How To Adjust The Speed On An Angle Grinder

Do-it-yourself smooth start for an angle grinder. Saving your money and protecting your power tool Change the electrical circuit of the angle grinder and make a do-it-yourself smooth start and extend the life of your tool.

Smooth start for do-it-yourself angle grinder. Saving you money and protecting your power tool

how to adjust the speed on an angle grinder

Due to the design features, the start of the angle grinder is associated with high dynamic loads. Due to the mass of the working disc, inertia forces act on the gearbox axis at the beginning of rotation. This entails some negative points:

  1. Axle loads during a sharp start create an inertial jerk, which, with a large diameter and mass of the disc, can tear the power tool out of the hands;

As a result, the brushes wear out and both windings of the electric motor overheat. By repeatedly turning the power tool on and off, overheating can melt the winding insulation and lead to a short circuit, with subsequent costly repairs.

High torque with a sharp set of revolutions prematurely wears out the gears of the reducer. Angle grinder;

In some cases, teeth may break off and the gearbox may jam.

Overloading the working disc can destroy it when starting the engine.

Therefore, a protective cover is required.

To better understand the mechanics of work, consider the device of the angle grinder in the drawing. All the elements experiencing overload during a sharp start are clearly visible.

Schematic drawing of the arrangement of the working bodies and control systems in the angle grinder

To reduce the harmful effects of a sudden start, manufacturers produce an angle grinder with adjustable speed and smooth start.

The speed control is located on the tool handle

But only models of the middle and high price category are equipped with such a device. Many home craftsmen purchase an angle grinder without a regulator and slowing down the starting speed. This is especially true for powerful specimens with a cutting disc diameter of more than 200 mm. Such an angle grinder is not only difficult to hold in your hands during start-up, but mechanical and electrical wear occurs much faster.
There is only one way out. To install the smooth start of the angle grinder yourself. There are ready-made factory devices with a speed governor and a slowdown in engine start at startup.

Finished soft-start control device

Such blocks are installed inside the case, if there is free space. However, most users of the angle grinder prefer to make a soft start circuit for the angle grinder by themselves and plug it into the break in the supply cable.

How to make a do-it-yourself smooth start of an angle grinder

The popular circuit is implemented on the basis of the KR118PM1 phase control microcircuit, and the power section is made on triacs. Such a device is quite simple to install, does not require additional adjustment after assembly, and therefore, it can be made by a master without specialized education, it is enough to be able to hold a soldering iron in his hands.

Wiring diagram for soft start adjustment for angle grinder

The proposed unit can be connected to any power tool designed for 220 volts alternating voltage. A separate removal of the power button is not required, the modified power tool is turned on with a standard key. The circuit can be installed both inside the housing of the angle grinder, and also in the break of the supply cable in a separate housing.

The most practical way is to connect the softstarter to the outlet that powers the power tool. The input (connector ХР1) is powered from a 220 volt network. The outlet (XS1 connector) is connected to a supply socket, into which the plug of an angle grinder is inserted.

When the start button is closed, the angle grinder, voltage is supplied to the DA1 microcircuit through the common power supply circuit. A smooth increase in voltage occurs on the control capacitor. As it is charged, it reaches its working value. Due to this, the thyristors in the microcircuit do not open immediately, but with a delay, the time of which is determined by the charge of the capacitor. Triac VS1, controlled by thyristors, opens with the same pause.

Look with a detailed explanation of how to make and which scheme to apply

In each half cycle of the AC voltage, the delay decreases in arithmetic progression, resulting in a smooth increase in the voltage at the input to the power tool. This effect determines the smooth start of the angle grinder engine. Consequently, the disc speed increases gradually, and the gearbox shaft does not experience inertial shock.

The time to speed up to the operating value is determined by the capacity of the capacitor C2. The value of 47 μF provides a soft start in 2 seconds. With this delay, there is little discomfort for starting work with the tool, and at the same time, the power tool itself is not subjected to excessive stress from a sudden start.

After turning off the angle grinder, the capacitor C2 is discharged by the resistance of the resistor R1. With a nominal 68 kOhm, the discharge time is 3 seconds. Then the soft starter is ready for a new start cycle of the angle grinder.
With a little modification, the circuit can be upgraded to an engine speed governor. For this, the resistor R1 is replaced with a variable resistor. By adjusting the resistance, we control the power of the engine by changing its speed.

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Thus, in one housing it is possible to make an engine speed regulator and a soft starter for an electric tool.

The rest of the circuit details work as follows:

  • Resistor R2 controls the amount of current flowing through the control input of the triac VS1;
  • Capacitors C1 and C2 are control components for the KR118PM1 microcircuit used in a typical switching circuit.

For simplicity and compactness of installation, resistors and capacitors are soldered directly to the legs of the microcircuit.

Triac VS1 can be any, with the following characteristics: maximum voltage up to 400 volts, minimum throughput current 25 amperes. The amount of current depends on the power of the angle grinder.

Due to the smooth start-up of the angle grinder, the current will not exceed the rated operating value of the selected power tool. For emergencies, such as a jammed disc of an angle grinder, a current reserve is required. Therefore, the nominal value in amperes should be doubled.

The ratings of the radio components used in the proposed wiring diagram were tested on an angle grinder with a power of 2 kW. The power reserve is up to 5 kW, this is due to the peculiarity of the operation of the KR118PM1 microcircuit.
Working scheme, repeatedly executed by home craftsmen.

Smooth start for do-it-yourself angle grinder. Saving you money and protecting your power tool

Due to the design features, the start of the angle grinder is associated with high dynamic loads. Due to the mass of the working disc, inertia forces act on the gearbox axis at the beginning of rotation. This entails some negative points:

  1. Axle loads during a sharp start create an inertial jerk, which, with a large diameter and mass of the disc, can tear the power tool out of the hands;

As a result, the brushes wear out and both windings of the electric motor overheat. By repeatedly turning the power tool on and off, overheating can melt the winding insulation and lead to a short circuit, with subsequent costly repairs.

High torque with a sharp set of revolutions prematurely wears out the gears of the reducer. Angle grinder;

In some cases, teeth may break off and the gearbox may jam.

Overloading the working disc can destroy it when starting the engine.

Therefore, a protective cover is required.

To better understand the mechanics of work, consider the device of the angle grinder in the drawing. All elements experiencing overload during a sharp start are clearly visible.

Schematic drawing of the arrangement of the working bodies and control systems in the angle grinder

To reduce the harmful effects of a sudden start, manufacturers produce an angle grinder with adjustable speed and smooth start.

The speed control is located on the tool handle

But only models of the middle and high price category are equipped with such a device. Many home craftsmen purchase an angle grinder without a regulator and slowing down the starting speed. This is especially true for powerful specimens with a cutting disc diameter of more than 200 mm. Such an angle grinder is not only difficult to hold in your hands during start-up, but mechanical and electrical wear occurs much faster.
There is only one way out. To install the smooth start of the angle grinder yourself. There are ready-made factory devices with a speed governor and a slowdown in engine start at startup.

Finished soft-start control device

Such blocks are installed inside the case, if there is free space. However, most users of the angle grinder prefer to make a soft start circuit for the angle grinder by themselves and plug it into the break in the supply cable.

How to make a do-it-yourself smooth start of an angle grinder

The popular circuit is implemented on the basis of the KR118PM1 phase control microcircuit, and the power section is made on triacs. Such a device is quite simple to install, does not require additional adjustment after assembly, and therefore, it can be made by a master without specialized education, it is enough to be able to hold a soldering iron in his hands.

Wiring diagram for soft start adjustment for angle grinder

The proposed unit can be connected to any power tool designed for 220 volts alternating voltage. A separate removal of the power button is not required, the modified power tool is turned on with a standard key. The circuit can be installed both inside the housing of the angle grinder, and also in the break of the supply cable in a separate housing.

The most practical way is to connect the softstarter to the outlet that powers the power tool. The input (connector ХР1) is powered from a 220 volt network. The outlet (XS1 connector) is connected to a supply socket, into which the plug of an angle grinder is inserted.

When the start button is closed, the angle grinder, voltage is supplied to the DA1 microcircuit through the common power supply circuit. A smooth increase in voltage occurs on the control capacitor. As it is charged, it reaches its working value. Due to this, the thyristors in the microcircuit do not open immediately, but with a delay, the time of which is determined by the charge of the capacitor. Triac VS1, controlled by thyristors, opens with the same pause.

Look with a detailed explanation of how to make and which scheme to apply

In each half cycle of the AC voltage, the delay decreases in arithmetic progression, resulting in a smooth increase in the voltage at the input to the power tool. This effect determines the smooth start of the angle grinder engine. Consequently, the disc speed increases gradually, and the gearbox shaft does not experience inertial shock.

The time to speed up to the operating value is determined by the capacity of the capacitor C2. The value of 47 μF provides a soft start in 2 seconds. With this delay, there is little discomfort for starting work with the tool, and at the same time, the power tool itself is not subjected to excessive stress from a sudden start.

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After turning off the angle grinder, the capacitor C2 is discharged by the resistance of the resistor R1. With a nominal 68 kOhm, the discharge time is 3 seconds. Then the soft starter is ready for a new start cycle of the angle grinder.
With a little modification, the circuit can be upgraded to an engine speed governor. For this, the resistor R1 is replaced with a variable resistor. By adjusting the resistance, we control the power of the engine by changing its speed.

Thus, in one housing it is possible to make an engine speed regulator and a soft starter for an electric tool.

The rest of the circuit details work as follows:

  • Resistor R2 controls the amount of current flowing through the control input of the triac VS1;
  • Capacitors C1 and C2 are control components for the KR118PM1 microcircuit used in a typical switching circuit.

For simplicity and compactness of installation, resistors and capacitors are soldered directly to the legs of the microcircuit.

Triac VS1 can be any, with the following characteristics: maximum voltage up to 400 volts, minimum throughput current 25 amperes. The amount of current depends on the power of the angle grinder.

Due to the smooth start-up of the angle grinder, the current will not exceed the rated operating value of the selected power tool. For emergencies, such as a jammed disc of an angle grinder, a current reserve is required. Therefore, the nominal value in amperes should be doubled.

The ratings of the radio components used in the proposed wiring diagram were tested on an angle grinder with a power of 2 kW. The power reserve is up to 5 kW, this is due to the peculiarity of the operation of the KR118PM1 microcircuit.
Working scheme, repeatedly executed by home craftsmen.

Smooth start and speed control

Smooth start-up of power tools 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 worn-out places of the spiral do not stand up and it burns out.

The same processes take place in the angle grinder. At the moment of switching on, the current rises sharply, because the driving forces need not only to move the armature, but also quickly gain the necessary speed. The effect of such a hard start can be the most deplorable. A winding break.

To reduce the likelihood of tool failure due to hard starting, it is necessary to modify the angle grinder and equip it with a small built-in soft starter.

Another improvement is the rotation regulator. Everyone knows from their own practice how inconvenient it is to work with a tool that does not have a rotation adjustment. If there is no such device in an electric drill, then it is difficult to choose the rotation speed and drill feed. This will either cause the drill to jam or break.

The lathe works in a similar way, in which there is a whole set of special gears for adjusting the spindle rotation. This largely affects not only the safety of the cutter, but also the quality of material processing.

Combine two advantages. Smooth start-up and shaft speed control using an electronic circuit. It is quite possible to assemble it yourself and install it directly into the machine body. With such a scheme, it will start smoothly without creating overloads in the windings and the network. And with the same scheme, it will be possible to adjust the speed in order to select the mode of operation with any material.

If you cut metal with significant thickness and hardness, then you need to maintain high speed. But when processing surfaces of low-melting materials, high speed will do more harm than help the cause. It needs to be reduced. It is dangerous to work with stones or tiles at high speed. And here it must be slowed down.

Even when grinding the disc, the rotation speed must be proportionally changed, because the linear speed of the disc edge will decrease. You cannot do without a speed regulator when working with a diamond cut disc, because at high temperatures it breaks down very quickly.

Everything suggests that if an angle grinder does not have a speed controller, then it must be made and installed in the machine.

Speed ​​controller for angle grinder: how to reduce speed and make a smooth start

The power tool in our workshop occupies one of the main places. Each electrical device performs all functions in accordance with technical data. What else would you like? I really want the tool not to fail for a longer time or not break at all. As a person gets used to a friend. A dog, so he gets used to an instrument.

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One of the basic tools is the angle grinder, which we call the angle grinder. It is a versatile tool that can cut, grind, clean the surface, saw boards and can be adapted to many more operations.

How to make a speed controller with your own hands

In order not to complicate the perception of the principle of operation in complex terms, the principle operation of the circuit can be explained simply. It has a sensing element that reads the amount of load. Depending on the read value, this element controls the shut-off device.

The principle of operation is similar to that of a water tap. In this case, you are the sensitive element that controls the water tap. The flow of water, depending on the need, becomes more or less. The same process takes place with the current.

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It is necessary to correctly understand the moment that we will in no way be able to increase the rotation speed more than that indicated in the characteristics of the angle grinder. We can only lower the turnover. If the maximum revs are 3000, then the range in which we can adjust the revs will be below this value.

In its simplest form, you can use a thyristor-based regulator circuit. He will feel and regulate. Two in one. This diagram has only five parts. It is very compact and fits easily into the case. Such a regulator will not work from zero rpm, but this is not necessary for an angle grinder.

If lower speeds are needed in the work, then it is necessary to use a different circuit on an integrated microcircuit, where the triac will be the locking element. Such a scheme will be able to regulate the speed from almost zero to the desired value.

And in that, and in another scheme, the main load falls on the shut-off element. It should be rated for voltages up to 600 V and for 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 the details of the thyristor circuit can be placed on a printed circuit board or simply by surface mounting. According to the second option, the parts are soldered on the printed circuit board. The printed circuit board can be manufactured in different ways. It can be etched out of foil-coated PCB, you can even cut it with a cutter, but it will turn out very rough. In principle, she can be asked to make a familiar radio amateur for a very modest remuneration.

When the finished board is ready, you need to choose a convenient place in the case of the angle grinder to install it. It is desirable 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, you need to check it. To do this, instead of an angle grinder, an ordinary incandescent lamp must be connected to the output. A copy with a power of 60. 40 W at 220 V. The efficiency will be obvious by changing the glow of the light bulb.

Now it remains to mount the device in the selected place and make a test run of the angle grinder. It will stop breaking out of your hands during start-up, and the speed will be smoothly adjusted by rotating the regulator.

What it is?

In angle grinders with a speed controller, collector motors with series excitation are used. They can operate on direct or alternating current. A motor of this type is easily controlled by changing the current in the circuit.

Due to the fact that modern regulators use key impulse control, they heat very little and can be built into the body of even a small-sized instrument. For regulation, a potentiometer is used, the knob of which is displayed on the handle of the machine.

Assembly order

It is best to use printed wiring for assembly. It holds the parts firmly. The diagram above is drawn in such a way that it can tell you how to arrange the parts. All the pins of the microcircuit go from the key in a circle in ascending order. Due to the need to cool the triac, the board size cannot be smaller than a matchbox.

It will be necessary to cool the triac, since in more or less powerful models, the angle grinder will drop about 10-15 W of power on it. Therefore, it is necessary to provide a place for an aluminum radiator for a triac. On a sheet of paper in full size, a wiring diagram is drawn and, with the help of a punch, the holes for the leads of the parts are transferred to a workpiece made of foil-coated PCB. The holes are drilled with a mini-drill with a diameter suitable for the conclusions of the parts.

Then, from the side opposite to the installation of the parts, carefully draw paths with nitro-lacquer, trying not to close them with each other. After drying, the board is etched with a solution of ferric chloride, or copper sulfate with ordinary kitchen salt. The etched board must be thoroughly rinsed with plenty of water and dried. The dried board is tinned using rosin and solder.

The pins of the parts are also tinned before being sealed into the board, trying not to overheat the semiconductor parts, especially the microcircuit. Before tinning, you can wipe the leads with alcohol, this can greatly facilitate the quality of tinning, especially if the leads were touched with your hands.

Features of mounting a finished block

When assembling the regulator into the case, you need to be careful not to overdo it with the density of the elements on the board. Otherwise, short circuits or overheating of elements are possible.

When assembled in a separate box, you can use an outlet or extension casing. This is a convenient and common option. In this case, it is imperative to somehow mark the finished product so as not to confuse it with a simple extension cord. Exceeding the load can burn the triac and current sensor R9.

If you use the option of embedding the regulator in the cord with an angle grinder, then here you need to take care of tightly inserting the cords into the body, using a rubber seal. This is necessary to avoid twisting the wires and getting moisture or metal dust into the case. It is desirable to protect the axis or wheel of potentiometer R2 at least from dust.