Devices for adjusting the voltage level supplied to the heating element are often used by radio amateurs to prevent premature destruction of the soldering iron tip and improve the quality of soldering. The most common power regulator circuits for a soldering iron contain two-positron contact switches and trinistor devices installed in a stand. These and other devices provide the ability to select the desired voltage level. Today, home-made and factory installations are used.
Simple power regulator for soldering iron
If you need to get 40 watts from a soldering iron per 100 watts, you can apply the circuit on the triac BT 138-600. The principle of operation is to cut a sinusoid. The cutoff level and heating temperature can be adjusted using resistor R1. A neon light serves as an indicator. Putting it is not necessary. A triac BT 138-600 is installed on the radiator.
Body
The entire circuit must be placed in a closed dielectric casing. The desire to make the device miniature should not affect the safety of its use. Remember that the device works from a voltage source of 220 V.
Trinistor power regulator for soldering iron
As an example, we can consider a device designed for a load of several watts to hundreds. The range of regulation of the rated power of such a device varies from 50% to 97%. The device uses a KU103V trinistor with a holding current of not more than one milliampere.
Negative voltage half-waves freely pass through the VD1 diode, providing about half of the total power of the soldering iron. It can be adjusted by the VS1 trinistor during each positive half-cycle. The device turns on in parallel to the VD1 diode. The trinistor is controlled by a phase-pulse principle. The generator generates pulses arriving at the control electrode, consisting of a circuit R5R6C1, which sets the time, and a single-junction transistor.
The position of the handle of the resistor R5 determines the time from the positive half-cycle. The power regulator circuit requires thermal stability and increased noise immunity. To do this, you can bypass the control transition resistor R1.
Chain R2R3R4VT3
The generator is powered by pulses of voltage up to 7V and a duration of 10 ms, formed by the R2R3R4VT3 circuit. Transition of the transistor VT3 is a stabilizing element. It turns on in the opposite direction. The power dissipated by the R2-R4 resistor circuit will be reduced.
The power regulator circuit includes a capacitor C1KM5, resistors - MLT and R5 - SP-0.4. Any transistor can be used.
Board and housing for the device
To assemble this device, a board made of foil fiberglass with a diameter of 36 mm and a thickness of 1 mm is suitable. For the case, you can use any items, such as plastic boxes or cases made of material with good insulation. You need a base for the plug elements. To do this, two M 2.5 nuts can be soldered to the foil so that the pins press the board against the body during assembly.
Disadvantages of KU202 trinistors
If the power of the soldering iron is small, regulation is possible only in a narrow region of the half-cycle. In the one where the holding voltage of the trinistor is at least slightly lower than the load current. Temperature stability cannot be achieved if such a power regulator is used for a soldering iron.
Boost regulator
Most temperature stabilization devices only work 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 necessary, unsolder a large old board.
The effective voltage is smoothed by an electrolytic capacitor, increases by 1.41 times and feeds the soldering iron. The constant power rectified on the capacitor will reach 310 V with a supply of 220 V. The optimum heating temperature can be obtained even at 170 V.
Powerful soldering irons do not need up-regulators.
Necessary details for the circuit
To assemble a convenient power regulator for a soldering iron with your own hands, you can use the mounting method near the outlet. For this, small-sized components are needed. The power of one resistor should be at least 2 watts, and the rest - 0.125 watts.
Description of the power boost controller circuit
An input rectifier is made on the electrolytic capacitor C1 with a bridge VD1. Its operating voltage should not be less than 400 V. The output part of the regulator is located on the field effect transistor IRF840. With this device, you can use a soldering iron up to 65 W without a radiator. They can heat up above the desired temperature even with reduced power.
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 devices C3, R5 and VD4. 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 regulator is not used with other electric devices.
Options for replacing parts in regulators
The DD1 chip can be replaced with a K561LA7. The rectifier bridge is made of diodes designed for a minimum current of 2A. The IRF740 can be used as an output transistor. A circuit does not need an overlay if all the parts are in good working order and no errors were made during its assembly.
Other possible options for voltage dissipation devices
Simple circuits of power regulators for a soldering iron are assembled, operating on KU208G triacs. All their trick is in the capacitor and neon bulb, which, changing its brightness, can serve as an indicator of power. Possible regulation is from 0% to 100%.
In the absence of a triac or bulb, you can use the KU202N thyristor. This is a very common device that has many analogues. Using it, 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 absorb possible interference from switching a triac or thyristor.
Dial indicator
A dial indicator can be integrated into the soldering iron power regulator for greater ease of use. It’s not difficult to do this. Unused old audio equipment can help with finding such items. Devices are easy to find in local markets in any city. Well, if one such is lying at home idle.
As an example, consider the possibility of integrating an indicator M68501 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. Surely you will have to pick up the R3 device additionally if another indicator is used. It is necessary to observe the 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 a soldering iron is 50%, that is, half less.
Conclusion
The power regulator for a soldering iron can be assembled, guided by many instructions and articles with examples of possible various schemes. The quality of soldering largely depends on good solders, fluxes and the temperature of the heating element. Complex devices for stabilization or elementary integration of diodes can be used in the assembly of devices necessary for regulating 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 convenient. 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 only work on lowering power. The raising regulator will have to be assembled independently.