# All Questions

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### 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 ...
201 views
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### What makes some commercial JFETs asymmetric?

In a MOSFET, the obvious cause of asymmetry is the fact that the source is tied to the body. But in a JFET, no such obvious answer exists, as the body, gate, and drain are all the same piece of ...
240 views

### Mystery 1974 vintage TI chip: N286M26

I inherited three of these Texas Instruments vintage ICs, marked N286 (regular size) and M26 (unusually large). The smaller pairs of digits on the right hand side, 74 and 18, are, I assume, the ...
359 views

### Analyze protocol used for Futaba VFD display, 3 data pins

I take apart a Samsung SMT-C7140 HD Unit (made obsolete by cable company, a shame) and found a nice display that I could probably reuse. It is a Futaba GL07-00006A (13-BT-246GINK). I tried to find the ...
192 views

### Photon count with ADC, am I doing it right?

I have this LED and I want to characterize this photodiode. The LED should produce light of 370 nm, but I measured it and it is around 358 nm, and at that wavelength the quantum efficiency ($\eta$) ...
1k views

### Receiver issues on STM32H7 interrupt-based SPI

I want to configure a simple interrupt-based SPI slave transmitter/receiver on a STM32H7 MCU. Even though I have quite a bit experience with the older series of STM32 ARM MCUs, it seems that a lot of ...
4k views

### Calculating the ESR of Capacitor

I try to calculate the ESR of a capacitor. I checked this datasheet: http://www.farnell.com/datasheets/2245214.pdf?_ga=2.167304311.817060034.1534770853-676261198.1531404202 I can see from the ...
10k views

### How can I model this common mode choke in circuit in LTspice?

How can the common mode choke in below diagram used in LTspice? By an inductor or transformer? How should be the circuit drawn in LTspice? I want to use this to filter out CM noises for single ended ...
256 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 ...
7k views

### Altium Designer: Polygon does not connect to the pads on the same Net

I'm trying to put a plane shield using polygon pour and I realized that some object is not connected to my polygon. In the picture below it is clearly seen that the GND through hole is not connected ...
479 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 ...
51 views

### Ham Transceiver to computer Interface design question

I am building a Ham transceiver to computer interface, which has the RS232 port controlling the PTT on the radio. The circuit currently calls out for a 1.2K resistor in series with the RTS line and ...
178 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 ...
310 views

### Circuit stable in the Bode diagram, unstable in step-response

I am designing a simple current control circuit and trying to simulate it in LT Spice. The circuit is not optimized for some real-world application, it's more a learning method for me to get grip on ...
1k views

### Adding foot control to tig welder

I've got a simple tig welder that uses a switch on the torch to start the welding current and a potentiometer on the front panel to set the amperage. Many welders make use of a foot pedal to start te ...
460 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'...
760 views

### Is this 0.5mm pitch BGA fanout OK?

I have not used any BGA packages before, but (lucky for me) my first one is a 0.5mm pitch device. Since the pitch is so fine, there is no room for vias between the pads, even at the smallest drill ...
1k views

### Why did this arduino burn out? SilentStepStick (TMC2130) stepper at 24V

I'm new to electronics. Attempting to bench-test a SilentStepStick stepper driver board, (based on a TMC2130) Using: Arduino Uno, a SilentStepStick driver board, a 0.6A stepper motor, and waterott ...
853 views

### 32.768 kHz Crystal Troubleshooting

I'm at my wit's end trying to get a 32.768 kHz tuning fork crystal to work and I don't know what I'm doing wrong. First, some background: I'm using a 16MHz crystal in conjunction with an Atmega 328P-...
2k 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 ...
519 views

### Designing single fault safety into class I device

I'm trying to wrap my head around safety standards for electrical equipment. My device is medical, so for me section 8 of IEC60601-1 is what really matters to me, but it's kind of my understanding ...
536 views

### Interfacing TDC sensor (inductive pickup) to a microcontroller

I'm trying to do some diagnostics on a classic car (aircooled VW). In particular, I'd like to monitor a signal that flags the TDC (Top Dead Center) on every engine revolution. The signal is available ...
825 views

### Is it possible to use Microchip's ZCD (Zero cross detect) circuitry in an isolated SMPS?

Let's say you have a device which is fed by AC line voltage and features an isolated SMPS. The switcher outputs 5 VDC, and that powers a PIC micro. I'm curious how is the Microchip's ZCD (Zero cross ...
753 views

### Lifepo4 current limiter with supercapacitor in parallell

I am making a LiFePo4/supercapacitor-hybrid. Spike current draw can reach 300A for a few seconds. The LiFePo4 batteries I am using is rated for 100A max discharge rate. In order to make sure the ...
469 views

### Piezo transducer preamp and AGC/compressor

I've been suggested this circuit as a good low-noise high gain piezoelectric transducer preamp (used to pick up really faint sounds in water). It is nice because it includes a high pass filter (yet ...
448 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 ...
231 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 ...
139 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 ...
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 (...
6k 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 ...
183 views

### Headphone Noise from Laptop SMPS

I have been facing an issue that has been a mystery to me for quite some time, and I wanted to see if someone here can potentially give me more insights on this so I can understand why it is happening....
548 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 ...
446 views

### Clearance through pcb

I've become fairly familiar with the clearance and creepage requirements of UL/IEC/etc 60950, 60730 and derived/related standards. I've just realised, though, that they only refer to distances through ...
36 views

### How to choose the right frequency when measuring coil inductance with LCR meter

I would like to drive a 12V DC hydraulic valve coil using a high side driver (VN7140AJ). The driver datasheet specifies the maximum demagnetization energy (page 24), and I would like to make sure that ...
39 views

### ARM Cortex-M4 VFMA (fused multiply-add) performance? 3, 2 or 1 clock? Forwarding?

I am working on some performance-critical DSP code destined to run on an ARM Cortex-M4. One particular section of the code (a sinc interpolation function) is dense with multiply-accumulate operations ...
81 views

### Output capacitance of MOSFET

I have read in several application notes that there exists a region called the Miller plateau where the current into the Cgd is large such that almost no current enters Cgs holding the Gate voltage ...
60 views

### Motor calculations for go-cart / go-kart

I built a basic wooden go-cart and I want to convert it to electric power, and my question is how to calculate the motor. I searched here and apart from this 24V 250W motors I can't see any similar ...
207 views

### Energy efficient inrush current limiting

Short version: looking for simple and energy efficient way to limit capacitive inrush current. Primary design goals are to minimize radiated heat and current draw during normal operation. The ...
165 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 ...
45 views

### Why duplex lap winding has twice as many current paths as simplex lap winding?

I found the statement of question on page 346 in the book "Electric Machinery Fundamentals, fifth edition" written by Stephen J. Chapman. When I searched for how duplex lap winding looks ...
176 views

### How can I identify a connector type?

How do I go about identifying an unknown connector, either from spec or measurement? For example, I've got a GM4632-730 DC motor, which unfortunately came without the cable (and to make things worse, ...
289 views

### Make old telephone ring

I recently found one of those old rotary dial telephones in my garage and amazingly it still is fully functional (I tested it by hooking it to the phone line). As I have no use for it as a telephone ...
176 views

### 36x LED 5730 in series: diodes burnt when LED driver (based on BP9833A or MT7854BD) powered up

Background: I have 18W, 36 LED lamp fixture which I cannot change. Originally it has 2x parallel 18off 5730 LEDs and 300mA driver. It works for some time, but diodes starts burning. I thought that ...
59 views

### Microcontroller output override another signal, protect uC when powered off

I have a digital signal from somewhere else and a microcontroller. The microctontroller can set it's output pins to be high, low, or high-Z. If the uC pin is high or low, I'd like the output to match ...
249 views

### Can silicon temperature sensor (e.g. KTY84)'s polarity be inferred if it's inaccesible - polarity band cannot be visually checked?

I have two electric motors at my disposal, both equipped with KTY84-130 silicon temperature sensors (PTC thermistors). The sensors themselves are buried deep within the innards of the motors and I don'...
84 views

### SD card SPI initialization Check Pattern Fail

I'm trying to interface a Swissbit 512MB (S-450u Series) SD card (datasheet here) with an ARM microcontroller through the card's SPI interface. The datasheet for this card says it's fully compliant ...
53 views

### RFID reader array using row/column RF switches (multiplexers)

I need an 8x8 grid of RFID readers arranged on an 8"x8" board. The RFID tags will be placed only millimeters above each antenna. I was wondering if I could use one 1:8 RF switch (e.g. pSemi PE426482) ...
586 views

### Is there any benefit to using twisted pair for short-distance I2C?

I know twisted pairs are important for differential signals, which I2C is not. I also know I2C is not intended to be used over long wires. However, I made a design where I need to use a cable to ...