I somehow decided to make an automatic speed controller for my motor, which I use to make holes in circuit boards; I was tired of constantly pressing the button. Well, I think it’s clear to regulate as needed: no load - low speed, load increases - speed increases.
I started looking for a diagram online and found several. I see that people often complain that PDM doesn’t work with engines, well, I think no one has repealed the law of meanness - let me see what I have. Exactly: DPM-25. Okay, since there are problems, then there is no point in repeating other people’s mistakes. I will make “new” ones, but my own.
I decided to start by obtaining the initial data, namely, with current measurements under various operating modes. It turned out that my motor at idle (idling) takes 60 mA, and at an average load - 200 mA, and even more, but this is when you start to specifically slow it down. Those. operating mode 60-250mA. I also noticed this feature: the speed of these motors strongly depends on the voltage, but the current depends on the load.
This means that we need to monitor the current consumption and change the voltage depending on its value. I sat and thought, and something like this project was born:
According to calculations, the circuit was supposed to increase the voltage on the motor from 5-6V at idle, to 24-27V with an increase in current to 260mA. And accordingly lower it when it decreases.
Of course, it didn’t work out right away; I had to tinker with the selection of the values of the integrating chain R6, C1. Introduce additional diodes VD1 and VD2 (as it turned out, LM358 does not perform its functions well when the input voltages approach the upper limit of its supply voltage). But, fortunately, my torment was rewarded. I really liked the result. The engine spun quietly at idle and very actively resisted attempts to slow it down.
I tried it in practice. It turned out that at such speeds it was possible to aim well even without punching, and even with a small catch... Moreover, the adjustment margin was so large that the number of revolutions depended on the hardness of the material. I tried it on different types of wood, if it was soft, I didn’t reach the maximum speed, if it was hard, I turned it to the fullest. As a result, it turned out that regardless of the material, the drilling speed was approximately the same. In short, drilling became very comfortable.
Transistor VT2 and resistor R3 heated up to 70 degrees. Moreover, the first one heated up at XX, and the second under load. A symbolic radiator in the form of a tin (aka case) reduced the temperature of the transistor to 42 degrees. I left the resistor in this mode for now; if it burns out, I’ll replace it with 2 pieces of 5.1 Ohm in series.
Here is a photo of the received device:
If anyone didn’t guess from the photo, the body is a tin from a used crown.
Yes, and also, do not supply more than 30V to the circuit - this is the maximum voltage for LM358. Less is possible - I drilled normally at 24V.
That's all. If someone has a more powerful motor, you need to reduce the resistance R3 by about the same amount - how many times more is your no-load current. If the maximum voltage is below 27V, it is necessary to reduce the supply voltage and the value of resistor R2. This has not been tested in practice, I don’t have any other engines, but according to calculations it should be like this. The formula is given next to the diagram. The coefficient 100 is correct for the values of R1, R2 and R3 indicated in the diagram. With other denominations it will be like this: R2*R3/R1.
Accordingly, if the parameters of your engine differ significantly from mine, you may have to select R6 and C1. The signs are as follows: if the motor operates jerkily (the speed rises and then falls), the ratings need to be increased, if the circuit is very thoughtful (it takes a long time to accelerate, it takes a long time to reduce the speed when the load changes), the ratings need to be reduced.
Thank you for your attention, I wish you success in repeating the design.
The signet is attached.
We discussed this earlier in this article.
Today we’ll look at a modification to a desktop drilling machine for printed circuit boards.
Namely: installing LED illumination of the drilling area and adding an automatic speed controller for the machine’s engine.
LED lighting for the machine
It is convenient to use LEDs for illumination from an LED lamp with AAA size AA batteries made in China.
Drilling machine with LED light on
Automatic speed controller for machine
The automatic speed controller works as follows - at idle speed the drill rotates at a speed of about 15-20 revolutions/min. (depending on the type, engine power), as soon as the drill touches the workpiece to be drilled, the engine speed increases to maximum. When the hole is drilled and the load on the engine is relieved, the speed drops again.
Schematic diagram of an automatic engine speed controller
Adviсe:
- The KT805 transistor can be replaced with KT815, KT817, KT819. KT837 can be replaced with KT814, KT816, KT818.
- Instead of R1, we temporarily place a jumper. Using resistor R3 we adjust the idle speed; the lower the resistance, the lower the idle speed. We solder R1 and reduce it until the motor reduces speed.
- By selecting resistor R3, the minimum engine speed at idle is set.
- By selecting capacitor C1, the delay in turning on the maximum engine speed when a load appears in the engine is adjusted.
- Transistor T1 must be placed on a radiator; it gets quite hot.
- Resistor R4 is selected depending on the voltage used to power the machine according to the maximum illumination of the LEDs.
- For each type of motor you need to select R1, R3: for the motor from the printer R1 - 7.7 Ohm; R3 - 520 Ohm; Power supply 12.6 V. For engine DPR-42-F1-03 R1 - 15 Ohm.
- If transistor T1 gets hot, you need to put it on a radiator.
- R1 - from 1 to 5W (depending on engine power)
The circuit is compatible with many types of engines. I tested it at 4 various types, works great for everyone!
I assembled a circuit with the indicated ratings and I was quite satisfied with the operation of the automation; I replaced the only capacitor C1 with two 470 microfarad capacitors connected in parallel (they were smaller in size).
Drawing of the speed controller circuit board
The printed circuit board of the automatic engine speed controller circuit looks like this.
Good afternoon. I present to your attention a regulator for picking printed circuit boards, the diagram is taken from Radio magazine for 2010. Assembled and tested - works great. There are no scarce parts in the circuit - only 4 common transistors and several passive radio elements that can be removed from any non-working equipment. Schematic diagram speed controller:
Operation of the mini drill regulator circuit
The elements vd1, vd2, r2, r3, vt1, r11 are used to assemble the idle speed regulator (hereinafter referred to as XO). Diode vd3 is a disconnector for the XO regulator and a current trigger assembled at vt2, r4, r7. The vd5 diode makes it easier temperature regime current sensor r7. Capacitor C2 and resistor r6 ensure a smooth return to the XO mode. On vd4, r5, c1 there is a starting current limiter (i.e. soft start). The composite transistor formed by vt3 and vt4 amplifies the currents of the previous nodes. In parallel with the motor, it is imperative to turn on the protective diode vd6 in the opposite direction, so that the EMF arising in it does not burn the radio elements of the regulator.
All resistors except R7 are used at 0.125 W, R7 at 0.5 W. It is advisable to select resistance R7 individually for each motor so that the current trigger operates clearly at the right moment, i.e. the drill did not slip off the core and did not jam.
I am attaching a photo of the assembled mini-drill speed controller and the printed circuit board topology I laid out. Transistor P213 must be turned on exactly as it is written on the board with the name “p213” (due to the reverse diode).
By using planar components, the board can be reduced in size to the point where it fits inside (or outside) the drill. As an option, this speed controller can be used to control the speed of any DC electric motors - in toys, ventilation, etc. I wish everyone good luck. Sincerely, Andrey Zhdanov (Master665).
To perform many types of work on wood, metal or other types of materials, it is not high speeds that are required, but good traction. It would be more correct to say - the moment. It is thanks to him that the planned work can be completed efficiently and with minimal power losses. For this purpose, DC (or commutator) motors are used as a drive device, in which the supply voltage is rectified by the unit itself. Then, to achieve the required performance characteristics, it is necessary to adjust the speed of the commutator motor without loss of power.
Features of speed control
It is important to know, what each engine consumes when rotating not only active, but also reactive power. In this case, the level of reactive power will be higher, which is due to the nature of the load. In this case, the task of designing devices for regulating the rotation speed of commutator motors is to reduce the difference between active and reactive powers. Therefore, such converters will be quite complex, and it is not easy to make them yourself.
You can construct only some semblance of a regulator with your own hands, but there is no point in talking about saving power. What is power? In electrical terms, it is the current drawn multiplied by the voltage. The result will give a certain value that includes active and reactive components. To isolate only the active one, that is, to reduce losses to zero, it is necessary to change the nature of the load to active. Only semiconductor resistors have these characteristics.
Hence, it is necessary to replace the inductance with a resistor, but this is impossible, because the engine will turn into something else and obviously will not set anything in motion. The goal of lossless regulation is to maintain torque, not power: it will still change. Only a converter can cope with such a task, which will control the speed by changing the duration of the opening pulse of thyristors or power transistors.
Generalized controller circuit
An example of a controller that implements the principle of controlling a motor without power loss is a thyristor converter. These are feedback proportional integrated circuits that provide strict regulation characteristics, ranging from acceleration and braking to reverse. The most effective is pulse-phase control: the repetition rate of the unlocking pulses is synchronized with the network frequency. This allows you to maintain torque without increasing losses in the reactive component. The generalized diagram can be represented in several blocks:
- power controlled rectifier;
- rectifier control unit or pulse-phase control circuit;
- tachogenerator feedback;
- current control unit in the motor windings.
Before delving into a more precise device and principle of regulation, it is necessary to decide on the type of commutator motor. The control scheme for its performance characteristics will depend on this.
Types of commutator motors
At least two types of commutator motors are known. The first includes devices with an armature and an excitation winding on the stator. The second includes devices with an armature and permanent magnets. It is also necessary to decide, for what purpose is it necessary to design a regulator:
Motor design
Structurally, the engine from the Indesit washing machine is simple, but when designing a controller to control its speed, it is necessary to take into account the parameters. Motors may have different characteristics, which is why the control will also change. The operating mode is also taken into account, which will determine the design of the converter. Structurally, the commutator motor consists from the following components:
- An armature, it has a winding laid in the grooves of the core.
- Collector, a mechanical rectifier of alternating mains voltage, through which it is transmitted to the winding.
- Stator with field winding. It is necessary to create a constant magnetic field in which the armature will rotate.
With an increase in current in the motor circuit turned on by standard scheme, the field winding is connected in series with the armature. With this inclusion, we also increase the magnetic field acting on the armature, which allows us to achieve linearity of characteristics. If the field remains unchanged, then it will be more difficult to obtain good dynamics, not to mention large power losses. It is better to use such motors at low speeds, since they are more convenient to control at small discrete movements.
By organizing separate control of the excitation and armature, it is possible to achieve high positioning accuracy of the motor shaft, but the control circuit will then become significantly more complicated. Therefore, we will take a closer look at the controller, which allows you to change the rotation speed from 0 to the maximum value, but without positioning. This might come in handy, if a full-fledged drilling machine with the ability to cut threads will be made from a washing machine engine.
Scheme selection
Having found out all the conditions under which the motor will be used, you can begin to manufacture a speed controller for the commutator motor. You should start by choosing a suitable scheme that will provide you with all the necessary characteristics and capabilities. You should remember them:
- Speed regulation from 0 to maximum.
- Providing good torque at low speeds.
- Smooth speed control.
Looking at many schemes on the Internet, we can conclude that few people are creating such “units”. This is due to the complexity of the control principle, since it is necessary to organize the regulation of many parameters. Thyristor opening angle, control pulse duration, acceleration-deceleration time, torque rise rate. These functions are handled by a circuit on the controller that performs complex integral calculations and transformations. Let's consider one of the schemes, which is popular among self-taught craftsmen or those who simply want to put to good use an old motor from a washing machine.
All our criteria are met by a circuit for controlling the rotation speed of a commutator motor, assembled on a specialized TDA chip 1085. This is a completely ready driver for controlling motors that allow you to adjust the speed from 0 to the maximum value, maintaining torque through the use of a tachogenerator.
Design Features
The microcircuit is equipped with everything necessary for high-quality engine control in various speed modes, from braking to acceleration and rotation with maximum speed. Therefore, its use greatly simplifies the design, while simultaneously doing all universal drive, since you can choose any speed with a constant torque on the shaft and use it not only as a drive for a conveyor belt or drilling machine, but also for moving the table.
The characteristics of the microcircuit can be found on the official website. We will indicate the main features that will be required to construct the converter. These include: an integrated frequency-to-voltage conversion circuit, an acceleration generator, a soft starter, a Tacho signal processing unit, a current limiting module, etc. As you can see, the circuit is equipped with a number of protections that will ensure stable operation of the regulator in different modes.
The figure below shows a typical circuit diagram for connecting a microcircuit.
The scheme is simple, so it can be completely reproducible with your own hands. There are some features that include limit values and speed control method:
If you need to organize a motor reverse, then for this you will have to supplement the circuit with a starter that will switch the direction of the excitation winding. You will also need a zero speed control circuit to give permission for reverse. Not shown in the picture.
Control principle
When the rotation speed of the motor shaft is set by a resistor in output circuit 5, a sequence of pulses is formed at the output to unlock the triac by a certain angle. The speed of rotation is monitored by a tachogenerator, which occurs in digital format. The driver converts the received pulses into an analog voltage, which is why the shaft speed is stabilized at a single value, regardless of the load. If the voltage from the tachogenerator changes, the internal regulator will increase the level of the output control signal of the triac, which will lead to an increase in speed.
The microcircuit can control two linear accelerations, allowing you to achieve the dynamics required from the engine. One of them is installed on the Ramp 6 pin of the circuit. This regulator is used by the manufacturers themselves washing machines, so it has all the advantages to be used for domestic purposes. This is ensured by the presence of the following blocks:
Usage similar scheme provides full control of the commutator motor in any mode. Thanks to forced acceleration control, it is possible to achieve the required acceleration speed to a given rotation speed. Such a regulator can be used for all modern washing machine motors used for other purposes.
Micro drill speed controller circuit
Very often when working and drilling holes in the board, we either put the microdrill down, then pick it up again and continue drilling. But often the engines heat up at high speeds, and it’s harder to pick it up.
Due to vibration, it can often slip off the board and create a cable. For these purposes, I suggest assembling DIY speed controller.
The principle of operation is as follows: when the load is small, then a small current passes and the speed is reduced, as soon as the load increases, the speed increases.
Device diagram:
A huge advantage of the device is that the engine runs in a lighter mode and the contact brushes wear out less.
This is the main answer to the question how to make the speed increase when drilling
Printed circuit board
Radio components for the regulator
The LM317 chip must be installed on a radiator to avoid overheating. No cooler installation required
Electrolytic capacitors with a rated voltage of 16V.
1N4007 diodes can be replaced with any other ones rated for a current of at least 1A.
LED AL307 any other. The printed circuit board is made on single-sided fiberglass.
Resistor R5 with a power of at least 2W, or wirewound.
The power supply must have a current reserve for a voltage of 12V. The regulator is operational at a voltage of 12-30V, but above 14V you will have to replace the capacitors with ones corresponding to the voltage.
The finished device starts working immediately after assembly.
Setting up and little things at work
Resistor P1 sets the required idle speed. Resistor P2 is used to set the sensitivity to the load; we use it to select the desired moment of increasing speed. If you increase the capacitance of capacitor C4, the delay time at high speeds will increase or if the engine runs jerkily.
I increased the capacitance to 47uF.
The engine is not critical for the device. It just needs to be in good condition.
I suffered for a long time, I already thought that the circuit had a glitch, that it was unclear how it regulates the speed, or reduces the speed during drilling.
But I disassembled the engine, cleaned the commutator, sharpened the graphite brushes, lubricated the bearings, and reassembled it.
Installed spark arresting capacitors. The scheme worked great.
Now you don't need an inconvenient switch on the micro drill body.
