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Instructions for making a speed controller for an angle grinder with your own hands. External speed controller for an angle grinder from a power regulator with Ali How to lower the speed on an angle grinder

Do you have an angle grinder, but no speed controller? You can make it yourself.

Speed controller and soft start for grinder

Both are necessary for reliable and convenient operation of the power tool.

What is a speed controller and what is it for?

This device is designed to control the power of an electric motor. With 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.

The regulator is not installed on all angle grinders.

Grinders with speed controller: examples in the photo

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:

Thin metal or soft wood requires a lower rotation speed. Otherwise, the edge of the metal will melt, the working surface of the disk will become washed out, and the wood will turn black from the high temperature.
To cut minerals, it is necessary to regulate the speed. Most of them break off small pieces at high speed and the cutting area becomes uneven.
To polish cars, you do not need the highest speed, otherwise the paintwork will deteriorate.
To change a disk from a smaller diameter to a larger one, you need to reduce the speed. It is almost impossible to hold a grinder with your hands with a large disk rotating at high speed.
Diamond blades should not be overheated to avoid damaging the surface. To do this, the speed is reduced.

Why do you need a soft start?

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.

Electronic unit in an angle grinder

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.

Types of devices with an electronic unit: examples in the table

Angle grinders with an electronic unit: popular in the photo

DIY speed controller

The speed controller is not installed in all models of angle grinders. You can make a block for regulating the speed with your own hands or purchase a ready-made one.

Factory speed controllers for angle grinders: photo examples

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.

PCB manufacturing

The simplest diagram is presented below.

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.

Installation of electronic components (with photo)

Prepare everything you need to mount the board:

Solder spool.
Pins to the board.
Triac bta16.
100 nF capacitor.
Fixed resistor 2 kOhm.
Dinistor db3.
Variable resistor with linear dependence at 500 kOhm.

Cut off four pins and solder them onto 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.

Diodes added here:

VD 1 - diode 1N4148;
VD 2 - LED (operation indication).

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.

Making a power regulator: video

Electronic unit testing

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.

Testing the power regulator with a tester and a lamp (video)

Connecting the regulator to the grinder

The speed controller is connected to the tool in series.

The connection diagram is shown below.

If there is free space in the handle of the grinder, then our block can be placed there. The 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.

Installing the regulator inside the angle grinder body: video

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.

The regulator is plugged into the network, and the instrument is plugged into a portable socket.

Speed controller for an angle grinder in a separate housing: video

Usage

There are a number of recommendations for the correct use of an angle grinder with an electronic unit. When starting the tool, let it accelerate to the set speed, do not rush to cut anything. After turning 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.

Do-it-yourself speed controller for an angle grinder.

Do you have an angle grinder, but no speed controller? You can make it yourself.

1 Speed controller and soft start for an angle grinder
2 Why do you need a soft start?
3 Electronic unit in the angle grinder

4 DIY speed controller
5 Use

Speed controller and soft start for grinder

Both are necessary for reliable and convenient operation of the power tool.

What is a speed controller and what is it for?

Angler speed regulator

The regulator is not installed on all angle grinders.

Grinders with speed controller: examples in the photo

Stayer SAG-125–900

Flex LE 9–10 125

Bosch PWR 180 CE

Metabo PE 12–175

EIBENSTOCK EWS 400

Thin metal or soft wood requires a lower rotation speed. Otherwise, the edge of the metal will melt, the working surface of the disk will become washed out, and the wood will turn black from the high temperature.

To cut minerals, it is necessary to regulate the speed. Most of them break off small pieces at high speed and the cutting area becomes uneven.

To polish cars, you do not need the highest speed, otherwise the paintwork will deteriorate.

To change a disk from a smaller diameter to a larger one, you need to reduce the speed. It is almost impossible to hold a grinder with your hands with a large disk rotating at high speed.

Diamond blades should not be overheated to avoid damaging the surface. To do this, the speed is reduced.

Why do you need a soft start?

Electronic unit in an angle grinder

Types of devices with an electronic unit: examples in the table

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

Angle grinders with an electronic unit: popular in the photo

Felisatti AG125/1000S

Bosch GWS 850 CE

DIY speed controller

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.

Factory speed controllers for angle grinders: photo examples

Bosh angle grinder speed controller

Speed regulator for angle grinders Sturm

Speed controller for angle grinders DWT

PCB manufacturing

The simplest diagram is presented below.

The simplest speed controller circuit

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.

Installation of electronic components (with photo)

Prepare everything you need to mount the board:

Solder spool.

Solder reel

Pins to the board.

Pins to the board

Triac bta16.

Triac bta16

100 nF capacitor.

100 nF capacitor

Fixed resistor 2 kOhm.

Fixed resistor 2 kOhm

Dinistor db3.

Dinistor db3

Variable resistor with linear dependence at 500 kOhm.

500 kOhm variable resistor

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:

VD 1 - diode 1N4148;
VD 2 - LED (operation indication).

Assembled regulator with LED.

Assembled regulator with LED

Making a power regulator: video

Electronic unit testing

Testing the power regulator with a tester and a lamp (video)

Connecting the regulator to the grinder

The speed controller is connected to the tool in series.

The connection diagram is shown below.

Connection diagram to the grinder

Installing the regulator inside the angle grinder body: video

Speed controller in box

The regulator is plugged into the network, and the instrument is plugged into a portable socket.

Speed controller for an angle grinder in a separate housing: video

Usage

2017-10-19

The need for a regulator arose due to the need to clean various kinds of rusty pieces of iron in the country before painting them. This can be conveniently done using a metal cord brush installed instead of a cutting wheel. However, since the grinder operates at maximum speeds around 10,000 rpm, the body vibrates quite strongly, and your hands get tired quickly.

The brush itself tries to catch on various irregularities and tear the grinder out of your hands, which is very dangerous. There is also an electric sharpener, which overheats sharpened chisels and thin drills at maximum speed. And the electric stove, despite the fact that it has a thermostat, strives to turn the heated food into coal.
To resolve the issue, Ali purchased an assembled 2000W network power regulator board for 100 rubles.
After successful testing of the regulator “on the snot”, the question of design of the device arose.
These boards have already been described several times on mysku, but the appearance of the assembled devices laid out for public display forced us to look for a more beautiful solution. I wanted to have a ready-made design that was as compact as possible. In Leroy Merlin, with a preliminary estimate of 30 rubles, I purchased a TDM junction box 65x65x50 mm.

At the moment, these junction boxes are not available in Leroy, I will explain why the choice fell on this one:

hinged non-removable lid
one blank side wall
suitable base size
the height is sufficient to accommodate the radiator.

The most compact socket offered was the Turkish Makel Siva Ustu, which today costs 93 rubles. A piece of unnecessary computer cable was used as a network cable.

To accommodate the board, the bosses protruding from the bottom were trimmed and a hole was drilled in the side wall for the regulator slide. In fact, the board is secured in the box only by the regulator body and the standard reinforcing corner of the board. The socket is attached to the box cover with two M4 screws.

The network cable is threaded through a hole in an insulating sleeve inserted into the box body “in reverse”. This installation of the coupling prevents it from being pulled out along with the power cable during careless movements. Since the conductors of the power cable touch the radiator, an additional piece of PVC tube cut and tied with electrical tape was placed on it.

I made marks on the body of the extreme positions of the regulator.

As episodic operation for more than a year with different consumers has shown, the radiator does not get particularly hot and remains warm in a closed box during long-term operation with powerful consumers.

As for cleaning rusty pieces of iron with a cord brush for an angle grinder, such work at lower speeds has definitely become more comfortable and less dangerous. The gyroscope effect is noticeably reduced. A couple of times the cord brush got snagged in the corner, but thanks to the reduced power on the shaft, the angle grinder was able to be held in my hands without injury. And the grinder itself heats up significantly less.
PS Grinder model BLACK&DECKER (B&D) CD 115, I’ve had it for 7 years now. Planning to buy +118 Add to favorites I liked the review +65 +138

(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.

Why adjust the rotation speed of the grinder disc at all?

When cutting metal of different thicknesses, the quality of work greatly depends on the speed of rotation of the disk.
If you are cutting hard and thick material, you must maintain maximum rotation speed. When processing thin sheet metal or soft metal (for example, aluminum), high speeds will lead to melting of the edge or rapid blurring of the working surface of the disk;
Cutting and sawing stone and tile at high speed can be dangerous.
In addition, the disk, which rotates at high speeds, knocks small pieces out of the material, making the cutting surface chipped. Moreover, different speeds are selected for different types of stone. Some minerals are processed at high speeds;
Grinding and polishing work is in principle impossible without adjusting the rotation speed.
By setting the speed incorrectly, you can damage the surface, especially if it is a paint coating on a car or a material with a low melting point;
The use of discs of different diameters automatically implies the presence of a regulator.
Changing a disk Ø115 mm to Ø230 mm, the rotation speed must be reduced by almost half. And it’s almost impossible to hold a 230 mm disc rotating at 10,000 rpm in your hands;
Polishing of stone and concrete surfaces, depending on the type of crowns used, is carried out at different speeds. Moreover, when the rotation speed decreases, the torque should not decrease;
When using diamond discs, it is necessary to reduce the number of revolutions, since their surface quickly fails due to overheating.
Of course, if your grinder works only as a cutter for pipes, angles and profiles, you won’t need a speed controller. And with the universal and versatile use of angle grinders, it is vital.

As a rule, budget angle grinders (angle grinders), popularly called grinders, do not have adjustable electronic modules in their design, which include an engine speed controller and a soft start. Over time, owners of such grinders begin to understand that their absence sharply reduces the functionality of the tool. In this case, you can modify the angle grinder by installing homemade devices on it.

When power is applied to the grinder motor, sudden increase in speed from zero to 10 thousand or more. Those who have worked with an angle grinder know well that it is sometimes difficult to hold it in your hands when starting, especially if a large diameter diamond disc is installed.

It is precisely because of such abrupt increases in engine speed that the mechanics of the device most often fail.

Also, during startup, a huge load is applied to the rotor and stator windings of the electric motor. Since a commutator motor is installed in the angle grinder, it starts in short circuit mode: the electromagnetic field is already “trying” to turn the rotor, but it remains motionless for some time, since the force of inertia prevents this from happening. As a result, the starting current in the motor coils sharply increases. Despite the fact that the manufacturer has invested a certain safety margin for the coils, taking into account overloads at start, sooner or later the insulation cannot withstand it, which leads to an interturn short circuit.

In addition to starting problems, the lack of speed control causes some discomfort. For example, an angle grinder's speed regulator may come in handy for certain types of work:

when grinding or polishing any surfaces;
when installing large diameter tools;
for cutting certain materials.

In addition, when roughing with wire brushes, there is a high probability of wire jamming in any gap. If the spindle speed was high, then the angle grinder may simply be torn out of your hands.

If you connect a power (speed) regulator with a soft start module to the angle grinder, then all the problems described above will disappear, the service life of the device will increase and the safety of its use will increase.

Homemade regulator circuit

One of the most popular schemes for smoothly starting an angle grinder engine with the ability to adjust the speed is presented below.

The basis of this regulator is the KR118PM1 microcircuit, as well as triacs, which are the power part of the device. Using this circuit, you can make a power regulator with your own hands, even without special knowledge in radio electronics. The main thing is that you know how to use a soldering iron.

This block works as follows.

After pressing the unit start button, electric current begins to flow, first of all, to the microcircuit (DA1).
The control capacitor begins to charge smoothly and after a while reaches the required voltage. Thanks to this, the opening of the thyristors in the microcircuit occurs with some delay. It depends on the time it takes to fully charge the capacitor.
Since the VS1 triac is controlled by the microcircuit’s theristors, it opens just as smoothly.

The processes described above occur in periods that become shorter each time. Therefore, the voltage supplied to the motor windings does not increase abruptly, but slowly, resulting in a smooth start of the angle grinder.

The time it takes for the electric motor to reach full speed depends on the capacitance of capacitor C2. The capacitor capacity of 47 uF allows you to start the engine in 2 seconds. When the angle grinder is turned off, capacitor C1 is discharged using 60 kOhm resistor R1 for 3 seconds, after which this electronic module is again ready to start.

If resistor R1 is replaced with a variable one, then you will get a speed controller that will allow you to reduce engine speed.

It is important that triac VS1 has the following characteristics:

the minimum current for which it is designed must be 25 A;
The triac must be designed for a maximum voltage of 400 V.

This circuit and the regulators made according to it have been repeatedly tested by many craftsmen on grinders with power up to 2000 Watt. It is worth noting that this device, thanks to the KR118PM1 microcircuit, is designed for power up to 5000 W. So he has a considerable margin of safety.

Ideally, to solder a speed controller for an angle grinder, you will need to draw a printed circuit board, etch the contacts with acid and then tin them, drill holes and solder the radio components. But everything can be made simpler:

solder all the parts of the circuit by weight, that is, leg to leg;
Attach a radiator to the triac (can be made from sheet aluminum).

A regulator soldered in this way will take up less space and can be easily placed in the body of the angle grinder.

How to connect a regulator to an angle grinder

To connect a homemade power regulator, no special knowledge is required, and any home craftsman can cope with this task. The module is being installed into a break in one wire, through which power goes to the grinder. That is, one wire remains intact, and a regulator is soldered into the gap of the second.

In the same way, you can connect a factory power regulator that costs about 150 rubles, which is often purchased by craftsmen in China.

If there is very little space in the grinder, then the regulator can be placed outside the instrument, as shown in the following photo.

Also, the regulator can be placed in a socket and used to reduce the speed not only of an angle grinder, but also of other electrical appliances (drill, sharpener, wood milling or lathe, etc.). This is done as follows.

The regulator is connected as described above - at a break in one of the wires of the power cable.

The following photos show what a finished socket will look like, having a built-in speed controller for an angle grinder, which can also be used for other electrical appliances.

Instead of a junction box, you can use any plastic case suitable size. You can also make the box yourself by gluing pieces of plastic together with a glue gun.