texts: What could cause a sub-pixel defect that is only visible under certain conditions?

texts:
An interesting but annoying pixel fault has appeared on the display of my laptop. At first glance it looked like a Stuck Pixel defect (one or two red, one blue and one green sub-pixel) but then I notices that it is only visible under certain conditions. Namely, when the column of the screen directly below it is very bright and the spot itself is surrounded by dark colors. That is the case for example when using a browser in incognito mode or using a dark theme in general. Interestingly enough it is completely invisible when the screen is completely white or completely black and moste other times, too. To illustrate that a little I'v attached a video in which I move a dark colored window below the faulty sub-pixels. You can see that its appearance only seems to be affected by the narrow column of the screen directly below it and that it only shows when that area is showing a very bright color. In fact, the more of that vertical area is bright, the more it is visible (as can be seen at the end of the video when I move the black window vertically). So I suppose it's probably not the classic stuck sub-pixel because that would not change depending on other parts of the screen, right? It's also there when booting into another OS. Does anyone have an idea what kind of issue could be causing this (graphics hardware, faulty cable, etc.) and whether it could be fixed?

Video of the phenomenon on vimeo.com


texts: "node" which can hold different values to be read by a sensor?

texts:
I have a question about sensors which are able to read values of specific "nodes".
The "nodes" in my context are like little metallic materials which can be placed somewhere i.e. within a flat wooden tile and have NO electrical connection.
A sensor should then be able to read values from them.

edited: more detailed example: (asked for by @andresgongora )

You have two items here. One is a small wooden board with 2x2 painted marks - just like a chess game with four fields. Then you have a stick to point onto those fields. When touching such a field you should be able to receive a message on your App on the smartphone.

The actual idea I'm not happy with:

  Sensors on each of the
  fields and actually an electrical component -> a microcontroller like
  an ESP8266 which reads the change of current on those sensors as they
  are being touched by some metallic device (the stick). Then the
  ESP8266 would deliver information to the App through WiFi.

The alternative way I'd like to do it:

  The former sensors on every field are now detached elements on the
  fields. They are not read by an microcontroller to receive any
  information about their changing state but are more likely able to
  hold a fixed state which might be predefined anyhow. The "stick" in
  this case is the "reader" in this case. It hovers/touches a field and
  can determine the difference by those fields. That way the stick has
  to be connected to the app to deliver this information. Most
  importently is that the fields hold predefined values in any case.
  This state should not be volatile and should last around 30 years.

Those nodes should be "progammed" to that value anyhow.

Sorry guys I know this is a weird question - but since so many fantastic things are possible thanks to microcontrollers and electrical components I kinda do not feel that stupid with this questions :D


texts:
I'm completely new to the world of PIC Microcontrollers and electrical engineering so please go easy :)

Anyway, I managed to program my PIC 16f627 to turn on three LEDs when push button (trigger button) is pressed and start a shut down sequence (basically each LED toggles off one after another with a 5 second delay in between) when another pushbutton is pressed (reset button). I've been testing this on a Velleman's K8048 PIC Programmer/ Experimentation board. PINs RA0 and RA2 are the inputs for the trigger and reset pushbuttons respectively while pins RB0, RB1, and RB2 are the output pins for the LEDs.

Working with the experimentation board is great but I want to move this to an actual circuit. The problem is I have no idea where to start. I've bought 3 LEDs (3.3 Volts each), some pushbuttons, and wire and I've constructed the following circuit:

(sorry for the horrendous schematic)

In the circuit I constructed, I first tested to see if the LEDs would work with 3 1.5 Volt AA batteries and they worked fine so I figured resisters wouldn't be necessary.

This does not work, however, and I'm totally lost. For reference, here is my code for the PIC. Its written in C using MikroC. It works on the experimentation board so I don't think its a problem

void main() {
    TRISB.RB0 = 0;
    TRISB.RB1 = 0;
    TRISB.RB2 = 0;
    PORTB.RB0 = 0;
    PORTB.RB1 = 0;
    PORTB.RB2 = 0;
    CMCON = 0x07;
    TRISA = 255;

    for(;;){
            if(PORTA.RA0 == 1 && PORTB.RB0 == 1 && PORTB.RB1 == 1 && PORTB.RB2 == 1){
                         delay_ms(5000);
                         PORTB.RB0 = 0;
                         delay_ms(5000);
                         PORTB.RB1 = 0;
                         delay_ms(5000);
                         PORTB.RB2 = 0;
            }
            if(PORTA.RA2 == 1){
                         PORTB.RB0 = 1;
                         PORTB.RB1 = 1;
                         PORTB.RB2 = 1;
            }
    }
}

Any help would be greatly appreciated. Thanks!


texts:
I power my board with 5V and I am working with ATMEGA8, so I don't need to reduce the voltage. Do I still need voltage regulator for stabilization?  And if I do, would this work?
I used here 5V regulator and I saw this scheme in datasheet. As I understood, first capacitor is for noise reduce and the other is regular bypass capacitor.
I am using USB cable. So do i need any stabilizator there? Is there a chance if i connect this to power source it will burn the source?
On ADC pins i have connected IR sensors.


texts: electrostatic and capacitors... more about the capacitor though

texts: done some reading, got me thinking. done some researching got me doubting... but my question is. is there a capacitor that doesn't degrade and doesn't lose capacitance over time? from all of my research it seems like this is the end conclusion but i think most of those answers were coming from the mindset of modern capacitors being used for modern technology... i'm wondering capacitors like a layden jar or some sort... do they degrade and lose capacitance over time due to 'age' principle? glass can store or hold stored energy as well last i remember and glass takes a long time to be biodegradable or no corrosion/oxidization... i'm very fascinated by electrostatic properties..


texts:
I have an FTDI chip (reference manual here) that translates USB from a PC to an SPI channel connected to an FPGA. I would like to test that the communication path between the PC and the FPGA is functional.

Probably the easiest approach would be to have a loopback test of some sort between the PC and the FPGA, where the PC drives the test, and the FPGA reflects all it receives.

The FTDI chip comes with a C API for SPI communication (example available here). On the FPGA side, I want to have to write minimal Verilog.

What would be the easiest loopback test I could have on the FPGA side that is compatible with this SPI API?


texts: How can I read the current from a monitor photodiode of a laser diode?

texts:
I bought a adl-65074tl-1 laser diode, I am trying to drive it and to read the feedback of the monitor photodiode with an oscilloscope. I am using a laboratory DC power supply and a multimeter for setting the voltage value of the diode to the 2.2 V (Iop).
After some trial and error, I built this schematic, I've add the resistor and the condenser for reducing volage spikes, but the source is quite stable.

simulate this circuit – Schematic created using CircuitLab
I don't understand how to read the current or the voltage from the monitor photodiode that from the datasheet should be on the pin 3.
Edit
The voltmeter symbol should be replace with an amperemeter. Eventually, I've discovered that my multimeter had a blown fuse. Replacing it I was able to read the current.


texts: How to send multiple command without using delay to serial port?

texts:
I am writing a serial communication program on LINUX to send command to PIC32 MCU.
When I am sending two command one after another as given in program MCU will perform action on first one only and if I give one second delay between command1 and commad2 it will perform action on both command.Is there any way I can achieve same one without using delay?

serial.c

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <errno.h>
int main(int argc,char* argv[])
{
    int fd;/*File Descriptor*/
    fd = open("/dev/ttyUSB0",O_RDWR | O_NOCTTY);
    struct termios SerialPortSettings;
    tcgetattr(fd, &SerialPortSettings);
    cfsetispeed(&SerialPortSettings,B115200);
    cfsetospeed(&SerialPortSettings,B115200);
    SerialPortSettings.c_cflag &= ~PARENB;
    SerialPortSettings.c_cflag &= ~CSTOPB;
    SerialPortSettings.c_cflag &= ~CSIZE;
    SerialPortSettings.c_cflag |=  CS8;
    SerialPortSettings.c_cflag &= ~CRTSCTS;
    SerialPortSettings.c_cflag |= CREAD | CLOCAL;
    SerialPortSettings.c_iflag &= ~(IXON | IXOFF | IXANY);
    SerialPortSettings.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG);
    SerialPortSettings.c_oflag &= ~OPOST;
    SerialPortSettings.c_cc[VMIN] = 10;
    SerialPortSettings.c_cc[VTIME] = 0;
    if((tcsetattr(fd,TCSANOW,&SerialPortSettings)) != 0)
        printf("\n  ERROR ! in Setting attributes");
    else
        printf("\n  BaudRate = 115200 \n  StopBits = 1 \n  Parity   = none");

    char command1[]="\xAA\x55\xCC\xD0\x00\x00\x01\x00";
    char command2[]="\xAA\x55\xCC\xD0\x00\x00\x02\x00";
    int  bytes_written  = 0;

    bytes_written = write(fd,command1,sizeof(command1));
    tcflush(fd, TCIFLUSH);
    //sleep(1);
    //if I not use one second delay MCU perform action on command1 only
    //if I use one second delay MCU perform action on both command1 and command2
    bytes_written = write(fd,command2,sizeof(command2));
    tcflush(fd, TCIFLUSH);
    close(fd);
    return 0;

                                                                                1,1           Top


texts: Is current direction always opposing when signals are reflected on a transmission line

texts:
Having read Dave Tweeds excellent description of reflections in electrical transmission lines, I thought I was one step closer to a full understanding of SWR.  However, later I was watching w2aew's description of how a directional coupler works and I'm a little confused.  In the snippet shown below, you can see where the reflected current is described as having the opposite direction to the incident current.

However, what I understood from reading Dave's answer is that in the case of short-circuit terminations it's a negative voltage that's reflected back along the line.  My understanding is that this negative voltage arises from the need to supply "additional" current into the short (2*I behind the reflected voltage wavefront).  But then, isn't the current moving towards the short or do I have that wrong?  I'm trying to reconcile my understanding of transmission line terminations (intuitively) with w2aew's description and failing owing to my own ignorance!


texts: Swapping out RJ-45 connector on Differential I2C circuit

texts:
I'm trying to use Sparkfun's Differential I2C Breakout circuit into my own design, and I'm looking to replace the RJ-45 connector. It's too big (having a footprint size of 15.24 mm x 15.24 mm), and I have some requirements that I need to meet. The original board uses an Ethernet cable to transmit the differential I2C signals across long distances. I'm trying to do the same with another connector.

Due to the environment that my project will be in, I have to use a shielded, twisted-pair cable, with the length of the slave sensor being 20 meters (max) away from the I2C master. With these constraints, I was thinking about using HDMI, due to it being readily available and meeting all of these requirements. However, based on some footprints I researched, the HDMI footprint is too big. Thus, I'm thinking about using a micro-HDMI to HDMI cable instead. HDMI has more than enough pins for my needs, but I was wondering if there were any other cable alternatives that will fit my needs and has a small PCB footprint?

EDIT: So, after some discussion and thinking, mini/micro HDMI might be okay in the long run for 3 meters, but in the long run, when I need 20 meters, HDMI is a no-go. It won't be enough to transmit power, so I'm going to need a higher gauge wire than AWG-30. I can't think of any pre-assembled cable assemblies that fit the length and other requirements for shielding, so is my only choice to make my own cables for this endeavor?

EDIT: To give more information about my board, it's more or less an I2C multiplexer board. I'm working off of a Raspberry Pi Zero and an Arduino Nano, and the size of the board is 2 inches by 3 inches. This configuration is meant to read from 8 I2C sensors, so I'm trying to fit eight differential I2C circuits onto one board. The Pi Zero and the Arduino have to be mounted on the board (though for the Pi, I'm not including the 40-pin header as it's not needed); therefore, most of the space is being taken up by the mounting holes of the Pi Zero and the Arduino's footprint, if that gives any indication of the amount of space I'm left with. So, with the 8 I2C sensors, imagine having 8 of the Differential I2C Breakout circuits on one board. I'm trying to find a connector that can deliver the two differential signal pairs as well as power/ground just like the RJ-45 used in Sparkfun's board. In terms of maximum size, given the size of the RJ-45, my max dimensions for the connector is approximately 10 mm by 10 mm. This is mainly just to ensure that there is enough space for adequate routing of the 8 differential circuits.


texts: Simple current measurement solution and testing its validity

texts:
I have tried to measure  current using SparkFun Hall-Effect Current Sensor Breakout - ACS712 and also tried using shunt resistor. It seems that each measured value is different from what I measured by multimeter. And I don't know which one is showing the correct value.

Is there any simple solution for measuring a current?
Also possibly more importantly, how can I test that the measured value is correct?

I want to start with a very simple circuit to test the current measurement and if it's verified that the measured value is correct, then I want to hook it up to the actual device, so that I don't damage the device accidentally.

Any suggestion is greatly appreciated.


texts: Autodesk EAGLE: PCB layout lost when copying from schematic

texts: On one panel, I'd like to have 4x4 'boards' that are all the same. When I copy the respective 'group' in EAGLE, I am losing the placement of the components with respect to each other in the PCB layout. How can I fix that?


texts: Help me to Identify whats wrong with this Circuit

texts:
I built this circuit which I found below Link

Source Link

I used the Parts as shown in circuit Diagram.

When I connect only a battery which is voltage lower than 12V without input power source no LED's Light up and if I connect a battery full charged without input power source Red LED Light up

When I connect input power source with a discharged battery both the LED's Light up. What could be the reason for that?

Regards


texts: Can anyone explain this pinout diagram? I only know that D+/- AMBA & DM are USB D+/- and H&L are for the CAN bus. What are do the blue and red contacts mean?


texts: Zigbee PCB layout - bad signal reception

texts:
I'm using Atmel's ATMEGA256RFR2 (link) for Zigbee (802.15.4).

However I could not reach more than a few meters of range between my nodes.

Here is the antenna design layout and schematics I'm using, could you find any defects in these design? Reaching 4-5 meters range with Zigbee sounds really weird to me as theses systems usually can do hundreds of meters for communication ranges.

Schematics:

Board's layout:

Antenna type: 2450AT18A100.

Update:

here is my new design, 50Ohm matching is not yet done, but I'm unsure about the VIAs around the antenna:

On the right there is no more space to have them. Is it a problem?
Are they close enough to each other? Distance between their centers are around 1.8mm.

Update2:

I have just make the board soldered however now the situation is a lot worse than before: the board is not able to connect to the Coordinator at all.

Even if I put it close the the Coordinator it does not connect.

So I believe something went wrong with this design again.

What shall be trivial to check to have at least a little chance to make these boards work?


texts: What is the purpose of the emitter resistor in a common emitter amplifier?

texts: I'm struggling to understand the purpose of the resistor circled in red, I know it has something to do with DC biasing and the feedback on the circuit (as the capacitor will cause AC bypass). But I'm struggling to understand the exact circumstance where this would be needed. Is it a change in supply voltage, or change in transistor beta? And the exact mechanism that would cause the resistor to solve the problem.


texts: How do I increase 3A fixed output current of a buck converter?

texts:
Basically I am making a solar inverter without any battery or charge controller that will directly convert the dc output coming from solar panels (6 connected in parallel) into 220V AC.I am using solar panels 50W each, having an open circuit voltage of 20V and the voltage varies between 15-20V during the entire day provided a minimum amount of sunlight is there.
Next, I am using a 12V buck converter circuit using an LM2576 and few more components to get a stable output voltage of 12V out of the panels.
Now this 12V DC is fed to an inverter circuit which converts it into a square/modified sine wave 220V AC at approximately 50Hz.
But, I am not getting  desirable power output. From 6 panels, all I am able to power is a 45W LED bulb along with a small 3W LED bulb.

Probably, one problem is with LM2576  buck converter IC. This IC  although providing a constant 12V output but it is rated at a 3A fixed output current. And I think probably this is the reason why we are unable to drive more loads. Is there a way to amplify current in this case? Or something else should be done which I am missing here ?


texts: Modifying a buck converter for lower current rating

texts:
I have been learning about buck converters and I think I understand the principle of their design. However, I am unsure of how a current rating would be calculated for a particular design.

The schematic below is rated at 3A (Vin=48v; Vout=5v). However, if I want to power a device that requires no more than 500mA, I presume (perhaps naively?) that a 1A rating would be sufficient, being conservative.

I understand that the main contributors to current rating in a buck are the diode,  inductor and output capacitor - by reducing the rating of these components I can make a much smaller PCB. So if I use, for instance, a 1A inductor and diode (the two largest components by far), will this affect the function of the circuit, and produce the same 5v output? And would a 1A component confer an overall 1A rating, or should some components be rated more conservatively to handle voltage spikes produced by ripple current?

Many thanks in advance for your wisdom!


texts: Detecting leakage from domestic microwave ovens

texts:
Is there any quick and easy way to determine if a microwave oven is leaking radiation from the door edges? By quick and easy I mean without buying a dedicated meter.

And if there is an undetected leak, how far do microwaves generated by a domestic microwave travel in air?


texts: Is D flip flop equivalent to frequency mixer (difference frequency) for square waves?

texts:
I was trying to make a frequency mixer (only difference frequency) for two square waves (PWM1, PWM2, both 0.5-4KHz range) using ONLY Arduino due.

I'm new to signal processing, and the only way I can think of making a differential frequency is purely mathematical,and only for sin waves:

$$sin(A-B)=sinAcosB-cosAsinB$$

The cos term is a problem because it involves 90 degree phase shift, so I cannot just use logical operators to express the function.

However during Googling I saw a statement that D flip flop can be used to produce only the difference term in frequency mixing.

That is, if I understand it correctly, attaching an interrupt to the rising edge of PWM1, in the ISP read the PWM2 value and write it to the output pin.

It make sense as the closer the frequencies of PWM1 and PWM2 is, the smaller the frequency of the output wave. However it seems too good to be true and I cannot figure out how this is mathematically equivalent to the difference part of the product of the two signals.

Will I get better accuracy if I use a real D flip flop ?

Clarification:

For 'frequency mixer' I mean the product of two signals.
$$2cosAcosB=cos(A+B)+cos(A-B)$$
For 'the difference part of frequency mixer' I mean only the term with differential frequency (A-B).


texts: I have a 9v battery that is only needed to output power during night time/when the sun is down, how can i do this?

texts: My main question is, am I able to use a solar panel to only allow power flow when it is dark outside?/When the Solar panel isn't receiving any light? What would the circuit for that look like? In the same way a garden light works?


texts: Achieving high-input impedance for a voltmeter front-end

texts:
So, I'm starting on the front-end for my digital project, figured out the ratios (100kΩ, 900kΩ, 9MΩ for ÷10 and ÷100), tolerances (0.05% - 0.1%) and temperature coefficients (< 50ppm/°C might work) I wanted and went to buy parts and was surprised to see that there are barely any 0.1% low tempco resistors in the megaohms range. Why is that? Even switching to 9.09M to stay within E96 and E192 still only gives a handful of results...

I did find the Caddock 1776-C67 and 1776-C671 which are better because of matching relative ratio tolerancs and temperature coefficiencients; however, I can't seem to find more options.

There's nothing wrong with the 1776 series; in fact, it's perfect, but it makes me think that I'm doing something wrong if this is the only option (or at least there are very few options.) Am I not supposed to be using a resistive voltage divider or at least not in these decades?


texts:
What does this symbol stand for?
Please tell me what this symbol means:


texts:
I have a USB-A 3.0 hub with ten ports. I've owned it for about 2 years now without any issues, until recently. About a couple of months ago I had a flash drive plugged into one of the ports on the hub and noticed it seemed to die much earlier than I had expected. Thankfully the data I lost I could get back, but it really concerned me when another flash drive in the same port died again a month after. These aren't cheap flash drives, either, they're really nice Kingston ones. They both visually appear to have the same controller, so my initial thought was that it's just a matter of cheap controllers. The flash drives were also plugged in and powered on 24/7, so I thought maybe that had something to do with it.
But then I decided on measuring the voltage output of the port to make sure it's not causing issues, and I discovered something interesting. The port where the 2 flash drives died is outputting about 5.48 volts. Curiously enough, the other two ports I checked output about 5.24 volts. I couldn't check all ten as the rest are occupied with other devices (all USB devices except my keyboard and mouse are storage devices, mostly HDDs but some flash drives).
My iMac outputs about 5.11 volts, a custom-built PC at about 5.08 volts and my Dell monitor at about 5.04 volts (it has USB ports, too).
My question is, how safe are all of these voltages, more particularly, the voltages from the hub? I use a lot of USB devices on my computers and using all ten ports on the hub would be very handy, but I don't want to risk damaging more drives if that's the case.
The most information I can find is "USB uses 5 volts," which doesn't help much here.

Update: I had a chance to disconnect all my drives from the hub. I reran the tests and found out that every port outputs a stable 5.42VDC (stable as in, the number didn't fluctuate for the 5 or so seconds it was connected). The wall adaptor should output 12VDC and outputs at the most 12.12VDC. No devices were connected at the same time during this measurement (update: with 7/10 I get the same results).
With that being said, is it still possible that this hub is usable? Could I potentially use a lower voltage adaptor to bring the voltage down to more acceptable levels? I ask because this hub I am using is really nice, and I'd hate to buy another one (I bought an Amazon basics one before and had problems with that). Of course, if it means risking my devices lifespans, I'll buy another hub.
I would like to note that the other devices on this hub, mostly WD My Passports (hub powered), one WD My Book (wall powered), a SATA Hitachi drive in a 3.5" Rosewill enclosure (wall powered), and a Crucial SSD in a Sabrent USB enclosure (hub powered) are all okay and have been plugged in longer than the flash drives that died were.


texts: Connect Nucleo ST-LINK to another Nulceo Board Target

texts:
I am having issues displaying serial data, when I connect a Nucleo ST-link to another Target.

My Pins Connections are as follows:
ST-Link  ->  Nucleo Board

VCC   -> From JP1 of ST-link to 3.3V of target
SWCLK -> To PA14 of Nucleo Board
GND   -> To GND
SWDIO -> To PA13 of Nucleo Board
NRST  -> To NRST of Nucleo Board
SWO   -> To D3/PB3 of Nucleo Board
TX    -> To TX/PA2/D1 of Nucleo Board
RX    -> To RX/PA3/D0 of Nucleo Board

I am able to upload software via drag and drop. It works fine.
However I am not receiving any data on my serial monitor(printf). I don't understand why. I also tried to swap the RX/TX, still did not work.
Can someone explain ?
#include "mbed.h"

DigitalOut myled(LED2);

Serial pc(USBTX, USBRX);

int main() {
    while(1) {

        pc.printf("LED ON \n");
        myled = 1;
        wait(.1);
        pc.printf("LED OFF \n");
        myled = 0;
        wait(1);
    }
}
```


texts: Arduino: What is the best way to receive and read Data with SoftwareSerial?

texts:
I have Arduino connected to a HC-06 bluetooth module.

I wan't to send data from some Android-Application I wrote to the Arduino and let Arduino do stuff depending on the received data. So far I'm Sending Integer values between 0 and 1024.

Unfortunately mySerial.read() won't come to an end here. It reads the Data as one big string.

My Modules RX and TX pin are connected to my Arduinos RX- and TX pin. (The console didn't show any data when I connected them to Port 10 and 11, so I thought this is how SoftwareSerial defines the RX and TX Port of Arduino...)

My Sketch:

#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11); // RX, TX
char character;
void setup()
{
  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);

}
void loop() // run over and over
{
    String Data = "";
    while(mySerial.available()) {
     character = mySerial.read();
     Data.concat(character);
    // Serial.println(Data);
     Serial.println("foo");
    }

This will output:

154888143201270341421501588671750825906975101110241005969922864792711629540451369290213140600

I can't read this data properly and I can't parse the data to some function to handle it, because mySerial.read() won't come to an end. There must be a better way to receive or send this Data.

My Bluetooth Output Stream Source:

public void sendPWM(int progress) {
            OutputStream tmpOut = null;
            try {
                tmpOut = mmSocket.getOutputStream();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                Log.e("error", "NO OUTPUT STREAM", e);
                e.printStackTrace();
                return;
            }

            try {
                // byte[] buffer = stringToBytesUTFCustom("1");

                byte[] buffer = String.valueOf(progress).getBytes();
                tmpOut.write(buffer);

                // tmpOut.flush(); /*I have turned this ON and OFF, to see if it
                // makes any difference*/

            } catch (IOException e) {
                // TODO Auto-generated catch block
                Log.e("error", "EXCEPTION DURING WRITE", e);
                e.printStackTrace();
            }

        }

I don't close the outputStream, because this will also cancel the connection with the HC-06 and I have to send a lot of data. I can't let the user reconnect to the module each time he sends data. Can you help me out here?


texts: Calculating characteristic impedance of a matching line

texts:
Attached is a question asking for the characteristic impedance of a matching line. A matching line of 0.25\$\lambda\$ has at its beginning an impedance equal to:
$$Z_{in}=\sqrt{Z_{c}Z_{L}}$$
if I am not mistaken.
Hence, in order to find the characteristic impedance one must first determine \$Z_{in}\$. I figured I could normalize \$R_{g}\$ wrt \$Z_{0}\$, which yields \$1\$, and then, using a SC, find \$Z_{in}\$ by moving towards the load a distance of 0.2\$\lambda\$. Is that correct? I'd appreciate your feedback.


texts:
When an AC signal is transmitted through a conductor, direction of flow of electrons is continuously alternated.

In wireless communication signal is transmitted through air, in this case which parameter of air is enabling current to propagate through it?

In conductor, electron from one atom moves to next, similar how electromagnetic wave move from one air atom to another?


texts:
I would like to use a watchdog timer as a way to do a proper power cycle in last resort, that is: power down for 1 second, then power up. I have come up with the following design:

The watchdog used here is a MAX6746, the load switch is a FDC6330. +5V_DCIN is plugged to a 5V DC, +5V goes to the rest of the circuit.
The capacitors set the timers at 1s active reset, 30s watchdog timeout.

The problem is it is stuck in a loop where every 1s the FDC6330 enables the power to +5V then instantly back to 0V. Any idea? I could not find such use cases on google, watchdogs are usually used to directly control a reset pin for a mcu.


texts: What is the purpose of resistance R1 and R2 in this circuit?

texts: I can't understand why the Resistance R1 and R2 are used in this circuit and why is the ground at position A fixed?


texts: I'm trying to improve my RF routing skills. I want to connect a 450 MHz trace (21mil width) to a RF6886TR13 power amplifier that has 6 RF_OUT pins. What is the best way to make this connection? I've added a screenshot showing what I mean.


texts:
Is it poosible to use user-defined typed in input/output of VHDL enitities?

ENTITY test IS
   PORT(
      input         : IN     std_logic_vector (0 TO 63);
      test_input:   out MY_TYPE;
   );

END test ;


texts: Difference between RF ferrite and normal ferrite

texts:
Why oscillation stops in a RF oscillator(over 100MHz) if I replace the air core Inductor with a normal ferrite core inductor ?

But starts oscillating again if I rewind the inductor over a RF ferrite core. (salvaged from TV balun)

So what's the basic difference between RF ferrite and normal ferrite ?


texts:
I'm using backup domain of stm32 for storing date and some important information. The board drives a thermal printer and some other parts that produce interference on power. It seems that sometimes it cause the corruption of RTC data.

Is it really possible that the voltage spikes affect on backup domain data?

If yes, is there any protection method for that?

Access to the backup domain in stm32 starts by the command "PWR_BackupAccessCmd(ENABLE)" to unlock that domain. Is it a good way to lock it again after each read or write access?


texts: Improve a car battery's performance with capacitors

texts:
These days, it got very cold in my area, and I started to think I need a new car battery. But then, as long as temperatures are above -10°C, my battery works fine. It just can't support the high current needed to start the engine when the temperatures are below -10°C. So my thought was:

Can I add capacitors to my car battery, that will help supply the needed current?

I found 6 Capacitors with \$2.7\text{ V}\$ and \$500\text{ F}\$ each on ebay for a total of 25$. If I put them in series, their capacitance should be \$\frac{1}{\frac{1}{500}\cdot6}\approx 83\text{ F}\$ at \$16.2 \text{ V}\$.

The energy in watt seconds would then be:

\$0.5\cdot83\cdot16.2^2\approx 10891 \text{ Ws}\$, which should be enough to start my small little engine (small gasoline engine rarely takes more than a second to start, even in cold temps, so that would be about 130 Amps for one sec).

Unfortunately, that's about as far as my knowledge of electronics goes. Can I really just attach the 6 Capacitors, which I connected in series, to the Battery? Is there something here I am not seeing, which would make it extremely impractical to do that? I can't seem to find anyone on the Internet doing this, which makes me sceptical. There are some people that use capacitors instead of batteries, but that seems like a bad idea to me since it won't last more than one start...


texts: Which device amplifies the optical signal in fiber optics?

texts:
My teacher ask me one question.
How the optical signal or information was transfered in fiber optics communication?

Then i explained it and use the word optical amplifier then teacher ask me what is optical amplifier i said which amplifies optical signal then again which device amplifies the optical signal in fibre optics communication?

I was dump at that moment i dont have the answer for it and i google it then i read about Doped fiber amplifier(DFA) but i didn't get it so can you give me any suggestion to understand it like any website or explain it.


texts:
Currently in my system we use 16 I/O expanders with I2C interface. I want to change it to CAN interface. Which is the best possible way without compromising the cost?
I tried searching for 16I/O expanders with CAN interface but the maximum I could get is 8I/O.
Are there any CAN to I2C converters, If yes I can use the same I/O expanders, just put a converter before.

Also looking for ADC with CAN interface!

Please help. Thanks in advance


texts: How input current affects circuit? Is it ignored?

texts:
All the examples I have seen so far, take the input voltage as-is and start calculating circuit current depending on on-board resistors using ohm's law etc.

Can you just ignore the original current rate? If it is doubled (say by using less resistant wiring) then it is double the electrons moving, it must have some effect, right?

Am i missing something?

Edit (1):

I am learning the basics, and everyone just seem to ignore the input current rating.


texts: Why does my single-supply non-inverting amplifier produce a wierd shape (depending on earphones)?

texts:
I built this circuit:

It is based on this design for a single-supply non inverting amplifier:

When I tested my output waveforms with earphone A I got normal results:

When I used earphone B, I got abnormal results:

Blue - Vout Red -Vin
I suspect this has something to do with earphone B pulling more current than earphone A, and the op-amp upper current restriction, though I am not too sure yet.
Why do you think the waveforms of voltage behaves this way?


texts: LTspice - "Fatal Error: In Missing node(s)"

texts:
I created the boost conveter in LTspice software, but when I try to run the simulation, there was an error message saying:
Fatal Error: In Missing node(s).
Can anyone help me out with the problem?


texts: Maximum Clock Input Frequency Datasheet Confusion

texts:
I was looking for an 8-bit parallel to serial shift register to use in a project I am making. Initially, I thought that the 4021 would work perfectly for what I need, however, after looking at the datasheet I am a little confused.

Below is a screen-grab of the TI Datasheet (http://www.ti.com/lit/ds/symlink/cd4021b-q1.pdf) (pg 6). I am confused as to why the maximum clock input frequency is listed as a minimum of 3 MHz.

I have never heard of an IC having a minimum input frequency so wondered if the problem is more just my understanding of what the information is telling us. At the top of the datasheet it also talks about the clock being run at a typical frequency of 12 MHz, which is a lot higher than I was planning to run it at.

As an alternative I found the 74HC165 (https://assets.nexperia.com/documents/data-sheet/74HC_HCT165.pdf) and any insight into if this is better or not would be appreciated as well.


texts: Calculate the maximum voltage across the resistor

texts:
I am using this LM63625 buck converter.

Input Voltage = 16V max
Output Voltage = 3.3V
Output Load Current = 0.45A
Switching Frequency = 2.1MHz.

I would like to calculate the maximum voltage across the R0202 20ohm resistor.

From the absolute maximum rating of the table, I find the maximum voltage across the CBOOT and the SW pin will be 5.5V.
If I use this voltage and substitute in the formula,  5.5V * 5.5V / 20ohm = 1.5W. I get 1.5W. But the resistor package is 0603 which has a maximum power dissipation of 0.1W.
How can I calculate the maximum voltage across the resistor?


texts: Is it possible to transfrom a transfer function into voltage?

texts:
So I have a control system which I'd like to control externally. I have the error signal from the system and I use an ADC to convert the signal to number. I have the transfer function of the system (calculated with CHR method). I want to use a PI (Proportional- Integral control). And I have a DAC to convert a signal back to an analog signal.
But now, I only have a transfer function: $$11.3 s^2 + 5.82 s$$
So how can I feed back this signal to the system?


texts:
Hi

I was working on this FT232RL USB to Serial Converter Circuit and now, in a doubt one thing. I understand that NC pins in the schematics have a cross Sign on them,but i didn't get this Pin12 CBUS4. As seen, the rest of the other pins have a cross sign but not this one. Is it another way of representing NC pin or is it connect


texts: Op-amps that get really close to the supply voltage

texts:
I've heard that I can get an Op-amp that will be able to get it's output to within a few millivolts of the supply voltage.

Do these exist? If so then where or how do I find them.

If you want specifics, it needs to be able to work at 3.6 volts, have two op-amps and be available in a SOIC 8.

Thanks.


texts: Difference between Push-Pull and Totem-Pole

texts:
I can't understand/see the difference between a push pull, for example a circuit like that:

And a Totem-Pole:

Have these circuit a transistor in the input so for get a thing like "double amplification"?


texts:
Let´s say I have a device with a bluetooth (BLE) 5.1 radio and I would like to know when, using a mobile phone, the power received from the device is good enough to stablish a reliable communication or I need to place it in another localization.

Is there a standard power value so I can decide wether to rate the connectivity as bad or good?
The radio of each mobile phone will be different so maybe there´s no standard, and this is what confuses me...how companies do this connection quality test?

Nonethless, maybe there´s a value at which any bluetooth radio of any phone would stablish a reliable communication.


texts: Effect of the neutral current to a system when a 3-phase facility is used as unbalanced

texts:
Normally 3 phase-systems are used for balanced loads like in 3-phase AC induction motors. I know that in a balanced star configuration the total current across the neutral is zero.

But what if each phases are loaded with different loads(unbalanced)? Obviously there will be non-zero neutral current. It seems that is the only difference between a balanced and an unbalanced 3-phase system.

Would such unbalanced use of 3-phase facility and thus a non-zero neutral current cause any kind of faults or harmonics in a system? Why?


texts:
The manual for the bno 055 (link below) has an attribute for the sensor labelled radius on page 33.

The radius takes up 2 bytes of memory,  the msb and lsb.

This already confuses me,  as the msb and lsb are bits,  but each register is for a whole byte.

Continuing,  the radius of the sensor has a property called the range of the radius.  The range is supposedly unitless, and is equal to +/- 1000 × LSB. I have searched both the document and the internet,  yielding nothing but data from proximity sensors.

What is a sensor's radius , and what do the msb and lsb represent on it?  Why do the SBs take up entire bytes?  What does the datasheet mean when it says +/- 1000 lsb for the value of the radius's range?

Sheet:
https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST_BNO055_DS000_14.pdf


texts: Standard SCPI commands - Hantek DSO4004C Series

texts:
I own an oscilloscope from Hantek (DSO4254C). Want to write my own library for accessing the DSO in C which uses the usbtmc driver in Linux. Are there some standard IEEE488 commands which the DSO supports? I can't find any information in the official SCPI manual from Hantek. Tried the standard *IDN? query first and it works as expected, but isn't documented in the manual.

Are there some other command/queries which are defined by the standard but not documented in the manual? I'm new with SCPI commands and the standard.


texts: How to determine the phase margin and transfer function of this bode plot?

texts:
I have some struggles to find the transfer function of this plot. We got the hint, that the "breaks" of slope can be assumed to be on vertical and horizontal lines. Also we should pay attention on the phase in the higher frequencies.

Am I right, that the phase reserve (margin) is approximately zero and that the amplitude margin is 100 dB?


texts: Proteus voltmeter value in simulation not right

texts:
I'm really new to Proteus, so if I'm doing something very wrong, sorry.

I'm messing around with the Proteus simulation but I don't understand why my voltmeter has given me a value when the circuit is open. I expected it to give a 0 V result. I tried adding a ground to the negative connection of the Voltage source but it didn't help.

Here is my circuit, with the simulation running:


texts: I have the current schematic with a full line of capacitor which I suppose are by pass capacitor. As you can see the schematic show a unique point of connection on the 56 pin however I suppose that each capacitor is supposed to be close to a particular pin. How do I know which pin each capacitor should go with  ?


texts:
I've heard that there is effectively a minimum wire size for vibrating environments. In other words, when designing wires that will experience vibration (in my case, an automobile), it's recommended to make all wires 24 AWG or larger, regardless of the amount of current they'll pass.

Is there any wisdom on this? How can I decide if my wires are big enough to avoid shaking themselves apart?


texts: How to delay astable 555 timer IC by ~1 min

texts:
My problem:
I've reproduced the 555 timer circuit from here: https://www.gadgetronicx.com/door-open-alarm-ic-555/.
Because of the specifics of my application I'd like the signal at the speaker to be delayed by 60 seconds. To clarify:

Reed switch gets disconnected
60 seconds delay
The alarm goes off (like it would normally)

Would be nice if someone could give me an easy and concrete tip. I'm a bloody beginner in electronics but I'd imagine there is some easy solution with a capacitor at the output pin of the 555.
Thank you in advance!


texts: Writing a single differential equation that describes the behaviour (electrical circuit)

texts:
Consider a circuit with \$L_{1}\$ and \$L_{2}\$ as inductors and \$C_{1}\$ and \$C_{2}\$ as the capacitors. \$I\$ and \$V\$ are the manifest variables

I want a single differential equation without the latent variables that links V(t) and I(t) (i.e. describes the behaviour)

Thus, taking the Laplace transform, we get

$$I=V\left(\frac{sC_{1}}{s^{2}L_{1}C_{1}+1}+\frac{sC_{2}}{s^{2}L_{2}C_{2}+1}\right)$$

Do I want to take the inverse Laplace transform here, or must I apply Laplace transforms on the equations derived by Kirchoff's laws:

I write \$I_{L_{1}}\$, \$I_{L_{2}}\$, \$I_{C_{1}}\$, \$I_{C_{2}}\$, \$V_{L_{1}}\$, \$V_{L_{2}}\$, \$V_{C_{1}}\$, \$V_{C_{2}}\$ as the latent variables.

Then I derive

\begin{equation}\begin{cases}I=I_{L_{1}}+I_{L_{2}}\\ I_{L_{1}}=I_{C_{1}}\\ I_{L_{2}}=I_{C_{2}}\\ I_{C_{1}}+I_{C_{2}}=I\end{cases}\end{equation}

\begin{equation}\begin{cases}V=V_{L_{1}}+V_{C_{1}}\\ V=V_{L_{2}}+V_{C_{2}}\\ V_{L_{1}}+V_{C_{1}}=V_{L_{2}}+V_{C_{2}}\end{cases}\end{equation}

\begin{equation}\begin{cases}L_{1}\frac{dI_{L_{1}}}{dt}=V_{L_{1}}\\ L_{2}\frac{dI_{L_{2}}}{dt}=V_{L_{2}}\\ C_{1}\frac{dV_{C_{1}}}{dt}=I_{C_{1}}\\ C_{2}\frac{dV_{C_{2}}}{dt}=I_{C_{2}}\end{cases}\end{equation}

After some elimination, I end up with

\begin{equation}\begin{cases}
I=I_{L_{1}}+I_{L_{2}} \\ I_{L_{1}}=C_{1}\frac{dV_{C_{1}}}{dt} \\ I_{L_{2}}=C_{2}\frac{dV_{C_{2}}}{dt}\end{cases}
\end{equation}

And \begin{equation}
\begin{cases}
V={L_{1}}\frac{dI_{L_{1}}}{dt}+V_{C_{1}} \\ V=L_{2}\frac{dI_{L_{2}}}{dt}+V_{C_{2}}
\end{cases}
\end{equation}


texts:
Below is a picture of my understanding of NAND flash memory operation.

NAND flash works by first erasing all the cells in a single block (essentially setting it to '1') and then selectively writing 0's. My question is- Since the word line is shared between all cells in a single Page, how does the NAND controller programmer a 0 into specific cells in a page?

For the NOR flash, it is easy to see that a specific cells can be programmed by using Hot electron injection (Applying a high voltage across a cell). But with NAND, its not possible to do so since NAND cells are in series with each other, and its not possible to apply high voltage to specific cells. So what's done in NAND is quantum tunneling, where the Word line is given a high voltage to write a 0. What's not clear to me is how can this voltage be made selective (in other words since the word lines are shared between cells in a page, the high voltage for programming a single bit to 0 shouldn't also 0 out the other bits in a page).


texts: What material can I lay over a capacitive touch screen to block its operation, while still allowing me to see it?

texts: I own a Kindle Voyage and would like to be able to hold it anywhere, not just along the edges, while reading.  So I'm looking for a material that's clear to read through, relatively lightweight, and that will block the touchscreen sensor from registering my touches.  What material can I cut to size for this purpose?


texts: Does anyone have any examples of the MD5 algorithm for a microcontroller (preferably an 8-bit one)?  Our project is going to use a Microchip PIC18 series device.


texts: How much high is the amplitude of stator-MMF of 3-phase 2-spp integral slot winding type machine as compared to 3-phase1-spp machine of same type?

texts:
Details:
No. of POLES=2; i.e 1-pole pair
SPP= slots per pole per phase
In my case,
amplitude of MMF of 3-phase 1-spp machine= 0.75;

Then what should be the amplitude of MMF for 2-spp machine ?
Is it 2x mmf of 1-spp machine?


texts: Connecting multiple voltage sensors with the STM32 Nucleo board

texts:
I want to connect multiple voltage sensors to the nucleo board. Lets say 4 voltage sensors of same kind with same address. So, I thought I could connect all the 4 sensors with the nucleo board with the help of I2C communication protocol.
Is this possible?
If possible I had a doubt that all the 4 voltage sensors will be having same addresses. But I want to call all the fours sensors at a time. How can I do this.
Please any help.


texts: Why the DC voltmeter does not read zero when it measures an AC signal?(Chua's circuit)

texts:
I have made a Chua's circuit that is nearly the same as the one in Kennedy 92(pdf). I don't have an oscilloscope yet, so I connect a DC voltmeter at the place where probes of oscilloscopes should be connected to. From my understanding, the current in the circuit should be alternating current, since the "double scroll" pattern is symmetrical about zero (it is a nonlinear oscillator).

The DC voltmeter only measures the average voltage over a short time period, something like 0.1 seconds. So it should show zero reading if it is connected to an alternating current.

However, when I actually do the experiment, no matter how I adjust the value of R(see diagram), the reading of the voltmeter across C1 never gets to zero. I know that for some values of R, the p.d. across C1 is not alternating. But for the double scroll to appear, average p.d. should be zero.

However, for values of R less than 1000 Ohms, the p.d. across C1 is quite small (about 0.2V)

Does that indicate that there are something wrong in the circuit, or is my understanding above wrong?

Or are the information above insufficient to draw any conclusion?


texts: Is it possible to regenerate lead-acid battery kept always charged?

texts:
I have a APC Back-UPS 280 I use for my server at home, and since power rarely fails, it is barely used. It only keeps the battery charged. The battery is 12 V, 7 Ah.

After about 18 months it started signaling battery to be replaced and I'm surprised, since it is a very short time. A APC Smart-UPS I also have has been going well for no less than 3 years, that is what I expected from the other one as well. Maybe the battery is of lower quality on the Back-UPS (neither of them is original).

Is it possible that the early failure depends on lack of "priming"? Maybe I could discharge the weak battery at 1 A (0.15 C) down to 11.8 V and recharge it to 14.0 V two or three times with an external charger.

Update

After reading the datasheet and the datasheet of a similar cell I found that the battery can stay continuously charged without the need of discharge cycles to maintain its capacity. The lack of discharge cycles was not the issue. The temperature inside the UPS could have caused a shorter life, but that much.

I opened the cap and I checked inside. I could see the gel but in one cell the gell appeared drier. I tried to add some liquid to that and to other cells and I connected a 2.5 A load to discharge the battery before recharging it. The initially drier cell was the only one gassing.

After flooding at this point all the cells (there was nothing to lose) I charged it with the UPS, to equalise the cells. When complete (5 hours, it was already mostly charged) I connected an even higher load (5 A) and now no gassing in any cell (as I said, they are all flooded now). It held 5 minutes without issues and with the expected voltage decrease as from the datasheet. The UPS now recognises the battery as good. I guess one cell was weaker and gassed during charge, resulting in drier gel and poorer performances.

I also made some ventilation holes in the case of the UPS.


texts: Why does frequency equal k/K where k=0,..., K-1 in Discrete Fourier Transform?

texts: I totally can't understand why f = k/K. What does k, K means, respectively?. I really want to know what they actually indicate in real world. Or, please give me an example. I spent 2 days night but could't catch the DFT.


texts:
This is a schematic diagram of the connector on a BA-5590 battery.

What is the "TCn" symbol?

Battery Datasheet


texts: How is water resistance of a device measured?

texts:
This question has relation to physics as well, but since it is electronic related, it is here.

I was watching a video that is testing the water resistance of Apple Watch. They say, at 3 feet the watch can stand for 30 minutes.

So, if I was to be developing an electronic device, how am I suppose to determine how water resistant my device is? Probably I wouldn't be putting multiple of my devices in water again and again for testing to see how long it can stand, right?

As far as I understand, 3 feet determines the water pressure.


texts:
I am building a small system to allow the FRDM K64-F to control some motors via a H-Bridge. My problem is I am sturggling to understand the documentation provided for the microcontroller.

Can anyone with some knowledge of the board provide information on what are the main GPIO pins of this board?

http://cache.freescale.com/files/32bit/doc/user_guide/FRDMK64FUG.pdf


texts:
I'm trying to design a State Machine that acts as a synchronous lock. There is only 1 input (X) and one output (Lock= 0, Unlock = 5v). The machine will only unlock if the following order is put in: 0* 1* 1* 0* 1* 1* 0. (An asterisk means I then push the clock button. So it should switch to unlocked after just changing the input from 1 to 0) Only this combination should unlock it. A reset button should also be included.

My professor gave us the State Table and Diagram for the project. I have tried to implement it using JK and D flip flops, to no avail.

A classmate said to try using a 4x16 Decoder, with active low output, to do the project. He said to NAND the 0 outputs, and use D Flip Flops.So I put a NAND to the zeroes of each Next State, and connect it to the D Flip Flops, right?

Also, how then do I get my output? Do I AND the 3 D Outputs (Qa Qb and Qc) as well as my X Input?

Additional information: We use TTL (0 and 5v only) and I have to design this out on a hardware trainer.


texts: Is it possible to draw more than 1 ampere from a USB port?

texts:
I am working on a project that needs about 2A current for the system to work. I don't need data communication just need power. How can I achieve this?
I saw several articles say that USB 2.0 supports 1.5A and USB 3.0 supports even more. But I am not sure this can be configured at the slave side. If possible how can I do this?
This question
discusses about sensing the pull up resistor. Can someone explain this?
I done research how to implement this. I couldn't find any material yet someone have actually done this.
I have read in this article, connecting 200ohm resistor between D+ and D- can draw 1.5 A. But my understanding this is something to do from the host side.

To activate the DCP, the D- and D+ pins are internally connected by a resistor of 200 ohms or less. This distinguishes the DCP from the original USB ports that carry data. Some Apple products limit the charge current by connecting different resistor values to the D+ and D- pins.


texts: Is there any cons with programming a atmega2560 every time the device starts?

texts: I will have a atmega2560 acting as a DMX encoder/decoder connected to a Onion omega2 (a small Linux computer). Is there any cons except longer startup time with programming the atmega every time the device starts up? This would make updating the firmware on the atmega really easy as I simply could replace the image and reboot


texts: where to find exact definition of i/p and o/p as used to define insulation resistance for AC DC converter?

texts:
Most AC DC converter datasheet use I/p and O/P to define insulation resistance

I am looking for the exact definition of these parameters as used in this context
( I know their definition for transformer winding but an AC DC converter is more complicated)

The reason I try to better understand these parameters is that  one of my current project requires that I float the DC output with respect to the general ground.


texts: What is the purpose of a T-gate or H-gate in a body-contacted SOI MOSFET?

texts: I've been banging my head against the wall with this question for hours. There are many examples of T-gate and H-gate structures that I've found, but I can't for the life of me figure out why the gate is shaped like it is. As best I can understand it, the gate is used as sort of a mask to prevent contact between the source, drain, and body. Is this correct, or is there some operational purpose that it serves?


texts: Vivaldi Antenna: size & max input power & software simulation

texts:
First, I've to say I'm a beginner in this field so please forgive me if my questions were not smart.

I was reading about Vivaldi antenna and I decided to do an experiment; I'm going to use a flat sheet of copper tape, a piece of FR4, and a coaxel cable.

I have the following two questions:

What is the impact of changing the size of the antenna?
What specifies the maximum input power namely in this experiment?
Is there a software that I can use to model & simulate the antenna accurately?


texts: Generating a desired pulse train in Xilinx ISE software

texts:
Need some help with VHDL and FPGA since I am new to it.

I have a Virtex-4 FPGA and I wish to generate a binary pulse train of 16 pulses from FPGA using VHDL programming. My desired pulse train will be like "1011100111000110" (min pulse width = 30 ns).

To be very precise wish to generate this pulse train and send it to a IO pin of FPGA so that I can observe it on scope. Also I don't want to send any input signals (such as input :std_logic_vector(15 downto 0)) except for clock and load. So I am wondering if I can write a VHDL code that is synthesizable and will give the desired output (with any approach such as FSM or counter or shift register).


texts:
I am designing a development board for STM32F103 microcontroller. I plan to implement an on-board USB for interfacing with the uC. I referred a few designs online and have always found some pull up logic on the D+ line.

Can someone please explain me the use of the pull-up logic and also tell me whether the 22R resistors are necessary or not.

This is the image I am using as a reference.


texts:
I have bought some resistors and I am trying to find their value. The thing is that in class they taught us that you use the gold strip to find which is the right side at first and then you check the other colours strips. The thing is that the resistors I got don't have a gold strip and they have more "other-colour" strips. I have searched in google extensively and also in this site (having found relevant questions) and I have found that resistors come in different styles but I have not found how to "translate" them in their value. Also most sites are calculators to put the colours and calculate the value but I don't know which is the side with which I must begin. These are some of my resistors:

There is this post but these resistors begin with same colour in both sides.

How do I find their value?


texts: Why the drop across NMOS enhancement mode load is V_t when driver is off?

texts:
In the enhancement load NMOS inverter, why is the voltage drop across the Transistor \$Q_1\$  when \$Q_2\$ is off, is \$V_t\$ ?

When \$V_{1}\$ is low, the transistor \$Q_1\$ is off. For the transistor \$Q_2\$, the voltages \$V_{ds}\$ = \$V_{gs}\$, therefore the \$V_{ds}\$ > \$V_{gs}\$ - \$V_t\$ and the transistor \$Q_2\$ is in saturation. Now, it can be said that as no current flows through \$Q_2\$ and \$Q_1\$ (except negligible leakage currents) then from the equation:

\$I_{ds}\$ = \$\frac{\beta_{gs}}2  (V_{gs}-V_{t})^2 \$

If \$I_{ds}=0\$ then \$V_{gs}=V_{t}\$.

Is this analysis correct? If it is, I want to know the physical process behind why this voltage drop exactly equals to \$V_t\$ occurs across \$Q_2\$ when no current flows through  \$Q_{2}\$? Shouldn't the drop be just 0 for ideal switch?


texts: Controlling DC brushed motor for dummies, please

texts:
First, let me explain that I know very little of electronics. Thus, please, forgive me if I am asking something very obvious or abstract. I have tried to Google this but I am obviously not using the right words as I find very little.

The problem: I have an auto-pilot that is supposed to control a hydraulic pump for a ram which will actuate a rudder. Well, I would like to use an electric 12 vDC brushed motor to control such rudder instead of the ram. The motor has a reduction and is connected directly to the output power for the hydraulic pump, which is 12 vDC, up to 25 amp and reverses the polarity when it needs to actuate in different directions. It works more or less and I would like to get rid of the 'less'.

Is it possible to have an interface between the output of the autopilot and the motor? ...so that:

It fades the voltage of the output. When the autopilot decides to apply power to the motor, it does it straight away. I would like to have some dumping on it so that the motor starts and stops smoothly. I have put some capacitors attached to the motor but am not sure is doing much; probably just absorbing peaks and filtering noise?
It brakes the motor when there is no voltage applied (by shorting it?) So, when the autopilot does think that the rudder is in the right position and does not provide power to the motor, the motor cannot spin freely.

In short, the power is 12VDC and reverses on demand of the autopilot. The motor is 12 VDC and there is no need to alter voltage or amp in the power.

I have seen many motor drivers but I believe there must be something simpler? This one can do what I want but I would then need to transform the -12/+12 output from the autopilot to 0/2.5/5 in order to use the analogue input of the driver. I am sure it must be simpler than this.

I obviously appreciate very much a full solution but I am very much willing to do my homework. Please, any advice or heading so that I can research further in the right direction?

Edit:
It seems I didn't explain well.
The autopilot is a controller and is fed by many sensors -heading, rate of turn, wind, rudder angle, GPS. It basically can follow a track or maintain a heading compensating for any forces. The problem is that it controls the rudder with a +/- 12 VDC, which is actually activating a DC motor is both directions. What I would like is to improve that signal and brake the motor when there is no current out of the autopilot, by shorting the motor I guess, and to apply those +/- 12VDC progressively, let's say with a period of 1/4 of a second, so that the motor starts and stops smoothly.

Added:

For a soft start. Could I use a simple circuit with a resistor, a capacitor and a MOSFET? Initially, the MOSFET is off and the current goes through the resistor, once the capacitor is charged, the MOSFET turns on and the resistor is bypassed.

And for braking it. Could I use a high power resistor in parallel with the motor controlled by a MOSFET?


texts: Is there a metal that will not interfere with smartphone reception as a case?

texts: I want to design an iPhone case that will include a metal plate on the back of it. Is there any kind of metal that will not interfere with the phone's reception?


texts: How do I change the LSB of the I2C address of the Sparkfun's MPU-6050 breakout board? From the schematics on the Sparkfun's web page ( https://www.sparkfun.com/products/11028 ) this pin (A0) is soldered to the ground, so the address is xxxx0, but there is a "solder jump" between the chip's A0 and this soldering. I would like to change the adress from xxxx0 to xxxx1 (connect A0 to VDD). I am supposed to connect this "solder jump" to VCC directly, or am I supposed to unsolder A0-GND first to prevent short-circuits to happen? I don't usually do electronics, so I don't want to blow up everything by trying to guess.


texts:
I'm looking for recommendations regarding development kits for Altera CPLD prototyping but I'm afraid I'm not sure what to look for. The budget isn't too much - around $200. While I'm leaning towards Altera, suggestions regarding Xilinx are also appreciated.

Though it does seem that Altera has better software than Xilinx. I'm thinking of programming the device in VHDL - would this be a good choice? Or is Verilog considered better?

I think having an LCD on the kit is a must but 7-segment displays would be very fun to play around with as well. Though I'm not sure how easy would it be to get a "stand-alone" CPLD working. Summary:

What should I look for when buying a development board? Should I stick with Altera's offerings or look beyond?
Is there a specific board that's considered the best in its class?
Assuming I get comfortable with CPLDs how difficult would it be to get a basic CPLD working on one's own PCB? What would I need to ensure that the device can be programmed while still in the system (In system programming?)


texts: What is the name of a device that would send input current out to my home and maybe upstream from a power device?

texts:
Please edit this since I'm too ignorant of electronics and electrical equipment to explain this well.

I'm looking for a device that I can create that would take AC or DC current from a power source and send it into my home and possibly upstream to the power company (if I have a net supply in my home). For instance, if I have a solar panel that produces DC current, what would be the device that I would make that I would want to plug the solar panel into that would then relay the power through my home and possibly to the power company if I have a net supply.

Is there a name for such a device, or names of components I would use for such a device? I would think it would have to be modular e.g. dc/ac conversion, voltage regulator, phase modulation, etc.


texts: I have a centre tap transformer 240V – 24V @ 250mA. I know I will get 12V between the centre tap and either of the other connections (I think one will be -12V), but will I have two 12V supplies at 250mA or 125mA?   And will the 24V supply be 250mA?


texts:
I think I understand how one can use an Arduino to program an external EEPROM memory chip. I am wondering if there are any memory chips that don't need any type of micro controller to operate. So, for example, some chip where the address/location in the memory is controlled only by setting high and low on certain pins. Are there, for example, any 256 bit chips that has 8 pins for the address and maybe 8 others for the data? I would mostly be interested in non-volatile memory.

I am not trying to do anything. I am just curious.


texts: 10 USB Hub ICs from 1 Crystal Oscillator?

texts:
I am designing a PCB with 10 individual USB hub ICs onboard. They all require a clock input and I am wondering if it is possible to drive all the clocks from a single crystal oscillator?

The hub IC is http://www.ti.com/lit/ds/symlink/tusb4020bi.pdf


texts: Symmetrical power supply: Rail fuses useful or dangerous?

texts:
I'm designing/testing power amp stuff with symmetrical power supplies (43V-0-43V). In the next future I'm planning to control all safety/healthy stuff (like over current / over voltage / temperature etc.) using a microcontroller/relais but...

... actually I'm using now nothing but only a pair of slow fuses on the supply rails. (beside one mains fuse) I saw, there are also some commercial designs using them.

Now I'm considering if this is a good idea at all to use those two independent fuses - even in the test phase. Because if only one fuse one single rail blows (instead of both), the supplied amp circuits /opamps will be powered unsymetrically, bias will be shifted dramatically, DC offset on the outputs will occur, semiconductors will get hot etc...

Do these independent rails fuses really make sense?
Are there any methods to make them blow both simultaneaously when failing?
Are there any simple and working over current protection methods for symmetrical PSUs?


texts: Why can't phasors be equated to a sinusoid?

texts: I'm having trouble understanding why a phasor for an AC sinusoid, let's say voltage (represented as Vrms/_50° for Vsin(ωt + 50°) to a current, for example) cannot be equated to the sinusoid in question. Sources such as my textbook say that it is wrong to do so, as the phasor is a complex constant, but should it still not represent the sinusoid?


texts: So I've been playing with an ATtiny45, and it occurs to me that I could probably brute force PWM by prescaling a timer to sysclock/64, then running ISR code that manually switches the outputs on or off depending on global variables set elsewhere in code or via IO. At max sysclock speed of 20MHz I oughta get decent resolution, and I'll get to use all my IO pins as PWMs instead of the two the chip provides, so the big question is...why not? Other than using up a lot of sysclock cycles, I don't really see disadvantages...could someone give me some?


texts: What's so complex in handling batteries that there's battery attendant specialty?

texts:
Dictionaries say there's "battery attendant" specialty. The name implies that's a specially trained person who somehow services batteries while they are in operation.

AFAIK the only kind of batteries that require maintenance is flooded lead-acid and the actual maintenance is adding distilled water. I don't see how this would require a designated specialty.

What's so complex in handling batteries that a designated "battery attendant" specialty exists and what does such specialist actually do?


texts:
I wrote a simple code to declare a queue and use it in verilog, but it always gives an error when I use ISE 14.6 synthesize tool.

module queues;
byte qu [$] ;

initial
begin
qu.push_front(2);
qu.push_front(12);
qu.push_front(22);
qu.push_back(11);
qu.push_back(99);
$display(" %d ",qu.size() );
$display(" %d ",qu.pop_front() );
$display(" %d ",qu.pop_back() );
qu.delete(3);
$display(" %d ",qu.size() );
end
endmodule

These are the errors:

Syntax error near "$"
byte is an unknown type
Module  ignored due to previous errors.

So what will be the problem? Is there any library that should be included ??!!


texts: What does input capacitance mean on an oscilloscope?

texts:
My oscilloscope is rated: 1Mohm || 12pF. It's a 100 MHz oscilloscope. However, I don't get the point of the capacitance. If I set my probe on 10X (it's switchable), then it inserts 9Mohm in series. Now we've created an RC filter with -3dB break point of: ~1.473 kHz, and yet, I get higher bandwidth with 10X probes and I certainly don't get a 1.4 kHz bandwidth limiter! What am I missing?

Also, I was simulating the circuit on a circuit simulator. With no probe resistance a 10pF cap conducts 1A at 100 MHz, which would be massive loading compared to the 1 Mohm impedence.


texts: Are rated cable ampacities per conductor or per circuit?

texts:
I'd like to construct a cable using connectors DigiKey 708-1190-ND to connect a 20A LED to its power supply. The connector is rated "32A". In this example the connector's third pin will not be connected to anything.

Is this connector:

(A) Safe, because the circuit current is 20A which is lower than 32A, or

(B) Unsafe, because a total of 40A is passing through the connector, which is higher than 32A.

Likewise, suppose I'd like to use a 4 pin connector to power two circuits each with 2.8A current. Do I need a cable/connector rated 2.8A, 2*2.8A, or or 4*2.8A?


texts:
I am a last class eee student and I started to study on digital filters. I want to design a 0-150 Hz band pass filter for getting started(I have not determined certain parameters, I want to do something that behaves like 0-150Hz analog bandpass filter. I say it because some experts come and asking always about details and advanced topics. I dont ask that. Just I said my intention, anyway...).(Also I know theory and fundamentals, I started the pyhsically implementation).

I have coded MCUs about 1 years. So I thought that, I could implement a digital filter using a dsPIC easyly. I asked some people to use dsPIC, almost everyone told about that as if it is a s*it. First question is about that, why signallers see the dsPIC as an enemy? Can't I do an digital filter with dsPIC, that behaves like 0-150 hz analog band pass filter?

Secondly, How can I get started with DSPs? For example, for MCU coding, I got a PICKIT2 programmer, downloaded an IDE, and wrote the C codes and the last, I flashed my hex to PIC using that programmer, so all things was that. But I don't know how to start with DSP coding and implementation. What is the requirements? I found some books which were written 15 maybe 20 years ago and DSPs which are in that books are not available yet. I googled also searched from Digi-Key to find a starter kit or any chip to start, and now I am very very confused. If you were me, how did you started with DSPs? (I am a student so low cost kits would be perfect for me)

Lastly, What is the exact discrimination between DSPs and ordinary MCUs? There are always turning the same things about these on the internet. Allmost all of web site writes like copied from wikipedia. The discrimination comes from architecture? For example, can't I use my raspberry PI 3, which has cortex CPU, as a DSP?

I hope some of members don't distribute the topic with details. I tried to ask clearly.

Thanks.


texts: Anyone got any idea what type of antenna these Wireless routers that have no "visible" dipole antenna on the outside use?

texts: Referring to these type of wireless routers' antennae like : Netgear N150 and Linksys E1500


texts:
I tried to follow this tutorial but the whole matrix is always lit and only one row and one column does not light.

I am pretty sure I did the wiring correct; I only have slightly edited the code since I dont have those potentionmeters to modify the x and y coordinate.

Here is the code I am using:

// 2-dimensional array of row pin numbers:
const int row[8] = {
  2,3,4,5,6,7,8,9 };

// 2-dimensional array of column pin numbers:
const int col[8] = {
  10,11,12,13,16,17,18,19  };

// 2-dimensional array of pixels:
int pixels[8][8];

// cursor position:
int x = 5;
int y = 5;

void setup() {
  Serial.begin(9600);
  // initialize the I/O pins as outputs:

  // iterate over the pins:
  for (int thisPin = 0; thisPin < 8; thisPin++) {
    // initialize the output pins:
    pinMode(col[thisPin], OUTPUT);
    pinMode(row[thisPin], OUTPUT);
    // take the col pins (i.e. the cathodes) high to ensure that
    // the LEDS are off:
    digitalWrite(col[thisPin], HIGH);
  }

  // initialize the pixel matrix:
  for (int x = 0; x < 8; x++) {
    for (int y = 0; y < 8; y++) {
      pixels[x][y] = HIGH;
    }
  }
}

void loop() {
  // read input:
  readSensors();

  // draw the screen:
  refreshScreen();

  delay(500);
}

void readSensors() {
  // turn off the last position:
  pixels[x][y] = HIGH;
  // read the sensors for X and Y values:

  x++;
  x%=8;

  if (x==0)
  {
    y ++;
    y%=8;
  }

  pixels[x][y] = LOW;
}

void refreshScreen() {
  // iterate over the rows (anodes):
  for (int thisRow = 0; thisRow < 8; thisRow++) {
    // take the row pin (anode) high:
    digitalWrite(row[thisRow], HIGH);
    // iterate over the cols (cathodes):
    for (int thisCol = 0; thisCol < 8; thisCol++) {
      // get the state of the current pixel;
      int thisPixel = pixels[thisRow][thisCol];
      // when the row is HIGH and the col is LOW,
      // the LED where they meet turns on:
      digitalWrite(col[thisCol], thisPixel);
      // turn the pixel off:
      if (thisPixel == LOW) {
        digitalWrite(col[thisCol], HIGH);
      }
    }
    // take the row pin low to turn off the whole row:
    digitalWrite(row[thisRow], LOW);
  }
}

Here is a photo:


texts:
Are the I2C and SPI protocols implemented in the integrated circuits?

For I2C,

There must be some circuit to be able to process the start bit, device address, internal register Address, Data and stop sent from the Master to the Slave

From my very limited understanding of electronics, the circuit would maybe be a shift register, slave address checker circuit built into the slave integrated circuit, MUX's for registers address

Does protocol mean that the implementation of rules for communication in the logic circuit is up to the user or manufacturer?


texts: Why are microwave oven transformer laminations not insulated?

texts:
I know that it is a peculiarly designed transformer, but I never found any explanation (and nor even questions) about that before.
I know that soldering the lamination in the edges for instance won't increase the losses in the core significantly, but what I didn't see anyone commenting is that it seems they aren't even insulated.
Or at least not in a couple MOTs I've dismantled. They're bare metal, they have no insulating layer between them.
Shouldn't that cause the core to be much more lossy?


texts: How to filter out everything except the laser light using linear array sensor

texts:
I use iC-LF1401 to capture line 128 x 1 in horizontal position. Parallel to this linear sensor, I've mounted linear laser (vertical light). How can I filter out linear sensor output, clear all except laser light?

Maybe some modulation? But how to do it?

For first tests i will use this linear laser(5V 650nm 5mW), hope it will be ebough for ~5-6 meters


texts: Is it possible to talk with Attiny85 via serial interface?

texts:
Alright, I know this question is pretty silly, but I have stumbled upon different posts saying opposing things. So to make a conclusion, does anyone knows for sure if it's possible to send data via serial communication to one of Attiny85 pins?

I would use CH340G to convert USB to serial from PC and then forward the info to Attiny85. Idea is to create a rather small device that could control 2-3 relays depending on the received commands. It would be nice that Attiny85 could reply to my requests and now just receive them (Rx/Tx) but Rx channel would work also.


texts: JFET-Transistor output characteristics in PSpice

texts:
I would like to ask if anyone can help me with the following problem. I would like to print the output characteristics of the JFET-transistor in PSpice. This is PMBFJ309, here is the datasheet. My test setup looks like this.
And here is the output.

The values of Vgs goes from top to bottom, starting from 0V to -4V, the increment is 0.25V. But when you compare this result to a datasheet, it's completely different.

So my question is, is there any way to get the same graph as from the datasheet.
There are .model characteristics.
.MODEL  PMBFJ309/PLP   NJF
+             VTO = -2.3973E+000
+            BETA = 3.81468E-003
+          LAMBDA = 3.80761E-002
+              RD = 2.33008E+000
+              RS = 2.33008E+000
+              IS = 3.02702E-016
+            CGS  = 6.50000E-012
+            CGD  = 5.70000E-012
+              PB = 6.83767E-001
+              FC = 5.00000E-001

Thank you in advance.


texts: An analog switch controlled by digital logic

texts: I am trying to control the movement of a remote controlled car by using a 8051 microcontroller. In the remote controller circuit there are four push buttons(forward, backward, left, right). I need to replace these 4 push buttons with 4 switches that can be controlled by digital logic signal coming from my MCU. However, the input voltages to these switches are sinusodial waves whose frequencies are 40 MHz and amplitudes vary in 0-3V range. What should I use? I have thought of something like a tri state buffer but they work with digital inputs as far as I know. I think a MOSFET could do the job but I don't exacty know how it works. Any ideas?


texts: Calculation of stray magnetic field from substation transformers

texts:
Say I want to assess the magnetic field attributed to some substation equipment and the cables in the substation area. Calculating the contribution from the cables and busbars are for my purposes done using the Biot-Savart formula. I do not have access to expensive modeling software (e.g. Narda EFC-400 or SUBCALC) - I have developed my own script for the Biot-Savart calculations in 3d/complex geometries.

However, I'm running out of ideas on how to calculate the stray field of the distribution transformers (in this scenario let's say it's a dry-type distribution transformer 1MVA). I suppose I could use mesurements from similar transformers, made right next to a similar transformer, as a starting point and then just assume that the field magnitude decays as 1/r^3 - but this will not capture any cancellation effects etc between the transformer stray field and the fields from conductors/busbars.

Is there any way to determine the stray field from a transformer without using measurements or FEM software? Old rule-of-thumb formulas would be sufficient.


texts: Brushless motor driver fails at PWM duty > 10%

texts:
I am trying to use an Allegro AMT49413 chip to driver a brushless motor.  The circuit kind of works with a PWM duty up to about 10% (if I give the motor a push first). But above 10%, the gates don't seem to be coming on properly.

I have carefully checked every aspect of the design and build, and everything seems to be correct, but I still can't make any progress.

According to the datasheet, p13, the PWM duty can be limited by selecting too high a value for the bootstrap capacitors. However, I believe I have my calculations correct for the SIR882 MOSFETS I am using:

Cboot = Qgate x 20 / Vboot
      = 18.3nF x 20 / 13v
      = 28nF

I have also tried moving down to 18nF, and it didn't seem to affect the maximum PWM duty.

Other settings:

Fosc       = 34kHz (from 1nF CT and 24k RT)
Dead time  = 1.4us (from 100k Rdead)
Blank time = 2us (from 1nF CT)
External PWM = 31.25kHz

Any ideas what might be causing the problem, or what I can investigate next?

Added: The High side MOSFETS are also getting quite warm.


texts: Build a high voltage probe to calibrate a 1.5 kV oscilloscope CRT supply voltage

texts:
I want to build a high voltage probe to calibrate my 1.5 kV oscilloscope CRT supply voltage.

Will just use this probe once to calibrate the scope so I don’t want to spend $200 on a probe and I mind the safety risks that it may involve.

Have seen several project examples. Some use several small resistors in series with capacitors in between. Others just resistors. Other just one HV resistor.

But before building anything I should consider what fits my multimeter DC Input Impedance which is 7.8 Mohm, right?

So what I need is basically a voltage divider capable of reducing the voltage 10 times. A 70 Mohm probe should achieve the 10x attenuation and bring 1.5 kV down to 150 V if I am not wrong.

I am planning to use one 50 Mohm and one 20 Mohm in series. Both high voltage resistors, rated at 1.5 kV and 1/2 W. Not planning to use any capacitors as well.

Frequency wise will I have any issues considering just this one time CRT calibration?

Is it worth a shot?


texts:
People keep telling me that Nonlinear loads causes current harmonics and when i ask them about what causes voltage harmonics, they tell me wherever there is current harmonics there is voltage harmonics.

So i did the experiment myself, powered a rectifier and DC motor using AC, and monitored using the Fluke PQ analyzer, the current THD was 32% but the voltage THD was almost 0% !

Could you please explain to me how harmonic voltages are created ?
and Does it happen in the case of inverters only ?


texts:
This small IC puzzles me, as I can't find any datasheet and even get an idea what it is. "C21SC" and "P134" are printed on top of it (it's SOIC8 package, if I am not mistaken):

Googling produced no results except for links for buying on alibaba.com.
Can anyone recognize what it really is?

UPDATE: Can it be this - 24C21 - 2-Wire Serial EEPROM?


texts:
From 100 watts OTL amplifier circuit using transistor MJ15003-MJ15004:

What is the purpose of C5 capacitor?

Why are there 3 diodes used? Not 4?


texts: How to measure microvolts of biopotential with Arduino?

texts: I'm new to electronics, so don't judge me harshly. I need to measure the biopotential of a human. I will place special electrodes on the skin, and need to measure the voltage on it. Ordinarily, the voltage is in range of 0.01 - 300 microvolts. I need to measure this voltage and collect it with the help of an Arduino (or maybe another similar microcontroller). How can I go about making this?


texts: In PCB DFM analysis; manufacturer highlighted TOEPRINT ISSUE. What is component TOEPRINT?

texts:
PCB manufacturer have highlighted component TOEPRINT issue.
Issue Statement: "Component is too close to another component TOEPRINT."

What is mean by TOEPRINT?


texts: Do laptop's power bricks provide constant voltage?

texts:
Some laptop power bricks say they provide 18V or 24V. I know that these values aren't applied as constant voltages to the laptop's battery because they must receive a much more complex power signal for optimal charging.

I don't know if the battery charging signal is calculated at the external power brick or by some component inside the laptop.

Should I expect a constant voltage from an external power brick?


texts: Is the Gate-Controlled Diode an instance of a trancitor?

texts:
I'm not sure it entirely counts. It certainly isn't useful in the way that the current-controlled voltage source is useful as the original transcitor paper describes, but more importantly, I am unsure how much its voltage output depends on current characteristics.
The gate-controlled diode is essentially an ordinary diode, but with a MOS gate fabricated on top of it. The electric field present on the MOS gate can increase the width of the depletion region, thereby controlling the breakdown voltage. I thought that this would make it a voltage-controlled voltage source (VCVS) in the same way that a MOSFET can be configured as a voltage-controlled current source (VCCS). But on the other hand, the configuration of the current-controlled voltage source transcitor in the original transcitor article appears to be able to develop voltage without needing a specific loading. (Then again, the hall-effect device described in the original paper appears to be a (passive, albeit nonreciprocal) hall-effect gyrator serving to convert current into voltage.)


texts: Topology choice for wide-output-voltage-range SMPS

texts:
I'm intending on building a off line (230VAC), 50W, isolated, constant-current switch mode power supply. This by itself is not a big challenge with the plethora of application notes and examples available.

However, a particular requirement that I have is i need to provide a voltage range on the output of 1V-100V.
For the 50W power level, I would expect a flyback converter to be the best topology, but my understanding of flybacks leads me to believe I cannot achieve that range on the output.

My question is; have I missed something with flyback topology design, and is there a different topology that is more suitable for the requirements?

EDIT:
The 50W quote for power is maximum power output. The minimum power output would be ~1W. So to keep the current constant, the supply could go between 1V and 100V.


texts: Current Consumption CD74HC4067 for battery powered application

texts:
I have some queries and would be very thankful if can clarify the below mentioned questions from the datasheet of CD74HC4067

Link: http://www.ti.com/lit/ds/symlink/cd74hc4067.pdf

Link to previous relevant question: Maximum current on CD74HC4067

Can you also provide an insight what the DC Vcc or Ground Current Icc = 50mA refers to. Is this current apart from the current per pin? I am using this in a battery powered application and current consumption is an important parameter in calculating the battery life.
Is the total current consumed equal to 25+50 = 75mA at a time?
Should I also include other currents like Input Diode Current, Drain Current and Output Diode Current?

Apologies for asking basic questions, I am new to battery powered electronic domain.


texts: Why is my DC motor losing torque when over voltaged

texts:
I have these small dc TAMIYA motors rated at 3v at around 2-3 amps. I also have a driver that I'm planning to use to drive the motor.

https://www.pololu.com/product/2992

I could not find any other driver that has a very low minimum voltage at a high current.

As you can see the driver has a minimum input of 6.5v, I am aware that over voltage  can reduce the lifespan of the motor, but I don't mind since there are a bunch of these motors here collecting dust.

At 6.5v motor does not spin (which is weird). Upon raising it to 7.5 it now spins, very very fast. So I lowered the PWM to 5% (I'm using an Arduino analogWrite with a value of 10) and slowly increased to more suitable RPM.

Now as am playing with the voltage I noticed that the motor loses torque as I increased its voltage.

Why is this happening ??

Also, while as I was playing with the PWM I also noticed that the torque also peaks at a certain PWM. Like at 10% the torque peaks, above and below values is just weaker.

Can anybody please help explain?

EDIT:

Another observation i have just noticed is that the driver gives out 7v, upon connecting to the motor the motor spins weakly. but upon upon connecting the motor to direct 7v it is much stronger in torque and speed


texts: Does metal toggle switch in simple AC lamp circuit need to be grounded

texts: I am getting into woodworking and would like to build a simple lamp like the one in this video on Youtube: https://youtu.be/BY5FzfxvZrg In the video, the lamp body/enclosure is built out of wood.  The switch used to turn the lamp on and off is a basic metal toggle switch mounted through the top of the wood enclosure.  I noticed in the comments that some have expressed concern that the switch is not grounded.  Is this lamp unsafe as-is, or should I ground the switch?  If it needs to be grounded, how would I do that?


texts: Can I use a rechargable battery with a PIR sensor designed to use two CR2032 batteries?

texts:
I use a PIR sensor that works with two CR2032 3v button batteries (in parallel).

The main problem I face is that the batteries are only lasting for less than one month.

Input voltage: 3V
Cut-off voltage: 1.33V
Quiescent current: 3.5mA
Current when triggering: 4.5mA for <200ms (need to quantify exactly for how long)
Peak current when triggering: 25mA for <200ms (need to quantify exactly how often and for how long since it occurs in some sparse occasions only, specially during the first 5 minutes)

I would like to replace those weak batteries with a nice rechargable one.

My idea would be to use a LiFePO4 3.2 V 400 mAh and simply connect its - and + in place of one of the two CR2032.

Since I am not an expert I would like to ask here before taking action.

Is mine a good and fairly safe choice?


texts: I'm looking at answers to calculating the frequency response, but i don't understand one line. what are they doing to go from the first line to the second line?


texts: How to distinguish the type of transistor amplifier

texts: I tutor students studying for an exam where they are likely to be asked to recognise a circuit, with a single transistor, as one of: a) a common base amplifier; b) a common emitter amplifier: c) a common collector amplifier. Is there a mnemonic or other easily remembered way to distinguish them?


texts: Why do we do open loop analysis for closed loop system? Why cant we directly analyse closed loop system?

texts: The intention to ask this question is that, just wanted to know the reason of breaking a loop for bode plot analysis


texts: Why does a relay open gradually when driven by 555 through an emitter follower?

texts:
A follow-up to my earlier post Why is the output from this astable 555 the reverse of it's simulation?

The 555 output drives a 2N2222. The 2222 emitter-follower with a 4.7 kΩ resistance to ground, in it's turn, attempts to drive a PCB mountable relay (I meant to drive a 3055 and then the relay but decided to try to drive the relay directly before including the 3055). To determine whether the relay is triggered an analogue multimeter (resistance) has it's leads applied to the contacts on the relay.

This is curiosity rather than a problem; when the 555 output goes high the relay makes a lot of noise, and the NC opens over around 10 seconds from 0 Ω resistance to around 1 kΩ slowing as it increases (some kind of logarithmic rise).

VCC = 12 V
Rb at 2N2222 = 330 Ω
Re at 2N2222 = 4.7 kΩ

EDIT: The relay JQC-3FC is connected at the take-off above R3 with the other end of the relay going to ground.

Applying 12 V to the relay directly switches the contacts instantaneously. Why the gradual opening through the timer circuit?


texts: Understand ground and ceramic non polarized capacitor

texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to learn some basics of electronics. I want to build a circuit for my raspberry with main components to use in programming.

An LED, a button and an analog thermistor reading and an analog photoresistor reading , all controlled separately. I learn on the Falstad website but I do not understand the flow of current between the two unpolarized capacitors and the ground on my schematic and I do not know if my schematic is good or not. I do not know if the current can charge (from the ground) non-polarized capacitors. I also have a negative voltage on OUT (GPIO18) when I simulate GPIO states and I do not understand why the voltage is negative when I unload and read the value for this pin and not for OUT (GPIO04) from my low electronic level. I'm learning analog reading with this site: building-raspberry-controllers-pi-part-5-read-analog-data-with-a-rpi. So, yes, to solve my problem, I can simply separate all the parts with its own ground but this will use an extra pin for 'ground' or '0V' and I want to understand my current schema.

I suppose with polarized electrolytic capacitors the current could not 'go up' but here the allaboutcircuit site advocates non-polarized ceramic capacitors.Can I use the same ground pin for my two analog reading pins? What's happening on the two capacitors and ground when, for example, one LED is in HIGH state ... Any help is welcome. Thank you


texts:
I would like to start to play with Arduino.

I've read that C and C++ are the official languages but I've also found other way to communicate using Python or Java for example.

Which programming languages are supported to program Arduino?
Are there any limitations using Python or Java?


texts: Thermocouple reading different from Commercial Datalogger when using Arduino

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A K-type thermocouple is connected to a thermocouple breakout board that outputs 1.2V to 8.8V that covers the entire -260C - 1380 °C of K-type thermocouple. This output is than divided by 2 using a potential divider made of two 10k ohm 1/4W 5% resistors, which is fed into an analog pin A0 of an Arduino Mega. The k-type thermocouple is not in contact with anything, essentially measuring the ambient temperature.

Problem: Using the Arduino sketch below, Arduino is measuring the temperature of about 10.6 deg C. However using a commercial temperature datalogger Omega HH309A, the measurement is 26.7 deg C.

Measuring the output of the thermocouple breakout board using a multimeter gives 2.19 V.

What could be the reason for this significant difference in measurement?

Sketch

void setup() {
  pinMode(tcPin, INPUT);
  Serial.begin(9600);
}

void loop() {

  // Take the average of multiple readings
  tempSum = 0;
  for(int i = 0; i < tempSamples; i++) {
    tc1 = analogRead(tcPin);
    voltage = tc1 / 1024.0 * 5000 * 2;  // in mV after correcting for V_divider
    tempSum += (voltage - 2.05) * 0.005;
    delay(100);
  }
  temp = tempSum / tempSamples;

  Serial.print("tc1: ");
  Serial.println(tc1);

  Serial.print("voltage: ");
  Serial.println(voltage);

  Serial.print("temp: ");
  Serial.println(temp);

  delay(1000);
}

Serial Monitor Output

tc1: 218
voltage: 2128.91
temp: 10.62
-
tc1: 217
voltage: 2119.14
temp: 10.60
-
tc1: 218
voltage: 2128.91
temp: 10.61
-
tc1: 218
voltage: 2128.91
temp: 10.63
-

Updated Arduino Sketch

void loop() {

  // Take the average of multiple readings
  tc1Sum = 0;
  for(int i = 0; i < tcSamples; i++) {
    tc1 = analogRead(tcPin);
    tc1Sum += tc1;
    delay(100);
  }
  tc1Average = tc1Sum / tcSamples;
  // Arduino ADC has 1024 steps
  // 10V max output from TC breakout board halved to 5000 mV before Arduino reads it
  voltage = tc1Average * 5.0 * 2.0 / 1024.0;  // in V after correcting for V_divider
  temp = (voltage - 2.05) * 0.005;

  Serial.print("tc1Average: ");
  Serial.println(tc1Average);

  Serial.print("voltage: ");
  Serial.println(voltage);

  Serial.print("temp: ");
  Serial.println(temp);
  Serial.println("-");

}

Output

-
tc1Average: 218.20
voltage: 2.13
temp: 0.00
-
tc1Average: 218.40
voltage: 2.13
temp: 0.00
-
tc1Average: 218.20
voltage: 2.13
temp: 0.00
-
tc1Average: 218.40
voltage: 2.13
temp: 0.00
-


texts: Interfacing 3.3V SD card MISO output to ATmega328P

texts:
I am attempting to write data to a SD card from a ATmega328P micro controller with no luck.  I've narrowed down the source of the problem to the MISO output of my SD card breakout board, which doesn't seem to be able to pull up all the way to 3.3V.  This is plain to see on an oscilloscope:

In the image above, the SD card is attempting to respond to the master with 0xFF.  However, it can only pull up to about 500mV.  Below is the clock signal, which I used as a sanity check to verify the oscilloscope was working.

My question is: What could be the source of this problem?  I feel as though the answer is staring me right in the face.  Perhaps I should take a break and come back with a fresh pair of eyes.

Hardware:

16 GB SD Card - TS16GSDHC10E
Sparkfun Breakout Board (www.sparkfun.com/products/11403)
ATmega328P on Arduino

More information:

SD card is powered from 3.3V supply pin on Arduino.
0-5V MOSI/SS/SCK signals are lowered to 0-3.3V by means of a resistive divider (560Ω over 1.1kΩ, I believe).
Some sources recommended a large pull-up resistor (~50kΩ) on MISO.  This didn't seem to do anything except add a 3.3V DC offset to MISO.  Strangely enough, removing the resistor did not remove the DC offset.