Angle grinder (grinder) MAKITA GA4530 without soft start. Photo 220Volt
When buying a cheap angle grinder, it will probably not have a soft start option . During startup, especially with a powerful angle grinder, you can feel all the “delights” of the jerk that the grinder produces when turned on. If you have a soft starter, the power tool will begin to do its job in a comfortable environment for the user . Undoubtedly, an angle grinder with this option costs more. However, it is possible to install a soft starter on the angle grinder yourself. This will solve the issues of saving money and will facilitate further operation - a device made by yourself is easier to repair if it fails.
Device
In grinders without a soft start, the windings of the commutator motor are immediately supplied with a 220 V mains voltage , and to bring it into working condition an increased starting current is required. The soft starter ensures a gradual increase in voltage and, accordingly, the current during startup also does not increase abruptly.
This starting mode can be achieved using a special electronic circuit . Its main component is a semiconductor chip , which controls another, more powerful semiconductor device, a triac, which supplies power to the electric drive of the angle grinder. The thyristors of the microcircuit operate with a delay in the supply voltage until the circuit capacitor is fully charged. The principle of operation of the microcircuit is successfully combined with ensuring a smooth start of angle grinders.
Microcircuits k1182, LM358
The most famous microcircuit for the K1182 soft starter. This microcircuit was created back in Soviet times and now it is not so easy to find. There are other more affordable chips, for example, LM358. Many modern angle grinders use the LM358 chip in the factory version of the device.
LM358 chip
Choosing a Miter Saw
It is impossible to imagine the woodworking industry without the use of special tools. One popular tool is a miter saw. Already from the name it becomes clear that its main purpose is to process the ends of workpieces, that is, to cut wood crosswise. This differs from a circular saw, which is used for longitudinal cuts.
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Understanding how to choose a miter saw is not a very difficult matter, but only if you understand the basic concepts and characteristics. Either way, a consultant will help you, but the process will go faster if you know what questions to ask. Further in the article we will look at the design of miter saws, their technical characteristics, additional functions and consumables.
Protective cover
The protective cover serves to protect the operator during operation. Even when the saw is turned on, a special casing covers the blade. As the workpiece is immersed, the casing moves away, revealing the disk.
Asynchronous motor
Among all types of motors, asynchronous is considered the most economical. It is reliable and makes little noise. Asynchronous motors are reliable because they have a minimum number of rubbing elements. This allows them to heat up little and not wear out for a long time - the only part that is subject to wear is the bearings.
Among the disadvantages is the high weight-to-power ratio. An asynchronous motor with a power of about 2 kW will weigh about 20 kg. This imposes some restrictions on its use, since using an overly heavy tool is not very convenient. In addition, when operating on electricity at industrial frequency, the engine will not be able to develop a rotor speed above 2850 rpm.
Laser guide
The presence of a laser allows you to see the trajectory along which the cut will take place
This is important when cutting at an angle, as you will spend less time preparing for work
Operating principle
The soft start device in a factory-made angle grinder is located inside the angle grinder body and is connected by contacts to the power button and the stator windings of the electric drive. It takes a certain time for the angle grinder to reach its nominal mode, and the electromagnetic field created by the uniformly increasing current and voltage through the stator windings causes the armature of the angle grinder drive to smoothly gain speed.
For grinders where the manufacturer does not provide such a device, usually in very rare cases it is possible to hide it under the body of the grinder. Most often it is performed in the form of a separate block, arranged in a break in the power cable circuit. However, this does not change the principle of operation.
Double-sided cut
Quite often, when attaching a sheet to a profile in difficult places, it is necessary to perform a double-sided cut. This method is used when designing window openings, door openings, and, if necessary, bypassing beams and other complex structures. What is the best way to cut drywall in this case? First you need to make a hole of a rectangular or square shape. You can cut it using such a simple tool as a hacksaw or a sharp knife. The cutting process is not difficult:
- First you need to mark the sheet with a simple pencil and ruler;
- on one side the sheet must be cut using a hacksaw, and on the other using a knife;
- Now the drywall is cracking and being cut off on one side.
Afterwards, you need to carefully process the edge using a roughing plane to get smooth edges. When the sheet is cut, you can fix it in the required place using self-tapping screws. After installation, joints and seams are puttied and pre-glued with a special mesh.
Disadvantages of angle grinders without soft start
Cordless angle grinder Metabo W 18 LTX 125 602174850 with soft start. Photo VseInstruments.ru
In addition to providing comfortable working conditions for the user, the angle grinder with soft start has a number of other advantages.
- The absence of a large starting current during the soft start of the angle grinder , which is several times higher than the nominal value of this parameter during operation, increases the reliability of the electrical part of the power tool. In this case, the winding wires do not experience overloads and do not crack, the commutator lamellas and brushes are not subject to wear from increased sparking, and processes that worsen the connection do not occur at the contact points.
- During a uniform increase in the speed to the nominal value, the angle grinder with a soft start does not experience increased dynamic loads that arise in its absence. An instantaneous acceleration of 6000 rpm or more does not leave its mark on the gear transmission and bearing units . They fail faster, so angle grinders without such a device are more often repaired.
Application in an angle grinder
During startup of an angle grinder (angle grinder), high dynamic loads occur on the tool parts.
Expensive models are equipped with soft starters, but not simple varieties, for example, angle grinders. An inertial jerk can tear an angle grinder out of your hands, and with all this there is a threat to life and health. In addition, when starting the electric motor of the tool, an overcurrent occurs and as a result, wear of the brushes and significant heating of the stator windings, the gearbox wears out and the cutting disc may be destroyed, which can crack at any moment and cause harm to health, and maybe even life. The tool must be secured and for this you should make an angle grinder with adjustable speed and smooth start with your own hands.
The simplest scheme
A soft starter with speed control on a thyristor KU 202 has received widespread use due to its very simple design (diagram 1). Its connection does not require any special abilities. It’s painfully easy to get radio elements for it. This regulator model consists of a diode bridge, a variable resistor (plays the role of a U regulator) and a thyristor option circuit (supplying U to the control output with a nominal value of 6.3 volts) from a Russian manufacturer.
Due to the size and number of parts, this type of regulator can be built into the body of a power tool. In addition, the variable resistor knob should be removed and the speed controller itself can be modified by installing a button in front of the diode bridge.
The main mechanism of operation is to regulate the speed of the electric motor of the tool by limiting the power in manual mode. This circuit allows you to use power tools with a power of up to 1.5 kW. To increase this indicator, you need to change the thyristor to a more powerful one (information about this can be found on the Internet or in a reference book). In addition, Honor also needs the fact that the thyristor control circuit will differ from the initial one. KU 202 is a good thyristor, but its significant drawback lies in its configuration (selection of parts for the control circuit). To implement a smooth start in automatic mode, circuit 2 (soft starter on a chip) is used.
Extension cord upgrade process
First, we disassemble the electrical extension cord and make a hole in the housing for a new wire, which will be connected to an external socket. We clean PVA 3 × 2.5 from both ends.
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How to make a starter unit for a power tool
There are quite a lot of options for independently equipping an angle grinder with a soft start device. Some of them are presented in the author's videos.
Starter unit based on LM358 chip
In the following video, the author shares his experience of independently manufacturing a soft-starter board according to a diagram taken from the Internet, based on the LM358 chip . The author made the housing for the board from a shampoo box, which speaks of the rich imagination of amateur craftsmen. The author did not just blindly copy the circuit from the Internet, but modified it by replacing the characteristics of some of its elements : transistors, diodes, resistors. The radiator for cooling semiconductor devices is taken from a tape recorder. In order to be able to place the soft start unit inside the body of the angle grinder, and not as in the case of the proposed option, a smaller board was developed.
Technology of work on the manufacture of the starting unit
The author of the following video describes in detail the work methods, components used and auxiliary technological materials for the manufacture of a soft starter. the k1182 microcircuit is taken as the basic element . The technology is not designed for use as the basis of a printed circuit board; the author calls such an assembly “surround mounting” technology. In this type of work, in addition to soldering, individual elements are fastened using fasteners, for example, this is how a triac is attached to a heat sink. The ready-made launcher is not universal for all angle grinders. On two angle grinders taken separately by the author, they reached the operating mode in significantly different periods of time.
One of the layout options for a homemade launch unit
As the initial option, the author of the following video chose a well-known assembly with the LM358 chip . Since the assembled starting unit did not fit inside the body of the angle grinder, the author “packed” only a triac with a radiator inside, due to good cooling conditions from the angle grinder’s fan wheel. The rest of the block, together with the microcircuit, was secured to the body of the angle grinder.
Using an iron as an additional load to reduce the speed of an angle grinder
This method does not specifically relate to the topic of soft start of an angle grinder. However, to understand the principle of operation of an electronic device, a dimmer , which is used to adjust the power (or number of revolutions) of an angle grinder, is quite acceptable. In the next video, the iron takes a certain power from the angle grinder, thereby reducing its speed.
The typical starter circuit diagram should be modified for each individual power tool
The author of the following video tells how he equipped his household grinder with a soft start device to increase its service life.
Important: the circuit may work perfectly for adjusting the brightness of the lamp, but for the necessary functioning of the angle grinder, upon startup, be unable to perform the task. To operate effectively, it must be “customized ,” namely, select the required resistor values, capacitor values, and possibly change the characteristics of semiconductor devices.
How to install a standard dimmer in an angle grinder to adjust speed
In the next video, the author modified the power button (made it spring-loaded) in order to use the capabilities of a purchased dimmer to adjust the speed of the angle grinder. After turning on the angle grinder, moving the button sets the required speed mode. The dimmer fixes this mode and when turned on again, it is set.
Modification for grinders interskol with a 15 A triac
Soft start for a device with 15 A triacs is considered universal and is often found in low-power types. The difference between the devices is their low conductivity. The circuit (device) for such a start involves the use of transceivers of a certain type, which operate at a frequency of forty Hz. Many species use comparators. Such parts are supplied with filters. The rated voltage of starters starts from 200 V.
Starters for angle grinders with a 20 A triac
Devices with 20 A triacs are suitable for professional grinders. Many types use special resistors. First of all, they can operate at high frequencies. The maximum temperature of the starters is fifty-five degrees. Most devices have a well-protected case. The classic scheme involves the use of 3 contactors with a capacity of thirty pF or more. Craftsmen believe that the devices stand out for their conductivity.
- The lowest frequency for starters is about thirty-five Hz. They can operate in a DC network. The model is connected via adapters. Such devices are perfect for two hundred W motors. Filters are very often installed with triodes. Their sensitivity indicator is 300 mV and no more.
- Quite often you can find special comparators with a protection system. If you look at foreign models, they have an integrated converter that comes with insulators. Current conductivity is produced at around five microns. With a resistance of forty ohms, the model can maintain high speeds for a long time.
Models for angle grinder 600 W
- For 600 W instruments, use starters with contact triacs; they have an overload of no more than ten A. Also remember that there are many devices with plates. They are good for their security and will not be afraid of rising temperatures. The minimum frequency for 600 W devices is 30 Hz. In this case, the resistance will depend on the supplied triode. If it is used linear type, then the above parameter will not exceed 50 Ohms.
- If we talk about duplex triodes, then the resistance at high speeds can reach up to 80 Ohms. Very rarely, models may have stabilizers that operate from comparators. In most cases, they are attached directly to the modules. Some types are created with wired transistors. Their lowest frequency starts from five Hz. They are afraid of overload, but can maintain huge speeds at 220 volts.
Devices for grinders at 800 volts
800 W devices can operate with low frequency starters. Triacs are often used at fifteen A. If you look at the diagram of the models, you should notice that they use special transistors whose current carrying capacity starts from 45 microns. Capacitors are used with or without filters, and the capacitance of the parts is no more than three pF. It is also worth knowing that starters may differ in sensitivity. Lever with speed control and soft start. Angle grinder Makita GA5030. The Makita grinder with speed control is one of the most popular models. The range of rotation adjustment will depend entirely on the maximum diameter of the nozzle.
Remember that there is a high probability of breakdown of the electric motor and breakdown of the device after not a soft start, but a sharp, jerky start. Therefore, it is better to make a limiter, fulfilling the restrictions can directly protect the engine. The device should also have a commutator motor, not an asynchronous one, so that everything can be safely turned off. The block is needed to supply power to the switching relays.
Well, and most importantly, the start button must be installed correctly, and even better, look at the electrical diagram before creating your own device. It is better to carry out repairs of models kr1182pm1, xs, 12, d3 carefully, because such devices are expensive.
How to connect, installation
For users of grinders who do not have electrical installation skills, you can purchase a separately sold soft start unit. You just need to install it correctly. There are two options for placing the starting device - inside the body of the angle grinder and, if not possible, outside.
In the next video, the author placed one of the purchased blocks inside it with the help of a slight modification of the angle grinder body. The two wires of the starting unit are connected according to the following diagram: one wire to the switch contact, the other to the stator winding of the electric drive.
In another video, the author also managed to place the purchased block inside the grinder. However, he chose a different connection scheme - to break the network. In this case, it is not important to consider where to connect the “zero” and where the “phase”.
How to check
At home, before assembling an angle grinder with a soft starter, it’s a good idea to check it for an open circuit. The following video tests a three-pin device. Usually there is a connection diagram . There are two network wires here, one goes to the electric drive. If you assemble a circuit with an indicator light and include a starter in it, then you can determine the break in it by the indicator light coming on/not coming on .
Star connection and its advantages
Reversible motor circuit 380 to 220 Volts
Each of the three working windings of the electric motor has two terminals - the beginning and the end, respectively. The ends of all three windings are connected to one common point, the so-called neutral.
If there is a neutral wire in the circuit, the circuit is called 4-wire, otherwise, it will be considered 3-wire.
The beginning of the terminals is connected to the corresponding phases of the supply network. The applied voltage on such phases is 380 V, less often 660 V.
The main advantages of using the star scheme:
- Stable and long-term non-stop operation of the engine;
- Increased reliability and durability by reducing equipment power;
- Maximum smooth start-up of the electric drive;
- Possibility of exposure to short-term overload;
- During operation, the equipment housing does not overheat.
There is equipment with internal connection of the ends of the windings. Only three pins will be output to the block of such equipment, which does not allow the use of other connection methods. Electrical equipment made in this form does not require competent specialists for its connection.
Connecting a three-phase motor to a single-phase network using a star circuit
