Solution to temperature runaway of electric soldering iron
The constant temperature electric soldering iron adopts a high Curie temperature strip shaped PTC constant temperature heating element inside, equipped with a fastening thermal conductivity structure. The characteristic is superior to traditional electric wire soldering iron cores, with fast heating, energy saving, reliable operation, long service life, and low cost. Low voltage PTC heating elements can be used in the field, making maintenance work easier.
Solution to temperature runaway of constant temperature electric soldering iron
The common malfunction of a constant temperature soldering iron is temperature runaway, which results in the temperature of the soldering iron being too high. On the one hand, it causes high-temperature oxidation of the soldering iron tip (the solder is also oxidized at the same time); On the other hand, welding at high temperatures can also easily burn out electronic components. When an electric soldering iron works at high temperatures for a long time, it is also easy to cause damage to its internal circuits, resulting in permanent loss of control and even inability to use. During the fault inspection, it will be found that the sliding contact of the temperature regulating resistor R2 is oxidized and produces poor contact, which is equivalent to the temperature being adjusted to the maximum upper limit, resulting in a high temperature of the soldering iron. There are two fundamental reasons for this: firstly, during the operation of the electric soldering iron, a portion of heat is transferred to the handle (built-in circuit) of the soldering iron, causing an increase in the temperature of the working environment of the circuit. After a period of time, it is easy to cause oxidation of R2's moving contacts; The second issue is that the current limiting resistor R1 in the rectification and filtering circuit dissipates heat, leading to an increase in the working environment temperature of the circuit and easily causing oxidation of the R2 moving contacts.
To prevent such faults from occurring, the following two methods for modifying the circuit are proposed for reference.
(1) Replacing adjustable resistor R2 with fixed resistor: First adjust R2 to reach the optimal temperature point for normal use of the soldering iron, then measure the value of R2 and replace it with a fixed resistor.
(2) Transforming rectifier circuits
Replace R1 with C (C ≈ 0.12 μ F) and parallel connect a diode D1
