Homemade constant temperature electric iron ----- Thermostat Electric Iron

Homemade constant temperature soldering iron, Thermostat Electric Iron Keywords: homemade constant temperature electric iron The simple constant temperature iron soldering iron sold on the market, its constant temperature control part is powered directly from the secondary thyristor. Once the problem often makes the components burns or crackled, the color of the device is damaged, and the mark cannot be identified. Repair brings difficulties. Here, we use a representative Guangzhou Huanghua Electronic Appliance Factory as an example to introduce the working principle of constant temperature soldering iron. The electric iron control temperature range is 100 ° C ~ 400 ° C, the temperature regulation mark is indicated low, medium, high, and temperature control accuracy nominal ± 5%, using a thermocouple sensor. The control circuit adopts the exchange of electricity, filtering, and regulating power supply solutions. See the figure below. The main electric AC220V is filtered by the R1 buck, D1 half-wave rectification, D2 cut regulation, and C1 filtering as a power supply voltage and temperature regulation of the comparison device IC. The IC-A3 pin is a thermocouple detecting voltage input (corresponding to the temperature value); 2 pin is a temperature regulation set voltage. After the voltage is compared between 2, 3 foot, output by 1 pin. The role of R5 is to feed back the input of the input to the same phase input terminal 3, so that the output lock does not change when the small signal fluctuates. When the thermocouple is lowered to the temperature; 3 foot level is relatively low, the output 1 foot is also low. Furthermore, the IC-B amplifier 6 foot is low to the 5 foot of the fixed biased, so that the output 7 is high. Since the IC-B5 foot voltage is obtained by voltage R6 and R7 by the AC220V, the frequency, the phase is completely the same as the AC220V. The AC voltage is output at the 7 pin after the DC DC. The AC voltage is reversely parallel (acting as a bidirectional diode) in C2, D4, D3, and D4 to trigger two-way thyristor, so that the corresponding voltage is added to the soldering iron wire to achieve a constant temperature.

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