325 thoughts on “Contact

    • hello friend, I am passionate about electronics and also am one of your admirers around the world. I wonder if you have some scheme of some electronic circuit able to control equipment from a distance, via mobile phone, gps, etc, because we need a device on and off the distance that can be locked. If you already have some mounted, I am interested in buying from you if it is not too high. I appreciate the attention, any questions can explain more detailed via Skype If you possess. thank you

    • hello friend, I am passionate about electronics and also am one of your admirers around the world. I wonder if you have some scheme of some electronic circuit able to control equipment from a distance, via mobile phone, gps, etc, because we need a device on and off the distance that can be locked. If you already have some mounted, I am interested in buying from you if it is not too high. I appreciate the attention, any questions can explain more detailed via Skype If you possess. thank you

    • Hello sir,

      I want to make 3RCA TO 6RCA Female cable and 3RCA TO 3RCA+RJ45 Female cable. Will you please provide me circuit for it. Pls do the needful


  1. 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….

    • to u and yr family.
      Sr i want to glow up 7000 to 8000 leds with 220 v ac and want them just blinking.
      Kindly guide and help me giving a appropriate ckt.

      Thanks and best regards in advance

  2. 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.

    • 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.


  3. 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:) .

  4. 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.

    • Hello Kanagaraj,

      It will be difficult to troubleshoot the problem because there can be many different reasons…by 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.

    • 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..

    • 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..

  5. 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

    • 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!

  6. 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

  7. 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,


  8. 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 melromendis@gmail.com)

    Thank You

  9. 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


  10. 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.


    • 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….


    • 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 .


    • 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 power.one contactor for Line or city power.Interlocking between these two contactor.After generator should stop.

  11. 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….

  12. 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 turns.to 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

    • 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:(

  13. 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

    • 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.


  14. 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.

    • 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..

  15. 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

  16. 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(michaelhappyg@yahoo.co.id)

  17. Title:
    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.

    • 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.

  18. 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,

    • 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.

  19. sir,please tell me an easy way to make a laboratory incubator which contain an air fiter and a co2 supply for pH alo.so please provide me the
    circuit and a cheapest way to make it.its necessary…….

  20. 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 ?

  21. 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?


    • 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….


  22. 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..

  23. 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.

  24. 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.

  25. 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

  26. 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.

  27. Hi Swagatam,
    I have some questions for the circuit diagram from: https://www.homemade-circuits.com/2012/02/how-to-make-150-watt-modified-sine-wave.html
    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.

    • 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.


  28. 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.

    • 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.

    • 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.


  29. 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.

    • 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 choke………..you can try electronic choke, might work…

    • 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.

    • 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.

  30. 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?..

    • 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.

  31. 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.

  32. 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


    • 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.

  33. 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.

  34. Sir,
    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.

  35. Hello,

    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

  36. 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

    • 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!



  37. 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.

    • 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.

  38. 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.

  39. 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: lohith.c.222@gmail.com

  40. 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.

  41. thanks
    do u have a circuit for controlling a motor by ir?

    for the previous
    walkie talkie
    what does AF means??
    is it a component?

  42. 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.

  43. 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 homemadecircuits@gmail.com please see it.It may help you.

  44. Sir,
    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?

  45. sir,

    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?

  46. Sir,

    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…………………………………………………………………………….

    • 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.

  47. 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 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.

    • hello sir,
      I have a 600VA Sukam Sonik Home UPS(having both ups and inverer mode).I have connected a 95ah tata green tractor battery to it.Battery gets full charged approx in 3 hrs.Battery is 1 month old,but backup is not good.two cfls(8W+14W) run for 2 hrs and then 1 wall fan (65W) it runs for only 3 hrs.
      I have checked with my multimeter that when battery reaches 13V inverter gives the full charge indication.I have also tried the switch behind the ups to switch between the inverter mode and ups mode but the backup remains same(3hrs approx)

      Where could be the problem is it in the inverter or battery?????

  48. Heloo again
    Thanks for your reply
    Yeah it will be nice
    So for the prescence time
    Can u provide me with an idea that will make the motor run bidirectionally
    Because I have to draw the pcb as soon as possible to make the design and submit it to the college
    Thanks alot

  49. hii Swagatam can you help me in designing a phase sequence detection relay. The circuit should detect whether the R Y B phase are in sequence or the sequence has been changed. if the sequence gets changed the circuit should activate the relay attached to it

  50. Hello Swagatam,

    First thank you for hosting this blog. It is very kind of you to give of your knowledge as you do.

    I am building a circuit that has a 12vDC in and a selection of other voltage and connection types out, such as 5v USB, a rotary switch selector for sending 3, 5, and 12 v DC to binding posts. I have drawn the schematic, but my knowledge of circuit design is VERY limited and I was seeking your guidance. Can visitors submit designs for your review?



  51. Dear Sir,
    I use a 12 Volt battery at 1200 mAmp and I use it on a RC quad copter, from it I get about 7 min flight time.
    What I like to do is use 3 batteries at the same time and a circuit that will automatically change to a new battery when the first has reached a low point of about 10 Volts. This way when the first battery is about 10v the circuit will change to the next new battery this way giving me another 7 min of flight and then the same will happen with the 3rd battery. Total flight time of 21min with 3 batteries. Can this be done? Another problem is that there should be a continues flow of power to the quad copter because if the power is cut when the switching is happening between the batteries the copter will stop flying and fall to the ground.
    Thank you for your time on this hope you can help.

    Best regards

  52. sir
    i have a solar panel of 12 v (5 w) dc …
    can you please tell me,what can i do with it?
    please tell me about its usage in lights or inverter charging…
    thanks in advance

  53. Hi Swagatam,
    Very interesting and informative site for those of us who like to experiment with electronic projects. It is actually by sheer chance that I found your site as I was searching for a laser pointer alarm circuit.
    I have been searching the internet for sometime hoping to find a circuit which can be used to monitor the position of a dog on a large piece of rural farm land as the dog approaches the fence. Is it possible to setup a transmitter – receiver arrangement with a range of 500 metres, maybe using the fence as an aerial and two identical receivers, one attached to a dogs collar and the other in the house. the receiver on the dogs collar to provide a vibration or similar effect(Not shocking). The receiver in the house to provide an audible sound to let us know when the dog has crossed over or has intentions of crossing the fence into a neighbours yard to tackle the cows.
    Do you have or know of any circuits which could possibly work?
    Should you want to contact me please use aubunnz@yahoo.com.
    Your assistance or/and any feedback would be appreciated.
    Kind Regards

    sir, i need a circuit for SPECIAL FEATURE to up grade ny conventional ups in to solar ups, with first priority given to solar, the charger has the INTELLIGENCE to connect& disconnect the AC mains to the ups depending up on the battery voltage level to ensure using solar as primery power& main only for the emergency

    max solar open circuit volt 50
    max solar panel capacity 60am
    sytem volt 12v
    battery full volt 14.5
    battery voltage main disconnect 14.5
    battery voltage main reconnect 11.5
    solar nite off , mains on NO MAINS disconnect
    LED indication 1. solar charging
    2. load on solar
    3. main on
    Capture.PNG Capture.PNG

  55. Sir,
    As for a project purpose I want to model a non-linear residential load like PC, CFL, Fridge etc as a harmonic current source in parallel with the fundamental impedance in the MATLAB/simulink

    please help me with the simulations
    thank you

  56. Dear Mr. Swagatam,

    You are putting in a tremendous effort.Thank you for your constant endeavour. You once mentioned about a 12V/1A smps circuit(using VIPer 22A).I want to run a string of LEDs (1-2W) for illumination purpose from AC mains.Should I add any of your suitable PWM circuit to the output of your smps circuit? Can you give some circuit for cheap,reliable 12V/3A smps in details as you have given for 12v/1A?It will be great help to me.Thank you in advance.

    Tapas Deb.


  58. hello sir iam basha your projects most sinceyarli warking
    your 2 to 5 kms fm transmitar project i like it sir so you made this project my adress send me sir this project money i paying sir
    please made and send me sir thanq

  59. helow sirr ……I hav got a project on single phase transformer……if u don't mind den can u plz say me abt its construction n components to required to build a one phase transformer……my gmail is pawan.singh2069@ gmail.com

  60. i have tda2030 2.1 system
    12v power 10w 8 ohm woofer freq responce 20Hz to 200Hz
    i want to add some bass-boost like
    200Hz = +7.3dB; 100Hz = +12dB; 50Hz = +16.4dB; 30Hz = +13.3dB

    10W Audio Amplifier With Bass-Boost with NE5532 is avalble on net
    but i can not made it so i need help
    how i make bass boost with tda2030 circuit

  61. Hello Swagatam!

    My name is Felipe (not anonymous as the title says) and I want to congratulate you for your awesome blog. I came across by your inverter circuit but there are tons of other interesting stuff to build.

    Keep that good work, I'm definitely subscribed. Greetings from Colombia!

  62. Dear Mr Swagatam, i am an electronics hobbyist and followed your work on this site for some time now. I have learned many things from it and i like to thank you for that. For my next project i like to make an inverter with parts salvaged from obsolete ups's. I have a 2kva transformer, a print board with 16 mosfets PN80NE0 full bridge driven by 2 ic's IR2110. Do you have a circuit with load dependent correction for me that i can use?

    Thanks in advance
    Best regards,

  63. Hello Swagatam –

    Your site is very good. Specially for those interested in Electronics & in Building. I have a Little Problem as I am just an electronic hobbyist. I am not aware much about the Components. Can make a Article page on this site explaining in details how to use PCB's, Correct way of connecting LED, Resisters, Diode's, Color Coding of Diodes, etc.

    This will help a New Hobbyist to learn a few circuits building. There are many Ready to build kits in the market and we get all the parts mentioned in your blog easily but are struck when we have to make the connections as we get confused as to which wire has to be connected to Positive point or Negative Point. If we connect it wrongly the project may fail and if the project involves main current then the damage may be Great.

    Hope you get my point.

    Thanks & Regards

  64. I made the circuit "Simple Door Bell Timer, with Adjustable Timing Facility" but it is not working. A few days ago I saw the same circuit in your site with some modification using bel8550 and 8050 transistors with some change. I am confuse that which one is correct and tested o.k. Please clarrify.

  65. Hello sir.
    I want to make simple SMPS welding machine for my personnel use .if u have any complete circuit and design please help me.

  66. Hello sir, I really need your help. Any suggestion of a circuit or electronics components I’ll be needed to build a circuit for an automated conveyor that could detect if the boxes are large, medium or small and sorted them to 3 different directions. The size of the conveyor is 10 inch by 18 inch. By the way sir I’m from Philippines and I’ am a currently second year college student taking up Electronics and communication engineering, and that project was my final requirements for industrial electronics sir. I really hope you’ll respond as soon as you saw this. Big thanks to you sir. Have a good day 

  67. Hi i have a request :D, if it's possible. a circuit for a DRL (day running light.) made with 10 LED white, the circuit for led must be with impulse (impulse control) a potentiometer for frequence control , frequence between (i can see the led blink -and- over eyes can percept). if you have a idee. V=12 V

  68. Hello Sir Can you tell me how many 1 watt LED I can use in series on 12v 500mAh charger usually use for modems etc. Do I need any resistor to do such. Regards

  69. hi Swagatam
    i have an ic voice recorder model vr330
    at first it was working well
    recently it always shut off "battery low" i replaced the battery but no success.. i used lm1117 3.3v but also the same result.. it always tell low battery and shut down..
    i checked every single item on the board but didnt find any item harmed
    is there any chance that i could fix it ?
    thank you

  70. Hello sir,
    I need a circuit which will make 12 volt relay initially On, as soon as I trigger, relay should get OFF until I restart the hole circuit. Relay should stay OFF irrespective of thereafter triggering.

  71. Hi,
    I need a circuit to start an Electric Generator automatically when power is failure, and then stop it when main power is ON. can you help me? is there any idea based on 555 timer sircuit using SPDT relay.I have a 3KV electric generator with selfstart option.

  72. 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.

  73. Do you work w/ a program like Altium Designer for schematics and PCB design and can you generate files for manufacturing? I need a whole series of measuring devices and switching modules for a modular climate control system built around an embedded ARM module like the Aria G25 http://www.acmesystems.it/aria

    Measuring devices like temperature, humidity and CO2 sensors to start with, all with a common current or frequency based output connected to a controller board that communicates w/ the ARM module through I2C. The CO2 sensor module doesn't need to be designed from scratch because there are already some modules on the market that need a converter circuit on the output only.

    Switching modules like simple relay boards and different capacity 110/220V AC PWM controllers from 4 to 12A all controlled over a low current 4-wire cable for I2C signal and power supply.

    All modules must be hot-pluggable and the system is controlled through a web interface. I take care of everything except the electronic designs. Paid and/or revenue share. I'm gonna start Q1 2015.

  74. Hi,

    Hope you are fine. 🙂

    The purpose of writing here is to share with you an idea of a project – to design a "heart rate monitor alarm" which can be made by using commonly available low cost components and which will produce an audible alarm whenever the pulse rate of anyone is found to be abnormal. It should meet the following conditions as well:

    a. Compact and light weight, therefore portable
    b. Consume minimum power, therefore should run 24×7 for a month or two from a couple of AA batteries or a 9 volt pack
    c. Should be fairly accurate in it's performance

    I know there are many such circuits available on the net but their performance and reliability are questionable. The unit can be very useful especially for elderly people (with / without a heart disease), for patients who are bed ridden and so on. When the heart either beats at a rate higher/lower than a set average threshold value, the alarm will sound loudly enough to alert people around the patient.

    I hope that my proposal is clear to you. However, if you have any doubt, please drop me an e-mail.

    Thank you,
    Kind regards,
    Raj Kumar Mukherji

  75. Dear Swagatam,
    I want to design DC to DC converter, Like 18 V from two battery 9V in series, by using I 200 or LM7809 to get 9 Volt with 600 mA, I can get the 9V from regulator, but I can not get 600 mA, How can I get the 600 mA.
    Thank you

  76. Dear Mr. Swagatam,

    Happy New Year 2015……
    GOD Bless You…….

    I come from Indonesia…
    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.

    Please Help me Sir,
    so I Need Timer 3 Hour intervals and now I Have Schematics Two Hours….Can you help us to change its?

    Uploading the circuit diagram is not possible here so I have sent it via your email address hitman2008@live.in and homemadecircuits@gmail.com

    Best Regards,

  77. Hello Swagatam,
    I was wondering if you could possibly assist me. on the blogs I have seen some diagrams for simple variable power supplies. Firstly I know very little about electronics, but with a shopping list and a diagram I am sure I would be okay. I would like to build a simple variable power supply with an input of 220/240 volt ac and an output variable voltage of approx. 1.5V to approx. 15V and a variable output current of up to approx. 100A. I have started zinc electroplating as a hobby (have sweaty hands and want to protect all my tools) the chemical company gave me these as a more or less dependant on my zinc plating bath size. At the moment the little 6V 8A Ryobi battery charger works for a few minutes, overheats and cuts out till it cools down again. I would really appreciate any assistance you could give me on this.
    Many thanks

  78. Hello Andre,

    I'll try to design the circuit for you soon and let you know, by the way please do not post on this page as it has stopped responding to comment postings

  79. hi am mukund and am electronics hobbyist lover
    i need video transmission via fiber optic in low cost use for cctv video signal
    if you have any idea pls support me
    mukund yadav mymukund@gmail.com

  80. Hi Swagatam,
    I want to design DC-DC converter using OP-AMP. Specification is 12 VDC input and 48 V DC output. Can you please give some related circuits

  81. hello sir,
    i want to make IR based fan regulator with 5 speed fan control it should not work like dimmer as dimmer based regulator make fans to create noise on slow speed. can u plz help me

  82. Dear Swagatam,
    Searching for small invertor circuits i reached this website , i got a 100 watt invertor circuit diagram on this website which uses
    4047ic and irfz44n mosfet and successfully got running invertor thank you very much for this.
    now on the same lines using this same 4047ic circuit i was trying to develop a smps with higher frequency unlike 50hz above
    this time using irf840 mosfet and ferrite core of size 35mmX28mmX12mm primary winding of 300turns and seconday 18turns
    i am facing the problem of irf840 getting hot quickly and also this ferrite core transformer making vibrating sound squeaking sound of
    the high frequency of about 12khz to 18khz , actually i am not electronic educated but mechanical engg but having very much interest in developing and trying self useful electronic circuits
    kindly help me understand what makes mosfet to go hot quickly and transformer making vibrating squeaking sound

  83. Hi Swagatam,

    Nice blog you have, I am actually looking for a transformer less power supply something like mobile chargers but i want to operate relay using it, could you please help me with this. Do you know any place from where i can order these circuits or if i can myself make it at home.
    Any help will be appreciated.

    Thanks & Regards,
    Saiyad Rasikh

  84. Hello Sir
    I am working on a project of designing 40W/15V SMPS. I have all schematics of 65W and triple output of 5V, 15V,-15V SMPS. for this SMPS feedback circuit is designed for 5V output. I want design Feedback circuit for 15V output. can you explain what changes i have to make for this and how would i chose parameters for feedback circuit. I am using NCP1203 for switching. My emailid is shefalip.06@gmail.com. Please sir send me your email id so that i could send you all schematics.

  85. It looks good that you are doing lots of hard work for all your projects
    But i here wanted to you to suggest you to make your website more ineteractive &attractive for the user
    becoz if your site will be interactive then people will often like to keep on visiting it's an important aspect with your
    toil hard work . Thank U

  86. hello sir this is shubham from maharashtra india,
    Sir my question is how general sine wave of a oscillator (consider colpits or hartly oscillator is differ from the sine wave which we use to power all AC powered equipment's. Is this possible that we can make a inverter circuit by using hartly or colpits oscillator, if yes then how? Please give me reply sir. Thanking you

  87. hello sir

    I am zulfiqar
    I want to make a project which control the the lights, fans (and other appliances that are used in one room)
    from the another room .
    I have to use two controlller and a single wire communication between them

    If i press light button light should be on of other room and i press fan button fan sholud be on
    I have to controll the 8 things using two controllers

    Kindly help me in makin my project I will be greatfull to you

  88. Hi again ,
    thank you for all help you providing 🙂

    i think this circuit could be useful and after searching many sites i could not found a good circuit !!!

    i need a circuit which get 2 input for 12 volt DC 5 AMP power supply , and give one them in output ,
    if primary power supply fails , secondary power supply take the action , something like Redundant Power Supply,

    to my knowledge we could do it in 2 way
    1- ORing Diodes

    would you please design a circuit like that ?

  89. I'm trying to make a circuit that will turn on them off a pair of 12v pumps in sort of a heart beat pattern, repeatedly. U haven't come closer. Any way you could help me with this?

  90. I'm trying to make a circuit that will turn on them off a pair of 12v pumps in sort of a heart beat pattern, repeatedly. U haven't come closer. Any way you could help me with this?

  91. hello sir ,this is vinod from mussoorie near dehradun.i am not an engineering student,but i have lot of interest to make different electronic items . sir i would like to know that is it possible to use usb drive in normal tv without hdmi and usb port, by putting some type of converter in between them.if yes please tell me the circuit diagram .

  92. hi sir i can you please design a circuit which will output 9v dc from a 12v battery efficiently . it can be by using ic 555. this will be use to run a rc toy car using 0.8A max. if possible can it be a variable output voltage dc. i have a 2n3055 transitor ,MJ11015 TRANSISTOR.

  93. Hello Sir

    This Is Aravind Sir

    I Like To Know How To Make A Transformer And Its Calculation And I Google It But I Cant Find The Proper Calculation Method And I Find Around 7 Method Of Calculation But Its Not Proper With Manufactures Standard And Can You Please Help Me To Know It Sir

    Thanks You

  94. This is just a simple question :
    Can i use a lower Ah battery charger(say 20,30)to charge a higher Ah battery ie 110Ah?What are the consequences?
    What is the difference in the charger circuit in both case?

  95. Dear swagtom sir! I have heard that we can communicate by intercom using main ac power line home to home , i need communicate with my friend , there is about 3km-4km between our houses, but our ac power line is same, can you give me circuit communicate with him? please!

  96. i need to assemble variable frequency(a pot can be use on output of 555 for variable amplitude) square wave funtion generator with frequenciies 1 Hz to 1MHz ,flexibility to vary amplitude of output ,555 should be used in astable mode and axact 50% duty cycle can be obtained on output plz help me sir in desining the above circiut i will be highly thankful to you

  97. Sir, plz help me in making a circuit with following details. A 12 V relay is to be connected such that a momentary push switch turns it on BUT but after release of switch the the relay should not turn off immediately, rather it should turn off after some time say roughly 1minute. Thanks

  98. Hi Swatagam!
    I would like to know if you could make a circuit that can activate a 12V 600ma stepper motor for 10 or 20 seconds every 3 hours or so. is that posible?
    Kind Regards,
    David Montenegro

  99. Hi Mate,

    I am designing a Spot welder Controller with an Arduino and there is a need for a in rush current limiter. Would it possible for you to design the "In-rush-Current-limiter" i have read that it can be done in several ways. I will be using this to drive a Microwave oven transformer modified by rewiring the secondary to 3 turns of 3AWG wire for spot welding 18650 cells.

  100. hello sir,

    i really liked the way you reply to queries and your good heart of sharing. May God bless you.

    please sir, am working on a project titled "remote controlled DUAL BAND MOBILE PHONE JAMMER"
    i hae tried searching for a working circuit diagram but hae been able to find one. please i will appreciate it if you could be of help. thank


  101. Dear sir, i am very fond of u, by u i love electronics, u r really genius, u made electronics very simple.
    Sir i would like to request clap switch and timer circuit for 8 volts led bulb which remain on for a long time
    Please help me to solve the circuit.
    Thanking u

  102. Hello,

    I love your website! I was looking at your circuit "twin or split battery charger" and I don’t see a value for the resistor between pins 1 &3, 7&5 for the LM358 is it 1k? I’m going to make a printed circuit board of this design using photo etching.

    My goal is to build a circuit that will charge one battery while running off another battery and when the run battery falls to a certain voltage level, switch to a charged battery. I am not looking to make an over-unity device; I am interested in experimenting with energy recovery to create long pulse motor run times. I expect the system to eventually die out but I want to see how long that process will take using air coils and back emf harvesting.

    Would this circuit work if I replace the batteries with two 100F 2.7v supercaps? Since the caps charge faster than lead acid batteries, this may help the efficiency of energy recovery during the run time windows.

    I love building things and your awesome ability to design such cool circuits makes people like myself enjoy hours of building these cool circuits and watching them come to life.

  103. Hello Swagatam. I was thinking about put a sensor on the gasoline line from my motorcycle tank, near top, between the tank and the carburetor, that would consist of a pair of (innox?) leads like some mm separated from each other. This would detect the electrical conductivity inside the line, in direct contact with the fuel and while there is gasoline wetting it, it would output 0 volts, and when not (i.e. gasoline is ended and the line is becoming empty from the top), it would output positive (12v?) so I could light a warning light on the dashboard to avoid getting engine cut on a sudden. I can quickly turn the valve from to reserve position in this case. So when sensor wet, 0V(0); sensor "dry" 12V (1). What do you think? Thanks Sir.

  104. Hi Swagatam I am a fan of ur work..
    I need a help.
    My laptop and mobile over charges each night.
    I want to creat a circuit that can start supply at desired time later i.e that 2 or 3 or 4 hrs later and supply should should be ON again for desired time .
    I would have to enter how much time later Supply will be on and off..

    Thnx man, Your work is really great.

    Please inform me if you are working on this project.

  105. Dear Mr.Majumdar, I am Kamal Kumar from Chennai.
    I hope to find a good circuit for a battery eliminator with output dc power ranging from 1.5 to 12 or 15V and with its PCB design etc. can you kindly give me the same I will be very thankfull. I have searched every where on the internet but nothing seems good for what I am looking for. Thanks in anticipation.

  106. Dear Mr. Swagatam Majumdar,

    My name is Srinivas Chakravarthi & I am working on Electro-Chemical project, for my lab work, I need an Universal Power Supply (AC/DC) with variable Voltage, variable Current & Time controlled Polarity Switching.

    My requirements are:

    Variable Voltage 0-100 (V),

    Variable Current 0-100 (A),

    AC or

    DC with or without polarity Switching (1 to 10 minutes variable).

    If you can make one such universal power supply unit, I shall be very much grateful to you.

    Thanks & Regards,

    P.Srinivas Chakravarthi.

  107. Hi Swagatam,

    I need a countdown timer with a relay which can be set to 1 to 5 minutes.
    I would like the timer to show the preset time on 7 segments e.g. 3 min. = 180 or 3.00
    When the time counts the 7 segments shall show the remaining time.
    When the time is up the relay must switch off.
    I don’t have Arduino and no skills in PIC programming yet.

    Can you help me out with a circuit / schematic?

    Thank you in advance,

  108. Hi,
    I recently by mistake bought LED bulb(Great Value) from South America which is 110V. But I want 220V LED Bulb as I'm in Sri Lanka. Now I'm trying to do some modification on LED driver. Please help me to do this & Fix this bulb to use from 220V. Which parts need to change on the driver ?

  109. Hi Swagatam,
    This is RSBirman.
    Do you have any circuit which indicates open earth and has a NO/NC relay contacts which can trip the contactor if the earth is not connected and this will avoid the instrument from getting on.
    The sensitivity should be adjustable.

  110. i like to build led sign but i have small knowlege with the pic16F And attiny 2313 That i try to study them. I asked my friend to help me because he has many knowlege in electronique than me.
    My dream is to drive many leds on one pin µcontroller. But i can't make it now.
    Perhaps swagatam will help me to solve this problem,thanks a lot for your good site.

  111. I want to make a led lighting circuit which will show the blood flow of human heart including open close indication of valve. Can you help me to do this project providing circuit diagram and details . I want to use 230 v ac supply for input. Kindly reply me in my email id uniqash@gmail.com.

  112. Hello Swagatam,

    I would like to meet you and discuss projects for welding machine. I am Mumbai based. My phone – 9820212263.

    Any time will be convenient to me. Please reply.

    Much awaiting,

  113. hi sir recently i purchased masquito bat and two days i used after that power of the battery completed, so tried to charge the battery its came one hour in charging time green light has glown, after one hour no green light came some small noise sound came from that green light is not coming so battery also not getting charge , so how to trouble shoot this circuit pls help me

  114. hello sir
    sir, In my flat there is a problem of light cutoff when alternating current gone. Our building's gate keeper start generator and we have to switch off all extra load (e.g fridge, a.c etc). There is nothing to notify when light comes again. Is their possible to detect generator current/voltage/freq. or alternating current/voltage/freq. . Please help me sir
    my gmail id is shivamchauhan20sep@gmail.com

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