How to install a speed controller on an angle grinder

How to reduce the speed on the angle grinder with their own hands?

Collector motors with series excitation are used in angle grinders with speed regulator. They can be operated with DC or AC current. This type of motor is easily regulated by changing the current in the circuit.

Since modern regulators use pulse-controlled key control, they do not heat up very much and can even be built into small tools. For regulation, a potentiometer is used, the knob of which is derived from the handle of the machine.

Why control the speed of the disc?

Different cutting or grinding speeds are required by the physical properties of the materials to be machined. High speed with low pressure is required when cutting hard materials that would otherwise crumble or split. Soft materials that are not resistant to heat (thermoplastics, wood), on the contrary, require low speed:

• ceramics: 10000 rpm;
• metal: 8000 rpm;
• hard plastics: 5 000. 8 000 rpm;
• wood: 3000. 5000 rpm;
• soft plastics: less than 2000 rpm.

All professional tools are equipped with a stabilized speed regulator, but inexpensive household angle grinders, power under 1200 W, are not always complemented by it. In this article we will talk about how to make such a regulator yourself to reduce the speed.

RPM regulator for angle grinder with their own hands

Although the creation of a speed regulator for angle grinder few people need, there are still models that have made manual adjustment of the speed of the disc. The adjustment of an angle grinder is much different from an electric electric screwdriver or drill because:

• A completely different grip is used during the work.
• Do not adjust during cutting. Adjustment should only be performed when the machine is off.

The speed of the blade must be adjusted

• When metal is cut (regardless of the thickness of the material) the result of the work carried out depends on the speed of the disc. If you are cutting metal of great thickness, the speed should be the highest. If you are working with thin materials, lower the speed as a high speed causes the disc surface to become washed out quickly.
• There is a definite risk if you are cutting tiles at high speed. Also the disk, rotating at high speed, begins to beat off small pieces of material, thereby making its surface brittle. Since the stone has a variety of types, a certain speed is used for each type. For many minerals high rotational speeds are used.
• If you are grinding or polishing, then the adjustment of speed angle grinder just need. If the speed is set incorrectly, the surface of the material will be spoiled. For example, material that has a paint coating can be spoiled.
• If discs of varying diameters are regularly used, there must be a speed regulator for the angle grinder. If you change the disc of the angle grinder to another one with a larger diameter, the speed must be reduced. You cannot hold a grinder that has a disc with a huge diameter.
• The choice of speed when polishing concrete material is dependent on the use of a particular type of bit. The torque must not diminish as the rotational speed decreases.
• If you use a diamond disc, then the number of its speed must be reduced, otherwise the surface due to overheating will begin to fail. Of course, if you use an angle grinder to cut pipes, angles, or profiles, then having a regulator is not necessary. But if the angle grinder is used for a variety of purposes, then a speed controller for the angle grinder is a must. All of these reasons show that having an angle grinder regulator is a must.

Description of angle grinder regulator

The angle grinder regulator is a rheostat (variable resistor) that reduces the voltage (all done by the regulator). It is necessary to control the amperage, because if the number of revolutions is reduced, there will be a decrease in the power of the construction machine. Consequently, there will be a reduction in torque. As a result, there will be a small value of voltage, and at a certain resistance of the electric motor will not be able to turn the shaft. Therefore, it is necessary to follow a certain scheme: The scheme of the angle grinder is made up of a soft starter module and directly the speed regulator.

Modern advanced models have a distinctive electronic system, and not everyone can afford to buy it.

Making the regulator yourself

How to make a regulator by your own? The desire to attach an ordinary electronic device, designed to change the electric power (dimmer) ends up in nothing. First of all, the dimmer for the angle grinder is designed for a different load. Also, the dimmer has no overlap with the control of the electric motor winding. Therefore, it is necessary to install a separate circuit. It is also necessary to think of where it will be located inside the body of the angle grinder.

An important point: if you do not have any experience working with electrical circuits, it is best to buy a ready-made regulator for angle grinder or angle grinder with the presence of this function.

A simple semiconductor device (thyristor regulator) can be constructed with your own hands. For this procedure will need 5 radio elements. The radio elements can be bought at the market. Due to its compactness, it is possible to safely conduct the placement of the prepared circuit in the angle grinder without damaging ergonomics and reliability. However, torque is not saved by reducing the RPM on the angle grinder. This version is best suited for soft metals, as well as tin, which has a small thickness.

If you are processing stone, you need to install a disk that has the size of 180 millimeters. Then you need to create a more complicated circuit of the regulator. In this circuit, the control module will be a chip KR1182PM1. This circuit has control over the amount of current at different speeds and also makes the loss of torque as little as possible when reducing the speed. When using this circuit, the operation of the motor is increased.

If the angle grinder is used as a circular saw, it is necessary to equip the angle grinder with a connection point. Thanks to such a point, the connection is made, and the speed can be adjusted remotely. You get a great homemade speed controller.

It does not depend on how you made the regulator, it is a mandatory component of the angle grinder, which makes the possibilities of work wider and allows you to comfortably use this construction tool. Also, after installing the regulator, it is necessary to conduct a test run of the angle grinder to check: whether the construction tool does not pull out of his hands. You can make an external speed regulator for the angle grinder with your own hands.

How to connect the device to the angle grinder, options

Connection of the regulator depends on what kind of device is chosen. If a simple circuit is used, it is enough to mount it in the mains power supply channel of the power tool.

Installing a homemade circuit board

There are no ready-made recipes for installation. Everyone who decides to equip an angle grinder with a regulator has it according to their goals and tool model. Someone inserts the device in the handle of the holder, someone in a special additional box on the housing.

In different models, the space inside the body of the angle grinder may be different. Some have enough free space to install the control unit. In others, you have to put it on the surface and fix it in some other way. But the trick is that, as a rule, there is always a certain cavity in the back of the tool. It is designed for air circulation and cooling.

This is usually where the factory speed regulator is located. The handmade circuit can be placed in this space. In order not to burn out the regulator, thyristors should be installed on the heat sink.

Features of the installation of the finished unit

When buying and installing the factory regulator inside the angle grinder, most often you have to modify the body. to cut a hole in it for the output of the regulating wheel. But it can have an adverse effect on the rigidity of the casing. Therefore it is preferable to mount the unit outside.

The thumbwheel changes the rpm

The numbers on the thumbwheel indicate the number of spindle revolutions. This value is not an absolute value, but a relative one. “1” for minimum RPM, “9” for maximum RPM. Other figures are for orientation during adjustment. The position of the wheel on the housing can be different. On a Bosch PWS 1300-125 CE angle grinder, a Wortex AG 1213-1 E or a Watt WWS-900 for example, it is located at the base of the handle. On other models, such as the Makita 9565 CVL, the adjustment wheel is in the end of the shroud.

The diagram of connection of the regulator to the angle grinder is not complicated, but sometimes it is not so easy to pull cables to the button, which is located at the other end of the device housing. The problem can be solved by selecting the optimal wire cross section or by placing it on the surface of the housing.

A good option is the installation of the regulator on the surface of the device or attachment to the mains cable. Not always everything works on the first try, sometimes the device has to be tested, and then make some adjustments. And this is easier to do when access to its elements is open.

Important! If there is no experience with electrical circuits, it is advisable to buy a ready-made factory regulator or angle grinder, equipped with this function.

Why do the angle grinder smooth start and speed regulator?

Modern angle grinders use 2 necessary options that increase the performance and safety of the equipment:

• speed regulator (frequency converter). a device designed to convert the speed of the motor in different modes of operation;
• soft starter. a scheme that provides a slow increase in motor speed from zero to the limit value when the unit is plugged in.

Are used in electromechanical equipment, in the structure of which the electric motor of alternating current with a collector is practiced. Contribute to reducing the wear and tear of the machine’s mechanical parts when switching on. They reduce the load on the electrical components of the machine by putting them into operation smoothly. As revealed by studies of the qualities of materials, especially the strongest production of contacting nodes are made in the process of sudden transition from a stationary state to the rapid activity. For example one startup of an internal combustion engine in a car equals to the wear of the piston and the group of compression rings by 700 kilometers of run.

When power is applied, there is a stepwise transition from a stationary state to wheel rotation at a rate of 2.5-10 thousand revolutions per 60 seconds. Anyone who has used an angle grinder knows very well the feeling that the tool directly “flies out of his hands. Just at this moment, most accidents involving the unit’s mechanical parts happen.

The rotor and stator windings feel the same load. An AC motor with a collector starts in the short-circuit mode, the EMF is already pushing the shaft forward, but the force of inertia does not yet allow it to spin. A surge of inrush current occurs in the motor coils. Even though they are designed for this kind of operation, in time there comes a moment (e.g. voltage drop in the supply line), when the winding insulator is unable to withstand and a short circuit occurs between the coils.

With the introduction of the instrumentation schemes of soft start and change of frequency of rotation of the motor all the above mentioned troubles disappear spontaneously. In addition, the issue of a sudden and significant voltage drop in the general power supply during the start-up of the tool is solved. It is clear from this that household appliances will not be in danger of failure. And the circuit breakers on the electricity meter will not trip and turn off the current in the apartment or house.

The scheme of soft start is used in medium and high price segment angle grinders, the knot of speed control. more and more in professional versions of angle grinders. Speed regulation makes it possible to process angle grinder to soft materials, to perform delicate grinding and polishing, because at high speed wood or paint will simply burn off. Auxiliary circuitry increases the price of the tool, but extends the life and degree of safety in use.

Speed regulator and soft starter. what are they for?

In today’s grinders apply two important functions that increase the reliability and safety of the tool:

• RPM regulator is a device designed to change the number of revolutions of the engine in different modes of operation;
• Soft start. a scheme that provides a slow increase in engine speed from zero to the maximum when the device is turned on.

Used on electromechanical tools that use a collector-driven motor. Help to reduce wear and tear on the mechanical part of the unit during switching on. Reduce the load on the electric elements of the mechanism, starting them up gradually.

As studies of material properties show, the most intense wear of rubbing nodes occurs during the sharp transition from a state of rest to the mode of rapid movement. For example, one run of internal combustion engine in a car equals to the wear of piston group by 700 km of run.

When power is on, there is a sudden transition from a quiescent state to disk rotation 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 is simply “tearing out of their hands. It is at this point that the vast majority of breakdowns related to the mechanical part of the unit occur.

The stator and rotor windings are under no less strain. Collector motor starts in short circuit mode, the motive force is already pushing the shaft forward, but the inertia is not yet allowing it to rotate. There is a start-up current surge in the electric motor coils. Even though they are designed for this kind of operation, sooner or later, there comes a time (for example, when the mains voltage surges) when the winding insulation fails and an inter-turn short circuit occurs.

When soft start and speed change circuits are included in the electric circuit of the tool, all the above mentioned problems automatically disappear. Among other things, this solves the problem of “voltage dips” in the mains at the moment of starting the hand-held tool. This means that your refrigerator, television set or computer will not be in danger of “burning out. And the fuse breakers on the meter will not trip and cut off the current in the house or apartment.

Soft-start scheme is used in grinders medium and high price categories, the block regulates the speed. mainly in professional models of angle grinder.

Speed regulation allows you to handle angle grinder soft materials, perform fine grinding and polishing. at high speed wood or paint will simply burn off.

Additional circuitry increases the cost of the tool, but increases service life and safety at work.

Design and electrical diagram of an angle grinder

Over the many years of existence of such a tool as an angle grinder, its appearance, as well as the internal structure has not changed much. To repair the angle grinder with your own hands, you need to know the device of its mechanical part, as well as electrical.

If you look at the figure below, you can see what parts make up an angle grinder.

• Wheel for adjusting the machine’s spindle rim.
• Electric motor consisting of rotor and stator.
• Start button. Sometimes a soft starter is connected to it.
• Shock-resistant plastic housing.
• Button for locking the spindle (used when changing tools).
• Safety coupling. Protects motor from overload if tool jams.
• Protective hood. Encloses tool and protects you from flying debris or chips in the work area and prevents you from injuring yourself if the tool, such as the cutting wheel, breaks.
• Nut that clamps the tool. can be unscrewed with the special key included in the scope of delivery of the power tool. There are also quick-action nuts that can be unscrewed without a wrench.
• Gearbox housing and gearbox itself. It consists of a block of gears that transmit rotational motion from the rotor to the spindle with the tool.

The illustration below shows the electrical diagram of an angle grinder.

The electrical part of the angle grinder has the following elements:

• electric cable with plug for connection to the mains;
• start button;
• stator;
• electric brushes (carbon or graphite);
• collector;
• armature (rotor).

The following illustration shows the connection diagram of the angle grinder, namely, its motor.

All components of an electric motor perform certain functions.

• The rotor is the shaft on which the coils and the collector are placed. The rotor, rotating in the magnetic field of the stator, transmits the rotary motion to the gearbox of the angle grinder.
• Collector. Represents the part of the rotor to which all control cables are connected. Electrical signals from the control box go through the collector to the motor. It is to the collector that the electric brushes are connected.
• Electric brushes. Their main task is to transfer the electric current from the power cable to the manifold.
• Stator. Consists of a coil with a defined number of windings. The task of the stator is to create a magnetic field, which, interacting with the armature, sets the latter in motion.

Diagram of a soft starter motor angle grinder with his own hands

Everyone who uses the angle grinder more than one year, it breaks. At first, every master tried to repair the sparkling grinder himself, hoping that it would work after replacing the brushes. Usually after such an attempt, a broken tool is left on the shelf with a burned-out winding. And you buy a new angle grinder to replace it.

Drills, screwdrivers, torches, routers are mandatorily equipped with a speed regulator. Some so-called calibration grinders are also equipped with a regulator, and conventional angle grinders have only a button.

Low-power angle grinder manufacturers do not deliberately complicate with additional circuits, because such power tools must be cheap. Of course, it is clear that the lifetime of an inexpensive tool is always shorter than that of a more expensive professional one.

The most simple angle grinder can be upgraded so that it will no longer damage the gearbox and the winding wires of the armature. These troubles mostly occur during a sharp, in other words, percussive start of the angle grinder.

All you need to do is just assemble the electronic circuit and fix it in the box. In a separate box, because there is very little space in the handle of the grinder.

A tested, working schematic is shown below. It was originally designed for lamp incandescence adjustment, that is, to work with an active load. Its main advantage ? simplicity.

• The highlight of the device soft starter, circuit diagram which you see, is a chip K1182PM1R. This chip is highly specialized, domestically made.
• The acceleration time can be increased by selecting the capacitor C3 of higher capacity. While charging this capacitor, the electric motor will pick up speed to the maximum.
• No need to put a variable resistor R1 instead. Resistor of 68 kOhm is optimally chosen for this circuit. With this setting you can smoothly start the angle grinder with a power of 600 to 1500 watts.
• If you are going to build a power regulator, then you need to replace the resistor R1 with a variable resistance. Resistance of 100 kOhm or more does not lower the output voltage. By short-circuiting the pins of the microcircuit, you can turn off the connected angle grinder at all.
• having inserted sevenistor VS1 of TC-122-25 type into power circuit, i.e. for 25A, you can smoothly start almost any commercially available angle grinder with power from 600 to 2700 W. And there is a large power reserve in case of grinder jamming. For connection of the power up to 1500W, it is enough to use imported semistors BT139, BT140. These less powerful electronic keys are cheaper.

The triac in the circuit above is not fully opened, it cuts off about 15V of line voltage. Such voltage drop does not affect the operation of the angle grinder. But when the semister heats up, the speed of the connected tool is severely reduced. This problem is solved by installing a heat sink.

This simple circuit has the additional disadvantage that it is not compatible with the speed controller installed in the tool.

The assembled circuit should be hidden in a plastic box. The case of insulating material is important, because you need to protect yourself from the mains voltage. You can buy a junction box at the electrical supply store.

A socket is screwed to the box and a cable with plug is connected, which makes this design look like an extension cord.

If experience allows and there is a desire, you can assemble a more complex circuit of soft starter. The following circuit diagram is standard for the XS-12 module. This module is factory-installed in the power tool.

If you need to change the speed of the connected electric motor then the circuit is more complicated: install a 100 kOhm trimmer and a 50 kOhm adjustment resistor. Or you can simply and roughly put a 470 kOhm variable between the 47 kOhm resistor and the diode.

It is desirable to connect a resistor of 1 megohm in parallel to the capacitor C2 (it is not shown in the schematic below).

Supply voltage of the LM358 chip is in the range of 5 to 35V. The supply voltage is less than 25V. That’s why you can do without the additional DZ.

Whatever softstarter circuit you have built, never run the connected tool under load. Any soft starter can be burned out if you are in a hurry. Wait for the angle grinder to spin up and then work.

Installation of a controller on an angle grinder

RPM regulator for angle grinder with their own hands can be mounted in four variants:

Regulator installation on angle grinder. scheme

• in the handle;
• into an external box, which is mounted in a convenient location on the body of the tool;
• in the cooling cavity (manufacturers use this option);
• to the mains cable.

Installation of an additional box does not require cutting of the housing for the output of the regulator, but the place should be chosen very carefully, so that the innovation does not interfere with a comfortable hold on the tool. Mounting in the handle or cooling cavity will require a hole to exit the adjustment wheel, here the main thing is not to lose the rigidity of the protective cover and well grind the edges, so as not to hurt your hands when working.

Often the best option is to mount it on a wire. In this case, the regulator is easy to test, no need to think about the place and method of attachment (duct tape and plastic housing is quite suitable). If desired, it can always be removed and converted.

Installation of a regulator on the angle grinder

Speed regulator for angle grinder with their own hands can be mounted in four variants:

Installation of the regulator on the angle grinder. scheme

• into the handle;
• in an external box, which is mounted in a convenient place on the body of the tool;
• in the cavity for cooling (manufacturers use this option);
• on the mains cable.

Installation of an additional box does not require cutting of the housing for the output of the regulator, but the place should be chosen very carefully, so that the innovation does not interfere with a comfortable hold on the tool. Mounting in a handle or cavity for cooling requires cutting a hole for the output of the adjustment wheel, the main thing here is not to lose the rigidity of the protective casing and well grind the edges, so as not to hurt your hands when working.

Often the best option is the mounting on the wire. In this case, the regulator is easy to test, no need to think about the place and method of attachment (duct tape and plastic housing is quite suitable). If desired, it can always be removed and reworked.

How to make with your own hands

To assemble independently RPM regulator according to the scheme will manage even a novice radio amateur. Parts for making such a device can be purchased at any specialized stores. In addition, they can be removed from the old, unnecessary board (in this case it is recommended to check them for proper functioning). To make the speed regulator yourself, you will need to:

• Assemble according to the instructions on the circuit board (thyristors are recommended to install on copper or aluminum radiator).
• Using an ordinary incandescent lamp perform a test of the assembled circuit for its functionality. After using this device and adjusting it, the lamp level should change.
• Install the finished product on the angle grinder.

At the final stage it is necessary to carry out a preliminary test of the work of the homemade controller. If the device works successfully, without failures, then it should be fixed, and then close the cover. If a simple circuit was used in the creation of such a homemade device, then it can be fixed in the channel, where the mains power to the angle grinder is placed.

It should be noted that there is no ready-made solution regarding the installation of a homemade controller board in the angle grinder. This is due to the fact that in different models of lathes, the free space can also vary. In some cases, if the free space directly inside the case is not enough to install the board, then it is mounted on its outer part.

However, it should be noted that in almost all models of angle grinders, there is a small void in the form of a cavity in the area of the back of the machine. The main purpose of such a cavity is that it provides air circulation and is part of the cooling system of the power tool. As a rule, the factory speed regulators are installed in this cavity. Therefore in the same place you can mount your own handmade circuit.

How to make with your own hands

Even a novice radio amateur will be able to assemble their own RPM regulator according to the scheme. Components for making such a device can be purchased at any specialized stores. It is also possible to remove them from an old, unwanted circuit board (in this case it is recommended that they are checked for their proper functioning). To make a speed regulator yourself it is necessary:

• Assemble according to the instructions on the circuit board (thyristors are recommended to install on copper or aluminum heatsink).
• Using an ordinary incandescent lamp perform a test of the assembled circuit for its performance. After using this device and adjusting it, the incandescence level of the lamp should change.
• Install the finished product on the angle grinder.

At the final stage it is necessary to conduct a preliminary test of the work of the homemade controller. If the device works successfully, without failure, then it must be secured, and then close the cover. If a simple circuit was used in the creation of such a homemade device, then it can be fixed in the channel where the mains power to the angle grinder is placed.

It should be noted that there is no ready-made solution regarding the installation of a homemade regulator board in the angle grinder. This is due to the fact that in different models of lathes, the free space can also vary. In some cases, if the free space directly inside the housing is not enough to install the board, then it is mounted on its outer part.

However, it should be noted that in almost all models of lathes, there is a small cavity in the back of the machine. The main purpose of such a cavity is that it provides air circulation and is part of the cooling system of the power tool. As a rule, the factory speed regulators are installed in this cavity. Therefore, in the same place you can mount your own handmade scheme.

Installing a homemade circuit board

Unacceptable off-the-shelf installation recipes. Who, who decided to equip the angle grinder regulator, has it according to their goals model of the tool. Someone inserts the device in the handle holder, someone in a special additional box on the housing.

In different models, the place inside the body of the angle grinder may be different. In some quite free space for the installation of the control unit. In others, you have to bring it to the surface and reinforce it with another method. But the trick is the fact that, usually, there is always a certain cavity in the back of the tool. It is designed for air circulation and cooling.

This is usually where the factory speed regulator is located. The made by yourselves scheme of course put in this place. Thyristors must be installed on the heat sink to prevent the regulator from burning out.

Connecting the soft starter

Electronic speed controller is mainly needed for home craftsmen to expand the capabilities of angle grinder in terms of grinding and processing of soft materials. Professionals tend to use specialized tools for certain types of work and use the angle grinder only for its intended purpose. The situation is different with the soft starter. For domestic tools, which have low power, this option is useful, but not necessary. But it is vital for professional grinders with drives over 1000 W. In addition to the above performance improvements, the soft starter is extremely important for operator safety. an angle grinder with a Ø 230 mm wheel and a power of 2000 W weighs 5÷6 kg, and to hold it during the start-up jerk requires certain efforts and a stable position.

The soft starter can be purchased from retailers and assembled yourself inside the housing of any angle grinder. The video below shows its installation on a new heavy-duty angle grinder, purchased by the author for cleaning work. This video is also interesting because its author, using an arrow device, demonstrates the magnitude of the current jump when turning on the angle grinder first without the soft starter, and then already with this device.

The most advanced control device for the angle grinder is the speed control system under load, which also serves as a speed regulator and provides a soft start. In the Internet you can find a scheme for making such a device on the chip U2010B, but it is complicated enough even for those who have elementary skills of radio amateur. Is it possible to buy a ready-made speed control unit and how much does it cost?? If anyone can answer this question, please share the information in the Комментарии и мнения владельцев.

Types of faults of electrical and mechanical parts of the drill

The most common problems with the electrical component are when the drill sparks on the brushes due to significant grinding or wear. Appliance with badly worn brushes will not start at all. A sign of problems with the motor is the absence of signs of its activation (sound, vibration, etc.). In a drill with speed control, reverse and speed control may no longer work.

Mechanical problems. bearing or gear mechanism failure, shaft failure. They are manifested by hum, intermittent stops of the device, slow rotation. Sometimes there are problems with the chuck: difficulties in disconnecting the drill bit, unscrewing the chuck from the shaft.

Necessary tools

Planning the procedure for repairing the drill with your own hands, you will need to prepare the following tools:

• screwdriver with nozzle;
• vise;
• bearing puller;
• Wrenches for nuts and ends;
• emery for grinding;
• ohmmeter and meggimeter;
• pliers;
• caliper.

To competently make an independent repair of the drill, you need to imagine the device of its electrical and mechanical stuffing. In this case, most faults can be repaired at home.