Wednesday, April 11, 2012

How to Make a Simplest Triac Dimmer Switch Circuit

We have already seen in many of my earlier articles how triacs are used in electronic circuits for switching AC loads.
Triacs are basically devices which are able to switch ON a particular connected load in response to an external DC trigger.
Though these may be incorporated for complete switch ON and complete switch OFF procedures of a load, the device is also popularly applied for regulating an AC, such that the output to the load may be reduced to any desired value.
For example triacs are very commonly used dimmer switch applications where the circuit is designed to make the device switch in such a manner that it conducts only for a particular section of the AC sine wave and remains cut OFF during the remaining parts of the sine wave.
This result is an corresponding output AC which has an average RMS value much lower than the actual input AC.
The connected load also responds to this lower value AC and is thus controlled to that particular consumption or resultant output.
This is what exactly happens inside electrical dimmer switches which are normally used for controlling ceiling fan and incandescent lights.

Simple and the Best Triac Dimmer Switch Circuit

The circuit diagram shown above is an classic example of a dimmer switch, where a triac has been utilized for controlling the intensity of light.
When AC mains is fed to the above circuit, as per the setting of the pot, C2 charges fully after a particular delay providing the necessary firing voltage to the diac.
The diac conducts and triggers the triac into conduction, however this also discharges the capacitor whose charge reduces below the diacs firing voltage.
Due to this the diac stops conducting and so does the triac.
This happens for each cycle of the mains AC sine wave signal, which cuts it into discrete sections, resulting in well tailored lower voltage output.
The setting of the pot sets the charge and the discharge timing of C2 which in turn decides for how long the triac remains in a conducting mode for the AC sine signals.
You might be interested to know why C1 is placed in the circuit, because the circuit would work even without it.
It's true, C1 is actually not required if the connected load is a resistive load like an incandescent lamp etc.
However if the load is an inductive type, the inclusion of C1 becomes very crucial.
Inductive loads have a bad habit of returning a part of the stored energy in the winding, back into the supply rails.
This situation can choke up C2 which then becomes unable to charge properly for initiating the next subsequent triggering.
C1 in this situation helps C2 to maintain is cycle by providing bursts of small voltages even after C2 has completely discharged, and thus maintains the correct switching rate of the triac.
Triac dimmer circuits have the property of generating a lot of RF disturbances in the air while operating and therefore an RC network becomes imperative with these dimmer switches for reducing the RF generations. The above circuit is shown without the feature and therefore will generate a lot of RF which might disturb sophisticated electronic audio systems.
The circuit of a dimmer switch illustrated below incorporate the necessary precautions for subsiding the above issue.




Parts List for the above enhanced fan dimmer circuit

C1 = 0.1u/400V
C2, C3 = 0.1/250V,
R1 = 15K,
R2 = 330K,
R3 = 33K,
R4 = 100 Ohms,

VR1 = 220K, linear
Diac = DB3,
Triac = BT136
L1 = 40uH

75 comments:

  1. Dear swagtam, I am looking for a fan dimmer switch, mostly a light dimmer are available. A light dimmer cannot work properly if we control a ceiling fan. Can you please give me some suggestions.

    ReplyDelete
    Replies
    1. Hi,

      you can build the last circuit shown above.
      C1 = 0.1u/400V
      C2, C3 = 0.1/250V,
      R1 = 15K,
      R2 = 330K,
      R3 = 33K,
      R4 = 100 Ohms,
      Diac = DB3,
      Triac = BT136
      L1 = 40uH

      Delete
    2. Sir, if we are to estimate the firing angle of triac, would C2 be sufficient or parallel combination of c1 and c2 ?

      Delete
    3. I built both previous circuits; none of them works. Not even as a light dimmer. Sorry for being direct.

      Delete
  2. hay Swagatam

    this looks awesome!! is there a way to incorporate a soft start?

    thanx again!!

    ReplyDelete
    Replies
    1. Hi Louis,

      Thanks!

      A soft start can be included here, but the modifications would make the circuit quite complicated.

      Delete
    2. Can the scheme for soft start to 2200W

      Delete
    3. yes it can be modified for this

      Delete
  3. Hello Swagatam

    I have a 20 liter electric storage water heater which has a 230V AC, 2KW electric heating element. The heating element is failing frequently primarily due to bad quality of water inducing faster corrosion of heating element. I decided to experiment with the current to increase the life of heating element. I want to limit the heating to about 80% of normal so that heating element runs at slightly cooler temperatures.

    I have BTA41-600B 41Amp Triac available to me. This triac has sufficiently high current rating for a 2KW coil. Two options come to my mind.

    1. Buy a electric fan speed regulator. These are available cheap and in plenty. Open the enclosure, identify the triac in the circuit and just replace the triac with BTA41-600B. The question is will this work? I am an electrical Engineer and I do build small electronic circuits on my own, but I have never built a circuit involving Triac.

    2. The other option is to build a simple circuit with a preset resistance connected to the gate. But what should be the rating of this preset resistance?

    There is one more question. Should I need to use a heat sink for this application?


    ReplyDelete
    Replies
    1. Hello Jaydeep,

      Modifying a fan speed controller would be a better idea. However you will need to replace the diac also along with the triac. The diac also needs to be equally powerful in order to support the triac gate current.

      Heatsink is a MUST for your application, make it as big as possible.

      Delete
  4. Hi Swagatam,

    I want to use the dimmer circuit above to to dim a LED light bulb. I will have
    120 v as input and want to control the dimmer with software through an Electric
    imp device which puts outputs 3.3v max as a trigger. I have this currently
    working with a relay that is triggered with the 3.3v output. My question is where
    can I put my 3.3 v trigger leads from the imp in your circuit?

    Thanks

    Charlie

    ReplyDelete
    Replies
    1. Hi Charlie,

      I am afraid you cannot use a triac dimmer for controlling an LED bulb because it's an capacitive/inductive load, not recommended to be used with triac dimmers.

      Any way there's no harm in trying, you will have to employ a handmade LED/LDR opto-coupler sealed inside a light proof box.

      The LED terminals should be connected to the 3.3V source possibly through a series resistor,and the LDR terminals should be connected across RV1 points, RV1 may be removed completely (in the first diagram).

      The series resistor value with the LED will decide the intensity of the LeD bulb, in other words,the intensity of the LED will be directly proportional to the intensity of the LED bulb.

      Delete
    2. Why the need for the LED/LDR opto-coupler?

      Delete
    3. The dimmer works on AC mains, while your trigger is from a low voltage DC source, the two mediums are not compatible, therefore the need of an opto...

      Delete
  5. hi sir, can i use this cercuit for charger trasformar praimary ac volt control, because the ac line voltage is up and down.i want to fix this problem by this cercuit. i want to charge my led battery conostant volt by controling ac volt. please solv my problem.oh my transformar is 15volt dc,210volt ac, 50amp. thank you

    ReplyDelete
    Replies
    1. Hi Rahamania,

      Yes you may do it....but that's not the right way of getting constant DC, in fact it won't help.... you should use voltage regulator IC with your transformer power supply such as LM317 or LM338.

      Delete
  6. ok thank you sir for your coments, but sir i want to control dc side voltage from transformar ac input side for my project benifite. plese help me sir, if i control transformar ac side input then i shine my project.make any diagram for me and my project. please answer me shortly. thank you sir.

    ReplyDelete
    Replies
    1. OK then you can make the circuit given in the above article, it'll be perfect for your project.

      Make the first circuit.....

      Delete
  7. Sir, please see the cercuit diagram of Indian Bimtex invarter cercuit diagram then publish their only charge option. how can charge that cercuit to battery conostantly.Please Sir, that diagram is very importat for me. i am waiting for your answer. thank you.

    ReplyDelete
  8. Sir, what is face control battery charger? Bimtex is apply this formula. Sir, i have no link for Bimtex diagram. Just i bought that cercuit from market and use. So i want to make same cercuit. i make drivar and power section but can not draw their chargeing site. So you are my last direction. Bimtex apply face contro system for charge led acid battery and it is very nice because i use this cercuit. I think they use scr tyn612m + 4n35 etc. please make any diagram like this for me. thank you

    ReplyDelete
    Replies
    1. I researched about phase control battery charger circuit but could not find any such circuit online. There are scr controlled battery charger circuits available but they require transformer and bridge rectifier for stepping down the mains AC.

      I'll try to design a compact one.... if it's feasible I'll inform you.

      Delete
    2. Hi Swagatam,
      am doing project on automatic speed control of ceiling fan depending on temperature. am an engineering student. can help me abt circuit and all. please...

      Delete
    3. Hi Anil,

      Yes I can design this circuit for you, but it might take a little time because presently I am busy with some other assignments.

      Delete
  9. Sir, can i use an alternative for triac instead of TIC226? if yes, what kind of triac can I use?

    ReplyDelete
  10. thanks so much! you are really a big help.

    ReplyDelete
  11. Hi Swagatam,

    can you do a circuit using triac and incorporate it to a 24 hrs timer to turn off the airconditon 1Hp?

    Regards,
    Mike L

    ReplyDelete
    Replies
    1. Hi Mike,

      I have discussed a few long duration timer circuits in this blog, these can be simply used with a triac for acquiring the required functions....I may possibly discuss it in a new post soon.

      Regards.

      Delete
    2. Thanks Swagatam...

      Delete
  12. Hi



    Im trying to build a circuit that can dimm LED lamps from 230 mains voltage. The triacs leading edge I have found causes overshoots and spikes in voltage and current which destroy LEDS due to the sharp rise times in voltage.
    I was using inductive, capacitive and resistive Ballasts to drop the voltage down enough to rectify and smooth.
    The only circuit that looks like working is the resistive ballast, Im using 1 smoothing capacitor after rectification.
    From simulation in LTspice the current drops nicely and almost linearly as i change the firing times of the triac.

    Would you have any ideas on how to get around the problems with the inductive/capacitive ballasts ?

    I thought your circuit would work until I read the comments

    thanks for your time

    best

    sct

    ReplyDelete
    Replies
    1. Hi, you can probably try a simple PWM controlled triac drive circuit using the ubiquitous IC555.

      please check out the last diagram in the following link:

      http://homemadecircuitsandschematics.blogspot.in/2012/12/high-current-triac-bta41600b-datasheet.html

      Delete
    2. Hi Swagatam

      Thanks for the advice, going to check the link right away.

      slainte

      Delete
  13. Hi Swagatam Majumdar

    that's a very good circuit, i was looking for a cheap method to reduse speed of a washing machine motor. The motor is AC with bruses there is no label on it, i need it for other use (Easter in Greece to be rotated five lambs) for example as i calculate it must have 30 rpm maybe less. So i need help if this is possible and what i will need to built it.
    Thank's in advance.

    ReplyDelete
    Replies
    1. Hi Nick, thanks!

      you may build the first circuit, if your motor is mains AC operated then the circuit will surely work with it.

      You may use a BT136 triac if the shown type is unavailable.

      Delete
  14. Hi Swagatam
    i was thinking how can i reduse speed of a washing machine motor i need it for other use (╬Ľaster in Greece, it will turn lambs) so i need very low speed 30 rpm or less. Can i use this circuit, is this possible and what i will need to use

    Thanks in advance

    ReplyDelete
    Replies
    1. Hi Nick, the above circuit will work for all mains operated AC motors, so you can use it for controlling a washing machine motor too.

      Delete
  15. Hi Swagatam!
    Can you please give us the power of the resistors of your circuits (e.g. 1/2 Watts, 18/ watts e.t.c.).
    Thanks in advance,
    Mitsos

    ReplyDelete
    Replies
    1. Hi Dimitris,

      all are 1/4 watt CFR rated....

      Delete
    2. Dear Swagatam,
      Thanks for the quick reply.
      I implemented your first circuit, with the following changes:
      - The potentiometer is 200K (two 100K in series) instead of 220K.
      - I didn't put a inductor.
      Unfortunately, it doesn't work.
      The DIAC is DB3TG 32V.
      I tried two TRIAC models: The Phillips BT131 800V 1A TRIAC, and the Littlefuse Q6012LH1LED HiCom (snuberless) TRIAC.
      In both cases, the TRIAC always conducts, and the sine wave on the oscilloscope is always full. I also tried different combinations of resistance.
      Moreover, I tried the simple circuit with only one firing capacitor. In this case, when I connect the power plug to the power socket correctly (L-L / N-N), the TRIAC is always ON. When I connect the power plug in reverse (L-N, N-L), the TRIAC is always OFF.
      Have you any idea of what might go wrong?
      The load is a simple 15W incandescent lamp. I implement the circuit on a breadboard. All connections tested extensively.
      Thank you in advance.

      Delete
    3. Dear Dimitris,

      Try the second circuit, it has been tested by me not once, but many times.

      R1 = 15K
      R2 = 330K
      R3 = 22K
      VR1 = 220K
      diac resistor = 47 ohm
      diac = DB-3
      Triac = BT136 or equivalent.
      C2, C3 = 0.1uF/250V
      C1 = 0.1uF/400V

      The first circuit is also correct and should have worked... anyway you may try the second one, will 100% work.

      Delete
  16. hi. I need to control welder output (50VAC-max 200A) help me pls. Thx

    ReplyDelete
    Replies
    1. what do you want to control voltage or current?

      Delete
  17. current please if its possible. Thank u.

    ReplyDelete
  18. hi. i want to control output current to adjusting welder. Sorry my english not well. Thx

    ReplyDelete
  19. current in ac circuits would be difficult to control without trasformer, if it would be a DC circuit then it could have been possible.

    ReplyDelete
    Replies
    1. i need to control kitchen machine ac motor 220/600w/60hz with 6 speed are above circuit do it or please tell me how to do it

      Delete
    2. plese, need to control kitchen machine 230/6oow/60hz need the circuit to control

      Delete
    3. Try the second circuit given in the above article.

      Use the following parts:

      R1 = 15K
      R2 = 330K
      R3 = 22K
      VR1 = 220K
      diac resistor = 47 ohm
      diac = DB-100
      Triac = BTA41/600.
      C2, C3 = 0.1uF/250V
      C1 = 0.1uF/400V

      Delete
    4. are this componant work with ac motor 600w 60hz

      Delete
  20. Very interesting article..
    I would like to know, how are the values calculated for R & C in case of ac motor dimmer? Please provide some link or doc which explains the calculation part in detail, if you have..

    Thanks..

    ReplyDelete
    Replies
    1. thanks, i don't know about the formula, but the diac is the center of focus here.

      It requires around 30V to fire....by determining how quickly it reaches the 30V mark alternately, we decide for how long the triac can remain switched ON for each cycle.

      the firing timing of the diac is controlled by the various timing components in the form of resistors and capacitors whose vales are appropriately chosen for the implementations.

      Delete
  21. Hi Swagatam, I want to create a dimmer switch for 3 series light bulbs 50W each, can I use this same circuit? Thanks in advance. By the way, this is a very good article, I've been searching for other circuit, and this is the best and very informative one.

    ReplyDelete
    Replies
    1. Hi Joana,

      Yes you can the same circuit for 3 bulbs in series, however putting bulbs in series will make their brightness low.

      Delete
    2. Hi, thank you for your very quick reply, what if I make the connection of the bulbs parallel? Also will it last for long hours? I plan to install it permanently on my house. :D

      Delete
    3. yes putting them in parallel would be the correct approach, however the triac won't hold more than 200 watts without heatsink, and 500w with heatsink attached, so be careful about that.

      if the above parameter is taken care of then it would be a permanent thing, no issues ;)

      Delete
  22. 1500w grinder machine to can i use bta 24 triac?

    ReplyDelete
  23. need to work with ac 600 watt 60hz ac motor use BTA40/600 or what

    ReplyDelete
  24. i want to control Tubelight with TRIAC switch. Is possible?
    i am going to connect the gate of the TRIAC to Arduino Board..
    Is possible? Reply me

    ReplyDelete
  25. Hi Sir -

    I would like to use a dimmer type switch to control the input from the main of a transformer which is rated at 2500W at 20amps.

    Would this circuit work & how would I spec out the components properly? Any help would be greatly appreciated.

    ReplyDelete
    Replies
    1. Hi Brad,

      You can try the second circuit, with the following pats:

      R1 = 15K
      R2 = 330K
      R3 = 22K
      VR1 = 220K
      diac resistor = 47 ohm
      diac = 100mA big diac
      Triac = BTA41/600.
      C2, C3 = 0.1uF/250V
      C1 = 0.1uF/400V

      Use a large heatsink for the triac.

      Delete
  26. Hello,
    I would like to implement your dimmer switch circuit but on an 120 V AC line at 60 hz for incandescent bulbs. What values should I use for the resistors, pot and capacitor?

    Thank You

    ReplyDelete
    Replies
    1. hello, you can use the same circuit for both 220v and 120v 50hz/60hz supplies

      Delete
  27. Please design a very simple ceiling fan dimmer circuit without L1 = 40uH parts.

    ReplyDelete
    Replies
    1. you can remove the inductor, it's for suppressing noise from getting into MW receivers which are no longer used today.

      Delete
  28. hi if i remove L1 = 40uH from the 2nd circuit diagram, can it use as ceiling fan dimmer?

    ReplyDelete
  29. I burned 5 Triacs because of miss rate of C1. It works fine in 110v (if it's not working, you are doing something wrong, or your triac is already fried). But in 220v, I believe that C1 must be 600v or above.

    ReplyDelete
    Replies
    1. C1 has no relation with the triac, so the triac will not burn due to its ratings....if at all anything burns it will be the capacitor itself.

      Delete

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