Analysis of schematic diagram of electric soldering iron welding CMOS circuit
When soldering a CMOS circuit, because the input impedance is extremely high, the induced electricity on the tip of the soldering iron is enough to break down the CMOS circuit. When soldering CMOS circuits, amateurs need to connect the tip of the soldering iron to the ground. Or unplug the power plug before welding, which is obviously very inconvenient. Especially when many solder joints need to be welded at one time, the frequent plugging and unplugging process is particularly inconvenient. in addition. Sometimes the temperature is not enough with a 20W electric soldering iron, and if you switch to a 20W or more electric soldering iron, the temperature is always too high, so. It is convenient to be able to adjust the temperature of the electric soldering iron and disconnect the power supply.
The circuit principle in Figure 1 is composed of a transistor switch circuit and a thyristor voltage regulating circuit, and the printed board diagram is shown in Figure 2. Now we only briefly explain the production problems: the button AN should be installed on the handle of the soldering iron, and it should be a convenient place to press during soldering. The back of the circuit board is bonded to the handle of the soldering iron with epoxy resin, and the two poles of the lead wire are soldered to the two poles of the circuit board with thin shielded wires. The length of the wire should be equal to the length of the soldering iron power cord, and both should be placed in the soft plastic sleeve.
The two ends of the button line are connected with a coaxial plug or a banana plug (CT in the figure), and the socket CZ2 is matched with it. Two sets of conversion contact relays should be used. If the two poles of the socket CZ1 are connected in parallel with a small AC voltmeter, it can be used as a temperature adjustment parameter. If not, you can also engrave a scale around the axis of the potentiometer W, so that you can roughly grasp the temperature of the soldering iron. The components in the circuit are selected according to the diagram, and there is no special requirement.
When in use, insert the soldering iron power plug and the button plug into their respective sockets, plug in the power supply, and adjust the temperature according to the welding requirements. When soldering, before the tip of the soldering iron touches the solder joint, press the button with your finger, and when you hear the sound of pulling in the relay, the surface of the tip of the soldering iron is not charged, and you can solder with confidence. When leaving the solder joint, lift your finger and the soldering iron is energized to heat up.
