texts: Why does this circuit cut out when an extra load is added?

texts:
I have a circuit that consists of an Arduino controlling a small PAM8403 based amplifier which is powered via an L7805CV voltage regulator. When I press a button the arduino sends an audio signal to the amp and switches on a SPST relay. The whole thing is powered by four AA Energizer Lithium batteries supplying about 6.65V.

Without anything connected to the relay (except the signal and GND pins) this circuit draws about 0.22A. However, I want the relay to switch on a small motor and heating coil that I connect to the same battery pack as all the other stuff, so that the motor and coil get powered on when the button is pressed.

However, when I press the button, the amplifier cuts out and the circuit behaves erratically. The motor and coil run fine, however.

If I connect the motor and coil to the same battery pack, I measure a current of roughly 1.5A. This seems well within the range of what the batteries can supply according to the datasheet.

What am I missing here? I don't see why the rest of the circuit is affected by a load that should be well within the power supply's limits.


texts:
Earphone cables are usually very flexible - does anyone know how much resistance they tend to have? Are they cable of carrying 2A at 5V? My guess is that they are copper strands, but I'm not sure how many strands there are to make them so flexible.

Could they be used as power cables?

Thanks


texts: For oscilloscope, what are the differences for Glitch Capture Channel and Sample Channel?

texts:
I'm using a Tektronix oscilloscope and I use only one channel. I export the data for that channel to a csv file and open it on my PC. I found the csv file actually contains data for two waveforms! One is called Glitch Capture Channel, the other is called Sample Channel. Then I plot out the waveform from these two sets of data. I found the waveform for the Glitch Capture Channel looks exactly the same with what I saw on the screen of the oscilloscope. While the waveform for the Sample channel looks very different.
What are those two channels? What are the differences? When should I use which?


texts: How to communicate over long distances (60 m) using serial communication from multiple serial devices connected to my PC

texts:
Previous post
As per my previous post which involved determining which type of serial connection is appropriate i.e. RS232, or USB. This was clearly RS232.
As a follow on post to that question. I have the following setup and would like some advice if this setup will serve its purpose for reliable communication via serial communication to the desktop PC.
Currently I have written a simple application on Visual Studio that allows my laptop to connect to a single reader, via an RS232 to USB adapter (The adapter is 2m long). I am just using this one reader for testing purposes. The reader sends through RFID tag numbers via this serial connection to my PC. This system works perfectly.
Now I would like to connect 4 RFID readers to my PC. So I would utilize 4 USB ports on my PC (my PC as 8 USB ports). My question is therefore how should I connect these readers with the below distances between each reader and PC?
In the previous post, recommendations were made to use a RS485 cable. Is it therefore okay to first convert the RS232 at the reader to RS485, then run the RS485 cable to the PC and finally use an RS485 to USB adapter to connect to my PC's USB ports?


texts: Questions about battery power supply and voltage regulator

texts:
I have a L7805ACP Voltage regulator and a 22 uF Brownout protection Capacitor. I don't know how to hook them up though. Does the capacitor come before the regulator in the circuit, and where do I line the pins up etc? I just don't know how to place it correctly.
The L7805ACP regulator says operates at 10V-35V, so I obviously assume that a 9V battery is out of the question. My question is should I use 8x 1.5V AA batteries or 10 of them? Like will the 10 batteries last longer or still drain at the same rate? Or maybe someone can reccomend a battery supply?


texts:
I've been trying for the past 2 days to get the USART2 controller (pins PD5 & PD6) working on the STM32L476VG Discovery, which allows for UART communication over the ST-LINK cable. I'm using the ARM GNU tools to compile the project in Ubuntu in a VM, using ST-Flash to write to the board's flash. I've generate example init code using the STM32CubeMX software and using this in my own code. The code compiles and links successfully, but whenever I connect to the COM port using TeraTerm in Windows (I make sure the board is disconnected from Ubuntu), I never see any output. I've tried using the built-in HAL_UART_Transmit function, and have also tried using my own uart_putc function to write messages.

Here is my main.c:

#include "stm32l476xx.h"
#include "core_cm4.h"
#include "stm32l4xx_hal.h"
#include "stm32l4xx_hal_uart_ex.h"
#include "uart.h"

volatile int32_t TimeDelay;
void SysTick_Handler (void);
void Delay (uint32_t nTime);
UART_HandleTypeDef huart2;
static void USART_Init(void);
static void HAL_UART_InitStruct(void);

int main() {
    // initialize systick clock
    SysTick_Config(10000);  //10 ms reload period

    // initialize test led (PE8)
    RCC->AHB2ENR |= RCC_AHB2ENR_GPIOEEN;
    GPIO_InitTypeDef GPIO_InitLED;

    GPIO_InitLED.Pin = GPIO_PIN_8;
    GPIO_InitLED.Mode = GPIO_MODE_OUTPUT_PP; //push-pull
    HAL_GPIO_Init(GPIOE, &GPIO_InitLED);

    // initialize usart params
    HAL_UART_InitStruct();
    USART_Init();

    while(1) {
        HAL_GPIO_TogglePin(GPIOE, GPIO_PIN_8); //testing application load
        uart_putc(42, huart2.Instance);
        //HAL_UART_Transmit(&huart2, "msg\r\n", 5, 0xFFFF);
        Delay(100);
    };

}

void SysTick_Handler (void) {
    if (TimeDelay > 0)
        TimeDelay--;
}

void Delay (uint32_t nTime) {
    TimeDelay = nTime;  // nTime specifies the delay time length
    while(TimeDelay != 0);  // busy wait
}

static void HAL_UART_InitStruct(void){
    GPIO_InitTypeDef GPIO_InitStruct;

    __HAL_RCC_USART2_CLK_ENABLE();
    GPIO_InitStruct.Pin = GPIO_PIN_5 | GPIO_PIN_6;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART2;
    HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);
}
static void USART_Init(void)
{

    huart2.Instance = USART2;
    huart2.Init.BaudRate = 9600;
    huart2.Init.WordLength = UART_WORDLENGTH_7B;
    huart2.Init.StopBits = UART_STOPBITS_1;
    huart2.Init.Parity = UART_PARITY_NONE;
    huart2.Init.Mode = UART_MODE_TX_RX;
    huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
    huart2.Init.OverSampling = UART_OVERSAMPLING_16;
    huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
    huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
    HAL_UART_Init(&huart2);
}

void _Error_Handler(char *file, int line)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  while(1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
void assert_failed(uint8_t* file, uint32_t line)
{
    /* infinite loop */
    /* use gdb to find out why we're here */
    while (1);
}

#endif

Here is my uart_putc function in uart.c:

int uart_putc(int c, USART_TypeDef* USARTx){
    // check USARTx interrupt and status register, and TX empty flag
    while (!(USARTx->ISR & USART_FLAG_TXE));
    USARTx->TDR = (c & 0xff);
    return c;
}


texts: I'm looking for a low budget current sensors for AC

texts:
I'm looking for a low budget (< 10$ per sensor) sensor for measuring AC current up to 20 A. I found many current transformers but they go up to 5 or 10 A.

Any idea what types would fit? Compensation, hall effect, current transformers?

My precision requirements are not very high... 2 to 3 % is enough.


texts:
Im trying to reflow some RF pcbs in a legit reflow oven. The PCBs material is "Rogers RO4003 305 Um" and 3 layer. (Its a very thin pcb)

If temperature is high enough to reflow the paste,  the pcb changes color , and gets a little burned, degrading its usability.

paste type : CIF Sn96 5Ag3Cu0.5  no lead

oven: CIF FT 03 (its a 2 heating element: quartz tube)

please suggest some hints to improve soldering process.


texts: How to program via ICSP when chip is in-circuit with interfering chips?

texts:
My Circuit is:

USBTinyISP <-usi/icsp-> ATTiny85 <-usi/i2c-> MCP4725.

That is, the USI pins used to program the t85 are also used for i2c in the final circuit.

When I try to flash-program the t85 in-circuit, it fails. If I disconnect the 4725's SDA line during programming, it works. I assume that the 4725 is confusedly pulling SDA low to ACK I2C packets and thus interfering with the shared MOSI line during programming. But if so, then my ICSP isn't truly In-Circuit :(. That is, if the circuit was permanent then I couldn't program the MCU except by removing it. Yet I see many circuits with ICSP headers on them that presumably work.

How do circumvent logical interference from the circuit when I program via ICSP? The only solution I can think of is to use a microcontroller with dedicated ICSP pins. But is there some other common-practice solution to this problem?


texts: Actuating a solenoid through a capacitor

texts:
I would like to actuate a latching solenoid through the following circuit:

simulate this circuit – Schematic created using CircuitLab

A capacitor is charged over a resistor. When this operation is completed, the switch changes position and the capacitor is discharged onto the solenoid.

The solenoid runs on 6-20 VDC
Coil resistance is 6 ohms
Pulse width is 20-100 ms
Coil inductance is 90 mH

How do I calculate the sizes of the capacitor and the resistor?


texts:
I am trying to use the circuit mentioned in the datasheet page 4 figure 4. But instead of using the op amp mentioned, I am using a lm324 to avoid using +-15v rails. I have triple checked the connections, but as soon as I turn on my circuit the chip heats up. I tried it with two different chips but every time the chip heats up as soon as I turn on the circuit. What may be the problem?

Edit Would keeping the BIT values as floating cause this? Because right now they are not connected to anything.


texts:
From the receiver circuit below, which is exactly the part that demodulates the RF signal?

I know, a typical circuit used for an envelope detector is composed of a resistor, a capacitor and a diode. Is that similar?

I' m a newbie and any help would be appreciated.


texts:
I have a 360W 36V Switch Mode PSU which I am using in a garden lighting system I have designed. I'm in the UK so it's running off 240V therefore can supply about 10A.

Each section of the installation (there are 6) has a Buck Converter connected to the DC side which drops the 36V DC down to 16VDC required for the LED drivers.

The Buck Converters I'm using are the XL4015 model, there are numerous sellers on the Internet:
https://www.ebay.co.uk/i/293073520634?chn=ps

The issue I'm having is that when I power up the Switch Mode PSU with more than say two buck converters, it won't start up (the power LED comes on dimly and it emits an unusual noise). I believe this has to to with startup current, since if I connect the Buck Converters one by one while the PSU is running, it works fine.

The lighting draws approximately 0.8A from the buck converter when fully 'on', so even with 6 of these (which is my plan) it's well within the operating limits of the SMPSU. I also recall when breadboarding I often saw a spark when connecting a buck converter, though the current draw was low once running.

Each buck converter is connected via a 2A fuse to the SMPSU. I have intentionally chosen the 'slow blow' type due to this startup peak.

In simple terms, what could I do to resolve this? My understanding of electronics is hobbyist level, I don't have much other than a basic test meter to play with! I'm looking at building a proper fuse board, so would like to incorporate some additional components into this ideally.

Would fitting an NTC thermistor (in series) between the SMPSU and each Buck Converter do the job?

Many thanks.

I have found the image below which believe shows the construction of the Buck Converter Boards. So with each added board to the SMPS I'm adding a 220uF capacitative load.


texts: How to Estimate Power to Ground Current?

texts:
I need to automate a power to ground test for a device which outputs 12V / 30A.

There is a .4 ohm resistive load connected to the device which it is driving, however if I remove that load and go straight to ground, the current will be much larger.

I = V/0 = Infinity

Of course the resistance of the conductor will not be exactly zero but I'm assuming the current will be very high, probably high enough to ruin my multimeter!  I'm trying to rate a relay to switch the load.

Do I just measure the resistance through the relay and the associated wires in order to gauge the inrush current requirement or is there a better way to do it?
(The problem with the former method is that I need to measure a relay I don't have.)


texts: Protection circuitry for AC/DC converter

texts:
I'm using the RAC02-GB (Datasheet) as an AC/DC converter and I'm confused about the protection circuit they included in the datasheet:

I want to make sure the AC/DC converter has the proper external protections but I'm a bit baffled by the datasheet's directions. I'm assuming the component labeled 'F' is a fuse but I'm not sure what the component labeled 'U' is. The datasheet lists the parameter "input fuse" as "internal" does that mean the protection circuit is already included in the converter and I don't need any external circuitry?

If I do need external circuitry, how do I spec the fuse and/or the component labeled 'U'?


texts:
I am needing a variable positive and negative output voltage ~(0-20)V with a 20+V input.  To handle this, I am using the LT1074.  I am using the two configurations from page 13.

To do this, I am planning on using a digipot on each to control the output. Unfortunately, they don't handle high voltages at pins well. Therefore, for + -> + configuration, i will need to swap out the R2 instead of R1

On the 2nd configuration, + -> - , I'm having a bit of trouble figuring out the voltages across R3 and R4.  -Vout is -2.21*(R3/R4+1).
My assumption is that Vfb is going to try to be -2.21, meaning R3, the larger resistor, is going to have a much smaller voltage drop then the smaller resistor, R4, which just feels wrong.

If any of you can help me with either the voltage drops, or what assumptions I make are fundamentally incorrect, i would appreciate it.

Thank you,
     James


texts: How to avoid noise in YHDC SCT-013-000 current transformer?

texts:
I have a SCT-013-000 current transformer which I have connected to Arduino Uno with a burden resistor of 33 ohms and the calibration value I am using is 60.
The problem is we are getting current values even after the load is switched is off/ power supply is off. Example when we are testing with 60W bulb the power values that are sensed are much higher.
As check for solution its been mentioned that the CT will work more accurate for higher current values.

Can experts please, suggest what can be done to get proper readings for lower currents.


texts:
I came across this schematic:

What do the dots in the transformer indicate?


texts:
I'm having a problem getting this GSM modem to work with an FPGA (Spartan 3). I've already implemented UART transmission on the FPGA side,the MAX232 to convert TTL->RS232, and 3.3V->5V logic level shifting to interface the FPGA with the MAX232.

I can see the messages sent by the FPGA  on my PC (using the Arduino Serial Monitor) with this FTDI Breakout. I can also communicate with the GSM Modem by using the Arduino Serial Monitor to enter the AT command mode and send text messages.

When I send the same message from the FPGA to the modem,however, I receive an empty text bubble on my phone. I've double checked the baud rate settings, the string structure (including a Carriage Return at the end of every text message) and the TX(FPGA)->RX(GSM) wiring order.

I'm still uncertain of why the arduino terminal can communicate with the modem, but the same message sent from the FPGA doesn't transmit to my phone.

UART Settings: 115200 baud, 8 data bits, 1 stop bit, no parity, no flow control.The VHDL UART transmission and 115200Hz clock frequency generator component is shown below for reference.

EDIT: How the modem works:

The modem requires the use of AT commands to it either through SMS or Serial to configure it. I need it to simply send text messages so to do this I have to set the baud rate that the FPGA will use i.e. the default one of 115200Hz and the work mode i.e. SMS. Then exit AT mode and resume transparent mode. See pages 5 and 7 for a description of transparent mode and an illustration of the transmission process

This is done externally to the FPGA with the software that comes with modem to run on a PC. Once the parameters are configured, whenever the modem starts up it will start in transparent mode. So all that has to be done is send your text message and terminate with a carriage return character to signify end of text.

So the modem is in transparent mode and waiting for the text message data when it's connected to the FPGA. The modem does not transmit any data to the host (FPGA/Serial Monitor) when in transparent mode. It only looks out for the text message data in i.e. RX(GSM)

Baud Generator:

 clk_115200Hz : process(clk,reset,clock3_tmp)
        variable a3: integer range 0 to 217;
            begin
                if(reset='1') then
                    a3:=1;
                    clock3_tmp<='0';
                elsif rising_edge(clk) then
                    a3 :=a3+1;
                if (a3 = 217) then
                    clock3_tmp <= not clock3_tmp;
                    a3 := 1;
                end if;
            end if;
         clock3 <= clock3_tmp;
     end process;

Uart Transmit:

  uart_transmit: process (clk,reset)
     variable bit_count: integer range 0 to 9:=0;
     begin
        if(reset='1') then
            tx_line<=idle;
            bit_count:=0;
            TX_DONE<='0';
            elsif rising_edge(clk)then
                if(enable= '1')then
                    if(TX_READY = '1')then
                     if(bit_count=9)then
                        TX_DONE<='1';
                        tx_line<=idle;
                        bit_count:=0;
                     else
                        tx_line<=TX_MESSAGE(bit_count);
                        bit_count:= bit_count+1;
                        TX_DONE<='0';
                     end if;
                    elsif(TX_READY = '0')then
                     tx_line<=idle;
                    end if;
              end if;
            end if;
     end process;


texts: Quantization results in harmonics in ADC FFT plot

texts:
This is taken from Analog-to-Digital Conversion by Marcel Pelgrom.

Okay, I understand that with 1-bit quantization, the output is block-wave (Square) and that of course when you do the Fourier Series, has harmonics. That makes sense.

What I don't understand is, how come when we go to higher quantization bit levels (2, 3, 4, 5), the harmonic power decreases? I mean there is still square/block waves asssociated with those, just with smaller jumps.

TLDR: Why does increasing number of quantization bits, decrease the harmonic power?


texts:
I am trying to use an EasyE4 (from Eaton) to measure several sensors in my stable. It needs to send a value to the database when it measures something from a sensor. How can I do this? Can i send this directly to a database or do i have to use a PHP script with a GET or POST, or does this not work?

Thanks in advance


texts: Zener-Resistor Combination at the Input of 7805

texts:
I have to drop 14.5 ~ 12V to 5V. Using 7805 will dissipate much heat. So,using below circuit will ease 7805 to drop less voltage and will generate less heat.

Using 7.2V 1W zener and 100 ohm 1W resistance :

What are the negative impact of adding zener-resistor combination at input stage of the circuit?

Will it add any efficiency in circuit. I have read that the 7805 are already replacement for zener-resistor combination, but I have seen people using these at input stage of 7805.

Thoughts?


texts:
I've made this circuit in Proteus, as a part of a practice report:

In real life it works, as I built and tested it. But in Proteus, when I want to run the simulation, I get these errors:

[SPICE] transient GMIN stepping at time=3.41026e-006
[SPICE] TRAN:  Timestep too small; timestep = 1.25e-019: trouble with instance d:u1:3.

I realized the error disappears when the gain of the amplifier is 1: that is, when I remove the resistor R1 (letting it be "infinite"). Otherwise, it won't work.

Why do I have this error, and how can I solve it?

UPDATE # 1

As @Andyaka pointed out, I tried with very small (as Proteus complained about 0 Ohm) resistance values. The circuit I got is this one:

But when I run the simulation, I get other errors :(

[SPICE] Gmin step [45 of 120] failed: GMIN=4.21697e-007
[SPICE] Gmin stepping failed
[SPICE] Source step [12 of 120] failed: source factor =  10.0000
[SPICE] Too many iterations without convergence.

UPDATE # 2

I tried the procedure @berto said in the answers section. I connected a load resistor of \$10k\Omega\$ to \$V_{\text{out}}\$ and the ground, and then connected the voltmeter in parallel with it, but I got these errors:

[SPICE] transient GMIN stepping at time=2.14996e-007
[SPICE] TRAN:  Timestep too small; timestep = 1.25e-019: trouble with node #b:u1:e3#branch.

Two interesting facts when I played with the circuit at this stage:

When I disconnect the voltmeter and put a load resistor of \$0 \Omega\$ (thus, a connected wire from \$V_{\text{out}}\$ to the ground), the simulation starts and continues with no errors.
When I disconnect the voltmeter but leave the proposed load resistor (\$10k\Omega\$) from \$V_{\text{out}}\$ to the ground, the simulation stops with the same timestep too small error.


texts: (Beginner question) The different ways a transistor can be connected to power source

texts:
I very recently just started exploring the world of electronics, and one thing is irritating me about transistors.

I know that if a current runs to the base, then the current will start to run from emitter to collector, and we could then take this current and use it for whatever we want, but I've seen setups where both the base and the emitter are powered. I don't understand why the emitter and base would both need to be powered, why not just power the base, since the emitter doesn't need to be connected for electrons to start flowing only the base does. Can someone help me understand why you would power both when powering the base seemingly does the same?


texts: Calculating the leaking current for a tantalum capacitor

texts:
I've been looking at these tantalum caps for a coin cell operated BLE device, but I'm a little confused by specified leakage current.  The datasheet lists the leakage current at <= 0.003CV uA.  With a 470uA cap at 6.0V, my calculated leakage current is 0.003 * 0.000470 * 6.0, which is 0.00000846.  The datasheet says that current is in uA.

Is the leakage current really 0.00000846uA?  Or is the C (capacitive) value in the equation supposed to be in uF, not F?  That would make more sense if the leakage current was 8.46uA, although that seems high for a "low leakage" cap.

And yes, I am well aware of the potential dangers of tantalums.  Operating voltage is going to be in the 3.0V - 2.0V range.  We have a few other (highly experienced) EEs working on this project, and I'm trying to get up the learning curve on some aspects of datasheet specs.


texts:
I am new to electronics, and don't understand what is termination and why it is needed, especially in digital communications.

Thanks


texts: What will be the real voltage along the line with a voltage source and a capacitor?

texts:
Take the following circuit:

If I do a simulation of this circuit I get this graph:

The strange thing is that in the simulator it gives the same voltage sine wave in the circuit, near the voltage source and near the capacitor.

In real circuit is it the same? Even if the wire is long between the voltage source and the capacitor?


texts:
I am diagnosing a legacy design that uses an AD7862 SAR ADC.

Input is 500 Hz, 2.4 Vpp sinusoid, relatively low noise.
Digitized output adds a noise component waveform +/- ca 0.25 Vpp.
The FFT spectral peak (7484 Hz) of the noise is close to the sample rate, 7782 Hz.  I expect a small amount of sample rate noise, but not this extreme amount.  The noise waveform appears sinusoidal as well, not as a typical quantization.
Of course I can FIR it after the fact, but would rather find root cause.
The digital control signals to ADC are ringing to the point where they almost reach V(INH) and V(INL) thresholds.  Could be false triggering?  Affecting the SAR process?  Otherwise digital signals are nominal.
Happy to share diagrams, etc.


texts: Why the common-mode gain of the differential pair is almost zero?

texts:
If you think of a better title, please do edit or let me know to edit, but this is how I thought I could word the question.

I am finding difficulty in understanding how a differential pair exactly works. I commonly find that textbooks first go through the 'tail' load being a perfect current source before using real world components.

Say, the tail load was a current source and that the entire circuit looked like this.

simulate this circuit – Schematic created using CircuitLab

Say the current through the current source I1 is Iss. If Vin1=Vin2 (i.e. common mode input) rises, then, textbooks say that the Vout1 and Vout2 both rise by equal amounts and that this is how common mode signals are removed (if we take Vout1-Vout2).

But if Iss is fixed by the current source and M1 and M2 are at identical states (Vin1=Vin2, R1=R2), then I believe I can assume that Id1=Id2=Iss/2. Since Iss is fixed, Id1 and Id2 cannot possibly change for varying (common mode) values of Vin1 and Vin2. So then, how could Vout1 or Vout2, ever possibly rise?

In other words, if Id1 is fixed as Iss/2, then Vout1 is fixed at Vout1 = (Iss/2)*R1 for as long as Id1=Id2=Iss/2, irrespective of what value Vin1 or Vin2 are at (as long as Vin1=Vin2).

This is inconsistent with what textbooks say and I don't understand why? Is there some mistake in my thinking?


texts: Polyester Capacitors for pulse applications

texts:
i have a circuit to be constructed, where i need to use PP pulse capacitors and i got my hands on Polyester capacitors, this is for pulse applications, im wondering if it could be used as a replacement, as the circuit is not functioning as it should and thats what i could narrow down the problem to be.

Thnx

Cheers


texts: OpAmp spice model that includes the Null Offset pins?

texts:
Do OpAmp spice models that also have the Null Offset pins broken out exist?

I'm looking for a model of TL071 and all i'm finding is the basic 5-pin model.

I'm trying to wrestle with an existing design. The original designer was using the null offset pins to zero the the output with a non zero input. I want to see if i can slightly improve the span of the zero capability. I'm struggling to find any information on how much range the null offset pins have and how to calculate the actual null offset voltage. My hope was to use a spice model that has the pins to help me out.


texts: Triac Switch Circuit using MOC3021 and BT136

texts:
I am tinkering with BT136 & MOC3021 optocoupler to control AC loads, and below is the schematic i have put together. I have a few doubts here.

Is the value of 100 ohm 1 watt correct on pin 6 of MOC3021
Is 50 ohm, 1 watt sufficient in snubber circuit.
Is 10 nF, 250 V sufficient or should I use 400 V.
Any other design issues / sugesstions for improvement.


texts:
According to the Battery University, charging a Li-ion cell to just 3.92 V is the optimal voltage to avoid stress and lithium plating. Problem is, nearly all consumer chargers focus on going to 4.2 V for longest battery life.
When charging, should you disconnect the (consumer) charger when the charging cell voltage reaches 3.92 V or charge until the cell hits the end of its constant current stage at 4.2 V and would subsequently settle down to around 3.92 V?
Sources:
Charging Lithium Ion batteries
How to prolong Lithium based batteries


texts:
I need to replace a plug on a mains powered device.  It uses a specialised connector (to make it difficult for hobbyists, I guess) so I want to replace it with a standard mains plug.  Unfortunately the cable connects to the PCB using some kind of spade/Faston connector, but there are millions of different variants of these and I have no idea which parts to buy!  Does anyone know what it might be, from the photo below?  It's kind of hard to get a good view, so let me know if a particular angle would help.  The plastic cover is 9mm wide, and the metal receptacle is about 7mm wide.  The device is rated at 24A, so I'm not sure if that means there is a special high-power variant needed.

Any ideas?


texts: Using one Mosfet to control the gate pin of another Mosfet

texts:
I am using Mosfets to power an RGB LED light strip with a Raspberry Pi:

https://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf

The I though the threshold voltage for the above Mosfet was low enough for the 3.3V supply from the Raspberry Pi to the gate pin but the LEDs are dim (the blue is the dimmest maybe because of different internal resistance in the strip?). I measured the voltage across the drain and source for each of the 3 Mosfets (red, blue, and green) at 7, 6, and 5 volts respectively. I attached the gate pin to the 5V pin on the Raspberry Pi and the lights lit up full brightness. Is it possible to wire up a circuit that uses the Mosfet's I currently have in place at 7, 6, and 5 volts to control the gate pins of three other Mosfets that then power the lights? i.e. I want to open a Mosfet's channel from Drain to Source by providing voltage to it's gain pin from another Mosfet's output. If not possible, is there something I could be doing wrong with the wiring or do I ultimately need to find another Mosfet with even lower threshold voltage? Below is the fritzing diagram I have been using with a 100k pull-down resistor.
Power Source is a 12VDC 1A supply

simulate this circuit – Schematic created using CircuitLab


texts: Type 3 compensator design for Buck-Boost converter

texts:
I'm practicing a design of a type 3 compensator for a voltage mode buck-boost converter, so I went through the book entitled "Switch mode power supplies Spice simulation and practical design"
The topology used for calculations of the different components of the compensator is shown below (Extracted from the book)

The specifications are as follows:

Vinmin=10v  (minimum input voltage).
Vinmax=15v (maximum input voltage).
Vout=-12   (Regulated output voltage).
Fs=100kHz  (Switching frequency).
Fc=5kHz    (Crossover frequency, chosen by the author to make the RHPZ after that frequency).
Iout=2A    (maximum output current)
Rload=6ohm (DC load resistor)

I have followed all the steps given by the author but I failed to find the same values found to the compensator component. The method used to place the poles and zeros of the compensator is the manual method and not the K factor method.
So the author proposed the following:

From the Bode plot, we can see that the required gain at 5 kHz is around -10 dB worst case.

To cancel the LC filter peaking, place a double zero close to the resonant frequency, 600 Hz

Since the zero occurs after the crossover frequency, we can place a first pole at 7 kHz

Place a second pole at one-half of the switching frequency, to force the gain to further roll
off, 50 kHz.

Using the manual placement method described in Chap. 3, evaluate all the compensator
elements.

R2 = 18.6 kohm   R3 = 456 ohm   C1 = 15 nF  C2 = 1.3 nF   C3=7 nF
When I apply, the equation encircled in red in the figure, I come out with a different value for R2.  I found R2=1.8kohm but the author finds R2=18k ohm and since C1 and C2 values depend on R2, so my compensator is not good and I do not get a sufficient phase margins.

Please can anyone ensures to me the value of R2 and does the equation encircled in red correct ?


texts: How to find stall current of servo motor?

texts: I am using 18 of this hobby servos for a hexapod, that are going to run simultaneously. Now I need to decide the power source, and need to determine the current needed. I know that the maximum current that a motor draws is its stall current, and it should run with lower current than the stall current. But no datasheet mentions the stall current. All of them mentions the stall torque, 1.6kg-cm(at 4.8V) in this case. And I cannot find any equation that calculates the stall current from stall torque and applied voltage. Some people suggested to actually stall the servo and find the current with an ammeter, but I'd rather find it by calculation. So how can I find the stall current?


texts:
I am looking for an element that permits me to irrigate automatically. I have seen that it exists something called solenoid valve. However, this valves require a continuous electrical consumption and in my case it cannot be allowed. They exist latching solenoid valves, that maintain a permanent magnetic field saving a lot of energy. Unfortunately, I have some problems with them:

I have been unable to find any datasheet.
They seem to be unable to permit high flows (I would need up to 10 liters/second).
They are said to be insecure.

So, the question is: Should I use a latching solenoid valve (and in that case, where could I find one?) or does there exist a preferred system such as, for example, an electric water tap?


texts: Trouble Identifying Electrolytic Capacitor

texts:
I believe this is a 33pF ± 5% 100v SMD Electrolytic Capacitor, but I'm unsure because of the value of the second line:

Am I reading it wrong? And where could I find such a replacement capacitor?


texts: Basically that's the question: Does this IC let me connect LEDs directly to the outputs or should I use transistors?


texts:
So we have a Kinetis MCU (Mk66fn2m0) which is 3v3, and needing to select a CS line of a 5V chip (CJ125 made by Bosch).

We used buffers for the main comms, but forgot the CS, just linking directly as a net and pcb trace.

Is there an easy way such as a pull-up resistor (and if so what value) to make the 5v slave's CS work with the Kinetisis 3v3 output pin?

Thanks


texts: Need help in understanding the mosfet reverse polarity protection circuit

texts:
I am working on reverse polarity protection circuit. I found out that most of the people are using the circuit as is mentioned below.

I have few concerns regarding the direction of MOSFET

Why is it connected in reverse direction (because if you connect other way also it works)?
The overall current is going through the body diode (because in p-MOSFET current flows from source to drain). How is it helping?


texts: 3 phase AC circuit supply potential difference

texts: How can the line  voltage be 220 V when in actual line voltage is the potential difference between 2 different lines. For ex:- Vry= 220 V. And why do we divide it by root of 3 to get phase voltage. Isn't phase voltage supposed to be bigger than line voltage? How can a potential difference be greater than the individual phase voltage? And assuming a balanced load the potential difference between 2 connections is zero. Like connecting a voltmeter to 2 same potential which would cancel out each other.


texts: Problem: \$\frac{4s + 2}{s(s-1)(s+2)} \$ Expectation of Root Locus Asymptote. (Control Systems)

texts:
My transfer function is \$\frac{4s + 2}{s(s-1)(s+2)} \$

Given that there are 3 poles and 1 zeroes, the amount of loci going to infinity is 3-1 = 2 loci = r. I calculated where the centroid of the asymptotes should be begin. The equation is the (sum of poles - sum of zeroes)/r = location of centroid on real axis. The centroid location I got was -.25, so I can't understand why MATLAB plotted the root locus otherwise. Given that there are 3 poles, there are to be 3 asymptotes. (1 on the real axis and 2 going off the opposite direction.) I illustrated the supposed asymptotes in black in the following image.

My problem is that the calculated asymptotes do not match up with my expectations. My calculated asymptotes are clearly not what MATLAB has calculated. Why and how so? I also did an angle computation using the formula (2q + 1)/r.


texts:
I have a 3d gain diagram from an antenna. How can I calculate the power of this antenna?

Thanks!


texts: How much power should 14.4W LED strip consume?

texts:
The question is not that dumb as it sounds because the answer is 8. And what I really want to know if there are different 5050 LED's or I've got some particulary bad batch or am I making a measurement misstake.

I've bought gauss 14.4 LED strip which is marked "5050-60P-12V-10D-V1.1" So 60 5050 LED's per meter. This should consume 14.4W boths according to descriptions of such strips and according to calculations on 5050 datasheet. But my power supply shows 2.0A at 12V for 2.95 meter strip. That's 8W per meter. Voltage on the other end of the strip is 11.6V. The reason seems to be that voltage drop on a single LED is 2.9V when it should be 2.3V. Voltage drop on a single LED is 2.9V. For each 3 LED's there are two 39 ohm resistors (marked 390, and measurements confirm that). And I've checked my power supply (HY 3005) with resistor load, reading seems correct: 0.17A at 4V for 23.5 ohm (two 47 in parallel).

Update:

I've made a mistake by not describing the strip properly and not giving datasheets. This is a warm white strip and it's target voltage is really 12 volts. It's for home usage and is meant to be used with 12V power supply which you can buy in the same store. That supplies can't give 14.4 volts.

Unfortunately manufacturers site is very uninformative so there is no point to linking to it. There is also no datasheet available and I don't know LED's manufacturer. So I can only use datasheets for similar LED's. 3V drop for white LED seems OK, 2.3V from unedited question was for red LED's, which is a mistake.

Conclusion:

All components in the strip seems to be fine, it's just designed to drain less power than specified at 12V. Probably that's made for extending lifetime. Or, as @TonyStewart.EEsince'75 noted, extra room is left to allow usage of the same strips in cars at 14.4V. By increasing voltage I can make it brighter and still will be within allowed current limits for LED's, but stock power supplies for that strips can be maximally adjusted to 13V.


texts: I have an LED strip that uses around 2A from 12V DC (25W). I will probably use less than the full strip, so if I cut the strip, will it draw more current (the voltage will stay at 12V) or less? I want to figure out if the LED's will get brighter or hotter if I use less of the strip.


texts: Let's say we have a DC source connected to an inductor. The orientation of the magnetic field through the inductor depends on which direction the coil was wrapped (right hand rule). But why do we not care about it's polarity when we use inductor in the circuit? I guess we do care about polarity in terms of mutual inductance, but what about when only one inductor is used in the circuit?


texts:
I am designing a PCB with a STM32 microcontroller, a GPS, DataLogger and X-Bee module. The power supply is a 12V Battery.
So in my project I need 5V and 3.3V, at the same time.
I don't know if it is a bad ideia to have a 5v linear regulator(input 12V) and using the 5v as input in a 3.3v LDO regulator.
I am aware of the Low Dropout properties of the LDO and the
power dissipation of the voltage regulator.
I came to this idea because the circuit used to shut down due to the temperature. I don't want to use a buck converter because I don't want to put an inductor in the same PCB with the X-bee(Radio Module).
Finally, my project is included in a car, so temperature is a thing(the engine or even sun)


texts: Small output voltage even if transistor is not triggered

texts:
I have created following optoisolated NPN transistor switch to run a solenoid valve. The circuit is triggered from the D2 pin of Arduino. When D2 pin goes high, the circuit does switch to correct ~12v output. But when the D2 pin is low, I consistently get small voltage somewhere between 0.3 to 0.6V. What's the reason of this?

The circuit is built with following:

4N25 optoisolator
TIP122
Arduino powered from PC, whereas switched circuit with 12V power adapter


texts: What is the common, normally open, normally closed?

texts:
I have the relay you see here:

How do I read that diagram - or specifically, which contact is the common, normally open, and normally closed contact?


texts:
In my first layout, with a 9.2k load I get a gain of ~55 (20mVpp in -> ~ 1.1Vpp out).

My current understand is that if I replace the resistor load with something else that presents as 9.2k (i.e. the Rin of the circuit) it should have the same gain. So I connected ALTload in its place (a copy of the same BJT amplifier circuit that has an Rin of 9.2k) but don't see what I was expecting at the same point in the circuit (after C3).

Can anyone guide me on what was flawed in my assumption/implementation?

It looks like the gain increased - Why?
What's causing the top peak to flatten out - Has it got something to do with the voltage dividor R5/R6 sets the upper limit @ 4.174V? I thought capacitor C3 would 'reset' the DC offset and the 1.1Vpp would be 4.174V +/1 0.55V?

Many thanks in advance
FYI - I largely followed the the example here (pg 10/slide 19): Small Signal Model
UPDATE:
I ran this simulation to find the Rin ~ matches what I expected:

UPDATE 2:
Added a transient sim of the circuit above to show non-linear source current as -per one of the comments:

What is meant by 'highly non-linear for many reasons` - Perhaps there are certain topics/concepts I can go and read up on in more detail to better grasp this?


texts: How to adjust output resistance with galvanic isolation?

texts:
I need to control the device (lighting LED driver) with 0-10V input.

It looks like the driver has 100 uA current source as it can be controled with 0...100% PWM, 0-10V or 0-100kOhm resistance:

So I need to put some element which will change it's resistance (or voltage) within given range (0...100K or 0...10V).

The problems are:

I don't have any power source on the left side except the current source from the driver,
it shouдd have galvanic isolation from the controller,
it should be cheap and small (so I'd like to avoid DC-DC converter).

This could be easily solved with PMW, however I need to build analog "0...10V" solution. Let's say it should work even if the adjust circuit has no RC filter.

I could put optocoupler working in the linear range on the controller output and adjust with input diode current. But if there is no feedback I will get temperature drift and over low accuracy problems.

Feedback (voltage measure through the galvanic barrier) is a problem it self within low budget device.

Is there any good (cheap and with accuracy let's say at least 10%) solutions for Regulator?


texts:
I would like to use the interface on link below. I tried to do exactly same except output because to test first, I gave output to LED from microcontroller.
My question is with MC1489. When i connected 5V to VCC, I always get continous signal from 3rd pin (1Y on datasheet.) It doesn't matter if I connect 24V input to pin (1A) or not.
How should I connect it exactly to control over output pin? What does the control pin do? In the interface schematic there is no connection to the control pin. Should it float or what should I connect there?
24Vdc to 5VDC Interface

Datasheet


texts: Trying to compute the power that the operational amplifier provides to a load

texts:
So here's the circuit

What is the power that the amplifier would need provide to the load (RL) if i inject a input signal (vin) in the form of a sine with 1kHz frequency and 1mV amplitude?

I know that the power provided to that load can be computed using:

(V0rms) ^2 / RL = (V0m) ^2 / 2RL , being V0m the amplitude of the output signal (also a sine).

Lets say the total output of the amplifier (3 stages) is 130, so i multiply v0m with 130 and put that value on the equation above?

Also, to find the maximum power that the amplifier can provide to that load without occurring distortion i will need to take into account VCC and VEE right?

Lets say VCC = 5V and VEE = -5V, the maximum amplitude for the output signal will be 5V=VCC ?

I kinda wanna ask a few more questions,

Now this op-amp with negative feedback is said to have a gain of 10. I need to choose the dimensions of R1 and R2 to make it right.

Here's my attempt,

i already have the values for Ad. Is this made right? I need to choose the values for R1 and R2 wisely i think.

What i dont understand is what is the point of having R3 in there? And what would the value for R3 has to be taking into regard what i said about R1, R2 and the gain. It is said to be ~R2//R1 but i dont know why.

And to compute the input impedance of that circuit (op-amp with negative feedback) what should i do? Can you guys give me any tips?

Last question, i need to find the current source (IF1) output impedance. I believe i need to do the small signal and try to obtain it from there? Honestly i still didn't try this and going to give this a chance tomorrow... But could you guys give any tips? Thanks.


texts: VHDL: What is correct way to model open collector output for FPGA?

texts:
I2C uses open collector outputs. FPGAs do not have such outputs. They do have tri state buffers though.

How should open collector output be defined in a VHDL for an FPGA?
How should open collector output be pulled high in testbench? i.e how model the pull up resistor e.g on SDA line that connects master to slave, in a testbench?


texts: proximity probe (sensor ) / eddy current pre-conditioning circuit

texts:
my goal is to use Arduino with 2 proximity probe sensor to achieve some output like orbit plot for a shaft mounted on a bearing

            the system

       the orbit plot

the proximity probe sensor has a negative voltage output from 0 to -24 volt, as the arduino accepts voltage only in the range of 0 to 5 volt,so I decided to use op-amp to invert and to scale down the voltage so instead of being in the range 0 to -24 v, it will be 0 to 5 v

worth mentioning that, the output of the proximity probe has 2 components:
1- DC out put that determines the position or the GAP
2- AC component on the top of that DC voltage to determine the vibration

my questions are :

1- how can I get to separate the ac from the dc component ? I mean like I want to use the DC value to determine the GAP and the AC to determine the vibration, should I use AC coupling ?

2- is this configuration and the whole idea applicable and reliable ? I mean using arduino and then using the op-amp invert and to scale down the voltage ? is there a better and cheaper way to do this?

please correct if I am mistaken at any point, sorry this is my first experience with this proximity probe thing, and some questions may seem silly and this is what I managed to get after a lot of searching


texts:
I am driving a large, complex HTN LCD with 3 Holtek HT1625 LCD drivers.  There are over 700 segments.
The data sheet for HT1625 LCD driver is here:
http://www.holtek.com.tw/documents/10179/116706/ht1625v170.pdf

The problem is the ghosting effect, where the LCD segments are being partially on when they should be off.

All segments should be off in this picture.

This image shows OFF segments are affected by the ON segments.  Some kind of crosswalks, I guess.

I measured the waveforms with a scope.
This is one of the COMMON signal when the board is NOT connecting to the LCD glass:

This is the same COMMON signal when the board is connected to the LCD glass:

I am trying to figure out whether it is the driver or the LCD signal layout.  Is there anything I can do to improve the display?  I tried different LCD bias voltages but they seem to affect the view angles more than the ghosting effect.

Any pointers are appreciated.

Thank you.


texts: MultiByte data integrity with DMA on STM32F3

texts:
Despite low-pass hardware filters on ADC inputs I am having a lot of erratic readings. There are 8 single-ended channels in DMA sequence and it is configured for cyclic sampling. Sampling time is set to maximum (601 cycles). The inputs connected to feedback resistors in actuators. Unfortunately, the power wires and feedback wires are in the same cable, without any shielding between them, so some noise is expected.

The results, however, are worse than expected - out of 4M samplings about 200K have more than 20 difference between consecutive readings, with maximum difference exceeding 2000 (on 4096 ADC range).

Now, my understanding is that "memory data size" in DMA configuration means it won't be changing one byte of the 16-bit conversion result while MCU is reading the other. Although it might simply be used for data re-packaging.

Just in case, I've replaced one target memory buffer with two and used half-transfer-complete/transfer-complete interrupts to make sure MCU is reading from one buffer while DMA is filling another. Did not make any difference.

The questions:

does "memory data size" safeguard from concurrent multi-byte memory access in any way?
if not, what else can I do to reduce noise? For example one trick on Atmel chips was to read and discard first ADC value, then read same channel again. I am not sure I can do this with cyclic configuration.

Note, that I am not asking for SW filtering methods. I have those prepared and tested many times before, and will use them in the final implementation anyway. What I am hoping for is some advice on reducing amount of spikes in the raw ADC output to begin with.


texts:
I came across an old circuit from work that discharges a capacitor (C1) into a step-up transformer to a low-impedance load.  This event is triggered by a pulse into an SCR, whom has a parallel RC filter across its gate-cathode terminals.  Both the Pulse amplitude and the capacitor's voltage may be in the 12V to 30V range, but they may not be equal.

I can fathom the filter capacitor (C2) -- this may prevent high-frequency noise from prematurely triggering the SCR -- but I cannot imagine the use of the resistor (R2).

Thoughts

Perhaps R2 simply provides a bleed path for C2?  That way, after Pulse has gone back to 0V C2 doesn't hold the gate open longer.  But from what I've seen, C1 discharges in the microsecond (or less) timescale whereas Pulse is high for a few milliseconds -- long after the SCR's holding current has diminished.

That's the only thought I have so far.  It just seems like R2 would bleed some current from the SCR gate's and load down the Pulse supply more than necessary.  Can anyone think of a reason that it's in there?

simulate this circuit – Schematic created using CircuitLab


texts:
I am using a STM32F103CBT6 as I2C Master. After sending the I2C Adress of the Slave I need to clear the Addr bit in the SR1 register. The Datasheet states:

"ADDR: Address sent (master mode)/matched (slave mode)
This bit is cleared by software reading SR1 register followed reading SR2"

Therefore i have two lines after the busy wait loop checking for the bit like this:

uint16_t a = I2C1->SR1;
uint16_t b = I2C1->SR2;

This works fine and the compiler won't optimize the reads, because the Registers are declared as volatile, but it warns me as the two variables are never read and therefore useless. I would like to get rid of these warnings. Is it guaranteed to work, when i change the lines like this:

I2C1->SR1;
I2C1->SR2;

Or should i clear the bit manually without reading SR2 ever ?

Thanks in Advance


texts:
Was reading the following:
"In order to deliver its full frequency response, a ribbon microphone needs to see an input impedance of at least 4-5 times its output impedance. For example, if a microphone has an impedance of 300-Ohms, the preamplifier should have an input impedance of 1200 to 1500 Ohms, or greater"

Why would lower impedance input on the mic preamp attenuate frequencies? I'm assuming high frequencies are attenuated?


texts: Unexpected wattage into charge controller (solar panels)

texts:
I'm building a solar system w/ battery for my camper van. Two identical 110W panels wired in parallel, going into an MPPT charge controller and battery (a Yeti 1000 by Goal Zero, 96.8Ah (10.8V) lithium).
When I measure the voltage and amperage directly from the panels, disconnected from the charge controller / battery, in peak sunlight with a multimeter, I got 20.4 volts and 4.69 amps or so for panel #1, and 20.4 volts and 4.58 amps for panel #2. When I disconnect the final cable that ultimately plugs into the charge controller / battery, and measure in the same way using the multimeter, I get 9.82 amps and 20.8 volts total.
However, when I connect it all back up, in peak sunlight, on the charge controller display, I'm seeing 85 watts or so. By disconnecting each panel, I determined that panel #1 gives around 30 watts, and panel #2 gives around 55 watts. This is on a ~40% charged battery. My main question is this -- why do the panels have similar measurements when measured in isolation from the rest of the system, but have this large difference (30 watts vs 55 watts) when it's all connected together?
I know the charge controller does some voodoo which necessarily drops the efficiency, but this is a pretty big drop. And it doesn't explain why the wattages of the two panels themselves are different. Also I'm in the middle of a heat wave, 105F+... could that somehow explain something?
Any ideas, or diagnostic tips? As a beginner, this is a great opportunity for me to learn about electricity. Thanks!
P.S.
Here's how it's all connected:
The two 110W panels have + and - MC4 cables coming out of them, which are plugged into MC4 "branch connectors" (MMF and FFM) to make them in parallel. Then the branch connectors are plugged into an MC4 extension cable (to be able to reach the battery), ~10 feet or so, with MC4 connectors at each end, which are then connected to an MC4 to Anderson PowerPole adapter, which plugs directly into the MPPT charge controller module of the Yeti 1000 battery.
Panel specs:
Peak power: 110W
Solar cell efficiency: 23%
Maximum power voltage: 17V
Maximum power current: 6.47A
Open circuit voltage: 20.06V
Short circuit current: 7.12A
Power allowance range: +/-3%
Maximum system voltage: 500V
Values at standard test conditions: Air Mass - AM1.5, Irradiance - 1000W/m2, Cell Temperature - 25°C
Battery specs:
Cell Chemistry: Li-ion NMC
Peak Capacity: 1045Wh (10.8V, 96.8Ah)
Single Cell Equivalent Capacity: 290.44 Ah @ 3.6V


texts: Reduce the size of the Arduino bootloader?

texts: Is there any way of reducing the size of the preloaded Arduino bootloader, to save some bytes for the program?


texts: In the transformer equivalent circuit,why the primary and secondary windings are not coupled with magnetizing inductance?

texts:
simulate this circuit – Schematic created using CircuitLab

The attached diagram is the equivalent circuit of a practical transformer. Why is the coupling shown only between primary winding and secondary winding of ideal transformer?

Suppose secondary is open. So 'i_s' is zero.Hence 'i_p' should also be zero (ideal transformer). If both primary winding and secondary winding currents are zero, then as per the model,no mutual flux is produced by ideal primary and secondary windings, and hence no EMF should be induced in both. (Note that in the model, coupling is only between primary and secondary of ideal transformer.) But 'v_p' is in parallel with 'Lm' and hence 'v_p' will not be zero. Similarly we know that 'v_s' is also not zero under open circuit conditions.

To explain this behavior, shouldn't both primary and secondary windings of ideal transformer have magnetic coupling with magnetizing inductance'Lm'? (Since model should have the same behavior as the actual device.)

Please note that I understand 'Lm' is not a physical inductor but it is only for representing the behavior of actual transformer.


texts: Purchasing a battery for a 12VDC, 5A device

texts:
I have a 12V 5A CPAP device that I'm looking to use while camping for 2 nights.  Therefore, I'm trying to determine a deep cycle battery to meet my needs without burning a hole in my wallet.  Based on calculations I've seen while browsing the net, I need a battery that can deliver 200AH.  Calculation is based on C'' found here:  http://www.powerstream.com/battery-capacity-calculations.htm

However, searching various car batteries at different stores, they are not listed as deep cycle, but rather CCA (Cold-cranking amps).  Searching for a 200AH Deep Cycle battery results in batteries that are over $300.

Am I calculating this incorrectly?  I was hoping to spend far less considering I won't use the battery very often.


texts:
One of the requirements I need for a device is to meet the UL/IEC-60950 standard. On the companies website I am looking at it mentions that "products are assembled and tested in company’s own ISO9001:2015 and IPC-A-610 certified facilities." What are the chances that this product meets the 60950?

(I have reached out to the company as well but just curious what the thoughts were of the community)


texts: Is there something wrong with my soldering iron?

texts:
I work with Sn 63 Pb 37, 1.8% flux solder which has a melting point of 187C, however, in order to reliably melt it I have to set my FX888D soldering station to 350C. Do I have a problem with my soldering station?

I measured the tip of the soldering iron at 258C when pressing into the temperature probe on my multimeter. Why is there such a difference between the specified and measured temperatures?

The tip does have a bit of play on the heating element inside the iron - could this be the issue? Maybe I need a new heating element?


texts: What does Expected Reliability of a Circuit Mean?

texts:
I am a computer Science student, and I have to write a program that models the expected reliability of a circuit given a circuit diagram. The issue is that I have no idea what that means, and my research has only come up with things that are very technical.

So can anyone give me a basic idea of what this means?


texts:
This is a follow up to an earlier post I made here. Below is the relevant portion of the schematic for this issue (stuff to the left of Y1 is in original post if necessary).

I have finally gotten this circuit working somewhat reliably with one exception. The original device (read layout) is intended to work at 5V. I have the original device and can verify that it does work properly at 5V. I just got my PCB back which has a copy of the circuit. I populated the board and fired it up and it seemed to work like a champ. I had both (original and copy) wired up on the bench and was looking at the output of each channel on the scope. Things looked great.

Then, I happened to notice that I was powering up the two from 3.3V as I've been switching between projects and did not change the power supply voltage when I last switched. I begin to adjust the voltage up toward 5.0V and I notice that right about 3.8V the output of the copy goes low and stays low up to 5.0V. I lower the voltage and it goes high (but toggles low when IR present) at about 3.6V. So, the circuit works at a supply voltage < ~ 3.6 V.

With the voltage set at 5.0V I start to probe around comparing all signals to the original. Following the individual inverter stages things look identical right up to the input of U1E (pin 11). As I vary the voltage across that threshold of roughly 3.6V that pin toggles. So, next I want to take a look at the output of U1D (pin 8). I found it quite difficult to probe this and watch the scope at the same time as the probe would slip off the contact point. So, I decided to take a piece of 3" wire wrap and tack it onto the pin so that I could grab a hold of it with the probe. I did that, fired it up and the circuit behaves quite nicely! It operates as expected. At this point I don't even have the probe on the wire I tacked onto the pin. So, the addition of this wire hanging from the pin has solved my issue.

I have two screen shots of the oscilloscope. The first is the screen shot with no wire tacked on to the output of U1D.

The second is the screen shot with a wire tacked to the output of U1D.

The blue trace is the output of the entire circuit (Q3 Collector). The magenta trace is the input of U1E (or cathode of D4). You'll notice I gave each two pulses from the transmitter. In the snapshot without the wire tacked you'll notice that the steady state is quite noisy.

Of course, hanging a wire off this pin is not a real solution and I don't understand why it works so that is the reason for my question. What should I do here? Just thinking out loud that it would be nice if I could fix a 'bias point' on the input of U1E so that minimal IR receive is necessary for a high.

EDIT:

There seems to be a 32.768 kHz oscillation at U1D (pin 8) with no IR signal present. This oscillation kicks in when the supply voltage is roughly 3.1V. By 3.6V to 3.8V it is prevalent enough to cause the output of U1E (pin 10) to drive low.


texts: How PN junction diode is used as temperature sensor

texts: I know the operation of PN junction diode. But I wonder how they use it as a temperature sensor.


texts: Diode circuit question. Got answer but not sure about nodal analysis

texts:
simulate this circuit – Schematic created using CircuitLab

So I have this circuit here. My assumption was that both of these are ON and then I go ahead and solve the circuit. The only thing is though, I'm not sure if my work is right. I did nodal analysis but I'm not really sure if I applied it correctly.

Does that look okay or did I mess up somewhere?


texts:
I am referencing this project: http://www.8051projects.net/wiki/I2C_Implementation_on_PIC

I am using PIC16F1847 and XC8 as opposed to PIC16F877 and HiTech C so I've had to make a few changes to the code. After making changes, my compiler gave me an error for the I2CWait function for the while statement. It says "unexpected token amp".

Here is the line in question:

while ((SSPCON2 &amp; 0x1F ) || ( SSPSTAT &amp; 0x04 ) );

I changed the register names to be consistent with my PIC's registers (below) but it didn't solve the problem.

while ((SSP1CON2 &amp; 0x1F ) || ( SSP1STAT &amp; 0x04 ) );

What changes do I need to make to this function so that this error does not occur?

[ Edited Wed Jun 29 2016, 03:37 PM ]


texts: I try to repair a Big Muff Pi Black Russian, which was assembled in 2001. Unfortunately, I don't understand the labeling of a broken pot. See picture below. Since the device was assembled in Russia, I believe the labeling is written in Russian. Does anybody understand from the picture, what replacement part I need to use?


texts: L298N (via 74HC595) motor control - unexpected voltage & motor not spinning

texts:
(Corrected version as last text was somehow corrupted)

I have made a circuit with L298N in order to control direction of 2 DC motors. When I power the circuit I noticed that voltage between 2 output pins is lower than expected.

When measuring voltage between 2 output pins I read around +- 5-6V instead of Vcc 9V.

Then I measured difference of each output pin to GND and when input was high, there was voltage as expected near Vcc (9V). But when input was low, there was somehow 4V on it.

I cannot figure out how does this voltage on pin occur. The end result is that voltage difference between output pins is too low to turn the motor.

I also tried to disconnect Enable pin to eliminate some possibilities and it worked as expected - voltage on output was 0V no matter the input state.

What am I doing wrong and is there a way to eliminate voltage on output pin when input is low.

I'm controlling input pins from shift register 74HC595.

Circuit schematics:

(Voltages were measured without a load)

UPDATE: I also tried to hook up the motor and then voltage between pins dropped almost to 0V: I then change Vcc to 12V and output on low input is still 3.96V. When motor is connected, voltage between output pins and GND is always Vcc and except when both inputs are low - then it droppes back to 3.96V.


texts: is it ok to operate a boost converter with the input higher than setpoint?

texts:
I have a supply rail which depending on battery condition and whether the system is on charge can range from approximately 9V (at low-battery cutoff) to 15V (with charger connected). From this I am currently powering a LM2586S-ADJ based boost converter which is currently set for an output voltage of 24V.
The 24V rail doesn't actually need to be as high as 24V. I have not yet figured out exactly what voltage it needs to be but I would guess around 14V or so.
I am considering reducing the set-point to improve system power efficiency. Possibly to a value below the maximum input voltage. It is not a problem for my circuit if the output voltage rises above the set-point when the input voltage is above the set point.
Are there likely to be any problems with operating a boost converter (specifically the LM2586S-ADJ but I'm also interested in more general answers) with an input voltage that may sometimes be above the set-point voltage?


texts:
If you initialize an array in Verilog, like:

input [2:0] A;

A[2:0] = 0;

Would that assign A[0], A[1], and A[2] the value 0? Or is there another way to do it?

Thanks for your help.


texts: MOSFET: Calculating \$V_\mathit{DSsat}\$ from \$k_n'\frac{W}{L}\$ and \$V_\mathit{Th}\$

texts: I'd like to know if it's possible to find \$V_\mathit{DSsat}\$ knowing \$k_n'\frac{W}{L} = 0.75\,\$m and \$V_\mathit{Th} = 1\,\$V?  Also, \$I_D = 1\,\$A.


texts: Efficient single cycle huffman decoding technique with wider input data?

texts:
I have a wider input data (Byte width) running in my system, and I'm implementing a huffman decoding on this incoming data. Since, the Huffman encoded words don't have the fixed length, hence I need to build a very complex state machine to cover all the possible combination for the decoding process to minimize the decoding time. (The primarily consideration of the implementation is to decode as many as words from the incoming data, and push the only incomplete encoded word to next cycle.)
I'm sure this implementation is less efficient especially it will easily to grow combinatorial logic which at the same time is hurting the system Fmax.
Is there any alternative technique that can ease the implementation? Still, fast decoding time is the primary consideration factor.
Example:

Input data per clock cycle : 8 data bit
Encoded word length: 1 bit / 4 bit / 5 bit / 6 bit / 7 bit

Case 1) In a single clock cycle, the input data can contain multiple encoded words, such as total 4 encoded word (3 x 1 encoded word & and 1 x 5 encoded word ), this is a very straight forward case as we can simply decode all the incoming data in a single clock cycle
Case 2) In a single clock cycle, the incoming 8 bits data only contain 1 x 6 bit length encoded word. In this case, we need to push the left over 2 bit data to be used in the next clock cycle decoding. Hence, the next decoding process need to decode from the 10 bits data instead the original 8 bits data.
Based on the case 2, If we apply it in all the possible decoding combinations, it will translate to a very bulky & complex logic. (The original problem statement)


texts:
Assuming an op-amp that is connected without any feedback.
Then in theory does Open-Loop Gain and differential gain convey the same information or am I missing something?


texts: Is there any difference between calling for less power and sending less power?

texts:
This is an "everyday" layman question, not a technical question.

I have an AC ceiling fan with three power settings (like some light-bulbs have three brightness settings). I also have a wall switch which is circular rather than on/off.

So I can either "ask" for less power (by changing the fan's setting) or "send" less power (by rotating the circular switch).

Is there an electrical difference between the two?


texts: How to read decade counter with minimum pins

texts:
I just obtained some of these counters for a project:

They have five connections for each slice labelled C, 1, 2, 4, and 8. As you increment the digit, the pins for the appropriate binary encoding are tied to the common pin.

I was hoping that I could tie all of the 1,2,4,8 pins together between all 5 digits, and then alternate which common pin was powered as I read the four common pins. That would let me read the whole unit with 9 pins.

Unfortunately the binary encoding causes connections on digits I am not reading to interfere with the digit I am interested in. I can't think of a good way to isolate the signals without just making 5x5=25 connections to my microcontroller, which I simply don't have io for. Is there a way to read this thing with fewer pins?


texts: Do these waveforms look appropriate for charging an 11.4 V, 3830 mAh lithium ion battery?

texts:
I'm putting together a wireless power transfer based battery charger to charge an 11.4 V, 3830 mAh battery from the output of a 15 V voltage regulator I made.

Due to a limited understanding of battery charging circuits, I'm not sure if the output of my simulation indicates that the circuit is functioning as intended to charge the battery. The voltage is very messy looking but the steady-state current looks close to where I think it should be in order to charge up the battery in 45 minutes to an hour.

Note that the simulation shows voltage and current from the 0.1 Ohm load I placed where the battery will be hooked up.

Here is the topology in LTSPICE:

Here is the waveform. The voltage is all over the place but the average current is around 1.3 Amps. GREEN is current at the load, BLUE is voltage across the load.

Should the messy voltage signal across the load be a concern if the steady state current is reasonably precise to the desired value? I placed a 0.1 Ohm resistor based on Battery University's suggestion of typical charging battery internal resistance.

Cheers


texts: Is power calculated using source voltage or load voltage?

texts: I am making a power meter that counts the mWh over the course of a battery discharging. I am using an arduino and an INA219 current shunt module. When the load is connected, the load voltage reported drops to 3.2v, from 3.8v when there is no load. My question is, do I calculate the power with 3.2v x current, or 3.8v x current?


texts: How long will a DS1307 RTC run on a CR2032 coin cell battery?

texts:
I have a homemade clock based on an atmega328 and a DS1307 Real Time Clock. When off, the DS1307 is powered by a 3V CR2032 coin cell, as usual.

If I leave the clock off most of the time, how long should I expect the coin cell to last?

I'm aware of the formulas for calculating the battery discharge time, but I'm probably failing at applying them right (I think). According to my calculations, it should last approximately 50 years based on 210mAh capacity of the battery and 500nA of current draw from the datasheet. But the current draw is so low that there must be other issues dominating the battery discharge rate.

So, does anyone have any better figures than I have? Any real experience? Did anyone's battery die before 10 years?


texts: ST-Link V2 Programming STG-850 PLC -- STM32

texts:
I'm trying to connect to a Barth STG-850 PLC for the first time and am using the ST-Link V2 programmer (not the ISOL version) and have been unsuccessful so far.

The crux of my problem likely stems from not having the recommended cable for connecting from the JTAG connector to the PLC, which is the VK-35 cable also sold by Barth. I ordered the cable but won't have it for 1-2 weeks, so I have been trying to connect without it.

I've powered the PLC externally with 12V. Connected the ST-Link to my PC and installed both STM32 ST-Link Utility and Keil MicroVision to try to establish connection with the PLC. For connections between the PLC and the JTAG connector I've connected the following:

After trying several options I seem to be stuck at two errors, either "Can not connect to the target" or "STLink USB communication error" although the USB comm error I can get to go away just by unplugging and re-plugging in the ST-Link. Both can be seen in this pic:

This is rather specific, but does the VK-35 cable do anything besides just connecting the corresponding pins?

One function I thought the cable might be doing would be to invert the reset pin (pin 5 on the PLC) since there is a "(inverted)" in the data sheet for the reset pin.

I've started focusing more on the reset pin since I've learned that to flash the software the reset pin is usually toggled in a sequence or held to a specific state. Also if I just plug the reset pin in how I've shown it wired above then the normally blinking status LED on the PLC goes out. Since I noticed the "(inverted)" comment I tried inverting the signal by passing it through an arduino and simply flipping the signal. That gets the PLC LED to stay blinking while the programmer is in but I still get the above errors.

I'm hoping that some of you with more specific knowledge on ISP's and/or STM32 MCU's will have better intuition on my problem.

PLC: https://barth-elektronik.com/en/mini-plc-stg-850.html

ST-Link V2 programmer: http://www.st.com/content/st_com/en/products/development-tools/hardware-development-tools/development-tool-hardware-for-mcus/debug-hardware-for-mcus/debug-hardware-for-stm32-mcus/st-link-v2.html

VK-35 Programming cable: https://barth-elektronik.com/en/connection-cable-vk-35.html

Thanks!

--------------- Additional Information

Below is the error log I get from the ST-Link Utility when I try to connect with the reset pin (pin 5 on the X4 connector) plugged into the ST-Link programmer. Changing the mode to "connect under reset" gives the same result.

USB communication error (65657) after target cmd F1 80 00 00 00 00 00 00 00 00
ST-Link get version failure
The detected STM32 firmware version (V0.J0) does not support the DAP read command.

When I try connecting without the reset pin plugged in I get the following error log from the ST-Link Utility:

ST-Link/V2 device detected
Target voltage detected: 0.000000
No target device detected: check JTAG signals
Error (4) while initializing ST-Link in JTAG mode

The "Target voltage detected: 0.000" makes me think I might have something mis-wired on the ST-Link JTAG side. The PLC has 3.3V and Gnd properly connected.


texts:
Recently, I heard one of my colleague said "the 16-bits ADC is enough for us, we can use 'oversampling' tech...". Finally I figured out his "oversampling tech" means to sample many many cycles (AC sampling). But I wonder if we don't improve the sample rate, what is the benefit from sampling many cycles? Can it increase the resolution of the ADC? So my question is:

I think "oversampling" means to improve the sample rate. Right?
What is the benefit from multiple cycle sampling?

My colleague's "oversampling" is as below:

If we want to measure 50 Hz AC signal, we set ADC's sample rate to 1000 Hz, and sample 10 cycles, that is (1000 Hz / 50 Hz) x 10 = 200 samples. If the result is not good, increase the cycles to 100, etc. Yes, he only increases the samples, but not the sample rate!


texts: what is the name of this component? it's from a power supply.


texts: What is The Difference Between PAM And ASK

texts:
In Digital Communication can We use  PAM in place of ASK
The Diagram is Given as

The Book Later Talks about Symbols.
I Don't Understand, in PAM we don't have specific signal as input like in ASK we provide the keying as the digital input, so we can either have 2-ASK
high/low(1 or 0) but in PAM the O/P value of the PAM circuit depends on the modulating signal.

Someone please Explain.


texts: what's the best track size for PCI card and 256 pin QFP chip?

texts:
I tried to develope PCB on altium,
what's the best track size for PCI card edge and 256 pin QFP chip ?
Thanks


texts: are there limits for the number of buck converters I can run off a single power supply

texts: I am trying to design an led array that includes 4 different types of leds. I am thinking of using several adjustable (cccv) buck converters in parallel on a single set of daisy chained PSU 24v 10A. In the design I could end up using up to 4 converters, 1 set to 19.2v @ 0.7A, 2 set to 19.2v @ 1.4A with PWM dimmer, and 1 set to 24v @ 1.05A. Those are the raw numbers using the Fv and Fc for the leds, I will likely end up slightly under current on all sets. What if any issues are there with this type of set up? Thank You


texts: Driving a 44Ω Speaker off a board that expects an 8Ω speaker

texts:
I'm turning a Western Electric 500 into a mobile phone using a FONA Feather.

I see the Feather want/expects an 8Ω speaker, but the speaker in the handset measures 44Ω.

I presume if I try to drive the handset speaker, the FONA won't have enough power and I'll barely be able to hear. Is that assumption correct?

What would be the best way to work around this? An amp in between the FONA and the headset? Or might it work OK without? Or another method?


texts: Verilog, Is this statement interpreted as I expect?

texts:
I've a verilog design where there's this line:

assign rb = (r == 0) ? 0 : (r == 01) ? g & t : (r == 10) ? g : g|t;

g,t are 1 bit values,r is a two bits value and rb is 1 bit.

I'm not a big expert in verilog, but I was wondering if such line is equivalent to

assign rb = (r == 2'b00) ? 0 : (r == 2'b01) ? g & t : (r == 2'b10) ? g : g|t;

Is it? If yes is the second better than the first? It's worth noting that the code compiles in the first case, and the output of the whole design outputs what I do expect.


texts: Do electric kettle's take longer to boil in the USA due to lower mains voltage?

texts:
This is an observation I am basing very much basing on anecdotal evidence. I have recently moved to the U.S from Europe, and have previously lived in New Zealand. I find that kettles (known as tea kettles here) take a lot longer to boil water in the United States.

Someone suggested to me that this is due to the lower mains voltage level (120 as opposed to 240V in NZ). Is this correct? I would have thought it would be easy to compensate for by increasing the current.


texts: send data to server using GET method and sim900a

texts:
I am trying to send my data to HTTP server using GET method. When i am sending some hardcoded  data manually it is getting stored in database successfully.

SIM900.println("AT+HTTPPARA=\"URL\",\"xxx.xxx.xxx.xxx:xxxx/xxxxxxxxx/api/iot/v1/save-data/10/20/\"");

This is working fine and my data is getting stored successfully.

But when i am trying to send real time data i am unable to send it successfully. Let's say

float h = DHT.humidity;

float t = DHT.temperature;

SIM900.println("AT+HTTPPARA=\"URL\",\"xxx.xxx.xxx.xxx:xxxx/xxxxxxxxx/api/iot/v1/save-data/t/h/\"");

It is storing the value as t and h instead of their real values.
I tried some different methods also.

SIM900.println("AT+HTTPPARA=\"URL\",\"xxx.xxx.xxx.xxx:xxxx/xxxxxxxxx/api/iot/v1/save-data/tempData=");

SIM900.print(t);

SIM900.print("&humdData=");

SIM900.print(h);

SIM900.print("\"\r\n");

But i am getting error.

Can anyone please help me and tell me how should i send my data to make it getting saved successfully.
Thanks in advance.


texts:
this question seems to be basic, while reading about early effect, that is base width modulation , one of it's consequence was written there is : "there would be a less chance of recombination in the newly formed "narrowed" base".
my question is why the chance is less? my guess is : because now the CB depletion region is more close to the emitter, so most of the electrons pumped by the emitter would feel a larger force applied by the depletion region on them so they won't get much chance to recombine and will be pushed towards collector, but if the depletion region is far enough from the emitter then many of the electron will not efficiently "feel" the force of the depletion region and will get bore and recombine and flow out through the base. Is this even close to correct?
also one more question is, since now the base is narrowed and there would be less chance of recombination, so most of the emitter pumped electrons will go to the  collector, so does it mean the base current will reduce?


texts: Why are fractal antennas able to receive so many more frequencies than a conventional one?

texts: Why is it that so much more different values of frequencies can be received by a fractal antenna than a conventional one? Is it because of the self-similarity, when you look at different scales of the antenna pattern? What´s the physics behind it?


texts: Could anyone please let me know which one is better for low current measurement? I'm going to measure power consumption of MCU and camera module, But it seems I can't use shunt resistor, because current will be less than 300mA and shunt resistor has large error for such low current measurement. However, I can't decide a proper tool to make it. If I could use the feedback ammeter, then I'd like to go for it to avoid bying the expensive current probe.


texts: Design of Window Comparator Circuit w/ Mutually Exclusive LED Indicators

texts:
The functionality I seek is as follows:

All LEDs off: Vsignal < 0.118VDC
LED1 fires: 0.118 < Vsignal < 0.1216
LED2 fires: 0.1362 < Vsignal < 0.146
LED3 fires: 0.151 < Vsignal < 0.1607
LED4 fires: 0.1853 < Vsignal < 0.1999

Between these firing windows, all LEDs should be off. The two ICs are an LM339 and a CD40147BE.

The noise from the signal voltage is <0.0002VDC. The accuracy should be to 0.001VDC.

I need to recalculate the resistor values for ref voltages, but I don't know how to connect multiple comparators together; all examples I've seen have been for a single window, not multiple.


texts: Can I replace a 1N4148 diode with a 1N4007?

texts:
My PC game controller broke and since I have some old PS1 controllers I was thinking about converting one to PC. After some googling I found all I need is a parallel port plug and some 1N4148 diodes. But I live in a small town in the mountains and is not easy for me to get new components, I was wondering if the 1N4007 diodes I have could replace the 1N4148.

  Reference: http://pinouts.ru/Game/playstation_9_pinout.shtml


texts: Thermal Stability of Electrolytic Capacitors

texts: Aluminium Electrolytic Caps do dissipate power .This can be significant when the ripple current is large leading to Ohmic heating due to the ESR .Reputable manufacturers do provide Ripple current information so self heating can be factored into the lifetime calculation.My question is Does the ESR change with temp ? If it has a pos tempco runaway is possible but paralleled devices will share .If the tempco is neg there is good overall thermal stability but there is the possibility of current hogging in the group leading to a cap failing while the others are fine .I have paralleled electros many times in order to get the total ESR down and never been punished.Has anybody had a bad experience?


texts: Speaker out (from laptop) to Mic in (Mobile phones)

texts:
My aim is to connect Mobile phone's Mic to Laptop headset out for injecting audio into mobile phone calls. So that Mobile phone calls should get answered automatically and system should play the recorded audio. This is not possible by programming Android or iOS. Hence i am looking for hardware approach. Searching online i got two different circuit diagrams. Not having much electronics exp, i am unable to decide which one would work. Need help to achieve this

Circuit 1:

Circuit 2 :

Note : I have tried circuit 2 and it worked well on iPhone but not on Android (Samsung). On Android audio was very garbled. Not sure whats the difference  ?

Any suggestions?


texts: 4 layer PCB controller below layer query

texts:
I have designed in 4 layer PCB.

My Controller placed on the PCB top side / first layer.
2nd layer full ground plane.
3rd layer Power plane (fill or not? please confirm.)
4th layer ground fill.


texts: How to create a electric gate which can move from Point A to B

texts:
I wanted to create an electric strip which will move from Point A to B and on discharge i.e 0 volt it will move to its original position.Like ,

The distance between point A and B would be small less than 1 cm , i tried with making a small electromagnet by simply charging the two ends of small copper
coil with 9v battery, but the force generated by it was small and i was not able to pull coil.
I can increase the number of windings or try with 12v battery but i don't think it would be of much use .Can anyone please suggest better approach


texts: Why is the voltage in this digitizer reduced

texts:
I am looking at this page and coming from little EE knowledge, it left me confused. First of all, it defines bandwidth as the following

  Bandwidth is defined as the measure of a circuit or transmission channel to pass a signal without significant attenuation over a range of frequencies. Bandwidth is measured between the lower and upper frequency points where the signal amplitude falls to -3 dB below the pass-band frequency. The -3 dB points are referred to as the half-power points.

Can someone explain that more simply? Also why is -3 dB considered half-power points. This definition kinda sounds like those coaxial cable splitters you can get for your home that have a frequency range printed on them. Is that what this definition is applying to?

Then I have a question about this part:

  If you input a 1 V, 100 MHz sine wave into high-speed digitizer with a bandwidth of 100 MHz, the signal will be attenuated by the digitizer’s analog input path and the sampled waveform will have amplitude of approximately 0.7 V. The value of ~0.7 V can be calculated by using the following equation:
  -3 dB = 20 LOG (Vppout / Vppin)

Why would inputting 1 volt peak to peak 100mhz sine wave into a digitizer output 0.7 volts peak to peak. I have heard Nyquist–Shannon sampling theorem said, but don't really understand it from a working standpoint (I assume it is applying here). If a signal is coming up at 100mhz and you are taking 100mhz samples, wouldn't that be enough to duplicate the 1 volt peak to peak signal? Also, how is the -3 dB applying to that formula? I don't see how it is involved.


texts: I have a heater in a 3 phase (415V AC, 230V per phase) timber kiln drawing 43A per phase. How many kW is this?

texts:
I'm new to this subject, but I want to learn. I have an electric heated timber kiln and I want to replace the electric heater with an equivalent rated oil burner, therefore I need to calculate the output power of the heater from the available information. The electric heater has an input of 3 phase 415V AC, 230V per phase. The amps per phase when the heater is running is 43A.

Is the power = 230V x 43A x 3 = 29670W ?


texts: Why do we generally add capacitors in series with AC sources when DC also exists in the circuit?

texts:
This is probably a noob question but, essentially, why do we often place capacitors in series with AC signal sources? I understand that we sometimes want to isolate the DC signal to "its own" circuit but is there any other reason why we do this, such as to protect a function generator from a high DC voltage?
Would there, for instance, be something wrong with the following circuit:


texts: NPN transistor: collector connected to ground?

texts:
I've never seen a NPN transistor with collector connected to ground. How does it work?

source: Tinkbox relay module pdf - http://tinkbox.ph/sites/tinkbox.ph/files/downloads/KEYES%205V%20Relay%20Module%20KY-019.pdf


texts:
Is it possible to change voltage without consuming power?
I have a 5V Arduino circuit that makes use of a wireless chip (NRF24L01) that runs on 3.3V.
My current approach to get 3.3V out of a 5V source is a voltage divider using a two resistors. It is cheap and very easy to setup. The disadvantage is that the consumption over the remaining 5V - 3.3V = 1.7V is lost / wasted. I run the circuit on an AA battery so power consumption has to be as low as possible.
Now I am looking for a way to not loose any power in the process of getting a 3.3V out of 5V. One approach would be to use a DC buck step down converter. It uses very little power to do so, but it also is more expensive than the voltage divider using resistors. There is also the possiblity to use an AMS1117, but I have no experience with that.
Is there a cheap and power saving solution for getting 3.3V out of 5V?


texts:
I'm currently using Quartus and I'm trying to make a 4 bit counter. I noticed that when I imported the built-in flip-flop that there is no Q bar output. It's the same issue with the JK flip-flop as well. I'm trying to make an asynchronous up counter

I need the Q Bar output as this will be connected to the 'D' input. I was thinking about adding the inverter on the Q output but I can't, as I'm making an up counter.

Thanks to all in advance.


texts: Bootstrap Capacitor Selection with IR2110/3

texts:
I'm going to be using two IR2113 ICs to control each side of an H-Bridge (intended for an Inverter application.) From the application note, the expression to find the bootstrap capacitor is as follows

$$
C > \frac{2[2Q_{g} + \frac{I_{qbs(max)}}{f} + Q_{ls} + \frac{I_{cbs(leak)}}{f}]}{V_{cc} - V_f - V_{LS} - V_{Min}}
$$

Following are the the values of the parameters that I was able to find:

Qg, Gate charge of High Side FET = 63nC.
I(qbs), Quiescent current for high side driver circuitry = 230uA.
Q(ls), Level shift charge required per cycle = 5nC
Frequency of Operation = 50Hz for one side, 20kHz for the other
Vcc, Supply Voltage, 12V
Forward voltage drop across bootstrap diode = 1.3V
Voltage drop across low side FET, 1.5V

I was not able to find the following values:

I(cbs - leak), Bootstrap cap. leakage current. Am I correct that if I use a ceramic capacitor, this value would be value and therefore can be ignored in the above expression?
V(Min), the application note states this is the minimum voltage between the Vb and Vs. Unfortunately, by looking at the suggested schematic (see below) I'm unable to understand what value should I be using for this.

For what its worth, by assuming that I can ignore capacitor leakage current and Vmin, I used the above expression and the values I found for a frequency of 50Hz. The capacitor size came out to be approximately 1uF. Does the capacitor need to be bigger than this in practice? If so, is there a rule of thumb saying how big? Is there a drawback to having a large bootstrap capacitor?


texts: Lattice FPGAs -- How to control skew on signals routed to IO pins?

texts:
Working with:

Lattice XP2-30 or XP2-40
Tentatively a BGA484;  almost certainly some BGA 1mm-pitch package
Synplify PRO, with SystemVerilog

Skill level:  Beginner / early-intermediate.
If I have a custom design (that is, to be implemented in a custom-made board) where there are several outputs for which timing must be matched to within, say, ±1ns (or whatever specified amount, perhaps less than 1ns), how can I ensure that these constraints are met?
Because I'm designing the board layout, I do not have the option to measure the skew, and then compensate for it by applying the opposite skew by adjusting the traces lengths.  Not only that:  I assume that any change in the HDL / re-synthesis / re-map / re-placement can potentially change the skew.
Another detail that constrains / complicates the problem:  I would like to map the IO pins such that the layout gets easier to accomplish;  for example, if I have the external chip (the one on the right in the image below) where I need to connect pins 1 to 5 with tight skew constraints, then that would strongly encourage the choice of FPGA pin assignments such that 1↔A16, 2↔B16, 3↔C16, 4↔D16, and 5↔E16 (just an example, assuming that A16 to E16 are IO pins), to have straight(ish) and near-equal-length traces and avoid using vias or having to "detour" some traces making a round behind the other one, etc.:

How can I ensure that the tool will be able (or will attempt) to implement things such that with that pin assignment, the timings and skew requirements can work?


texts: Toy-like plastic strip for allowing turn-on

texts:
I'm currently working on an electronic design who need to be turned on just once and continue to run until the battery die.
I was searching for a way to do that and the most obvious was to use a plastic strip who act like a "remove before flight" lock.
A lot of toys and small consumer products use that but I didn't found any specific component which can allow that.

I know that on most of these devices, a plastic strip in inserted before the battery to prevent electrical connection between the circuit and the anode or cathode. But I would like to know if there is a component which could allow that without putting it on the battery. Since my design could make the initial launch very unpractical due to the position of the battery.

I will reply the first three comments:

the product is shipped with the battery already inserted. Due to confidentiality reason, the final custommer don't have to access the device.
Nice idea. Unfortunately, my geometrical limitations will probably not allow that. But I will study it.
It's the only way for me to control that the system is launched only when really used by the final custommer. Long time stocking of the full product could impact the battery life during normal use.


texts: Power supply 0-30 volt reverse voltage protection

texts:
I have made a bench power supply that can erogate 0-30 volt and 0-2 A.
Now, how can i protect my bench power supply from reversed voltage applied to it's output?

Typical p or n mosfet circuit dosent work in this circumstance-

I am thinking to create a separate circuit with a separate floating ground to sense a reverse voltage applied to the output of the power supply, but i am looking for an easier way to do it!

A diode, in antiparallel, and a fuse would do the job, but i am looking for something more reliable!

Any suggestion?


texts:
If the zeros were on the imaginary axis, it sure would have been  a NOTCH filter.

But, since the complex conjugate zeros are on the left of the jW axis,
the transfer function has second order terms in both numerator and denominator.

I tried the Bode plot of the transfer function and ended up getting a high pass filter by assuming zeros at z1,z2= -1+i , -1 -i and poles at p1= -3 and p2= -5.

But does the asymptotic approximations end up with correct results?

How can i identify the type of filter if the transfer function is not in any of the standard forms ,for example , in case of a notch filter :

edit: i agree with the fact that there are many other filters apart from the 5 basic ones,but is there any way of predicting the behavior (approximating) given any pole-zero plot like the one above.


texts: What's wrong with my experiment to observe harmonics caused by receiver saturation and non-linear behavior?

texts:
I've been trying to devise an experiment to produce a third order harmonic in radio receiver that's been saturated, but I'm not seeing the expected results.
My understanding of the theory is that when you drive an amplifier (like a receiver front end ), past the point of linear operation whether by an on or off frequency signal, it will produce harmonics of and primary frequencies input into it.  (  See diagram below )  I thought I could observe this effect with a handheld two-way radio and 2 signal generators I have on hand.
My experiment set up is thus:  A multiple band, 2-way FM transceiver, programmed to to receive on 471MHZ and two signal generators. One signal generator generates an FM 157MHZ signal, modulated with a 1kHz tone, the other signal generator is used to produce an unmodulated CW carrier.  Note that 157MHZ x 3 = 471MHZ. I expected that I could use the CW signal to force the receiver into non-linear operation causing the amplifier to produce 3rd order harmonics of the 157MHZ FM signal injected below saturation.
First I inject the 157MHZ signal into the 471MHZ radio.  At about -60 dBm the receiver of the radio would open and produce a fairly clean 1k tone: this to me indicates that the FM signal forced the receiver into non-linear operation, causing the 3rd order harmonic, 471MHZ to be demodulated on the radio. This I expected. Next, I used a combiner to inject the 157MHZ FM signal and the CW signal into the receiver.  I injected the FM signal first to find the spot where the receive became non-linear and demodulating the 1k tone.  I decreased the FM signals power just below the threshold.  Then I turned on the CW generator and increased the power slowly. I assumed that the CW signal would drive the receiver into non-linearity causing the receiver to produce the 3rd order harmonic of the FM signal, and thus the receiver would open up with the primary FM signal injected at a lower power than by itself.
The results were not what I expected.  No matter what frequency or power level the CW was set to, it didn't seem to affect when the receiver opened up.  If the FM signal was set so that it's 3rd order harmonic was being received, I could overload the receiver by cranking up the CW wave though, so I know it was getting into the receiver.  I was expecting that the CW signal would force the receiver into non-linear operation, and that I would be able to receive the 3rd order harmonic of the FM signal at a lower threathold than by itself.  Anyone have an idea why I didn't see what I expected?


texts: GPS parity decoding, how to get D29 and D30 of previous bits?

texts: According to ICD GPS 200C, to decode the bits of a word you need to have the bits 29 and 30 of the previous word, this means that to get the bits 29 and 30 of the previous word you should know the bits 29 and 30 of the word before and so on. Now my question is that how do I start decoding? If I start receiving the bits, I don't know about the bits of the previous word because I didn't receive them, so how do I decode this first word I receive ?


texts: What does the "2" indicate in 2:4 format for Excellon drill files?

texts:
For Excellon drill files, I know that the number after the colon indicates the precision, i.e.

2:3 has 1 mil resolution
2:4 has 0.1 mil resolution
2:5 has 0.01 mil resolution

However, I don't know what the number before the colon indicates.  What does the "2" mean?


texts: Is it possible to have an ARM SBC drive two e-ink displays?  With the low costs e-readers like the B&N Nook Touch, I am interested in buying two just to extract the e-ink displays.  The only problem is I don't know how to go about getting an ARM SBC to drive two e-ink displays.  Any thoughts?