How does a soldering iron work?How a soldering iron works

“How a traditional soldering iron works. The traditional electric soldering iron is to wrap the nickel-chromium heating resistance wire on the heat-resistant insulating material such as mica and ceramics, and then apply electricity after heating to generate heat, and then transfer the heat to the soldering iron tip.

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How a traditional soldering iron works. The traditional electric soldering iron is to wrap the nickel-chromium heating resistance wire on the heat-resistant insulating material such as mica and ceramics, and then apply electricity after heating to generate heat, and then transfer the heat to the soldering iron tip.

The alternating current is applied to both ends of the soldering iron core through the power cord. Since the soldering iron core belongs to a kind of heating resistance wire, it can directly convert the electric energy into heat energy, and then conduct the heat energy to the soldering iron head through the conduction of heat, which can be used after heating. to weld.

The temperature control range of the electric soldering iron is 100℃～400℃, the temperature adjustment marks indicate low, medium and high positions, the temperature control accuracy is nominally ±5%, and a thermocouple sensor is used. The control Circuit adopts the direct step-down, filtering and voltage-stabilizing power supply scheme of AC mains.

The mains AC220V is stepped down by R1, half-wave rectified by D1, clipped and stabilized by D2, and filtered by C1 as the power supply voltage of the comparator IC and the voltage source for temperature regulation. IC-A ③ pin is the thermocouple detection voltage input terminal (corresponding to the temperature value); ② pin is the temperature setting voltage. After comparing the voltage between the two ends of the ② and ③ pins, it is output from the ① pin.

The function of R5 is to feed back a small part of the input to the non-inverting input terminal ③, so that the output lock remains unchanged when the small signal fluctuates. When the thermocouple detects that the temperature is low; the level of pin ③ is lower than that of pin 2, so that the output pin 1 is also low. Then, make the ⑥ pin of IC-B amplifier low relative to the ⑤ pin of the fixed bias, and make the output ⑦ pin high. Since the IC-B ⑤ pin voltage is obtained by dividing the voltage of AC220V by R6 and R7, the frequency and phase are completely the same as AC220V.

After comparing with the DC of pin ⑥, output AC voltage at pin ⑦. The AC voltage is inversely connected in parallel with C2, D4, D3 and D4 (acting as a bidirectional diode) to trigger the triac, so that the corresponding voltage is applied to the heating wire of the soldering iron to achieve the purpose of constant temperature.