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22 votes
0 answers
2k views

Switch from JTAG to SWD with bitbang sequence on STM32F103VB

I am trying to switch from JTAG to SWD without any external devices. Why? Because I would like to use the SWO pin to send a stream of logging information to another device. To accomplish this ...
  • 411
14 votes
0 answers
766 views

What is this weird EMV pin on my credit card?

I recently got a Venmo card, which is my first card with contactless support. I was looking at the EMV pins and noticed a very weird design. In the middle of the ground pin, there is this long, thin ...
10 votes
0 answers
256 views

Speed of compound wound dc motor

This is homework. Given a 500W, 200V compound wound motor with constant shunt field and a series field that varies with armature current, how do we calculate the change in motor speed. I know the ...
  • 101
9 votes
1 answer
784 views

Convert analog piezo "transition" to digital signal

I'm trying to get what amounts to a knock indication into a microcontroller input from a piezo sensor. It's looking fairly good now at the fifth iteration, and about ready to provide digital levels ...
9 votes
2 answers
4k views

Dual active bridge converter

I'm having issues calculating the power losses associated with the operation of a bidirectional isolated dual active bridge DC/DC converter. The converter is controlled using phase shift modulation (...
  • 91
8 votes
1 answer
184 views

Phase noise of op-amp

Suppose I have a carrier signal with low-ish RF frequency (a few MHz) that I can reasonably amplify with an op-amp. How can I estimate the added phase noise due to the amplifier? For microwave ...
  • 1,336
8 votes
0 answers
513 views

Looking for criticisms for a VNA-like meter I am designing

I would like some help from anyone who could let me know any flaws or improvements in my design they can find and help me reconsider any last minute design fixes before I send my new project off to be ...
7 votes
0 answers
126 views

Is birefringence exploited or otherwise meaningfully observed anywhere in electronics?

Birefringence is a property of certain materials where the refractive index of the material is dependent upon the polarization and direction of propagation of light through it. I recently learned ...
  • 7,499
7 votes
1 answer
166 views

Why does current flow direction matter in welding?

In DC welding, there are two configurations - direct current electrode positive (DCEP) and direct current electrode negative (DCEN). When the electrode is negative, the current flows from electrode to ...
  • 3,117
7 votes
2 answers
387 views

Rigid-Flex PCB Fabrication: Window opening vs slot opening

We had issue with one of the rigid-flex design cracking at the joint of Rigid and flex intersection. It is important to note that this is second batch of same PCB and PCB was not cracking in first ...
7 votes
1 answer
391 views

Incrementing net name for group in Eagle

I want to make 50 copies of the block below, but I need incrementing numbers on each of the net labels (these will go to a connector). I do not want each block connected to the other blocks. It would ...
7 votes
3 answers
567 views

GPS power consumption MTK3339 vs SirfIII for periodic logging application

I am currently working on redesigning a SirfIII based battery operated GPS logger. A MTK3339 based GPS module has been selected due to overall (advertised) performance. The GPS logger uses a ...
  • 652
6 votes
0 answers
61 views

Burned motor controllers: possible root causes analysis

On a submarine robot we built, during an operation, we recently had 3 defect thruster motors (the internal power PCBs have many burnt components, 2 of the motors cracked open due to internal pressure)....
  • 2,741
6 votes
0 answers
164 views

What textbook is this problem from? (circuit analysis)

A somewhat unusual question: Some years ago, the following problem appeared in a test I took during my Bachelor's in electrical engineering. Later, the professor told us which textbook he took it from,...
  • 61
6 votes
0 answers
1k views

Is JTAG faster than SWD for debugging on an STM32F with STLINK-V3SET programmer?

There is a new STLINK-V3SET programmer that someone dropped off on my desk today. It supports USB 2.0. My thinking is that if SWD is the bandwidth limiter in the signal chain then a new programmer isn'...
  • 65.3k
6 votes
1 answer
607 views

Modeling scalar control of PMSM

I have met with a scalar control algorithm for a permanent magnet synchronous motor. I haven´t heard about it before so I decided to develop a dynamic model to further analyze this control algorithm. ...
  • 885
6 votes
1 answer
146 views

Phase shift near saturation mitigation in input stage amplifier -- How does this work, why does this work?

I'm trying to understand how this circuit works on the input stage to the 4192A Impedance Analyzer. Apologies for the quality... this is the best scan I could find. The design is furnished with the ...
  • 279
6 votes
2 answers
812 views

PWM on phototransistor

I am pulsing the VDD with 50% duty cycle at a frequency of 188 Hz (PWM). I get some weird spikes on my output TP3. Am I missing something about phototransistors? Here is the picture of the IR circuit ...
6 votes
0 answers
320 views

Home made passive tablet pen

I have an old wacom tablet at home, its really big and I'd like to use it but I've lost the pen for it. It uses pens with passive LC circuitry. The board creats an EM-field (I can see it on my ...
5 votes
0 answers
125 views

Novel CAN bus design - needs criticism

I'm designing a CAN bus interface for a PCB I'm working on. CAN and high speed/long distances are new to me, so I have a list of concerns about my design ideas, and I would appreciate someone with ...
5 votes
0 answers
81 views

x86 Motherboard Bring Up - Intel Tiger Lake UP3 CPU

For those who has experience with Intel x86 motherboard design and bring up. I'm in the middle of motherboard bring-up that has Intel Tiger Lake UP3 CPU. Seems like I had a good run so far at power-up ...
  • 593
5 votes
1 answer
478 views

Reading the analog pin A0 on Wemos D1 Mini

I am doing a personal project with a Wemos D1 mini and one thing that was of interest to me was to detect a servo-motor stall. Very glad to find an useful answer to this question: How do I detect ...
5 votes
1 answer
1k views

ESD protection for ESP32 GPIOs

I want some of the ESP32's GPIOs to be accessible via 3.5mm headphone jacks or RJ11 jacks and therefore need suitable ESD protection. I wonder how much is needed for optimal protection. Conditions/...
  • 51
5 votes
4 answers
455 views

Bridge rectifier low voltage

Power supply for headphone tube amp gives me 10-12V lower voltage comparing to the schematic (my measurements are in red for amp under load). Current under load is about 70 mA. Using simple formula : ...
  • 51
5 votes
2 answers
645 views

How to meaningfully compare Xilinx MCS files?

Brief I have two different boards with Xilinx designs that might be the same design. I am trying to compare the different MCS files to see if the designs in them are in fact the same design. Can this ...
  • 2,458
5 votes
2 answers
3k views

How to calculate and measure motor constant for stepper motor?

I am working on a project using ST4118D30004 stepper motors and powerSTEP01 drivers. The ST4118D30004 is a bipolar stepper motor with 4 wire connection. While researching how to find the optimal ...
  • 151
5 votes
0 answers
159 views

Frequency locking for averaging resampling

Background I've done a long one-shot measurement of a periodic signal by an oscilloscope. Thus, I've captured around 250 periods of a signal. The signal itself is a pseudo-random binary sequence at ...
  • 57
5 votes
1 answer
417 views

How do current spikes over limit affect Lithium battery life?

In one of my application, I am using Tadiran Lithium Thionyl Chloride Batteries MODEL TL-5934. In the data sheet , the max pulse current shows 50mA. However, in my application, we have low duty cycle ...
5 votes
1 answer
4k views

STM32 UID decoding

In my project I need to make readable 96bit UID, in reference manual is described how the number is encoded: ...
  • 428
5 votes
1 answer
327 views

DDR(2-4) Training and Length Matching

Today I learned about the concept of memory training for DDR2, 3, and 4 (I'm not sure if DDR1 has it). The purpose of memory training is to correct for skew in data, address, and command bits being ...
  • 464
5 votes
0 answers
520 views

Understanding EGSM-900 (LTE 8 band) electromagnetic spectrum

I am trying to fully understand the physical layer of the GSM standard. For doing that I am looking at the E-GSM-900 band (mostly used in Europe). In my country these frequencies has been assigned to ...
  • 175
5 votes
2 answers
1k views

How to plot Nyquist plots?

By using the open loop transfer function for a control system, how would you then sketch the Nyquist plot by hand? I'm aware you'd substitute any \$s\$ term for \$j\omega\$ and then rationalise the ...
5 votes
1 answer
507 views

MCU HIB pin only pulls Buck/Boost EN pin every-other Hibernation

MCU: TM4C1294NCPDT Buck/Boost Converter: TPS63051 Hib dedicated LDO: MIC5504-3.3YM5-TR I have a LiPo battery coming into the board, feeding both the TPS63051 and the MIC5504. Tiva's HIB pin is ...
5 votes
1 answer
787 views

JTAG oscillations/noise

I've got a board with two Altera CPLDs on it with a bit of a programming problem: programming it via JTAG fails. The JTAG lines run through the first board, through a flex, and a few emerge on the ...
  • 51
5 votes
0 answers
159 views

Testing strategies for testing a Scheduler

We have developed an in-house Scheduler which is based on Rate-monotonic scheduling. We have 6 tasks (5 actual tasks and 1 idle task). Our scheduler works on 1msec timer interrupt. Before sending it ...
  • 3,185
5 votes
1 answer
7k views

RGBHV (VGA) to YPbPr Converter and Waveforms?

Purely for hobby, I am working on an RGBHV (VGA) to YPbPr (Component) converter circuit for old games consoles modified to output RGBHV on a VGA cable. From the game consoles, the RGB signal is taken ...
5 votes
1 answer
879 views

Thermal Modeling of 0805 Thick Film Chip Resistor

I recently got confronted with the question what peak/pulse power a standard 0805 thick film resistor can withstand. Background: We are designing a 2kW bidirectional DCDC converter. The Primary side ...
  • 652
5 votes
1 answer
565 views

Charge mode piezoelectric signal conditioning

I have a charge-mode piezoelectric dynamic pressure sensor (datasheet link) that I want to read a signal from. If you look at the datasheet it says the sensor outputs are in a balanced and floating ...
5 votes
1 answer
2k views

Current capacity of copper wires in vacuum

I’d like to know the current carrying capacity of copper wires in vacuum. The current plan (NPI) calls for sending ~3 amps through the vacuum space of a cryostat. Has anyone done this? Have any ...
4 votes
0 answers
122 views

Identify kind of cable with markings such as "WE-B 2 PAIR" on the jacket

While cleaning out our back yard shed, I came across a coil of cable of a kind that I have never seen before (image below). It was left here by the previous home owner, who worked in some kind of ...
4 votes
1 answer
98 views

Short circuit in ribbon cable

My ribbon cable assemblies are creating intermittent short circuits that cause my Atmega328p microprocessor to spontaneously reset. The setup: 60-conductor .05 ribbon cable made by 3M (long ago when ...
4 votes
0 answers
39 views

Does gate oxide thickness define switching speed of transistor?

This book states that 'a thin-gate oxide is designed to achieve the high speed on and off switching of the MOSFET'. My understanding is that the on-off time of a FET is determined primarily by the ...
  • 2,673
4 votes
0 answers
54 views

What does "process size" mean? Why and how has that meaning changed over time?

In this question, I am mostly thinking about the history of process sizes for CPUs. About 25 years ago, I seem to remember that (with the caveat that I am not sure that the term in use in english was &...
4 votes
0 answers
97 views

Estimate base-spreading resistance from Gummel-Poon model

I'm attempting to calculate the base-spreading resistance of BJTs from manufacturer-provided SPICE models, which use the Gummel-Poon model. This Agilent publication (Internet Archive link here, if ...
  • 933
4 votes
0 answers
82 views

Addressing poor Earth resistance on hill top

I work in a radio station situated on a hill top. The Earth resistance measured at this location is quite high, measuring around 9 Ω. There is no deep gorge nearby to make a fresh Earth Pit. How can I ...
  • 341
4 votes
1 answer
49 views

Ground loop impedance when measuring pH of salty/conductive liquids

I have a reservoir of conductive liquid (~2000 μS). Inside that liquid are two sensors: a pH sensor and a conductivity cell. The conductivity cell is a two-terminal device and submerged. When ...
  • 183
4 votes
1 answer
70 views

Connecting a PHY to another PHY on a same board

I would like to connect voltage-mode PHYs with internal terminations back-to-back. After doing some research, it looks like simple AC coupling caps can work, but it's better to use a transformer, ...
4 votes
0 answers
66 views

Do I need a clock crossing circuit for signals clocked by mirrored PLLs?

Assume that within an FPGA, I have two data streams that are being driven by two clocks. The two clocks are generated by 2 physically separated PLLs (still within the same FPGA), both of which have ...
4 votes
0 answers
114 views

Review of electric circuit with Arduino

I am currently working on a project for which I am in charge of the electronic circuit. Since I have never worked with electronics before, I am really desperate and unsure whether what I am doing is ...
4 votes
0 answers
102 views

Can this Raspberry Pi UPS circuit work?

I created following UPS circuit to shutdown my Raspberry Pi 3A+ properly: I would really appreciate if somebody can review my circuit. I know it's a little bit hard to read, but I'm sorry. I'm a ...

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