texts: How was this equation for finding current written?

texts:
It doesn't make any sense because at \$t\gt 0\$ the two circuits are disconnected (the left and right portion).

How has \$25 i_x\over 20\$ been calculated?


texts:
In circuit b there is a Zener, LED and transistor the voltage of base I assume is 12 V - 6.2 V = 5.8 V so I guess Ve is Vb - Vbe = 5.8 V - 0.7 V = 5.1 V but I can't guess the current which is passing the LED.
Then can I guess the voltage of 200 Ω?

Example: 6.2 - 0.7 = 5.5.

How can I solve it?


texts: Do stator windings on a permanent-magnet synchronous three-phase ac motor have sinusoidal distributions?

texts:
In motor-drives textbooks (e.g Ned Mohan's Electric Motor Drives), the text states that the stator windings on ac machines (e.g. PMAC three-phase motors and induction machines) are, in theory, sinusoidally distributed in the air gap. That is, the conductor density as a function of the mechanical angle (for a two-pole motor) can be written
$$ n_s(\theta)=\frac{N_s}{2} \sin(\theta) $$
where \$N_s\$ is the number of turns. This is not possible in practice due to the slots, but it is approximated.

Is this true for modern PMAC motors ? If we consider one of the three phases, are there more conductors per angle at 90 and 270 degree angles from the magnetic axis than there are at f.ex 60 and 120 degrees ? I tried to find photos, but could not so easily see this...


texts: Can I replace watch quartz with DS3231 32 kHz output?

texts:
I'd like to know if it's possible to synchronize classical quartz clock by replacing inbuilt quartz crystal with DS3231's 32 kHz output. I need to synchronize my analog watch with RTC DS3231.

Am I supposed to simply remove quartz crystal and conenct DS3231 output? There are two wires coming from the watch IC, the crystal is connected between them. I think one is XTAL1 and the other one XTAL2, but which is which?
I wonder is it even possible?

I heard it's about connecting 32 kHz output to XTAL1, so "2?" and frequency corrector are not connected then? I'm clueless.


texts: KiCAD - Moving and rotating components with wires connected

texts:
I'm a major major noob to KiCAD and having done a couple of tuts in Eagle, I do like the separation of footprints from the schema.

But one thing that took me by surprise is that the wire connections don't stay connected or become weird angled if I move or rotate the components.

I know I can move the components with G or right-clicking and selecting Drag to retain the wiring, but it no longer stays at right angles and starts going in every direction. Is there any way to avoid that?

Secondly, is there any way to rotate the component while maintaining the wire connections?


texts: Power Key Design for Variable Voltage Power Supply

texts:
I am trying to design a circuit with 2 different contours:

Controlling contour: a STM microcontroller powered by a 3V battery.
Power contour - a variable voltage power supply (1.23V - 20V, up to 5A) powered by a AC-DC laptop converter.

The microcontroller should be able to close and open the power circuit. It should be relatively fast (up to dozens/a few hundred milliseconds) and should not drain the battery too fast.

I assume I have to use a combination of an optocoupler (which has a low power consumption) with a transistor:
I came up with a simple design which, however, would not work, due to the variable voltage in the power contour.

What would be a better design for such a power key?


texts: Configuration Settings of 18F4550 in a header file

texts:
Recently I was wondering if is there any option to move my Configuration bits to a header file?.
right now I'm using the 18f4550 microcontroller,with mplabx IDE,and my developed code entirely is in one principal file called main.c,in order to improve the debugging process with my code,I would like to receive any advice for structure code development.
I've tested with something like this but I can not reproduce it in my mplabx.

#include < stdio.h>
#include < delays.h>
#include < p18f4550.h>
#include < timers.h>
#include < xlcd.h>

#pragma config PLLDIV = 5       // (CRISTAL DE 20 MHz),Divide by 5 (20 MHz oscillator input)
#pragma config USBDIV = 2       //USB clock source comes from the 96 MHz PLL divided by 2
#pragma config CPUDIV=OSC1_PLL2 //Primary Oscillator Src/1][96 MHz PLL Src/2]  cpu trabajara a 48Mhz.
#pragma config FOSC = HSPLL_HS  //HS oscillator, PLL enabled (HSPLL)
#pragma config FCMEN = OFF      //Fail-Safe Clock Monitor disabled
#pragma config IESO = OFF       //Oscillator Switchover mode disabled
#pragma config PWRT = ON        //Power-up Timer Enable bit
#pragma config BOR = OFF        //Brown-out Reset Enable bits: Brown-out Reset
                                //enabled in hardware only (SBOREN is disabled)
#pragma config BORV = 0         //Brown-out Reset Voltage bits,Maximum.
#pragma config VREGEN = ON      // USB voltage regulator enabled
#pragma config WDT = OFF        //WDT disabled (control is placed on the SWDTEN bit)
#pragma config WDTPS = 32768    //Watchdog Timer Postscale Select bits>> 1:32768
#pragma config MCLRE = ON       //MCLR pin enabled; RE3 input pin disabled
#pragma config LPT1OSC = OFF    //Timer1 configured for higher power operation
#pragma config PBADEN = OFF     //PORTB<4:0> pins are configured as digital I/O on Reset
                                //If i need to use the RBx as analog in/out set this bit to ON
#pragma config STVREN = OFF     //Stack full/underflow will not cause Reset
#pragma config LVP = OFF        //PROGRAMACION EN BAJO VOLTAJE
#pragma config XINST = OFF      // Instruction set extension and Indexed Addressing mode enabled
                                //the above bit is used  enterely for debug program in circuit (ICPORT)
#pragma config CP0 = OFF        //Code Protection bit disable for 0,1,2
#pragma config CP1 = OFF        //
#pragma config CP2 = OFF        //
#pragma config CPB = OFF        //Boot Block Code Protection bit:
#pragma config CPD = OFF        //Data EEPROM Code Protection bit.
#pragma config WRT0 = OFF       //Write Protection bit for 0,1,2 is not write-protected
#pragma config WRT1 = OFF
#pragma config WRT2 = OFF
#pragma config WRTB = OFF       //PROTECCI?N DE ESCRITURA PARA EL BLOCK DE BOOT
#pragma config WRTC = OFF       //Configuration Register Write Protection bit,disable
#pragma config WRTD = OFF       //Data EEPROM Write Protection bit,is not write protected
#pragma config EBTR0 = OFF      //000800-001FFFh
#pragma config EBTR1 = OFF      //Boot Block Table Read Protection bit,disable between
#pragma config EBTRB = OFF      //000000-0007FFh and 002000-003FFFh
#pragma config CCP2MX = OFF
#pragma config DEBUG = ON       //ENABLE FOR PICKIT 3
#define hola=3;

void main(void){
..code
}

After do this I might have something like this

#include < stdio.h>
#include < delays.h>
#include < p18f4550.h>
#include < timers.h>
#include < xlcd.h>
#include < bits.h> // or something like that
#define hola=3;

void main(void){
..code
}

Any advice or suggestion will be ok.


texts: Two audio sources, one default and one 3.5mm audio jack, one output

texts:
I hope this is the correct forum for this question, I don't have a background as a electrical engineer, just a hobby.

I have a problem that I can't figure out. I have two audio sources, one default and one 3.5mm mono audio jack. The plan is to use the default source as long as a cable isn't connected to the audio jack. The audio jack has three pins; ground, audio, and a pin that is connected to the middle pin as long as a cable isn't inserted in the audio jack. I plan to use a Raspberry Pi as the micro controller for the project and the Pi is the default audio source.

I might have misunderstood the mono jacks pins, see image below.


texts: Which equipment is required to test the no radio device for compliance with electromagnetic compatibility (EMC)?

texts:
I am designing a device that has no intention to transmit or receive any radio waves but it has CPU, large PWM driven LED indicators so may be some higher frequencies inside. To make sure we pass the EMC easily and without "iterations", I would like to test it (at least approximately) by our own engineers. We would like to know how exactly the measuring device is named so we could purchase it and what are the minimal specs for it. I tried to google that, there is a big variety of them and some are horribly expensive. Do I need exactly spectrum analyzer when analyzing the spectrum may not be my requirement?
What is the minimal required equipment for this task and how this could be done?


texts: D Flip Flop Toggle -- Q into Hex Inverter into D, Unstable Output, Help

texts:
simulate this circuit – Schematic created using CircuitLab

I created the above circuit.  There is essentially a switch that is normally high.  I press a button.  Using a NTE4049T hex inverter, I create a low to high edge transition.  This provides the clk input to a 74HCT175 D flip flop.  Everything is run at TTL, 5 Volts.  The output of the D flip flop is fed into another NTE4049T hex inverter to then feed the D input of the flip flop.

Ideally, when the button is pressed, I would create a toggle of the Q output line.

This does not happen.  In fact, there is some oscillation at the signal output, but no finite transition of state.

I realize that this is a result of continuous toggling/bad design.  How is this problem solved?  If I chained the output of the D flip flop into another flip flop, also clocked to the same edge, to then generate an inverted output for the first flip flop, would that solve the state oscillations?  Could I pass the output through a series of buffers to create a time delay?

The first pic is the waveform of the switch with the rc network.  There is an instaneous drop when the switch is depressed.  This drop, through an inverter, is what causes my clk signal to go high.

The pictures below show a high level view of the Q signal output as well as a zoomed in image at the tail where the Q signal then goes back low.  I believe in this tail section the capacitor is charging.  I'm not sure why it would cause the d flip flop to again trigger.  There should not be a rising edge?

The light blue line represents the clock transition signal on the flip flop.
The yellow line represents the D signal being fed into the flip flop.
The dark blue line represents the Q signal of the flip flop, just before going into the inverter.  The inverted output will again feed the flip flop a D.

How is a problem like this solved in practice if I cannot solve it in the above design?  Thanks


texts:
I have 8 chips of 512 Mb DDR3 interfaced with the processor with point to point Data & fly by Address/command topology.

I need to remove 1 DDR3 & keep it unmount. The rest 7 DDRs should work normally. Which DDR chip, I should remove from communication or signal Integrity prospective.


texts: Bigger resistors in place of a level shifter on a SD reader?

texts:
This item, a MMC/SD card reader module with 3V3 LDO and 10k pull-ups, has a schematic with an interesting tidbit in a big red box:

  Change R3, R4, R5, R6 resistance [from 2R7] to 330-470 [ohms], [then] you can use [it in a] 5V system

How can this be true? Is it wishful thinking, some part of the MMC/SD standard I don't know about, or something completely different?


texts: Stepper motor current specifications - 12V/350mA, but draws more at lower speeds?

texts:
I have on hand a simple 12V/350mA stepper motor

the datasheet is lacking, so I can only assume 12V is the maximum sustained voltage and 350mA is again, the maximum associated current. The datasheet also lists the winding resistances as 35 Ohms, which I have verified.

What I found is that while driving the stepper at a rate of about 0.5 revolutions per second that it would draw 350mA at 12V. However, if I were to decrease or increase the speed of rotation, the motor would draw more or less current, respectively. Why is this? I am planning on testing this later today, but is it then necessary to drive the motor at a lower voltage to abide by the current constraints?

In summary for 12V supply:

0.25 rev/sec => 450mA

0.5 rev/sec => 350mA

3 rev/sec => 150mA


texts: Alternator and voltage regulator recommendation(s) for antique engine based 12V power source

texts:
What would be good hardware to provide 12V DC for battery bank charging driven by an antique stationary engine that does not run at a steady RPM?

These old engines can run on practically any liquid that will burn but it's very difficult to get one to run at a steady pace.  I have a 7HP engine that runs at a couple of hundred rpm.  Torque output is massive due to a very long stroke so it can be geared up to run an alternator or generator at a much higher RPM.


texts: Analog power pins vs Digital power pins on chips

texts:
We usually have digital & analog power/voltage pins on our ICs. Analog power most probably for PLLs etc & Digital Power for Core. So, my questions are :-

The different Analog & Digital power pins are just to avoid noise from one to another?
We can generate a Voltage from DC-DC converter & provide to wither Digital or Analog Voltage Pin?
Is there any difference in Analog and Digital Voltage supplies practically?
Can I provide same Voltage source to Analog as well as Digital Pin (Assuming I need 1.8V Digital & 1.8V Analog)


texts: Why is resistance increasing while I'm measuring using a multimeter?

texts:
I have two copper strips with a one-megaohm resistor between them. That makes the resistance between the two strips 1 M ohm. I am measuring resistance between two copper strips using a multimeter.

With this arrangement, the reading on the multimeter shows 985 K ohm.

Now I put one water drop in between the strips, then as it is in parallel with the one-megaohm, and since water has some resistance, the equivalent resistance between those two copper strips will reduce.

That is what is happening, and the multimeter reading shows 473 ohm; that is correct. But the problem is, it starts increasing slowly like 475, 478, 482.... to 736 K ohm after some 5 to 10 minutes before I turn the multimeter off.

I thought it may be that the water drop might not be at the same position and there may be a little bit of spreading so that might be the cause of resistance change, but the question is why it is always increasing and not decreasing, and why so much of change like from 475 to 736 is a huge change of approx 200 K ohm. I believe there is some other reason. Can someone give a solution to this problem?


texts: I've stumbled upon a LED's datasheet that includes a strange recommendation. They want me to drive the LED at >5mA for reasons of "long term performance." I've never seen a similar thing anywhere else, what's the rationale behind it?


texts: Simulating the Y capacitor effect on an SMSP transformer in SPICE

texts:
I read this question and still have some confusion about it.

If Y capacitor suppresses EMI and we know that the \$ X_c=\frac{1}{2 \pi f C}\$ this means to me that for higher frequencies the capacitive reactance becomes lower. That is to say the Xc becomes higher for lower frequencies.

The EMI here is created by the fast switching of transformers.

How can we simulate this and see this EMI creation and capacitor suppression by simple signal generator, a transformer, a capacitor and maybe with some resistors in SPICE? Can you provide a simplistic diagram? A simple circuit where one can see the effect of the Y capacitor's exitance.


texts: Would I get a better lumen output and improved thermal characteristics for the same wattage if I get a higher rated LED?

texts:
I'm planning on building a bright DIY high CRI LED video/photo floodlight out of the following components and considerations:

High-power Neutral White (4000K?) LED rated at 95 CRI
No add-on lens so I get the most uniform and wide-angled light output
ARCTIC Alpine 11 Passive (capable of passively cooling Intel CPUs up to 47 watts)
Thermal Adhesive
12V Power Adapter
Boost/step-up converter with current-limiting ability
Miniature wattage meter (maybe)
An target maximum drive power target of ~40W

I don't know what thermal adhesive to get yet for the most ideal thermal conductivity, whether that'd be a one-piece silicone based, a two-piece Arctic Silver, or something similar.

My LED Chip research has been done exclusively on Cree LEDs and I'm confident that they are the best brand for me to go with, but I'm open to other suggestions if there are any.

I've narrowed down my options to these:

CMA:

CMA1516-0000-000N0Z0AL5A (41W)
CMA1825-0000-000N0Z0AL5A (61W)
CMA1840-0000-000N0Z0AL5A (87W)

CMT:

CMT1420-0000-000N0Z0AL5A (49W)
CMT1922-0000-000N0Z0AL5A (57W)
CMT1925-0000-000N0Z0AL5A (64W)
CMT1930-0000-000N0Z0AL5A (77W)

From what I see, their CMA series LEDs were released in Q4 2017 while their CMT series came out in Q1 2018. I'm leaning more toward a CMT chip considering their prices are about the same while having potentially better lumen density and efficiency characteristics (I'm not entirely sure though).

How will a higher wattage LED driven at 40W scale in terms of lumens, thermals and heat tolerance/durability? Does CPU TDP-dissipation apply equally to heat-dissipation of an LED?


texts:
I searched multiple forums about microcontrollers and FPGAs but I couldn't find the answer were I was looking for.

I have to make a choice of whether I'm going to use a microcontroller/minipc like a Rapsberry Pi or something like a Zynq SoC.

What I want to do is: detect vibrations with a geophone sensor, use an ADC to send the information to a controller, then use a DAC to send a counter signal towards an actuator.

I would still like to be able to display the incoming and outgoing signals and tune the outgoing signal in a way that I can counter a specific frequency.

Currently I'm using a fanless pc, some amplifiers, DAC and ADC to do the computations and a external laptop to tune the signal (with MATLAB).

Now, I Would like to come up with a solution to use a smaller way to do the calculations.
I checked the Rapsberry Pi, but the range in Volts for the DAC - ADC are very low: -0.3 to +0.3V. I'm looking for a range between +/-10V and 16 bit.

Also, I still need to be able to tune and display the signals. Maybe two chips, one for calculations and one for communication to the user interface?

Thank you.


texts: Choose Vcc for MOSFET driving a 48v Motor

texts:
The circuit above is used to drive a 48v motor as shown. I am using:

IRF3205 MOSFETs (datasheet)
IR2110 High and Low side driver (datasheet)
22uF bootstrap capacitor for PWM frequency of 30 KHz.

I managed to find online and here on the website the meaning of bootstrap circuitry and how it provides the extra voltage to overcome the high side MOSFET source voltage. The problem I am facing is the choice of a suitable Vcc value.

I am running the motor on 4 sealed Lead-acid 12V 12Ah batteries in series for a total of 48v. The data sheet of the IR2110 shows a maximum value for Vcc =25 V and I see this makes sense as the maximum voltage that the IRF3205's low side Gate can take= 20V with respect to the Source.

If I choose Vcc= 25V, which I think will already blow up the low side MOSFET's gate, then on the high side I will get total of 50V minus the voltage drop across the bootstrap diode, since the capacitors will be charged with 25V and we have Vcc=25V giving a total of 50V. This is not sufficient to turn on the Gate of the high side MOSFET since its Source will have 48V so Vgs=50-48=2V

How can I achieve a Vgs>=8V with the restriction of Vcc given that I can't use an external supply other than my four 12v sealed Lead acid batteries that are in series?


texts: Conversion from VHDL to sysgen block diagram

texts:
I made my own custom board that contains a clock oscillator to drive an FPGA. I wrote some VHDL code. The script simply re-routs a 10-bit input (SIGIN) to the 10-bit output (SIGOUT) on the rising edge of the internal clock CLK10, which is derived from the global input clock (CLK160), it outputs a CLK160/8, and performs some asynchronous logic:

entity testMod is
   Port(    CLK160   : IN  STD_LOGIC;
            IN1      : IN  STD_LOGIC;
            IN2      : IN  STD_LOGIC;
            IN3      : IN  STD_LOGIC;
            OUT3     : OUT STD_LOGIC;
            SIGIN    : IN  STD_LOGIC_VECTOR(9 DOWNTO 0);
            OUT20    : OUT STD_LOGIC;
            SAMP_CLK : OUT STD_LOGIC;
            SIGOUT   : OUT STD_LOGIC_VECTOR(9 DOWNTO 0) := (OTHERS => '0'));
   end testMod;

architecture Behavioral of testMod is
   component CLK_DIV8  is   port (CLKIN : in STD_LOGIC; CLKDV : out STD_LOGIC );end component;
   component CLK_DIV16 is   port (CLKIN : in STD_LOGIC; CLKDV : out STD_LOGIC );end component;
   SIGNAL    CLK10  : STD_LOGIC := '0';
   SIGNAL    CLK20  : STD_LOGIC := '0';

begin
U1: CLK_DIV8  port map(CLKIN => CLK160,CLKDV => CLK20);
U2: CLK_DIV16 port map(CLKIN => CLK160,CLKDV => CLK10);

OUT20    <= CLK20;                                      -- 20MHz output clock
SAMP_CLK <= IN1 AND IN2 AND CLK10;                      -- asynchronous AND
OUT3     <= IN3;                                        -- direct asynchronous in-out

CLK_PROC: PROCESS(CLK10)
BEGIN
    IF RISING_EDGE(CLK10) THEN  SIGOUT <= SIGIN;        -- re-route on the rising edge
    ELSE NULL;
    END IF;
END PROCESS CLK_PROC;
end Behavioral;

Now, I wish to reproduce this code in Xilinx System Generator using block diagrams. However, after going through the UG640, I still can not figure out how to properly translate such a simple code:

Could someone suggest the approach how to translate this code into the block diagrams? Maybe a link to a comprehensive tutorial? Answering any of the following questions would be also greatly appreciated:

How can I get an access to the master clock so I could derive my CLK20 and CLK10?
How to make SIGIN <= SIGOUT only on the rising edge of the CLK10?
How to simply output a derivative of the system clock (OUT20 <= CLK20)?
How to pass input signal directly to the output independent from the system clock (OUT3 <= IN3)?
Why when I generate HDL Netlist using system generator I get a source file of 400+ lines and some additional source files as opposed to manual writing of the source code that is about 20 lines and no other source files?


texts: Does the line on a zener diode correspond with the line in the symbol?

texts: For a normal diode, the thin line on the component corresponds with the line of the symbol. Is this the same for a zener diode?


texts: Why do many resistor kits deviate from E6/E12?

texts:
I noticed that the resistor kits I've seen appear to be based on E6 or E12, but they skip certain values in favor of near neighbors. For instance, the 1000 decade of my kit contains: 1k, 1.2k, 2k, 3.3k, 3.9k, 4.7k, and 5.1k. Is this because whoever put the kit together couldn't get a good price on 6.8k resistors (E6), but got a screaming deal on 2k and 5.1k (which aren't standard values until E24)? Or is it because these extra resistors are commonly needed in designs? (A nonstandard standard, if you will.)

Here are two decades from another kit:

100 120 150 180 200 220 270 300 390 470 510 680 820
1k 1.5k 2k 2.2k 3k 3.3k 3.9k 4.7k 5.1k 5.6k 6.8k 7.5k 8.2k

They're not even consistent with each other! Is this based on common existing designs, a factory's current surplus, or is there actually a better method than choosing an E series?


texts: Problem with NPN transistor in MOSFET circuit

texts:
simulate this circuit – Schematic created using CircuitLab

Gentlefolk, I am attempting to build a circuit to switch power through a P-CHANNEL MOSFET device. I believe I am on the right track, but I appear to be frying my NPN transistors (2N2222) as soon as the NPN base goes high (5v). The smell is pretty putrid and I am probably knocking a year off my life every time I breathe in the fumes. Not quite sure what I am doing wrong here. R1 is simply a dummy load resistor. In the production circuit, this is where the equipment sits.

I am simply trying to use the NPN to drag the MOSFET base to ground which should turn on the MOSFET and allow current to pass. There should only be 17mA through R2 which shouldn't be enough to fry the device. Any idea what I'm doing wrong here?


texts: Precautions while handling DC Series and Shunt motors

texts:
I have been searching the net and have only found the following precaution for the DC series motor and Shunt dc motor and that is that never start series motor without load and shunt motor on load.

Are there any more precautions?


texts: How to use JTAG to connect external ST-LINK/V2 with STM32F407VG discovery board?

texts:
I want to isolate the on-board stlink, and use an external ST-Link/v2 to program/flash the board. I have a 20-pin JTAG connector. This is just a temporary, proof-of-concept project.

I have removed the jumpers from CN3 pins as instructed here:

How to Use an External ST-Link/V2 with the STM32F4 Discovery Board

I cannot comment on that post because I do not have enough rep points.

I connected:

(JTAG) SWDIO -> PA13

(JTAG) SWCLK -> PA14

(JTAG) GND -> GND

(JTAG) VAPP -> 3V/VDD, as instructed

Also, the post says not to connect the USB. I am not sure which USB this is referring to. An external ST-Link/v2 needs to be powered by an USB, and so does the board. I have tried this: 1)connect only the ST-Link/v2 usb, but this is not enough to power the board. 2)connect only the board usb, but this does not power ST-Link/v2.

I am a beginner and I am using the Linux terminal. I have successfully flashed an example "blinky" program to the board.
I would be very grateful if someone could assist me. Thank you.


texts:
The DAC is the 20 bit precision AD5791 which provides an output span across the +/- Vref inputs (power supply being greater than Vref). However, I want an output almost 3x that span. I can do this by putting an opamp on the DAC o/p, or I can feed the precision +/-5V reference voltages I am using through a couple of opamps.

Naturally, I am trying to keep the noise as low as possible. Which is the best approach?


texts:
I can't get the relay to work in my example. Transistor gets really hot.
When connecting&disconnection relay wire between diode and transistor and I can hear soft click from relay. But when changing digital pin output high/low then relay doesnt react.


texts: Building a motion/activity tracker with AVR Atmega or ARM?

texts:
I have worked with IMU and an Arduino before to build a motion/activity tracker. Even after making it wireless, the whole system is quite big due to the individual breakout boards that hold those chips and sensors.

My goal is to make this thing smaller and after some research, I thought I could use AVR Atmega chip as the main brain and connect all sensors to it.That was the plan until I read about those commercially available fitness trackers that use ARM chips. Now I am a bit confused and would appreciate your feedbacks regarding this matter.

My questions are:

What are the advantages and disadvantages of building this with AVR Atmega vs. ARM?
How about circuit design? If I were to buy individual chips and make my own PCB board, do you think this is doable by someone like me? (Not an expert)
What are the things that I need to make this work? For example, for the atmega, i think I need the avr-isp programmer. How about ARM?  What about the softwares? Any other items?

Thank you for your feedback.

Update: I have edited my questions.


texts: Need help in making an automatic battery cut-off switch

texts:
I want help in making a automatic cut-off circuit to stop charging of the battery when the potential across the battery reaches 13.3 Volts. The problem is that I want to cut-off the Solar panel from circuit by measuring the potential of the battery.
The battery that I'm using is a 12V bike battery rated 9AH/10HR.
If you have any other suggestions then please tell.
Thanks in advance


texts: Identifying SMD Resistor with a code that contains a colon

texts:
What are the blue components seemingly labeled "69:1" in the attached image?
There is reason to believe that they are resistors, but of what value?

I thought perhaps the ":" is a "00" written on top of each other - but I couldn't find a 5 digit SMD resistor coding convention.


texts: Arduino SPI connection WHO_AM_I register on IMU

texts:
I have an inertial measurement unit (IMU) sensor that communicates over SPI. I use Mega2560.

I want to read one simple WHO_AM_I register.

On documentation:

  SPI Operational Features

  Data is delivered  MSB first and LSB last
  Data is latched on the rising edge  of SCLK
  Data should be transitioned on the falling edge of SCLK
  The maximum frequency of SCLK is 1MHz
  SPI read and write operations are completed in 16 or more clock cycles (two or more bytes). The first byte contains the SPI Address, and the following byte(s) contain(s) the SPI data. The first bit of the first byte contains the Read/Write bit and indicates the Read (1) or Write (0) operation. The following 7 bits contain the Register Address. In cases of multiple-byte Read/Writes, data is two or more bytes:

  SPI Address  format

MSB              LSB
R/W  A6  A5  A4  A3  A2  A1  A0

  SPI Data  format

MSB              LSB
D7  D6  D5  D4  D3  D2  D1  D0

On Registermap WHO_AM_I:

Hex Add / Dec Add /  Register Name / Serial I/F / bit7 / bit 6 ..... bit 0
75 / 117 / WHO_AM_I / R /  WHOAMI[7:0]

Pin Assigments:

51 > SDI
52 > SCLK
50 > SDO/ADO
53 > CS

#include <SPI.h> //add arduino SPI library;
//list of all registers binary addresses;
byte WHO_AM_I           = 0B01110101;

byte Read  = 0B10000000;
byte Write = 0B00000000;

//chip select pin on arduino;
const int CS = 53;
/*
SPI.h sets these for us in arduino
const int SDI = 11;
const int SDO = 12;
const int SCL = 13;
*/

void setup() {
  Serial.begin(57600);
  //start the SPI library;
  SPI.begin();
  //initalize the chip select pins;
  pinMode(CS, OUTPUT);

}

void loop() {

byte rValue = ReadRegister(WHO_AM_I);

Serial.print(Read | WHO_AM_I,BIN);
Serial.print(" > Value: ");
Serial.println(rValue);
delay(1000);

}

byte ReadRegister(byte Address){
  byte result = 0;
  digitalWrite(CS, LOW);
  SPI.transfer(Read | Address);
  result = SPI.transfer(0x00);
  digitalWrite(CS, HIGH);
return(result);
}

void WriteRegister(byte Address, byte Value){
  digitalWrite(CS, LOW);
  SPI.transfer(Write | Address);
  SPI.transfer(Value);
  digitalWrite(CS, HIGH);
}

But it returned 0.


texts: Practical Limit of Feedback Control Systems WRT Bandwidth

texts:
In a digital feedback control system, I'm interested in the practical limit of what the correctable bandwidth is.

For example, given a very simple system:

A sensor can sample a simple X position error signal at 100Hz (like a camera)
An actuator has a bandwidth of 100KHz to correct for position errors (effectively, assume the system can respond instantaneously to commanded actions)
Input is sinusoidal, with non-negligible noise characteristics
The input is linear, stable, and minimum phase.
Controller is purely digital, as is all sensing equipment.

Having no intuition about the limits of feedback control systems, I would assume that such a controller would be able to correct for an input motion an order of magnitude lower than the sampling frequency with no problem. So a 10Hz sin wave would be sampled 10x, and the system can respond adequately to attenuate the input signal. Is 1 decade of separation of sampling and disturbance frequency enough to correct for? Or in general do you need more like 5 decades of separation?


texts:
In the " Fruit Battery Project" where you are using copper and zinc wires connected to a  fruit to generate power and transfer it over to a LED light. What happens once you connect the two wires to the fruit? Are electrical currents just automatically rushing through the wires?
After that what happens once you connect the wires to a LED light? Are the currents flowing through the wires? Which wires holds what acids?


texts: What is the easiest way to reduce quiescent current in a AB power amp?

texts:
I'm trying to design an push-pull amplifier for a 4 ohm load, it works with a 48 V source.

This is the latest design I did:

(Input and output are in those two capacitors and the potentiometers are used to set the output DC point and the push-pull bias voltage)

In order to have less crossover distortion, I always end up having voltages in the order of 0.6V constantly applied to the emitter resistors (In pratice, because in the simulations everything always goes easier).

The problem is: Once my load is 4 ohms, I can't put any greater emitter resistors, or it'll have too much lossess. But with two 0.2 ohm resistors, it ends up having a quiescent current of 1~1.5 A, which is very great.

I'm not even sure if, in this way, the emitter resistances will be able to prevent thermal runaway, because they'll heat up fast.

The transistor on that VBE multiplier will be installed between the other two in the heatsink, but I don't know how fast it will runaway.

Being that there are plenty Class AB power amplifiers that work with such loads and voltage ranges and they don't have a quiescent current like that.

What am I missing?


texts: Ground Fault Protection in Unearthed HV Systems

texts:
I'm working somewhere that uses an unearthed 3.3kV network for safety critical drives.  I've been learning about ground fault detection on ungrounded systems, using VT's and measuring voltage across a broken delta arrangement to detect ground fault:

(Source)

I'm confused as surely the star point on the VT's effectively ground's the ungrounded delta connections, negating the purpose of having an ungrounded system in the first place? Each phase will now have a reference to ground, allowing for phase-ground faults?

Am I thinking about this the wrong way?


texts: What to do with unused TTL and CMOS outputs?

texts:
Just about everything I've read on the Web, including on this site, say that unused TTL and CMOS outputs should be left floating.  However, this TI article, Designing with Logic, states:

  Unused outputs of a device should not be left unconnected (open).

This is stated at the very end of Section 3, at the bottom of page 7.

Why the discrepancy? Is the referred to article wrong?


texts: How do I design the shading ring of an induction disc relay?

texts:
Can anybody guide me to any resource which gives the formulae for estimating the phaseshift caused due to a shading ring in an electromagnet? Specifically I am thinking of the shading ring in an induction disk relay.

Regards
Abhishek


texts:
I want to be able to talk on the microphone of my Headset A and send that signal out to the earphones of my Headset B. Something similar to what I show you on the image below.

For that purpose, I bought the piece below, which I can place in between both (it requires some power) to achieve my goal.
https://www.aliexpress.com/i/32949115279.html

It actually works but there is some noise on the output signal that I can easily hear on the earphones of Headset B. For example, when the room is in silent and even not talking, I can hear that noise.
Then, I was thinking to build or configure some mic (pre)amplifier or something similar that let me achieve my goal.
(I have to say that I'm not an expert on this field)
I got the following 3 pieces on Amazon because they claim they reduce the noise or something like that but I don't know if they are exactly what I'm looking for and how to configure them.

Noyito - 12V High-fidelity Microphone Pickup Module Noise Reduction Microphone Amplifier Board High Sensitivity Kit
https://www.amazon.com/gp/product/B07CQBJDTZ

Acxico - AD828 - Stereo Dynamic Microphone Preamplifier Board Pickup Module DC 3.8V-15V MIC Preamp Module
https://www.amazon.com/gp/product/B081YRNRP6

Koobook SSM2167 - Microphone Preamplifier Board Preamp COMP Compression Module DC 3V-5V
https://www.amazon.com/gp/product/B07TWC2MQB

Could you please, let me know if I can use them to achieve my goal?
Or if you have in mind any other way to do that, could you please, let me know?
Thanks in advance!


texts: Relation of Voltage of a line and its cross section area?

texts: For a given power delivered, if the working voltage of line is raised to n times, then cross sectional area of line conductor would reduced to?


texts: AVR debugging on Linux with Eclipse and AVaRICE

texts:
I'd really like to be able to debug on i.e. an Atmega328p on Linux with Eclipse as described on avr-eclipse.sourceforge.net

After quite some research, it seems an JTAGICE mkII should work fine with both avrdude and AVaRICE. But a JTAGICE mkII seems outdated and is quite expensive, besides the clones from Kee Electronics and Waveshare which seem to work fine.

The latest AVaRICE from SVN supports JTAGICE3 but as far as I could find out only with firmware 2.x. There is also the Atmel-ICE Basic but even though it looks similar I was told it is not a JTAGICE3 so it probably won't work with AVaRICE.

So, the only way is to go for one of those JTAGICE mkII clones or is there anything else that works on Linux with Eclipse?


texts: We are looking to purchase DS18B20 temperature sensors from a supplier who claims to manufacture them themselves - but I cannot work out if DS18B20 is a product name for Dallas instruments (i.e. buying from other sources is not recommended) or whether DS18B20 refers method of measuring temperature.


texts: Voltmeter resolution increase by having several in series

texts:
The problem
I am trying to measure quite precisely a voltage around 7.2V on a line of a PCB with a voltmeter. In this voltage range, my voltmeter only displays 3 digits. So the reading is something like 7.26V. However, I would like to have 4 digits of resolution.
Idea to solve the problem
To increase the resolution, I connected two voltmeters in series to have the voltage they each measure drop at half the range and benefit from the 4 digit resolutions. When doing so, the first voltmeter is stabilizing at 3.626V. The second one starts its reading, stabilize shortly at 3.626V but soon after restart its reading and repeat this sequence indefinitely.
The question
Is it possible to consider the total voltage to be twice 3.626V, so 7.252V? Is there a risk that the voltmeters are interfering each other in their reading, and I cannot use this result?
Schematic
How I connected the voltmeter on my circuit.


texts: I was wondering if anybody was using PLL (Phase Locked Loop) in DIY hobby project? If yes what was the application? Did you made it from discrete components (as opposed from one placed in uController or FPGA) ?


texts:
I recently bought a solar cell rated at 3v and 200mA dc to power a 1.5v dc motor that is used as an air pump for my aquarium.All the 1.5v solar cells available here have low ampere like 50mA or so.

So how can i drop the voltage supplied by the solar cell to 1.5v while doubling the current
to 400mA.also is it possible for me to do this with just resistors??I'm a complete Noob here.

Thanks in advance..


texts: How can I set the quiescent current for a grounded-emitter amplifier?

texts:
I'm currently learning about common-emitter amplifiers in AoE3. I learned how to set the quiescent current for an emitter-degenerated amplifier. I simply choose \$V_E\$ and \$R_E\$ such that \$I_E = I_{quiescent} = V_E/R_E\$.

Now the book started explaining grounded-emitter amplifiers (common-emitter amplifiers with no \$R_E\$). It gives the following schematic and quote:

simulate this circuit – Schematic created using CircuitLab

  The voltage gain is \$G = -g_mR_C = -R_C/r_e = -R_CI_C(mA)/25\$, so for a quiescent current of 1 mA, the gain is -400. But \$I_C\$ varies as the output signal varies. For this example, the gain will vary from -800 (\$V_{out} = 0, I_C = 2mA\$) down to zero (\$V_{out} = V_{CC}, I_C = 0\$).

  Art of Electronics Third Edition, pg. 94 (emphasis mine)

The thing that I don't understand is how can I set the quiescent current to be 1mA like the book is suggesting. I've been messing around in simulators and the only way I can get 1mA to flow through \$R_C\$ instead of 2mA, is if I set the base bias to 21V. But that doesn't seem right to me. Especially since on the next page, the book gives an example:

  As an example, in a grounded emitter amplifier powered from +10V, biased to half the supply (i.e., \$V_{drop} = 5V\$), we measured a distortion of 0.7% at 0.1V output sinewave amplitude and 6.6% at 1V amplitude; these values are in good agreement with the predicted values.

  Art of Electronics Third Edition, pg. 95 (emphasis mine)

So how can I set the quiescent current for a grounded-emitter amplifier?


texts: CPU fan connected to solar panel will run but wont start

texts:
I'm trying to run a 12V 0.09A CPU fan directly off a 5W solar panel (not ideal, I know). The panel runs the fan fine, even in morning and evening sun. However, the fan will not restart without a push whenever the panel loses sun (fan stalls). I'm assuming the panel is not ale to supply sufficient starting current. I've tried connecting a 9,900 uf capcitor in parallel, but this did not help. Any suggestions on how to make this work? Bigger capacitor? Different fan?

Thanks!

Fan: https://www.microcenter.com/product/253152/ec5010m12ca-ball-bearing-50mm-case-fan

Solar Panel: panel:https://www.amazon.com/ECO-WORTHY-Polycrystalline-Panels-Module-Charging/dp/B00OZC19AY/ref=sr_1_4?crid=273WUMSMTKUA&keywords=5+watt+solar+panel&qid=1564748631&s=gateway&sprefix=5+watt+sol%2Caps%2C306&sr=8-4


texts: How does one determine the type (AC v. DC) and operating voltage of small motors?

texts: I've become fascinated by Rolling Ball Sculpture (RBS) and plan to start building my first one soon. Typically a RBS uses a low-voltage, low-RPM motor to carry the marbles to the top of the structure where they begin their journeys down the track. I've been scavenging fan and turntable motors from old guitar amps, computers, microwaves, etc., but am at a loss as to how to determine the type of motor (AC v. DC) and operating voltages of these normally-unmarked motors. Thank you in advance for any help you can provide.


texts:
I have a PCB and trying to measure the maximum junction temperatures of the major components in the PCB which in full working mode. For example like Input Diodes, Buck Regulator ICs, Aluminium Electrolytic capacitors and other Discretes.
I have placed my PCB inside the thermal chamber at 95degC and made the board full operational and measured the temperatures of the components by placing the thermocouples (K-Type) on top of the ICs, diodes and other components as mentioned above.
My questions :

I measured the temperatures of the components on their surface and found to be in the range of 110degC to 120degC. But this is the Surface temperature of those components, right? How can I practically measuring the junction temperature of those components so as to find what margin I have ? Is it something like I add 20% to the measured surface temperature value to arrive at the maximum junction temperature of the components? Or is there another way to measure the junction temperature of the components?

What are the other important things that I need to calculate or note during this thermal stress testing?


texts: What kind of driver should I implement in buck convertors

texts: I have a couple of questions. In the diagram below, when the current falls to 0 , the NMOS is supposed to turn off. Similarly when the voltage error increase the PMOS turns off. However in the diagram both the signals are given to a driver. What is this driver component and how d it decide which signal to send out? How should I implement it in terms of transistors? The picture is taken from


texts: struggling to use MOSFETs as switches: is the problem my circuit or the choice of mosfet?

texts:
We are using an arduino to selectively apply 5V to the gate of MOSFETs, with the intention that current will only be allowed to pass through our solenoid from the supply in the situation where both the MOSFETs that a particular solenoid is attached to have a gate voltage of 5V.  5V appears to be above the threshold voltage for these MOSFETs (IRF520) but we are getting much less current than expected unless we increase the gate voltages.  Can anyone explain this? Is it a problem with our circuit or the choice of parts? Is using two MOSFETs back to back like this a bad idea?

We will eventually be controlling a larger grid of electromagnets to selectively turn them on for several seconds at a time, up to 5 at a time.  This grid will be up to 17x17 so it is not ideal to use a MOSFET for every magnet!


texts: What is meant by lightning dissipates through a vehicle's body?

texts:
I have read a lot of articles and other post relating to what happens when lightning strikes a vehicle or evening a building with metal.
However, I cannot grasp one part. This is when lighting strikes a metallic object like a vehicle and the energy gets dissipated around the metallic body, how is all that energy in essence destroyed.
I know that energy cannot be created nor destroyed, so maybe destroyed is the wrong word. How is the energy not stored in the metallic object? From a scientific point of view, how does all this energy just get "neutralized"
I would also think that a car battery negative terminal is also connected to the vehicle's body. So when lighting strikes on the body the energy from the lighting strike is also travelling through the battery via the negative terminal. The fact the body is metal, electrical current can flow through it. How does the battery not blow up?


texts: Difference between Buried Photodiode and Pinned Photodiode

texts:
What is the difference between Buried Photodiode and Pinned Photodiode?
I understand that the P+/N/P structure where the P+ and P layers have the same potential is the Pinned Photodiode.
So what is the buried Photodiode?


texts: faster extend 8-bit mask to 16-bit for MCU

texts:
Using an 8-bit flag register, the goal is to generate a 16-bit mask for manipulating a 2-byte settings register where adjacent pairs of bits control a channel, e.g. writing 0x2 (0b10) for channel 2 would be to take 0x04 (0b00000100) from the flag register and generate 0x0030 (0b0000000000110000) to be ANDed with a constant setting mask 0xAAAA (0b1010101010101010), resulting in 0x0020 (0b0000000000100000).

The equivalent digital logic "circuit" to generate the mask would look like this:

One seemingly straightforward way of implementing this in software is to shift one bit out for every two in (i.e. serial approach), paying attention to endianness. In CPU12 assembly (big endian):

    LDX     #2     ;counter: 2 bytes
L1  LDY     #4     ;counter: 4 bits
    LDAA    flag   ;get flag register
L2  LSRA           ;shift lsb into carry
    PSHC           ;copy carry (ccr)
    LSRB           ;shift carry into msb
    PULC           ;paste carry
    LSRB           ;shift carry again
    DBNE    Y,L2   ;loops 4 times
    PSHB           ;store half-result (1 byte)
    DBNE    X,L1   ;loops 2 times
    PULD           ;retrieve resulting mask (2 bytes)

(1) Is there a faster algorithm for this procedure without resorting to wiring up 24 MCU pins as illustrated, or a lookup table; e.g. one that is able to process multiple bits concurrently? (2) Is there a name for this procedure?


texts:
What I want to achieve is something similar to the following entity. Now I want data_(x)_i to be an array of std_logic_vector, with each individual length definable at component instantiation.

entity module_A is
    port(
        rst_i      : in  std_logic;
        clk_i      : in  std_logic;
        data_0_i   : in  std_logic_vector( 1 DOWNTO 0);
        data_1_i   : in  std_logic_vector( 2 DOWNTO 0);
        data_2_i   : in  std_logic_vector( 3 DOWNTO 0);
        data_3_i   : in  std_logic_vector( 4 DOWNTO 0)
    );
end entity module_A;

I tried the following code

utils.vhd:

package utils is
    type int_array_t is array (integer range <>) of integer;
    type data_array_t is array (integer range <>) of std_logic_vector;

    function get_width (
        int_array: int_array_t
    ) return integer;

end package utils

package body utils is
    function get_width(
        int_array: int_array_t
    ) return integer is
    begin
        for i in 0 to int_array'length-1 loop
            return int_array(i);
        end loop;
    end function;
end package body;

module_A.vhd:

entity module_A is
    generic(
        DATA_WIDTH : int_array_t := (2, 3, 4, 5)
    );
    port(
        rst_i  : in  std_logic;
        clk_i  : in  std_logic;
        data_i : in data_array_t(DATA_WIDTH'range)(get_width(DATA_WIDTH)-1 DOWNTO 0)
    );
end entity module_A;

Modelsim throws the following error

  ** Error: D:/WORKSPACE/PERSO/HPD_ALT/RTL/RTL/pkg_utils.vhd(24): Parameter for attribute "left" must be locally static.

Is there a way to achieve what I want?


texts: Charging four 12 V lead acid batteries in series or parallel?

texts:
I just installed a 48 V ebike conversion kit on one of my bicycles.  I will power it with 4 12 V, 12 Ah, lead acid batteries connected in series because of the cost of 48 V, 12 Ah lithium batteries designed for the purpose.  (I may buy the lithium batteries later if I find that I use the bike regularly.)

My question is in regards to charging the batteries.  It seems that I have three choices:

1) Charge each battery individually with a 12 V charger.

2) Charge them in parallel with one 12 V charger.

3) Charge them in series with a 48 V charger.

I currently own two 12 V chargers and no 48 V chargers.  I am thinking that charging them in two banks of two, in parallel, would be my best option without buying more chargers.  Any comments on the pros and cons of any of these options would be appreciated.


texts: what is the problem with led trainer in arduino?

texts:
currently I am trying to develop a light trainer by arduino , as a begging I used 3 led and 3 push button ,the led must work randomly and when the ledX is flash the user press push bottonX and so on of course I must use approximate sensor or something similar to be more reliable

when uploading following code all leds continuous week glow (flash) what the problem? thanks for help.

int ledselect = 0;
int led1 = 11;
int led2 = 12;
int led3 = 13;
int pb1 = 4;
int pb2 = 5;
int pb3 = 6;
void setup() {
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
pinMode(pb1, INPUT);
pinMode(pb2, INPUT);
pinMode(pb3, INPUT);
}
void loop() {
int ledselect = random(3);
switch (ledselect) {
case 0: //if ledcolor equals 0 then the led1 will turn on
digitalWrite(led1, HIGH);
if (pb1== HIGH) ;
digitalWrite(led1,LOW);
break;
case 1: //if ledcolor equals 1 then the led2 will turn on
digitalWrite(led2, HIGH);
if (pb2== HIGH) ;
digitalWrite(led2,LOW);
break;
case 2: //if ledcolor equals 2 then the led3 will turn on
digitalWrite(led3, HIGH);
if (pb3== HIGH) ;
digitalWrite(led3,LOW);
break;
}

}


texts:
I tried cutting my old Gameboy Advance SP Charger wires out since the adaptor doesn't work anymore. I am planning to attach it on a USB cord to replace the adaptor.

I have noticed that the wires aren't colored red and black which is the usual.

The wires are enclosed in a single black wire and inside there was a color green wire and a naked wire.

I want to know which is the positive and which is the negative among the two.


texts:
I'm trying to figure out what's the DTFT of \$ (-1)^nx[n]\$. (I'm given the DTFT of \$x[n]\$)

So I tried this, but I can't figure out how to proceed from here, if this is even correct.
Any help and advice would be appreciated!

\$F_{DTFT}\{ (-1)^n x[n] \} = \sum\limits_{n=-\infty}^\infty (-1)^n x[n] e^{-i\theta n}\$

\$=\sum\limits_{even \space n's}x[n]e^{-i\theta n}-\sum\limits_{odd \space n's}x[n]e^{-i\theta n} =\$

\$=\sum\limits_{k=-\infty}^{\infty}x[2k]e^{-i\theta 2k}-\sum\limits_{m=-\infty}^{\infty}x[2m+1]e^{-i\theta (2m+1)} = ?\$

Thanks!


texts: In testing for a parasitic drain in my truck with this meter in ammeter mode, I realized the scale of the amp reading is ambiguous in that the reading does not change with the decimal point. This being the case, I am not sure if the output is in amps or milliamps. Can someone shed some light on what is happening?


texts:
I want to make a PCB that is hexagonal and has a it's sides of 51 mm. I've tried inserting a .svg file into Eagle but it didn't work, I've also tried using the polygon tool but I don't know how to make the sides a specific size.
Can someone please help me?


texts: Resistance between the terminals of a star configuration?

texts:
The derivation of the delta-star transformation rules is based on the fact that the resistance between terminals 1,3 is R1+R3
I can't see how we can consider R1,R3 just two resistances connected in series between terminals 1 and 3 with R2 having no significance in this arrangement.
Can someone enlighten on this?


texts: strange results from transmitter radiation calculation

texts:
This table was taken from:http://www.emfwise.com/distance.php

At that site a formula:
Power Density = P/4Πr2
was used in order to calculate the power density(mW/m2)
according to the distance from the transmitter.
On that table the transmit power of the transmitter
is 30mW and you can see how the power density decrease
in according to the distance from the transmitter.
When i used the formula(Power Density = P/4Πr2)
to calculate the power density in according to the distance that
shown in the table,all the results are ok(as in the table).

For example:
30/4Π(0.3*0.3) =~26.5mW/m2

30/4Π(5*5) =~0.100mW/m2(~100uW/m2).etc.

But when i used a distance that less than 30cm,
i got a power density results that higher than the transmitted
power of the transmitter itself and this result doesn't make sense.

For example:
30/4Π(0.2*0.2) =~60mW/m2.

Why do i get that strange results?
and how can i calculate power density at distance less than
30cm,that won't give me strange results?


texts: I am currenty using the TS5MP646 http://www.ti.com/product/TS5MP646 . I need to build a 4:1 mux. I was wondering if I need to use 3 muxes, or can i just short the MIPI traces together and control it using OE pin on the mux?


texts: Why is my output voltage offset of 4.5 Volts?

texts:
When using an LM386 amplifier with  an internal gain set to 20, it is powered by Vcc equaling 9 V. My input is a short sound as seen in the graph as the green line. My output is the blue line.

Why is the output offset from the input voltage?


texts: How do circuits work where from the touch of a button on the wire of a headphone, you can pause or play music?

texts: I am creating a project for my engineering course. I ve decided to make headphones that have the ability to pause music when taken off from the ears and vice versa. I will be using long lever switches as well. How will i be able to create a circuit where pressure is applied to the ear pads from wearing it and causing the music to play or stop. Please help me. I don t know too much about electronics and i thought that it would be a bit of a challenge.


texts: Why must this capacitor be a "low leakage" type?

texts:
I was reading this article discussing non-inverting opamps and when presenting the above single-rail opamp circuit it gave the following not regarding capacitor C2:

  Capacitor C2 type:   It is important that this capacitor must be a low leakage type. If not the leakage could cause the output to hit the voltage rail if there is some gain in the circuit.

Why the "low leakage" requirement? Wouldn't any leakage current simply be compensated for by OpAmp action?


texts: What is the typical frequency drift of an astable 555 circuit over its lifetime?

texts:
I am involved in qualifying a sine wave generator that is using a first order LPF and a 555 timer in astable configuration to generate a sine wave(-ish) output.  I would have designed it differently, but we already made the board, so I have to work with the design the best I can.  The designer has placed the corner frequency of the first order LPF at 100kHz and the oscillator is running at 230kHz.  A variable gain stage (not an op-amp, but similar, with 7M ohm input resistance) calibrated with a variable resistor is being used to set the final gain, so output amplitude from the filter doesn't matter except that it must remain constant. The output frequency isn't critical, but the peak output voltage is.

Because the oscillator is running in a region of the filter where gain changes -20dB/decade, the frequency has an impact on the gain.  I was hoping someone could tell me how much 555 timers change in frequency from use to use to help me assess how much trouble this design is in.  All components are surface mount.  I know capacitors and resistors change with temperature; the device should always be within a 15 degrees Fahrenheit range when in use. Also, I am unfamiliar with how much surface mount capacitor capacitance changes over long periods of time.


texts: What is the difference between a beacon node and a wireless sensor node? In addition to positioning information, beacons can provide temperature measurements. In that case what would be the difference between the beacon and a wireless sensor with temperature sensors? Are they interchangable ? Can a wireless sensor network be formed of beacons?


texts: I2C Communication on STM32 fails with Digital Analog Converter

texts:
I am using a MCP4706A2T-E/CH digital analog converter. I try to get the I2C communication running but for what ever reason I always get a HAL_ERROR message. The STM chip I am using is the STM32F042K6Tx. Here are my I2C configurations:
static void MX_I2C1_Init(void)
{

  /* USER CODE BEGIN I2C1_Init 0 */
    HAL_StatusTypeDef status;
  /* USER CODE END I2C1_Init 0 */

  /* USER CODE BEGIN I2C1_Init 1 */

  /* USER CODE END I2C1_Init 1 */
  hi2c1.Instance = I2C1;
  hi2c1.Init.Timing = 0x00101D2D;
  hi2c1.Init.OwnAddress1 = 0;
  hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c1.Init.OwnAddress2 = 0;
  hi2c1.Init.OwnAddress2Masks = I2C_OA2_NOMASK;
  hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c1) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure Analogue filter
  */
  if (HAL_I2CEx_ConfigAnalogFilter(&hi2c1, I2C_ANALOGFILTER_DISABLE) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure Digital filter
  */
  if (HAL_I2CEx_ConfigDigitalFilter(&hi2c1, 0) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN I2C1_Init 2 */
  uint8_t test[1] = {0x06};
  status = HAL_I2C_Master_Transmit(&hi2c1, 0xC4,test, sizeof(test), 100); //00000110
  uint8_t blub = 0;
  /* USER CODE END I2C1_Init 2 */

}

It does not matter what I put in the test array nothing is send (status is always HAL_ERROR). The adress of my chip is 0x62. I have to shift this adress by a 0 since we send 8 bits so it becomes 0xC4.
I think that my address is correct. Do you have any idea what I do wrong? (I double checked my wireing). Here is a picture of the CubeMX setup:


texts:
I have designed a boost converter with a 400V output which uses a PFC IC
For regulation, the IC measures the output via a potential divider which is fed into a pin on the IC

The IC is looking for approx 2.5V so with 400V output I use a divider with 3M and 19k

All is good in the world, very basic stuff

Now I am looking to protect the IC, I had a failure where I lost a ground and a voltage exceeding the 5V max was applied to the IC pin and the smoke was let out

To avoid this possibility I would like to clamp the maximum voltage to the pin and I thought lets drop a zener in there, in parallel with the 19k resistor so any misbehaviour will be clamped

When I actually sat down and thought about it I realised that 3M resistor is going to seriously limit the current and the zener wont be able to get past the knee point which typing this made me think it might not matter the voltage would still be limited. I dont want any regulation just protection

I plan on adding a TVS diode as well but thats just for spikes I dont think it can be expected to work with constant DC applied

Am I still ok to use a zener in this application?

Is there a better way?

Edit

Added schematic showing the zener in place, as you can see R2 and R8 come to approx 3M


texts: mpasm - overlapping variables in a udata directive

texts:
In MPASM it appears I can do this to make paylen_lo and bytesleft have the same memory location:

            UDATA
paylen_hi   RES     1
bytesleft   RES     0
paylen_lo   RES     1

This uses the same type of trick as used with CBLOCK where 0 bytes is reserved for a location, thus causing two labels to be at the same location.

MPASM warn with "Warning[231] No memory has been reserved by this instruction" but the map file shows the location being shared correctly.

My problem is - this does not seem to be documented and thus makes me worry it's a hack. The alternatives I've tried are:

bytesleft  EQU  paylen_lo
           #define bytesleft paylen_lo

The first does not work and the second is fine. Do the more experienced PIC developers stick with defines? The only advantage of the hack above is that the symbol is created.


texts:
I have a 3d printer with wires that run from the extruder heating block to the circuit board. I want to modify the wires with some kind if connector that I can easily remove the hot ends for maintenance.
One of the fans has this locking connector which is really easy to use. I'd like to get more of them for the other parts. What kind of connector is it?


texts:
I conducted an experiment where I constructed a Full AM signal and changed the message signals amplitude to change the modulation index of the Full AM signal. I then increased the amplitude of the modulator chip until a DSB-SC signal was made. Although they look really similar, I was wondering what the difference between them is.

It is clear from the pictures that the amplitude of the DSB-SC signal is lower than the full AM. I also understand that the DSB-SC signal does not carry a carrier signal.

Can somebody tell me what the difference of the two pictures I have uploaded are please?


texts: Question about function set_dont_touch_network

texts:
I was trying to debug a script written for synthesis using Synopsys primetime.

Can someone explain me what is the function of set_dont_touch_network?

I have these 2 statements:

set_dont_touch_network [get_ports scan_enable*]
set_dont_touch_network [get_ports resetb_i]

What's is the difference between adding an asterix at the end of a signal or not? Can someone explain?


texts: Why is it not right to use the classic Vo = Vin*R2/(R1+R2) voltage divider formula in the marked area? I want to obtain the voltage, in terms of Vs, in the non inverting input of the op amp. But if I use a normal voltage divider, I’m not getting the expected result.


texts: How to connect uC to PC using RS232 with minimum number of signals?

texts:
The standard 9 pins RS232 connector has 9 pins. Those are:

1 -- DCD -- Data Carrier Detected
2 -- RxD -- Receive Data
3 -- TxD -- Transmit Data
4 -- DTR -- Data Terminal Ready
5 -- GND -- Signal Ground
6 -- DSR -- Data Set Ready
7 -- RTS -- Request to Send Data
8 -- CTS -- Clear to Send Data
9 -- RI  -- Ring Indicator

If I need bi-directional communication it is obvious that I should connect RxD and TxD. What should I do with other signals/pins - connect to ground, left open, need to drive them with appropriate signals according to protocol?
If I care only about uni-directional connection can I connect only RxD or TxD?
What are the consequences of not using/connecting certain signals. What software on PC side expect to have those signals? What functionality will be lost?

NOTE 1: I am using here word "connect" in sense of logical connection -> for electrical connection I would require level shifter circuitry such as MAX232)
NOTE 2: I am pin limited on uC - I do not mind connecting any signals on the board (like pulling them up/down).


texts:
I want to create a circuitry for switching to backup power (small battery) in case of mains power failure for my ADSL modem (to avoid the internet going down in such scenario).

This is a basic circuitry however I have only very basic knowledge of electrical and electronics and hence need help.

The below diagram shows what I am trying to create. Request help on how to create this "instant switching circuitry".

Modem specs: Current=0.6A Voltage=9V


texts:
I am planning on using the XL7026 buck converter IC in an upcoming project because of its dirt cheap cost, small package and wide input voltage range.

However, there is one concerning aspect of the chips's design I have come across:

Notice the floating ground created thanks to the low-side shunt, R3. Even a few tens of millivolts drop with current will disturb more sensitive ICs. I am imagining that removing the shunt will have no effect on the converter's normal operation, effectively creating a very low voltage drop. This will, sadly, make the IC's current limiting useless and potentially damage the chip if I draw too much, such as capacitor charging at startup.

Would it be possible to use a high side shunt and inject the voltage differential across it into OGND (re-referenced to GND, of course)?


texts:
Preamble

I need an small isolation transformer for 0-6V 400Hz AC (this is my external signal, amplitude is the value):

I should get <10mA load from the primary signal source, and in the same time I need minimal size of the transformer. For <10mA at 6V 400 Hz the primary inductance should be >238 mH (coil impedance is \$2\pi f L\$).

Typical transformers that I found with such an inductance is pretty big, but I found also Bourns LM-LP-1001L that have very confusing values in datasheet. Help me please understand it.

Amble

The datasheet says that DC resistance of primary coil is 90Ω, and impedance at 1kHz is 600Ω, so I calculated the coil's inductance 81 mH. But datasheet says inductance is 2.8H! What is wrong here? And if 2.8H is the correct value, how do so small transformer can have so big inductance?


texts: Is DC voltage gain the change in offset and AC voltage gain the change in amplitude of the input waveform?

texts:
I can't find an explanation on this site or elsewhere that addresses this concept as directly/simply as I suspect is possible, surprisingly. Maybe I'm a bad searcher, but it's not for lack of trying.

I made two graphs demonstrating what I currently interpret DC gain and AC gain to mean.

That is, DC gain affects the offset of the waveform and AC affects the amplitude of the waveform.

Is my understanding correct? If not, I'd greatly appreciate an explanation of the difference at a similar level to this (if possible).

(This question and diagram is not 'homework'; I'm just trying to understand an introductory level concept.)


texts: I know a device I am making can run continuously using two AAA non-rechargeable batteries (namely Energizer Alkaline Max, at 5 volts) for X hours, and I'd like to provide advice on what rechargeable batteries the user can also use. (also AAA) How can I calculate which mAh-rated batteries will be needed for X hrs?


texts: Measuring battery voltage fluctuations and spikes in an analog wall mounted clock when the second hand ticks

texts:
As the title suggests, my goal is to be able to pickup minute voltage fluctuations of an AA battery cell of the wall-mounted clock, each time the second hand ticks.

My first intuition would be to ac-couple the battery into an op-amp, perhaps a low-noise instrumentational amplifier, and feed the output into a microcontroller.

Any suggestions is appreciated.


texts:
I just made a "home made" adjustable power supply and I want to attach a voltmeter to the output so I can easily set voltage using a potentiometer. I don't want to complicate my circuit with a microcontroller with ADC so I want to use a mini voltmeter.
I managed to get the following voltmeter:

The problem is that I have no idea how to use it as I don't understand that freaky scale and notations.
It only have two pins. I tried to connect to fixed power supplies but I can't correlate power supply voltages to value indicated.
Have you used something like this in the past? How to use it? How to place it on a circuit?
PS: It is very small, 25mm x 25mm
PS2: It does not have any code on it.


texts: Is it good practice to couple the grounds of isolated supplies with capacitors

texts:
I once saw the following on an isolated dc/dc converter data sheet and have been doing it ever since with my dc/dc converters, but I wanted to ask to make sure it actually makes sense.

Whenever I have two isolated dc/dc converters, I have been coupling their grounds with a high voltage (~3kV) very low value capacitor like so:

Where AGND and BMG, AGND and SCG, and AGND and GND are all split across switching isolated dc/dc converters.

Does this make sense, and what does it actually achieve?


texts:
I am starting a project where a 12V LED Strip should slowly fade in and out.
With a Lab Bench Power Supply I figured out that the fading can be done by changing the voltage between 9V and 12V but also by changing the current between 0A and 200mA.

Which approach is better and what would be a basic circuit to accomplish this?
I have most common components available (MosFets, 555, Capacitors ...)


texts: How to stop LEDs from dimming in small circuit

texts:
I wired up a simple circuit (below) which was designed using the "Every Circuit" website/app. It's a small LED circuit used inside a costume prop. When the master switch is pressed, the 3 LEDs light up. Then when a "momentary push" trigger is pressed, the other (top) green LED lights up. All works fine, but when the trigger is pressed in, the 3 lights in series seem to dim ever so slightly.

The "dim" can be seen in this video over on Instagram (hopefully you can see it) https://www.instagram.com/p/Bqh2x6YDASG/

The dim doesn't bother me too much, and I might just leave it as it adds a bit of character to the model, but I was wondering if anyone knew how to fix it so that the LEDs don't dim at all.

My electronics knowledge is extremely basic. I've heard of using a voltage regulator, but I didn't think it would be needed as the circuit seemed to run fine when I built it on "EveryCircuit.com".

Any help is appreciated.


texts: Calculating series resistors for I2C/SPI lines to reduce EMI and ringing

texts:
How do you determine if a series resistor is needed for I/O lines, and what value is needed? Where should the series resistor be placed?

My assumption is the resistor should be placed as close to the source as possible (in case of CLK and MOSI, it should be placed close to the master, etc). Is there a way to calculate series resistance needed? Would placing series resistors on the I2C affect performance since I2C relies on pull-ups?

My assumption is the following might be of importance:

Output drive strength / output resistance of the IC driving that particular line.
Trace length, impedance, inductance.
Return paths.

Is there any formula?

If we keep the data lines short enough, are resistors still needed? If not, how short is short?


texts: Dangers of overloading a 2.5A rated plug

texts:
Got  an old soviet samovar (tea kettle) and wanted to put a new plug on it as the sovet one doesn't plug into proper EU sockets.

I have a 2.5 A / 255v ungrounded plug, which I can use, but an curious as to how much current these plugs can actually take.

Likly the samovar is 2kW, so there will be short periods of 8ish amps boi going through it. And so far I haven't noticed it heating up.

Do you suspose that the plug is save?
I opened the kettle itself and the inside is clearly more scary and dangerous than the plug sovet safety standards and age of the I insulation , but I'm curious to know if the plug can handle the load, as I'm sure it's rated at 2.5 but it's got more metal than the wire itself.


texts:
In the context of understanding neurons as parallel circuits (see for instance here  page 12), the following formulas are used:

C = \$ \frac{Q}{V} \iff \$

C * V = Q \$\iff \$

C\$\frac{dV}{dt}\$ = \$\frac{dQ}{dt} \iff \$

C*\$\frac{dV}{dt}\$ = \$I_{C}  \$

With C = capacitance; V = Voltage; Q = Charge; \$I_{C}\$ = Capacitive current

My questions:

(1) As far as I know, current is defined by \$ I = \frac{Q}{t} \$ as charge (Coulomb) over time (seconds). Here, however, the change of charge over time is equated with current. How is this justified?

(2) Both charge and voltage are differentiated, capacitance remains constant, however. Why is that?

(3) What is the capacitive current in this context? Is this current flowing through the circuit, or rather movement of particles on the capacitor's plate?


texts: Can Fritzing automatically position my components on a PCB?

texts:
Thanks for looking. I am new to Fritzing and think it's autoroute capabilities are great!

That said, I am wondering if there is a way to auto-position the components in the PCB view in order to get the best layout and routing of traces?

For the particular board I am working on, placement of the components is not important but I am constrained by a fairly small pcb size.

Thanks in advance.


texts: Interfacing multiple SPI data input into EBI memory for access in verilog

texts:
I have several SPI peripherals that collect data into the FPGA and I have an EBI memory module to communicate data from FPGA to micro controller.  I am having a hard time understanding the best way to collect the data from the SPI peripherals and allocate it in the EBI memory.  The SPI collect 16 bytes of data each and the EBI holds 8KB.

I am currently thinking that each SPI needs to have a small memory of 16*16 that once the SPIs finish collecting a memory manager would then go through each and write them into the EBI memory so once done the micro controller can collect them.

Is this over complicating, necessary or completely wrong ?


texts:
Vendor doesn't have the following components:

MOSFETs:
   P-channel MOSFET    IRF9Z34N
   N-channel MOSFET   IRLZ24N
   N-channel MOSFET   2N7000
   N-channel MOSFET   IRFZ46N

Diode:          1N5818
OpAmp:      MC34074P

Is there a quick way to find out equivalent components?


texts: Can a time-varying magnetic field pass a metal sheet?

texts:
I'm using CT (Current Transformer) to measure the current flowing on the power line. The frequency of the current is 13.56 MHz. CT appeared to be metal-shielded (This metal case of CT may be to be grounded).

CT has a toroidal shape and the power line under the measurement passes through the center hole of the CT, so azimuthal magnetic field around the power line induces EMF (ElectroMotive Force) on the coil inside the CT. This EMF is measured so the current on the power line is measured. This is the basic story of how CT works.

If the current frequency is low like 10 Hz, then I fully accept that CT really works. But I'm now confused at a high-frequency operation. The current is the source of the magnetic field and when the current oscillates, there is not only the magnetic field but also the electric field. The combined field is what we call an EM (ElectroMagnetic) wave. My frequency is 13.56 MHz which is a rather high-frequency, so the power line should play as an EM wave emitting antenna. EM wave generated from the power line propagates to CT first. However, CT has a rather thick metal case (much thicker than the skin depth at this frequency) so EM wave will be reflected from it. It means the magnetic field as a part of the EM wave fails to reach the coil inside the CT so CT should not work! I think the only way for CT to work is that the magnetic field alone pass through the metal so they get in touch with the coil. But..Is it really possible? The time-varying magnetic field can exist alone without the electric field?

Of course, there is a number of commercial CT in the same type which work well even for higher frequency. Could you please give me some idea of breaking this confusion?


texts: Turn on a 7812 Voltage regulator using an Arduino?

texts: I'm using an Arduino in a project, but this is not an Arduino question! I'm able to switch 5+ volt high or low using a digital write pin. I need to use a 7812 voltage regulator to regulate voltage coming in to some other power transistors, but it does not need to be on at all times consuming power and creating heat. I'm wondering if I can use an NPN transistor to turn on/off the GND to the 7812. Is it just as simple as hooking up the NPN to the 7812? Also, will I need a high power NPN since the 7812 will be drawing upwards of 1.4 amps? Is there a much better way to switch the 7812 on and off?


texts: How capacitor values are determined in this circuit

texts:
I am following the course on control systems from edx. I have this circuit as  part of practical exercise. I would like to understand how the capacitor values were determined in this circuit

The 47uF is for power supply filtering
The 47nf is for reduce the switching speed of PWM
The two 2.2uf capacitors for filtering noise signals from motor

The circuit is powered by arduino and the motor is powered by an external 5v 3A power supply. The lessons say that the motor can draw up to 2 A, If i assume the ripple voltage is 2 v and main freq is 60 hz, then the ripple frequency is 120 hz, the current that the capacitor can take/give is

$$ I = C \frac{\Delta V}{\Delta T} $$

which gives 11.2 mA only

$$ I = 47 \times 10^{-6} \times \frac{2}{\frac{1}{120}} = 11.2 mA $$

However the lesson says the motor can draw up to 2A how is this capacitor sufficient?


texts: Voltage and Current relationship in generation

texts:
Please could someone explain why the current is 180 Deg out of phase with the voltage when measured at the generation point and then in phase with the voltage when measured at the load point. I am purely talking about a resistive load. We can talk about VAr (Reactive Power, leading, Lagging, inductive, capacitive) later. I would really appreciate if someone who studied this could share a bit of their knowledge. I can provide examples of sine waves recorded that verify my above statement if required. I have the data, just having a hard time trying to get my head around it. thanks in advance - Mark

Thanks for the response. Brian and The Photon are relating to what im saying. By convention current entering a load is positve and leaving a power source is negative thus 180 out of phase.
To answer some other questions about my post. The measurements are recorded on a Transient Fault Recorder that has micro second accuracy.
The system is a HVDC Interconnector and it has Inverter and Rectifier Modes.
In Rectifier mode (drawing power from the grid) the Current is in phase with the Voltage but in Inverter mode (delivering power to the grid) the Current is 180 deg out of Phase with the voltage.
I understand that it all has to do with the direction of the current and how its represented but i bet if i was a few hundered yards up the road at the first load point and i was able to look at the wave forms on an oscilloscope the Voltage and Current would be in phase again.
Maybe it is just the way the CT's are orientated.
I might have just answered my own question


texts: Minimum diode current / realtime clock battery backup

texts: I know there is a minimum forward voltage for diodes, however, is there a similar property for current? I'm trying to use something like a BAT54C as a steering diode such that a 3V lithium battery acts as a backup power source, so my current will be in the range of 0.7uA. My application is in powering a DS1347 Realtime Clock IC, which does not have an independent Vbat input.


texts: How do I make the parts layer smaller in a Fritzing part?

texts:
I am using Fritzing to create a schematic of a recent project. I am using several 'parts' from the parts bins. I had to go find a part to add, and I have imported it.

I got the part here:
SMD based 4 x Relay Board

It is exactly what I need. I have imported it into "Mine" parts bin. But The "parts layer" of this item far exceeds the size of the part. So it makes a big gray area that covers other parts and doesn't look good.

Question: How do I make this parts layer / gray area smaller?

(Note: The attached screenshot shows this. I have added notes onto the screenshot to show exactly what I am describing, and what I am desiring to do.)

Context:

I could probably just change the order and put it on bottom, but I still want to understand for the future how to make things like this smaller
I have tried editing the part, etc. but nothign gets me to the point where I can re-size this gray area.

Thank you.

Under the view menu are layers. If I deselect the parts layer, the gray disappears (along with much of the graphic.) This seems to indicate that it's the "parts layer" which is too big. It seems I might need to figure out how to make that layer smaller. I have tried clicking, editing, looking for 'handles' I could click and drag to resize, etc. without success yet.


texts: Camera external trigger; What is the shutter signal?

texts:
There is a Sony RX10 III camera which also has a external trigger for it.
The goal is to send a signal from a micro-controller (Arduino & optocoupler in between) to release the shutter.
I thought I could just short the GND to the shutter pin like with older cameras, but with this particular camera it didn't work. You can see the pin-outs made by some nice people here.
I dismantled the external trigger and de-soldered the USB connector cables, but it seems there is more to it than just shorting.

I don't know what the circuitry is doing. From testing I was able to figure out, that the Green wire seems to do the focusing; this leaves the white for shutter. Just shorting doesn't work here though. I have read in the post I linked that there is resistors used sometimes for some custom protocol.
Here is a picture showing my interpretation on what is connected to what.

I hope some of you can help me figure this out. Unfortunately I only rarely have access to the camera, so I would like to do this with as little trial and error as possible.
If more info is required please ask. Thank your for your help.


texts:
According to this Wikipedia article:

  It can use nearly all of the energy in a single-cell electric
  battery, even far below the voltage where other circuits consider
  the battery fully discharged (or "dead"); hence the name, which
  suggests the notion that the circuit is stealing energy or "joules"
  from the source. The term is a pun.

Why is it that having multiple batteries in series would not work?

What would happen if the battery was full? (I would assume the device would not oscillate, therefore doing nothing until it was low enough to trip the transistor?)


texts: Component with an impedance that has a negative real part

texts:
Is there an electrical component such that its impedance has a negative real part ?

Fact: Any electrical component made from resistors, inductances, capacitors (connected in possibly complex ways using series or parallel connections recursively) must have an impedance of a non-negative real part.

Proof: Suppose that there exists a way to connect the components (R,L,C) in a possibly complex ways using series or parallel connections recursively to get an impedance with a negative real part. Choose the connection of R,L,C that uses the least number of connecting wires. Let's call this component COM.


texts: what is the application of fault tolerance system in microcontroller

texts:
I want to ask, is there any application of the fault tolerance ability in microcontroller? I was a bit confused, will there be any fault when the microcontroller perform something if the input is right? if there is, what is the example of it?
Sorry if the question is dumb.


texts: Is it possible to measure the voltage and current of a load with this circuit and Arduino?

texts:
I'm trying to measure the voltage and current for a DC-AC converter in my car with Arduino.

I know it would be easier, more accurate and cheaper to use breakouts with INA226 like this. But this question is purely from my curiosity.

I'm thinking about a circuit like this with a shunt resistor.

Voltage : V0
Current : V1/R

(V0 : the voltage at analog input 0, V1 : the voltage at analog input 1)

But Arduino can't measure voltage higher than 5V (Arduino Reference, analogRead()). Besides, if the voltage drop in the load was very low, voltage higher than 5V might be applied to V1.

Then I came up with an idea using a voltage divider.

Voltage : V0 * (r1 + r2) / r2
Current : V1/R2

r1 + r2 should be large enough to avoid drawing too much current to the tributary. R1 + R2 should be small enough to prevent voltage drop.

But I feel I'm missing something. Can this quite simple circuit measure the voltage and current?

EDIT 2018-3-11 15:49 GMT

The current will be up to 25A since the max power consumption of the load is 300W.


texts: Does a Ground plane in Eagle still need connections?

texts:
Before I added a ground plane my ratsnest was showing the needed GND connections which I still needed to make. I added a Ground plane and now they are automatically gone. Is this normal?

I can remember that in the past I used a VIA to connect certain components to the ground plane, but that doesnt appear to be needed here, why?

I illustrated the old ratsnest with the orange lines drawn on the image.
Any other remarks about the design are welcome as well, always eager to learn.


texts: How it is possible to make bad audio amp?

texts:
After discovering how great op amps are, and that some extremely good ones--especially at low power levels--are available at reasonable prices, I wonder why all audio amplifiers, big or small, don't achieve excellent performance by simply combining a good small-signal op amp with a simple output stage.

I mean, with opamp there is no need to worry about all these bias voltages & temperature stability, just stick opamp and any unmatched darlington transistors, and you are good to go.

Any pitfalls?


texts:
QUESTION:

I'm having a hard time figuring up what the Thevenin Voltage is along with Thevenin Resistance for this circuit below. I'm also confused on what I'm suppose to do when there is a current source thrown in or multiple sources of any kind thrown in. Do I convert them all to voltage sources before I even start figuring Thevenin Equivalent?

I arrived at the following answers. If they are wrong could you provide a brief explanation on how you figured each answer and a solution to my last question above.

R (TH) = 1.57K ohms
V (TH) = 44.8 Volts

NOTE: I didn't know how to enter the Load Resistor in my Simulator. Therefore the break in the circuit on the far right is where it's placing the Load Resistor at.


texts:
EM waves are classified into types according to the frequency of the wave: these types include, in order of increasing frequency, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

Its said that electromagnetic waves are produced by the accelerating/oscillating charges. So suppose i have a conductor connected to a AC source.

Can i ideally produce all these electromagnetic waves of different frequencies by changing the frequency of current/voltage to the conductor ? How the frequency of the electromagnetic waves is related to the frequency of the alternating current in the conductor ?

Is there any equation that relates the two frequencies ?

Or simply to generate the electromagnetic wave of 8×10^14 Hz (light), i will have to oscillate the charges with the frequency of 8×10^14 Hz in the conductor ?

Or all these electromagnetic waves will be produced in any other different ways ?


texts: I am having a tough time finding Vds, I tried to do VDD-ID*RD-VSS. but this appears to be wrong? would someone be able to poinnt out the mistake im making ?


texts: Interpretation of FFT FMCW Doppler radar results

texts:
After a lot of research and help from the users here, I managed to do some FFT and signal processing in my first time in my life :)

I have got the following figure, which shows one peak frequency, but the strange thing is the range is 0, however I was putting the radar into a wall... so I expect at least some distance.. How would I interpret the results ? Is it a problem of coding ? or how would I verify that the signal processing is correct?

x = complex(ResultI, ResultQ);

D = 64;

 N=512; %FFT size
m1=reshape(x,length(x)/D,D); %generating matrix ---> each row showing range info for one period AND each column showing number of periods
[My,Ny]=size(m1');
win=hamming(Ny);
m2=(win*ones(1,My));applying window for sidelobe reduction (in time domain)
M2=(fft(m2,2*N)); %First FFT for range information
M3=fftshift(fft(M2',2*D)); %Second FFT for doppler information
[My,Ny]=size(M3);

If anyone interested here is the I/Q data from 4 channels

and the full matlab code that reads the I/Q and do FFT on them
http://www.mediafire.com/file/gcj13keakb8mkf7/MATLAB.zip


texts: Mains powered NMOS 100KHz switch with push-pull MOSFET driver

texts:
I'm trying to design a mains powered switched resistive load to inject high frequency (100KHz) noise current into mains wiring to facilitate magnetic tracing of in wall wires (I know about the electric-field based tracing).
See the schematic below.
I'm planning to use a CMOS 555-timer to drive a NMOS switch using a power resistor (R4) as the load  (31K for 10mA peak current).
To keep things simple I'm trying to power the 555 IC with a simple 300K resistor + 5.6V zener regulator.
The 1mA current the supply is capable of is not enough to switch the MOSFET (M1) fast enough so I've added a 2uF cap (C4) to provide the peak current needed.
Now the 555-timer also has limited sink and source currents so I thought about using a PMOS/NMOS pair as a push-pull driver (M2/M3) for the main MOSFET M1.
But my simulation is showing that with this arrangement both M2 and M3 are ON at the same time for most of their on time and this results into conduction from VCC trough M2 and M3 to ground. This way the zener is not getting any current and the supply voltage stays low at 2.4V and the voltage on M2's and M3's gates (OUT of the timer) stays between Vcc and Ground because there's not enough current left to charge the gates' capacitance in 1 cycle. This keeps both M2 and M3 partially ON at the same time and we've got a stable state that it's stuck in.
If I somehow could prevent the timer from starting until C4 is charged to the supply's target voltage of 5.6V then the charged capacitor could provide enough peak current to switch M2 and M3 in one cycle, but I'm not sure what's the easiest way of achieving this.
Any suggestions are appreciated.
Edit: The simulation gives the expected results when I drive M1 directly from the OUT pin, but the real timer won't have enough source/sink current as I mentioned above.
LTSpice model.


texts:
I have a circuit that draws little power (under 5mA), it accepts 2 MIDI signals and does some switching. I'm not using the standard optically isolated circuit as there is only signal manipulation done by the circuit - not connected to anything "audio".

As written above, the device accepts two MIDI signals. Each has a voltage ref. pin as part of the current loop. That voltage might be 3V, 3.3V or 5V.

My circuit will work fine with a voltage going low as 2.8V and as high as 3.3V.

When VCC = 5 V, then R = 220 Ω. When VCC = 3.3 V, then R = 33 Ω.

Questions are:

In order to power my circuit I need to tap into one of the voltage lines of the input/s. At any current time there could be a single input or two inputs with the voltage lines being 3V, 3.3V or 5V with the two devices not necessarily have the same voltage. How can I select the line which is 3V or 3.3V in case it is present and if not step-down the 5V to 3.3V (LDO regulator). But how does the selection or bypass being done?
The logic signal are referenced to the voltage line (same voltage for logic 0 or 0V for a logic 1). I need to translate all the input signals to the voltage the circuit is operating in. So if the circuit is powered from 3V I need to have 3V signals going through without alternation, however a 5V signal would require stepping down. How can I achieve this?

Simple power OR-ing using MOSFETS (as diodes), although this does not work as should in the simulation (any ideas why). This is one part of the solution.

simulate this circuit – Schematic created using CircuitLab


texts: AVR bitwise operation: making a NOT with a microcontroller

texts:
I'm programming an ATtiny10, i have two spare pins, one of which is the external interrupt pin on PB2, and i want to write the inverse of that signal to PB1. I want to spare a component, since i have already the uC and some pins.

So far, the best option i could come up with, is:

PORTB = (PORTB & ~(1<<PB1)) | ((~PINB & (1<<PB2))>>1)

Used in the IRQ routine associated with the change of INT0.
Basically clearing the PB1 bit, inverting PINB, masking it and shifting to the right by one place.

The other option is using an if statement and branch the code, which doesn't really satisfy me.

Is there an easier way to do this, that i cannot see?


texts:
I have this emergency switch that I need to mount on a control cabinet. I googled but cannot find any tutorial or picture on how this switch supposed to be mounted.

Am I supposed to mount the whole thing outside the enclosure? But then the whole switch (B) will protrude too much and looks ugly aesthetically. Am I suppose to detach A from the switch where A is outside of the enclosure and the rest hide inside the enclosure? But it requires me to disassemble the internal switch plastic parts to do that.


texts: 5V Power Supply oscillates once another consumer is turned on

texts:
I live in Europe and we have 230V coming out of the power outlet. I have several consumers on one outlet: 5V DC supplies for Router, HDMI-Switch, Ambilight, one Computer, one Macbook and a fan). The Ambilight is just some LEDs controlled by an Arduino. When I turn on the fan the Ambilight flickers for a short moment.

I found this kind of strange and used my oscilloscope to measure the output of my 5V DC power supply when turning on the fan:

The result is quite shocking. I added a 330uF capacitor and the result got better but is still not satisfying (notice that the graphs have different scales one is 5V @ 200ns and the second is 2V @ 500ns):

I also measured another 5V DC power supply and the result was almost the same (amplitude was a little bit lower).

EDIT: After a few MS the output voltage returns to a steady 5V DC.

Is this a problem with my power lines (too many consumer) or just some very bad 5V power supplies?

What could I do to smooth the output of my 5V power supplies (more capacitors? what size?)


texts: Embedded Programming for Beginners: Arduino or Raspberry Pi?

texts:
I'm a computer science student and I'm eager to expand my knowledge on embedded programming and electrical engineering.

I've read here that using tools like the Arduino microcontroller is a good way to start.

I'm primarily a Java and Python programmer but have some experience in C++. Furthermore I have toyed with ArchLinux.

A small project I'd like to do is controlling some lightbulbs via Wi-Fi over my Arduino/Pi.

From what I've read both the Pi and Arduino are intended for students but I can't figure out which is more suitable for someone like me who wants to understand how computers work on the low level.

As a beginner I will run into many questions, so a big and helpful community (which I hear the Pi has) is a big plus.

So which one is more suitable for a self-teaching beginner: Arduino or Raspberry Pi?

Thanks in advance.

Edit:

From your many great answers and also these worthwile articles I came to the following

Conclusions

I choose Arduino as an entry point to embedded programming because it is a simpler system than the Pi and lets me work closer to the metal more easily.
There is value in going deeper: I might study AVR or mbed microcontrollers at a later time to learn more about the low level details of computing.
Both devices allow me to program without an operating system, which is what I want (at first).
I also found projects that use one Pi to control an Arduino. I find this intriguing as both devices are quite affordable and I like to use the power of Linux that can run on the Pi.
Additionally I've found this book that should help me to learn more about electrical engineering while experimenting with Arduino.
It seems difficult to do my lightbulb project with the Arduino. But that's ok. I'm sure I can think of other motivating projects or get inspiration here or here.

Thank you all for your answers.


texts:
I have made serial adder on verilog.
it consists of shift registers based on always@(posedge clk or posedge reset)
In testbench, i wanna shift after shift.
@(posedge clk) control_bit = 2'b11; @(posedge clk) control_bit = 2'b11; @(posedge clk) control_bit = 2'b11;
But this way, shift registers are not working shift after shift.
It works only 1 time.
Is there any way?


texts: how to connect micro to µPD6379A (NEC Dac IC)

texts:
We want to use µPD6379A in our project. after a lot of search we've found no data (code example or schematic hint) about using it on internet.
Can anyone guide us on using that IC.
Any advice would be much appreciated.


texts: Timer to provide a short pulse after a power-up delay

texts:
I've been searching for a long time for a timer circuit that activates a relay for a short time(less than 1 sec.) after a few seconds(5 to 10 sec) when the current is switched on.

There are many circuits with a switch to activate the timer but for this use it should start counting after switching the device automatically and give a short pulse on the relay.

[Edit to be verified by OP.]

               _______________________
Power   ______|
              .  5 - 10s  .__
Output  __________________|  |________
                          >1s<


texts:
I understand that an HDMI cable contains essentially 4 shielded twisted pairs, along with additional control lines. Each of the twisted pairs is specified, to my understanding, to be a balanced transmission line with a characteristic impedance of 100Ω.

Now, since (ISO 11801) category 6/7 (shielded) twisted pairs are also balanced transmission lines, with a characteristic impedance of 100Ω, I'd assume that such a cable (or two), given enough (shielded) twisted pairs to carry all of the signals, can serve as an alternative medium to the standard HDMI cable (with the proper connectors at the end).

However, it seems that an "HDMI over Cat. 5/6/7" solution requires a device which is called a "balun" on both ends, at the interface between the proper HDMI and the ISO 11801 cable.

I understand baluns and transformers have a role at the interface of cables with different impedances, or when one is balanced and the other isn't. However, in this case, the lines in both standards are specified to be balanced 100Ω lines.

Why then are "baluns" required in this case? Are they really baluns, or do they provide some other function?

Thanks in advance.