Scheme of soft start of a power tool on a triac. How to connect a soft start on an angle grinder
This article will discuss the scheme soft start grinders from available parts. Since the soft start is not installed in the whole tool, this can be fixed and you can independently assemble a simple soft start circuit for the grinder and do it yourself. This device will help upgrade your tool and make it less dangerous and more convenient.
If you often work with a tool, then you probably encountered the following problem: the engine, whether it be a grinder, a circular saw, a planer or other equipment, starts up very sharply. Such a sharp start is fraught with many troubles: firstly, there is a high starting current, which does not affect the wiring in the best way, secondly, a sharp start of the engine quickly wears out the mechanical parts of the tool, thirdly, ease of use decreases, when starting the grinder you have to hold on tight, she strives to break out of her hands. In expensive models, a soft start system is already built in, which easily copes with all these troubles. But what if this system does not exist? There is a way out - to assemble a soft start circuit yourself. In addition, it will be possible to use it with incandescent bulbs, because most often they burn out at the moment of switching on. A soft start will significantly reduce the possibility of a light bulb to burn out quickly.
Soft start circuit
On the Internet, there is often a soft start circuit built on a rather rare domestic K1182PM1R chip, which is not always easy to get now. That is why I propose to assemble an equally effective circuit, the key element of which is the affordable TL072 chip, you can also put the LM358 instead. The time for which the engine gains full speed is set by capacitor C1. The larger its capacity, the more time it takes to overclock, the most optimal option is 2.2 microfarads. Capacitors C1 and C2 must be rated for at least 50 volts. Capacitor C5 - at least 400 volts. Resistor R11 will dissipate a decent amount of heat, so its power must be at least 1 watt. Any low-power transistors can be used in the circuit, T1, T2, T4 have an n-p-n structure, you can use BC457 or domestic KT3102, T4 has p-n-p structure, BC557 or KT3107 will do in its place. T5 - any suitable seven-storer in terms of power and voltage, for example, BTA12 or TC-122.
Soft start manufacturing
The circuit is assembled on a 45 x 35 mm printed circuit board, the board is routed as compactly as possible so that it can be built into the body of a tool that requires a soft start. It is better to solder the power wires directly to the board, but if the load power is small, then you can install terminal blocks, as I did. The board is made by the LUT method, photos of the process are presented below.
It is advisable to tin the tracks before soldering the parts, so their conductivity will improve. The microcircuit can be installed in the socket, then it can be easily removed from the board. Resistors, diodes, small capacitors are soldered first, and then the largest components. After the assembly of the board is completed, it must be checked for correct installation, ring the tracks, wash the remaining flux.
First launch and testing
After the board is completely ready, you can check it for operability. First of all, you need to find a low-power light bulb for 5-10 watts and plug it into the board into the 220 volt network through it. Those. the board and the light bulb are connected to the network in series, and the OUT output remains unconnected. If nothing burned out on the board, and the light did not light up, you can turn on the circuit directly to the network. The same low-power light bulb can be connected to the OUT terminal for testing. When connected, it should smoothly dial up the brightness to the maximum. If the circuit is working properly, more powerful electrical appliances can be connected. With prolonged operation, the sevenistor will probably heat up slightly - there is nothing to worry about. If there is free space, it does not hurt to install it on a radiator.
Dangerous mains voltage is present on the board during operation, so safety precautions must be observed. In no case should you touch the parts of the board when it is connected to the network. Before turning on, make sure that the board is securely fixed and that no metal objects that can lead to a short circuit will fall on it. For reliability, it is recommended to fill the board with varnish or epoxy, then even moisture will not be afraid of it. Successful assembly!
Soft start video
Many power tools fail due to motor wear. At modern models Bulgarians have a soft starter. Due to him, they are ways to work for a long time. The principle of operation of the element is based on changing the operating frequency. In order to learn more about the launcher, it is worth considering the diagram of the standard model.
Soft starter
The standard soft start circuit of an angle grinder consists of a triac, a rectifier unit and a set of capacitors. To increase the operating frequency, resistors are used that pass current in one direction. The starter is protected by a compact filter. models are supported low. However, in this case, much depends on the maximum power of the motor, which is installed in the grinder.
How to connect the model?
The connection of the soft start grinder is carried out through an adapter. Its input contacts are connected to the rectifier unit. It is important to determine the zero phase in the device. To secure the contacts, you will need to check the performance of the starter through the tester. First of all, negative resistance is determined. When installing a starter, it is important to remember the threshold voltage that the device can withstand.
Diagram of a device for a grinder with a 10 A triac
The soft start circuit of the grinder, made by hand, involves the use of contact resistors. The polarity coefficient for modifications, as a rule, does not exceed 55%. Many models are made with blockers. A wire filter is responsible for protecting the device. Low frequency transceivers are used to pass current. The process of lowering the threshold voltage is carried out on the transistor. The triac in this case acts as a stabilizer. When connecting the model, the output resistance at an overload of 10 A should be about 55 ohms. Covers for starters are suitable on a semiconductor basis. In some cases, magnetic transceivers are installed. They handle low speeds well and can maintain the nominal frequency.
Model for angle grinders with 15 A triac
A soft start for an angle grinder with 15 A triacs is universal and is often found in low-power models. The difference between the devices lies in the low conductivity. The soft start circuit (device) of the grinder involves the use of contact-type transceivers that operate at a frequency of 40 Hz. Many models use comparators. These elements are set with filters. The rated voltage of the starters starts from 200 V.
Starters for angle grinders with triac 20 A
Devices with 20 A triacs are suitable for professional grinders. Many models use contactor resistors. First of all, they are able to work at high frequency. The maximum temperature of the starters is 55 degrees. Most models have a well-protected case. The standard scheme of the device involves the use of three contactors with a capacity of 30 pF. Experts say that devices stand out for their conductivity.
The minimum frequency for starters is 35 Hz. They can work online direct current. Connection of modifications is carried out through adapters. For 200 W motors, such devices are well suited. Filters are quite often installed with triodes. Their sensitivity index is no more than 300 mV. Quite often there are wired comparators with a protection system. If we consider imported models, then they have an integrated converter, which is installed with insulators. Current conductivity is provided at around 5 microns. With a resistance of 40 ohms, the model is able to stably maintain high speeds.
Models for grinder 600 W
For grinders at 600 W, starters with contact triacs are used, in which the overload does not exceed 10 A. It is also worth noting that there are many devices with linings. They stand out for their security and are not afraid of high temperatures. The minimum frequency for grinders at 600 W is 30 Hz. In this case, the resistance depends on the installed triode. If it is applied linear type, then the above parameter does 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 have stabilizers that work from comparators. Most often they are attached directly to the modules. Some modifications are made with wired transistors. Their minimum frequency starts from 5 Hz. They are afraid of overloads, but are able to maintain high speeds at
Devices for grinders at 800 W
Bulgarians for 800 W work with low frequency starters. Triacs are quite often used at 15 A. If we talk about the circuit of models, it is worth noting that they use expansion transistors, in which throughput current starts from 45 microns. Capacitors are used with and without filters, and the capacitance of the elements is no more than 3 pF. It is also worth noting that starters differ in sensitivity.
If we consider professional angle grinders, then 400 mV modifications are suitable for them. In this case, the current conductivity can be low. There are also devices with variable transistors. They warm up quickly, but are not able to maintain high speeds of the grinder, and their current conductivity is about 4 microns. If we talk about other parameters, then the rated voltage starts from 230 V. The minimum frequency for models with broadband triacs is 55 Hz.
Starters for grinders 1000 W
Starters for these angle grinders are made on triacs with an overload of 20 A. The standard device circuit includes a triode, a stabilizer lining and three transistors. The rectifier unit is most often installed on a wire basis. Capacitors can be used with or without a filter. The minimum frequency of the conventional model is 30 Hz. With a resistance of 40 ohms, starters are able to support large overloads. However, problems may arise at low speed grinders.
How to make a starter from a triac TS-122-25?
Making a soft start for a grinder with your own hands with a triac TS-122-25 is quite simple. First of all, it is recommended to prepare a contactor resistor. Capacitors will be required of a single-pole type. In total, three elements are installed in the starter. The capacitance of one capacitor should not exceed 5 pF. To increase the operating frequency, a contactor is soldered on the plate. Some experts say that it is possible to increase conductivity through filters.
The rectifier unit is used with a conductivity of 50 microns. It is able to withstand large overloads and will be able to provide high speeds. Next, in order to assemble a soft start on the grinder with your own hands, a thyristor is installed. At the end of the work, the model is connected through an adapter.
Assembling the model with triacs of the VS1 series
You can assemble a soft start for an angle grinder on a VS1 triac with your own hands using several rectifier blocks. Capacitors for the device are suitable linear type with a capacity of 40 pF. It is worth starting the assembly of the modification by soldering the resistors. The capacitors are installed in series between the insulators. The rated voltage of a quality starter is 200 V.
Further, in order to make a soft start for the grinder with your own hands, a prepared triac is taken and soldered at the beginning of the circuit. Its minimum operating frequency should be 30 Hz. In this case, the tester must show a value of 50 ohms. If there are problems with overheating of capacitors, then dipole filters should be used.
Model for angle grinders with regulator KR1182PM1
To assemble a soft start for a grinder with your own hands with the KR1182PM1 regulator, a contact thyristor and a rectifier unit are taken. It is more expedient to use a triode for two filters. It is also worth noting that three capacitors with a capacity of at least 40 pF are required to assemble the starter.
The sensitivity index of the elements must be 300 mV. Experts say that the triac can be installed behind the lining. It must also be remembered that the threshold voltage should not fall below 200 V. Otherwise, the model will not be able to work at a reduced speed grinder.
When starting an electric motor, a starting torque occurs, which sags the voltage due to the occurrence of starting currents. They are 9 times higher than the operating currents. This has a bad effect on the stable operation of electrical appliances, reduces the life of the engine. This is because the start of the engine begins to be delayed and its windings overheat. Experts advise adding devices to the motor network that can make it start smoothly. Home craftsmen also learned how to make do-it-yourself devices for soft starting an electric motor.
Overloads at start of electric motors
The moment of starting is the beginning of the movement of the motor shaft connected to the transmission devices. At this point, the motion of the rotor is rather unstable. Transmission mechanisms make the shaft rotate under heavy load. Such instability will inevitably lead to impact loads, and this has a bad effect on the transmission devices. This greatly affects the key of the motor shaft and the gearbox.
The soft start device smoothes the loads at start-up. The movement of the shaft starts with very small revolutions, and the speed gradually increases. This means that there are no shocks and loads on the transmission mechanisms. This is the principle of operation of the soft start of the electric motor.
It is worth noting that soft start devices that are manufactured in factories are universal devices. They can be used for various tasks. First of all, this is a smooth start of the electric motor, its gradual braking, protection of the electrical network and devices from dangerous overloads. Anyone can find a suitable product for certain tasks. Such devices have the big disadvantage is the high cost. But you can make a soft starter for an electric motor with your own hands, spending the minimum amount on this Money and time.
DIY soft start device
It is worth considering the type of soft start device for an asynchronous electric motor using the KR1182P chip. It is necessary for a three-phase electric motor with a voltage of 380 volts.
It has some useful features that are worth describing:
- The windings in an electric motor are connected in a star.
- The output keys are powerful thyristors connected in parallel-counter circuit.
- Damping chains are included in the circuit in parallel with the thyristors. Here they are applied purposefully. Their main task is to prevent false switching of thyristors.
- Varistors are necessary to absorb the switching interference that occurs in the circuit.
present in the chain and power unit, which consists of a rectifier, capacitor and transformer. A similar block is needed to provide power to the switching relays. After rectifier bridge stands at the exit integrated stabilizer. It provides a stable voltage of 12 volts at the output. Additionally, it is able to provide protection against short circuits and various overloads.
How to make a power tool soft starter yourself
Brief description of the device
The most common circuit is made using a control phase control microcircuits KR118PM1, and its power circuit is implemented on triacs. Such a device is quite easy to assemble and does not require long settings after installation. Therefore, a person without special skills is capable of doing it. You just need to know how to use an electric soldering iron.
Such a device can be connected to all types of power tools that powered by AC. An additional removal of the power toggle switch is not needed here, since the upgraded electric tool will turn on from the factory button. This device can be placed inside the grinder or in the break of the power cord in a homemade case. The most popular is to connect the soft starter directly to the outlet that feeds the electric tool. The input connector receives power from a 220-volt network, and a socket is connected to the output connector, which will power the angle grinder.
When the start button of the angle grinder closes, then according to the power circuit, current will be supplied to the control microcircuit. The control capacitor will gradually accumulate voltage and as it charges, it will reach the required operating value. After that, the thyristors under the control of the microcircuit will not open immediately, but with a slight delay, the value of which depends on the charge of the capacitor. The thyristor-controlled triac will open after the same amount of time.
With each half-cycle of the alternating voltage, the delay time decreases according to the law arithmetic progression. As a result of this, the value of the voltage supplied to the angle grinder gradually increases. A similar effect and provides a smooth start of the motor of the power tool. Thus, its speed increases smoothly, and the gearbox shaft is not subjected to inertial loads.
The amount of time to gain speed to the required value depends on the capacitance of the input capacitor. The 46 microfarad capacitance is able to provide a smooth start in 3 seconds. With such a delay, there is no strong discomfort at the beginning of working with the grinder, and she herself will not be subject to heavy loads from a sudden start.
When the power tool is turned off, the input capacitor begins to discharge using a special resistor. Using a resistance rating of 67 kilohms, the amount of time to fully discharge is no more than 4 seconds. The soft starter is then ready again for a new start of the power tool.
With a little work, such a scheme can be improved to a high-quality motor speed controller. You need to change the discharge resistor to a variable resistance. By adjusting it, you can control the maximum power of the motor, thereby changing the speed. In other words, in a single case, it becomes possible to manufacture a soft start device for an angle grinder and a motor speed controller.
The main elements of such a device work like this:
- The resistor is able to control the value of the current that flows through the control output of the triac.
- Two capacitors help control the chip, which are used in the factory wiring diagram.
- To compactly and easily make the installation, it is necessary to solder the capacitors and resistors directly to the legs of the microcircuit.
- The triac can be installed absolutely anyone, but with certain technical characteristics. The allowable voltage should be up to 380 volts, and the smallest throughput current must be at least 24 amperes. The value of the current directly depends on the maximum power of the grinder.
Due to the soft start of the power tool, the current value will not be higher than the nominal value for a particular tool model. In emergency situations, for example, jamming of the cutting disc of an angle grinder, a certain margin in terms of current value is simply necessary. That is why the rated current must be at least doubled.
The disadvantage of small cheap angle grinders is the lack of a soft start and speed control. Everyone who turned on a powerful electrical appliance in the network noticed how the brightness of the network lighting drops at that moment. This is due to the fact that powerful electrical appliances at the time of startup consume a huge current, respectively, the voltage in the network sags. The instrument itself can fail, especially Chinese ones with unreliable windings.
The soft start system will protect both the network and the tool. Also, there will be no strong kickback (shock) at the moment of switching on. And the speed controller will allow you to work for a long time without overloading the tool.
The presented scheme is copied from an industrial design, installed on expensive devices. It can be used not only for a grinder, but also for a drill, milling machine, etc., where there is a collector motor. For asynchronous motors, the circuit is not suitable; a frequency converter is required there.
First, I drew a printed circuit board for a soft starter system, without components for speed control. This is done on purpose, because. In any case, the regulator must be wired. Having a diagram, everyone will figure out what to connect where.
In the circuit, the regulating element is the dual operational amplifier LM358, which controls the power triac BTA20-600 through the transistor VD1. I did not get it in the store and put BTA28 (more powerful). For a tool up to 1kW, any triac with a voltage of more than 600V and a current of 10-12A is suitable. Because the circuit has a soft start, then the starting currents will not burn such a triac. During operation, the triac heats up and should be installed on a radiator.
The phenomenon of self-induction is known, which is observed when the circuit is opened with an inductive load. In our circuit, the R1-C1 circuit extinguishes self-induction when the grinder is turned off and protects the triac from breakdown. R1 from 47 to 68 ohms, power 1-2W. Film Capacitor 400V.
Resistor R2 provides current limiting for the low voltage part of the control circuit. This part itself is both a load and, to some extent, a stabilizing link. Due to this, after the resistor, you can not stabilize the power. Although there is a variant of the same circuit with an additional zener diode. I did not install it, because. the supply voltage of the microcircuit, so, is within the normal range.
Possible replacements for low-power transistors are indicated below the diagram.
The adjustment of the regulator is done using a multi-turn resistor R14, and the main adjustment is done with a resistor R5. The circuit does not give power adjustment from 0, but only from 30 to 100%. If you need a simpler powerful regulator from 0, then you can assemble a variant that has been proven over the years. True, for an angle grinder, getting the minimum power is pointless.
We check the performance of the circuit by connecting a 220V light bulb with a power of 40-60W. If the brightness is adjustable, then disconnected from the network we check the triac for heat dissipation by touch. It must remain cold. Next, we connect the board to the grinder and check the smooth start-up and speed control without load. If everything is in order, we proceed to testing under load.
So a cheap grinder turned into a medium-level tool.
Assembly Components
- LM358 can be bought
- S9014 can be bought
A grinder, or a grinder, is often simply necessary on the farm to perform metal work. In addition, it can be used to clean both wood and stone materials. It is difficult to imagine the performance of industrial work without a grinder. This is a tool that will suit both a professional in his work and an amateur in household chores.
When doing do-it-yourself work, it is important that the power tool has a soft start. This is especially true if you often have to work, and the network does not withstand the voltage of the tool.
Budget options for angle grinders - angle grinders - have a number of disadvantages:
- The power tool does not have the possibility of a smooth, soft start. This can lead to power outages, as the angle grinder consumes a large amount of electricity in the first seconds after being turned on. There is also a huge probability of damage to the electric motor and breakage of the tool after it is not a soft start, but a sharp, jerky one.
- A power tool, especially a simple Chinese one, does not have a speed controller (by adjusting the speed, you can ensure the long operation of the tool without load on it).
Therefore, when choosing a tool, it is very important to pay attention to parameters such as speed control and the presence of a soft start. In addition, when choosing an angle grinder, you should pay attention to power. Here the main indicator is the volume of work performed.
If the work is not large-scale and not frequent at the household level, then a power tool with an adjustment of 125 mm and a power between 600-900 watts is suitable.
For volumetric work on an industrial scale, angle grinders should be used about twice as powerful. More to the main indicators except specifications, refers to safety. Bulgarian should be safe. What does it mean? Firstly, as already mentioned, the presence of a soft start, which prevents power surges during switching on. Automatic fuses necessary for an emergency stop of the motor during a system failure. The fuses serve as a regulator when the wheel is stuck. Provides dust protection. It is necessary with frequent use of the grinder so that dust does not accumulate in the tool.
The heat dissipation function is important. The heat sink protects against overheating. During operation, especially if the work is long, the body of the machine is subject to strong heating, so that there is no overheating and heat dissipation is necessary. When overloaded, the angle grinder stops - this happens during heating approaching 200 ° C. Well, balancing the disk serves to reduce unpleasant vibration and beating of the tool during operation, old worn disks are especially susceptible to this effect. Paying attention and paying attention to safety when choosing a tool and when working with it is very important.
When choosing a tool, it is worth noting that there are angle grinders with one and two handles. Here you should rely solely on convenience. Two-handed models are likely to be more comfortable to hold, however, such tools are heavier in weight, one-handed models will also have to be held with two hands, but such angle grinders are smaller in size and weight.
Bosch is the market leader in power tools. The tools of this company have all the necessary characteristics from convenience to safety. Also, the advantages of Bosch tools is that there is good ventilation.
Bt136 600E: voltage regulation switching circuit
Cheap grinders that do not have enough power, manufacturers do not burden with voltage regulation switching circuits, otherwise such grinders would not be cheap. When starting the grinder, if it is smooth, the process is carried out through an adapter connected by contacts to the rectifier unit. The rectifier unit converts the current.
But sometimes it makes sense to upgrade the angle grinder using the established scheme. The electrical circuit is assembled quite simply. It is not difficult to make it, and if you wish, you can connect not only an angle grinder, but any other tool to the finished circuit. However, the tool must have a commutator motor, not an asynchronous one.
A do-it-yourself approach to creating a circuit would be as follows:
- To get started, you should download the board, if it is not there;
- The triac Bt136 600E is used as a power link;
- During operation, the triac will heat up; in order to avoid this, a heat sink is installed;
- The resistors used give resistance to current, providing current suppression;
- The regulator is tuned by a multi-turn trimmer;
- To check, connect a light bulb;
- After connecting, the light bulb must be turned off - the triac must be cold;
- Connecting the resulting circuit to the grinder.
If the board is connected correctly, the triac and the angle grinder resistors should start smoothly, and the use of the speed should be regulated. After that, you can test the grinder in action. Similar knowledge may be needed when repairing motor malfunctions. For example, when the voltage rises or there is an incorrect balancing.
Do-it-yourself speed controller for a grinder
When using ingenuity to create a speed controller with your own hands, you can use soldered controller boards for a sewing machine or vacuum cleaner. In addition, the components for the regulator are inexpensive and can be easily purchased if possible. It is worth noting that in the device the gearbox is necessary to support a certain number of revolutions and speed. If the speeds are increased, then the reason is most likely in the stator. The stator needs repair. Repairing the stator is possible at home.
The operation of the collector motor is provided by any kind of electrical voltage. When changing the voltage power, you need to reduce or increase the number of revolutions. Changing this number helps just the same thyristor regulator revolutions.
Regulator assembly steps:
- First you need to unscrew the handle of the grinder, evaluate the place and figure out where to place the elements of the circuit (if there is no place, then you can make the device in a separate box);
- The resistor can be made of aluminum;
- Under the condition of slight heating of the triac, the radiator is small enough;
- Next comes the soldering of the structure.
In conclusion, there is sizing with epoxy resin for fixing. homemade device can work for years. There are times when the device, after turning on, accelerates at higher speeds - this means that the stator winding is closed. In this case, a loop closure has occurred. The stator requires repair, most often it needs to be rewound.
What are the typical malfunctions: the winding breaks or burns, a short circuit occurs, an insulating surface breaks through.
Making a speed controller
An electric grinder is impossible without a speed controller so that it is possible to lower the speed.
The controller circuit from the point of view of physics looks like this:
- Resistor - R1;
- Trimmer resistor - VR1;
- Capacitor - C10;
- Triac - DIAC;
- Triac - TRIAC.
The electronic regulator is not only built-in, but also remote for convenience. In grinders from Bosch, electronics sets the speed from almost 3 thousand to 11.5 thousand. There is no load on the power of the meter, all indicators are taken into account. The tool will not make it difficult to reduce the number of revolutions and increase them. Adjustable speeds are simply necessary for any grinder work.
We make a soft start for a power tool with our own hands (video)
Only at first glance, it seems that the grinder may never be needed in life, that there will be no situations when it will come in handy, and even more so when it has to be repaired. Of course, you can turn to professionals, or you can determine the malfunction yourself and try to fix it.