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roderel masibay said…
hi sir your diagram is realy good is original im roderel from phillipines one of your televiers of your diagram
Swagatam said…
Hi Salamn,
I think you should use a three pin connection, your socket must be equipped with an earthing connection, the "earth" wire from the three pin plug may be just connected with any metal part of your laptop.

If you want a short-cut way, just invert the present 2pin plug....meaning, remove it, flip itand fix it back in the socket such that the pins positions get interchanged into the socket holes.

There's cannot be any other option except the above two....
salman said…
thank you very much sir for your reply. I am really impressed that you don't ignore new persons with foolish very basic questions.. (you are very generous about sharing your knowledge and tips very few people does that)may God bless you.
but as I mentioned earlier that in my country Pakistan there is no ground connection in almost every home, so only 2 prong sockets are being used.
I have tried your suggestion about flipping the plug it didn't help. still get shock from laptop's body bare foot and I am already using 3 prong to 2 prong converter socket because my laptop's power supply's plug has three pins. but still same problem..
I was wondering that :-

1) if I use isolation transformer will it help?
2) your suggestion about flipping plug worked on my refrigerator very well because this fridge had the same shocking problem but it is solved after just flipping plug!.. thank you very much.
Swagatam said…
You are welcome salman, I guess presently you are using an SMPS module for your laptop. As far as I know an smps also consists of an isolation transformer, so it should not produce shocks at all. It simply means that your smps is leaking somewhere or is faulty. You can try replacing it with a new one.

A transformer type power supply can also be used, but you will have to make a precise one as per your laptops specs, or you may ask your local dealer for the right one if you intend to buy a ready made piece.

salman said…
Thank you sir I understand your point. I will get back to you in few days inshaAllah just to inform if this problem solved or not. and what solution did solve this... thanx again no need to say any complements because all complements are not enough for your efforts. just i want to say keep it up:) .
Swagatam said…
I appreciate it...thanks!
Anonymous said…
Hello sir..

This is Kanagaraj..

We have a Electronic choke Tube Light..Its having problem..

Tube is 36w..

Input rate is normal 230v AC..

The problem is the tube does not start fully..At both the ends its only glow very little and in between the tube is like a off state..

We have checked the tube with other working one..And We found that there is no problem with tube..

So the problem is with the electronic choke output..

So please tell me how to check the output value ??

And on the PCB all components looks good..No burnt components on the PCB board..

The tube light model is "Asian Lumini T8".

Please tell me the way to solve the problem..

Thanking you.

Swagatam said…
Hello Kanagaraj,

It will be difficult to troubleshoot the problem because there can be many different the way did you check the tube in some other good choke? Confirm the tube working by connecting it over a good fixture.

In most cases the power devices of ballasts are the one which get damaged.
Anonymous said…
Hello Sir..

Yes sir i have checked the tube in other working choke..Its working well in that one..

And yes sir..Am also thing the problem is with power device of the ballast..

Can u tell me your email sir..??

So i can mail my choke screenshots...Then you can suggest me some option to check the circuit parts..

Swagatam said…
I am afraid that won't help, just by seeing the picture I won't be able to find the fault...there are many complex operations and checking that might be required, so it's difficult..
timmy.magic said…
hi Swagatam,

I came accross your 'Car Burglar Alarm System' blog while searching for a way to trigger a mobile phone-call if a prowler interferes with an electrified chain-link fence. Ideally I'm hoping to find something that a layman can follow and put together, though I suspect this is going to require an off-the-shelf (latch?) system to detect the necessary voltage changes.

Normally I'm pretty good at finding stuff on Google (that's how I know about the 'latch' thing!), but I just don't have any more relevant terminology - do you have any suggestions or leads for me?

Kudos for publishing your expertise! Tim
Swagatam said…
Hi Tim,

Thank you very much!

Making the trigger circuit won't be difficult, but integrating it with a cell phone such that the cell phone starts calling a specified number can be difficult to make, especially for a layman.

The idea will need opening a cell phone and wiring its call button terminals with the external trigger circuit.

If feasible I'll surely address one such circuit in my blog soon.

Many thanks, and welcome to my blog!
kkaranjia said…
Mr Swagat Majumdar this is Kurush Karanjia from Vadodara Gujarat. I just has a telephonic talk with you and you requested to write on you r blog so i m writing my requirements here. I have certain solar panels and interested in designing solar power conditioning unit(PCU) to connect to the system. I am an electrical engineer so all i could design was a blog diagram but not the details as i don't have much experience in electronics. I m attaching my requirements of the PCU along with the blog diagram please help in any way you can.

the details of the type of grid tie solar PCU i require

1. Mppt Charge controller.
2. Reverse current Protection.
3. Islanding protection.
4. Pl=load power, Ps=solar panel generated power, Pb= Battery output power.
if Ps>Pl load should run on solar and left over should charge battery.
if Pl>Ps but less then inverter capacity the load should b supplied by
if Pl>Ps,Pb and greater then inverter capacity and solar available then load
should be supplied from main and solar through inverter synchronously, if
solar not available then through battery and mains synchronously
if solar and battery both not available then load should be supplied
directly by mains.
5. charging of batteries through mains should be made optional to consumer
via manual switch

Rest all protections that are available in inverter.

I m not able to connect my blog diagram here so if u permit i will send u that in mail
Swagatam said…
Hello Kurush,

I have understood you question, I'll try to design the required circuit for you soon. But kindly note that this idea will become public as you would get it in the form of a published article in this blog.

Amit Solankurkar said…
Hi Swagatam,

Thanks for your blog, and it is interesting. I am very much interested in high quality audio and video. I want to connect my TV to my home theater but the problem is my TV has a Optical Toslink O/p and HT has Coaxial I/p. I have tried buiding for a toslink to coaxial converter but I am not able to find the Toslink Reciever IC which is TORX 17X. No dealer in pune knows about this. Do you have any alternative for this?

Thanks in Advance,

Swagatam said…
Hi Amit,

You are most welcome!

I would suggest not to build it, rather buy the unit ready-made.

Please check the link below, you can order it online:

kkaranjia said…
Thanks a lot for your help and i don't mind if you post it on the blog. We would me more happy if more people use this circuit as it will help to harness more electricity form the solar panel and and cause less wastage. I will be waiting form your reply and i have made a blog diagram so if for reference you want it i can mail it and if help or in formation is required feel free to contact me on my id or on my Mobile No: 09924525574
Swagatam said…
Hi Kurush,

OK that's great thanks!

Actually presently I am a little busy with a few external assignments so I wouldn't able to post it very soon, but I'll try to do it within a week or so.

I think I have already published all your requirements in this blog in parts though and with alternative titles.

Anyway, you can send the block diagram to I'll check it.

Thanks and Regards.
kkaranjia said…
i forgot to write one requirement that the inverter should be transformerless and the DC voltage level of system should be 12v,24v or 48v if possible
Swagatam said…
I am sorry, transformerless inverter won't be possible because i don't have any working circuit of it.
kkaranjia said…
can we not use DC converter to change the voltage level before the inverter circuit instead of transformer in after inverter circuit and can the inverter be DSP based ?
Swagatam said…
If a DC voltage converter circuit becomes available which would be able to convert 12V DC to 220V DC, then probably we can go ahead with transformerless inverter circuit....
kkaranjia said…
its available i have downloaded some from net so i can send them to you on our email id and you can go through them if you want
kkaranjia said…
please go to this link and you will find the circuit.
Melro said…
Dear Sir,

I am Melro from Sri Lanka,

These days I am searching for circuit to light 6” inch Tube light. While go through the internet I found your blog. Your blog is marvelous, lot of details were there. My target is to build aquarium light for my aquarium. I found the 6” florescent UV light from the market, my purpose is put 6 lights in my aquarium. Could you please tell me the way to build the circuit for it. (My mail is

Thank You
Swagatam said…
OK you can send it to me.
Swagatam said…
I'll check the link.....
Swagatam said…
The part numbers are not clear and the image is not getting it's difficult to trace.
Swagatam said…
Dear Melro,

You may try the circuit shown in the following link:

The transformer may be replaced with a smaller 6-0-6/500 mA and the battery power source may be replaced with a small AC/DC 6V adapter.
Melro said…
Thank you very much for your quick reply
Melro said…
how can i put six (6” florescent UV light), is it serial or apparel
kkaranjia said…
ya i know that but i sent it only for the reference. If you can help using the circuit shown in figure the please do.
Swagatam said…
You can put them in parallel.
Swagatam said…
If the IC number is not clear we cannot guess on what principle the circuit is functioning.

Actually I have already published the concept in one of my articles given below, but unless it's confirmed it cannot be much useful:

Chris de sarthe said…
Hi, Swagatam, i've been doing electronics as hobby for 3 year now and i just discovered your website, i'm really exited about all the shematics i find on it! thank you for you great work of sharing. Regards

Swagatam said…
Hi Chris,

You are most welcome!:-)

kkaranjia said…
ok no problem, i will figure out something for it but can u just make the rest of the circuit with normal inverter and post as soon as possible
kkaranjia said…
hii swagatam sorry to disturb you again but is there any progress with the design. The design is required on bit urgent basis so if u can post it bit faster i will be very thank full
Swagatam said…
Hi Kurush,

I'm feeling it difficult to design the circuit as per your block diagram.

I can provide the circuits in separate parts, you will have integrate them together, if that's OK you can name the sections and I will provide them to you.

kkaranjia said…
its ok please send them in parts i will try and integrate them and if i will require any help i will ask you again. And what problems do you have please tell them if possible i will solve them if possible. And even if the final circuit is not as per the bock diagram yet full fills the requirements then its ok.
Swagatam said…
OK, I'll try to put my version of the design together and send it to you soon.
kkaranjia said…
ok thanks a lot for your help
kkaranjia said…
can we put the pulse transformer on the DC side for voltage level transformation instead of low frequency transformer on AC side??
kkaranjia said…
please go through this link to see for transformer less inverter
kkaranjia said…
please go to the link below as it may b helpful as it has a working circuit but of 150va...
Swagatam said…
The above circuit looks perfect to me, and since it's a tested design it should be reliable.
kkaranjia said…
hii i have opened a samsung charger with an op of 5v and 0.55a so is it possible that i can increase the current level on output side.
Swagatam said…
Hi Kurush, I've tried to design the set up requested by you, kindly view it here:

You will have join all the stages together by combining the linked article diarams.
Swagatam said…
You will need to modify the transformer secondary winding for increasing the current or voltage
kkaranjia said…
the transformer is a pulse transformer not the AC transformer,,,,
Swagatam said…
you will have to modify the pulse transformer winding.
Nasir said…
Hi Mr Swagatam

Really feel good and like too much your blog .I need your help .I need a timer ckt which on for 5 or 10second and then off for 5 second and again repeat on for 5 or 10second and so on or 3 times repeat this and then remain off until power cut off.

Swagatam said…
Hi Nasir,


You can make it by using a 4093 IC as shown in the following article:
Nikhil said…
hi Swagatam.....
i wanted to make a led lighting for my 4x2ft aquarium. i need at least 400 strawhat led circuit each of 5mm. can you please design the circuit....
Swagatam said…
Hi Nikhil,

I have noted down your request and will publish it very soon in my blog....keep in touch.
Nasir said…
Thanks for your prompt response.The out put for 4093 can drive the transistor with relay ? Also i have checked your all ckt but i could not found Auto Power ON Main failure circuit for Generator.Can you guide or help regarding this circuit....

Swagatam said…
Yes the output of 4093 can easily support a relay driver stage.

auto power on generator?? it can be very simply done using a single relay.
Nasir said…
Yes But need to start and stop the generator also need to use magnetic contactor for Line power and generator power for auto switching from one to another .Still there is no complete schematic like this not available so you have better idea regarding this if you make,Its my request to you please.
I have seen using PIC controller but that is not possible for the person who don't know about embedded programming so just need simple using timers and relays and magnetic contactor.Please consider it .

Swagatam said…
Can you provide the specifications point by point?
Nasir said…
Its just like,when line power or city power turned off then generator should start automatically and give power through magnetic contactor ,after that when power come again the generator should stop automatically.
There is Timer ckt to start the generator and contactor for supply contactor for Line or city power.Interlocking between these two contactor.After generator should stop.

Swagatam said…
I'll check it and try to design it....
Nasir said…
Thanks I will wait for your prompt response .....
Ravipal Singh said…
hi,sir i am Ravi from India.i am using a SMPS inverter circuit.using a ferrite core transformer with the ratio of 1:30 make 310 volt dc.i placed all the components as per design.the voltage on 1rfz44 gate is approx.6volt _ve dc.but on ac,it is more than 20 volts.i am using sg 3525 as a pulse driver,pin 6 is grounded through 3.3k,pin 5+7 grounded through 4.7nf,9 grounded through 68nf,8 with 100 nf grounded.i connect the circuit with the transformer but it didnt show any result.will you help me to build this project.i think the problem is in the transformer,but not sure how is it.please help.thanks
Swagatam said…
Hi Ravipal,

Making the transformer correctly is the most difficult part, especially when you don't have an example working unit.

I won't be able to help you with this project, because I have no idea regarding designing of transformers:(
Rafael Santo said…
hello swagatam
how are you sir my name is Rafael I'm so happy to finally find a site like yours
first of all let me say thank you for all you good work and for you time

i have this particular case and i hope you can help me
I'm trying to power led on my motorcycle wheels and i have try many things some of them have last for like three months but i haven't find a permanent one
and i was wonder if you have any suggestion on how to power the led to stay on even when the bike is in motion
i have been reading about wireless power to transfer power from one coil to other coil but don't know how to wire it or what components to use to make my own and i don't know if it will me safe for the electric system of the bike
thanks in advance for any help you can give me
nishant said…
hi,I am from Ayodhya UP fresher electronics engineer,i always read ur every article published on this blog,it helps me to buildup my practical knowledge.i have a question.hope u will help me.
i have microtek PC ups,before in Summers approx 1 months before my area had low voltage problem(as well as voltage fluctuation problem) due to which my ups could not start it always switches to BACKUP mode so I buyed an automatic voltage stablizer(1KVA) now there is no low voltage problem then also ups works some time fine but some time it has same problem of switching to backup mode inspite of good voltage(220-250V) input.
Swagatam said…
Hello Rafael,

Welcome to my blog!!

Your requirement is very interesting but difficult.
If anybody becomes successful in designing an effective and efficient way of transferring power without wires even across a distance of around a couple of feet..... the person would become rich.

I have never tried this type of project but it's too intriguing, and I'll surely like to have a go at it.

If I succeed will reply you immediately with the updates.

Swagatam said…
I think there may be a loose contact problem. Check all the plug connections of the UPS properly...or the problem might be somewhere inside the UPS with the involved connectors..
hi sir, can u help me design a power supply to operate 3W White leds from mains. i want it to be compact(ie without bulky transformer) , i was thinking of capacitor power supply but the current required for 3W LED is much higher than its capacity.
so can u please help me out
thank you
michael said…
hello swagatam
i'm michael from indonesia, i want full wave shunt regulator for small motorcycle, i hope u will help me
from me michael(
Swagatam said…
Hi Navneeth,

You can try the circuit given in the following link:
Swagatam said…
Hello Michael

I'll try to design the circuit..... will inform you when it's done.

GBU too:)
i tried and it does not deliver enough current to get the max effficiency and brightness for a 3W LED. what abt a circuit with smps topology. i tries googling but cudnt find a suitable circuit. can u please help me design one.
Swagatam said…
Making an smps at home won't be easy for you, it would be better to buy a small 12/500mA smps power supply and then use it to drive the led with a series 10 Ohm resistor.

You may also try a mobile charger, use it with a 3 Ohm series resistor.
Melro said…
Hello swagatam,

Could you please tell me the diver circuit for run 3 no of 5W led light for parallel.


Swagatam said…
Hello Metro,

You will have to buy a 12V 5 amp smps adapter for driving them.

Connect them in series along with a 8 Ohm resistor
how costly are these smps?
Swagatam said…
very cheap, around Rs100/-
Risetofly said…
I want Automatic phase changer (RY RB YB) phase to phase if voltage low in each phase

In my home each phase having 220V and having 3phase (RYB).
We have low voltage 80V to 110V in each phase.
I decided to make Automatic phase changer phase to phase.
Like if R has low voltage then Y and B phase should work without neutral or
if Y has low voltage then R and B phase should work. or
if B has low voltage then R and Y should work.

This project is for personal use and there is not crime only safety i want.

1. Electricity is free for tribal area because of backward area. Having no luxury facilities.
2. In each phase has low voltage like R=80V, Y=100V, B=110V.
3. I want to use Voltage 240V (Phase-Phase) as i don't use neutraland load is 35A maximum each phase.
4. I use three sockets for three phases. When i get current low in one phase and i use another two phases for load chaning manually.
5. when any phase became low then we take out cable and put in each phase (R and Y) or (R and B) or (Y and B). like in R= phase cable and Y= Neutral cable from stablizer to ouput for load. See below in diagram.
6. We have special sockets of 60A. Always changing cable 35mm is risky because if phase voltage become low then we usually change phase to other phase and cable naked tip may possible to touch with any person if there is no saftey.
7. I want to stablize voltage upto 250V from phase to phase like R=110V and Y=100V became 200V around up and down.
9. I'm using equipment like fridge=220V, Washing Machine, Motor pump, A/Cs etc lightings.
10. I don't want to damage all equipment and human loss.
11. At 100% load there will be not more than 35-40A in each phase.
12. my house 20yard x20yard so source within 5 meter from house. we dont have meter ok.
13. Intentionally electricity company makes vary and reduce voltage from 220v to 80V in each phase because electrcity free.
Swagatam said…
I don't have much knowledge about three phase connections, however I'll try to figure out the whole thing, If I succeed in developing the required circuit, will inform you immediately with the update.
many thanks for ur quick reply.:)
doesnt the 3W LED require abt 700mA ryt. so wont it be a over kill?
i have another doubt regarding the design of a LED lamp which will work on mains as well as battery.i want to use nicd battery(6V battery packs).the transformer is 8-0-8 1.5A. so while charging the battery wont the volatge drop to level of battery and wont that affect the working of lamp.
i intend to use the leds in series in ac connection and in parallel in battery mode.(already designed switch connection for that).
Swagatam said…
Yes you are correct, in fact a 3 watt LED would consume above 1 amp.

If the AC/DC supply is bifurcated into two streams, one for charging the battery and another for driving the LED, the problem would be eliminated. This may be done using a couple of 1N5402 diodes.
can u just give a simple diagram for that?
Swagatam said…
I think using two diodes also won't help, the voltage will drop anyway while charging the battery.

There would be a slight difference only in the illumination of the LEDs, so probably that shouldn't make much of a difference.

There's no way to overcome this issue.
~!jesseloop said…
hey swagatam,
I recently built a magnetic coil (like a shakelight) which had voltage input (1.14volts) integrated into the coil, and also because my coil produces alternating negative and positive signal, I used an old cell phone charger to redirect the alternating signal both back into the coil, and into another lead-acid cell (a completely depleted 9v) and if I activated a sequence through the coil for a while, then for several hours afterward without any activation I will still be increasing voltage into the receptor cell. This continued this way for nearly a day, eventually producing over a full volt of charge into the cell.
Now it does not work, and because I still get negative and positive signal when I activate the coil, that there is a component in the modified "rectifier," if you will, that has failed. I wish I could find which component has failed, and create an identical circuit with a component (or a series of components) which would not fail, and would still continue to generate power on its own. I saw this one other time happen also but disbelief caused me to move on to other projects... now I want to make this work.
I really like the way you respond to your readers. This is one of the best blogs I have seen in terms of electrical circuits.
You are a brilliant engineer and very helpful to people.
warm regards,
Swagatam said…
Hey Jess,

There are a few confusions. Why is the 1.14V input is required? And a cell phone charger will not respond to anything lower than 85V, so how is it helping the cause, moreover after switching off the mechanism the battery keeps charging, this also looks quite unbelievable.

Anyway for rectifying the generating AC you can incorporate a simple bridge/capacitor network using four diodes(1N4007) and a 1000uF/25V capacitor.

Making a bridge rectifier has been explained in the following article:

The capacitor may be connected across the positive and the negative of the bridge.

Thanks very much Jess....I truly appreciate your response!

Best Regards.

what if i use two bridge rectifiers and make a dual supply using the centre tap?
Swagatam said…
No, that won't help either unless you use completely separate transformers, two of them, one for the LEDs and the other for charging the battery.
alryt then i i guess i will use a switch to toggle battery charging.
is it possible to make a simple circuit to set the max charging time of battery to 10 hrs ?
vinay pandey said…
sir,please tell me an easy way to make a laboratory incubator which contain an air fiter and a co2 supply for pH please provide me the
circuit and a cheapest way to make it.its necessary.......
michael said…
hi bro...
ty for your attention....GBU
Swagatam said…
It would be better to add a overcharge cut off circuit, you may build the second circuit shown in the following link:

Interchange the pin#2 and pin#3 so that it works as an overcharge cut off instead of low voltage cut off.
Swagatam said…
Hi Bro, I have posted the required circuit here:
Swagatam said…
Hi Vinay,

I have no idea how to make the respective gas filters, but still I would research the matter and post the circuit it its feasible.
thank you for the circuit.
is it better to use 3 nos of 1W led or 1 nos of 3W led?
Anonymous said…
Hi sir , thanks for all your explanation , i am from Palestine gaza , i want to ask can you explain how i can build A stabilizer with 4 relay system 1kva ?
Swagatam said…
3nos 1 watt led is better because it will help to distribute light in all directions.
Swagatam said…
Please refer the following article:
michael said…
hi bro....
I try to make dc analog cdi for small motorcycle, can you give reference for this? ty...GBU
Swagatam said…
Bro, you can try this circuit....
Steve Parkhill said…
Hi Swagatam,

I'm interested in designing a circuit for a lithium-ion battery so that it can be used as an emergency power source for my cell phone. I'd like to be able to charge the lithium-ion battery using a 5VDC supply and then use the charged battery to supply 5VDC to my cell phone so that I can re-charge the cell battery. The difficulty for me is figuring out how to keep this circuit as small and efficient as possible. Could you help me with this?

Swagatam said…
Hi Steve,

I think using Ni-Cd Cells would be better instead of Li-Ion because they are easier to manage.

Put three 1.2V Ni-Cd AAA cells in series and your cell phone charger pack is ready.

Charge the Ni-Cd pack at home using a good 4.5V Ni-Cd charger, and you are all set to take it outdoors with you, whenever your cell phone gets flat, connect the pack with the cell phone for a quick and smart refill.

I would be addressing this as a new article in my blog very soon....

Nimesh said…
sir ,i have design problem, can we use the same transformer for charging as well as interesting purpose,ie when the mains is available the battery will charge through the transformer, and if it fails the circuit work as an inverter uses the same transformer that give back the supply to the mains (or to other one ). inverter and charging circuits are individually available but uses separate transformers for charging and inverting purpose so plz help me to design such an inverter..
Swagatam said…
Hi Nimesh,

I'll try to design the circuit, it might be possible if we use many changeover relays for the implementations.
pnitiga said…
Dear Swagatam, Could you please provide Hybrid charger for Inverters which can be easily incorporated to the existing inverters. (For eg. 800VA/12V-150AH battery). I searched your blog and found some very useful circuits in the same category..but it was for 6V and low power applications. The main concern is, during power failure in the day time, we must be in the position to charge the inverter battery using Solar panels and also utilizing the battery for AC loads(inverter mode). When the panel output goes low, we could switch to mains to charge the battery. This would be helpful for peoples from tamil nadu, especially. We have 16 hours of power cut everyday, FYI. Thanks in advance.
Swagatam said…
Dear pnitiga,

I have already designed one high current battery charger circuit, you can see it here:

Your second requirement has been covered in the below given link, though it's not exact, can be easily customized:
Risetofly said…
Dear Swagatam

The circuit for charger high current 10 to 20 amp which you mentioned in circuit diagram. I want this circuit automatic instead of pressing switch on. Is it possible to provide me information for automatic circuit instead of switch.
Swagatam said…
Dear Risetofly,

You can refer the last circuit in the following article:
network advise said…
hi swagatam
this srinu toram
i had a problem with my microtech ups all mosfet are bunrt. i found one of side mosfet numbers STP60NF10 and another side STP80NF55 ON pcb board both mosfet are equal or not ? each section had 8nos mosfets suggest me please
thanks & regards
Risetofly said…
Dear Swagatam
First of all Thanks for helping regarding circuit.
I'm attaching automatic phase changer (APC) circuit diagram from websites.
I want to ask this APC circuit can modify for 3 phase. Like phase to phase (1-2),(1-3),(2,3). I requested you before on above mentioned paragraph.
i also want to use this circuit for each phase 35A. Is this possible that each phase provide upto 50A from this circuit.
Please give me advice for further action.
Swagatam said…
Hi Srinu,

One is 55V, another one is 100V.... however both are N-channel and 80A rated so I think both are equal.
Swagatam said…
Hi Risetofly,

I'll try to understand it and come up with a suitable solution....
network advise said…
thank you very much swagatam
Anonymous said…
Hi Swagatam,
I have some questions for the circuit diagram from:
1). it says that it uses a baterry 12V, 30AH. But i have a baterry 12v, 61AH.
is good for this circuit?
2).TRANSFORMER = 12-0-12V, 20 AMP. I can use one of 12v-0-12v 10AMP?
3). R12 is a rheostat to change frequency (for europe,romania is 50Hz)?

If you can answer the subsections would be great.
Thank you very much.

John, Romania.
Swagatam said…
Hello John,

Yes you may go ahead with the available components, they will work.

R12 is a potentiometer for adjusting the RMS of the output with standard mains AC RMS value.

The frequency of the circuit has been fixed to 50 Hz.

Anonymous said…
Hello Swagatam,
Which of circuits for inverters you proposed is recommended for laptops(i need a circuit diagram with minimum 200W )?
Please tell me the link.

Thank you very much!
John, Romania.

Swagatam said…
Hello John,

Though I haven't tested it practically, you may try this circuit:
Anonymous said…
can you please change the scheme for 150W maximum wanna be fewer transistors bdy29 ?(for low costs and to be good for laptops).

Thank you very much.
Swagatam said…
You may include only a pair of output transistors in place of 4 will produce 150 watts
Dear Sir,

I want to check current wave i dont have CRO. it cost is very high to buy it. i have computer in computer. what software i can use and check it please let me know.

Thanks & Regards,
Dear Swagatam,

Solar Panel/AC Mains, Relay Changeover Circuit in this circuit you use relay it will work only 10A but if it is 30A we have to use mosfet circuit if you have can you send me the circuit.

Thanks & Regards,
Swagatam said…
Dear Amarendra,

Download Goldwave (free version), there you can test and analyse waveforms....but you will have to convert the voltage to less than 1Vpp before applying.
Swagatam said…
Dear Amarendra,

30 amp, 50 amp relays are also available which can be used, relays provide two way changeovers, mosfets can't provide two way changeovers.

Anonymous said…
hi sir,

your circuits are impressed.. we have two cfl lamps of each 18W. i need to connect these two lamp with one choke of 40W. i tried both series and parallel. but only one light is glowing. other one just take off and shut down.. what will be the solution ?. is that possible to glow two cfl in single choke.
Swagatam said…
I think there's no solution for this problem, because different tubes may have slightly different firing timings so cannot be lit together through one can try electronic choke, might work...
nishant said…
hello Sir,
This is Nishant from a small town near Ayodhya.I hve completed my electronics engg in 2011 and currently preparing at home.Since towns in Up has very frequent power cut therefore almost every house has 12v 30AH or 35AH locally manufactured lead acid car battery.(Battery capacity not written on battery but by seeing the size of exide maxx 30ah and 35ah matches with local battery).
So as to utilize the energy efficiently instead of cfl I planned to use led.I had some 5mm white dome type ultra bright led.I connected 3 of them in parallel, and 470ohms 1/4W limiting resistor with every led.When i connected to battery(12v),led lighted but the resistors got heated up.Will more wattage resistor will solve the problem.According to my calculation R=(12-3.3)/20m =435ohms but i could get nearest value as 470ohms. P={(20m)^2}*470 =0.174W.But When i measured the current across the circuit multimeter reading was 0.5A.Please tell me what is wrong?..
Swagatam said…
Hello Nishant,

Increasing the wattage of the resistors should solve the problem.

However with 12V as the source you should connect three of them in series with a 150 Ohms resistor, instead of connecting in parallel.

Even though 470 Ohms with each led is absolutely correct, connecting in series would produce better results.

For reading current connect the meter in series with the supply.
Anonymous said…
thanks for your time sir, actually we used electronic choke only.. both the tubes are same. choke has 4 wires and cfl lamp also 4 wires.. finally it glows like half voltage. is there any problem in distribution.
Swagatam said…
I am not sure about this, may be you can try putting the tubes in series with an electronic choke.....but you may have to modify the ballast choke winding someway for that.....still just assuming.
Juan said…
Hi Swagatam,

I always find your bolg very interesting.

I want to know if this would be possible

I have a cabinet in with I put a magnetic switch with normally closed and normally open contacts. (today, I only use one of them)

Today, when you open the door, the light that is on top turns on

I would change the circuit so that:

1. Open the door once so the circuit is ON, after a given time, the light turns off (although the door hasn't been closed and is opened). If I ever want to turn on the light, I have to close the door and reopen it.

2. add a LDR to turn on the light ONLY if there isn't sunlight in the room. With LDR in series with the load is enough?

The system is 12V. Should I use the famous 555? (all I've seen is with tiggers (push buttons), which is not my case)

Thank you.
Swagatam said…
Hi Juan,

It can be done very simply. I'll design the circuit and inform you when it's published.

Thanks and Regards.,
Dear Sir,
My name is Amarendra I want to learn circuit degain. Can u provide online training to me pls tell me how mch fee cost and how u can gime training cont me 8886240240.
Swagatam said…
I am sorry Amarendra, a live online support won't be feasible due my hectic schedules.
Atul said…
Hi Swagatam

I am Great fan of you, I like to go through your blogs and also the comments.

So finally I got inspired and start to work on very simple requirement of mine.

I have idea and tried to put in format of circuit.

So can you basically help me to understand will it practically work or are there any other component required like capacitor or else to make sure relay wont go in loop.

Below is my requirement and the circuit

1> Manual start of the motor by Push button,
2> It will also provide the supply to Step-down X’mer and Motor
3> O/p of the Xmer will activate the SS relay and state will be on hold.
4> Once the water level reaches , sensor switch will be open
5> This will disconnect the input to the SS Relay .
6> And hence the supply to the X,mer will also get disconnected Stopping the Motor.

Uploading the circuit diagram is not
possible here so I have sent it via email.

Thanks and Regards

Swagatam said…
Hi Atul,

Thank you very much! You are most welcome.

Your idea is very nice.......I am trying to understand your diagram... since symbols are not used for the various components tracing the voltage paths is getting a bit difficult.

However it looks definitely feasible.....we have to keep the float switch connection away from the mains, that is important.

I'll try to figure it out and inform you soon here.

Actually I have already used this concept in the below given article, in a different way, though.

Best Regards.

nishant said…
Hello Sir,
I own a 1KVA automatic voltage stablizer,it has problem that when power comes there is sudden rise in voltage for very short instant(Due to which my 2 cfls& 2 bulbs got fused) after that its voltage stablizes.Since it is in guarantee period ,I have taken it to the place from where i have byed it,he checked it by varying the input voltage,stablizer worked fine.I think a delay in the output will solve the problem.Can you please suggest a circuit which could be connected externally so that guarantee is also continues and problem is also solved.
Hello Nishant,

You can try the followng modification:

Open the stabilizer and look for the transistor which controls the output load relay.

If the transistor is an NPN, connect a 1000uF/25V capacitor across its base and ground or emitter, if the transistor is a PNP then connect the capacitor across its base and positive.
nishant said…
There are three BC547 transistors, each emitter is already connected with 100uF/40V capacitor and ground.Output is taken along each capacitor and fed to corresponding three 24V relays respectively.
What to do?replacing 100uF/40V capacitor with 1000uF/25V will solve the problem???
The capacitor needs to be connected across the base and ground of the transistors. Do it for all the three transistors, a 220uF/25V would do for trying purpose, don't use 1000uF/25V.
Dear Sir,

I need 850VA Inverter I will pay money pls cont me 8886240240 Amarendra
Dear Amarendra,

I really don't have a 850VA inverter circuit presently so I won't be able to help you in this regard, I am very sorry.

Anonymous said…
Hello sir you have a circuit tester CCFL lamps used in LCD ... Thank you very much.
ATTE: Amir.
Hello Amir,

Presently I do not have this circuit, will try to find it on the net.
Star Gazer said…

Just found your site, very cool.
Perhaps you may be able to assist my son and I with the construction of a circuit for his science fair project.

He is 13 and attempting to confirm the charge/mass ratio of the electron by reproducing the JJ Thompson experiment. His strong suit is in theoretics and mathematics and not so much the engineering.

We are using COTS products for the cathode ray tube and power supply but need to construct a variable strength electromagnet to demonstrate and cause deflection fo the electron beam. Our goal is an electromagnet which we can vary in strength and measure, perhaps by measuring the strength of the power source with and ammeter.

If you have any suggestions for a circuit diagram, we would be most appreciative and any guidance will of course be appropriately sited in his references.

Cheers and Happy New Year,

mark and alex
Thanks Mark,

I have already published one related circuit in this site which illustrates the process of controlling the strength of an electromagnet, I think this is what you might be looking for, please check it here:

Happy new year to you and the little scientist, and all the best for the project.

Anonymous said…
Hi from Canada !! My name is Mike . thank you for your work . would it be possible for you , if you have time ! to make me a design for a 1000 watts electronic ballast for metal halide lamp ? a variable one would be even better . I have 120 volts here,
Something simple to build if possible
thank you very much and Happy New Year
Anonymous said…
hello sir i want to make a 24v 30A pwm motor controller.pls.pls.pls help sir.............
Hi Mike! Thanks!

A 1000 watt ballast will be difficult for me to design, I tried to find it on the net but I couldn't find any.

By the way you can go for LEDs instead of the proposed type of lamp for better efficiency and light.

And a Happy New year to you, too!

You may try the following circuit:

The IC supply should be around 12V and the motor supply may be up to any desired value
Anonymous said…
OK, I'll do it soon, and inform as soon as it gets posted...
kkaranjia said…
what is pot and can it give same output as 360 degree self centering joystick??
it's a control knob device, for example the one which are used in electronic fan dimmers.
kkaranjia said…
ok i understood its a variable resistor so the circuit u can provide will work with the analog joystick as it also has 2 variable resistors in it. I want to control 2 servo DC motors of around 2hp so please suggest some pwm controller for it and wanna use auduino processor if its confortable with you
There's one simple circuit here, you may try it:
kkaranjia said…
Thanks for the circuit it will be help fill but will it be able to with stand the curent for 2hp DC servo motor and here i need to use to controller with the pots or variable resistor as i needs to control 2 wheels of a bot and want that during turns the speed of one motor should fall sown to 15 percent of the other motor. and till i think with your circuit motor can be controlled in only one direction.

please go on the below link you might get some reference
kkaranjia said…
please help with interfacing the controller with pwm motor driver and a variable resistor with the controller. arduino processor have the analog input on board so we can directly give the inputs to the processor board directly from the variable resistors
You can check the following link, the actual design is given at the end of the article:
In the above circuit you will have to connect a variable voltage input to pin#11 of the 0 volt the motor speed will be minimum and it will go on increasing as the voltage is increased...upto 12V max.

sorry, I am not sure how to integrate it with an aruino processor.
kkaranjia said…
i need to continuously vary the speed in both directions so if it will be very helpful if i can eliminate the use of bidirectional switch and control the speed in direction using a pot. using the middle of the pot as the 0 position . Also motors i want to use are 72 volt 2hp c motors so what type of switches are required to be used
I am sure there's some easy way of implementing this but cannot presently figure out....I'll try to find a suitable solution, if it's feasible will contact you back.
Anonymous said…
Hello sir Swagatam. I am a faithful follower of your articles and electronic projects. I have a question, I have a variable power supplies 1.25vcc to 25vcc x 4 amps with a second potentiometer for fine adjustment of tension, but I think it would be better if you could vary the output current with a circuit to vary the current from 100mA to 4 amps ... you have to add a circuit.
Thank you very much.
ATTE: Ariel.
Anonymous said…
Hello sir. built this Over Voltage And Low Voltage Protection Circuits: but the shakes so much for connecting relay as well to disconnect ... I solve this problem .. thank you very much.
Thank you Ariel,

You will need to open the power supply and find a suitable point in the circuit for doing the required modifications, it cannot be done through an external circuit.

Alternatively you can try building an entirely new circuit with its own voltage and current adjustment facilities.
Melro said…
hello, is there any transformer less power supply for pot put 12V DC and handle about 3A

For 3 amp current, an SMPS is the only option, no other forms of transformerless power supply would handle such high currents.
Anonymous said…
Hello swagatham,
i am lohithashwa from bangalore.I have an spare DC 12v 20amps portable (automobile)air compressor .I desperetly require an transformer with input AC 220v & output 12v,20amps with + - terminals for indoor domestic use .kindly mention the shop address in Bangalore where it is sold .my email:
Hello Lohith,

I am situated in Mumbai, so I have no idea about shops in Bangalore.
Sultan Allawati said…
Hello swagatam
Do u have a simple circuit for walkie talkie?
Hayan Fadhil said…
Hi, I find your website very useful. Is it ok if you can help with this query:

Design a circuit to give uninterrupted 5 V dc power supply with 110 V 60 Hz line voltage as input. The dc output should be available in case of power outage (110 V line supply). In case of line failure, the circuit should switch to backup source that should be designed using a solar panel.
Hello Sultan,

You can check this link:

Please refer to this diagram:

You may replace the battery with a solar panel, and connect a 7805 IC at the junction of D1/D2. the output from the 7805 may be used for the desired application.
I am sorry, the above circuit won't be applicable with a solar panel.

You could do it simply by using a 12V relay with the following arrangement.

Add a 7812 IC after the solar output so that the solar voltage becomes regulated at 12V.

apply this 12 volt to a 12 relay coil.

Connect the pole of the relay to a 7805 IC input pin, connect the N/C to the (+) of a 12V adapter, N/O to the (+) of the 7812.

Make the all the grounds (negatives) as common terminal.

The desired output may eb taken across the 7805 output pin and common ground.
Anonymous said…

do u have a circuit for controlling a motor by ir remote??
Anonymous said…
do u have a circuit for controlling a motor by ir?

for the previous
walkie talkie
what does AF means??
is it a component?
presently I do not have it, but will try to design and post it soon.
AF stands for audio frequency
Hay I m Fahad,
Sir is there any cct regarding microcontroller based digital clock using seven segment display,
kindly help me about this.
Udayan said…
Hi Swagatam Majumdar,

I am a frequent visitor on your blog.

I just want to ask something regarding a Mosquito bat.

Every time when i buy a bat it wont last much, is there any alternate circuit for the bat, normally the output driver transformer fails. It is not available in the market.

Appreciate your comments
Hi Udayan,


I think it's the battery that becomes weak or bad, not the transformer or the circuit, you can probably try replacing the battery and check.
nishant said…
Hello Sir,
I have a 1KVA automatic voltage stablizer.It has one defect that when it is switched on, very high voltage is outputted for about 1.5s(therefore cfls and bulb got fused frequently) after that, voltage is ok.I have opened the stablizer it consist of an autotransformer,4 24V relay each relay connected to a seperate circuit(each circuit consisting of 10K preset,BC547,zener diode,BDX53BFP npn darlington pair transistor IC,220uF/63v capacitor,100uF/40V capacitor ,4 diodes and some resistors).These circuits are powered by a stepdown transformer and output of these circuit are taken across corresponding 100uF/40V capacitor and fed to corresponding relay.What to do in order to tackle the problem.please help me.I am sending the hand drawn circuit diagram by seeing the pcb to your mail id please see it.It may help you.
Hello Nishant,

I have replied you in the email.
Hay I m Fahad,
Sir is there any cct regarding microcontroller based digital clock using seven segment display,
kindly help me about this.
nishant said…
Capacitor 220uF/63V can be used in place of 220uF/50V?I cannot get 220uF/50V here because i am living in a town area.If 220uF/63V cannot be used,can u suggest other values?
I have a couple of very good circuits, I'll try to post them soon....
nishant said…

1.I want to clarify that +ve of capacitor has to be connected to base of bc547 and -ve of capacitor to ground?

2.Each bc547 has to be connected with capacitor since there are four in number because there are separate relay(four) circuit for respective relays?

3.And you have said that if it does not works connect capacitor across anode of zener and positive supply .In connecting capacitor across zener and +ve supply,capacitor's +ve has to be connected to +ve of supply or zener's anode?
raigon jose said…

My name is raigon jose and i am from kerala

And i made 1 solar street light with 12 VOLT 100 WATTS panel & 42 ah SMF battery & Lights 1 watt Edisson LED 20 Numbers

( 3 V x 4 ) A pair of 4 Led Series -------- 12 v ( 5 Rows) 20 WATTS Total

I have a problem faced from automatic ldr switching Circuit
LDR SWITCH CIRCUIT Installed in light Dom
LDR is installed inside the light cover
When evening 5 'O Clock the Light will be switch on & morning after 7.30 am will be switch off

When i searched about this problem i got u r website

In that circuit when we adjust that preset ,i think it will switch on only after the dark will come to ldr

Give me one solution for to adjust time of switching on and off lights..................

PLEASE HELP ME........................................................................................
this page is not responding to comments, please do not use it for commenting.
Sultan Allawati said…
Hi swagatam
Onc i emailed u about controlling a dc motor by ir remote contrlloer
I found a circuit on the internet and already implemented but the idea of it to run the motor only in one direction any ideas to make it bidirectional
Here is the link.
Waiting ur reply
Thanks a lot
lihtnesr said…
Hello Sir,

Im an avid DIYer. Recently, i was looking to make a DRL(daytime running light) for my car using 1 watt smd LEDs.

But i couldn't find an appropriate circuit for my need. I want to drive Eight 1watt LEDs from my car battery.

I would very much appreciate if you could design a simple and rugged circuit to drive 8 x 1watt leds from a 12-14v input.

Im also planning to add a heat-sink to dissipate any heat generated by the leds.

Thanks & Regards,
Hello Senthil,

I have noted down your request, and would try to publish the article soon in my blog.

Hi Sultan,

very soon I will be posting a similar circuit idea which would have much better features than in the given link, including bidirectional rotational facility.
lihtnesr said…
Hello Sir,

I went through the DRL circuit that you have posted. Now i understand that the circuit would produce a LED chasing sequence.

And i guess there has been a misunderstanding.

The day time running light im looking to do is constant type, the "running" word means the car's running.

Please refer to this link

The 8 high power LED's must be in ON state.

Please make a circuit for this if possible.

Hello Senthil,

This page is not responding to comments, however I have read your comment which you have posted, I'll do the required corrections in the DRL circuit.
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