Thermostatic soldering iron temperature out of control solution
Constant temperature soldering iron internal use of high Curie temperature strip PTC thermostatic heating element, equipped with fastened heat conduction structure. Characterized by superiority over traditional hot-wire soldering iron core, rapid heating, energy saving, reliable, long life, low cost. With low voltage PTC heating core can be used in the field, easy maintenance work.
The common failure of constant temperature soldering iron is the temperature out of control, the result of which causes the temperature of the soldering iron to be too high. On the one hand, it leads to high temperature oxidation of the soldering iron head (the solder is also oxidized at the same time); on the other hand, it is easy to burn the electronic components when soldering at high temperature. When the soldering iron in the high temperature work for a long time, but also easy to cause its internal circuit damage, resulting in permanent loss of control or even can not be used. In the fault check will be found in the temperature control resistor R2 sliding contacts are oxidized to produce poor contact phenomenon, which is equivalent to the temperature is adjusted to the maximum upper limit, and thus the temperature of the iron is high. The root cause of two points: one is the soldering iron work to the handle of the iron (circuit built-in) to transfer part of the heat, so that the circuit working environment temperature increases. After a period of time it is easy to cause the oxidation of the dynamic contacts of R2; Secondly, the current limiting resistor R1 in the rectifier filter circuit dissipates the heat and causes the circuit to work at an elevated ambient temperature is also easy to cause the oxidation of the dynamic contacts of R2.
In order to prevent the occurrence of such failures, the following two methods of modifying the circuit are proposed for reference.
(1) fixed resistor instead of adjustable resistor R2: first adjust R2, so that the temperature of the soldering iron to reach the optimal temperature point for normal use, and then measure the value of R2, with a fixed resistor instead.
(2) Modify the rectifier circuit: the circuit structure is shown in Figure 3.
Replace R1 with C (C ≈ 0.12 μF) and connect a diode D1 in parallel.
