Microdrill power supply. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

 Comments on the article

To improve the convenience of using a microdrill when drilling holes in printed circuit boards, radio amateurs use various devices for its power supply [1-3]. The algorithm of their work is simple. In the absence of a mechanical load, a reduced voltage is supplied to the electric motor of the microdrill, at which the frequency of rotation of its shaft is low. With an increase in load (during drilling), the current consumed by the electric motor increases and the supply voltage automatically increases to the nominal value, which ensures normal drilling. At the end of drilling, the voltage and shaft speed are reduced again.

Fig. 1

The algorithm of operation of the proposed device is the same, the scheme of which is shown in Fig. 1. It is designed to work with the standard power supply of the microdrill. Its basis is an adjustable integrated voltage regulator LM337T (DA1). As you know, the output voltage of this stabilizer depends on the voltage at its control input (pin 1), which in this case is set by the resistive divider R5R6. Without load, the current through the motor M1 is less than the threshold value, so the voltage at the current sensor - resistor R2 is not enough to open the transistor VT1. In this mode, the voltage on the electric motor is set with a tuning resistor R5 so that its shaft rotates relatively slowly.

With the start of drilling, the load on the motor shaft and the current consumed by it increase. The increased voltage drop across the resistor R2 opens the transistor VT1 and through the resistor R4, voltage is supplied to the control input of the stabilizer DA1 from the negative power line. This leads to an increase in voltage on the motor, so the frequency of rotation of its shaft increases. At the end of drilling, the current consumed by the motor decreases, the transistor VT1 closes and the output voltage of the stabilizer decreases again.

The threshold for opening the transistor is set by a trimming resistor R1, and the maximum voltage on the motor is set by resistor R4. Capacitor C2 provides a smooth increase and decrease in the supply voltage of the electric motor, C3 suppresses interference during its operation. Diodes VD1, VD2 limit the voltage drop across the current sensor R2. They can be omitted if, at the maximum current consumed by the electric motor, it does not exceed 1,2 ... 1,4 V.

Parts of the device - almost any small-sized, no special requirements are imposed on them. The voltage stabilizer DA1 must be equipped with a heat sink with a cooling surface area of ​​at least 20 cm2. Resistor R2 is selected so that in idle mode the voltage drop across it does not exceed 0,2..,0,3 V, and when drilling increases to 0,9 ... 1 V.

Fig. 2

A diagram of a device that can be used with any power supply that provides sufficient voltage and current for the operation of the electric motor is shown in fig. 2. Unlike the first one, it contains a rectifier bridge VD1-VD4 and a parallel voltage regulator DA2. Therefore, even if the power supply is not stabilized, the voltage on the electric motor will change within strictly established limits. In addition, if the supply voltage is alternating, it is rectified by the diode bridge VD1-VD4 (the ripple is smoothed out by the capacitor C1), and if it is constant, then it is supplied to the device elements in the required polarity, regardless of the polarity of the input voltage.

The idle speed of the motor shaft is set by the trimmer resistor R9, the threshold current value at which the transistor VT1 opens, by selecting the resistor R1 (roughly) and the trimmer resistor R2 (smoothly), the maximum voltage on the electric motor is resistor R7. The ratings of the elements in the diagram are indicated for powering the DPM-ZON1-9 electric motor. The modes of its operation are as follows: no-load current - 120 mA at a voltage of 3 V, current in the drilling mode - 600 ... 700 mA at a voltage of 8 V.

Fig. 3

The details of the device are mounted on a printed circuit board (Fig. 3) made of foil fiberglass. Fixed resistors - MLT, S2-23, R1-4, tuning resistors - SPZ-19a, capacitors - imported oxide. The voltage stabilizer DA1 is equipped with a U-shaped heat sink, bent from a strip of sheet (3 mm thick) aluminum alloy with dimensions of approximately 50x19 mm.

We can replace the KT3102B transistor with any of this series, the TL431CLP voltage regulator with any foreign analogue in the TO-92 package or the domestic KR142EN19, 1N4002 diodes with any 1N400x series. Instead of the LM337T chip, the LM317T can be used in both devices, but in this case it is necessary to change the polarity of the inclusion of oxide capacitors, diodes and an electric motor, use a pnp transistor (for example, the KT3107 series), and in the second device also swap resistors R6, R7 and conclusions 2 and 3 chips DA2. In addition, it should be noted that the pinout of the LM337T and LM317T microcircuits (in the T0-220 package) is different: the latter has an input - pin 3, and an output - pin 2.

The appearance of the mounted board is shown in fig. 4. It is placed in a plastic case of suitable dimensions. The power switch can be inserted into the break of any power line.

Literature

1. Saglaev S. Convenient microdrill. - Radio, 2009, No. 9, p. 29, 30.
2. Glibin S. Prefix for microdrill control. - Radio, 2010, No. 7, p. thirty.
3. Gureev S. Drill power supply. - Radio, 2011, No. 5, p. 33.

Author: I. Nechaev

See other articles Section Power Supplies.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive Compact optical quantum switch 30.10.2020 Quantum computers based on lasers with qubits in the form of trapped ions are interesting, but very cumbersome. The laser beam travels many meters across a whole system of mirrors, lenses and other equipment before hitting a pair of entangled ions. Scaling such systems up to hundreds and thousands of qubits is another concern. Especially when you consider that the traps (qubits) are cooled almost to absolute zero. But there is a solution to the problem, and it has been tested. A few years ago, a group of researchers from MIT proposed directing a laser beam at qubits not through air (as in the example in the photo below), but through waveguides inside a chip with an ion trap. This proposal was recently implemented by a group of scientists from the ETH Zurich (ETH Zurich). Researchers have designed, built and tested what is essentially an optical quantum switch that could pave the way for scalable general purpose quantum computers. A silicon chip with 100 nm thick waveguides was fabricated using a classical process technology. In the picture you can see a schematic representation of the chip in the place where the laser beam breaks free - exits the tip of the waveguide inside the chip and hits a pair of entangled ions. Ions, in turn, are captured by two electrodes - each with its own, and together they are in an entangled state in such a system. In the proposed solution, the waveguides can be separated to control many very densely packed traps. This simplifies the optical system and protects it from interference and errors. In production, such traps will be very cheap, but the main thing is that such solutions will help to significantly and cost-free increase the number of qubits in optical quantum computers.

Other interesting news:

▪ Smartphone charger converts household noise into electricity

▪ carrot concrete

▪ Ink supercapacitor

▪ seaweed cheese

▪ Marvell PA800 anti-tamper chip

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Metal detectors. Article selection

▪ financial management article. Crib

▪ article How is ice cream made? Detailed answer

▪ mushroom article. Travel Tips

▪ article Both charge and weld. Encyclopedia of radio electronics and electrical engineering

▪ article Four robbers. Focus Secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024