texts: How to know which element replaces which for a cache?

texts:
If I assume that the first element of the matrix that is fetched to the D-cache is a[0][0], for associativity 4, please tell me which element in which matrix that will write over a[0][0] in the D-cache. Since the formula for set associativity is

  In a set-associative cache, the set containing a memory block is given
  by (Block number) modulo (Number of sets in the cache)

How can I know from this code, compiled and run as MIPS assembly in a MIPS simulator, which element that will write over a[0][0]?

/* matris.c */
#include <stdio.h>
#include <idt_entrypt.h>

#define MATRIXSIZE 16
#define MATRIXSIZE_ROWS 16
#define MATRIXSIZE_COLS 16

/*
 * addera two matriser
 */
void matrisadd( int res[MATRIXSIZE_ROWS][MATRIXSIZE_COLS],
                int   a[MATRIXSIZE_ROWS][MATRIXSIZE_COLS],
                int   b[MATRIXSIZE_ROWS][MATRIXSIZE_COLS] )
{
  int i,j;

  for(i=0; i < MATRIXSIZE; ++i) /* variera rad-index */
    for(j=0; j < MATRIXSIZE; ++j) /* variera kolumn-index */
      res[i][j] = a[i][j] + b[i][j];
}

int main()
{
  static int   a[MATRIXSIZE_ROWS][MATRIXSIZE_COLS];
  static int   b[MATRIXSIZE_ROWS][MATRIXSIZE_COLS];
  static int res[MATRIXSIZE_ROWS][MATRIXSIZE_COLS];
  int i,j, Time;

  /*
   * initiera matris a och b
   */
  for( i=0; i<MATRIXSIZE; ++i)
    for( j=0; j<MATRIXSIZE; ++j)
    {
      a[i][j] = i+j;
      b[i][j] = i-j;
    }

  flush_cache();              /* toem cachen */
  timer_start();              /* nollstall tidmatning */

  matrisadd( res, a, b);

  Time = timer_stop();                /* las av tiden */
  printf("Time: %d\n",Time);
}


texts: I need help controlling the 'sled' motor of a CD-ROM, based off of a datasheet

texts: I have a CD-ROM that I would like to use the stepper motor from. I specifically would like to use the existing driver for it. The circuit diagram for this driver, the BD7907FS, is below. I understand how the stepper motor works, but do not know how to use this chip to control it. I am used to a 'step' and 'dir' pin, where as it appears, this IC has a "SLED IN1" and "SLED IN2" pin (pin 28 and 29), which I assume is how you control the sled's stepper motor. I could also use help determining the input voltage for said pins.


texts: Why don't we say alternating voltage and direct voltage instead of AC and DC?

texts:
Considering that, usually, current is a consequence of a voltage over a load, why do we focus on current when talking about alternating or direct electrical quantities (i.e alternating current and direct current)?

In the control of static converters, for instance, normally we have a voltage reference that is either alternating or constant. In electric generators, it is an induced alternating voltage that is produced from the resulting spin of the machine's rotor. Transformers relate voltages, even without any current flowing.

Wouldn't it be more accurate to say AV/DV instead? Maybe this is something that we say just because "everybody does"? Maybe it's historical, but it would be interesting to know where all this started.

There is a related question (Why is DC Voltage called Direct Current ?) where some answers mention the fact but doesn't really explain why is it.[

Thanks!


texts: Required output impedance for ADC input?

texts:
On the Atmel ATmega328P on the Arduino Uno, the ADC RAIN value is 100 MΩ - which I assume is the ADC input impedance. However, in the datasheet it says "The ADC is optimized for analog signals with an output impedance of approximately 10 kΩ or less."
How do you figure out the ideal output impedance to work with the ADC? I'm trying to figure out how this applies to other discrete ADCs which have an input impedance that varies with sampling frequency.  For example, on one part the input impedance varies from 125 kΩ to 65 MΩ. How would I figure out what the max allowable input impedance should be?
Also - am I even asking the right questions here or am I missing something huge?


texts: Help with ISO 14230 K-Line initialisation

texts:
I have an OBD-II scanner hardware built using STM32 and it is working fine with most vehicles.But I'm facing difficulty with ISO 14320 K-Line fast.

Even though the firmware works fine when tested with an emulator it constantly fails when it is scanning an actual KWP-Fast car.

A brief of KWP-Fast: We sent a wake-up pulse followed by a sequence of 5 bytes to initialize the communication between the scanner and the car's ECU. And in return to this, we must receive 7 bytes along with a reflection of the 5 bytes we sent. But I'm only receiving these 5 bytes and nothing else. This is the scenario for the car environment, but when tested with an emulator I receive the needed 7 bytes too.

Does anyone have experience with ISO 14320 K-Line protocol who can help me with their past experience? I'm having a "Timeout" waiting for those 7 bytes.

*Are there specific ECU address that a tested/scanner must be communicating with?

*Since it worked with an OBD emulator the timing must be right, or is it at the timing my firmware is screwing up?

*I refer to the ISO documentation and so the logic must be right, and so I assume I'm trying to communicate with a wrong or non-existing ECU and so does not receive any response. (same as point 1)

*Do we need a wake-up pulse when scanning a car? As wouldn't that already be done by the internal ECUs.


texts:
I need to choose a heatsink and a fan for cooling a three phase rectifier. Let's say that the total power dissipation is 1.8kW and that the rectifier is made of three half bridge IGBT/diode modules where each switch dissipates 300W.

With Rth,jc (junction to case) for the IGBT and diode and Rth,cs (case to sink) I have calculated Rth,sa (sink to ambient) thermal resistance of a heatsink that should be used.

However, since there are six IGBT/diode modules I was wondering if I need to divide the final Rth,sa by 6. If I do this I get unreasonably (in-my-not-a-big-expert opinion) low Rth,sa of 0.015K/W and would require a heatsink of 240x120x300mm size with forced air cooling in which case the air velocity should be 20m/s.

This particular heatsink weighs 9kg and this air velocity on a Beaufort wind scale corresponds to number 9 for which the land conditions are: Twigs break off trees; generally impedes progress according to Wikipedia. So I have strong doubts about this...

Is this value of Rth unreasonable or I should stick to 0.9K/W ?


texts: why the 555 timer output is not the same as my calculation

texts:
Hi may i ask why is my calculation for the 555 timer of U2 is not the same as the simulator. U1 output signal 22064.24Hz, 92.81% duty cycle.
t=1.1* R_1*C_1
t=1.1* 10k* 2.2n
t=1.1* 10k*2.2n
t=0.0242ms
From my calculation i got 0.0242ms for the monostable output but the simulation result is kind of off for U2(out) output which doesnt seem to match up with my calculation and why is the result is not uniform?

schematic diagram ^

U2 output signal ^

trigger for U2 and output from U1^


texts: Connecting Open-Drain inputs or outputs together with one resistor

texts:
I had a couple of quick questions.  I am designing a board using 10 IO expanders which I'll use as inputs.  Each has an !INT pin which is open drain and pulled high to 5v through a resistor.  Can I attach all of these pins together to effectively create a 10 input 'AND' of all the interrupt pins to be read by a uC?  Additionally, each of these chips has a !RESET pin that also operate open drain and are pulled high to 5V through a resistor.  Could I effectively reset all of my chips at the same time by connecting them together and pulling the line low?  Finally, I know that I2C operates using open-drain inputs/outputs and you need the pull-up resistors decently close to the actual chips but since my !INT and !RESET lines aren't going to switch at nearly the same frequency, could I get away with a single pull-up resistor for each of the two lines?

The IO Expander I'm using:
http://www.nxp.com/documents/data_sheet/PCA6416A.pdf

I2C Bus Switcher:
http://www.ti.com/lit/ds/symlink/tca9548a.pdf


texts: STM32F103 TC\TXE bits are set automatically after USART1 clock enable

texts:
I'm trying to enable the USART1 periferial on Stm32F103 MCU.
My code looks like this:

#include "stm32f10x.h"

void UARTInit(void);
void GPIOInit(void);
USART_InitTypeDef USART_1;

int main()
{
    SystemInit();
    GPIOInit();
    UARTInit();
    USART_SendData(USART1, 0x12);
    while (1)
    {

    }
}

void UARTInit()
{
    RCC ->APB2ENR |= RCC_APB2ENR_USART1EN;
    USART_StructInit(&USART_1);
    USART_Init(USART1, &USART_1);
    USART_ITConfig(USART1, USART_IT_TC, ENABLE);
    USART_Cmd(USART1, ENABLE);
}

void GPIOInit()
{
    RCC -> APB2ENR |= RCC_APB2ENR_IOPAEN |RCC_APB2ENR_AFIOEN;
    GPIOA-> CRH &= ~GPIO_CRH_CNF9;
    GPIOA -> CRH |= GPIO_CRH_CNF9_1;
    GPIOA -> CRH |= GPIO_CRH_MODE9_1;

    GPIOA->CRH  &= ~GPIO_CRH_CNF10;
    GPIOA->CRH  |= GPIO_CRH_CNF10_0;
    GPIOA->CRH  &= ~GPIO_CRH_MODE10_1;
}

As you can see, i firstly enable clock for USART1 and after that initialize it.
Before executing this: RCC ->APB2ENR |= RCC_APB2ENR_USART1EN all bits in USART registers are set to 0 (see first attached image).
But when clock is enabled, TC and TXE bits are set to 1, even when USART is not enabled yet. (see second screen).

So, if you have any ideas why ths happens - i'll be very appreciate for yours help. Thanks.


texts: Can I somehow use one PWM output to set various LEDs to different brightness?

texts:
I would like to build a project in which 15 groups of LEDs are set to a brightness level.  I have an Arduino with digital PWM outputs (which can mimic a range of voltages.)  How can I do this?

One idea: connect each LED to a capacitor and use a transistor array to charge these capacitors with a voltage which will produce a controllable brightness in the LEDs?  I was thinking that I could charge each capacitor with a different voltage, then re-charge them every 10th of a second of so to maintain the set level of brightness.

If so:

Will I need to use a small capacitor to turn the initial PWM output into a voltage?

How big will the individual LED capacitors need to be to maintain illumination?

How often will the capacitors need to be charged?

How will I need to use resistance in the circuit?

simulate this circuit – Schematic created using CircuitLab


texts: What if the current draw is greater than the rated discharge of a battery?

texts:
I have a 48 volt, 20 kW motor that I need to supply with power.  I am looking at a configuration of 16 LiFePo4 cells each in series, each 200 Ah rated at 1 C.  At that rated capacity, it would seem the most power I could draw is half that, or 9.6 kW which means a lot of unused power to the engine.

If that is correct, the 200 Ah cells must be 2 C rated to make use of the 20 kW of power.  Is that correct?  (Note: the 20 kW is occasional short-duration peak, not the normal range. Normal use would be 10 kW - 15kW.)

Then I thought, what if I had a larger motor than 20 kW, say 40 kW? How do you feed a hungry power draw like that if only 2 C 200 Ah cells were available?  If I had 32 cells, divided into two 16 bank 48 V batteries (say, bank 'a' and 'b'), and banks 'a' and 'b' were wired in parallel to each other, would that satisfy the current draw to a 40 kW motor?


texts: How to design a transistor current switch for synchronization circuit?

texts:
The following diagram is a practical diagram for derivation of the clock signal from the received waveform itself (Synchronization) in baseband PAM systems.

I'm looking for a typical circuit for the "Transistor current switches". I have no Idea of how it should be designed.


texts:
I have 2 wireless modules connected to mbed micro-controllers by serial and they can communicate fine, however the data transfer is one direction at a time (like transmitting down 1 wire).

I need to create a protocol in software to handle the communication between the 2 modules as I need 2-way communication, however I dont understand how to accomplish this in code.

Does anyone have an idea on how to do this?

Regards,
Nick


texts: Current and power-on time in LED multiplexing

texts:
Supposing to multiplex a LED matrix, after a certain number of columns the LEDs power-on time becomes too low in order to ensure a good LEDs brightness so you need to increase the current in order to compensate the decrease of the power-on time. Until now, in this situations, I always did empirical tries in order to understand what's the correct ratio between power-on time and current. Is there any general rule that allows you to calculate the right current starting from the power-on time and vice versa in order to obtain a good brightness? Or is the empirical method the only way?

On the Internet I see that, in multiplexing, some people don't use resistors for the LEDs saying that if you turn on the LED without any current limitation for a very low time it will not damage. Obviously in this case the LED is very bright but is this technique completly safe for the LED or affects its lifetime? In the case where there is a safe time for which the LED can be turned on without current limitation, which is it?


texts:
First off: I'm brand new to microcontroller development, so please forgive me for the simple question. I'm trying to learn for my FIRST robotics team so we can use the MSP430 to handle some extra sensors.

I'm working on understanding/configuring the Unified Clock System. I want it to run on the 25 MHz setting. I've been reading the family guide and device specific datasheet. I think I have a basic understanding. My code is below:

/*
* Objective: have SMCLK run at ~25 MHz for driving an SPI device
*/
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer
__bis_SR_register(SCG0); //Disable FLL
UCSCTL0 = DCO0+DCO1+DCO2+DCO3+DCO4 ; //DCO 31 bit and MOD bit 0 [THIS IS NOT WORKING]
UCSCTL1 = DCORSEL_4; //Select frequency range on http://www.ti.com/lit/ds/symlink/msp430f5529.pdf page 31
UCSCTL2 = 0x000; //Select no loop divider
UCSCTL3 |= SELREF_2; //Set FLL reference to REFOCLK (only internal)
UCSCTL4 |= SELS__DCOCLK; //Select SMCLK clock source to be DCOCLK
P1DIR |= (BIT0 + BIT2); //irrelevant
P2DIR |= BIT2; //Set P2.2 as out direction to monitor clock
P2SEL |= BIT2; //Select P2.2 as SMCLK output defined in http://www.ti.com/lit/ds/symlink/msp430f5529.pdf pg 84
__bic_SR_register(SCG0); //Enable FLL

However, this isn't working well, resulting in a very strange oscilliscope output for two reasons:

The output's waveform is not how I usually see the clock output. Usually I see something resembling a sin wave, now I see something very different.
The waveform shows the clock to be running at ~2 MHz not the desired 25.

Ignore the green line.


texts: Test current carrying capacity of conductor

texts: For research purposes, I would like to determine how much current a conductor like a line of conductive ink would be able to carry. What is a good and safe way to test this?


texts:
Today in our signals and systems lecture we were going through a particular problem then our professor took a signal and broke into its constituent parts he drew this diagram------

Horribly out of scale and sorry for thatI didn't understood how the highlighted portion was missing in the output(That vertical line from (0,1) to (1,1)..) i asked him but he further confused me...

Is his diagram even correct?

Where does that part go?How to visualize it ?

Horribly out of scale and sorry for that*

  EDIT-----------------------------------

*

Below i posted an image about composition/decomposition of a signal

1>> What my professor drew in the class.

2>> What i think is correct intuitively.

Which one is correct?One of them is wrong,why?

What basic concept am i missing in the composition/decomposition of a signal?


texts: In Transient Analysis, what happens when free electrons are applied to a matrix of resistors that don't have a ground?

texts:
I'm trying to figure out what happens to a 30 Volt supply when it is attached to a circuit of resistors which are not grounded.  I know that eventually (steady state) the voltage of the circuit should equal the voltage of the supply, but at that point there would be zero free electrons traveling through the resistor net since there is nowhere for them to travel out of the network.  The only place for them to escape would be back into the supply which supplied them in the first place.

Assuming the resistor net was truly at 'zero' with respect to the supply ground at the beginning.  My best bet is that the free electrons would charge into the resistor net and upon finding zero escape path, would return through the original supply by artificially increasing their voltage until the supply allowed them to escape to ground (or however it chooses to deal with the situation).  At this point the resistor net is now 'at rest' but at a relative steady state potential of 30 Volts.

Let's assume we're using a series of 3 metal oxide resistors with 10k resistance and 50 nH of parasitic inductance.  (http://www.resistorguide.com/inductance/ ) What I can't figure out, is what happens to free electrons when they 'hit the end' of the circuit and somehow return upstream back into the supply for their steady state condition to occur.

I understand that inductors have the ability to artificially increase voltage above their supplied current in order to try and preserve their 'current momentum'.  Does that increased voltage eventually cause a reverse flow of electrons backwards through the circuit and cause the supply to be the lowest potential point in the circuit to create an outflow of free electrons?  Or do the electrons just return backwards through the inductive field despite the field trying to keep them on the 'floating' side of the resistor?  I think I'm just not sure what the mechanism would be for reduction of the parasitic inductance of un-grounded resistors and for dealing with the free electrons which charged the inductors in the first place.

If you can help me with the theory, can you also help me with the math behind it?  I'd like to understand and be able to model these behaviors.  Thank you!


texts: What is the maximum voltage that a RJ9/RJ10/RJ22 can carry?

texts: I want to use a 4p4c modular jack for carrying isoSPI data and 12V at <1.5A and am not sure if the connector or cable could handle that


texts: Does conventional current impede qualitative understanding of any circuits?

texts:
We know that "conventional current" is the historical notion of the flow of positive charges. And that, in reality, the charge carriers are negatively charged electrons and that they flow in the opposite direction.

For simple circuits, it makes no difference: a battery in series with a resistor and a lamp has the same behavior whether we think of positive charges moving "left" through the lamp or negative charges moving "right." We can also think about more complex circuits containing nonlinear elements like transistors - again, we qualitatively understand the circuit's behavior in the same way regardless of the conceptual direction.

Are there any circuits whose qualitative practical behavior is difficult or impossible to understand if we're thinking about current flow in the "conventional" direction? Where we really need to think of electrons flowing in the proper direction to understand why a certain LED turns on, or why a frequency response curve has a dip in it at a certain place, or why a certain EMI effect is happening?

Edit: I'm not concerned with intimate understanding of, say, quantum-level processes that happen in semiconductors, unless the notional current direction in such processes has a behavioral impact that would be of concern to an electrical engineer (or a consumer).


texts: How to make sense of the signal trace of differential signal

texts:
I am trying to understand following signal trace picture that is shown on the wiki page of 1553 Bus. The Bus has balanced differential pair wires.

As the 1553 bus has differential signals on the twisted pair of wires it means that the physical arrangement of the oscilloscope probe was that the probe SIGNAL and GND pins would be connected on the differential wire-pair. As there is no 'ground' wire in the 1553 bus so the oscilloscope probe GND will not be connected to any 'ground' potential but one of the two differential wires will act as the reference potential point (ground) for the oscilloscope input signal.

In the picture I can see 3 voltage levels, Low, Mid and High.
My understanding is that when the Bus is quiet then both lines are at 0 volts w.r.t their signal ground so their difference will also be 0 volts. It looks like this is the 'Mid' signal level case.

I could not understand how the Logic '0' and '1' is translated as 'Low and 'High' in the above signal trace on the oscilloscope? If I want to draw the individual signals on the differential lines w.r.t. to the signal ground then what would be those 2 signal traces that produces the trace as shown in the above picture?


texts:
If VCE is negative in a PNP transistor does that mean that it is in saturation? Note: not given the saturation value.

This is related to a homework question.

Thanks


texts: Measuring the external memory power consumption in FPGAs?

texts: I am trying to get a power/energy breakdown of DDR3 and core logic. I used Quartus power analyzer tool to get the power estimates, but I am not sure whether it includes the power consumption of external memory like DDR3, HBM. In general, how do we measure/model the power consumption of the external memory access in Intel FPGAs?


texts: FXOS8700CQ - Arduino core I2C doesn't work, SoftI2C does

texts:
I use the Arduino core libraries in my latest project (ATMega328P MCU)

I'm trying to talk to an FXOS8700CQ via I2C. Reading register 0x0D should return 0xC7.

The typical Arduino Wire library method,

Wire.beginTransmission(address);
Wire.write(subAddress);
Wire.endTransmission();
Wire.requestFrom(address, (uint8_t) 1);
uint8_t data = Wire.read();

gives the following incorrect reply:

Using a SoftI2C library from off the web I get the following correct reply:

What is the difference that makes one work but not the other?
I'm using 10K pull-ups, are they too high?


texts: PN junction voltage drops in a Saturated BJT

texts: Let's say we've got our BJT operating in its saturation mode. Can we make (a rough) approximation now and make calculations for the circuit assuming that both Ube=0.7V and Ubc=0.7V (for an npn). Or do these values change in sat mode?


texts: Use mobile to power external LED(bulb) via a Micro USB port?

texts:
I have heard people using OTG cable and a USB cable to charge one mobile from another mobile. I was wondering, Could I use the micro USB port directly to power external devices like LEDs.

I cut up the adapter wire and connected the micro USB in my mobile.
The external 2 leads have no output at all.

I searched on the internet to how to turn on the power of the micro USB in mobile. I didn't find any material.
I searched app store to find an app that uses a protocol to power on the USB port. But No results

How can I do it?


texts: No alternatives to isopropyl alcohol to clean TFT displays?

texts:
I'm using pure (99,99%) IPA to clean the surface of small TFT displays (less than 2 inch) to eliminate any trace of dust and (accidental) silicone before mounting them in a sealed slot beneath a small plexiglass window.
I use special paper-wipes (no dust) for the cleaning operation. Nevertheless I'm quite disappointed from the fact that, after evaporation, the isopropyl-alcohol leaves always a visible halo on the surface.
It takes me a lot of time to eliminate such halo by using... the water vapor from my breath. Only in this way I can to definitely clean the surface.
There are no other products leaving zero residuals than the IPA?


texts: What is the effect of an amplifier on an LC tank?

texts:
Consider a simple circuit like this:

The tank on the right is an oscillator
and the amplifier provides in-phase "boost" to the tank to keep the oscillations going.
its controlled by the feedback from the lower capacitor.

When Vout starts rising above the baseline ( 0 - 90 degree of sinusoid ) the center capacitor is receiving current from the inductor and increasing its voltage.
Flow of current is like C <== L
now the amplifier provides in-phase push which makes Vout even higher and stronger.

so the amplifier action charges the center capacitor more and more. So flow is like Amplifier ==> C makes C have more voltage

But, what is the effect of the amplifier action on the inductor ?
The amplifier also sees the inductor and should push against its current ?
Red - Vout = Vc
Green - Amplifier Action
Blue = L Current

Note:

C gains +ve charge 0-90 deg of Vout. Current L ==> C
C looses +ve charge 90-180 deg of Vout. Current L <== C
C gains -ve charge 180-270 deg of Vout. Current L <== C
C looses -ve charge 270-360 deg of Vout. Current L ==> C


texts: Multiple output noise analysis with LT spice

texts:
If I want to do a noise analysis I do this in LT spice:

.noise V(adc1) V6 dec 12 0.01 1e9

Where V(adc1) is the voltage for the output node of the analysis and V6 is the source.

Question: Is there a way to have two nodes in the analysis?

Sometimes I copy circuits modify one and and compare the two circuits.


texts:
I've been asked to reattach the positive cable that got ripped with the pad from a board given that I own a soldering iron. It seems simple enough to just jump it from a trace.
Scraped a bit of the mask off from the pad space at P1, yet I don't get anything at all while measuring for continuity from the negative cable to the exposed trace.
The whole board is covered in some resin if that helps.
As I see it the big traces starting in P1 are clearly separated so those should be the negative and positive sides so the magic pixies should go from one side to the other, but they seem real lazy.
What am I not understanding?

Edit: this board is for showing battery level on some boat, theres a counter soldered on the other side


texts: Why is Δt constant in phase shift measurement?

texts:
I would like to ask for some help with phase shift plotting. To be precise, with time delay between two waveforms.
I am measuring two currents using an oscilloscope.

channel A (blue) is my current clamp.
channel B (red) is my shunt resistor, plugged into the wire supplying current to the clamp.

I use formula: angle = 360 * f * Δt. I noticed that regardless of frequency, Δt is almost constant (small fluctuation perhaps due to measurement error). Could anyone explain why is Δt a constant?
Overall, I got Bode plot of phase angle vs. frequency that looks sensible. However, I would “expect” Δt to change with frequency.

f=1 kHz, Δt=6 us;

f=10 kHz Δt=6.2 us;

Phase

Magnitude


texts: PCB thermal isolation from 230VAC-12VAC transformer

texts:
I was thinking on creating a dual layer PCB where on one side I would put the MYRRA (45043) AC-AC PCB mount transformer, and on other side the remaining components. In other words I would have the AC tracks along with DC tracks, low DC amperage and up to 16A on some AC tracks. And at this point I started thinking:

Is there any way to isolate the heat generated by the AC-AC transformer to the other side of the board?
What special consideration should I take when mixing AC and DC tracks on the same PCB?
There's some calculators on the net to calculate track width and so on, but I could not figure out how much heat it will be generated from transformer.
Taking into consideration that same tracks could be at certain point up to 16A AC, should I consider an inner layer (for isolation purposes), instead of an external one? Is it recommendable, good practice, or is that plain old nonsense?

Any help would be gratefully appreciated. Some literature I should read and other things I should consider... please let me know...


texts: Dual 50v DC boost converters in parallel?

texts:
I'm very new to electrical components, should I be on this website? I'm modifying an electric scooter to run at 50 volts as opposed to its rated 24 volts.

The most I’ve seen the motor draw is 45 amp at 35 volt up an incline, and I've done some research and I think its possible to use a 95 Ah car battery to power 2 of these generic 1500 W 30 amp boost converters in parallel by using a 5 watt resistor on both positive output terminals?


texts: What are these 0.1'' header 'pin protectors' called?

texts:
I was browsing Hackaday a few weeks ago and came by these 0.1 header "pin protectors". I have tried googling every term I could imagine and searched all related categories in Digikey and Mouser, but I had no luck finding any information on them.
What are these called? Where can source them from?


texts: I would like to design a circuit which when moves should give out a voltage. So I would like to choose an accelerometer for this application. I wish to go for single-axis accelerometer which is quite good enough for my application. I need to understand what are all the parameters that we need to understand before going for the selection.


texts: How is a varactor diode used in a circuit when it only has 2 terminals?

texts:
I've been reading about varicaps, and I'd like to try to use one in an op-amp integrator circuit to be able to adjust the gain.

My confusion though is that every varactor diode datasheet I've read indicates that only 2 pins are used, like a normal diode.  The capacitance is supposed to change with reverse voltage across the diode, but how then is the capacitor supposed to be used in useful way?

Only 2 pins used in both package types!

Doesn't make any sense to me, since obviously you can't keep the diode at a constant reverse voltage AND use it in any type of circuit where an alternating waveform is applied. I was expecting them to have a 3rd pin where an external control voltage was applied.

What am I missing?


texts: Capacitor matching/replacement - different voltage

texts:
I have a bad capacitor in my ceiling fan.

The numbers on the old capacitor read as 4.5 280v/ 5 250v/ 5 250v.

I'm having a difficult time finding the 4.5 280v.

Can I use a 4.5 250v in its place?


texts: ICs that convert an AC signal into its true rms value

texts: I need to convert the instantaneous voltage output from my current transducer to a true RMS voltage output. Can anybody please suggest an IC that can perform this function.


texts: Given the current and voltage of a consumer electronic device, how to calculate its power draw?

texts:
Given a device that uses electricity from the wall socket (220-240V AC@50Hz or 110V AC@60HZ), and it has its current draw specific (i.e 1A), how can I calculate the power (in watts) that it consumes?

I know that for DC current, the calculation is very simple (Current multiplied by voltage) but I understood that for AC the calculation is rather more complicated.

Also, its quite unreasonable that my charger, that uses 1.5A AC, would consume 345W and only output 19V * 4.74A = 90.06W (255W turning into heat) and it won't get extremely hot. Also, it is rated above 80% efficiency, which doesn't meet the previous calculation.

How can I calculate an electric device's power usage given its current and AC voltage?


texts:
I am creating the following diode clipping circuit:

The input signal, Vin, offset is removed and the signal is amplified using an op-amp. Then there are two diodes designed to clip the signal to +/- 0.7V. The clipped signal then goes to another op-amp, R4, where a gain and an offset are applied (not showed).

The diodes I have chosen are MBD701 and have a forward voltage of 0.7V at 10mA. The op-amp used is an AD4177 and is capable of outputting 25mA. I was wondering if I can use R3 to control the current across each Diode? My understanding is if the current across R3 is equal to 15mA and the op-amp outputs the max current of -25mA since the impedance of the diode is low in the forward direction, then -10mA will then leave the R3 and output node. If R4 impedance is very large, I can assume that almost all of the -10mA current will go across the diode. Is this logic valid or are the OP amps capable of outputting greater current than on the datasheet? Also is there a way to calculate the impedance of a diode?

Thank you


texts:
I was wondering if there are any resources on building a USB mass storage device on a breadboard. I know it's not practical, but I thought it would make a fun side project and so I decided to do it. As far as I could find, all the USB controllers are all surface mount and don't come in DIP package. Sorry if this sounds really nooby, I'm really new to electronics.

I try googleing, but I couldn't find any up-to date resources. Helpful pointers will be appreciated.


texts: 12v DC Motor with variable power suipply

texts:
Im looking at buying a 0-30V 0-5A variable regulated power supply to play around with dc motors ranging from 3v to 12v and varying amps. I plan to connect them directly without using mosfets, transistors or switches of any kind, just looking to vary the speed of them for use with 3D printed models.

My question is, can I do this successfully without needing a fly-back/snubber diode or without overloading the capacitors in the power supply? Im only new to electronics and have read a lot about needing fly-back diodes when dealing with mosfets and inductive loads but cant seem to get a good answer when it comes to directly using nothing but a dc motor.

Thanks in advance.

Just looked into powering the dc motors more and I was reading that a short circuit protected power supply wont work with DC motors, is this true? because every power supply i can find has that built into it.


texts:
I have this schematic which is from the USB to UART section of an ESP32 development kit schematic. I'm fairly new to reading schematics and I'm just wondering what a few things are:

The green box
'ACTIVE' on the suspend pin
Why is one of the resistor values (I'm assuming that's what it is) in green when the rest are blue?

Update: Here is the whole section of the schematic for context:


texts: Magnetometer tilt compensation without accelerometer

texts:
I need to use the magnetometer in a device to accurately determine how many degrees the user twists (rotates in x-y plane) it. I don't care about absolute orientation, just the angular delta. Of course the user can hold the device in any orientation. Essentially, this is like a doorknob that isn't attached to anything.

I tried atan2(x, y) but the resulting anglular delta varies depending on the device's orientation. Some research suggests that tilt compensation is needed, but all solutions are for correcting compasses based on knowing the gravity vector.

In this application, accelerometer, gravity, gyro data are not available -- just the magnetometer. This means that the pitch & roll used in typical solutions aren't available. However, I'm not looking for true headings, just rotation in x-y.

Can anybody explain the math & solution for this? I realize this is strictly speaking a programming question, but this is stuff that only an EE would know.

The application is typically used such that the x-y plane is rarely, if ever, perpendicular to the earth's field, so sqrt(x2+y2) > 0.

The magnetometer is an AK8975 3-axis MEMS soldered to the device with no gimbal-type leveling arrangement. Hard-iron calibration is already taken care of. Sampling rate is 40 Hz whereas the fastest you can twist your hand back & forth is less than 5 Hz. The magnetometer's orientation is totally unknown since the magnetometer's axis is fixed to the device and the device can be in any orientation. Nothing is known or can be assumed about gravity nor the device's orientation or location.

[Later] Did an experiment where I took the device and lay it flat on a swivel chair facing North, then rotated it thru 360. The chair seat is level with the ground. Here's the chart:

x=blue, y=dark green, z=red, sqrt(x^2+y^2+z^2)=aqua
The x-axis is elapsed seconds, y-axis is uT.

Two things jump out at me:

Shouldn't the aqua-colored magnitude be flat? The trough is 30 vs. 45 for the flat part. Otherwise, is this a tipoff that this sensor is grossly mis-calibrated? Or is this an indication that tilt compensation is needed?
The x & Y peaks are slightly offset and have slightly different ranges, but not by that much. This, I'm willing to shrug off as error, as opposed to the 30:45 difference for the magnitude which seems sufficient to mess up any calculations.
The Z is flat as expected


texts: Operational amplifier conversion of a sinusoidal wave

texts: Ok guys my question is: Is possible to turn a sinusoidal wave into a square wave with just an operational amplifier?


texts: Effect of insulated high voltage wire to micro-controller

texts:
I am investigating a home appliance product which is reported out of order. Having disassembled and checked, I found the power and ground pin of the micro-controller is shorted.

In this product, there is a high voltage ion generator  which will generate about 3 kV. The wire with the 3 kV potential has a 6 kV DC rated insulation jacket. This wire can be very close to the micro-controller (and the electronic board) inside the product. I have done a 3.5 kV hi-pot test of this wire (supplying the voltage between the wire conductor and the insulator) and there is no current leakage.

Although there is no current leakage from the wire conductor to the outside of the wire, will the high potential of the wire damage the micro-controller (the micro-controller is working around 3.3 Vdc, so the potential difference between the wire conductor and the micro-controller can be 3 kV)?


texts: Building PCB mountable inverter for an EL panel

texts:
To a circuit for a light installation I want to add an inverter for powering an EL panel. Ideally, the inverter can be mounted on a PCB.

Input voltage: 5 V
Output voltage: to power an EL panel at maximum brightness

For the EL Panel - Green 10cm x 10cm offered by seeed (just a random pick), recommended input is:

120 V
1500 Hz – 2000 Hz

I found 12 ICs on Digi-Key to drive EL inverter circuits with 5 V of input (screenshot). None of these, however, is able to output frequencies in the range of 1500 to 2000 Hz.

These ICs don’t work for the intended purpose, right?

Are there other options, or should we better just use a fully assembled EL inverter?

(The fully assembled EL inverters normally are not PCB mountable. The only PCB mountable inverter that we found, called WE-50, is unfortunately not very powerful, i.e. the brightness of the connected panel was quite low.)


texts: Average Voltage of a 3phase full wave bridge diode rectifier derivation

texts: Why three phase bridge rectified waveform is integrated over the half period \$\pi/6\$\ to find the average voltage? Should it not be integrated over \$\pi/3\$\, as the wave form repeat itself after \$\pi/3\$\ which is the time period of this waveform. Below is the waveform and related derivation. The book is Power Electronics 3rd Edition by Muhammad H. Rashid, page no 93.


texts: Atmel AVR - Integrated programmer onboard

texts:
I'm pretty new in microcontroller programming. But i wounder, I'm designing a circuit with Atmel ATUC256L3U, the cicuit is going to be used to home automation. The microcontroller is going to be controlled over ethernet connection.

Is it possible to integrate a programmer and USB port onboard of the PCB, so don't have to take out the microcontroller out every time I want to re-program it?


texts: Initial value for 32 bit register made using D F/F in verilog

texts:
I am trying to make a 32-bit register using 32 negative edge trigerred D F/F. Here is the verilog code for D F/F:

module dff(q,d,clk,reset);
    input d,clk,reset;
    output q;
    reg q;
    initial
        q<=1'b0;
    always @(negedge clk)
    begin
        if(~reset)
            q<=d;
        else
            q<=1'b0;
    end
endmodule

Here is the code for 32-bit register:

module reg_32bit(q,d,clk,reset);
    input [31:0] d;
    input clk,reset;
    output [31:0] q;
    genvar j;
    generate for(j=0;j<32;j=j+1)
                begin: reg_loop
                dff d1(q[j],d[j],clk,reset);
                end
    endgenerate
endmodule

Now, I expect that when I include the module reg_32bit in another module and try to read the register using q, then I should get all 0's initially. But when I try to do so, I get all x's instead.

What am I missing here?


texts: Utility of Field Programmable Analog Arrays

texts:
The only FPAA-related question I can find is THIS, but it doesn't really introduce me to the area.

The concept seems like a nifty thing to have as part of an analog toolkit.  I can't necessarily see implementation in deployable devices in any of my work, but I can see the possibility of some sort of quick and dirty prototyping environment, perhaps replacing bins of op amps and passives, making the electronics bench a bit more portable.   I'm wondering if this is worth pulling the trigger on this summer.

In terms of a question, do those in the know believe that such a tool can serve as sort of a very portable analog electronics bench for the right sort of prototyping jobs.

Also, I can't really tell if the FPAA has any holding power.  The main player I see is Anadigm.  Are there any others?  Is one maker enough to depend on?  If this is as convenient an idea as it seems to be, why hasn't it become popular?

Lastly, can anyone recommend, from personal experience, a good toolchain/devkit?


texts: How much current should I pass through battery to break through sulphate deposits?

texts:
I recovered an aged SLA from the pile dated 2003 marked 6V 4.5AH. It has .97V in it. As I recollect, thumb rule for a charging current would be about 500mA at 7V or better.

A breadboarded LM317 may be capable of doing this.

Given it's age, should the battery be given a high current jolt initially to break through any sulphate buildup? How long should this be maintained? How does one confirm desulphation success?


texts: Insane power dissipation on EL34 tubes in push-pull power stage

texts:
Here's my circuit:
(now without voltages)

It uses two EL34s biased to -30V (fixed bias).
Here's the loadline (made with this calculator):

When no signal is applied voltage on EL34 anodes is 360V, as expected, and current is around 40mA, as expected.
However when I apply 50V p-p signal (V8 and V9 are generating phase inverted signals), weird things start to happen:

Power dissipation on EL34 anodes is going up to 110W. Signals on EL34 grids are correct.

[AFTER EDIT, corrected inductances]
I'm running this simulation in Micro-Cap 12.
I suspect that something is wrong with transformer. Speaker transformer is Hammond 1650HA, and I've used component named 'centap' for transformer, and copied inducance values from 1650HA's datasheet. (11.3H primary, which results in 2.825 to center tap, and 214.5mH for secondary 8 Ohm output).

(Inductance values are now corrected, thanks for pointing it out)

Loadline was generated with transformer primary impedance of 6.6k Ohm.
Datasheet says that primary impedance is 6.6k, and secondary has three outputs for 4,8 and 16.
There was nothing about impedance when I was defining transformer in micro-cap. Since only values that I could specify were inducances, I thought that setting proper inductances implies that all other values are also correct. However when I plot impedance of transformer, I see that these values have nothing to do with 6.6k (or 3.3k each)

The question is: is something wrong with my circuit, or it's just issue with the software?
In case it's issue with software, could anyone who has experience with micro-cap 12 tell me how to properly simulate Hammond 1650HA in this software?

EDIT: This circuit is using the same transformer, and is almost identical(in fact when I modified my circuit to be exactly identical I'm still getting wrong results). It's author build it and it worked for him, his EL34s didn't melt or explode, so I think my circuit is also correct, and therefore I think there are two possibilities:
1. I've implemented 1650HA incorrectly
2. I've measured power incorrectly.

EDIT 2:
Since impedance of transformer should be 3.3k for each side, I've replaced it with 3.3k resistors, and now I'm getting correct power measurements, power dissipated on EL34s is slightly below 20W, and average power on load is ~32W.


texts: Can I use 1 transistor to switch on and off 3 loads?

texts: I am running an ESP32 microcontroller with a Co2 sensor, a real time clock (RTC), and an SD card reader.  I will be putting the microcontroller into deep sleep and waking it every hour.  I want to switch off the power to the aforementioned components before the microcontroller goes into deep sleep and turn the components back on after the microcontroller wakes up.  Can I use 1 BJT npn transistor to switch off power to all three components?  I was also thinking of using three transistors with a common base signal... i.e. using just one GPIO pin to control three transistors.  Thanks


texts: What is 'Nonrepetitive Peak Surge Current' in diodes?

texts: I just went through many datasheets of diodes but didn't understand the term "Nonrepetitive Peak Surge Current". Can someone please explain this to me?


texts: How do you use a EZP2019+ programmer with an ATTINY85 with avrdude?

texts: I need to burn micronucleus on the ATtiny and only have an EZP2019+ programmer and I also need to set the ATtiny to 16MHz clock speed, how do I do that?


texts: Constant current sink circuit for battery load simulating, microamp current draw

texts:
I need to create a constant current sink circuit such that I can simulate current draws from a battery, and analyze the battery behavior. I'll be testing a battery that is 3.1V with 12mAh capacity. I need to draw current in various patterns (i.e. repeated cycles of 15 minutes 1.5microamp, then 5 seconds 7mA, 30 minutes 1.0microamp, then 3 seconds 10mA, etc).
The battery voltage remains at 3.1V when a microamp current is drawn, but the voltage drops when 7mA is drawn. This voltage drop is what I need to analyze. Thus, I need a circuit that will ensure constant current is drawn regardless of what the battery voltage drops to (expected drop is to between 2.4V and 1.8V after repeated cycles).
This is what I am able to find online (picture of schematic below): http://www.ti.com/lit/an/slaa868/slaa868.pdf
However, I am having a hard time finding appropriate parts and setting appropriate resistor currents to achieve the current sink range of 1.5uA to 7mA. Can anybody point me in the right direction to appropriate MOSFETs and op-amps I should be using here? The circuit needs to be very precise, I can't think I'm drawing 1.5uA but actually be drawing 30uA or 30uA.
I also plan to measure the  battery voltage as I run different tests using an Arduino, and control the DAC with an Arduino. I've found this DAC that should be pretty easy to use with Arduino: https://cdn-shop.adafruit.com/datasheets/mcp4725.pdf. 2.7-5.5V max output.


texts: Is this line Instrumentation Amplifier's rail or not?

texts:
A document related to analog input connections to daq boards depicts the IA of a daq system as in following diagram:

In all their examples the IA's rail is tied to AIGND. I indicated this with a red arrow above.

Is this line (which I point between the IA and the AIGND) negative rail of the amplifier? Because if so it means they are tying the negative rail to AIGND which is a bit confusing to me.


texts:
I came upon this circuit at the power supply input:

The power is usually supplied by the VBUS pin. Now, how dows the circuit work? What is its purpose? I think it is a sort of ideal diode, but can you explain the theory behind?

Also what happens if I apply the power (5V) directly on the DCIN net?

If you are curious, this is part of the Orange Pi Zero schematic


texts: Which is the objective of an Base-emitter resistor?

texts:
Can someone explain me the purpose of the resistor R2? If I remove R2, the circuit will perform the same result, won't it?

simulate this circuit – Schematic created using CircuitLab


texts: Charge current for a 8000 mah lipo battery?

texts: I have a 3.7V lipo battery with 8000 mah nominal capacity. From what Ive seen online, the charging current should be 8A for a 8000 mah battery. Is that true? Will charging it at a lower current damage the battery?


texts: How does Dc biasing affect the Q point BJT

texts:
In order to amplify an AC signal, its required to provide a DC offset in order for no negative values of current to go through the input. Input signals and output signals oscillate centred on the Q point. What would this look like for a an AC signal not DC offset?
Would the input signal literally just be stretched vertically and then some of it will be clipped?


texts: Simple question, what does it mean to have a transmission line (RS-485 in my case) balanced vs unbalanced?


texts: Are there short-circuit-proof electrolytic capacitors?

texts:
For my studio photography I have a set of Prolinca strobes rated at 500 Ws. They fire in 1/2000 of a second, meaning that they deliver \$\frac{500 J}{1/2000 s}=1MW\$ for a jiffy. (No wonder that this causes a rather loud "clac" sound.)
I've always wondered how the capacitors can survive this. Are there electrolytic capacitors which allow repeated shorting?

(If the caps work at rectified 230V they must be 10 000\$\mu\$F to store 500J)


texts: How to get distinct output voltages in LM3914 dot/bar cimparator IC?

texts:
I am using LM3914 for testing soil moisture content. Based on the water content, the  output of the IC needs to reflect.I am using the IC in the bar mode.

Now, the issue that i am facing is that, when the LED is OFF(i.e.OUTPUT IS OFF) and when the LED is ON (i.e. OUTPUT PIN IS ON), there is a very small difference in the voltage on the PIN.

I need 2 distinct voltages- 1)Greater than 3.1 V 2) GND(<0.8V)  since i need to connect the output pins of  the IC to a communication circuit.
Could anyone please help me?


texts:
While reading a book on opamps I came across this output offset voltage compensating circuit.

They used thevenin's circuit looking at Ra from point T:

Then they converted a part of the first circuit the this:

But what I don't understand is how can the given circuit can have both resistance  Rmax as well as voltage Vmax at the same time? Why have they shown both the things together in the same circuit. Like if the resistance were Rmax, voltage would have been zero at point T. Can anyone explain please!

Thanks!


texts: What is the minimum output frequency according to this datasheet?

texts:
Can this DDS output down to 0.05Hz sine?

I think the resolution is 0.0291 Hz. Does that mean that is also the miimum freq. it can synthesize?


texts: How to calculate voltage gain with bypass capacitor?

texts:
May i know is there an "exact" formula to calculate the voltage gain for a capacitor value that is neither fully short circuit/fully open circuit for an AC path?
So far from online sources, authors of the page just mentioned use 1/10 of the resistance value and it will be consider a short circuit.
https://www.electronics-tutorials.ws/amplifier/input-impedance-of-an-amplifier.html
By taking an example of the circuit below, if without the bypass capacitor C2, the voltage gain will be approximately $$A_v=\frac{4800}{450}=10.67$$
while with the presence of a capacitor that consider "big" enough will be a short circuit to the 450ohm reistor, with IE=3.64mA, $$r_e'=\frac{25.9mV}{3.644mA}=7.107$$ then $$A_v=\frac{4800}{7.107}=675$$
So if using a capacitor value that is neither too big to fully short and too small to fully open, the voltage gain for this circuit must lies somewhere between 10.67<AV<675 correct?
If so what the formula to obtain the gain?
is it
$$A_v=\frac{R_3}{r_e'+(R_4||\frac{1}{jwC})}$$

simulate this circuit – Schematic created using CircuitLab


texts: MOSFET current at very low temperature (4K)

texts:
I am trying to model the current at low T. To do so I need to compute the integral between the fermid diract statistic and the conductivity, with respect to energy. My problem is that I cannot understand how can I have something different than 0 for a PMOS as my functions seems totally disconnected in the sens that if one is not zero, the other one is :

and what I get using python :

I guess I am missing something but I cannot see it..


texts: How to determine quality of headphone earbuds by spec sheet?

texts:
I have been doing some work with cheap headphone earbuds for quite a while now. I was wondering, when buying earbuds in bulk, if there was any way to tell what the sound quality would be before purchasing. Obviously one would expect more expensive earbuds to be of higher quality, but there is always the chance that they are just a scam.

I've noticed there is an Ohm value for each headphone and some other metrics like speaker size that are listed within each earbud spec sheet, but I dont know which of these are more important for sound quality. Also, I've taken apart some more expensive earbuds and found that they have fluffy yellow stuff (magnetic shielding?) lining the wires that probably helps drown out noise. Lastly, I'm wondering if gold-tipped TRS/TRRS plugs would make a difference over silver or aluminum ones.

Really, I'm just looking to determine the general sound quality of bulk headphones before purchasing them so that I can make an educated compromise before purchasing them.


texts: IC's in high altitude and low temperatures

texts:
What happens to IC's when trying to operate them in extremely harsh cold and high altitude environments like Mt Everest?

Could you take any ordinary phone or computer up there an expect it to work? I believe the altitude at base-camp is aprox 18,000 feet. Perhaps heating may not be a huge problem since its awfully cold-perhaps too cold for devices to start after a while?


texts:
I want to make a wooden chess board that you can play on with regular pieces (i.e., not modified pieces that make use of RFID codes, magnets, …), but that is connected to a software that takes notice of my moves and acts as the second player.

I have been thinking about how to detect pieces on the board, and I have made the decisions that I do not need to recognize which piece is where: The "truth" is within the software, so if I move a piece from A to B, the software is able to find out which piece was moved.

So, I had the idea to drill two holes into each field of the chess board, one in the center, and one in the upper right corner:

The one in the center will be used for a brightness sensor to detect whether a piece is standing on the field or not.
The one in the corner will be used for an LED to show which piece the user has to move for the computer, so that the real-world situation matches the software situation again.

I want to use a Raspberry Pi as hardware foundation for the software to run, which will be written in Node.js (but that should not be important for this question).

So, what I end up with is 64 brightness sensors, and 64 LEDs, that I need to address individually. In other words: I need 64 outputs, and 64 inputs. And of course this is something a Raspberry Pi does not handle out of the box - and I think that there has to be a better way than to have 128 I/O ports.

Since I think that detecting the board's state is the more important task, I started to search the web how to handle a 8x8 matrix of switches. I found the suggestion to use a micro controller that scans the columns of the board sequentially, and in each columns detects whether a row (= a field) is used or not.

This would reduce complexity to having 8 outputs and 8 inputs (to be able to read the board's state).

On this, I have a few questions:

Are my thoughts right, i.e. is this the correct approach, or is there a better alternative that I should watch out for?
As I have no experience with micro controllers, what do I need to look out for? Do I just need a micro controller with 16 pins, that is programmable in a language that I am able to write, or …?
Has anybody built such a board and has some advice or knows of a tutorial that walks you through the process?


texts: If a silicon cyrstal is connected to a battery does current flow through the wire?

texts: In a circuit consisting of a pure silicon crystal with each end attached to a different terminal of a battery via conducting wire, is there a current flowing through the wire? It seems that there is no current flowing through the crystal because the flow of the holes cancels out the flow of the electrons, but is there current flowing through the wire?


texts:
This may be an off topic question, but I'm sure many of you have the knowledge and experience to help out here.

A quite complicated motherboard was flexed. The resulting symptoms include cross-talk or noise on some data lines going out to the display. The symptoms get worse when lots of video data is transferred. This could be due the fact that more data is getting transferred and therefore more data is getting corrupted by the noise or it could be due to the SMPSs working harder to power the GPU resulting in more noise. It could be a combination of the two, but at the moment I suspect a bypass capacitor on one of the SMPSs on the motherboard either cracked or the solder holding it on cracked.

Question: Besides a visual inspection with a microscope, is there a way to test for a faulty capacitor/solder joint that likely failed in an open state on a PCB? A hairline crack in a SMD capacitor or in the solder joint somewhere on a large PCB seems difficult to find through visual inspection.


texts:
Va is 10 V, M1 is OFF; Vc and Vd are both 95 mV and M3 and M4 are ON. Good, that is that expected, but why M2 is ON here? The gate of M2 is grounded. Vb measures 735 mV, which is strange!

Here, I added a resistor to the bottom. Va is the same, as expected; Vb is 5.3 V. Very strange. Vgs for M2 is -5.3 V, how can this MOS still able to turn itself ON? Both VC and VD are about 5 V, but with VD slightly higher than VC.


texts: How to prevent switching direct and/or inductive noise on a PCB?

texts:
I'm designing a power source for one of my projects and I couldn't find a better way to reduce the voltage drop on 7805 regulator other than using a switching regulator (LM2596).

The switching regulator output goes through an additional LC filter (with tantalum caps) and from there to a linear regulator:

The filters and linear regulator should filter out most of the switching noise, my only concern is that the noise can spread through the PCB traces, here's the one sided PCB design (those front coppers are actually jumpers):

LM2596 current is not going to exceed ~200mA.

I don't have any experience in designing switching regulators and handling noise, all I did was "pouring" the ground line.

How can I reduce the output noise (as much as possible but reasonable) in this specific design?
How to prevent the inductive noise in PCB design?


texts: Smart load switch with inrush control and overvoltage lockout

texts:
After I finish making my dc-dc buck-bost converter, voltmeter and ammeter I decided to add a smart load switch to my power supply in order to have the posibility to connect electric motors, bulbs or any element that generete big inrush currents at startup.
Here is my write diagram. I am using the ltc7004 ic (https://www.analog.com/media/en/technical-documentation/data-sheets/LTC7004.pdf) as a load switch.

I have 2 question regarding to this:
1- How can I control INP pin without using a microcontroller. This pin is CMOS input compatible.
2- This switch will tolerate a short circuit? In the datasheet I not found anything.


texts:
I recently purchased an MQ137 Ammonia sensor and breakout board. Unfortunately the item came with the two parts separated with no markings as to the orientation. Can anyone advise on the pin layout?

There item is from here I believe this is the datasheet


texts:
When I read that the conversion clock of an ADC is for example 2 MHz. Does it mean that the ADC perform the analog to digital conversion of n-bit every T=1/2MHZ=0.5 micro second?

This is what is written in the text: With a 2-MHz conversion clock, the ADC can perform an 8-bit single conversion in 6 μs or a 10-bit single conversion
in 7 μs.

I do not understand how these micro second times are derived.


texts:
Is it possible to add a piezo buzzer to a counter:

my example:

(countD<70)

so 1 melody at =0
2nd melody 10,20,30,40,50,60
3rd melody 70

This is what I was playing around with:

if (countD=0)
buzz(2, 2500, 500);
++counter;

putting into this:

    if (countD<70)
    {
    if (countB<10) {
        digitalWrite(ledArray2[countB],LOW);
      }
      if (++countB>=10) countB=0; // For some reason changing this from 20 to 10 makes array not long pause
      if (countB<10) {
        digitalWrite(ledArray2[countB],HIGH);
      }
    countD++;
    }
    }
}
}

Any ideas if its possible?, Im sure it is but I cant find any documentation to help me.

so does this look okay?? 2500, 4000, 6000 I assume is the pitch or tone? so we get one melody for 0 and the second melody from 10-60 third dif melody on 70

 if (countD<70)

if((countD) == 0) buzz(2, 2500, 500);
if((countD % 10) == 10 - 60) buzz(2, 4000, 500);
if((countD % 10) == 70) buzz(2, 6000, 500);
{
        if (countB<10) {

Edit 2:

void buzz()

{
if(((countD % 10) == 0)) && ((countD > 10) && (countD < 70)))
{
buzz(2, 4000, 500);
}
else if((countD % 70) == 0)
{
buzz(2, 6000, 500);
}}


texts:
On this board, I'm trying to identify the burned component, which I believe might be a capacitor.
When zooming in, I think I recognize "47" written on the first line, and maybe "16V" on the line below. This board is powered by a 15V power supply.

I don't know if it's a capacitor. It might be, because the empty space nearby (which was empty when disassembling) could have been a replacement for a non-SMD version of the capacitor, and it's labeled "C1".

I don't know what 47 means.
Is it 47µF?
Is it .47µF?
Is it 47pF?

With only 2 numbers, I can't read it.

May you give me some hints please?


texts: Can I safely and efficiently connect batteries parallel to a DC source?

texts:
I'm building a custom radio system for a friend by using a car-audio setup built into a boom-box-like container. I have everything wired up, and it works well enough. In testing though, I've run into an annoyance... the radio system (being designed for use in vehicles) depends on a constant battery power to maintain its settings and memorized channel presets.

Here's how I've hooked up the power so far:
LCD monitor AC adapter (output: 12V, 6A, 72W)
This source is directly connected to the radio via 2.5mm jack.

There is a power switch between the main power hookup for the radio and the source. (The radio wiring harness has provided a memory backup wire which is connected to the source parallel to the main power hookup for the device... this allows you to cut off the radio (and its face lights) while maintaining power consumption necessary to keep the internal memory alive.

I'd like to hook up some batteries parallel to the incoming 12 VDC source current such that the main source can run the system while it's plugged in, but the batteries would operate the system without interruption if the main source were disconnected long enough to move to another wall outlet.

My main questions are:
Can this be done safely and efficiently?
Are there any considerations I've missed (like power regulation or special charger hardware); it seems pretty simple as I'd be using 12v batteries and a 12v source.
If this is feasible, which type of batteries could best handle potentially frequent 80-90% discharge/charge cycles without suffering damage?


texts: do LCD TVs also use phosphor coated screen? if not, then what is the cause of their after-glow in the dark for few seconds? since we know that glow in the dark stuffs glow generally because of phosphors but i want to know if LCD TVs do not contain phosphor coated screens to form images then why do they glow in dark for few seconds after being turned off?


texts:
I have used timer interrupt in my application, mainly for timing reasons like timeout detection for processes,pulse generation etc, every 1 ms.
Now i have a doubt.

Suppose in main(), if im doing another operation like, maybe writing to a SPI Flash a huge chunk of data, and the timer interrupt occurs,will the data writing process stop due to interruption by timer ISR or data be corrupted due to interruption by timer ISR?
Im just wondering if whether the timer interrupt time is decided considering such operations that make up the complete application code?

If so,if a SPI flash write takes about 5ms and timer interrupt happens every 1ms, how can i keep track of timeouts,pulse generations etc without compromising of data corruption scenarios,because now ill have to change the timer interrupt to greater than 5 ms, and then i cant keep a reference of timeouts for processes where small timeouts like 1 ms may be needed.

  Update

Im using a hardware timer, and when the interrupt occurs,il be using a software timer counter(variable) in the ISR,to keep track of time.


texts: How much does it cost to have a custom ASIC made?

texts:
I have browsed several ASIC manufacturer's webs, but I haven't found an actual number.
I assume there would be a fixed cost associated with creating masks and such and then there will be a cost per unit.

  Note: that I don't actually want to have an ASIC made, I'm just curious.


texts: Li-Ion battery charging, termination current (ITERM)

texts:
How much does termination current (ITERM) affect the level of capacity in a Li-Ion battery?

I mean, in a given capacity (say battery 3.7V 1000mAh) how much charged would a battery be when the ITERM current is a) 20mA, b) 60mA, c) 180mA?

I known that the ITERM does matter when the charger is in the Costant Voltage phase and battery is being charged at its maximum regulation voltage, usually 4.2V.
Therefore the charger stops its work when in CV phase the current drops below the ITERM value.

But I can't understand what difference would be in the total charge when this current was bigger or smaller.
I do understand that the current level would be smaller in bigger values of ITERM but How can I calculate how much is this level?


texts: Transforming image for close eye viewing

texts: If I were to print a image on a transparency and hold it really close to my eyes (the same distance as glasses on my spectacles) the image would become blur and I would be able to see the background environment. Is there a way so that I can transform the image such that the image is viewable as an overlay to the background.


texts: OrCAD PCB Designer PSpice Automatic Route

texts:
The Automatic Route on the OrCAD PCB Designer, is always drawing a line width of 0.1270 (default), but i need a line width of 0.5000, like is shown on options menu and inside the red oval on this image, the NINV yellow line is 0.5000 because i did manually "Add Connect F3", but for some reason the Automatic Route always draw yellow lines width of 0.1270, the problem here is for example in this Capacitor C1, 3 lines are passing between Pin 1 and Pin 2, which is impossible for me to implement that in a real circuit board, only one line at max is allowed to pass between Pin 1 and Pin 2 on this Capacitor C1.

So my question is in what menus do i change the line width of Automatic Route ?


texts: Li-Po batteries; Is random/incomplete charging hamful for the battery?

texts:
Sometimes when my Li-Po batteries are getting charged I have to leave home for some unforeseen  task. I never leave Li-Po batteries unattended while they are being charged. In such situations I am always in a fix whether to delay the task until the battery is completely charged or if it is fine to turn the charger off and resume when I am back?

Obviously I will not be using any such partially charged battery on the R/C aircraft and there will be no discharge event before I come back and restart the charge process.

Is this harmful for battery?

Charging Mode: Balance

Battery Type : Li-Po

Charger: It would be great if the answer applies generally to smart balancing chargers.


texts: How do I size fuses to handle sudden changes in AC line voltage into a capacitive load?

texts:
Suppose I have a rectifier on the AC line, followed by some caps and a load.

simulate this circuit – Schematic created using CircuitLab

If the AC line is suddenly increased, there's a current surge into the capacitor. This can happen when power is applied, during a line surge, or when recovering from a line dip. A precharge circuit can help with power application, but it's less helpful after a dip.

The only things limiting this current surge are the impedance of the circuit components and lanes, ESR of the cap, and inductance of the AC line. The line inductance looks like it should dominate. So there's an LDC circuit between the line inductance and the cap. It's like a tank circuit, except it looks like you'll only get one pulse out of it instead of a decaying ring wave. But there, I'm stuck.

How do I compute the peak and width of the current pulse into the caps, so as to size my fuses appropriately?


texts:
As I am trying to create a relay model in ngspice, I thought of a subcircuit with one inductor and two current switches with a common port, like this:

.SUBCKT RELAY coila coilb common no nc L_coil=5mH
LRelay    coila coilb L_coil
S1Relay  common no coila coilb relaySwitchOn
S2Relay  common nc coila coilb relaySwitchOff
.model relaySwitchOn  CSW it=1m ih=0.2m ron=1n roff=10g
.model relaySwitchOff CSW it=1m ih=0.2m ron=10g roff=1n
.ends

as I thought to have two current based switches, that both depends on current in the inductor, but each one uses a different model so that if first switch is on, the other if off, and if first is off, the other is on, by using different ron, roff values for each switch model.

is this a good approach?

also, I tried to read the manual for inductor, and I’ve used CSW model type as above, but I got this error:

["Error on line 0 :"]
["  s.x1.s1relay 4 7 6 1 x1:relayswitchon "]
["incorrect model type"]
["Error on line 0 :"]
["  s.x1.s2relay 4 8 6 1 x1:relayswitchoff "]
["incorrect model type"]

thanks for any info in the right direction

EDIT2

Here is the relay in action that I am trying to implement:


texts: Altium Designer IPC Footprint wizard error for chip components

texts:
It is the first time I am designing a PCB with surface mount components. I am trying to generate footprints for 0805 resistors and capacitors, and 1210 capacitors using the IPC footprint wizard which is built into Altium.
The issue is that I am not sure if it is generating the correct foot prints. When I compare the footprint generated, to that given by a component manufacturer, the dimensions can be significantly different.

For example in the case of the 0805 capacitor. https://search.murata.co.jp/Ceramy/image/img/A01X/G101/ENG/GRM21BR61H475KE51-01.pdf

I generate the footprint in Altium using the wizard and it generates pad Dimensions of X = 1.45mm, Y = 1.25mm and Pad spacing of 1.7mm. The spacing between the pads is only 0.45mm (very close). It looks like this:

The datasheet recommends the pads to be X = 1.4mm, Y = 1.65mm, and Pad spacing of 2.6mm. The Pad Spacing parameter is always the most drastically different from datasheets whenever I use the wizard. If I draw the pads according to the datasheet, then it looks this this. The pads are a lot more spaced apart

My question is, can I trust the IPC wizard? Are the foot prints generated by it still ok, even though they are very different than those recommended by manufacturers? I just don't want to spend so much time designing the PCB, only to find out the pads are incorrect after I get the boards made. Sorry, it probably is a question that has a very obvious answer but it is my first time doing this so I don't know what to follow. Your help would be really appreciated.


texts: What's the actual difference between voltage gain, current gain and power gain?

texts:
Why do we intend to obtain different gains at different places?
In an emitter follower for example,

There's no voltage gain, but there's current gain and therefore it has power gain. Okay, how's that different and  useful from having an voltage gain? And what's the difference between current and power gain. In power amplifiers,

  Since any more voltage amplification would lead to distortion, we
  amplify the power(current).

What effect does amplifying power bring with it?


texts: Can anyone identify this resistive component?

texts:
I got this components:

Resistance about 9 to 10 Ohms.
I am unable to identify this components.

edit:
Thank you so much answering this question.
Yes it is a 0.15A PTC fuse. ITrip is about 0.5A and it is very slow.


texts:
Assuming that the FPGA has a clock multiplier to get much faster frequencies internally, what is good choice for an external crystal?  Let's say I've got a Virtex 7 class FPGA, and I plan to run internally at ~150 MHz and have an external peripheral that needs at 283.0 MHz. The strawman choice for the crystal frequency is currently 40 MHz, but I'm not sure why that was picked.

Is there a minimum frequency?  Maximum frequency of course is dictated by the PCB routing, so I can understand not going too high. But what prevents going lower?

My gut feeling is that anything in the 10 to 50 MHz range is reasonable, but are there trade-offs?


texts: How to control ESC (electronic speed controlling) using a micro controller.?

texts: I found on internet in some articles that only customized ESC's for brush less motors can be controlled with a micro controller not ESC's (ESC's for brush-less motors) that available in market. is that true? or there is no restrict of controlling a brush less motor speed using a micro controller with a ESC which available in market?


texts: Leveraging DC series circuit to power higher voltage LED panel

texts:
I have a IKEA RGB Dioder set where each channel requires 12Vdc (& 1.25W), I want to connect this to my Phidget LED 64 Advanced.

Each channel on the Phidget can provide a maximum of 5Vdc with 80mA, from what I understand I need a resistor in the series to connect three 3 channels to provide sufficient voltage for one LED panel? What type of resistor will I need?

EDIT:  I'm currently using what @clabacchio suggested where 7.5Vdc is provided by one transformer and the Phidget bumps up the rest. Only the Red LED cannot achieve perfect on/off switching but I should be able to mitigate this via stepping down all Red LEDs


texts:
The circuit DC to DC converter, using 555 to control the Vout, but my circuit waveform is not stable.
How can I fix this problem.

Waveform of Vout.


texts:
I am writing a manufacturing specification for our contract manufacturing.

So far, the smallest component on our PCB is a 0402 resistor, however, I would like to specify a process that will be capable of handling our future requirements.

A design requirement we have is the reduction of the PCB layout size.  As such it might be better to go to 0201 resistors in the revision.

Does anyone know the differences between 0402 and 0201 footprint resistors?  Is it purely power and price or are there other things worth considering?

edit: interesting frequency response relation documented here: http://www.vishay.com/docs/60107/freqresp.pdf
"reduction in parasitic impedance for smaller cases sizes"


texts: can I use a Miller Solar engine for RF applications?

texts:
I'm thinking of using a Miller Solar Engine to power a Arduino clone with a RF transmitter.  i.e., solar panel + super capacitor  + low-power Arduino + RF95W.

However, I read that MSE's are ground-switching solar engines, and I'm not sure what that means.  Would this be suitable for RF applications?

This is the part of the documentation that concerns me:

  One thing to note is that the MSE1/MVSE is a “ground switching” solarengine. That is, it acts by turning on/off the
  ground line to the circuit it’s driving. It shouldn’t prove to be a problem with most circuits, but it may be worth
  remembering while troubleshooting.

Could I use a LTC3225 supercap charger instead?


texts:
I have an LED Flash which I want to trigger on and off just before and after my camera captures an image for a Machine Vision application. Any ideas on what circuit set-up I can use for doing this?
The Flash uses a 7.4V, 2200mAh 16.3Wh Li-ion battery. This is a link for the Flash I intend on using: https://www.amazon.in/Digitek-LED-D204-Professional-Battery-Charger/dp/B01A5ZS98O/ref=pd_cp_147_2?_encoding=UTF8&psc=1&refRID=Y64HXVVGE3093911NP92


texts: Increasing the Voltage Output of a Solar Cell

texts:
I'm working on a project where I'm going to charge a battery using a solar cell. The cell is capable of outputting a maximum of 4 A, but only 0.5 volts (2W).

My question is, how can I charge the battery with only one cell? I understand I'll have to step up the voltage in some way, but I'm not sure how. I read that I can use boost converters, but don't these need a steady voltage for them to work properly? The solar cell probably won't be outputting its max voltage output all the time.

Ideally, I can regulate the voltage output of the cell to something like 2.4 volts (a single battery is rated at 1.2 volts).


texts: Will current pass without any resistance?

texts: I've learned that a resistor converts some electrical energy into heat energy while the current flows through it and thus causes a power loss, but what if there's not any resistance in a circuit. Will current still flow?


texts: How to Power a Controller and Motor Driver off same 24V source

texts:
I am trying to find the optimum electrical design for my project.

The project is a remote control vehicle that is moved by 2 DC motors, controlled by an arduino MC and powered by 2 X 12V 4Ah batteries.

Motor 1: 24V, 200watt, rated current- 14A. Motor 2: 24V, 10watt, 1A

To control the speed of each motor I bought a Dual DC driver module.
http://www.ebay.com/itm/3V-36V-Dual-Motor-Driver-Board-Module-H-bridge-DC-MOSFET-IRF3205-15A-Peak-30A-/171205708868?hash=item27dca7cc44:g:JKEAAOSwR0JURgQC

For testing I have been running the motor driver and arduino off separate sources. But the vehicle needs to run everything off the 2x12V batteries.

I know I need to drop the Voltage down for the arduino, but I don't know the best way to do it. I don't want to be wasting power, as the vehicle needs to travel a specified distance therefore power efficiency is important.

Note: I thought maybe to tap off from one of the batteries so that I am only dropping from 12V, more research stated this will cause unequal battery power and is not a good option. Is this correct?

Any suggestions are greatly appreciated. I am unsure of noise and filtering so any insight here would be much appreciated too.


texts: What is the input - output voltage relationship of an LM317 voltage regulator circuit?

texts:
I'm looking to create the simple adjustable voltage regulator below

However, I am confused by the input-output voltage relationship. Looking at the LM317 data sheet (https://www.onsemi.com/pub/Collateral/LM317-D.PDF, pages 1,2 and 7 in particular), the Vref (the voltage across resistor R1) is specified as being a constant 1.25V.

Page 2 under characteristics of Vref states
"Reference Voltage, 3.0 V ≤ VI−VO ≤ 40 V ... "

What is the input-output relationship in the LM317?
Can Vin be any voltage as long as Vout is between 1.25 - 37V but the
difference between Vin and Vout (Vin - Vout) cannot be greater than
40V or less than 3V?
is Vin - 3 the maximum allowed Vout?


texts: How does register type modifier work on different CPU architectures?

texts:
This question is to clarify my doubt against this register storage class.

when a variable is register qualified ,compiler puts the variable in a cpu register other than RAM for ease of access. so there are  registers available on a CPU for general purpose (allows user to use it freely)? ( I'm not going to ask does it mean any SFR (i don't like to change the meaning of SFR )
On a PIC MCU(maybe applicable to base line only) SFRs and general purpose registers (which is the only RAM I believe) exist together. Here I cant think of any optimization with a 'register' or there is ?

Could someone explain how does it achieve the optimization in terms of speed (of access) on other architectures?

Or the above questions all out of many misconceptions?


texts: What type of relay is proper to use for this motor driver application?

texts:
Regarding my previous question diagram, I now want to size a solid-state relay(safety relay) for the driver of a servo motor as illustrated below:

Relay will activate when there is fault.

But since the load is inductive in this case i.e the load is a motor; Im worried if I use a electromagnetic relay or a random fire SSR there may occur inductive spikes during relay action(?). Is it better to use a relay with zero-crossing relay for this kind of application?


texts:
I have some interrupt let's say from UART to make a real example:

void USART2_IRQHandler(void)
{
    int i = 0;
    if(USART_GetITStatus(USART2, USART_IT_RXNE) != RESET)
    {
        static uint8_t cnt = 0;
        char t = USART_ReceiveData(USART2);
        if((t!='!')&&(cnt < MAX_STRLEN))
        {
            received_string[cnt] = t;
            cnt++;
        }
        else
        {
            cnt = 0;
            if(strncmp(received_string,"connection",10) == 0)
            {
                USART2_SendText("connection ok");
            }
            else if(strncmp(received_string,"sine",4) == 0)
            {
                DAC_DeInit();
                DAC_Ch2SineWaveConfig();
                USART2_SendText("generating sine");
            }
            else
            {
                USART2_SendText("unknown commmand: ");
                USART2_SendText(received_string);
            }
            for (i = 0; i <= MAX_STRLEN+1; i++)         // flush buffer
                received_string[i] = '\0';
        }
    }
}

But interrupt code should run as fast as possible. And here we have some time consuming functions inside.

The question is: What is the correct way to implement interrupts which call time consuming functions?

One of my ideas is to create flags buffer and flags in interrupt. And process flag buffer in main loop calling appropriate functions. Is it correct?


texts: Charging a big capacitor from a weak power supply

texts:
Let's say I need to charge a 4m7 (4700uF) capacitor to 5V, from a 1.5V battery with an internal resistance of 100 ohms. I'm trying to use a typical transformer joule thief with something like soft-start, to reduce the initial capacitor current.

I found a problem with unstable capacitor voltage, changing in different periods (about 10s). Sometimes the voltage drops to 2 volts, sometimes it rises to 3V.

Where is the problem? I can't find it.

Edit:

To make it clear, Q1 makes a pulsed voltage, after D1 is high voltage DC which start to charge C1 via R3. When voltage on cathode of D1 is higher then 2.1V Q2 opens and charge C1 directly.
I add a R3 to limit initial charging current to prevent attenuation of oscilation because of high load.

After connecting of power supply it starts nice and I measure on C1 3.6V. After few seconds it slowly and continuously falls to 1.5V or 2V, then rise to 3V again.


texts: Alternative to emitter-follower for simple BJT voltage regulator

texts:
I want to make a voltage regulator from one or two BJTs and a zener diode. However, I would like to be able to make full use of supply voltages when they are lower than the voltage that the regulator would otherwise supply. Perhaps a circuit with a transistor that would saturate. The problem with the circuit below is the 0.7v drop of the transistor, plus the additional drop required across R1. Please could someone recommend a circuit?

simulate this circuit – Schematic created using CircuitLab


texts: How do you use an oscilloscope to detect radio waves intercepted by a transistor radio?

texts:
I'm planning to conduct an experiment involving electromagnetic waves (specifically radio waves) and the resistance imposed on them by different materials. It is my understanding that in order to do so, I should connect the transistor radio picking up the radio waves to an oscilloscope in order to measure the signal strength. However, I'm not sure how I would do this.

Though, I may be going about this all wrong, so any additional information would be greatly appreciated.


texts: Based on the design of stepper motors, having no exposed electrical parts, is it then conceivable that they will work submerged in water or other fluids?


texts:
It is fairly simple to make an old USB 2.0 device USB-C compatible. This is quite well known and can be seen "in the wild" as well for instance here. In the Universal Serial Bus Type-C Cable and Connector Specification under 3.5.2 we can catch a hint, that this little trick works for USB 2.0 hosts as well (observing the correct CC signaling with 56 k).
However, for an old USB 3.1 Gen. 1 (USB 3.0) host I have not found much information. All the USB 3 cable assemblies in the standard assume an USB-C host. I would like to make this host USB-C ready in a simple way with an adapter, but as I see it without additional active devices I would have to sacrifice the Super Speed and fall back to High Speed, right? Below the mapping USB-C to USB-A 3.1 (Rp signaling on CC1 and CC2 is omitted) is displayed and I am confident that I can get High Speed out of this.
USB-C           USB 3.0 / 3.1 Gen. 1

VBUS          > VBUS
D1-, D2-      > D-
D1+, D2+      > D+
Shell > Braid > Shell
GND           > GND

But could I simply connect one Super Speed pair like
USB-C           USB 3.0 / 3.1 Gen. 1

SSRX1-        > StdA_SSRX-
SSRX1+        > StdA_SSRX+
SSTX1-        > StdA_SSTX-
SSTX1+        > StdA_SSTX+

and the smart thumbdrives will figure it out while the stupid ones won't?


texts: Multiplexing buttons using shift register - high impedance output

texts:
I have experience with 74HC4094, and I believe the 74HC595 is essentially the same - the datasheet says they have "tristate output", but that is only when OE is low - then all pins are tristate.

What I'd want is that high would be high, and low would put the output pin in high impedance mode (aka tristate). It is intended for multiplexing buttons, in order to save IO pins on the micro.

How to achieve this, best?

Is there some other chip with this functionality - or maybe, how can I do it myself?
I thought of adding diodes to the output, but it'll probably not work good, because of the voltage drop.
Maybe there's some other solution, like chip specifically meant for multiplexing buttons?

With the diodes, it'd be something like:

--u--+           +-------------//--+
     |---data-->-|                 |->- to next shift reg.
  uc |--clock-->-|  shift register |->-
     |--store-->-|                 |->-
     |           +-------------//--+
     |             |    |    |
     |             V    V    V diodes
     |             |    |    |
     |              |-   |-   |-   buttons
     |             |    |    |
     |-<--sense----o----o----o---
-----+

I'd just send 1 to data, and then zeros, moving the 1 through all my buttons. The "sense" wire would have pull-down (or pull-up if the diodes were reversed).


texts: Help me identify this IC marked "CI" next to the LiPo battery. (It's not the charger IC)

texts:
The IC (descriptor U5) with its peripheral resistors (R55, R84, R59) is right next to the battery connector, on the path prior to connecting to the battery charger IC (which is the ISL9230). The IC is marked "CI" and it is a SOT563-6 package (1.6mm x 1.6mm x 0.6mm). The schematic of the circuitry around the IC, as well as an educated guess about the internals of the IC are drawn below.

The circuit is from a wireless mouse that charges with a USB connector. I've seen designs that use one or two PMOS's and a zener diode for reverse polarity protection and I've also used dual channel mosfets in the past that come into a SOT-563 package. So my current guess is that the "CI" marked IC is a P-channel, N-channel MOSFET that is connectd like in the drawn schematic.
By probing the body diode of the NMOS at the bottom I read 0.7V forward bias from S2 to D2. Also, when the USB cable is connected, G2 is pulled high and VD2 (pin 3) is equal to VS2, which is ground. So I'm convinced that this is the NMOS.
As for the PMOS above, I also measure around 0.8V forward voltage across VD1 (pin 6) and VS1 (pin 1), so I assume this is the PMOS.
I am pretty sure the function of this IC is to isolate the battery from the rest of the system when the SW is off and the USB is disconnected.
The problem is:

I've searched all of the P&N channel MOSFETS in this packeage from the digikey abd mouser library and none of them are market "CI". SI1024x-T1 from Vishay has a "C" marking but it's a dual N-channel MOSFET.

All, literally all the N &P channel MOSFETS I've searched have the NMOS at the top (pins 1,2,6) and the PMOS at the bottom (pins 3,4,5), which is complementary to the internal circuitry I've drawn for the IC.

So my question is if the internal circuitry I've drawn is correct or is this a different type of IC than I initially thought.
Ideally, I am looking for the part number of this specific IC marked with "CI". But I will also accept any answer that explains what type of IC that would be (dual NMOS/dual PMOS/NMOS&PMOS etc) and what its purpose is.


texts:
I am in the process of designing an ECG circuit to detect heartbeat abnormalities. I have two question regarding the AD8220 datasheet:

What is the function of the 2.2pF, 10pF capacitor, 10k, 15k resistors, and the diodes prior to the AD8220?
What is the function of the capacitor on the OP2177 right leg drive circuit?


texts: 9v Power for Digitial Circuit -- Parallel or Series Voltage Regulator Split

texts:
I'm building a simple project that consists of a 9v LED, a 5v Gas Sensor and a 3.3v micro controller.  All the devices have low current draw, so I'm not really worried about hooking them up in parallel.

I was thinking that the 9v LED could be directly connected to a battery.  In parallel with that I would like a 5v and 3.3v voltage regulator, where both of the voltage regulators would power the other two components.

I've looked at this thread:
Power Supply Design - Multiple Voltage Regulators but got some mixed signals regarding hooking up the voltage regulators in parallel or series, and was wondering if anyone could give me a definitive answer on best practice? Additionally, I've seen some articles that encourage bypass capacitors to help smooth out the DC signal, because I'm connecting directly to a battery I can ignore that, correct?

The LED is a MegaBrite (https://www.sparkfun.com/products/10236)

The gas sensor is a MQ-3 (https://www.sparkfun.com/products/8880)

and the microcontroller is an MSP430 (breadboard/launchpad version)

simulate this circuit – Schematic created using CircuitLab

Thanks for your help!


texts: Change in PLL settling time as a result of halving charge pump current/doubling loop filter capacitor

texts:
I have a PLL that is operating unstably at some temperatures.  I have been able to show that reducing the charge pump current from 128uA to 64uA ensures that the PLL will operate stably at the same temperature point where it would otherwise be unable to lock.

Rather than have a software based solution I would like to achieve the same result (a locking PLL across my temperature range) by changing the loop filter components.

----+----+----
    |    |
Cs ---  --- Cp
   ---  ---
    |    |
 Rs \    |
    /    |
    \    |
    |    |
----+----+--- Please excuse the diagram, not access to imgur.

Since halving the charge pump current was sufficient to stabilize my loop would doubling the loop filter capacitance Cp (shown above) provide the same result.  Currently my component values are Cs = 3300pF, Rs = 6.81kOhm, and Cp = 33pF.

$$
\Delta V_1 = \Delta V_2 = \Delta V,
$$
$$
i_1 = 2i_2,
$$
If the period of time where the charge pump is conducting (phase difference) is fixed then
$$
Q_1=2Q_2,
$$
$$
\Delta V = \Delta Q/C
$$
As a result the doubling of the value of C with the same charge pump current is effectively the same as halving the charge pump current and leaving C fixed.

I realize that this will change the loop filter bandwidth as well as impact the settling time.  Is there a way of getting a rough estimate of how this will impact the settling time?    I was hoping to get an answer as a delta from the existing implementation (e.g. the settling time will double.)  What other impacts might such a change have to the PLL's behaviour?


texts: Super capacitor directly on the power supply

texts:
simulate this circuit – Schematic created using CircuitLab

I have an atiny with an RF emitter which would detect the 220V AC off in the circuit and send a radio signal.

to do this I use 2 super capacitor (1.5F 2.7v each ) to send the signal before dying. I've done some tests and putting the two super capacitor in series in my 5V power supply and it is working. But It seems that super capacitor have special design with charging and discharging.

can I use them like this or it is more complicated?

Thank you


texts: Amplification of load cell signal with AD623 IC

texts:
I am trying to amplify the signal from a load cell using an AD623 instrumentation amplifier.

(source: instructables.com)
Please refer to https://www.instructables.com/answers/Amplifying-load-cell-signal-with-AD623-problem/
for the schematic. The common mode voltage is 4.5 Volts.
1K resistor is supposed to give 100x amplification. It is instead giving me around 50. My differential voltage is 0.8mV while my output is 42mV (52.5 gain). Note that I have placed the capacitors (0.1 uF and 10 uF from Vs to ground) but are not shown in figure. What might be going on? Is there a chance the AD623 is ruined? I don't think I'm doing anything wrong here, plus I've read a lot of blogs and haven't figured it out yet. Note that when I double the differential voltage, the amplification remains around 50. And when I change the resistor to 200ohms (500x multiplication according to datasheet), I get around 250x multiplication which is also half. So amplification is quite accurate, but half of what is said in datasheet.


texts:
New here, noob about electronics. I am in a bit of concern, I caused the minus and plus to touch on the source that powers my amplifier with two channels (TDA2040 transistors). After that short, one of the channels sounds less loud than the other. Though in the specs is mentioned that these transistors have a built in short circuit protection.
Could it be damaged?
And if I may need to change one of them, could I better change them both with TDA2050, on the same board without changing other components there?
And a third question, I'm trying to make sure if I did well putting a diode on the 'minus' coming from the power source to the amp so the current to flow from the minus away, but not towards the amp. It is a voltage marge to affect that diode, at a 18V power supply? Did it impede the proper tension to fill into the whole circuit beyond the diode's limitation (I don't know exactly how a diode function, I know that a LED has a voltage limitation that's why I presume any diode must have one)?
Thanks a lot for any suggestions/explanations. Good day.

Does anybody know what is the difference between TDA2040, and TDA2040A? Thanks.


texts: How to determine approximate type of SMD Ferrite Chip

texts:
I am reverse-engineering a device so that I can develop my own, compatible device.  There are a number of SMD Ferrite Chips (size 0603) inside.

A quick look at Digikey shows that there are almost 600 different size 0603 Ferrite Chips in stock and active.

I'm looking for guidance on how I can characterize the original parts and come up with a suitable alternative.  Measuring the DC resistance is easy.  But I'm not sure about the rest.

What approach might allow me to choose a suitable device?

[Edit]

This is for an interface to a digital walkie-talkie.  UHF band:  400 - 470 MHz.  Speaker & Mic connections are my main concern.

My first thought (after I posted my question) is to use a cheapie spectrum analyzer and signal generator and spot-check attenuation using the 50 Ohm input impedance of the spectrum analyzer.

I'm not sure what else I should be looking for..


texts: Is there anyway to fit a breadboard into a 1.5 inch wide space?

texts:
I am working on a model rocket and want to add electrical parts to it via a breadboard inside.
The space I have to work with is only about 40mm wide.
Is there any kind of breadboard that can fit in this space or any way to modify a breadboard to fit in this space?


texts: Building NXP QN9020 firmware on GNU/Linux?

texts:
I just inherited a project that is based on the NXP SDK samples, (not quite sure which one). It is currently being built with µVision 4; but I would like to convert the build system to use avr-gcc or similar.

Code Excerpts

This is the first few lines of one of the .uvopt files.

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<ProjectOpt xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="project_opt.xsd">

  <SchemaVersion>1.0</SchemaVersion>

  ### uVision Project, (C) Keil Software

This is the first few lines of one of the .uvproj files.

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<Project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="project_proj.xsd">

  <SchemaVersion>1.1</SchemaVersion>

  ### uVision Project, (C) Keil Software

This is the first few lines of one of the .scvd files.

<?xml version="1.0" encoding="utf-8"?>

<component_viewer schemaVersion="0.1" xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" xs:noNamespaceSchemaLocation="Component_Viewer.xsd">

This is part of a comment block in of one of the source files.

 * Copyright(C) 2015 NXP Semiconductors N.V.
 * All rights reserved.
 *
 * $Rev: 1.0 $

Research

Keil forums:

GENERAL: IS THE LINUX OPERATING SYSTEM SUPPORTED?

NXP Product page:

QN902X: Ultra low power Bluetooth LE system-on-chip solution

Other similar questions:

Move embedded programming from Keil to Linux


texts: Problem with microphone powering up a comparator circuit

texts:
The circuit below is supposed to turn on a LED when the microphone input reaches these levels:

1V, 3V, 5V, 7V.

What this circuit does in real life is when we turn on the power, all 4 LEDs light up.

When we remove the mic amplifier, it doesn't power up the LEDs since it only produces mV.

When we changed the amplifier gain, it lights up 2-3 LEDs but speaking to the microphone doesn't turn on the remainng LEDs.

Our instructor suggested that the impedance of the microphone and our circuit does not match. Is that the reason or can any other fix be done?

The OP-Amps inside the indigo box is part of a LM324 IC while the outside Op-Amp is a 741 IC.