Devices for adjusting the voltage level supplied to the heating element are often used by radio amateurs to prevent premature destruction of the soldering tip and improve soldering quality. The most common soldering iron power control circuits contain two-positron contact switches and trinistor devices mounted in a stand. These and other devices provide the ability to select the desired voltage level. Today homemade and factory installations are used.
Simple power regulator for soldering iron
If you need to get 40 W from a 100 W soldering iron, you can use the circuit on the triac VT 138-600. The principle of operation is to trim the sinusoid. The cutoff level and heating temperature can be adjusted using the resistor R1. The neon bulb acts as an indicator. It is not necessary to set it. A triac BT 138-600 is installed on the radiator.
Case
The whole scheme must be placedin a closed dielectric housing. The desire to make the device miniature should not affect the safety of its use. Remember that the device is powered by a 220V voltage source.
Trigistor power controller for soldering iron
As an example, consider a device designed for loads from a few watts to hundreds. The range of regulation of the rated power of such a device varies from 50% to 97%. The device uses a trinistor KU103V with a holding current of not more than one milliamp.
Negative voltage half-waves pass freely through the VD1 diode, providing about half of the entire power of the soldering iron. It can be adjusted by the trinistor VS1 during each positive half-cycle. The device is turned on in anti-parallel to the diode VD1. The trinistor is controlled according to the pulse-phase principle. The generator generates pulses that are fed to the control electrode, consisting of the R5R6C1 timing circuit and a unijunction transistor.
The position of the handle of the resistor R5 determines the time from the positive half-cycle. The power regulator circuit requires temperature stability and improved noise immunity. To do this, you can shunt the control transition with a resistor R1.
Chain R2R3R4VT3
The generator is powered by pulses of up to 7V and 10 ms duration generated by the R2R3R4VT3 circuit. The transition of the transistor VT3 is a stabilizing element. It turns on in reverse. The power it dissipatesthe circuit of resistors R2-R4 will be reduced.
The power regulator circuit includes a capacitor S1KM5, resistors - MLT and R5 - SP-0, 4. Any transistor can be used.
Board and housing for the device
For the assembly of this device, a fiberglass board with a diameter of 36 mm and a thickness of 1 mm is suitable. Any objects can be used for the case, such as plastic boxes or cases made of a material with good insulation. You will need a base for the plug elements. To do this, two nuts M 2, 5 can be soldered to the foil so that the pins press the board to the case during assembly.
Disadvantages of SCRs KU202
If the power of the soldering iron is small, regulation is possible only in a narrow half-cycle region. In the one where the holding voltage of the SCR is at least slightly lower than the load current. Temperature stability cannot be achieved when using such a soldering iron power controller.
Boost Regulator
Most of the devices for temperature stabilization work only to reduce power. You can adjust the voltage from 50-100% or from 0-100%. The power of the soldering iron may not be enough if the power supply is lower than 220 V or, for example, if you need to desolder a large old board.
The operating voltage is smoothed by an electrolytic capacitor, increases by 1.41 times and feeds the soldering iron. The constant power rectified by the capacitor will reach 310 V with a 220 V supply. The optimum heating temperature canbe obtained even at 170 V.
Powerful soldering irons don't need boost regulators.
Necessary parts for the circuit
To assemble a convenient power regulator for a soldering iron with your own hands, you can use the surface mounting method near the outlet. This requires small components. The power of one resistor should be at least 2W, and the rest - 0.125W.
Description of power boost controller circuit
The input rectifier is made on the electrolytic capacitor C1 with the bridge VD1. Its operating voltage should not be less than 400 V. The output part of the regulator is located on the IRF840 field-effect transistor. With this device, you can use a soldering iron up to 65 W without a heatsink. They may get hotter than the desired temperature even when the power is reduced.
The key transistor located on the DD1 chip is controlled by a PWM generator, the frequency of which is set by the capacitor C2. The parametric stabilizer is mounted on the C3, R5 and VD4 devices. It powers the DD1 chip.
To protect the output transistor from self-induction, a VD5 diode is installed. It can be omitted if the soldering iron power control will not be used with other electrical appliances.
Possibility of replacing parts in regulators
Chip DD1 can be replaced by K561LA7. The rectifier bridge is made of diodes designed for a minimum current of 2A. The IRF740 can be used asoutput transistor. The circuit does not need an overlay if all the parts are in good order and no errors were made during its assembly.
Other possible voltage dissipation options
Simple circuits of power regulators for a soldering iron are assembled, working on triacs KU208G. All their cunning is in a capacitor and a neon light bulb, which, by changing its brightness, can serve as an indicator of power. Possible regulation is from 0% to 100%.
In the absence of a triac or a light bulb, a KU202N thyristor can be used. This is a very common device that has many analogues. With its use, you can assemble a circuit operating in the range from 50% to 99% power.
A ferrite ring from a computer cord can be used to make a loop to extinguish possible interference from switching a triac or thyristor.
Arrow indicator
The dial gauge can be integrated into the soldering iron power regulator for greater ease of use. It is quite easy to do this. Unused old audio equipment can help you find these items. Devices are easy to find in local markets in any city. Well, if one of these is lying around at home.
For example, consider the possibility of integrating the M68501 indicator with an arrow and digital marks into the power regulator for a soldering iron, which was installed in old Soviet tape recorders. The tuning feature is the selection of the resistor R4. Definitely have to pick up the device R3additionally if another indicator is used. It is necessary to maintain an appropriate balance of resistors when lowering the power of the soldering iron. The fact is that the arrow of the indicator can display a decrease in power by 10-20% when the actual consumption of the soldering iron is 50%, that is, half as much.
Conclusion
The power regulator for a soldering iron can be assembled using many instructions and articles with examples of various possible circuits. The quality of the soldering depends largely on good solders, fluxes and the temperature of the heating element. Complex devices for stabilization or elementary integration of diodes can be used when assembling devices necessary to regulate the incoming voltage.
Such devices are widely used to reduce as well as increase the power supplied to the heating element of the soldering iron in the range from 0% to 141%. It is very comfortable. There is a real opportunity to work at voltages below 220 V. High-quality devices equipped with special regulators are available on the modern market. Factory devices work only to reduce power. The step-up regulator will have to be assembled by yourself.
