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Home » Home Electrical Circuits » Mini Welding Machine Circuit for Small Welding Jobs

Mini Welding Machine Circuit for Small Welding Jobs

Last Updated on May 7, 2022 by Swagatam 50 Comments

A small transformerless welding machine circuit can be built using a few high voltage, high value capacitors and a rectifier diode, the following article explains more on it. The idea was requested by Mr. Tun.

In one of my earlier posts we came across a full fledged 100 amp SMPS welding inverter circuit for working with reasonably bigger joints and metals.

The Design Concept

Being an SMPS based design and involving high power specs, the above circuit is complex and may be out of the reach of the new hobbyists.

As requested by Mr.Tun a homemade small scale welding machine circuit is what most of the new hobbyists and mechanical engineers would be looking at for solving their occasional work bench metal welding jobs.

A mini welding machine without using complex circuitry could probably be built using a capacitive power supply as shown in the following diagram:

mini welding machine without using complex circuit using a capacitive power supply

The idea shown above is an ordinary capacitive power supply circuit incorporating extreme capacitors in terms of their values.

Circuit Operation

At the input side we can see a formidable 500uF/400V capacitor, while on the output side also a similar rated capacitor can be seen positioned for reinforcing current.

The most basic parameter essential in a welding system is a high current, so that an extremely high temperature can be formed at the short-circuit junction, over the metal joint in question.

This high current generation can be achieved either by using a high watt transformer or an SMPS version of the same which we discussed in the first paragraph.

A transformer could be too bulky and heavy, while the SMPS circuit too complex for the newcomers, the only alternative way to achieve the high current welding through a relatively simpler design is perhaps by employing the high current capacitive power supply as shown above.

The 500uF/400V capacitor can be expected to generate bursts of current upto as high as 36 amps @ 220V, and reinforced with the complementing output filter capacitor this current can be expected to do some serious welding actions.

You can verify the above mentioned specs by using the following two calculator software:

Reactance Calculator

Ohm's Law Calculator

The shown push button enables the user to achieve the welding job through shorts bursts, and not through a continuous arcing, which can be dangerous, and anyway is not recommended in welding operations.

The input 500uF/400V capacitor looks massive and it might not be readily available in the market, therefore this can be built by using 500 numbers of 1uF/400V PPC capacitors wired in parallel, this could occupy some space, but still the method is easily achievable.

Use Non-Polar Capacitors

This capacitor needs to preferably a non-polar capacitor, however since a diode is positioned in series means an electrolyte capacitor could also serve the purpose without issues.

The second capacitor at the output side can be an electrolytic type for sure.

For more current, the values of the caps could be increased to higher limits, that's the only parameter that needs to be focused on.

Advantage and Disadvantage

The advantage of this circuit is that it is small, cheap, and can be quickly built and used. The disadvantage is that it is very dangerous since there may be AC voltage at the output, therefore you will have to handle the whole system wearing rubber hand gloves.

CAUTION: The mini welding machine circuit explained above is not isolated from mains and has the potentials to kill a person within seconds, therefore extreme caution is advised while handling this equipment in the powered condition.

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About Swagatam

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!

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Reader Interactions

Comments

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  1. Ali says

    Hi dear,
    thanks for your best site,
    Inpute voltage is 220 v? How can i use it ?like a welding machine to connect output?
    Can melt Iron?
    Thank you

    Reply
    • Swagatam says

      Thanks Ali!

      This circuit won't melt iron but join iron with the help of welding rod.

      just connect the iron which needs to be joined with one of the output terminals, and the other output terminals with a welding rod, now touch the welding rod end at the point on the iron which needs to be fused…

      Reply
    • Ali says

      Thanks Swagatam,
      input is 230 V AC?
      560uf 450v can i use?
      what is the model 50amp diode?
      50 amp push is a fuse?
      thank you

      Reply
    • Swagatam says

      yes will do.

      50 amp diode is required for rectification.

      the 50amp push is a push button which is required to be pushed and released while operating the power supply

      Reply
  2. Jeremiah Michael Rebello says

    Hey there,, I have a 470uF 250v cap,, can I use it?
    Also what is the component no for 50A diode.? I have 5A diodes, can I put 10 in parallel to achieve 50A??

    Reply
    • Swagatam says

      470uF/250 can be tried and will work as long as the input voltage does not exceed the 250V mark.

      please search online regarding "50amp diode" you will be able to find a suitable one.

      5A diodes in parallel will not help, and is not recommended

      Reply
  3. Tun says

    Hi sir,i need to show me how to step down 230VAC/2A to 150VAC/2A

    Reply
    • Smartdude says

      You should put the 230v line wire on top of the step, and depending the number of taps each one will have a specific voltage drop (230v/no.of tapping). The last one is at the lowest level and should be connected to ground. The output you take it from the desired step and the ground.

      Reply
  4. Swagatam says

    Hi tun, I do not have asn SMPS version at the moment, however you can build an iron core based auto-transformer for the achieving the results

    Reply
  5. Unknown says

    Hi sir please show how to make a 0-40v 0-3a smps

    Reply
    • Swagatam says

      you can try the following concept

      https://www.homemade-circuits.com/2017/06/12v-2-amp-smps-circuit.html

      the Rfbb can be changed for getting different voltages at the output

      Reply
  6. Chunyelu says

    Pls sir,is there any chances of electrocution as this circuit is not isolated with transformer.

    Reply
    • Swag says

      yes definitely there is…even in transformer based welding machines you will have this danger

      Reply
  7. dennis rollo says

    HI SWAG how to make this as adjustable current

    Reply
    • Swag says

      Hi dennis, you can put different ranges of capacitor from 100uF to 500uF and add a selector switch to chose from them….

      Reply
  8. Abba says

    sometimes I hear electronics student say their capacitor exploded, though I never encountered such a situation but I really want to know the cause and how to prevent that from happening. am referring to the capacitor used in transformerless power usually connected in parallel with resistor in AC lines.

    Reply
    • Swag says

      Capacitor will blow when the the supply voltage across its terminals exceeds the printed breakdown voltage value. In transformerless power this may happen due to sudden current surge when the capacitor is unable to stop the rise in voltage and bursts, a resistor and zener network will normally prevent this situation.

      Reply
  9. Abba says

    thanks a lot
    what is the used of the capacitor the one in series with the mains? if its only function is to provide small constant current then why don’t we use a fuse instead?

    Reply
    • Swag says

      Abba, fuses are not designed to suppress current they are designed to blow off as soon as the rated current is exceeded through them. A Capacitor cannot be compared to a fuse

      Reply
      • Abba says

        thanks a lot for the reply

        Reply
  10. Satish D. Naik says

    Sir, Can you please give me a simple transformerless welding inverter circuit with 230v AC input for arc welding of small jobs, brcause in the above circuit description, it is mentioned for short burst of current and not for continuous arc welding.

    Regards,
    Satish Naik
    +91-9590018250

    Reply
    • Swagatam says

      Satish, an SMPS welding circuit can be quite complex, I do not have an easier version at this moment with me.

      Reply
      • Satish D. Naik says

        Sir, then can I use the above circuit (Mini Welding Machine Circuit for Small Welding Jobs) for small welding jobs?

        Regards,
        Satish Naik

        Reply
        • Swagatam says

          Yes you can try it, if the power is not sufficient you can add more capacitors in parallel

          Reply
          • Satish D. Naik says

            Thanks, I will try it.

            Regards,
            Satish Naik

            Reply
  11. Patrick says

    I made an arc welder off 2 microwave transformers. I love the output (but can’t tell the exact amps).
    What I’m looking to do I see make an amp-regulator that would enable me to comfortably weld thin automotive sheet metal. Please help me with a circuit layout to add to my welder and achieve the results.
    Thanks.

    Reply
    • Swagatam says

      The only way to limit current in a high current AC system is by adding resistive load in series. You can probably add a 2000 watt heater coil in series, or as per the specs of the welding machine

      Reply
  12. Sabbir says

    Capacitors name please

    Reply
  13. Sabbir says

    Mini welding machine
    2 capacitors 500uf 400v
    1 capacitors 500uf 400v ppc
    1 capacitors 500uf 400v none poler capacitors
    1 capacitors 500uf 400v electrolyte capacitors
    Please tell me two capacitors name
    How to make 50amp diode

    Reply
    • Swagatam says

      Capacitors don’t have names, only specifications which you have already mentioned in your comment. The input side is non-polar and the output side is polarized.

      Reply
  14. Steve Zulu says

    Hi! What’s the current and voltage output at the welding point?

    Reply
    • Swagatam says

      220V, 25 amps for a second

      Reply
  15. Steve Zulu says

    Hello again! I am intrigued by the simple welding circuit. You say I could use a polar capacitor in place of the non polar, since there’s a diode. Can I connect the negative of the cap to the anode!

    Reply
    • Swagatam says

      Yes you must connect the negative of the capacitor with the anode of the diode

      Reply
  16. Steve Zulu says

    Can you manufacture some pcb’s …qty 10+. Can you do that from a schematic? Without me having to upload a member file?

    Reply
    • Swagatam says

      sorry I don’t manufacture PCBs at the present moment. You won’t need a PCB for this simple design, you can do it over a stripboard

      Reply
  17. Sky Yarbrough says

    I like your straight forward down to earth articles, thanks for sharing. I have a problem I sure you can help me with. I need to build a high-voltage DC power supply which will be used as an arc generator. (Not for welding, more like a tesla generator). My input is 117VAC RMS and I have a Hammond 733A transformer which gives me 2.5kVAC CT. My question is what diodes should I use to make my bridge rectifier? The power supply output will be connected to 5 high-voltage computer controlled switches to tungsten rods around a central tungsten ground rod. Any given switch will be active for 10ms or less at any given time.

    Reply
    • Swagatam says

      The diode specs will depend on the load current. For example if the current drawn by the load is 50 amps, then the diode will also need to be rated at 50 amps (in this case because the duration is only 1 ms)

      Reply
  18. alkali jacob says

    good time to you sir, please the input and output voltage please

    Reply
    • Swagatam says

      hello alkali, input can be 120V AC or 220V AC, output will be = input AC x 1.41.

      Reply
  19. AJTIKUMAR VK says

    Dear sir
    how to add a capacitor discharging circuit for a battery spot welding machine’s out put ? can you post a diagram when you free.

    Reply
    • Swagatam says

      Dear Ajith, what is the maximum voltage specifications that you require for the applications?

      Reply
      • Ajithkumar says

        Input 220 Vac
        Out put 3-6 Vdc
        Current 1000amps to 3000Amps variable.

        Thanks for reply.
        Ajith

        Reply
        • Swagatam says

          6V, 3000 amps is huge, I do not have an SMPS circuit for this specification at this moment.

          Reply
  20. Muhammad abubakar says

    Hi sir,thanks for the wonderful post I have few questions regarding this welding machine
    1.i have couple of 6A10 which I intended to connect them in parallel to achieve the specified current rating but you mentioned in the comments that connecting diods in parallel will not help, pls I need to know why doides cannot be connected in parallel to maximize current.
    2.what are the minimum voltage and current required for a well functioning welding mechine? because I have a 5kva stablizer transformer ,can rewind it?if yes,what would be the output voltage and current?
    3.is the above circuit a d.c or a.c mechine?
    4. Can both the two capacitors be electrolytic polarized capacitors?
    Pls sir do not mind me asking too much questions am just a newbie.anticipating your response sir.thanks again for the good job.

    Reply
    • Swagatam says

      Hi Muhammad,
      1) diodes cannot be connected in parallel because semiconductor devices do not have exactly identical characteristics and all the devices may not conduct together causing one of them taking the entire load at once and burning. You can add a 1 ohm 1 watt resistor in series with each diode and then add the combination in parallel.
      2) I do not have an expertise in welding so cannot suggest much about their specifications.
      3) The above circuit is DC, but you can also use the AC version, simply by removing the diode and the filter capacitor.
      4) The left side capacitor cannot be polarized, it must be a non-polar capacitor.

      Reply
      • Muhammad abubakar says

        I appreciate your response sir thanks again

        Reply
        • Swagatam says

          You are welcome Muhammad.

          Reply
  21. Moro Abdul Latif says

    I like it but I fear to atemp bcz u said it is dengerious.help me with another circuit that can be safe when welding.

    Reply
    • Swagatam says

      The other option is using a large transformer with high current output DC

      Reply

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