texts: Why does my mainboard power the cathode to turn the Power-LED off?

texts:
Close to all desktop motherboards have a pin header that is supposed to power an LED on the front of an enclosure with to indicate that the computer is on.
In the documentation for my board, these pins are described as "Power LED Signal anode (+)" and "Power LED Signal cathode (-)".

This made me curious and by measuring both pins with a multimeter seperately, I found out that the anode on the board is always supplied with 5V (compared to GND) as long as the PSU is connected to AC current while the cathode is supplied with 5V normally and gets pulled down to ground potential when the PC is turned on.

What I would've expected was the cathode being connected to GND directly and the anode being pulled down normally and pulled up to 5V when the PC turned on.

Is there a good reason why the manufacturer would choose to do this? Is there any advantage in powering a LED this way over the way I described? Is this probably even common practice with desktop mainboards?


texts: I am repairing a Haier RF-5210-11 refrigerator power control board; found this damaged capacitor. The circuit board has a "RTC" designation on it at the capacitor location, and the capacitor itself is only labeled with 005  04. I cannot find any information on the specs for this capacitor so I can replace it. Any one have information on this capacitor?


texts:
I've created a layout and I want to generate gerber files for further production. I'm using Cadence OrCAD software. But when I try to Create Artwork, I'm getting an error.

I've checked the dbdoctor file and there's an error that applies to the logo in the silkscreen
ERROR: in ARC SEGMENT center = (-113.118 2.774)
  class = PACKAGE GEOMETRY
  subclass = SILKSCREEN_TOP
  Part of Symbol Def LOGO_18X10MM_SILKSCREEN.
  ERROR(SPMHUT-144): Illegal arc specification.

0 warnings, 1 errors detected, 0 errors could be fixed.

I tried to delete some curved segments but it didn't solve the problem. How can I approach that problem?


texts: What enables the home appliances and electronics to work on single-phase?

texts: Talking about the home appliances and electronics, if it is single phase that we are using in houses and currents get to zero every half cycle, how do the home appliances (using AC) and electronics (using AC as rectified to DC) continuously function (inspite of periodically recieving 0 current)?


texts: Why do current transformers saturate with high short circuit currents?

texts: When there is a severe short circuit current due to the faults in transmission lines ,sometimes current transformers get saturated.Voltage of the faulty line drops sharply but ct still saturates.As far as I know it is the voltage that saturates the core not overcurrent.Am i missing something?


texts: Miniature Traffic Light with Raspberry Pi: Wiring many LEDs

texts:
Background:

I am a Civil Engineer specialized in traffic control devices and I have a small hobby project to build a scale model traffic light system. I can manage and control the traffic light pattern programming on my own using a Raspberry Pi (plus this gives me the ability to implement dynamic and programmed control, and interface with serious traffic control schema and possibly real traffic data). I just need help with wiring many LEDs on the hardware side :)

I followed this tutorial http://www.raspberrypi-spy.co.uk/2012/06/control-led-using-gpio-output-pin/ just fine (including using an external power source instead of Pin 2), but I am likely going to run into the problem of too few GPIO connections for all the traffic lights.

Next I tried multiplexing with an LED Matrix http://www.appelsiini.net/2011/how-does-led-matrix-work. Multiplexing works, however, the lights are usually dimmer, I doubt this will scale well, and this tends to magnify the control complexity.

Core question:

Short of getting some expansion card on the Raspberry Pi, are there any other tricks I could use to control multiple LED's with fewer 0/1 signals?

One thing about traffic lights is that they usually come in blocks of three, only one of which is ever active at a time. Is there some relatively simple circuit out there that would enable me to 'toggle' a block of LEDs using a single 0/1 signal?


texts: Comparator have hysteresis with pull-up resistor?

texts:
I didn't add any hysteresis to below circuit but there's ~500 mV delay between output going high and low,  output goes high at 7.5 V but goes low at 7 V:

simulate this circuit – Schematic created using CircuitLab
I think the current through the pull-up resistor keeps the transistor on but isn't the LM393 supposed to prevent that by sinking the pull-up current to ground so the output can be without any hysteresis?
What is causing this unwanted hysteresis?


texts: Lithium battery charger and balancer circuit (or IC)

texts:
I am working on a project which sould charge and balance 4 to 6 (maybe 8 in future) serial connected lithium cell batteries (~4000 mAh capacity) with about 4A of charge current.

First I looked for IC which can do this anything and communicates through I2C. But I realized that this is not that simple.

I found this great application note:
http://www.cypress.com/file/70891/download

I divided the project into two parts:

THE CHARGE CIRCUIT:

My planes are build a charge circuit from this document (highlighted with red)

Also I made some simulation on this circuit changing the duty cycle of 100 kHz PWM signal changes the charging current. With 60 % duty cycle I get about 4.5A (but this of course is a function of many things).

The microcontroller will get feedback from this charge current (with INA169) and it will change the duty cycle of the PWM signal to achive desired CC and CV charging.

THE BALANCE CIRCUIT:

For balancing you need to measure very precisely cell voltages (you need many resistor dividers), turn on/off balancer FETs, this is a so many parts, so I decided to go for dedicated IC with integrated FETs and with I2C communication.
I guess 50 - 100 mA for balancing current per cells will be enough. I choose the BQ76925 or ISL92408.

The batteries will be high quality well cell matched. Its needed to charge them in 1 hours and fully balance them in about 2-3 hours more.

My question for larger experts will these things work together?

UPDATE1:
Bruce Abbott: Sry, Yes I mean ISL94208

Andy aka: Thanks for your suggestion. That is what I need. Now it looks like I will use LTC6811-2. LTC knows everything what I need.

My other idea for balancing is use free pins of STM32 F0 or F3 MCU (12 or 14 bit ADC) with resistor dividers (e.g. for 4th cell 1k : 5k resistors). What precision can I achieve with this configuration? +/-10 mV is enough, I think.


texts: Bluetooth Mesh and Bluetooth Broadcasting

texts: I have been reading up about Bluetooth recently and I just want to know if it is correct to say that all Bluetooth 5.0 have the broadcasting feature?  Is that the broadcasting feature also found in Bluetooth Mesh?


texts: How to know whether a potentiometer is a linear potentiometer or audio potentiometer?

texts:
In general, how can you tell?

As a specific example, how would I know from looking at the following datasheet? http://www.alps.com/products/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK09K/RK09K1130AV7.html


texts:
For my venture into microprocessing, I decided to go with Atmel AVR due to the vast resources available. The Arduino seems to have a lot as well, not to mention their starter kits seem more "at my level."
The problem is I want to learn it in assembly first, and then go to C/C++ or whatever Arduino uses, but I've heard Arduino won't take AVR assembly. Is this true? Is there any way around that?
Edit: I would go with the ATMEL STK500, but for a first timer it looks VERY complicated. Is there any reason why I can't just get an 8 bit AVR and put it on a breadboard and experiment that way? (I guess I'd have to figure out how to interface them as such.)
Edit2: This is what I was thinking
http://www.adafruit.com/index.php?main_page=product_info&cPath=17&products_id=193


texts: Is it possible to get the full spectrum of a RGB diode (3 prong input) through 1 GPIO pin?

texts:
I apologize if this question is not well formed. I am an amateur in this field.

I have the requirement to independently control a plurality of RGB diodes from a single microcontroller. Each diode has 3 input pins (each corresponding to one of R, G, & B). This is the led.

I want to hook each of these diodes up to a Adafruit Trinket; however the Adafruit Trinket only has 5 GPIO pins, which, I am guessing would only allow me to control the RGB spectrum of one diode and 2 colors on another diode. (3 + 2 = 5).

As per my requirements, I need to independently control 6 diodes, which, as I understand, would require 18 GPIO pins; far more than are available on the Trinket.

I am wondering if there's some other smart way to somehow control the full RGB spectrum on one diode using just one GPIO pin; or if there's some standard way to control these diodes that I am not familiar with; for example, extending the number of GPIO pins on a board, etc.

If not, and each diode does require 3 GPIO pins, I wonder how someone would go about prototyping a device that requires many GPIO pins yet also needs to be physically very small (similar in size to the Trinket). Would I just go about using a larger board that accommodates more GPIO pins and plan on downsizing considerably when the custom PCB is made?

Thanks in advance.


texts: How should I wire up ground when using an ATX power supply to power an Arduino and several LED strips which in return are controlled by the Arduino?

texts:
Forgive me if this seems like a basic question but I want to make sure I wire these things up correctly.  Currently, I have several LED strips that I am controlling with an Arduino and they are powered by a separate 5v DC power adapter.  In that case I have tied in the ground for the DC power adapter to the ground on the Arduino board.  The Arduino board itself is then powered by the USB on my computer.

Now, I've decided to upgrade my setup to leverage an ATX power supply.  The Arduino will be powered by the 5v stb & ground pins on the 24 pin molex connector and the LED strips will be powered from the 5v & ground pins on the 4 pin molex connectors.  The LED strips are programmable via the DIO pins on the Arduino board and I plan to wire the Power On pin from the 24 pin molex connector to one of the Arduino's analog pins so I can use the Arduino to turn the supply fully on to power the strips.

Now my question, sorry for being so long winded.  Do I need to run a ground wire between each LED strip back to the Arduino?  Since this is all from one supply it will be the same ground so it seems like it would be redundant and not needed.  Below is a quick sketch of how I think things should be wired up.  If I needed the additional ground wire I was going to run it from each 4-pin molex connector back to the ground pin on the Arduino.


texts:
I'm using BeagleBoard-xM McSPI to drive an MCP42050 digital potentiometer. Before using the SPI chip itself I'll try bitbanging through 3 GPIOs (but my question relates to both configurations).

BB outputs 1.8V for logic high (and, I think, 0V for low). But MCP42050 needs >3.5V for high (VDD = 5V, which is a must) and <1.5V for low.

What I need? A level shifter of course (3 actually, for each SPI signal). The problem is: I need to make one using only shelf components (common BJTs, resistors, FETs and so on).

I've seen this question and one of its answers almost resolved my issues.

Based on Glaser's solution (most voted), I've though myself to cascade two NPN BJTs sharing common emitter. Input signal connected to first BJT's base (limited by a R1 resistor). First BJT's collector connected to second BJT's base. And both collectors connected to 5V through two resistors (R2 and R3).

I could not find in MCP42050 datasheet how much current do I need to drive its input, so I suspect very little is needed. And that's why I've thought about a high value for all resistors, like 4k7 or 5k6.

Additional info: I think I don't need very high frequencies. The higher frequency involved is SCK signal, in bursts of 16 cycles, and BB-xM McSPI can work with frequencies as low as 4kHz (it froze when I tried 3kHz). The shift is unidirectional.

Here my questions:

Will it work?
How to compute R1, R2 and R3?
It would be very nice to have both BJTs in a single component (Darlington pairs come to mind), but I don't know whether there is a shelf component for this. Do you know?
I don't mind loosing some BJTs (to runaway breakdown, for example); but I do mind burning my BB-xM. How can I protect it against such accidents (specially when fiddling with resistors values)?
Any other suggestion (instead of my cascading BJTs circuitry)?

Thanks. Sorry if they are newbie questions; they'll get harder as I improve my skills.

Edit

As noted by NickT there is a better circuit, using a single FET plus 1 resistor.

But now I stepped in another problem: I just found that BSN10A is not that common. Been to 6 local shops and no one have even heard of it. So now I'm looking for an equivalent component or circuitry.

Besides, the 4th question is still valid: how can I protect the Beagle?


texts: xcircuit: make user defined object (hit m key) doesn't give a pop-up dialog like the docs say

texts: I'm using xcircuit v3.10 rev 12 on arch linux. When I draw a new object and press the m key (or select edit-> make user object) the docs say I should get a popup dialog prompting me for a name.  Nothing comes up.  Any ideas?


texts: A question about lightning protection for a sensor mounted outdoors

texts:
There is an ultrasonic-windsensor which will be mounted on a bridge in winter. Maybe several of them.

It seems like for outdoor use this device should be earth grounded(probably through mains earth? since no earth on bridge). In the manual the reason is given as radio freq. interference and lightning.

People are asking why would there be RF interference on a bridge in the middle of no where and why would lightning affect this device.

Would a lightning not a direct strike on such device but nearby still affect the performance or damage it?


texts: I am trying to get an 74ls279 SR latch to hold a state, but it's not working. I am using a full-size solderless breadboard, a 3V power supply, and an LED to view its state. The LED flickers and loses its state when it should be giving a solid 1, and it turns off immediately once I turn off the S input. What am I doing wrong? Is it the breadboard, the power source, of the IC itself? Please tell me!


texts: PCB tracing - Ground plane and Power plane?

texts:
Is it generally a bad idea, in simple or moderately heavy circuits, having two layers, to have a power plane in the top and a ground plane on the bottom?

The tracing would become much easier, there wont be virtually any noise, better heat dissipation and aesthetically the circuit would be layed out neatly.

Also, is there any handy guide to refer, when to use a thicker trace for different values of current?

Thanks.


texts: LTSpice: why does my .MEAS 3dB calculation disagree with the cursors on the plot?

texts:
I'm exploring the .MEAS command with the following simple BJT Class-AB amplifier:

And am getting the following results from my .MEAS commands in the error log:

vout_max: MAX(mag(v(vout)))=(27.4778dB,0°) FROM 10 TO 1e+010
vout_3db: vout_max/sqrt(2)=(24.4675dB,0°)
f_3db: freq=(142.323dB,0°) at 1.30662e+007

The results for vout_max and vout_3db seem correct, they agree with the plot to at least 2 decimal places.

I'm very puzzled by the results for f_3db however. It appears to call V(vout) crossing the -3dB point at 13.06MHz, where the plot (screenshot below) has it at 19.41MHz.

Why are these numbers so different?
Have I written these .MEAS commands wrong?

I expected these to agree to at least several decimal places given they're both calculated from the same simulation run.


texts:
reacently started a new project - to add Bluetooth to Atmega2560 chip.
I'm familiar with NRF52 and HC-05 bluetooth modules. But wanted to experiment with AK1595 BLE IC, because i didn't need an extra MCU and its smaller and cheaper. And UART protocol suits my needs also.
So i made the circuit as in datasheet. But i cant get it to advertise.
As i understand when AK1595 chip powers on  - reset pin should be low, and SET1 - low also. After all is powered on i need to make reset  pin high, few microseconds later SET1 pin high. Than switch TXON pin on (from low to high), and than it should start to advertise? What I'm missing?
Using BLE app on mobile to check it.
AK1595 - Datasheet
Any help would be very appreciated.


texts: Where are the sensors of the EMF/RF meter on the circuit board?

texts:
In the attached photo you can see the PCB of a simple EMF/RF meter.
This meter shows, at the same time, the values of the electric field,
magnetic field, and power density (see small illustration on the right/bottom of the photo).
Where are the sensors (magnetic field sensor, electric field sensor, and RF radiation sensor) located on that circuit board?


texts:
I bought a cheap DC charger a couple of days back and I have been using it to charge my headphones and other small electronics.
I recently noticed that there is small amount of AC, less than 1V, coming from the DC charger. It shoots up to more than 1V AC when the switch is off. I tested my other branded chargers, and they all had less than .5V AC in them when I measured using my multimeter.
I am not an expert in electronics and it doesn't make any sense to me why the DC charger has AC in its output.

Does anyone know why this happens?
Is this bad for devices/ batteries?
Is there any circuit we can use to remove this AC from DC chargers?


texts: How to find the charging time of a capacitor given a frequency and an amplitude

texts: In the circuit above, suppose the input pulse signal has an amplitude of 1V and a frequency of 1 kHz. The resistance is 56 kilo-ohms and the capacitance is 1 nF. So if I want to find the charging time, should I simply find the time constant (R*C) and then multiply it by 5 (because it takes a 5 time constants to fully charge a capacitor)? Or will the frequency and amplitude come into play?


texts: Can an Android tablet serve as USB Host and be charged simultaneously through a single port?

texts:
A number of Android tablets are powered through the Micro B USB port but also provide USB Host support through the same port (e.g. Motorola Xoom 2, Acer A510/700). I need to be able to use USB Host support while charging, at the full power the device accepts (or at least sufficient power to keep the tablet from draining under modest use).

I have rigged up a system with splitter cables and a powered hub. This works on some devices (HP TouchPad, Archos) but not others (Google/Asus Nexus 7, Coby Kyros). And when it does work,  it slow charges (probably at USB 2's 500ma).

How can this problem be solved? Are there any solutions on the market that will solve my problem? I see there are some USB chips by Silego (their Battery Charger ID line) that may solve the problem, but I don't know of any cables, hubs, etc. that use it.


texts: STM32F4 DSP noise with inbuilt ADC and DAC

texts:
I'm trying to perform signal filtering with STM32F407VGT. I've set up the ADC and DAC to work synchronously, triggered by a timer at 42kHz, and using DMA. The idea is to process half of the buffer while ADC is filling the other half. However, even without any processing, I'm getting a periodic noise in my signal(picture attached). Seems like some portion of the buffer is always messed up. Why is this happening and how can I fix it? I'm also attaching the relevant sections of my code here.
Both ADC and DAC operate in 12bit mode and are triggered by Timer2. Both use DMA in circular mode.

    #define DATASIZE            64
    #define FULLBUFFSIZE        128

    uint32_t adc_val[FULLBUFFSIZE];
    uint32_t dac_val[FULLBUFFSIZE];
    static volatile uint32_t* inbuffPtr;
    static volatile uint32_t* outbuffPtr;

    void process_DSP()
    {
        for (int n=0; n<DATASIZE; n++)
        {
            outbuffPtr[n] = inbuffPtr[n];
        }
    }

    void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef* hadc)
    {
        inbuffPtr = &adc_val[0];
        outbuffPtr = &dac_val[DATASIZE];
        process_DSP();
    }

    void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
    {
        inbuffPtr = &adc_val[DATASIZE];
        outbuffPtr = &dac_val[0];
        process_DSP();
    }

    int main(void)
    {
      HAL_TIM_Base_Start(&htim2);
      HAL_ADC_Start_DMA(&hadc1, (uint32_t *) adc_val, FULLBUFFSIZE);
      HAL_DAC_Start_DMA(&hdac, DAC_CHANNEL_1, (uint32_t *) dac_val, FULLBUFFSIZE, DAC_ALIGN_12B_R);
      .
      .
     }


texts: Understand RFID credit card protection case

texts:
My parents bought credit card case which protects against RFID sniffing (aluminium foil but only on one side of the case), i was skeptical because i thought it would work only on one side.

So i got my RFID reader and surprisingly (for me), i could not read the card while it was in the case (on one side or the other), can you help me understand why?

Thank you.


texts: How to setup slave addressing with a HT16K33 in Proteus?

texts:
I have setup the following circuit in Proteus :

A PIC12F1822 is connected to a HT16K33 using an I2C bus.
I want to configure the HT16K33 to use the following address :

A0 = 1 A1 = 0 A2 = 0

I have setup the pins as explained in the HT16K33 datasheet:

According to the documentation, the address send by the master should be :

1 1 1 0 A2 A1 A0 R/W

I send 0xE2 (0b11100010). However, it does not work, the HT16K33 does not send a ACK :

Here is my code :

I2C1_Init(100000);
I2C1_Start();
I2C1_Wr(0xE2);

If I send 0xE0 (the default address), it works (a ACK is send).


texts:
I am trying to build a raspberry pi gameboy emulator with a custom board inside of a gameboy adv sp shell. I decided to use an open-source board made by some guy on the internet and I will be modifying a few things on the board such as the power switch to an OEM power switch for authenticity.

My question is as follows: how could I change the schematic from a DPDT switch to a SPST? Images here:

Apparently the DPDT switch is connected to things like keepalive, +3v, enable, shutdown, and the rest of the connections go to other parts of the board.


texts: What is the truth table for a logic NOT gate with two inversion bubbles?

texts:
I am currently reversw engineering a PCB and it contains a D-type register chip. The chips internal circuit diagram shows a NOT gate with two bubbles on it both in the front and the back. My question is if this is the same as a buffer or if this case some other meaning? And it would be great if a truth table could be included in the answer.

Datasheet: http://www.ti.com/lit/ds/sdls090/sdls090.pdf


texts: ESR and ESL, small package vs large (SMD)

texts:
I was wondering if someone could explain why larger package capacitors (1210) are supposed to have more ESL and ESR than a smaller - say 0603 package?

I would imagine the larger package is still essentially many 0603 equivalents in parallel for a multilayer ceramic.
Say we are comparing a 0.1-1uF 0603 to a ~10uF 1210 package, wouldn't the 10uF be more effective for decoupling? Why are smaller packages recommended for decoupling when larger packages "seem" better in my mind.

Many thanks!


texts: Have I correctly solved this RLC problem?


texts:
I'm looking to take inputs via keyboard by Arduino mega through USB cable (Serial monitor Inputs), and send them to nodemcu through serial communication (TX - RX ) so I can send it to a server (from wifi module in nodemcu).
I have tried to write the codes for both Arduino and NodeMCu can someone help me to correct them
I will be very thankful if someone can help me
Arduino mega Code--------------------------------
#include <SoftwareSerial.h>
SoftwareSerial trans(19,18);

String scr ="";
String User = "";
String Request = "";
String Roomid = "";
String Email = "";

void setup()
{
   Serial.begin(115200);
   trans.begin(115200);
}

void loop()
{
    Serial.println("Enter your User ID.");
    while (Serial.available() == 0){}
    User = Serial.readString(); //Reading the Input string from Serial port.
    Serial.println("Enter your Request.");
    while (Serial.available() == 0) {}
    Request = Serial.readString();
    Serial.println("Enter your Roomid.");
    while (Serial.available() == 0) {}
    Roomid = Serial.readString();
    Serial.println("Enter your Email.");
    while (Serial.available() == 0) {}
    Email = Serial.readString();
    Serial.println("-------------------------"); //Showing the details
    Serial.println("YOUR User ID:" + User);
    Serial.println("YOUR Request ID:" + Request);
    Serial.println("YOUR Room id:" + Roomid);
    Serial.println("YOUR EMAIL:" + Email);
    Serial.println("Thanks You...");
    Serial.println("");
    scr = User+Request+Roomid+Email;

    trans.write(scr);
    while (Serial.available() == 0) {}
}

NodeMcu Code---------------------------------------------
#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266HTTPClient.h>
#include<SoftwareSerial.h> //Included SoftwareSerial Library

const char* ssid="SLT-4566";
const char* password="1234";
int data;
const char *host = "0.0.0.0"; //Your pc or server (database) IP, example : 192.168.0.0 , if you are a windows os user, open cmd, then type ipconfig then look at IPv4 Address.

void setup() {
  // put your setup code here, to run once:

pinMode(2,OUTPUT);
 delay(1000);
  Serial.begin(115200);
  WiFi.mode(WIFI_OFF);        //Prevents reconnection issue (taking too long to connect)
  delay(1000);
  WiFi.mode(WIFI_STA);        //This line hides the viewing of ESP as wifi hotspot

  WiFi.begin(ssid, password);     //Connect to your WiFi router
  Serial.println("");

  Serial.print("Connecting");
  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(250);
    Serial.print(".");
    delay(250);
  }

  //If connection successful show IP address in serial monitor
  Serial.println("");
  Serial.println("Connected to Network/ssid");
  Serial.print(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());  //IP address assigned to your ESP

}

void loop() {
  // put your main code here, to run repeatedly:

data = Serial.read();
Serial.println(data);

}


texts: how to select capacitor for a crystal oscillator

texts:
Here is a 32 MHz crystal from one of TI's reference design

The BOM list defines the crystal as

" CRYSTAL, OSCILATOR, 32MHz, 10pF, 10PPM/+10PPM, ‐40DEGC/+85DEGC, SMD"

It is for a MCU (ARM M3) and the datasheet has this sub-chapter:

Here is the link to 32 MHz Crystal Oscillator chapter:

When I use the above CL formula:

CL = 1 / (1/12pF + 1/12pF) + Cp = 6 pF + Cp

Another reference design of TI that uses a chip from the same family has the below crystal

all the other definations are the same as above formulas and notes. The BOM defines the crystal as:

  Crystal, 32.000MHz, NX3225DA, 10/15ppm, 16 pF  ! Temp range -30 - +85 deg C !

CL = 1 / (1/27pF +  1/27pF ) + Cp = 13.5pF + Cp

I could not really understand how C341 and C351 values are chosen, could anyone please explain it?

And How do you assume Cp's value?


texts:
I can't understand the SPI timing diagram, I had search through various websites for timing diagram but I have no idea how to interpret this timing diagram of WIZ850io. I am currently trying to form a SPI connection between MCU and WIZ850io.
So,I have the following question:

What does Tov,Tdh,Tchz means?
Does understanding the timing diagram is crucial in powering up (not sure if it is the right term, but I want to read/write the data) the W5500 Ethernet Controller Chip within it ?
Does duration/period (red bracket) consider as don't care state?
According to https://www.wikiwand.com/en/High_impedance tri-state(aka Hi-Z) does not affect the circuit, if so what is the purpose of tri-state?

Any example given or website as reference/study material is highly appreciated.Thanks in advance.


texts: Can you tell me more about "re-enterable" potting compound?

texts:
I heard the term "re-enterable potting compound", which is a gel-like (possibly hard?) material that can be used to fill electronics enclosures for water intrusion protection and other things.

What is meant by "re-enterable", exactly, and what forms does it tend to come in?

I assume this means that it can be removed and the device re-worked if necessary, although it could simply mean "probe through".

If my assumption is right, how does one "re-enter"? How is the compound cleaned without damaging any electronics or other possibly sensitive items that it's covering?

I used to work with PCBs and transformers that I suppose use non-re-enterable potting or conformal coating, and re-working those can be a huge pain, but probing was never a problem (on the PCBs). A sharp thin probe would work, and the hole could be repaired.

Here is another question about removable water protection, however "re-enterable" isn't used anywhere. I presume the answer there by D_Weight might be close.


texts:
Vo for the clipper  circuit where Vi = 10sin (6280t) and diodes are 0.6 volts.

I think the simple form of the circuit is like this.

if we don't calculate the resistors. Could the output signal be this way?


texts: What kinds of semiconductors are used for high voltage devices?

texts: IIRC, gallium nitride is one of them. But what about silicon? What do they use for making thyristor valves found in High Voltage Direct Current power stations?


texts: Practical buck converter output voltage too high for given duty cycle

texts:
I'm attempting to implement a buck converter as shown in the schematic using a p-channel mosfet as a switch. I'm having difficulties implementing this circuit practically. The simulation produces a correct output voltage. The gate voltage switches between 38V(off) and 30V(on) (not exceeding vgs_max) in the simulation and in my implementation as expected with duty cycle = 0.5. So it appears the mosfet driver part is correct. However, for some reason the output voltage of my implementation is not half the supply voltage as in the simulation. It is around 36v and only when I reduce D to really low values does the output voltage begin to drop significantly. The mosfet I am using is FQP17P06. I have tried swapping it in case it was broken but it doesnt affect the output.

Are there any problems with my schematic? What could be causing this behaviour (assuming there are no breadboard/wiring problems)?


texts:
I had a circuit on PCB. I used solder with acid-core to solder it. This combined with my mess soldering caused various shorts between components.

One of those components was MOSFET transistor BUZ11 which due to shorts heated up to the point of slight discoloring of radiator and giving a little smoke before I shut off the power.

I wonder what could cause this heat up. Current that was fed through circuit was about 2A. Well within range of this component. Voltage was 15V. There were no oscilators, no inductors, just two capacitors.

So the question is: How to heat up MOSFET transistor without passing through it (drain-source) more current than it can handle or applying higher voltage than it can handle.


texts:
I built an audio mixer, and tested it with two different pairs of headphones. When I test it with one pair of headphones (I'll call Headphones #1), there is no noise (except for a few "pop" sounds when it first connects). When I test it with the second pair of headphones, there is very audible noise/crackling.

The only difference in specs that I'm aware of between the two pairs of headphones is the impedance. Headphones #1 is about 30 ohms, and Headphones #2 is lower impedance at around 8 ohms.

Given the below circuit, in which V1 and V2 are input audio signals, and the output is connected to a headphone channel, can you see a reason why noise would occur with Headphones #2? Why would a lower impedance headphone be subjected to audible noise with this circuit, or could it be due to a different characteristic?

The 1k resistor at the output is a discharge resistor I put in to prevent popping.


texts: UART clock into receiver and transmitter

texts:
So below is a receiver diagram taken from:
https://people.ece.cornell.edu/land/courses/ece4760/PIC32/Microchip_stuff/Ref_Manual/section_21_UART.pdf
I can see that there is a clock "BAUD rate clock from baud rate generator"
It enters into the divider, is this the divided clock?
Or is it the system clock which is divided by the control signal BCLKx?
Also what is the component:
Start bit detect, parity check, stop bit detect, shift clock generator, wake logic
Thanks


texts: In verilog is legal to implement a reset using assign?

texts:
I am trying to add a reset to a counter and I have this code, that syntethize perfectly:
module syncRX(clk, signal, detect);
    input clk, signal;
    output [7:0] detect;

    reg [7:0] detect_aux = 8'b0;
    reg rst;
    assign detect = detect_aux & ~rst;

    freq_div div(.clk(clk), .clk_1khz(clk_1khz));

    always @(posedge signal)
        rst <= 1;

    always @(posedge clk_1khz)
        detect_aux <= detect_aux + 1;

endmodule // top

module freq_div(input clk, output reg clk_1khz);
    reg [12:0] count = 0;
    always @(posedge clk)
     begin
        if(count == 6000)
            begin
                clk_1khz <= ~clk_1khz;
                count <= 0;
            end
        else
            count <= count + 1;
     end
endmodule

The problem is that
    reg rst;
    assign detect = detect_aux & ~rst;

Seams do nothingh. Is legal that I am trying?
Thanks


texts: Arduino: How can one control a 2-wire DC motor with PWM?

texts:
I want to control the speed of a two-wire DC motor using PWM. I already managed to control a 4-wire motor, but now I need to use a two-wire motor.

I would connect it to the Arduino directly, but the pins won't provide enough mA
 current to control the motor properly.

Is there a good way to provide energy to the Arduino and the motor plus controlling the motor using PWM?

Specifications of my Motor:

Rated voltage: 1.3V
Rated current: 65mA max
Starting voltage: 0.75 V
Stall current: 170mA max


texts:
I tried to use my MSP430G2553 launchpad with a keypad using

http://www.pjrc.com/teensy/td_libs_Keypad.html
http://bildr.org/2011/05/arduino-keypad/
http://www.instructables.com/id/Using-the-sparkfun-12-Button-keypad-with-the-ardu/
http://www.ti.com/lit/an/slaa139/slaa139.pdf (i just tried schematic
with Energia code)
http://little-scale.blogspot.com/2011/10/how-to-connect-keypad-to-arduino-simple.html
(prints blank lines in same row , buttons doesn't work except 2,5,8,0
and they print "y")

.

#include <Keypad.h>
const byte ROWS = 4; //four rows
const byte COLS = 3; //three columns
char keys[ROWS][COLS] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'#','0','*'}
};
//byte rowPins[ROWS] = {5, 4, 3, 2}; //connect to the row pinouts of the keypad
//byte colPins[COLS] = {8, 7, 6}; //connect to the column pinouts of the keypad

byte rowPins[ROWS] = { P1_5, P1_4, P1_3, P1_2 };
// Connect keypad COL0, COL1 and COL2 to these Arduino pins.
byte colPins[COLS] = { P1_0, P1_7, P1_6 };

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup(){
  Serial.begin(9600);
}

void loop(){
  Serial.print("Serial test\n");
    delay(100);
  char key = keypad.getKey();

  if (key != NO_KEY){
    Serial.println(key);
  }
}

None of them works, they only print "Serial test" and thats when i press RESET. I tried using latest keypad library from ARDUINO site or the libraries that in those tutorials.

Do i need a different way to wire up the keypad to launchpad or need a different library?


texts: Frequency response of 2nd order RC low-pass filter

texts:
I am trying to calculate the frequency response of the following circuit:

simulate this circuit – Schematic created using CircuitLab
The two extra GND points are used to show that Vi and Vo are measured in relation to the ground.

Here are 2 methods for this:

Method 1

Method 2

The first method is the one I thought. As you can see, I used the formula of voltage divider two times. But the frequency response I found is different from the one in the 2nd method. At this point, let me clarify that the 2nd method supposes R1=R2=R and C1=C2=C but either way the frequency response is different. Basically, the 2nd method finds the same function as in here: http://sim.okawa-denshi.jp/en/CRCRkeisan.htm
I suppose one of the methods is wrong, but why?

Sorry for not typing the equations but I thought this would be a waste of time. If something is not clear please ask me to clarify it.


texts: In my PCB editor, both LQFP and TQFP have the same footprints, except the TQFP has shorter leads than the LQFP. Is that the only difference?


texts: How do I control several individual LEDs with Arduino?

texts:
I am working in a book store and I have the task of making an indication of a book place in the Library Cupboard with LEDs. I need to control about 300 LEDs with Arduino. What is the optimum way to do this task?

I think I can't use shift registers because I need to power each LED separately from the others.


texts:
Is there any data to show that 0402s are relatively flex crack resistant due to their size?
I can find lots of references about 0805 and larger capacitors cracking due to board flex, but I can't find any test results for 0402 caps.
Is this perhaps just because they are so small that it is fairly difficult to get enough board deflection to crack them?


texts: how to calculate recombination lifetime for holes for a specific diode?

texts:
I need to calculate \$\tau_p\$ (recombination lifetime for holes) for a specific diode (1N4004).

We were able to do it with an experiment using the following equation:

$$t_{sd} = \tau_p\ln\left(1 + \frac{I_f}{I_r}\right)$$

where \$\tau_p\$ was isolated. This is for a laboratory. We are not asked to find the real value, but out of curiosity I'd like to know the validity of our results. I have the datasheet of the diode, but I can't find the real value of \$\tau_p\$.

Is there a way to calculate it from values in the datasheet, or to find it on the internet?

Constants list:


texts: Controlling 10 high power LED with a Raspberry Pi

texts:
I'm trying to figure out how to control 10 Luxeon Rebel LED (700mA) from a Raspberry Pi. I want to be able to turn them on and off from code, but I don't need to have two or more LEDs turned on at once, always one LED at a time.

First of all, I don't know much about electronics, so that's why some questions might seems obvious. I did some research and before ordering all the parts I would like to know if I made mistakes.

I plan on using this BuckPuck Driver to drive the LEDs. I though that I could put the LEDs in parrallel, and use a 2N2222 transistor as a switch. Is that the best way to go ?

To find the value of the resistors R2, R4, R6, etc, I used the gain found on the datasheet (30), and the base emitter value (0.6V/1.2V). The GPIO of the Raspberry PI being 3,3V it's 3.3 - 0.7 = 2.6V and 23.3 mA = 111 Ω. Is that correct or do I misunderstand something ?

Do I need a resistor between the LED and the transistor, and if I need one, how do I found the value ?

Finaly, I would like to be able to dim the light using PWM, it seems to be feasible with the CTRL and REF pins of the BuckPuck, but I don't really understand how it works.

Here is a schematics showing only three LEDs (with 10 LEDs the image was too small).

simulate this circuit – Schematic created using CircuitLab

Thank you !


texts:
I need to make a square wave generator to control a stepper motor driver.
It needs to be controlled with a potentiometer and get an output range from 40 Hz to 4 kHz.

I don't know a heck of a lot about electronics and I have been doing lots and lots and lots of research but I don't understand enough about it to figure this out on my own so far.

First off, can this even be done with just one potentiometer and second, how would I go about doing it?


texts: How to get started with AVR Microcontrollers?

texts:
I have an AVR ATMega32A Microcontroller, a Programmer that supports my microcontroller, a breadboard and some electronic stuff like AC power supply, 5 RGB LEDs and...
I also have CodeVisionAVR installed and I'm familiar with the C language.

I want to connect one of the RGB LEDs to the microcontroller and write a program for it to turn on the LED, and then rotate the color of the LED (change hue smoothly).

I have no experience, (I repeat, NO EXPERIENCE) in electronics. So please help me to complete this project using those things.

Thanks very much.


texts:
I am trying to create a Raspberry Pi Hat which has my usb hub and a mosfet which turn on and off the power on individual port.
There are different way to do this: Transistor, Mosfet, Relay, but I have chosen Mosfet for the lower consumption if the usb has to be on for a long time ( everything runs on battery ).
Unfortunately my knowledge of mosfet made the pcb not working as I was hopping, so I tried to add a transistor PNP and buying different rate ( 500ma, 1A ), the transistor worked but didnt let pass enough current even if it says 1A.
I am a bit confused on what I have made wrong and if my idea to use the VCC rather than GND line is correct.
I do understand that PNP should be use on the positive line and NPN on negative lines, right?
This is my schematic:

My temporary solution is to connect a relay to switch on and off, which works, but I want to make my pcb as small as possible by using a mosfet ( smd ).


texts: In an astable multivibrator, why doesn't negative feedback prevent the output from ever saturating?

texts:
What I understand of an astable multivibrator so far is this:

The output saturates to one of two extremes, which drives the capacitor in the negative feedback loop to either charge or discharge.
Once there is a discrepancy between the inverting and non inverting terminal voltages (|v+| < |v-|), the positive feedback amplifies that difference and pushes the output to the opposite of the two extremes mentioned above.

For example, if the output was initially at +Vsat, the capacitor would charge until it got to +beta * Vsat. Once it exceeded this upper threshold voltage, however, v- would be greater than v+, which would drive the op amp to negative saturation (-Vsat). The process would repeat as the capacitor discharges from +beta * Vsat to -beta * Vsat; beta here is R1/(R1+R2).
My question is as follows. During the portion of the time that |v-| > |v+| (either during capacitor charge or discharge), why is the negative feedback not coming into play and quickly equalizing the two voltages? Can we assume that the positive feedback of the schmitt trigger works faster than the negative feedback involving a resistor and a capacitor? Is there some sort of a "battle" between the two feedbacks and one ends up "winning" eventually?


texts:
I am using LTC4421 power path controller to route the power between cable and battery in a robot. The output of the power path is feeding 2 dc-dc converters and 2 faulhaber motor drivers.
The power path controller fails to start without a significant delay in starting dc-dc converters and motor drivers. I added RC delay circuitry at the dc-dc controller enable pins. Now it starts fine as long as the motor drivers are unplugged. I cannot add a delay circuit into the motor drivers, which carry either linear or switching power converter for the internal logic.

I poked with a scope and what I observed is that LTC4421 indeed begins to drive power transistors after a power input is validated. Then voltage at the source (the output) of the power path transistors reaches a certain level (usually between 2-5V) LTC4421 stops raising gate voltage and just hangs in a half opened state failing to start the system.
I am using the same transistors as the reference manual suggests. The current measuring resistor is routed using Kelvin connections. There is a ground pour under the LTC4421 related circuitry. I do not see a point in a power path controller needing lots of additional delay circuitry, I assume I am doing something terribly wrong. I can add a picture of my layout upon request. Please Help.


texts: P-Channel MOSFET not behaving as expected

texts:
I bought some IRFD9024 p-channel MOSFETs, and for some reason there seems to be a diode drop from the SOURCE to the DRAIN. As far as I understood it, the body diode is from the DRAIN to the SOURCE as illustrated by the datasheet:

To provide some context, here is my complete circuit. It uses a push button to short the capacitor, after which the voltage slowly increases again, providing a chosen amount of time for the regulator to deliver 5V to a microcontroller.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to understand the idea behind filtering the carrier wave from the AM signal to obtain the modulating signal.

There is some explanation in this source:
http://reviseomatic.org/help/2-modulation/Amplitude%20Modulation.php

which mentions:

A diode is used to pass the radio frequency signal in one direction only.

A low pass RC filter is used to pass the audio frequencies and decouple or smooth out the radio frequencies.

Two ideas confuses me:

Why is diode used before using the RC filter? Why not just using the RC low-pass filter to filter out the audio signal?

Another thing I wonder is that the plots for AM modulation showing side bands.. They are not the frequency domain of the AM signal right? I mean the following confuses me because it doesnt show the audio signal freq. in x axis. as if there is no audio freq. component.

edit:

Below simulates an AM 1 MHz carrier with a 500Hz modulating signal:

AM in time domain:

AM in FFT:


texts: Understanding harmonics of different Amplifier Circuits (A,AB,AB w/OP-Amp)

texts:
I have been test the circuits for amplifiers and got somewhat stuck in understanding the results for the FFT's harmonics.
With a standard type B I was able to get this graph for the harmonics

for this circuit

In here I seem to get quite a few harmonics and a high distortion. If I was to add a diode (so it becomes a class AB) then it changes to this:

Second Harmonics onward seem to have become really low. If I was to finally adjust the drop off and connect an op amp i get the final result:

for the circuit

Any way I can make sense scientifically from the results? Only obvious result I found was the reduction of appearant harmonics the less distortion we end up getting.(assuming its because we are getting rid of 2ndary sine waves turning it into a pure-er sin wave). What else am I supposed to know?


texts: Design of circuit for controlling high power LEDs

texts:
Hello EE Stack Exchange!

I am a mechanical engineering student that needs some help with a circuit. I am have an extremely limited background in circuits so I have to apologize in advance for this question. This is the circuit I was able to get together to turn a light on and off using a transistor and relay:

This is great and I think it would have worked but the requirements changed before I could test this. I now need 2 LEDs in parallel. This isn't ideal since I only have access to a power supply of 6v for two 3.3V LEDs in parallel. This is on a device that has a 6v power supply and a 3.3v arduino. Two LEDs in parallel can consume 1.4A to 2A at this voltage. What is the best option here for getting parts to support a circuit like this? Do I get a transistor like this? Do I need to change the circuit further?

Any help is appreciated.

Specific parts used in previous version are:

KEMET EC2-4.5NU Relay

LD1117V33 Linear voltage regulator

CREE XML2-W318 LEDs

2N3904 Transistor


texts: How to use transistor models provided as Spice netlists in KiCad?

texts: I would like to use device models provided by EPC for their GaN MOSFETs in a KiCad simulation. The models (https://epc-co.com/epc/DesignSupport/DeviceModels.aspx) are provided as subcircuit Spice netlists. Can I create a new sub-schematic, import the netlist into the schematic, then create a symbol for the sub-schematic and use it in another schematic for simulation?


texts: I want to design my first PCB from schematic to finish, what do I need to learn first?

texts:
I an an electrical engineer with some 10 years of experience in software development. Lately I have got a chance to design my first PCB but I am not sure what type of resource I need to master before I can design and deliver one (all by myself).

First I know i need to get hold of PCB Software. I have followed Eagle Cad and Altium and I think have got a fair amount of hold of it.
Before I can design my PCB, I need to draw schematic. For schematic I need to understand microcontroller really well. Does that means I need to fully understand all part of datasheet that I will be using in my design (for ADC, RTCC, etc)
I am confused about learning curve, what should I do first. How long will it take.

Can someone guide me what I need to master before I can deliver a PCB, all by myself. Lets start with a simple project of setting up a clock and display it on COG display.


texts:
Is there such thing as a breadboard that can you can add solder to directly to make a prototype design more permanent? Eventually the design will need to be translated onto an actual PCB but in the meantime for quick semi permanent prototyping.

Does something like this exist?

Edit:

Sorry, to clarify my question, I'm aware of the strip boards and have used them but they are not very friendly when trying to produce prototype quantities of boards on the order of 10 or so. The problem with them is you can't test the board without adding solder to find out if it works or not (when you have lots of little wires, it gets really messy really quickly. It would be very nice to just plug in a whole bunch of wires, test it to know that it works and then just mass solder everything in sight on the back of the board and know that stuff will still continue to work).

I was wondering if there was an actual plug-able breadboard which works exactly like a regular breadboard except has holes on the opposite side to add a blob of solder to make the design more permanent.


texts: Circular/ Elliptical patch antenna design

texts: I am trying to design a circularly/elliptical polarised antenna like the one in the picture. My frequency is 915MHz, a dielectric constant of 4.4, the thickness of the substrate is 1.6mm, thickness of copper is 0.1mm. I know how to obtain the radius of the patch but how do you calculate the microstrip line feed size and the size of the substrate?


texts: Charging li-ion cell using constant-voltage

texts:
I need the li-ion battery for power failure backup on an old phone used as a sip-phone.  The battery needs to keep it running less than 15 minutes so far from full is OK.  The old battery with constant plugged in charger did not last, suddenly it became thicker.

I have an old charger with a max voltage of 4.5V, with a diode in series the voltage stabilize at 3.88V.  How will the cell cope with that constant voltage for let us say 5 years. I guess the real need for the battery as supply will be maximum 4 times a year, and always less then 15 minutes.  I tried from a fully charged battery and that kept it running for more than 3 days.

A regular charging circuit like whats built in to the cellphone battery has the goal to keep the battery fully charged so you may use the phone for hours or days between charging, my goal is to have a unit with battery backup witch I may leave for years without maintenance.  The battery backup does not have to last for a long time without power.  Maybe I just should go for a huge battery of electrolytic capacitors with a voltage limit of at least 8V, and keep it charged at 4V.  That capacitor bank will have need loots of room compared with e.g. an 18650 cell. I am not sure the tp4056 will be OK for such use. Do you think so?


texts: How can excitation be used of an alternator to control the power factor?

texts: Looking for ways the excitation of an alternator can control its power factor?


texts: Reading Humidity Sensor Measurement via I2C

texts:
I have a Honeywell humidity sensor which communicates with a STM32F4Discovery microcontroller.
In this following datasheet, it is written, that to start a measure cycle, first a write bit (0) must be sent, then, after the measurement cycle, one can fetch the 14 bit resulution data. This is the following sequence:

Now, I have have the following code, written with STMCube software using HAL libraries:

uint8_t buf[2]; // 2 bytes
while(1){
 if (HAL_I2C_IsDeviceReady(&hi2c1, 78, 5, 10) == HAL_OK){
   res = HAL_I2C_Master_Transmit(&hi2c1, 78, 0, 2, 5); // start the writing cycle with bit 0;
   if (res == HAL_OK){
     HAL_Delay(40);
     res = HAL_I2C_Master_Transmit(&hi2c1, 78, 1, 2, 5); // read the data (read bit 1)
       if (res == HAL_OK){
         val = ((int16_t)(buf[0] & 0x3F) << 8) | ((int16_t)buf[1] ); // combining the bytes
         humidity = ((float)val/16382.0)*100.0;
       }
       HAL_Delay(500);
    }
  }
}

My question: is this code correct for reading the value? My final humidity value is a bit off, by about 10% so I wonder, if the error comes from the electrical parts and wiring scheme or am I missing something in the code?

Also, how is the 0x3F byte calculated? What does it affect here and how to determine what value it should have?


texts: Voltage Mode Control of a DC-DC Buck converter

texts:
My previous question was about a hysteretic-style buck converter:

Buck Converter Control Scheme- Why isn't just a comparator not enough?

By what I gather from previous answers, a hysteretic-style buck converter would not work efficiently as the switching frequency is not constant, resulting in output ripple.

Here is the schematic of standard Voltage Control Mode scheme:

The control loop has two main parts: error amplifier and voltage comparator. An error amplifier is a differential amplifier with a high gain.

I understand that to maintain switching frequency constant, the error voltage is compared with a sawtooth(of fixed frequency) and the output of comparator (VR) controls the duty cycle.

What is the function of an error amplifier here?

Even if the output was directly compared with a sawtooth wave, the switching frequency would have remained constant.

What I've read is that an error amplifier is essentially an integrator in this case.
How does an integrator help here? Is the function of capacitor is just frequency compensation?

Help me out! This is a difficult topic for me and there aren't many resources available :(

** Update **
The output of integrator would be a ramp with negative slope at very low frequencies. How does that help? Why only an integrator?


texts: How should an AND-OR-INVERT gate look like?

texts:
I was asked to implement a logic expression (F = A'B' + C'D' + AC') with AND-OR-INVERT(AOI) gates. I made the circuit (Figure 1) below, but I looked it up on Wikipedia and found that AOI gates are made out of two AND gates and a single NOR gate. So I made the second circuit (Figure 2), but their outputs were different eventhough their inputs were the same. I would really appreciate it if someone could explain this to me, thanks.
Figure 1

Figure 2


texts:
simulate this circuit – Schematic created using CircuitLab

I am designing a control system for a Hydraulic Valve Amplifier Card (Bosch VT-VSPA2-1) and I need to send an analog input signal to the card, which the card translates into valve spool movement in the proportional valve. The analog input on the card ranges from -10 VDC (100% reverse flow) to +10 VDC (100% forward flow) and 0V being no flow. It also requires Re > 100kOhms (which I'm not sure what that means and is a questions in itself).

I am using a 24VDC/3.75A power supply to power the card. Can i use (2) 5 Ohm Rheostats (one (+) voltage, one (-) voltage) to vary the voltage to the analog input on the card? The input voltage needs to be field adjustable.


texts: Replacement mains cable for Elehot Hair Clipper ET-H121 (Strange D shaped 2pin socket)

texts: I'm looking for a replacment power cable for an Elehot hair trimmer with an odd D shaped socket as shown in the attachment. I've spent hours googling without success. Any help gratefully received. .


texts: AC to DC without transformer. How does this thing work?

texts:
I disassembled a Chinese-made flashlight and found they use just capacitors to bring down the voltage instead of a transformer. They are using it to charge small lead-acid battery.

My question is how a capacitor alone can be used to bring 220 V down to 6 or 12 V?


texts: Is there a standard for writing device drivers for microcontrollers?

texts:
I have written device drivers for microcontrollers using AUTOSAR. But I was interested in knowing if there are other standards for device drivers. I am planning to write for TIVA TM4C123GH6PM. It has an ARM Cortex-M4F Processor Core.

My main goal is to write drivers that could be used by others too, and wouldn't require much knowledge of the hardware from them.


texts: Displaying different numbers in 4-Digit 7-Segment Display using VHDL

texts:
I am trying to display 4 different numbers on my display. Currently I am using a dip switch to input the number and displaying the same number in all of the digits. Now i want to change it and not input it from the dip switch. Instead I want to give 4 different signals. For example I was thinking S1 <="0001";, S2 <="0011"; , S3 <="0011"; , S4 <="0111"; .
The problem is that from what I see in the design there are not 7(actually 8) pins for each display, but  8 for all of them. So how do I display different numbers at the same time?

Current working code (it does what you see in the second picture) :

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity seven_segments is
port(
    clk       : in  std_logic;
    bcd       : in  std_logic_vector(3 downto 0);
    dig_pins  : out  std_logic_vector(3 downto 0);
    segment7  : out std_logic_vector(6 downto 0)
    );
end entity;

architecture Behavioral of seven_segments is

begin

    BCD_process : process (clk)
    begin
        if rising_edge(clk) then
            case  bcd is
            when "0000"=> segment7 <="1000000";  -- '0'
            when "0001"=> segment7 <="1111001";  -- '1'
            when "0010"=> segment7 <="0100100";  -- '2'
            when "0011"=> segment7 <="0110000";  -- '3'
            when "0100"=> segment7 <="0011001";  -- '4'
            when "0101"=> segment7 <="0010010";  -- '5'
            when "0110"=> segment7 <="0000010";  -- '6'
            when "0111"=> segment7 <="1111000";  -- '7'
            when "1000"=> segment7 <="0000000";  -- '8'
            when "1001"=> segment7 <="0010000";  -- '9'

            when others=> segment7 <="1111111";
            end case;
        end if;
    end process;

    DIG_pins_process : process (clk)
    begin
        if rising_edge(clk) then

        end if;
    end process;

end architecture;


texts:
Trying to retrofit an old Peltier wine cooler and I a question about the wattage and heat calculations.

If I have a 12V power source (switched)  so the maximum Wattage it can convert to heat is (105W)

If I were to connect some sort of cooling system capable of dissipating 120W of heat (such as a CPU cooler)

Would that be adequate heat removal to allow the cool side to continue to decrease the temperature to below ambient? Or have I oversimplified the heat movement calculations too far?

simulate this circuit – Schematic created using CircuitLab


texts:
I have been reading about grounding lately because I learned that this issue is very important for high frequency design and I got the idea that we have to think about the return current to avoid ground loops.
I am designing a board that should take into consideration this element.
So I am planning to have a single ground plane  and seperate the digital and analog tracks from each other so they don't interfere.

My first question :  Does the digital/analog power have to follow the same principal with analog/digital traces ? I mean do I have to place digital plane under digital traces and the same thing for analog ?
My 2nd question, will the power supply placement(/gnd) will make the analog return current carry some noise from the digital circuits in its way as show in the figure below ? or  do we consider just the ground plane and the return happening localy below the traces ?
My 3r question, I read that using multiple ground planes can tranform the PCB into a dipole antenna. Knowing that I need ground planes both under the top and bottom layer for the components I am placing . Should I limit the surface of these plane to the straigt minimum and place them only under the components instead of placing them on the whole layer ?

I hope this was clear. Let me know so I can clarify my questions more.
I really appreciate your opinions about this. Thank you so much.


texts: How to decide earth trace width in protection circuit?

texts: I am using the earth trace for protection circuit in telecom system. The protection circuit includes MOV, sidactor & fuse.  So please suggest How to calculate the Earth trace width.


texts:
I want to start a project where i'll sample directly from the audio jack.
Now i don't know what the sampling frequency should be.
I don't know what is the maximum frequency of sound, i don't know it it is straight analog volumes, or if a special protocol is used.

So, anyone knows what frequency do i have to sample?

EDIT: The purpose is to record all traffic from the audio jack and store it to an SD card


texts: Criteria for considering transmission line effects due to phase delay

texts:
Below drawing illustrates a transmission line where the source voltage is:

$$v_s(t)=V_0 x\sin\omega t$$

After reading some texts about the subject, I concluded how to decide whether one must consider transmission line effects or not. If I'm not wrong, to consider transmission effects, basically there must be a considerable phase delay between the source and the load voltages.

Let's say just nearby the source the voltage is approximately equal to \$v_s(t)\$. And let's say the length of the line is \$L\$.

At the end of the line near the load we can say the voltage is delayed so it will be around \$v_s(t-\Delta t)\$.

So here \$\Delta t\$ can be written in terms of the velocity of propagation \$v_p\$ and the line length \$L\$ as:

$$\Delta t = \frac{L}{v_p}$$

So the delayed voltage can be written as:

$$v_s(t-\Delta t) = V_0 x \sin\omega(t-\Delta t)$$

or simply

$$v_s(t-\Delta t) = V_0 x \sin\omega(t-\frac{L}{v_p})$$

from above equation we can easily see the phase delay \$\phi\$ becomes:

$$\phi = \omega\frac{L}{v_p}$$

My question is:

We've just written the phase delay \$\phi\$ as:

$$\phi = \omega\frac{L}{v_p} = 2\pi f \frac{L}{v_p} = (2\pi)\cdot\left(f\frac{L}{v_p}\right)$$

(groupped). Now I see that many text conclude when the \$\phi\$ is large the transmission line effects must be taken into account. Obviously they conclude that increasing the frequency will dramatically increase \$\phi\$ and one must consider transmission line effects.

But knowing that if a phasor in complex plane is shifted by \$2\pi\textrm{[integer]}\$, the phasor actually comes to the same point. There is no phase delay.

Imagine we found the phase delay as \$2\pi\textrm{[integer]}\$. Does that mean we should still consider the transmission line effects even though we calculate zero phase delay?

If the phase delay is \$2\pi\textrm{[integer]}\$, and the integer is \$1000\$ does that mean the voltage is moving like a wave and we should consider transmission line effects? (I think we should since we are dealing with moving waves)

But what if the phase delay \$\phi\$ in radian is \$0.1\$ or \$1\$ or etc. What is the criteria to consider the transmission line effects due to \$\phi\$? For \$\phi>\$ what we should consider transmission line effects?


texts: How should I set up my text in Eagle for the maximum chance of success?

texts:
I've just finished routing a board in Eagle, and now I want to work on the silkscreen and texts. I have a few questions, however:

I chose "always vector font" before I did anything, but my texts still claim to be "proportional". Should I worry about this, or will this be ignored because of the "always..." setting?
What is the minimum size font that is likely to be printed and legible? Sparkfun's tutorial recommends reducing the size to 50 mils (.05, or 1.27mm), and I've read somewhere that one should set the ratio to something higher than the default 8% or some lines may not be printed. What is the recommended minimum?
Is it normal that all my parts end up "smashed" in order to put the text in sane places?
Is it recommended to include values as well as names, or do these merely take up space that would be useful for something else?


texts: What is this electrical component on a Time Crisis II I/O PCB?

texts:
I have a Nanco Time Crisis II That has a bad I/O board. Power is getting to the board, but not making it to the chip on the board (activity LEDs not flashing).  I’m trying to trace where there may be a problem but there are components on the board I don’t recognize.

What is component FL1 & FL2?  They have 3 legs and the only other marking on it is 222.  How do I test it?  Can I test this in-circuit?


texts: Are there any software where electrical, mechanical, thermal as well as control modeling and simulation be done for the design of battery pack of electric vehicles?


texts: First schematic - Critique my ATMEGA-328P design

texts:
I'm a software engineer looking to dabble in making electronics, and want to design my own board.  I thought that an Arduino would be a good place to start, so I created this with an ATMEGA-328P.

Could someone provide input on the accuracy and function of the design, and how I could improve?  Thanks in advance.


texts: Non blocking ++ equivalent in Systemverilog

texts:
The ++ operator in Systemverilog is blocking.
Is there a non-blocking equivalent to it ? Or are we bound to use the more verbose x<=x+1 form if we want to keep it non-blocking ?


texts: Converting single ended to differential signal with differential amps

texts:
I want to transform my 0-5V analog signal to differential signals. I have on hand a bunch of TI INA106KP. I'd like to use one to invert my signal and the other one to non-inverting. The doc show how to get a inverting and a buffer. The buffer however has a gain of 11. Can I still use the two together?

also, is a simple voltage divider good enough to power this? I want to run my signal down 20ft of shielded twisted pair wires.


texts:
I have the following load cells:

I'm using the following HX711 amplifier

Every guide i can find on the internet describes how to connect a load cell with four wires to the amplifier. How can i connect a load cell with three wires to the amplifier?

Thanks in advance.


texts: How to calculate Real Power and Power Factor using an Oscilloscope?

texts:
I'm trying to calculate the Real Power consumption of my device in Stand-by mode, but to do that I need to figure out its power factor due to:

\$\text{Real Power} = V_\text{rms}\times I_\text{rms}\times PF\$

Now, my device like many other IT devices doesn't have a perfect sinusoidal current curve, so I can't just calculate the phase shift can do cos(theta).

I read through some documentation for an Arduino application and apparently you can calculate Real Power by doing several instantaneous samplings of current and voltage and multiplying them and just get the average. So I took out my scope and decided to get 1000 samples.

Here is the graph:

I exported this data to an excel sheet and got the following values:

\$V_\text{rms} = 118.96V\text{ (RMS)}\$

\$I_\text{rms} = 0.02024A\text{ (RMS)}\$

\$S \text{ (apparent power)} = 2.40792\text{ VA}\$

\$P \text{ (real power)} = 0.93713\text{ W}\$

This gives me a power factor of

\$PF = 0.93713/2.40792 = 0.38919\text{  ← This is a very low power factor.}\$

I used my Kill-a-Watt device and it tells me my power factor is somewhere around 0.6 average.

I tried investsigating online if I missed something, and I noticed a website that said that the current probe for the scope should have it's "flow arrow" pointing to the source, in my case my AC outlet. I noticed I had it the otherway around and corrected this. The graph is bellow:

The gives me almost the same RMS values, but when I try to calculate Real Power by multiplying instantaneous Voltage and current readings and averging them out I get a Real Power of:

\$P = -1.02W\$

Can any of you guys with more experience point me in the right direction. What am I doing wrong?


texts: Verilog Synchronous bit alternator (Quartus/Modelsim) - Altera FPGA

texts:
I am trying to make a simple bit alternator for the purpose of learning how to use verilog for FGPA design and how to simulate in modelsim. Here is my code:

module top (
    input wire clk,
    output reg data
);

initial begin
    data = 1'b1;
end

always @ (posedge clk)
begin
    data = ~data;
end
endmodule

Here is my attempt at simulating the program in modelsim. I set the clock period to 100ps and gave the data/clock an initial value of 1, yet the waveform shows strange results.

Perhaps I'm not using modelsim correctly? or is something missing from my code? Any help would be appreciated!


texts: Substition of electrolytic capacitors in surface mount applications

texts:
I understand there are advantages and disadvantages against using electrolytic capacitors over others, such as ceramic, but from what I understand the main reason of choosing electrolytic caps is usually because of their larger capacitance.

In the simplest form, why else might you choose electrolytic over other counterparts? I ask purely based on physical size reasons. Both footprint size and height of electrolytic over a ceramic capacitor is much larger.

Using this circuit as an example:

If I could get a ceramic capacitor at the capacitance of 10uF and within my voltage requirements, which from my initial searches I can, what problems would I experience if I were to change, if any?

Fortunately from my searches, 10uF seems to be very close to the max of non-electrolytic capacitors, but as I say I need much smaller components for my design, where size is important.

Finally, when searching SMD footprint standards, the common packages seem to be 0402, 0603, and 0805, where they increase in physical size respectively, but also power rating, which suggests to me I should use as large of a package as possible, but what other attributes from these packages should I pay attention to when selecting?


texts: Quantifying the piezoelectric effect of ceramic capacitors

texts:
In comparing ceramics vs tantalums one of the oft cited disadvantages  is the tendancy for ceramics to exhibit a piezoelectric (i.e. microphonic) effect.  Old-school technicians talk about ceramic disk capacitors "singing along to the music" in audio circuits.

I am having great difficulties trying to quantify this effect. The closest I have is a Kemet paper.

So, is this effect still significant in modern X75/X5R capacitors (for example)?  Does it vary by package size and manufacturer?  What frequency range will cause problems?  What sort of noise (microvolts? millivolts?) can be expected to be generated and at what frequencies?

Most papers discuss audio circuits, but primarily I am interest in applications with vibrations under 200Hz (sometimes much less).


texts: Sending serial signal of HT12A encoder by wire over 25 meters distance

texts:
This question has been asked many times, but I couldn't find something regarding sending out serial binary pulses from HT12A encoder over long distance.

The wire will be running beside of AC 220v wires, so will it work efficiently without noises or voltage loss ??


texts:
This question is derived from the answer to another question What is the input current of the 74HC595

The answer makes a note to the OP, that he should also consider power dissipation capacitance.

My question is what power dissipation capacitance ? And where would it come into play in terms of designs ?


texts: Controller area network received message filtering mechanism

texts:
I am working on some CAN communication project which allows us to control some external device attached to one node from some other node.
The CAN bus is a broadcast network and hence a message sent by a node will be received by every other CAN node on the bus.

My requirement is that I need to implement a filtration mechanism for the nodes so that a node will only act upon those received messages for which it is configured (using some GUI utility). So I need to implement this filter mechanism in my code. I am using an STM8SAF52Ax microcontroller with IAR Embedded Workbench as my development environment.

How could I implement this filter process of CAN messages? I also did web search and read many other tutorials, but still I am unable to figure
out what is to be done. There are use of CAN filter ID and filter mask, but I am unable to decide what value to be loaded in these and how to
calculate these values.


texts: PIC16F84A wont run my program on a breadboard

texts:
I have written a program on the PIC16F84A and it seems to work perfectly on the PIC testing board. After i had created the program and assembled it onto the PIC, i placed it onto the breadboard and connected all of the inputs and outputs and power lines.

I am using a 2.2 Kohm resistor and a 23 pico farad capacitor for my oscillator values. i have also connected MCLR to V+ WITHOUT a resistor. The rest of my connections are perfect.

However, when i press the push switch to add an input there is no output onto my LED.Do you know if there is a problem with my MCLR connection or is my oscillator speed the fault here or is it something else?

I have tested the program repeatedly to make sure the chip is not damaged or the program is wrong.


texts: Replacing optocoupler with a more reliable and durable device

texts:
I am working on a project where I need to have some sort isolation from a machine sending out highs and lows in terms of 24vdc to 0vdc respectively. And I'm using a microcontroller like ESP32 that works on 3.3vdc to read these signals.
My current prototype setup is pretty straightforward. I'm using a PC817 optocoupler with a 4.7K resistance. And everything works pretty well.
My question is more related to having a improved design which can multiply the reliability and durability of the whole set-up. From my research I've been able to summarise that optos tend to wear out in long run and are prone to failure if they don't get a healthy environment to work with.
My production model will be using multiple optocouplers, over 20 and switching on and off about 3-5 times every second and there's literally zero margin of error.
I figured out that Digital isolators like SI8422, or ADUM or ISO series from different manufacturers etc are much more reliable than an optocouplers but sadly I'm unable to find any proper source to buy them, and 4-5 days of research gave me only a few options but then they are way too costly than expected.
Just wanted to understand if there are more reliable and "easy to get" options available? Any other device which can give me an isolation like I would get from the PC817. One way was to use Darlington array chips like ULN2003 or ULN2803 with proper resistance for each input but I don't think it'll be a real isolation.


texts: Can someone explain how it derived the bandwidth for spread spectrum on following link http://www.ausairpower.net/OSR-0597.html (paragraph 9)?


texts: Circuit for flashing LEDs for airplane model wing, tail and beacon lights using 555

texts:
I am working to make flashing LEDs for my airplane model. There are three LED pulse sequences on the picture below where to flash LEDs respectively.

So how do I design a circuit using an astable multivibrator using the IC 555 timer?

How do I design resistor and capacitor values?


texts: Signal to Noise Ratio and Inflection point (PSRR measurement in Oscilloscopes)

texts:
I have a 3.3V LDO for which I am supposed to do the PSRR measurement.

I have a keysight scope to do this. While looking at this PSRR YouTube tutorial from Keysight, I have a few doubts.

Around 5:20sec, he tell that there is wiggle in the waveform due to the Signal to Noise ratio. What is the signal here and what is the noise? Is that 200mV(p-p) which is mentioned before during the test setup the signal or the noise? Please clarify which is the signal and which is a noise?

He also mentions that it can be corrected by increasing the amplitude above 200mV. How is this possible?

Around 10:00sec, he mentioned that there is something called as inflection around 2.5MHz. Can someone help me understand what is inflection that he is talking about and why does it occur?

Please. I have tried reading/researching a lot before coming here seeking answers. Please help me understand


texts: Embedded Software Reliability Metric is short-term or long-term in time

texts:
If I test an embedded software (and the product based on this software) today and it fulfills all the customer requirements successfully at this point in time then I can safely say that this software is reliable.

But if the customer requirements change in the future then what software metric should I measure today that can tell me how easy or difficult it will be to do the required change in this software in future?


texts: What are the various ways in which an I2C bus may hang

texts:
I am very new to electronics and have entered in the territory of I2C bus. Want to understand the behaviour of compliant devices as per I2C protocol specification.

One condition as per the link below is when a master controller is reset in midst of a transaction. That is to say the slave engaged does not knows what to do now.

https://www.i2c-bus.org/i2c-primer/analysing-obscure-problems/blocked-bus/

I do not understand how does this calls for bus hang? The master which was restarted could always start a new transaction and the slaves should be able to read it.
Is there any other way in addition to the what is explained above to cause a bus hang?
Can such a problem be caused by software driver?


texts: Is this stackable low RPM generator design viable?

texts:
I'm trying to invent viable hand-crank energy generator for charging phones and similar low-power appliances. I want to avoid gears altogether in the design, because they are hard to manufacture at home and because I don't want to lose any of the already small power generated by hand to friction between gears. With a single axis device, there is almost no friction or wear.

The concept looks like this:

This is what it would look tiled. The idea here is that you can tile it indefinitely, the only limit is your own strength (and patience when putting it together).

The magnets will be neodymium magnets. There's intentionally six of them but only five coils - this aims to reduce the "zero point" strength - the most stable point of attraction between coil cores and magnets.

The coils would have ferrite cores and each would have its own rectifier.

The magnets will be altered in polarity so that two opposing magnets will always be attracted to each other and therefore exert maximum possible field over the coil.

Questions:

Is this a good design for low RPM (40-100 RMP)?
What would be the ideal number of turns if the target voltage is 5V, given the aforementioned RPM?
Are ferrite cores good idea? Or should I use iron or air cored coils instead?


texts: Secure storage of Data in external EEPROM

texts:
I am working in designing of a prepaid energy meter.
One of the most things I should store are (private key, credit and cumulative energy).

The private key is stored only once.
The credit and cumulative energy are stored every few hours or when the power goes off (it is normal in my situation).

I was using a flash memory in my previous design and I discovered its disadvantages in such application. I got some memory corruption and deletion when writing while the d.c supply is going down to 0.

If I stored the credit in the EEPROM, any one can access it.
The microcontroller (dsPIC33CH128MP508) don't come with internal one.

I have only few seconds (~2s) to store these data before the power supply dies. My clock is 4MHz and the dsPIC is 16bit. Therefore, if I need to encrypt the data in EEPROM it should not cost more than 2 seconds.

My question is: How to overcome the security issue when storing in external EEPROM in such applications?


texts: Transformer power supplies, which one would have a 24VAC secondary when the DC output is 9vdc > 12vdc > 15vdc > 32vdc

texts:
I need 24VAC 300ma for a solenoid and have these old transformer power packs with outputs of: 9vdc, 12vdc, 15vdc, 32vdc.
I'm willing to crack open one and use the transformer but I only want to open the one that would have or be close to having the 24VAC secondary.
Which one's the lucky one.
The solenoid specs: 24Vac 50Hz 8VA > 8VA / 24 = 333ma should work fine?
Unfortunately it was a successful failure. I got the 24VAC from the Power pack but on connecting a distinct unhealthy hum was present from the solenoid with 24VAC at 370ma. It did not sound right.
I then tried DC power packs I have and all quiet, no humming just V/V opening and closing sound:
12VDC at 250ma
18VDC at 490ma
24VDC at 570ma
30VDC at 770ma
Solenoid says 'ac' but works better with DC, I have absolutely no idea!


texts: Tools required to burn code in a quad flat microcontroller

texts: I always have a doubt that how do firmware engineers dump code into a quad flat microcontroller(with or without leads)? For a starter kit there is already connection like USB or some SPI ,I2C headers to burn the code. I know that for Dual inline Package there are some programmers in the market.Then what about quad flat micros used in industrial application?How do you all proceed?


texts:
I want to understand the purpose of capacitors and variable resistor in the following audio amplifier circuit. Here is its datasheet.
C118 at amplifier output pin.
C424 between amplifier input and output pins.
VR3 between amplifier input and output pins.
Can we disconnect PIN3 of VR3 from PIN7 of Opamp? I cannot understand the purpose of this connection. PIN3 can be either left floating or maybe connected to ground to do volume control function through VR3. Please correct me if I am wrong here.

The power supply of the circuit is +/- 15 VDC.
Edit:
If the circuit include 2 stages and the first stage is without the feedback resistor as in following diagram then is it ok?

In my second circuit diagram what is the meaning of 'Audio+' and 'Audio-' labels? Does it means that I can connect my mono headphones on these two points instead of using a 0 V (GND) reference for the headphones jack?


texts: Why does connecting a high-current device to my digital circuit cause weird behavior?

texts:
I have a

arduino
microcontroller
other digital thing

and when I connect a

motor
pump
heater
other high current thing

I experience

weird ADC measurements
reboots
crashes
errors in digital communication
other unexpected behavior

My power supply is properly sized to power all these devices. I don't have an oscilloscope so I can't see much what's actually happening in the circuit. What's a likely cause?


texts: How is battery life measured in devices?

texts:
I have a thermostat (Siemens REV200) which runs on 2 AA batteries. I've put in 2 brand new (A brand) batteries but the device keeps showing me low battery power signals. How do electronics usually measure battery life?

I was thinking of connecting a power supply to it which exceeds 3 volts or 2 amp. Would this be a solution?


texts:
I have got schema of li-po battery protection circuit.

translation of czech title of components:
Napěťová reference = voltage reference
Zátěž = output of protection circuit

Battery has got 2.75v cut-off voltage, i want to have reserve.
But I do not know what component should I use, so can I use these:
voltage reference = MCP1501T-10E/CHY.
comparator = AS393P-E1
transistor = BS250P-DIC
Can someone help me?


texts: How to structure an application, and driver code for UART - the concept of decoupling the data

texts:
So I'm writing drivers for UART on STM32 and even though I kind of have an idea on laying out the structure, I'd still want to clarify prior to implementing, and also considering how essential it is to keep the code clean and organized.

So I have main.c, sensor.c (application file that uses UART layer), hal_usart.c (which is the driver file).

I have heard different things regarding how application code should have no clue whatsoever about the driver APIs, and read up an article the other day that you could decouple the sensor code from HAL driver code using function pointers but not sure how I could do that here, and if that will decouple it considering I'm still passing a reference to USART_Handle struct that contains info like baudRate, parityControl, wordLength, reference to USART_TypeDef etc.

Below is a snippet of my idea:

// main.c
static USART_Handle pUSART;

int main(void) {
   // initialize clocks/HAL

   // ...initialize USART struct

   // Get data via UART (calling application API)
   GetData(&pUSART);
}

// sensor.c
void GetData(USART_Handle *pUSART) {
     HAL_USART_TX();
     HAL_USART_RX();   // assuming data is stored in one of the struct members
}

// hal_usart.c
void HAL_USART_TX() {}
void HAL_USART_RX() {}

```


texts: Is the conventional current direction assumed to be from - to + in US Air force training videos?

texts:
1)

https://youtu.be/a8casNPDvI4?t=354

I'm not sure if I'm misinterpreting, but I couldn't get past this point in the video as it seems they are assuming the current flows from - to + and its confusing me a lot.

2)

Also in another video they seem to assume the flux direction in a solenoid in reverse to what my textbook says (right hand rule)
https://youtu.be/X0WnddW5gZI?t=208

Are they using a different convention or is my understanding flawed ?


texts: MSP430 how to make configurable ISRs in a module (Code composer studio C)

texts:
I have a question that I think the answer to is quite simple. But I've been unable to find a straight answer to.

If i have this service routine in some module foo.c

#pragma vector = SOME_VECTOR
interrupt void fooISR(){
    dosomething;
    IFG = 0;
}

if i have in my main.

#include "foo.h"

Then it appears that the fooISR() does indeed get loaded into the SOME_VECTOR and the ISR will trigger whenever the corresponding IFG is set.

I wanted to ask if this is the right way to write modules that utilize interrupts. Because with this approach the fooISR() will be in the SOME_VECTOR whenever I include foo.h this doesn't really allow for much configuration for the person working in main.

For example if in main.c I wanted to access some functionality of foo.c but wanted to write a separate ISR for SOME_VECTOR I'd be outta luck with this method right?


texts:
I can't find information for the IC in the picture. It's a socketed 8 pin DIP that is part of the controller of a CNC machine. As far as I can see it receives signals from a microcontroller and then connects to a pair of 75176B which in turn connect to a Delta ASDA B2 servocontroller.
Thanks in advance.


texts: Why a capacitor improves the power factor and connecting reactor in parallel avoids increase of voltage

texts:
When we read the power transmission or Circuit Theory,the book will teach us two things

  1.we can  connect the capacitor in parallel to improve the power factor

  2.we can connect the reactor in parallel to avoid the increasing of voltage

If we can connect the capacitor in parallel to improve the power factor, can we connect the "inductor" in parallel to improve the power factor? If not, why?
Why won't we connect the inductor or capacitor in parallel to avoid the increasing of voltage?


texts: Electrolytic Capacitor Voltage Rating vs capacitance

texts:
I have always believed that it was ok to replace a capacitor with a slightly higher voltage rated one. eg 16v with 25v.Going higher than this would risk the capacitance value being out at the working voltage.
However I just read the following quote from this pdf

  Electrolytic capacitors are non-ferroelectric with a very low dielectric constant. Their capacitance is derived from a very high surface area and nanometer thick dielectric layers. Their capacitance is not a function of applied voltage.‐Design Solutions For DC Bias In Multilayer Ceramic Capacitors (August 2010 Electronic Engineering Times)

So does this rule not apply to aluminum electrolytics?
Eg will I have no issues replacing an electrolytic 25v 100uf with a 50v 100uf assuming both are low esr, similar footprint and good quailty?


texts: How can increasing the wait states increases the speed of Processor?

texts: I saw in a datasheet where for 0 wait states the Max speed is 30MHz and 1 wait state the speed could go up to 60MHz. My understanding is as you add the wait states the speed comes down as the processor waits for the data.


texts: Is space division multiplexing really multiplexing?

texts:
I don't know much about electronics, but happened upon the Wikipedia article for Multiplexing, which defined it as:

  a method by which multiple analog or digital signals are combined into one signal over a shared medium

Shortly after are listed different types of multiplexing, among them Space-division multiplexing:

  the use of separate point-to-point electrical conductors for each transmitted channel

An example given was a stereo audio cable.

But it seems to me that if you have seperate physical streams of data (conductors in this case)- you haven't really 'multiplexed' your streams- there are still two seperate streams of data on two seperate physical conductors.

It might just be terminology, but I'm curious if there's something fundamental I'm missing.


texts: Help me to resolve this error in this LTSpice Simulation

texts:
Below is LTspice simulation in which this error occurs.
The error is Unknown subcircuit called inc xu1 n001 n003 op opamp
How do I fix this error?


texts:
I am using LTspice to simulate voltage measurements from a circuit. I noticed, with exactly the same circuit components, each time I obtain different results. I assume it is due to thermal noise. (is that right?)

Then I wonder is there a way I can set seed to the SPICE simulation so that my results are reproducible.

To provide more detail: I did a Transient analysis. I am running a circuit with amplifiers, multipliers, resistors and capacitance for 200mS. I run the same circuit with nothing changed (I literally quit LTspice, open again, and hit Run button for the same schema), I found the voltage measurements at one node for the two runs are different. They stay the same for the initial ~30mS, then start to have a lag, then go on completely different tracks. Since nothing about the circuit has changed, I suspect it is caused by thermal noise. Please let me know if there could be other reasons.

Many thanks!


texts: Conduction Period;Half wave rectifier;Battery

texts:
How can we calculate the conduction period of the diode when a half-wave rectifier is used to charge a 12 Volts Battery  through a resistance 'R'? Given the input is fed by 34 Volts AC with turns ratio 2:1

My Approach:
we know for half-wave rectifier: $$\omega \times \Delta t = \surd((2 \times V_r)/V_p) \quad $$ $$Given \quad V_{pm}=34V ,V_o=12V\quad and \quad Turn \quad ratio=2:1 $$ $$\implies V_{sm}= 17V$$
Also we know: $$V_o=V_{sm}-(V_r/2)$$ $$\implies12=17-(V_r/2)$$ $$\implies V_r=10V$$ $$\therefore \omega \times \Delta t =1.08 \quad in \quad rad \quad or \quad 62.14^o$$
but answer is given as 120 degree ; so where am i wrong and how to proceed ....any suggestions..??


texts: How does a computer calculate a sin value? Logically, when I think about it the only apparent way is to put many sin values into memory, and when a sin value needs to be "calculated" it would just pull data from a specific memory address.(ex. sin(x) would pull data from the memory address containing the value of sin(x) )That seems like the only possible way to do it. Or is there a function which can be used to calculate the sin of a value? I'm really trying to ask how a computer calculates sin on a base level. Is there a way to approximate sin values using a different function composed of more "basic" operations, and the ALU would be able to do multiple "basic" operations to approximate the sin value, or is it just pulling values from memory?


texts:
I need to vary the speed of a DC geared motor using software (Raspberry Pi SW GPIO).

The motor is 3 V DC geared micro motor @150 rpm. At 3 V full 'speed' the motor is very powerful for my needs having sufficient torque. However when I change the duty cycle to decrease the speed, then the torque is also reduced (presumably as duty cycle halves voltage).

Is there any way to maintain torque via software?
If not, then any idea how the Anki Cozmo/Vector robots do this (see The Best Cozmo Commercials by Anki)?


texts:
I would like to use 2 SCRs in antiparallel configuration to control the power to a all resistive load (20A) using 240Vac (line to Line). Pretty typical configuration and part of a lot of SCRs datasheets. The application has a ON/OFF switch that controls in part if the SCRs are ON (using zero crossing firing)

The problem to overcome is the failure on an SCR. If an SCR fails short you lose control to the load. So I have added a second set of SCRs for redundant control. One set controls the "Line side" of the load and the "Return-side", such that if one SCR fails the other set of SCRs would allow control of the power.

Yet the problem with that, is the fact that, if an SCR fails short, the load will have power for half a cycle on one end of it, while the other end is effectively disconnected. That causes a potential corner case safety failure if a person "turned OFF" the switch but the load has a potential on one of the legs.

My question is how can you create a FAIL safe SCR. A fuse will not work as the current will be within the limits. My device needs to work at -40C.


texts: High dV/dt turning on BJT switching Circuit due to Miller capacitance

texts:
I have this BJT Switch circuit.

Ccbo- collector base capacitance , Cleak- PCB layout parasitic capacitance.
In a design recommendation, I have a point which states - "Verify that the switch does not momentarily activate when its input supply is enabled.  A common cause of this is miller capacitors (gate-drain / base-collector) in the switch to limit slew rate / current surge.  Any capacitors to limit slew rate should be gate-source / base-emitter capacitors"
It is recommending to add capacitor between base and emitter.
My questions
Question 1: How does High dV/dt affect this? Does it mean when the Input VBAT goes from 0V to 12V very quickly, the transistor will turn ON? How will the transistor turn ON - because you need both transistor base-emitter voltage (assume to be more than 0.6V in this case) and base current to flow into Q2 for the transistor to turn ON? And how does it happen during dV/dt?
Question 2: How does adding a capacitor between base and emitter help to reduce this effect? I agree that the capacitor will reduce the dV/dt but why should it be added between Base-emitter of Q2? Why can't it be added between VBAT and ground? Won't a capacitor added between VBAT and ground also reduce the dV/dt?
I have gone through and found that similar to a resistor voltage divider, 2 capacitors in series also acts as a capacitor voltage divider? Can someone please explain how?
Question 3 : Is this a common emitter circuit as the emitter is common to both input and output?
Just want to understand in simple basic terms on what high dV/dt will do in the below case and how the high dV/dt effect is bad and how it is mitigated by adding a capacitor across base-emitter of a transistor? If the value of the capacitor can be calculated, how is it done?


texts: Do I need USB isolator for laptop computer?

texts:
I have a product which is powered from main AC power. I need to serial communicate the product with a computer, for example sending some bytes to the product by the terminal program in the computer. I have a USB-to-UART converter to communicate with the product. However I worry that the AC power from the product will damage my computer's USB port. If I am using a laptop computer powered by the battery (not the AC main), do I still need a USB isolator to connect the USB-to-UART converter to my laptop computer?

Please provide reason instead of just answering yes or no.
Thank you very much.


texts: Voltage follower with LF411 shows -6dB instead of 0dB

texts: I designed the circuit shown in the first picture. It is a voltage follower realised with a LF411, connected to its output is a load of 10k and an AC source on its input with an amplitude 0.5V. I am wondering why the simulation (PSpice 9.1) shows me a more or less constant amplification of -6dB until 1MHz, where I would actually expect 0dB. Does anybody know why the amplitude response looks like that (see second picture)?


texts: Is there an alternative to GCV (generator control voltage) to synchronize frequency sweep measurements?

texts:
A friend is taking a course in electronics engineering and asked me for help reproducing a lab experiment in frequency sweep measurement techniques. Students build a small RC filter and use a function generator to produce a sine wave sweep and show the frequency plot on an oscilloscope using X-Y mode, much like a Bode Plot.
The classroom function generator has a GCV (generator control voltage) output which is fed to the X (ch 1) input of the scope, and apparently produces a 0-5 V DC signal that corresponds to the position of the sweep.
Both my friend and I have more modern, though inexpensive, function generators (e.g. Rigol DG822) that have BNC outputs labeled Sync/Ext Mode/Trig/FSK but after extensive consultation with the user guide, no outputs appear to be able to produce a GCV equivalent.
Is there some way to produce a Bode Plot of a basic RC filter using hobby-level oscilloscope and function generator? (Is "GCV" an antiquated term I am not finding an equivalent/replacement for?) I can't think of a way to properly reproduce the lab results without some sort of "sweep position" indicator that the classroom function generator, an older Leader LGF-1300S, has.