Grinder with soft start: device and connection of the starter

The grinder or angle grinder is a very useful tool on the farm when working with various surfaces. Such a tool dramatically eases many tedious processes. It can be used to process, sand or cut metal, wood, stone or plastic materials. Most modern grinders are initially equipped with a "soft start" function. What is the use of this function?

What is the soft start function for? The reason is that when the grinder is turned on, a lot of voltage is suddenly applied to its engine. This has an extremely negative effect on the electronics of the instrument, and also wears out the wiring. It is the sudden power surges that most often put the grinder out of order. In addition, with a sharp start, it is rather difficult to hold the instrument in your hands, because it begins to shake and lead to the side. All this can lead not only to breakage of the instrument, but also to injury. That is why most manufacturers have equipped their models with a soft start function and speed control.

The function of adjusting the revolutions is useful in that various types of work can be performed with such a grinder. The speed of rotation of the disk is selected depending on what needs to be done with the angle grinder - to grind, polish or cut the material. The speed of rotation of the discs can affect the quality of the surface cut. For example, for hard surfaces, a high rotation speed of the disk is required, and for softer surfaces, on the contrary, a low speed is required. Grinding work is very difficult without a wheel speed regulator.

On modern grinders, the soft start function is already installed, but some craftsmen independently supply their grinders with a soft start device. In principle, it is not so difficult to put a limiter.

You can purchase ready-made devices for soft start, or you can make such a device yourself. Below is one of the most famous schemes for a soft starter of a tool.

So, for the manufacture of a soft start system you will need:

• microcircuit - KR1182PM1;
• R1 - 470 Ohm R2 - 68;
• C1 and C2 - 1 microfarad - 10 volts;
• C3 - 47 microfarads - 10 volts.

The essence of the work of such a device is the following characteristics.

• When the device is turned on, the voltage from the network begins to flow to the microcircuit (DA1).
• Then the control capacitor starts to charge gradually. After that, the device reaches the desired voltage indicator. For this reason, the thyristors open in the microcircuit with a slight delay. The period of this delay depends on the time it takes for the capacitor to fully charge.
• Triac VS1 will also open gradually. This is because it is also controlled by thyristors.

These processes are carried out in periods that gradually become smaller. And for this reason, the voltage that is supplied to the grinder's engine does not grow in jumps, but gradually. Thanks to this, the grinder turns on smoothly.

The capacity of the capacitor C2 directly affects the time it takes for the motor to fully start to work. The capacitor, which has a capacity of 47 μF, starts the device in about 2-3 seconds. And at the moment when the grinder turns off, the capacitor C1 is discharged using a 60 kΩ resistor R1. This happens in about the same time as turning on. The tool can then be run again for further work.

How to choose the right angle grinder? To do this, it is worth using several basic criteria.

To choose the right tool, it is worth deciding on the specific type of work to be performed with this tool. Grinders can be of different types: mains, with batteries, gasoline and pneumatic.

Network models are perhaps the most common. Such grinders work from a home network, that is, from a simple outlet. Such models of the tool have high power, compactness and high speed of rotation of the cutting discs.

Cordless devices are deprived of this disadvantage. They have a special mount for power supplies that are charged from the mains. After charging, you can work with such a tool without any wires. Usually, such grinders have compact dimensions and small diameters of cutting discs. As a rule, such models are more expensive than standard tools. Also, the period of their operation is limited by the capacity of the power supply.

Gasoline models of grinders are rare. Such devices are large in size, because they need a fuel tank, as well as an internal combustion engine. Among the advantages, it is worth highlighting the high power of these models, a wide range of choice of disks and autonomy. The negative aspects include their weight and volume, high noise levels and, of course, additional fuel costs for the operation of the device.

Pneumatic models of angle grinders are often used for production purposes. and very rarely for household work. These are unusual grinders that work on a stream of compressed air and need a special compressor. For such models, the problem of overheating is completely eliminated, and the period of operation can be limited only by the human factor. Also, such models are the lightest and quietest.

For simple work on the processing and grinding of surfaces, light models of grinders with a small diameter of the cutting wheel are suitable. For work on cutting durable materials, it is worth choosing more powerful and, accordingly, bulky equipment with a large diameter of discs. The diameters of the discs can be from 125 (minimum size) to 230 (maximum size) mm - that is, the range of sizes is quite wide. The universal cutting disc diameter is 180 mm. Such a circle can be used for both surface treatment and material cutting.

When choosing a disc, it is worth conducting a careful visual inspection. Even minor damage and chips can lead to extremely sad consequences. By the way, almost 90% of accidents when working with a grinder are due to a defect in the cutting discs.

Convenience of work is also an important selection criterion. The grinder should be equipped with comfortable handles, should not slip out of the palm and have a lot of weight. Many grinders have an electronic relay to protect against power surges and overloads.This is a useful feature, so it is worth choosing a tool with such a fuse.

If you need to connect the soft start function to the grinder with your own hands, then you need to do this through an adapter. The input leads of the conductor must be connected to the rectifier unit. The correct definition of the zero phase plays an important role in this. The contacts of the device are fixed with a blowtorch. In order to check the performance of the device, you must use a special tester.

Among other things, the speed controller of the grinder can be placed directly in the socket. The tool will work from it. The connection requires a junction box, a socket and a regular mains cable. A hole must be made in the junction box (can be drilled) to accommodate the AC regulator. The board is placed inside the box, and the socket is attached to it. This regulator is applicable not only to the grinder, but also to any device that will be connected to this outlet.

So, above it was considered for what purposes the grinders have a soft start function and a cutting wheel speed controller. Usually, these functions are already built into modern tools, but if they are absent, if you really want to, you can install them and connect them yourself.

For information on how to make a soft start for a grinder, see the video below.