by Marek Ples
| Device for Measuring the Tissue Puncture Force Profile (μC) | |
| Driver for Camera and Equatorial Telescope Mount (μC) | |
| Low-Voltage Solid-State Tesla Coil for Educational Use (an) | |
| Robot with AAM Module - Walking Flame Thrower (μC) | |
| The Ionization Chamber and 220Ra (an) | |
| The Voice of Energy: Plasmophone (an) | |
| Acoustic Levitation (an) | |
| Simple Hardware Speech Synthesizer (μC) | |
| Whiteboard Drawing Robot (μC) | |
| Miniature Radio Receiver Without Integrated Circuits (an) | |
| Simple CNC Plotter (μC) | |
| More | |
μC - microcontroller project; an - analog project |
The purpose of this work was to design and construct a device capable of recording the puncture force profile of human or animal tissue using needles typically employed in amniocentesis procedures.
To achieve this goal, it was necessary to establish design assumptions, develop the mechanical structure, prepare the software, and carry out a series of tests. The initial prerequisites for the project were defined as follows:
To allow easy replacement of damaged parts, ensure component availability, and maintain compatibility with commercially available 3D printers, the entire device was designed with these requirements in mind. To meet these goals, an ATmega328P microcontroller from an Iduino Nano board was selected to eliminate the need for additional soldering or custom-made components. The preloaded bootloader was erased from the flash memory, and the microcontroller was programmed via the ISP interface using a USBasp programmer. The internal software was written in the BASCOM programming language.
To measure the force acting on the needle, two 26×26 mm strain gauge sensors with a measuring range of 50 N were used, along with an HX711 amplifier for signal acquisition and data processing. To minimize thermal drift affecting the sensors, the two units were mounted back-to-back. The depth of needle penetration was measured using a 3D-printed arm with a ring guide connected to a linear potentiometer. The voltage output from the potentiometer changed as the needle advanced into the sample, allowing precise measurement of needle tip depth based on the potentiometer’s linear response.
Figure 1 shows the construction of the measuring device.
Fig. 1 - Measuring device
A - main body with a slot for pressure sensors; B - stiffener that keeps the needle straight; C - arm for measuring the needle penetration depth; D - potentiometer housing; E - back cover
All parts were designed to ensure full compatibility with a Prusa MK3S+ 3D printer. After assembly and setup, the complete device appeared as shown in Fig. 2.
Fig. 2 - Complete laboratory setup
As it turned out, a kitchen sponge proved to be an excellent base for the samples.
Created device can serve as a form of cheap alternative to expensive, market-available devices when there is no necessity for resolution greater than 0.1N.
The presented device was developed in collaboration with my colleague G. Gruszka, MSc Eng, and other team members. This work, in which I am actively involved, has been accepted for presentation at a scientific conference:
Astrophotography, or astronomical imaging, involves capturing photographs of celestial objects, events, and regions of the night sky. In addition to recording detailed images of extended bodies such as the Moon, Sun, and planets, modern astrophotography can reveal objects invisible to the naked eye, including faint stars, nebulae, and galaxies. This is achieved through long-exposure techniques, as both film and digital cameras can collect and accumulate photons over extended periods.
Fainter stars and deep-sky objects have such low brightness that, to capture them in a photograph, the exposure time must be relatively long. While typical daytime photography uses shutter speeds measured in fractions of a second (such as 1/800 s or faster), astrophotography often requires exposures lasting from several minutes to even a few hours.
When taking long-exposure photographs of the night sky, the Earth's rotation on its axis produces an intriguing effect (Fig. 3).
Fig. 3
Movement of stars on the celestial sphere (visible Orion constellation and others).
Long-exposure photography can capture mesmerizing star trails formed by the apparent motion of stars across the night sky as the Earth rotates on its axis (Fig. 4).
Fig. 4 - Star trails
Telescope mounts and other equipment that compensate for the Earth's rotation are used to achieve longer exposures without blurring the observed objects. These include both commercial equatorial mounts and homemade tracking systems. However, mounts can experience inaccuracies caused by gear backlash, wind, or imperfect balance, so a technique known as auto-guiding is employed as a closed-loop feedback system to correct these errors (Fig. 5).
Fig. 5 - My astrophotography setup consists of a small Maksutov telescope paired with a digital SLR camera and an autoguider, both equipped with lens heaters, all mounted on an equatorial mount.
In my work, I apply techniques that involve capturing multiple images, sometimes thousands, and combining them through an additive process known as stacking. This method sharpens images, reduces atmospheric distortions, compensates for tracking errors, enhances the visibility of faint objects with low signal-to-noise ratios, and minimizes the effects of light pollution. Simply put, instead of taking a single long-exposure photograph, stacking combines multiple shorter exposures into one image with improved overall quality.
To support the use of a digital SLR camera as a sensor in astrophotography, I built a dedicated device called AstroDriver (Fig. 6).
Fig. 6 - The AstroDriver
A - Remote trigger cable socket for a digital SLR camera; B - Display (2×16 characters); C - External power supply socket;
D - Main power switch; E - Selection knob; F - Connector for an external device
The core of the device is an ATMEGA8 microcontroller equipped with an external 8 MHz quartz crystal resonator. A problem arose when it was found that at low temperatures, the LCD display’s response time increased significantly while its contrast decreased. To allow the controller to operate reliably for hours at temperatures below 0 °C, a heating element was used to keep the key components of the device at an optimal temperature. The firmware, written in C, occupies about 50% of the microcontroller’s FLASH memory.
The AstroDriver is essentially a specialized intervalometer equipped with additional functions useful in astrophotography. Menu navigation is controlled by an encoder with an integrated push-button switch. The device offers three main operating modes:
Fig. 7
In the normal mode, the user can select the interval between photos within a range from 1 s to 99 h (with exposure typically limited to 30–120 s, depending on the camera model). The bulb mode allows setting both the interval and the shutter speed in the same range of 1 s to 99 h. In both normal and bulb modes, the digital SLR can be set to enter standby between shots to reduce power consumption. The device automatically sends a signal to wake the camera before the next exposure. Additionally, the system provides the ability to control external devices through two independently programmable, galvanically isolated outputs (one normally open and one normally closed). All parameters are stored in non-volatile EEPROM memory.
The Astro mode requires connecting the AstroDriver to both the digital camera and the equatorial mount’s control system. This allows the automation of the polar alignment process, which involves aligning the telescope mount’s rotational axis parallel to the Earth’s axis. This step is essential for the equatorial mount to accurately compensate for the Earth’s rotation.
The AstroDriver facilitates long-exposure photography, ensuring that stars remain sharp and no trails are observed (Fig. 8, vide Fig. 4).
Fig. 8 - Stars with no trails
The AstroDriver is highly useful for accurately setting up an equatorial mount and capturing astrophotographic images. Figures 9–11 present example photographs of deep-sky objects that I captured using the described technique.
 Fig. 9 - The Horse Head Nebula |
 Fig. 10 - The Pleiades |
 Fig. 11 - The Orion Nebula |
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The device proved to be highly versatile and was also useful in other applications, such as time-lapse photography. This made it possible to create videos showcasing relatively slow processes, including the formation of Liesegang rings (Vid. 1) and the growth of silver crystals in silica gel (Vid. 2).
I built the AstroDriver in 2016, and since then it has operated flawlessly, even under intensive use.
A Tesla coil is an electrical resonant transformer circuit designed by Nikola Tesla in 1891. It is used to generate high-voltage, low-current, high-frequency alternating-current electricity. Tesla experimented with various configurations consisting of two, and occasionally three, coupled resonant circuits.
A Solid-State Tesla Coil (SSTC) uses power semiconductor devices—typically thyristors or transistors such as MOSFETs or IGBTs—triggered by a solid-state oscillator circuit to switch voltage pulses from a DC power supply through the primary winding.
I built a very simple device based on an electronic circuit known as the Slayer Exciter. Its construction requires only one transistor and a few additional electronic components. The key element of the device is a pair of single-layer coils wound on a hollow plastic tube (Fig. 12).
Fig. 12 - Primary and secondary coils
My miniature Tesla coil, small enough to fit in the palm of a hand and powered by a 9 V battery, is shown in Fig. 12.
Fig. 13 - Miniature SSTC
The electromagnetic field around the device is strong enough to easily induce glow discharges in a mercury lamp (Fig. 14) and a fluorescent tube (Fig. 15).
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Studying the anatomy of insects inspired me to design walking robots. While exploring the technological and educational applications of this field, I came up with the idea of creating a simple, educational robot. The main goal was to use easily accessible materials and tools, keeping construction costs low while offering anyone interested a chance to learn the basics of design. This concept led to the creation of the MUTRA robot, which features the following:
I based the mechanical design on my earlier educational robot, REKSIO, incorporating several significant improvements.
Fig. 16 - MUTRA
To facilitate the robot’s use in educational and popular-science lectures, I equipped it with an Audience Attraction Module (AAM) designed and built entirely by myself. The AAM functions as a remotely controlled flame generator (Fig. 17). The sight of a small robot producing a controlled flame on demand captures the attention of even the most disengaged audiences and helps spark interest in the topic being presented.
Fig. 16 - MUTRA in action
For safety, a propane–butane mixture was used as the fuel for the flame generator. A standard balloon serves as the gas reservoir, which keeps the fuel stored at relatively low pressure; in the event of accidental ignition, the gas would burn off rapidly, reducing the hazard compared with high-pressure tanks. The gas outlet is actuated vertically by a servo mechanism, and ignition is initiated electrically.
Several levels of protection have been implemented to minimize the risk of accidents. I must emphasize that MUTRA may be operated only by myself and other trained personnel, under controlled conditions and in accordance with applicable safety regulations; it is not intended for use by untrained individuals.
Fig. 17 - Berserk mode
The ionization chamber is the simplest type of gaseous ionization detector and is widely used for detecting and measuring various kinds of ionizing radiation, including X-rays, gamma rays, and beta or alpha particles.
The term ionization chamber refers specifically to detectors that collect all the charges created by direct ionization within the gas through the application of an electric field. It utilizes the discrete charges produced during each interaction between the incoming radiation and the gas to generate an output in the form of a small direct current. This means that individual ionizing events cannot be measured, so the energy of different radiation types cannot be distinguished; however, it provides an excellent measure of the overall ionizing effect.
Ionization chambers can be built in various ways. Their operating principle is so elegantly simple that they can be made from inexpensive, readily available materials and used for both research and educational purposes. In Fig. 18, an ionization chamber constructed by me from a metal can and copper wire is shown. I used a simple DC amplifier, which makes it possible to observe changes in electric current on a multimeter; as can be seen, the current increases significantly when a sample of the radioactive isotope emitting alpha radiation (241Am) is placed near the chamber.
Fig. 18
The half-life, t½, is the time required for a quantity of a substance to decrease to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms persist.
To determine the half-life of a given radionuclide, an ionization chamber can be used. In this experiment, I chose the radon isotope 220Rn as the subject of study. Radon is a colorless, odorless, and tasteless noble gas, and therefore undetectable by human senses.
Radon has no stable isotopes. Thirty-nine radioactive isotopes have been identified, with atomic masses ranging from 193 to 231. The most stable is 222Rn (t½ = 3.8 days), which is a decay product of 226Ra, itself a decay product of 238U. The 220Rn isotope is a natural decay product of the most stable thorium isotope, 232Th, and is commonly known as thoron.
This particular radon isotope possesses several features that make it especially suitable for the described experiment. One of them is its short half-life (< 1 min), which allows relatively accurate determination within a short measurement period. During radioactive decay, it emits alpha particles that are easily detectable in the ionization chamber. Obtaining radon for experimental purposes is straightforward, as it accumulates naturally in containers holding thorium or its compounds.
The setup shown in Fig. 19 was used to measure the half-life of 220Rn. The ionization chamber (A) was made from a metal can with a diameter of approximately 20 cm (7.9 in), while a smaller can housed the DC amplifier with bias regulation (B). This circuit enables voltage measurement (multimeter C) proportional to the ionization current generated within the chamber by the radon isotope introduced through a syringe (D). The system is powered by a single 9 V battery (E).
Fig. 19. Experimental setup
A - Ionization chamber; B - Bias regulation; C - Multimeter (low-cost model); D - Syringe; E - 9 V battery
Before starting the measurement, the power supply must be connected, and the bias adjusted so that the output voltage reads 0 V.
The actual measurement begins at the moment when a defined volume of air containing 220Rn is injected into the chamber. From that point onward, the output voltage should be recorded at known time intervals. The voltage initially increases and then gradually decreases as the radionuclide decays.
The graph in Fig. 20 presents the data obtained during a single measurement performed using the described method.
Fig. 20 - The decrease in output voltage as a function of time
Orange – experimental data; Blue – regression curve
The half-life of radon can be determined as the time interval during which the radioactive activity, represented by the measured voltage, decreases by half—for instance, from the value U1 to U2 (U2 = U1/2). In this case, t½ = t2 − t1.
In a single measurement, the half-life was determined to be 56.2 s, while the reference value reported in the literature is 55.6 s. As shown, even with such simple and low-cost equipment, it was possible to determine the half-life of 220Rn with remarkable accuracy.
In addition to projects with scientific value, I also work on creations made purely for the joy of experimentation or simply for fun. My work on generating sound through thermal vibrations of plasma formed within an electric arc belongs to this category.
I conducted my first experiments using a plasma speaker that I built based on the ZVS circuit. This device, equipped with a suitable transformer, is capable of generating high voltage (in my case, about 20 kV). By modulating the output current, I produced variations in the temperature and gas pressure of the electric arc, which in turn generated sound and allowed melodies to be played, in this case, the Cuckoo Waltz (see Video 4). The sound was extremely loud, causing significant distortion in the signal recorded by the microphone.
Vid. 4 - the Cuckoo Waltz on Plasmophone
In subsequent experiments, I used a modern CRT television flyback transformer with an integrated tripler, driven by a TL494 chip. This setup enabled me to generate an electric arc nearly 10 cm (3.9 in) long. The resulting sound was deafeningly loud at close range, and in my opinion, the writhing electric arc is truly mesmerizing (Vid. 5).
Vid.5 - Ievan Polkka on Plasmophone
All the sounds heard in Videos 4 and 5 are produced by the vibrating plasma of the electric arc.
I must emphasize an important point: these types of experiments can pose a serious risk to life, particularly due to electric shock or thermal burns. Such work should only be performed by qualified specialists with the necessary knowledge and experience.
Acoustic levitation is a technique used to suspend matter in air against gravity by means of acoustic radiation pressure generated by high-intensity sound waves. Typically, ultrasonic frequencies are employed, rendering the sound inaudible to humans because of the high intensity required to counteract gravity.
Several methods can be used to generate the sound, with the most common approach involving piezoelectric transducers, which efficiently produce high-amplitude output at the desired frequencies.
In my research, levitated particles are trapped at the nodes of a standing wave (Fig. 21c) formed between a sound source (Fig. 21a) and a reflector (Fig. 21b).
Fig. 21 - Acoustic levitation,
my setup
This method relies on the particles being much smaller than the wavelength, typically around 10% or less, and the maximum mass of the levitated particles is generally on the order of a few milligrams. It is important to note that if the particle size is too small relative to the wavelength, the particles will behave differently and move toward the antinodes. This levitation setup is single-axis, meaning that all particles are confined along the central axis of the device (Vid. 6).
Vid. 6 - Levitation of small objects with sound
Speech synthesis refers to the generation of artificial human speech. This is achieved using a computer system known as a speech synthesizer, which can be implemented in either software or hardware form. A text-to-speech (TTS) system is one example that converts written text into spoken language. Alternatively, other systems convert symbolic linguistic representations, such as phonetic transcriptions, into speech. Specialized computer programs are often employed for this purpose, as producing natural, human-like synthetic voices requires considerable computational power.
Computer-based speech synthesis began in the late 1950s. In 1961, physicist John Larry Kelly Jr. and Louis Gerstman used an IBM 704 computer at Bell Labs to synthesize speech, notably recreating the song "Daisy Bell". In 1968, Noriko Umeda developed the first text-to-speech system in Japan. During a visit to Bell Labs, Arthur C. Clarke, a science fiction writer, futurist, inventor, and undersea explorer, witnessed the demonstration and later incorporated it into the climactic scene of his screenplay for 2001: A Space Odyssey, in which the fictional computer HAL 9000 sings the same song before being shut down by Dave Bowman.
During my work in the field of robotics, it became clear that having a hardware-based, real-time speech synthesis capability would be valuable. Various solutions exist, such as using Arduino with dedicated libraries or integrated circuits like the SpeakJet. While these options are undoubtedly useful, most of them generate speech in English, and there remains a lack of devices capable of producing speech in Polish. Therefore, I decided to construct my own hardware synthesizer.
I used an ATMEGA8 microcontroller (16 MHz) as the main component of the device. Sound samples, in the form of phonemes isolated from my own voice, were stored in a 256-Kbit AT24C256C serial EEPROM memory. This chip is I2C compatible, which makes communication and data transfer between the processor and memory highly convenient.
At the early stage of development, it became evident that the task I had undertaken would not be easy. It was necessary to design a custom phonetic-grammatical engine capable of interpreting text and selecting phoneme samples from a database to be played back in the correct order and at an appropriate (sometimes variable, for intonation) speed. The firmware I wrote occupies nearly the entire available memory of the microcontroller, yet it performs flawlessly, transforming text into intelligible Polish speech (Vid. 7).
Vid.7 - In action
My synthesizer enables speech synthesis from any text transmitted to the device via UART. The system autonomously interprets and adjusts intonation, rhythm, and speech pace based on punctuation marks such as periods, question marks, exclamation points, and commas. It is also possible to include additional commands within the text to control the volume and speed of the generated speech.
This project was developed for educational purposes and is based on resources available here.
The hardware platform consists of an Arduino Uno, a motor driver (L293D chip), and two Nema 17 stepper motors. The device is controlled by Polargraph software running on a computer, with communication between the laptop and the robot established via USB.
The robot’s drawing element, a whiteboard marker, moves along toothed belts driven by two Nema motors positioned in the upper corners of the board. The gondola is equipped with a servo mechanism that allows the marker to be raised or lowered onto the board surface. This setup enables the robot to draw virtually any single-color graphic on the board by importing an *.SVG vector file into the application running on the laptop (Vid. 8).
Vid. 8 - Robot drawing on whiteboard
Using the described technique, the robot can create even more detailed drawings. (Vid.9).
Vid. 9 - Next drawing
Simple radio receivers have long been a subject of fascination for electronics enthusiasts, especially beginners. Their straightforward design makes them an ideal starting point for learning about radio waves, signal detection, and amplification. Building a basic receiver gives aspiring engineers hands-on experience with essential components such as coils, capacitors, and diodes, while also fostering a deeper understanding of circuit behavior. Despite the dominance of digital technology, these simple receivers continue to captivate hobbyists, offering both an educational challenge and the satisfaction of tuning in to radio broadcasts with a self-built device.
A compact and easy-to-build AM radio that fits inside a matchbox effectively demonstrates the principles of amplitude modulation and signal detection (Fig. 22). Using just a few common components, including a ferrite rod, several transistors, and a germanium diode, it allows hobbyists to experience the excitement of tuning in to real broadcasts with a handmade device.
Fig. 22 - Radio compared to a matchbox
Here is a recording of a broadcast that demonstrates the sound quality achievable with a properly built and tuned receiver:
Vid. 10 - Sound quality of the Matchbox Radio
I recorded the audio by placing a microphone next to the earphone connected to the receiver.
How can you build a miniature radio receiver? I have prepared a detailed guide, which you can find here.
For educational purposes, I drew inspiration from a project shared on Thingiverse: https://www.thingiverse.com/thing:4579436, designed by DAZ.
This device is a small-scale machine designed to draw using a pen or marker (Vid. 11). It is constructed from inexpensive and readily available components, making it an excellent educational project for beginners interested in electronics and mechanics.
Vid. 11 - Plotter in action
The plotter is powered by an Arduino Uno running GRBL firmware, which interprets standard G-code instructions used in CNC machining. Three 28BYJ-48 stepper motors independently control the X, Y, and Z axes, with the Z-axis motor responsible for raising and lowering the pen. All mechanical parts are 3D-printed, making the machine easy to customize and upgrade.
Fig. 23 - Finished drawing
This type of project provides a practical introduction to the fundamentals of CNC principles, motion control, and 3D-printed mechanical design. It is an excellent hands-on opportunity
For more information about these and other experiments, please visit www.weirdscience.eu. You can also contact me by email (moze.dzis@gmail.com).