texts:
On a custom board I have an ADC which measures -5V to +5V. And outputs in Hex via SPI like this:

0x8000 to 0x0000 = most negative to 0
0x0000 to 0x7FFF = 0 to most positive

I just started studiyng ADCs so I am not sure what is going on. I beleive I have negative full scale of -5V and positive full scale of +5V.

Questions:

What this numbering system is based on? Is it two's complement?
Why there is no 0xFFFF value?
How can I convert these numbers to a real voltage?


texts:
I'm trying to form an equation for the charge of a capacitor when it's charged through a resistor from a voltage source

The standard equation for a charge is:

$$ Q = V \cdot C \cdot (1 - e^{-t / RC}) $$

But this equation is valid only when V is a constant DC voltage.

How do you go about calculating the charge when V is some function of time, \$V(t)\$?


texts: LTSpice buck converter output voltage too high

texts:
I am designing a 311V to 48V buck converter in LTSpice using ideal components for now.

I am using a 48V/311V = 15.434% duty cycle in V2 which controls S1:

This is the simulation output:

Below is the inductor current and downstream switch voltage at steady-state:

I don't understand why the output voltage is ~52.1V instead of 48V. I tried different SPICE directives for the switch from various tutorials online but I get the same result. I also tried decreasing the max time step to 1u, to no avail.

Any idea why this is happening? Thanks


texts: How do I connect these two parts of solution?

texts:
A differential amplifier is fed in a balanced way with the source resistance Rs which is in series with each base.Show that a mismatch ΔRs between the values of the resistances of the source brings a Vos =(1/2β)*ΔRs

I have drawn the amplifier and solved the exercise up to the point like in the figure.

Now,here I need to find ΔI so then I can find ΔVc=-ΔI*Rc and then Ad=Rc/re and then Vos=ΔVc/Ad

So I know how to solve it.The part I am stuck and where I need your help is finding ΔI.According to the solution manual,the above calculations should result in

But how do I get this?


texts:
I was wondering about the precision of ESC's. Specifically can I ensure their output motor RPM from different ESC/motor pair is the same function of pwm, assuming I have accounted for the specific ESC/motor pair engagement pulse width? Engagement pulse width = the shortest duty cycle which spins the motor.

My controller outputs a signal with pulse width proportional to the desired propeller rate (plus engagement width). But sadly this isn't translating to actual propeller rate. In short om1=om2=om3=om4 does not translate to equal RPMs. My equations are

duty1=(int)((2000-min1)*om1/6000+.5f);

pulsewidth1=min1+duty1;

where duty1 is the additional duty cycle in microseconds, min1 (integer) is the engagement pulse width for ESC1/motor1 in microseconds, om1 (double) is the desired propeller rate (rad/s) and I assume 6000 is the max prop rate in rad/s.
pulsewidth1 is the final duty cycle of signal (500hz) sent to ESC1.

Would appreciate if anyone knows more details about precision of ESC's, or proper calibration, and can share them!

Thanks,

Thomas


texts: What are the purposes of these capacitors?

texts:
My son and I took apart a small electronic toy and were wanting to see the inside. Once we cracked it open I saw this circuit and couldn't figure out what each piece did. I think I understand the purpose of C2 (reducing noise from the motor but I'm unsure about C1 and C3. Thanks!

Note: This is my first time ever making a schematic. It is likely inaccurate.

Secondarily, when I measure voltage near the capacitors (from battery to switch) the readings seem odd. My measurements are in the low mV range and fluctuate. Why is that?
EDIT: I updated the schematic based on feedback. The thought is that C1 is a PTC and my schematic was inaccurate.

simulate this circuit – Schematic created using CircuitLab


texts: Effects of restricting most significant bits

texts:
So i have calculated the settling time for the capacitor C in an RC circuit. The RC circuit is the result of connecting an ADC with a mutiplexer. The ADC is a 12-bit type.

In the assignment information was given in order to fulfill the equation Vc=Vin(1-e^-t/RC) in order to find the time t (t=1164.487 ns).

Now the time is still the parameter that is to be calculated but only 6 of the most significant bits of the result should be taking into account. So i was wondering, what is the effect of just looking at the 6 most significant bits of the result? What factors changes going in to calculating the settling time of the capacitor once more?

Thanks!


texts: I wonder if its possible to run a common 16x2 LCD with 3.3v power supply. Its datasheet shows supply voltage = 5V. Are there any 3.3V variants of 16x2 LCD modules?


texts: What is the difference between usb root hub and usb host controller?

texts:
From the oracle wiki (usb controller):

  The USB host controller has an embedded hub called the root hub. The
  ports that are visible at the system's back panel are the ports of the
  root hub.

What I understand from this is that the root hub merely is a point where all usb hubs come toghether.

-Is the root hub a piece of hardware, or is it a term used to denote the point where all data from usb devices come toghether?

-There are different types of interfaces between the root hub and the controller (UHCI,OHCI,EHCI), is it then correct to think of the controller as a "middleman" between the root hub and the actual computer?


texts:
I am recreating the Adafruit Powerboost 500c Circuit, but I want to reduce the LED's I need down to one. It has four LED's to represent the following signals, next to which I put the desired behavior for my circuit:

BLUE - Power (I don't care about this signal)
RED - Low Battery - The LED should be lit when the battery is Low.
ORANGE - Charging - The LED should be lit when the battery is charging.
GREEN - Fully Charged - The LED should be unlit when the battery is charged.

I am removing the BLUE LED and R5. I am removing the GREEN LED and R7. I want to light a single LED if either the input to the RED LED or the input to the ORANGE LED is high. I wasn't sure if just hooking both inputs to an LED without other circuitry was a good idea so I googled "OR Gate circuit" and discovered three possibilities: a Diode OR Gate, a transistor OR Gate, and an OR Gate IC. If any of these is the best choice, which is it and why? If none is best, then what is?

Note: I asked this question before in an attempt to ask in a "generic as to be helpful to others" way and I was told that I needed to provide more details (among other comments on my poor circuit design that, while helpful, didn't answer my question). I provide more details and the thread was too old to warrant attention and, consquently, I did not get the answer I was looking for. I would delete my old question if I could, as I clearly presented it poorly.


texts:
My question may seem stupid but for a REFRESH operation on a single-rank DDR4 with multiple DRAM devices, how to properly estimate the DRAM power consumption ?

I tried to use Micron Power Calculator and I get a result for the  for one device. I don't know if I should multiply this value by the number of DRAM Devices, I heard of All-bank Refresh where refresh operations seem to be pipelined across banks. How does it work when there are multiple DRAM chips on the same DDR4 bus ? Does each chip start a REFRESH operation at the same time ? Then the total Refresh power consumption equals the value for a single chip multiplied by the number of DRAM Chips ?


texts: How is the voltage across a capacitor measured in a passive LPF circuit with no ground?

texts:
Say we have a low pass filter circuit as the one that follows:

If I want to study how the charging/discharging of the capacitor works, I need to apply the universal equation for voltage. However, this implies that apart from knowing the final voltage that we are trying to reach (10 V in the example), I also need to know the initial voltage drop across the capacitor. Generally, I would say it is 0 V at t = 0, but I realize this is wrong because my Professor said that in this case, it would be -10 V at t = 0. Does this have to do with the fact that there is no ground in the circuit? I am having a hard time visualizing this.

I appreciate any help.


texts: Can I use a capacitor and a transistor to create a circuit which automatically turns off an LED after a period of time?

texts:
I'm extremely new to electronics and I find I learn things better when I have physical examples to examine. I'm trying to understand the way capacitors and transistors work on a practical level, and I thought this might be a good way to get a better understanding.

So, let's say I have this circuit:

Supposing the capacitor is fully discharged when the battery is first connected, would the LED light and then switch off after about 15 seconds? Here's my reasoning, and my (extremely ignorant and naive) expectation of how the circuit will flow:

When the battery is connected, current flows through R1 into C1, charging C1
5RC = 5 * 3000 * 0.001 = 15, so C2 should take 15 seconds to charge up
During that time, current is flowing into the base of T1, allowing current to flow between the collector and emitter, thus powering the LED
When C1 is fully charged, current stops flowing into the base of T1, therefore current stops flowing between the collector and emitter, therefore the LED switches off.

Have I fundamentally misunderstood how capacitors work in DC circuits, and perhaps how transistors work too? If so, how could this circuit be reworked to produce the outcome I'm expecting (i.e, a circuit which uses a capacitor and a transistor to automatically switch off an LED after some period of time)?


texts: Why speed of the wind turbine permanant magnet synchronous generator speed reduces when connected to the load

texts:
I have 100 W vertical axis wind turbine which is mounted on PMSG. And its generated 3 phase voltage is converted to dc using H bridg rectifier. When I connect the load, the turbine speed will reduce. Why it happen
 so?


texts: Solving differential equations numerically using Arduino

texts:
Is it possible to use an Arduino/Arduino Mega or a Maple (STM32 based board) to perform realtime numerical integration using a Runge Kutta algorithm(for simple physics simulations)?

If not would the addition of a FPU coprocessor like the uM-FPU v3.1 make it possible?


texts: I want to use a SSR (AD-SSR6T25-DC-280A) to switch on and off a 24 VAC water solenoid valve. The solenoid has an in-rush current of .9A, with a 400mA holding current. I want to mount the SSR in an enclosed panel without a heat sink or ventilation. My question is this...will the SSR release enough heat to cause extreme temperatures in the panel. I want the inside of the panel to remain at around 70 degrees Fahrenheit.


texts:
I'm making a module where a microcontroller can control RAM with only 10 GPIO pins (8 is data D0 through D7 and 2 are control).

One thing I want to do is that the moment a control line is raised, I want a reset to occur on a 74HC164 shift register if the highest data pin (D7) is set.

At first I was thinking using D7 and the control line as nand gate inputs and the reset as the output, but the problem with that is both lines must stay high, but I can't do that with the GPIO line because I use each state for a different purpose For example, low=accept data, high=shift register contents, low-to-high transition=reset, etc.

Is there something like a simple logic gate where an event can happen only when an input is on its rising or falling edge?

At first I was thinking utilizing a monostable multivibrator, but that involves additional timings which could make my project run slower. Are there other alternatives?


texts:
I'm doing some SMD hand soldering occasionally and am looking for a better way of getting SMD resistors from a strip, so their orientation is upside up and their reading is e.g. from left to right.
I normally just peel off the cover foil, but then the "pile" looks like the picture below.
I thought of removing the foil and use adhesive tape to get them out. Then, the resistors are aligned equally, but upside down, so, not practical.

So, what are ways to get SMD resistors from a strip, such they are upside up and aligned equally?

BTW, to get a clearer picture I showed 1206 resistors, but I mainly use 0603 (Imperial code).


texts: PIC warning 364 related to initialization of const

texts:
There are no answers to this on the internet that I could find, and I've looked twice over the last 4 months.

In MPLab v8.88 using the Hi-Tech ANSI C Compiler, I have this line of code:

const   uint8 SUM_THRESHOLD_MIN = 15;   /* comment edited out   */

and I get the warning:

Warning [364] C:\*directory edited out* \ *filename_edited_out*.c; 273.35 attempt to modify object qualifed const

(excuse the edits, but I felt I should edit out personal yet superfluous details).

It is not my code, and I'd just use a #define, but others want to use a const (for those that don't know: using a const guarantees a proper typecast of a value, and can save you from some weird issues related to typecasting and data types; it's not my favorite way of doing it, but it's not a bad idea either).

There are several const initializations happening in the same block of code, and they all give me this warning.  They are in a .c file, in a void function.  I have other files with void functions where I initialize const uint8's and there are no warnings in those files.  I searched globally, and found no other instance of the variable except where it gets used in the void function (so there aren't any issues with redefining or anything like that).  To be clear, these const's are not part of any structure or anything strange, they are just declared in the void function in the .c file.

I have uint8 properly typedef'd, and not #define'd (see comments).

Can someone help me get rid of this warning?

EDIT:
If I paste one of the const uint8's into another .c file directly after a const uint16 that doesn't throw the error, like this:

const uint16 rate_bias_time_constant[NUM_RATE_CHANNELS][RATE_BIAS_STEP_MAX] =
    {30,120,480,960,  300,120,180,240,  300,120,180,240 }; // comment edited out
const   uint8 SUM_THRESHOLD_MIN = 15;   /* comment edited out   */

I get warning 364 in this file for this const uint8 but not for the const uint16. If I change SUM_THRESHOLD_MIN from a uint8 to a uint16, I still get the warning.  For completeness, if I change it from all uppercase to all lower case, I still get the warning.
If I change the line to, e.g.:

const uint8 SUM_THRESHOLD_MIN[2] = {15,2};  /* comment edited out   */

There is no warning.


texts: Basic question on temperature compensation of resistive bridge circuits

texts:
Many force transducers like this one are made up of Wheatstone bridges and they have sensitivity which relates the force/stimulus change to the voltage change. This small voltage change then is amplified by an instrumentation amplifier.

But I hear sometimes a phrase called "temperature compensation". Is it something done by a circuit in the amplifier or done mechanically in the transducer? I read couple of articles I have some information but I'm not sure I got it what it is all about. The reason is some of people I know talk things like "is the force transducer temperature compensated?" I'm not sure if they know what they talk about so I was trying to learn the meaning of it.

Below figure is from a text:

Is it nonsense to say: "Is this strain gauge(or a Wheatstone bridge sensor) temperature compensated"?

Can compensation only be done by a circuitry in the amplifier stage(not in sensor/Wheatstone/force transducer stage) which both sense the temperature and regulates the sensitivity? How is it done?


texts: Thermostat for induction heater with small coil

texts:
I bought a ZVS 1000w induction heater
I would like to control it with a thermostat in order to control the temperature of my steel piece.
I hold the piece with a clamp and I don't want to put a sensor inside the coil.
what would be other options? Infrared or laser ? coupled with which kind of thermostat? something up to 1100 or 1200° C I guess as I only put small piece of metal in.

Obviously, this is a hobby project so I don't want to spend thousand of dollars


texts: Does this voltage to current amplifier setup work?

texts:
I'm trying to drive a current-controlled load circuit with a higher current than in the initial circuit. As far as I'm aware for the following voltage to current amplifier the load doesn't affect the current through R2. Does this mean the load can be a BJT controlled circuit with its own voltage supply without affecting the current through R2?

simulate this circuit – Schematic created using CircuitLab


texts: Do processor commands and values have binary codes?

texts:
I am working on a diy computer and I am struggling to understand how processors handle information. I would like my diy computer to be able to do the bare minimum, for example calculator, output text. But since I will only be using commands in binary, do I have to come up with my own syntax for command handling. Such as: Data (some binary digits), adress (adress in binary), how to handle the information (binary code for a command)

I'm no expert in computer science, but as far as I understand, each 2 bits have a hexadecimal value and all bits have a decimal value. So if I program my diy cpu to think that say 1001 = add how will I be able to differentiate between that command and the decimal value?


texts: Controller that supports multiple LCDs, ideally up to 5

texts:
Are there any controllers that support multiple LCDs? Ideally I'd like to connect up to 5 LCDs to a single controller. The sort of LCDs I'm mainly interested in are smallish units around 320 x 240 such as this one.

It would be even better if the controller was compatible with the .net Micro Framework but that's not essential.


texts: GET request from ESP-01 client to pushingbox doesn't work - 400 bad request

texts:
I have my ESP-01 connected to a USB-to-TTL converter and I send AT commands through Terminal (by bray).

What I want to do is to put the esp-01 into client mode, then connect to pushingbox and finally send a GET request with my deviceID (API) to pushingbox. Then a notification will come to my android through my newtifry account.

I have tested the pushingbox scenarios from my PC and newtifry notifications comes to my android as expected.
Also when I type the url with my deviceID ( http://api.pushingbox.com/pushingbox?devid=xxxxxxxxxx ) in the address bar it works fine.

BUT when I try to do the same thing with esp-01, when I send the get request I receive a 400 Bad request (Your browser sent an invalid request). I changed the GET request format several times but the same thing happens.

I believe that the GET request I send is incomplete somehow but I cannot figure out what is missing.

Note: Terminal doesn't recognize \r and \n as single byte characters ( so \r\n = 4 bytes ===> one for each character \ r \ n). So the URL string I send is the number of URL characters + 4 bytes for every \r\n in the string.
For example if the URL string is 88 characters (bytes) long with \r\n\r\n in the end I add 8 characters.

Below I display the exact sequence of commands I send every time and also the different versions of the GET request I have tried to send so far with no success.

AT+CWMODE=1
AT+CWJAP="SSID","pswd"
AT+CIPSTART="TCP","api.pushingbox.com",80
AT+CIPMODE=0
AT+CIPSEND= number of characters of the GET request (bytes)

GET /pushingbox?devid=xxxxxxxxxxxxxxxx HTTP/1.1\r\nHost: api.pushingbox.com\r\n\r\n

GET /pushingbox?devid=xxxxxxxxxxxxxxxx HTTP/1.1\r\nHost: api.pushingbox.com\r\nConnection: close\r\n\r\n

GET /pushingbox?devid=xxxxxxxxxxxxxxxx HTTP/1.1\r\nHost: api.pushingbox.com\r\nUser-Agent: ESP8266\r\n\r\n

GET /pushingbox?devid=xxxxxxxxxxxxxxxx HTTP/1.1\r\nHost: api.pushingbox.com\r\nUser-Agent: ESP8266\r\nConnection: close\r\n\r\n

GET /pushingbox?devid=xxxxxxxxxxxxxxxx HTTP/1.1\r\nHost: api.pushingbox.com\r\nUser-Agent: ESP8266\r\nContent-Type: text/html\r\nConnection: close\r\n\r\n

GET /pushingbox?devid=xxxxxxxxxxxxxxxx HTTP/1.0\r\n\r\n


texts:
I designed my first PCB and had it manufactured, but there was no solder mask on the manufactured PCB. Is there a specific setting that i need make in order to enable the solder mask layer? I am using Altium Designer.

Thanks


texts: What is the best way for measuring the temperature for a weatherstation. The temperature would be between about -30°C to 30°C and I would like to have a accuracy of about 0.1°C to 0.5°C. I was thinking about using some Temperature Resistors in parallel but I think I won't get the high accuracy for this. With another temperature sensor like the lm75 there is a too high inaccuracy.


texts:
I've built a UART-RS232 converter based on max232 and it works well... but not for what I need :)

According to Maxim's datasheet the RS232 side signal voltage should be theoretically +/-10v (5v * 2), but in practice it is +/-8v.

This isn't a problem when you use the interface on standard RS232 ports but in my case it simply doesn't work and investigating on the PCB of my device of interest, that exposes a DB9 connector, I've found it isn't a real standard RS232 port but the RX and TX pins are connected, through 2 transistors, to a microprocessor UART interface.

This kind of port works well with the PC RS232 that uses a +/-12v voltage levels so I suspect the max232 output is simply too low for it.

Is there a way to boost up the max232 +/-8v output to +/-12v??
If it's useful I can take 12v from the device.

Edit: What about "combine" two identical RS232 signal (max232 has two converter but I'm actually using only one of them) forming a new signal equal to twice voltage level? Is it possible?

Edit2 - 2013/05/22:
The signal voltage levels don't seem to be the problem just because that device works using a USB-RS232 adapter and in this case the signal levels are about +/-6.5v (at least on my converter).

I drew the interface circuit from the device pcb to better understand what's happening :)

Notice: I don't know if that diode is a zener or not

Then I made some new tests using my breadboard sniffing data directly from the cable.

I found that the RS232-RX part works as expected: if I "stimulate" the device sending data on the RS232-TX not from the max232 but from the PC serial port the device replies as expected on the RS232-RX line and the max232 translates the received signals as expected.

So at this point I need to know in which max232 output line and my PC serial port output line are different. What should I try in your opinion??

Edit3 23/05/2013:
Just to better explain what I'm speaking about...

simulate this circuit – Schematic created using CircuitLab


texts: SSD1306 128x32 OLED Initialization problem

texts:
I'm trying to run the SSD1306 128x32 on a NUCLEO board. But I can't get the thing to properly initialize. This is my initialization sequence.

'''

ssd1306_WriteCommand(0xAE); //display off

ssd1306_WriteCommand(0xA8); //Set MUX Ratio
ssd1306_WriteCommand(0x1F); //sets to 31

ssd1306_WriteCommand(0xD3);//Set display offset
ssd1306_WriteCommand(0x00);//no offset

ssd1306_WriteCommand(0x40 | 0x00);//Memory Start

ssd1306_WriteCommand(0xA0); //column address mapped to 127 //Start left or right

ssd1306_WriteCommand(0xC8); //COM output mode //Start top or bottum

ssd1306_WriteCommand(0xDA); //COM pin hardware configuration
ssd1306_WriteCommand(0x02); //configuration

ssd1306_WriteCommand(0x81); //contrast control
ssd1306_WriteCommand(0x7F); //set to

ssd1306_WriteCommand(0xA4); //Entire Display ON

ssd1306_WriteCommand(0xA6); //Normal/Inverse A7 for inverse

ssd1306_WriteCommand(0xD5); //set oscolation frequency
ssd1306_WriteCommand(0x01); //set to

ssd1306_WriteCommand(0x8D); //set charge pump
ssd1306_WriteCommand(0x14); //enable charge pump

ssd1306_WriteCommand(0xAF); //turn on screen

'''

But whenever I run the this all I get is a bunch of randomly active pixels. Am I missing something?


texts: Why is the output of the precision rectifier 0 when the diode does not conduct?

texts:
From Wikipedia: "When the input voltage is negative, there is a negative voltage on the diode, so it works like an open circuit, no current flows through the load, and the output voltage is zero."

When the diode is off, shouldn't V- be equal to Vin if we are assuming infinite open loop gain? In that case, isn't Vout = Vin instead of 0 when the diode is off?

*** EDIT:
To address some of the comments, open loop gain is the gain when no feedback is used. So even if the diode is off, there is an open loop gain A on the node directly in front of the diode on the output. This of course Doesn't reach Vout, but it's there.

If there is an infinite open loop gain with no feedback, as is the case in the ideal d̶i̶o̶d̶e̶ op amp, then this equation must hold: Vout = A(V+ - V-)

If the open loop gain is infinity, then Vout/A = 0 = V+ - V- --> V+ = V-. If the input resistance is also infinity, then there's no current going into Vout and it should be zero, but it's also Vin by virtue of there being infinite open loop gain.

Edit 3:

I've answered my own question below and removed my answer from the question.


texts: How to mimic the blurring effect of a high speed oscillating tool.

texts:
I been searching for a while for information for this problem and have only realized how lost I am truly am.

For my project I wish to recreate the blurring effect of a high speed oscillation with a motor attached to an arm (video here). How I have achieved this so far is by using a oscillating multi tool like the "Chicago Electric Oscillating Power Tool"

I attached my aluminum arm to the tool and got the effect that inspired this project. The only problem is that the tool is hard to mount down, very aggressive, shakes a considerable amount and makes a lot of noise as a tool without the arm even attached.

What I need help with is figuring out how to select a motor that does what I need and not any more. The motor needs to have the power to oscillate at a high enough speed to blur the object to the human eye. The multi tool oscillates at "21,000" OPM for example. I have considered taking the system an alarm clock uses to oscillate and convert the RPMs of a motor into OPMs.

How would I scale this up for a larger force? What type of motor should I be using? Why do motors get the RPMs they do? How do I start a search for a motor that has the RPMs and the power to do this operation?

To be even pointed in the right direction would be very appreciated.

Thank you


texts: Variable declared in code but doesn't exist in memory

texts:
I declared some variables and matrices globally in PIC16F887A code, but when I simulate that code on Proteus, one of the matrices doesn't exist in the "PIC CPU variables" window, while all the other variables and matrices exist. Why's that?

void burnLEd(unsigned char,unsigned char);
void display();
void find_Dir();
unsigned char matrix[8][8];
unsigned char len=4;
unsigned char max_len=32;
unsigned char btn=6;
unsigned char v_c=1;
unsigned char v_r=0;
unsigned char i=0;
unsigned char j=0;
char pos_c[10];
char pos_r[10];

void main()
{
    TRISB=0;                              //output for matrix rows
    TRISD=0;                              //output for matrix cols
    TRISA=0;                              //output for keypad rows
    TRISC=255;                            //input from kepad cols
    PORTA=255;
    PORTB=255;
    PORTD=0;
//Matrix initial values to zero == all LEDs off
    for(i=0; i<8; i++)
    {        for(j=0; j<8; j++)
             {        matrix[i][j]=0;
             }
    }
//Snake's initial configuration_________________________________________________
//setting its positions
    for(i=0; i<len; i++)
    {        pos_r[i]=7;
             pos_c[i]=3-i;
    }
//putting points onto Matrix
    for(i=0; i<len; i++)
    {        matrix[pos_r[i]][pos_c[i]]=1;
    }
//main LOOP_____________________________________________________________________
    while(1)
    {      find_Dir();
//updating position of the head
           pos_c[0]=pos_c[0]+v_c;
           pos_r[0]=pos_c[0]+v_r;
//checking if snake's beyond the Screen
           if(pos_c[0] > 7)
           {           pos_c[0]=0;
           }
           else if(pos_c[0] < 0)
           {    pos_c[0]=7;
           }
           if(pos_r[0] > 7)
           {           pos_r[0]=0;
           }
           else if(pos_r[0] < 0)
           {    pos_r[0]=7;
           }
//updating rest of the body of snake
           for(i=1; i<len; i++)
           {        pos_c[i]=pos_c[i-1];
                    pos_r[i]=pos_r[i-1];
           }
//putting positions on the Matrix
          matrix[pos_r[0]][pos_c[0]]=1;
          matrix[pos_r[len-1]][pos_c[len-1]]=0;
//Displaying on Matrix
           for(i=0; i<2; i++)
           {        for(j=0; j<2; j++)
                    {        display();
                    }
           }
    }
    while(1);
}

void find_Dir()
{    PORTA=1;
     if(PORTC == 2)
     {       btn=2;
              v_c=0;
              v_r=-1;
              return;
     }
     PORTA=2;
     if(PORTC == 1)
     {        btn=4;
              v_c=-1;
              v_r=0;
              return;
     }
     if(PORTC == 4)
     {        btn=6;
              v_c=1;
              v_r=0;
              return;
     }
     PORTA=4;
     if(PORTC == 2)
     {        btn=8;
              v_c=0;
              v_r=1;
              return;
     }
     PORTA=0;
}

void display()
{   for(i=0; i<8; i++)
     {       for(j=0; j<8; j++)
             {      if(matrix[i][j] == 1)
                    {               burnLED(i,j);
                    }
             }
     }
}

void burnLED(unsigned char row,unsigned char col)         //PORTB=rows,PORTD=cols
{    PORTB=255 ^ (1<<row);
     PORTD=0 | (1<<col);
     Delay_ms(1);
}


texts:
At the creation of a lowpass filter, I did not account the series resistance of the the inductors. Now, of course, the simulation and measured S-Parameters do not fit.

In the pictures the "right_simul"-graph is the simulation with series resistance values added to the inductors.

Now my question is: Is there a way I can still get similiar results like the ones of the simulations without the series resistance values?

EDIT: I used higfrequency indcutors which were winded.

EDIT2: DRC (what should be DCR) -> series resistance


texts: "Working" tri-state MOSFET Push-Pull leakage

texts:
I have been working for a while on this design, where there are 9 push-pulls that should drive a charliplexed LED array. Therefore the circuit must be able to provide three states, namely: HIGH(12V), LOW(GND), and HIGH-Z.
As you can see in the attached image, each MOSFET is individually controlled by two GPIOS. For now, I am doing this with an Arduino MEGA, but later I will do it on my own board with a Ugs=3.3V and keeping the 12V.
Datasheets: DMC2400UV, DMN2990UD

At first instance the circuit fulfilled its purpose, however, there are three effects that I would like to fix for the next batch and I would like to ask you what would be a good approach.

On some occasions when turning on an LED, there is a leakage that makes other LEDs turn on.

My theory is that an NMOS or a PMOS is not completely OFF (HIGH-Z is not achieved), this may be due to a weak pull-up/down, as I consider 47k to be a somewhat high value. It may also be due to a MOSFET that got damaged during reflow or simply it arrived defective.

The fastest on/off frequency is 1ms, which in theory should be totally ok for these transistors (~20ns worst case), however, at all times I could perceive the flickering of the LEDs.

Here I enter unknown territory and excuse my ignorance, but could this be due to a malfunction of the input capacitance of the NMOS and PMOS, which are 37.1pF and 46.1pF respectively, and thus, the lack of a series resistor to the GPIO that limits the gate charge current?

Regarding the "safety clearances", although the maximum conditions in which the MOSFETs will work is 12V@30mA, I consider that the maximum Uds of the DMC2400UV is somewhat close (20V), that is why I am thinking of changing it for the DMG1029SV but I don't know if I am overlooking some feature that makes it incompatible to my implementation. Also the DMN2990 for the DMN2004VK only because rework on SOT-963 has been hell due my hand shakiness.


texts: Difference between simulated and constructed filter

texts:
I recently designed a passive RL ladder filter to obtain certain specifications for anti-aliasing purposes (circuit shown below and simulated in LTSpice). The response I got in LTSpice was very satisfactory.

After constructing on breadboard I measured the response by doing a frequency sweep with persist on in FFT mode on a digital oscilloscope. The response was not at all as expected from the simulation. The cut off frequency measured in the circuit was much higher firstly. This I partly expected due to use of inductors (20% tolerance) and ceramic capacitors (10% tolerance). What I was not expecting was the massive ripple in the pass band region. There was about a 7dB difference between the tallest peak and the trough whereas in simulation the ripple was tiny. The filter ended up being sufficient to stop anti-aliasing (the stop-band attenuation was more important than the cut off frequency for my purposes) and I didn't bother to change it. I'm just wondering if anybody might know what went wrong or maybe on best practice for building RL ladder filters? In general if something works in simulation I expect at least semi-resemblance in practicality so I'd like to know what may have gone wrong for future purposes. What might cause such bad ripple in an RL ladder filter?


texts: Help on finding the polarity of the capacitor

texts:
While heating up my dead graphics card in the oven, one of the capacitors detached from the board. The board itself clearly indicates the location of the positive side. However, I have not encountered this type of capacitor before and am unsure which one of the contacts on it is the positive one.

This is the video card. The positive end is clearly indicated.

And this is the capacitor.

Sorry for low resolution images, I only have access to my webcam. The markings on the capacitor are as follows:

F
7Y2b
331
16

Google search for capacitor markings showed no usable results.

Trying to ignore the possible foolishness of using an oven as a resoldering tool, please advise on determining capacitor polarity. Which contact is the positive one?


texts: solar panel to d.c motor power conversion

texts:
I am using a 50 W solar panel.

So for that what will be the suituable rating of the DC motor to achieve a speed of 3000-3500rpm?

In this case could we use a 250 W and 24 V DC motor?


texts: Can silicone sealant be used to insulate and waterproof electronic components?

texts: Well, can it, when it is in direct contact with the components and circuitry?


texts:
I am using this proportional valve driving circuit:

The valve is 24V, 2W, driven with a 2kHz PWM. I hear an acoustic noise coming from the EMI-Filters L49, L77. I know that the noise is coming from the filters, because when I short them, I do not hear it anymore.
Question 1: does this operation reduce the lifetime of the filters?
Question 2: how to reduce the noise? Do I need the EMI filter, or is some kind of standard ceramic capacitor better? The NFM41PC204 is discontinued anyway, so I need to select something else - what should I take care of? Is there a better filter arrangement in general for this task?


texts: Making aluminium conductive for an RF shield enclosure

texts:
I'm not sure if it's appropriate to ask here, but I would assume many people in electronics would have experience with this.

I'm enclosing an RF sensitive PCB into an sealed aluminium enclosure. Aluminum is chosen because it is lightweight for shipping, and also a good thermal conductor which is required as the enclosure acts as the heatsink.

The big concern however, is that the circuit needs to be grounded to the aluminium enclosure for proper shielding. If the enclosure is not conductive and low impedance GNDed to the PCB then there are problems with internal noise generation from switching circuits being transferred to RF sensitive parts of the circuit.

The PCB slides into a railing and the edges of the PCB have exposed GND rails. Aluminum is not conductive on the surface due to its oxidization effects, and I have no way of applying some sort of pressure or screw to the enclsoure to force conductivity through the oxide layer.

What can be changed however it the coating on the aluminium. From doing research it looks like the coating I require is nickel plating, or tin plating. I've also looked into RoHs safe class 3 chromate conversion, but even this writes that some contact pressure is needed for conduction. Tin plated steel may be an alternative, but is a poor thermal conductor and is much heavier.

Does anyone have experience with conductive aluminum for RF shielded enclosures? What is commonly used? Does tin or nickel plating aluminum cost a lot more?

EDIT: Added an example image of the enclosure and PCB.


texts: How does flyback converter with two MOSFETs work?

texts:
This is the schematic.

Both switches are in phase (On and Off at the same times).
When both SW are On, current flows through primary transformer coil, entering from the top side of it, and leaving through the dotted side, finally going to  the ground through the lower switch. Diode on the secondary does not conduct (reverse biased). Energy is being stored in the magnetizing inductance - an inductor parallel to primary coil of transformer (integrated part of transformer, not shown in the schematic drawing). Output of the converter is energized by output capacitor.

When switches are off, magnetizing inductance provides magnetizing current that enters primary windings of the transformer through the dotted side, and is transferred to the secondary side in such a way that current leaves the dotted side of the secondary, and the diode is forward-biased.

If this is correct, the question arises about the two diodes on the primary side, how do they turn on?
When switches are abruptly turned off, leakage inductance (inductance in series with the transformer), will oppose quick current drop, and will induce a voltage of same polarity as input voltage in order to slow down current decrease. This voltage can be quite large and can damage MOSFETs.
Finally the question: How exactly do those two diodes turn on? MOSFETs are turned off by external gate-driving circuit, and they will instantly go Off (open circuit). Then how will lower diode draw current, from where? Then, where this current goes, where is it dissipated?

Thanks


texts:
I am trying to get two Atmega328ps to talk to each other over RS485 with MAX485 as transceiver. Below is the scope trace of D+ and D-.

Yellow : 485A line,
Cyan : 485B line,
Blue: A - B (Differential)

Here it is a simple transition from 1 to 0, however the waveforms appear corrupted.

Currently the configuration is 9600 8-N-1. There are only 2 nodes and 120 ohm terminating resistors are installed on both ends.
I also added fail safe bias resistors (560 ohm) on one side as per standard suggestions but it did not help.
Currently one node transmits 8 bytes every 500ms and the other reads them and displays them on 7 segment display. Due to this corruption, incorrect values are displayed.

I have tried to simply send data to a PC (through RS485-USB converter) and view that data though PuTTY, RealTerm etc and see nonsense data. I have tried multiple baud rates, odd/even parity without success. Sending data from PC and echoing it back results in garbage data.

Any ideas to solve this issue are greatly appreciated.

Edit: Schematic as requested.


texts: Replacing a piezoelectric speaker with an electromagnetic one

texts:
I'm making this circuit:

(source: vk2zay.net)
where X1 is a piezoelectric speaker or ear piece.
However, the only kinds of speakers I can get in time to finish this project are electromagnetic ones (we found one in a Father's Day card, and another from a radioshack project).
The page here that explains the circuit makes it seem like the piezoelectric speaker is required, but is there a way that I can modify this circuit to use an electromagnetic speaker instead of a piezoelectric one?


texts: Max handling power for a 10w speaker resistor

texts: I have been told that a non-inductive or inductive resistor used for speakers can only handle 10 watts if it is a 10 watt resistor, which makes no sence because they do use even 5 watt resistor in a 160 watt setup. So my question is how do I know how to tell how much they can truly handle before failing or what is the general rule on how much they can use?


texts: How to extend the power and volume buttons on a tablet (Linx 7)?

texts:
I have many times extended pushbuttons for different applications, but this time I need to extend the buttons of a tablet computer for an art installation.

The tablet is a Linx 7 and inside there is a small ribbon cable that connects the three buttons (power, vol+, vol-), which I need to extend (although only power would be enough). It's too small to solder a wire, so I was wondering if anyone knows a good solution. Searching on forums and blogs I just found one person who found a successful way, but it happened that his tablet (Nexus) had another spot where he could solder the power wires.

Is there any kind of small ribbon (10 pin) adapter for PCB soldering? Is there any other option?

Thank you very much for your help, attached are the pictures.


texts:
I have been working on the design of a circuit that can measure a voltage within the range of 25-40 volts.
But I wanted to design a protection stage, since I will use a microcontroller for the ADC and other components.
My idea is to design a good crowbar circuit to activate after 41 ~ 42V.
When I did the research on the crowbar website, I noticed that it is a simple circuit to make and simulate.
I understand that the circuit "activates" when it exceeds the voltage that we have given it. My question is the following: What criteria or what formulas should I use to size the resistors?
I have simulated the circuit and it has not worked. I read in a forum that if I put a switch and activated it simulating the overvoltage input, it worked but nothing so far.

[...] the circuit on the right is working well and does its job. Please don't see that circuit. The only thing I want is to make a protection circuit for overvoltages. For that I searched the Internet and there were several options, some very basic and others more complex, in the end I chose to use CROWBAR. The circuits where the amplifiers that are used as voltage followers are, please do not see them. Those circuits work fine. The only thing I want is a protection circuit, that when it exceeds 40 volts, it makes a short and protects the circuit from overvoltages.
I am going to explain a little so that you understand the schematic, since I uploaded a screenshot of the entire schematic. This schematic is a design of a circuit that I designed to be able to power a microcontroller and at the same time measure the voltage, with the same voltage that is taken from the solar panel. This circuit works very well and gives me the values I need both at the output of the first voltage follower (the one above) with a voltage regulator for the power supply and at the output of the other voltage follower (the one below) to be able to measure with ADC.
I want to protect my circuit using a crowbar. My problem is that I don't know if I'm sizing it right. For this I use a 15 volt zenner diode. So if I want my system to be protected for voltages greater than 40V, what I have to do is say ok 40 Vdc input voltage is equal to the voltage of the zenner diode Vz and the voltage of the resistor Vr. But how do I size the resistance value? Then I solve for the value of the resistance from the equation Vr = 40-15 Vr = 25 .
Now I look for the reverse current of the diode to be able to obtain the ohms of the resistor. The reverse current is 5microAmps. And it gives me that the resistance is 5 Mohm

Figure 1: Circuit Design of my sensor and the crowbar section

Figure 2: Datasheet of the zener diode, I use 15V zener diode

I added an RC filter, but it doesn't work too.

Figure 3: RC filter


texts: Linear regulator drawing power when powered from output only

texts:
I have a microcontroller circuit with a 3.3v linear regulator providing power when run by a 5v supply, the circuit can also be run directly from a 3v battery which connects to the output side of the regulator.

I have found that when powered from the battery the regulator consumes 20mA.

Is there a proper way of designing this type of circuit so that when powered by the battery the linear regulator is isolated and doing nothing?

I am trying to keep the circuit design as low cost as possible so I would like to stick with a cheap 3.3v regulator and change the circuit some other way.

Any advice would be appreciated,
Thanks


texts: Trying to control the feild current of a AC generator with a MOSFET transistor and PWM will this work?

texts:
Trying to help out a fellow vet. He needs a replacement AVR for a 25KVA 60hz generator.

There is a generator output when I flash the field. I am going to monitor the voltage output to control the field. The generator also has 2 CT's and a shunt trip breaker. I am going to use the CT's to monitor for over current to trip the breaker. I am going to use a ATmega328P micro. to control and monitor voltage, current, oil pres., water temp., and RPM. I should say, I am going to try.


texts: Windshield motor with ATX power supply keeps shutting down

texts:
I need to connect my windshield motor (12V) to my ATX power supply from old computer. I've tested the motor on my bench power supply and i draws around 1,5A @ 12V, so it should be well in range of the supply capabilities. But when i power the supply (PS_ON wire to ground) and connect my motor, the supply instantly shuts down.

I think the short protection circuit of the supply may be kicking in, but I'm not quite sure - the motor has very low resistance. ('cause it's a coil)

What do you think? Can adding some capacitors in parallel might help?


texts: Can I use a mosfet as a switch to power arduino?

texts:
I have a project in which I intend to use a NE555 timer to turn the arduino on/off on specific intervals.
I don't want to use the ne555 output directly because of the current limitations of the chip.
I was wondering if I can connect the timer output to a P-channel Mosfet gate and get my output from its drain?

Here is the schematics.The resistor is supposed to be arduino board.

Since there is no way to really simulate this I wanted to be sure before I assemble the circuit so I appreciate if you could point out any possible problems.


texts: Does MOSFET switching gate drive current depend on supply voltage?

texts: I am using a 3-phase MOSFET driver to drive power MOSFETs for a motor controller. When I connect the circuit to a 24V supply (H-bridge supply) and enable the switching at 25 kHz, the driver gets warm. However, when I connect it to a 40V supply (for the final application) the MOSFET driver gets much warmer. Is the driving current supposed to increase with increased supply voltage? I am not sure because the gate-source voltage on the high-side MOSFETs is the same; the driver just needs to supply 40+Vgs to the gate instead of 24+Vgs to the gate. If the gate charge is the same, why would it take more current to drive it at a higher drain voltage?


texts: Should I design with "N" parts or newer parts?

texts: I noticed there are parts with "N" in the part name, for example the 1N4148 diode and the 2N2222 transistor, etc. What is the history of these parts? Where did they come from and why do they have these part numbers? Are they somewhat obsolete, like the discrete digital logic parts? Manufacturers seem to be coming out with new parts, are they necessarily improvements over the old "N" parts?


texts: Mechanical to electric to mechanical.... Power loss to expect

texts:
I have a 3hp lawnmower engine. My engine hypothetical rpm range from 3k to 6k.

If I was to connect it to a generator or motor with similar power rating at similar top rpm, lets say a 2000 watts 6000rpm dc motor.

If 1hp is 0.7kw, would I then be able to directly power four smaller 500 watt motors without having a battery?

Looking at building a AWD go kart where the gas engine rpm regulate the speed..


texts: Why FM stereo uses DSB-SC instead of VSB?

texts:
Using vestigial sideband instead of double sideband supressed carrier could make the baseband stereo signal more compact.

Would there be any other benefits or downsides of employing VSB?


texts: Can i still calculate the \$I_3\$ without transforming norton to thevenin circuit?

texts:
Calculate the \$I_3\$ value,i know i can calculate the \$I_3\$ easily with transforming norton to thevenin circuit and KVL ,and i can know \$I_3=2A\$

simulate this circuit – Schematic created using CircuitLab

However,i ask myself "if i don't want to transform norton to thevenin circuit,can i still calculate the \$I_3\$?" so here is my thinking,however ,i found that i can't calculate the \$I_3=2A\$

simulate this circuit

\$6+2=I_2+I_3 =>8=I_2+I_3\$,so it seems like \$8A\$ current is divided across two parallel resistors,

so i think \$I_2=8\times \frac{4}{(3+2)+4}=3.55\$,and \$3.55=2+I_3\$,so \$I_3\$ should be \$1.55\$.where am i wrong in this method?


texts:
I am currently working on a project that involves 6x NEMA 23 stepper motors, rated at 2.8A - 2.5V each.

I have been doing extensive research on what drivers and power supply I should use. From my knowledge, I have decided to use a 10A, 12V Switching Power Supply, and to use the L298N Stepper motor drivers. I just require confirmation that the parts I have chosen will all work properly together - any guidance would be appreciated.

The data sheet for the Motor: RS Pro Hybrid, Permanent Magnet Stepper Motor 0.9°, 1.26nm, 2.5 V, 2.8 A, 4 Wires

The data sheet for the Driver: L298 DUAL FULL-BRIDGE DRIVER


texts: Medium Range Two Wire Bus Recommendations?

texts:
Do you have any recommendations for a medium range (~10 meters) two-wire bus?
My supply voltage is 24V and I'll have a single master with ~50 slaves connected to it.
I've looked into:

I2C - Great but won't reach that long (Capacity limit, bus buffers might be an option though)
SPI - Not two-wire, but kind of the same deal as I2C
CAN - An option, but this is more of a multi-master bus and probably needs a termination resistor
RS485 - Seems like the best choice so far, could use an UART-RS485 transceiver, but still needs a termination resistor like CAN does


texts: Heating operational amplifier OP284FSZ-REEL7

texts:
Task: to make a square wave with a frequency of 1 kHz in the voltage range (-12V - +12V), using a PWM signal with voltage (0V-5V).

Circuit:

Originally LM258WYDT (ST) was used as an operational amplifier, it did not heat up, but since it was not from the Rail-to-Rail series, there was a 1.5V drop at the output, which did not allow us to give out a voltage close to 12V. So I decided to switch to Rail-to-Rail, for these purposes I found OP284FSZ-REEL7 (AnalogDevices). After replacing with this amplifier, the value of the output voltage became close to 12V (+-11.85V), but the operational amplifier began to heat up (after 5 minutes its temperature was about 45-60 degrees).

I did not find a short circuit, but noticed that at the output of the voltage divider (R1, R2), instead of 2.5V, the voltage became 4.5V. On the LM258WYDT, this voltage was 2.5V. Perhaps there are elements on this input of the operational amplifier that should lift it?

Unfortunately, at the moment I do not have an oscilloscope and I can not see the output signal.

My suspicions:

The amplifier is not designed for such a load or, conversely, it is not enough for it, and it begins to oscillate.
Is this an accurate amplifier, perhaps additional elements are needed for its operation?
The amplifier is damaged.

Parameters of currents from datasheets:

LM258WYDT

Input current: 5mA (DC)
Source output current (Isource): 20-60mA
Output sink current (Isink): 10-20mA

OP284FSZ-REEL7

Supply current: 2.25mA
Output current: 10mA

Question: What could be the reason?


texts: Measuring Noise and Ripple using multimeter

texts: I would like to do a noise and ripple measurement using a simple DMM. Is there a circuit which I can add on to capture the peak-peak noise and ripple, feeding the output into a multimeter ?


texts: ATmega stopped working after changing CKDIV8 fuse

texts:
I have ATmega32U4. I connected it via SPI programmer and in Atmel Studio I have read their signature properly. It was working. Then I cleared and programmed CKDIV8 fuse. Clock was set to internal RC. After that the device stopped responding. No other fuse i have changed. Since that time it don´t respond to any SPI command and also it does not respond to any JTAG command.

Do you know what happened to it and how to fix it?


texts: Heating element as resistor for motor fan assembly in heat gun

texts:
Repairing the heat gun is not an option at this point, but out of curiosity I want to dig deeper into the problem:

There are four wires associated with the heating element assembly, two of which connect with the motor and ventilation fan assembly.

One heat gun pushes air without noise. In this case, the heat gun does not produce substantial heat, but the motor runs at a normal speed and there is no noticeable vibration.

The other heat gun produces heat, but the motor is going so fast my friend labelled it as "broken." The instrument vibrates and the noise is obnoxious. At first I believed there was something wrong with the fan assembly, such as an imbalanced or missing fan blade, but switching the fan parts produces the same result. I believe the faster operation is due to an electrical difference.

Has anyone encountered this before? Maybe the heating element doubles as a resistor for the fan / motor assembly? Lacking the equipment to test for this has left me guessing.


texts:
Im working on a project where I need characterise the noise from a power supply so I can then design some filters. The power supply provides 5V, 12V and -12V to a set of analogue sensors (hence the need to characterise the noise and filter).

I am after some advice on which measurements to perform to get a good understanding of the noise. Initially I was thinking of just probing each power line with an oscilloscope set to AC coupling and then looking at the amplitude of the ripple (power is regulated by a flyback converter so I expect some ripple) and look at the amplitude of any other noise present. After thinking some more I was thinking perhaps using a spectrum analyser may also be useful to look at what frequencies are present so I can make sure I have appropriate filtering.

Does anyone know of any other measurements which would be useful for characterising the noise?


texts: why do I get noise on the output of the LM386 when I connect speaker but not when I connect a resistor?

texts:
I recently made a circuit to test out LM386 audio amplifier for the first time on solderless board. I relied on the datasheet circuit shown below:

First I connected a 7.5ohm resistor at the output instead of a speaker. I get a clean sine wave at the output. The upper wave is the input while the lower wave is the output.

However, when I replace it with this speaker,

the output (and input) seems to become corrupted. Here is the scopeshot:

(1) Why could this be happening?

Besides this I am trying to figure out a few more things.

(2) Why do we have the output connected to ground via a 0.05uF capacitor and a 10ohm resistor in most schematics in the datasheet? What purpose does this serve since this is clearly not a filter.

(3) This is clearly a single supply amplifier topology. However, even if I provide it with a 100mV p-p signal, the negative cycle still shows at the output. How come???

(4) Why is output always capacatively coupled to a speaker? Is it because the DC signal may overheat the speaker?

(5) The bypass pin is used to prevent signal degradation as per the data? It says this pin may grounded or a capacitor used. How do I know which one I should do?

Finally, I made another interesting observation. Initially the output was completely corrupted, it was looking like this:

Then I realized that oh there is noise on the supply rails. When I added a 0.1uF capacitor, the noise went away and the amplifier output became a sine wave (when driving a 7.5ohm resistor). The noise looks like this:

I used AC coupling to be able to look at the noise.
(6) Why does the supply noise above cause the amplifier to completely fail? Somehow without the smoothing capacitor, both input and output become corrupted.


texts:
I'm aware that neon sign transformers (NSTs?) produce high voltage - up to 15kv.  But I cannot picture what's inside of one.  Wikipedia seems to indicate that they may be a form of resonant transformer but provides no diagram.  Googling "resonant transformer" shows images that may be laminated core or toroidal based, close proximity series transformers, but it's hard to tell.

What would a typical NST look like if it was cut open, and would it be possible (not that I want to try) for someone to home-build a HV transformer like a NST?

Note: I'd never trust myself to build one, so that may answer the second part of the question - if I wanted a tesla coil, I'd buy a working NST


texts: How does the primary and secondary voltage of a transformer be in the opposite phase in the vector diagram?

texts:
simulate this circuit – Schematic created using CircuitLab

According to the polarity marking, the input and the output voltage should be in the same phase. I've included a simulation result which also shows that the input and the output have no phase difference.

But while studying the phasor diagram I have found that all phasor diagrams showing that the primary and secondary voltages are in the opposite phase. [N.B. polarity marking is the same as the picture above].


texts: Can I connect TV internal Speakers to 3.5mm plug?

texts: I had 48" broken TV with good speakers. I removed them from mainboard where each comes with 2 pins. Can I connect them to RCA male and then connect to 3.5mm to RCA adapter where I can use it for computer or laptop?


texts: There are a ton of buck converters that can step-down 7.4V to 6V. But looking at their specs, all of them can't seem to handle the typical LiPo high current discharge rate of say 60A. Is there something I am missing?


texts: How can USB Type C be backward compatible with older USB standards, given that they have different number of pins?

texts: USB type C use 24 pins. The older USB standards use 4 pins. The 2 standards are not even electrically and mechanically compatible. How does USB type C achieve backward compatibility with the older USB standards?


texts:
I want to use an H-Bridge module as a switch in a 12V DC circuit and would prefer, if possible, for ease and simplicity, to use a full-bridge gate driver such as the IRS2453DS. The H-Bridge comprises 4 IGBTs, rated for 75A, and the intention is for a very slow switching rate of 4 to 8Hz.
From the H-Bridge switch datasheet, the gate capacitance of these IGBTs is about 4.3nF, and the gate charge 166nC. The saturation voltage is 15V and the Vgs threshold is ~4V. (Gate-Source leakage current 120nA).
Because the switching rate is so slow - on/off periods in the millisecond range - my understanding so far is that the typical 0.26A sink and 0.18A source currents of this specific gate driver are sufficient for the gate capacitance involved. The bootstrap capacitor incorporated is 0.1μF, well above the gate capacitance.
My question then is whether, broadly speaking (if such is even possible in electronics), this full-bridge driver is even anywhere close to appropriate for such an application, and if not, why not? Any guidance would be much appreciated.


texts: Miscalculating the nominal power using nominal current and voltage of a VFD

texts:
A variable frequency drive datasheet has current parameters named as I2N and I2hd. If Im not mistaken these currents are the per line currents for the drive output as follows where I showed in red color below:

If that is correct the following information makes me confused:

For the yellow encircled VFD nominal power PN above is given as 5.5kW.

But if I use the nominal current and voltage I dont calculate the power as 5.5kW. I calculate as:

PN = sqrt(3)x I x U =  1.73 x 11.9A x 380V = 7.8kW

Is that difference because they are also multiplying with an estimate power factor or is 380V line voltage is wrong? Where am I thinking/knowing wrong?


texts: Should I include a JTAG port on my product?

texts: Both my microcontrollers on my project (dsPIC33FJ128GP804 and PIC24FJ64GA004) support JTAG boundary scan testing. Should I wire these up and expose a JTAG port for hackers? The product is intended to be open hardware and as such be modified. ICSP and ICD ports will also be exposed. Of course these ports and traces take up space - so is it worth it? Would people be able to use them with basic PIC micros?


texts: Building a Lightsaber with pretty much on electrical experience

texts:
I bought a third party toy fx style "lightsaber" recently. It only has the light effect which is brilliant. I wanted to add sound to it on a budget so I took the pcb out of an old style toy and wired it in. It works fine, however, the batteries become boiling to touch in under a minute.
The saber, with just the light effect was powered by 3 AA batteries and the   board from the old toy was powered by 3 C cells.
I've now got both the boards (with the wires that went to the bulb on the old board connected to the battery points on the new one) running off 6 AAAs wired from 2 caddies in serial.

So, questions are, why do the batteries feel like they are about to explode? and how do I make sure I'm not damaging the boards with under or over voltage? Any help would be greatly appreciated!


texts: LED driver circuit with both analog and pwm control

texts:
I would like to design an LED driver circuit that allows for simultaneous analog and pwm control. That is, I would like to set the the LED current using an analog signal and then be able to switch using another pwm signal. I have a design with the analog control shown below. Is there a simple way to add the pwm control to this circuit?

I realize that there are numerous high level components that solve this problem but I am using this as a test case to learn basic electronics and would like to solve it using low level components.


texts:
I am building a small controller box based on an Arduino or similar MCU board.

There are upto 6 buttons on the controller.

In regards to ground, can I daisy chain the ground round all switches? Fundamentally it seems to work ok.
For example:
Arduino GND--> Btn1 --> Btn2 --> Btn3 etc.

Or is it better to have a single wire to each button from the Arduino GND pin.

This seems an easy way in terms of less wiring.

The wire is 7/0.2 (24AWG).

What are the pro's and cons here?

Additionally, there are 3 GND pins on the Ardunio, why would you use all 3?


texts:
I have made a clock using the schematic below to run 8 segment displays. There are 6 of them.  All the displays share the same ground, which then goes to the n-MOSFET (bottom right of the schematic), which can dim all the displays via PWM from an Arduino.

I am also using the clock for other purposes.  I noticed that when I illuminate the DP (via the 470 ohm leg of the UDN2981 - Out 8) on any one of the displays, all the displays show faint lighting of their unlit segments. This only occurs when the PWM from the Arduino is low (ie the display is dim), not when the PWM is high(ie display is bright).

I cannot figure out why this would occur, and how to stop it.  Any help would be greatly appreciated.


texts: Arduino's Resolution with Multiple Analog Inputs

texts: Resolution of an analog to digital conversion means the ratio between the maximum value of the measured signal to the number of data point that it can resolve(0-1023). So for Arduino(10-bit) my resolution is 5V/1024=4.88mV. Now I wonder if this value changes when I read voltage from multiple analog inputs. For example if I read analog values from 5 inputs, is this means that my resolution decreases to 5*5V/1024=24mV?


texts:
What would be the resulting voltage in a DC circuit like this:

Where there are three voltage sources, it seems that two are in parallel(20V,5V)
opposing 15V source So would the total voltage be (20V + 5V - 15V?)

Here is the similar circuit but with a load that is at 2 Ohms:

V1 + V2 are together opposing V3 correct?


texts:
My BIOS died (ASUS M2N SLI Deluxe motherboard) on me and I would like to remove it from its place. But I cannot figure out whether it is socketed or soldered. Here is a picture of it: http://i.stack.imgur.com/KjzPm.jpg

(I will not try to desolder, don't have the skills. Hope it is socketed. )


texts: How do I learn-by-practicing digital circuits - MIPS R2000 (or similar) processor or board?

texts:
I already do have a book which I am studying for a university course. I've searched online to buy a development kit for MIPS R2000 (or similar) and have been suggested the MIPS CI20. Don't know if or how that would be suitable for practicing. I would like to get my hands dirty with:

building a simple processor (or at least designing and get it shipped
to me)
understanding how a board is made, how all the pieces are put together and if possible, learn, technically, to remove/add/substitute parts of a board (buying and using equipment for soldering on boards).

Where do I start from? What do I buy first?


texts: Discharging radial electrolytic capacitors

texts:
I'm a beginner/intermediate in electric engineering and had to discharge a few electrolytic capacitors last week in a hobby starter kit (not too high voltage) and now I have to discharge some more caps - but this time they are radial instead of axial - meaning that both leads come out of one end and they're mounted vertially on the pcb board.

How can I access the leads to discharge them? Do I have to get under the pcb board (which has been mounted above another pcb board so I'd have to unscrew a lot of things) - or can I hook one end of a wire (with alligator clips) to the ground, hook a resistor on the other end and touch the capacitor somewhere near its positive side or does the wire absolutely have to come in contact with the positive lead underneath the cap?


texts:
I am designing a system with this module.
I was refering the example circuit as shown below -

.

I am in doubt for the R1 wattage and the purpose of the RL circuit (R1 and L1). What does this circuit do ? Is it a filter ? If yes then what type ?

My system draws about 14Amps, so will the wattage be = 0.3*14*14  ?


texts:
I'm looking to power nichrome wire from battery. The problem I ran into is that desired length/width of the wire has very small resistance ~ 8 Ohm.

Several kinds of batteries I've tested have internal resistance much higher then that, which leads to wire staying cold and battery getting hot.

Is there any way to increase current drawn from the battery? Some kind of amplifier maybe?

Edit:

1.2V(rechargable) and 1.5V one, while not getting hot itself did not provide enough power to heat the wire.
3V did not provide enough power, even stacking 3 of them in series, only provided about 1V of voltage on the wire, and not enough amperage to heat the wire.
9V battery did provide enough amperage to heat the wire, but at the same time got very hot very quickly itself.

PS. I was wondering if https://en.wikipedia.org/wiki/Joule_thief might work for this purpose?


texts: Simplest and chepest way to provide 3.3V@150mA from power supply running at 6Vrms@120mW

texts:
I have a power supply that can provide 6Vrms (50kHz) and 130mW max (maybe a bit more). Unfortunately, for my project I need a peak of 150mA in 3.3Vdc (ESP8266) in regular basis during TX but most of the time the consumption will be limited in order to save power supply.
I heard about supercap and/or battery solution to powerup the circuit but I do not know if it is a valid solution and I would like to keep the circuit as simple/cheapest as possible (and I have limited space/volume) ...
As I have limited knowledge in electronic I need some input from you guys ...


texts: Electric field throughout a semiconductor

texts: Suppose I have a semiconductor bar of length 2mm and I am applying a potential difference of 2V across it. Will the magnitude of electric field be same throughout the bar OR will it be different at different lengths(example different for x=0.5mm and x=1mm) ?


texts:
Rt is thermistor. Rb is bias resistor, which value I need to calculate. The temperature that I'm interested in is giving Rt resistance range of 4k...115k. What I want is to scale this to whole ADC resolution, which is 10 bit ie 0...1023. So when Rt = Rb ADC will convert it to 511. Not sure if it's possible, but ideally I would like to get 0 ADC reading when Rt = 4k and 1023 when Rt = 115k (or the other way).

Internally in MC I have lookup table, which will convert ADC value to temperature, according to curve described in thermistor datasheet.


texts: Does Linux regmap handle repeated start/stop i2c transaction?

texts:
I'm bringing up ADV7610 on Linux Kernel v4.14 on TI AM5728 platform. The Kernel module for this device is failing to successfully probe the device:

[ 4081.446593] adv7604 0-004c: GPIO lookup for consumer reset
[ 4081.446598] adv7604 0-004c: using device tree for GPIO lookup
[ 4081.466818] adv7611 0-004c: Error -121 reading IO Regmap

I've learned that the ADV7610 uses repeated start/stop transfers. This is the raw traffic during driver initialization by reading the 0xEA (hardware ID) which the value is 0x20:

    modprobe-2124  [001] ....  4055.146719: regmap_hw_read_done: 0-004c reg=ea count=1
    modprobe-2131  [001] ....  4081.466725: regmap_hw_read_start: 0-004c reg=ea count=1
    modprobe-2131  [001] ....  4081.466733: i2c_write: i2c-0 #0 a=04c f=0000 l=1 [ea]
    modprobe-2131  [001] ....  4081.466734: i2c_read: i2c-0 #1 a=04c f=0001 l=1
    modprobe-2131  [001] ....  4081.466811: i2c_result: i2c-0 n=0 ret=-121
    modprobe-2131  [001] ....  4081.466814: regmap_hw_read_done: 0-004c reg=ea count=1

You can see above that the driver is not receiving any data (n=0). This also explains why i2cdetect fails to detect the device (it simply writes slave address on the bus in read mode).

On the other hand, i2cget command works because it handles repeated start/stop:

    i2cget-2021  [000] ....   538.751863: i2c_write: i2c-0 #0 a=04c f=0000 l=1 [ea]
    i2cget-2021  [000] ....   538.751867: i2c_read: i2c-0 #1 a=04c f=0001 l=1
    i2cget-2021  [000] ....   538.752202: i2c_reply: i2c-0 #1 a=04c f=0001 l=1 [20]
    i2cget-2021  [000] ....   538.752204: i2c_result: i2c-0 n=2 ret=2

You can see above that the i2c_reply (repeated start) gets sent before reading the correct data back(i2c_result … n=2)  in the next line.

I'm puzzled because I actually do not suspect there is a bug in either the Linux regmap/i2c subsystem or in the driver itself (adv7604.c). However, that doesn't leave much room for error. What might be going on here..?


texts: MAX7219 Arduino Issue with 7 Segment display

texts:
I have followed the tutorial here MAX7219

Now when i wire it up to a 4 Digit 7 Segment display, and run any code changing the display I get all the segments on all digits lit up

#include "LedControl.h" //  need the library
LedControl lc=LedControl(12,11,10,1); // lc is our object
// pin 12 is connected to the MAX7219 pin 1
// pin 11 is connected to the CLK pin 13
// pin 10 is connected to LOAD pin 12
// 1 as we are only using 1 MAX7219
void setup()
{
  // the zero refers to the MAX7219 number, it is zero for 1 chip
  lc.shutdown(0,false);// turn off power saving, enables display
  lc.setIntensity(0,8);// sets brightness (0~15 possible values)
  lc.clearDisplay(0);// clear screen
}
void loop()
{
  lc.setDigit(0,0,'0',false);
  delay(1000);
  lc.setDigit(0,0,'7',false);
  delay(1000);
}

The above code should clear the display so that all segments are off and change the 1st digit to a '0' then a '7' and loop.

No matter how I change the code this does not happen they just all stay lit up, I have even rewired a few times and tried a different IC.

Has anyone had any experience with this setup or these chips. I have read that 2 capacitors between the +5v and GND help so added them 10uF (Electrolytic) and 100nF. No yet still no change.

Any help or ideas would be great, I don't have a logic analyser to debug (Getting one at christmas!).

Thanks, Hughesy


texts: A Counter Which Counts Two Different Sequences

texts:
I have a question which asks me to design a counter which counts two different sequences.
The question goes like this:
Design a counter which counts 0,4,6,8,12,14. When the counter reaches 14, it is going to stop and stay like that for 3 minutes. After this 180 seconds is over, this same counter it is going to start counting like a basic up-counter (0, 1, 2,.....15) (I can design a second counter only for the 180 seconds waiting process).
I have constructed the Truth Table for the two sequences, but I am having a hard time with my Karnaugh Maps. Because sometimes I need to write two outputs for the same cell (a logical 1 and 0). For example while evaluating my J1 input there is both a logical 1 and logical 0 for the 0100 cell. I do not know how I am going to handle them. Can you help me with that? Is there any particular method? (I need to use J-K Flip Flops to design the counter).


texts:
I am trying to build an op-amp circuit for a Hall effect sensor. The Hall effect sensor has an output range of 2.01V to 2.87V, and is fed to the Vin of the op-amp circuit below. The output V_out range is measured to be 3.71V to 0.81V. The 3.71V is largely off from calculations, which should be near 4.8V. The op-amp unit is a MCP602, which should give rail-to-rail output.

Using the same MCP602 op-amp as a comparator, I still get an output of only 3.71V. Swaping the op-amp for a LM358 unit, I still get a maximum output voltage of about 3.70V.
What could be the problem? Is it possible that all the op-amps I purchased are all faulty?


texts:
I need to interface a USB MIDI keyboard to a microcontroller host.
The microcontroller will be receiving MIDI commands from the USB and occasionally sending MIDI commands.

I'm wondering if there are any implementations on popular microcontrollers like STM32, PIC24 / 32, FTDI etc. that already exist.

I found a company called Hobbytronics that used to make such a board based on the PIC24FJ64GB002,

http://www.hobbytronics.co.uk/usb-host-board-v2

so it seems possible to do it, however I can't find additional info regarding the USB MIDI Host stack on Microchip's website.

I won't mind going for a FTDI midi to serial chip if anything like that exists.


texts: How stable are temperature controlled crystal oscillators?

texts:
This question is not as obvious as it might seem. Consider this, concerning Rubidium clocks:

  All commercial rubidium frequency standards operate by disciplining a
  crystal oscillator to the rubidium hyperfine transition...

So at a fixed temperature, and over a few seconds (say 10 seconds), is a regular crystal oscillator stable to part per billion accuracy?


texts: Galvanic Corrosion of Copper, Aluminum, and ENIG Plating

texts:
I need to attach a heat sink to a PCB.  The PCB is a 560 mm x 9 mm strip of LEDs. The LEDs vary from mid-power to high power. I have a pure copper solution for the high power.  I am investigating the lower power end where a 25 mm wide strip would be sufficient for thermal management. The lower end, mid power, is budget sensitive and am experimenting with aluminum extruded heat sinks.

My concern about an aluminum heat sink is galvanic corrosion where aluminum touches copper.  In the first prototype for the pure copper the thermal pad on the PCB were unplated bare copper.

This image shows the pure copper thermal path from the LED's thermal pad to 1/2" copper water pipe.

This is the footprint for another prototype recently fabed.  It shows the copper thermal path from a Cree XP or OSRAM high power LED.  The center pad of the footprint is the LED's thermal pad.  It goes to a copper strip along the edge which gets screwed to either an aluminum bar or copper bar.

With a thinner copper bar I can get the copper bar closer to the LED reducing thermal resistance.

I have new strips with ENIG plating.

HASL plating is not an option
This is using a footprint for an Oslon SSL similar to the KiCad image above.

The next experiment is to try three different aluminum extrusions.

I used the ENIG assuming I can screw either aluminum or copper to ENIG with very little chance of galvanic corrosion but have no idea why I believe that may be true or not. If not, it's still a nice planar surface.

I have purchased 0.062" thick $2.75 6061 T4 aluminum (1.35" wide) and $5.50 C110 copper (1" wide) bars 24" in length.

I am going to assume for this issue that the aluminum will do as well as the copper.

The bars screw to the PCB and the heat sinks screw to the bar.

I assume there will be a problem with a copper bar mating with the aluminum heat sink.  I could use a thermal tape TIM like 3M's 5 mil Thermally Conductive Adhesive Transfer Tapes. Or screw the parts together with a thermal compound.

I could use an aluminum bar screwed to the PCB and there will be no problem with the mating of the bar and heat sink.

The questions:
Will there be a galvanic corrosion issue with the ENIG and copper or aluminum?

Will there be an issue with the copper bar and aluminum heat sink?


texts:
Can someone explain to me how I can change the layout order of my 4 layer board in eagle.

I'm sure this is really a silly question, I'm coming from Kicad so I'm a bit green here.

It's not obvious to me how I would do this

Currently its (1+2*15+16)

Layer 1- GND ||
Layer 2 - Signal 1 ||
Layer 3 - Signal 2 ||
Layer 4 - VCC

But what I need is

Layer 1- Signal 1 ||
Layer 2 - GND ||
Layer 3 - VCC ||
Layer 4 - Signal 2

I'm sure its something simple, but not clear how to do it.

Thanks


texts: Coupling differential line to a single ended daq

texts:
Sorry for the primitive drawing but it was for clarity of the question:

If a differential balanced signal will be conveyed to a single ended inputs of a DAQ, what would be the proper connection?

Following the above illustration, the signal comes from a balanced driver where A and B are inverted. S is the shield of the two core cable. The signal is coupled through XLR. But on the receiver end we only have a single ended receiver or DAQ. In this case how should be the proper coupling there?

A to X is for sure. The rest is not so clear:

B to Y and S floats? Or S to Y and B floats?


texts: Electrochemical Measurements Using Lock-In amplifier

texts:
I'm trying to measure small electrochemical signals using a trans-impedance amplifier fed into a lock-in amplifier.

I have an electrochemical cell that poses a very high impedance (100s of MegaOhms) that I feed a triangle wave into (5V P-P) the excitation frequency ranges from 1Hz to 100kHz.

The current across the cell is amplified with a trans-impedance amplifier with variable gain. One problem is that there is a lot of noise in the measurement, mainly due to the strong RF fields around (due to the experimental setup). I have been RF shielding and passively low pass filtering the output to get rid of some noise, but the output waveform is still very noisy, especially at high gain.

I have a feeling that lock-in amplification might be the solution but I am not sure how to set it up. I have a model 5210, Princeton lock-in amplifier at my disposal. I have tried splitting the driving signal and feeding one end as reference to the lock-in. I then feed the output of the trans-impedance amplifier into input channel A and record the X and Y outputs. With various filter settings and phase adjustments, I wasn't able to recover any signal successfully. The resulting I-V curve from similar experiments look a bit like this:

I'd appreciate any help with setting up the amplifier, am I using it correctly or is this approach fundamentally flawed? I have little understanding of the theory behind the instrument so I'm feeling slightly lost at the moment.


texts: Finding the cutoff frequency of an electrical conduit

texts:
I'm trying to calculate the cutoff frequency of an electrical conduit of 2 cm diameter. (Material of the conduit is not given)

The solution given is

  Lowest mode TE11 mode \$\gamma = \sqrt{(\frac{1.84}{a})^2-\omega^2\mu
 \epsilon} = 0\$ at cutoff gives \$f_c = 87.8\text{ Ghz}\$

I tried using \$a = 0.02, \mu\text{ (free space)} = 4\pi \times 10^{-7}, \epsilon \text{ (free space)} = 8.85 \times 10^{-12}\$ to find \$f_c\$, but the value I got was 4.39 GHz, half of the given value.

What am I doing wrong here?


texts: Nordic Nrf51822. Where to get the clock source for external SPI Slave

texts:
I need to connect an external SPI device . Cannot figure out where do get the Clock source for Nrf51822.
The datasheet says:
"The GPIOs used for each SPI interface line can be chosen from any GPIO on the device and are
independently configurable. This enables great flexibility in device pinout and efficient use of printed circuit
board space and signal routing.
The SPI peripheral supports SPI mode 0, 1, 2, and 3."
But no mention about the clock. Can I reuse somehow the clock reference (crystal) used by the Nrf51822 chip or I need to create an ad-hoc clock reference for slave SPI ?


texts: Can I exceed the rated voltage of a motor if I limit its current?

texts: I have a mini motor that's rated at 3 volts. Does this mean that the 3 is the number of volts that will produce the desired amperage for the motor? Could I technically make it work by plugging it into a 10,000 volt circuit and add resistance until it's at the same amperage as it would be for 3 volts?


texts:
I have designed many boards since graduation in my position as Hardware Engineer, but none of these boards tested its electromagnetic compatibility with the standards.
However in all my designs I have tried to apply all the guidelines for EMC.
I want to know how to be sure of my design that it will take the certification, what are the previous steps before taking the boards to the testing house.


texts: Measure relative position between two IMUs

texts:
I'm trying to create a system where I need to measure the relative orientation of the edge of the arm with respect to its base:

The apparatus will be like in the diagram above. To measure the relative position I'm currently using two 9DoF IMUs - MPU9250 connected to Teensy LC (one at the edge and the other at the base), and using quaternion values.

The requirement of taking the relative position is, this arm can rotate around the base in all directions (except below the base-surface). and the system itself can rotate in any direction. But while rotating, the arm will not change the position, it'll remain in the initial position.
For example, here is another position the system can be:

As shown, the relative orientation of the edge has not changed, based on its base. Also I'm not interested in determining the position/direction of the whole system, just interested in the relative position of the edge with respect to the base.

Here are some more examples:

At the moment I'm using the Madgwick Quaternion update algorithm to calculate the quaternions and use the following equation to calculate the relative orientation:

void quatDiff(float* E, float* rw_B)
{
    float B[] = { rw_B[0], -rw_B[1], -rw_B[2], -rw_B[3]};

    float q00 = (E[0] * B[0] - E[1] * B[1] - E[2] * B[2] - E[3] * B[3]);
    float q11 = (E[0] * B[1] + E[1] * B[0] + E[2] * B[3] - E[3] * B[2]);
    float q22 = (E[0] * B[2] - E[1] * B[3] + E[2] * B[0] + E[3] * B[1]);
    float q33 = (E[0] * B[3] + E[1] * B[2] - E[2] * B[1] + E[3] * B[0]);
}

E and rw_B are the quaternions return from two IMUs (edge and base).

My questions are:
Is this method a reliable and a valid method to calculate the relative quaternion orientation of two IMUs.
If so, is this equation is correct for comparing values.


texts:
I am trying to connect the O/P from TCXO (FOX Electronics FOX924B. 20 MHz, 2.5 PPM, 3.3 V supply, Output HCMOS VOL = 0.5 V and VOH = 80% of VDD) to 74HC240 buffer, which I am also running at 3.3 V.
I am not getting anything at the output of the buffer. But as per the datasheet of 74HC240 from Motorola, it is capable of running at 3.3 V. Where I am making the mistake? I will provide any further data, circuit diagram if required.


texts: How can i measure voltages on each phases of a 3 phase system, Using a microcontoller?

texts:
How can i measure voltages on each phases of a 3 phase system. The measurement is to be processed by a microcontroller.

Is there any special chips available, or do i need to use the ordinary Transformer-->ADC technique??


texts: direct digital synthesis low pass filter

texts:
I am designing a sine wave generator using a dds chip (ad9833).  The system parameters are:

frequency range of 1-12 MHz
spurs and harmonics down to -50 dBc
Output power atleast 10 dBm

Since the frequency is changing, the low pass filter cutoff has to be adjustable.  My first thought was to have a mosfet controlled capacitor bank, but the capacitances of the transistor are limiting the range of the cutoff.  I have also tried varactors but I am having trouble simulating them in LTSpice.  I would like for this circuit to be an LC filter.  Last resort is to have different filters for different key frequencies, like 1 MHz, 2 MHz, 4 MHz, 8 MHz, 16 MHz, but how would I switch between filters using a microcontroller?


texts: How can I use a voltage to control the pulse width of a 555?

texts:
I have a variable PWM signal at 13.2 kHz. I want to control a servo with this signal, but the servo needs a much lower frequency, at most 80 Hz. My first idea was to use two binary counters, a NOT gate, and an AND gate. That should do the trick, but it's definitely not the best solution. It requires a lot of ICs with a lot of unused pins. Also, the servo is looking at a pulse about 1-2ms wide, not a full PWM, so only about 8% of the PWM range would be useful.

Using an RC filter, I can just convert the original signal to an analog voltage. Is there any way I can use this analog voltage to control a 555 to get the signal I need?

My only experience with the 555 is using a pot to adjust the duty cycle.


texts:
I am confused why many books and sites call normalized parasitic delay as " ratio of diffusion capacitance to gate capacitance in a particular process" .

According to me its delay of gate when it drives no load and a crude method for its calculation  is to count diffusion capacitance on output node and divide by 3 which is that of standard inverter. So how is that definition equivalent? I' m posting a photo of book page also which states the same:


texts: Need help understanding the concept of "Circuit model of a discharging RL circuit"

texts: I don't understand the statements for t<0 and t>0. Why does this happen?


texts: Which are main purposes of bipolar transistors?

texts: In school, we learned a lot about transistors but I still don't get its point. I understand gain and amplification of voltage or current or both, but I don't get it how can it be used for example as a switch. I really want to understand transistors because of their widely use. At least someone recommend any good book about transistors.


texts: Programming PIC with PICkit3 - do I need enabled MCLR?

texts:
I'm working with PIC12F629. It has 8 pins (6 for I/O). I need to use MCLR pin as input pin (for a button), so I have to disable MCLR (I guess).

After first programming I want to be able to program microcontroller again.

Datasheet says, that PIC12F629 supports:

  "In-Circuit Serial ProgrammingTM (ICSPTM) via two pins"

I know, that there are LVP and HVP programming modes in PIC microcontrollers, and I probably have to use LVP, however I'm PIC newbie and I don't know if PicKit will just work with MCLR disconnected, or do I have to do something etc.

My question is:

How do I program PIC12F629 with PicKit3 when I need all 6 I/O pins (including MCLR)?


texts:
I am building a large  garden peice in wood, which I hope to illumine from within, powered by a small, (perhaps 90x65, 6v, 0.6w 100mA as space is limited) solar panel.
After testing, I noticed that this small power supply is insuficient to even enable a charge controller, let alone charge the USB (1x18650 battery) power stick, I suspect that the current is too low to "wake up" the charge controller?

Whilst considering smaller batteries, or replacing charge controller with a diode, I had a "capacitor" moment, and wondered whether this could be an alternative, if even even better solution?

The ultimate goal is to be able to maintain enough charge during the day to illuminate an LED of any colour (pure white requires a lot more power and pale yellow is more than adequate tho I can use any colours which are more efficient, but I need two of high contrast). I have a photoresistor switch which will also take a little power from the solar panel.
Furthermore... I wondered if a combo cap/battery might work well?

My guess is that this is essentially  the same circuit used by a solar garden path/accent light... space within the item is not an issue, only the location for the solar collector mounted on the smallest, topmost panel of the assembly, approx 100mm dia.

My reseach so far indicates that a 6v 1F cap can light 12ohm LED for approx 8 hours, but I need far more understanding to know if this calculation is correct, and am very unsure about the resitance of the LED

Any help would be great?


texts:
Normally shared frequency analogue1 radios (CB, aviation, etc.) can't receive when transmitting, because the signal being transmitted is much louder and will jam any signal from different transmitter.

Is it possible to somehow subtract the transmitted signal to be able to pick out signals from other transmitters even when transmitting? Is there any published design that allows receiving while transmitting or at least detecting that there is another transmission in progress?

1 Or digital, but with short packets collisions are less disruptive and there are other ways around the problem like slot allocation.


texts: I would like to ask if my answer to this simple circuit is correct?

texts: The problem is to find the values of \$ V_x \$ and \$ i_3 \$. I was reviewing DC using KVL and KCL and I would like to check if I got the answers right!


texts: How to reduce VOC of solar panels to match the MPPT of inverter

texts:
I will have an off grid solar panel system to run my deep well 5,5 Hp water pump. I already got 24 of 250Wp 36,3 Voc panels and 3 phase Delta VFD C2000 inverter/driver. for this system I need to wire all the panels in serial to get 540-800 Voc for pump driver. This part is ok.
I want to use another 5KVA inverter with some batteries to run devices (Tv, Fridge, ...) in a small village house and 1-2 Hp small 230v motors for spraying (only during the day). I already have 24 panels for waterpump and I want to use those panels when I don't need water. However inverter can take up to 90 Voc 50 amps to charge 48V batteries. I can use some relays and make few parallel panel until 50 amp, but this system might be risky in the case of a relay fault.
If it is possible I want to reduce high Voc to match 90 Vmax 50 amps inverter input for solar panels.
Efficiency of dc to dc conversion is not and issue since I will have plenty of panels waiting all day for nothing.
Can you please give me and idea how can I do this with low budget?


texts: Difference between Net metering, Feed-in tariff and power purchase agreement

texts: I have been reading on wikipedia about the 3 different kinds of compensations, when it comes to renewable energy, however, the 3 types of compensation seem identical to me. If I have produced excess energy, I would feed it in the power grid and get compensated for this. So what is the difference between the 3 methods (if there is any at all)?


texts: I know that real power is the power consumed by the circuit. But what about average power? Are they the same?


texts: What does the hole size and diameter of a via means in Altium? What do they actually represent?

texts:
For my school project, I am designing a small PCB. For routing the signals I need to use a via. There will be around 500mA current flowing through the via. I am using 0.5mm traces to route the signals. At present, I have selected 0.75mm hole size and 1.35mm diameter for the via. Are these values okay? It might be a silly question but if someone could kindly explain to me what these two values actually represent and what's their significance?
Thank you
Hello, thank you very much for your reply. it was really helpful. I have a two-layer board and I have 35um copper both on the top and bottom layer.  Regarding the plating thickness, isn't the bottleneck here the thickness of the copper within the via hole? I performed a check in the website:
http://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/ .
I am attaching a screenshot here:

Here I have assumed the plating thickness to be 10um(very small) and it shows me the via has an estimated Ampacity of 1.74 amps. I might be missing something here and also my assumption of the plating thickness has been done by checking some other articles here in StackExchange. I would b highly glad if someone could kindly clarify if my estimation is correct.
Thank you again.


texts: 4 layer board back bypass capacitor power plane connection guideline reason

texts:
I'm reading Power Bus Decoupling Guidelines for Printed Circuit Boards with Widely Spaced Power Distribution Planes.

And they have these recommended connection configurations for bypass capacitors placement relative to the bypassed component:

The first case where both the component and the capacitor are on the same side I think I understand why the component's and capacitor's connections to power plane 2 are closely spaced. This should be to minimize the inductance of the component's power pin's connection to the bypass capacitor. And this low inductance is important for supplying the component's internal as well as I/O current surge demands.

But I'm not getting the reasoning for the second case with the component and capacitor on the opposite sides of the board. Why is this different connection configuration needed? It seems this adds extra distance for the currents to travel increasing inductance. Why wouldn't one connect the adjacent pins of the capacitor and component to the same power plane?


texts: STM32F103 - CubeMX - Timer and Interrupt

texts:
I have a program which sets the TIMER1 on the STM32F103 as Output Compare no Output.

In the main.c I have a simple variable, which I set to 1, and in the interrupt handler of TIM1 I have set it up so that variable is 2. In main, I also send the value of the said variable every one second.

All I get on UART is "1111", so the interrupt is never called. Why is that?

main.c:

uint16_t testPixel = 1;
uint8_t myChar[5];
[...]
HAL_TIM_OC_MspInit(&htim1);
[...]
 while (1)
  {
    itoa(testPixel, myChar, 10);
    HAL_UART_Transmit(&huart1,myChar,sizeof(myChar),10);
    HAL_Delay(1000);
  }

TIM1 set-up generated by CubeMX

static void MX_TIM1_Init(void)
{

  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;
  TIM_BreakDeadTimeConfigTypeDef sBreakDeadTimeConfig;

  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 0;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 80-1;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  if (HAL_TIM_OC_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }

  sConfigOC.OCMode = TIM_OCMODE_TIMING;
  sConfigOC.Pulse = 10;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCNPolarity = TIM_OCNPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  sConfigOC.OCIdleState = TIM_OCIDLESTATE_RESET;
  sConfigOC.OCNIdleState = TIM_OCNIDLESTATE_RESET;
  if (HAL_TIM_OC_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }

  sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_DISABLE;
  sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_DISABLE;
  sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_OFF;
  sBreakDeadTimeConfig.DeadTime = 0;
  sBreakDeadTimeConfig.BreakState = TIM_BREAK_DISABLE;
  sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
  sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_DISABLE;
  if (HAL_TIMEx_ConfigBreakDeadTime(&htim1, &sBreakDeadTimeConfig) != HAL_OK)
  {
    Error_Handler();
  }

}

stm32f1xx_it.c:

extern testPixel;
[...]
void TIM1_UP_IRQHandler(void)
{
  testPixel = 2;
  HAL_TIM_IRQHandler(&htim1);

}

Thank you!


texts: Capacitor across an ideal current source

texts:
How long will the capacitor below charge? Given that both the current source and capacitor are ideal.

If someone says the capacitor will be charging up to its capacity, what is the capacity of this capacitor?

simulate this circuit – Schematic created using CircuitLab


texts: How to Calculate Saturation Current of a Transformer?

texts:
Is this Method applicable to calculate?
My confusion is mainly regarding with Load current.
My knowledge is, that load current is nothing to do with saturation of transformer.


texts:
General question: Is the charge circuit/protection circuit the same for a 14500 and 18650 cell?
(I assume so because of the same nominal voltage, but wanted to make sure)
My specific case:
https://www.waveshare.com/wiki/Solar_Power_Manager <- This charge circuit is for 14500 cells, but could i use it to charge 18650 cells with a different batteryholder?