Analysis of CMOS circuit schematic diagram for soldering iron
When soldering CMOS circuits, due to the extremely high input impedance, the induced current on the soldering iron head is sufficient to break down the CMOS circuit. Enthusiasts need to ground the soldering iron when soldering CMOS circuits. It is obviously inconvenient to unplug the power plug before welding. Especially when many solder joints need to be welded at once, frequent insertion and extraction processes are particularly inconvenient. Additionally. Sometimes the temperature is insufficient when using a 20W electric soldering iron, but if you switch to an electric soldering iron above 20W, you may feel that the temperature is too high. Therefore. It is convenient to adjust the temperature of the electric soldering iron and disconnect the power supply.
The circuit principle consists of a transistor switching circuit and a thyristor voltage regulating circuit, as shown in Figure 2 on the printed circuit board. Here is a brief explanation of the manufacturing issues: the button AN should be installed on the soldering iron handle and should be easily pressed during welding. The back of the circuit board is bonded to the soldering iron handle with epoxy resin, and the two poles of the leads are shielded with fine wire. The two poles are soldered onto the circuit board, and the outer periphery of the conductive rubber contacts is glued to the board with oxybutadiene adhesive. The length of the shielding wire should be the same as the soldering iron power wire, and both should be sheathed together in a soft plastic sleeve.
Connect the two ends of the button wire with a coaxial plug or a banana plug (CT in the picture), and match the socket CZ2. Two sets of switching contact relays should be used, and if a small AC voltmeter is connected in parallel to the two poles of socket CZ1, it should be used for temperature control parameters. If not, a scale can also be engraved around the W axis of the potentiometer to roughly grasp the temperature of the soldering iron. The components in the circuit are selected according to the diagram, without any special requirements.
When using, insert the power plug of the soldering iron and the button plug into their respective sockets, plug in the power, and adjust the temperature according to the welding requirements. When welding, before the soldering iron head comes into contact with the solder joint, press the button with your fingers and hear the suction sound of the relay. The surface of the soldering iron head is not charged, so you can weld with confidence. When leaving the solder joint, lift your finger and heat up the soldering iron with electricity.
