Speed regulator for do-it-yourself angle grinder

Ways of connecting the regulator to the inside of the angle grinder body

There is more than enough space in the grip part (rear handle) of the angle grinder to install a regulator with such dimensions. In low-power angle grinders, the free space is usually located closer to its end, and in more powerful ones. between the handle and the motor or in the handle itself (see photo below). Special skills are not required to install such a regulator, since it just needs to be included in the open circuit of the power supply of the electric motor of the angle grinder.

The video below shows the resuscitation of an old angle grinder equipped with a speed controller. Interesting push-button control of the number of revolutions with memorization of the value after turning off the supply voltage.

What is soft start

The electronic circuitry for smooth start-up of the angle grinder is based on the same principle as the speed controller circuit. It also uses a triac to limit the supply of power to the electric motor. But unlike the speed controller, the control pulses to the triac are not formed by manually setting the resistance in the RC-chain, but by an electronic circuit that forms a sequence of pulses with a decreasing delay duration. The diagram below shows how the pulse shift time is shortened and the power supplied to the angle grinder motor increases.

Since the soft start and the speed controller work on the same circuitry, electronic units are produced that combine the functions of both of these devices.

Why do you need to adjust the speed of the angle grinder

Any angle grinder is structurally “sharpened” to work only with a cut-off or grinding wheel of a certain diameter. In total, there are six most common diameters in the range from 115 to 300 mm, which correspond to six groups of spindle speeds at idle speed. For example, angle grinders with Ø125 mm wheels have a rotational speed of about 11 ÷ 12 thousand rpm, and with wheels Ø150 mm. 9 ÷ 10 thousand rpm. Such values ​​of the spindle speed are due to the fact that cutting discs are designed for high-performance processing of hard materials (metal, stone, ceramics) at cutting speeds up to 80 m / s.

However, when cutting and especially grinding soft and tough materials, completely different cutting parameters are required and, accordingly, the use of a tool with a speed controller. And this applies not only to wood and plastics, but also to steels, titanium and aluminum alloys. For example, processing of plastics and soft types of wood occurs at cutting speeds from 8 to 12 m / s, grinding of titanium and stainless steel alloys. within 15 ÷ 20 m / s, and even ordinary steel is ground at no more than 30 m / s. Therefore, the rotation speed of grinding attachments for grinders should be several times less than the passport one. It should be noted that in the bulk of the angle grinder speed controllers are inherently power controllers supplied to the electric motor of the angle grinder. That is, a decrease in the number of revolutions is achieved by reducing the power of the source by up to 15% of the nominal. But for grinding and cutting soft materials, this does not really matter, because in this case, a little power is initially required.

How to make a smooth start for an angle grinder with your own hands

Do-it-yourself speed regulator for an angle grinder: application features, schematic diagram, installation inside the case. What is soft start and how to connect it. Timing diagrams of the speed controller and soft start.

Almost all models of grinders in the lower price range lack such useful options as adjusting the spindle speed and soft start. If you have a desire and some skills, you can make a speed controller for an angle grinder with your own hands, although it is much easier to purchase a ready-made electronic unit for several hundred rubles. The speed control expands the capabilities of the angle grinder and allows it to process soft materials at lower cutting speeds. In addition to the speed controller for an angle grinder, a very useful function is a soft start, which smooths out a sharp increase in current in the windings of an electric motor at the moment the voltage is applied to it. This prevents an abrupt increase in torque and “sagging” of the supply network. In addition, the smooth start-up reduces shock loads on the motor and angle grinder gearbox, which protects them from premature wear.

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Soft start connection

The soft starter can be purchased in retail chains and independently mount any angle grinder inside the case. The video below shows its installation on a new powerful angle grinder purchased by the author for cleaning work. This video is also interesting in that its author, using a pointer device, demonstrates the magnitude of the current jump when the angle grinder is turned on, first without a soft start, and then with this device.

The most advanced angle grinder control device is the load-speed control system, which also acts as a speed controller and ensures a smooth start. On the Internet, you can find a scheme for making such a device on the U2010B microcircuit, but it is quite complicated even for those who have the initial skills of a radio amateur. Is it possible to purchase a ready-made speed control unit and how much does it cost? If anyone can answer this question, please share in the Комментарии и мнения владельцев.

How to assemble a regulator with your own hands?

A simplified and rather reliable frequency converter for an angle grinder is constructed with your own hands from available electrical parts. Below is a diagram showing all the required components for mounting on a printed circuit board of the device of interest to us.

  • symmetrical triode thyristor (or triac, triac) DIAC (DB3);
  • resistor (resistance) R1 (its parameters should be 4.7 kOhm);
  • additional triac VT136 / 138 (TRIAC);
  • capacitor C1 (400 V, 0.1 μF);
  • additional resistance VR1 for 500 kOhm.

A similar scheme operates according to the following method.

  • The charging time of the capacitor is modified by an auxiliary resistor (it is called the trimmer). When voltage is applied to the circuit, the triacs are in the closed position, and a zero voltage value is observed at the output.
  • In the process of charging the capacitor, an increase in voltage is noted on it, which leads to the opening of the DB3 triac. As a result, the voltage falls on VT136 / 138. This thyristor element also opens up, and an electric current flows through it.
  • After that, the symmetrical components are closed again and remain in a similar status until the capacitor is completely recharged in the opposite direction.
  • Ultimately, at the conclusion, we obtain a deterministic signal of finite energy, complex in configuration. Its exact range is determined by the period of performance of the functions of the circuit capacitor. auxiliary resistance. resistance R1.

Triacs are usually located on a printed circuit board. It is easy to create it from textolite (multilayer extruded plastic is used, consisting of heat-insulating fiber and foil). Individual craftsmen cut the board with a cutter. It is practiced to place the circuit elements using the hinged mounting method. Triystres are mounted only on an aluminum or copper heat exchanger. It plays the role of a good heat sink.

The test of the assembled device is carried out using an ordinary 40-60 W incandescent lamp. Connect it to the circuit and start to regulate the glow power. If the brightness changes, then you have done everything correctly. Now you can start installing the regulator in the shell of the angle grinder. This is not very easy to do, since it is necessary to ensure that the auxiliary device does not interfere with you when using the angle grinder.

You will need to calculate the installation location of the homemade control device yourself, in accordance with the design features of the angle grinder. The installation of the circuit is performed:

  • in an additional box mounted on the unit body;
  • into the handle of the holder;
  • into a small empty niche (it is designed to cool and circulate air masses) in the rear area of ​​the angle grinder.

The circuit itself is connected to the device by integrating it into the electric power supply channel of the angle grinder. With this, you, I suppose, will not have difficulties.

Electronic device testing

Before connecting the unit to the angle grinder, check it. Take a plug-in electrical outlet. Insert 2 wires into it, one of which connect to the board, and the other to the network cable. Connect another wire to the network board. As you can see, the regulator is connected in series in the electrical circuit. Connect a light bulb to the circuit and test the operation of the device.

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For what purpose is the angle grinder low speed?

The integrated wheel speed control option enables the gentle handling of materials such as wood or plastic. At lower speeds, comfort and safety are increased. This option is most practical in radio and electrical installation, service stations and studios engaged in restoration.

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In addition, among professionals who use power tools, there is a judgment that the more trivial the device is arranged, the more reliable it is. And it is advisable to take the additional service “stuffing” beyond the boundaries of the angle grinder. With this approach, equipment maintenance is greatly simplified. In this regard, some companies deliberately produce portable individual electrical controllers that are connected to the network cable.

How to make a speed controller for an angle grinder with your own hands?

If you have an old angle grinder among your tools, take your time to get rid of it. Using a simple wiring diagram, the tool can be improved by adding an option for adjusting the speed. Due to the usual control device, which you can create with your own hands within a few hours, the functions of the tool will significantly expand. By reducing the number of rotations per unit of time, the angle grinder can be used as a sharpening and grinding unit for different types of materials. There will be additional opportunities for the use of auxiliary equipment and attachments.

Why do an angle grinder need a smooth start and a speed controller?

In modern angle grinders, 2 necessary options are used that increase the characteristics 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 circuit that provides a leisurely increase in engine speed from zero to the limit value when the unit is connected.

They are used in electromechanical equipment, in the structure of which an alternating current electric motor with a collector is practiced. They help to reduce the wear of the mechanical part of the unit when it is turned on. Reduces the stress on the electrical components of the machine by bringing them into operation smoothly. As studies of the qualities of materials have revealed, a particularly strong development of contacting nodes is produced in the process of a sudden transition from a stationary state to rapid activity. For example, one start of an internal combustion engine in a car is equal to the wear of the piston and a group of sealing rings to 700 kilometers.

When power is applied, an abrupt transition is made from a stationary state to the rotation of a circle with a speed of 2.5-10 thousand revolutions in 60 seconds. Anyone who has used an angle grinder is well aware of the feeling that the tool “flies out of hand”. Just at this moment, most of the accidents associated with the mechanical part of the unit happen.

The rotor and stator windings are equally stressed. An alternating current electric motor with a collector starts up in a short-circuit mode, the EMF already pushes the shaft forward, but the inertia force still does not allow it to rotate. A jump in the starting electric current arises in the coils of the electric motor. Despite the fact that by design they are designed for such work, over time a moment comes (for example, with a voltage drop in the mains) when the winding insulator is not able to withstand and a short circuit occurs between the turns.

The simple way to control the speed An Angle Grinder

With the introduction into the electrical circuit of the instrumentation schemes for adapting a soft start and changing the frequency of rotation of the motor, all the above-described troubles spontaneously disappear. In addition, the issue of a sudden and significant decrease in voltage in the general power grid during the start-up of the tool is being resolved. Hence, it is clear that household electrical appliances will not be at risk of failure. And the automatic switches on the electric meter will not work and turn off the current in an apartment or house.

The soft start scheme is used in angle grinders of the middle and high price segment, the speed control unit is more and more in professional modifications of grinders. The speed control makes it possible to process soft materials with an angle grinder, to carry out delicate grinding and polishing, since at high speeds the wood or paint will simply burn out. Auxiliary electrical circuit increases the cost of the toolkit, but extends the service life and the degree of safety in use.

Connecting the regulator to the angle grinder

The frequency converter is connected to the instrument in series. If there is free space in the handle of the angle grinder, then this device can be placed there. The surface-mounted circuit is glued with epoxy, which will serve as an insulator and vibration protection. Move the variable resistance resistor with a plastic handle outside to adjust the speed.

Installation of the regulator in the cavity of the angle grinder housing

The electronic device, assembled separately from the angle grinder, is encased in a dielectric material as all components are energized. A portable electrical outlet with a cable is fixed to the body. The handle of the variable resistance resistor is brought out. The regulator is connected to the mains, and the tool to a portable power outlet.

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How to connect the device to an angle grinder, options

The connection of the regulator depends on which type of device is selected. If a simple circuit is used, it is enough to mount it in the mains supply channel of the power tool.

Installing a homemade board

There are no ready-made installation recipes. Anyone who decides to equip an angle grinder with a regulator positions it according to their purpose and tool model. Someone inserts the device into the handle of the holder, someone into a special additional box on the case.

The space inside the angle grinder body may vary from model to model. Some have enough free space to install a control unit. In others, you have to bring it to the surface and fix 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.

Cheap DIY Speed Controller[REDUCER] for Angle Grinder, Drill Machine

speed, regulator, do-it-yourself, angle, grinder

Usually, this is where the factory speed regulator is located. A DIY scheme can be placed in this space. To prevent the regulator from burning out, the thyristors should be installed on the radiator.

Device manual

The basic rule when operating an angle grinder with a homemade speed controller is to observe the work and rest mode. The fact is that the engine operating at the “regulated” voltage is especially hot. When sanding at reduced speeds, it is important to take frequent breaks so that the collector windings do not burn out.

It is also highly discouraged to turn on the tool if the speed controller is set to a minimum. the undervoltage is not enough to spin the rotor, the collector lamellas will remain in short-circuit mode, and the windings will start to overheat. Unscrew the variable resistor to the maximum, then, turning on the angle grinder, reduce the speed to the desired value.

Observance of the correct order of switching on and adjustment will allow you to operate the angle grinder for an unlimited time.

Angle grinder CHEAP speed controller

In addition, it should be understood that the speed control on an angle grinder follows the principle of a water tap. The device does not increase the number of revolutions, it can only lower them. It follows from this that if the maximum passport speed is 3000 rpm, then when the 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, 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.

Assembly order

    An electrical circuit is assembled on a printed circuit board or surface-mounted.

How to make a do-it-yourself angle grinder speed controller

If you have an old angle grinder in your arsenal, do not rush to write it off. Using a simple electrical circuit, the device can be easily upgraded by adding the function of changing the frequency of revolutions. Thanks to a simple regulator, which can be assembled with your own hands in a few hours, the functionality of the device will increase significantly. By reducing the rotational speed, the angle grinder can be used as a grinding and sharpening machine for various types of materials. New possibilities appear for the use of additional attachments and accessories.

Basic electrical diagram

In order to assemble the simplest speed controller for an angle grinder, you need to purchase the parts shown in this diagram.

  • R1 is a 4.7 kΩ resistor;
  • VR1. trimmer resistor, 500 kOhm;
  • C1. capacitor 0.1 μF x 400 V;
  • DIAC. triac (symmetrical thyristor) DB3;
  • TRIAC. BT-136/138 triac.

Why is an angle grinder low speed?

The built-in disc speed control allows you to delicately handle materials such as plastics or wood. At low revs, the comfort and safety of work is increased. This function is especially useful in electrical and radio installation practice, in car services and restoration workshops.

In addition, there is a strong belief among professional users of power tools that the simpler the device is, the more reliable it is. And the additional service “stuffing” is better to take out of the power unit. In this situation, the repair of equipment is greatly simplified. Therefore, some companies specifically produce remote individual electronic controls that are connected to the power cord of the machine.

speed, regulator, do-it-yourself, angle, grinder