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Automatic Voltage Stabilizer Circuit for TV sets and Refrigerator

Here we will study the design of a simple automatic mains AC voltage stabilizer which can be applied for safeguarding appliances like TV and refrigerators from fluctuating voltages.

A voltage stabilizer is a device which is used to sense inappropriate voltage levels and correct them to produce a reasonably stable output at the output where the load is connected.

How the Circuit Functions

Referring to the figure we find that the proposed automatic voltage stabilizer circuit is configured with the single op amp IC 741. It becomes the control section of the whole design.

The opamp is wired as a comparator, we all know how well this mode suits the IC 741 and other op amps. It’s two inputs are suitable rigged for the said operations.

Pin #2 of the IC is clamped to a reference level, created by the resistor R1 and the zener diode, while pin #3 is applied with the sample voltage from the transformer or the supply source. This voltage becomes the sensing voltage for the IC and is directly proportional to the varying AC input of our mains supply.

The preset is used to set the triggering point or the threshold point at which the voltage may be assumed to be dangerous or inappropriate. We will discuss this in the setting up procedure section.

The pin #6 which is the output of the IC, goes high as soon as pin #3 reaches the set point and activates the transistor/relay stage.

In case the the mains voltage crosses a predetermined threshold, the ICs non inverting detects it and its output immediately goes high, switching ON the transistor and the relay for the desired actions.

The relay, which is a DPDT type of relay, has its contacts wired up to a transformer, which is an ordinary transformer modified to perform the function of a stabilizer transformer.

It’s primary and secondary winding are interconnected in such a manner that through appropriate switching of its taps, the transformer is able to add or deduct a certain magnitude of AC mains voltage and produce the resultant to the output connected load.

The relay contacts are appropriately integrated to the transformer taps for executing the above actions as per the commands given by the op amp output.

So if the input AC voltage tends to increase a set threshold value, the transformer deducts some voltage and tries to stop the voltage from reaching dangerous levels and vice versa during low voltage situations.

220V voltage stabilizer circuit diagram

Parts List
You will require the following components to make this homemade automatic mains voltage stabilizer circuit:
R1, R2 = 10K,
R3 = 470K or 1M, (lower values will enable faster voltage corrections)
C1 = 1000 uF / 25 V
D1, D2 = 1N4007,
T1 = BC547,
TR1 = 0 – 12 V, 500 mA,
TR2 = 9 – 0 – 9 V, 5 Amp,
IC1 = 741,
Z1, Z2 = 4.7V/400mW
Relay = DPDT, 12 V, 200 or more Ohms,

Approximate Voltage Outputs for the Given Inputs

200V ——– 212V
210V ——– 222V
220V ——– 232V
225V ——– 237V
230V ——– 218V
240V ——– 228V
250V ——– 238V

How to Set Up the Circuit
The discussed simple automatic voltage stabilizer circuit may be set up with the following steps:

Initially do not connect the transformers to the circuit, also keep R3 disconnected, and keep the relay disconnected.

Now, using a variable power supply, power the circuit across C1, the positive goes to the terminal of  R1 while the negative goes to the line of D2’s cathode.

Set the voltage to about 12.5 voltage and adjust the preset so that the output of the IC just becomes high and triggers the relay.

 Now lowering the voltage to about 12 volts should make the op amp trip the relay to its original state or make it de-energized.

Repeat and check the relay action by altering the voltage from 12 to 13 volts, which should make the relay flip flop correspondingly.

Your setting up procedure is over.

Now you may connect both the transformer to its appropriate positions with the circuit, and also restore the R3 and the relay connections across their original points

Your simple home made mains voltage stabilizer circuit is ready.

When installed, the relay trips whenever the input voltage crosses 230 volts, bringing the output to 218 volts and keeps this distance continuously as the voltage reaches higher levels.

When the voltage drops back to 225, the relay gets de-energized pulling the voltage to 238 volts and maintains the difference as the voltage further goes down.

The above action keeps the output to the appliance well between 200 to 250 volts with fluctuations ranging from 180 to 265 volts.

242 thoughts on “Automatic Voltage Stabilizer Circuit for TV sets and Refrigerator

  1. hi MR. Swagatam…i'm posting this comment regarding one of your project published in http://www.brighthub.com. the name of the project is "Build a Cell Phone Controlled Door Latch".i still have a few problems while connecting the circuit. so, would you mind helping me solving few problems in completing the project?thanx..

  2. Yes you can ask your questions here right now, or….I'll be posting all my Bright Hub articles
    here, so may be you can wait for some days and put your questions in the relevant article…as you wish.


    1. Dear swagatham sir,
      I'm very happy see people like you and I really appreciate your hard work sir.My requirement is wireless emitting and receiving of power from one place to another place.Distance between the receiver and emitter will be decided later but wireless distribution of power[AC/DC] concept is possible or not sir…
      If so please help me to achieve knowledge on this concept.
      And bye the bye my name is Jithendra Reddy.K from Hyderabad,Andhra Pradesh,India.I'm a Btech. ECE student.
      My mailing address is jithu565@gmail.com.
      First sorry for any gramer mistakes amd THANKS in advance for you sir…..

    2. Thank you Jitendra,

      The concept of transmitting electricity wirelessly is still in the experimental stages, and has not been a 100% success so far….so at our level it's definitely not feasible…small set ups can be tried but it won' be useful unless we are able to transfer significant amount of current across the terminals without using wires.

    1. Hi Abdul,

      If you are using TR2 as 12-0-12 then you can cut the center tap, alternatively you can use TR2 as 0-24V, without a center tap.
      P1 is a 10K preset, linear. You can use any value between 5K and 50K.


    1. Hi,

      TR1 is only for controlling the circuit, so a 500mA transformer is enough, TR2 is the stabilizer transformer which should be a powerful one, a 10 amp will do.


    2. Hi Mikel,

      Yes you can modify TR2 for handling any level of power.
      You will need to modify the relay also along with TR2 for controlling a 1 HP load.
      But the above circuit is a simple design, so please don't except a high degree of stabilization accuracy from it.


  3. Hi Mr. Swagman,

    is there any modification in this circuit if i use a 110V for TR1 and the output of TR2 will be 230V?


    1. Hi Mikel,

      TR1 has no connection with TR2, TR1 is used only for powering the electronic circuit.
      You will need to design TR2 as per your requirement for getting 220v from 110v.


  4. i notice that there is 3 diode in the circuit, but in your list is only two. is it similar diode for the protection of the relay?

  5. Hi Swagatam,

    my transformer is not good. how can i reduced the 16Vdc to my tr1. do i need a regulated power supply?


    1. Hi,

      No problem, you can use the 16v to drive the circuit, just add a 50 Ohm resistor after the input diode, this will control excess current. Don't use a regulated power supply, or else the circuit will fail to sense voltage ups and downs.


    2. No, in series with D1, in between D1's cathode and the circuit positive line, means the voltage has to pass through the resistor before reaching the circuit..

  6. for testing this circuit. do i have to put the positive between R1 and zener diode? and the negative to the cathode of D2 connected to relay?


    1. Hi Swagatam,

      i have a problem with my circuit… i only got 6v in my output that can't trigger the relay. i used 12v relay , 5.6v zener diode, 10K preset.

    2. i am using a 12v transformer…
      12-0-12 750mA

      my power supply is variable regulated to test the circuit, but when i test it in the circuit the output voltage from bc547 is only 6v.

      i check the circuit and it's all in place.

      what would be wrong?


    3. Connect an LED in series with R2, the positive of the LED will go to pin#6 of the IC.
      Now adjusting the preset up/down should switch the LED On and OFF. If this does not happen there might be something wrong with the connections or the IC.
      Do this first then we can proceed further after wards.

    4. the LED goes ON and OFF but it is not to bright… i check the voltage of LED, it's only 2volts. do i have to change the IC or other components? i only got 4.5v going to relay.

      please help…


    5. 2 volts is more than enough for triggering the transistor, in fact transistor requires just 0.6 volts for triggering, the transistor may be faulty or connected wrongly.

      For testing the transistor, remove R2 end from pin#6 and touch it manually to the positive supply, check whether the relay is operating or not.

    6. its working now… i change the transistor.

      AC output when relay is OFF = 248V
      ON = 233V

      is this normal?


    1. Don't you think instead of going into so much of complexity, it would be better if you used a 0-12V transformer? Then you could directly make everything according to the above circuit….

    2. you may incorporate a 12-0-12 transformer but use only the center tap and any one of the other end wires……the other end wire can be left unused.

  7. Hi Swagatam,

    i have a problem when testing the circuit. the relay always activated even i lower down the voltage up to 10V. what could be the problem?

    hope you can help me with this.


    1. Hi,

      Connect an LED in series with R2, it should switch ON/OFF in response to the preset adjustments….proceed next as per the article explanation.


    1. Without base drive no transistor can operate…when you disconnect R2, the base drive is removed, a good transistor will never activate in this situation.

    2. i remove the R2 from pin#6 and put it directly to positive and it energize the relay. but the testing with the LED it's not working. what would be the problem?

    3. what is the pin configuration of the transistor?




      i am confuse because when i search the pin of BC547, i got this two pin layout.

      pls help


    4. Hi Swagatam,

      i already replace BC547 for 3x but it is not working yet. no lit at LED and the relay not energized.

      pls help me with this problem.

      can u give me a PCB layout?


    5. Connect led positive to pin6, connect led negative to a 1K resistor and connect the resistor to ground.
      Now check the led On/OFF switching by adjusting the preset up/down.
      If this does not happen then something's wrong with the connections or the IC.

    6. you will have to undestnad the functioning of an opamp first, when voltage at pin 3 becomes more than pin 2, the output becomes positive and vice versa, it is as simple as that….
      make this happen, if this is not happening then there might be some fault with your connections.

    7. why is it that its working when LED was connected but when i connect the R2 directly to pin#6 the relay was always energized? even i adjust the POT the relay wont de-energized.

    8. It's because of the leakage voltage present at the output of the IC, when an led is introduced, the leakage voltage is blocked by the LED due to its high forward voltage rating.

  8. Hi Swagatam,

    What should I do to prevent the leakage?

    And also, even if our current lowers to around 208v the relay still won't de-energized. Why is that?

    1. Hi,

      You can keep the LED connected with R2 if that is helping to keep the transistor switched OFF.

      The opamp should be set to trigger at around 228volts.

      So below 228 volts the relay will produce a higher voltage at the output which would be around 228+18 = 246, this proportion is maintained for all input voltages below 228.
      If the input voltage exceeds above 228, the relay trips and pulls the output voltage to 228-18 = 210V, this voltage proportion is maintained for all the input voltages above 228.


  9. deva
    i want to know the component across D2 & where is the connection between relay triggering circuit and relay? it looks as if they are isolated

  10. hi,
    u have given that it can operate between 180 t0 265 volts, if u observe it we get 35 volts it can boost & it can buck for 50 volts as 230 volts is the required constant voltage…

    1. Hi it goes like that:

      The opamp should be set to trigger at around 228volts.

      So below 228 volts the relay produces a higher voltage at the output which would be around 228+18 = 246, this proportion is maintained for all input voltages below 228.

      If the input voltage exceeds above 228, the relay trips and pulls the output voltage to 228-18 = 210V, this voltage proportion is maintained for all the input voltages above 228….

  11. pls how do calculate the voltage drop between the zener diode and the resistor at pin#2? and for the comparator does it compare the difference between the inputs and amplify the result??

  12. You can check it with a multimeter by placing the red prod to pin#2 and black prod to the ground. Be sure to keep the meter at the DC volts range above 6 volts.

    The transformer voltage to the opamp varies proportionately with the AC mains variations, which is detected by the opamp and the output is appropriately triggered.

  13. Hi, can u tll me the factor that decides the relay ratings?
    because it should be able to trip or connect the tr2 so if we change tr2 12-0-12v to 9-0-9 v is it necessary to change relay to 9v?

    1. Hi, actually a 2 amp transformer would support only upto 20 watts of load, so I'm afraid it would be useless, at least 5 amp transformer will be required which would support a 50 watt load (appliance).

    2. hi,
      i think as load is connected to 230 volts, 2 amp. transformer should be good enough to take load of around 450 watts.


  14. Hi Eng'r Swagatam,

    what is the difference between 12-0-12 to 9-0-9 for this circuit? why did you change it from 12-0-12 to 9-0-9?


    1. Hi,

      Suppose the relay is set to activate at 228 volts, with 12-0-12 that's equal to 24V , there would be a boost of 228+24=252volts, that's too high.
      Similarly if the relay trips at 225, the cut would be back to 225-24=201V, that's too low.

      Therefore a 9-0-9 is more suitable which would provide a boost and cut within 18 volts range.

  15. balu..
    hi i'm using tr2 of 12-0-12,2A rating and connected the relay triggering circuit first ,but relays starts trips at <12v(say 11.2v)…,did i need to change preset resistor (i'm using 10k) ..since i think ckt needs more than 10k??how much i have to use for the circuit to trip the relay beyond 12.5v

  16. Hi Swagatam,

    i'm done with this circuit but it's not perfect, because i put the LED across R2 and Base of the BC547 permanently to run. and i also reverse the T1, Emitter going to the Coil of the relay and Collector going to diode D1.

    i have another problem because when my local AC goes to fluctuate in range of 227.5~228.5 my Relay keeps on Energized and De-energized, and it is not good because the power going to the output is not stabilized. it will only stop when it reach 227 or 229.

    can you help on how the relay will work perfectly when it reach to critical fluctuation.

    hope to help me with this.

    Thanks and Regards,

    1. Hi Oliveros,

      Connect the transistor exactly as shown in the diagram, reversing will produces entirely wrong results.

      This is a crude type of stabilizer because it uses very few number of parts, so please do not expect high degree of accuracy from it.

      By the way did you follow the setting up procedures, as given in the article??

      Please do everything as suggested in the article and then you can tell me the results.


    2. Hi,

      yes i do all the setup on this article but my problem is when i connect the transistor in original position the relay is always energized. it will not de-energized even my local source is below 225Vac

      Thanks and Regards,

    3. Hi,

      OK please make modifications as given in the new diagram above, this time it should work without fail.

      Holding the transistor with the printed surface toward you, with pins downward, the right lead is the emitter, the center is the base and the left lead is the collector.


  17. Sir,
    I want to make this stabilizer..and i found your article is very helpful.
    Now, i am having some problem with the circuit diagram. Like, which pin of dpdt relay ar connected with the transformer? and in which port of the transformer??
    And i am doing this with 12-0-12/5amp transformer. It has 2 pin in high voltage side, and 5 in low voltage side(like 12V,0V,common,0V,12V), I have to take o/p from two 12V pin..right?? den what will be the return path in secondary??

    1. Hi Suvo,

      Connect exactly as shown in the diagram, see your transformer from top and it can be compared to the diagram, keep the high voltage side toward the right side.

      Join the center two wires of your transformer together, and connect the extreme end wires to the circuit.

      In the diagram, the relay is shown in the N/C position that is in the normally closed position.


  18. Sir, my doubt is still not cleared from your ans.
    I am asking which pin is N/O, N/C and common relay pin in the diagram??
    Or let me make the ans easier for u…the extreme end wires of the transformer (secondary side) will be connected with N/C pins of the relay, right?

  19. hi..
    that new circuit in what way better than old one ..,i'm doing currently old one ,can i continue with old is there any problems?

    1. Hi,

      The difference is that pin #3 of the IC in the new circuit is fixed at half the supply voltage via R1, R3, while in the old circuit it is not accurately set by the zener.
      However the manual setting of the preset anyway adjusts all differences, so it doesn't make much of a difference, both the circuits equally good.

  20. Sir,
    What is the function of D1 here( the left one in the circuit). Coz, I know to be a rectifier at least two diodes are needed..
    And one more question..is it AC or DC powering the control circuit of 12V???

    1. D1 is for rectifying the 12 AC from the transformer and C1 is for filtering, it's a half rectifier which becomes quite equivalent to full wave due to the presence of capacitor C1.
      You can use four diodes for better response.
      The circuit is powered with DC

    1. If 12V corresponds to 220V input, then you can easily calculate what input would produce 12.1V, (which is set as the tripping point of the relay)

  21. hi…sir i connected every thing according to design and problem is around 220v the relay makes nosiy sound (o/p fluctuates more) and i'm not getting the required output…like it boost for 12 v and buck >30 v …please can you tell me where i went wrong ??

    1. Hi,

      You may connect a 100uF/25 cap across the base and the ground of the transistor.

      Please read the article to know the working of the stabilizer, it will not produce 12 boost and 30v buck as you are expecting.

      Do the transformer/relay wiring as shown in the diagram, use a 9-0-9v transformer for TR2.

  22. hi..sir the above circuit worked nice…thanks for the support and someone asked me that in above circuit in TR2 due to series connection of primary and secondary the current will be more in secondary side (for higher load 10A using same rating of tr2 also)…the secondary will burnt out (due to higher ct. in secondary)?? is it true?

    1. Hi Swagatam,

      i make a test on both circuit. it was working when i use a variable power supply but when i connect it in actual power supply TR1 (0-12V, 750mA), TR2 is not connected yet. it won't de-energized?

      what could be the problem?

      Hope to see your reply..

      Thanks in advance,

    2. Hi Swagatam,

      Im using 10k preset.
      My problem was when the relay energized by adjusting preset manualy on a high voltage (230v). It will not de-energized when the voltage goes down to 224v. I have to adjust preset manualy to de-energized the relay, and when the voltage goes high to 230v, i have to adjust the preset again manualy.
      What is wrong with it? Do i have to change preset value or some other ompobents?
      i was testing the modified circuit. The first circuit problem was, there is a delay when im testing it with a variable supply.
      please help me, what i have to do next?


    3. Is your opamp working correctly? This circuit is basically a simple opamp comparator which compares voltages at the pins 2 and 3. voltage at pin 2 is fixed with the potential divider network, now if the voltage at pin 3 goes above the level which is at pin 2, the output would respond.
      Now since opamps are very sensitive they will usually respond with differences of even 1 volt.

      Just check again with a DC variable supply and check at what difference of voltages the relay is tripping? Remove any capacitor if you have connected at the base of the transistor to cancel the delay effect

    4. yes… in variable its about 3volts differences to energized and de-energized the relay. do i have to change my opamp?

  23. Hi,

    Its already fixed. I change the opamp and it running now. Thanks a lot for your support.
    do you have a circuit for protection on overloading for this project?


  24. Thanks sir swagatam… i will just wait you to post the overload protection circuit for this project.

    More power to you!

    1. Actually I am not getting time to update my blog presently, I'll surely do it very soon, please if possible remind me again after a couple of days.

      Thanks and Regards.

  25. Hi swagatam,

    Why is it that my relay is flickering when the voltage is 229-230. I put a capacitor to transistor but the problem is the relay won't energized and de-energized. What should i change to work it perfectly?


    1. Does the positive of the capacitor goes to the positive of the relay coil and the negative of the capacitor goes to the emitter of the transistor?

    1. It can be used for the application, if the relay and the transformer are rated appropriately, however it must be noted that the circuit is very crude and primitive.

  26. Hi Swagatam,

    Thanks for all your effort to help me fixed all the problem. now my voltage stabilizer is running perfectly.
    i am just waiting for your overload protection circuit to be post here.

    Regards and more Power to You,

  27. good working
    I will have a few questions
    how many volts the output voltage when input voltage is 180V
    What is the output voltage deviation
    Did you use a resistor in the relay
    Do you have continuous power at the ends of the relay coil

  28. Hi Mr.Swagatam
    You blog is excellent. No words can Appreciate you enough for the passion and dedication you put here. And regarding the circuit i'm not clear of how TR2 functions can you explain how TR2 function in detail (step by step)so that i can use a Tranny of my choice.

    1. Thank you very much!

      TR2 secondary and primary are wired in such a way that when the relay toggles, the output from the transformer either raises the voltage by 18V or reduces the voltage by 18V depending upon the relay contact position. The value 18V is the voltage rating of the TR2 secondary, which is added or deducted from the mains input for regulating the output voltage accordingly.

    2. Thank you very much, So it means
      1) If the supply is say 220vac and the relay is in n/c position the 220vac passes thro' secondary and by induction from primary it gains an additional 18Volts (ie.,220+18=238vac output).

      2) And if the supply increases say 240vac the relay is in n/o position now the supply passes thro' secondary but in the opposite direction against magnetic induction and so it sheds 18volts (240-18=222vac output) am i correct.

      3)If the above is correct a 6-0-6(0-12) and 12-0-12(0-24)secondary will modify the output by 12V and 24v respectively is this correct.

      4) If so, with proper modification of the voltage comparator and relay can we use a TR2 with multitap sec.

      5) If you could add the Over Load Protection circuit with High(250v)& Low(180v) Voltage Cut-off if possible there can't be anything better than this, it would make this Stabilizer and Ideal One.

    1. Thank you, that is Brilliant and I have never heard of using transformer in such a way until now and I checked the above circuits they were awesome.
      7-Stage Op Amp Controlled Mains Voltage Stabilizer Circuit and 5 KVA to 10 KVA Automatic Voltage Stabilizer Circuit both are same except for the Relay being Replaced by SSR. I have some doubts and i have asked them in the respective posts. Kindly explain them also. Thanks.
      And By the way I'm Parvath from Coimbatore(TN)and I'm a Hobbyist, It a Pleasure to know you.
      With Warm Regard,

    2. Thanks very much.

      I have discussed a few voltage cut off circuits in this blog, you can easily find them by searching them through the above given search box,

      Thanks and Regards,

  29. hello sir Swagatam. I have a problem in my town I have only 190vca or 200 vac I want to know how to raise 220Vac with a transformer, that is the transformer voltage is connected and how? from already thank you very much.
    ATTE: manuel Argentina.

  30. hi swagatham

    i want the circut for connecting the inverter power and mains to the dpdt relay and inverter power should pass to the tube and fans when the main power off

  31. this small voltage stabilizer is for fluctuation b/w 180v to 265v.
    i am asking that what changes we done for fluctuation b/w 120v to 265v to have a constant output 220v when load is there

  32. Hi Mr Swagatm
    Sir I'm new comer to the electronics.so I've to ask you some basic questions about your diagram
    (1) In your circuit, where is the connection point to the centre tap
    of TR2 If not Can I use 18v/230(5A)transformer instead of gaven on
    your diagram? If so why do you say 9v-0-9v/230 transformer?
    (2) There is no sign of the value for P(Preset). How ever can you say
    what is the best value of it?
    (3) In some comments you'd advised to connect some instrument to the
    ground,I don't mind, Do you mean Is it neutral line of main supply
    or ground line of supply?
    (4) In your circuit diagram, there is no sign of ground line . How I
    connect my refrigarator to the ground line after connect the
    stabilizer to avoid shock?

    1. 1) 18V transformers are normally not available therefore I mentioned 9-0-9v which are easily available. 0-18V will do as there's no center tap used here.

      2) A 10K preset can be used for P1.

      3) Instruments?? Is it DMM you are referring to? It must be connected to the negative of the power supply and not to the neutral.

      4) The metallic enclosure that you would use for the circuit will become the ground or the "earth" connection which should be linked with the respective earth pins of the 3-pin sockets.


    2. Hi Mr Swagatm
      Thank you very much for your reply to my questions First

      In question no3 by mistake I entered the word "Instruments" It must be corrected to the word "component" I mean capacitor, resistor etc…
      According to my knowledge there are two negative lines in the circuit One is AC-main supply's negative (We called it neutral) Other is TR1's output negative.
      However I can understood your reply. I thought it is TR1's output negative ok! Am I correct? If not correct me
      Thank you very much Mr Swagatam.

    3. Hi….

      The line to which pin#4 of the IC is connected is the negative of the circuit.

      The mains AC lines have no connection with the circuit, it's solely meant for the appliances.


  33. hello sir I have a problem I have only 160vca stress and want to upload a transformer 220vac 12 +12 x 10 amp. I connect the wires? for 220vac on output. thank you very much. jose

  34. how do I raise the voltage of 160 VAC to 220 VAC with a transformer, as I have to set the transformer de transformer is 12+12v


    1. you will need a 25-0-25 transformer. Connect the one of the secondary wires with one the primary wires, apply mains to the primary wires, and measure the voltage across the free secondary wire and any of the AC mains inputs.

      If you find reduction in the voltage by 50 V, just switch the secondary wire connection to the other primary wire, this time you will get a +50V boost across the free secondary wire and one of the AC inputs.

  35. hello sir I have a problem I had designed all the circuit according to your schematic but i could not understand th relay connections.
    plz make the connections easier to understand

    1. You can see three small circles, two on one side and one on the other side.

      The two circles at the left side are the N/C and N/O contacts. The upper circle is the N/C while the lower one is N/O.

      The single circle at the right is the movable pole contact.

      In the figure the upper circle is connected with the pole.

      There are two sets of the above contacts as shown in the figure.

      Both the sets move simultaneously and is controlled by a single coil which is connected to the transistor.

    2. Hello Swagatam,
      I had knowlegde about tha relay contacts as u told as above but i have a confusion that which point is linked or connected to which contact???
      Kindly provide us point configuration on relay connections according to your circuit diagram. We have followed the connections that you have shown in ur schematic diagram but we remain unable to get the required output and our transformer got heated

  36. Sir so if i use 30amps relay do i still need a contactor? do i need a 12 volts regulator or do i power the circuit directly from the rectifier circuit. or is they any circuit you can refer me to for more efficiency, and can i use 1amp instead of the 500ma. thanks for your quick response.

    1. OK, if you are using a contactor then no need of using a 30 amp relay, a contactor is perfect for actuating a motor

      ……then there shouldn't be any problem……????

  37. kindly explain how l can use this site to send my circuit to you or send me your e-mail so that l can send it as attachment. THANKS FOR ALL YOUR EFFORT IN DEVELOPING PEOPLES KNOWLEGDE IN ELECTRONICS. ladipo K.O (fut, Akure, Nigeria)

  38. We have varying ac input (ranging from 10-18V and current 50-100mA). We want to stabilize this fluctuation. Can we use this circuit ?. If we use this circuit what modifications do we need in this circuit ?
    Sir, Please help me..

  39. the project is either adding +12 volts or deducting it in the output, what will happen if the power supply is at its normal value (exactly 220 volt)?

  40. Sir i have a voltage fluctuation problem at my house so my 18 watt tube gets blown off again and again in short period of time so i wanted to know is there any modification to be done in the Electronic ballast for protection such as a fuse or something like that?? Please suggest me sir….

  41. hi sir i build this circuit but it don't work sir i connected everything properly,sir you show T2 as a centertap 9-0-9 but in the circuit it don't connect to anywhere please i need your help sir thank you.How to Make a Small Homemade Automatic Voltage Stabilizer for TV sets and Refrigerator

    1. Hi zinnaboy, T2 is a 0-18v trafo which can be achieved by using a 9-0-9 trafo with center tap shorted. the center tap does not connect anywhere.
      The circuit will definitely work if the settings are done correctly, and if the circuit is built without errors.

  42. Hi sir i forgot something so the 2 relay have to switch same time when the circuit is power? (2nd)question please where is the relay coil i can only see 1 coil or its should be ignore (3rd)question can i set the circuit without variable power supply? thank you sir please don't ignore my question stay bless.

    1. Hi zinnaboy, yes both the relays should operate together, preferably it should be a DPDT type meaning a relay having double sets of contacts but a single common coil. That's why you can see only one coil.

      If you want to use two separate relays then you can simply connect both the coils parallel with each other across D2

      You cannot set it without a variable power supply. It will be required.

  43. hello mr swagatam, I'm looking to make a very high power voltage regulator, DC to DC. the required voltage is nearly 380 (moteur triphasé), any advices or simple shematic that could help. thank you

  44. hello my name is ariel of buenos aires Argentina. can you help me?
    in my area there are always low voltage 185 / 190vca .. I have a transformer 12v x 10 amps .. the question is: how I can connect to climb a little tansion …
    from already thank you very much.
    ATTE. ariel from Argentina.

    1. hello ariel, your transformer will produce an increase of only 12V, meaning if the mains level is at 185, adding your trafo voltage will make it just 185 + 12 = 197V

      Buy a 12-0-12V/10amp trafo, this will boost the voltage to a useful level…i'll explain you how to do once you get it.

    1. Muzamil, yes you can use the above shown circuit for safeguarding TV, fridge etc, but the transformer TR2 will need to be upgraded as per the load amp rating.

  45. HI Mr.Swagatam Majumdar how are you,
    You have good experience in electronics,I need hex cod pic 16f676, 5 step automatic voltage stabilizer with circuits diagram.I will be very thank full to you.

  46. I have a stabilizer of 1KV of output Voltage Range of 220-240,but of late it produces output range of 250 -260…..why and how can i cure it…plz help

    1. it could be happening due to any of the two reasons, either you have changed your battery with a new one and therefore the full charge of the battery is causing the extra voltage or the internal voltage correction setting is disturbed due to some reason…you can also check with a some kind of load connected and see if the voltage drops…

  47. sir i am having trouble connecting relay to the circuit.. i have dpdt 8pin relay and its pin configuration. sadly i cant get to wire it correctly can you please simplify by telling the connection scheme..like the collector of transistor is connected to COIL OF relay…
    2) how can i use 2 SPDT relays 5 terminals instead of 1 DPDT 8terminals

    1. Asim, if you want to use 2 SPDT relays, then you just have to connect the relay coils of both the relays in parallel across the collector/positive line as shown in the diagram.

      as for the contacts, first identify the N/C, N/O and pole of the two relays, then simply join their N/C, N/C….N/O, N/O, and pole, pole together, and finally wire the common ends of these contacts to the transformer as indicated in the diagram.

    2. when i am trying to calibrate the cicuit the relay is flickering even on 11-13v supply and the preset seems to be not doing anything at all
      please elaborate the callibration process please

    3. keep the relay disconnected while calibrating, use an LED indication instead, for fixing the cut-off threshold, once the setting up is completed you can connect the relay back

      keep R3 disconnected while calibrating, reconnect it once the calibration is done.

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