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Hi that's a CH32V003 Compute Module i design some time ago, nice specs with 48 MHz clock and tiny for a 2k flash product; Regard Jean-François submitted by /u/InterestingSink7547 [link] [comments]

Yep! Here's a low voltage DC to low voltage AC inverter courtesy of Gemini: https://preview.redd.it/7a5u173kpk9g1.png?width=659&format=png&auto=webp&s=101f64caa0acd3a89574e1fe1c8317a5076f871f submitted by /u/Linker3000 [link] [comments]

Нова навчально-наукова лабораторія протезування, медичної реабілітації та ерготерапії в КПІ ім. Ігоря Сікорського kpi пт, 12/26/2025 - 17:26

Hey everyone! This is qron0b! A low-power binary wristwatch that I built every part of it myself, from the PCB to the firmware to the mechanical design. Check out the Github repo (don't forget to leave a star!): https://github.com/qewer33/qron0b The watch itself is rather minimalistic, it displays the time in BCD (Binary Coded Decimal) format when the onboard button is pressed. It also allows you to configure the time using the button. The PCB is designed in KiCAD and has the following components: ATtiny24A MCU DS1302 RTC 4x4 LED matrix (16 LEDs) 74HC595 shift register (as the LED matrix "driver") CR2032 battery holder AVR ISP programming header A push button The firmware is written in bare-metal AVR C and is around ~1900 bytes meaning it fits the 2KB flash memory of the ATtiny24A. It was quite a fun challenge to adhere to the 2KB limit and I am working on further optimizations to reduce code size. The 3D printed case is designed in FreeCAD and is a screwless design. The top part is printed with an SLA printer since it needs to be translucent. I ordered fully transparent prints from JLCPCB and I'm waiting for them to arrive but for now, it looks quite nice in translucent black too! This was my first low-power board design and I'm quite happy with it, it doesn't drain the CR2032 battery too much and based on my measurements and calculations it should last a year easily without a battery replacement. submitted by /u/qewer3333 [link] [comments]

Crowbar circuits have long been the go-to safeguard against overvoltage conditions, prized for their simplicity and reliability. Though often overshadowed by newer protection schemes, the crowbar remains a classic protector worth revisiting.

In this quick look, we will refresh the fundamentals, highlight where they still shine, and consider how their enduring design continues to influence modern power systems.

Why “crowbar”?

The name comes from the vivid image of dropping a metal crowbar across live terminals to force an immediate short. That is exactly what the circuit does—when an overvoltage is detected, it slams the supply into a low-resistance state, tripping a fuse or breaker and protecting downstream electronics. The metaphor stuck because it captures the brute-force simplicity and fail-safe nature of this classic protection scheme.

Figure 1 A crowbar protection circuit responds to overvoltage by actively shorting the power supply and disconnecting it to protect the load from damage. Source: Author

Crowbars in the CRT era: When fuses took the fall

In the era of bulky cathode-ray tube (CRT) televisions, power supply reliability was everything. Designers knew that a single regulator fault could unleash destructive voltages into the horizontal output stage or even the CRT itself. The solution was elegantly brutal: the crowbar circuit. Built around a thyristor or silicon-controlled rectifier (SCR), it sat quietly until the supply exceeded the preset threshold.

Then, like dropping a literal crowbar across the rails, it slammed the output into a dead short, blowing the fuse and halting operation in an instant. Unlike softer clamps such as Zener diodes or metal oxide varistors, the crowbar’s philosophy was binary—either safe operation or total shutdown.

For service engineers, this protection often meant the difference between replacing a fuse and replacing an entire deflection board. It was a design choice that reflected the pragmatic toughness of the CRT era: it’s better to sacrifice a fuse than a television.

Beyond CRT televisions, crowbar protection circuits find application in vintage computers, test and measurement instruments, and select consumer products.

Crowbar overvoltage protection

A crowbar circuit is essentially an overvoltage protection mechanism. It remains widely used today to safeguard sensitive electronic systems against transients or regulator failures. By sensing an overvoltage condition, the circuit rapidly “crowbars” the supply—shorting it to ground—thereby driving the source into current limiting or triggering a fuse or circuit breaker to open.

Unlike clamp-type protectors that merely limit voltage to a safe threshold, the crowbar approach provides a decisive shutdown. This makes it particularly effective in systems where even brief exposure to excessive voltage can damage semiconductors, memory devices, or precision analog circuitry. The simplicity of the design, often relying on a silicon-controlled rectifier or triac, ensures fast response and reliable action without adding significant cost or complexity.

For these reasons, crowbar protection continues to be a trusted safeguard in both legacy and modern designs—from consumer electronics to laboratory instruments—where resilience against unpredictable supply faults is critical.

Figure 2 Basic low-power DC crowbar illustrates circuit simplicity. Source: Author

As shown in Figure 2, an overvoltage across the buffer capacitor drives the Zener diode into conduction, triggering the thyristor. The capacitor is then shorted, producing a surge current that blows the local fuse. Once latched, the thyristor reduces the rail voltage to its on-state level, and the sustained current ensures safe disconnection.

Next is a simple practical example of a crowbar circuit designed for automotive use. It protects sensitive electronics if the vehicle’s power supply voltage, such as from a load dump or alternator regulation failure, rises above the safe setpoint. The circuit monitors the supply rail, and when the voltage exceeds the preset threshold, it drives a dead short across the rails. The resulting surge current blows the local fuse, shutting down the supply before connected circuitry can be damaged.

Figure 3 Practical automotive crowbar circuit protects connected device via local fuse action. Source: Author

Crowbar protection: SCR or MOSFET?

Crowbar protection can be implemented with either an SCR or a MOSFET, each with distinct tradeoffs.

An SCR remains the classic choice: once triggered by a Zener reference, it latches into conduction and forces a hard short across the supply rail until the local fuse opens. This rugged simplicity is ideal for high-energy faults, though it lacks automatic reset capability.

A MOSFET-based crowbar, by contrast, can be actively controlled to clamp or disconnect the rail when overvoltage is detected. It offers faster response and lower on-state voltage, which is valuable for modern low-voltage digital rails, but requires more complex drive circuitry and may be less tolerant of large surge currents.

Now I remember working with the LTM4641 μModule regulator, notable for its built-in N-channel overvoltage crowbar MOSFET driver that safeguards the load.

GTO thyristors and active crowbar protection

On a related note, gate turn-off (GTO) thyristors have also been applied in crowbar protection, particularly in high-power systems. Unlike a conventional SCR that latches until the fuse opens or power is removed, a GTO can be actively turned off through its gate, allowing controlled reset after an overvoltage event. This capability makes GTO-based crowbars attractive in industrial and traction applications where sustained shorts are undesirable.

Importantly, GTO thyristors enable “active” crowbars, in contrast to conventional SCRs that latch until power is removed. That is, an active crowbar momentarily shorts the supply during a transient, and gate-controlled turn-off then restores normal operation without intervention. In practice, asymmetric GTO (A-GTO) thyristors are preferred in crowbar protection, while symmetric (S-GTO) types see limited use due to higher losses.

However, their demanding gate-drive requirements and limited surge tolerance have restricted their use in low-voltage supplies, where SCRs remain dominant and MOSFETs or IGBTs now provide more practical and controllable alternatives.

Figure 4 A fast asymmetric GTO thyristor exemplifies speed and strength for demanding power applications. Source: ABB

A wrap-up note

Crowbar circuits may be rooted in classic design, but their relevance has not dimmed. From safeguarding power supplies in the early days of solid-state electronics to standing guard in today’s high-density systems, they remain a simple yet decisive protector. Revisiting them reminds us that not every solution needs to be complex—sometimes, the most enduring designs are those that do one job exceptionally well.

As engineers, we often chase innovation, but it’s worth pausing to appreciate these timeless building blocks. Crowbars embody the principle that reliability and clarity of purpose can outlast trends. Whether you are designing legacy equipment or modern platforms, the lesson is the same: protection is not an afterthought, it’s a foundation.

I will close for now, but there is more to explore in the enduring story of circuit protection. Stay tuned for future posts where we will continue connecting classic designs with modern challenges.

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

• SCR Crowbar
• Where is my crowbar?
• Crowbar Speaker Protection
• Overvoltage-protection circuit saves the day
• How to prevent overvoltage conditions during prototyping

The post Crowbar circuits: Revisiting the classic protector appeared first on EDN.

I’ve always been intrigued by “small-scale” energy harvest where the mechanism is relatively simple while the useful output is modest. These designs, which may be low-cost but may also use sophisticated materials and implementations, often make creative use of what’s available, generating power on the order of about 50 milliwatts.

These harvesting schemes often have the first-level story of getting “a little something for almost nothing” until you look more deeply in the detail. Among the harvestable sources are incidental wind, heat, vibration, incremental motion, and even sparks.

The most recent such harvesting arrangement I saw is another scheme to exploit the thermal differential between the cold night sky and Earth’s warmer surface. The principle is not new at all (see References)—it has been known since the mid-18th century—but it returns in new appearances.

This approach, from the University of California at Davis, uses a Stirling engine as the transducer between thermal energy and  mechanical/electrical energy, Figure 1. It was mounted on a flat metal plane embedded into the Earth’s surface for good thermal contact while pointing at the sky.

Figure 1 Nighttime radiative cooling engine operation. (A) Schematic of engine operation at night. Top plate radiatively couples to the night sky and cools below ambient air temperature. Bottom plate is thermally coupled to the ground and remains warmer, as radiative access to the night sky is blocked by the aluminum top plate. This radiative imbalance creates the temperature differential that drives the engine. (B) Downwelling infrared radiation from the sky and solar irradiance are plotted throughout the evening and into the night on 14 August 2023. These power fluxes control the temperature of the emissive top plate. The fluctuations in the downwelling infrared are caused by passing clouds, which emit strongly in the infrared due to high water content. (C) Temperatures of the engine plates compared to ambient air throughout the run. The fluctuations in the top plate and air temperature match the fluctuations in the downwelling infrared. The average temperature decreases as downwelling power decreases. (D) Engine frequency and temperature differential remain approximately constant. Temporary increases in downwelling infrared, which decrease the engine temperature differential, are physically manifested in a slowing of the engine.

Unlike other thermodynamic cycles (such as Rankine, Brayton, Otto, or Diesel), which require phase changes, combustion, or pressurized systems, the Stirling engine can operate passively and continuously with modest temperature differences. This makes them especially suitable for demonstrating mechanical power generation using passive thermal heat from the surroundings and radiative cooling without the need for fuels or active control systems.

Most engines which use thermal differences first generate heat from some source to be used against the cooler ambient side. However, there’s nothing that says the warmer side can’t be at the ambient temperature while the other side is colder relative to the ambient one.

Their concept and execution are simple, which is always attractive. The Stirling engine (essentially a piston driving a flywheel), is put on a 30 × 30 centimeter flat-metal panel that acts as a heat-radiating antenna. The entire assembly sits on the ground outdoors at night; the ground acts as the warm side of the engine as the antenna channels the cold of space. 

Under best-case operation, the system delivered about 400 milliwatts of electrical power per square meter, and was used to drive a small motor. That is about 0.4% efficiency compared to theoretical maximum. Depending on your requirements, that areal energy density is somewhere between not useful and useful enough for small tasks such as charging a phone or powering a  small fan to ventilate greenhouses, Figure 2.

Figure 2 Power conversion analysis and applications of radiative cooling engine. (A) Mechanical power plotted against temperature differential for various cold plate temperatures (TC). (Error bars show standard deviation.). Solid lines represent potential power corresponding to different quality engines denoted by F, the West number. (B) Voltage sweep across the attached DC motor shows maximum power point for extraction of mechanical to electrical power conversion at various engine temperature differentials (note: typical passive sign convention for electrical circuits is used). Solid red lines are quadratic fits of the measured data points (colored circles). Inset shows the dc motor mounted to the engine. (C) Bar graph denotes the remaining available mechanical power and the electrical power extracted (plus motor losses) when the DC motor is attached. (D) Axial fan blade attachment shown along with the hot-wire anemometer used to measure air speed. (E) Air speed in front of the fan is mapped for engine hot and cold plate temperatures of 29°C and 7°C, respectively. White circles indicate the measurement points. (F) Maximum air speed (black dots) and frequency (blue dots) as a function of engine temperature differential. Shaded gray regions show the range of air speeds necessary to circulate CO2 to promote plant growth inside greenhouses and the ASHRAE-recommended air speed for thermal comfort inside buildings.

Of course, there are other considerations such as harvesting only at night (hmmm…maybe as a complement to solar cells?) are needing a clear sky with dry air for maximum performance. Also, the assembly is, by definition, fully exposed to rain, sun, and wind, which will likely shorten its operation life.

The instrumentation they used was also interesting, as was their thermal-physics analysis they did as part of the graduate-level project. The flywheel of the engine was not only an attention-getter, its inherent “chopping” action also made it easy to count motor revolutions using a basic light-source and photosensor arrangement. The analysis based on the thermal cycle of the Stirling engine concluded that its Carnot-cycle efficiency was about 13%.

This is all interesting, but where does it stand on the scale of viability and utility? On one side, it is a genuine source of mechanical and follow-up electrical energy at very low cost. But that is only under very limited conditions with real-world limitations.

I think this form of harvesting gets attention because, as I noted upfront, it offers some usable energy at little apparent cost. Further, it’s very understandable, requires exotic materials or components, and comes with dramatic visual of the Stirling engine and its flywheel. It tells a good story that gets coverage and likely those follow-on grants. They have also filed a provisional patent related to the work; I’d like to see the claims they make.

But when you look at its numbers closely and reality becomes clearer, some of that glamour fades. Perhaps it could be used for a one-time storyline in a “McGyver-like” TV show script where the hero improvises such a unit, uses it to charge a dead phone, and is able to call for help. Screenwriters out there, are you paying attention?

Until then, you can read their full, readable technical paper “Mechanical power generation using Earth’s ambient radiation” published in the prestigious journal Science Advances from the American Association for the Advancement of Science; it was even featured on their  cover, Figure 3, proving The “free” aspects of this harvesting and its photo-friendly design really do get attention!

Figure 3 The harvesting innovation was considered sufficiently noteworthy to be featured as the cover and lead story of Science Advances.

What’s your view on the utility and viability of this approach? Do you see any strong, ongoing applications?

Related Content

• Nothing new about energy harvesting
• An energy-harvesting scheme that is nearly useless?
• Niche Energy Harvesting: Intriguing, Innovative, Probably Impractical
• Underwater Energy Harvesting with Data-Link Twist
• Clever harvesting scheme takes a deep dive, literally
• Tilting at MEMS Windmills for Energy Harvesting?
• Energy Harvesting Gets Really Personal
• Lightning as an energy harvesting source?
• What’s that?…A fuel cell that harvests energy from…dirt?

References

• Applied Physics Letters, “Nighttime electric power generation at a density of 50 mW/m2 via radiative cooling of a photovoltaic cell”
• Nature Photonics, “Direct observation of the violation of Kirchhoff’s law of thermal radiation”

The post Does the cold of deep space offer a viable energy-harvesting solution? appeared first on EDN.

📰 Газета "Київський політехнік" № 45-46 за 2025 (.pdf) kpi пт, 12/26/2025 - 13:22

Національна премія науковцям кафедри високотемпературних матеріалів та порошкової металургії kpi пт, 12/26/2025 - 11:49

На війні загинув випускник нашого університету Віталій Блощиця kpi пт, 12/26/2025 - 11:33

The AEK-AUD-C1D9031 is ST’s latest AutoDevKit automotive development platform for audio applications, enabling engineers to play audio with only a microcontroller rather than a far more costly DSP. It features an SPC582B60E1 general-purpose MCU and the FDA903D Class D audio amplifier, which provides current-sensing capabilities. Hence, not only does this combination allow designers to easily and efficiently add audio applications such as simulated engine sounds, but it can also detect if a speaker is disconnected. Moreover, as a standalone MCU system, it offers enhanced resiliency by operating independently from the main infotainment system.

The booming challenges of bringing audio to cars More than just music

There’s a lot more audio in cars than most assume. When consumers think about it, they typically envision their entertainment system, which remains a critical component. However, there are chimes, warning bells, notification dings, and so many other audio cues that enhance the user experience. In addition, many of them must be available before the entertainment or even the engine is switched on, meaning that not all of them can rely solely on the sound system that drivers and passengers use to listen to music. Furthermore, since electric cars are so quiet, thanks to the absence of a combustion engine, manufacturers add sounds for safety and to improve the user experience.

More than just a central entertainment system

The problem is that while audio in cars, and acoustic vehicle alerting systems (AVAS) are far from new, they are also not easy to implement and can easily add to the bill of materials. Indeed, the cost of a DSP, an equaliser, and all the components needed by the audio pipeline can quickly add up, which is why many manufacturers opt for a central entertainment system. The problem is that it is a complex system for what are, in effect, computationally trivial tasks, and engineers need to account for safety considerations. For instance, a critical audio warning must still play regardless of the main speaker volume, which requires the design of safeguards and other complex systems.

More than just cars

Teams working on modules are also looking to reuse their systems in many more types of vehicles than just the car they originally had in mind. Whether we are talking about two- or three-wheeler trucks or something as small as a forklift, all require AVAS, and being able to reuse a system across many more platforms provides tremendous economies of scale. However, this isn’t possible when using an entertainment system designed primarily to play music from a phone or the radio. Consequently, more and more makers are taking a different approach to audio alerting systems, exploring solutions that are simpler, more cost-effective, and more flexible.

The resounding solutions of the AEK-AUD-C1D9031 The AEK-AUD-C1D9031 A different melody: a new approach to AVAS

The AEK-AUD-C1D9031 is a development platform that helps car makers approach AVAS differently, and many customers have already adopted it to address these challenges. At its core, it is one of the most straightforward systems possible. Playing sound is as simple as sending power to the module. Thanks to its SPC58 microcontroller, it doesn’t need a complex operating system or workarounds to fit a platform designed to perform a myriad of other functions. The AEK-AUD-C1D9031 even demonstrates how developers can use a dedicated mute pin, which makes turning the sound on and off far simpler. Similarly, the current-sensing feature of the FDA903D amplifier means engineers don’t need to add additional components, thus further reducing the bill of materials.

Familiar tunes: common standards and practices

Developers can use standard interfaces, which save significant development time. For instance, they can talk to the flash or program the amplifier via an I2C interface, or use I2S to send audio samples. In practice, programmers can play audio samples directly from storage, further eliminating the need for intermediate steps. Developers will have to sample the sounds, as they cannot use a compression format like MP3. For instance, they can play a pre-recorded engine noise from a traditional uncompressed WAVE file and then attach a potentiometer to an AEK-CON-C1D9031 connector board plugged into the AEK-AUD-C1D9031 to interact with the sound.

Indeed, it is possible to run a demo that modifies the sound output based on potentiometers that users can move sideways. By using bit-shifting, developers can lower or increase the pitch. Similarly, increasing or decreasing the number of samples directly impacts playback speed. Hence, it’s through those mechanisms that developers can simulate an engine accelerating or decelerating without using expensive DSPs or EQs. Similarly, the system can generate one note at a time to reproduce complex melodies without having to play a traditional file. In fact, ST developed a demo that uses AutoDevKit and the AEK-AUD-C1D9031 to play the famous Rondo All Turca.

Music to engineers’ ears: more features, less complexity The AEK-CON-C1D9031

The AEK-AUD-C1D9031 also shows the advantages of a system independent of the central infotainment system. Since the SPC582B60E1 supports CAN bus, plugging our platform into an existing car safety architecture is simple, enabling engineers to trigger critical alerts very quickly. In most traditional systems, offering all these features would require a far more complex integration process. It’s why we have seen module makers adopt the AEK-AUD-C1D9031. By offering the SPC582B60E1 and the FDA903D on a cost-effective platform, we were able to offer a set of features that help them stand apart, without taking away from the budget they had allocated to other, more costly parts of the vehicle, like the battery management system or onboard charging.

The post ST’s AEK-AUD-C1D9031 making audio more accessible with an SPC58 MCU and a FDA903D in the 1st all-in-one AVAS board appeared first on ELE Times.

Rohde & Schwarz India extended a warm welcome to His Excellency Dr. Philipp Ackermann, Ambassador of the Federal Republic of Germany to India, during his visit to the corporate facility located in New Delhi. This significant event signifies a notable advancement in the mutually beneficial relationship between Germany and India. The visit is anticipated to foster increased collaboration in the spheres of advanced technology and innovation, further enhancing the partnership between the two nations.

The Ambassador’s visit aimed to throw light on Rohde & Schwarz’s growing presence over the last three decades, along with highlighting the company’s expanding research and development (R&D) capabilities, planned investments in infrastructure, and enhanced technological competencies, which are also in line with the ‘Make in India’ initiative.

Dr Ackermann was given an overview of the company’s state-of-the-art R&D test laboratories, its work in niche electronics technology areas, and its plans for future innovation and growth during his visit, where he also interacted with the engineering and leadership teams to understand their technical capabilities and long-term vision.

His Excellency Dr Philipp Ackermann remarked:

“It is encouraging to see German technology companies like Rohde & Schwarz making long-term commitments in India. The company’s focus on R&D, local competence development, and high-quality engineering reflects the strong foundation of Indo-German cooperation in technology and innovation.”

Speaking on the occasion, Yatish Mohan, Managing Director, Rohde & Schwarz India, stated: “We are deeply honoured to host His Excellency Dr Ackermann at our facility. This visit underscores our commitment to advancing technological excellence in India and reflects the shared vision of fostering stronger economic and innovation ties between our two nations.”

Rohde & Schwarz India is committed to deepening Indo-German industrial collaboration, driving innovation through local R&D initiatives, and contributing to the nation’s self-reliant manufacturing ecosystem.

The post Indo-German Tech Cooperation Strengthens with German Ambassador’s visit to R&S India appeared first on ELE Times.

This is my analog semi-automatic battery tester. It mesure battery capacity. Ti does it by discharging the battery via resistor, and measuring current and time. It has analog electronic circuit that automaticly turns the resistor off when battery woltage with load fall to 10,2V. It also turns of the clock, and turns the green LED on. The only thing than you need to do is to look for average current, and look for the time on clock, then you multiple time and current to get capacity. I * t = C 3,2A * 3h = 9,6Ah The circuit is quite complex. On the bottom of the circuit we have BJT with 9,6V zener diode, so it detects when battery voltage is below 10,2V(Base of BTJ isnt getting 0,7V ). When this happens, it lock the BJT and opens the road for voltage to accumulate in capacitor. Once capacitor is charged, it can not be discarged becouse of diode, the only way is vie RESET switch. When capacitor is full, it opens the GATE of MOSFET, and makes the Base of second BJT low, so it stops sending current towards RELAY. RELAY then opens the circuit with resistor and the battery is relieved of load. So its Voltage increses from 10,2V(with load) to 11+V and again makes the base of first BJT high. But it cant discharge capactitor becouse od diode and the circuit remebres the state so it does not osscilate betven load, and no load. When you reset the capacitor, the relay can be turned on. The white LED is simply there becouse i didnt have an oiptimal zener, so i combined one zener with LED to create 9,5V voltage drop. AA batery is for clock. Ive done the test with fully discharged battery, for presentation submitted by /u/No-Raspberry381 [link] [comments]

З Різдвом і Новим роком! kpi чт, 12/25/2025 - 15:10

📋 Для українських науковців продовжено безкоштовний доступ міжнародних наукових ресурсів kpi чт, 12/25/2025 - 15:01

Stephen Woodward’s “Ignoring the regulator’s reference” Design Ideas (DI) (see Figure 1) is an excellent, working example of how to include a circuit in the feedback loop of an op amp to support the stabilization of the circuit’s operating point. This is also previously seen in “Improve the accuracy of programmable LM317 and LM337-based power sources” and numerous other places[1][2][3]). I’ll refer to his DI as “the DI” in subsequent text.

Figure 1 The DI’s Figure 1 schematic has been redrawn to emphasize the positioning of the U1 regulator in the A1 op amp’s feedback loop. The Vdac signal controls U1 while ignoring its internal reference voltage.

Wow the engineering world with your unique design: Design Ideas Submission Guide

A few minor tweaks optimize this circuit’s dynamic performance and leave the design equations and comments in the DI unchanged. Let’s consider the case in which U1’s reference voltage is 0.6 V, Vdac varies from 0 to 3 V, and Vo varies from 5 to 0 V.

The DI tells us that in this case, R1a is not populated and that R1b is 150k. It also mentions driving Figure 1’s Vdac from the DACout signal of Figure 2, also found in “A nice, simple, and reasonably accurate PWM-driven 16-bit DAC.”

Figure 2 Each PWM input is an 8-bit DAC. VREF should be at least 3.0 V to support the SN74AC04 output resistances calculable from its datasheet. Ca and C1 – C3 are COG/NPO.

The Figure 2 PWMs could produce a large step change, causing DACout and therefore Vdac to quickly change from 0 to 3 V.

Figure 3 shows how Vo and the output of A1 react to this while driving a hypothetical U1, which is capable of producing an anomaly-free [4] 0-volt output.

Figure 3 Vo and A1’s output from Figure 1 react to a step change in Vdac.

Even though Vo eventually does what it is supposed to, there are several things not to like about these waveforms. Vo exhibits an overshoot and would manifest an undershoot if it didn’t clip at the negative rail (ground). The output of A1 also exhibits clipping and overshooting. Why are these things happening?

The answer is that the current flowing through R5 also flows through R3, causing an immediate change in the output voltage of A1. That change causes a proportional current to flow through R4. However, the presence of C2 prevents an immediate change in Vo and delays compensatory feedback from arriving at A1’s non-inverting input. How can this delay be avoided?

Shorting out R3 makes matters worse. The solution is to remove C2, speeding up the ameliorative feedback. Figure 4 shows the results.

Figure 4 With C2 eliminated, so are the clipping and the over- and undershoots. The A1 output moves only a few millivolts because of the large DC gain of the regulator, and because it is no longer necessary to charge C2 through R4 in response to an input change.

Vo now settles to ½ LSbit of a 16-bit source in 2.5 ms. Changing C3 to 510 pF (10% COG/NPO) reduces that time to 1.4 ms. Smaller values of C3 provide little further advantage.

The Vo-to-VSENSE feedback becomes mostly resistive above 0.159 / (R · C3) Hz, where:

R = R3 + R5 · R1a / (R5 + R1a)

In this case, that’s 1600 Hz, well below the unity gain frequency of pretty much any regulator, and so there should be no stability issues for the overall circuit. Note that A1’s output remains almost exactly equal to the regulator’s reference voltage. This, and the freedom to choose the R5/R1a and R2/R1b ratios, leaves open the option of using an op amp whose inputs and output needn’t approach its positive supply rail.

The (original) DI is a solid design that obtains some dynamic performance benefits from reducing the value of one capacitor and eliminating another.

Related Content

• Ignoring the regulator’s reference
• Improve the accuracy of programmable LM317 and LM337-based power sources
• A nice, simple, and reasonably accurate PWM-driven 16-bit DAC
• Enabling a variable output regulator to produce 0 volts? Caveat, designer!

References

1. https://en.wikipedia.org/wiki/Current_mirror#Feedback-assisted_current_mirror
2. https://www.onsemi.com/pdf/datasheet/sa571-d.pdf see section on compandor
3. https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/14/CircuitCookbook_2D00_OpAmps.pdf see triangle wave generator, page 90
4. Enabling a variable output regulator to produce 0 volts? Caveat, designer!

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🎥 Новий Навчально-науковий центр «КПІ-Технополіс» у КПІ ім. Ігоря Сікорського kpi ср, 12/24/2025 - 20:53

I've made an ARM based single-board computer that runs Android and Linux, and has the same size as the Raspberry Pi 3! Why? I was bored during my 2-week high-school vacation and wanted to improve my skills, while adding a bit to the open-source community :P I ended up with a H3 Quad-Core Cortex-A7 ARM CPU with a Mali400 MP2 GPU, combined with 512MiB of DDR3 RAM (Can be upgraded to 1GiB, but who has money for that in this economy). The board is capable of WiFi, Bluetooth & Ethernet PHY, with a HDMI 4k port, 32 GB of eMMC, and a uSD slot. I've picked the H3 for its low cost yet powerful capabilities, and it's pretty well supported by the Linux kernel. Plus, I couldn't find any open-source designs with this chip, so I decided to contribute a bit and fill the gap. A 4-layer PCB was used for its lower price and to make the project more challenging, but if these boards are to be mass-produced, I'd bump it up to 6 and use a solid ground plane as the bottom layer's reference plane. The DDR3 and CPU fanout was really a challenge in a 4-layer board. The PCB is open-source on the Github repo with all the custom symbols and footprints (https://github.com/cheyao/icepi-sbc). There's also an online PCB viewer here. submitted by /u/cyao12 [link] [comments]

EDN Design Ideas (DI) published a design of mine in May of 2025 for a passive two-way current mirror topology that, in analogy to optical two-way mirrors, can reflect or transmit. 

That design comprises just two BJTs and one diode. But while its simplicity is nice, its symmetry might not be. That is to say, not precise enough for some applications.

Wow the engineering world with your unique design: Design Ideas Submission Guide

Fortunately, as often happens when the precision of an analog circuit falls short, and the required performance can’t suffer compromise, a fix can consist of adding an RRIO op amp. Then, if we substitute two accurately matched current-sensing resistors and a single MOSFET for the BJTs, the result is the active two-way current mirror (ATWCM) as shown in Figure 1.

Figure 1 The active two-way current sink/source mirror. The input current source is mirrored as a sink current when D1 is forward biased, and transmitted as a source current when D1 is reverse biased.

Figure 2 shows how the ATWCM operates when D1 is forward-biased, placing it in mirror mode.

Figure 2 ATWCM in mirror mode, I1 sink current generates Vr, forcing A1 to coax Q1 to mirror I2 = I1.

The operation of the ATWCM in mirror mode couldn’t be more straightforward. Vr = I1R wired to A1’s noninverting input forces it to drive Q1 to conduct I2 such that I2R = I1R. 

Therefore, if the resistors are equal, A1’s accuracy-limiting parameters (offset voltage, gain-bandwidth, bias and offset currents, etc.) are adequately small, and Q1 does not saturate, I1 = I2 just as precisely as you like.

Okay, so I lied.  Actually, the operation of the ATWCM in transmission mode is even simpler, as Figure 3 shows.

Figure 3 ATWCM in transmission mode. A reverse-biased D1 means I1 has nowhere to go except through the resistors and (saturated and inverted) Q1, where it is transmitted back out as I2.

I1 flowing through the 2R net resistance forces A1 to rail positive, saturating Q1 and providing a path back to the I2 pin. Since Q1 is biased inverted, its body diode will close the circuit from I1 to I2 until A1 takes over. A1 has nothing to do but act as a comparator.

Flip D1 and substitute a PFET for Q1, and of course, a source/sink will result, shown in Figure 4.

Figure 4 Source/sink two-way mirror with a D1 flipped the opposite direction, and Q1 replaced with a PFET. 

Figure 5 shows the circuit in Figure 4 running a symmetrical rail-to-rail tri-wave and square-wave output multivibrator.

Figure 5 Accurately symmetrical tri-wave and square-wave result from inherent A1Q2 two-way mirror symmetry.

Stephen Woodward’s relationship with EDN’s DI column goes back quite a long way. Over 100 submissions have been accepted since his first contribution back in 1974.

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Designers are looking to reduce the cost of drone systems for a wide range of applications but still need to provide accurate positioning data. This however is not as easy is it might appear.

There are several satellite positioning systems, from the U.S.-backed GPS and European Galileo to NavIC in India and Beidou in China, providing data down to the meter. However, these need to be augmented by an inertial measurement unit (IMU) that provides more accurate positioning data that is vital.

Figure 1 An IMU is vital for the precision control of the drone and peripherals like gimbal that keeps the camera steady. Source: Epson

An IMU is typically a sensor that can measure movement in six directions, along with an accelerometer to detect the amount of movement. The data is then used by the developer of an inertial measurement system (IMS) with custom algorithms, often with machine learning, combined with the satellite data and other data from the drone system.

The IMU is vital for the precision control of the drone and peripherals such as the gimbal that keeps the camera steady, providing accurate positioning data and compensating for the vibration of the drone. This stability can be implemented in a number of ways with a variety of sensors, but providing accurate information with low noise and high stability for as long as possible has often meant the sensor is expensive with high power consumption.

This is increasingly important for medium altitude long endurance (MALE) drones. These aircraft are designed for long flights at altitudes of between 10,000 and 30,000 feet, and can stay airborne for extended periods, sometimes over 24 hours. They are commonly used for military surveillance, intelligence gathering, and reconnaissance missions through wide coverage.

These MALE drones need a stable camera system that is reliable and stable in operation and a wide range of temperatures, providing accurate tagging of the position of any data captured.

One way to deliver a highly accurate IMU with lower cost is to use a piezoelectric quartz crystal. This is well established technology where an oscillating field is applied across the crystal and changes in motion are picked up with differential contacts across the crystal.

For a highly stable IMU for a MALE drone, three crystals are used, one for each axis, stimulated at different frequencies in the kilohertz range to avoid crosstalk. The differential output cancels out noise in the crystal and the effect of vibrations.

Precision engineering of piezoelectric crystals for high-stability IMUs

Using a crystal method provides data with low noise, high stability, and low variability. The highly linear response of the piezoelectric crystal enables high-precision measurement of various kinds of movement over a wide range from slow to fast, allowing the IMU to be used in a broad array of applications.

An end-to-end development process allows the design of each crystal to be optimized for the frequencies used for the navigation application along with the differential contacts. These are all optimized with the packaging and assembly to provide the highly linear performance that remains stable over the lifetime of the sensor.

It uses 25 years of experience with wet etch lithography for the sensors across dozens of patents. That produces yields in the high nineties with average bias variations, down to 0.5% variant from unit to unit.

An initial cut angle on the quartz crystal achieves the frequency balance for the wafer, then the wet etch lithography is applied to the wafer to create a four-point suspended cantilever structure that is 2-mm long. Indentations are etched into the structure for the wire bonds to the outside world.

The four-point structure is a double tuning fork with detection tines and two larger drive tines in the centre. The differential output cancels out spurious noise or other signals.

This is simpler to make than micromachined MEMS structures and provides more long-term stability and less variability across the devices.

The differential structure and low crosstalk allow three devices to be mounted closely together without interfering with each other, which helps to reduce the size of the IMU. A low pass filter helps to reduce any risk of crosstalk.

The six-axis crystal sensor is then combined with an accelerometer for the IMU. For the MALE drone gimbal applications, this accelerometer must have a high dynamic range to handle the speed and vibration effects of operation in the air. The linearity advantage of using a piezoelectric crystal provides accuracy for sensing the rotation of the sensor and does not degrade with higher speeds.

Figure 2 Piezoelectric crystals bolster precision and stability in IMUs. Source: Epson

This commercial accelerometer is optimized to provide the higher dynamic range and sits alongside a low power microcontroller and temperature sensors, which are not common in low-cost IMUs currently used by drone makers.

The microcontroller technology has been developed for industrial sensors over many years and reduces the power consumption of peripherals while maintaining high performance.

The microcontroller is used to provide several types of compensation, including temperature and aging, and so provides a simple, stable, and high-quality output for the IMU maker. Quartz also provides very predictable operation across a wide temperature range from -40 ⁰C to +85 ⁰C, so the compensation on the microcontroller is sufficient and more compensation is not required in the IMU, reducing the compute requirements.

All of this is also vital for the calibration procedure. Ensuring that the IMU can be easily calibrated is key to keeping the cost down and comes from the inherent stability of the crystal.

Calibration-safe mounting

The mounting technology is also key for the calibration and stability of the sensor. A part that uses surface mount technology (SMT), such as a reflow oven, for mounting to a board, which is exposed to high temperatures that can disrupt the calibration and alter the lifetime of the part in unexpected ways.

Instead, a module with a connector is used, so the 1-in (25 x 25 x 12 mm) part can be soldered to the printed circuit board (PCB). This avoids the need to use the reflow assembly for surface mount devices where the PCB passes through an oven, which can upset the calibration of the sensor.

Space-grade IMU design

A higher performance variant of the IMU has been developed for space applications. Alongside the quartz crystal sensor, a higher performance accelerometer developed in-house is used in the IMU. The quartz sensor is inherently impervious to radiation in low and medium earth orbits and is coupled with a microcontroller that handles the temperature compensation, a key factor for operating in orbits that vary between the cold of the night and the heat of the sun.

The sensor is mounted in a hermetically sealed ceramic package that is backfilled with helium to provide higher levels of sensitivity and reliability than the earth-bound version. This makes the quartz-based sensor suitable for a wide range of space applications.

Next-generation IMU development

The next generation of etch technology being explored now promises to enable a noise level 10 times lower than today with improved temperature stability. These process improvements enable cleaner edges on the cantilever structure to enhance the overall stability of the sensor.

Achieving precise and reliable drone positioning requires the integration of advanced IMUs with satellite data. The use of piezoelectric quartz crystals in IMUs for drone systems offers significant benefits, including low noise, high stability, and reduced costs, while commercial accelerometers and optimized microcontrollers further enhance performance and minimize power consumption.

Mounting and calibration procedures ensure long-term accuracy and reliability to provide stable and power-efficient control for a broad range of systems. All of this is possible through the end-to-end expertise in developing quartz crystals, and designing and implementing the sensor devices, from the etch technology to the mounting capabilities.

David Gaber is group product manager at Epson.

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• ST Launches AI-Enabled IMU for Activity Tracking and High-Impact Sensing

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