DIY repair of a construction hair dryer

In detail: DIY repair of a building hair dryer spiral from a real master for the site my.housecope.com.

We all are familiar with such an auxiliary tool in construction as a construction electric hair dryer, which we are used to using for removing paint and varnish coatings.

The basic principle of operation of a construction hair dryer is not much different from an ordinary hair dryer that we use to dry our hair.

Accordingly, the electrical circuit of a building hair dryer is similar to the electrical circuit of an ordinary hair dryer.

An explanation will be given in the stated topic:

electrical diagram of a building hair dryer;
the principle of the construction hair dryer;
possible reasons for the malfunction;
elimination of these malfunctions.

Consider the electrical circuit in Fig. 1 of the building hair dryer:

One diagonal of the diode bridge is connected to an external source of alternating voltage 220V.

The other diagonal of the diode bridge is connected to the electric motor.

The electrical diagram consists of the following elements:

toggle switch performing the control temperature mode - K1;
a toggle switch that controls the speed of the blowing speed of the electric motor rotor - K2;
toggle switch for disconnecting heating elements - K3;
fan motor - M;
capacitor - C;
Heating elements - RTEN;
diodes - VD1, VD2.

Through the diode bridge circuit of one diagonal of the bridge, the rectified current of two potentials +, - is supplied to the electric motor. When passing from the anode to the cathode, the current flows with a positive half-cycle of the sinusoidal voltage.

Two capacitors connected in parallel in an electric circuit serve as additional smoothing filters.

The blowing speed occurs due to the variability of the resistance in the electrical circuit, that is, when the speed toggle switch is switched to the highest resistance value, the rotation speed of the electric motor rotor decreases due to the voltage drop.

Video (click to play).

The number of heating elements of heaters in this scheme is four. The temperature regime of the construction hair dryer is carried out by the temperature control toggle switch.

The heating elements in the electric circuit have different resistance, - accordingly, the heating temperature when switching from one section of the electrical circuit to another - heating the heating elements will correspond to its resistance value.

The general appearance of the construction hair dryer with its names of individual parts is shown in Fig. 2

The following electrical diagram of the building hair dryer in Fig. 3, is comparable to the electrical circuit in Fig. 1

There is no diode bridge in this wiring diagram. Blowing speed control and temperature control - occurs when switching from one section of the electrical circuit to another, namely:

when switching to a section of an electrical circuit - consisting of a diode;
when switching to a section of an electrical circuit that does not have a diode.

When a current flows in the anode-cathode junction of the VD1 diode, which has its own resistance, the heating element2 will heat up according to two resistance values:

resistance at the transition anode - cathode diode VD1;
resistance of heating element heating element 2.

When a current flows in the anode-cathode junction of the diode VD2, the voltage supplied to the electric motor and the heating element1 will take the lowest value.

Accordingly, the speed of rotation of the rotor of the electric motor and the heating temperature of the heating element for a given section of the electric circuit will correspond to the direct transition of the current of the diode VD2. Heating of the heating element heating element1 for a given section also depends on its internal resistance, that is, the resistance of the heating element is taken into account.

The main reasons for the malfunction of the construction hair dryer here can be called the malfunction of the electronic elements:

Most often, such a malfunction occurs with a sharp jump in an external source of alternating voltage. For example, the cause of a capacitor malfunction is caused by the fact that the capacitor plates are closed when there is a voltage jump between themselves - short-circuited.

Of course, such a possibility of a malfunction as a rupture in the stator winding of an electric motor, winding burnout, is not excluded.

Minor malfunctions include such reasons as:

oxidation of the temperature control toggle switch contacts;
oxidation of the contacts of the toggle switch for controlling the blowing speed;
oxidation of the contacts of the toggle switch for disconnecting the heating elements;
a wire break in a network cable;
defective plug lack of contact.

Diagnostics to identify the cause of the malfunction is carried out by the "Multimeter" device.

When replacing a capacitor, its capacity and voltage rating are taken into account.

When replacing a diode, the resistance of two values is taken into account, in the directions:

from anode to cathode;
from the cathode to the anode.

As we know, the value of resistance from anode to cathode will be significantly less than from cathode to anode.

With an electric motor, if it malfunctions, things are more complicated. With such a malfunction, it is easier to replace the electric motor than it is permissible to rewind the stator windings. But even such work is doable - who is directly involved in such repairs. In this case, the following is taken into account:

the number of turns in the stator winding;
section of copper wire.

Such a malfunction as burnout of the heating element is not excluded. Replacing the heating element is carried out taking into account its resistance value.

Consider the device of electric motors and how exactly it is necessary to diagnose electrical machines, as they are usually considered in the section on electrical engineering.

For an illustrative example, photographs of several types of such electric machines are presented - related to collector motors. The device and principle of operation are admissible two collector electric motors:

- is no different. The difference in electric motors is only in the rotor speed and in the power of the electric motor. Therefore, we, as it were, will not sharpen our attention in the sense that explanations are given that are not related to the electric motor of the construction hair dryer.

The electric motor of the building hair dryer is asynchronous, collector, single-phase alternating current.

Image - DIY repair of a construction hair dryer spiral

The rotor device does not require any explanation, since everything is shown in the photograph in Fig. 4 and a schematic representation of the electric motor rotor.

asynchronous collector motor single-phase alternating current

The electrical diagram of the collector motor in Fig. 5 is as follows:

In the circuit, we can notice that the collector motor can operate on both alternating and direct current - these are the laws of physics.

The two stator windings of the electric motor are connected in series. Two graphite brushes in contact - in electrical connection with the motor rotor collector.

The electrical circuit closes on the rotor windings, - accordingly, the rotor windings in the electrical circuit are connected in parallel through the brush-collector sliding contact.

diagnostics of stator windings of an electric motor

The photograph shows one of the methods for diagnosing the stator windings of an electric motor. In this way, the integrity or insulation breakdown of the stator windings is checked. That is, one probe of the device is connected to any of the brought out ends of the stator windings, the other probe of the device is connected to the stator core.

In the event that the insulation of the stator winding is broken and the winding wiring shorts to the core, the device will indicate a zero resistance value in the short circuit mode. It follows from this that the stator winding is defective.

The device in the photograph indicates a one when diagnosing - this does not mean that this stator winding is suitable for operation.

It is also necessary to measure the resistance of the windings themselves. Diagnostics is carried out in the same way, - the probes of the device are connected to the removed ends of the wires of the stator windings. With the integrity of the windings, the display of the device will indicate the resistance value possessed by this or that winding. If one or another stator winding breaks, the device will show "one". If the wires of the stator winding are short-circuited with each other as a result of overheating of the electric motor or for other other reasons, the device will indicate the lowest zero resistance value or "short circuit mode".

How to check the resistance of the rotor winding with a device? - To do this, you need to connect the two probes of the device to two opposite sides of the collector, that is, you need to make the same connection that the graphite brushes have in electrical connection with the collector. The diagnostic results are reduced to the same indications as when diagnosing the stator windings.

What is a collector in general? - The collector is a hollow cylinder consisting of small copper plates of a special alloy, isolated from each other and from the rotor shaft.

In the event that the damage to the collector plates is insignificant, the collector plates are cleaned with fine-grained emery paper. Again, this amount of work can be performed directly only by specialists who repair electric motors.

The electrical circuit in Fig. 7 consists of a battery and a light bulb, this circuit is comparable to that of a pocket flashlight. One end of the negative potential wire is connected to the stator core, the other end of the positive potential wire connects to one of the brought out ends of the stator windings. If the wires are connected the other way around, that is, "plus" to the stator core, "minus" to the output end of the stator winding, nothing changes from this.

In the presence of insulation breakdown, when the stator winding is closed with the core, the light in this electrical circuit will be on. Accordingly, if the light does not light up, then the stator winding is not closed with the stator core.

This method of diagnosing Fig. 7 is not complete. Accurate diagnostics is carried out only with an Ohmmeter device or a Multimeter device with a set resistance measurement range, for subsequent measurement of the resistance of the stator windings.

With the help of a hair dryer, you can heat up old varnish or paint to remove them from the surface. During construction, it is used to solder metal, as well as to facilitate the handling of plastic pipes. In a heated state, they lend themselves well to bending. This tool is very whimsical, and in case of improper use it will have to be repaired, and this is not an easy task.

Consider how to repair a building hair dryer with your own hands. A person can always contact specialized service centers for such a service, but this is not always advisable. In some cases, breakdowns can be diagnosed independently, respectively, and the repair of the construction hair dryer itself can be done. Before that, it is imperative to get acquainted with the device device. This is where the instruction should begin.

Opening the device reveals a small motor, heating element and fan. The heated air exits through the nozzle. Everything is simple enough. Basically, the structure does not differ from an ordinary hair dryer. The only difference is the higher power of the device. The performance of the equipment directly depends on how many liters of air it can pass through itself in 1 minute. Many hair dryer models on the market today have a number of additional functions.These include:

Using a building hair dryer.

temperature control;
air flow regulation;
selection of the required operating mode;
numerous additional attachments that will significantly simplify the work with this or that material;
LED indicator that determines the heating temperature.

Of course, these are not all the options that a building hair dryer can have. There are others. You should always remember that the more there are, the more difficult it is to make repairs.

Breakage of such a tool can occur at any time of its operation. It is especially unpleasant if this is in the midst of construction work. In most cases, the person himself is to blame, who is often negligent about the power tool. The main breakdowns are considered to be the bend of the power cord, a malfunction of the button for turning on the tool and adjusting the temperature. Of course, more global breakdowns can also occur.

Wiring diagram for a hair dryer.

For example, a motor or fan may be damaged. The heating element is not eternal in this respect. Most of the faults can be diagnosed on their own, but there are those that have to be identified for a long time. In this situation, it is best to contact a specialized service center.

If a person is confident in his abilities, then he can repair the hair dryer on his own.

The most difficult breakdowns include engine or fan breakdown. In most cases they need to be replaced and it is difficult to find the right spare parts.

Before proceeding with repair work, it is imperative to inspect the device.

Already at this moment, most of the troubles can be identified. Be sure to pay attention to the on and off buttons of the tool, as well as the state of the wiring. Perhaps the cord was just broken in some place or the plug was broken. All this can be determined already at the preliminary stage of work.

Next, you just need to check the hair dryer in different operating modes. First you need to check if heating is on. If not, then the problem lies in the malfunction of the coil, that is, the heating element. For a more accurate diagnosis, it is worth using a tester.

Sometimes you have to use various devices and disassemble the device in order to see its state inside. If you have to disassemble a hairdryer, and it has a complex structure, then you need to acquire a high-quality camera in order to capture all the stages of disassembling the unit. You may also need tools such as a screwdriver and a soldering iron.

The revision consists in the fact that it is necessary to analyze the damaged parts, to determine the main centers of corrosion. It is they that, in some cases, can serve as prerequisites for the oxidation of contacts. It is imperative to inspect all conductors, a spiral and a fan that are located in the equipment.

Next, you can engage in the replacement of those parts that are out of order. The spiral can be replaced by yourself. If any conductor has fallen off, then you will have to take a soldering iron and solder the element in place. The fan can be replaced, but you will have to look for a similar unit. In the case of the engine, things can be sad. If it burns out, then it will not be possible to repair it on your own. You will have to contact the service center for help.In this article we will tell you about building hair dryers, the reasons for their main malfunctions, and how to eliminate them. In addition, we will describe some of the upgrades and improvements that can be done with your tool.The figure below shows the electrical diagram of a building hair dryer.The main elements of the tool are the motor, fan and heating element. Image - DIY repair of a construction hair dryer spiral

The heating element is nothing more than a spiral wound on a ceramic base. In many models, the manufacturer builds in a thermal sensor, which, in case of overheating, turns off the power to the hair dryer.Nichrome is usually used as a material for spirals. Possessing a certain resistance, the spiral picks up some of the heat as the current passes through it and releases it into the environment, thereby providing a continuous hot air flow.

With intensive use of the tool, its breakdowns are not uncommon. They are very different. We will now tell you how to figure out what exactly can break.

The first step is to carry out a visual inspection of the hair dryer. Pay close attention to buttons, switches, power cord, plug. A fairly common cause of a breakdown is a violation of insulation or a wire break at the joints with the case. If the wire is damaged, it must be cleaned in this place and insulated with adhesive tape. If the buttons for switching on and switching temperature modes are malfunctioning, they should be replaced with new ones.

If this is not the reason, then you should diagnose the operation of the instrument in different modes. The hair dryer can only supply cold air. In this case, it is required to inspect the heating element of the device - a spiral. If there is no air supply, your attention should be paid to the fan or motor. Replacing a heating element, fan or wires is a simple and inexpensive procedure in itself, which cannot be said about replacing an electric motor. If it breaks down, repairing the hair dryer becomes meaningless.

In the process of work, the user may not be satisfied with some constructive factory solutions, so he decides to modify the hair dryer.In general, tool modernization can be directed towards specific goals. We will present some of them below:

Possibility of using various attachments.

Adjusting the air flow when installing small parts.

Make independent the disconnection of the spiral from the fan and vice versa - for rapid cooling of the tool.

During the operation of the tool, certain malfunctions appear. Let's take a look at the experience of the user of the Interskol hair dryer. What can the future hold for you?

In the first year of the hair dryer's life, it became impossible to adjust the temperature - the reason lay in the overheating of the triac and its failure.
The already familiar fracture of the power cable at the point of abutment to the instrument body. This problem is solved by installing a double rubber cable.
The high resistance heater winding has been broken. The reason could be both a factory defect and the rubbing of the nichrome winding on the edges of the ceramics due to heating-cooling processes. In the process of replacing the winding, it was necessary to replace the thermal fuse, which was triggered when the engine suddenly stopped.
By the end of the second year of operation, the plain bearings in the engine failed.

This is a common list of malfunctions that can occur in the device over three years of use of the tool. In addition, there were other minor defects such as the loss of voltage on the heating element coils. This does not mean that all this will manifest itself in your hair dryer model, but these are the things that you should pay attention to when buying and using a hair dryer.

In this article, we have tried to highlight as much as possible all the problems that arise during the operation of the hair dryer. Buy this tool or not - as always, it's up to you.

The hot air dryer is a universal power tool that is used in the household for construction or renovation work. With its help, surfaces for painting are prepared, plastic pipes of any diameter are bent during the installation of water supply and sewerage systems, operations with heat-shrinkable materials, soldering and many other works are performed. If at the right time the building hair dryer was not at hand, you can do it yourself. This task is especially relevant for those who do not have a constant need for this tool, so it is not economically feasible to buy it for performing one-time work.A construction or technical hair dryer is a power tool designed for local heating of surfaces with a stream of hot air. Outwardly, it looks like an ordinary household appliance, only it has a slightly larger size and creates a higher temperature - up to 650 o C. A thermofan consists of the following main parts:

housings made of heat-resistant plastic with a pistol grip and openings for air intake;

a thermal insulating casing, inside which a heating element is located in the form of a nichrome spiral wound on a ceramic base;

an electric motor mounted behind the casing, at the location of the air intake openings, and a fan impeller mounted on its shaft;

nozzles through which hot air is supplied outside;

buttons for turning on the tool;

power cable.

The construction hair dryer consists of a heat-insulating casing with a heating element, an electric motor and a device control mechanism

Some hair dryers are equipped with temperature controls and indicators, as well as the ability to turn off the heating function when the fan is running. The last addition to the design is necessary for cold blowing of heated parts in order to cool them faster.

A building hair dryer can either be completely made from scrap materials, or you can remake a regular household hair dryer for drying hair under it. In the first case, you need to think about what to make and how to connect together the three main components of this simple tool - an electric motor, a heating element and a fan. When converting a household hair dryer into a technical one, you need to remember that many of its parts are not designed for operation in high temperature conditions. Therefore, you need to take care of thermal insulation or replacement of these parts in advance.

In order to make a technical hair dryer from a similar household appliance or material at hand, you will need:

an electric motor or a cooler from a computer (instead of these units, which are necessary to provide air supply to the nozzle through a heating element, it is quite possible to use a regular aquarium compressor with the required power and performance), when converting a household hair dryer, a standard engine is used;
nichrome spiral (or a thread that you have to wind up in a spiral yourself). In household hair dryers, it is designed for a lower temperature, so it needs to be replaced;
metal plates for the blades, if there is no ready-made fan or it has low-melting blades;
a metal tube for the nozzle (when upgrading a household hair dryer, it will be required for the nozzle of a new heating element);
electrical cable for the power cord;
a piece of rubber pipe for thermal insulation of the handle; a corrugation from an old vacuum cleaner is best suited for this purpose;
thermal insulation materials - asbestos cord, fiberglass, liquid glass or various ceramic inserts. A homemade hair dryer can be made from scrap materials and a computer fan

When making a technical hair dryer, it is necessary to take into account the correct order of its operation, so that the fan or the air supply compressor is turned on first and only after it is the heating element. Disconnecting elements must be done in reverse order.. To fulfill this condition, it is necessary to provide for the possibility of separate switching on / off of these parts of the tool.

The electrical part of the hair dryer must be powered through an alternating current rectifier in the form of a diode bridge.

A conventional diode bridge is used to rectify the alternating current in the power supply unit of the hot air gun.

Separation of the coil of the heating element is necessary to ensure two temperature conditions.

It should be borne in mind for what work you want to make the tool. For example, simplifying the design by replacing an electric motor with a fan with an aquarium compressor will greatly facilitate the task, but will make the hair dryer less mobile.

The easiest way is to make a construction hair dryer, in which the air is supplied by a compressor. To make such a device with your own hands, you must:

It remains to connect the bolts on the rear plug to the 36–42 volt transformer, and connect the air supply hose from the compressor to the copper tube. It is clear that only a limited range of works can be performed with such a tool, but its functionality will increase significantly if you make or buy replaceable nozzles (nozzles).

The easiest way is to make a building hair dryer with your own hands, by remaking an ordinary household hair dryer for it. Both of these instruments are similar in design, so the main challenge to be solved is increasing the power of the hair dryer. If a household appliance gives out a temperature of up to 60 o С, then we need to get a directed air flow at the outlet with a temperature of 500-600 o C. To achieve this, you need to adhere to certain rules:

choose for modernization a household hairdryer with a ceramic or, in extreme cases, with a plastic body, but made of high-quality heat-resistant polymer;

replace the internal parts of the device, which are made of fusible plastic, by making copies of them from textolite or other heat-resistant material;

isolate the parts of the old structure from the new heating element as much as possible, using any available thermal insulation materials.

Having picked up a suitable faulty household hair dryer, you can start modernizing it. This requires:

The simplest device for mechanized winding of a nichrome spiral consists of the following parts: 1 - vise, 2 - wooden block, 3 - nichrome thread, 4 - mandrel, 5 - electric drill

Semicircular grooves are cut in the bars, forming a hole of sufficient diameter to accommodate the winding rod with the wound wire. The rod itself is inserted into the drill chuck, and a nichrome wire is fixed at its end. The structure is clamped in a vise tight enough to hold the bars and allow the wire to pass between them when winding.

For manual winding, the same principle is used, but instead of a drill, a wrench is used, and the free end of the mandrel is enclosed in a supporting surface with a bearing. You can slightly modify the design by removing the vice, and support the rod from both ends for winding onto the bearing assembly.

When winding a spiral, you need to follow some rules:

winding should be done without stopping or loosening the thread tension;

do not guide the thread with your hand, but only with wooden blocks to avoid serious cuts;

do not allow the wire to bend, which may not break immediately, but will burn out very quickly at the bend;

it is necessary to choose the length of the winding rod with a margin and taking into account the possibility of fixing it in a vice or on supporting surfaces.

When winding, the turns should be laid tightly to each other. It is better to then stretch the spiral to the desired length.In order to make a construction hair dryer with your own hands, complex fixtures and tools are not required. You just need to be smart and come up with the most convenient design. It is advisable that your homemade product was made taking into account the needs that have arisen, as well as from the expectation of using it for the future. After all, the hot air gun will certainly be useful to you in the future for the production of construction, repair or installation work. Household hair dryer operation The hair dryer operates on a 220 V, 50 Hz network. Any hair dryer has two main parts - a heating element and an electric motor. As a rule, a nichrome spiral is used as a heating element, it is it that provides warm air. In hair dryers, DC electric motors with a power of up to 50 watts are mainly used, there are exceptions. Passing through the spiral, the current loses its initial strength, since the spiral has a certain resistance, it is this current that is rectified by the diode bridge and supplied to the electric motor. Electric motors in hair dryers are designed for voltages of 12, 24 and 36 volts, only in very rare models electric motors with a power supply of 220 volts are used, in this case, the voltage from the network is directly supplied to the electric motor. A propeller (propeller) is attached to the rotor of the engine, which provides heat removal from the spiral, it is thanks to this that a sufficiently strong directed flow of warm air is obtained at the outlet. The power of the hair dryer depends on the thickness of the spiral used and the power of the installed electric motor. The brought hair dryer was disassembled, it turned out that the problem was a broken track on the board with switches. After filling it with solder, the device started working normally.But most often, the main reasons for inoperability are a broken spiral, an inoperative engine, contacts of switches that have melted from heat, a broken mains wire or plug. What the hair dryer consists of: Elements in the diagram: 1 - diffuser nozzle, 2 - body, 3 - air duct, 4 - handle, 5 - cord twist protection, 6 - “Cold air” mode button, 7 - air flow temperature switch, 8 - flow rate switch air, 9 - "Turbo" mode button - maximum air flow, 10 - a loop for hanging a hair dryer. Wiring diagram for a simple hair dryer A DC voltage is supplied to the electric motor, obtained by means of a diode bridge consisting of four diodes (or simply from one diode).Let us single out two elements of the circuit that are consumers (loads), these are the spiral and the diode bridge (we do not consider the motor, since it is the load of the bridge). In the circuit, the elements are located in series (one after the other), which means that the voltage drop across each of them will depend on its resistance and their sum will be equal to the mains voltage at the third position of the switch.Most of the entry-level hair dryers have a simple wiring diagram, in such hair dryers there is only one switch that turns on the fan and heating element. Heaters can be made in various modifications, but in all hair dryers they are made of nichrome coiled into a spring.However, almost all simple modern hair dryers have 2-3 steps of power and air flow regulation.More advanced hair dryers have smooth controls for the airflow speed and air temperature. Rules for the use of hair dryers The recommended maximum run time is 5 minutes. At the end of the work, remove the temperature regulator to a minimum, leave it on a cold blower for half a minute, and only then turn off the hair dryer. Try not to take it with wet hands, otherwise moisture may get on the internal elements of the circuit, which can lead to a short circuit.

A construction hair dryer, an irreplaceable thing in amateur radio. I will not list all the possibilities of use, I bought it when I had to pack 3m of flexible tires in a heat-shrink tubing. I took the cheapest one because I intended to use it not for professional, but for amateur purposes.

With the first task, (packing the flexible bus), the hairdryer did a great job, and I was even glad for a good purchase.

Then there were some other applications, and at one point it was noticed poor activation at increased power.

Quickly scattering it for parts, I made sure that the reason was in the switch (poor contact of the terminals did the trick).

Replacing the switch was not a problem, the problem was different. Before my eyes lay a "blank" that could be modernized to suit your needs.

To be able to use the nozzles, temperature stabilization is necessary.
For use in the installation of radio components, it is necessary to change the strength of the air flow.
The hairdryer needs to cool to store it in the box. That is, it should be possible to turn off the heating of the spiral, without turning off the fan.
In turn, the operation of one fan makes it possible to use a hair dryer to cool something, etc.

Actually, all of the above was introduced into the body of the cheapest hair dryer.

Turning on the power of the hair dryer.

After turning on the power, the cooling mode is set:

The heating of the coil is turned off.
The fan runs at the first speed position.
The lower limit of the airflow temperature setpoint has been set.
The seven-segment display shows the air flow temperature.
The "temperature" LED indicates, above or below the set point, the temperature of the air stream. If the temperature is higher than the set point, - green lights. If it is lower, it is red.

Air flow temperature setting.

The air flow temperature is set using the +/- buttons.

The minimum setting is 60 * C, the maximum is 630 * C.

The temperature changes in steps of 10 degrees.

The first short press on the temperature change buttons activates the temperature setpoint menu. Subsequent short pressing of the +/- buttons will change the temperature setpoint in increments of 10 degrees. If the button is held for more than one sec., The fast scrolling of the setpoint values is activated.

If the buttons are not pressed for more than one second, there is an automatic return to the air flow temperature display menu.

Changing the air flow rate.

The speed change is made using the +/- buttons, and has seven gradations. If the button is held down for more than one second, the accelerated "scrolling" is activated.

The speed indicator is a bar of LEDs.

The number of LEDs illuminated is proportional to the air flow rate.

Turning on the heating of the spiral.

Heating is switched on using the "heating" button.

Each press of the button will turn on or off the heating of the coil.

The glowing of the red LED indicates that the heating of the coil is on.

No glow, - heating is off.

Construction and details.

The whole structure of the temperature and air flow rate regulator is assembled on two boards.

Impulse power block. At the output it has + 16V for powering the fan motor, and two + 5V for powering the digital and analog parts of the regulator.
Triac regulator, heating power of the hair dryer spiral. The method of skipping mains voltage periods is used, with a uniform distribution in time.
Power switch, PWM fan motor speed controller. The hardware PWM of the microcontroller is used, with a frequency of 30 kHz.

Control and display unit. Includes, five control buttons, one three-digit seven-segment indicator of the measured air flow temperature, and its setpoint. Ten light-emitting diodes, seven of them, are a bar for indicating the air flow rate. Two, - temperature status indicator (above, below the set point). One, - indicator of turning on the heating of the spiral.
Thermocouple amplifier, and MK.

Both boards are made using the method of laser-ironing technology. The first board with one-sided mounting of radio components, soldered to the terminals of the fan motor. The second, with two-sided mounting, is fastened with four self-tapping screws to the cover of the hair dryer. It is also the front panel of the control module.

Electrical diagram.

The entire circuit is divided into seven functional units:

Impulse power block.
Coil heating control unit.
Thermocouple amplifier block.
Heating element and thermocouple.
Fan motor control unit.
Microcontroller.
Input-output module.

Impulse power block.

The power supply is assembled on a TOP224 microcircuit, according to the original circuit

The power supply provides the circuit with three voltages:

16v - for powering the fan motor, maximum current 1A.

5vc - for powering the digital part of the circuit, current up to 0.5A.

5v - for powering the analog part of the circuit, current up to 0.05A.

Self-made assemblies, choke L1 and transformer TV1.The choke is wound on the "coil" frame, and must have an inductance of up to 10 µH, and also be able to pass the corresponding current of 1.5A.

The transformer is taken from a 20-watt energy saving machine. The central part of the core is 5x5mm. The number of turns of the primary winding was selected according to the "bald calculator". And in my case it was 72 turns. Was wound with a wire with a diameter of 0.23 mm. The secondary winding has 8 turns folded in four, the same wire is 0.23mm. The feedback winding has 7 turns, also folded into four wires. At maximum load, when the fan is powered from a full voltage of 16V, the transformer and the TOP224 microcircuit begin to heat up. However, due to the proportional increase in cooling (air flow), the temperature did not exceed 45 * C, at an ambient temperature of 32 * C. The measurements were carried out with an infrared thermometer DT8220, by the way, very convenient in this respect.

Of course, before making such transformers on your own, it is advisable to study the relevant literature. Because many points, assemblies and winding of the transformer are not considered here.

Coil heating control unit.

The coil heating control circuit is based on the BTA41-600 triac.

Taken from the datasheet on MOC3063, and has no special features. An optocoupler with a line voltage zero detector provides "quiet load control". But since the load is of the order of two kilowatts, an incandescent lamp plugged into the same outlet will "show" the operation of the PI regulator (it will simply blink slightly).

Thermocouple amplifier block.

The thermocouple amplifier circuit is based on an AD8551 operational amplifier.

This time, the wiring diagram is not taken from the datasheet, but it is pretty standard. The task of the amplifier is to enhance the emf of the thermocouple, therefore the OOS capacitance C10 is of great importance in filtering impulse noise. The low-pass filter at the output of U4 suppresses the 50 Hz component of the output signal. The gain is selected using the R24 resistor (roughly). A more accurate calculation is already done programmatically.

Heating element and thermocouple.

The design of the heating element has undergone a slight change. The coil of the fan motor power supply has been removed. And a thermocouple is inserted.

In the photo, the virgin state of the heater, the state after the alteration, unfortunately has not been immortalized. But there is nothing complicated there. The white wires that go to the motor power are removed in place with their spiral. The thermal fuse is connected using a crimp (not soldering) to the opposite end of the spiral with a resistance of 33 Ohm. The black wire of the additional spiral is simply bite off, and the end of the spiral remains in the ceramic. The red wire remains intact.

The thermocouple is passed through the vacant channel, where the thermal fuse used to be. The cold junction end of the thermocouple is connected to the board with screws. The cold seal is hidden under the red heat shrink tubing. The cold junction temperature is monitored by an internal MK thermometer. And in practice, it makes little difference, (1-2 * C).

Fan motor control unit.

The air flow is controlled by changing the speed of the fan motor. The turns, in turn, depend on the supply voltage. One of the simpler control methods is PWM (Pulse Width Modulation).

Hardware PWM is provided by MK. The selected frequency is 30 kHz, which makes it possible to do without a key driver. An intelligent transistor BTS113A is used as a key. And it can be replaced by a field-effect transistor with a "logic input".

Microcontroller.

The circuit uses MK PIC16F1823, this is a fourteen-lead stone. The clock frequency is 30 MHz, which makes it possible to process the incoming information quite quickly. Conclusions RA0, RA1, RA3, not used, left for development (if any).

Input-output module.

In view of the small number of pins in the MK, and a large number of display and input elements (buttons), it was decided to use the 74HC164 shift register.

Transistors VT1-VT4 are soldered from some kind of board, and according to the designation on the case they are suitable for BC817 or BC337, in the SOT23 package.

LED1-LED10 LEDs, also in SMD version, but can be replaced by 3mm without significant changes to the printed circuit board.

Video (click to play).

P.S. This article is presented not so much for repetition as for an incentive to search for new approaches and solutions when creating your own amateur designs.

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