texts:
I have a small dedicated controller built around an Arduino that accepts commands from a PC over USB (serial). The communication is one-way -- the controller never sends data back to the PC.

Now I need to extend the controller to handle more duties, but there's no room physically or program-wise, so I'm adding a second box with another Arduino that will accept the extended commands.

I can't alter the controlling PC application or add another USB port to the PC. The application controls the hardware and is in turn driven by a script. It can only talk to one serial port (physical or virtual) at a time. We can alter the script but not the hardware/application. So my hope is that I can just bridge across the D+/- lines to feed the second controller.

If this were straight serial I'd have no problem, but with USB in the middle I see issues ahead, because the PC will want to enumerate both Arduino USBs, right?

Is there a solution here I'm overlooking? Can I use USB passively, as a listener only, with the second controller?


texts:
Could we connect two 5 Volt phone chargers of different ratings in parallel for quick charging with a diode as shown(rectangles being the chargers)

Please excuse me for the drawing I made..


texts: What are the consequences of a source terminator resistor that is too high of a resistance value?

texts:
What are the consequences of a source terminator resistor (placed in series with the output) that is too high of a resistance value?  Is it just a slower rise time at the input, or are there other consequences?  Do I make ringing/reflections WORSE at the input if the source terminator is too high?

I am wondering what can go wrong if I just put a source terminator resistor in series with an output that makes the series resistance greater than the characteristic impedance of a short transmission line? (When I say transmission line, I'm talking about wire of a few inches, paired with a ground wire of same length.)


texts:
I succeeded in making a small high voltage arc without using electronics components (diodes, transistors,.. ) using this diagram:
motor turn on & off a switch connected to power supply and homemade HV transformer:

simulate this circuit – Schematic created using CircuitLab

When I simulate this setup, it generate positive and negative arcs. This means that the output will not charge a HV capacitor.

Is there a way to get only one sign pulses (+arc or -arc) , (without using HV diode or flyback)?
Is there any way to make a working HV diode?

The goal is charging a HV capacitor at its maximum voltage (several hundred kV with any way).
I want to raise the voltage more so I want to attach the output of the first transformer to the primary of tesla coil.

simulate this circuit

Will the result of tesla coil charge the capacitor?
Do I need HV diode to charge HV capacitor?
Is there any way to rise voltage at maximum?


texts: Differences between 220pf 1000V capacitors

texts:
I need to replace a popped capacitor. Externally, it looks almost like

(source)

except for the first letter: in my case it is R and not B.

It is in the power supply board of a TV. I would like to replace it with an equivalent one, or even with a stronger one (with the same features, but better materials), to avoid this problem to reappear.

Is there a difference between B 221K 1KV in the photo and my R 221K 1KV?
May these alternative 1 and alternative 2 be equivalent to R 221K 1KV for my purposes? Why?

As far as I know, they differ at least in the ceramic insulator, being X5F in alternative 1, and Y5P in alternative 2.

According to the Capacitor Letter Codes Table in this page, the 221K mark could refer to a 220 pF capacitace.

Edit

I am sure it is a capacitor and not an MOV because the electrical symbol of a capacitor is printed on the PCB, referred to this component.

Before thinking about modifying the circuit with a line filter, I would like to find a suitable capacitor, which is electrically equivalent to the original one.

This product suggested in the comments has a different capacitance value. In the same site, I found instead:

C322C221JDG5TA;
C330C221GDG5TA.

Both of them are 220 pF. After a first look at the datasheet, they seem to differ only as regards the external dimensions.

My question is still: from the PCB electrical perspective, given the original one marked as R 221K 1KV, are they able to replace it? Why?


texts: Turn on microcontroller by sensor, auto power off - how?

texts:
To minimize battery power consumption I want the microcontroller only to be powered when a sensor's output is high. After the microcontroller finishes a task, it should cut its power off again.

I found schematics for latching power circuits activated by buttons, as for example this:
https://randomnerdtutorials.com/latching-power-switch-circuit-auto-power-off-circuit-esp32-esp8266-arduino/

Would it be enough to just replace the button in the schematic above with a NPN transistor of which the base is connected to the sensor output? (The sensor has to be powered, of course)

I know that this is an easy question, but I'm a beginner and didn't find any full circuits with the functionality I want so I want to be sure.

Alternatively:
For the button-activated auto-off circuits there is a ready-to-use product/module:
https://www.pololu.com/product/2808
Do you maybe know if something similar exists for my use-case?


texts: Solid State Output Tube Driver for a SE guitar amp

texts:
I'm learning as I go once again. Consider this output stage segment from a guitar amplifier I physically built:

The LND150 is an "depletion mode" MOSFET, whereas the IRF820 is a normal "enhacement mode" MOSFET. Their drains are connected to a 360vdc source (not shown).

The green section amplifies the line-level input from the FX_RCV to ~30vac. This is often called "Effects loop recovery" stage.

The red section forms a solid state "dc-coupled cathode follower" to be able to supply large amounts of current to the output stage. This helps reduce the tonality changes from using the RV7 master volume.

With guitar amplifiers, they sound incredible when the output stage is overdriven. There are several limits to how far you can push a stage though, one is blocking distortion. In this circuit, blocking distortion can be produced by the c15 capacitor discharging.

I'd like to eliminate the red section. Then, I'd like to have a transistor (or a pair of transistors) directly drive the grid on the output tube, without need coupling capacitors.

While I'm pretty new at analog design! I'm here asking this question because I don't know what I don't know! If I can get a bump in the right direction, that'd be very useful.

Thank you very much!

EDIT: The red section is actually in the amplifier to try and -prevent- blocking distortion, but eliminating the cap completely would be the most ideal solution!

EDIT: sstobbe pointed out I got my terminology messed up on enhancement/depletion mode


texts: EAGLE PCB Delete all nets in a selected area

texts:
I have a section in my schematic which is full of shenanigans. I want to delete all the nets in the selected box with a single command. Is it possible? I mean only delete nets and not anything else:

If I have to do it manually  I have to click 1 million times.


texts: Detection range of unintentional emissions by battery powered video recording devices?

texts:
I have read about unintentional radiators, but wonder about what their unwanted emissions detection range can be in low background noise, referring to battery powered motion-sensor activated video recorders with local storage.
Would there be, apart from EMF emission also the possibility of ultrasound noise coming from microprocessors or other circuit components?
Which unwanted signals would be more likely to stand out?
Thank you


texts:
ARM 11 is based on Powerful ARMv6 instruction set architecture.
But I am not able to figure out if it has;

1-MMU

2-Sufficient RAM for porting Linux

Can someone enlighten me?


texts: How to test internal resistance on small lithium polymer cell?

texts:
I'm coming from a computer science background, and will be writing some software to automate battery testing. I have background in math, but little to none in physics or electronics. Please consider this in your answers.

That said, how would I go about testing the internal resistance of a small lithium polymer cell by hand?


texts:
I am trying to understand relay circuits better. I have two circuits in question below.

Left Image I understand Pins 2 and 9 are the coil contacts. I would wire a microcontroller outpin pin to a transistor and Power Supply (Pin 2) to control the coil activation (Ground Pin 9). I don't understand what would connect to Pin 5 and 6 since I am used to seeing just one Pin at the source of relay circuits like Pin 1 in the Right Image.

Right Image Pins 2 and 5 are the coil contacts. I would wire my microcontroller and Transistor as a switch circuit similarly to above explanation. Power supply + end to Pin 1 and Load to Pin 3 and - end of Load to - end of Power supply, is that correct?

I believe Right Image is more simple to understand but not sure at all about Left Image. If both my explanations are wrong please correct me. Also, if possible can you explain how once the coil is activated how the lever/switch moves? Based on the orientation in the circuit images I don't see how the lever moves to either pin. Unless the image is not the correct orientation of the mechanical components inside the relay. Finally, is it clear if these circuits are latching or non-latching or should the datasheet tell me that?


texts: Is it possible to connect Li-Ion Batteries in series?

texts:
I've two identical 5V akku packs and need a 10V Power supply.
So is it possible to connect these two akku packs in series to reach this or are there any critical issues, that can occur?

Thank you!


texts: Algorithm for "short-circuit" current draw

texts:
Alrighty let's pretend that the circuit contains no resistance other than the battery internal resistance and the wire's resistance itself,

Would this be a correct algorithm? (Using OHM'S law)

BR - Battery internal resistance
WR - Wire Resistance

V / (BR + WR) = A

I am just trying to understand the basics before diving into more of the mechanics of our crazy world.


texts:
To amplify small signal we need to bias M1 and M2 in saturation mode.
Obviously, M2 is always in saturation because Vgd = 0.
However, how should I bias M1 in saturation?


texts: Do 2 conductors (1 grounded via resistor) reach equipotential, before surplus electrons drain to earth?

texts:
Case I: a negative conductor makes contact with a neutral conductor. Negative donates some electrons to neutral, until there is 0 potential difference. Then they both are slightly negative.
This happens quickly. (Assuming they are good conductors.)

Case II: the neutral conductor is grounded (via a resistor) to earth.
When they make contact, all surplus electrons drain to earth.

How does the resistor affect the movement of electrons?
Will both conductors reach equipotential first, before surplus electrons
drain to earth? (Because they make contact with each other without a resistor in between. The resistor is between them and earth.)


texts: Short Circuit Output Current - IC Definitions

texts:
What does "Short Circuit Output Current" mean? Does it mean that the voltage output will be to 0V at this specified current? So what would be the maximum current sourced without having a large impact on the voltage output? There is no graphic, it would be nice to have the voltage output in function of the load!

Here is the datasheet: https://datasheet.octopart.com/FAN4174IS5X-Fairchild-Semiconductor-datasheet-8824583.pdf

Thank you very much and have a nice day!


texts: Insertion of transmission lines and effects on reflection coefficient

texts:
I have a doubt on a step usually performed in matching network design. Consider a load ZL: a method for getting impedance matching (for instance with an amplifier) is that of inserting a transmission line in order to modify its impedance, like in the following picture:

This operation can be seen also in terms of reflection coefficient. Precisely, I found this relation:

where ΓL is the reflection coefficient of the Load. My question is a bout a generic case in which ZL may be also another transmission line, a port etc

where does this relationship come from? Are there any assumption (for instance that the transmission line must have the same characteristic impedance of ZL - in case is a transmission line - , or it must be a no loss line etc) for it?


texts:
How do you work out the maximum current a buck converter can handle at different voltage outputs? The one I am looking at specifies :

300W 12A Adjustable CC CV Step Down Buck Converter 7-32V To 0.8-28V Power Supply
Non-isolated step-down module, constant current and constant voltage module (CC CV), charging module
Input voltage: 7-32V
Output voltage: 0.8-28V (continuously adjustable)
Output Current: 12A

For example, if I have a motor connected to the output and have the following configurations, what is the maximum current the converter can supply?

24v in, 12v out
24v in, 9v out
24v in, 6v out

I thought it would be the power over the output voltage, so in the first example, 300/12, but that is 25A, which seems far too high

I'm not sure how the specified 12A relates?


texts: Transfer function of a second order capacitive accelerometer

texts:
In order to find the transfer function of the accelerometer MMA7361L based on the information given in the data sheet 1  I first made a hypothesis that it a second order sensor since it has a resonance frequency

the frequency response would look like this

but when I came to express the proper frequency and the damping factor I expressed in terms of \$F_c\$ the cut off frequency and the resonance frequency \$F_r\$ but when I came to see in the data sheet the cut of frequency is 400Hz  and the resonant frequency is 6KHz which is making me confused because the cut off frequency should be after the resonance frequency, did I start from a wrong idea ? is there an other information that could help me get to the the proper frequency and the damping factor of my accelerometer.


texts: PIC 16F887 unable to store UART data in buffer

texts:
ESP8266 and pic 16f887 both are serial connected with baud rate 9600.problem is when ESP send data to 16f887 then the microcontrolle unable to store receive data in its buffer.

#include <xc.h>
#include <stdint.h>

__CONFIG(FOSC_HS & WDTE_OFF & PWRTE_OFF & MCLRE_ON & CP_ON & CPD_ON & BOREN_ON & IESO_OFF & FCMEN_ON & LVP_OFF);
__CONFIG(BOR4V_BOR40V & WRT_HALF);

#define _XTAL_FREQ 20000000L

unsigned char MsgFromPIC[] = "\r\nYou typed :";
unsigned char MessageBuffer[64];

int i=0;
void Delay1Second(void);
unsigned char ReadUSART(void);
void putsUSART(unsigned char c);
void ESPWrite(char* st);

void interrupt INTISR(void)
{
    //check if the interrupt is caused by RX pin
    if(PIR1bits.RCIF == 1)
    {
        if(i<64) //our buffer size
        {
            MessageBuffer[i] = ReadUSART(); //read the byte from rx register
            if(MessageBuffer[i] == '\r') //check for return key
            {
                ESPWrite(MessageBuffer);
                for(;i>0;i--)
                    MessageBuffer[i] = 0x00; //clear the array
                i=0; //for sanity
                return;
            }
            i++;
            PIR1bits.RCIF = 0; // clear rx flag
        }
        else
        {
             ESPWrite(MessageBuffer);
             for(;i>0;i--)
                    MessageBuffer[i] = 0x00; //clear the array
             i=0; //for sanity
             return;
        }
    }

}

void main(void) {

    RCIF = 0; //reset RX pin flag

    RCIE = 1; //Enable RX interrupt

    //****Setting I/O pins for UART****//
    TRISC6 = 0; // TX Pin set as output
    TRISC7 = 1; // RX Pin set as input
    //________I/O pins set __________//

    /**Initialize SPBRG register for required
    baud rate and set BRGH for fast baud_rate**/
    SPBRG = 129;//129@9600;
    BRGH  = 1;
    //_________End of baud_rate setting_________//

    //****Enable Asynchronous serial port*******//
    SYNC  = 0;    // Asynchronous
    SPEN  = 1;    // Enable serial port pins
    //_____Asynchronous serial port enabled_______//
    //**Lets prepare for transmission & reception**//
    TXEN  = 1;    // enable transmission
    CREN  = 1;    // enable reception
    //__UART module up and ready for transmission and reception__//

    //**Select 8-bit mode**//
    TX9   = 0;    // 8-bit reception selected
    RX9   = 0;    // 8-bit reception mode selected
    //__8-bit mode selected__//

    INTCONbits.PEIE = 1;    // peripheral intrrupt enable
    INTCONbits.GIE = 1;     // GLOBL interrupt enable

   // putsUSART('k');

    while(1) //infinite loop
    {

    }

    return;
}

unsigned char ReadUSART(){
    while(!RCIF );

    if(OERR){
        CREN = 0;
        CREN = 1;
    }

    return RCREG;
}
void putsUSART(unsigned char c){
    while(!TXIF);
    TXREG= c;
    //while(!U1STAbits.TRMT);
}
void ESPWrite(char* st){
    char k=0;
    for(; k<i; k++){
        putsUSART(st[k]);
    }
}


texts: Can't modify global variables in interrupt, despite having declared them volatile

texts:
I can't seem to get my global variables (low, high) to change inside my interrupt, despite having declared them volatile. Below is my code.

I find it strange that I can modify my global variable 'change' but modifications to 'low' and 'high' don't seem to work. I know for sure that my interrupt is being completed, since the text is reprinting to the LCD display, just that the numbers aren't being modified.

I marked out the most relevant locations with "HERE" where I think that the problem is most likely at. I also tested whether it's just because the variable turn is always 0 by adding code at the end of the ISR to see whether the global variables change or not. They don't.

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include "lcd.h"
int state;
volatile int low; //HERE
volatile int high;
char scount[5];
char snum[5];
char mode;
volatile char change=0;//HERE
int main()
{
    char b_high;
    char b_low;
    DDRD=0xf0;
    DDRB=0b00000011;
    PORTD |= 0b00001000;
    PORTC |= (1 << PC1);
    PORTC |= (1 << PC2);
    PORTB |= 0b00100000;
    PCICR=0b00000010;
    PCMSK1=0b00000110;
    sei();
    init_lcd();
    writecommand(0x01);
    moveto(0x80);
    stringout("Low:    ");
    stringout("High:    ");
    moveto(0xc0);
    stringout("Change:high");
    int low=70;
    int high=85;
    moveto(0x84);
    itoa(low, scount, 10);
    stringout(scount);
    moveto(0x8d);
    itoa(high, scount, 10);
    stringout(scount);
    while(1){
        b_high = PIND & 0b00001000;
        b_low = PINB & 0b00100000;
        if(!b_high)
        {
            moveto(0xc7);
            stringout("high");
            mode=0;
        }
        if(!b_low)
        {
            moveto(0xc7);
            stringout("low ");
            mode=1;
        }
        if(change)//HERE
        {
            if(mode)
            {
                //low+=turn;
                itoa(low, snum, 10);//HERE
                moveto(0x84);
                stringout("   ");
                moveto(0x84);
                stringout(snum);
            }
            else
            {
                //high+=turn;
                itoa(high, snum, 10);//HERE
                moveto(0x8d);
                stringout("   ");
                moveto(0x8d);
                stringout(snum);
            }
            change=0;
        }
    }
    return 1;
}
ISR(PCINT1_vect)
{
    int turn=0;
    int pstate=state;
    int bitA = PINC & 0b00000010;
    int bitB = PINC & 0b00000100;
    bitA=bitA>>1;
    bitB=bitB>>1;
    state=bitA+bitB;
    if((pstate==0&&state==1)||(pstate==1&&state==3)||(pstate==3&&state==2)||(pstate==2&&state==0))
    {
        turn=1;
    }
    if((state==0&&pstate==1)||(state==1&&pstate==3)||(state==3&&pstate==2)||(state==2&&pstate==0))
    {
        turn =-1;
    }
    if(mode)
    {
        low+=turn;//HERE
    }
    else
    {
        high+=turn;//HERE
    }
    high++;//test code, high is still not modified in the main()
    change=1;//HERE
}


texts:
Considering the following circuit, how do I reliably protect the transistor Q1 from exceeding the collector current rating:

simulate this circuit – Schematic created using CircuitLab

This is supposed to be a driving circuit for a PMOS with a delay to keep the PMOS off for a minimum amount of time after the OC input has been deasserted. The exactness of the time delay is not too critical but should be around 20ms minimum.


texts: What will be the current of a 24V ATX power supply?

texts: I have an ATX power supply with a +12V 8A line and a -12V 0.8A line. I assume if I used the -12V as ground to provide 24V, then the maximum current provided by the 24V line would be 0.8A?


texts: Confusion with Wheatstone bridge resistor terminology in datasheets

texts:
An off-shelf instrumentation amplifier manual has the following indication for Rb:

And this force-transducer gives the following resistance parameter:

I guess Rb is each single resistor value of the Wheatstone bridge.

But what could be meant by input resistance and output resistance regarding the force-transducer?


texts: why capacitor accumulate less charge in higher frequency

texts:
it always said that the higher the frequency, the less charge will accumulate
because when in higher frequency, there is less time for capacitor to accumulate electrons.
and in lower frequency, there will be more time for capacitor to accumulate electrons.

but in higher frequency, although the time for accumulating is less but the current is larger
so how to conclude that in higher frequency, the total charge accumulated in capacitor is small ?


texts: Component designators on multi-pcb projects

texts:
I am currently working on a project that goes over multiple PCBs for the first time and realised that i don't know what the "standard" or best practice for component designators over two (or more) boards. Do designators start over on each board, do they have like an earlier designator (i.e. board one R001- R099, board two R101-R199, etc)?

The boards are going to be panelized and sent off to a pick and place in china, so how would it work if you had two boards with designators that start again?


texts: Not getting any reading from FTDI UMFT201XB USB-to-I2C module

texts:
I got the FTDI UMFT201XB USB-to-I2C module in order to interface with an I2C peripheral through a USB port on my Windows 7 computer.

The VCP drivers seem to install correctly, and a COM port is assigned to the module, and can be opened by a terminal emulator. However, I cannot seem to get any signal in or out of the module. That is, I see no activity when I send data through the port, or receive any data when I connect an I2C device to it (this was debugged using a scope). I have also verified that the RESET isn't on.

I found very little helpful information out there on how to get this module to work, so if anyone has experience with it, or with similar FTDI modules, my question is: what are the steps that I need to take in order to get the module to communicate?


texts: Is it worth using tip activator to replace the protective coating on the iron tip (or should I replace the tip)?

texts:
I have a 48W ZD99 Solder Station. The protective coating on the iron's tip is starting to peel/break off. I believe this is due to a combination of moisture in the air where I live and incorrect care for the iron on my part. (I started using it before I knew that applying flux and tinning it would keep it in working order.) The current state of the iron's tip can be seen in the image below:

The slightly lighter area is where there is still coating. If you look carefully, you can see the ragged line between the coated and uncoated areas.

I have read soldering tip issues and the answers thereto, which suggest that it's possible to get something called "tip activator" for recoating tips and that it works reliably well. Assuming that I can't buy any from the stores I usually go to, what's my next best option.


texts: How do you cast an integer as a time in VHDL?

texts:
For the purposes of simplifying a test bench, I would like to set various delays by changing numerical values at the top of the file. I'd like to do something like:

input_frequency : integer := 1000000;
...
constant t_per : time := (1. / input_frequency * 1000000000.) ns;

... which does not compile.

Right now I'm hardcoding:

constant t_per : time := 1000 ns;

I have not been able to get the upper example to work using the variable keyword either.

Is there a way around hardcoding times in VHDL?


texts: LTspice: How to convert .asc file to netlist?

texts: Using LTspice I can create .asc files which contain the information about my circuit. Is there a way to convert this information to a netlist? I am looking for a way to create a component and then add it to the library. I can use a text-editor to write it directly and then save it as a .lib file. However for more complicated circuits I would like to use the LTspice GUI and to create such components. Converting .asc to netlists would be a way I can think of. Any relevant ideas are appreciated.


texts: If Li-Ion battery is deeply discharged, is it harmful for it to remain in this state unused?

texts:
It is well known that Li-Ion batteries should not be deep discharged.

But sometimes they do discharge deeply. Is it OK for the device to remain in such state for a long time (and recharge again only when the device is needed again after a year) or it should be charged back as soon as possible?

In other words, the battery was discharged deeply.  Now I need to know the best way to prevent further damage to the battery.  Should I recharge it immediately or leave it in a deeply-discharged state until I need it again?

Does deeply discharged battery have higher or lower self-discharge compared to normally charged battery?


texts: How to convert a 3.3V signal to 5V for a Mosfet gate

texts:
Based on the question 4-5-v-on-gate-of-mosfet-while-switch-open I ask this more generic question.

Main project: I want to create a 16x8 (or so) multiplexed LED circuit
Sub project: Creating a 2x2 LED matrix, typically this form:

GPIO->resistor->Mosfet->LED->Mosfet->GND

The mosfets are used to use for the LED external (5V) power.
The resistor is for current limiting the LED.

I made this on a breadboard, using all 5 V (also from GPIO) and it works. The mosfets are 2N7000's).

However, when I tried to use for GPIO 3.3V, and using logic level shifters to convert from 3.3V to 5V I ran into problems (Gate always on, independent on GPIO).

So my main problem is to achieve this:

GPIO (3.3V) -> resistor -> Mosfet Gate (5V)

How should I convert this?
The only solution I can think of is a level shifter. Or a voltage/resistor dividor, but that only works to lower the voltage, not to increase it.


texts:
I'm a first time user of both LED lights and this website so i hope i can get some help.

i've bought some RGB LED lights and connected 5 reels ( 5x5M ) all to the one power supply, which inevitably eventually blew up. Now i'm not sure if the LEDs are fine or if they blew too. But they were all connected in series but powered from both ends (using the one supply), and lead to same receiver etc. As they are lining the roof of my room i'm trying to work out if there is a way to run all of the LED strips from a power supply without it blowing up if they are connected in the same way i had it..
Is this even possible?

Heres details about the products i used:
AC 110-240V adapter, connected to a 12v DC plug which was plugged into the WIFI controller, which then lead to a 4 pin connecter which was split into two 4 pin connecters which is where the two ends of the 5x5M LED strips met.


texts: I am looking for an open source (or just free) software for creating electric schemes. It would be better if your program could do other schematics (for instance, installation schemes of physical experiments) and if it would be crossplatform.


texts: Where do active display converters get their power from?

texts:
I have bought a mini Display Port to HDMI/VGA/DVI active converter.
It works on VGA, but VGA is broken [dimmed screen? and I don't know how to fix that] on the monitor (so my only option left is HDMI).

I went and connected the HDMI, changed input on the monitor to HDMI and behold.... nothing. I figured it could be because the monitor isn't supplying power to this active converter so I might solder a few wires to it and take a power adapter (appropriately rated) and hook it up. So here I am, with the probes in my hand, figuring out which HDMI connectors should provide the power (I don't know). But befor I am going to potentially destroy this device, how can I determine where it (should) get its power from?

Top:

Bottom:


texts: Why is the current control knob in DC voltage source kept at maximum initially?

texts:
In a DC Voltage Source(0-15-30V), why do we need to keep the current control knob at maximum at the beginning?

Note : I am using this DC Voltage Source for basic experiments of electronics like getting characteristics of P-N junction diode, zener diode, etc. This advice came from my instructor in the course 'Electronic Devices and Circuits Laboratory' and is also mentioned in the laboratory manual.


texts: Using a voltage divider on LED IC driver output

texts:
Would using a voltage divider on the outputs affect the drivers operation?

The Driver is a 24 channel current sink IC that will be used for automotive interior lighting.

LED will have a Vf of 3.3v @ 20 mA.
Using 12v supply to calculate power dissapation from the  data sheet formula
give a total of 5170 odd mWs which is larger then the IC can sink.

Tried to post the equaation but it gets messed up.

The whole application will have aprox 120 RGB LED but would like to avoid using a seperate 5v supply for the LEDs

TLC5947 data sheet

TLC5947 Output circuit diagram:


texts: Which are the physical factors that determine the maximum transportable resolution of a cable (for instance: HDMI)?

texts:
Which are the physical and electrical factors that determine that an old generation HDMI can transport for instance  1080p resolution, while a new HDMI (2.0) arrives at 4k?

Is it due to a different attenuation of the cable, to a different communication protocol etc?


texts: Is it possible to import a netlist from Multisim into Kicad?

texts: So at the moment I'm using two different programs for modeling circuits. Multisim and KiCad. I use Multisim because it allows me to do SPICE simulations, something that KiCad doesn't allow me to do. I then need to route the circuit on a PCB, something that Multisim by itself can not do. That's where KiCad comes in. I've used KiCad before to route circuits on a PCB and it's worked out well for me. The problem is the netlist that Multisim outputs doesn't work when I try to import it in KiCad. What I think is going on is that the .net file type used by KiCad runs a different format than the one in Multisim. Is there a way to convert these two files so they are compatible?


texts:
I understand that highly integrated semiconductors enable physically diminutive devices. Microcontrollers with CPU, RAM, flash, power supply, a wide assortment of peripherals, all on a single piece of silicon are available for very cheap.
Why do our devices like laptops and phones still use multiple chips and so many passive components?
I understand capacitors and inductors are expensive to implement on silicon, then why not a single chip plus a bunch of those passives?


texts: Controlling a Stepper-Motor with 2 H-bridges

texts:
I think that I may have come up with a possible way to control a bipolar stepper motor using 2 simple H-bridges. The idea is to control the direction and the steps of the motor by switching the direction of the current flow using the H-bridges. Unfortunately, I am running into a few annoying issues. I am using a ROB-09238 bipolar, 1.8 degree step value stepper motor. I have an external voltage source of 12volts@5amps. For one, the rated current of the stepper motor is 0.33 amps, does this mean at max that the stepper motor will use is only 0.33 amps, or is this the average amperage? I am using a Raspberry Pi to output 3.3V and control the base of the transistors. The goal is to create an NPN transistor H-bridge using regular 2N2222 transistors. Will these transistors do the job?  What is the required resistance value on each of the transistors to do the job efficiently without blowing the transistors?

No matter what I do to calculate the resistance value for the base of the transistors, I either make them get really hot, or can't even get enough current through the H-bridge to properly light an LED. I don't think that I am wiring it wrong because in my circuit simulation program, I get the same results. I have messed around with the resistance values within the program and still can't appear to get what I am looking for.

simulate this circuit – Schematic created using CircuitLab


texts:
In the following circuit:

What would be the small signal model for op amps 2, 3? I am not sure how to connect Rin for instance and how to represent graphically (in my circuit) the short-circuit transconductance and the unity open-circuit gain.


texts:
I am in a research team.  We are designing a circuit system for powering a DC motor with battery and super capacitor. The battery and super capacitor power the motor separately and the motor gives regeneration power back to the super capacitor (motor driver allows for regen.) Can experts in this field confirm that the circuit will work safely? (Without voltage spike, etc.)
Also, do I need a flyback diode with the motor or any of the relays for the induction spike?


texts: Series voltage reference unstable with a series resistor

texts:
I am using the MAX6035 as a 5V reference that draws 5mA load current. To protect the input from transient spikes, I thought a simple resistor and zener diode circuit would work well. I noticed that the circuit was drawing more current than expected so I did a little digging. With a 1kOhm series resistor to the input and a 1kOhm load resistor (to simulate 5mA of load current), I was seeing oscillations at the IN pin of the MAX6035. Even in the simulation below, the oscillations occur until I bump up the input capacitance.

The current solution is to add more capacitance to the input pin (1uF vs. 0.1uF) and that seemed to fix the issue at room temperature. However, when running it at -55degC, the oscillations show up again, but to a lesser degree.

I am not necessarily looking for a solution to this specific issue, but an understanding to how a series resistor affects the operation/stability of a series reference. Any references (no pun intended) to reading material is greatly appreciated.


texts:
I came across the Isola IsoStack website that lets me test PCB stack-up using Isola substrates:
https://www.isola-group.com/isostack
My project is using a stripline design with a 1oz copper inner layer and trace width of 0.010". The tool calculated impedance at 50 ohms for my stackup but it complains that it violates an IPC-2141A constraint where trace height over trace width must be less than or equal to 0.11. The tool used 0.00125" for 1 oz copper height and my width of 0.010" to get a ratio of 0.125.
Can someone give me an overview on how this ratio applies to trace/signal behavior? If my signal is only DC-50Mhz, does it still apply or can be ignored? I tried to search for IPC-2141A and any term matching height/width ratio and most results talk more about current capacity or, oddly, hole aspect ratios.
Below is a screenshot of the parameters and constraints, the T/W is the constraint in question:


texts: My PIC16F628As keeping dying with a Pickit3

texts:
I have hooked up my PIC16F628As to my PICKIT like this:

simulate this circuit – Schematic created using CircuitLab

Yet 3 already died after a few writes, yet the datasheet claimed to support thousands of writes.
I get the following Error after a few (3-4) writes:

Address: 0 Expected Value: 3fff Received Value: 2ffe

I wired it up according to specification, am I doing something wrong?


texts: Display large decimal number using seven segments display

texts:
I have a 8bit value on the output of ADC. I need to show this number on 3 seven segment displays. How to do it? I'm working in Multisim 11.0.

You can see a scheme of ADC that I have:

Two blue schemes on the right converts BCD to value on the displays and it works correct while value less then 9. But when it is bigger, displays show wrong value.

P.S.: This Question has as one of the answers the link to the DM9368 Data Sheet, but is seems that there is no such scheme in Multisim.

P.P.S.: In fact, I need only 6 bits if number to display values from 0 to 64.


texts: Multisim. Why the parameters of voltage in osciloscope and voltmeter diferent?

texts:
I have simple design:

and the oscilloscope graphic:

The Voltage of oscilloscope and voltmeter mismatches.
The oscilloscope value is higher.
Why and how can I fix it? I'm using Multisim 13.


texts: How fast will a resistor heat up under high power?

texts: I am building a circuit for some induction coils on a coilgun, and it will draw about 1.75A from a 12V power source (I know it probably won't be very powerful, but it is difficult to find resistors that will allow a higher current). To keep the current at 1.75A, I am planning on using a PWR221T resistor, which is rated for 50W at 25 degrees C. The details sheet also says that, without a heatsink, the resistor is only rated for 2.25W. I am going to be building my circuit on a breadboard, and I'm worried that I will run out of space if I add a heatsink (It also has two Darlington transistors that will probably require heatsinks and a few other circuits). However, each inductor coil is going to be switched on for only a split second, so will I the resistor (and the Darlington transistors) actually heat up enough to necesitate a heatsink? My original plan was to have 1 resistor for both coils, but I could also use two so that they're used separately.


texts:
I'm designing an ESC with a small microcontroller running at 3.3V. The BLDC motors I have chosen are extremely small, and run best at 3.7V. I have the power supply for both of these (3.7V is VBATT, 3.3V is obtained using a buck converter). They are 3 phase, and the controller needs to be sensorless. I would like to measure RPM and current usage as well if it doesn't mean I will have an overly complicated design.

All the docs I have found are great for higher voltages, and ridiculous currents (I will max out at ~5Amps at 3.7V, I don't necessarily need to design a 100V, 300A ESC).

Questions I have:
Is there a reference design I can follow somewhere around the net?
What kind of protection circuitry should I use?
How simple can I go?
Are there any ICs that will simplify the circuit even further?
Any other recommendations/tips/pointers?

Thanks for your time,
Mike


texts: Why is there a transistor between the MCU and LED?

texts:
In the answer for this question (Does my circuit need decoupling caps?) there is a transistor between the attiny85 and the led.
I understand that if the mcu isn't capable of providing enough current for a sensor, you have to do it the way the schematic shows, instead of controlling it directly trough the mcu. But I think that is not the case.
So, why? Is there any advantage?


texts: How to mute microphone in 2-way communication when the speaker is active?

texts:
I'm making my own two way intercom for my house. There will be a speaker and microphone above the front door of my house (as well as a camera). When someone rings my doorbell, I get a notification on my phone and am able to see the video.
The issue is that when I enable the microphone on my phone to talk to the person, I want to disable the outside microphone automatically to prevent feedback.
I'd like to do this with hardware. Can I do this with an NC relay to cut power to the mic; having the speaker voltage controlling the relay coil?
EDIT: Below is what I'm trying to accomplish. I ordered a few sound activated switches, but they will not work for my application. After some more research I think I found what I'm looking for - line audio detectors. The problem is the few for sale are audiophile devices upwards of $100. So I'm going to make my own. Just need some advice on the questions in my schematic.


texts:
I am looking to power a LED, given an input signal \$v_{in} = A \sin(2\pi ft)\$, where 150 < f < 15 kHz, and 1 < A < 5 Volts. The only caveat is that I only want the LED to turn on if a specific frequency is met, that being 800 < f < 1200 Hz, but let the LED remained turned off if the frequency is outside that range. In order to filter out unwanted frequencies, I've implemented a cascaded low and high band-pass sallen-key filter. At this stage, I'm trying to determine how I might use this filtered signal to either power or control the switching on of the LED.

If I were to let this filtered signal control the switching of the LED, I have considered using a SPST relay to activate a sub-circuit which the LED would run on, however I have not had much experience with relays, and so I would really appreciate advice on how I might achieve this.

If I were to use the filtered signal to power the LED, I have considered using a rectifier to turn the AC signal to DC signal, but then I am not sure how I would tune the DC voltage to correctly power the LED light itself. (i.e. 1.8V for a Red LED, or 2.1 or Green, etc). Again, I am not very experienced, and would appreciate some advice on this issue.

Thanks!


texts: How can a Zener diode maintain a constant voltage?

texts:
A Zener diode in reverse bias more than breakdown starts conducting. If you increase the reverse bias:

It conducts more i.e current in it increases
The voltage across it remains same

I think I get all except 2 above. Why does the voltage across it remain constant even when the reverse bias is increased?


texts: AC/DC Motor Running in the wrong direction

texts: So I have a floor buffer that has 115v AC motor on it. Recently the motor seems to be running in the wrong direction so that the driver flies off of it. I have replaced both rectifier bridges and the motor is still running in the wrong direction. There is no stationary switch or start/Run capacitors on this motor. It has the magentic field, Comuntator and 4 carbon brushes. This motor is also a variable speed with a speed controler.


texts: Run electric motor CW & CCW with DP-DT switch

texts:
I have a Harbor Freight drill press 1-1/2 hp, running on 120 volt, capacitor start.

Is it possible to run CW & CCW rotation, using a DP-DT switch?

Motor has four wires coming out of it, all with color and numbers.
black #1/gray #2/red #3/yellow #4

The picture is from the motor, if this is possible please show the wiring diagram. Thanks.


texts:
I want to design amplifier that do the following summation

$$V_o = 2V_1 +3V_2 +5V_3 $$

the difficult arose when design with one op-amp and all voltages are referenced to the ground .

I tried with making non inverting amplifier with gain = 7 (any gain more than 5), then putting three resistor in the non inverting input (R1 for \$V_1\$ and R2 for \$V_2\$ and R3 for \$V_3\$)
making superposition three times i have three equation.

But i can't solve them; it's very difficult for me.
Does anyone have an idea?


texts:
It is rare to see a snubber circuit added transistor like that.
On the secondary side, an NPN transistor is paralleled to a snubber capacitor.

How does it work?
Is it useful or just little improvement?
What are the advantages and disadvantages of this snubber compared to an RC snubber without a transistor?


texts: What is the best way to take multiple near-simultaneous pictures from 6 cameras on a development board?

texts:
I thought I could use a powered usb hub, connect the 6 cameras to it, connect the hub to the raspberry pi and capture the images one after the other quickly using the motion package. But I can't find cheap, tiny (hopefully under 20 x 20 x 30mm) usb cameras with at least 3 mega pixel resolution. Is it a good idea to open a few usb webcams and see if they fit my size requirements?

If I can't find small, cheap, good usb cameras, I'll try using CMOS sensors, but I can't find out how to actually use more than one camera sensor with a development board. I'll appreciate any pointers on that. For example, how can I go about using six of these cameras - https://www.sparkfun.com/products/8667 - on one board?

The actual project is to take multiple pictures covering 360 degrees and upload them to a web server. All cameras will have to fit in as small an enclosure as possible (budget is $300 including the development board). I apologize if these are real noob questions - I'm new to electronics and have only done basic projects on raspberrypi and arduino till now.


texts: I was reading the LM2734Z datasheet and in the PCB Layout Considerations section, it says "There should be a continuous ground plane on the bottom layer of a two-layer board except under the switching node island."  What is it?


texts: How to reduce the amplitude of my PWM signal?

texts:
I'm using a PWM control signal that ranges from 0-24V to drive a stepper motor. However, the datasheet in the driver says it should range 0-5V.

How can I bring down the amplitude of my PWM control signal? Would I use a 5V regulator or does a potentiometer make more sense? If neither of these, then what?


texts:
Regarding a DC motor designed to operate at a voltage up to 22 volts: If this motor is powered by a 18.5 volt lithium battery, will it not produce more torque than if the same motor is powered by a 14.8 volt lithium battery? I know more volts create more speed, but the increased current available in the 18.5 volt pack will provide the additional torque, right? If this is true, will the same motor stall at different amperage depending on how much voltage is being supplied?

Thank you for your replies.


texts:
I'm using an 18650 (4.2v unknown mah) to power 14 leds (2v 20ma) in parallel with a 100ohm 1w resistor on each led. Everything has been running fine for 12 hours now with no problem.

My understanding is the resistors should drop voltage from 4.2 to 2v but my volt meter shows no change. Am I understanding resistors right? Any help in explanation would be greatly appreciated.


texts: Can a sensor connect directly connect to the server?

texts:
The question is simple, and I am not doing any SE in here. I googled first, I didn't find an answer. So, people of electronics, I am not from electronics so don't know where to look exactly.

Just an example scenario below (no SE in any way):

I have a sensor dht11, how do I connect exactly that to a server via wifi.Now I am able to connect to raspberry pi and then to a server from raspberry pi.

How do I go about? I am not asking in here for any secret blueprint of some secret stuff. I know it is available online, I don't just find it because I am not from this domain.

Any helpful links are highly appreciated. Will return back to the "electronics" stack exchange in specific, once I gain expertise in this domain.

(If this is not a right place to ask this, kindly comment on where should I post this)

Thanks!


texts: Smart charger - how to detect current and voltage of different battery packs and then charge them accordingly

texts:
I am thinking of designing a smart charger for a few of my bikes/scooters, etc

detects current and voltage of the pack (30-60V, 1-5A)
charges the pack accordingly in the CC-CV mode, fast-charging when possible

All of these battery packs are li-on based (mostly 18650, 21700).

My questions are:
- how does the charger figure out what is the maximum permissible voltage for a pack?
- respectively, what about the max current?
- are there any ICs for that?
- can I go with a transformer based charger or do I have to use a switch-power (or maybe some other type like capacitive - although I would like the efficiency to be reasonable).

I know it is a layman question - I am quite new to electronics, but I would like to steadily learn and practice more.

Many thanks in advance.


texts: How can I multiplex my oscilloscope probes?

texts:
Let's say that I'm tasked with the job of measuring the propagation delay of each inverter in a 7404 hex inverter.  I've got a pulse generator, a power supply, and an oscilloscope with two probes, so I have everything I would need to perform this measurement.  If I only had to do this once, it would be easy to physically attach the probes as necessary to make each measurement.

Now, let's say that I'm given 1000 of these inverters and I need to make 6000 measurements.  I'm stuck with the same equipment- pulse generator, power supply, oscilloscope with two probes.  There might be a better way to word this, but my basic question is- what techniques can I use to multiplex my oscilloscope probes that won't significantly affect my propagation delay measurements?

I've been messing around with and generally dancing around this problem for a while now so I have done some research and found a few ways, each with some pros and cons:

Analog switches and multiplexers are easy enough for me to control, but I haven't been able to find ones which have a -3dB bandwidth anywhere near what I'd need.  Additionally, this solution doesn't scale well- I don't think passing a signal through multiple levels of switching is a good idea.
RF relays have a high enough bandwidth and seem like they'd scale well enough to a large number of test points, but driving the relays is a bit of an issue.  Even latching relays would require a relay driver chip and probably another PCB layer to route everything on.
RF switches seem to all require bypass capacitors at the inputs and outputs and generally dislike DC, plus the same scaling issue as the analog switches.

One might read my question and say, "well, you know your options, try them all and find out which one works the best."  I appreciate this but I know there has to be more to this problem than I might even know.  Perhaps there are other ways of doing it than I listed above, or maybe someone reading this has encountered this exact issue and can point me in the right direction.  I'm leaning towards the RF relays myself at this point.


texts:
I would like to know if there is a 100% safe option today to prevent firmware copy from MCUs. Most MCUs can have an option set at programming that will block any code extraction, but this is usually easy to hack, specially if you use acids to get acess to the die and probe it.

I saw once that some MCUs use cryptographic solutions, but I am not sure how they work, I assume they probe some external hardware for specifc keys, but this is easy to change in the code once it's extracted.


texts: Touch application with PIC16F183x possible?

texts: I could'nt find any information about touch applications in the datasheet from the PIC16F183x controller. Ist this controller fine for touch applications? It's in a list with supported devices for the mtouch library.


texts: Q1113 Ir sensor verilog and Fpga board,how to program?

texts:
I have been working with s one of the line IR sensor from sparkfun(Q113). It has 3 port a vcc, ground and signal. As I know one way to find if the object is black or white is through reflection of light. And it has a capacitor inside the sensor, and we have to charge it through the fpga and if it detect the black color then the capacitor discharges. Now I have to declare one port in fpga as input and output and find out what time it took to discharge and determine the movement of body go forward or backward.
my question is how to figure out the capacitor discharge rate so to go forward or backward and how to write code for bidirectional input. I am using Ja1 port of fpga(BASYS 2)
 code..

module top(
input  mclk,      // The standard clock
input  direction,  // Direction of io, 1 = set output, 0 = read input
input  data_in,    // Data to send out when direction is 1
output data_out,   // Result of input pin when direction is 0
inout  Ja1     // The i/o port to send data through
);

reg [7:0] a;
 reg [7:0] b;

assign Ja1  = direction ? a : 1'bz;
assign data_out = b;

always @ (posedge mclk)
begin
   b <= Ja1;
   a <= data_in;
end

endmodule


texts:
I start from the telegrapher's equation: \$-\frac{dV(z)}{dz}=(R'+j\omega L')I(z)\$, where \$V(z)\$ and \$I(z)\$ are the phasors of voltage and current respectively, in the transmission line model. \$R'\$ and \$L'\$ are resistance per unit length and inductance per unit length respectively.

The solution to the wave equation \$\frac{d^2V(z)}{dz^2}-\gamma^2V(z)=0\$ where \$\gamma=\sqrt{(R'+j\omega L')(G'+j\omega C')} \$ has the form \$V(z)=V_o^+e^{-\gamma z}+V_o^-e^{\gamma z} \$. \$G'\$ and \$C'\$ are respectively the conductance per unit length and capacitance per unit length of the transmission line.

From the telegrapher's equation we get: \$-\frac{dV(z)}{dz}=\gamma V_o^+e^{-\gamma z}-\gamma V_o^-e^{\gamma z}=\gamma (V_o^+e^{-\gamma z}-V_o^-e^{\gamma z})=(R'+j\omega L')I(z)\$

\$I(z)=\frac{\gamma}{R'+j\omega L'}(V_o^+e^{-\gamma z}-V_o^-e^{\gamma z})\$

...and I'm stuck here.

Given that characteristic impedance \$\frac{V_o^+}{I_o^+}=Z_o=\frac{V_o^-}{I_o^-}\$, how do I arrive at \$Z_o=\frac{R'+j\omega L'}{\gamma}=\sqrt{\frac{R'+j\omega L'}{G'+j\omega C'}}\$?

I'm not sure how to get \$Z_o\$ from \$\frac{V_o^+e^{-\gamma z}+V_o^-e^{\gamma z}}{I(z)}=\frac{V_o^+e^{-\gamma z}-V_o^-e^{\gamma z}}{I_o^+e^{-\gamma z}+I_o^-e^{\gamma z}}\$


texts: Difference Amplifier - Signal Attenuation

texts:
I am planning on using a difference amplifier IC much like the AD8206 to measure the differential voltage across a high side shunt in order to monitor the current.

I chose a differential amplifier over a current sense amplifier (CSA) IC because its more robust to large input differences, less sensitive to input filtering and I don't have a need for high speed current measurement so the lowered bandwidth is ok for me.

The issue with differential amplifiers verse CSAs is that they attenuate the signal before feeding it into its internal amplifiers. Is this an issue? I don't fully understand the ramification for input signal attenuation. I get that its a reduction in amplitude so possible resolution?
The CMMR is worse in differential amplifiers than CSAs. But why do I care? I am struggling to grasp the importance of CMMR in application. I know that in an ideal world an op-amp only applies a gain the differential between the 2 inputs and ignores the common mode. From my reading I've found [common mode voltage = (V1 - V2) / 2]. So High CMRR rejects the gain associated with that common mode voltage? Can someone illuminate the application importance for CMMR?

Thank you for your time.


texts: What exactly makes small quantity PCB production costly compared to large quantity PCB production?

texts:
The per-PCB cost of manufacturing a small number of PCB is 10 times or more compared to the per-PCB cost of manufacturing a large number of PCBs.
So what is it exactly that adds to the cost?
People say there is setup cost or initial cost, what is it exactly? What steps in manufacturing need a special setup and cost this much?
I know there is printing of transparent film, but is it that costly?


texts: Generic 433MHz receiver, how to derive output signal voltage

texts:
I have a 433MHz receiver modules (Model number MX-05V) The input voltage is listed as 5V but they don't list the output voltage.
I have seen this used without level shifting in a project in conjunction with an ESP32 module that requires 3.3v signals.
In researching how this was safe I found an answer that suggested that the output voltage would be input/2 but I'm unsure how this or why this is.
Unfortunately the answer didn't provide detail, it just happened to mention it in passing.
(https://electronics.stackexchange.com/a/103357/274778)
In short, my question is in two parts:
What is the signal HIGH voltage (in theory ~2.5v?) for this receiver?
Why is it that?
Below is the schematic for the part and a link to a product listing for it, note that on the listing the schematics are labelled backwards.
It's listed as a superhetrodyne receiver and what I take to be the output circuit makes use of a duel opamp (LM 358) but my understanding is too flakey to derive the output voltage from this arrangement.

Links to example of part:
https://hobbycomponents.com/wired-wireless/1054-433mhz-transmitter-receiver-modules-with-antenna
https://hobbycomponents.com/wired-wireless/615-433mhz-wireless-receiver-module-mx-05


texts:
I've this circuit, I haven't connected the transistor yet, I want to check the proper function of the circuit before so I don't burn nothing.

What is the correct way to check the output signal, pins 5 and 7, I don't have a differential oscilloscope just a regular one and I'm not sure if is correct to connect it to the pins 5 and seven directly.
What I've tried is to put a led with a series resistance of 820 ohm between at the output, pins 5 and 7, but the led doesn't turn on, although the pin seven has a signal because the led turn on if I connect it between 7 and ground.

How can I check, the if the circuit is generating the correct signal before I connect the transistor?


texts: Measuring R1 in induction motor equivalent circuit and parameter extraction from test

texts:
I always had this question that I never really found written anywhere and I have the good or bad habit of not believing my teachers when answering this kind of odd questions.
Whenever I read about the induction motor equivalent circuit R1 is always the resistance of the stator winding. Great! I have a stator, how do I get R1?
My first guess is to measure the resistance value between one phase and neutral in Y (star) connection. That or take the resistance value between phases in Delta connection and divide it by 1.5 to get the resistance of only the winding that connects them directly.
Second question:
To extract the parameters of the equivalent circuit, I tested the motor in Delta connection, with the rotor blocked and in free running mode. Is V1 the phase to phase voltage? What about Is? Should I test it in Y instead? I have V(t) (phase to phase) and I(t) that I got using an oscilloscope and a current probe.
Equivalent circuit with variable names:

(source: myelectrical.com)


texts:
I've just started using SPI on a dsPIC, and I noticed some strange behavior on a waveform (see image below). SPI module is configured in the master 8-bit mode. On the shown waveform you can see a byte 0xAB, and that the SPI module "prepares" the data line one clock cycle before the first clock pulse. Why is that? If I send 0x7B (first bit of this byte is 0), then the data line stays low before the first clock pulse. If I send 0x7B and 0xAB just after the first byte, everything is fine, i.e., there is no one dummy clock cycle between the two bytes just "to prepare" for 0xAB.

The SPI mode is as follows: idle state is high, active state is low (CKP=1); serial data changes on transition from idle to active state (CKE=0).


texts: Voltage drop on transformer's secondary winding experiment

texts:
I've read things about it but I couldn't understand it. Let's say I have a 3-phase transformer and voltage of secondary winding is 230. When I keep adding 1k resistors (as load) in paralel it goes like 229V, 228V, 227V... But if I add just inductors or just capacitors in paralel it stays 230V. Why is that?

I may sound really simple but I am really confused. I am not an electrical engineering student by the way.


texts: Wemos D1 Mini led dimly on during deep sleep

texts:
I have been experimenting with Wemos D1 mini for deep sleep and came across the video on this topic ( Youtube Link: Wemos D1 Mini Low Power) to reduce the power consumption of the board by disabling the UART during battery operation.
As I am supplying 3.3V directly to the Wemos, after removing the copper trace as shown in the video (so that CH340 does not get 3.3V during normal operation via battery, but it gets its 5V supply when connected to the USB for programming), everything should be normal and wemos should have a better power consumption.
However, the build in blue LED on the ESP12-F is lit dimly during the deep sleep mode and I am afraid that it might eat up quite a lot of current. I do not have the possibility to measure the current at the moment, but I assume the GPIO2 has some leakage currents and/or it is pulled down during the deep sleep, which cause the LED to turn off (which does not fit totally, as the GPIO 0 and 2 of ESP8266 shall be pulled up internally for booting up).
Or the suspicion is that, the removed trace causes the CH340 UART chip behave weirdly and having some floating outputs, causing the LED lit dimly, which is supported by the interesting observation, when USB is connected to supply power to the CH340, the LED is turned off.
Does anyone have an idea, what the reason could be and how the dimly lit LED can be turned off during the deep sleep? What am I missing here?
Thank you


texts: Which freeware analysis software most closely resembles the functionality of Matlab DSP toolbox

texts:
I'm looking for some freeware that will do (as much as possible) of what Matlab does DSP-wise...

Filtering tools
Modulation
File I/O (as I need these to compare vhdl simulation results to software computed results)

I've used both Scilab and Octave.  I'm wondering which one (or another unmentioned option) would be the best freeware DSP design replacement.


texts: I'm doing AC theory as an electrical apprentice now, and my lecturer said that inductive reactance and capacitive reactance both work with Faraday's law, or back-EMF, is this correct for capacitive reactance as well?


texts: Can a 3-axis magnetometer be tilt compensated when moving/accelerating?

texts:
I have a magnetometer, accelerometer and gyro which all go swimming (attached to a person.) Data is logged and I now have a sample of that data.

I want to calculate the magnetic heading the user was travelling in. However, all the documents I can find on tilt compensated compasses (they're mostly applicable to phones) do not mention anything about accelerating at the same time, which happens in my application.  It seems to me like this would make tilt compensation very difficult; it would only be possible when stationary.

Does anyone know if it's possible?


texts:
I am new to electronics so I apologize in advance for incorrect terminology.

I have an existing circuit which can be powered with either 13.4v or 14.4v. What I would like to do is treat that voltage difference as a binary switch, where the 13.4v power is OFF and the 14.4v power is ON.

So basically I want to build a circuit that can have an input voltage of 13.4v or 14.4v which would equate to an output of 0v or 14.4v respectively.

I have found and looked into MOSFET transistors as they seem to be the most reasonable way to achieve this but I can't find one that has a gate-source threshold voltage high enough. As in, I can find a 14v Vgs MOSFET but the Vgsth is always too low, usually 6,7 volts. I need the OFF output voltage to be 0v. This is leading me to think this might not be the correct approach.

EDIT: I also want to include that the maximum current draw on the circuit could reach 8 amps but on average should be closer to .5/1 amps.

Can I achieve the circuit I described above with just one MOSFET? Or is what I'm even trying to do reasonable/possible?

Thanks for your time.


texts: Is induction motor's rotor speed or torque change with delta or star connection?

texts:
An induction motor's synchronous speed Ns is given as:

Ns = frequency * 120 / number of poles

This formula is independent of the voltage applied to the windings.

On the other hand, I know from basic theory that if the voltage across a solenoid is increased its magnetic flux will increase. And more magnetic flux will create more force on a current carrying wire.

Would the speed of the induction motor's rotor change with delta or star connection? And is there a formula explicitly shows such dependency between stator winding voltage(delta or star) and rotor speed? Would a three phase fan  motor rotate faster if connected delta instead of star?


texts: Using one DC motor driver for multiple motors that aren't going to be used simultaneously

texts: I'm trying to control 20 DC motors with an Arduino but I don't have enough pins to connect all the motors simultaneously. I only need one of the motor running at a time. How can I switch between motors on single driver? I have a dual channel L298N motor driver card.


texts: How to simplify these two voltage sources (same frequency) into one so I can calculate the current then the power absorbed by each element


texts: I/O Resistance of common source MOSFET with source degeneration

texts:
Common Source MOSFET with source degenerations looks like this

I am a bit confused about different input and output resistance statements (provided by different sources).

Some of them say that applying Rs to circuit DOES NOT change input and output resistances even a bit (which I hardly believe).

But the others say that Rs "boosts" AC output impedance which probably means that Rs increases output impedance.

But I can't find any formula which could explain what is happening with output resistance. (Such as for CS without Rs --> Rout = Rd || Rload || ro )

Can someone explains me what really happens with ouput resistance in CS source degeneration transistor circuit?

*I get the rest advantages as improved linearity, lower voltage gain, etc.


texts: calculating the RMS noise of an accelerometer

texts:
I would like to measure the noise density (microg/sqrt(Hz)) of an accelerometer and then compare the measured one with the typical value in the datasheet.

I know the sensitivity and the sampling frequency; The general formula is also known:               N_RMS=PSD×√BW

The BW will be equal to the half of the sampling frequency.
referring to the following page:
http://cache.freescale.com/files/sensors/doc/app_note/AN4075.pdf

I should calculate the standard deviation and multiply STD by the inverse of sensitivity. But my question is how to calculate the standard deviation in the LSB (count) format?

Thank you


texts:
Currently we are using the following power supply scheme:

This solution effectively separates the analog sub-part of the PCB from the noise of the digital sub-part.

Now we are going to use the following scheme:

The main benefit is decreasing the BOM cost. But would it separate the digital and analog sub-parts of the PCB?

LDOs are low noise parts (LP2980AIM5-3.3). The digital load - 20mA. The analog load - 10mA


texts:
Why nand flash memory comes in "large" package sizes?
Even in TSOP, package is too wide and "big".


texts: Won't a potentiometer powered by a dc supply cause a short-circuit at lower end of the range?

texts:
Many tutorials in the Arduino or Raspberry Pi community simulate an analog sensor with a potentiometer. The potentiometer, being a passive device, is powered from the same DC power source that supplies the microcomputer. Usually, the +5V (or +3.3V) and GND pins on the Arduino or Pi are used for this purpose.

This doesn't seem safe to me. Suppose we turn the potentiometer all the way down in this configuration. The resistance should be 0 Ohms and that should short the DC power supply. Yet, this is just what many tutorials like this one here recommend: https://www.instructables.com/id/How-to-use-Potentiometer-Arduino-Tutorial/

How come? I always include a resistor in series with the potentiometer to avoid this situation but no one else seems to think this necessary. Thanks in advance for any help.


texts: Unexpected behaviour with pow(2,x) in Embedded C

texts:
I am a newbie in Embedded C (solo learner). I am using it to drive around a robot (using the ATmega2560 with 14.7456 MHz). I am experiencing some unexpected behaviour with the following code:

int j = 2;

PORTJ = pow(2, j) - 1;

Now I expect 3 to be seen at port J. However, I see 2. Moreover, if I do this:

PORTJ = pow(2, 2) - 1;

then it works fine (that is, I see 3 at port J). The reason I want to do this using a variable is because my actual code is this:

int j = 0;

while(1)
{
    j = (j + 1) % 9;

    PORTJ = pow(2, j) - 1;

    _delay_ms(500);
}

This works for all values of J except for j = 2. What am I doing wrong here? I have recently started so I don't know much about this. Any help is appreciated.


texts: I'm looking to build a video/audio or just video transmitter and receiver for use in robots. I'm primarily doing it as an excercise, but I'd love to be able to get a range of 100-200 meters. I'd love any books or other materials you would recommend on this topic or on radio design. I'm an EE student, but I'll read anything you can provide. Thanks.


texts:
I am currently researching a touch/force sensor for my project. Purpose of this post is to get your help in sensor selection.
Below is the information about the project so that you can get insight regarding the requirements:

Person A wears a jacket. We are able to modify the jacket, e.g.
can put sensors inside it or cover it with special conductive surface
and etc.

Person B has a stick which is also open to modifications. Once
B's stick hits the A's jacket, we are able to sense this hit.

So, in a nutshell, aim is to make a clothing & stick pair that is able to detect a hit.
I want to note that measuring the force is not mandatory(even though I would prefer to read the scale of hit), just detecting a touch is sufficient (jacket-stick contact).
Also, it is not mandatory to know that the origin of the hit is from the stick(however this feature would also be beneficial). In other words, if third person would approach person A and kick him in the jacket, it is ok to measure it as well.
I have been thinking about sensor/material selection for the jacket. I am thinking about piezoresistive force sensors. They come in plate-like shapes, which I believe I can fit inside the jacket until whole jacket area is covered with them. Though, I am afraid about what will happen in a scenario when there is no external hit, but the person just moves(runs, stretches) and thus deforms them.
I also thought of this: To make the surfaces of jacket and the stick electrically active in a such way that once they touch each other, "circuit" will be closed and we will be able to detect that. I think similar approach is used in fencing. But I believe rain, or spill of water on the jacket can cause problems.
I wanted to ask your suggestions, considering that there are many novel technologies, probably special fabrics and etc. What kind of sensing mechanism(measurement method or sensor) would be the right one for this application?


texts:
I'm trying to make my own nucleo board using STM32F303ZET6. I have downloaded and inspected the schematic documents that stm shared.
I will use this board as rocket flight computer so I want the board to be able to:

Read sensor data using I2C. (BMP180,BMP280,LSM6DS33,BNO055)
Use SPI port for the RF module and SD card.
Use UART port to read GPS data from NEO-M8N.

All the screenshots that I have posted here are from the STM32F303ZE schematic. You can click here.
For the programming part of this board I want to use the STLink V2 part from the original NUCLEO-F303ZE. So I will just rip the part off the pcb and use it externally. And then I will have jumpers from the programmer board to my board to be able to program my board.
Question #1: Can I replicate only the connections below with jumper cables (also 3V3 and GND) to program the board I want to make.
*
Question #2: Can I just connect all the VDD and VDDA to 3V3, connect all the VSS and the VSSA to GND?
Question #3: On the schematic there are 2 oscillators for the MCU. 8MHz and 32.768KHz (Is the 32.768KHz oscillator 32MHz or 32KHz? I don't understand the notation.) I want to use the MCU at 72MHz clock speed but I don't understand how that can be reached with these external oscillators. Can I reach this value with the internal clock? If I want to use te internal clock should I remove the oscillators?
Question #4: I have seen opamps on the schematic do I need it for the functions that I have listed above?


texts:
I am using an STM32L1 on a Nucleo-L152RE board. I have to devices I control through serial running at rather high baudrates, so I am trying to enable DMA on the USART. With the code below I can launch one Rx DMA, but the second one, which I start from the ISR never completes:

void uart_receive_dma() {

    DMA_InitTypeDef  DMA_InitStructure;

    DMA_DeInit(DMA1_Channel5);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t) &USART1->DR;
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t) buffer;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = UART_PACKET_SIZE;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
    DMA_Init(uart_rx_dma_channel[handler->uart_index], &DMA_InitStructure);

    /* RX */
    DMA_ITConfig(DMA1_Channel5, DMA_IT_TC, ENABLE);
    DMA_Cmd(DMA1_Channel5, ENABLE);
    USART_DMACmd(USART1, USART_DMAReq_Rx, ENABLE);
}

void DMA1_Channel5_IRQHandler(void){

    DMA_ClearITPendingBit(DMA1_IT_TC5);
    uart_receive_dma();

}

int main(void) {

    RCC_Configuration();
    GPIO_Configuration();
    NVIC_Configuration();
    USART_Configuration();
    /* First Rx, works and MA1_Channel5_IRQHandler gets called
    uart_receive_dma();
    while(1);
}

The first DMA transfer works well, so I guess I am not clearing something before starting the second one, but I can't figure out what it is.

Depending on some external conditions, the real code doesn't always restart the DMA transfer from DMA1_Channel5_IRQHandler but restarts it from somewhere else, that's why I can't use the DMA in circular mode.


texts: Battery powered light curtain of 100-150 LEDs

texts:
I have a hobby project of putting together a light curtain of 100-150 LEDs (3V, 20mA). It is meant to be used in an event outdoors without mains power. It could be operated with bunch of ordinary batteries and it should operate around two hours.

It would have a main rail without lights and then strips of 10 LEDs hanging down from it.
Any ideas for construction?

Edit: LEDs are simply all on, no controls needed.


texts:
Kind of a random question, but what are the blue wire-clamp-things in the image below called?

I see those everywhere, and I think they'd be awesome to have in a grab bag...


texts: Power for programming an AVR chip on PCB

texts: I am working on a pcb that has an on board AVR microcontroller. I am providing a 6 pin programming header for the chip but I want to be able to program the chip without powering the rest of the board. What is the normal setup for something like this? I am thinking I can throw a Zener Diode on the power line to prevent power to the chip from flowing back onto the board and the rest of the components. During normal operation it is just powered from the power plane. Is this a good setup?


texts: Current Feedback (CFB) operational amplifier

texts:
Here is my task:

Comparator with CFB operational amplifier is shown. It is known Vm=2V and w=314rad/s. Draw time diagram of voltages Vp and Vm, where Vp is voltage on positive input and Vm is voltage on negative input. What is amplitude of voltage Vd=Vp-Vm?
Any idea how to solve this?


texts:
Is there a circuit either passive or not that can transform the value of a resistance with a fixed ratio ?

For example if the input resistance to the circuit is 5000 ohm and the ratio is 50:1 , the output resistance is 100 ohm.

and if the input resistance is 100k ohm , the output is 2k ohm and etc.


texts: What does it mean for a MOSFET to be fabricated in a 0.4nm (or any length) process?

texts:
It was mentioned in a problem where the drain current was supposed to be found with the given parameters. There was channel length modulation. The problem was solved seemingly without taking this 0.4nm into account.
I know it's not the channel length or width because they were given to be different numbers.
I couldn't find what this means after vigorous googling for half an hour, all that comes up is similar problems that also ignore this value.
Edit: If it's the feature size (see 1st comment), which I looked up to find that it's the minimum channel length, how would that affect the operating point? We also used Lmin values in place of L in some problems so they seemed to be the same. What are the cases this value would be used as the channel length to find drain current?


texts: Is there a place to get sample printed circuit boards?

texts: I'm planning on building a project, but it involves me probably using some circuit boards. Most if not all of my parts that I have I got from SamTec, who gives free samples of different kinds of connectors, etc. All in all is there a way to get (free) sample PCB's?


texts: On measuring the common mode gain of an op-amp using a simulator?

texts:
I have been trying for a while now to measure the common voltage gain of the LM741, which according to Op Amps: Design, Application, and Troubleshooting page 21 is around 6, using Multsim and Orcad. The images bellow are from the same reference.

So, in theory, if I realize the circuit above, and set the common input voltage to some value, I should get around 6 times this value at the output. Using Orcad with 1 mV at the input:
I get around 4 V at the output:

Whereas with Multism, for the same values as in Orcad, I get 14 volts at the output, which I believe means the amp is saturated.

Why are all these values so inconsistent with each other? And is it even possible to measure the common gain using a simulator?


texts: Having trouble with a frequency to voltage converter for universal frequency input

texts:
I'm having trouble with a frequency converter. The data sheet is given here.

I set the converter for universal frequency input and voltage output. These can be configured by DIP switches. The diagram from the data sheet is given as below:

And here is how I do the wiring:

I use a 12V power supply, and as an input I couple 0/10V pulse train by using a function generator to the terminals 2 and 3 above. The pulse train is exactly 0..10V and I followed the advice on section 8.7 at page 20 to set the pulse properly.

I checked the DIP configuration too many times and I'm wondering whether my wiring is wrong. Just to make sure here is my DIP config:

For SW1: ON ON OFF OFF ON ON

For SW2: OFF ON OFF OFF OFF ON OFF ON OFF OFF

According to the data-sheet if I configure the DIP switches as above I should get 0 to 5V voltage output mapped from 1Hz to 300Hz frequency input range from a pulse train input.

But I get a constant 17.6V output by the voltmeter whatever the input frequency is, it is constant even though I don't hook up any input. The RED indicator flashes with 2.8Hz which data sheet says(at page 21) it happens when the "Sensor fault or invalid DIP switch configuration".

I spent several hours but no luck. Is the connection from the function generator to the terminals 2 and 3 correct?


texts: How close to ground is close enough for a relay?

texts:
I'm building a simple circuit based on a relay and transistor to switch a fan for use on my boat. A digital pin from an arduino is connected to base of an NPN transistor, the emitter to ground and the collector to the ground pin of the relay. The circuit does not properly switch. However, if I short the emitter to the collector, the circuit functions fine (although not triggered by the pin). I took out a multimeter and the voltage from collector to emitter reads 0.02v. Is this enough to throw off the pin? Why is there any voltage at all?

EDIT: Extra info. 5V relay, 2N3904, pin from micro > 1k > base
                                                        |
                                                       10k Pull down
I do have a protection diode across the coil.


texts: Maximum rotation rate for digital compass

texts:
How well do digital compass ICs (e.g. HMC5843) cope with when rotating rapidly?  If I were to rotate one at 1000 RPM, what kind of signal could I expect to get from it?

Would the measured bearing lag considerably, or would the chip simply be unable to calculate a heading at all?

Added: please note, I'm not asking about the sample rate. That is mentioned in the datasheet for every digital compass. What no data sheet seems to mention is if there is a fundamental bandwidth limit for this magneto-resistive technology.


texts: Possibly unstable output of linear power supply due to very large current amplfication

texts:
I'm designing a linear power supply with an op-amp as error amp and a Sziklai pair as output stage as a hobby project (see schematic below).
I'm worried, that the output Vo will be unstable/unpredictable due to the very large current amplification from the output of U1 to the output of the power supply Vo. Maybe leakage and/or noise currents will be enough the turn the output on.
I have simulated the circuit in Orcad Pspice, and there it works fine, but I fear that it will not in practice.
Has anyone an idea how to remedy the potential problem?


texts: Arduino 16x2 LCD weird symbols after relay-switch

texts:
I am using my arduino to automatically change water of my aquarium. The program runs fine, the pumps, heaters and valves are controlled by relays. When connected to my laptop, I can see via the serial monitor it works and goes trough the program well. But now my LCD gives weird symbols after switching the relais on/off.   I have read quite some questions and answers already about these problems, but no univocal clear answer.

My main question: Can the disturbance also come due to the 'physical' distance from the lcd to the relais?

Let me include the picture of my setup so far (still in testing phase, and I'm not that good at electronics, so maybe you're going to laugh about my setup:

As you can see, the arduino is right above the relais, next to a 24V DC power supply for the valves, and the switch-plugs are connected to the relays. The relays will switch 2 pumps (30W) but also a heating elements of 300W.

My question: Can the weird symbols only be caused by current trough wires like discussed in this topic? Or does the 'physical' distance also cause troubles?

Also:
these relais I thought were Solid State Relais but probably are not, since the same webshop is selling 8-relay board named as Solid State Relais as well:p.
might that give me a solution? Here a link to the schematic of the relays I'm using now: schematic. (Considering that since I saw this comment in the topic linked above):

  Look at the datasheet for the "Relay". The input to the relay is actually driving a tiny SSR, which switches the actual power to the relay itself. Since the input to the relay thingie is a SSR input, I don't see a diode really doing anything

If anyone can help me with this problem would be great, I've already read quite a lot about these problems, but don't understand how to solve it.
If it is fixable with capacitors, resistors or snubbers, please attach a little drawing with it if possible. Thanks for the time everyone!


texts: Were mask ROMs with stock contents ever sold? or why not?

texts:
To clarify: did any of the mask ROM or discrete IC vendors make and sell ROMS (or effective ROMs optimized by giant Karnaugh map) with fixed non-proprietary contents that could be used in building a circuit from stock, in addition to the normal custom ROMs.

A primary application would have been pre computed look-up-tables of really any common single-variable function.

For example:

A 64x8 ROM holding a quarter of a sine wave, or a "256x8" holding the full circle.
A ROM converting integer n to ln(n) and a companion converting fixed-point m to e^m.

There seem to be some 74-series chips that could be interpreted this way according to the listing on Wikipedia.

74408 - 8-bit parity tree
74630-35 - Error detection and correction chips

But these seem to be the exception rather than the rule and are likely to be much more efficient in practice.

If catalog stock ROMs were never sold why weren't they?  What made them a bad fit for applications that could use them but couldn't justify custom silicon?


texts: Can you drive a MOSFET directly from a microcontroller?

texts:
I am trying to build a MOSFET switch circuit.
The MOSFET I am looking to use is FDN327N.
For MOSFET switches, I would add a resistor to limit the initial current rushing into the gate of MOSFET to protect whatever driving it. But for the FDN327N, gate charge is only 4.5nC and I am wondering if the gate resistor makes sense (in my mind it will only slow the switching and does nothing).
Is there any harm for switching the FET that has such a low gate charge directly from the microcontroller?


texts: How to choose flip flop type for implementation?

texts: How to choose flip flop type for implementation in moore or mealy state diagram? I can't understand this thing. Could someone help me? There are t-type, d-type, s-r type, j-k type. How to choose one of best flip flop?


texts: Bluetooth audio stream to commercial headset

texts:
I would to connect my simple audio player (Arduino + https://www.sparkfun.com/products/11125 ) to a Bluetooth headset you can buy at the market.
How can I do ? Is it possible ?


texts:
I have obtained the Karnaugh diagram (pictured below) and now I'm trying to obtain the Boolean expression of K3 through this diagram. My inputs are Q1, Q2 and Q3. I'm trying to "group" 1's and X's together (where the X stands for the don't-care-variable). Now I'm not sure in what way I can group these 1's and X's. Can my groups overlap? Or should they be separate? I know the groups can only be the size of a power of 2.
Here are the options:
Original table:
Option 1:

Option 2:
Option 3:
Can someone explain to me which "boxing" of values I should use to obtain my Boolean expression? Are my boxes allowed to overlap? Maybe there are other options for grouping this diagram?
Any help is appreciated! :)


texts: Level converter usage when Vccb not present

texts:
I'm looking at incorporating a LSF0108 level shifter into a design to convert bidirectional GPIO signals from a 1.8V CPLD (Vcca) to an off-board device via ribbon cable. The header contains a voltage reference at one of several known voltages (1.8V, 2.5V, 3.3V, and 5V possible), which I have connected to Vccb.

The issue I'm running into is the datasheet calls for the enable pin to be connected via pull-up resistor to Vccb. Because there is an offboard connector, Vccb may not always be present when power is applied to Vcca. The suggested layout also calls for a .1uF decoupling capacitor on both the Vcca and Vccb rails. The datasheet also mentions that if either Vcca or Vccb are grounded, then this will also disable translation.

On to my question: how can I ensure that Vcca or Vccb are effectively grounded when a cable isn't attached? Using a pull-down doesn't seem right especially since the enable pin is pulled up when Vccb is present.

(Apologies in advance, I'm a hobbyist trying to step up his game and I'll gladly read any reference you can put in front of me!)


texts: In the bode plot of control systems , how can i calculate the maximum forward path time delay?

texts: i have a question in my last exam in control that i couldn't pass , and here it is in question (d) , any hint of how to do it , the exam is from 100% from 60 , so these two marks will actually contribute to about 5 %.


texts: Cant identify part even if it has numbers on it

texts:
i have this part but i cant find any datasheet about it or what it is , or what can i use for replacement

To me it seems DS3907 HY1MG1  but nothing on the internet not even related

Here is a full image:

Here is the board:

Thank you in advance


texts: Are there any high energy density (i.e. zinc-air or lithium-manganese dioxide) batteries without high internal resistance?

texts:
For my wild life camera, I want a small cell that can provide 0.5W for 8 hours or more. It doesn't seems rechargeable lithium ion batteries have that energy density. I don't mind if the cell is non-rechargeable, so I've considered the lithium coin cells and zinc-air batteries.

But it seems the internal resistance on those are terrible:
For a CR2477, I estimate the resistance at 910 ohms!   Energy density = 2.96 MJ/L

For a 675 hearing aid cell, I estimate 34.7 ohms. Energy density = 6 MJ/L !

So if I use those, there's no way I can draw 0.5W, if at all, without having all the energy consumed by IR? (is IR the only factor causing lower capacity?)

Is this a fundamental limitation to those battery chemistries or can someone point me to cells that allow higher current draw?

According to Wikipedia's energy density page, it claims there are non-rechargeable lithium batteries with an energy density of 4.32 MJ/L. That would be awesome, but where do I find them? (I'm only seeing 2.96 MJ/L for a CR2477 coin cell).


texts: Powering nichrome, possible to do it with AC?

texts:
I am working on making a little nichrome-tipped pen for wax welding and planning to use a benchtop supply to provide the small amounts of DC needed to heat up the wire. Figuring out the right power and voltage requirements is pretty complicated.

Anyway, I was wondering hypothetically if a nichrome wire could be powered with AC electricity instead of DC? If so, I was thinking you could use a step up transformer to reduce the current of line voltage to power the nichrome more efficiently than by using a diode-based conversion to DC.


texts: Custom package in EagleCAD not aligning to grid

texts:
I'm trying to make a custom package in eagle, and somehow the pads of my part got misaligned w.r.t. the grid.

Is there any convenient way to correct for this when it happens?

I know about the cmd+left click for an individual component, is there a way to do something like that for a whole group?


texts:
I've designed a circuit using an MCP73871 (link below) and some lithium ion 18650 cells. I'm confused by the under-voltage lock-out (UVLO) on that chip as it's not clear (to me at least!) whether it stops devices draining the cells when they get too low, or whether it just turns itself off, and therefore requires some other way to cut the current-draw off.

Can anyone throw any light on this, and if I do need a separate low-voltage disconnect, could anyone recommend a solution please?

http://ww1.microchip.com/downloads/en/DeviceDoc/20002090C.pdf

[EDIT] Having  tested the circuit, there's 2mA draw from the "out" pins, when the supply voltage is <2.5V. Should it shut that load off or does that require a separate mosfet and control circuit/IC?

thanks,
Danny


texts: Possible to use a Double Layer Capacitor (SuperCap) instead of Electrolytic?

texts:
I'm working with a 3V/100mA circuit design that requires short but infrequent bursts of nearly 200mA.  A larger power supply is out of the question.

A Capacitor plantation of about 4000uF would cover it, except that there isn't enough physical room (height and area) on the board.

Could I simply use a super-cap like a PAS414HR-VA5R? Or is more components required to manage the super-cap?  Also, would the life time be at least as long as a regular electrolytic cap?


texts: Unclear formula for LED resistor calculation

texts:
On this page:
LED Series Resistor Calculator and Formula

Vs, Vf and If can be filled in and the resistor is calculated.
The formula is even added: R = ((Vs - Vf) / If)

However, when e.g. filling in 5 Vs, 2 Vf, 0.02 If, Resistor is 125

While if I calculate it manually

R = ((5 - 2) / 0.02) = 150

To make it more unclear, when Vs == Vf, it is advised still to use a resistor and it gives a value (which it does), while the formula should give 0 ohm. So I have the idea the resistor value is calculated 'better', but the formula notation is wrong. But what is correct?


texts: Quartz Crystal and Resonance Frequencies

texts:
Let's consider this equivalent electrical model of a crystal:

The evaluation of its series self resonance frequency is quite simple: it is sufficient to impose that the reactance of L1 is equal and opposite to that of C1, and this leads to the result:

But I have some problems about determining the parallel resonance frequency. Precisely, I read this procedure:

From which we get:

But I do not understand the equality of reactances set at this passage:

In fact we are evaluating a parallel resonance frequency, and so we should impose that the susceptances of the two parallel elements, (L1, R1, C1) and (C2), are equal and opposite. And because of the presence of R1, the susceptance of (L1, R1, C1), i.e. its admittance's imaginary part, is not simply equal to the reciprocal of the reactance of L1 and C1.


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The minimum power rating of a zener diode is defined as the maximum power that can be dissipated through it in a given circuit.
Why do we define it in the opposite way? Minimum power rating should be the minimum power dissipated in the diode.
Can anyone please clarify.


texts: Does electric field generated by changing magnetic flux generate an opposing magnetic field?

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According to Faraday's law a changing flux through a loop will create an Electric-field curling around that loop. And if the loop is a conducting wire the current looping will create an opposing magnetic field as below(Lenz):

But what if there is no wire and no current but just the circulating/looping Electric-filed around an imaginary loop? Would that Electric field generate an opposing magnetic filed as well?


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I'm struggling to get my head around induction motors. Specifically, from what I can see the rotating magnetic field created by the 3 phases creates flux lines which sweep across the rotor bars which induces current in the rotor. Right? So why does this need to be AC? I've also read that the alternating current induces current in a rotor.

Basically, what causes the induction? The alternating current or the rotating magnetic field?

Apologies for the noon question but my research suggests that both create induction


texts: Limiting the Current of a Constant Current LED Driver which is Driving a Halogen Bulb

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I am powering a 12V, 35W halogen bulb with a MeanWell HLG-100H-20B constant current power supply. The "B" version of this power supply has a really neat dimming control system which lets one control the output current via a potentiometer, a variable voltage source, or PWM. This MeanWell unit can pump out 4.8A at its maximum setting, which is obviously too much for my 35W, 12V bulb. To reach full brightness on my bulb, I only need roughly 3A (~60% current from the MeanWell unit). Unfortunately, the "B" version of this unit does not have an adjustable maximum output current like the "AB" version does, and the "AB" is not in-stock anywhere.

So, regardless of how I control the output current, I can't let it get past 3A. This is pretty easy to do (I can just limit my PWM pulse duration or pot resistance, etc.), but my fear is that a failure or a goof-up in the control circuit could make the output current higher than 3A. I do have DC fuses to prevent the lights from blowing, but I'd like to avoid replacing fuses as much as possible.

Is there any sort of module method for limiting the current at a specified value? If my PWM source goofs up and the MeanWell unit starts outputting 4A, for example, I'd want something to cap the current going to the lights or fuses at 3A. Perhaps some sort of current divider circuit with a transistor or two to open an additional circuit path?

Thanks in advance for any advice. By the way, I'm a mechanical design engineer with limited electronics experience (if you couldn't tell) so please let me know if I'm spewing nonsense here.

EDIT: I think I figured it out, like 10 minutes after posting this question. See my crappy paint drawing below. Basically, I'll put 6.87 ohms of resistance in parallel with the bulb+fuse. The current division means that when the system is at max power (4.8A) the bulb's path will only experience ~3A. This will scale linearly with output current.


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In what ways can a Hobbyist with Electronics extend the life of a mechanical relay and overall make it safer to use?

Or is it really not worth it as in Damage it going to occur regardless? Maybe using a Capacitor or something to store charge and let it drain out naturally? or is this not really possible using a mechanical relay?

Lets pretend for a moment Solid State Relays are out of the picture.


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I have seen that if we have a thermocouple made up from some metals AB, and we are also able to construct two more thermocouples made up from metals AC and BC, then the emf in thermocouple AB equals \$emf_{AC}-emf_{BC}\$. Why is this?
Also, what would be the resistance in such circuits (like thermocouples with a voltmeter)? I'm confused since the conductors are made up from different materials.


texts: How does the voltage drop to negative values at t = 0 when the voltage starts with 0 V?

texts: I understand that the voltage in the inductor is 0V because it behaves as a wire with a constant dc source while the switch is closed. But why does it drop to a negative value  when the time t = 0 and the switch opens, instead of remaining as zero?


texts: Resistor in series with a Diode conducting conditions

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When having a resistor(R) in series with a diode(D), i keep seeing that in order for the diode to be conducting electricity the voltage on the branch R+D should be higher than the diodes potential.
But what happens to the voltage drop on the resistor, why doesn't it get calculated?