Voltage spikes 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 circuits at home.
What is Voltage In Rush
A sudden voltage 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.
Working Design
The circuit of a Simple AC Mains Surge Protector Device below, which shows how to make a simple homemade AC mains high current 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.
Sudden high AC 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.
Transient Protector Using Inductors and MOV
Question Regarding Surge Prevention in Electronic Ballast
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
Solution
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:
Using an NTC and MOV
The following image shows how two different sudden high voltage suppressor devices could be tied up with the mains line for achieving a double edged safety.
The NTC here enables an initial switch ON current in rush protection by offering a higher resistance due to its initial lower temperature, but in the course of this action its temperature begins increasing and it begins allowing more current for the appliance until a normal working conditions achieved.
The MOV on the other complements the NTC output and makes sure that in case the NTC is unable to stop the up-surge onslaught correctly, it switches ON itself shorting the residual high transient content to ground and as a result establishing a safest possible supply for the connected load or the appliance.
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Voon Yongjian says
Hi sir,
I am designing a surge protection device for lightning. Is the design above is suitable for it? Can I replace the resistor with an inductor because i saw it somewhere in other website?
Basically my input supply will be 240 Vac, what is the value of clamping voltage of MOV is suitable? Can I use MOV with 240V clamping voltage?
Thanks!
Swagatam says
Hi Voon, if the lightning strikes directly into the house wiring then no surge suppressor would be capable of stopping it.
MOV can suppress only minor electrical surges, not lightening related surges….to suppress lightning related surges the best idea would be to employ a triac based crowbar circuit as described here
https://homemade-circuits.com/2017/03/surge-arrestor-circuit-with-surge.html
the high voltage capacitor and diode can be ignored and removed.
you can also include an MOV/inductor suppresor as per your initial requirement in conjunction with the above design.
RAO says
Namasthe,
I am talking about the " Ajantha make wall clock : OLC Quartz 104, Model. computer century Calendar", which I am using. There is a supply module inside the clock. Every time there is a power shout down in our area and the power comes up, the clock fails. The watch repairer says supply unit is burnt. So I just wanted to incorporate a surge suppresser to this clock externally.
Swagatam says
OK I understood, the in-built power supply could be an SMPS based…..as expressed in above comment you can try connecting an NTC in series with any of the supply lines, and also connect an MOV across the two supply lines after the NTC.
I'll try to update the diagram soon for your reference
RAO says
I have an electronic digital calendar clock, its supply unit has bagged off three times due to surge voltage in the mains. I want to incorporate a simple sure suppressor for it. it may be drawing less than on ampere current. what value components are recommended. please advise me if any simplest circuit which I can assemble myself.
Swagatam says
Normally any god power supply will never burn with minor supply fluctuations….what kind of supply unit have you been using? Is it SMPS based or transformer based?
I would suggest you to use your cellphone charger for the purpose which has all the protections in-built
still if you are interested to build your customized surge suppressor, you can try an NTC in series with any of the input mains supply lines, and additionally connect an MOV across the two supply lines after the NTC.
Ravi kumar says
Hi Swagatam,
I'm planning to install a surge suppressor for the whole house at the mains AC panel (next to the meter board) is there a standard part available available off the shelf or do we need to design one and install. i was able to find CHSPT2MAX from Eaton, but its too expensive, any suggestions…
Swagatam says
Hi Ravi, you an industrial MOV, in conjunction with the following delay ON relay crcuit, adjust the delay time to may be a second or so, and connect the relay contacts with the house wiring.
https://homemade-circuits.com/2013/02/make-this-simple-delay-on-circuit.html
Industrial MOV sample is discussed below
https://homemade-circuits.com/2015/01/high-power-industrial-surge-suppressor.html
patrick vaz says
Hi Swagatam,
How are you,
A friend of mine had his TV friend due to a voltage surge,
Voltage Input from the mains line is 230V, sanctioned current is 6amps. want to help him out.
Can I use the circuit mentioned above 2 MOV with 10ohms 2 watt resistor,
-what should the value of the MOV be.
– what should the value of the fuse be in terms of AMPs.
– should a Indicator lamp be added in the circuit after the fuse,
Kindly advise.
warm regards
Swagatam says
Thanks Patrick, I am good!
yes you can try it, just replace the resistors with 1 ohm 2 watt, because 10 could be a bit too high.
MOV could be rated at 350V (clamping voltage)
fuse could be an 8 amp rated….
indicator lamp is optional, it can be added for indicating a blown fuse
patrick vaz says
Hello Swagatam,
Thank you so much,
Apart from the Mains, it could be added in different sections of the house, where sensitive equipments are such as TV/ Music systems etc., just to be safe.
Is this okay ?
warm regards
Swagatam says
Thanks Patrick, yes you can use an MOV with every appliance but MOV has its own restrictions too, for example it might not withstand the surge if it lasts for more than a millisecond, and could cause a short circuit and fire, therefore a series fuse also becomes mandatory.
Alternatively you can use a single powerful MOV near the main DP of the house, the MOV specs are explained below
https://homemade-circuits.com/2015/01/high-power-industrial-surge-suppressor.html
By the way all modern equipment already include a built-in MOV in their system
shivtej nirmal says
What MOV VALUE and part no
Swagatam says
can be a 350V MOV
Narciso Calzo says
Hi Swagatam,
I was looking for a surge suppressor device circuit diagram and was directed to your site. Upon reading about you and going through the comment and replies between you and your readers, your patience in answering all the queries really put me in great admiration to you. I came across so many people like you in the web but you are different from them, they can't respond.
Recently I just decided to become a hobbyist in electronics although I don't have a formal education or training about it but a steward/stewardess can land a commercial plane with the guidance of the ground controllers( this is from a movie).
I was inspired by a friend that showed me his DIY audio amplifier and it works well. I asked him for the details and he gave me copies of schematics, pcb layout, parts list as well as procedures of adjustments but it is limited to a 100W into 8ohm power. I want to evolve this to a 350W,8ohm design. The design uses 2SC5200 output devices and TIP41C drivers.
Can you give me suggestions, advices or even a new design from you, or, is it okey to publish the circuitry since it was designed by an EE in order for you to go through it and come up with solutions and recommendations to meet the desired power for my first project.
Actually I have already etched the pcb the very conventional way. By the way I am from the Philippines, work as a material eng'r in a construction company.
Nice knowing you Swagatam.
Your new reader/jollower,
Osic
Swagatam says
Hi Osic, thanks so much! I appreciate your enthusiasm and wish you the very best!
Amplifiers can be quite difficult circuits as they require precision and balance at every node and stages of the circuit and so far I have not been able to master these gadgets due to their complex concepts and configurations.
So I am really sorry I won't eb able to assist you with amp designs, therefore I would recommend you to select a schematic which is originally designed to suit your specifications instead of modifying a design having a different specifications.
I have a 100 watt simple mosfet amplifier circuit in this site designed to work with around 35V normally which is capable of generating upto 300 watts power simply by using a higher voltage input of around 100V…however it requires a 4 ohm speaker, If you wish you could try that design also!!
Narciso Calzo says
Okay Swagatam I will take a look at your design. Thanks Swagatam, more power.
Lim says
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.
Swagatam says
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
Makhon Barooah says
ko good, but we want buy pcg/ components/ etc in india. is it possible in india?
Swagatam says
yes, it' possible.
Mark Mare says
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
Swagatam says
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.
Mark Mare says
Thank you very much Sir.
cloyd mamontayao says
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.
Swagatam says
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:
https://homemade-circuits.com/2014/09/testing-mov-metal-oxide-varistor-surge.html
cloyd mamontayao says
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
Swagatam says
…please toggle the share option…
cloyd mamontayao says
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.
Swagatam says
Hi Cloyd,
you can probably try using the devices explained in the following article:
https://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
cloyd mamontayao says
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.
Swagatam says
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.
Roberto Carmona says
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…….
Swagatam says
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.
Makhon Barooah says
Value of MOV and best company product….thnx.
Makhon Barooah says
Plz. value of MOV and best one company product……thnx.
Swagatam says
company is not important as all are good, the clamping voltage rating should be 50 V more than the input mains supply voltage.
Nilesh says
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
Swagatam says
Hi Nilesh,
I am fine, thanks!
You can try the design that's shown in the following article:
https://homemade-circuits.com/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.
chris.sorbi says
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
Swagatam says
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:
https://homemade-circuits.com/2011/12/how-to-make-accurate-7-stage-op-amp.html#uds-search-results
Shersingh Badhoriya says
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….
Swagatam says
Hi Shersingh,
you can use a 350V RMS, @5amp rated MOV.
Anonymous says
sir can i use this circuit as telephone surge protector
Swagatam says
telephone surge protector?? i didn't get the application, can you pls explain it?
Anonymous says
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.
Swagatam says
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.
Anonymous says
Can U plz. provide ckt. diagram of suge protector including EMI/RFI filter with 230V AC line tester.
Thanx in Advance
Swagatam says
For what application do you want to use it?
Anonymous says
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
Swagatam says
You can incorporate thermistors and MOVs together, resistors can be avoided then.
for knowing more about thermistors, you may refer to this article:
https://homemade-circuits.com/2013/02/using-ntc-resistor-as-surge-suppressor.html
Anonymous says
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.
kristin says
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
Swagatam says
I'll try to design it, if it's feasible for me I'll inform you.
cire peric says
Hi… about the surge protector you gave to krishna, can i incorporate it to my existing AVR for additional protection of my HDTV?
Swagatam says
Please indicate which circuit you are referring to.
cire peric says
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?
Swagatam says
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.
rajgs says
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?
rajgs says
Hey,
May I know why you need two MOV's and two resistors between them?
kristin says
Ok. If you can give me that.
Thank you very much
kristin says
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
kristin says
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
kristin says
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
kristin says
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?
kristin says
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
kristin says
Hello Sir
I just have one question the circuit shown above i should connect it between Line -neutral am i correct?
kristin says
thank you sir. i will try and let u know.
Bourgeoisie247 says
Hey swagatam, can this circuit be incorporated into the over and under voltage protection circuits you talked about at: www.brighthub.com/engineering/electrical/articles/68396.aspx