texts: Is there a way to self hardreset /restart microcontroller?

texts:
I am using STM32F4 MCU I'm trying to implement OTA update on it most of the work is done. Now when we switch the firmware from old to new firmware it requires restart. In order to switch to new firmware I need to hard reset it or restart it which fails the purpose of OTA

Basically I want to restart/ hard reset microcontroller after it receives new firmware start from different memory address.


texts: Topology for 1st order active low-pass filter

texts:
I have seen two different designs for a low-pass filter:

1) A resistor and capacitor in parallel in the feedback loop, combined with an input resistor on the - input, + tied to ground.

2) An input resistor, followed by a capacitor shunt into the positive terminal, and a voltage divider to ground for the feedback loop.

Obviously #1 is inverting and #2 is non-inverting, but what are the other trade-offs when deciding which to use in general?

Schematic for a visual aid:

simulate this circuit – Schematic created using CircuitLab


texts: How to check that blast furnace is full?

texts:
I'm working on blast furnace oven, I need to check if it's full with materials in levels one , two and three as shown :-

The main problems:
It's very hot as you see in the picture (200°C to 900°C), thus I need to protect my sensors from this heat and also I need them not to be affected with the emissions.
Can I use IR sensors, camera or ultra sonic to solve this problem?
Update 1:-
The oven is used to melt down lime stones. I'm afraid that the heat could damage the sensors or that dropped stones may hit them.


texts: Trying to understand the relationship between voltage, current, and power

texts:
Please forgive this ultra-noob question, but I'm a bit confused. I've been reading about how neither voltage nor current alone constitute power in a DC circuit. Instead, power is a combination of both voltage and current. Alright... But if current is the flow rate of electrons through a circuit and if it's true that voltage causes current, then doesn't current alone already imply voltage? Why doesn't this mean then that current on its own indicates power?

Muchas gracias.


texts: Using laplace transform to find the expression for voltage in the circuit

texts:
Let's say we have the following circuit:

Generator in the circuit has sinusoidal waveform \$u_g(t)=\sin\omega t\$.
Other known values: \$ L=0.25H\\ R=1\Omega \\ C=0.5F \\ \omega=1 \frac{rad}{s} \\ k=1\$

Before the P2 switch is closed, we had steady state in the circuit, at the same time, switch P1 was in the position 1. At one of the moments, when voltage on capacitor is at its maximum, switch P2 closes and switch P1 goes to the position 2. Determine the expression for capacitor voltage after that moment.

I know that i need to analyze this circuit in steady state before switches change their position in order to find initial values for the capacitors and inductors.

Basically, what i need here is the expression for the current in the circuit and voltage on \$C\$. When i consider this circuit in the laplace domain, it is the same as it is here, since there is no energy in \$C\$ and \$L\$ before the first steady state.

Since generator is sinusoidal, we have that \$U_g(S)=\frac{\omega}{s^2+\omega^2}\$

furthermore, if we look at the circuit, we have that \$U_g(S)=I(s)(Ls-kLs+\frac{1}{Cs} + R + Ls -kLs)\$

Since k=1, this becomes:
\$U_g(S)=I(s)(R + \frac{1}{Cs} )\$

From here, we have:

\$ I(S)=\frac{U_g(S)}{R + \frac{1}{Cs}} =\frac{\omega}{s^2+\omega^2}\frac{1}{R + \frac{1}{Cs}} \$

and then since \$U_c(S)=\frac{I(S)}{Cs}\$ we have

\$U_c(S)=\frac{\omega}{s^2+\omega^2}\frac{1}{Cs(R + \frac{1}{Cs})} =\frac{\omega}{s^2+\omega^2}\frac{1}{RCs + 1} \$

Now, based on values we have, these two expressions become:

\$I(S)=\frac{1}{s^2+1}\frac{1}{1 + \frac{2}{s}}=\frac{1}{s^2+1}\frac{s}{s + 2} \$

\$U_c(S)=\frac{1}{s^2+ 1}\frac{1}{\frac{s}{2} + 1} =\frac{1}{s^2+ 1}\frac{2}{s+2} \$

Now, when i decompose these two expressions using partial fraction decomposition i end up with:

\$I(s)=\frac{2}{5} \frac{s}{s^2+1} + \frac{1}{5} \frac{1}{s^2+1} -\frac{2}{5} \frac{1}{s+2}\$

\$U_c(s)=-\frac{2}{5} \frac{s}{s^2+1} + \frac{4}{5} \frac{1}{s^2+1} +\frac{2}{5} \frac{1}{s+2}\$

Which means that \$u_c(t)=(-\frac{2}{5}\cos t + \frac{4}{5}\sin t +\frac{2}{5}e^{-j2t})u(t)\$

\$u(t)\$ is heaviside function

Now, how am i supposed to determine when is this \$u_c(t)\$ maximum value, i mean first derivative method could be option but it seems too complicated in this particular example due to the fact that all these functions can be expressed as exponentials with different arguments so finding maximum would be quite messy job. Usually, with problems like this, i always ended up with single sine (or cosine) and maximum could be determined by inspection easily, so i am thinking that i maybe made a mistake somewhere. So i am wondering what i did wrong here. Any help appreciated!


texts: Hard fault on only one of two identical STM32F405 boards

texts:
So I've made two prototypes of a new custom board with a STM32F405RG microcontroller at heart and while one of them works totally fine, after a few seconds or more I'm getting a hard fault on the second one.

To investigate the origin of the hard fault I turned on the full assert in StdPeriph library and found the DMA_Cmd function from the library to be the first place where something goes wrong (or a first place where something wrong is detected).

It begins like this:

void DMA_Cmd(DMA_Stream_TypeDef* DMAy_Streamx, FunctionalState NewState)
{
    /* Check the parameters */
    assert_param(IS_DMA_ALL_PERIPH(DMAy_Streamx));
    assert_param(IS_FUNCTIONAL_STATE(NewState));
    (...)
}

Apparently, the IS_DMA_ALL_PERIPH macro produces a false result, suggesting that the DMAy_Streamx variable isn't actually a DMA stream.

Here's what the macro looks like:

#define IS_DMA_ALL_PERIPH(PERIPH) (((PERIPH) == DMA1_Stream0) || \
                                   ((PERIPH) == DMA1_Stream1) || \
                                   ((PERIPH) == DMA1_Stream2) || \
                                   ((PERIPH) == DMA1_Stream3) || \
...
more of the same
...
                                   ((PERIPH) == DMA2_Stream6) || \
                                   ((PERIPH) == DMA2_Stream7))

The weird thing is that it's called from the same context every time (with a DMA1_Stream4 value), and the argument of the function definitely is a DMA stream.

So I decided to dive into the register values and assembly. Instead of the assert_param macro I set a simple trap to catch the first occurence of the fault and inspect the register values (the function gets called properly thousands of times before the fault occurs):

if(IS_DMA_ALL_PERIPH(DMAy_Streamx) == 0) {
    while(1);
}

Here's the disassembly of the relevant part of the function:

08000aac:   ldr     r3, [pc, #136]  ; (0x8000b38 <DMA_Cmd+140>)
08000aae:   cmp     r0, r3
08000ab0:   push    {r4, lr}
08000ab2:   mov     r4, r0
 485        if(IS_DMA_ALL_PERIPH(DMAy_Streamx) == 0) {
08000ab4:   beq.n   0x8000b14 <DMA_Cmd+104>
08000ab6:   adds    r3, #24
08000ab8:   cmp     r0, r3
08000aba:   beq.n   0x8000b14 <DMA_Cmd+104>
08000abc:   adds    r3, #24
08000abe:   cmp     r0, r3

...
12 identical checks here
...

08000b0a:   beq.n   0x8000b14 <DMA_Cmd+104>
08000b0c:   adds    r3, #24
08000b0e:   cmp     r0, r3
08000b10:   beq.n   0x8000b14 <DMA_Cmd+104>
08000b12:   b.n     0x8000b12 <DMA_Cmd+102>

So, the r0 value gets copied to the r4 register and then is successively compared to different values, stored in r3.

But the weird thing happens when investigating the register values after the program falls into the trap (loops at 08000b12):

r0  0x40026078 (Hex)
r1  0x0 (Hex)
r2  0x40003800 (Hex)
r3  0x400264b8 (Hex)
r4  0x40026070 (Hex)
(...)
sp  0x1000fe50
lr  0x800225b (Hex)
pc  0x8000b12 <DMA_Cmd+102>

What? r0 value is copied to r4, gets compared to r3 without changing it's value and somehow after those comparisons r0 and r4 differ in value by 8?

I thought at first that maybe some interrupt code stops this function in the middle and corrupts the value of r0, but I don't think that's possible - the code I've shown gets called from the ISR of a 0 Preemption Priority, which means it cannot get preempted by other interrupts (other than fault exceptions, NMI and other stuff I don't use).

Does anyone have any idea what could be the cause of this weird behaviour?


texts: Is electricity wasted when you've connected, say a mobile charger but are not using it?

texts:
I know that the answer is yes. It is consumed, but in very little amount. My question is how it consumes electricity.

When the phone isn't connected the circuit is open at the phone end of cable, then how does electrons move around the circuit, because electricity is consumed when a circuit is completed and electrons can move around (I think so).


texts:
I am using STM32VL discovery board(STM32f100rb6).. Using this code for USART setup (including baud-rate):

#include "main.h"
#include "LCD-HD44780.h"
void UART1_init(void)
{
    lcd_clear();
    /* Enable GPIOA's Clock from APB2, Bit2->1  */
    RCC->APB2ENR |= BIT2;
    //Enable USART1 Clock
    RCC->APB2ENR |= BIT14;

    /* UART1 : UART1_RX: PA10 -> input Floating: (GPIOA_CRH -> reset state so leave it)*/

    /* UART1 : UART1_TX: PA9  -> alternate function push pull */
    GPIOA->CRH |= BIT4 | BIT5; //Output mode 50Mhz
    GPIOA->CRH |= BIT7; // Alternate function output Push-pull

    //Enable UART
    USART1->CR1 |= BIT13;
    //OVER8=1
    //USART1->CR1 |= BIT15;
    //Word Lenght 8 bit reset mode
    //SET 1 STOP Bit reset mode
    // BaudRate config (baudrate=1200)-fclk=24MHz
    //OVER8=0->baurdate=(fclk)/(16*USARTDIV)
    //DIV_Mantasia=1250;
    USART1->BRR = (uint32_t)(1250 << 4);
    //Enable Transmit,Send IDLE Frame as first data
    lcd_writeString(cprintf(USART1->BRR));
    USART1->CR1 |= BIT3;
    while (!(USART1->SR && BIT7));//Wait until TXE is 1;
    while (!(USART1->SR && BIT6));//Wait until TC is 1;
    //Send
    USART1->DR = 1;
    while (!(USART1->SR && BIT7));//Wait until TXE is 1;
    while (!(USART1->SR && BIT6));//Wait until TC is 1;
}

and this code for clocks setup:

#include "stm32f10x.h"
#include "custom.h"

void SystemInit(void)
{

    /* Enable HSI-RC Bit0->1 */
    RCC->CR |= BIT0;

    /* Set PLL Source As HSI/2 Bit 16->0 */
    RCC->CFGR &= ~BIT16;

    // Set PLLMUL to 6-> Bit 20 ->1 */
    RCC->CFGR |= BIT20;

    //Set SYSCLK Source As PLL bit 1 ->1
    RCC->CFGR |= BIT1;

    // Set AHB Prescalar to 8 bit[7:4]: 1010
    //RCC->CFGR |= (BIT5 | BIT7);

    /* Select HSI as System Clock */
    //RCC->CFGR &= ~BIT0 & ~BIT1; // OR Nothing (Reset State)

    /* Set AHPR prescalar as Bit7 ->0 */
    //RCC->CFGR &= ~BIT7; //Or reset state

    /* Set APB2 prescalar to 1 BIT13->0 */
    //RCC->CFGR &= ~BIT13;

}

need this:

#include <stdint.h>
#ifndef CUSTOM_H
#define CUSTOM_H
#define BIT0  (uint32_t)0x1
#define BIT1  (uint32_t)0x2
#define BIT2  (uint32_t)0x4
#define BIT3  (uint32_t)0x8
#define BIT4  (uint32_t)0x10
#define BIT5  (uint32_t)0x20
#define BIT6  (uint32_t)0x40
#define BIT7  (uint32_t)0x80
#define BIT8  (uint32_t)0x100
#define BIT9  (uint32_t)0x200
#define BIT10 (uint32_t)0x400
#define BIT11 (uint32_t)0x800
#define BIT12 (uint32_t)0x1000
#define BIT13 (uint32_t)0x2000
#define BIT14 (uint32_t)0x4000
#define BIT15 (uint32_t)0x8000
#define BIT16 (uint32_t)0x10000
#define BIT17 (uint32_t)0x20000
#define BIT18 (uint32_t)0x40000
#define BIT19 (uint32_t)0x80000
#define BIT20 (uint32_t)0x100000
#define BIT21 (uint32_t)0x200000
#define BIT22 (uint32_t)0x400000
#define BIT23 (uint32_t)0x800000
#define BIT24 (uint32_t)0x1000000
#define BIT25 (uint32_t)0x2000000
#define BIT26 (uint32_t)0x4000000
#define BIT27 (uint32_t)0x8000000
#define BIT28 (uint32_t)0x10000000
#define BIT29 (uint32_t)0x20000000
#define BIT30 (uint32_t)0x40000000
#define BIT31 (uint32_t)0x80000000

char* cprintf(int integer);
int strlenght(char str[20]);
char int2char(int i);
char* revstr(char* str);
#endif

I am arranged to have 24Mhz as USART1-fclk and baud-rate-1200, but when I analyze output by seleae logic-analyzer,found out actual baud-rate is 400 not 1200.(images are appended).
baud-rate=1200

same one by baud-rate=400:

where is the mistake??


texts: I have a Freescale MPC8640-based board with 4 Micron DDR2 chips of 128Mx16 density (total of 1GB) attached to it. The memory has been mapped to address range from 0x0000_0000 to 0x3FFF_FFFF. While testing the memory, we found that "Address test" using own address was failing for memory addresses ending with 0x1c39 or 0x9c39. I am not able to decode the exact hardware lines which is resulting in this issue. Can anyone enlighten me on how to debug this issue further?


texts: I came across a question that is really puzzeling me. I did some basic calculation for a cell phone transmitter. I based on 900Mhz band and assumed a 20Km distance to a cell tower. On top of that I assumed a 99.99% reliability which comes to almost 38 dB for the fade margin. I also assumed a +6 dBi gain for the TX and RX antennas, and reciver power of -100dBm. My calculations showed me a 45 dBm which is almost 23 watts. so I am really confused that how a cell phone with a 5 V battery can operate on these basis and actually run for a long time. am I not having correct assumptions about the hardware design or are they very well designed to perform such a comm link


texts: I have a 3v3 SPI bus with a SDcard on it. I would like to know visually when data is being written to the card. Are there any potential problems with adding a small (1206) SMD LED in parallel as an indicator?


texts: Peak output current of a Full-Wave Bridge Peak Rectifier

texts:
I am attempting to design the first section of my power supply. In this case, I am going through my calculations for the Rectifier section. I am simulating my circuit with PSpice and while most of my calculations agree with my Spice simulation, my calculated diode current is way off.

Here is the circuit I am designing:

Here is my input voltage (red, across the secondary coil), and my output voltage (green, across the resistor/capacitor)

Everything so far matches my calculations perfectly. Now for the part that has me stumped:

Here is my diode current (blue), load current (green), and capacitor current (red). As you can see, my simulation tells me that the total current = 540mA

Alright. I'm working with:
Vr = peak-to-peak ripple voltage = 1V
R = load resistance = 1k-ohm
C = filter = 270.8uF
Vin(peak) = Secondary voltage peak = 24(sqrt2)

My calculations of the peak output current give me 855mA, while the PSpice sim gives me 540mA. I am using the equations from the Sedra/Smith book, provided in the peak rectifier section. Is there something I'm missing here? Thanks!


texts:
I have an embedded board, based on Allwinner V40, which has a serial (UART) interface at TTL voltage levels. I access this interface with a little adapter board (MAX232) and a RS232->USB adapter.

Normally, this interface is configured to send debug information (/dev/ttyS0 under linux). I can turn that on and off, and I can send and receive data as I want. However, something else sends data exactly every ten seconds. This is what the junk looks like (10 seconds between each line, recorded at 9600 baud, the third line has been sent by me).

For reference, this is the first line in hex:

0A 05 31 04 41 6C 4E 0A 02 39 02 F3 F0 F4 F7 F1 F1 F6 F3 F1 F6 F1 FF FF FF FE FF FF FF FF FF FF FF

I've tried changing the baud settings etc., in case something else is sending with a different baud rate, but that lead to nothing. I also attempted disabling Bluetooth, since Raspberry Pis have a similar problem when Bluetooth is enabled. That did not help, but it also does not get worse if Bluetooth is actively used.

This is a two-wire UART, there is no flow control. UART 0 is wired up to PB22 and PB23 on the SoC, which seems correct. From my sys_config.fex (I'm using the legacy/Allwinner kernel):

[uart0]
uart0_used       = 1
uart0_port       = 0
uart0_type       = 2
uart0_tx         = port:PB22<2><1><default><default>
uart0_rx         = port:PB23<2><1><default><default>

[uart0_suspend]
uart0_tx         = port:PB22<7><1><default><default>
uart0_rx         = port:PB23<7><1><default><default>

I'm hoping somebody recognizes the bit pattern and could tell me what causes it. Any ideas?


texts: How do i know what resistor value, that's attached to a BLDC motor, i should use in order to get a torque of 100 lb-ft put on my actuator?

texts:
Motor P/N is M-3441Y-LN-02D.
Back EMF [Ke] is 38.95 (Vpeak/Krpm).
Continuous torque 2.495 lb-ft.
User manual.
I want to run the actuator coupled with the BLDC motor 60:1 gear ratio in reverse.
So the actuator will run at 50 RPM and the BLDC motor will run at 3000 RPM. I will rectify the 3 phases of the BLDC motor into DC voltage, then add the resistor. Would the torque constant (Nm/A) equal my back EMF constant of 38.95 (Vpeak/Krpm)?
If so, would i convert the rpm into radian/second?
It just seems that the more resistance I add to the rectified BLDC motor, the more torque should be applied to the actuator?
Thanks all.


texts: Highside Driver leaking when GND is unconnected

texts:
I am using an Infineon ITS4200S-SJ-D highside switch to control power to a resistive load. Internally the part is basically a PFET with some additional features.

I have a 10k pulldown on pin 2, +12V on pin 5, and a 100ohm resistive load on pin 3.

Everything works great except I notice that if I connect the load and the +12V before I connect the GND I get a leakage current to the load.

I know that the simple answer is "always connect the GND cable first."
But I'm wondering if someone can give me an idea for a simple circuit that I can add to prevent this leakage and keep the load totally un-powered until both of the power supply cables are connected correctly and I activate the input at pin 2.

Here is the schematic. for troubleshooting I have disconnected the microcontroller activation line as indicated by the little red X. The problem I'm trying to solve is when the +12V cable is connected and the GND cable is unconnected I see about 15mA through the load.


texts: How do I set up a lumped element equivalent circuit?

texts:
In the treatment of metamaterials, optical problems and antennas, very often a simplified model is extracted by considering only lumped elements. In some cases this is fairly obvious, for example in this paper, which shows a split-ring resonator with its equivalent circuit.

The straight wires act like inductors, and the capacitor-shaped element in the middle acts like a .. capacitor. So far so good.

But how would this model change if I include a dielectric slab and a ground plane behind the element?

Or how can I approach this in other cases, for example for this coplanar waveguide?

Is there a cookbook-style, systematic recipe how to set up the equivalent circuit of such a system? Where do I start? It seems to me there are loads of capacitances and inductances everywhere - when should I stop including them? And where do the geometric and electric parameters of the original structure come in when evaluating the final circuit (surely I would like to calculate the inductance from the crosssection and length of the wire)?

An answer would be either an explanation how it works in general, insightful examples of different cases or some guidelines as to where I can read about it in detail. At the moment, these equivalent circuits seem to fall out of the sky for me and it's not clear to me, how authors arrive at them.


texts:
everyone. I am researching into the "holding" of electricity. I found out about capacitors, but I am not sure that I understand. If you charge a capacitor with a battery in a circuit like this:

simulate this circuit – Schematic created using CircuitLab

, disconnect the capacitor, then connect the capacitor into a circuit like this:

simulate this circuit
will the capacitor power the LED? If not, then how so? Any answers are appreciated.


texts:
Is it good practice to use resistors (parallel to load) on LDO output?
The MIC29302WU LDO I've bought has ~7 mA minimum current requirement for stability reasons.
What other/better options I have? (Ignoring it, using Zeners (why?), NTC resistors ,...)


texts:
In my current lecture about Analog IC Design the prof mentioned on the side that the output resistance of the following voltage divider is \$ \frac{R}{2} \$. Can someone explain me why that is the case?

simulate this circuit – Schematic created using CircuitLab


texts: PWM to analog voltage conversion for communication between two microcontrollers

texts:
I want to use this schematic for sending PWM signals from an STM32F0 Arm microcontroller to an ATtiny85. I want to convert the PWM signal to a proper analog voltage, so that the ATtiny analogRead() function can detect a proper ADC value from 0-1023 and assert the voltage and perform a particular action based on the analog voltage detected. So, IO1 in the schematic is directly connected to one of the STM32F0 PWM pins, and the CONTROL pin in the schematic is directly connected to an analog pin of the ATtiny85.

NOTE: Both the STM32F0 and ATtiny85 are running on 3.3V supply, thus operating at 3.3V logic level.

Questions:

Is this a proper method to do PWM to analog voltage conversion?
Is there any way to improve the output accuracy of the STM32 and the detection accuracy of the ATtiny85 in this circuit design?
Are the resistor and capacitor values are good enough for this use case? And what specific SMD parts could be used for this application? Like the type of capacitor, the voltage and capacitance rating, resistor type and sizes etc.

There's a little bit of caveat that I forgot to mention. The STM32F0 controller in question has pre-flashed firmware which only allows me to pull-up or pull-down or generate a PWM signal through the IO pins available. If I hack into the firmware, apparently it voids the FCC and CE certifications and warranty of the product. So, the API is pretty limited.


texts: how to protect a 12 volt operating DC LED Bulb from 230 volts mains supply

texts:
I have made a DC Led BULB (7 watt) which is working on 12 volts input.
By the way its input voltage range is 12-48 volts DC (using BP 1601 regulator ic)
Now problem is that when i gave some bulbs to an NGO members.
Some of them tried to operate it on 230 volts mains supply.which malfunctioned DC LED driver circuit.
Now i want to protect this 12 volt operating circuit from ac mains supply.
I tried and failed !!!

I used bridge rectifier to convert ac to dc means 230 AC to 230 DC then i m unable https://electronics.stackexchange.com/editing-helpto step down 230 Volts DC to 12-48 Volts DC.

Any other way to bipass AC input!!!

like over voltage protection,surge protection,over current protection,short circuit protection etc...i want a extra protection which wrong input type protection."MAINS POWER SUPPLY Protection for any DC circuit either it is operation on 3.3 v or 5 v or 12 v input"

:-) Fixed the circuit myself.


texts: Which is easier to solder: TSSOP or QFN?

texts:
Which package easier to solder on home-brew PCBs:

TSSOP
QFN

I generally use solder paste and hot-air / hot-plate.


texts:
Why do we ground radios? As far as I know an antenna is an open circuit...
So we just need to put and filter to remove noise and we are ready. However in most schematics I see the antenna is grounded. Why is that????


texts: ADC / data acquisition board - general layout question

texts:
For one of my current projects, I am designing a small data acquisition board.
However, I am currently not sure about the overall layout of the board.

Here are 2 possible variants I came up with. First of all, the position of the connectors is necessary for these positions, due to mechanical constraints.

My question is actually regarding the position of the I2C expander and its position. The LED's it drives have to be in this position for visibility.
The I2C expander has to be powered by the digital supply.
The state of the LED's will not change during data acquisition and also the I2C bus will not have to transmit any data during the acquisition.

So here are my questions:

which of the 2 layouts is better in terms of EMI / radiated emissions?
For the case, that the LED state does not change during acquisition, do I have to expect any other negative effects on the ADC due to the constant LED currents / I2C expander quiescent currents?
If 1 and 2 are both not optimal, what have I missed and how could I arrange it better?
For case 2, would it be better to have the GND left unconnected on 1 side of creating a loop with the analog plane in the middle?

The ADC I'm planning to use is an ADS8881 - Product page - Datasheet

The MCU I'm planning to use is an STM32F103 - Product page


texts: CCM PFC - Duty Cycle and Pout Misunderstanding

texts:
Suppose a PFC working in CCM. Vout is hold constant thanks to the duty cycle.  Pout is also constant over the time. Suppose the input rms voltage Vin_RMS drops ! For a CCM boost PFC, the duty cycle is given according to the following relation (at least the average duty cycle as the duty cycle is varying for adjusting the input current to a sinusoidal waveform) : $$D = \frac{Vout - Vin}{Vout} $$
So if Vin drops, the duty cycle increases.
Then Isense (the current sensed by the PFC controller which is equal to the input current) according to the datasheet, (I verified the property just for curiosity not because I thought it was wrong) :

$$Iisns = \frac{(1-D)*Vm}{Gdc*Risns}$$

Vm correspond to the output voltage of the error amplifier (between Vref and the feedback output voltage). The maximum Vm is given into the datasheet, we will consider it at its maximum (worst case), so we can simplify the expression as follows :

$$Iisns = k*(1-D)$$

So if Vin decreases, the average duty cycle increases, and it means that the maximum admissible Iisns (input current) has decreased too. What does it means ? The input power is lower as Vin and Iin have decreased. Nevertheless Pout is still the same. Where is my mistake ? The input power shoould be the same. So the rms input current should increase ! ?

If you are interested here are the sources :
https://www.infineon.com/dgdl/an-1166.pdf?fileId=5546d462533600a40153559aabdf1128
https://www.infineon.com/dgdl/ir1155spbf.pdf?fileId=5546d462533600a4015355c431f9164b
https://www.infineon.com/dgdl/an-1077.pdf?fileId=5546d462533600a40153559563801007


texts: Operational amplifier parameters: Input bias current, Input offset current, input offset voltage

texts:
I've been reading about input offset voltage, bias current, and current offset for a few days now and still can't get some things straight.

I'll summarize what I understand and then pose the questions below. Please correct me if I'm wrong, it's difficult to find confirmation for these ideas.

1) Input offset voltage - Caused by mismatch in the input terminals of the opamp and specifies the voltage across the terminals that must be applied in order to get an output voltage of zero.

2) Input bias current - caused by the finite input resistance of the opamp and results in an "error" voltage drop that depends on the input impedance seen from the opamp terminals.

3) Input offset current - caused by a mismatch between the input bias currents of the individual terminals (not sure what this results in).

My questions are the following:

1) Does the input offset voltage simply add a DC component to all supplied AC signals, or is it relevant only when you want an output voltage of 0? Would one get rid of this offset voltage by simply AC coupling the input signal by adding a capacitor (and a resistor to ground)?

2) Is the best way to minimize the bias current by adding compensation resistance on the opamp terminal(s), so that the same potential difference appears across both terminals and the common mode signal rejection begins to take effect? What about when the bias signals are not matched on each terminal (which is what the input offset current specifies)?

3) What effect does the input offset current have on the output signal? Does it also introduce an error into the "actual" incoming signal?

I am fairly new to analog design and I'm trying to design an amplifier circuit that amplifies signals in the mV range (to also give output signals in the mV range, so low gain). This signal is being fed to expensive equipment (much, much, much more expensive than the amplifier circuitry) and I don't want to damage this. At the same time, I can't introduce significant errors into the signals that give me an amplified signal that is not representative of the original signal. I also need to quantitatively account for these errors.

Thanks!


texts: 120v to 24v 40va transformer damaged, replaced with 120v to 24v 15va transformer

texts:
Powermaster J51 electric gate motor tested, working. Problem is that remote relay does not engage despite new transformer. If the relay is helped (manual push) it will engage and remain engaged until the end of the cycle. Could the change in the rating of the transformer from 40VA to 15VA be the reason?
The original transformer was damaged by hurricane Maria. Only replacement found was the 15 VA one.


texts: What is AO222 based design in concept of design of CMOS cell library?

texts:
I am reading a paper "Static Implementation of QDI Asynchronous Primitives" by P. Maurine, J.B. Rigaud, F. Bouesse, G. Sicard, and M. Renaudin.

They designed a cell library using AO222 gate, What is that exactly? Can anyone point to any document that shed a bit of light on this "AO222" term which I never heard of.


texts: Oscillator slows down when my hand hovers over it

texts:
I'm teaching myself VHDL using this MAX II CPLD board.

I designed a frequency divider and 4-bit counter in VHDL using the onboard 50MHz oscillator. It seemed to work as the onboard LEDs are flashing in the right way, but I noticed that they flash slower when my hand is near the chip or the onboard crystal oscillator.

The oscillator is in a 4-pin metal package. It has markings 50.000 and e552. It's X1 in the board; pics are in the above link. Not sure if it contains a crystal or uses some other technology.

Some pictures of the board, especially the area between the CPLD and the oscillator. I think the clock goes from X1 through R5, then to the bottom side, then back to the top side, then to pin 62. Pin 62 is the only pin on the right side of the chip that doesn't go to the pin header at the right side of the board, roughly in the middle of the MAX II label.

It might be a problem of floating inputs, but the counter doesn't have any input pins (not even a reset!). I don't need to tie all unused 72 I/O pins to ground, do I? Here is the VHDL:

entity SpdifTest is
    port(
    CLOCK: in std_logic;
    LED: out std_logic_vector(3 downto 0)
    );
end SpdifTest;

architecture rtl of SpdifTest is
    signal output : std_logic_vector(3 downto 0);
    signal count : std_logic_vector ( 23 downto 0 );
begin

    process(CLOCK)
    begin
        if (rising_edge(CLOCK)) then
            count <= count+1;
            output <= count(23 downto 20);
        end if;
        LED <= not output;
    end process;
end rtl;

Here are the pin assignments in Tcl (pin 62 is the clock):

set_location_assignment PIN_62 -to CLOCK
set_location_assignment PIN_40 -to LED[0]
set_location_assignment PIN_43 -to LED[3]
set_location_assignment PIN_42 -to LED[2]
set_location_assignment PIN_41 -to LED[1]

Is there something else I missed, or maybe the board is faulty? The same thing happens with a similar board (with EPM570 instead of EPM240).


texts: Changing my fluorescent lamp to led lamp

texts:
I am planning to design a LED lamp using a 6V power supply from a lead-acid battery with a rating of 4.5Ah. I want to connect 20 LEDs  (LED's rating is 20mA 2V) in parallel to achieve maximum brightness. I calculated the resistor I will use is about 100 ohms to 120 ohms.

What power rating of the resistor must I use?
Is my calculation correct and
what is the the current in each branch.


texts: Why is current rating for multicore cable lower than single core with the same cross section?

texts:
As per this resource, a single core 10 AWG (5.3 mm2) copper cable is rated for up to 52 amps, while the same cross section cable of 43 cores and more is only allowed to carry up to 15 amps.

Why is that? Why do multiple cores make it more dangerous to carry the same current?


texts:
I'm curious as to what recommendations can be made concerning charging routines for a typical lithium ion battery found in a device like a cell phone. The primary goal I have is to maintain the usable life of the battery for as long as possible. In my mind a battery is still usable if it can hold a charge for at least a day under minimal/mild use, such as a few short phone calls and/or text message each day. For the confines of this question I'm sticking with the cell phone's default charger and default hardware/software.

Things I'm looking to be answered would be:

Should I try to keep the battery at "full charge" (as determined by the manufacturer) as much as possible? Or should I try to cycle the power from full to nearly empty before recharging?
Should charging be performed routinely (i.e. every night before going to bed), or should I let the battery charge indicator determine my charging patterns?
My phone in particular has a message pop-up saying that I should disconnect my phone from the charger to "conserve energy". Should I follow that advice and allow the phone to use the battery, or should I try to leave the phone plugged in until I want to leave for somewhere?
What's the reasoning behind your answer? And I suppose most importantly how much does it matter with Li-ion batteries (i.e. how much more life can I expect using a good practice vs. a bad one)?


texts: I am getting a Cyclone II-based Altera DE1 FPGA board to experiment with. I know a lot about programming, a bit about electronics and very little about FPGAs. What books or other resources would you recommend to someone like me to get started?


texts: PCB design for hand soldering exposed pad

texts: The (battery managing) IC I want to use has an exposed pad for thermal relief.  I am designing the PCB and want to hand solder the chip on the board.  I have read that you can drill VIAs to connect the exposed pad to a ground plane.  I would solder the pins (easy enough) and then solder through the VIAs to the ground pad.  Is this the best practice?


texts: Can I make a step up transformer using these components?

texts:
I have a step down transformer that converts from 220 volt to 15 volt.
I want to connect the secondary coil of this transformer to the output of 555 IC that produces ( 5 volt / 100 KHz ).

Is there any increase in voltage at the primary coil ? Is it square wave ?

How can I calculate the voltage and current at the primary coil ?

How much the frequency of 555 affect the output voltage ?


texts: How to calculate the neutral wire size of a home (department)?

texts:
I know that in electrical grid, Neutral wire is a non current carrying conductors so its cross section area is smaller than the cross section area of the live conductors. I think it has half of size of the live conductor.

Is this rule valid for a department or a small home that uses 1 phase only? If I'm buying the neutral cable for a home, Should it be less that or equal live wire ?

My country does not have grounding system. The wall outlets have two ports only (220V / 50Hz). But the neutral of distribution transformers is grounded.

Thank you,


texts: Lattice Machxo3 FPGA configuration using I2C

texts:
I have a Lattice Machxo3 FPGA based design / board and currently I am configuring the FPGA using JTAG. As per the datasheet I2C also can used as the FPGA configuration interface. Is it possible to use the I2C as the primary interface to configure instead of JTAG? The datasheet mentions that I2C can be used for reconfiguration. I just want to confirm.

Also, is there any same code available wishbone interfacing to configure FPGA?


texts: To what extent can frequency improve speed?

texts:
Circuit A has a throughput of 50 Megabits/second (Mb/s) running at 33 Mhz, while Circuit B has a throughput of 70 Mb/s running at 50 Mhz. It is clear that running a circuit at a higher frequency can increase the speed of operation. But to what extent can the frequency of a circuit be increased in order to rank up its speed?

It's easy to say Circuit B outperforms Circuit A, but that is ignoring the fact that Circuit B runs at a higher frequency. A 'naive' way to account for the difference in frequencies is to normalize both circuits to run at the same frequency, say 50 Mhz in this case, which will reveal the true capabilities of the two implementations.

But it's not that straightforward is it?


texts: Is it possible to receive information if the received power is below the noise floor?

texts:
This relates to my previous question, which I think I have asked in the wrong way:

How to insert background EM noise into pathloss equation?

I wasn't really interested in detectability of the signal, and I have phrased that question very ambiguously, so let me ask what I would really like to know.

Question:

What I would really like to know is that is it possible to establish a communication channel (sending information) if the received power level of the  signal, received by the receiver antenna is below the noise floor.

Let me explain:

I did more research on this and the power level is usually expressed in dBm or dBW. In this question I will be expressing it in dBW.

Then we have the power inserted into the transmitter antenna, and we have the path loss equation to determine how much of that is attenuated by the time the signal reaches the receiver antenna.

So we have two dBW values, and my theory is that the power received by the antenna in dBW has to be higher than the noise floor in dBW.

1)

For the sake of this argument let's use a transmitter/receiver antenna 20 cm long, at 5 Ghz frequency at 1 meter from each other. Again I am using the maximum gain fundamentally possible, because I am also looking whether the communication channel can be established at all, so I have to insert the most extreme values in order to determine the fundamental limit. In this case both antennas have a gain of 16.219 dB which is the maximum gain they can have at this frequency, and by maximum I mean a gain higher than this would violate the laws of energy conservation. So these antennas are in theory perfect lossless antennas. This is a far field equation so for simplicity I choose to use the Friis formula.

So the path loss equation reveals that this communication channel has a ~ -14 dB path loss. So if we are inserting 1 Watt of power, the receiver antenna should receive no more than -14dBW.

2)

I've stumbled across a paper:

http://www.rfcafe.com/references/electrical/ew-radar-handbook/receiver-sensitivity-noise.htm

It claims the minimum sensitivity for a receiver antenna is this:

$$ S_{min} = 10* \log_{10}( (S/N)*k*T_0*f*N_f ) $$

$$where$$

S/N= Signal to noise rate
k = Boltzmann constant
T0 = Temperature of the receiver antenna
f = frequency
Nf= noise factor of the antenna

And this is also a dBW unit. This formula would describe the noise floor at that frequency.

Going back to our calculation, the paper recommends, in best case scenario, when a skilled manual operator is involved a 3 dB S/N ratio (max), we will use 290 Kelvin for room temperature, the frequency 5 Ghz as above, and the noise factor I will ignore since we assumed a perfect antenna earlier.

This would give us -104 dBW noise floor.

Therefore since the received power level is -14 dBW and the noise floor is considerably lower at -104 dBW, and this assumes a best case scenario with generous estimates, as in the best case scenario.

So in this example, communication is possible, very much. However if the received power level would be lower than the noise floor, then it would not be.

So my hypothesis is that if:

Power Received > Noise Floor , then communication is possible, otherwise it's not

Since the power received is way higher than the noise received, it means that communication at this frequency is theoretically possible.

Practically speaking of course issues could arise as the gain would be lower, and the antenna operator would receive too many false positives at such strict S/N rate (3 db), so in reality the noise floor would probably be 50-60 dB higher. I haven't calculated that.


texts: Cannot run BLDC motor at peak current and low RPM

texts:
I have a hub motor:
https://www.uumotor.com/4-5-inch-350w-hub-servo-motor.html

I know that the motor requires 12A but I can only supply 2.5A using my motor controller. The problem I have is when I want to turn in place using these motors, I need 2.5A at low RPM but for some reason, I cannot supply more than 1A and can only supply above 1A if I increase the speed.

Why is that? Why can't I supply a maximum current (using PID) at low speed?


texts: Designing a 3 mode smart solar battery charger with MPPT

texts:
I'm trying to design a solar charger with MPPT feature that runs in 3 modes (bulk, absorption and float) depending on the state of the battery. The logic is implemented in a fast micro controller and the dc-dc converter utilised is a buck converter. After doing my homework (lots of readings and research) I still have a couple of questions that I find confusing.

Correct me if I'm wrong on this. Do we only use MPPT during the bulk mode? If yes, we use it only if the charging current generated is less than the current threshold?
How, and by what means can I calculate the duty ratio of my transistor during the absorption and float mode in a manner to achieve a constant charging voltage with a maximum threshold charging current? Same thing also for the constant current charging.
While digging answers for question #1 I found that TI manufactures solar battery charge controller IC (bq24650) that has the capability of regulating the charge voltage and the current voltage with high accuracies. They mention that they use internal loop compensators to do this. Digging in the high level schematic they have I found that the reference voltage feedback VFB and the current feedback SRN & SRP (SR is a current sensing resistor) are inputted to a compensation network. Does anyone know how this compensator network was designed? I would like to implement something similar in software (I'm not asking how to implement it in software).

When changing the duty ratio to achieve regulation, the charging voltage and current can't be predicted because changing the duty would take us to another point on the I-V of the PV which is not predictable. Or is it?

Thank you!


texts: What does line impedance stabilization mean?

texts:
What exactly does line impedance stabilization mean?

What parameters of line impedance are stabilized and how?

How does line impedance / source impedance vary with frequency?


texts: Is a class I infra red laser range finder with range 30-40 metres possible?

texts:
For our warehouse, we need to build a range finder for monitoring purposes. We have the following constraints:

Use infra red lasers only
Range should be at least 30 metres
Only class 1 lasers permitted

We would be glad if you could tell us about the theoretical feasibility of such a range finder. If it is not possible than is there a work around ?

Also could you tell us how much is it going to cost ?

Thank you so much !


texts: How is it possible to force \$v(t)=\cos(t)\$ as voltage input to a fully discharged capacitor?

texts:
Let initial charge on capacitor  \$Q=0\$ and say \$v(t)=\cos(t)\$ is applied for one period(\$2\pi\$ seconds) across the capacitor. Then the current will be \$i(t) = C\cos(t+\pi/2)\$. Clearly the initial current is also \$0\$.

So at \$t=0\$, the charge on capacitor is \$0\$ and the current is \$0\$.
How can the initial voltage be \$\cos(0)=1V\$ ? How is it possible to have any voltage with \$0\$ charge? Doesn't this fail \$Q=CV\$ ?


texts: Variable Voltage with MOSFET using Arduino?

texts:
fairly new to Arduino and all things relating to it. I have tried searching for the answer but to no avail. At least, it wasn't in terms that I could grasp.

I have a circuit that I want to be able to change the voltage via an arduino. The power source is is approximately 3.7v with 20A of power. Basically, I don't know what the correct component to use with this amount of amps. I though I could maybe use a digital potentiometer, but it doesn't seem that it is the correct part because there is too much current.

I know you can use a MOSFET as a switch. I was wondering if it is possible to turn the switch on and off with PWM and use that to change the voltage. So for example, if I had a duty cycle of 50%, the voltage across the cicuit would be 1.85V. Is this possible or is this even remotely the correct way to do this? Any help would be appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: How to measure the "efficiency" of a generator?

texts:
I've built "linear generators" (a coil on a tube, with a free magnet inside), with different layouts and I want to measure which is one "is the best", or, at least, make some kind of profiling on them.

I know that it's not exactly "efficiency" (maybe potency?), but I want to know, how would I compare them to find which one is the best in a "quantitative way"?

Edit: my current idea is to drop the magnet inside the tube, from a fixed point above the coils. The magnet should have the same energy when passing the coil, so I could measure the efficiency. The problem is, how would I measure that? It would be the current on a resistor? The total charge on a capacitor?


texts:
I've been a software dev for a while, but never really did a lot with hardware so please forgive me if this question is really basic.

I have an Arduino project I am trying to set up that involves a photocell. Most of my Arduino knowledge so far is from the book Getting Started with Arduino. They have a section that actually talks about photocells. Below is the diagram they give for building a circuit.  I have two questions about it.

First, what is the point of the resistor (seeing how the photocell is basically a light sensitive resistor)?  Why couldn't the circuit just be "5V to photocell, photocell to A0"?

Second, if my project has already used the 5V pin (its for an LCD display) could I rig the circuit up to start at a digital pin (which would be set to output 5V) to photocell back to A0?  If not, how would I power the photocell?

Normally I'd just try this (without the resistor) and see what would happen, however I don't have a spare Arduino and don't feel like frying this one quite yet.


texts: Are all antennas traveling wave antennas?

texts:
I've been reading a lot about traveling and standing waves, and I am right now reading about traveling wave antennas, to my understanding ALL antennas should be traveling wave antennas, but this is not the case of what i read online, and there is also not too much information about it.

For instance, the Wikipedia article states that the most common type of traveling wave antenna are the beverage and rhombic antenna.

I can't find much information about this, care to explain to me why? Is it because the propagation pattern of the wave has to meet some standards in order to be in the traveling wave category? Or are all antennas(like the ones in the microwave dishes and all others used in transmission and reception) really traveling wave antennas as i believe? and so are all waves(talking about radio waves in this case) that propagate traveling waves? Does modulation play any role here?


texts:
I am trying to build a circuit to power a compressor that blows an air horn:

I put my DC power supply directly on the positive and negative ends of the compressor and while it does turn on, it most definitely is not generating enough air to blow one let alone two of the air horns. I don't have any air leaks. The compressor/air horn is brand new. Ramping up the power through the circuit does yield more air pressure but not nearly enough to blow the horns. Anything I'm doing wrong?

Compressor/air horn: Zento Deals 12V DC Super Loud Dual Trumpet Air Horn Compressor Kit


texts: What should be the sampling frequency for a square pulse train in a DAQ system?

texts: Since a square pulse has very high harmonics how to obtain a good resolution of pulses? For example if we have pulse train around 500 Hz could we treat it as a typical analog signal and sample it with 1500 Hz? But if we do it I suspect that we will not have clear rising edges since it square pulse has very high component. Of course we cannot sample with infinity but I!m wondering if there is a standard sampling rate for sampling square pulses to obtain a clear pulse shape for each pulse?


texts: Drop 0.7V using a diode for use of a lithium battery with a 3V mouse?

texts:
I plan to use a rechargeable lithium 3.7V battery in my wireless mouse, which takes 2 AAAs. As I understand it, I could theoretically drop 0.7V using a diode in series with the mouse, but would it be safe for me to do so consistently? I will charge the lithium battery safely using a charging circuit (TP4056) (without the voltage dropping diode obviously) but can I safely use a 3.7V lithium with my mouse using just a diode as voltage protection? The voltage would often be between 3.7 and 4.2 volts, which leads to 3 to 3.5 volts into the mouse - and by design it would draw little current too, such that the diode should not overheat due to current draw.

Thank you.


texts: Confusion about serial operation of CS4344 DAC, what is MCLK?

texts:
After repeatedly reading through the datasheet of the CS4344, I am having trouble fully understanding the purpose of the MCLK pin in serial operation.

In my research I have found that MCLK pins are typically mentioned in I2S operation of audio DACs like this one, however I am trying to use this DAC with serial (referred to as 'left justified' in the datasheet) operation. I get that MCLK is used as the main clock for the internals of the DAC. Do I need to apply a signal to this MCLK pin or is it not needed in serial mode?

The datasheet also mentions external SCLK mode, I understand this as slave mode essentially. In external mode, can I just send data to it using DIN and SCLK? Will MCLK be generated internally or must I generate this as well?


texts:
Please I need help identifying the type of filter this is. I just could not work my way from the function to the type. Not just identifying it, I need help with how to work back and forth on any filter. Thanks a lot

@Tyler I just uploaded a picture. How do I go from here.


texts:
I built myself a power monitor a few years ago that works and I was trying to simplify mine by cutting out an expensive and hard to find 12V ac:ac adapter.  I am familiar with a voltage divider and it's operation makes perfect sense to me in the context of a DC circuit.  Ie the voltage drop across elements is proportional to their resistance vs the series resistance.  But I realized that I actually built a AC voltage divider (a 10:1 transformer with a voltage divider).  I was surprised when I looked up an AC voltage divider and found it is exactly the same for resistive dividers.
In my head the voltage comes from one direction in an DC circuit. It starts high (we'll say 12V) and drops  say 10V as it runs through the first resistor (10kohm) and drops the last 2 volts as it goes through the last resistor (2kohm).   But in an AC circuit, as the phase goes past 180 degrees the voltage  on the 2kohm side would now go to 12V (lets just talk absolute amplitude to keep it simple), so I would expect that it would drop 2V and the voltage divider to measure 10V now, and the last 10V to drop as it goes across the 10kohm resistor.  The one on my power monitor makes sense to me because I add a DC bias which prevents it from ever changing directions, but none of the online resources I have seen indicate that that is necessary.
Can anyone explain to me why the direction of current flow doesn't matter for the AC voltage divider?  I mean if I flip the polarity on a DC voltage divider, it makes a different, so why not for an AC divider?  Or does it make a difference and I am just missing something in my search online, like they are only considering voltage at 90deg or something like that?


texts: How long does it take to recharge a car battery after starting?

texts:
Assuming a typical lead-acid, 12 V car battery (typically at 13 V or so fully charged), and that it takes roughly 500 A over 3 seconds to start an engine, how long will it take to recharge the battery at any given charge rate?

Here's my attempt from what I remember about physics:

12.8 V * 500 A = 6400 W

Over 3 seconds that's 19,200 joules.

So, in a perfect world where all the current goes right back in to the battery and whatnot, how long does it take to regain all my joules and put them back in my battery?

Given a 2A charge rate:

14 V (output of charger?) * 2 A = 28 watts

Here's where I'm a little shaky. What's next? Divide the joules by the wattage to get time? Seems like it:

19,200 joules / 28 watts = 11.4 minutes.

That's it? 11.4 minutes at 2 A and all 19,200 joules are back? Seems hard to believe. My charger also has a 10A setting. So that means in about 2.5 minutes, it'll be "recharged".

So, are my assumptions correct? Do you really just use the charging voltage to calculate this, it seems like you would need to put the charging voltage in relation to the battery's capacity/voltage/whatever.


texts: Where to include Stomp Switch on this Boost Pedal Schematic?

texts:
I'm new to electronics and I am having trouble figuring out this schematic. I understand the circuit but I do not see where the foot switch would come into play and or would be connected. Any help would be great, thanks!

Schematic is here: https://imgur.com/DQ6xxLf


texts: Why turn-on speed of a MOSFET is linked to diode reverse recovery time

texts:
Here is a quote from section 3.4 "Speed-Enhancement Circuits" in "Fundamentals of MOSFET and IGBT Gate Drive Circuits" written by Texas Instruments:

  When speed enhancement circuits are mentioned, designers exclusively consider circuits that speed-up the turn-off process of the MOSFET. The reason is that the turn-on speed is usually limited by the turn-off, or reverse recovery speed of the rectifier component in the power supply. [...] the fastest switching action is determined by the reverse recovery characteristic of the diode, not by the strength of the gate drive circuit. In an optimum design the gate drive speed at turn-on is matched to the diode switching characteristic.

The model considered in the document is the following:

Image source: Simplified Clamped Inductive Switching Model - Figure 3 from "Fundamentals of MOSFET and IGBT Gate Drive Circuits by Texas Instruments"

At the beginning, the mosfet is off, so Id is zero and Vds is equal to Vout plus the diode forward voltage. Vdrive is equal to Vdrive_low.

Now, Vdrv step to Vdrive_high. As Ciss (Cgs + Cgd) was previously discharged, the voltage across Cgs begins to charge, Cgd is also charge because Vgs increases and Vds is clamped. At a certain time, Vgs increases to Vthreshold. Id starts to increase linearly with Vgs (linear region). As Idc is constant, the current through the diode is equal to Idc-id (id is equal to the current through the mosfet). Ciss continues to be charged. At a certain point Id is equal to Idc and the diode stops conducting and Vds is now not clamped. At this moment occurs reverse recovery time of the diode. As Vds decreases, Cgd must be charged, this is the miller plateau… I described rapidly the processes but if you are interested, you can find more information by reading "Fundamentals of MOSFET and IGBT Gate Drive Circuits" written by Texas Instruments.

My question is: Why is the turn-on speed linked to the diode reverse recovery time?


texts:
In a transmission line, the condition for minimal distortion (caused by the line) are when (R/L = G/C) in the line, right? However, I don't see any reference to that in any application notes or reference guides that I read of microstrips or striplines or high frequency designs. The only condition that I read for the signal integrity is for reflections (impedance matching). Is there any reason for that? Is it just for simplification of the model or I'm just looking at bad quality info?

There is distortion in a line when you can't write the signal in the output as:

V2(t) = K * V1(t-tau)

That means that the signals are not same (without counting the attenuation and displacement of the signal).

There is going to be distortion in the line unless:

a-) Z_0 doesn't depend of the freq.
b-) alpha doesn't depend of the freq.
c-) V_p doesn't depend of the freq.

All of those conditions are ok when R/L = G/C

If you think about a,b,c : you are changing the characteristics in the line trough the frequency spectrum, so if you are going to change more some frequency components of the signal than others, so that is distortion in the line.

You can see more of the theory of distortion in t.line in this book in section 4.2.


texts:
I'm working on a solar powered project which requires two voltage levels - 3.2v-4v @ 2A for one element an 6v-12v @ 500mA for another.
My initial plan was to use a 12v lead acid battery with a solar panel and a charge controller. I would then regulate the voltages. However, the size and weight of lead acid batteries is a bit of a concern for this particular project and so I looked into using a lithium battery. The problem I had with this was that I could only find solar charge controllers for 3.7v lithium batteries, nothing for higher voltage lithium batteries (no decent ones at least).
I came up with the idea of using two 3.7v lithium charge controllers. I could then use one of them to power the 3.2-4v element while also using them in series to power the 6-12v element. Of course the overall Ah rating would be the lowest of the two and they would discharge at different rates. I'm wondering if this is still a feasible solution though. I've added a block diagram of my idea below. I'm open to other suggestions too.


texts: Receiving a 4 to 20mA signal with R Click board

texts:
I have this sensor that is supplied with 12V and gives out a 4 to 20mA signal.

Would this 4 to 20ma receiving board be capable of reading the signal? I wasnt sure if the 12V would blow the board.


texts:
I have just started to learn how a microprocessor works and I have some questions.

I have read that the way the microprocessor read/writes data is by setting the address on the address bus, then setting high/low the read/write wire of the control bus and then to set the address bus valid control wire high to confirm the address we want to read. I read that this activate the memory chip select.

I didn't understand the 3rd part which says to set the address bus valid control wire high and what exactly the memory chip select purpose is.

Is there any chance that when we initially set the address and the read/write to high/low not to work thus we want the third step to set the address valid?


texts: Pow Management IC: Li-Ion 2.8 - 4.2V; Sys Volts: 3.3V

texts:
I am designing a consumer Li-ion powered system with the following constraints:

The system volts has to be 3.3V
Li-Ion battery charging range is 2.8 - 4.2V
Charging is to be done via a standard USB charger.
All aspects of battery charging - charging profile, safety timers, input current programming etc are expected.
[Desirable] the battery and system is isolated via switch.

I have been searching for "power management ICs" and "Li-ion battery chargers". So far my results have all yielded a battery charger IC only - on battery backup, system volts follow battery volts. I would want an internal buck-boost regulator to provide regulated 3.3V o/p.

e.g BQ40z60, TPS6502x, TPS6502xx, Max77818, LTC4040 (step up regulator only!)

A boost regulator will not work since system volts need to be @ 3.3V (and not at 5V)

My current solution has a BQ24250 for the battery charging and then a TPS63030 as a buck-boost regulator.

Questions:

Are such ICs even available?
Please recommend some.

Thanks!


texts: Best way to multiplex button lines on existing circuit

texts:
I have a target device that has push buttons that when pressed send a constant 3.3v signal to the MCU button input GPIO's until released. Externally from a different device (perhaps a Raspberry Pi) I would like to stimulate the MCU button input GPIO's while still permitting the original buttons to work.

Is it safe to just connect a 3.3v pin I control to the same MCU button line as the button?


texts: Digital to Analog conversion in Multisim

texts:
Here is schematic for Analog to Digital conversion:

Here are two Digital to Analog converters in Multisim:

Which one should I use? I want to connect it at output of ADC to get original sine wave. How should I connect it (which pins should I use)?

EDIT:
I found answer, however, other problem occurs :)
Here is schematic with 8bit DAC:

Here is transient analysis, showing input and output sine wave:

What are voltage spikes at output signal?


texts: Microphone mute anti-pop circuit works but still picks up a little audio

texts:
I built a simple microphone mute circuit that appears to be pretty common. It mutes the mic without making a popping sound by shorting the connection through a capacitor.

It works pretty well, but if I blow into the mic or tap it hard, it is able to pick that up. I first noticed this when watching audio level meter on my computer. The actual audio that it picks up sounds like high pitch feedback.

Is there any way to eliminate this? I'm planning to control the switch with an arduino, so I will have additional power + logic available if there is a more clever solution.

I am testing with two PC headset microphones. I measured their resistance at ~800ohm and ~1100ohm.

Currently I'm using a 470uf 16v cap and a 10k resistor. I've also tried swapping the cap with: 330uf, 100uf and swapping the 10k resistor with a 100k resistor.

Here is the circuit I am using - just the left diagram (taken from 5v Electret microphone to PC mute switch pop help):


texts: eliminate 24v - ground loop that is destroying components

texts:
simulate this circuit – Schematic created using CircuitLab

I built a suitcase boom box using a cheap BT Rx module and an amplifier module. The BT module is 12 vdc and the amp has an upper voltage input of 24Vdc, so a pair of 5 Ah 12vdc batteries was chosen to power it. My plans are to power the amp from the batteries in series, and use the CT for the - side of the BT rx.

The problem is the audio - output is connected to power - on the amplifier, so when I connected everything, delicious smoke emanated from the BT Rx, ending its short life. What is the simplest way to eliminate the 24v - on the audio connection between the amp and rx?

The modules I used:
https://www.amazon.com/UEB-Bluetooth-Decoder-Wireless-Speaker/dp/B06Y2BCCV6/
and
https://www.amazon.com/WINGONEER-TPA3116D2-Subwoofer-Amplifier-DC12V-24V/dp/B01M70KGSN/


texts: How does the Microsoft Surface table detect objects?

texts:
I saw that the Surface table (now called PixelSense) detect objects.
The strange thing is that it's basically an IR screen with LCD on bottom.
How does it "scan" them then?

Here's a video
http://www.youtube.com/watch?v=I0QBivma6j8


texts:
I am trying to measure the current using sense resistor method.

Low Side Current Sensing method:

I am using shunt resistor in the low side, there will be a voltage drop across the resistor.
Since the voltage drop is very small, using op-amp we can amplify to the required voltage level for microcontroller's ADC input.

The ratings are I = 30 & R = 0.001 (2 watts)

Voltage drop across the resistor,

Vrsense = IR
        = 30 * 0.001
        = 0.03 volt

Power dissipation in resistor,

P = I * I * R
  = 30 * 30 * 0.001
  = 0.9 Watts

Op-amp gain,

Vout = Vrsense * (1+ Rf / R1)
     = 0.03 * (48)
     = 1.44

My doubt is LM358 has a maximum power supply of 36 volts, but I am using 50 to 60 volt. I thought that the input channel will allow zero current, so by giving such a supply will not be a problem. Since I am new to op-amp correct me, friends, if I am wrong. Or I have to use some other op-amp.


texts: Prevent corrosion of circuit board fallen in water

texts:
I apologize in advance if this question is off the topics answered on this forum. Some hours back my drone fell into some dirty water. I was able to rescue the device, unplug its battery, open up its circuit board, dry it thoroughly using a hairdryer and finally putting it in place. It worked fine afterwards.
But my question is how I could prevent or rather reduce the chances of the circuit board been corroded soon?


texts: What would be the most efficient way of wiring a solar power bicycle?

texts:
I have an electronic bicycle; 350 motor that runs off a 17.5 Ah battery at 36 volts. I've just ordered three 12 volt, 150 watt solar panels, that I'll wire in series to total 450 watts; giving 12.5 amps at full rating. I've got an MPPT controller to boost the charge voltage.

However, the battery is limited to 2.5 amp charge current, meaning that the 10.5 will be wasted I suppose?

Would it be better to wire the panels direct to the motor, where any excess can top up the battery, which can be used when solar power is less then what's demanded by the user.

Is this possible? Or will the MPPT controller sort this out?

Thanks for any help


texts: Good inductor parameter for GHz frequency matching chosing

texts:
I want to buy inductor and capacitor for matching circuit of antenna in about 1.6GHZ.
I searched the net for some inductor for example 3.7nH and i collided with lots of parameter!!
I know concept of parameters like  SRF & Q .But for example it told something like 25 @ 200MHZ, and witch SRF is better for me and why? I think about 2GHz is ok, isn't that? And i found no Q in 1.6GHZ.How can i chose these and other parameter?
Please explain them.


texts:
I have a process that I would like to model in order to tune my PID controller. For this I want to perform a closed-loop step test.

What PID configuration do I need for the test? For example all the articles I can find show a PID response with no overshoot, so do I configure my PID controller for the largest gain with no overshoot? Or does the amount of gain not matter as long as there is no overshoot?

It seems like a catch-22 having to tune the PID to model the process in order to tune the PID. What am I missing here?

Note - each run of the PID controller takes me 15/20 minutes, so I would prefer to model it rather than repeatedly run tests and tweak.

Thanks!


texts: Maximum message size for polynomial CRC-8 0x07 and hamming distance = 3

texts: I am looking for maximum message size for my CRC-8 0x07 polynomial for Hamming distance = 3. Do you know some website with these types of information? Or possibly, do you know how to calculate it? I couldn't find one with 0x07.


texts: Usually audio inputs use protection diodes that shunt into the power supply rails of the device they're protecting. But is this really necessary? Why are TVS diodes not used here? Yes, some are high capacitance. But they have low capacitance parts that are ~3pF or less for DSL modems and such. If a TVS diode can shunt from input pins to the chassis at the entry point of the enclosure, would that not be better?


texts: Ideal integrator op-amp DC offset at output?

texts:
i have a question with this ideal op-amp integrator circuit

where R=1k and C=1uF. Then i put a 50mV 100Hz square wave at the input and get the following response, which is what i expected and calculated beforehand.

(I'm aware that this is not a real practical integrator and this question has been taken account before making this post.)

The thing is, that you can see some sort of "DC offset" which I'm being questioned on why is it there. My explanation would be that when i have an input pulse, the op amp would have to drain (or supply) current through the capacitor and resistor in order to achieve the voltage across the resistor and sustain the virtual ground. This current is constant, hence charge in the capacitor grows linearly and so does voltage. Assuming the capacitor is initially discharged, the first pulse charges it to a value A and the contrary pulse discharges it to zero. A and then zero, A and then zero and so on in a triangular symmetrical way, so the average voltage is A/2. Of course the output voltage is the capacitor voltage because of the virtual ground.

At every cycle the voltage starts/ends at zero since the integral of every whole cycle of this signal is zero, that makes sense too.

I don't know why this "DC offset" wouldn't be there as it makes sense, but still my answer is not taken as valid. Is there some transient response I'm not seeing? Would the signal start at t=-infinity change anything?


texts:
I'm in the process of transitioning from Arduino work to just using bare microcontrollers, and I've got a question that might be quite basic (but I've searched around and haven't found an answer for it yet).

I have an LED that I know should be quite bright when powered--and is when hooked up to an Arduino--but is very dim when hooked into an atmega328 pin.  I'm powering the chip through the SparkFun Pocket AVR Programmer, and the LED is being powered through a resistor.

Is the voltage output from the atmega when powered by the programmer much lower than that of an Arduino?  Am I doing something wrong?


texts: How to bias a diode clamp with a voltage divider?

texts:
As you know a diode clamp is a circuit to protect sensitive circuits from excessive voltage. One approach to change clamping level is to use voltage dividers. most resources and textbooks represent a schematic like this:

and in case that diode is silicon, they compute maximum output voltage this equation:
$$
V_{out} = \frac{R_2}{R_1 + R_2}V_{dc} + 0.7\space(volts)
$$

as I understand we are permitted to use such equation only if Rs is very large relative to R1 and R2.

I tried to design diode clamp that limits output voltage up to 2.7 Volts. I used two approachs. first approach is this :

and another one is this :

Both approach have same result, but i want to know which one is more practical and reliable?


texts: Very high resistance between gate and ground in MOSFET amplifiers

texts: I always see a very high resistance between the gate and the ground in n-channel MOSFET common-source amplifier. What is it's role? I think it is to prevent the signal input from bypassing the MOSFET and going to ground directly, but I am not sure. Am I right or wrong?


texts: How to accomplish parameterized subcircuits in LTSpice?

texts:
I am trying to play around with beta ratio effect of CMOS inverter. To do so I need to have parameterized subcircuit so I can adjust the ratio of PMOS beta over NMOS beta and achieve HI-skewed or LO-skewed inverters.

How do you define parameter x in a sub-circuit?

What I need to do is to define a sub-circuit like this:

.subckt inverter_035_x in out VDD GND
XM1 out in 0 0 NM W={x*1u} L=0.35u
XM2 out in VDD VDD PM W={x*3u} L=0.35u
.ends inverter_035_x

and then set x in every instance of the subcircuit so I can achieve different transistor width per instance.

How to set x and pass it to a sub-circuit instance?


texts:
I am powering an off-grid ESP32 project from a 12v battery (12v because that's what the connected pump and solenoids use). The ESP32 is directly on PCB; I'm no longer using Dev Kits. I'm needing a regulator that brings the 12v down to 3v3 for the microprocessor, one that uses minimal current to conserve battery power. The 12v input may rise to over 14v as there's a solar panel involved with charging the lead acid battery, which affects my choice of regulator.
The data sheet for the LF33 (https://www.mouser.co.uk/datasheet/2/389/lfxx-1849555.pdf) shows quiescent current 12mA or less (target < 1mA) but I'm seeing in the region of 20mA with or without components (such as the ESP32) downstream of it. Edit: the excess seems to be downstream of the regulator.
A direct swap on the same PCB with a DC-DC converter (https://www.mouser.co.uk/ProductDetail/CUI-Inc/VXO7803-1000) reduces current down to 7mA, so it's clearly something up with how I'm using the regulator. But I can't figure it out. The relevant part of the schematic is:

Edit; added full schematic (though the ESP32 isn't placed on the PCB for this test board)

Edit; the problem is downstream of the regulator, so I've updated the question title.


texts: What is the minimum spacing between inductors to prevent cross talk?

texts:
I have to put three inductors in a box. The inductors are air core with a diameter of 6in and a height of 4.5in. The value is going to be about 16uH. The inductors will see about 50Arms continuous at about 4kHz. Each inductor is on a leg of a 3 phase output.

How far apart should the inductors be to reduce the cross talk to a minimum?

Are there any rule of thumb for spacing such inductors?


texts:
I have a continuous bipolar signal that can vary between  ±1 mV and I would like to figure out the best way to measure it with high resolution without introducing a lot of noise.

My first thought is to amplify the signal with a instrument amplifier (looking at INA333) and digitize with a MCP3421 18-bit differential ADC.  Using a gain of 8 and internal 2.048 V ref on the MCP3421, I believe the FSR is ±256 mV.   I'd like to amplify my signal to use this FSR and get as much resolution as I can.

Is using an instrument amplifier the best way to go about this?
How can I use an instrument amp and maintain a bipolar output to feed to the ADC (do I use 2 opposed instrument amps?)
Is this possible to do without using a negative power supply for the reference?  My board will be 0-5 V.
Any suggestions for the best way to do this are welcome (and greatly appreciated).  I would love to see some schematics too if possible!


texts: BTS6163D Struggles to turn on LEDs with long cable

texts:
I have a circuit that turns on and off LED's utilizing BTS6163D ProFET's for overcurrent protection and open circuit detection. So far it seemed to be working without any issues until I tried a different type of light.
For some reason these new lights struggle to turn on, there is an oscillation at around 1.26khz from about 4.4v to 27v (lights are powered with 26v) measured at the output of the BTS6163D. If the light is manually disconnected and reconnected to the BTS6163D without disabling the input pin, the oscillation goes away. If the BTS6163D cycled off and back on via the input pin the oscillation comes back. Shortening the cable between the light and the BTS6163D lessens or even removes the oscillation which leads me to believe this has something to do with induction caused by turning on the light over the long cable.
Is it possible the BTS6163D is shutting down from a false short circuit detection? If that is the case, why is it coming back right away, shouldn't it latch off?
Upon further inspection, the old lights show maybe 1-3 oscillations before fully turning on, however, they always fully turn on no matter the cable length. The old lights pulled around 500mA and the new ones are about 400mA, could this make that big of a difference?
The cable is 14 gauge around 50-100ft.
I am really at a loss here, I already have multiple boards manufactured and would rather not have to scrap them. Any help would be greatly appreciated!
Please see the datasheet and scope images below.
https://www.infineon.com/dgdl/Infineon-BTS6163D-DS-v01_00-EN.pdf?fileId=5546d4625a888733015aa3da01a1101e
Voltage measured at the output of BTS6163D.

Yellow is the voltage at the output of BTS6163D and purple is at the light.

This is the original light.


texts: Only some of my inductive sensors are working with my board

texts:
I am working on a board which has six inductive sensors.
I am using optocouplers for isolation between sensor output and MCU. Four of them work fine and two show very unreliable behaviour.
When I detect a metal object,the voltage at the Zener diode (3.3V) is 0.70 V which is fine but when I connect a microcontroller GPIO pin to read the voltage at same point (Zener diode 3.3 V) is 0.254 V and sometimes when there is no metal detection then the voltage at (Zener diode 3.3 V) is 1.154 V but it should be 3.3 V.
I already raised this issue in another forum and people suggested that there could be design issue or cold solder issue. I made a new board on perforated PCB but issue is still same, even after swapping them.

Inductive sensor operating voltage: (10-30V)
Output voltage is :(23.32 V) when supply voltage is (24V)
Optocoupler :PC817
Pull-up resistor:4.7K

Sensor data sheet.


texts: Low pass filter issue - is the 10k resistor part of the circuit?

texts:
This may be a really simple question but Op Amps still confuse me a little. I have a low pass filter circuit as shown below.

My question is whether the 10k resistor is part of the filter circuit or is it just for input current biasing reasons. If it is part of the filter circuit how do you derive the transfer function?

From looking at it i initially thought that the filter was the 47 Ohm resistor and capacitor then using 1/2*piRC that would give the cutoff frequency but i am not sure this is correct.

Thanks for your help - its really appreciated!


texts:
I'm using the hall effect sensor A1301EUA-T, I'm feeding it with 5V. At the VOUT output when there is no magnetic field there is 2.5V. When approaching the NORTH POLE of the magnet VOUT ranges from 2.5 up to 5v. When it approaches the SOUTH POLE of the VOUT magnet it varies from 2.5 up to 0v. To have a variation in VOUT from 0v to 5v I need 2 magnets, move one away and bring the other closer. My question is: how do I have a variation in VOUT from 0v to 5v approaching just one magnet, that is, I want it when I have no magnetic field close to the sensor I have 0v in VOUT?

Here is my circuit:


texts: LTC4001 Can charge my 1s4p Li-ion battery pack?

texts:
I was trying to design a battery charger for my application where I have made a pack of 1s4p cells where each cell is having 2600mAH and Charging rating as 4.2V. So can I consider it as 1 cell?
Can I use LTC4001 - 2A Synchronous Buck Li-Ion Charger for this pack?

LTC4001 Datasheet


texts:
ı want to make  a Multistage Amplifier with the following features.But ı dont know how to arrange dynamic range ,multistage amplifier and noise?How can ı desgin it?

Maximum output voltage is 10 V p-p. The amplifier should be able to provide a dynamic range of over 60 dB. The dynamic range is defined as maximum output voltage divided by maximum noise signal at the output. The amplifier bandwidth should be limited to 1-200 Hz, such that high-frequency noise is blocked. Low-frequency noise (1-200 Hz) usually has amplitude of up to 100 nV p-p, with input impedance of 4 k


texts: Can't achieve the goals in designing and simulating Resonator circuit

texts:
Goals

I need to design resonant parallel circuit and simulate it with LTSpice so that it match with the design requirements correctly.

Requirements

Source Impedance  \$R_s = 100\ \Omega\$
Load Impedance \$R_l = 1\ k\Omega\$
Resonant Frequency \$f_o = 100\ MHz\$
Bandwidth \$BW_{3dB} = 150\ kHz\$

Schematic

Approach

Find the value of the Quality Factor \$Q\$

\$Q = \frac{f_o}{BW_{3dB}}\$

\$Q = \frac{100\ MHz}{150\ kHz}\$

\$\therefore Q = 666.\overline{6}\$

\$\$
Find the value of the Parallel Resistance \$R_p\$

\$R_p = 100 // 1k\$

\$R_p = \frac{100\ \cdot\ 1k}{100+1k}\$

\$\therefore R_p = 90.\overline{90}\ \Omega\$

\$\$
Find the value of the Parallel Reactance \$X_p\$

Consider the fact that \$Q = Q_p = Q_s\$

\$Q_p = \frac{R_p}{X_p}\$

\$X_p = \frac{R_p}{Q_p}\$

\$X_p = \frac{90.\overline{90}}{666.\overline{6}}\$

\$\therefore X_p = 0.1\overline{36}\ \Omega\$

\$\$
Find the value of the Inductance \$L\$

\$X_p = 2 \pi f_o L\$

\$L = \frac{X_p}{2 \pi f_o}\$

\$L = \frac{0.1\overline{36}}{2 \pi\ \cdot\ 100 \times 10^6}\$

\$\therefore L = 217.0294679\ pH\$

\$\$
Find the value of the Capacitance \$C\$

\$X_p = \frac{1}{2 \pi f_o C}\$

\$C = \frac{1}{2 \pi f_o X_p}\$

\$C = \frac{1}{2 \pi\ \cdot\ 100 \times 10^6\ \cdot\ 0.1\overline{36}}\$

\$\therefore C = 11.67136249\ nF\$

\$\$

Frequency Response

Bandwidth

Insertion Loss

Insertion Loss is the ratio of power or voltage of the output with load and without the load. At the resonant frequency the reactance of the circuit is equal to zero, so it'll form a simple voltage divider.

\$IL = 20\ log_{10}{\left(\frac{V_{outWithLoad}}{V_{outWithoutLoad}} \right)}\$

\$IL = 20\ log_{10}{\left(\frac{\frac{R_l}{R_s+R_l}V_{in}}{V_{in}} \right)}\$

\$IL = 20\ log_{10}{\left(\frac{1k}{1.1k}\right)}\$

\$\therefore IL = -0.8278537032\ dB\$

Questions

Why at resonant frequency I got \$-16.228\ dB\$ on the simulation graph instead of \$-0.827\ dB\$ which I calculated from Insertion Loss before?
Why at both cutoff frequency of \$99.925\ MHz\$ and \$100.075\ MHz\$ from the simulation graph I got \$-16.35\ dB\$ instead of \$-3.827\ dB\$?
If impedance load causes insertion loss, then what does impedance source causes loss at? How to calculate it? Is it the something that is missing with my calculation?
Is there something wrong with my approach? I have also tried double precision settings on the LTSpice with .OPTIONS numdgt=7 and the results are still the same.


texts:
In Japan I saw a simulation of internet based communication in the The National Museum of Emerging Science and Innovation (Miraikan). It attempted to replicate ascii characters moving along a 8 part wire using combinations of marbles rolling along.

I've just finished reading Charles Petzold's book, Code: The Hidden Language of Computer Hardware and Software. In it Charles explains building relays into gates, gates into logic components, and logic components into computing machines.

I wondered if a mechanism existed that simulated a switch using marbles.

My question is: Is it possible to explain a transistor (or vacuum tube or relay) using a marble-based switch for students?


texts: How can I have a rising edge close a relay for a fixed time?

texts:
I have a problem that I don't know what the solution is called, but I would bet that there are many solution.

Problem: I have to short-circuit two pins on a mainboard (power switch) when a rising edge on a control wire (voltage is turned on and stays on) is detected, but these two circuits have to be separated without any direct connection, so I can't just plug the computer on the voltage but have to use some sort of relay, which closes two contacts (but only for a short time) when powered.

The wave form would look something like this:

What is the name for this type of circuit?

Thanks in advance!


texts:
I need to send commands from an usual laptop to the ESP8266. (Thus no CP2102, just 3.3V Vcc and GND)
How can I do this?

I tried to start a TCP server with the AT+CIPSERVER command, however, the server has to be started every time the module starts.

It's not clear for me how I should set HIGH or LOW for a GPIO pin on ESP8266 module over Wireless.

Please help.


texts: VHDL: Setting upper bits of variable to zero during assignment with shorter variable

texts:
When one has something like

    variable a    : unsigned (3 downto 0);
    variable b    : unsigned (1 downto 0);

and one wants to assign the lower b'length bits of b to a, is it necesary to do

a)

a(a'left downto b'length) := (others => '0');
a(b'length -1 downto 0)   := b;

or can the same be achieved with

b)

a                       := (others => '0');
a(b'length -1 downto 0) := b;

or is there

c)

even a more elegant way?
Option a) seems to work, but everytime I want to use it, I get a bad feeling that this might not be the proper way to do it.


texts: What is conservation of flux linkage ?? Please explain with suitable diagram. I understand charge conservation and textbooks usually say that flux linkage conservation is analogous to that, but they rarely explain this in detail.


texts:
I understand that wave soldering is typically used for soldering through-hole components as shown in this picture:

However I read that wave soldering can also be used for SMD components:

my question is if the solder wave "touches" the entire SMD component (as the picture suggests) or only its leads. If the wave touches the SMD component can this damage the component?


texts: Why avalanche breakdown in a PN junctions is said to be caused by minority carriers?

texts:
Reverse bias increases the depletion region (the "space charge region"). Remembering that electrons travel from (-) to (+) terminal, and that in reverse mode the (+) terminal is attached to the n-doped side of a PN junction, I would expect that current generation through avalanche breakdown is occuring due to majority carriers.

 (source)

What am I missing here?


texts:
I am trying to compare watts exiting the battery vs watts being consumed by the bulb.

I have set up a test circuit shown below.

Should not A-B watts match C-D watts??

Sorry for such a basic question...I'm learning here...


texts: Adding a DC bias to an AC voltage at the base of a transistor

texts:
I came across circuits probably using an AC at the base to probably amplify it. I also came across the voltage divider to add a DC bias.

simulate this circuit – Schematic created using CircuitLab

Neglecting the values of the components and supplies. Is the reason we add this DC bias to not have the voltage go to a negative value because that would damage a transistor?

And just to be sure, the voltage at the base would be a sine wave with the DC bias as the baseline, correct?


texts: 240V PCB Layout - Critique on design requested

texts:
Hi all, I was wondering if I could get some critique on my first PCB layout. The schematic is a direct copy from here.

It is for a 240V Dimmer 10A, and I am after comments on my PCB design.

For clarity, here are the parameters I applied.

Grid Size: 100 mils
Tracks Digital - 10 mils
Tracks AC Sense - 20 mils
Tracks AC Power - 150 mils
Triac Middle Pin staggered - 150 mils

The plan would then be to get this made at a fab house with 2 oz copper.


texts: does CompactRIO modules have builtin pull-up/down resistors

texts:
I have Compact RIO 9076 with 4 different modules: NI-9205 (Analog Input), NI-9264(Analog Output), NI-9402 (Bidirectional Digital I/O), NI-9403 (Bidirectional Digital I/O). I have several 3rd party sensors: mass flow sensor , pressure sensor, reed magnetic proximity sensor and another humidity sensor.

For some of the sensor, it's needed to communicate using I2C protocol, which requires in/out port and pull-up resistor. Do the modules include pull-up resistor inside? If so, what is the reference voltage for them, and how should I enable it?

I looked into their manuals and didn't find any information on pull-up/down resistors. Also, I didn't find information online.

Also the OVAL RV21 (Reed magnetic proximity sensor) require pull-down resistor. Do the modules include pull-down resistor inside? If yes, what is the reference voltage for them and how should I enable them?

Does CompactRio have modules with builtin pull-up/down resistors?

Sensors:

Sensirion SFM3000 (mass flow sensor) - powered with 5 V and I2C High is 3-5V;
First-Sensor HDI0611ARZ8P5 (pressure sensor) - powered with 5V and I2C high is 5V;
OVAL RV21 (Reed magnetic proximity sensor) - powered with 10V and requires pull-down;
Humidity sensor - powered with 3V and I2C high is 3V.


texts: Gain-bandwidth product and open loop/closed loop gain

texts:
I'm reading the TI-precision lab of opamp.
And I'm confused with the calculation of the BW_CL (bandwidth of th close-loop).
I'm prettry sure the BW_CL= GBPW/GAIN_CL.
This is very clear refer to enter link description here
What I cannot understand is why can we find/use the close-loop gain on the bode plot of "Open-loop gain vs frequency" ?
As I see I get the bandwidth when open-loop gain = 40dB !?!?


texts: What is the optimum distance between a micro-controller and a crystal on a PCB?

texts: I wanted know what should be the optimum distance between a microntroller(AT89C51ED2) and a crystal of frequency 11.0592MHz?


texts: LC Filter Design with coaxial input and output

texts:
I was trying to design a Chebychev high pass filter of 400MHz corner bandwidth, 0.2db ripple and 5 poles.

I am confused with the proposed design in this filter design calculator.
This calculator asks for the characteristic impedance of the filter input and output. Then it draws a schematic with a resistor in series at the input and a resistor in parallel at the output, with the values corresponding to the given impedances above.

In general, does it mean that one have to physically introduce these resistors in the circuit ? (I'm surprised)
same question if you use coaxial cables at the input and the ouput, and you enter a value of 50 Ohm for the characteristic impedances.
in 2. above, assuming you have not to introduce any resistor, why is the input resistor of their schematic in series and not in parallel (a parallel resistance would by what is seen by the input no?)


texts: 108 rows of grapevines, each row 650 feet long.  Suspend a nichrome enameled wire along each row in order to raise the temperature of the air within 18 inches of the wire 6 degrees Fahrenheit.  What kind of transformers and controllers?  220 V AC is all that is available.  No three phase.


texts: Can size of a module's port be input as a parameter in Verilog?

texts:
I have a hardware algorithm that compares two operands, each (keyBits) bits long, and returns a logical one if the first operand is less than the second, and returns a logical zero otherwise. This algorithm works for any integer value of (keyBits) greater than one. So can I write my algorithm with the following Verilog code, by passing (keyBits) in as a parameter? I haven't tried compiling or simulating this code; quite frankly I don't know how to do either. Can anyone help me with that?

module lessThan ( lfLessThanRg, left, right);

parameter integer keyBits = 2;
integer maxBit = keyBits - 1;

output lfLessThanRg;
input [maxBit:0] left, right;

wire[maxBit:0] notLeft;
wire[maxBit:1] ltHere, ltEve, ltBelow, equal;

or( lfLessThanRg, ltHere[ maxBit], ltEve[ maxBit]);

genvar integer bit;

generate
  for (bit = maxBit; 0 < bit; bit = bit - 1)
  begin
    and( ltHere[ bit], notLeft[ bit], right[ bit]);
    and( ltEve[ bit], equal[ bit], ltBelow[ bit]);
    or( equal[ bit], notLeft[ bit], right[ bit]);
    not( notLeft[ bit], left[ bit]);
    if (1 < bit)
    begin
      or( ltBelow[ bit], ltHere[ bit - 1], ltEve[ bit - 1]);
    end
  end
endgenerate

and( ltBelow[ 1], notLeft[ 0], right[ 0]);
not( notLeft[ 0], left[ 0]);

endmodule
```


texts: From times to times I see different code examples that have " ... else Null" strings in if-statements and it's something I don't get. I've learned and I stick to the idea that the best way to model nothing is write no code.  But is there any difference in these aproaches? if not then why do people write this "else null"?


texts: What is "Vref" of ADC in a microcontroller datasheet?

texts:
I'm kind of lost in the datasheet of the µC.
I'm using an XMC4700 µC. I will connect a voltage divider to the input of the ADC to measure the voltage.
I found the equations to calculate the result. Only I'm not really sure what the \$ Vref \$ is.

The supply voltage of the µC is 3V3.

This is a link to the data sheet and a pic of the ADC operation conditions. Can you tell me if I have an internal \$ Vref \$ source ? and what it is?

Datasheet


texts: Meaning of coupling factor for a resonance cavity

texts:
I was reading this paper about resonant cavities, and on page 6 it introduces the concept of coupling factor β, which is defined as the ratio between the power loss in the total circuit (including the resonant cavity and the source) and the power loss inside the cavity.

But, which is the physical meaning of the coupling factor? What does it mean, in terms of electromagnetic waves, that the system is undercoupled, overcoupled, or critically coupled?


texts:
I purchase the following hobbyist motor:

http://www.digikey.ca/product-detail/en/PKN12EB105C1/P14353-ND/2417077

How can I get a feedback from this motor? The design of D.C. motor that I found on Internet are open loop "regulation" if you can call it regulation, but if I want to implement a PID I need a measurement of the current speed or position depending of the kind of regulation.

How can you measure the speed/position of these hobbyist motors?


texts: Can I put a bunch of 220 uF caps together to get a higher uF value? or is it best to replace with the same value of cap.


texts: What to do when there is no ground cable?

texts:
I'm trying to connect a heating cable (heating tape) which is constant wattage type. This cable requires 240V. However, I realized there is no ground cable as you can see in the picture below. it only has two identical bus wires that will be heated up. I am going to connect a neutral wire to one of the bus wires and live cable to another bus wire (using temperature controller and SSR).

Is there any way I can ground (earth) this cable? Also, one question is, what is the purpose of the wire that is covering the yellow cable? Is it only for the protection?


texts:
Does anyone have some cool ideas for a use of a scripting language on an embedded system?  I'm thinking about the eLua project specifically.

Basically, you need a micro with at least 64k of RAM, 256k of Flash, the Newlib C library, and a gcc compiler, (AVR32, ARM7, Cortex-M3 are all supported right now among others), and you can send it (or program it to load) scripts.  It doesn't need an OS, but it lets you use your micro (which is far too small for embedded Linux) much more like a general purpose computing device, by allowing programs not flashed into the program memory to be run.

The current project has a number of example applications, but none of them seem to do anything that you can't do with a program burned into Flash.  The big difference that I can see is that you can send each program separately, and run different programs without resetting.  In addition, you can use it interactively (Change your program flow with your decisions at the keyboard, rather than having to code everything.

How would you use such a device?  Would you give it a keyboard and character LCD, and write your own scripts while it sat on your desk?  Would you simply use the scripting language to simplify programming of more complex applications?  (Like the games currently available on the project site?)  Or would you do something completely different?  I'm getting started with it and looking for project ideas.

Edit: You can send it programs over whatever protocol you want to use (UART, SPI/I2C etc., USB, Ethernet), load them from an SD card, whatever your chip supports.  Just wanted to clarify that it didn't have to be in a reprogramming-friendly environment.

Edit2: Most of my projects are for my personal use, or for sharing with like-minded friends, not often for sale to the general public.  I expect users of my projects to be interested in and familiar with embedded systems, and able to pick up the rudimentary use of a scripting language without too much trouble.  I might use them around the house or in the car, or more likely in the shop as an aide to designing and debugging more new projects. I also might propose it to my boss at work, where we manufacture and design embedded systems. Or, I might use it on an engineering project for school.


texts: Can you implement WLAN on a ZigBee chip?

texts:
I've spent my afternoon browsing around the web looking for a microcontroller that has integrated WLAN (802.11), but I haven't managed to find any on the market. There are lots of cheap microcontrollers on the market that work in the 2.4 GHz band and usually they support the ZigBee protocol (802.15).

Since these chips work on the same frequency and some of them use the same modulation that is employed by WLAN, I'm not sure if it's possible or not to implement WLAN using these chips. I know ZigBee is a totally different protocol, but does this mean that they actually don't support any other protocol, or does it mean that it isn't impossible but I'd have to sort of "reinvent the wheel" and build my own networking stack from scratch?