Voltage converter on the microcontroller to power the measuring device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters

 Comments on the article

The proposed device is a 3 V DC to 9 V DC converter. It is made in the dimensions of a nine-volt Krona battery and is intended to replace it in self-powered measuring instruments. Primary voltage source - two salt or alkaline galvanic cells of size AAA. It is possible to use Ni-MH batteries of the same size. Converter efficiency - 66...81%.

The converter circuit is shown in fig. 1. Its main component is an ATtiny13A-SU (DD1) microcontroller clocked by an internal RC oscillator. The step-up voltage converter is implemented on a transistor VT1, an inductor L1, a Schottky diode VD1 and a capacitor C4. Transistor VT2 disconnects the load from the converter in the "sleep" mode of the microcontroller. Zener diode VD2 and resistor R5 protect the elements of the converter in the event of an interruption (shutdown) of the load. In normal operation, there is no current through the protective circuit.

Rice. 1. Converter circuit

The converter is designed to operate on a constant load. Its output voltage is not stabilized and depends on the supply voltage. For example, it drops to 7,6 V when the supply drops to 2,5 V.

For a more complete use of the energy of the primary power source and maintaining the output voltage at a given level, the DD1 microcontroller, when starting the converter, checks the voltage at its output. To do this, part of the output voltage from the trimmer resistor R4 is fed to the input PB4 of the microcontroller, which operates in the input mode of the built-in voltage comparator.

All components of the transducer are placed on a 48x26 mm board made of 1 mm thick fiberglass laminated on both sides. Its drawing and arrangement of parts are shown in Fig. 2. On the side of the board, free from parts, four contacts for connecting batteries are soldered into the holes intended for them. The contacts are cut from 0,3 mm thick brass sheet. The height of the contact is 10 mm, the width is 5...8 mm, the length of the petal for soldering into the hole is 2 mm, the width is 1,5 mm.

Rice. 2. Converter board and placement of elements on it

Oxide capacitors are TECAP size D, other capacitors and resistors are size 1206 for surface mounting. Trimmer resistor R4 - SP3-19a-0,5 W, inductor L1 - LQH43CN101K. The choice of inductor significantly affects the efficiency of the converter. For example, replacing the choke mentioned above with a slightly larger RLB0712 increases the efficiency by 3 ... 5%, but, unfortunately, the dimensions of the converter go beyond the dimensions of the Krona battery. To mount this inductor on the board, contact pads with holes are provided, marked L1'. It is mounted in a "lying" position. Replacing the BAT1 diode originally used in one of the converter options as VD41 with an MBR0540 made it possible to increase the efficiency by 2%.

A view of the assembled transducer from the parts side is shown in fig. 3, and from the side of the installation of batteries - in fig. 4.

Rice. 3. View of the assembled transducer from the parts side

Rice. Fig. 4. View of the assembled converter from the side where the batteries are installed

The microcontroller program uses its eight-bit fast PWM timer and analog comparator. The pulse repetition frequency with PWM is chosen equal to 37500 Hz - the maximum possible at a microcontroller clock frequency of 9,6 MHz. An internal reference voltage source is connected to the non-inverting input AI N0 of the analog comparator.

Table

1 - not programmed
0 - programmed

The controlled output voltage supplied to the PB4 pin of the microcontroller is fed to the inverting input of the AIN1 comparator through the ADC multiplexer. The output status of the ACO comparator is checked by the timer overflow interrupt handler T0. When ACO=1, there is an increment of the value in the timer comparison register, which increases the duty cycle of the pulses that control the transistor VT1 of the converter. With ACO=0, this value remains unchanged because the output voltage has already reached the set 9V.

The converter off timer is implemented in software and is a counter decremented by interrupts from the timer T0. The initial value written to the registers of this counter is calculated by the program using the formula N=T_off37500, where T_off - the required duration of the converter before shutdown, s; 37500 - control pulse repetition frequency, Hz. The program is given T_off=900 s (15 min). After this time, the microcontroller "falls asleep", switching to the POWER DOWN micropower consumption mode.

It is possible to control the converter using the optional button SB1, the connection of which is shown in the diagram in fig. 1 with dashed lines. An external interrupt request, generated by pressing this button, returns the "sleep" microcontroller to the operating mode. And if you click on it while the converter is running, the microcontroller will switch from working to "sleep" mode, turning off the converter. To operate the button in various modes, the program generates delays with a duration of 0,5 s. In the "sleep" mode of the microcontroller, the converter consumes only 6 ... 10 μA, therefore, if there is a button in the SA1 switch, there is no need and it can be omitted by replacing it with a jumper.

If the SB1 button is missing, then after the shutdown timer has expired, switching on the converter with the SA1 switch is possible only after two minutes. During this time, with the switch open, the microcontroller consumes the energy stored in capacitor C2 and is in "sleep" mode.

The converter is designed without being tied to a specific type of measuring device that requires a supply voltage of 9 V. Modification of such a device comes down to installing an SA1 switch or an SB1 button in it. For convenience, they can be connected to the converter using miniature connectors. The reverse replacement of the converter with the Krona battery does not cause difficulties.

After mounting all the parts on the board, except for the L1 inductor and checking it for open and short circuits, set the R4 resistor slider to the middle position and proceed to programming the microcontroller. The codes from the CONVERTER-DC2.hex file attached to the article must be loaded into the microcontroller program memory. Its configuration must be programmed according to the table. Please note that the CKDIV8 bit programmed by the microcontroller manufacturer must be deprogrammed.

All pads necessary for connection with the programmer are available on the board. If the programmer works only with a supply voltage of 5 V, apply the same voltage to the power supply circuit of the microcontroller. A voltage of 3 V will need to be supplied to the board after successful programming.

Measure the current drawn by the meter with which the converter is to be used, and load the converter with a suitable resistance resistor. After installing the inductor L1 in place, apply power to the converter and adjust the output voltage with a tuning resistor R4, making it

equal to 9 V. Moving the trimming resistor slider to its lower output according to the circuit increases the output voltage, and decreases it in the opposite direction. Please note that the program changes the output voltage only when the power is turned on or when the microcontroller wakes up from sleep mode.

Switch off the inverter, connect a real load to it and switch it on again. If the voltage differs from the required, correct it with a trimming resistor R4. Then measure the current drawn from G1 and G2 and calculate the converter efficiency. For one of the samples I made, it turned out to be 74% at a supply voltage of 3 V and 64% at 2 V. With a converter in which the RLB0712 choke is installed, an efficiency of 78% and 66%, respectively, was obtained.

If, with an input voltage of 3 V and a load current of 6 mA, the output voltage is set to 9,2 V, then with an input voltage of 2 V, it will decrease to 8,5 V. With further discharge of the supply battery, when the output voltage drops to 6,5 V, the low battery symbol appears on the indicator of the measuring device.

I made two copies of the converter: one for powering the DT930F+ multimeter, and the second for the MY6243 capacitance and inductance meter. These devices do not have a sleep timer, so it was not uncommon to completely drain their batteries due to forgetfulness. After installing converters in them, such troubles stopped.

The microcontroller program can be downloaded from ftp://ftp.radio.ru/pub/2017/01/conv.zip.

Author: N. Salimov

See other articles Section Voltage converters, rectifiers, inverters.

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 Wireless Microphone Nikon ME-W1 Nikon 04.03.2015 Nikon has unveiled the new ME-W1 omnidirectional mono wireless microphone that can record sound up to 50m away. The ME-W1 microphone is compatible with any camera that has the appropriate connection jack, and not just Nikon solutions - special cables (sold separately) must be used to connect the microphone to cameras from other manufacturers. The system consists of a small transmitter and receiver with dimensions of 23 x 74,6 x 23,3 mm, data exchange between which is carried out via Bluetooth. According to Nikon, one AAA battery charge is enough for three hours of continuous operation (battery capacity is not specified). The ME-W1 is designed to record audio using both a transmitter and a microphone receiver. Sound can be recorded using only the microphone, or both the microphone and the receiver. And this means the ability to focus only on the subject of the recording, or record a two-way conversation. The unit is equipped with a mono audio input, and if you want to record in stereo, you can use the ME-1 stereo microphone (sold separately) that connects to the dedicated ME-W1 microphone jack. Degree of protection ME-W1 against moisture - IPX5 (protection against water flows from any direction).

Other interesting news:

▪ Now I understand why we need an appendix

▪ Subminiature Digital Camera CardCam

▪ Plastic for household recycling

▪ Fuel from sleeping tea

▪ Holidays threaten childhood obesity

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Note to the student. Article selection

▪ article Humiliated and Insulted. Popular expression

▪ article Who got the oil first? Detailed answer

▪ article Installer of steel and reinforced concrete bridges. Standard instruction on labor protection

▪ article Capacitance meter of electrolytic capacitors. Encyclopedia of radio electronics and electrical engineering

▪ article Funny fan. 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