If you have an old angle grinder in your arsenal, don’t rush to write it off. Using a simple electrical circuit, the device can be easily upgraded by adding the function of changing the speed. Thanks to a simple regulator that you can actually assemble with your own hands in a few hours, the functionality of the device will increase significantly. By reducing the rotation speed, the grinder can be used as a grinding and sharpening machine for various types of materials. New opportunities are emerging for the use of additional attachments and accessories.
The built-in disc speed control function allows you to delicately process materials such as plastic or wood. At low speeds, operating comfort and safety increases. This function is especially useful in electrical and radio installation practice, in car services and restoration workshops.
In addition, among professional users of power tools there is a strong opinion that the simpler the device is, the more reliable it is. And it is better to move the additional service stuffing outside the power unit. In this situation, equipment repair is greatly simplified. Therefore, some companies specially produce remote, separate electronic regulators that connect to the machine’s power cord.
Modern grinders use two important functions that increase the reliability and safety of the tool:
They are used in electromechanical tools that use a commutator motor in their design. Helps reduce wear on the mechanical part of the unit during switching on. They reduce the load on the electrical elements of the mechanism by putting them into operation gradually.
As studies of the properties of materials have shown, the most intense production of friction units occurs during a sharp transition from a state of rest to a mode of rapid movement. For example, one start of an internal combustion engine in a car is equivalent to 700 km of mileage in terms of wear on the piston group.
When the power is turned on, an abrupt transition occurs from a state of rest to rotation of the disk at a speed of 2.5–10 thousand revolutions per minute. Those who have worked with an angle grinder are well aware of the feeling that the machine simply “rips out of your hands.” It is at this moment that the overwhelming number of breakdowns associated with the mechanical part of the unit occur.
The stator and rotor windings experience no less load. The commutator motor starts in short circuit mode, the electromotive force is already pushing the shaft forward, but inertia does not yet allow it to rotate. A jump in starting current occurs in the coils of the electric motor. And although they are structurally designed for such work, sooner or later a moment comes (for example, during a power surge in the network) when the winding insulation cannot withstand and an interturn short circuit occurs.
When soft start circuits and changes in engine speed are included in the electrical circuit of the tool, all of the above problems automatically disappear. Among other things, the problem of voltage “dip” in the general network at the moment of starting a hand tool is solved. This means that the refrigerator, TV or computer will not be at risk of “burning out”. And the safety circuit breakers on the meter will not operate and cut off the current in the house or apartment.
The soft start circuit is used in angle grinders of medium and high price categories, the speed control unit is used mainly in professional models of angle grinders.
Adjusting the speed allows you to process soft materials with a grinder, perform fine grinding and polishing - at high speed, wood or paint will simply burn.
Additional electrical circuits increase the cost of the tool, but increase the service life and level of safety during operation.
The simplest power regulator, suitable for an angle grinder, soldering iron or light bulb, is easy to assemble with your own hands.
In order to assemble a simple speed controller for an angle grinder, you need to purchase the parts shown in this diagram.
Schematic diagram of the speed controller
Trimmer resistor VR1 changes the charging time of capacitor C1. When voltage is applied to the circuit, at the first moment of time (the first half-cycle of the input sinusoid), triacs DB3 and TRIAC are closed. The output voltage is zero. Capacitor C1 charges and the voltage across it increases. At a certain point in time, specified by the R1-VR1 chain, the voltage on the capacitor exceeds the opening threshold of the triac DB3, the triac opens. The voltage from the capacitor is transmitted to the control electrode of the TRIAC triac, which also opens. Current begins to flow through the open triac. At the beginning of the second half-cycle of the sinusoid, the triacs are closed until capacitor C1 is recharged in the opposite direction. Thus, the output produces a pulse signal of complex shape, the amplitude of which depends on the operating time of the C1-VR1-R1 circuit.
Assembling this circuit will not be difficult even for a novice radio amateur. Spare parts are available and can be purchased at any store. Including desoldering from old boards. The procedure for assembling the regulator using thyristors is as follows:
The connection of the regulator depends on what type of device is selected. If a simple circuit is used, it is enough to mount it into the power supply channel of the power tool.
There are no ready-made installation recipes. Anyone who decides to equip an angle grinder with a regulator places it in accordance with their goals and model of the tool. Some people insert the device into the handle of the holder, others into a special additional box on the body.
In different models, the space inside the angle grinder body may be different. Some have enough free space to install a control unit. In others, you have to take it to the surface and attach it in a different way. But the trick is that, as a rule, there is always a certain cavity in the back of the instrument. It is designed for air circulation and cooling.
Cavity at the back of the device This is usually where the factory speed controller is located. A DIY diagram can be placed in this space. To prevent the regulator from burning out, the thyristors should be installed on the radiator.
When purchasing and installing a factory regulator inside an angle grinder, most often you have to modify the body - cut a hole in it to allow the adjustment wheel to come out. But this may adversely affect the rigidity of the casing. Therefore, it is preferable to install the device outside.
The adjustment wheel changes the speed
The numbers on the adjustment wheel indicate the number of spindle revolutions. This value is not absolute, but conditional. “1” - minimum speed, “9” - maximum. The remaining numbers serve as a guide for regulation. The location of the wheel on the body varies. For example, on the Bosch PWS 1300–125 CE, Wortex AG 1213–1 E or Watt WWS-900 angle grinders, it is located at the base of the handle. On other models, such as the Makita 9565 CVL, the adjustment wheel is located at the end of the housing.
The connection diagram of the regulator to the angle grinder is not complicated, but sometimes it is not so easy to stretch the cables to the button, which is located at the other end of the device body. The problem can be solved by selecting the optimal wire cross-section or by placing it on the surface of the casing.
The regulator is connected according to the diagram
A good option is to install the regulator on the surface of the device or attach it to a network cable. Not everything always works out on the first try; sometimes the device has to be tested and then some adjustments made. And this is easier to do when access to its elements is open.
Important! If you have no experience working with electrical circuits, it is more advisable to purchase a ready-made factory regulator or angle grinder equipped with this function.
Attaching to the power cord
The basic rule when operating an angle grinder with a homemade speed controller is to adhere to the work and rest schedule. The fact is that an engine operating at a “regulated” voltage gets especially hot. When grinding at low speeds, it is important to take frequent breaks so that the commutator windings do not burn out.
It is also highly recommended not to turn on the tool if the speed regulator is set to minimum - the reduced voltage will not be enough to rotate the rotor, the collector lamellas will remain in short circuit mode, and the windings will begin to overheat. Unscrew the variable resistor to the maximum, then, turning on the angle grinder, reduce the speed to the desired value.
Following the correct order of activation and adjustment will allow you to operate the angle grinder for an unlimited period of time.
In addition, it should be understood that adjusting the speed of rotation on an angle grinder occurs on the principle of a water tap. The device does not increase the number of revolutions, it can only decrease them. It follows from this that if the maximum nameplate speed is 3000 rpm, then when a speed controller is connected, the angle grinder will operate in a range lower than the maximum speed.
Attention! If the angle grinder already contains electronic circuits, for example, it is already equipped with a speed controller, then the thyristor controller will not work. The internal circuits of the device simply will not turn on.
Equipping the angle grinder with a circuit for adjusting engine speed will increase the efficiency of using the device. and expand its functional range. This will also save the technological resource of the grinding machine and increase its service life.
tehznatok.com
Power tools occupy one of the main places in our workshop. Each electrical device performs all functions according to technical specifications. What else would you like? I really want the tool to last longer or not break at all. Just as a person gets used to a friend - a dog, so he gets used to an instrument.
One of the main tools is an angle grinder, which we call an angle grinder. This is a universal tool that can cut, grind, clean surfaces, saw boards, and can be adapted to many other operations.
Smooth starting of a power tool is the main guarantee of its longevity. Remember when a light bulb burns out? Most often at the moment of switching on. Because after connecting to the electrical network, the load increases sharply. The damaged parts of the spiral cannot withstand it and it burns out.
The same processes occur in the grinder. At the moment of switching on, the current increases sharply, because the driving forces need to not only move the armature, but also quickly gain the required speed. The effect of such a hard start can be the most deplorable - winding breakage.
To reduce the likelihood of tool failure due to a hard start, it is necessary to modify the angle grinder and equip it with a small built-in soft start device.
Another modification is the rotation regulator. From personal experience, everyone knows how inconvenient it is to work with a tool that does not have rotation adjustment. If an electric drill does not have such a device, then it is difficult to select the rotation speed and feed of the drill. This leads to either jamming of the drill or its breakage.
A lathe works similarly, in which there is a whole set of special gears to adjust the rotation of the spindle. Not only the safety of the cutter, but also the quality of material processing largely depends on this.
You can combine two advantages - soft start and adjustment of shaft speed using an electronic circuit. It is quite possible to assemble it yourself and install it directly into the car body. With such a circuit, it will start smoothly without creating overloads in the windings and network. And with the same scheme, it will be possible to regulate the speed in order to select the mode of operation with any material.
If you cut metal with significant thickness and hardness, then it is necessary to maintain high speeds. But when processing surfaces of low-melting materials, high speed will do more harm than help. It needs to be reduced. It is dangerous to work with stone or tiles at high speed. And here it needs to be reduced.
Even when grinding the disk, the rotation speed must be proportionally changed, because the linear speed of the disk edge will decrease. You cannot do without a speed controller when working with a diamond-cut disk, because at high temperatures it is destroyed very quickly.
Everything suggests that if the grinder does not have a speed controller, then one must be made and installed in the car.
In order not to complicate the perception of the operating principle with complex terms, the fundamental operation of the circuit can be explained simply. It has a sensitive element that reads the load value. Depending on the read value, this element controls the locking device.
The operating principle is similar to that of a water tap. In this case, you are the sensing element that controls the water tap. The flow of water, depending on the need, becomes more or less. The same process occurs with current.
It is necessary to correctly understand the point that we cannot in any way increase the rotation speed beyond that indicated in the characteristics of the angle grinder. We can only lower the speed. If the maximum rpm is 3000, then the range in which we can adjust the rpm will be below this value.
In the simplest version, you can use a thyristor regulator circuit. He will both feel and regulate. Two in one. This circuit has only five parts. It is very compact and easily fits into the case. Such a regulator will not operate from zero speed, but this is not necessary for an angle grinder.
If lower speeds are needed in operation, then it is necessary to use another circuit on an integrated circuit, where the locking element will be a triac. Such a circuit will be able to regulate the speed from almost zero to the desired value.
In both schemes, the main load falls on the locking element. It must be designed for voltages up to 600 V and currents up to 12 A. If your grinder is more powerful than 1 kW, then the locking element must withstand a load of up to 20 A.
All parts of the thyristor circuit can be placed on a printed circuit board or simply mounted. According to the second option, the parts are soldered on a printed circuit board. A printed circuit board can be manufactured using different methods. It can be etched from foil PCB, you can even cut it out with a cutter, but it will turn out very roughly. In principle, you can ask a radio amateur you know to make it for a very modest reward.
Radio-electronic elements are inserted into the manufactured printed circuit board. They can be purchased in specialized stores or at radio markets. The ratings of each should not differ in rating and rated power. It is advisable to install a thyristor or triac on a heat sink - an aluminum or copper radiator.
When the finished board is ready, you need to choose a convenient place in the grinder body to install it. It is advisable to install it so that it is convenient to use and so that it does not interfere with the work process.
Before installing the circuit in the car, it must be checked. To do this, instead of an angle grinder, you need to connect a regular incandescent lamp to the output. An example with a power of 60 - 40 W at 220 V is suitable. The performance will be obvious by the change in the glow of the light bulb.
Now all that remains is to mount the device in the chosen location and perform a test run of the angle grinder. It will stop breaking out of your hands during startup, and the speed will be smoothly adjusted by rotating the regulator.
instrument-blog.ru
Do you have an angle grinder, but no speed controller? You can make it yourself.
Both are necessary for reliable and convenient operation of the power tool.
This device is designed to control the power of an electric motor. With its help you can regulate the speed of rotation of the shaft. The numbers on the adjustment wheel indicate a change in the rotation speed of the disk.
Angler speed regulator
The regulator is not installed on all angle grinders.
The lack of a regulator greatly limits the use of the grinder. The rotation speed of the disk 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 corners, pipes or profiles. Reasons why a regulator is necessary:
The presence of such a launch is a very important point. When starting a powerful power tool connected to the network, a surge of inrush current occurs, which is many times higher than the rated current of the motor, and the voltage in the network sags. Although this surge is short-lived, it causes increased wear on the brushes, the motor commutator and all the tool elements through which it flows. This can cause failure of the tool itself, especially Chinese ones, with unreliable windings that can burn out during switching on at the most inopportune moment. There is also a large mechanical jerk during startup, which leads to rapid wear of the gearbox. Such a start extends the life of the power tool and increases the level of comfort during operation.
The electronic unit allows you to combine the speed controller and soft start into one. The electronic circuit is implemented on the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Grinders of different power and price categories can be equipped with such a block.
The speed controller is not installed in all models of angle grinders. You can make a block for regulating the speed with your own hands or purchase a ready-made one.
Such regulators have a simple electronic circuit. Therefore, creating an analogue with your own hands will not be difficult. Let's look at what the speed controller for grinders up to 3 kW is assembled from.
The simplest diagram is presented below.
The simplest speed controller circuit
Since the circuit is very simple, there is no point in installing a computer program for processing electrical circuits just because of it. Moreover, special paper is needed for printing. And not everyone has a laser printer. Therefore, we will take the simplest route of manufacturing a printed circuit board.
Take a piece of PCB. Cut to the size required for the chip. Sand the surface and degrease. Take a laser disc marker and draw a diagram on the PCB. To avoid mistakes, draw with a pencil first. Next, we start etching. You can buy ferric chloride, but the sink is difficult to clean after it. If you accidentally drop it on your clothes, it will leave stains 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 hydrogen peroxide. Add half a tablespoon of salt and a packet of citric acid up to 50 g. The solution is made without water. You can experiment with proportions. And always make a fresh solution. All copper should be removed. This takes about an hour. Rinse the board under running water. Drill the holes.
It can be made even simpler. Draw a diagram on paper. Glue it with tape to the cut out PCB and drill holes. And only after that draw the circuit with a marker on the board and etch it.
Wipe the board with alcohol-rosin flux or a regular solution of rosin in isopropyl alcohol. Take some solder and tin the tracks.
Prepare everything you need to mount the board:
Cut off four pins and solder them into the board. Then install the dinistor and all other parts except the variable resistor. Solder the triac last. Take a needle and brush. Clean the gaps between the tracks to remove any possible shorts. The triac with its free end with a hole is attached to an aluminum radiator for cooling. Use fine sandpaper to clean the area where the element is attached. Take heat-conducting paste of the KPT-8 brand and apply a small amount of paste to the radiator. Secure the triac with a screw and nut. Since all the parts of our design are under mains voltage, we will use a handle made of insulating material for adjustment. Put it on a variable resistor. Use a piece of wire to connect the outer and middle terminals of the resistor. Now solder two wires to the outer terminals. 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 you also 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 body of the angle grinder.
If you want to install an LED indicator in the speed controller, then use a different circuit.
Regulator circuit with LED indicator.
Regulator circuit with LED indicator
Diodes added here:
Assembled regulator with LED.
Assembled regulator with LED
This unit is designed for low-power angle 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 board for heat dissipation and the bta16 triac.
Before connecting the unit to the instrument, let's test it. Take the overhead socket. Install 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 card. 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.
The speed controller is connected to the tool in series.
The connection diagram is shown below.
Connection diagram to the grinder
If there is free space in the handle of the grinder, then our block can be placed there. The surface-mounted circuit is glued with epoxy resin, which serves as an insulator and protection against shaking. Bring the variable resistor with a plastic handle out to regulate the speed.
The electronic unit, assembled separately from the angle grinder, is housed in a housing made of insulating material, since all elements are under mains voltage. A portable socket with a network cable is screwed to the case. The handle of the variable resistor is displayed outside.
Speed controller in box
The regulator is plugged into the network, and the instrument is plugged into a portable socket.
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 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 operating by slowly turning the variable resistor knob.
The good thing about a grinder without a speed controller is that 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 grinding machine, can be used for a drill, drill, or circular saw. For any tool with a commutator motor. Of course, it’s more convenient when the control knob is on the instrument, and you don’t have to go anywhere or bend over to turn it. But here it’s up to you to decide. It's a matter of taste.
legkovmeste.ru
If the angle grinder is not equipped with a speed controller, is it possible to install it yourself? Most angle grinders (angle grinders), commonly known as grinders, have a speed regulator.
The speed regulator is located on the body of the angle grinder Consideration of various adjustments should begin with an analysis of the electrical circuit of the angle grinder.
The simplest representation of the electrical circuit of a grinding machine
More advanced models automatically maintain rotation speed regardless of the load, but tools with manual adjustment of disk speed are more common. If a trigger-type regulator is used on a drill or electric screwdriver, then such a regulation principle is impossible on an angle grinder. Firstly, the features of the tool require a different grip when working. Secondly, adjustment during operation is unacceptable, so the speed value is set with the engine turned off.
This is what the assembled speed controller board looks like The engine speed controller is not just a variable resistor that lowers the voltage. Electronic control of the current strength is necessary, otherwise, as the speed drops, the power and, accordingly, the torque will decrease proportionally. In the end, a critically low voltage value will occur when, even with the slightest resistance of the disk, the electric motor simply cannot turn the shaft. Therefore, even the simplest regulator must be calculated and implemented in the form of a well-developed circuit.
And more advanced (and therefore expensive) models are equipped with regulators based on an integrated circuit.
Integrated controller circuit. (the most advanced option)
If we consider the electrical circuit of the angle grinder in principle, it consists of a speed controller and a soft start module. Power tools equipped with advanced electronic systems are significantly more expensive than their simpler counterparts. Therefore, not every home craftsman is able to purchase such a model. And without these electronic units, all that remains is the electric motor winding and the power button.
The reliability of modern electronic components of angle grinders exceeds the service life of motor windings, so you should not be afraid of purchasing a power tool equipped with such devices. The only limiting factor can be the price of the product. Moreover, users of inexpensive models without a regulator sooner or later come to install it themselves. The block can be purchased ready-made or made independently.
Trying to adapt a regular dimmer to adjust the brightness of the lamp will not yield anything. Firstly, these devices are designed for a completely different load. Secondly, the operating principle of the dimmer is not compatible with controlling the electric motor winding. Therefore, you have to mount a separate circuit and figure out how to place it in the instrument body. IMPORTANT! If you do not have the skills to work with electrical circuits, it is better to purchase a ready-made factory regulator, or an angle grinder with this function.
Homemade speed controller The simplest thyristor rotation speed controller can easily be made independently. To do this, you will need five radio elements, which are sold on any radio market.
Electrical circuit of a thyristor speed controller for your instrument
The compact design allows the circuit to be placed in the body of an angle grinder without compromising ergonomics and reliability. However, this scheme does not allow maintaining torque when the speed drops. This option is suitable for reducing speed when cutting thin sheet metal, carrying out polishing work, and processing soft metals.
If your grinder is used for stone processing, or discs larger than 180 mm in size can be installed on it, you need to assemble a more complex circuit, where the KR1182PM1 microcircuit, or its foreign equivalent, is used as a control module.
Electrical circuit for speed control using the KR1182PM1 microcircuit This circuit controls the current strength at any speed, and allows you to minimize the loss of torque when they decrease. In addition, this scheme is more gentle on the engine, extending its life.
The question of how to adjust the speed of the tool arises when it is stationary. For example, when using a grinder as a circular saw. In this case, the connection point (machine or socket) is equipped with a regulator, and the speed is adjusted remotely.
Regardless of the method of execution, the angle grinder speed controller expands the capabilities of the tool and adds comfort when using it.
A grinder, or grinding machine, is often simply necessary on the farm to perform metal work. In addition, it can be used to clean both wooden and stone materials. It is difficult to imagine performing industrial work without an angle grinder. This is a tool that is suitable for both a professional in his work and an amateur in household work.
When doing work with your own hands, it is important that the power tool has a smooth start. This is especially true if you often have to work, and the network cannot withstand the voltage of the tool.
Budget options for angle grinders - angle grinders - have a number of disadvantages:
Therefore, when choosing a tool, it is very important to pay attention to such parameters as speed control and the presence of a soft start. In addition, when choosing an angle grinder, you should pay attention to power. The main indicator here is the volume of work performed.
If the work is not large-scale and not frequent at the household level, then a power tool with an adjustment of 125 mm and a power of between 600-900 W is suitable.
For large-scale work on an industrial scale, you should use an angle grinder that is approximately twice as powerful. In addition to technical characteristics, one of the main indicators is safety. The grinder must be safe. What does it mean? Firstly, as already mentioned, the presence of a soft start, which prevents voltage surges during switching on. Automatic fuses necessary for emergency stop of the motor during a system failure. The fuses serve as a regulator when the circle jams. Provides protection from dust. It is necessary when using an angle grinder frequently to prevent dust from accumulating in the tool.
The heat dissipation function is important. The heat sink protects against overheating. During operation, especially if the work is prolonged, the machine body is subject to strong heating so that there is no overheating and heat removal is necessary. When overloaded, the angle grinder stops - this happens during heating, approaching 200 o C. Well, balancing the disk serves to reduce unpleasant vibration and beating of the tool during operation, old worn disks are especially susceptible to this effect. Paying attention and paying attention to safety when choosing a tool and when further working with it is very important.
When choosing a tool, it is worth noting that there are grinders with one and two handles. Here you should rely solely on convenience. Two-handed models will most likely be more comfortable to hold, however, such tools are heavier in weight; one-handed models will also have to be held with two hands, but such angle grinders are smaller in size and weight.
Bosch is the leader in the power tools market. The tools of this company have all the necessary characteristics from convenience to safety. Another advantage of Bosch tools is that there is good ventilation.
Manufacturers do not burden cheap angle grinders that do not have sufficient power with voltage control switching circuits, otherwise such angle grinders would no longer be cheap. When starting the grinder, if it is smooth, the process is carried out through an adapter connected by contacts to the rectifier block. The rectifier block converts the current.
But sometimes it makes sense to modernize an angle grinder using an established scheme. The electrical circuit is assembled quite simply. It is not difficult to make, and you can, if desired, connect not only an angle grinder, but any other tool to the finished circuit. However, the tool must have a commutator motor, not an asynchronous one.
A homemade approach to creating a circuit would be as follows:
If the board is connected correctly, the triac and resistors of the angle grinder should start smoothly, and the use of the rotation speed should be regulated. After this, you can test the grinder in action. Such knowledge may be needed when repairing electric motor faults. For example, when voltage increases or improper balancing occurs.
If you use your ingenuity to create a speed controller with your own hands, you can use soldered control boards from a sewing machine or vacuum cleaner. In addition, the components for the regulator are inexpensive and can be easily purchased if possible. It is worth noting that the device requires a gearbox to support a certain number of revolutions and speed. If the speeds are high, then the reason is most likely in the stator. The stator requires repair. Repairing the stator is possible at home.
The operation of the commutator motor is ensured by any type of electrical voltage. When changing the voltage power, you need to reduce or increase the number of revolutions. The thyristor speed controller helps to change this number.
Regulator assembly steps:
Finally, it is glued with epoxy resin to secure it. A homemade device can work for years. There are cases when the device accelerates at higher speeds after switching on - this means the stator winding is short-circuited. In this case, a turn short circuit occurred. The stator requires repair, most often it requires rewinding.
What are the typical malfunctions: the winding breaks or burns, a short circuit occurs, the insulating surface breaks through.
An electric angle grinder is impossible without a speed controller, so that it is possible to reduce the speed.
The regulator circuit from a physics point of view looks like this:
The electronic regulator can be not only built-in, but also remote for convenience. In Bosch angle grinders, the electronics set the speed from almost 3 thousand to 11.5 thousand. There is no load on the meter's power, all indicators are taken into account. Reducing the number of revolutions and increasing them is not difficult for the tool. Adjustable rotation speeds are simply necessary when working with an angle grinder.
Only at first glance, it seems that an angle grinder may never be needed in life, that situations when it will come in handy, much less when it will have to be repaired, will not arise. Of course, you can turn to professionals, or you can identify the problem yourself and try to fix it.
All budget angle grinder options have several disadvantages. Firstly, there is no soft start system. This is a very important option. Surely all of you have plugged this powerful power tool into the network, and when you start it, you have observed how the intensity of the light bulb, which is also connected to this network, drops.
This phenomenon occurs due to the fact that powerful electric motors consume huge currents at the moment of starting, due to which the network voltage sags. This can damage the tool itself, especially those made in China with unreliable windings that may one day burn out during startup.
That is, the soft start system will protect both the network and the tool. In addition, at the moment of starting the tool, a powerful kickback or push occurs, and if a soft start system is implemented, this, of course, will not happen.
Secondly, there is no speed regulator, which will allow you to work with the tool for a long time without loading it.
The diagram presented below is from an industrial design:
It is introduced by the manufacturer into expensive devices.
You can connect not only a grinder to the circuit, but also, in principle, any devices - drills, milling machines and lathes. But taking into account the fact that the tool must have a commutator motor.
This will not work with asynchronous motors. A frequency converter is required there.
So, you need to make a printed circuit board and start assembling.
A dual operational amplifier LM358 is used as a regulating element, which, using transistor VT1, controls the power triac.
So, the power link in this circuit is a powerful triac of the BTA20-600 type.
There was no such triac in the store and I had to buy a BTA28. It is a little more powerful than what is shown in the diagram. In general, for motors with a power of up to 1 kW, you can use any triac with a voltage of at least 600 V and a current of 10-12 A. But it is better to have some reserve and take 20 A triacs, they still cost a penny.
During operation, the triac will heat up, so it is necessary to install a heat sink on it.
To avoid any questions about the fact that the engine, when starting, can consume currents that significantly exceed the maximum current of the triac, and the latter can simply burn out, remember that the circuit has a soft start, and starting currents can be ignored.
Surely everyone is familiar with the phenomenon of self-induction. This effect occurs when a circuit to which an inductive load is connected is opened.
It's the same in this scheme. When the power supply to the motor suddenly stops, the self-induction current from it can burn the triac. And the snubber circuit dampens self-induction.
The resistor in this circuit has a resistance of 47 to 68 ohms, and a power of 1 to 2 W. Film capacitor for 400 V. In this embodiment, self-induction is a side effect.
Resistor R2 provides current suppression for the low-voltage control circuit.
The circuit itself, to some extent, is both a load and a stabilizing link. Thanks to this, after the resistor it is possible not to stabilize the power supply. Although the network has the same circuits with an additional zener diode, it is pointless to use it, since the voltage at the power pins of the operational amplifier is within normal limits.
Possible replacement options for low-power transistors can be seen in the following picture:
The PCB that was mentioned earlier is only a soft starter board and does not have any speed control components. This was done on purpose, since in any case the regulator must be output via wires.
The regulator is adjusted using a 100 kOhm multi-turn trimmer resistor.
If you need a more powerful regulator, it can be assembled according to the following scheme:
If everything is in order, then after disconnecting from the network, you immediately need to check the triac by touch - it should be cold.
If everything works fine - the grinder starts smoothly and the speed is regulated - then it’s time to start testing under load.
Attached files:
Scheme for connecting an analogue CCTV camera to a TV or computer Connecting a digital CCTV camera
(angle grinders), commonly known among Bulgarians, have a speed regulator.
The speed regulator is located on the body of the angle grinder
Consideration of various adjustments should begin with an analysis of the electrical circuit of the angle grinder.
simple representation of the electrical circuit of a grinding machine
More advanced models automatically maintain rotation speed regardless of the load, but tools with a manual disk are more common. If a trigger-type regulator is used on a drill or electric screwdriver, then such a regulation principle is impossible on an angle grinder. Firstly, the features of the tool require a different grip when working. Secondly, adjustment during operation is unacceptable, so the speed value is set with the engine turned off.
Do-it-yourself speed controller for an angle grinder.
Do you have an angle grinder, but no speed controller? You can make it yourself.
Both are necessary for reliable and convenient operation of the power tool.
This device is designed to control the power of an electric motor. With its help you can regulate the speed of rotation of the shaft. The numbers on the adjustment wheel indicate a change in the rotation speed of the disk.
Angler speed regulator
The regulator is not installed on all angle grinders.
Stayer SAG-125–900
Flex LE 9–10 125
Bosch PWR 180 CE
Metabo PE 12–175
EIBENSTOCK EWS 400
The lack of a regulator greatly limits the use of the grinder. The rotation speed of the disk 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 corners, pipes or profiles. Reasons why a regulator is necessary:
The presence of such a launch is a very important point. When starting a powerful power tool connected to the network, a surge of inrush current occurs, which is many times higher than the rated current of the motor, and the voltage in the network sags. Although this surge is short-lived, it causes increased wear on the brushes, the motor commutator and all the tool elements through which it flows. This can cause failure of the tool itself, especially Chinese ones, with unreliable windings that can burn out during switching on at the most inopportune moment. There is also a large mechanical jerk during startup, which leads to rapid wear of the gearbox. Such a start extends the life of the power tool and increases the level of comfort during operation.
The electronic unit allows you to combine the speed controller and soft start into one. The electronic circuit is implemented on the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Grinders of different power and price categories can be equipped with such a block.
| Name | Power, W | Maximum frequency disk rotation, rpm | Weight, kg | price, rub. |
| Felisatti AG125/1000S | 1000 | 11000 | 2,5 | 2649 |
| Bosch GWS 850 CE | 850 | 11000 | 1,9 | 5190 |
| Makita SA5040C | 1400 | 7800 | 2,4 | 9229 |
| Makita PC5001C | 1400 | 10000 | 5,1 | 43560 |
| Flex LST 803 VR | 1800 | 2400 | 6,5 | 91058 |
Felisatti AG125/1000S
Bosch GWS 850 CE
The speed controller is not installed in all models of angle grinders. You can make a block for regulating the speed with your own hands or purchase a ready-made one.
Bosh angle grinder speed controller
Speed regulator for angle grinders Sturm
Speed controller for angle grinders DWT
Such regulators have a simple electronic circuit. Therefore, creating an analogue with your own hands will not be difficult. Let's look at what the speed controller for grinders up to 3 kW is assembled from.
The simplest diagram is presented below.
The simplest speed controller circuit
Since the circuit is very simple, there is no point in installing a computer program for processing electrical circuits just because of it. Moreover, special paper is needed for printing. And not everyone has a laser printer. Therefore, we will take the simplest route of manufacturing a printed circuit board.
Take a piece of PCB. Cut to the size required for the chip. Sand the surface and degrease. Take a laser disc marker and draw a diagram on the PCB. To avoid mistakes, draw with a pencil first. Next, we start etching. You can buy ferric chloride, but the sink is difficult to clean after it. If you accidentally drop it on your clothes, it will leave stains 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 hydrogen peroxide. Add half a tablespoon of salt and a packet of citric acid up to 50 g. The solution is made without water. You can experiment with proportions. And always make a fresh solution. All copper should be removed. This takes about an hour. Rinse the board under running water. Drill the holes.
It can be made even simpler. Draw a diagram on paper. Glue it with tape to the cut out PCB and drill holes. And only after that draw the circuit with a marker on the board and etch it.
Wipe the board with alcohol-rosin flux or a regular solution of rosin in isopropyl alcohol. Take some solder and tin the tracks.
Prepare everything you need to mount the board:
Solder reel
Pins to the board
Triac bta16
100 nF capacitor
Fixed resistor 2 kOhm
Dinistor db3
500 kOhm variable resistor
Cut off four pins and solder them into the board. Then install the dinistor and all other parts except the variable resistor. Solder the triac last. Take a needle and brush. Clean the gaps between the tracks to remove any possible shorts. The triac with its free end with a hole is attached to an aluminum radiator for cooling. Use fine sandpaper to clean the area where the element is attached. Take heat-conducting paste of the KPT-8 brand and apply a small amount of paste to the radiator. Secure the triac with a screw and nut. Since all the parts of our design are under mains voltage, we will use a handle made of insulating material for adjustment. Put it on a variable resistor. Use a piece of wire to connect the outer and middle terminals of the resistor. Now solder two wires to the outer terminals. 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 you also 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 body of the angle grinder.
If you want to install an LED indicator in the speed controller, then use a different circuit.
Regulator circuit with LED indicator.
Regulator circuit with LED indicator
Diodes added here:
Assembled regulator with LED.
Assembled regulator with LED
This unit is designed for low-power angle 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 board for heat dissipation and the bta16 triac.
Before connecting the unit to the instrument, let's test it. Take the overhead socket. Install 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 card. 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.
The speed controller is connected to the tool in series.
The connection diagram is shown below.
Connection diagram to the grinder
If there is free space in the handle of the grinder, then our block can be placed there. The surface-mounted circuit is glued with epoxy resin, which serves as an insulator and protection against shaking. Bring the variable resistor with a plastic handle out to regulate the speed.
The electronic unit, assembled separately from the angle grinder, is housed in a housing made of insulating material, since all elements are under mains voltage. A portable socket with a network cable is screwed to the case. The handle of the variable resistor is displayed outside.
Speed controller in box
The regulator is plugged into the network, and the instrument is plugged into a portable socket.
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 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 operating by slowly turning the variable resistor knob.
The good thing about a grinder without a speed controller is that 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 grinding machine, can be used for a drill, drill, or circular saw. For any tool with a commutator motor. Of course, it’s more convenient when the control knob is on the instrument, and you don’t have to go anywhere or bend over to turn it. But here it’s up to you to decide. It's a matter of taste.
2017-10-19
