Automatic Voltage Stabilizer Circuit for TV sets and Refrigerator

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.
Here we will study the design of a simple automatic mains AC voltage stabilizer which can be applied for the above purpose.

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 IC 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,
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

INPUT------OUTPUT
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.

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.

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.


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233 comments

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Anonymous
December 20, 2011 at 1:28 PM delete

hi MR. Swagatam...i'm posting this comment regarding one of your project published in 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..

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December 20, 2011 at 1:31 PM delete

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.

Regards.

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January 12, 2012 at 6:52 PM delete

what are the specification of TR2?
if it is a step transfomer then how can it steps up the i/p voltage when i/p is greater than 230V?

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January 12, 2012 at 7:09 PM delete

Hi Abdul,
TR2 is 12-0-12V sec./230V or 120V prim. 5 Amps, the entire functioning has been explained in the article, kindly go through it once again.
Regards.

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January 16, 2012 at 11:14 PM delete

what is the P1 & its value? is it our own choice? 10k can used or not?

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January 17, 2012 at 12:59 PM delete

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.

Regards

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January 22, 2012 at 5:54 PM delete

preset is a three terminals..how many terminal are used here?all 3 or 2??

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January 22, 2012 at 6:07 PM delete

yes it's a three terminal, all the three terminals are used here.

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Anonymous
March 24, 2012 at 1:57 PM delete

Hi Sir Swagatam... Can i use 3amp and 10amp for TR1 and TR2?

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March 24, 2012 at 4:32 PM delete

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.

Regards.

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Anonymous
March 25, 2012 at 1:33 PM delete

even a higher AMP for TR2 is possible?

thank you very much and more power to you.

MikeL

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Anonymous
March 25, 2012 at 1:39 PM delete

can i use this for a 1hp aircon?

thanks...

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March 25, 2012 at 2:06 PM delete

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.

Regards.

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Anonymous
March 25, 2012 at 7:13 PM delete

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?

Thanks...
MikeL

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March 25, 2012 at 9:09 PM delete

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.

Regards.

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Anonymous
March 29, 2012 at 1:03 PM delete

Hi Swagatam,

waht is the value of zener diode?

thanks...
MikeL

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March 29, 2012 at 1:36 PM delete

You can use any value between 3 and 6 v.

Regards.

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Anonymous
March 29, 2012 at 3:08 PM delete

what is the value of the zener diode?

thanks...

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Anonymous
March 30, 2012 at 2:12 PM delete

what about the DPDT relay? is it 8pins?

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March 30, 2012 at 2:13 PM delete

Yes it's a DPDT relay with 8 pins....

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Anonymous
March 30, 2012 at 2:34 PM delete

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?

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March 30, 2012 at 3:14 PM delete

Yes all three diodes barring the zener diode, are all 1N4007...

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Anonymous
April 3, 2012 at 4:08 PM delete

Hi Swagatam,

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

thanks...

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April 3, 2012 at 5:17 PM delete

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.

Regards.

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Anonymous
April 3, 2012 at 5:48 PM delete

thanks a lot mr. swagatam...

more power to you

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Anonymous
April 3, 2012 at 5:56 PM delete

how many watts of 50 ohm resistor?

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Anonymous
April 3, 2012 at 6:26 PM delete

is it parallel after D1?

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April 3, 2012 at 7:42 PM delete

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..

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Anonymous
April 3, 2012 at 9:35 PM delete

ok sir thanks...

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Anonymous
April 3, 2012 at 9:48 PM delete

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?


thanks...

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April 3, 2012 at 10:01 PM delete

No, across the preset, as explained in the article.

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Anonymous
April 4, 2012 at 2:23 PM delete

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.

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April 4, 2012 at 3:01 PM delete

The relay voltage should match the transformer voltage otherwise it won't operate....so please use a 12 transformer.

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Anonymous
April 4, 2012 at 3:12 PM delete

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?

thanks...

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Anonymous
April 4, 2012 at 3:16 PM delete

do i have to change the value of the preset? because i only got 6v maximum...

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April 4, 2012 at 4:18 PM delete

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.

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Anonymous
April 4, 2012 at 7:03 PM delete

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...

thanks

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April 4, 2012 at 7:46 PM delete

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.

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April 4, 2012 at 7:48 PM delete

please also check the supply voltage to the circuit, is it 12 volts?.....

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Anonymous
April 4, 2012 at 10:57 PM delete

its working now... i change the transistor.

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

is this normal?

Thanks...

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April 5, 2012 at 8:33 AM delete

Compare it with the input AC, the output should lie within 205 to 250 at input extremes of 180 to 275v...

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Anonymous
April 5, 2012 at 11:08 AM delete

What should I do if the input is 238 and the output of the automatic voltage stabilizer is 268?

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April 5, 2012 at 11:46 AM delete

Adjust the preset such that the relay operates at around 225 input volts...

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Anonymous
April 5, 2012 at 2:33 PM delete

Hi Mr Swagatam,

Can i use 24v relay for this circuit? is there any modification?

Thanks

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April 5, 2012 at 2:46 PM delete

Yes, but the transformer will also need to be of the same voltage.

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Anonymous
April 5, 2012 at 3:31 PM delete

only the TR1 is to be replaced to 24-0-24 or 0-24, the circuit is the same?

thanks...

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April 5, 2012 at 5:32 PM delete

0-24v will do, but the IC pin 7 will need a regulated power from a 7812 IC

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Anonymous
April 5, 2012 at 9:58 PM delete

do you have the circuit for this type of power supply? how will i integrate it to the existing circuit?

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April 6, 2012 at 8:32 AM delete

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....

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April 6, 2012 at 8:34 AM delete

I would suggest you to use a 12v relay and a 0-12v transformer

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Anonymous
April 6, 2012 at 8:52 AM delete

can i use 12-0-12 transformer for the supply or just 0-12?

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April 6, 2012 at 9:01 AM delete

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.

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Anonymous
April 9, 2012 at 4:42 PM delete

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.

Regards

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April 9, 2012 at 5:07 PM delete

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.

Regards.

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Anonymous
April 9, 2012 at 6:28 PM delete

Hi,

even R2 is not connected the relay is activated...

is pin 1,5 and 8 of ic 741 is not connected?

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April 9, 2012 at 6:34 PM delete

The transistor is either faulty or wrongly connected, please check it.

pin1,5,8 of the IC are not used, N/A pins.

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Anonymous
April 9, 2012 at 6:42 PM delete

i already check the transistor, it's good... 1-collector 2-base 3-emitter

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April 9, 2012 at 7:47 PM delete

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.

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Anonymous
April 9, 2012 at 9:15 PM delete

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?

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Anonymous
April 9, 2012 at 9:21 PM delete

what is the pin configuration of the transistor?

1-collector
2-base
3-emitter

or

1-emitter
2-base
3-collector

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

pls help

thanks

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Anonymous
April 10, 2012 at 8:09 AM delete

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?

thanks

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April 10, 2012 at 10:03 AM delete

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.

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April 10, 2012 at 10:06 AM delete

hold BC547 with print side facing you....
In this position, the right side pin is emitter, center is base and the left side pin is collector.

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April 10, 2012 at 10:16 AM delete

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.

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Anonymous
April 11, 2012 at 8:09 PM delete

thanks a lot Mr. Swagatam... it is working now

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Anonymous
April 13, 2012 at 8:16 AM delete

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.

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April 13, 2012 at 9:15 AM delete

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.

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Anonymous
April 13, 2012 at 10:45 AM delete

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?

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April 13, 2012 at 10:58 AM delete

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.

Regards.

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Anonymous
April 13, 2012 at 7:43 PM delete

Thanks a lot!

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Anonymous
April 14, 2012 at 4:42 PM delete

deva
hi,
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

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Anonymous
April 14, 2012 at 5:06 PM delete

hi swagatam,
how much costly this project???

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April 14, 2012 at 8:50 PM delete

Hi,

It's the relay coil, when it gets switched by the transistor, the attached contacts get energized.

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Anonymous
April 20, 2012 at 5:37 PM delete

Mr Swagatam I want to know the function of each of the components used in the construction.

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April 20, 2012 at 6:47 PM delete

I've already explained it in the article.

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Anonymous
April 23, 2012 at 3:45 PM delete

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...

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Anonymous
April 23, 2012 at 3:55 PM delete

can we use 15:0:15 transformer (TR2)

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April 23, 2012 at 8:25 PM delete

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....

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April 23, 2012 at 8:26 PM delete

No, 15-0-15 would make it a 30volt boost/cut, that's too high, use 9-0-9 only.

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Anonymous
April 25, 2012 at 10:25 PM delete

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??

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April 26, 2012 at 7:41 AM delete

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.

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Anonymous
April 27, 2012 at 1:37 PM delete

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?

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Anonymous
April 27, 2012 at 1:39 PM delete

hi...if i want in range 220 to 230v output ..what should we change in circuit?

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April 27, 2012 at 1:42 PM delete

prabhu..
hi...if i use tr2 ampere rating 2A is there any problem to circuit..?

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April 27, 2012 at 2:40 PM delete

No problem, you may use it.

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April 27, 2012 at 2:41 PM delete

It will require a more sophisticated circuit with more number of relays

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April 27, 2012 at 2:44 PM delete

Hi,

TR2's voltage is meant for the output load and has no connection with the relay coil voltage, the coil voltage should match TR1 voltage rating

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Anonymous
April 27, 2012 at 7:27 PM delete

prabhu
hi.. can you just tell me what r application of 2A rating TR2 if we use ,like for in home appliances ?

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Anonymous
April 28, 2012 at 8:26 AM delete

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?

Tnx,

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April 28, 2012 at 9:16 AM delete

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).

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April 28, 2012 at 9:29 AM delete

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.

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Anonymous
April 28, 2012 at 11:40 AM delete

Hi,

thank you much for the explanation.

Regards

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Anonymous
April 28, 2012 at 3:51 PM delete

hi..
Can we need check polarity for the tr2?

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April 28, 2012 at 5:20 PM delete

Hi,

Connect the prim/sec wires of TR2 exactly in accordance with the diagram, otherwise it would give results.

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April 28, 2012 at 5:21 PM delete

.....otherwise it would give wrong results

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Anonymous
April 28, 2012 at 7:05 PM delete

Thanks for the reply. but i meant calculations

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Anonymous
April 28, 2012 at 9:48 PM delete

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

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April 29, 2012 at 8:39 AM delete

Follow the steps as given in the article, preset value does not require any modification.

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Anonymous
April 29, 2012 at 10:18 PM delete

hi..
instead of preset resistor ,can i use same rated POT to vary resistance?

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Anonymous
April 30, 2012 at 4:36 AM delete

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,
Oliveros

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April 30, 2012 at 9:04 AM delete

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.

Regards.

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April 30, 2012 at 9:07 AM delete

A Pot can easily get disturbed by external vibrations in the long run so a preset is preferred which is more rigid.

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Anonymous
April 30, 2012 at 11:18 AM delete

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,

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April 30, 2012 at 12:02 PM delete

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.

Regards.

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May 2, 2012 at 12:36 PM delete This comment has been removed by the author.
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May 2, 2012 at 12:43 PM delete

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??

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May 2, 2012 at 12:54 PM delete

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.

Regards.

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May 2, 2012 at 1:07 PM delete

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?

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Anonymous
May 2, 2012 at 10:10 PM delete

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?

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Anonymous
May 3, 2012 at 5:48 AM delete

Hi,

for the modified circuit, is the testing will be the same with the old circuit?

Thanks

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May 3, 2012 at 8:22 AM delete

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.

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May 3, 2012 at 8:44 AM delete

Testing procedure will be the same for both the circuits

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Anonymous
May 5, 2012 at 12:18 PM delete

hi..
from the above circuit need i connect NC1 and NO2 of relay to be shorted??

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May 7, 2012 at 10:18 PM delete

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???

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May 8, 2012 at 8:50 AM delete

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

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Anonymous
May 9, 2012 at 7:33 PM delete

hi..,sir what happens if i seted the relay to trip at 12.1v?and orginal position at 12v?

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May 9, 2012 at 9:39 PM delete

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)

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Anonymous
May 10, 2012 at 9:29 PM delete

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 ??

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Anonymous
May 11, 2012 at 12:09 AM delete

irfan
hi... i think R2=10k will be high ,please can you give me why 10k ohms is desgined ??

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May 11, 2012 at 7:54 AM delete

Hi Irfan,

Can you please tell me, why do you feel its high??

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May 11, 2012 at 7:59 AM delete

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.

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Anonymous
May 11, 2012 at 7:09 PM delete

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?

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May 11, 2012 at 9:33 PM delete

That's great news!
The secondary and primary windings are appropriately balanced so nothing will burn, unless the output load is above 10A.

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Anonymous
May 26, 2012 at 8:27 PM delete

Hi Swagatam,

what is the type of 100uF/25V? Ceramic or Electrolytic?

Thanks,

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May 26, 2012 at 9:38 PM delete

It is an electrolytic capacitor.

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Anonymous
May 31, 2012 at 10:06 AM delete

The capacitor 100uF/25V? Do i have to connect it to the base and emitter of the transistor?

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Anonymous
June 1, 2012 at 4:31 AM delete

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,

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June 1, 2012 at 11:47 AM delete

Hi,

Did you fine tune the preset? Adjust the preset properly for making the relay operate.

Regards.

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Anonymous
June 1, 2012 at 8:28 PM delete

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?

Regards,

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June 1, 2012 at 9:04 PM delete

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

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Anonymous
June 1, 2012 at 9:11 PM delete

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

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June 1, 2012 at 10:05 PM delete

Actually the opamp should respond with 0.5V differences, so I think your 741 ic might be faulty, just try with a new one.

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Anonymous
June 3, 2012 at 11:41 PM delete

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?

Regards,

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June 4, 2012 at 9:53 AM delete

My pleasure!

I'll try to possibly workout an overload protection circuit and update it here.

Best Wishes.

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Anonymous
June 4, 2012 at 1:09 PM delete

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

More power to you!

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Anonymous
June 7, 2012 at 6:01 AM delete

Hi Swagatam,

Any news for overload protection circuit?

Regards,

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June 7, 2012 at 6:44 PM delete

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.

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Anonymous
June 8, 2012 at 7:40 AM delete

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?

Regards,

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June 8, 2012 at 8:14 AM delete

Remove the cap from the base of the transistor and connect it across the relay coil, it should rectify the problem.

Regards.

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Anonymous
June 8, 2012 at 9:10 PM delete

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?

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June 9, 2012 at 10:03 PM delete

positive to positive, and negative to transistor's collector....

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June 10, 2012 at 1:26 AM delete

Can this circuit be used as voltage stabilizer for 1 ton Air Conditioner?

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June 10, 2012 at 11:20 AM delete

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.

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Anonymous
June 10, 2012 at 11:47 AM delete

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,

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June 10, 2012 at 8:56 PM delete

Hi ---,

Thank you, yes I remember, but as I told you I'm busy with some other projects, I'll surely help you once I finish them...
Regards.

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June 11, 2012 at 3:47 PM delete

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

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Anonymous
June 25, 2012 at 10:26 AM delete

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.

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June 25, 2012 at 5:32 PM delete

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.

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Anonymous
June 26, 2012 at 9:09 AM delete

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.

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June 27, 2012 at 9:51 PM delete

Yes you have understood absolutely correctly.

By the way I have designed many better stabilizer circuits, you may see them here:

http://homemadecircuitsandschematics.blogspot.in/2011/12/how-to-make-accurate-7-stage-op-amp.html

http://homemadecircuitsandschematics.blogspot.in/2011/12/build-solid-state-scrtriac-controlled.html

http://homemadecircuitsandschematics.blogspot.in/2011/12/diagram-shows-rather-simple-voltage.html

Thanks and Regards.

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Anonymous
June 29, 2012 at 9:53 AM delete

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,
Parvath.

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June 30, 2012 at 5:26 PM delete

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,

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Anonymous
July 4, 2012 at 12:37 AM delete

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

a.m.choudhary

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Anonymous
July 18, 2012 at 8:16 AM delete

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.

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July 18, 2012 at 10:26 AM delete

Hi Manuel,

Please see the following article, you will learn how to modify an ordinary transformer for getting high and low voltages from normal voltage:

http://homemadecircuitsandschematics.blogspot.in/2011/12/how-to-build-2-stage-mains-power.html

Regards.

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August 21, 2012 at 6:54 PM delete

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

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August 22, 2012 at 11:23 AM delete

Hi Sandy,
I'll surely try to produce the design for you soon.....

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August 26, 2012 at 6:54 PM delete

sir .
i am not any professionalist
so i just want the simple wire connection between all circuits of 300 watt stabilizers like ( relay, transformer etc )

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August 26, 2012 at 7:15 PM delete

which stabilizer circuit are you referring to?

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August 27, 2012 at 12:30 PM delete

You can follow the wiring diagram of the circuit provided in the above article, it's similar to a standard 300 watt TV stabilizer.

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Anonymous
September 6, 2012 at 9:39 PM delete

Hi Swagatam,

any news of the overload protection for this circuit?

Regards,

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September 7, 2012 at 9:54 AM delete

I have noted down the request and have made a draft article heading, so this time I won't forget, it might take a couple of days but it won't escape....

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September 8, 2012 at 4:25 PM delete

Please check out this post:

http://homemadecircuitsandschematics.blogspot.in/2012/09/mains-ac-overload-protection-circuit.html

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Anonymous
September 19, 2012 at 9:30 AM delete

Hi Swagatam,

i already made of two circuits of this blog... which is the best circuit? this last one?

Regards,

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September 19, 2012 at 10:38 AM delete

The first circuit is good and should provide optimal results....

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September 19, 2012 at 10:39 AM delete

I mean the one which is shown above....

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October 12, 2012 at 9:58 PM delete

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
thanks

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October 12, 2012 at 10:05 PM delete

You can find a much bigger range stabilizer here:

http://homemadecircuitsandschematics.blogspot.in/2011/12/how-to-make-accurate-7-stage-op-amp.html

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Anonymous
October 27, 2012 at 2:06 AM delete

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?
THANKS

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October 27, 2012 at 8:33 AM delete

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.

Regards.

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Anonymous
October 27, 2012 at 6:34 PM delete

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.

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October 27, 2012 at 9:59 PM delete

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.

Regards.

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Anonymous
November 10, 2012 at 9:30 AM delete

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

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November 10, 2012 at 5:36 PM delete

Hello jose, I did not understand your question.

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Anonymous
November 11, 2012 at 9:03 PM delete

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

jose

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November 11, 2012 at 10:15 PM delete

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.

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Anonymous
November 27, 2012 at 10:01 PM delete

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

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November 28, 2012 at 9:41 AM delete

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.

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Anonymous
December 2, 2012 at 8:49 PM delete

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

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December 2, 2012 at 9:50 PM delete

I have indicated the N/C, N/O contacts in the diagram, please check it.

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January 9, 2013 at 12:33 AM delete

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.....
Regards

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January 9, 2013 at 1:47 PM delete

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.

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Anonymous
January 17, 2013 at 2:00 PM delete

sir is there any additional taping need for the stabilizing transformer

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January 17, 2013 at 7:15 PM delete

No, it will be exactly as shown in the diagram.

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January 20, 2013 at 3:42 PM delete

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.

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January 20, 2013 at 5:46 PM delete

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......????

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January 20, 2013 at 7:33 PM delete

Sir, the TR2 is step up transformer? Or auto transformer? Can we use this syetem for the 230 V ac?? Kindly reply..

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January 21, 2013 at 10:19 AM delete

TR2 is an ordinary step up transformer....the circuit is made for 220V operation.

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Anonymous
January 22, 2013 at 11:33 AM delete

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)

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