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220V/120V LED String Light Circuit using a Single Capacitor

220V/120V LED String Light Circuit using a Single Capacitor

The post explains how to make a LED string light which can be operated from 220V mains through a single inexpensive PPC capacitor. The idea was requested by Mr. Basit Momin.

Technical Specifications

I am trying to make AC 1 watt led bulb like 6.2 v 3 amp miniature lamp or festival decoration lamp so it will be easy to solder led without seeing plus and minus of leds , so it will be easy to solder led in series without seeing plus and minus of led so pleas help

Actually I want to make 100 nos of led toran of 2 array each array of 50 leds I am trying to convert leds in AC bulbs like 6.2 v festival decoration lamps so that's my question sir

Can we run the LEDs without the circuit by adding some ics to each led. I want to run it direct on 230v AC without any circuit like festival series lamps.

Basit Momin

Analyzing the Circuit Request

Hello Basit,

LEDs are different from filament bulbs and are much vulnerable to current fluctuations, without a dropping capacitor the LEDs will start blowing off with the slightest voltage fluctuations if connected directly or through resistors.
Therefore a recommended capacitive power supply circuit has to be used with it.

Basit: So we cannot make AC led Series bulbs ?

Solving the Circuit Issue

You'll have to include the high voltage isolating capacitor, rest of the components can be eliminated.

make two 50 LED series and connect their opposite ends together, meaning the anode end of one series should be connected with the cathode end of the other series in both the ends.

Now simply connect one end of this assembly to one of the mains terminals while the other to the other mains terminal through a high voltage capacitor.

The whole set up will be too dangerous to touch, exercise adequate caution.

The Circuit Diagrams


Testing the above LED string light design using a single PPC capacitor:

The idea looks simple and feasible and also quite reliable due to the large number of LEDs in series taking care of the initial surge current.

The large number of LEDs makes sure that the total LED forward drop is close to the AC mains value which enables restricting the initial current to a reasonable level.

If we assume the forward drop of the shown white LEDs to be around 3.3V, then with 50 LEDs in series it gets to approximately 3.3 x 50 =  165V, though not too close to 220V but sufficient enough to just counter the initial surge from the PPC capacitor which acts like a momentary short circuit each time power is switched ON.

Probably 90 numbers would be just adequate and perfectly safe.

As can be seen in the above diagram, there are 50 LEDs on the upper string joined in series and an identical string with an identical number of LEDs at the lower side of the design.

The free ends of these two series are connected to each other but using the opposite polarities, that is the anode side of one string is made common with the cathode side of the other string and vice versa.

The mains AC is applied to these common joints through a PPC high voltage capacitor.

A nominal 0.33uF is shown in the diagram assuming that 5mm LEDs are used in the circuit.

We know that mains AC is fundamentally composed of alternating current which changes its cycle polarity 50 times a second, constituting the 50 Hz spec.

The LED strings are deliberately connected with their opposite end polarity so that one string illuminates in response of one half AC cycle while the other string for the other opposite AC half cycle.

Since this is supposed to happens very quickly (50 times per second) the human eye is unable to distinguish the fractional lapse or shutting off of the strings, and both the strings appear to be lit up brightly and continuously.

The above design was successfully built and tried by Mr. Ram, the following picture provides a dazzling performance proof  for the same.

The circuit was also built and tested by Mr. Raj, who is also an avid follower of this blog, the picture below was sent by him for the readers viewing pleasure.


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

52 thoughts on “220V/120V LED String Light Circuit using a Single Capacitor”

  1. Hi, I like to connect a series of normal 5mm white or blue LEDs directly to 220v AC main. Pls suggest me a circuit for that.
    A string of LEDs consists of 5-15 LEDs. So the string may contain 8 or 10 or 12 LEDs. The circuit should give proper voltage to the LEDs.

  2. Dear Mr. Swagat,
    good morning, I appreciate the way you guide. I have two questions-
    1. you wrote that 90 leds will be adequate and safe so it means two strings of 45 leds (total 90 leads) or two strings of 90 leds (total 180 leads)
    2. pl give an idea how much light this circuit will give in comparison to incandescent bulb in watt/lumens

    I have one more request pl share a circuit using 1 watt led or 10 watt led that can replace 100 watt incandescent bulb. it would be nice if it is mains operated without transformer if not necessary. its ok if it is dc operated using 220 v secondary.
    Thanks, Sudhir

  3. sir, I'm using about 4 to 5 led drivers given on this blog & its working very well. I couldn't find any capacitor on the circuit board of that lighting excepting diode bridge so I tried it. Ok. now want to know, is 0.22uF ppc cap & diode bridge sufficient to drive a single 5mm white led? or is it need to add an electrolytic cap at output?

    • 0.22uF will provide roughly 10mA to 12mA current so that might not be enough for 5mm 20mA LED, you can try 0.33uF/400V capacitor with a bridge rectifier

      …a filter capacitor can be added to make the glow smooth without flickering, and also add a 3.3V zener in parallel with the LED for max protection.

    • thank you so much Swagatam sir.
      I am getting very much help from ur blog. and most important thing is, you communicate with everyone who needs proper guidence. I m so thankful of this blog & you.
      I will come again with my next difficulties.
      Thank you so much sir.
      Have a nice evening!

    • hi swagatam sir.
      I m Shrinivas, I have purchased mains operated Led lighting with dual color led. the lighting has 54 no. of dual color led. when I opened the circuit box, there is only diode bridge. so I made 93 no.s led in series and connected it to main through only bridge as I found in that lighting. but as soon as I switch the button on, the fuse on the power plug as well as main line board blown. I wonder why this happened. can u figute out this problem sir?

  4. If one rectifies 110 US mains, one gets 180V DC.. It is best to value max voltage at that, and bright white 5mm often have a 1.8 to 2.2 v FVD.. Meaning 90 of these 2 volt LED's in each direction, typically using 20 mA each. My question is, do we value power consumption in one direction, or both? 3.6 Watts or 7.2??

  5. Please remove the previous comment. That was probably a faulty capacitor. Now its working, although the flickering is slightly noticable.
    Here is a picture; postimg.org/image/k0tfh6dab/

    • That's great Raj, the flickering will be there due to the absence of a rectifier and a filter stage.

      I did not delete the previous comment just to maintain the comment sequence and allow the readers to know about the proceedings correctly.

  6. Helo Swagatam, yesterday I made the circuit shown above with 100 x 5mm LEDs. The only difference was the capacitor, which was rated at 650volt/1200volts instead of 400volts as shown. Now, when I give AC supply, the LEDs are very dim, why is that?

  7. Hi, I have found my problem, which are:
    1. My multimeter probes have a resistance of 1.3 ohms, which was adding up when I was measuring the resistors.

    2. The breadboard on which I was working also had an internal resistance which was also adding on the total value.

    These two factors took a lot of my time, so I would request you to add these points in projects like 'constant current limiter circuit' where we have to deal with very small amount of resistances.

    About my project, I have successfully finished building a circuit for lighting my 20Watt LED. The circuit is, a 12V adapter, then a voltage booster circuit, then the LM317, then the LED. Since the LED needs about 30V, so the voltage booster is necessary.
    Total cost was about Rs.300/-, without the adapter and LED.

  8. I think I will go with LM317 on each LED. Can you give me a link where mica isolators are found online? It is not available locally.

    Another question, have you ever used those big 5watt resistors? I bought 3 for 0.5ohm and on measuring found all of them to be around 1.5ohm. Another 1ohm 5W resistor is showing 2.7ohm ('1E' written on resistor). Are these type of resistors unreliable? Or is my multimeter not capable of measuring such small values?

    • OK, that's great.

      if you Google "mica insulator kit for transistors buy" you'll come across many relevant links.

      the resistors may not be too accurate with their values, but in your case it's definitely the multimeter that's not showing the correct value, and anyway no multimeter will be capable of measuring such small values in their normal Ohm, or kOhm range…unless these are equipped with a milliohm range.
      alternatively you can use 1 ohm, 1 watt carbon resistors in parallel for achieving the desired value, this will allow you to get more accurate and manageable results

  9. These are a typical 10 watt LED ratings:

    Model – 10 watt.
    Color – White.
    Forward voltage (VF) DC 9 – 12v.
    Forward current (IF ) – 1050 MA.
    Output lumens – 800 – 900LM.
    Life span – 50,000 hours.
    operate voltage – 9v to 12v DC.

    • Thanks Raj, however the above circuit is not recommended for high wattage LEds, it may be suitable only for low current, high quantity LEDs as depicted in the above article.

      for your case you will have to opt for an SMPS adapter, heatsink, current controller etc….. and these are not much complicated, I have comprehensively covered all these parameters in this blog,

    • Regarding using a computer psu to run a large number of LEDs, say, I want to run 20 x 10W LEDs; can I connect all the 20 LEDs in parallel to the 12V supply? How will the current be controlled? Since the LEDs are in parallel, connecting a LM317 for each LED is not feasible.

    • if the power of the psu is rated to handle well above 200 watts then you can use it for the mentioned purpose, you can connect all the modules in parallel across the output of the power supply.

      And yes using LM317 in series for each module would be great, and would provide maximum safety against over-current.

      If possible mount the ICs over the same heatsink which are used for the LEDs, this will ensure extra thermal protection for the LEDs.

      But make sure the IC is separated from the heatsink with a mica isolator to avoid a short circuit

  10. Great idea for running LEDs directly on AC. I think most people turn away from LED lighting because the need for an adapter.
    Can you please help me out here? I need to run 4 no. of 10watt LEDs. How to modify the circuit?
    Also, how long will the LED survive without a current limiter and in a 50Hz supply?

  11. Sir then wat will be the capacitor for 5mm leds if I connect 3 capacitor in parallel for 5mm leds it will be correct for that

  12. Sir i have polyester film capacitor of value 1uf 400v can I add 3 nos of capacitor in parallel for this circuit

    • 5uF/400V….. but you must include 50+ LEDs in series as mentioned previously, 90 is most preferable for 220V, and 45nos for 120V

    • you are welcome Basit, yes all types of LEDs can be used, but the input capacitor will need to be upgraded accordingly.

      also at least 50 or above quantity is recommended (@220V) for preventing surge vulnerability.

  13. Got it working with 334 /400. I connected all 52 in series. Added NTC and MOV for extra surge protection. Thank you very much.

  14. Sir, what will be the exact part number for 0.33uf 400v. I m unable to get if value mention in uf.

    I was trying to do same and you helped me before but when I try to light up 52 led in series ( 5mm ultra bright 35ma) with 474j/400v , 474j/250v nothing happen even after using bridge rectifier. I have some ppc capicator of value like 105j/250, 475k/250v, 474k/250v. Please help how I can light up 52 led in series. if not possible easily for 52 led then I can your above mention method by dividing it in 27 n 27 and will need help to get the exact value of capacitor.


    If possible also help how to know the part no if value mention in uf / volt and
    calculate uf if value mention in format like 474k/25v.

    • Ram, the LED strip will not light up if even one LED is connected with a wrong polarity, so if all your 52 LEDs are connected with the right polarity in one direction it will surely light up.

      you can use the above technique but using less number of LeDs will mean greater risk to surge current.

      for 0.33uF the code will be 334

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