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Soldering Iron Temperature Controller Circuit and Working


Soldering Iron Temperature Controller Circuit & Working

In case you are an digital fanatic, you then have to be accustomed to soldering iron system. That is usually used to design electronic circuits on PCB. In case you are not using an adjustable soldiering iron for soldering, then likelihood is you may end up damaging your IC and even the system.

The voltage requirement of a soldering machine totally is dependent upon the solder scores of the elements used within the system. For example, a small system or IC needs solely 5 Watts power whereas a large system may need 25- 30 Watts iron. A few of the large units also want even 50 Watts or more depending.

Soldering irons are of wide range with totally different power capability. Usually, the gadget runs at 230V AC mains with no temperature controller obtainable. That is the rationale we’ve got decided to design a low-cost temperature controller for soldering iron on this article.

Typically, deterioration in the soldering iron tip might cause because of the constant power consumption. To beat this difficulty, we will use a temperature controller along with the iron to manage the temperature as per requirement. The soldering iron present out there with temperature controller is damn costly and isn’t easily reasonably priced by everyone.

On this article, we will probably be designing a temperature controller for soldering iron through the use of primary digital elements like resistors, DIAC, and TRIAC. Before beginning with the design means of this circuit, let us talk about the prime elements used in the circuits specifically DIAC and TRIAC. As resistor and capacitors used in the circuit don’t want any rationalization and is sort of conversant in each hobbyist and we have now already mentioned them in details as properly.


DIAC is a discrete electronic element that is also referred to as symmetrical set off diodes. This can be a bi-directional semiconductor change that can be used in both forward and reverse polarities. DIAC are fairly often utilized in triggering of TRIAC, means used in the combination of DIAC-TRIAC. One of the fascinating information concerning the DIACs is that they’re bi-directional units during which any of the terminals can be utilized as the primary terminal.

Operation of DIACs

DIACs begins conducting voltage only after a sure breakdown voltage is exceeded. A lot of the DIACs have a breakdown voltage of round 30V however the precise breakdown voltage completely is determined by the specifications of that element sort. When the breakdown voltage is reached, the element resistance decreases abruptly. This leads to a pointy drop of voltage across the DIAC and the corresponding current will increase within the outcome. When the current falls under the holding present, the DIAC switches again to its non-conducting state. Right here, the holding current is a degree at which the DIAC stays at its conducting state.

Each time the voltage within the cycle falls, the system is reset to its conducting state. DIACs present equal switching to each halves of an AC cycle because the conduct of the gadget is equal in each the instructions.

Development of DIAC

DIACs are manufactured in three layers and five layers structure. Allow us to see the construction of each one by one.

Three-layer construction

In this structure, the switching occurs when the reverse biased junction experiences the reverse breakdown. This is probably the most commonly used DIAC in practical on account of its symmetric operation. This three-layered DIAC can reach the breakdown voltage of round 30V typically and able to providing sufficient improvement in switching characteristics.

Five-layer construction of DIAC

The five-layer construction of DIAC could be very totally different in term of operation. This system construction varieties an I-V curve which is just like the three-layer version. You’ll be able to say that this construction seems to be like two break-over diodes related again to back.

Purposes of DIACs

DIACs are of great use in electronics because of the nature of its symmetric operation. A number of the common purposes embrace:

  • It may be used along with the TRIAC system to make the switching symmetrical for each the halves of AC cycle.
  • DIACs are extensively used as mild dimmers or domestic lightning
  • DIACs are also used in fluorescent lamps as starter circuits


Because the identify suggests, TRIAC is a three terminal system that controls the move of current. It’s used to regulate the present move in AC for each halves. It is a bi-directional system, also a member of the thyristor family. TRIAC behaves as two typical thyristors related back to again with each other.


In simple phrases, TRIAC might be triggered into conduction by each unfavorable and constructive voltages with both adverse and constructive trigger pulses utilized to its GATE terminal.

In a lot of the AC switching purposes, the gate terminal of TRIAC is hooked up to the primary terminal.

Development of TRIAC

The development of TRIAC is of four layers. This gadget can conduct in both course when triggered by a single pulse.  The PNPN is positioned within the constructive course and NPNP within the unfavourable path. It acts as open circuit change that blocks present in its OFF state.

There are 4 modes during which TRIAC could be operated specifically:

Mode I + : MT2 current is constructive and Gate Present can also be constructive

Mode I – : MT2 present is constructive and Gate Present can also be adverse

Mode III + : MT2 current is unfavorable and Gate Current can also be constructive

Mode III – : MT2 current is adverse and Gate Present can also be damaging


The TRIAC is triggered into conduction by a constructive present utilized on the Gate terminal. This is labeled as mode I within the above discussion. You can even set off the TRIAC by a unfavorable gate current, which comes into mode Ι–.

Following the same process, in Quadrant ΙΙΙ, triggering with a adverse gate present, –ΙG can also be widespread in both mode ΙΙΙ– and mode ΙΙΙ+. Modes Ι– and ΙΙΙ+ are, nevertheless, less delicate configurations that require a great amount of current at Gate terminal to trigger triggering than the more widespread TRIAC triggering modes of Ι+ and ΙΙΙ–.

TRIACs require a minimal holding present to take care of conduction at waveforms cross over point.

Purposes of TRIAC

  • It’s extensively utilized in management and switching software utilized in household
  • It’s used as a part control system in a lot of the AC purposes
  • That is additionally used for controlling the velocity of followers
  • It’s utilized in motors
  • Additionally it is used as brilliance control in lamps

We hope that you have got a great information of DIACs and TRIACs. We’ve mentioned the working of each the units within the above dialogue that will help you perceive using both the elements within the soldering iron temperature controller. Aside from these two, we’ve got used a potentiometer in our circuit to regulate the temperature with a knob.

Collect the following elements to design the soldering iron temperature controller circuit:

  • Resistor – 2.2 okay (1 nos.)
  • Potentiometer – 100 Okay (1 nos.)
  • 400V capacitor – zero.1uF (1 nos.)
  • DB3 DIAC (1 nos.)
  • BT136 TRIAC (1 nos.)

Related Challenge: Visitors Mild Management Digital Challenge utilizing IC 4017 & 555 Timer

Circuit Diagram of Soldering Iron Temperature Controller

This soldering iron temperature controller could be very easy to design. The circuit is made utilizing a few of the easiest electronic elements mentioned within the above listing. One end of the 2K resistor is related with the DIAC terminal and one other end is related with the 220 V power supply via a potentiometer to regulate the temperature. In other end, DIAC is related with the TRIACs gate terminal to regulate the switching of the TRIAC.


Working of Solder Iron Temperature Controller

The temperature of this controller circuit might be diversified from the maximum value, to manage the warmth dissipation. Connect this circuit to the soldering iron to make an increase in iron temperature shortly very quickly. The TRIAC related right here within the circuit, switches the high present and voltages over both elements of an AC waveform. The TRIAC is fired in several angles to get totally different temperature ranges from zero degrees to most. The related DIAC controls the firing in both directions. Here, you should use the potentiometer to set the temperature accordingly.

The working of this soldering iron temperature controller could be very simple and straightforward to know. You simply want to attach the circuit with the soldering iron to differ the temperature accordingly.

Software of Soldering Iron Temperature Controller

The soldering iron temperature controller is used to regulate the temperature of a soldering iron. You’ll be able to connect this controller to scale back the rising time of soldering iron temperature. That is very useful when you are soldering the sensitive elements.

Backside Line:

The soldering iron with temperature controller, are quite costly and never reasonably priced for everybody. Here, this temperature controller for soldering iron is designed with very low value and primary electronic elements. You need to use this together with your soldering iron to routinely management the temperature. We’ve additionally defined the working and specifications of the primary elements that’s TRIAC and DIAC in our above dialogue. This will probably be very helpful in understanding the working of soldering iron with ease. We hope that now you will be able to design this low energy and highly reliable circuit with none inconvenience.

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