increasing C2 is not helping, increasing C4 is increasing power voltage more than 15V so Zener diode is limiting the voltage and I thing this is not good because it might be burned someday and the circuit may be damaged. And a little flickering is still there. I think that on the ventilator it won't be so disturbing as on the lamp. I thing I can live with that 🙂 .Thanks for help.

  34. hello mr swagatam,
    how to replaced the ic 4060 with lm555 in this circuit? I want a circuit using lm555 and triac bta25 ? and how to adjust the time ,I need only 10-15 seconds time to run heater and motor?

    • hello, you can use a monostable 555 IC circuit and connect its pin#3 to a triac in the same manner as shown in the first circuit above,

      this set up will allow you to get the required delay as soon as the pin#2 of the IC is grounded via a push button

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