Small welding machine. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Small welding machine. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / welding equipment

The small-sized welding machine brought to the attention of readers allows you to make welding joints of thin metal plates, work with it as an electrograph ("pencil"), and make drawings of conductors of breadboard printed circuit boards on foil-coated fiberglass.

Often, when repairing household appliances containing an autonomous power source, for example, a battery of galvanic or rechargeable cells of AA, AAA sizes, you can see that the elements are interconnected by strips of thin metal foil by resistance welding. When replacing faulty elements, connecting them by soldering, if not completely damaged, then reduce their service life as a result of overheating.

Small Welding Machine
Fig. 1

To connect such elements by resistance welding, as well as to carry out other minor welding work, a small-sized welding machine was developed, the diagram of which is shown in Fig. 1. Welding - capacitor contact.

The device contains a step-down mains transformer, a rectifier, storage capacitors, a power-on indicator and a button for supplying voltage from the storage capacitors through large-section wires to the working electrodes.

Small Welding Machine
Fig. 2

When the mains voltage is supplied by the switch SA1, the mains voltage, reduced by the transformer T1, is supplied to the rectifier, assembled on the diodes VD1, VD2 according to the voltage doubling scheme. Storage capacitors C1-C3 are connected to the output of the rectifier. The capacitors are charging, the power-on indicator lights up - the HL1 LED. The voltage on the charged capacitor C3 is set to 20 ... 25 V. When welding, wires with welding electrodes are connected to terminals XT1, XT2. The electrodes are installed at the welding site, for example, as shown in Fig. 2, and press the button SB1. From the pulse of the discharge current of the storage capacitors at the point of electrical contact of the two parts to be welded, the metal rapidly heats up, it melts and a welded joint occurs. The HL1 LED goes out. After releasing the SB1 button, the indicator lights up again, which indicates that the capacitor C3 is charging and the next welding point can be performed. The charging time of the capacitor is about 30 s.

The T1 transformer is made on an armored magnetic circuit W 10x20 mm. The author used a mains transformer from a burned-out cell phone charger. The primary winding contains 4350 turns of PEL 0,1 wire, the secondary - 242 turns of PEL 0,29 wire. Diodes VD1, VD2 are replaceable by others with a permissible average forward current of at least 0,5 A. Capacitors are imported. LED HL1 - any low-power. Switch SA1 - PMD1-1. The contacts of the SB1 button, in order to avoid burning, must withstand a current of several tens of amperes.

Rice. 3 (click to enlarge)

The design of the apparatus is shown in fig. 3. The body consists of a base and a cover made of 0,7mm thick roofing iron. On the front panel of the base there is an HL1 LED, a SA1 switch, and two flat clamps for connecting wires from the working electrodes. A holder with a fusible insert FU1 is installed on the rear wall of the panel and a power cord is brought out. The remaining elements of the device are installed inside the case. The transformer T1 is attached to the base with screws and nuts using a U-shaped bracket, and the capacitor C3 is fixed with a flat clamp. Capacitors C1, C2 are fixed on a board made of foil-clad fiberglass with clamps made of copper wire by soldering.

The board is attached to the base with a screw and nut. Diodes VD1, VD2 and resistor R1 are soldered directly to the corresponding terminals of capacitors C1-C3. The wires from the working electrodes are fixed in flat clamps with screws, which makes it possible, in the presence of a set of electrodes with different wire lengths, to change the welding current within certain limits. The electrodes are made in the form of pointed copper pins (see Fig. 2) with a diameter of 3 mm. Each pin is placed in the body of a ballpoint pen, from which the core is removed. Button SB1 is fixed on one of the cases with a pin.

The device can make electrographic inscriptions on metals, as well as make drawings of conductors of breadboard printed circuit boards, for example, on foil-coated fiberglass. To do this, a thinner pin 1 mm in diameter, also pointed at the end, is fixed at the end of one of the working electrodes. According to the pattern of conductors printed on the board, with the SB1 button pressed, the gaps between the conductors are burned out. Next, the board is checked for the presence of unburned jumpers, and if they are, they are burned out. The board is washed with solvent and dried.

The welding process described above is carried out with plates up to 0,1 mm thick. Welding of plates from 0,1 to 0,2 mm is carried out differently. In places of welding with a core, bulges are preliminarily made. Next, the plate is installed at the welding site, the pointed end of the working electrode is placed in the bulging recess and the button is pressed.

When working with a welding machine, safety precautions must be observed. Be sure to wear protective goggles!

Author: L. Stepanov

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Air data rate 0.3 - 500 kbps
Modulation types 2-FSK, 2-GFSK, 4-FSK, 4-GFSK, OOK, and ASK
Low consumption in active mode:
6,7mA RX
10mA TX @ +10dBm
Sleep Consumption 600nA (with timer)
Fast wakeup and fast synth setup time
Automatic retries and confirmations
Suitable for Wireless M-Bus systems; 802.15.4g
Case 4x4 mm QFN
Operating temperature -40...+85 °C

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Comments on the article:

Vladimir
I read this article with interest. Thank you. I just purchased lithium batteries from Alik and need to weld them with nickel plates. But there is a question about the scheme? What is the output voltage on the secondary winding? And is it possible to use a conventional bridge instead of doubling diodes? Who knows please help.

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