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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Power supply for 42 V electric soldering iron. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies Produced in the last century, domestic electric soldering irons EPSN with a power of 40 W for an operating voltage of 42 V are unsightly in appearance, but, unlike beautiful imported counterparts, they have a long service life: a copy purchased in 1987 worked for about 26 years (more than 10000 hours) and would probably still work if it hadn't been thrown away by mistake. Since the author had a stock of such soldering irons, and also because these products are still being produced and are on sale, it was decided to make a power supply for them with an isolating step-down transformer and a phase power regulator. On fig. 1 shows a diagram of a power supply that is designed to power alternating current electric soldering irons with a power of up to 60 W, designed for an operating voltage of 40 or 42 V, with a power of up to 40 W with an operating voltage of 36 V, and you can also briefly connect an electric soldering iron with a power of 25 ... 30 W for an operating voltage of 25 V, the minimum power is not limited. It is also possible to connect incandescent lamps with an operating voltage of 48 V with a power of up to 60 W to the regulated output, the minimum power is not limited. To expand the functionality of this power source, there is an output that receives a bipolar unstabilized DC voltage of +22 ... 37 and -22 ... 37 V, which can be used, for example, to establish and repair UMZCH, scanners, inkjet printers, regarding high-voltage voltage stabilizers.
The alternating mains voltage 230 V is supplied to the primary winding of the step-down transformer T1 through the fuse-link FU1, the closed contacts of the SB1 switch, the thermistor RK1 and the two-winding choke L1. The LC filter C1L1C3 reduces the level of interference both from the side of the network and from the side of the device to the network (from a working phase power controller). The NTC thermistor RK1 reduces the starting current of the device. Voltage 2x25 V from the secondary windings of the transformer through the fuse-links FU2, FU3 is supplied to the rectifier bridge VD5. Capacitors C5-C8 smooth out the ripple of the rectified voltage. With the capacitance of these capacitors indicated on the diagram, a load that consumes current up to 1 A can be connected to the output socket XS0,5 for a long time. LEDs HL1, HL2 glow when the device is connected to the network. A phase AC power regulator is assembled on a low-power trinistor VS1 and a powerful triac VS2. The load is connected to socket XS2. The power supplied to the load is regulated by a variable resistor R1. The greater the resistance of this resistor introduced into the circuit, the less power will be consumed by the load connected to XS2. When the current through the control transition of the trinistor VS1 reaches a sufficient value, it will open, the triac VS2 will open with it and the supply voltage will be supplied to the load. Capacitor C2 provides a delay in the opening phase. The L2C4R9L3C9 filter reduces the level of noise generated by a working phase regulator. electric soldering irons designed for a supply voltage of 40 and 42 V at a reduced mains voltage, the secondary windings of the transformer T1 and the phase regulator assembly are designed for an increased voltage of 46 ... 48 V, which will be less at a reduced mains voltage. In addition, a short-term supply of increased voltage to the soldering iron may be necessary, if necessary, to desolder or solder massive parts, when mounting or dismantling multilayer printed circuit boards. Since such electric soldering irons usually carry out "rough" work, stabilization of their supply voltage is not provided. At the same time, the power supply unit can operate only in one of two modes: either as a phase AC load power regulator, or as a source of bipolar DC voltage. Most parts of the device are installed on a fiberglass board with dimensions of 120x87 mm, the mounting is double-sided hinged (Fig. 2). Variable resistor R1 - SP-1, SP3-30a, SPO-1, SPZ-33-32 with a linear characteristic, tuning R2 - any small-sized, for example, SP4-1, SP5-2, SP3-39, RP1-63M. NTC thermistor RK1 - from a pulsed imported power supply, any NTC, SCK with a resistance of 10 ... 33 Ohms at room temperature will do. The remaining resistors are RPM, MLT, OMLT, S2-14, S2-23 or imported analogues. Capacitor C2 - K53-14, K53-4, K53-1, K53-19, K53-30 or imported tantalum or niobium equivalent; C5-C8 - K50-35, K50-68, K50-24 or imported analogues with a rated voltage of at least 63 V (the larger the capacity, the better); C4, C10 - film; C9 - ceramic, C1, C3 - imported high-voltage film. Switch SB1 - PKN-41-1-2, KV3, ESB99902S, ESB76937S, KDC-A04, JPW-2104 or any similar, designed for switching mains voltage of 250 V at a load current of up to 2 A. Fuse holder FU1 - DVP4-1 , DVP7. Instead of FU2, FU3 fuse links, you can use LP60-250 or LP60-300 polymer self-healing fuses, which will increase the usability of the device.
Diodes 1 N4004 are replaceable by any of 1 N4002-1N4007, UF4002-UF4007, 1N4934GP-1N4937GP, 11DF1 - 11DF4, KD221D, KD243B, KD258A. Instead of the D3SBA20 diode bridge, any of the D3SBA10, BR31, KVRS101, KBL01, D4SB60L, FBU-4J will do. The VD5 diode bridge and the VS2 triac are installed on a common heat sink in the form of a duralumin plate measuring 75x55x2 mm. Possible replacement of the triac KU208G - KU208V or any of the MAC320A8FP, MAC320A6FP, MAC320A10FP, MAC228-6FP, MAC228A6FP, MAC228-8FP, MAC228A8FP, MAC212A8FP, MAC212A10FP R2, R6. If a very sensitive instance of the triac comes across, it will be necessary to replace R7 with a resistor of lower resistance. Trinistor VS1 - any of MCR100-6ZL1, MCR100-008, MCR100-8RL, P0102DA1AA3, P0111DA1AA3, P0118DA1AA3, 2U107G, X00602MA1AA2, X0202MA1BA2, X00602MA1AA2, KU103V, KU103A . The step-down transformer T1 is a modified TC90-2 from a domestic black-and-white semiconductor TV (TC90-1 is also suitable). Having disassembled the magnetic circuit, all secondary windings, except for windings with leads 5, 9, 5' and 9', are removed, and then an additional winding containing 34 turns of PEV-2 1,12 wire is wound on each frame. Before assembling, the halves of the magnetic circuit are thoroughly cleaned of old glue, moistened with BF-2 glue, then docked and tightened with nuts (do not overdo it, otherwise you can either tear off the welded bolts or crush the tape magnetic circuit). During installation, the main and additional windings are connected in series, as shown in the diagram. In the case of refinement of the transformer, in which the primary winding has a tap for a voltage of 237 V, it is connected to the network using this tap. If you completely rewind the secondary windings, you can provide additional taps for integrating this design together with the device described in the author's article "Power Supply for Low-Voltage Soldering Irons". A self-made transformer can be wound on a W-shaped magnetic core with an average core section of about 14 cm2. The primary winding should contain 820 turns of winding wire with a diameter of 0,43 mm, and the secondary - 2x94 turns of wire with a diameter of 0,8 ... 1 mm (it is recommended to wind this winding with a wire folded in half). The assembled transformer is impregnated with varnish ML-92, KO-916K or paraffin. It should be noted that in all articles of the author, without exception, the primary winding of home-made network power transformers is designed for the modern standard mains voltage of 230 V AC 50 Hz, therefore, when repeating old designs, it is not necessary to recalculate the transformers. Inductor L1 - two-winding from a switching computer power supply. Any similar one with a total winding resistance of no more than 3 ohms will do, the inductance is the more the better. Inductor L2 - also ready, from the raster correction unit of a large-format kinescope TV. Wound with litz wire on an H-shaped ferrite magnetic circuit. Any similar one with an inductance of 1000 ... 3000 μH with a winding with a resistance of up to 1 Ohm is suitable (if this inductor is excessively inductive, unstable operation of the phase regulator with a low-power load is possible). Inductor L3 - several turns of a double-folded stranded installation wire with a copper cross section of 0,5 ... 0,75 mm2wound on an annular magnetic circuit with an outer diameter of 12 ... 20 mm from low-frequency ferrite or permalloy. The power supply is mounted in a metal case measuring 269x93x105 mm from the power supply of the computer "Electronics KR-02" (analogous to the amateur radio computer "Radio-86RK"). All installation connections, through which the mains current 230 V flows, are made with a stranded installation wire in thick double (PVC / rubber) insulation. A view of the layout of parts in the housing is shown in fig. 3, and the appearance of the device - in Fig. 4.
For the first time, the manufactured PSU is connected to the network through an incandescent lamp with a power of 60 ... 100 W at 235 V, connected in series with a FU1 fuse. When the PSU is operating without load, the lamp should not glow. The author's version of the device, in the absence of a load, consumes about 7 W of power from the network at a voltage of 231 V - this is a very good result for a transformer of such power with a U-shaped magnetic core. If the power consumption is noticeably higher, then this may mean either the presence of short-circuited turns in the transformer windings, or the poor assembly quality of its magnetic circuit. A phase regulator assembly is established at a nominal mains voltage of 230 V, two incandescent lamps connected in series with a power of 2 W each for a voltage of 60 V are connected as a load to the XS36 socket. Resistor R4 sets the upper voltage limit at the XS2 socket, trimming resistor R2 - lower (18. ..20 V). It should be noted that in this case, multimeters assembled on microcircuits of the ***7106 series (ICL7106, 572PV5) are not suitable for measuring the effective voltage, use more "smart" multimeters. Author: A. Butov
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