Each of us at home has some kind of electrical appliance that has been working in the house for more than one year. But over time, the power of technology weakens and does not fulfill its intended purpose. That's when you should pay attention to the insides of the equipment. Basically, problems arise with the electric motor, which is responsible for the functionality of the equipment. Then you should turn your attention to a device that regulates the engine speed without reducing their power.
Types of engines
The power-sustaining speed controller is an invention that will breathe new life into an electrical appliance, and it will work like a newly purchased product. But it is worth remembering that engines come in different formats and each has its own limiting work.
The engines are different. This means that this or that technique operates at different frequencies of rotation of the shaft that triggers the mechanism. The motor may be:
- single phase
- two-phase
- three-phase.
Basically, three-phase electric motors are found in factories or large factories. At home, single-phase and two-phase are used. This electricity is enough to operate household appliances.
Power speed controller
Work principles
The 220 V motor speed controller without loss of power is used to maintain the initial set shaft speed. This is one of the basic principles of this device, which is called a frequency regulator.
With it, the electrical appliance operates at the set engine speed and does not reduce it.. Also, the engine speed controller affects the cooling and ventilation of the motor. With the help of power, the speed is set, which can be both raised and lowered.
The question of how to reduce the speed of a 220 V electric motor was asked by many people. But this procedure is quite simple. One has only to change the frequency of the supply voltage, which will significantly reduce the performance of the motor shaft. You can also change the power supply of the motor, while using its coils. Electricity management is closely related to the magnetic field and motor slip. For such actions, they mainly use an autotransformer, household regulators, which reduce the speed of this mechanism. But it is also worth remembering that the engine power will decrease.
Shaft rotation
Engines are divided into:
- asynchronous,
- collector.
The speed controller of an asynchronous electric motor depends on the connection of current to the mechanism. The essence of the operation of an asynchronous motor depends on the magnetic coils through which the frame passes. It rotates on sliding contacts. And when, when turning, it turns 180 degrees, then according to these contacts, the connection will flow in the opposite direction. Thus, the rotation will remain unchanged. But with this action, the desired effect will not be obtained. It will come into effect after adding a couple of dozen frames of this type to the mechanism.
Collector motor is used very often. Its work is simple, since the passed current passes directly - because of this, the power of the electric motor is not lost, and the mechanism consumes less electricity.
The washing machine motor also needs power adjustment. For this, special boards were made that do their job: the engine speed control board from the washing machine has a multifunctional use, since when it is used, the voltage is reduced, but the rotational power is not lost.
This board has been tested. One has only to put diode bridges, choosing an optocoupler for the LED. In this case, you still need to put the triac on the radiator. Basically, engine adjustment starts at 1000 rpm.
If you are not satisfied with the power regulator and lack its functionality, you can make or improve the mechanism. To do this, you need to take into account the current strength, which should not exceed 70 A, and heat transfer during use. Therefore, you can install an ammeter to adjust the circuit. The frequency will be small and will be determined by capacitor C2.
Next, you should adjust the regulator and its frequency. When output, this pulse will go through a push-pull transistor amplifier. You can also make 2 resistors that will serve as an output for the computer's cooling system. To prevent the circuit from burning out, a special blocker is required, which will serve as a double current value. So this mechanism will work for a long time and in the right amount. Power control devices will provide your electrical appliances with many years of service at no extra cost.
The motor from the washing machine, excellent for homemade products, has too high speed, and a small resource at maximum speed. Therefore, I use a simple homemade speed controller (without power loss). The scheme was tested and showed excellent results. Turnovers are regulated from about 600 to max.
The potentiometer is electrically isolated from the mains, which increases the safety of using the regulator.
The triac must be placed on the radiator.
Almost any optocoupler (2 pcs), but EL814 has 2 oncoming LEDs inside, and asks for this circuit.
A high-voltage transistor can be installed, for example, IRF740 (from a computer power supply), but it's a pity to put such a powerful transistor in a low-current circuit. Transistors 1N60, 13003, KT940 work well.
Instead of the KTS407 bridge, a bridge from 1N4007, or any one for> 300V, and current> 100mA is quite suitable.
Signet in .lay5 format. The signet is drawn "View from M2 (soldering)", so that when outputting to a printer, it must be mirrored. Color M2 = black, background = white, do not print other colors. The board outline (for trimming) is made on the M2 side, and will be an indicator of the board boundaries after etching. It must be removed before soldering parts. A drawing of parts from the mounting side has been added to the signet for transfer to the signet. She then acquires a beautiful and finished look.
Adjustment from 600 rpm is suitable for most homemade products, but for special cases a circuit with a germanium transistor is offered. The minimum speed was reduced to 200.
The minimum speed was 200 rpm (170-210, the electronic tachometer does not measure well at low speeds), the GT309 transistor T3 was installed, it is direct conduction, and there are many of them. If you put MP39, 40, 41, P13, 14, 15, then the speed should still decrease, but I no longer see the need. The main thing is that such transistors are like dirt, unlike the MP37 (see the forum).
Soft start works great, True, the motor shaft is empty, but from the load on the shaft during start-up, I will select R5 if necessary.
R5 = 0-3k3 depending on the load;; R6 \u003d 18 Ohm - 51 Ohm - depending on the triac, I don’t have this resistor now ;; R4 \u003d 3k - 10k - protection T3;; RP1 = 2k-10k - speed controller, connected to the network, protection from the operator's mains voltage is mandatory !!!. There are potentiometers with a plastic axis, it is advisable to use!!!This is a big drawback of this scheme, and if there is no great need for low speeds, I advise you to use V17 (from 600 rpm).
C2 = soft start, = motor start delay time;; R5 = C2 charge, = charge curve slope, = motor acceleration time;; R7 - C2 discharge time for the next soft start cycle (at 51k it is about 2-3 seconds)
List of radio elements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| T1 | Triac | BT139-600 | 1 | To notepad | ||
| T2 | Dinistor | 1 | To notepad | |||
| VD | Diode bridge | KTS407A | 1 | To notepad | ||
| VD4 | rectifier diode | 1N4148 | 1 | To notepad | ||
| C2 | Capacitor | 220uF x 4V | 1 | To notepad | ||
| C1 | Capacitor | 100nF x 160V | 1 | To notepad | ||
| R1 | Resistor | 3.3 kOhm 0.5W | 1 | To notepad | ||
| R2 | Resistor | 330 ohm 0.5W | 1 | To notepad | ||
| R3 | Resistor | 470 kOhm 0.125W | 1 | To notepad | ||
| R4 | Resistor | 200 ohm 0.125W | 1 | To notepad | ||
| R5 | Resistor | 200 ohm 0.125W | 1 | To notepad | ||
| V1 | optocoupler | PC817 | 2 | To notepad | ||
| T3 | bipolar transistor | GT309G | 1 | To notepad | ||
| C2a | Capacitor | 47uF x 4V | 1 |
When using an electric motor in various devices and tools, it always becomes necessary to adjust the speed of rotation of the shaft.
It is not difficult to make an electric motor speed controller on your own. It is only necessary to find a high-quality circuit, the device of which would be completely suitable for the features and type of a particular electric motor.
Use of frequency converters
Frequency converters can be used to adjust the speed of an electric motor operating from a network with a voltage of 220 and 380 volts. High-tech electronic devices allow you to smoothly adjust the speed of the electric motor by changing the frequency and amplitude of the signal.
Such converters are based on powerful semiconductor transistors with wide-pulse modulators.
Converters using the appropriate control unit on the microcontroller allow you to smoothly change the engine speed.
High-tech frequency converters are used in complex and loaded mechanisms. Modern frequency regulators have several degrees of protection at once., including load, voltage current indicator and other characteristics. Some models are powered by a single-phase voltage of 220 volts and can convert the voltage to three-phase 380 volts. The use of such converters allows the use of asynchronous electric motors at home without the use of complex wiring diagrams.
Application of electronic regulators
The use of powerful asynchronous motors is impossible without the use of appropriate speed controllers. Such converters are used for the following purposes:
The operation scheme used by frequency converters is similar to that of most household appliances. Similar devices are also used in welding machines, UPS, PC and laptop power supplies, voltage stabilizers, lamp igniters, as well as monitors and LCD TVs.
Despite the apparent complexity of the circuit, it will be quite simple to make a 220 V electric motor speed controller.
The principle of operation of the device
The principle of operation and the design of the engine speed controller are simple, therefore, having studied the technical points, it is quite possible to carry them out on your own. Structurally, there are several the main components that make up the rotation regulators:
The difference between asynchronous motors and standard drives is the rotation of the rotor with maximum power when voltage is applied to the transformer winding. At the initial stage, the indicators of the consumed current and the power of the motor increase to a maximum, which leads to a significant load on the drive and its rapid failure.
When starting the engine at maximum speed, a large amount of heat is generated, which leads to overheating of the drive, winding and other drive elements. Thanks to the use of a frequency converter, it is possible to smoothly accelerate the engine, which prevents overheating and other problems with the unit. When using a frequency converter, the electric motor can be started at a speed of 1000 rpm, and subsequently smooth acceleration is provided when 100–200 engine revolutions are added every 10 seconds.
Making homemade relays
It will not be difficult to make a homemade 12 V electric motor speed controller. For this to work, you will need the following:
- Wirewound resistors.
- Multi-position switch.
- Control unit and relay.
The use of wire resistors allows you to change the supply voltage, respectively, and the engine speed. Such a regulator provides stepwise acceleration of the engine, has a simple design and can be performed even by novice radio amateurs. Such simple homemade step controllers can be used with asynchronous and contact motors.
The principle of operation of a homemade converter:
In the past, mechanical regulators based on a variator or gear drive were the most popular. However, they did not differ in due reliability and often failed.
Homemade electronic regulators have proven themselves from the best side. They use the principle of changing step or smooth voltage, they are durable, reliable, have compact dimensions and provide the ability to fine-tune the operation of the drive.
The additional use of triacs and similar devices in the circuits of electronic regulators makes it possible to ensure a smooth change in the voltage power, respectively, the electric motor will pick up speed correctly, gradually reaching its maximum power.
To ensure high-quality adjustment, variable resistors are included in the circuit, which change the amplitude of the incoming signal, providing a smooth or step change in the number of revolutions.
Circuit on a PWM transistor
It is possible to regulate the speed of rotation of the shaft for low-power electric motors using a bus-transistor and a series connection of resistors in the power supply. This option is easy to implement, but has a low efficiency and does not allow you to smoothly change the engine speed. It will not be particularly difficult to make a 220 V collector motor speed controller using a PWM transistor with your own hands.
The principle of operation of the regulator on the transistor:
- Bus transistors used today have a sawtooth voltage generator with a frequency of 150 Hertz.
- Operational amplifiers are used as a comparator.
- Changing the rotation speed is carried out due to the presence of a variable resistor that controls the duration of the pulses.
Transistors have a flat constant amplitude of pulses, identical to the amplitude of the supply voltage. This allows you to adjust the speed of the 220 V motor and maintain the operation of the unit even when the minimum voltage is applied to the transformer winding.
Due to the possibility of connecting the microcontroller to a PWM transistor, it is possible to automatically tune and adjust the operation of the electric drive. Such converter designs may have additional components that expand the functionality of the drive, ensuring operation in a fully automatic mode.
Introduction of automatic control systems
The presence of microcontroller control in regulators and frequency converters makes it possible to improve the operating parameters of the drive, and the motor itself can operate in fully automatic mode, when the controller used smoothly or stepwise changes the speed of the unit. Today, microcontroller control uses processors that have a different number of outputs and inputs. Various electronic keys, buttons, various signal loss sensors, and so on can be connected to such a microcontroller.
On sale you can find various types of microcontrollers, which are easy to use, guarantee a high-quality adjustment of the operation of the converter and the regulator, and the presence of additional inputs and outputs allows you to connect various additional sensors to the processor, on the signal of which the device will reduce or increase the number of revolutions, or completely stop supplying voltage to the motor windings.
Today, various converters and motor controllers are on sale. However, if you have even minimal skills in working with radio components and the ability to read circuits, you can make such a simple device that will smoothly or stepwise change engine speed. Additionally, you can include a control triac rheostat and a resistor in the circuit, which will allow you to smoothly change the speed, and the presence of microcontroller control fully automates the use of electric motors.
Do you have a grinder, but no speed controller? You can make it yourself.
Speed controller and soft start for grinder
Both are necessary for reliable and convenient operation of the power tool.
What is a speed controller and what is it for?
This device is designed to control the power of an electric motor. With it, you can adjust the speed of rotation of the shaft. The numbers on the adjusting wheel indicate the change in disc speed.
The regulator is not installed on all angle grinders.
Bulgarians with a speed controller: examples in the photo
The lack of a regulator greatly limits the use of the grinder. The speed of rotation of the disc affects the quality of the grinder and depends on the thickness and hardness of the material being processed.
If the speed is not regulated, then the speed is constantly kept at maximum. This mode is only suitable for hard and thick materials such as angle, pipe or profile. Reasons why a regulator is necessary:
- For thin metal or soft wood, a lower rotation speed is needed. Otherwise, the edge of the metal will melt, the working surface of the disk will become blurry, and the wood will turn black from high temperature.
- For cutting minerals, it is necessary to regulate the speed. Most of them break off small pieces at high speed and the cut becomes uneven.
- You do not need the highest speed to polish cars, otherwise the paintwork will deteriorate.
- To change the disk from a smaller diameter to a larger one, you need to reduce the speed. It is almost impossible to hold a grinder with a large disk rotating at high speed with your hands.
- Diamond blades must not be overheated so as not to spoil the surface. For this, the turnover is reduced.
Why you need a soft start
The presence of such a launch is a very important point. When you start a powerful power tool connected to the network, an inrush current occurs, which is many times higher than the rated current of the motor, the voltage in the network sags. Although this surge is short-lived, it causes increased wear on the brushes, the motor commutator, and all parts of the tool through which it flows. This can cause failure of the tool itself, especially the Chinese one, with unreliable windings that can burn out at the most inopportune moment during switching on. And also there is a large mechanical jerk at startup, which leads to rapid wear of the gearbox. This start prolongs the life of the power tool and increases the level of comfort when working.
Electronic unit in angle grinder
The electronic unit allows you to combine the speed controller and soft start into one. The electronic circuit is implemented according to the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Such a block can be supplied with grinders of different capacities and price categories.
Varieties of devices with an electronic unit: examples in the table
Angle grinders with an electronic unit: popular in the photo
DIY speed controller
The speed controller is not installed in all models of grinders. You can make a block for speed control with your own hands or purchase a ready-made one.
Factory speed controllers for angle grinders: photo examples
Bosh grinder speed controller 
Speed regulator grinders Sturm 
DWT angle grinder speed controller
Such regulators have a simple electronic circuit. Therefore, creating an analogue with your own hands will not be difficult. Consider what the speed controller for grinders up to 3 kW is assembled from.
PCB manufacturing
The simplest scheme is shown below.
Since the circuit is very simple, it makes no sense to install a computer program for processing electrical circuits because of it alone. Moreover, special paper is needed for printing. And not everyone has a laser printer. Therefore, let's go by the simplest way of manufacturing a printed circuit board.
Take a piece of textolite. Cut off the required size for the chip. Sand the surface and degrease. Take a marker for laser discs and draw a diagram on the textolite. In order not to be mistaken, first draw with a pencil. Next, let's start etching. You can buy ferric chloride, but after it the sink is poorly washed. If you accidentally drip on clothes, stains will remain that cannot be completely removed. Therefore, we will use a safe and cheap method. Prepare a plastic container for the solution. Pour in 100 ml of hydrogen peroxide. Add half a tablespoon of salt and a sachet of citric acid to 50 g. The solution is made without water. You can experiment with proportions. And always make a fresh solution. Copper should be all etched. This takes about an hour. Rinse the board under a stream of well water. Drill holes.
It can be made even easier. Draw a diagram on paper. Glue it with adhesive tape to the cut out textolite and drill holes. And only after that draw the circuit with a marker on the board and poison it.
Wipe the board with an alcohol - rosin flux or a regular solution of rosin in isopropyl alcohol. Take some solder and tin the tracks.
Mounting of electronic components (with photo)
Prepare everything you need to mount the board:
- Solder coil.
- Pins in the board.
- Triac bta16.
- Capacitor 100 nF.
- 2 kΩ fixed resistor.
- Dinistor db3.
- Variable resistor with a linear dependence of 500 kOhm.
Bite off four pins and solder them to the board. Then install the dinistor and all other parts except for the variable resistor. Solder the triac last. Take a needle and a brush. Clean the gaps between the tracks to remove possible short circuits. Triac free end with a hole is mounted on an aluminum radiator for cooling. Clean the area where the element is attached with fine sandpaper. Take the KPT-8 heat-conducting paste and apply a small amount of paste on the radiator. Secure the triac with a screw and nut. Since all the details of our design are under mains voltage, we will use a handle made of insulating material for adjustment. Put it on a variable resistor. With a piece of wire, connect the extreme and middle terminals of the resistor. Now solder two wires to the extreme conclusions. Solder the opposite ends of the wires to the corresponding pins on the board.
You can make the entire installation hinged. To do this, we solder the parts of the microcircuit to each other directly using the legs of the elements themselves and the wires. Here, too, you need a radiator for the triac. It can be made from a small piece of aluminum. Such a regulator will take up very little space and can be placed in the grinder case.
If you want to install an LED indicator in the speed controller, then use a different scheme.
Regulator circuit with LED indicator.
Diodes added here:
- VD 1 - diode 1N4148;
- VD 2 - LED (operation indication).
Assembled controller with LED.
This block is designed for low-power grinders, so the triac is not installed on the radiator. But if you use it in a powerful tool, then do not forget about the aluminum heat transfer board and the bta16 triac.
Making a power regulator: video
Electronic unit test
Before connecting the block to the instrument, we will test it. Get an overhead socket. Insert two wires into it. Connect one of them to the board, and the second to the network cable. The cable has one more wire left. Connect it to the network board. It turns out that the regulator is connected in series to the load power circuit. Connect a lamp to the circuit and check the operation of the device.
Testing the power regulator with a tester and a lamp (video)
Connecting the regulator to the grinder
The speed controller is connected to the tool in series.
The connection diagram is shown below.
If there is free space in the handle of the grinder, then our block can be placed there. The circuit, assembled by surface mounting, is glued with epoxy resin, which serves as an insulator and protection against shaking. Pull the variable resistor with a plastic handle out to adjust the speed.
Installing the regulator inside the angle grinder body: video
The electronic unit, assembled separately from the grinder, is placed in a case made of insulating material, since all elements are under mains voltage. A portable socket with a network cable is screwed to the body. The handle of the variable resistor is brought out.
The regulator is connected to the network, and the tool is connected to a portable socket.
Speed regulator for a grinder in a separate case: video
Usage
There are a number of recommendations for the correct use of an angle grinder with an electronic unit. When starting the tool, let it accelerate to the set speed, do not rush to cut anything. After turning it off, restart it after a few seconds so that the capacitors in the circuit have time to discharge, then the restart will be smooth. You can adjust the speed while the grinder is running by slowly turning the knob of the variable resistor.
A grinder without a speed controller is good because without serious expenses you can make a universal speed controller for any power tool yourself. The electronic unit, mounted in a separate box, and not in the body of the grinder, can be used for a drill, drill, circular saw. For any tool with a commutator motor. Of course, it is more convenient when the control knob is on the tool, and you don’t have to go anywhere and bend over to turn it. But now it's up to you to decide. It's a matter of taste.
Collector motors can often be found in household electrical appliances and power tools: a washing machine, grinder, drill, vacuum cleaner, etc. Which is not at all surprising, because collector motors allow you to get both high speeds and high torque (including high starting torque ) - which is what is needed for most power tools.
At the same time, collector motors can be powered by both direct current (in particular, rectified current) and alternating current from a household network. To control the speed of rotation of the rotor of the collector motor, speed controllers are used, and they will be discussed in this article.
First, let's recall the device and the principle of operation of the collector engine. The commutator motor necessarily includes the following parts: a rotor, a stator and a brush-collector switching unit. When power is applied to the stator and the rotor, their magnetic fields begin to interact, the rotor eventually begins to rotate.
Power is supplied to the rotor through graphite brushes that are tightly attached to the collector (to the collector lamellas). To change the direction of rotation of the rotor, it is necessary to change the phasing of the voltage on the stator or on the rotor.
The rotor and stator windings may be supplied from different sources or may be connected in parallel or in series with each other. This is how collector motors of parallel and series excitation differ. It is collector motors of series excitation that can be found in most household electrical appliances, since such inclusion makes it possible to obtain an overload-resistant motor.
Speaking of speed controllers, first of all we will focus on the simplest thyristor (triac) circuit (see below). This solution is used in vacuum cleaners, washing machines, grinders, and shows high reliability when working in AC circuits (especially from a household network).
This circuit works quite unpretentiously: at each period of the mains voltage, it is charged through a resistor to the unlocking voltage of the dinistor connected to the control electrode of the main key (triac), after which it opens and passes current to the load (to the collector motor).
By adjusting the charging time of the capacitor in the triac opening control circuit, the average power supplied to the engine is regulated, and the speed is adjusted accordingly. This is the simplest regulator without current feedback.
The triac circuit is similar to the usual one, there is no feedback in it. In order for current feedback to appear, for example, to maintain acceptable power and prevent overloads, additional electronics are needed. But if we consider options from simple and unpretentious circuits, then a triac circuit is followed by a rheostat circuit.
The rheostat circuit allows you to effectively control the speed, but leads to the dissipation of a large amount of heat. It requires a radiator and efficient heat dissipation, and this is energy loss and low efficiency in the end.
More efficient controller circuits on special thyristor control circuits or at least on an integrated timer. The switching of the load (collector motor) on alternating current is carried out by a power transistor (or thyristor), which opens and closes one or more times during each period of the mains sinusoid. This regulates the average power supplied to the engine.
The control circuit is powered by 12 volts DC from its own source or from a 220 volt network through a damping circuit. Such schemes are suitable for controlling powerful motors.
The principle of regulation with microcircuits at direct current is of course. A transistor, for example, opens at a strictly specified frequency of a few kilohertz, but the duration of the open state is adjustable. So, by turning the knob of the variable resistor, the speed of rotation of the rotor of the collector motor is set. This method is useful for keeping low speeds of the commutator motor under load.
Better control is precisely DC regulation. When the PWM operates at a frequency of about 15 kHz, by adjusting the pulse width, the voltage is controlled at approximately the same current. Say, by adjusting the constant voltage in the range from 10 to 30 volts, they get different revolutions at a current of about 80 amperes, achieving the required average power.
If you want to make a simple regulator for a collector motor with your own hands without any special requests for feedback, then you can choose a thyristor circuit. All you need is a soldering iron, a capacitor, a dinistor, a thyristor, a pair of resistors and wires.
If you need a better regulator with the ability to maintain stable speed under a dynamic load, take a closer look at the regulators on microcircuits with feedback that can process the signal from the tachogenerator (speed sensor) of the collector motor, as is implemented, for example, in washing machines.
Andrey Povny
