How to adjust the speed in a drill. Drill button connection diagram - we fix the tool ourselves! Making a speed controller with your own hands
All budget options for angle grinders have several drawbacks. First, there is no soft start system. This is a very important option. Surely all of you have included this powerful power tool in the network, and when you start it, you have watched the glow of the light bulb, which is also connected to this network, drop.
This phenomenon occurs for the reason that powerful electric motors at the time of startup consume huge currents, due to which the mains voltage sags. This can destroy the tool itself, especially Chinese-made ones with unreliable windings that may one day burn out during start-up.
That is, the soft start system will protect both the network and the instrument. In addition, at the moment the tool is launched, a powerful recoil or push occurs, and in the case of a soft start system, this, of course, will not happen.
Secondly, there is no speed controller, which will allow you to work with the tool for a long time without loading it.
The diagram below is from an industrial design:
It is introduced by the manufacturer into expensive devices.
You can connect to the circuit not only the "grinder", but, in principle, any devices - a drill, milling and turning machines. But taking into account the fact that the collector motor should be in the tool.
With asynchronous motors, this will not work. It needs a frequency converter.
So, you need to make a printed circuit board and proceed with the assembly.
A dual operational amplifier LM358 is used as a regulatory element, which controls a power triac using a transistor VT1.
So, the power link in this circuit is a powerful triac of the BTA20-600 type.
There was no such triac in the store and I had to buy BTA28. It is slightly more powerful than what is according to the scheme. In general, for engines with a power of up to 1 kW, you can use any triac with a voltage of at least 600 V and a current of 10-12 A. But it is better to have some margin and take 20 A triacs, they still cost a penny.
During operation, the triac will heat up, so it is necessary to install a heat sink on it.
So that there are no questions about the fact that the motor at start-up can consume currents that significantly exceed the maximum current of the triac, and the latter can simply burn out, remember that the circuit has a soft start, and starting currents can be ignored.
Surely everyone is familiar with the phenomenon of self-induction. This effect is observed when opening a circuit to which an inductive load is connected.
The same is true for this diagram. When the power supply to the motor abruptly stops, the self-induction current from it can burn the triac. And the snubber circuit dampens the self-induction.
The resistor in this circuit has a resistance of 47 to 68 ohms, and a power of 1 to 2 watts. Film capacitor for 400 V. In this embodiment, self-induction as a side effect.
Resistor R2 provides current suppression for the low voltage control circuit.
The circuit itself, to some extent, is both a load and a stabilizing link. Due to this, after the resistor, you can not stabilize the power. Although the network has the same circuits with an additional zener diode, it is pointless to use it, since the voltage at the power supply terminals of the operational amplifier is within normal limits.
Possible replacement options for low-power transistors can be seen in the following picture:
The circuit board mentioned earlier is only a board for the soft starter and does not contain any speed control components. This is done on purpose, because in any case, the regulator must be output using wires.
The regulator is tuned using a 100 kΩ multi-turn trimmer.
If you need a more powerful regulator, then it can be assembled according to the following scheme:
If everything is in order, then after disconnecting from the network, you immediately need to check the triac by touch - it should be cold.
If everything is working fine - the "grinder" starts smoothly, and the speed is regulated, then it's time to start testing under load.
Attached files:
Scheme for connecting an analog CCTV camera to a TV, computer Connecting a digital video surveillance camera
So, the article by Alexei Sidorkin:
I think that every person in his life had more than one event or incident for which he could not find a suitable explanation in any way, remaining a secret for a long time. This is what happened with my drill.
My son-in-law Dmitry got this Bosch PSB 500 RE drill in May 1998 to equip his newly acquired apartment. At that time, not everyone had such a prestigious tool (power 500 W, speed control, reverse rotation, the possibility of shock mode - a “perforator”) in the household. The purchase caused quiet envy - I had a simple Soviet drill without any "bells and whistles". My daughter gave the Bosch drill later after the tragic death of her son-in-law during an accident in 2002.
Of course, my use of the tool was not “every day from morning to evening”, the drill was used for household needs, as in most ordinary families, plus the summer season in the country.
Fig.1. General view of the drill BoschPSB 500 RE.
The drill worked properly, successfully fulfilling all its options and functions ... and suddenly, 5-6 years ago, the speed controller stopped “obeying” - at any position / setting of the wheel / handwheel of the regulator, when the trigger was pressed, the drill immediately gave full speed without any smoothness. The first thing that came to mind, why there are no low speeds, is that the speed control circuit of the drill “burned out”. But by that time, other tools appeared on the farm, including a screwdriver and another drill in the village, and the work of the Bosch drill in low-speed mode was not so relevant, the hands never reached the troubleshooting.
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More recently, I had to carefully work with a drill, and its high speed turned out to be very inopportune, and there were no other tools with a cartridge at hand. Not far from the house there is a workshop for the repair of household appliances. They told me there that the speed controller (hereinafter referred to as RO) for the Bosch drill is only “on order”, wait at least 2 months, the cost of work is 500 rubles.
I decided to figure it out on my own, after all, a power equipment adjuster, albeit retired.
Himself an adjuster, but went to the workshop? If it is urgent, but for a couple of hundred (earlier it was called “for a bottle”), then there is no point in “uncovering your rifle”, others should also be allowed to live.
I opened the drill, disconnected the RO (two detachable knife-type electrical contacts, two “under the screw” and one screw for fastening the power wire - Fig. 2).
Rice. 2. Connecting the speed controller to the drill.
The drill speed controller is a separate unit. In Figure 3, two halves (cover and body) of an already opened RC are almost life-size, the material is plastic, the halves are fixed “on latches” between themselves.
Rice. 3. Speed regulator of the drill with the cover removed
Figure 3 shows: 1 - contact group; 2 - sliding contacts; 3 - resistor strips; 4 - handwheel of the adjusting screw; 5 - reciprocating trigger spring.
In the case of the speed controller for the drill, there is a contact group 1 and sliding contacts 2 in the form of two spring plates, driven by pressing the trigger and returning to their original position under the influence of the reciprocating-squeezing spring 5.
In the cover there is a capacitor (bottom) and a board (top) with electronic elements and two resistor strips 3, along which, when the trigger is pressed, contacts 2 slide to smoothly change the speed of the tool. The resistor strips are lubricated to protect the strips, reduce friction and prevent sparking of the sliding contacts.
An adjusting screw with a handwheel 4 on the trigger limits the depth of the trigger and the distance / length of sliding of the contacts 2 along the resistor strips 3, thereby determining the adjustment range and the maximum speed of the drill. If the adjusting screw is completely unscrewed, then the trigger, when fully pressed, closes the contact group to directly turn on the drill engine, bypassing the electronic adjusting elements, and the engine runs at the maximum possible speed (3000 rpm).
The drill speed controller circuit is almost identical. The differences are only in design and dimensions.
The scope of my work included checking the clarity of the trigger when pressed, the interaction of parts of the contact group, rotating the adjusting screw, leveling the distribution of lubricant on the resistor strips, cleaning accessible places from accumulated dust and dirt. No malfunctions, malfunctions or suspicious moments were found. In other words, he conducted a small revision, after which he assembled a drill, turned it on and ... turned on the speed controller , as if nothing had happened!
Thus, the repair of the Bosch drill speed controller was reduced to a banal cleaning!
Many assumptions could be made regarding the causes of the temporary illness of the drill - from a blow or an unnoticed fall of the tool to malfunctions in the electronics. However, the analysis of the situation still tends to disrupt the operation of the “sliding contacts - resistor strips” pair for an unknown reason, it is enough that a speck (particle) just gets under one of the sliding contacts - and that’s it, there will be no adjustment. This is also evidenced by the inclusion of the tool immediately at full speed, which is possible only when the contact group is triggered.
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But whatever you say, it turns out that the tool turned out to be the electrician himself and repaired himself!
Question from a reader
A reader, Alexander, contacted me by mail with the following request:
Good evening. I came across your blog where you repair a Bosch drill. I have a similar problem, only I have almost nothing to do with electronics. Foolishly, I dismantled the trigger of a bosch gsb 1600 RE drill. Everything worked fine before, somehow assembled, now the soft start does not work. Maybe in the wrong order and put the parts in the wrong place. I am attaching a photo of the disassembled. I hope it helps, the drill is good.
Photo of the disassembled Bosch drill button:
Bosch drill repair. The disassembled trigger is a button with a speed controller.
Bosch drill repair. Disassembled trigger - button
I don't know how to help the reader. Maybe someone will share their experience?
(UShM), in the common people of Bulgarians, have a speed controller.
The speed controller is located on the angle grinder body
Consideration of various adjustments should begin with an analysis of the electrical circuit of the angle grinder.
the simplest representation of the electrical circuit of a grinder
More advanced models automatically maintain the rotation speed regardless of the load, but tools from a manual disk are more common. If a trigger-type regulator is used on a drill or an electric screwdriver, then such a regulation principle is not possible on an angle grinder. Firstly, the features of the tool suggest a different grip when working. Secondly, adjustment during operation is unacceptable, therefore, the speed value is set with the engine turned off.
Why regulate the speed of rotation of the grinder disk at all?
- When cutting metal of different thicknesses, the quality of work is highly dependent on the speed of rotation of the disk.
When cutting hard and thick material, it is necessary to maintain the maximum rotation speed. When processing thin sheet metal or soft metal (for example, aluminum), high speeds will lead to edge melting or rapid blurring of the working surface of the disc; - Cutting and cutting stone and tiles at high speed can be dangerous.
In addition, a disc that spins at high speed knocks out small pieces from the material, making the cut surface chipped. Moreover, different speeds are selected for different types of stone. Some minerals are just processed at high speeds; - Grinding and polishing is basically impossible without speed control.
By setting the speed incorrectly, you can spoil the surface, especially if it is a paintwork on a car or a material with a low melting point; - The use of discs of different diameters automatically implies the mandatory presence of a regulator.
Changing the disk Ø115 mm to Ø230 mm, the rotation speed must be reduced by almost half. And it’s almost impossible to hold in your hands with a 230 mm disk rotating at a speed of 10,000 rpm; - Polishing of stone and concrete surfaces, depending on the type of crowns used, is carried out at different speeds. Moreover, when the rotation speed decreases, the torque should not decrease;
- When using diamond discs, it is necessary to reduce the number of revolutions, since their surface quickly fails due to overheating.
Of course, if your angle grinder only works as a cutter for pipes, angles and profiles, a speed controller is not required. And with the universal and versatile use of angle grinders, it is vital.
An electric drill is an indispensable assistant in all types of home repairs: it can be used to perform a number of tasks from mixing paints, wallpaper paste to the main purpose - drilling various holes. The power button of the product is subject to rapid wear, which often has to be repaired or replaced with a new one. To carry out this rather simple operation, the user needs a drill button connection diagram and knowledge of the most common malfunctions of this important part.
This seemingly simple device, during use, gives signals to the user that he will soon need repairs, but not everyone understands them. If the drill starts to work with temporary interruptions or the button requires more pressing than before, then these are the first symptoms of incorrect operation of this part.
When you use a cordless drill, the first step is to measure the battery voltage with a tester - if it is less than the nominal, then it must be charged.
In this case, we are particularly interested in the state and functionality of the on / off button of the product. Checking the correctness of its operation is quite simple: you need to unscrew the fasteners of the main body, remove the top cover and check the voltage of the wires going to the device by plugging the power cord into a power outlet. When the device shows a voltage supply, and when you press the button, the product does not work, this indicates that it is broken or has happened burning of contacts inside the device.
Regular on/off button
Repairing or replacing a drill button is considered a simple process, but you need to have certain skills - if you carelessly open the side wall, many parts can scatter in different directions or fall out of the case.
As it was written above, the button may not function due to oxidation or burning of the contacts. To fix this, you need take it apart, observing the following order.
- Carefully pry out the catches of the protective cover and open it.
- Remove deposits on the contacts with alcohol, or clean them with sandpaper.
- Then assemble and test.
If everything works fine, then it means that the reason was in the contacts, otherwise it is required button replacement.
You should be aware that a special layer is often erased, which is applied under the rheostat slider during manufacture - in this case, the button must also be replaced.
Quite often, the drill button connection diagram is used to test the functionality of the entire structure: only if it is available, it is possible to carry out partial repairs or to correctly connect the button if it is replaced. The diagram must go with product instruction manual, if for some reason it is not there, then you can search on the Internet.
Power button with reverse / speed control
The button for the drill shown in the photo, in addition to the reverse, has a built-in speed controller for the electric motor. This design is characterized by increased complexity, therefore, it is not possible to disassemble it without special skills: as soon as you open the case, all the parts will “scatter” in different directions, since they are supported by springs. Without knowing their correct location, it will be impossible to assemble the entire structure back - it’s easier to buy a new one, and make the connection by referring to a special diagram that can be found on the Internet.
Modern drills are produced with a reverse, so the button performs several functions at once:
- the main inclusion of the product in the work;
- adjustment of rotation speed of the electric motor;
- turning on the reverse - changing the direction of rotation of the motor rotor.
Attention! The reverse control and the speed controller are located in different housings - they must be checked separately.
It must be remembered that in modern products speed controller is located on a special substrate, and during manufacture it is filled with a compound - an insulating compound, which, after hardening, protects all parts from mechanical, thermal and chemical influences. Therefore, it cannot be repaired.
As can be seen from the connection diagram, when there is a drill button in it along with a reverse, rotation is switched using special tumbler. In this case, plus or minus is applied to different brushes, so the motor armature rotates in different directions.
You should not disassemble the start button of the drill yourself in case of its complex design - disconnect the wires and take it to the service center, where professional specialists will carry out a complete diagnosis and repair.
Our assistant can drill different materials, so there is often a lot of dust and waste. After each use, clean the drill, then the next time you use the device will work like a Swiss watch: without failures and annoying stops.
Oddly enough, but a hand-held electric drill can be used not only for its intended purpose, but also somewhat non-standard. So, with this tool you can make homemade machines. For example, drilling machine, circular, grinding and so on. However, it should be noted that not all electric drills have such a function as speed control. But in home-made machines, speed control is an integral function.
Of course, most modern drills are equipped with speed controllers. So, there is a special trigger on the body of the drill, which, by changing the position, increases or decreases the speed. But, almost all the built-in controls fix the frequency only when pressed to the maximum. At the same time, there is no fixation at medium and low speeds, which is a significant drawback. Also, the drill may be in an uncomfortable working position, which makes adjustment difficult.
A fairly effective and simple solution to this problem will be the manufacture of an external speed controller. You can make such a drill speed controller with your own hands, and quite simply. As such a regulator, you can use a dimmer - a device for adjusting the degree of illumination. In the manufacture, it is necessary to use other items, namelyplug and socket. Schematically, you can see this device in the figure below.
Note that the execution of such a controller can be performed in several ways. The simplest are two: with the use of a circuit breaker, and without it. It is worth considering that such a device is homemade, and when dealing with an electrical network, be careful when making and using it.
Now, a little more about manufacturing. Performing the first option, pick up the socket, and screw two wires to its ends so that one is longer. Then, connect the long end to one of the terminals on the plug. Fasten the second wire to the connections at the dimmer, and connect its second output to the second terminal of the electrical plug. When using the second option, it is necessary to make several changes to the circuit, namely, place a circuit breaker on the wire between the plug and the dimmer. As a rule, ordinary switches are installed in dimmers, but we need an automatic one, which, in which case, will disconnect our device from the network.
Thus, the drill speed controller is ready, and for convenience it can be placed in a special case, or fixed on a wooden panel.
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