Table of contents:
- Do-it-yourself speed regulator for a grinder
- Speed controller and soft start for grinder
- Why do you need a soft start
- Electronic unit in angle grinder
- DIY speed controller
Video: How To Make A Speed Controller For A Grinder With Your Own Hands, How To Decrease Or Increase The Speed + Video Instructions
Do-it-yourself speed regulator for a grinder
Do you have a grinder, but no governor? You can make it yourself.
1 Speed controller and soft start for grinder
- 1.1 What is a speed regulator and what is it for
- 1.2 Grinders with a speed controller: examples in the photo
- 2 Why do you need a soft start
3 Electronic unit in angle grinder
- 3.1 Types of devices with electronic unit: examples in the table
- 3.2 Angle grinders with an electronic unit: popular in the photo
4 Do-it-yourself speed controller
- 4.1 Factory regulators of revolutions of grinders: photo examples
- 4.2 Manufacturing a printed circuit board
- 4.3 Installation of electronic components (with photo)
- 4.4 Making a power regulator: video
4.5 Testing the electronic unit
4.5.1 Testing the power regulator with a tester and a lamp (video)
4.6 Connecting the regulator to the grinder
- 4.6.1 Installing the regulator inside the body of an angle grinder: video
- 4.6.2 Regulator of revolutions for the grinder in a separate housing: video
- 5 Use
Speed controller and soft start for grinder
Both are necessary for the reliable and comfortable operation of the power tool.
What is a speed regulator and what is it for
This device is designed to control the power of the electric motor. It can be used to adjust the speed of rotation of the shaft. The numbers on the adjusting wheel indicate the change in the rotational speed of the disc.
Bulgarian speed regulator
The regulator is not installed on all grinders.
Grinders with speed control: examples in the photo
Flex LE 9-10 125
Bosch PWR 180 CE
Metabo PE 12-175
EIBENSTOCK EWS 400
The lack of a regulator severely limits the use of the sander. The speed of rotation 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 revs are constantly kept at maximum. This mode is only suitable for hard and thick materials such as a corner, pipe or profile. The reasons why the presence of 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 disc will be washed out, and the wood will turn black from the high temperature.
- For cutting minerals it is necessary to adjust the speed. Most of them break off small pieces at high speed and the cut becomes uneven.
- You don't need the fastest speed to polish your cars or the paintwork will deteriorate.
- To change a disc from a smaller diameter to a larger one, you need to reduce the speed. It is almost impossible to hold with your hands a grinder with a large disc rotating at high speed.
- Diamond discs must not be overheated in order not to spoil the surface. For this, the revolutions are 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 mains, a starting current rush occurs, which is many times higher than the rated motor current, the mains voltage sags. Although this burst is short-lived, it causes increased wear on the brushes, the motor manifold and all parts of the tool through which it flows. This can cause the instrument itself to fail, especially the Chinese one, with unreliable windings that can burn out at the most inopportune moment during switching on. And also there is a large mechanical jerk at startup, which leads to rapid wear of the gearbox. This start-up prolongs the life of the power tool and increases the comfort level during operation.
Electronic unit in angle grinder
The electronic unit allows the speed controller and soft start to be combined into one. The electronic circuit is implemented according to the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Such a block can be supplied to grinders of different power and price category.
Varieties of devices with an electronic unit: examples in the table
disk rotation speed, rpm
|Weight, kg||price, rub.|
|Felisatti AG125 / 1000S||1000||11000||2.5||2649|
|Bosch GWS 850 CE||850||11000||1.9||5190|
|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
Flex LST 803 VR
DIY speed controller
The speed regulator is not installed in all models of grinders. You can make a block for regulating the speed with your own hands or purchase a ready-made one.
Factory regulators of revolutions of grinders: photo examples
Bosh grinders speed regulator
Bosh grinders speed regulator
Regulator of revolutions of grinders Sturm
Regulator of revolutions of grinders DWT
Regulator of revolutions of grinders DWT
Such regulators have a simple electronic circuit. Therefore, creating an analogue with your own hands will not be difficult. Consider what the speed regulator is made of for grinders up to 3 kW.
Manufacturing a printed circuit board
The simplest scheme is shown below.
The simplest speed regulator circuit
Since the circuit is very simple, it makes no sense because of it alone to install a computer program for processing electrical circuits. Moreover, you need special paper for printing. And not everyone has a laser printer. Therefore, let's go the simplest way of making a printed circuit board.
Take a piece of PCB. Cut the size required for the microcircuit. Sand and degrease the surface. Take a laser disc marker and draw a diagram on the PCB. In order not to be mistaken, draw with a pencil first. Next, let's start etching. You can buy ferric chloride, but after that the sink doesn't wash well. If you accidentally drop it on clothes, stains will remain 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 of hydrogen peroxide. Add half a tablespoon of salt and a sachet of citric acid to 50 g. The solution is made without water. You can experiment with proportions. And always make a fresh solution. All copper should be vented. This takes about an hour. Rinse the board under running well water. Drill holes.
It can be made even easier. 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 common solution of rosin in isopropyl alcohol. Take some solder and tin the tracks.
Installation of electronic components (with photo)
Prepare everything that will be useful for mounting the board:
Pins to the board.
Pins to board
100 nF capacitor.
100 nF capacitor
Fixed resistor 2 kOhm.
Fixed resistor 2 kΩ
Variable 500 kΩ linear resistor.
Variable resistor 500 kΩ
Bite off four pins and solder them into the board. Then install the dinistor and all other parts, except for the variable resistor. Solder the triac last. Take a needle and brush. Clean the gaps between the tracks to remove possible short circuits. The triac with a free end with a hole is attached to an aluminum radiator for cooling. Use fine emery paper to clean the area where the element is attached. Take KPT-8 heat-conducting paste and apply a small amount of the paste to the radiator. Secure the triac with a screw and nut. Since all the details of our structure are energized, we will use a handle made of insulating material for adjustment. Put it on a variable resistor. With a piece of wire, connect the extreme and middle terminals of the resistor. Now solder two wires to the outer terminals.Solder the opposite ends of the wires to the corresponding terminals 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 wires. A radiator for the triac is also needed here. 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 grinder body.
If you want to install an LED indicator in the governor, then use a different circuit.
Regulator circuit with LED indicator.
Regulator circuit with LED indicator
Added diodes here:
- VD 1 - diode 1N4148;
- VD 2 - LED (operation indication).
Regulator with LED assembled.
Regulator with LED assembled
This unit is designed for low-power grinders, so the triac is not installed on the radiator. But if you are going to use it in a powerful instrument, then do not forget about the aluminum board for heat dissipation and the bta16 triac.
Making a power regulator: video
Electronic unit test
Before connecting the unit to the instrument, we will test it. Take the overhead socket. Mount two wires in it. Connect one of them to the board, and the other to the network cable. The cable has one more wire left. Connect it to the network board. It turns out that the regulator is connected in series to the load supply 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 regulator is connected to the instrument in series.
The connection diagram is shown below.
Connection diagram to the grinder
If there is free space in the grinder's handle, then our block can be placed there. The surface-mounted circuit is glued with epoxy, which serves as an insulator and shake protection. Bring out the variable resistor with a plastic handle to regulate the speed.
Installing the regulator inside the body of an angle grinder: video
The electronic unit, assembled separately from the grinder, is placed in a housing made of insulating material, since all elements are energized by the network. A portable socket with a power cable is screwed to the housing. The handle of the variable resistor is brought out.
Speed controller in box
The regulator is connected to the mains, and the tool to a portable socket.
Speed controller for grinder in a separate case: video
There are a number of recommendations for the correct use of a 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 in operation by slowly turning the variable resistor knob.
A grinder without a speed regulator is good because, without serious costs, you can make a universal speed regulator yourself for any power tool. The electronic unit, mounted in a separate box, and not in the body of the grinder, can be used for a drill, drill, circular saw. For any tool with a brushed motor. Of course, it is more convenient when the regulator knob is on the instrument, and you do not need to move anywhere and bend over to turn it. But it's up to you to decide. It's a matter of taste.
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