AC Mains Surge Protector Circuit

Spikes or voltage surges can sometimes be a big nuisance as far as the safety of the various electronic appliances are concerned. Let's learn how to make a simple AC Mains surge protector device at home.


A sudden surge or a spike is basically a sharp rise in the voltage lasting not more than a few milliseconds but enough to cause damage to our precious equipment almost instantly.

It thus becomes imperative to stop or block these from entering vulnerable electronic gadgets like our personal computers.

Commercial spike busters are though available pretty easily and cheaply too, cannot be trusted and moreover have no reliability test arrangement so it becomes just a "assuming" game, until it's all over.

The circuit of a Simple AC Mains Surge Protector Device below, which shows how to make a simple homemade AC mains surge protector device is based on very simple principle of "speed breaking" the initial jolt through components who are well equipped in the field.

A simple iron resistor and MOV combination are more than enough to provide the protections we are looking for.

Here R1 and R2 are 5 turns of iron wire (0.2mm thick) over a 1 inch diameter air core each followed by an appropriately rated varistor or an MOV connected across them to become a full fledged spike protector system.

Surge entering the input of spike  are effectively tackled and the "sting" absorbed in the course by the relevant parts and a safe and clean mains is allowed to go through the connected load.

Mains Surge Protector Circuit

An e-mail from one of my followers:

Hi swagtam,

 I found your email address from your blog. I really need yr help. Actually my company has customer in china we make UV lamps and we use electronic ballast for it. now the problem is in china because of Over Voltage the ballast burn out so i design circuit which is in attachment which dosen't help either?

so i found your
Ultimate High/Low Voltage Protector Circuit which i wants to build. or can you tell me the update if i can do in my circuit that will be great.
sorry if i am bothring you. but i really really need yr help to save my job
thanks
Thank You
Krishna Shah

My Reply to Mr. Krishna:

Hi Krishna,

According to me the problem may not be with the voltage fluctuations, rather it's because of the sudden voltage surges that's blowing of your ballast circuit. 

The diagram shown by you may not prove very effective, because it does not incorporate a resistor or any kind of barrier with the MOVs. You may try the following circuit, introduce it at the entry point of the ballast circuit. Hope it works:







Share this

Related Posts

Previous
Next Post »

62 comments

comments
Bourgeoisie247
December 16, 2011 at 9:47 PM delete

Hey swagatam, can this circuit be incorporated into the over and under voltage protection circuits you talked about at: http://www.brighthub.com/engineering/electrical/articles/68396.aspx

Reply
avatar
December 17, 2011 at 8:08 AM delete

Hi Bourgeoisie,

Yes, it can be incorporated in the over voltage protection circuit.

Welcome to Swagatam's Homemade Circuit Blogspot :-)

Thanks for visiting!

Reply
avatar
December 27, 2011 at 6:36 PM delete

thank you sir. i will try and let u know.

Reply
avatar
December 28, 2011 at 12:47 AM delete

Hello Sir

I just have one question the circuit shown above i should connect it between Line -neutral am i correct?

Reply
avatar
December 28, 2011 at 9:26 AM delete

Hi Kristin,
Yes it is to be connected to the LIVE and Neutral input mains voltage.

Reply
avatar
December 29, 2011 at 1:51 AM delete

Hello sir,

how to decide value of fuse? in any circuit and also what value of fuse can we use in above ckt if mains voltage 230v.

thanks

Reply
avatar
December 29, 2011 at 1:15 PM delete

Hi Kristin,

The maximum safe current is the fuse rating that must be used.
So if suppose your max allowable current is say 15 amps, then you use a 15 amp fuse and so on.

Regards.

Reply
avatar
January 11, 2012 at 12:44 AM delete

Hi Swagatam,

Can you able to help me to make LI-ON and NI-MH battery charger using induction charging? I don’t know how to do it. I have Li-on battery with 3.6V and 2000mAh.Please can you help?

Reply
avatar
January 11, 2012 at 8:44 AM delete

Hi Kristin,
Please provide some more specs about the circuit, so that I can come up with an appropriate design.

Regards.

Reply
avatar
January 11, 2012 at 6:44 PM delete

ok i have to one project which is i wants to connect one UV LED to a circuit and from that circuit i connect that to NI-MH or LI-ON rechargeable battery and whenever charfe is not there through indication LED we can put that Whole unit for charge in HOlder which is made of Induction. i mean we can do induction charging.

right now i don't know much about LED specs. i will let you know by tomorrow. so you can help me.

thank you very much

Reply
avatar
January 12, 2012 at 8:45 AM delete

Hi Kristin,

This concept is new to me and I haven't done any practical project involving magnetic induction, I'll try though, but I cannot guarantee the results.
I'll post the design soon within a couple of days, just check back in-between.

Regards.

Reply
avatar
January 12, 2012 at 6:53 PM delete

in short i need to make a design which is for chraging any NI-MH battery. also i found that charging ckt for LI-on will be different from NI-MH. because overchraging may explode LI-ON battery.

one LED(not UV) has 3.6voltage and approx. 700-1000mA current. also NI-MH battery is 3.6v and 2000mAH. actually below i copied the battery details.

Features and Benefits

•High quality 1.2 V 4/5 A 2000mAh rechargeable Nickel Metal Hydride (Ni-MH) battery
•High capacity (2000mAh)
•Make your own battery packs in any combination of shape and voltage with easy soldering
•Ideally suitable for making mini battery pack for remote controlled (RC) aircraft.
•Ultra high capacity, 40% more running time than Ni-Cd battery.
•Very long cycle life and Rapid battery charge up
•Significant savings (60 % or more) from any retail stores.
•Battery tested based on International Electronic Commission (IEC) standard to ensure capacity, quality and life time.
•6 months warranty.
Technical Specifications

•Dimension: Height 43 mm, Diameter 17 mm
•Weight: 30g.
•Capacity: 2000 mAh
•Voltage: 1.2V
•Standard Charge: 20 hours @ 100 mA
•Rapid Charge: 2 hours @ 1000 mA

Reply
avatar
January 12, 2012 at 7:22 PM delete

Hi Kristin,
The above specs are all known to me, so it was not required.... I wanted to know about the circuit that you want, do you want just an automatic Ni-Cd charger circuit?

And what is role of the UV LED,

Please explain all these in steps, how do you want the circuit to function?

I have already published one article related to induction charging, you can find it in the blog homepage.

Regards.

Reply
avatar
January 16, 2012 at 8:19 PM delete

Hi Swagatam,
it is a flashlight which has a Blue LED.Right now i use 1 Ni-MH battery to run that LED no Circuit. But now i need a circuit which i use to run LED and also an induction charging circuit to charge the NI-MH battery.

thanks

Reply
avatar
January 17, 2012 at 12:50 PM delete

Hi Kristin,

I can design the charger and the LED driver circuit, but the induction charging system will be difficult, because I'm not entirely familiar with the concept.

Regards.

Reply
avatar
January 17, 2012 at 11:43 PM delete

Ok. If you can give me that.

Thank you very much

Reply
avatar
January 18, 2012 at 8:40 AM delete

Hi Kristin,

I'll do it within a couple of days and publish it.

Regards.

Reply
avatar
June 25, 2012 at 10:14 AM delete

Hey,

May I know why you need two MOV's and two resistors between them?

Reply
avatar
June 25, 2012 at 5:34 PM delete

just for extra safety, even a single one will mostly do.

Reply
avatar
June 26, 2012 at 8:09 AM delete

Thanks for your response. I'm sorry if my questions sound dumb to you, most of the surge related terms are new to me.
As regards to my question earlier, wouldn't there be some voltage drop across a resistor. So why would be we wasting some power there. And why would we need a resistor on the neutral?

I have noticed that you have two or three surge protection ckts on this blog, do any of them will pass surge voltage of 500V-6000V?

Reply
avatar
June 27, 2012 at 9:57 PM delete

The resistor value can be calculated and adjusted as per the load current, in fact the resistor is introduced for dropping voltage during higher voltages and thus safeguarding the load from the inrush.

500V and above voltages are far too high, and probably not applicable for circuits presented in this blog by me...

Reply
avatar
August 27, 2012 at 9:16 AM delete

Hi... about the surge protector you gave to krishna, can i incorporate it to my existing AVR for additional protection of my HDTV?

Reply
avatar
August 27, 2012 at 11:44 AM delete

Please indicate which circuit you are referring to.

Reply
avatar
August 27, 2012 at 3:18 PM delete

sir, the surge protector i'm talking about is the one with two MOV and two 10ohm 2watt resistor. or sir can i ask a surge protector design that works with my HDTV with 220V working voltage? what would be the recommended MOV values?

Reply
avatar
August 27, 2012 at 3:58 PM delete

The above circuits have not been verified practically, so I would suggest that you buy a "spike buster" from the market, because it is your costly HD TV that is at stake.

Reply
avatar
December 14, 2012 at 2:29 AM delete

I want to design A PCB board

The board must have the dimensions shown in the drawing. Only the area 1.250 X 0.800
will be populated

1. Act as a voltage indicator:

Below a certain voltage (12-12.5V), the led will be RED.
Over a certain voltage (12-12.5V) the led will be GREEN.

2. It will monitor the current of one or two fans

If one fan fails under a one-fan operation (no current draw), the LED will flash RED
One fan will draw 0.075A

If either fan fails under a two-fan operation (no current draw), the LED will flash RED
One fan will draw 0.075A
The other 0.12A

Reply
avatar
December 14, 2012 at 9:49 AM delete

I'll try to design it, if it's feasible for me I'll inform you.

Reply
avatar
Anonymous
February 7, 2013 at 2:22 PM delete

HI sir!

Sir can i connect this circuit in line 1 to line 2 with ground main voltage? What i mean is the main voltage, line1 to ground = 110v, line2 to ground = 110v, line1 to line2 = 220v.

Thanks

Jojo l.

Reply
avatar
Anonymous
July 15, 2013 at 12:34 AM delete

Sir,

Good day! How would I design a surge protection circuit without causing any effects in the voltage (e.g. voltage drop across the resistor)? We are developing a power quality meter and will incorporate a surge protection in the high side of voltage sensing circuit.

Thanks!
-Pierre

Reply
avatar
July 15, 2013 at 9:01 PM delete

You can incorporate thermistors and MOVs together, resistors can be avoided then.

for knowing more about thermistors, you may refer to this article:

http://homemadecircuitsandschematics.blogspot.in/2013/02/using-ntc-resistor-as-surge-suppressor.html

Reply
avatar
Anonymous
August 10, 2013 at 11:05 AM delete

Can U plz. provide ckt. diagram of suge protector including EMI/RFI filter with 230V AC line tester.

Thanx in Advance

Reply
avatar
August 11, 2013 at 1:12 PM delete

For what application do you want to use it?

Reply
avatar
Anonymous
August 11, 2013 at 1:55 PM delete

I want it for PC, i already have ups but some times when mains fails PC restart and i think it is due to Spike problems.
Thanx for your reply.

Reply
avatar
August 12, 2013 at 11:47 AM delete

No it's not due to spike, it's due to a split second late response from the UPS, try with a new good quality UPS and you won't find this issue happening.

Reply
avatar
Anonymous
December 11, 2013 at 10:33 PM delete

sir can i use this circuit as telephone surge protector

Reply
avatar
December 12, 2013 at 7:50 PM delete

telephone surge protector?? i didn't get the application, can you pls explain it?

Reply
avatar
December 28, 2013 at 12:21 PM delete

Hi....Swagatam can u give the VA rating of mov & fuse of above ckt u used above....when my ckt I/p current is 130mA and o/p current is 170mA & o/p voltage is 167 when I/p voltage is 230V for electronic ballast. ....so please share it with me asap....

Reply
avatar
December 28, 2013 at 8:09 PM delete

Hi Shersingh,

you can use a 350V RMS, @5amp rated MOV.

Reply
avatar
April 19, 2014 at 6:06 AM delete

Hi,

Is it possible to use this diagram for a single wire ground return system? My power line is a single phase 240V and the neutral is coming from a copper rod in the ground. The voltage fluctuates a lot and i would really like to protect my devices (Mainly motors and VFD's) and some computers. Do you recommend any other systems like high and low surge protection? Also, what protection rating should i expect (high voltage vise)

I appreciate your response in advanced.

Chris

Reply
avatar
April 19, 2014 at 9:55 AM delete

Hi,
the above circuit will only help to control surge in-rush to some extent but won't control the voltage fluctuations.

you would need a voltage stabilizer circuit for tackling the issue effectively, one design has been discussed below which may be tried or procured readymade:

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

Reply
avatar
May 28, 2014 at 11:52 AM delete

Hi Swagatam ,

How are you ? hope doing well.

If want to draw constant 220 v AC at any point

Generally input is
Low - 110v / 130v AC
High - 230/260 v AC

Required Output
220 V AC (Stabilized)

Can you please suggest best circuit . if Tranformerless will preferable.

Thanks
Nilesh Patil

Reply
avatar
May 29, 2014 at 9:35 AM delete

Hi Nilesh,

I am fine, thanks!

You can try the design that's shown in the following article:

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

a transformerless design could be very difficult since it would involve complex mosfet drivers, ferrite inductors etc, so I think using the traditional iron core transformer would be much easier, although a little bulky.

Reply
avatar
October 6, 2014 at 7:39 AM delete

Plz. value of MOV and best one company product......thnx.

Reply
avatar
October 6, 2014 at 7:41 AM delete

Value of MOV and best company product....thnx.

Reply
avatar
October 6, 2014 at 5:43 PM delete

company is not important as all are good, the clamping voltage rating should be 50 V more than the input mains supply voltage.

Reply
avatar
October 23, 2014 at 2:48 AM delete

Hi Mr Swatam. Cogratulation for your extraordinary electronic web page.......

I write from México. My question is: For a 120v nominal voltage, what should be the value of the resistors, and the maximun peak voltage and Joules for the MOV's ?

Thanks in advance for your help.......

Reply
avatar
October 23, 2014 at 9:48 AM delete

Thanks Roberto,

for 120V you can select 200V as the clamping voltage for the MOV, the resistors are not critical they are just for complementing the MOVs, any value between 0.5 ohms to 1 ohms will do the job.

10 ohm is far too big and must not be used, it's incorrectly shown in the diagram.

Reply
avatar
August 14, 2015 at 7:14 AM delete

Hi Mr. Swatam, do you have a schematic diagram for TVSS or SPD for resedential use only. pls include the value of materials.

thank you so much.

Reply
avatar
August 14, 2015 at 5:23 PM delete

Hi Cloyd,

you can probably try using the devices explained in the following article:

http://www.homemade-circuits.com/2015/01/high-power-industrial-surge-suppressor.html

put these directly across the wires that enter the house wiring.

the value can be of 350V/50amp

Reply
avatar
August 22, 2015 at 9:30 PM delete

Hi Sir Swagatam, thank you for your response. i want to ask you more question sir about TVSS/SPD , This is for our thesis sir and i'm hoping that you can give us more details about the connection. we are troubling of our design sir because we would like to make a TVSS device that will connected parallel to the source (40A Breaker), thus we doubted our design due to its connection if it can really suppress the voltage surge. i will show you our design sir and were hoping that you can give us some advice on how to fully get the right design.
thank you for your time sir Swagatam, best regards.

Reply
avatar
August 22, 2015 at 9:44 PM delete

this is the diagram of our device sir.. the source is Line to Line. we just put the ground into the device for the MOV's.

https://drive.google.com/open?id=0B786VWhN4zxiTzlmeUhQRml4R2M

Reply
avatar
August 22, 2015 at 9:56 PM delete

The upper diagram sir is what we wanted to do (parallel to the source) but we are not sure if it can supress the voltage surge thats why we decide to design another (lower diagram) which is connected in series from the source. i'm begging for your expert suggestion and advice sir that can help a lot to our device to function and for us to pass the subject. thank you sir SWAGATAM.

Reply
avatar
August 23, 2015 at 7:36 PM delete

Hi Cloyd,

The link which I suggested you in the earlier comment can be effectively used as a transient voltage surge suppressor.

Other option is in the form of diodes which is explained here, these also need to be connected parallel to the input mains supply:

https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode

The image provided by you is not opening, please make it "public" by selecting the share option.

Reply
avatar
August 23, 2015 at 7:37 PM delete

...please toggle the share option...

Reply
avatar
August 23, 2015 at 7:41 PM delete

normally all TVSS devices are extremely reliable and can be trusted for the necessary actions.

you can refer to the following article for more info:

http://www.homemade-circuits.com/2014/09/testing-mov-metal-oxide-varistor-surge.html

Reply
avatar
November 27, 2015 at 9:21 AM delete

Dear Mr Swagatam

Firstly thank you for this great website, i have built a few small projects of your design, i have become extremly interested in transient voltage and the long term damage it does. I will test the above circuit and give some feed back.

What i would like to ask is (if you perhaps have an existing) a design where one can "monitor" the transient voltage on a incoming line (the main grid). I understand that there are "in line counters". This can be a great tool to take the readings before and after the unit install.

Will this be possible?

Again thank you for the great site and info.

Best Regards
Mark
South Africa
mrmcon@gmail.com

Reply
avatar
November 28, 2015 at 9:08 AM delete

Thank you dear Mark,

The simplest way could be to connect a digital ammeter in series with the MOV that may have a feature to latch up to the reading corresponding to the transient value each time power is switched ON.

If it's possible I'll try to design and post it for you.

Reply
avatar
November 28, 2015 at 6:49 PM delete

ko good, but we want buy pcg/ components/ etc in india. is it possible in india?

Reply
avatar
Lim
January 16, 2016 at 3:18 AM delete

Hello!
A friend of mine was thinking of building a surge suppressor and voltage regulator by using ARM microprocessor. He was thinking of using inductor plus MOVs together. Do you think it is feasible?
Thank you.
Lim.

Reply
avatar
January 17, 2016 at 10:47 AM delete

Hello,

MOVs don't require any external triggering circuit for activating, it's a self-actuated device so I don't think an MCU could be used for operating an MOV

Reply
avatar

Readers are requested not to include external links while commenting. For consulting a diagram, upload it on Google Drive and provide the link here.