Збирач потоків

КПІ ім. Ігоря Сікорського, БО БФ «КОЛО» та Beredskapslyftet реалізують міжнародний проєкт «Ерготерапія без кордонів» в Україні kpi пн, 05/25/2026 - 16:11

While its vehicle battery resurrection skills are uncertain at best, this device also offers other useful abilities.

Two-plus years back, within my teardown of my PowerStation PSX3:

which I described at the time as being:

…(among other things) a portable recharger and jump-starter of vehicles’ cells. It’s also a portable tire inflater. And it’s an emergency light and USB power source, too…

I took advantage of the opportunity to also editorially “rip” into three newer solid-state and Li-ion battery-based versions of the same concept:

I tried three of these widgets, one claiming to deliver 1200 A of “peak” cranking juice:

Another spec’ing 1500 A:

And a third that promised to deliver 2000 A:

They all promptly went back to Amazon as full-refund returns. Now granted, if someone had left their interior dome light on too long and the battery was drained too low to successfully turn over the engine but still had some “life” one of these might suffice…And I’ll grant them one other thing: they’re certainly small and light.

But 2000 A of cranking current? Or even 1500 A? Mebbe for a fraction of a second, the time necessary to drain an intermediary capacitor, but not long enough to resurrect a significantly drained battery. Therefore, the quotes I put around the word “peak” earlier. Such products exemplify the well-worn saying, “mileage may vary”. Give me an old-school lead acid battery instead, any day!

Regarding my “They all promptly went back to Amazon as full-refund returns” comment, while that was my original intent, I didn’t end up fully actualizing it. The “1200 A” and “1500 A” variants indeed did get shipped back to the retailer. But, curiosity-motivated, I decided to keep the “2000 A” model, Spanarci’s ZETA2000, around if for no other reason than as a future teardown candidate.

Calling Cupertino…

That future is today. As usual, I’ll start with some outer box shots (sparing you the blank sides), as usual accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes:

Although my skepticism about the device’s jump-starting potential is already obvious at this early point in the writeup, I was admittedly impressed by the aesthetics and overall packaging of the product. Dare I even say it was Apple-reminiscent?

The cleverly labeled “Never Say Never” envelope, reminiscent (at least to me) of SpaceX’s three autonomous spaceport drone ships (i.e., floating rocket booster landing pads), “Of Course I Still Love You”, “Just Read the Instructions” and “A Shortfall of Gravitas”, contains literature bits:

Gee, I wonder what’s inside this translucent plastic sleeve?

To stretch the suspense, I’ll temporarily set it aside and investigate the lower box level instead:

Within is the to-vehicle battery cable harness, conveniently accompanied by USB-A-to-USB-C and USB-C-to-USB-C cables useful both for recharging the device’s internal battery pack and for powering other connected devices. Hold that thought:

Here’s the male connector at the end of the cable harness…

Burlesque finale

And here’s what it plugs into…

at out dissection patient, finally unswathed for its reveal. Top first:

Here’s the front:

Underneath the rubberized flap labeled “INPUT OUTPUT” at the right end are, likely unsurprisingly, first a bidirectional USB-C PD 30-W connector used for both device charging and for charging/powering another tethered device, such as a smartphone. The other, USB-A in form factor, is unidirectional (output-only) for similar tethered device “juicing” purposes.

Onward. Left side:

Rear; under this flap, cryptically (ha!) labeled “JUMPER CABLE” is the battery-cable harness connector you saw earlier:

And what the heck is that on the right side? A multi-LED strip, creating a 300-lumen four-mode (50% and 100% brightness stable, and both SOS and strobe pattern) flashlight, that’s what it is!

Last but not least, here’s the bottom view:

accompanied by a zoom-in of the specs:

Before opening ‘er up, I’ll note a few other feature set nuances. Like the conventional (i.e., AC-powered) solid-state charger that I tore down earlier this month, it supports various safety features such as short-circuit and “reverse” protection:

That said, there’s also “FORCE” support for dead cells and daring users:

The teardown’s the thing…

And now, let’s dive inside. Zoom back out on that earlier bottom overview shot and you’ll discern eight round rubber pieces, one in each corner and two more both at top and bottom:

I bet you can guess what comes next:

Eureka! Screw heads (trust me, they’re there, deep inside the recessed dimness)!

And what comes after that, dear readers? You got it right:

Dare I draw another analogy to Apple craftsmanship? Seriously, I’m impressed with the neatness and overall robustness of the insides, too!

Here’s the inside of the case topside:

…wherein I’ll detail the insides of the thing

And the overview that’s likely of greater interest to all of you!

Dominating the landscape, aside from the display, that is:

is the largest IC on this side, at center (horizontally) and toward the bottom (vertically). It’s Holtek’s HT67F489 8-bit RISC microcontroller, unsurprisingly with an integrated LCD controller and also containing (among other things) 8 Kwords of flash memory (4 Kwords on the more modest HT67F488 sibling, which the datasheet informs me (PDF) has been discontinued, anyway), 256 bytes of RAM and 64 bytes of EEPROM (none on the HT67F488). Also note two mode-select switches at far right, which mate to rubberized front panel buttons.

Let’s get that PCB out, shall we? Three screws hold it in place:

Guess what comes next?

In addition to noticing the now-absent screws (and their previously visible heads) in the next photo, I’d also like to draw your attention to the smaller but still-square IC to the right of the aforementioned HT67F489. It’s Southchip Semiconductor Technology’s SC2001 USB-PD controller. Given what you already know about the capability of the USB-C connector on the front of the device, this chip’s presence and functions shouldn’t be a surprise.

Here goes nothing:

My, what a big power source you have…

At left is the 44.4 Wh lithium polymer battery pack:

To its right is a beefy Sanyi Seiko SEV8-P-112DM 4-pin high-power relay:

soldered to a mini-PCB:

And the remainder of the compartment mostly consists of a bunch of now-disconnected wire harnesses:

The destination of one of them was, I admit with no shortage of chagrin, initially identity-baffling to me, until I pulled it out. See that gold-colored half-oval to the far right?

Oh yeah. The LEDs. Duh on me:

Underneath that large green region on the PCB underside is, as far as I can feel, nothing notable save for mounting-bracket sites and solder points related to the LCD on the other side:

The PCB-mounted speaker in one corner delivers a loud “beep” tone if, for example, you’ve got your to-battery connections reversed:

The one next to it is “just” an inductor (L1 is peeking out from the PCB under the white glue):

It, along with the rest of the components surrounding it (and some of those on the other side), implements a largely unmemorable power management subsystem.

In closing, I’ll share a side view of the USB-C and USB-A connectors; since the PCB is upside-down from its normal operating orientation, so are they:

…the better to incinerate you with, my dear

With that, I’ll close for today. Speaking of closing, I’ll keep the device disassembled for a while post-publication of this teardown. Then I’ll carefully reassemble it in the hopes of resurrecting it. If you smell smoke, see flame, or hear a loud “boom”, you’ll know my efforts didn’t succeed.

—Brian Dipert is the associate editor, as well as a contributing editor, at EDN.

Related Content

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• NOCO’s Genius 1: A trickle charger that tries harder
• A battery charger that loudly hums: Dump it or just make it dumb?
• Dead lead-acid batteries: Desulfation-resurrection opportunities?

The post Portable jump starters: A dubious primary use case, but not a total waste appeared first on EDN.

КПІ ім. Ігоря Сікорського — на «Фестивалі кар’єри» на ВДНГ kpi пн, 05/25/2026 - 12:33

Gas discharge tubes (GDTs) harness the physics of controlled sparks to provide reliable surge protection, making them a fundamental safeguard for modern electronic circuits.

They are deceptively simple devices that rely on ionized gas to tame the chaos of voltage surges. When a transient spike threatens sensitive circuitry, a GDT responds with a controlled spark, safely channeling excess energy away from the system.

Compact, rugged, and reliable, these components have become indispensable in applications ranging from telecom lines to industrial equipment. In essence, GDTs turn sparks into protection, making them a cornerstone in the engineer’s surge-defense toolkit.

It’s worth noting that GDTs are sometimes referred to as plasma arrestors. The two names describe the same device; a sealed tube filled with inert gas that forms a plasma arc when voltage exceeds its breakdown threshold. “GDT” is the term most often used in engineering literature and standards, while “gas plasma arrestor” tends to appear in catalogs or marketing to highlight the plasma discharge mechanism.

Inside the spark: How GDTs work

From the first spark to the final safeguard, gas discharge tubes show how even the simplest devices can deliver powerful protection where it matters most. To understand why, let us take a closer look at how they work.

At the heart of a GDT is a sealed chamber filled with inert gas such as neon or argon. Two electrodes face each other across a small gap inside this chamber. Under normal operating conditions, the gas is non-conductive, and the tube behaves like an open circuit. But when a voltage surge pushes the potential across the electrodes beyond the breakdown threshold, the gas ionizes. This ionization triggers a plasma discharge—controlled spark—that suddenly makes the tube conductive.

The plasma arc provides a low-resistance path, diverting the surge current safely away from sensitive components. Once the surge subsides and the voltage drops below the sustaining level, the plasma extinguishes, and the tube returns to its insulating state. This simple cycle—breakdown, conduction, recovery—is what makes GDTs both rugged and reliable in protecting circuits against transient overvoltages.

Figure 1 A medium-duty 2-electrode gas discharge tube safeguards telecommunications, industrial, and consumer electronics from voltage surges. Source: Bourns

Shared sparks, shared protection

Building on the fundamentals, the next nuance lies in how protection is applied across conductors. A two-lead GDT serves as a straightforward single-path protector, perfect for shunting individual DC rails or coaxial cables to ground. But when you place two separate two-lead tubes across a data pair, they will never fire at precisely the same instant, leaving a harmful “transverse voltage” between the lines.

A three-lead GDT solves this by enclosing both conductors in a common gas chamber. The moment one side ionizes, the entire tube triggers, discharging both lines to ground simultaneously. This synchronized action delivers the balanced protection that sensitive telecommunications and differential data circuits demand.

Figure 2 A 3-lead GDT ensures simultaneous crowbar action across differential lines, preventing unbalanced residual voltages during a surge event. Source: Littelfuse

It’s important to note at this point that standard GDTs are commonly available in both 2- and 3-electrode configurations, whereas high-voltage variants are primarily limited to 2-electrode designs with select 3-electrode exceptions. While 2-electrode devices are typically deployed for either line-to-ground or line-to-line protection, a 3-electrode GDT provides the advantage of addressing both protection paths within a single component.

Practical implementation of GDTs

When selecting a GDT for a specific application, the primary objective is to ensure the device remains inactive during normal operation while reacting instantaneously to overvoltage transients. This requires careful evaluation of key electrical parameters, starting with the DC spark-over voltage. To prevent “nuisance” triggering, the GDT’s minimum breakdown rating should typically be 1.2 to 1.5 times the peak operating voltage of the system.

Furthermore, because GDTs are “crowbar” devices, engineers must account for follow-on current, the current that continues to flow through the ionized gas after the surge has passed. If the system’s power source can sustain this arc, additional current-limiting components or a coordinated circuit design may be necessary to ensure the GDT successfully resets to its high-impedance state once the transient is cleared.

However, follow-on current is often absent from GDT datasheets because it’s not a fixed constant of the device, but rather a system-dependent behavior. A GDT is essentially a triggered short circuit; once ionized, its resistance drops so low that the resulting current is determined almost entirely by your power supply’s voltage and internal impedance.

While manufacturers provide the arc voltage and the glow-to-arc transition current, they cannot predict your specific source’s capacity to sustain that arc. Consequently, engineers must use those parameters to calculate the “holdover” risk themselves, often necessitating components like metal oxide varistor (MOV) to effectively “starve” the arc and allow the GDT to reset.

To round out the technical profile, several other parameters define a GDT’s performance and longevity. Maximum impulse spark-over voltage is critical, as it indicates the highest voltage level the device allows during a fast-rising surge before it triggers. To gauge durability, engineers look at nominal impulse discharge current, which is the peak surge current the GDT can survive for a set number of pulses, and alternating discharge current, which measures its ability to handle sustained AC faults.

Additionally, maximum capacitance must be minimal to ensure signal integrity in high-frequency lines, while minimum insulation resistance ensures the GDT remains electrically “invisible” until a surge occurs.

Figure 3 Plot illustrates the GDT voltage breakdown characteristic. Source: Author

As a worthy take on paper, the GDT’s protective behavior is defined by its transition through distinct electrical phases, captured sequentially in Figure 3. The process initiates with the sparkover voltage, the exact point where the internal gas ionizes and becomes conductive. Immediately following this breakdown, the voltage falls to a relatively stable plateau known as the glow region, where current flows but remains limited.

As the surge energy intensifies, the device undergoes the rapid glow to arc transition, the critical threshold where the discharge collapses into a highly conductive plasma. This leads immediately to the arc voltage, the final “crowbar” state where the voltage drop plummets to its absolute lowest point. Identifying this transition sequence is vital, as the low arc voltage is precisely what triggers the risk of sustained follow-on current from the system’s power source.

GDTs are often evaluated against IEC 61000‑4‑5, the international surge immunity standard, because their protective behavior directly addresses the transient overvoltages defined by this test. The standard specifies surge waveforms—most notably the 1.2/50 µs voltage impulse and the 8/20 µs current impulse—to replicate lightning‑induced or switching transients. In these scenarios, GDTs act as frontline protectors, clamping and diverting surge energy away from sensitive equipment to ensure compliance and resilience.

Bonus insight: How to test a GDT surge arrestor

Have you ever wondered how to verify whether a GDT surge arrestor is still healthy and ready to protect against lightning, static, or electromagnetic pulse (EMP) events? An EMP is a sudden burst of electromagnetic energy—often from lightning strikes, solar storms, or even man-made sources—that can damage sensitive electronics. The only definitive way to confirm a GDT’s readiness is to make the device “fire”.

The most reliable approach is a DC high-voltage ramp test, performed with a power supply or a megohmmeter. Because a GDT behaves like an open circuit under normal conditions, you gradually increase the DC voltage across its terminals until it reaches the rated breakdown point. To ensure safety and prevent excessive current once the tube fires, a series resistor should always be included in the test circuit. This resistor limits the surge current, protects the power supply, and prevents overstressing the GDT during repeated tests.

Sparking applications, igniting ideas

Gas discharge tubes prove their worth across a wide spectrum of systems. In telecommunications, they safeguard MDF modules, xDSL equipment, RF systems, antennas, and base stations. In industrial and consumer electronics, they protect power supplies, surge protectors, alarm systems, and even irrigation systems.

Positioned in front of and in parallel with sensitive lines—power, communication, signal, and data transmission—GDTs shield equipment from transient surges caused by lightning strikes or switching operations. Under normal conditions they remain invisible to the signal, but when an overvoltage surge arrives, they switch to a low-impedance state and divert the energy safely away from the circuitry.

These sparks of protection are more than circuit defense; they are design opportunities. For makers and engineers, the challenge is to take this proven sequence from sparkover to arc and reimagine it in your own projects. Every surge control is a chance to build systems that are not only safer but smarter. So let the sparks inspire you: experiment boldly, refine relentlessly, and turn protective theory into resilient innovation.

T. K. Hareendran is a self-taught electronics enthusiast with a strong passion for innovative circuit design and hands-on technology. He develops both experimental and practical electronic projects, documenting and sharing his work to support fellow tinkerers and learners. Beyond the workbench, he dedicates time to technical writing and hardware evaluations to contribute meaningfully to the maker community.

Related Content

• Power-Back Surge Protection Circuit
• Overvoltage-protection circuit saves the day
• Robust overvoltage protection in high-density electronics
• How to prevent overvoltage conditions during prototyping
• Gas Discharge Tubes: Old Protection in a New Bottle–Literally

The post Gas discharge tubes (GDTs): From sparks to circuit protection appeared first on EDN.

Just got these in their original packaging yesterday! submitted by /u/Electrical_Car_6067 [link] [comments]

submitted by /u/1Davide [link] [comments]

Guys go n check out this project to know more about the communication protocol. submitted by /u/Starkk0077 [link] [comments]

yeah see i'm new to this electronics stuff i've only had this kit for like a day or two, like a dumbass i fried the E segment on that little 7 seg but i really wanted to still use it for something, so i grabbed some LEDs and made one on a mini breadboard that even shares the same pinout as a normal 7 seg (see those 5 empty holes on the edge of the bottom left of the board, those are the bottom pins on a normal 7 seg and the top ones are of course on the other side of the board, and since there's no DP i just made it a grounding pin) i wanted to make it all the same color LEDs but my little dinky starter kit here only has 5 of each color so i just did what i could i've got a video of me testing it, i wanted to post that too but the sub wouldn't let meeeee submitted by /u/AftonsAssCheeks [link] [comments]

submitted by /u/nexo420x [link] [comments]

submitted by /u/AutoModerator
[link] [comments]

After using square grid papers and Figma projects I remembered we can create web apps with the help of AI assistants and I created a web app to help with coming up neatly organized breadboard wiring. submitted by /u/Big-Rent6905 [link] [comments]

📰 Газета "Київський політехнік" № 19-20 за 2026 (.pdf) Інформація КП пт, 05/22/2026 - 20:33

Medical imaging has become one of the most critical pillars of modern healthcare to provide insights into diagnosis, treatment planning, and disease management. However, the very success of imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) has created a growing challenge of data and decision-making. As imaging generates more information to interpret, artificial intelligence helps to improve these systems by supporting faster, smarter workflows for higher-accuracy diagnoses.

The volume of imaging studies has increased substantially over the past decade, putting additional pressure on the shortage of radiologists. At the same time, technological advances in scanner hardware have enabled the acquisition of thinner slices and higher-resolution images, with a single CT or MRI exam consisting of hundreds or thousands of images.

In clinical settings, the challenge is not whether scans have sufficient data but whether the health system can reconstruct, review, quantify, and interpret the data fast enough to support timely clinical decisions. We look at the use of AI and some of the popular deep-learning models in medical imaging and diagnostics while also examining how AI is being integrated across the imaging workflow.

AI enhances medical imaging systems such as CT or MRI scanners by supporting faster, smarter workflows for higher-accuracy diagnoses. (Source: Adobe Stock) AI across the medical imaging pipeline

AI is moving medical imaging and diagnostics from early-generation concepts and narrow automation toward broader integration across the imaging pipeline. The integration of AI is augmenting a wide range of tasks, from the moment an exam is ordered to the final clinical interpretation, to improve speed, accuracy, consistency, and efficiency. This approach addresses the critical bottleneck in the modern imaging workflow, turning a linear and often manual process into a more optimized, data-driven, and intelligent system.

The influence of AI begins even before a single image is acquired. This includes administrative and logistical steps that are important for optimization. For example, natural-language-processing models can analyze a patient’s clinical history and the reason for an exam within the electronic health record to help automate the selection of the most appropriate imaging protocol.

During the acquisition stage, AI contributes to image quality and efficiency. In CT, AI can automate and optimize scan ranges and radiation dose parameters based on the patient’s specific anatomy to ensure diagnostic-quality images are obtained at the lowest possible radiation exposure.

Image reconstruction is another impactful application of AI. Deep-learning reconstruction has changed this process. These models are trained on a large dataset of high-quality images to produce images with significantly lower noise and higher signal-to-noise ratio from under-sampled or low-dose raw data. For MRI, this means scan times can be reduced by up to 75% in some cases, without sacrificing image quality.

Once the images are created, AI is used for analysis and interpretation. In this phase, it helps radiologists in extracting clinically relevant information. Automated segmentation is the key task in which AI algorithms delineate anatomical structures, organs, or pathologies with high precision. This is an important prerequisite for quantitative analysis and is used to accelerate standardized assessment workflows, such as for the prostate imaging reporting and data system.

After the segmentation, AI tools for detection and triage can screen images for critical findings, such as intracranial hemorrhage, pulmonary embolism, or large vessel occlusions in stroke patients. However, AI in this setting is changing the order, speed, and consistency of review. A triage algorithm can bring a suspected emergency case to the top of the queue, while the radiologist remains responsible for confirming the findings, considering clinical context, and issuing the final report.

AI models in modern imaging diagnostics

The growth in powerful deep-learning architectures today serves as the engine for modern medical AI to perform complex tasks such as detecting minute pathological changes, precisely segmenting anatomical structures, and fusing information from different clinical sources.

Convolutional neural networks (CNNs) have become the go-to architecture for most AI medical imaging applications, especially in radiology. Their design is inspired by the human visual cortex and is well-suited for processing grid-patterned data such as images.

While CNNs are useful for classification tasks, medical imaging requires a more granular understanding of spatial information, such as tracing the boundaries of an organ or tumor. This task involves assigning a class label to every pixel in an image. For this purpose, encoder-decoder architectures, most popularly the U-Net, have become the de facto standard.

The U-Net design addresses this challenge by combining semantic context with low-level, high-resolution spatial information. The architecture has two main components: the encoder and the decoder. As the image data goes deeper into the encoder, the spatial resolution decreases, but the number of feature channels increases. This allows the architecture to capture context-rich information from the image.

The decoder’s role is to take the compressed, high-level feature representation from the encoder and progressively up-sample it back to the original image resolution to generate a pixel-wise segmentation map. It achieves this by using a learned transposed convolution to increase spatial dimensions.

The U-Net architecture uses skip connections that create a pathway for information to flow from the encoder to the decoder at corresponding levels of resolution. This fusion provides the decoder with the fine-grained spatial details that were lost during the down-sampling.

This is necessary in many diagnostic cases that are not a simple classification problem. The model not only needs to identify that a tumor, lesion, or abnormality is present, but it also outlines the boundary, calculates volume, compares change over time, or separates healthy tissue from pathology. This pixel-level requirement is why encoder-decoder architectures have become key to segmentation workflows.

The success of this concept has led to variants designed to further improve performance. U-Net++, for example, introduces nested and dense skip pathways to reduce the semantic gap between the encoder and the decoder feature maps, while Attention U-Net integrates attention mechanisms that allow the model to focus on the most relevant image regions. Other advanced versions, such as nnU-Net, provide a self-configuring framework that automatically adapts the network architecture and preprocessing steps for any given segmentation task.

However, CNNs have limitations in modeling long-range dependencies and global context within an image. This led to the exploration of Vision Transformers in medical imaging. Transformers can model relationships across wider image regions, which is useful for tasks in which pathology, anatomy, and clinical context are distributed across a larger field of view.

But at the same time, they face a domain gap between the natural images on which many of these models are pretrained and the unique characteristics of medical images. The black-box nature of these models raises concerns about interpretability, which is important for clinical trust and high-stakes decision-making.

How AI improves medical insights

Integrating AI into medical imaging brings enormous improvements in speed and operational efficiency. By automating time-consuming tasks at multiple stages, AI targets the workload pressures and delays that modern radiology faces. This results in faster diagnoses and more timely patient intervention.

AI is also increasing the accuracy of the diagnostic quality of medical imaging by reducing variability. Human interpretation is always subject to limitations because of fatigue, perceptual errors, and inter-reader variability, whereby different radiologists may interpret the same image differently. AI provides a more powerful set of tools to augment human perception.

AI systems are particularly strong in pattern-recognition tasks and have demonstrated the ability to detect subtle abnormalities that may be missed by the human eye. In lung cancer screening with CT, for example, studies have shown that AI algorithms can achieve a nodule-detection sensitivity exceeding 95% for nodules of 4 mm or larger.

In lung cancer screening with CT scans, AI algorithms can improve nodule-detection sensitivity and reduce the risk of a missed diagnosis. (Source: Adobe Stock)

A research study shows that AI detected 8.4% more lung nodules in patients with complex lung diseases. Similarly, in mammography, AI models have performed comparably to human experts in detecting breast cancer in certain validation studies. These systems function as a highly effective second reader that can help radiologists focus on potential concerns and reduce the risk of a missed diagnosis.

In addition, radiomics is built upon the foundation of AI-driven quantification. For example, radiomic features extracted from pre-treatment CT images have been used to predict survival in lung cancer patients, while signatures from MRI scans have shown a correlation with recurrence risk in glioblastoma patients.

What’s next

The current advancements are setting the stage for a future in which AI will be deeply integrated into diagnostics and patient care. One of the most important future directions is the maturation of multimodal AI and foundation models for a wider range of data types, including imaging, genomics, proteomics, digital pathology, clinical notes, and even real-time physiological data from wearable sensors.

The future of AI is likely to be one of human-AI collaboration. AI will handle the data-intensive tasks of detection, measurement, and quantification, while radiologists focus on higher-order tasks of complex synthesis and clinical correlation.

The post AI-powered medical imaging: Turning data into faster diagnoses appeared first on EDN.

Surface-mount polymer positive temperature coefficient (PPTC) devices are widely used resettable protection components in modern electronic systems. These devices are commonly selected when designers require automatic recovery after a fault, which makes them useful in consumer electronics, telecommunications equipment, industrial systems, and medical devices.

Despite their widespread use, detailed SPICE models for these components remain uncommon. Datasheets typically provide static electrical characteristics, but dynamic models that allow designers to simulate real operating conditions are rarely available.

Yet many practical operating scenarios can be reproduced effectively through simulation. Examples include overcurrent or short to ground events on a USB 5-V supply line, short circuit faults on a lithium-ion battery, or motor stall protection under varying ambient temperatures.

The value of such simulations is clear: they illustrate the consequences of complex overcurrent conditions or potential failure scenarios before hardware is built. In particular, modern simulation tools such as QSPICE make it possible to evaluate large parameter sets quickly, allowing designers to explore how protection devices behave under a wide range of electrical and thermal conditions.

However, modeling these devices accurately raises important questions. Designers must consider whether the model includes the large tolerances inherent to these components, whether ambient temperature influences the results, whether device aging after a trip event is represented, and how trip-time curves versus fault current are incorporated.

All these concerns are valid. If models are to be used effectively, these factors must be addressed so that simulations produce results that reflect real-world behavior.

PPTC SPICE model genesis and thermal fundamentals

From a functional perspective, a PPTC device can be approximated as a thermal mass with a baseline electrical resistance at ambient temperature. When a fault current flows through the device, resistive heating raises the internal temperature. Once the temperature reaches the trip temperature (Ttrip), the device undergoes a rapid increase in resistance. This sharply reduces the current and stabilizes the device at an elevated temperature.

The heat balance of the system can be described by the following equation:

In this equation:

• Cth represents thermal capacitance
• dT/dt represents rate of temperature change
• D represents thermal conductivity constant
• Tamb and T represent ambient and device temperature
• R(T) represents temperature-dependent resistance
• I represents fault current

Before tripping, the resistance can be approximated as a linear function of temperature using a temperature coefficient:

From equations (1) and (2), we derive and simplify:

In fact, here 𝑇𝑎𝑚𝑏 = T25 = 25°C

By integrating equation (3) from t = o to ttrip and from T = 25°C to T= Ttrip, we get:

When the theoretical curve derived from this model is plotted and compared with measured device data, differences become apparent, as shown in Figure 1.

Figure 1 The theoretical trip-time versus fault-current curve is compared with representative measured data. Source: Vishay

The simplified single thermal block model reveals clear limitations at both low and high fault currents. At high currents, the ideal slope of ln (trip time) versus ln (fault current) should be −2, because trip time is inversely proportional to dissipated power, which scales with the square of current.

In practice, the observed slope is significantly flatter. This indicates that additional physical mechanisms influence the thermal response at high current levels. At low fault currents, the theoretical curve rises more steeply than measured results. This discrepancy arises because a PPTC cannot be modeled as a single thermal mass dissipating heat through a single thermal resistance.

Additional factors include:

• Heat dissipation through solder joints and PCB copper
• Delayed thermal propagation in the polymer structure
• Resistance changes caused by device aging

Practical SPICE modeling of PPTC devices

Under lower current conditions, the thermal behavior of a PPTC device can be represented more accurately using a multi-stage thermal network. An example of this approach is shown in Figure 2, where a three-stage thermal Cauer network represents heat flow inside the device.

Figure 2 Here is an example of a three-stage thermal Cauer network representing heat flow within a PPTC device installed in an application circuit. Source: Vishay

In this model:

• Tpptc represents temperature of internal polymer material
• Telectrode represents temperature of device electrodes
• Tpcb represents temperature at PCB solder joint
• Tambient represents far-field ambient temperature

Each stage includes thermal resistance and thermal capacitance elements that model heat transfer between nodes.

The simulations described in this work were implemented in QSPICE, which provides powerful parameter-sweep capabilities. This allows multiple device and environmental parameters to be varied simultaneously, enabling thousands of simulations to be performed in a short time.

Once the thermal parameters are adjusted to match measured trip-time behavior, the simulated results closely reproduce measured data. The comparison between simulation and measurement is shown in Figure 3.

Figure 3 Simulated trip-time versus fault-current characteristics is compared with measured data. Source: Vishay

Remaining deviations are largely attributed to measurement conditions and inherent device tolerances. Nevertheless, the multi-stage thermal model provides a substantial improvement over the simplified single-block model.

Additional model features can also be incorporated, including:

• Resistance aging following a trip event
• Failure behavior when applied voltage exceeds rated limits
• Ambient temperature dependence

Influence of ambient temperature

Ambient temperature has a strong influence on PPTC device behavior. The simulation circuit used to investigate this behavior is shown in Figure 4:

Figure 4 An example application circuit is used to evaluate PPTC behavior under surge conditions at different ambient temperatures. Source: Vishay

Two successive voltage pulses are applied under varying temperature conditions. The resulting waveforms are shown in Figure 5.

Figure 5 Simulation results display device response to successive voltage pulses at different ambient temperatures. Source: Vishay

Here, several effects can be observed:

• Trip time varies with ambient temperature
• Device resistance increases following the first trip event
• Excessive voltage may force the device into a short circuit state

Because of this temperature dependence, datasheets typically provide thermal derating curves describing how allowable current varies with ambient temperature. An example of such a curve is shown in Figure 6.

Figure 6 A typical thermal derating curve illustrates how allowable hold current decreases as ambient temperature increases. Source: Vishay

The behavior behind this curve can also be reproduced through simulation. The circuit used for this analysis is shown in Figure 7, and the corresponding simulation results appear in Figure 8.

Figure 7 A simulation circuit is used to evaluate device behavior under varying load resistance and ambient temperature conditions. Source: Vishay

Figure 8 Simulation results display trip-time behavior as temperature and load conditions change. Source: Vishay

From these results, the variation of fault current as a function of ambient temperature can be extracted. The resulting simulated derating curve is shown in Figure 9.

Figure 9 The simulated thermal derating curve is derived from the SPICE model. Source: Vishay

Application simulations

Once realistic device models are available, they can be used to simulate complete application circuits.

USB power supply protection

A typical USB protection circuit is shown in Figure 10.

Figure 10 The application circuit illustrates a USB power supply protected by a PPTC device. Source: Vishay

Simulation results for plug-in disturbances and short circuit events are shown in Figure 11.

Figure 11 Simulation results show device response during plug-in events and short circuit disturbances. Source: Vishay

At 100 ms, a load short circuit is introduced. The PPTC device transitions from a low resistance state to a high resistance state, limiting the current.

Motor stall protection

An example motor protection circuit is shown in Figure 12.

Figure 12 The circuit example of a small electric motor is protected against stall conditions using a PPTC device. Source: Vishay

Simulation results demonstrating the stall event appear in Figure 13.

Figure 13 Simulation results show motor current increase and protection device trip during a stall event. Source: Vishay

When the motor stalls, I(Vspeed) drops to 0, and the current rises sharply. The protection device heats and transitions to a high resistance state, limiting current and preventing thermal damage.

Lithium-ion battery short circuit protection

The simulated battery protection circuit is shown in Figure 14, with results presented in Figure 15.

Figure 14 The simulation circuit represents a lithium-ion battery system with short circuit protection. Source: Vishay

Figure 15 Simulation results display surge current and resulting resistance increase after a load short circuit. Source: Vishay

At lower ambient temperatures, the device responds more slowly, allowing higher surge currents before tripping.

QSPICE modeling upside

The SPICE modeling approach described here demonstrates that realistic PPTC device behavior can be reproduced by fitting model parameters to datasheet characteristics and incorporating accurate thermal representations.

Using a simulation environment such as QSPICE enables designers to explore these behaviors efficiently through extensive parameter sweeps and transient analysis. The models can account for:

• Resistance tolerance
• Aging effects
• Ambient temperature dependence
• Overvoltage behavior

By incorporating these models into full application simulations, designers gain insights that cannot be obtained from datasheets alone. Nevertheless, simulation should always be complemented by laboratory validation before releasing a design into production.

Alain Stas is head of product marketing for non-linear resistors at Vishay.

Related Content

• QSPICE: Transient Domain Analysis
• QSPICE Simulator for Electronic Circuits
• QSPICE: A Simulation Tool for Power Circuits
• QSPICE: Introduction to the Simulation Environment
• QSPICE Revolutionizes Power, Analog Device Circuit Simulation

The post From specification to simulation: Modeling PPTC devices in QSPICE appeared first on EDN.

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