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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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The post Active two-way current mirror appeared first on EDN.

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

The post Aiding drone navigation with crystal sensing appeared first on EDN.

Баскетбол. Студентська ліга м. Києва. Стартуємо гучно! kpi ср, 12/24/2025 - 13:04

The South Wales-based compound semiconductor cluster CSconnected has announced MicroLink Devices UK Ltd as an awardee of the CSconnected Supply Chain Development Programme — Call 2...

Another day, another dodgy device. This time, it was the continuity beeper on my second-best DMM. Being bored with just open/short indications, I pondered making something a little more informative.

Perhaps it could have an input stage to amplify the voltage, if any, across current-driven probes, followed by a voltage-controlled tone generator to indicate its magnitude, and thus the probed resistance. Easy! . . . or maybe not, if we want to do it right.

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

Figure 1 shows the (more or less) final result, which uses a carefully-tweaked amplifying stage feeding a pitch-linear VCO (PLVCO). It also senses when contact has been made, and so draws no power when inactive.

Most importantly, it produces a tone whose musical pitch is linearly related to the sensed resistance: you can hear the difference between fat power traces and long, thin signal ones while probing for continuity or shorts on a PCB without needing to look at a meter.

Figure 1 A power switch, an amplifying stage with some careful offsets, and a pitch-linear VCO driving an output transducer make a good continuity tester. The musical pitch of the tone produced is proportional to the resistance across the probe tips.

This is simpler than it initially looks, so let’s dismantle it. R1 feeds the test probes. If they are open-circuited, p-MOSFET Q1 will be held off, cutting the circuit’s power (ignoring <10 nA leakage).

Any current flowing through the probes will bring Q1.G low to turn it on, powering the main circuit. That also turns Q2 on to couple the probe voltage to A1a.IN+ via R2. Without Q2, A1a’s input protection diodes would draw current when power was switched off.

R1 is shown as 43k for an indication span of 0 to ~24 Ω, or 24 semitones. Other values will change the range, so, for example, 4k3 will indicate up to 2.4 Ω with 0.1-Ω semitones. Adding a switch gave both ranges. (The actual span is up to ~30 Ω—or 3.0 Ω—but accuracy suffers.) Any other values can be used for different scales; the probe current will, of course, change.

A1a amplifies the probe voltage by 1001-ish, determined by R3 and R4. We are working right down to 0 V, which can be tricky. R5 offsets A2a.IN- by ~5 mV, which is more than the MCP6002’s quoted maximum input offset of 3.5 mV. R2 and R6–8 help to add a slightly greater bias to A1a.IN+ that both null out any offset and set the operating point. This scheme may avert the need for a negative rail in other applications.

Tuning the tones

The A1b section is yet another variant on my basic pitch-linear VCO, the reset pulse being generated by Q4/C3/R13. (For more informative details of the circuit’s general operation, see the original Design Idea.) The ’scope traces in Figure 2 should clarify matters.

Figure 2. Waveforms within the circuit to show its operation while probing different resistances.

This type of PLVCO works best with a control voltage centered between the supply rails and swinging by ±20% about that datum, giving a bipolar range of ~±1 octave. Here, we need unipolar operation, starting around that -20% lowest-frequency point.

Therefore, 0 Ω on the input must give ~0.3 Vcc to generate a ~250 Hz tone; 12 Ω, 0.5 Vcc (for ~500 Hz); and 24 Ω, ~0.7 Vcc (~1 kHz). Anything above ~0.8 Vcc will be out of range—and progressively less accurate—and must be ignored.

The output is now a tone whose pitch corresponds to the resistance across the probes, scaled as one semitone per ohm and spanning two octaves for a 24 Ω range (if R1 is 43k).

The modified exponential ramp on C2 is now sliced by A2b, using a suitable fraction of the control voltage as a reference, to give a “square” wave at its output—truly square at one point only, but it sounds OK, and this approach keeps the circuit simple. A2a inverts A2b’s output, so they form a simple balanced (or bridge-tied load) driver for an earpiece. (There are problems here, but they can wait.)

R9 and R10 reduce A1a’s output a little as high resistances at the input cause it to saturate, which would otherwise stop A1b’s oscillation. This scheme means that out-of-range resistances still produce an audio output, which is maxed out at ~1.6 kHz, or ~30 Ω. Depending on Q1’s threshold voltage, several tens of kΩs across the probes are enough to switch it on—a tad outside our indication range.

Loud is allowed

Now for that earpiece, and those potential problems. Figure 1’s circuit worked well enough with an old but sensitive ~250-Ω balanced-armature mic/’phone but was fairly hopeless when trying to drive (mostly ~32 Ω) earphones or speakers.

For decent volume, try Figure 4, which is beyond crude, but functional. Note the separate battery, whose use avoids excessive drain on the main one while isolating the main circuit from the speaker’s highish currents.

Again, no power is drawn when the unit is inactive. (Reused batteries—strictly, cells—from disposed-of vapes are often still half-full, and great for this sort of thing! And free.) A2a is now spare . . .

Figure 3 A simple, if rather nasty, way of driving a loudspeaker.

Setting-up is necessary, because offsets are unpredictable, but simple. With a 12-Ω resistance across the probes, adjust R7 to give Vcc/2 at A1b.5. Done!

Comments on the components

The MCP6002 dual op-amp is cheap and adequate. (The ’6022 has a much lower offset but a far higher price, as well as drawing more current. “Zero-offset” devices are yet more expensive, and trimmer R7 would probably still be needed.)

Q3, and especially Q1, must have a low RDS(on) and VGS(th); my usual standby ZVP3306As failed on both counts, though ZVN3306As worked well for Q2/4/5. (You probably have your own favorite MOSFETs and low-voltage RRIO op-amps.) To alter the frequency range, change C2. Nothing else is critical.

As noted above, R1 sets the unit’s sensitivity and can be scaled to suit without affecting anything else. With 43k, the probe current is ~70 µA, which should avoid any possible damage to components on a board-under-test.

(Some ICs’ protection diodes are rated at a hopefully-conservative 100 µA, though most should handle at least 10 mA.) R2 helps guard against external voltage insults, as well as being part of the biasing network.

And that newly-spare half of A2? We can use it to make an active clamp (thanks, Bob Dobkin) to limit the swing from A1a rather than just attenuating it. R1 must be increased—51k instead of 43k—because we no longer need extra gain.

Figure 4 shows the circuit. When A2a’s inverting input tries to rise higher than its non-inverting one—the reference point—D1 clamps it to that reference voltage.

Figure 4. An active clamp is a better way of limiting the maximum control voltage fed to the PLVCO.

The slight frequency changes with supply voltage can be ignored; a 20°C temperature rise gave an upward shift of about a semitone. Shame: with some careful tuning, this could otherwise also have done duty as a tuning fork.

“Pitch-perfect” would be an overstatement, but just like the original PLVCO, this can be used to play tunes! A length of suitable resistance wire stretched between a couple of drawing pins should be a good start . . . now, where’s that half-dead wire-wound pot? Trying to pick out a seasonal “Jingle Bells” could keep me amused for hours (and leave the neighbors enraged for weeks).

 —Nick Cornford built his first crystal set at 10, and since then has designed professional audio equipment, many datacomm products, and technical security kit. He has at last retired. Mostly. Sort of.

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• Power amplifiers that oscillate— Part 2: A crafty conclusion.
• Revealing the infrasonic underworld cheaply, Part 2
• A pitch-linear VCO, part 2: taking it further
• 5-V ovens (some assembly required)—part 2

The post Tuneful track-tracing appeared first on EDN.

Hello everyone, last week I posted my AM radio in a 4layer pcb design. I got loads of good suggestions as well as people saying that 4layers was overkill. Here is the two layer design! And thanks for all the suggestions I may upgrade this design using transistors to amplify the rf signal. Schematics First layer GND with 9V island Second layer GND Original Post submitted by /u/S4vDs [link] [comments]

Інженерні тижні «KPISchool» для учнів 9–11 класів у КПІ ім. Ігоря Сікорського kpi вт, 12/23/2025 - 13:36

Japan-based power electronics manufacturer Fuji Electric Co Ltd and automotive parts maker Robert Bosch GmbH of Reutlingen, Germany have agreed to collaborate on silicon carbide (SiC) power semiconductor modules for electric vehicles (EVs) that feature package compatibility...