texts: Synthesis Result : RTL vs Technology Map Viewer

texts:
I am evaluating this code below.
But I saw that the logic output of the RTL and Technology Map Viewer are different.
I use Quartus Prime Elite Edition.
Am I missing something?

this is the truth table

                      RTL                          Technology Map
A    (NOT A)   p_a    ((A XOR p_a) AND A)          ((NOT A) AND p_a)
0      1        0           0                            0
0      1        1           0                            1
1      0        0           1                            0
1      0        1           0                            0

library ieee;
use ieee.std_logic_1164.all;

entity keypad is
port (
    clk             : in std_logic;
    rst             : in std_logic;
    a               : in std_logic;
    b               : in std_logic;
    c               : in std_logic;
    d               : in std_logic;
    e               : in std_logic;
    keypad      : out std_logic_vector (4 downto 0)
    );
end entity keypad;

architecture rtl of keypad is

signal p_a, p_b, p_c, p_d, p_e  : std_logic;

BEGIN

KEY:    process(A, B, C, D, E, rst, clk)
        begin
        if      rst = '1' then
            p_a <= '0';
            p_b <= '0';
            p_c <= '0';
            p_d <= '0';
            p_e <= '0';
        elsif clk'event AND clk='1' then
            p_a <= A;
            p_b <= B;
            p_c <= C;
            p_d <= D;
            p_e <= E;
        end if;
        end process;

keypad(4) <= '1' when a /= p_a and a = '1' else '0';
keypad(3) <= (B XOR p_b) AND B;
END architecture;

I appreciate any suggestion.


texts: Count the number of times a button is pressed using ATmega

texts:
I have to count the number of times a button is pressed in 5 seconds and display it on an LED array.

If the number of times the button is clicked is 1 then the last LED should glow (0001 - binary value of 1). Similarly for 2 clicks, the third LED should glow (0010 - binary of 2).

But when I try this, I always get the output for the case 0, no matter how many times I click the button.

What is the problem?

#include<avr/io.h>
#include<avr/interrupt.h>
#include<util/delay.h>

int extratime=0;
int num_presses=0;

int main(void)
{
  DDRD = 0b11111111;
  PORTD = 0b00000000;
  DDRB = 0b11110000;
  PORTB = 0b00000000;
  char button_state;

  TCCR1B = (1 << WGM12);
  OCR1A = 15625;
  TIMSK = (1 << OCIE1A);
  sei();
  TCCR1B |= (1 << CS12) | (1 << CS10);

  while(1)
  {
    if (bit_is_clear(PINB, 0)) //button is pressed
    {
      if (button_state==0) //was previously not pressed)
      {
        num_presses++;
      }
      button_state=1;
    }
    else
    {
      if (button_state==1) //was previously pressed
      {

      }
      button_state=0;
    }

  }
}

ISR(TIMER1_COMPA_vect)
{
  extratime++;
  if(extratime == 5)
  {
    switch(num_presses)
    {
             case 0: PORTD = 0b10010000;
                     _delay_ms(10000);
                     break;
             case 1: PORTD = 0b10000000;
                      _delay_ms(10000);
                      break;
              case 2: PORTD = 0b01000000;
                      _delay_ms(10000);
                      break;
              case 3: PORTD = 0b11000000;
                      _delay_ms(10000);
                      break;
              case 4: PORTD = 0b00100000;
                      _delay_ms(10000);
                      break;
              case 5: PORTD = 0b10100000;
                      _delay_ms(10000);
                      break;
             default: PORTD =0b11110000;
                     break;
    }
    extratime = 0;
    num_presses = 0;
  }

}

this is my new code even this doesnt work....
    #include
    #include
    #include

int extra_time=0;
int num_presses=0;

int main(void)
{
    DDRD = 0b11111111;
    PORTD = 0b10000000;
    DDRB = 0b00000111;
    PORTB = 0b00000000;
    char button_state;

    TCCR1B = (1 << WGM12);
    OCR1A = 15625;
    TIMSK = (1 << OCIE1A);
    sei();
    TCCR1B |= (1 << CS12) | (1 << CS10);

    while(1)
    {
      if (bit_is_clear(PINB, 0)) //button is pressed
    {
       if (button_state==0) //was previously not pressed)
     {
    num_presses++;
     }
     button_state=1;
    }
      else
     {
       if (button_state==1) //was previously pressed
     {

     }
      button_state=0;
     }

     if (TCNT1 >= 15625)
    {
      if (extra_time == 5)
       {
         switch(num_presses)
       {
           case 0:
                 PORTD = 0b11100000;
                 break;
           case 1:
                 PORTD = 0b00100000;
                 break;
           case 2:
                 PORTD = 0b01000000;
                 break;
           case 3:
                 PORTD = 0b01100000;
                 break;
           default:
                 PORTD = 0b10100000 ;
                 break;
          }
         extra_time = 0;
     }
     else
     {
         ++extra_time;
     }
     TCNT1 = 0;
     }
   }
  }

Pls help ..
I have to submit this project tomorrow.


texts: doesn't ohm's law applied to every thing?

texts:
I've read that voltage is high in step up transformer due to greater no. of turns it makes sense but why it reduce current?I have done a lot of search on it but there is only one answer.that is to make power constant.doesn't it violate ohm's law?
There is constant voltage of 220 is applied to our household appliances.it means current passes through them depend upon resistance of appliance.I have read that the resistance of a filament bulb is very high than simple energy saver bulb or LED.it means more current passes through energy saver or LED bulb then why power consumption of filament bulb is high than LED.
I am student of first semester in EE.my basic concept are vague which is headache to me.I do a lot of search.but very rear answer satisfy me


texts: Is it possible to detect a transmitter that comes within a certan range?

texts:
I know nothing of electronics. My experience is with software engineering, not electronic engineering. This is a "Is it possible?" type question. If it isn't possible, where are the barriers?

I'm asking this in light of Friday's tragedy in Newtown, CT, which I'm sure we're all familiar with.

Naturally, this has invoked a renewed debate on gun control. But it seems to me that what we need is not more gun control -- people have the right to own guns.

What we need is a system that keeps guns out of certain public places, and this is a problem that only an automated system can effectively solve. We can't have airport-style security in every school and mall.

Here's what I'm thinking about.

I'm a student in college, and we are issued ID cards with a radio signature of some sort. We flash them in front of scanners to get into buildings on campus.

Is it not possible to build a comparable technology INTO GUNS? To require that all fire-arms sold and purchased in the United States are built with an embedded wireless-detectable signature?

Is it not possible to then place wireless detection systems around schools and malls which can detect if such a signature comes past a designated boundary, thus putting the area on lockdown and automatically summoning the police before the incident has even begun?

And the firearms belonging to police and current military would of course not set these systems off; their signatures would match "SAFE".

Then the only task left to the government is enforcing this manufacturing requirement (a much more tractable problem) and cracking down on aftermarket modifications.

Is my proposition unreasonable? It seems so obvious that I'm sure there must be a reason it hasn't already been done.

If it is possible, and nobody else wants to try it, can you point me in the direction of the topics I should educate myself on to better understand how such a technology would work?

EDIT:

In response to the first answer:

I do realize that a non-powered component would require close proximity. But I do not believe it would be a difficult task to move this technology forward to the stage where it does not require close proximity. If they can build a particle collider -- if they can get to the moon -- if they can build an iPhone -- if they can do all the incredible things you hear about them doing every day -- they can develop a method to detect a radio signature at a distance of 500 feet. Absolutely. This is not science fiction.

As for removing/destroying the component: Say this component took the form of a micro-chip embedded into the metal. Now say, for a given model of a gun, there are five locations on the gun where it could fit.

Say 100 instances of this model are manufactured. For 20 of them place the chip in location A. For the next 20, location B, and so on. This would require a change in the manufacturing process, but not an unreasonable one, nor a prohibitively costly one.

Then mix the 5 subtypes and sell them in homogeneous batches -- a person wouldn't know where the component was on their particular gun. They would have to cut through the gun in myriad places to find the component they seek to destroy. They would destroy the gun in so doing. It would be borderline impossible.

As for sniffing -- a person would need to understand what the detection system was looking for in a signature, exactly what information would NOT set off the system. If the internal information scheme was kept secret, this is not a concern.

As for getting innocents in trouble-- a person would have to know what sort of signature the detection system was looking for, what kind of information it would convey. Easily kept secret. The people with the ability to break such a system would rarely overlap with the people looking to commit murder.

However, I have yet to think of a way around the Faraday cage.


texts: Altium missing self-made components in SCH Library

texts:
I've been following along a tutorial with Altium and have been making my own components for the schematic and PCB libraries. The schematic library components are missing when I reopened the project, however the PCB components and footprints are still there. The schematic itself can still see the components. See pictures.

Here's the component library panel to right of schematic

PCB Library

SCH Library with no components

I've tried reloading the project, different views, just at a loss here.

Altium version 17.0.10


texts: bridge from wireless mesh network to mobile device over bluetooth or wifi

texts:
My company builds devices that communicate over both cellular and wireless mesh networks.  The devices gather data from industrial equipment and send that data over the Internet to our servers.

Currently our mesh network is homegrown. We're considering switching to another wireless mesh network: iDigi, Synapse, or an equivalent self-configuring mesh.

For data collection when no device in a location has good cell signal, we'd like to enable connectivity from mesh to smartphones carried by service technicians who periodically visit our devices.  The idea is for the technician's phone to suck up un-sent data from the mesh and upload that data to the cloud when the phone next connects to the Internet. It's not financially practical to add bluetooth or wifi to our devices-- we must use mesh for all non-cellular wireless connectivity.

All the mesh solutions we're considering use different radios than you'd find in a phone (no wifi-based mesh options met our requirements), so we need a bridge between the mesh and the phone.

Technicians' phones are either newer Android devices or older Windows Mobile 6.x device. We can't add cables or dongles to technicians' phones because they're too likley to be broken or dislodged-- this means relying on the phone's existing bluetooth or wifi capabilities to communicate to the bridge.

So we need a mesh-to-phone bridge that:

is rechargeable with a battery that lasts at least 12 hours.
fits easily in a technician's pocket
wirelessly communicates to the phone over wifi or bluetooth
ideally is an off-the-shelf device we can buy or resell, although if we need to make a custom device one we can do so (as a last resort)
ideally costs under $300 US

Got any suggestions for a good solution that meets these requirements, or at least comes close?  Feel free to recommend a specific mesh implementation as well as a solution to by mesh-to-phone bridge problem.

The ideal solution would be a rechargeable mesh-to-bluetooth bridge, but I haven't found any of those from any mesh vendor.

The next-best option would be off-the-shelf components we could bundle together, like a mesh-to-serial bridge securely bolted to a serial-to-bluetooth bridge.  Or a mesh-to-USB bridge combined with a USB-to-wifi bridge. And so on.

My next favorite option is to assemble a solution from 3rd-party modules on our own circuit board and case.

My least favorite option is to plug a serial cable into the device and a serial-to-bluetooth bridge like this one. This solution means lost tech time fiddling with (and breaking) cables so we'd like to avoid this if at all possible.

Got ideas?


texts:
I recently came across a sensor that had a "push-pull" output. I can't find anywhere how to read such an output:

Is it some particular kind of analog output?
I would want to read it with the MSP430G2553 (using energia or code composer).


texts:
I have drawn the above schematic by reverse engineering a locally available LED Bulb. I was expecting to find an IC in the driver board but instead found this discrete circuit.

Googling "Discrete LED Driver" does not return a lot of relevant hits. From my understanding, I think C4 and L1 form a tanked circuit which drives the base at startup. Once the collector is pulled low, a voltage is induced on L1 via L2 and this cycle continues (?).

I do not understand how this circuit is regulating it's current through the LEDs as it is a constant current driver.

I am hoping someone more experienced here could explain the workings of this circuit to me.

Some info I left out: The output voltage can go upto 94V and the current is a steady 133 mA.


texts: DC motor & microcontroller sharing power suply: dc motor shuts off after a few seconds of running

texts:
I have the following circuit:

When I close the mosfet gate (i.e. set pin 1 to high), the dc motor will run for a few seconds and unexpectedly then stop. Inspecting with a multimeter, I found that pin 1 has unexpectedly gone low suggesting that the microcontroller has reset itself. I would imagine this is due to some sort of noise from the dc motor but I thought a flyback diode would fix the problem. What is causing this to happen?


texts: Does the LT Spice monte carlo simulation definitely output the max and min voltage for any number of simulation runs?

texts:
I have the following circuit, in which i need to calculate max and min voltages possible (considering resistor tolerance).

 Does running a monte carlo simulation consider the absolute max and min values of voltage output that can be obtained at every point in the circuit, or is it purely based on number of iterations in the step command? Basically, if I do only two rounds of simulation, I must get the absolute max and min voltages at every point in the circuit. Is this method the right one for my needs? If not, please provide a step-by-step solution for my case.


texts: Are disconnected PV panels damaged when exposed to sunlight?

texts: Can PV solar panels be exposed to sun without being connected to controller and batteries?  Have fixed panels on RV, and would like ability to switch (at controller input) to moveable panels on ground when parked shady area. Hoping to avoid having to cover fixed panels on very tall trailer.


texts: Verilog: Register File assignment not updating on clock pulse

texts:
I wrote some fairly simple code in Verilog to implement a 32-bit deep, 8-bit wide register file. However, when I actually run a behavioral simulation of the thing the two data-read lines (rd0_data and rd1_data, respectively) seem to be utterly nonreactive.

I think it's possible I made some mistake in how I built out the inputs and outputs or the "mem" variable, but after fiddling with it for hours I'm sort of lost.

module reg_file#(
        parameter DATA_WIDTH = 8,
        parameter ADDR_WIDTH = 5
    )(
        input rst, clk, wr_en,
        input [ADDR_WIDTH-1:0] rd0_addr,
        input [ADDR_WIDTH-1:0] rd1_addr,
        input [ADDR_WIDTH-1:0] wr_addr,
        input [DATA_WIDTH-1:0] wr_data,
        output [DATA_WIDTH-1:0] rd0_data,
        output [DATA_WIDTH-1:0] rd1_data
    );

    integer i; //For the reset operation
    reg [DATA_WIDTH-1:0] mem [0:31];

    assign rd0_data = mem[rd0_addr];
    assign rd1_data = mem[rd1_addr];

    //Update w. synchronus reset
    always @(posedge clk) begin
        if(rst) begin
            for (i = 0; i < 32; i = i + 1) mem[i] <= 0;
        end else begin
            if(wr_en) begin
                mem[wr_addr] <= wr_data;
            end
        end
    end

endmodule

Behavioral Simulation output:

My test bench code is as follows:

module reg_file_tb;
    reg rst, wr_en, clk;
    reg [4:0] rd0_addr, rd1_addr, wr_addr;
    reg [7:0] wr_data;

    wire [7:0] rd0_data, rd1_data;

    // Instantiate the register file (using positional-association for instantiation)
    reg_file dut
    (
        rst, wr_en, clk, rd0_addr, rd1_addr, wr_addr, wr_data, rd0_data, rd1_data
    );

    integer i;

    initial begin
        // Initial values
        wr_en = 1;
        rd0_addr = 5'd0;
        rd1_addr = 5'd0;
        wr_addr = 5'd0;
        wr_data = 8'd255;
        i = 0;

        // Pulse the reset signal for only one clock cycle
        clk = 0;
        rst = 1;
        #20;
        clk = 1;
        #20;
        clk = 0;
        rst = 0;

        for (i = 0; i < 16; i = i + 1)
        begin
            // Sample conditional stimulus: if i equals 4, set the write enable to HIGH
            /*if (i == 32'd4)
            begin
                wr_en = 1;
            end*/

            // Sample conditional stimulus: when i equals 5, change the rd1_addr to 10
            if (i == 32'd5)
            begin
                rd1_addr = 5'd10;
            end

            // Pulse the clock in this for-loop
            clk = 0;
            #20;
            clk = 1;
            #20;

            wr_addr = wr_addr + 5'd1;
            rd0_addr = rd0_addr + 5'd1;
        end
    end

endmodule

Any helpful guesses or tips would be very much appreciated.


texts: Circuit Implementation of Dynamical Systems - Lorenz Equations (Failure Analysis)

texts:
Let me begin with the disclaimer: I am a mathematician and not an electrical engineer. That being said, surely I am missing something simple. For classroom demonstrations in dynamical systems, I have been constructing analogue computers from op-amp circuits. Some of the circuits are of my own design, and some are copied from other scientists. All of them have been successful except for this one, by Cuomo & Oppenheim, 1993, Physics Review Journal:

This circuit is designed to mimic the Lorenz Equations (rather, a re-scaled version thereof). The [x] are analog multipliers (AD633JN), and I am using NTE858M op amps. I have checked my work and I am convinced that I have built correctly. I have also verified the accuracy of the schematic, and I cannot find any discrepancy between the circuit and the corresponding dynamical system. The only output is a millivolts noise.

Why does this implementation fail?

Here is a link to the author's paper for more detailed information:

http://www.rle.mit.edu/dspg/documents/CircuitImplementation_000.pdf


texts: Installation of MSP430's IDE Energia in Ubuntu

texts: I am trying to install Energia for Ubuntu but until now the only thing that I have successfully managed to do is download the binary release version for Ubuntu! I have searched everywhere to find instructions and there some forums that try to provide them but they don't! I have started to lose my faith. Does any of you working with MSP430 microcontroller can explain simply how to install Energia in Ubuntu 14.04? Please don't provide links to other sites/forums because I am 100% sure that I have checked them all. Literally I have searched up to the 7th page in Google and every single page is purple as a result of visiting them all...


texts: Can ferrite beads be used on digital PWM output?

texts:
I am thinking how to reduce the EMI noise of the large LED indicators driven by tlc5947. This chip has digital outputs that limit/regulate current through light emitting diodes by switching on and off. The internal oscillator runs at about 4 MHZ and it looks like quite a powerful circuitry, 12 V, 600 mA for all assembly.
One of the ideas coming to mind is to use ferrite beads sequentially with LED diodes in the output. The concerns against are that be these inductors, they may generate the voltage spikes when current is turned off. From the other side, some sources say that ferrites do no accumulate as much energy as a coil of relay that would absolutely require a diode.
There are 24 channels per chip, and there are multiple chips, so this means lots of ferrite beads. But they are quite small and rather cheap so probably can be mounted if the bead is enough. With such amount of components, adding extra capacitors, resistors per every channel looks like no fun.
Could anybody with the knowledge say how good is the idea to put ferrite beads on the digital PWM output of the LED control chip running at 4 MHZ? I understand that the best would be to build the two prototypes and measure with near field probe (that would show the difference between the versions but not 'good enough' - 'not good enough') or at least just directly the waveform. There is a job and cost to build however. Maybe there is some generic knowledge on how good the idea is.
The goal is just to reduce the possible EMI noise. The indicators work very well, they do not even thing to flicker or the like.
P.S. Answers of the kind I should not be designing the circuit just because I am asking this question are out of scope.


texts: SPI waveform on Raspberry Pi is not clean, and I'm wondering why

texts:
I have a Raspberry Pi Zero Wireless and I wish to connect it to an FPGA via SPI.  I have done some SPI tests with my 100 MHz oscilloscope and see the images shown below. The Raspberry Pi correctly outputs the text "Test" using a simple C program.

The SPI is running at 1 MHz. The waveforms do not look very clean, and I am wondering why. They are not clean on the rise and fall points. I am using hookup wire to connect to the GPIO Pins. Ultimately, I wish to make this much faster than 1 MHz. Why are there spikes in the waveforms?

I am not using any pull up or pull down resistors. Should I? The wires are simply connected to the GPIO header. The chip select line (yellow) has some anomalies that I wish to get rid of/learn about.


texts: Finding required maximum current rating for a diode which will run in PWM mode

texts:
Consider a diode rectifier which will transfer a PWM signal. The duty cycle rate of this PWM signal is \$D\$ (\$0 \le D \le 1\$). The diode on state current is \$I_{ON}\$, and no current will be drawn when the PWM is low (resistive load). And the datasheet says that the maximum continuous forward current of the diode is (\$I_{FM}\$).

How do I determine \$I_{FM}\$ (i.e.; choose a diode) from given \$D\$ and \$I_{ON}\$ values? Can we always assume that \$I_{FM} = D \times I_{ON}\$ for all duty cycle rates and PWM frequencies?

Please list other circuit specifications needed for making this calculation, if there is any.


texts: RC Debounce: Is there a benefit to placing the capacitor in parallel with the switch?

texts:
I've always seen RC debounce circuits drawn wire the capacitor tied to the same potential as the switch.
E.g.

if the switch is high-side, the cap is high-side
if the switch is low-side, the cap is low-side.

Like this:

But, for a normally open switch, this has the issue of transience at boot-up. At t=0, C1 acts like a short, giving an unwanted rising edge on boot to the signal.
Is there any disadvantage to tying the capacitor to the opposite logic level as the switch? Like this:


texts:
I am attempting to create a 0-5V analog output signal. No need to drive a load. I desire to control this via a 3.3 digital MCU.

I have attempted to translate the 3.3v PWM to 5v via a n channel mosfet and then through a single or double RC low pass filter.

This there a more accurate or better way to do this besides using a separate IC to do so?

simulate this circuit – Schematic created using CircuitLab


texts: I am interested in theoretically calculating the current consumption for a design I am currently working on. My final goal is the design of the proper power management circuit. I am a bit confused on which current values I should pick from every datasheet in order to approach a descent and "realistic" calculation. For example, I plan to integrate a TXS0108E IC. At page 6, electrical characteristics table, what is each current reported? I have done some search and found that I_I and I_OZ are leakage currents, right? But then the test conditions for the I_CCA and I_CCB include zero I_O. Should I include only dynamic values for my estimation or leakage ones as well? Which ones are dynamic and which are leakage?


texts:
So in a simple DC series circuit, why do some globes shine more brightly than others? And which ones are the brightest? Obviously each consumes a certain amount of voltage but I don't think the brightness decreases through each lamp- more like the middle is the brightest (or something crazy like that, or I could be wrong about literally everything).
I'd appreciate any clarification.
Thanks

simulate this circuit – Schematic created using CircuitLab


texts:
I have been designing and prototyping a PCB for the last couple of months. I'm at the point where I'm extensively testing these boards before going into production. I have come across multiple reliability issues, like a USB or CSI bus not working on multiple PCBs after 2 or 3 weeks. These issues did not show up when I initially powered up the device and tested it with all peripherals connected. So I'm fairly certain that these reliability problems are caused by manufacturing error as I hand assembled these boards and had multiple boards not function correctly during the initial power up. My plan is to have the board house assemble the PCB to eliminate most assembly issues and I have a plan to test these manufactured boards. However, I want validate my design before I drop some money into professional assembly.

What are some common industry standards to validate the PCB layout? I came across this checklist which might be a good start to ensure a good layout, but are there any other steps that I need to take to verify the layout/design?


texts: Why does an unloaded D.C. motor draw significant current?

texts: I have a small water pump with a brushed D.C. motor that is designed to operate off a 12 volt battery. With no load on the pump the current drawn from the battery is around 3 amperes.  If the motor RPM continues to rise until the back-EMF nearly equals the supply voltage, why is the pump drawing such a large current?  The     mechanical losses are from brush and bearing friction and windage . I suppose that under no load the iron losses will greatly exceed the copper losses        .  It seems out-of-place for the power going to the motor to be ~36 watts.  What is going on?


texts: What is the purpose of these extra 'level shifter' BJTs on a MOSFET H-Bridge?

texts:
I am working on a 2WD Arduino project. Making the H-Bridge myself, and not using an IC like the L293 is a requirement for my project. After searching a while, I came across this, and based on this I made my own MOSFET based H-Bridge circuit:

I have some idea of how MOSFETs operate, and I can understand the working of this simpler H-Bridge:

However, I cannot understand how the BJTs in the first circuit work. From what I understand, when no current flows in to the base of Q5 BC547, it is in cutoff mode, and the 12V from Vcc drop across the R5 and the gate resistor R6, resulting in Vgs=0 and driving the MOSFET Q3 into cut off. On the other hand when logic is applied to the base of Q5, it goes into saturation mode. How this results in the MOSFET Q5 turning on is what I don't understand.

Also, please let me know if there are any problems with this design.


texts: Why is the voltage fluctuating at a divider connected to input of a DC-DC switching regulator?

texts:
Let me start by saying that I'm a noob at this.

I had the following circuit:

In place of the DC-DC I was using a RECOM R-78HB12-0.5. Here's its datasheet. The DC-DC provides 12V, stepped down from a 14S Li-Ion battery in order to power the CA V3. The CA V3 has an input for monitoring battery voltage - Vex - which accepts voltage in the 0-5V range. To provide that voltage, a divider is used - R1,R2. The values I used were 150K, 4.7K.

Once powered on, I measured fluctuating voltage at Vex. It would range between close to the expected value to less than half. The fluctuations didn't seem to exhibit any specific pattern except that if the system was off for some time, it would start close to the expected value.

Can anyone explain what may have been going on? Is there something obvious that I should have done in regards to the DC-DC hook up or could that have been caused by bad connection?


texts: How to determine the rated voltage for 3 phase motor

texts:
I have an unlabeled 3 phase motor (based on the size probably 5 HP) with 3 pairs of wires and a schematic picture for wye and delta connections. Since there’s no label I have no idea what the rated voltage is. I tried to run it with a 240V VFD at 60Hz base frequency and it makes an unhappy noise and the VFD trips.
I suspect it is a 480V motor. How can I determine the rated voltage for this motor?


texts: MLCC - Can I use high voltage rated caps for very low voltage scenarios?

texts:
Is there any important reason why I can`t use high voltage mulilayer ceramic capacitors for low voltage scenarios? For example 50V or 100V rated MLCCs for 3.3V DC applications?

I have bad eyes, and have trouble soldering 1206 or smaller packages, and higher rated caps always have much bigger (and easier to solder) packages. I can't use THT/DIP components everywhere because of the PCB layout.

According to this note from Maxim, it seems that capacitance is always more stable for lower voltages. But what about ESR, leakage and so on? Could there be any issues?

Note: My typical scenarios are mostly decoupling caps - using OS CONs for SMPS power. Anyway I could have still trouble finding big SMT 15pF caps for a XTAL ... :(


texts: Help me understand and fix this dimmer circuit

texts:
I have a table lamp which has a busted dimmer control. When I bought it the dimmer used to kinda work but then after a few days it worked only when the rotary knob was turned all the way high. After a while it broke completely and won;t even light up. I removed the lamp and tested it and the lamp works fine. So I decided to do a tear down and see whats inside.

This is what I found inside.

I managed to trace the circuit and here it is. I hope it's correct. If it's wrong do let me know.

I did some testing with my cheap multimeter and found out the values of 2 resistors, one being 1k and the other 5k. The pot showed no resistance at all which means the pots probably the part that went bust? but the pot switch works fine in continuity test.

Kindly explain how this circuit works to me and what went wrong here? Thanks in advance.

Update: ZY 406 might be an SCR, PCR406 in TO-92 package like user " Spehro Pefhany" suggested. So I have updated the diagram with this change in symbol.


texts:
I'm using GDB to debug a program for a Cortex M3. In the functions where the program crashes, when I execute line by line (using n), I eventually get:

(gdb) n
0x0800f498 in ?? ()

now if I backtrace (using bt) right after I get:

(gdb) bt
#0  0x0800f498 in ?? ()
#1  0xfffffff8 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

What exactly do the addresses 0x0800f498 and 0xfffffff8 refer to? How did I arrive there? Would looking at the linker map file help?

Edit: When I do info registers this is what I get:

info registers
r0             0x2001ffe8       537001960
r1             0x0      0
r2             0x0      0
r3             0x7ada53e6       2061128678
r4             0x0      0
r5             0x0      0
r6             0x0      0
r7             0x0      0
r8             0x0      0
r9             0x0      0
r10            0x0      0
r11            0x0      0
r12            0x0      0
sp             0x2001ffb0       0x2001ffb0
lr             0xfffffff9       4294967289
pc             0x800f499        0x800f499
fps            0x0      0
cpsr           0x1000023        16777251


texts: Can anyone identify this capacitor and its rating?

texts: It's got the company brand name, but they have not responded. Company is JAMICON.


texts: EAGLE - set part to a different layer without mirroring it

texts:
I need to set a new layer for a part without actually mirroring it.
I have many pin headers already set up on my board and wired up, but I need some of them to face the other way (Set them to bottom layer). This is just an aesthetic feature, but it would be nice to know if I should populate it on top or on the bottom layer. I can't just mirror it, because the pins would be mismatched and would not work.
Is there some way this could be done?
Creating a new library part would be a possible solution, but with how many pin headers (and different sizes of them) there are, it would be very time consuming. (But it seems this is the only way so far)
The only thing I want is to print the outline on bottom layer of the silkscreen.
On the attached picture, I need one of them to face the other way, without changing the wiring, if possible.
Thanks.
Edit:
I only need the outline of my pin header (what is visible on the silkscreen after manufacturing) to be on the bottom layer. The routing will stay the same.


texts: Tool or method to listen to a custom RS485 bus traffic

texts: How do I listen to a CFLink bus for data? The said bus was implemented on top of RS485. I've tried hooking it up using an RS485 to serial adapter and RealTerm but I've got nothing returned even though the bus was having some activity.


texts:
Is it possible to show only the ground planes like the one given in the figure?
Thanks


texts: DC 12V to AC inverter, can make a product to dual voltage 110V and 220V in a single inverter?

texts:
I have searched quite a while for a nice
DC 12V to AC inverter, should have dual voltage 110V and 220V output in a single inverter (with universal sockets)? but not seeing options yet, I see many ones saying dual voltage, but actually have 110V version or 220V version, they're not in a single inverter, wonder is it some technical difficulty or something else, just being un-popular?

Update: It's because from the years international travel I have collected quite some small appliances, like hair dryer bought when was in Switzerland (1000 watts working with ~230V only), and electric cooker from Japan (600 watts working with ~110V only), I will continue have many international travel like 3months in UK, 2 months in Japan, 2 months in Africa; want to make all them work at some off-grid 12V DC lithium battery powered places, wonder is there an easy DC 12V to AC dual 110V 220V voltage in a single inverter?

For example, this product https://amzn.to/2RSJmmN can convert DC 12V to AC 110V, or DC 24V to AC 220V;  can I have 2 set of 12V batteries in series to get DC 24V, then easy to have both AC 220V (when two batteries in series), or AC 110V (when two batteries in parallel)?

and the above product is 5000W Power Inverter DC 12V to AC 110V, costs $65, now I am willing to pay 2x cost for two products, one for 110V output and one for 220V output, can any vendor make the two in a single product? (to save space/weight when traveling) is 2x cost enough to make such a single product?   or 3x costs?


texts: Does op-amp open loop gain change with DC input voltages versus small-signal AC input

texts:
I was wondering whether or not DC voltages can be amplified by op-amps. I thought about a typical Miller op-amp structure (differential pair input) and I suppose it could amplify a DC voltage.
I am slightly confused though, does the open-loop gain of the op-amp as a whole not change when faced with DC input voltages compared to small-signal AC voltages? We always derive our op-amps small-signal gain, DC large-signal gain will be different right?
From the Analog IC Design concepts I have learned, we always used to talk about the small-signal gain of different amplifier stages (common-source, gate, etc.) The DC voltages was just for bias. For example, lets say my amplifier was a MOS common-source stage with a drain resistance, the open loop small-signal gain would be -gmRd. But that's only small-signal, not a DC voltage.


texts: Confusion with the gain concept of an amplifier

texts:
Before asking my question I want to briefly write about the basic meaning of the power gain.

Below is a model of an amplifier:

It shows the source input and amplifier output from left to right. In the middle there is the amplifier with the voltage gain A.

For simplicity above, both the source and amplifier output impedance is zero.

So the voltage at the input of the amplifier is exactly v1.
And the voltage at the amplifier output is v2 = A*v2.

For the input and output power hence p1 and p2 we can write:

$$p1 = v1^2/Z1  $$
$$p2 = v2^2/Z2 $$

Now the power gain is defined using 10 based log:

Power gain(dB) = \$10*\log(\frac{p2}{p1})\$

which can be rewritten as:

$$10\log[\frac{\frac{v2^2}{Z2}}{\frac{v1^2}{Z1}}]$$

So finally we can write it as:

Power gain(dB) = $$20\log(\frac{v2}{v1}) + 10\log\frac{Z1}{Z2}$$

My question:

Now the second part of the last power gain equation confuses me.
It is because, according to that equation the gain is impedance dependent.
Only if Z1 = Z2 we can omit it.

But when we have an amplifier such made with an opamp or a single transistor why we never talk about Z1 and Z2 when it comes to gain? We say "the gain of the amplifier is such". Imagine an amplifier made with an opamp using negative feedback, I cant see in the gain equation Z1 = Z2. I guess if this model were for an opamp Z1 would be the input impedance and Z2 would be the total load at the output.(?) But seems we do not take them into account when we derive the power gain.(?)

I hope I could express where I'm stuck at clearly.


texts:
I'm experiencing an effect somewhat like GSM frame-rate audio breakthrough in my auditory systems - completely different frequencies but equally wideband. I've noticed it occasionally in the past - always at this precise time of year.
Sounds hard to describe but perhaps something like a tinkling of small bells, a scraping of hooves (perhaps akin to those of Rangifer tarandus ) and perhaps a distant, deep and resonant 'Ho ho ho ho'?
I'm told that NORAD (North American Aerospace Defense command ) have had possibly related issues and have implemented an official NORAD tracking system  active specifically at this time of year.
Any clues?
Regardless, merry Christmas.
______________________________
One might hope this post would survive a few hours before suffering the inevitable fate.


texts: Which parts of this rotor can be made out of plastic?

texts:
I'm asked to redesign a rotor, by making as much parts of it as possible out of plastic. The issue is its weight, we want to make it as light as possible. Especially the shaft & axis of it is the issue; can it be made plastic?

I don't have the rotor physically, I only have photos and drawings of the same kind of rotors. The bad thing is that, I have to give my report/idea before seeing it myself.

I'm not able to make a comment about this rotor, because it is very different from the rotor types I saw until now. I don't understand why it has only one winding (and why it is perpendicular to the axis), and I don't understand the reason of having those triangular N-S parts.

The below are some pictures that I found on the web. Can you please give your answers by referring to these pictures.

Picture #1

Picture #2

Picture #3

Picture #4

Picture #5

Picture #6


texts: Why am I getting 10V at the opamp output instead of 0v?

texts:
I have a design that it is based on the CAMPBELL (MAXREFDES4#): 16-BIT HIGH-ACCURACY 4-20MA INPUT ISOLATED ANALOG FRONT END (AFE) reference design from Maxim. This is how the original looks like:

And it uses the following voltage supply:

As you can see, it has two 5V regulators taking their output from a 12V regulator. Then on the opamp/ADC circuit, the 12V supply is feeding the opamp directly and the two 5V regulators are supplying voltage to the ADC and voltage reference.

The whole idea of this reference design is to have the SPI signals isolated from the main processor in this manner:

Due to budget and space constraints, because I need four of these "channels", I had to modify it from the original and I decided to eliminate the SPI isolation chip since I would require two. I did this because it's a rather expensive component and I don't really need the isolation. Also, because this board is powered by 3.3V and the OpAmp requires 12V, the original circuit also contains a step-up transformer that I'm eliminating as well because I have a 12V power supply on my board.

Additionally, the grounds are joined together by a ferrite, so I just decided to remove the ferrite and have a common ground plane for all the circuit on my PCB.

The final design, the one is not working correctly, looks like this:

The power supply looks like this:

And the GND plane looks like this:

You can see there that is just a continuous and uninterrupted GND plane.

So I essentially have the same circuit than the original, or do I?

The 12V go directly to the OpAmp, I have the two 5V regulators, one for AVDD and other for DVDD (I had to add a 12V-to-6.5V regulator in the middle because the 5V regulators get really hot with the 12V directly). The only big difference is that on the PCB, instead of having two separate planes for AGND and DGND joined together by a ferrite, I have one GND plane for all the board. But still essentially the same to me.

Now the weird thing that I don't understand, is that on my board when I measure the voltage at the output of the +5V AVDD regulator I get 6.75V! which doesn't make sense! Also, when I measure the voltage at the ADC input I get 10.7V! and I have no idea why. In another test I performed, I removed the AVDD regulator completely, desoldered it from the board, but I still get the same 6.75V on AVDD!!

That doesn't make any sense at all! I measured trying to see if there is a short circuit with another part of the board but the AVDD power rail is completely independent and it doesn't have contact with any other traces or rails. This is an image of how the AVDD rail looks like on the board (The square at the bottom is the +5V AVDD regulator).

The voltage on the AVDD rail only went to 0V when I also removed the 12V supply of all the OpAmps which I also don't understand.

Here is a closer look of one of the channels that include the OpAmp, the ADC, the voltage reference, and the passives.

To remove the OpAmps 12v supply I cut the traces that go to the pin 5 of U8. It is also when I remove the 12V from the OpAmps that the output of the AVDD regulator goes to 5V as it should be.

So, what is going on??? The circuit looks good to me, I don't understand what is happening.

If someone is willing to help I could share the Altium Designer files, I just need to know desperately what is going on.


texts: Is this a proper way to use a transistor?

texts: Are there any problems with the way this works, or a more effecient way of doing this? Although this works fine on my breadboard I feel this may be improper. I was unsure where to put the negative terminal of the battery which switches the transistor, and putting it on the collector seems to work. Is this because it flows from the base, to the battery, and then from the battery to the collector, allowing the larger current to flow to the emitter, or is that logic all screwed up? Thank you :)


texts: How to solve this circuit with dependant current source and resistors that are neither parallel nor in series?

texts:
I've spent more than 3 hours with the idea that we should find current across every resistor in terms of \$i_{10}\$. This is somehow not working, I mean putting the KCL (Kirchoff's Current Law) equations of different nodes into each other just makes left and right sides equal. It doesn't give any value of \$i_{10}\$. The dependent current source only makes it more difficult. Please guide me on the best approach to solve this question or if you're kind enough give the solution.
The solution will be highly appreciated!


texts: Battery is 12 volt and motor is 3.7 volt....will it work?

texts:
I have a battery that says it has a working current of 4.6A and rated voltage of DC 12V
I need the battery to power a motor for a fan that says it has a voltage of DC 3.7V
Will it work? What will happen?


texts:
I've been buying wire-to-wire and wire-to-board Molex connectors that look like this:

from a local hardware store for years (the image is taken from SparkFun, which sells them with the crimp terminals and wire pre-installed).

I'd now like to buy a large number of them from an online supplier (e.g., DigiKey or Molex themselves) but I can't figure out what specific type of Molex connector they are. Molex's site has quite a variety of connectors and I'm finding it difficult to determine which product line these ones belong to.

Their pitch is approximately 2.5 mm (possibly 2.54) and they use crimp terminals that are held in place by a raised metal "flap" (one per terminal) that catches on a narrow rectangular hole in the plastic casing (in the photo above, these holes are on the underside of the female end of the connector).


texts: What is the design tool for Lattice HDR-60 Video Camera Development Kit?

texts:
I have recently received HDR-60 Video Camera Development Kit. I was excited to do some verilog coding for HDMI interface. Design software I have downloaded was iCEcube2 2017.08 (Licence will provided from Lattice-semi based on the shared MAC address). But unfortunately iCEcube2 2017.08 won't support LatticeECP3-70 (BGA484) which is present in the HDR-60 dev-kit.
Can anyone suggest a design software to program HDR-60? I understand that there is another tool Lattice Diamond, that also I have tired and it also showed as tool wont support LatticeECP3-70. Kindly advice.


texts: Replacing phone battery with power supply

texts:
I have an old phone (nexus 5) that I want to use for a project. I need to replace the battery with a permanent power supply, I've found the 3 pins of the battery and made a breakout connection with 1/10" headers instead of the stock battery connector. The phone will boot fine with a battery connected this way. The phone runs at 4.2v, ~500±100mA.
The issue is the phone won't boot on my bench PSU. Recovery mode works but Android powers off midway through boot. I suspected it was the lack of a thermistor in the third battery pin that made it shut down. I measured the resistance and added a fitting resistor between the battery monitor pin and ground (56k). However, the phone wont boot either.
I also suspected a power spike that my power supply could not handle could be the culprit. But after adding a 4700μF cap the issue persists.
I have anoter nexus 5 motherboard that behaves just the same.
What else can be causing the phone to act differently with the power supply and the battery?
Ps: I have access to te UART port of the phone, the kernel does not print anything relevant and the phone shuts down at random boot events, sometimes glitching the line, so I think this is hardware or at least isolated from the main processor.


texts:
I've just soldered a SOIC-16 am26c32 on to a breakout board.

The datasheet shows the orientation of the chip by means of a semi circle at one end (http://www.ti.com/lit/ds/symlink/am26c32.pdf). However, on the actual device, there is no such semi circle to be found - only the name of the chip.

Am I to assume that pin 1 is the bottom left, when the chip shows the writing the right way up?


texts: NXP LPC GPIO Glitches on every power up. How to solve?

texts:
I've been using NXP LPC microcontrollers for some time. One problem that I've faced in several projects is that every time the MCU is powered and a GPIO is setup to LOW logic level and output, a glitch in the GPIO pin happens.

The trace below was captured in one of the GPIOs of a LPC1548 and shows that the glitch has 1.84V and lasts for 1.26ms.

Even considering that this glitch has low amplitude and is fast, anything connected to the GPIO can have undesired behavior on board power up.

Some time ago didn't know about this behavior I connected the GPIO to a MOSFET gate that was controlling a TRIAC (for AC motor control). Because of this glitch problem, everytime the system was turned on, the motor quickly bumped/shaked. In this particular problem I had to change the MOSFET from N channel to P channel and invert the GPIO logic so it won't glitch anymore. Problem fixed.

Anyway, I'm having this problem again in a project that I cannot keep changing or adding components to the board (for space and costs constraints).

Does anyone knows how can I eliminate this glitch?


texts: Failure for parallel - parallel two-port network

texts:
I'd like to know what's the simplest example of two-port parallel-parallel network that fails Y=Ya+Yb.
Just as two T networks fail series-series connection, I thought that two Pi network would fail parallel-parallel, but it isn't true.
Could you help me giving a simple example?


texts:
PNP and NPN transistors in the circuit have identical Is values. Based on the PNP transistor is connected to a DC voltage source.

k = 1.38064852×10-23 J/K
qe = 1.60217662 ×10-19 C
Is = 0.69 fA at 17°C
VA = ?
β = 100 A/A (in Forward Active and Soft Saturation Regions)

Determine VOUT and IC when Vx=0.8V. Which region is the transistor operating at?
Determine VOUT and IC when Vx=0.75 V. Which region is the transistor operating at?
Determine VOUT and IC when Vx=0.85 V. Which region is the transistor operating at?

Solution:

VT = kT/q, so VT = 25 mV

In PNP, IC = Is eVEB/VT, but how to determine VEB?


texts: FSM binary number divisible by 5 truth table

texts:
I am having trouble seeing if my truth table based on the exercise's instructions is correct (mostly because the instructions are really confusing me and the TA's explanation really didn't help, this is kind of my last resort).
Instructions:

Consider a circuit that has a data input Data and a reset input Reset and a single
output Z.
The output Z should be asserted true (set to 1) whenever the string of 1s and 0s entered since the last assertion of Reset, when interpreted as an unsigned binary integer, is divisible by 5. Otherwise it should be set to false (0). Assume that the two inputs act independently, i.e., they can change at the same time. Also, approach this problem using a Moore machine, where the output Z’s value is associated with being in a particular state, and not with the transition itself. This will be explained further in class - the parity-checker FSM is an example of a Moore machine. Finally, use the following properties:

If a%5=α and b%5=β then (a+b)%5=(α+β)%5.
If a current string has a numerical value of x then placing a 0 on the right hand side results in a string having a value x + x and placing a 1 results in a string having a value x+x+1.

UPDATE (more instructions that the professor has relayed now):Derive a symbolic state transition table for this problem (a finite state machine). Now, choose a state encoding and then, using D flip-flops that are rising-edge triggered, derive expressions for the output Z and the new states as functions of the current states and the current inputs.
This is the truth table that I came up with:
Q2   Q1  Q0  D R |  Q2' Q1' Q0' Z
0    0    0  0 0 |  0   0   0   1
             1 0 |  0   0   1   0
             0 1 |  0   0   1   0
             1 1 |  X   X   X   X

0    0    1  0 0 |  0   0   1   0
             1 0 |  1   1   0   0
             0 1 |  1   1   0   0
             1 1 |  X   X   X   X

0    1    0  0 0 |  1   0   0   0
             1 0 |  0   0   0   1
             0 1 |  0   0   0   1
             1 1 |  X   X   X   X

0    1    1  0 0 |  0   0   1   0
             1 0 |  0   1   0   0
             0 1 |  0   1   0   0
             1 1 |  X   X   X   X

1    0    0  0 0 |  0   1   1   0
             1 0 |  1   0   0   0
             0 1 |  1   0   0   0
             1 1 |  X   X   X   X

where Q2,Q1,Q0 represent the remainder present state in binary form and Q2',Q1',Q0' represent the remainder next state in binary form. Inputs: D=Data, R=Reset. Outputs: Z (The X represents some next state that isn't important (from what I understood of the instructions) since D and R are independent.


texts:
I have a quick question on this example problem on (ideal) OpAmp analysis. I understand the basic cases of negative and positive feedback, and how there is a virtual short between the input pins of the opamp. Things just seem to get a bit confusing once we implement more than one opamp and start connecting inputs and outputs and, welp, I guess I need some help understanding this one:

My steps towards a solution:
(Let's call the OpAmp on the left the first OpAmp and the one on the right the second OpAmp)

There is virtual short between ground and the inverting input on the first opamp. There must be a voltage drop across the first resistor with value R equal to V_in...
This means a current flows equal to V_in / R through the first resistor. This current cannot go through the OpAmp so it goes through the two 4R resistors.

This is where things get tricky. How do you find the voltage drops across the two 4R resistors? You can't just assume the current is split evenly between the two resistors.

What would the next step be? Any help would be greatly appreciated!

Thanks,

Matthew


texts: Proper algorithm to charge LiPo batteries

texts:
We are going to develop a new LiPo battery UPS circuit for our handheld. I have read couple of articles and almost all of them recommend to charge the battery based on the following curve. I have also read articles that authors say that reaching the 4.2V limit is sufficient for most cases. Someone please guide me on this issue.

Recommended charge curve:


texts: Do "multiplicative" current mirrors exist?

texts: What I am talking about is something like a mismatched current mirror. Like the following where the left transistor and the right transistor are unmatched therefore the drain source current are different by a factor K. Is this possible?


texts: Controller to use 18 volt power tool battery to power 20 volt laptop

texts:
I would like to use my 18 volt Bosch lithium ion batteries to power my Thinkpad laptop which accepts a 20 volt power supply via an USB-C connector.
I think I need some sort of "smart" controller but I have no idea what it is even called or what to look for. I think the controllers that I have found in Google searches have been for the opposite purpose - using an AC wall charger to recharge a battery.
My goal is the opposite: I want to use a fully charged battery to recharge my laptop.
This seems like it's close to what I want but appears to only accept 3 Volt input. Sorry for the nob question, I have no idea what I should be looking for.


texts: Circuit for voltage division and DC shift doesn't work

texts:
I've connected the circuit below on a breadboard and tested it in the lab:

Components:

\$R_{1}=1\,M\Omega,\;R_{2}=40\,k\Omega,\;R_{3}=R_{4}=R_{5}=R_{7}=R_{8}=20\,k\Omega,\;R_{6}=49.9\,k\Omega\thickapprox50\,k\Omega,\;R_{9}=R_{10}=10\,k\Omega,\;R_{11}=5.1\,k\Omega\thickapprox5\,k\Omega,\;R_{12}=1\,k\Omega,\;R_{13}=R_{14}=R_{16}=R_{17}=R_{18}=R_{19}=2\,k\Omega,\;R_{15}=5\,k\Omega\$

$$$$

\$C_{1}=470\,\mu F,\;C_{2}=1\,\mu F\$

$$$$

\$V_{CC}=15\,V,\;V_{EE}=-15\,V\$
$$$$
op-amps are of the type LM358P.
$$$$

The upper part takes the DC component of an input signal through a passive low-pass filter, divide it by 5 through the voltage-divider network (note that R3 and R4 are in parallel), then add 2.5 V to it.

The lower part take the AC component of an input signal through capacitor, divide it by approximately 10 through the voltage-divider network (note that R12 and R13 are in parallel), then add 2.5 V to it.

The problem is that the output appears completely different from the theoretical values:

For the upper circuit, when the input was a DC voltage of 5 V, the
output was around 10 V instead of 3.5.
For the bottom circuit, when the input was a sine wave, the output
was completely distorted. It couldn't be recognized as a sine wave.

I don't know where the problem could be. The simulation results of the circuit give results as expected.


texts: How much current can I draw from a battery?

texts:
I would like to build a portable bluetooth speaker and I would like to know how much current I can draw from a battery like this?

The battery is rated on 3.7V and I want to supply this amplifier with a step up dc dc converter. The amplifier suggests 3A 12V power supply.


texts: Why do these two single supply noninverting amplifers not work but the third does?

texts:
Why don't Circuit 1 and 2 work?

Circuit 1:

I don't get gain of 4 but of about 1 like buffer amplifier.

Circuit 2, I just connected R2 to ground and the Vcc/2 generated using R4 and R5 to noninverting input of opamp:

More mysterious; here the opamp is stuck at vcc.

Circuit 3, similar to circuit 2 but now there is a capacitor between R2 and system ground:

This one works.

EDIT:

OK, thanks for the answers. I want to reach a conclusion now. I conclude that the following circuit from SLOA058 page 6 is wrong:

Since I use a voltage divider to created Vcc/2, this circuit simply will not work. Do you agree? It seems that this application note has wasted a lot of my time.


texts:
I have one stepper motor, it's a permanent magnet.
Does the 3 wires unipolar exist? can a 3 wires unipolar system be created from the 4 wires bipolar
I didn't find any structures of it.
Ines


texts: Identify this symbol: two circles overlapping

texts:
The attached screenshot is from a schematic in a datasheet.  I know that the flat-topped arrow is a diode, but I don't know what the pair of looped circles are.  Can anyone help me out?  If there's a good online symbol reference, please share the link!

Thanks!


texts: Is a potentiometer an actuator or sensor?

texts:
While I was taking notes I get confused by the component named "potentiometer", I don't know in which category I should place it.
If I'm correct the definition of a sensor is broadly "a component that converts other form of energy to electrical form" and an actuator is the reverse.
Is a potentiometer a sensor or an actuator or both or neither?


texts: Reverse-design simple µC boost converter: How to calculate ideal frequency & pulse width

texts:
I aim to create ~400V @ <1mA from a 12V/2A supply to supply a Geiger-Mueller tube using a simple µC driven boost converter for a Geiger counter. The converter consists of just an inductor and a MOSFET, followed by a voltage tripler circuit. The µC provides PWM and implements a simple control loop using the built-in ADC.

Empirically, I've determined some duty cycle around 125kHz to nicely create the 400V, keeping the setup stable around 55°C at the vicinity of inductor / FET.

I was now wondering how to lower the temperature of the system.

I'd like to understand how to approach designing such a boost converter backwards, i.e. using parts from the drawer/bin, and then calculating suitable operating frequencies and duty cycles to achieve the most efficient converter possible.

I'd appreciate help and pointers for the mathematical treatment or other guidance.

Thanks!


texts:
I'm trying to do a simple LIN bus sniffing in my car with an Arduino.
This should be possible with a simple voltage divider if I'm not wrong.

Would this schematic work?

0-12V in
       |
     [10k]
       |
       +-->0 to 4.86V out to Arduino
       |
     [6k8]
       |
      VEHICLE GND


texts: Configuring BLDC motor for low-speed application

texts:
Given: I need to the simulate sinusoidal forces on a wind-tunnel model using a bench-top setup. I've designed a rig where I spin a load at high speeds to generate centrifugal centripetal forces, and those forces--which will periodically align completely in the X, Y, or Z directions--will serve as my sinusoidal forces.

I will mount the rig on top of a six-axis load cell, and I will measure the periodic forces via the load cell.

At this point, my load consist of a TBD-length aluminum or steel rod. I've derived the following expression for my loading given the rod's mass/unit length (\$\rho^{l}\$), desired centripetal force (\$F_c\$), the length of the rod (\$L\$), and the distance from the end of rod to installation bolt hole (\$d\$):

$$
F_c = \rho^{l} (\frac{L^2}{2} - Ld)\omega^2
$$

or, when re-arranged to solve for \$\omega\$:

$$
\omega = \sqrt{\frac{F_{c}}{\rho^{l} (\frac{L^2}{2} - Ld)}}
$$

Problem: For safety, I'm trying to keep the forces and speeds low. To generate a 2 lb. (8.90 N) load and a 20 lb. (89.0 N) load (one load needs to be 10X greater than the other) with a 4 inch (0.0762 m) long, 0.5 in (0.0127 m) diameter steel rod, I require spinning my rods at 467 RPM (48.9 rad/s or 7.8 Hz) and 1478 RPM (154.7 rad/s or 24.6 Hz) respectively.

Originally, I just bought 2 hobby BLDC motors and figured I'd command "slow" speeds via the ESC, but now I realize that they operate way too fast for my 2 lb load without some sort of reduction. A quick test of the Viking motors at 2 cells and a "slow" PWM command (1 ms/20 ms pulse) yielded average speeds around 1200 RPM.

My questions:

Given that I only have 2 weeks to run my experiment, will a brushed
DC motor like this work for the 2 lb. load, or is the motor
going to wear out? More abstractly, what is the usable continuous-operation lifespan of micro brushed DC motors?
How strong are the ball bearings in small, hobby BLDC motors?
Could my Viking motors withstand a 20 lb. radial force? More abstractly, what is the radial force limit on small, hobby BLDC motors?
Would you recommend some other motor system for this low-speed application?
Stepper? BLDC with smaller \$K_v\$? BLDC + speed reducer?

Many thanks, and please let me know how I can improve my question.

UPDATES: Your comments/answers and further research on my end are pushing me towards buying some sort of speed reducer for both motors/loads. I will operate my motors at 4000 and 6500 RPM, and I will use 11.73:1 and 4.5:1 speed reducers + external ball bearings to safely reduce 4,000 RPM and 6,500 RPM to near 467 RPM and 1477 RPM respectively.

Thanks to @John Birckhead for making me think about this: My steel rods have mass of 0.098 kg, length of 0.102 m. When the rod is perfectly parallel to the ground, rotating the rod will require torque (T) of 0.053 Nm | T = mgL/2 = 0.053 Nm. If \$K_\tau = \frac{1}{K_V}\$, then my motor has a Kt of 0.0023 Nm/A, and generating 0.053 Nm of torque will require 22.8 A (!). This is greater than the max current rating of the motor (16.7 A). I understand momentary current spikes from a motor are OK, but can a motor sustain momentary current spikes for many cycles? This gravitational torque will fight my motor for a fraction of every cycle.


texts: How to deal with the opamp input offset in a circuit with multiple opamps with inputs connected together?

texts:
My question is somewhat similar to this one asked here before. I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

The input signal is being fed to two (possibly three) inverting operational amplifier circuits. The positive input of each opamp is used to adjust the input offset to a desirable value. Resistor R11 is added because the input is a voltage drop from the 50Ω resistor. Another thing I should mention is that the input signal scale is approximately from 0 V to 10 mV.

The problem is that these circuits affect each other. This behaviour is explained in the answers to mentioned question, so I'm trying to design a different circuit. I have read this tutorial by AD and a similar by TI. So, there are several methods of adjusting the input offset. I'm using the one for the inverting opamp circuit and the impedance of my voltage source is not low enough so these circuits don't work correctly together. I thought of the following solutions:

Use a non-inverting circuit. Offset adjustment can be done like this:

simulate this circuit

However, I'm worried about connecting multiple opamps together. In the above circuit, R2 changes the input signal; will multiple opamps with inputs connected together affect each other in this case?

Simulate the whole circuit and optimize resistor values so all the opamps will have a correct gain. This method would produce a lot of optimization goals which would be difficult to achieve. How stable a circuit built like this would be?


texts:
I designed the following circuit so that the output voltage is Vout = 0.625V. But after actually building the circuit and testing I get Vout = 0.95V.

So obviously I was wrong but I can't manage to get the computation right, can you put me on the good track? How to get this Vout = 0.95V?

OP284 Datasheet


texts: What is the purpose of the 10kΩ resistor in this circuit?

texts:
Below is a simple circuit involving an Arduino, a push-button, and an LED. However, I don't quite understand what the purpose of the resistor is. Wouldn't the circuit function without it?

Note: Since this question is concerning the behaviour of the circuit rather than the functioning of the Arduino, I've posted this here instead of the Arduino stack exchange.


texts: Pipelined Radix-2 DIF FFT SDF Architecture

texts:
I want to implement Radix-2 Single-path Delay Feedback (SDF) Decimation-In-Frequency FFT with Pipelining in VHDL.
I am trying to understand the below architecture as described in this MIT OpenCourseWare Lecture

Since its a DIF FFT, shouldn't the upper half of the data be directly passed on to next stage without requiring multiplication with twiddle factor? Is there a multiplexer which controls multiplication and not shown in the diagram? Can anyone please elaborate on this architecture.


texts: Controlling Triac w/optocoupler, need some help with optocoupler datasheet

texts:
Loads: Some baseboard heaters (1500W max, some motors, 12A max).

I have no experience using Triacs and optocouplers.

Triac: T3035H-6T,
Datasheet: http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00263568.pdf

Optocoupler: MOC3062SM,
Datasheet: http://www.mouser.com/ds/2/149/MOC3062M-196063.pdf

Optocoupler is driven by a 5V micro controller output which will be on as long as the load needs to be on.

I am planning to control the Triac with the MOC3062SM optocoupler, and would like your comments on the example circuit in the datasheet (Basic Applications).

I am uncertain about how to dimension (watt) the two 360 ohm resistors on the 240VAC load example.

I mean, if the optocoupler triac is conducting as long as LED is on, then 1/3A is flowing in the resistors, and producing a cozy 80W. So I guess I am not understanding the workings of the optocoupler, as I cannot believe we need to dissipate that kind of heat.

EDIT: I just realized the 1/3A is just momentary, the load takes the bulk of the voltage as soon as the triac fires...

Or does the optocoupler switch off a certain number of degrees into the cycle?

Your input will be appreciated.


texts: Choosing gain to get desired system response

texts:
I have to choose a gain so the step response fits a couple of criterias. The criterias are:

Maximum overshoot 20%
Settling time between 0.8s and 1.3s
Rise time between 0.8s and 1.1s

At first I tried to find out the desired pole location. I used the following equations

Overshoot: cos(arctan(y / (-x))) = 0.45595 (used Mp=e^(-pi*zeta/sqrt(1-zeta^2)) to find out the minimum damping ratio 0.45595)
Settling time: x = -4.89 and x = -3.556 (used ln(0.02)/ts to find out required real part)
Rise time: (pi + y / x) / y = 1.1 and (pi + y / x) / y = 0.8

The overlap of the area between those curves would be the desired pole location which looks like this.

Now, the block diagram looks like this

Its root locus looks like this (overlapped with the desired pole area)

As you can see, no gain would satisfy the requirements. Well, we can modify Kx a little bit and also add derivative and integral parts.

Kx = Kp + Kd * s + Ki / s (Kx is supposed to look like this, it's a requirement)

What I did was adding a little Kd so the root locus goes through the desired pole area, then I'd pick a point on the root locus to get the required gain. (I chose Kp=1 and Kd=0.135 to plot the root locus)

So the total gain should be

Kx = 5.29 * (1 + 0.135 * s)

right? Well, it does not work. I used stepinfo() to get the system response

    RiseTime: 0.3907
SettlingTime: 0.5625
 SettlingMin: 0.9084
 SettlingMax: 1.0152
   Overshoot: 1.5246
  Undershoot: 0
        Peak: 1.0152
    PeakTime: 0.8490

which is WAY off. Rise time isn't even close to the desired response and neither is settling time. What did I do wrong?

This is my code in Matlab

s = tf('s')
gain = 5.29;
Kp = 1;
Kd = 0.135;
Ki = 0;
Kx = parallel(tf(Kp, 1), parallel(tf([Kd, 0], 1), tf(Ki, [1, 0])))
p = 5/(s+5) * 1/s
pk = Kx * p;
h = 1;
figure(1)
rlocus(pk)
figure(2)
t = feedback(gain*pk, h);
step(t)
stepinfo(t)


texts: 455 KHz Double tuned IFTS for Wideband MW AM reception

texts: Vintage AM MW radios often had double tuned IFTs .The shape of the frequency response curve is well documented elsewhere .The coupling coefficient of these double tuned transformers is low and the Q is high probably to aim for KQ =1 .These old school IFTs do not have taps and   therefore  are high impedance devices that      are intended for Valve radios.I have rebuilt several valve car radios with   a cascode JFET IF amp to match these old IFTs .The sound on AM is fantastic compared to the muffled AM sound on most modern car radios .This brighter sound is because the Double tuned transformers do not sideband cut like the single tuned IFTs and narrow band ceramic filters found in the AM sections of more  modern car radios .These old junk box IFTs could be unreliable and I do not have many of them .The tightly coupled single tuned 455 KHz IFTs that are used on transistor radios is easy to find .If I used them then the retro car  radio would sound just like a modern one so there is no point in that .How could I configure 2 standard single tuned IFTs to perform like a Double tuned IFT?


texts: VHDL integer overflow in not taken `when` branch

texts:
In the architecture of some VHDL entity I have something like this:

type some_array is array(integer range <>, integer range <>) of std_logic;
signal foo : some_array(0 to 3, 0 to 3);

(...)

some_loop: for i in 0 to 3 generate
    something(...) <= foo(i-1, i-1) when (i > 0) else '0';
end generate some_loop;

I expected this to work fine, since foo is only indexed when i > 0. Unfortunately, it seems that VHDL / ghdl evaluates the i-1 even when i > 0, because when I run the testbed for this entity ghdl complains: ghdl:error: overflow detected.

Is this something to be expected? What's the best solution / workaround?


texts: I want to run big circuits by HSPICE. Does HSPICE have any limitations? (for example on number of nodes)


texts: Capacitors in parallel with voltage sources

texts: Why can't capacitors be connected in parallel with ideal voltage sources? In various questions involving it we were asked to ignore the capacitors, by our teachers without valid explanations.


texts: Nyquist theory for sampling data from TMP36

texts: Is there any way to make sure that sampling temperature(voltage) using arduiono UNO  from TMP36 sensor does not violate Nyquist theory?


texts: Getting Accelerometer values from MPU 6050

texts:
I m trying to read accelerometer values from mpu 6050 in atmega328p (Arduino UNO). I want an embedded c program that's why don't wanna use any external lib. So I read about I2C protocol, read the datasheet of MPU 6050, register sheet of MPU 6050 and developed a code as per my understanding.
Here's the code

#include<avr/io.h>
const int MPU_addr=0x68;
void i2c_init() {
  TWSR=0x00;
  TWBR=0x48;
  TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
}

void i2c_start() {
  TWCR=(1<<TWEN)|(1<<TWINT)|(1<<TWSTA);
  while((TWCR&(1<<TWINT))==0);
}

void i2c_stop() {
  TWCR=(1<<TWEN)|(1<<TWINT)|(1<<TWSTO);
}

void i2c_write(uint8_t data) {
  TWDR=data;
  TWCR=(1<<TWINT)|(1<<TWEN);
  while((TWCR&(1<<TWINT))==0);
}

uint8_t i2c_read(unsigned char isLast) {
  if(isLast==0) {
    TWCR=(1<<TWINT)|(1<<TWEN)|(1<<TWEA);
  }
  else {
    TWCR=(1<<TWINT)|(1<<TWEN);
  }
   return TWDR;
}

int main() {
  uint16_t i;
  i2c_init();
  i2c_start();
  i2c_write((MPU_addr<<1)|(1<<0));
  i2c_write(0x6B);
  i2c_write(0);
  i2c_stop();
  Serial.begin(9600);
  while(1) {
    i2c_start();
    i2c_write((MPU_addr<<1)|(1<<0));
    i2c_write(0x3B);
    i2c_start();
    i2c_write((MPU_addr<<1)|(0x00));
    i=(i2c_read(0)<<8)|i2c_read(0);
    Serial.println(i,BIN);
  }
return 1;
}

The problem is in the while loop, the program hangs after the i2c_start(); call.
I have checked this by putting a Serial.println("a"); after that line, but nothing gets printed on the serial monitor. I have also checked that the program enters the while loop successfully. So can anybody help where is the problem in the code?

Note:
1. All the i2c function(s) are in accordance with the book "The Avr microcontroller and the embedded system using assembly and C" by Ali Mazidi".


texts:
I'm getting weird values when using the QEI on the dspic33. The QEI counter goes up to about 32700 then goes to negative 32650 and starts decrementing  to 0 where it starts from 32700 and starts increasing again. I was wondering why the QEI is going weird negative decrease. I have attached the code where i intialize the QEI and how i get the value. Could it be a weird casting or bit shift going on.

void QEI2_Init(){

PMD3bits.QEI2MD = 0;
// QEI CONTROL REGISTER
QEI2CONbits.QEIEN = 1;
QEI2CONbits.QEISIDL = 1;
QEI2CONbits.PIMOD = 0;
QEI2CONbits.IMV =0;
QEI2CONbits.INTDIV = 0;
QEI2CONbits.CNTPOL = 0;
QEI2CONbits.GATEN = 0;
QEI2CONbits.CCM = 0;        // 00 = quadrature encoder mode

//QEI1IOC = 0;
// QEI I/O Control Register
QEI2IOCbits.QCAPEN = 0;
QEI2IOCbits.FLTREN = 0;
QEI2IOCbits.QFDIV = 0;
QEI2IOCbits.OUTFNC = 0;
QEI2IOCbits.SWPAB = 0;
QEI2IOCbits.HOMPOL = 0;
QEI2IOCbits.IDXPOL = 0;
QEI2IOCbits.QEBPOL = 0;
QEI2IOCbits.QEAPOL = 0;
QEI2IOCbits.HOME = 0;
QEI2IOCbits.INDEX = 0;
QEI2IOCbits.QEB = 0;
QEI2IOCbits.QEA = 0;

// QEIxSTAT: QEI STATUS REGISTERS (REGISTER 17-3)

//QEI1STAT = 0;
QEI2STATbits.PCHEQIRQ = 0;
QEI2STATbits.PCHEQIEN = 0;
QEI2STATbits.PCLEQIRQ = 0;
QEI2STATbits.PCLEQIEN = 0;
QEI2STATbits.POSOVIEN = 0;
QEI2STATbits.PCIIRQ = 0;
QEI2STATbits.PCIIEN = 0;
QEI2STATbits.VELOVIRQ = 0;
QEI2STATbits.VELOVIEN = 0;
QEI2STATbits.HOMIRQ = 0;
QEI2STATbits.HOMIEN = 0;
QEI2STATbits.IDXIRQ = 0;
QEI2STATbits.IDXIEN = 0;

POS2HLD = 0;
POS2CNTL = 0;
VEL2CNT = 0;
printf("QEI Init Done\n");

 }

void calculateEncoderPos()
 {
    qelo2 = POS2CNTL;
    qehi2 = POS2HLD;
   encoder.encoder2Count =  (long int)qehi2 << 15 | qelo2;
   printf ("Pos Low:%d \t", qelo2);
   printf ("Pos High:%d \t", qehi2);
   printf("encoder2Pos:%ld\n", encoder.encoder2Count);
}


texts:
I'm currently doing a lot of work in measuring transfer functions of circuits. One thing that crops up a lot is mains frequency noise:

As you can see there is a huge 11 dB leap at 50 Hz, followed by harmonics all the way up past the end of the amplitude response.

There also seem to be some side-bands around the 50 Hz. By this I mean observing the TF close to 10 Hz it is quite clean, but upon approaching 50 Hz there is an increase in noise. I don't have enough resolution to really see what this looks like properly but to me it seems like side-bands.

My question: what causes the distortion in the mains noise?

Is the power already heavily distorted when it reaches my sockets? Or is caused by the circuit? (Which for reference is a DAQ measuring an RC circuit). Is that intermodulation distortion around 50 Hz or just time-varying behaviour of the mains power?

EDIT:

To obtain the above figure, an RC circuit of 2 MΩ and 56 pF is being driven with a wide-band multi-sine signal of frequencies between 1 Hz - 192 kHz for 1 second. 100 seconds are concatenated which are then averaged for noise suppression. The FFT of the averaged output signal is then found, and divided by the FFT of the input signal (deconvolved). This results in the transfer function of the RC circuit.

However there is significant mains interference on the measured signal which has not been removed from averaging. This appears in the transfer function as a peak at 50 Hz and several harmonics. There is also disturbance around the 50 Hz peak.


texts: Calculating the voltage drop of two Zener diodes in series? (reverse conducting)

texts:
I'm building a circuit powered from a 12V 55mAh (A23 battery).  Needless to say that power consumption is a primary concern.  The circuit is an ATtiny85 which is driving 13 LED's (in 5 groups).  I initially used a voltage divider circuit to reduce the 12V down to 5.5V to supply the ATtiny85.  This worked but I found the voltage divider was eating up too much current, 5mA, even when the microcontroller is put to sleep and all LED's are turned off.  When active it consumes 5mA to 7mA.  I replaced the voltage divider with two 1N4733A 5.1V Zener Diodes in series:

simulate this circuit – Schematic created using CircuitLab

This circuit works beautifully for saving power.   Power consumption with this circuit is in the micro-amp range when the ATtiny is sleeping (too low for me to measure) and consumes only 0.1 mA to 0.3 mA when the ATtiny is awake and pulsing the LED's.  A FIFTY fold decrease in power consumption.

The trouble with the new circuit is that it is very sensitive to the supply voltage.  At 12V input (using a bench power supply) the circuit fires up and works well.  I get around 5.1V at Vcc.  At 11.5V supply voltage the circuit will not start.

When I was using a voltage divider instead of the diodes the circuit worked well down to about 8V supply voltage.  With the diode setup it needs 12V to start and will keep running down to about 11.5V before it shuts off.

Is there a way to modify this circuit so that it works over a wider range of supply voltages?  Ideally down to around 6V (as the battery discharges).  The datasheet's I've looked at for the Zener diodes don't mention anything about the expected voltage drop across the diode when it's conducting at the breakdown zener voltage.  If I replace D1 and D2 with 3.3V Zener's should I get the same voltage drop?  I'm not sure how to calculate the expected voltage drop at Vcc.


texts: Picking right Bipolar Junction Transistor

texts:
I want to make switch to turn on 12V 48mA siren and I need to triger the switch with 2,4V I was searching for 2 hours but I dont understand how to pick the right transistor but I know it have to be the NPN type and sorry for my english its not perfect,
i want to combie this

http://www.ebay.co.uk/itm/Infrared-Laser-Alarm-Switch-Sound-Light-Alarm-Motion-Sensor-Security-Kits-Q5M2-/282551608245?hash=item41c96363b5:g:YQYAAOSwiQ9ZVzwK

with this siren http://www.ebay.com/itm/Wired-Mini-Horn-Siren-Home-Security-Sound-Alarm-System-120dB-DC-12V-New-/122270305338?epid=2119152374&hash=item1c77e0cc3a:g:tVwAAOSwSlBYyru6

Thanks a lot for help


texts: Radio frequency propagation near-field/far-field

texts:
What is the difference between the near-field and far-field radio frequency radiation?

Is it true that the near field radiation is caused by the the energy dissipated at the end of the antenna connected to the oscillator, but far-field radiation and propagation is caused by the repeated, energy-shifting interaction between the electric field and the magnetic field.


texts: Measure DC current with current transformer

texts:
Is it possible to measure DC electrical currents with some type of split core current transformer?
Or it is only for varying currents?
EDIT
Considering a zero-flux CT, could someone show me the basic external circuit that goes with it?
I want to measure the current out of a solar panel going to the battery.


texts:
Is it possible to make a lossless resistor model in spice? I want to test the large signal model of my DCM SEPIC converter (without linearizing it). OrCad's PSpice library doesn't seem to have it, but is it possible to make a model somehow?

The lossless resistor is a two port element consisting of a resistor and a power source, such that the power apparently consumed by the resistor is produced by the power source.


texts: I tried to solve a RLC circuit and I obtained the matrix. I tried to do a circuit in Scilab, but I didn't obtain a sinusoidal response. The output is in the capacitor and the input is the step function. Why didn't I get the sinusoidal response?


texts: Confusion about ccfl inverter transformer

texts:
I have this transformer that came from a ccfl inverter and the pins on it are confusing me a bit.

I've tested every pin and only pin 3 and 6 seem to form the primary winding and somehow pin 1 and 8 form a connection? no pins on the secondary seem to form a winding.

why would pin 1 on the primary side connect to pin 8 on the secondary?
If pin 1 and 8 form the secondary, why?

other angles

http://i.imgur.com/6zQvw0J.jpg


texts: Does antenna feed line length affect impedance

texts: I built my own antenna but when I measure the impedance (VNA) I see they are off.  One is 30+25J, the other 15 + 10J.  I built these by hand, the only difference I see is the feed line to one is about 1/4 inch loner than the other one.  Of course there could be other differences I don't understand yet.


texts: What's the rationale behind this choice of resistor for a BJT common collector amplifer?

texts:
As part of a design lab, we're using a common collector amplifier, and the instructor's choice for the emitter resistor makes no sense to me.

The power rail is at V+=15 volts, and the load is 8 ohms. The design specifications give us a power across the load of 5mW. We assume capacitors are large enough to ignore for the AC signal.

We want maximum voltage swing, so we say the emitter DC voltage is approximately 7.5V, half of our positive rail... ok, makes sense for a rough design. From the given power and resistance, we know the current through the load has an amplitude 35mA, and the voltage across the load has an amplitude of 0.28V, from ohm's law and the usual power equations. Then we say the total emitter voltage is AC + DC, and swings from 7.22V to 7.78V.

Here's the part that confuses me: the instructor claims that the emitter resistance should follow the relation

$$R_{E}\geq \frac{7.22V}{35mA} \approx 200\Omega  $$

Where does this relation come from? What's the rationale behind it?


texts: IEEE 4 machine system: Need help in computing the bus admittance matrix


texts: Why does this current limiter circuit oscillate?

texts:
I'm trying to make a 0-25 mA current limiter. I want to take a control voltage of 0-5 V as input and have it control a current of 0-25 mA through a restive load (the restive load may vary between 0-200Ω, it's represented as R2 below).

Here is my circuit:

T1 is a P-channel mosfet (P/N FQT5P10) and O1/2 is a rail-to-rail op-amp (P/N OPA2170). I want the varying voltage at V2 to control the current through R2.

The O2 op-amp is used to make a differential amplifier with a gain of 2. Example: 25mA of current through the load R2, op-amp O2's output should be 5V (marked CSense). The output from op-amp O2 is then the input to op-amp O1. Op-amp O1 compares the control voltage with O2's feedback to limit the current. Or at least that's my intention.

I have simulated this circuit in NL5 circuit simulator, and it works great in the simulation. But today I actually built the circuit, and it oscillates.

I have triple checked my pin-out and wiring, and messed around with lots of other things, but the circuit still just oscillates. When V2 is a higher value the oscillation is slower. What I am seeing on the DSO is that mosfet T1 goes between full on and full off, and CSense is a triangle wave that varies in amplitude with the control voltage. A higher control voltage makes CSense have higher amplitude and lower frequency. The oscillation frequency varies from about 50kHz to 150kHz.

I can post screen shots from my DSO if it helps.

I've been working on this all night, and it's starting to drive me crazy. Any help at all would be greatly appreciated.

Thanks!

Edit: I built the circuit in CircuitLab. It works perfectly there too. Why not in real life?

simulate this circuit – Schematic created using CircuitLab

Update: I have changed R3 to 10K. It reduced the frequency of oscillation to ~20-30 kHz.

Update Everyone is focusing on O1, but I think the problem is in the O2 circuit. Below is a DSO screen shot. V2 is at 1.25 VDC. The yellow trace is the voltage over R2 @ 100Ω. The red trace is the output of O2 (marked as CSense in my schematics). I would expect the red trace to be 2x the yellow trace, but instead it's a completely different shape! What in the world is going on?

For clarity: I would expect the yellow line to be 0.625 VDC, and the red line to be 1.25 VDC (same as the V2 input). Also my power supply is ~8 VDC here, things blow up at 24.


texts:
Can a type 2 or type 3 compensator be applied on an LDO?
What methods can we use in order to stabilize our Error Amplifier?


texts: How to vary amplitude of my custom pulse generator?

texts:
I'm attempting to build a custom pulse generator that I can trigger with a digital I/O pulse. So far I've used a TI SN74LS123N Retriggerable One-Shot Multivibrator in combination with a 22 pF cap and 10 k + 100k potentiometer to create nice looking square wave pulses from 200 ns to 2000 ns.

The voltage levels of the output pulses range from 110 mV (low) to 3.4 V (high), which is congruent with the datasheet. What I need though is an adjustable voltage range from 0 V to anywhere from 2.5 or above, the critical part of the range being the in the 10s of millivolts to about 1.5 V. The adjustment should come from a potentionmeter and the circuit should drive a 2 k to 100 k Ohm load.

What is the best next stage to complete my pulse generator?

Here are my ideas/attempts:

Follow with an opamp configured as a comparator, followed by a potentiometer to adjust output between low and high, followed by a voltage follower to drive the load. The issue is that non-deal opamps (for the comparator) have non-zero low voltage (5mV in my case with a LM358A. I need zero volts low voltage.
Use a +/- supply opamp for the comparator and voltage follower and clamp negative parts to ground with diodes (???).
Find different opamps/comparators that have a true zero V low voltage level (???).

How can I best finish my pulse generator with the least amount of stages?

Edit: Besides minimizing components, the major issue I'm trying to solve is to get the "low" part of the pulse as close to zero volts as possible. Even rail-to-rail op amps have non-zero minimum output voltage. One idea I've stumbled upon can be found here: Single Supply Op Amp with True Drive to GND.


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We are trying to calculate how many I2C slaves we can hook up the I2C bus.
We tried to run a square wave through a serial resistor and measure the rise time but we get a strange result. More nodes decrease the capacitance, not increasing it as expected.

Is there another way to get the capacitance?


texts: Is there a display technology that unites red, green and blue subpixels into a single pixel?

texts: After checking out this question about a visual side effect caused by separation of each pixel into subpixels (red, green and blue), I thought that there might be a way to unite the subpixels into whole pixels using square matte filters. Various displays are built in a way that makes the formations of subpixels non-square, or even different size of subpixels, and subsequently their count, so I'm not sure if it could work with those (unless they'd have some odd shape). Is there any such thing on the market?


texts: Is it possible to use the RTS pin as DTR?

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I'm deveoloping a project with a raspberry Pi that involves serial communication. In order to properly handle voltage levels, I used a max3232 converter between the raspberry and the external device connectors.

Max3232 has two transmit lines and two receive lines. A pair of them is used by Tx and Rx (transfer and read the data buffer), whereas the other pair are labeled by default as the RTS/CTS flow control lines, as you can see in the picture.

My problem is related with this second pair: I would need a DTR line instead of the RTS. My first thought was to simply connect the RTS line to the DTR pin on the external device.

Is this idea valid?. Flow control pins are just the same with different names or are they governed by different schemes?


texts: Reading image, sound, binary file from nonvolatile memory for FPGA

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For applications that require design on FPGA which shall make use of several image files, sound files or other forms of files, can they be simply included in the FPGA design configuration file? In any case if these things are stored in an external flash or EEPROM memory, is there a reference design that:

Shows how to put them in this external memory
Create a design which knows where to read in the external memory
It reads it and then send this data to the output device?


texts: Anyone here working with the Cypress PSoC6? Having trouble running the blinky program

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I have a PSoC 6.3 Pioneer Kit (HW REV 11) and am having trouble running any of my own (or example) programs on the PSoC.
I have the latest PSoC Creator (V4.4) installed with PDL V3.1.4 and the latest KitProg firmware update (Firmware version 2.10.878). I just created a new example project in PSoC Creator of the DualCoreBlinky application and compiled an ran it. It compiles just fine, and seems to program just fine, but nothing happens on the board (no blinking LED). I confirmed that the KitProg light blinks momentarily while it is uploading the firmware so it seems that the board is responding. No noticeable errors or warnings in PSoC Creator.
To troubleshoot, I tried running the debugger with a breakpoint set at the beginning of the Main function of the M0+ core. When I set the Target to the M0+ and hit debug, PSoC Creator jumps to the debug view but never halts at the breakpoint I set. When I hit the pause button. I'm dropped into a disassembly somewhere and if I press the step into or step over buttons, nothing changes. If I press the step out button, I get the error: "The run request failed. Encountered error (Warning: Cannot insert breakpoint 0. Cannot access memory at address 0x160022a6 )"
I also tried making my own blank program on the CM0+ core to blink the LED with the following code inside the for loop for the CM0+ core:
/* Place your application code here. */
Cy_GPIO_Write(LED_0_PORT, LED_0_NUM, 1);
CyDelay(500);
Cy_GPIO_Write(LED_0_PORT, LED_0_NUM, 0);
CyDelay(500);

NOTE: I created a digital pin in the schematic called LED and connected it to Pin 0[3] on the chip.
But again, the same problem. It programs fine but nothing happens, and I can't step through the code. Any idea what is going on? I'm hitting a brick wall here so far.


texts: How do I quantify the reverse current in a diode?

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I am using a string of six diodes between a 4 kV, current limited, power supply and a capacitor to charge it to 4 kV.  I then shut the supply off, hoping to leave the capacitor at 4 kV making it available to power a flash lamp.
There is no other impedance in series, so the forward current during charging is power supply limited during charge (0.5 A). When the power supply is turned off, the diodes go into reverse recovery and current flows back into the power supply.
How much reverse current will there be? The diodes are fast recovery, 1000 V diodes (SF5408).  I assume the duration of the reverse current will be within the RR spec (75 ns), but what is the peak current?
Another question I have is: Do diodes in a string all go into reverse recovery at the instant the string is reverse biased? That would result in the RR current all adding together and have a higher peak, with short duration (75 ns).  Or do they get reverse biased in sequence, making the current peak lower, but longer duration (6 x 75 ns). Or somewhere in between?


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I built simple CE amplifier in Multisim:

and make AC analysis, the phase are:

What is the reverse near 10 kHz? I make the identical circuit in LTSpice but there is no any equal to Multisim on phase output created with LTSpice. What is it? May be it's a difference in behaviour of AC analysis in Multisim in comparing to LTSpice? In Multisim I set v_out/v_in for an output graph but in LTSpice there is no manual settings I found, only ac analysis without output options exists. May be I see any other variable in LTSpice in output graph in comparing to Multisim?


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I am working on a project that uses 3 voltage regulators from a 12V input.

INPUT 12V >>[8V reg]>> 8V >>[5V reg]>> 5V >>[3.3V reg]>> 3.3V

I am wondering if is it safe to use an external power supply and apply 5V directly at the output of the 5V regulator to test the 3.3V regulator.

The same would go for the 5V regulator. I would apply 8V at the output of the 8V regulator while leaving its input open.

Is this method safe? Is it safe in general to apply power at the output of a voltage regulator without feeding its input?

Thank you in advance!


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These are from an old military PCBs. pl. help me identify these.

14pin soic


texts: Practical examples to determinism and periodicity of analog signals?

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What I understand from deterministic signal is that we can define it as a function. Same thing is valid for a periodic signal. But periodicity and determinism are are treated as independent categories in analog or digital signal processing if I'm not completely wrong. I saw many definitions purely abstract or mathematical.

Instead of going into abstraction too much is it possible to give a real life example to these signals?

For instance, if I set the function generator to output a sine wave I would call this signal as "deterministic and periodic". But besides this I cannot imagine others as practical examples.

So to me the easiest one was "deterministic periodic signal" which is the ideal function generator output.

Can we give a similar examples to a "deterministic aperiodic",  "non-deterministic periodic" and "non-deterministic aperiodic" signal? Some of these might not exist but I'm trying to relate these to real and prectical examples.


texts: Thevenin equivalent circuit of a battery

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I am a newbie to electronics so I need some help.
I was reading about Thevenin equivalent circuits and I am pretty confused.
I have the question like this:

I have a 2V battery which draws a maximum of 10A. What's the Thevenin equivalent circuit of that?

So, the first thing I think I should to do is to find R using Ohm's law. So, R = 0.2 ohms.

And now I would just draw it.
Is Thevenin equivalent like this?

If not, could you please give me steps how to solve this?


texts: Using microphone for heart beat (BPM) calculation in wearable device?

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I am not a expert here. But for a software project of mine I was scratching my head for a wearable device which can monitor heart rate continuously (battery efficient). I have one wearable device Sony MIO fuse which measure heart rate using PPG technology which most of the other wearable device use.

I did some research and found some links:
https://ieeexplore.ieee.org/document/5504744/
https://www.computer.org/csdl/proceedings/bsn/2010/4065/00/4065a139-abs.html

which is effective and also battery efficient. Also to listen to heart beat the most ancient technique has been through sound only (stethoscope).

Now my question is why wearable device maker are not using this technique. May be using touch microphone we can listen sounds inside body on wrist. Are there any technical complications to it?

Hope my question is not confusing and I am hoping I am posting it to right forum. Please comment if it need improvement. Like I said before this is not a field of my expertise.

Thanks.


texts: Why are wave variables a and b normalized to sqrt(Z0) rather than just Z0?

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With reference to the equations below; why are the wave variables normalized to the root of the characteristic impedance rather than just the characteristic impedance itself?

equations sourced from: http://www.ece.rutgers.edu/~orfanidi/ewa/ch14.pdf


texts: Why include a small resistance between op-amp stages

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I have been reading through TI's reference material on constructing a current source.

http://www.ti.com/lit/an/sboa046/sboa046.pdf

In figure 52 there is a 150ohm resistor included between the output of the instrumentation amplifier and the input of the OPA633 op-amp.

I have seen this also done in some other circuits but don't understand why. What is the purpose of this resistor and how is its value decided.


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I'm having problem with inputs of my PIC.

There is somethink like "default value" on all inputs set to logical 1 so if I want to change the state I need to pass GND.

How can I turn it "otherwise"? This is begining of my code:

#include <htc.h>
#include <pic.h>
#include <pic16f627a.h>

__CONFIG(WDTE_OFF & PWRTE_OFF & FOSC_INTOSCCLK & MCLRE_OFF & BOREN_OFF & LVP_OFF & CPD_OFF & CP_OFF);

int main (void)
{
    unsigned int i, j;

    unsigned short count = 0;

    TRISA = 0;
    TRISB = 0b11110000;
    PORTA = 0;
    PORTB = 0;
    nRBPU = 0;
    CMCONbits.CM = 7;
    ...

I don't understand electronics very much and I'm also kind of new to programming in C.

Thank you for any help.


texts: Can I create a continous gap in iron powder cores?

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The iron powder core material, as you may know, has a continuous air gap in its structure. However, do you think it is possible to add a continuous air gap (for example 1mm) to the iron powder cores?
I know that we can add this kind of air-gaps to ferrite material, but is it going to create a problem if we add a gap in iron powder cores?

thank you