We connect a low-voltage soldering iron to a 220 network without a transformer

I have been using low voltage soldering irons for a very long time. It just so happened that I got a few of them. They are powered by a safe 42 volts. Usually they are connected to a transformer, but I don’t have one. I use a quenching capacitor for power. About the calculation of the capacitor - further.

Making a 42 V soldering iron attachment


We connect a low-voltage soldering iron to a 220 network without a transformer

The case for the power supply of the soldering iron will be the case from an old DVD drive. I'm thinking of painting it, apparently I'll have to leave the sticker, with a guide for the disk underneath it. Removing it creates a hole, which I don’t need.
We connect a low-voltage soldering iron to a 220 network without a transformer

I'll make the front panel out of plastic. I'll use some orange plexiglas scraps that I had in stock.
We connect a low-voltage soldering iron to a 220 network without a transformer

The switch will be toggle switch T3. You can use any current from two amperes.
We connect a low-voltage soldering iron to a 220 network without a transformer

We calculate the quenching capacitor using a simple formula. My soldering iron has the following parameters:
  • - power 65 watts;
  • - operating voltage 42 volts;
  • - operating current 1.54 amperes.

The piece of paper shows a detailed calculation of the capacitor capacity. It turns out. we need a capacitor with a capacity of 22 mF.
We connect a low-voltage soldering iron to a 220 network without a transformer

I took old capacitors, they were in the old soldering iron power supply housing. I sanded and painted them. Blue capacitors are 4 mF each, two capacitors are 20 mF each. The operating voltage of the capacitors must be at least 350 Volts. Those that are 4 uF, I have for 450 and 600 volts. Those that are 20 mF each are 200 volts, so I’ll turn them on in series. At the output we get a capacitance of 10 μF with an operating voltage of 400 volts. A 470 kΩ discharge resistor is soldered onto one of the capacitors. When disconnected from the network, it discharges the charge of the capacitors.
We connect a low-voltage soldering iron to a 220 network without a transformer

We cut out plugs for the body. The orange one is the front one, it's made of plexiglas.
The white plug is the back one, it is made of PVC plastic.
We connect a low-voltage soldering iron to a 220 network without a transformer

I'll spray paint the DVD drive housing.
We connect a low-voltage soldering iron to a 220 network without a transformer

On the plexiglas panel I make markings for: a socket, a toggle switch and a neon lamp. The neon lamp can be replaced with an LED connected through a resistor.
We connect a low-voltage soldering iron to a 220 network without a transformer

I secure the 4 mF capacitors with a bracket. Black capacitors, fastened together using a corner.
We connect a low-voltage soldering iron to a 220 network without a transformer

I screwed the legs on the bottom. In the role of legs, covers for medical vials.
We connect a low-voltage soldering iron to a 220 network without a transformer

PVC back panel. I fastened it with screws and drilled a hole for the power cord. The capacitors were soldered in parallel. I solder the power cord to the toggle switch.
We connect a low-voltage soldering iron to a 220 network without a transformer

One of the network wires, through a toggle switch, goes to the socket. The second wire is through the capacitor to the socket. The neon lamp is connected from a toggle switch.
When turned on without load, the voltage is about 160 volts.
We connect a low-voltage soldering iron to a 220 network without a transformer

With a soldering iron connected, the voltage is about 40 volts.
We connect a low-voltage soldering iron to a 220 network without a transformer

This is what the power supply turned out to be. Affordable and reliable. I've been using this method for a very long time. You can also calculate a capacitor for any low-voltage load.
We connect a low-voltage soldering iron to a 220 network without a transformer

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Comments (20)
  1. Guest Victor
    #1 Guest Victor Guests 29 October 2018 17:08
    1
    The neighbor in the garage turned on the soldering iron through a resistor-stove)) We need to show him this method.
  2. Valery I.
    #2 Valery I. Guests 29 October 2018 17:48
    15
    Do not repeat this design under any circumstances - the insulation of low-voltage soldering irons may not withstand the phase voltage of the network, the tip and metal parts of the soldering iron will be under voltage relative to the ground. Connect a low-voltage soldering iron only through a transformer with good inter-winding insulation - do not be fooled by the advice of such “smart guys”.
    1. Yuri Alexandrovich
      #3 Yuri Alexandrovich Guests October 30, 2018 09:02
      6
      Valery, why are you sinning in isolation? The insulation material is the same for both 220V and 36V soldering irons! And the voltage reduction circuit itself, by dropping across a capacitor, has been used since the advent of low-voltage soldering irons since Soviet times for home use - a 36V 40-60-70 watt soldering iron was sold complete with: voltage reduction box; rosin, solder; replaceable tips; plastic non-burnable tape for soldering polyethylene.
    2. Guest Victor
      #4 Guest Victor Guests October 30, 2018 09:39
      0
      In Soviet times there were similar boxes. It was called the “additional device or capacitor” type. I think that mica will withstand even more stress.The applied voltage to the winding in this case is the rated voltage of the soldering iron. Modern, cheap lamps with LEDs are built using a similar scheme. Many years ago, they came up with the use of a capacitor as a balancing resistor. Just google it and you'll find everything.
  3. Sergey K
    #5 Sergey K Visitors 29 October 2018 19:19
    3
    The main drawback is that someone will think that the soldering iron is low-voltage, and therefore safe, but here you have mains voltage, which will either burn the microcircuit or even break through to the case, the insulation is not designed for mains voltage
  4. Yuri
    #6 Yuri Guests 29 October 2018 19:59
    0
    Soldering iron with 220V network. It is not galvanically isolated, therefore it poses a potential threat of electric shock. Capacitors are not a solution; a transformer is needed.
  5. Sergey.
    #7 Sergey. Guests 29 October 2018 20:22
    0
    I used this principle. I made a 40w 220v for a soldering iron. And as in this article. It will just break through the conduit. And you will be covered in foil. Yes, it can fly into your eyes.
    1. Guest Victor
      #8 Guest Victor Guests October 30, 2018 09:41
      0
      From what? Will the capacitor or soldering iron explode?
  6. popvovka
    #9 popvovka Guests 29 October 2018 20:53
    2
    Where does it say it's safe? Low voltage in the network and norms)
  7. yurij
    #10 yurij Guests 30 October 2018 15:05
    1
    A low-voltage soldering iron is used for electrical safety purposes, and therefore it must be connected via a transformer. Power supply through a capacitor does not eliminate the galvanic connection with the electrical network. By the way, the capacitor capacity for a 220 V 50 Hz network can be calculated using the empirical formula C = 15I, where C is the capacitance of the capacitor Mkf, I is the current in Amperes.
  8. Evg
    #11 Evg Guests November 2, 2018 09:55
    1
    The point of using low-voltage soldering irons is galvanic isolation!
    1. popvovka
      #12 popvovka Guests 2 November 2018 20:11
      0
      Not only. If there are a certain number of them, they will outlive modern ones!
  9. Guest Victor
    #13 Guest Victor Guests November 8, 2018 10:04
    0
    What kind of safe forty-two volts are we talking about, they are dangerous in themselves (read the documents), and when connected through any type of ballast, they will not have any advantage other than low power over ordinary two hundred and twenty-volt soldering irons. And I used such a circuit, with a capacitor and a closed resistor (so as not to “bite”) back in the seventies of the last century.
    1. boyfox
      #14 boyfox Guests 12 November 2018 10:54
      0
      Well, find the PEU and read it.
      42 AC and 110 DC..
  10. Alexander_57
    #15 Alexander_57 Guests 13 November 2018 20:29
    1
    "When turned on without load, the voltage is about 160 volts."
    It would be nice to learn Ohm's law at school. Without load, after the capacitors there will be the same 220 volts as in the network.
    By the way, “20 mF” is 20 millifarads, or 20,000 microfarads. The absence of the Greek "mu" on the keyboard is not yet a reason to miss such a mistake.
    1. popvovka
      #16 popvovka Guests 15 November 2018 13:43
      0
      Multimeter what does it show? It can be seen that it is 160 volts.