texts: What effect does resistance have on a diode's characteristics? (regarding IV curves)

texts:
I can't seem to find much information online regarding resistance values and diode behaviour.

Am I right in saying that the IV curve of a diode is independent of any external resistance? For example say you set up a standard Si-diode and a 100Ohm resistor in series and plot the IV curve. Would you expect the same IV curve if you repeated the test using a 1kOhm resistor in place of the 100Ohm?


texts: STM32 Protection Diodes and Voltage over VDD

texts:
I have a 3 color LED that I'm controlling from an STM32. VDD for my mcu is controlled by a switching regulator set to 3.0v . Unfortunately the forward drop on the  the green led is 3.2 volts. This forces me to source current from the battery attached to my board ( 3.8v lipo). So the anode of each led is connected to the battery, and each cathode is connected to a resistor and then an io pin of my SMT32.

If  you cruse the SMT32F* reference manuals you'll find out that each IO pin has a set of protection diodes attached (see below). The problem is when I shutdown the Switching regulator it effectively ties vdd to ground. So we have a path from the battery through each of the leds through a resistor finally though the protection diode to vdd which is tied to ground. I need to turn off the switching regulator to conserve battery power.

My question is does anybody know the forward drop on these protection diodes? If its high enough then i don't have to worry about current flowing through the leds and protection diodes to ground. If it isn't I'm assuming I'll have to put a between the mcu and the regulator unless somebody else has a clever soltuion to this problem.


texts: Pull Up Resistor Value for temperature sensor

texts: I read that there needs to be a pull-up resistance for dht22 when connected to arduino. When dht22 is close, arduino's internal resistor value is enough, we have to add external resistor. I want to know the exact relation that for X-meters, you should add an external resistor. Can anyone give some info about this?


texts: Why does the ATTiny84 have both an analog comparator and an ADC?

texts:
I have been reading through the datasheet for the ATTiny84A, and noticed that it has both an analog comparator and the ability to use its ADC in unipolar or bipolar differential mode. From what I can tell, the main difference is that the comparator is faster, but it can only tell whether signals differ.

Are there any other benefits the comparator has over the ADC?
Are there situations in which one would be more accurate than the other? Will the either the comparator of ADC be more sensitive to small differences in input?
One use case mentioned for the bipolar differential mode of the ADC was to determine the polarity of a signal. Wouldn't the comparator be better suited for this?


texts: What Dupont wires fit into pin machine headers?

texts:
I currently only have machine pin headers lying around.

However, none of my Dupont wires fit into them.

What sort of pre-made wire fit into these, and what are they named?


texts: How can I create a female jumper wire connector

texts: How can I create the female side of wires like these to fit 2.54mm spaced headers? What would the part inside the enclosure be and what is the name of the enclosure? I'm struggling to find them on UK suppliers' websites.


texts: RF Design / Calculations - 433.92MHz, PCB antenna, values of capacitors

texts:
I'm doing a RF remote control project using a PCB with microcontroller and with simple onboard antenna layout as transmitter and a 433.92MHz receiver RWS-371F-6 model. Here is the datasheet of the receiver: https://www.es.co.th/Schemetic/PDF/RWS-371F-6.PDF

I don't have knowledge about RF design, just electronics and MCU programming. I'm using manchester encoding/decoding @ 1000bps to improve the communication distance from receptor board to the transmitter. 'RF-TX' is a 0V~5V signal.
The circuit of RF was copied from a board of a garage door opener, but I included my own microcontroller to the PCB schematic and I have a prototype of my board. The values of resistors (150 Ohms, 47K, 47 Ohms) was also copied from the garage opener transmitter board. Here I am showing the layout of my board and the values/part number of the components. I've mounted few pF combination values (0805) for C2/C3. I have a capacitor sample book with many values on pF range, many values from 1 to 22pF. The communication TX/RX is working correctly, but I want to check if I can increase the distance range by using ADEQUATE VALUES FOR C2/C3. Currently I'm using both as 1pF.

At the receptor, I'm using coil loaded antenna with 1/4 of wavelength, the same of the picture, tomorrow I will try a straight rigid wire of 1/2 of wavelength.

Well, as said, my doubt is around the correct values of C2/C3, can somebody who understand of RF desing calculate them easily? Or does this generate a kind of service I have to contract a RF designer to calculate them to me?

Regards.


texts: Mesh-Analysis, Ohm's Law & Passive Sign Convention

texts:
I am using Fundaments of Electric Circuits 5ed and I have a few questions about Passive Sign Convention with respect to Ohm's Law & PSC

FYI passive sign current (PSC) is based on this diagram: https://en.wikipedia.org/wiki/Passive_sign_convention#/media/File:Passive_sign_convention.svg

On page 40, it states: to find the voltage of the circuit (i.e. V1 and V2):

simulate this circuit – Schematic created using CircuitLab

I get what to do above, however, once I get to page 83 for mesh analysis, ohm's law somehow changes and PSC is no longer used (I think):

simulate this circuit

So my question is:   why did we change from ±i in  ohm's law (page 40) to V_higher - V_lower (page 83) in ohm's law?


texts: What's wrong with this circuit built on opamps?

texts:
I have built this circuit in the LTSpice, but it refuses to simulate the operation using normal solver, but shows great results using alternate. This source says

  Be suspicious of circuits that need something like the alternate solver or cshunt. To me, it means something in the circuit is poorly behaved; in other words, there is something in a model that is not realistic.

What is not correct with this circuit?

Alternate solver:

Further playing with the circuit cutting the fat from it I figured out that this simpler circuit also can not be solved by normal solver, not drawing output graph at all in version XVII, and saying "timestep too small" in earlier version:

But if I remove R2 normal solver performs job well, and output graph is drawn and as of expected shape.

I used pulse voltage source as an input to the circuit; in real life it will be a MOSFET transistor, and resistors of 150+430 are required to have it functioning properly. As I do not know the exact circuit built on the MOSFET (it is inside the chip), I have difficulties reconstructing it for simuation.

Opamp I used is 70p input bias current to minimally alter the input voltages. I used AD8062 before, but it has relatively high bias voltage and current and it affected the source and thus end result.

I know that simulators are not perfect, but want to know your opinion if there's any obvious mistake I have made in the circuit.


texts: Why isn't this astable multivibrator oscillating?

texts:
This is the schematic for a modified astable multivibrator I've built. I incorporated the diodes in order to get a sharper rise time, and therefore produce actual square waves.

Principle of Operation (As I Understand It):

One transistor will turn on first due to minute differences in the gain of the transistor. Assume Q1 turns on first.

1) Q1 Turns on.
2) The left side of C1 is at .7V. The right side of C1 is at 0V.
3) C1 charges through R3 at \$T = R_3C_1\$.
4) When C1's right plate achieves .7V Q2 turns on. Because Q2 was previously off, the right side of C2 was at rail voltage during the previous state. Since the right plate has dropped 5V the left plate also 5V. The negative voltage at C2's left plate is coupled to Q1 holding it off.
5) R4 charges C2 from negative rail voltage to +.7V at which point the states switch and the process repeats.

Unfortunately, this oscillator is producing a standard voltage. This is confirmed by a simulation.

What's the problem? What are the errors in my thinking?

EDIT

See related question here.


texts: How do they get good primary-secondary isolation on concentric windings?

texts:
I've seen plenty of transformers physically constructed with both (or all, if more than two) windings wound concentrically around the center of an E-core--in fact, that seems to be the most common type of transformer out there. And yet, the only thing separating the primary from the secondary in this case is a thin layer of plastic--I've even seen some in which the inter-winding plastic was actually torn through in places (presumably because it was wound too tightly). And these transformers are ubiquitous in chargers and cheap power supplies, where the primary would be 120/240V mains!

So my question is, how on earth can you have good isolation between the windings in this situation? Magnet wire is certainly not sufficiently well-insulated on its own, and I can't see how that super-thin plastic between the windings could possibly make it isolated enough to pass safety checks.

Or do they not pass safety checks, and that's why they're so cheap?


texts: What are situations to use an actual EEPROM over using emulated EEPROM in flash?

texts:
I am using stm32 which offers EEPROM emulation on its flash.

Given that an external EEPROM cost money, wouldn't using flash makes sense all the time? Currently, my use case is to store config settings and EEPROM emulation is good enough. What are some situations which justify using an external EEPROM?


texts: Help! Arduino `INPUT_PULLUP` not inverting

texts:
I have a situation where I tried setting pins on my Atmel Mega328P to INPUT_PULLUP. I was told to expect an inverted input: a +5V would result in LOW reading and a GND would result in HIGH reading. However, what I found is the exact opposite. I tried checking my +5V and GND with some LEDs and they are definitely +5V and GND.

Below is my arduino code; I know it's not very efficient, but that's besides my point. My IDE is Eclipse C++.

#include "Arduino.h"
int count = 0;
void setup() {
    Serial.begin(115200);
    pinMode(PIN2, INPUT);
    pinMode(PIN4, INPUT);
    pinMode(PIN5, INPUT_PULLUP);
    pinMode(PIN6, INPUT_PULLUP);
}

void loop() {
    byte i = 0;
    if(digitalRead(PIN2) == HIGH) i += 1;
    if(digitalRead(PIN4) == HIGH) i += 2;
    if(digitalRead(PIN5) == HIGH) i += 4;
    if(digitalRead(PIN6) == HIGH) i += 8;
    Serial.println(i, BIN);
    delay(1000);
}


texts:
Between my engineering classes and out-of-class projects, I'm always having to clear my breadboard every time I attempt a project. I would like to invest in some good, quality breadboards to conduct out-of-class projects on. Therefore, I have a couple questions I would like your expertise on.

I've always favored the more general layout, without the terminals that can be added to the breadboard. I don't always need these with little projects I'm doing, like Arduino projects. From what I've experienced, smaller boards that I can manipulate (move around) are always nice to have. Also, boards that are very long give me the option to utilize more components. From your expertise/experience, what type would you recommend for small projects, and would you lean more towards the longer or wider boards or towards the small ones?

I know it's dependent on the type of project; however, any suggestions/guidance is appreciated in understanding the ups and downs of each.


texts:
I'm trying to read a pushbutton press and turn a led in case its pressed. I have the following code. I have a 1k resistance with the LED and I'm connecting the push button directly to RD0. But the led is always on! If I disconnect vcc it kinda "works". What am I doing wrong?

#define _XTAL_FREQ 8000000

#pragma config FOSC = INTRC_CLKOUT, WDTE = OFF, PWRTE = ON
#pragma config MCLRE = ON, CP = OFF, CPD = OFF, BOREN = OFF
#pragma config IESO = ON, FCMEN = ON, LVP = OFF

#include <xc.h>
#include <pic16f887.h>

void main() {
    PORTD = 0;
    TRISD = 0;
    TRISD0 = 1;
    RD1 = 0;
    OSCCON = 0x70;

    while (1) {
        if (RD0) {
            RD1 = 1;
        } else {
            RD1 = 0;
        }
    }
}

simulate this circuit – Schematic created using CircuitLab


texts: Using a dual winding transformer to provide dual winding AC and DC of a single winding

texts:
Ok, this feels like a stupid question, but my google-fu is not with me today.
I have an application in which I have a need for both 12V DC (or thereabout) and 24V AC.
I have a transformer that has two windings of 12V each. In the schematic below I have one winding connected to pin 1 and 2 and one winding to pin 3 and 4 of J3.
The first winding (1,2) is connected to the bridge rectifier and provides the DC voltage.
Connector J7 is connected to J3 pin 1 and 4 and provides the 24V to some other part of the device.
The thing is, most examples on the internet I can find about dual winding transformers make the center tap a ground and use it to provide both positive and negative DC thru the rectifier, but I do not need a negative voltage rail. To mee it seems this should work to. But because my electronics knowledge is rusty and I cannot find an example of this, I'm doubting. Am I missing a ground connection or something other reason why this won't work?
I could of course just build it, but I am away from home and do not have acces to my parts bin. So I someone could just say yes or no (in case of no please do correct me.)


texts: Why is there no sine wave oscillator chip?

texts:
I'm trying to make a simple but good sine wave generator that will produce 1Vpp @ 1kHz.

Sine waves are nature's oscillations.  They're everywhere.  So you'd think that it would be a piece of cake to make an electronic sine wave.  Apparently not so.  SE is riddled with questions on how to make them.  There are currently 9 Similar Questions showing on the right hand side of this screen.  Most of them seem to have problems.

Low pass filters, high pass filters, ring oscillators and Wien bridges with exotic filament bulbs from 1960.  Digital to analogue converters and Arduinos.  Most don't seem to work or can't be made to oscillate in a simulation package.  Some produce triangles instead of sines.  Some designs require knowledge of inductors.

Why is this so hard?  Square, saw tooth and triangular waves seem to be easy, yet they don't readily exist in nature.  Since they are so useful, I would have thought that I'd just buy a sine oscillator chip (like a NE555 sine variant) , add a resistor and capacitor and off I go with a 99.99% pure wave.  Am I missing something, but it seems that simple electronics are not particularly compatible with sine wave generators?


texts: Why do we use a wide-band amplification in order to reproduce a sharp pulse without distortion?

texts:
I was reading some content with regards to the Fourier Transform and the uncertainty principle. In the book I was reading that

Due to the uncertainty principle, in electronics we use a wide-band amplification in order to reproduce a sharp pulse without distortion.

I do not understand the above sentence, so could someone explain why do we use a wide-band amplification in order to reproduce a sharp pulse without distortion and how is it related to the uncertainty principle of the Fourier Transform?


texts: Why not implement 1Gbps, when all I need is 20Mbps?

texts:
Background

I am working with a client on a large project which requires a custom networking chip to be designed to solve the data transfer requirements within the project. The network is intended to send small packets a few inches from one PCB to another over a single twisted pair cable. We will be designing and specifying the network protocol, and another company will be responsible for the silicon implementation.

I estimate that 20Mbps data rate between nodes will easily cope with the amount of data that needs to be sent, with plenty of head room should the amount of data increase in the future.

Problem

The client is asking me why I am specifying only 20Mbps. Why not something like 1Gbps?  Wouldn't that be better?  Intuitively, I feel that cranking up the data rate massively beyond what would be needed is a bad idea.  Initially, I thought that the cabling would need to be shielded (which I don't want), but looking at the Ethernet cable categories, I see that Gigabit Ethernet can run on Cat 6 cable, which doesn't need to be shielded.

Other Constraints

The project is desperately space constrained, and do we don't have room for things like magnetics, unless it's a very small component (0603 max).
The cables need to be as slim and flexible as possible.
The device will run from plug-in power, so there is no particular low-power requirement.

Question

What are the problems, in terms of silicon design, cabling, and anything else, that may be faced at 1Gbps, that wouldn't be nearly as bad at 20Mbps?  Should I go with my client's suggestion of implementing the network at 1Gbps, or should I insist on implementing only what is required?

We're under strict NDA, so I can't give too many details about our requirements. But please leave a comment if clarification is needed.


texts:
I'm trying to get this variation on the classic circuit to work. Pardon the awkward VCC label. The voltage is 4.5 volts, though these batteries are only supplying 4 at the moment. I have an LED and a 330 resistor on the output an an indicator.

The goal is to get the third transistor fully saturated to switch on and off as much current as it can safely handle while pushing a minimum of current through the oscillator to minimize its own drain, particularly through where it dumps straight to ground. This way, I could use this as a module to hook up arbitrary loads (within reason) to switch on and off.

No matter how I play around with various resistances and capacitor sizes, but the effect is always the same. The indicator is always just on. A few times, I would see it blink about two times and then go steady. Checking the math on how quickly it should oscillate given the values here, this shouldn't be a case of it going faster than the eye can perceive.

When I look up schematics where people have this circuit tapped for output, they usually take output from the same net as the capacitor's positive terminal. This seems strange to me and makes me worry that the design below is then somehow wrong.

What puzzles me is that just before bread-boarding this one up I did the same circuit, but without the boosting transistor, putting the output of both transistors each through an LED, using 3v supply, and some different resistor and capacitor values, and have something that works beautifully.

How should I go about debugging this and where could I have gone wrong?


texts:
I have a 17" laptop monitor with a 1920x1200 (WUXGA I beleive it's called? or just UXGA?) resolution which I simply love. Now, assuming the laptop dies before the monitor does, would anyone know if it would be possible to salvage the monitor? Are the interfaces somehow standardized (can I simply solder some cable to a DVI connector and plug it in, more or less) or do they all depend on make and model? I'm guessing the power supply will be the least of my problems..

In this particular case, it's a Dell Inspiron 9300.

Thanks.

Wasn't sure how to tag it, and 'new users can't create tags', so sorry about that. :)


texts: Tactics for Controlling Heat in a High Current Bridge Rectifier?

texts:
I'm having trouble controlling the heat from running a bridge rectifier (Similar to http://www.amazon.com/1200V-Single-Bridge-Rectifier--QL100A1200V/dp/B00EZ8BUMU/ref=sr_1_2?ie=UTF8&qid=1459556648&sr=8-2&keywords=100amp+bridge+rectifier) at high current for fast electrochemistry. The low voltage (9V) high current (40-50A) keeps heating up the bridge rapidly and will lead to thermal runaway if not managed by cutting the power by a switch. As my bridge rectifier comes with a large heat sink, similar to the one in the amazon link, I'd like to know some other options available for controlling the heat generated by the bridge to increase the time I can use it without cutting the power.

Options I know about:

Air Cooling (Essentially having a fan (the bridge is in a box I made out of medium density fiberboard, bolted) push air through the box through a few holes, cooling the bridge) (Uncertain about effectiveness given the intense heat buildup)

NOTE: The bridge is a full wave bridge rectifier. The bridge is mounted 90 degrees from how it would be sitting on a table and lies on the side of the box. (Which isn't necessarily the best for convection, but it will lie directly in the air current path of a fan)

Water Cooling:
All Options are by thermal conduction.

1)Indirectly: The mounting bolts stick out of the box by about 3", this leaves more than enough space to attach a great thermal conductor, such as aluminium flat bar (Looks like: https://www.google.com/search?q=aluminium+flat+bar&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj9l6CX3O7LAhXIlh4KHbaXCyYQ_AUICCgC), to the mounting bolts and having them in a container of cold water underneath. The idea here is that the aluminium will try to equalize the temperature of the bolts which are being heated by contact with the bridge and thus, cool the bridge as the bridge will spend heat energy trying to heat the bolt.

2)Directly: Immersing the bridge in water (I have no idea if this type of bridge is water tight, hypothetically it should be) a quarter way up to the base (which is rather high) (Done to ensure no shorts due to water), which seems reasonable. The water level can be maintained by putting it in a container with holes drilled at the 1/4 mark of the bridge and refreshed by a carefully placed supply hose.

3)All In: Total submersion in reasonably pure distilled water (might work, I'm not sure if the two AC nodes will be able to conduct all that well in relatively pure distilled water at 120V) (I'm aware of distilled water contamination)


texts: Increasing peak to peak voltage using 1:2 balun

texts:
I came across this post on TI E2E forum.

In this post user wants to drive LMK04832 PLL IC  clock inputs using a sine wave.
User has a source of sine wave with -1.53dBm or 0.528Vpkk which they will use to drive LMK clock inputs.

LMK04832 input clock level requirements are:

Now since user has 0.528vppk input signal so to increase the peak to peak
voltage they are planning to use 1:2 TC2-1TX+ balun and drive the LMK clock inputs differentially.

This balun has around 0.5dB insertion loss, so taking this into account, they have calculated that the voltage at differential(balanced) side will be 1.33 times of voltage at unbalance side.

So, peak to peak voltage at balanced side will be 1.33*0.528 = 0.7vppk.
They have assumed that LMK clock inputs are high impedance so they will not draw too much current.

But on the forum TI engineer said the following :

"Ideally, if the input to a 1:2 balun is X dBm, then the power on each of the differential output pin will be X-3 dBm. (We cannot get more energy from a passive device!)"

But I think a balun is a kind of transformer which idealy keeps the power level on input and output same and voltage/current changes accordingly.

So, my question is :

Can we increase the voltage using 1:2 balun and in doing so balun will keep the power level same at balance and unbalance side?


texts:
I am using DMA for ADC and UART on my project and ADC has higher priority than USART. The ADC handles joystick and the UART handles keyboard. The ADC has 2 byte buffer and the USART has one byte buffer.

While all data was streaming , I traced the USART buffer and I saw that when I moved joystick it affects UART buffer content. On the other hand, the UART buffer was not giving those values as an output in interrupt callback; It was working well. That means it was giving the correct value that came from keyboard.

When I traced buffer directly, the UART buffer changes whenever I move the joystick, yet the interrupt was returning the correct keyboard data.

Okay, I know only one DMA channel works at a time and priority defines this but I am still confused how this is happening. There must be something about DMA buffer which I can not explain.


texts:
I have read that if you don't unlug the charger from the socket after charging your phone, although it is not connected to the phone, it still consumes power and your electricity bill adds up.

On the other hand if I leave the charger plugged without the phone I assume the only power is reactive power and in residential buildings we don't get charged for reactive power.


texts: Voltage and current of a capacitor while discharging

texts:
What will be the values of voltage and current across the load at t = 0+ instant as soon as it is connected across a fully charged capacitor ?

Is voltage and current at t = 0+ instant independent of load resistance ?


texts:
We currently have a DC to DC converter (12V to 5V), but it seems that the V- of the input and output have a difference of around 1V. However, we need to have a single reference everywhere. Can I safely connect V- of input and output?

It's this one: https://www.meanwell.com/Upload/PDF/RSD-30/RSD-30-SPEC.PDF


texts: Microcontroller support strings or other libraries

texts: I heard some microcontrollers have a poor (or no) support for <string>s as a data type of C/C++ when programming. How to know if a microcontroller supports strings or other C/C++ libraries?


texts:
a friend of mine came to me with a question and I thought I'd ask you guys for some insight. They were wondering if it would be possible to speed up a regular wall clock so that it would cycle twice as fast as normal. It wouldn't need to be extremely accurate, but if it were accurate to within 10% (ie. one rotation of the second hand would be between 27 and 33 seconds) that would be nice. I think I have a basic idea of how regular quartz clocks work, but I'm really shaky on most of the details, so here were my two thoughts:

Inside a quartz clock, there will probably be a crystal soldered onto a PCB somewhere. If you could find a crystal with the same footprint and pinout that vibrates roughly twice as fast, popping off the old crystal and soldering the new one in would probably work. This would be really easy to do, but I see a few problems. For starters, finding a crystal that meets the listed requirements might be a challenge. Also, I'd imagine that at some point the crystal's vibration gets converted into a square wave. Since the conversion circuitry is based on vibrations, I'm guessing that this all happens within a single package, so you'd need to find a replacement which also has the same drive as the one you're replacing. If the conversion happens externally somehow, you'd still need to make sure that it will work properly with a crystal that's vibrating twice as fast and that its output is linear. I don't think this is the case though, because I'd imagine a "100kHz crystal oscillator" means a crystal with circuitry outputting a 100kHz square/sine wave rather than a crystal actually vibrating at 100kHz.
It might be possible to just yank out the entire crystal/oscillator and replace it with some external driver like a GPIO pin from a microcontroller. Assuming the oscillator's output is relatively slow (it looks like a common clock oscillator speed is 32kHz) and it's driving level isn't super different from a regular GPIO pin, you could just disconnect the oscillator entirely and solder a GPIO pin from something like an Arduino Micro to the pad where the oscillator used to be connected. Then you could drive the GPIO pin with the microcontroller's own oscillator/clock divider and just simulate a crystal. As far as I can tell, the main problem with this approach would be interfacing and making sure that the microcontroller's square wave roughly matches what the old oscillator was putting out

That's all I could really think of. I don't see any humongous, glaring oversights in either line of reasoning, but I thought I would ask you guys if I'm missing an obvious solution or if both of these are totally impossible. I plan on taking apart some analog clocks over the next few days and poking at them to see the characteristics of their oscillators, but I was hoping that somebody here would have a better idea than me of roughly how they work

Thanks


texts:
This is the circuit:

I've simulated it and got a current of 30.76mA at the voltage source (5V).
With this I've calculated the total resistance to be 162.5 Ohm.
Each resistors is 100 Ohms big.

But why is this the case?
My first (and only) intuition for the resistance was R_t = 100 + (100 || 200 || 200) = 150 Ohm


texts: MOSFET Drivers to decrease turn on/off times

texts:
Using MOSFET drivers, can one decrease the turn on/turn off time of MOSFETs than indicated in their datasheet.

If so, by how much? Is it in the scale of orders or just barely?


texts: Three wire parallel transmission line (TDR)

texts:
I have a three wire parallel transmission line with a length of around 1000m. The wires are really close to each other. I want to sample the response of the transmission line for two different pulse shapes.
Wire 1 will be used as the common ground.
In wire 2 a fast needle shaped pulse will be fed in with a pulsewidth of around 1µs.
In wire 3 a square wave pulse will be fed in with a pulsewidth of around 100µs.
When the signals are fed into the wires at the same time, how will the signals affect each other because of the shared ground?


texts: Honeywell Dead Reckoning Module GPS Problems

texts:
This was previously posted in the Stack Exchange forum and I was referred here.

I'm currently trying to connect a Honeywell DRM4000L to a GPS module. The DRM is a dead-reckoning device which takes a GPS input and outputs the location by serial. Currently, I have a GS407 GPS module connected to the DRM. Every time I try the GPS pass-through function on the DRM, I get gibberish output.

I also have an FTDI cable connected to the GPS and I'm getting the correct NMEA data. The data coming in from the GPS is all formatted correctly when connected directly to the computer. The DRM data is also coming in correctly, but it doesn't see an NMEA data stream and thus does not initialize with the GPS data. It only has track information based off of the inertial sensors (INS).

The GPS is set to 9600 baud and the DRM host port is set to 9600, so the DRM should be seeing all the correct GPS data. The baud rate from the DRM to the computer is also 9600.

Is anyone seeing anything that I'm not seeing? Thanks!


texts: How to interface a Blackberry Torch with a serial device?

texts:
I have a Blackberry Torch that needs to send 10 bytes per second to a serial device.  The serial device will probably be a basic stamp 2 or other microcontroller.  The Blackberry does not need to receive any data.

Is there an interface that will let me do this for less than $50?

Using the Wifi or Bluetooth connections are the obvious choices but those options look more expensive.

I also thought about using the headphone jack to send out different frequencies and an intermediate circuit could convert the sound into bytes, but I'm not sure where to start with that cicuit.

Thanks.


texts: op amp rail to rail voltage follower latching up

texts:
I have selected a TS922 op amp to use in a voltage follower configuration. The specs for the TS922 in summary are:

Rail-to-rail input and output
Low noise: 9 nV/√Hz
Low distortion
High output current: 80 mA (able to drive 32 Ω loads)
High-speed: 4 MHz, 1 V/μs
Operating from 2.7 to 12 V
Low input offset voltage: 900 μV max.
Latch-up immunity

The voltage follower configuration is

Supply voltage is 5 V.

To test I am using a simple 10k pot arrangement (range v supply to gnd) to apply a voltage to the input (pin 3) with a voltmeter measuring the output on pin 1.

My issue is that the TS922 output latches up to 4.7 V if the input voltage rises above 3.6 V. If the input voltage is less than  3.6 V the TS922 behaves as a voltage follower.

To try to identify why this is happening I have tried:

placing a light load (2k resistor) from pin 1 to ground - no effect
grounding the inputs to the other dual amp in case there was some interaction - no effect.

Is there something I am missing??  Otherwise I suspect the markings on this device don't match what is inside.

I would ALSO appreciate any advice on other op amps which are close to the TS922. The most important specs are:
- single supply 5 V.
- rail to rail input/output.
- high output current capability > 50 mA.

I know I can search for devices - but I am hoping someone has experience with a device that works well.

Thanks in advance


texts: Here is my circuit schematic below. PT4115 feeds LEDs. Load current is 200-215mA and switching frequency is 500kHZ. How do i calculate pi filter or what is the best values for pi filter in this design ?


texts: Rotary Sensor Potentiometer SP280X series

texts: I have a novatechnik rotary sensor potentiometer SP2801 100 002 001.Th datasheet shows that it has a maximum electrical angle of 100 degree.But I saw that we can move the pot in any direction any number of times.Then what does this maximum angle mean and how to locate it if it is there(the datasheet mentions the 0 degree and 100 degree angle).


texts: Motor current consumption and power do not match

texts:
I am working on a design and need to calculate the energy consumption of this motor:

https://www.maxonmotor.com/medias/sys_master/root/8825428410398/17-EN-256.pdf.
 (Part No. 339252)

The manufacturer's specifications states:

Nominal current (max. continuous current): 0.402 A and
Nominal voltage: 12 V.

Based on this, my understanding is that the power consumption of the motor should be 0.402 A x 12 V = 4.824 watt

However the manufacturer lists this motor as 1.5 W.

How is this adding up? Shouldn't this be a 4.8 W motor? Can you please help me understand how the current (0.402 A) and voltage (12 V) and power (1.5 W) are related? Is there anything else in that specification sheet that I am missing?


texts: Will external high electric field strength erase flash memory?

texts: Simple question - given that electric fields are used to program and erase flash memory will placing such a memory in an external high voltage gradient damage them, or damage the bit integrity? I am thinking of fields of around 1 MV/m


texts: Is a Switched Reluctance Motor (SRM) a AC motor or a DC motor?

texts:
Is the current in a coil of an SRM alternating or not? I understand that we are giving a DC supply (say battery) but isn't the current reversing its direction. If yes, then it would be called AC but is there a way/design to have unidirectional current (DC) and still be able to operate the motor as an SRM?
Simply put, how would one classify a Switched Reluctance Motor?


texts: Transistor logic to drive h-bridge with negative voltage source

texts:
Shown below is a H-Bridge circuit I have used to drive the cathode of a VFD display with a source voltage of +2.4V with a +3.3V digital logic level.

I have decided to switch the cathode source voltage to -2.4V from the +2.4V in order to increase efficiency elsewhere in the system. Obviously this presents problems with the simplicity of driving the H-Bridge, which is unfortunate because I'm terrible at figuring out transistor logic.

How would the H-bridge driver have to be adapted if the source cathode voltage was -2.4V, but the digital logic controlling it was still +3.3V?

Thanks.

EDIT:
The N-channel MOSFETS are BSS138. The P-channel are BSS84.
The 3.3V digital logic interface is connected directly to a PIC16F.


texts: Remove/exclude exposed pad of QFN package from PCB layout

texts:
I am doing a PCB layout with a Atmel/Microchip MCU ATSAML21E18B-MUT which has QFN-32 package 5x5mm. This board can have a maximum of 20x40mm and I am having problems with space because the circuit is not very little and also there is an NFC antenna on-board that occupies 14x14mm on both sides.

The drawing of "32 pin QFN" is on page 1123. The datasheet does not mention if this pad should or not be connected to GND or other signal.

Here is the link of the datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/SAML21_Family_Datasheet_DS60001477B.pdf

Check my current drawing of QFN-32 package on the current layout below, there is a 2.8x2.8mm square pad in the center, also known as exposed pad. I want to delete it... in order I can route tracks and vias below the QFN package. Doing this I would finish the layout easily.

And, when assembly the boards, place an electrical insulation material between the IC package and the board, to guarantee there will be no short-circuit between the center pad of the QFN-32 package and a via or track, for example, if the solder mask don't guarantee.

Then, in this case, can I securely remove the center pad of the QFN-32 from the PCB layout? Does somebody here already did this?

OBS1: It is a double-side board, there is no possibility to go multilayer.
OBS2: The IC does not heat.

The package:


texts: Difficulty in understanding charge controller for solar and wind energy

texts:
I am having difficulty in understanding one control box which is used to charge the battery using solar and wind energy as well as power the load at the same time. I have attached the picture below

I understand the part of the wind turbine but what I don't understand is the part where it shows the positive terminal of solar panel, battery and load should be connected together. How can this work? since the battery is charging (connected to solar panel) as well as discharging (connected to load) at the same time?

In my mind I was thinking the controller would be more like this the following,
, here you have separate connection point for each components which make sense to me but in my previous picture I don't understand. Can any one answer this for me.


texts: Will a vacuum tank shield against microwaves?

texts:
I am working on an experiment that involves 50-250W of microwave radiation.  The antenna will be inside a small vacuum chamber (~2ft Dia x 3ft long) with ~1.5" steel walls.  There are a handful of small (~4" Dia) plexiglass windows.
My question is this:
Is there a safety concern?
More specifically:
Will the tank shield the microwaves?
At what power do microwaves become dangerous?


texts:
In a video at Kickstarter a project called Tapcaps is mimicing human capacitance for triggering touches to a capacitive touch screen (the iPhone). At 0:45 in the video we can see a glimpse of the device. It kind of resembles an RFID tag.

Can anyone explain how this device works?


texts: Battery still drawing tiny current when fully charged

texts:
I have a device (a vaporizer) which contains a rechargeable battery. The battery only takes a couple of hours to recharge, but sometimes I end up leaving it charging overnight. I have monitored the current drawn by the device when charging, and to my mild annoyance it still draws about 0.02A even when fully charged.

I don't know how to stop this small current draw. I also don't know whether I need to worry about this (i.e. whether it's decreasing the battery life). I have two choices when leaving the device charging overnight -- I can either use the mains, or a portable USB battery (i.e. use a second battery to charge the device). My portable USB battery turns off automatically when current draw is zero -- however the current draw of 0.02A pulled by the device even when fully charged stops my USB battery from switching off.

Is there something which I can buy, which has a USB input and output (or a micro USB input and output) and which stops conducting electricity if less than about 0.05A is flowing through it? Or is there a USB battery which turns off when less than about 0.05A is being drawn from it?

Some more details -- I know very little about the rechargeable battery in the vaporizer. There is no mention of what battery type it is in the manual; it's a portable vaporizer, so its job is to heat something up to 200 degrees celsius and keep it at this temperature. The specs on the device are that it wants a 5V input to charge and max power input is 10W; the charger that came with the device is 2A so this checks out. I bought one of these:

https://www.amazon.co.uk/Muker-KCX17-Voltage-Multimeter-chargers-capacity/dp/B01BTRLVYQ

to monitor the current of the device whilst charging; it typically starts at 1.5A and then drops to around 0.02A when fully charged.

My main concern is that this constant drawing of a small amount of charge will degrade the battery in the device. A secondary concern is that leaving it to charge overnight represents a fire risk; most devices I have stop taking charge after some time and if I'm charging them with my USB battery then the battery switches off; this does not.

Am I fussing about nothing?


texts: Double Pulse For Each Incoming Pulse -> Double Stepping Stepper Motor Control

texts:
I used to have a 15 deg stepper motor; now I have a 7.5 deg stepper motor.

The ideal thing is to change the software to output the pulse control at double the rate to achieve the same rotation rate. But b/c I don't have the software source I can't easily change it.

To avoid this issue , I would like to create some HW that goes inline with the existing control output that will issue two pulses for each incoming pulse.

Delay based solutions for frequency doubling don't seem to be a good solution as their delay element would have to vary for each input frequency.

Is a PLL a good option? A small micro-controller? Any other suggestions?


texts: Selecting a transistor - Reading transistor datasheets

texts:
I am trying to select a transistor part and figure the actual current calculations in my circuit.

I have 30mA of collector (load current). This is the transistor I am choosing for my design : https://www.onsemi.com/pub/Collateral/MMBTA05LT1-D.PDF

MMBTA06

So, Once I have figured out the collector current through my transistor, I need to calculate my required base current.
But while calculating the required base current, how will I choose the Hfe value? In the datasheet it is given as 100 (For Ic=100mA and Vce=1.0V)

The graph in fig 5, gives Ic vs Hfe, but the Vce is 1.0V. And in fig 6, Ic vs Vce(sat), the gain is fixed as 10. How will I take values from this graph when the conditions are different from my application.

My actual Ic is just 30mA. How will I fix my gain now?

I am going to operate the transistor in linear region. It would really help me if one could tell me which graphs we need to consider in the transistor datasheet for my current calculations.

And I am calculating Min, typ and max current values for my circuit. So, I am considering -40,+25 and +85degC temperatures. Can someone help me with the calculations.

Please help.

Thanks.


texts: Miniature heater with more-or-less constant temperature. Need tip on element

texts:
I'm a software engineer with very basic knowledge of electronics.
I have a project in which I want to make a small (cylinder of length about 100-150mm and diameter 20-30mm), localized heater that stays at an absolute temperature of about 50-60ºC.

I researched beforehand, but I'm not sure I understand everything I've found.
Would a thermal cutoff work? I know I could also use a resistor, but doesn't the temperature produced vary depending on the ambient air temperature?

Basically, my question is how can I control the max temperature of the heating element with the smallest possible solution?


texts: what determines the correct values for bridge rectifiers?

texts: I want to fit led lighting in a model railway coach, how ever the + and - have to be correct for a led to work. If I use a bridge rectifier this will solve the problem. The track suplies 12 volts at 5amp for DC controlers and upto 20 volts at 5amps for DCC. Would a 1.5 amp 100 volts bridge rectifier be suitable for this job?


texts: Is a 115V rated transformer expected to accept US mains voltage (120V)?

texts:
< question completely reworded since people thought I was looking for appliance repair instructions >

Many "Power Transformers" are rated at 115V or 230V. It seems to be the most popular rating. See this list for an example:
http://www.digikey.com/product-search/en?pv1393=61&FV=fff4000c%2Cfff8012f&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

Here is a specific example:
http://www.tamuracorp.com/clientuploads/pdfs/engineeringdocs/3FD-3XX.pdf

However, mains voltage is 120V (per leg) in the US. I'm confused that these are all rated 5V BELOW the expected mains voltage.

Is it expected that these transformers are for use with mains inputs? If so, why is the rating 5V below the mains voltage? If not, why is the rating so close to the mains level?


texts: LED Driver Using Boost Converter, startup problem

texts:
I am trying to drive a led using a DC-DC boost converter.
The circuit worked at first, I ran the led for 2-3 hours without issue (a few days ago).

Today I flipped the switch to turn the led on and right when it turned on the light started flickering and smoke came from the boost converter. After closer inspection one of the mosfets had burned (see image):

The Boost converter is rated for 250Watt 10A (link: https://nl.aliexpress.com/item/32793038906.html?spm=a2g0s.9042311.0.0.27424c4dDRHkKW).

The led (100W , 30-34v, 3A forward current) is current limited (using one of the pots on the boost converter) to just under 3A and the led is running at approx 32v at this Amperage.
Therefore, P≈96Watt which the converter should easily handle.

link to LED:https://nl.aliexpress.com/item/32831596858.html?spm=a2g0s.9042311.0.0.27424c4do24sCZ
I have the 'white' version

I've read about 'LED inrush current' and think this might have caused the booster board to fail. Could this be the reason for the board failing or is it likely to have another cause?

If the issue is the inrush current how could i prevent/lower the current spike when turning on the led? would it help to start the led at a lower voltage using PWM (paired with arduino in my case) and increase the voltage slowly up to 32volt  to potentially lower the current spike/prevent the board from failing? Does anyone know how conventional LED drivers get around this problem?

Shematic of my circuit:

I am using a PWM IC to dim the led, here's a link to it: https://nl.aliexpress.com/item/32665973238.html?spm=a2g0s.9042311.0.0.27424c4dUxGjE5

If I am doing something wrong please tell me. Any input will be greatly appreciated. Thank you very much!


texts:
I need to find the Thévenin resistance and FEM of this circuit:

I am a little confused why my answer is wrong. I mean, we could just calculate the resistance equivalent and go on with the calculations, but i really want t know where is the error in my attempt here:
First, i calculated the current through the circuit. Of course nothing flows on the resistance 7 Ohms, so the circuit is just the above part. Using basic equation: \$80-6I-20-6I => 60 = 12I => I = 5 A\$, so that the EFM would be \$\epsilon = -20-6*5 = -50 V\$.
Now we need to calculate the current of the short circuit, where the resistor next to 20V is zero. \$80-20-6I_{sc}=0 => I_{sc}= 10 A\$. So technically, the equivalent resistance would be \$\epsilon=RI_{sc} => R = 5 Ohms\$. But this is wrong... Why?


texts: Power MOSFET blew up when increased duty cycle from 5% to 10%

texts:
First, these are the components I'm using on my PCB, click on them to see the datasheets:

U7: Infineon 1EDI60N12AF MOSFET Gate driver

Q6: Infineon IRF250P224 Power MOSFET

D5: Fairchild (ON Semiconductor) RURG5060 Freewheeling diode

U1: Infineon TLI4970-D050T4 Current Sensor

The schematic is attached below. Sorry if I'm not using some right symbols. I took the schematic from the PCB software.

Vbus voltage comes from rectified and filtered mains (110VAC).
PWM frequency is 10 kHz.

The gate driver is isolated, so GND1 is ground from the rectifier, and GND2 is the digital ground.

I tested the PCB with two different PMDC motors:

Motor 1:
130VDC
25.5A

Motor 2:
130VDC
27A

These are the steps that I followed before the transistor blew:

I tested the circuit with a light bulb first. Everything ok.
Removed the bulb, then I connected Motor 1 with no load. Everything ok.
Removed Motor 1, I connected motor 2 with a slight load. It started ok at 5% of duty cycle. Then, I increased duty cycle to 10% and the transistor blew up, so the motor went to max speed uncontrollably.

I haven't programmed the fast overcurrent detection from the current sensor. That way I would have probably saved the MOSFET.

The question is... what could be the cause of this? high dv/dt and di/dt? need an snubber?

Update: I've blown up a second MOSFET at startup of the motor. I've replaced the FET with this IGBT IKW50N60DTP and so far it's working well. Anyways, I will capture some waveforms soon.

Go to this link to see a piece of the PCB where the parts are located:
https://i.imgur.com/4UWVIGm.jpg


texts:
\$x(t)=e^{st}\$ is the input to the system. \$x(t)\$ is not going to present in this question anything else than the exponential \$e^{st}\$ where t is time and s is a complex valued parameter.
\$H(s)\$ is the transfer function of the system.
\$y(t)\$ is the output of the system
$$ y(t)=x(t)*h(t) = \int_{-\infty}^\infty h(\tau) x(t-\tau) d\tau = \int_{-\infty}^\infty h(\tau) e^{st}e^{-s\tau}d\tau $$
$$ y(t) = e^{st}\int_{-\infty}^\infty h(\tau) e^{-s\tau}d\tau = e^{st}\mathcal{L}\{h(\textbf{t})\} = x(\textbf{t})H(s).  $$
This is my derivation of the equation \$y(t)=H(s)x(t)\$. Is it correct?
if this derivation is correct, That means the overall response is \$H(s)x(t)\$. But according to my understanding, \$H(s)x(t)\$ only gives the forced response. The overall response should be calculated by inverse Laplace transform of \$H(s)X(s)\$. Where does this discrepancy come from? Thanks!
BTW, this is not derived by me,this derivation was done by Professor
Ali Hajimiri at time 4:09


texts: When does controlled impedance on a PCB matter?

texts:
Suppose I have a PCB that contains a microprocessor, or an FPGA (a "controller"). This "controller" drives a single-ended signal to an LVDS driver IC and a single-ended signal to a connector that goes out of the board. The output of the LVDS driver IC is then driven to the same connector that goes out of the board, as a differential pair.

If the board is specified as a board with controlled impedance, that is, 50ohms for single ended, and 100ohms for differential signals, does that specification only concern the signals going out of the board (single ended signal coming directly out of my controller and the output of the LVDS IC)? In other words, what significance does the characteristic impedance have for the signal that is not leaving my board (single ended signal going from the "controller" to the LVDS driver IC)?


texts: How to simulate the depression of a push button connected to an Arduino, with another Arduino?

texts:
I have an Arduino which uses several push buttons to simulate the keypad of a digital door lock. This microcontroller remembers the last four depressed buttons and turns a LED to green if the code is correct.

Now I would like to crack this lock with another Arduino which would send the De_Bruijn_sequence on the keypad  to brute force it open. (See 'Uses' paragraph on this page)

Which component do it need to simulate a depression of a push button on the first circuit ? How fast can it be done ?


texts: Why is the Exciting Current zero in an ideal transformer?

texts:
An ideal transformer having infinite permeability core is supposed to have zero exciting current.

An ideal transformer has infinite permeability core, which means that all the flux in the universe would want to settle inside the core, which in turn would mean that the core has an infinite flux. The relationship to exciting current is given by :-

Now given that PHI --> Infinite & mu --> Infinite, wouldn't the mathematical proof of the above equation to prove that Ie is zero be of the form :-

My question:

Most books use the flux to be finite to prove that exciting current is zero, but fail to tell as to why they are considering the flux to be finite  given that they started the concept by assuming an infinite permeability core meaning that the flux accommodated in the core would be infinite.
Is there any other proof for this mathematically, or is this the right one and I have got the concept wrong. If so where exactly?


texts: How to determine capacitor and inductor values for parallel tank circuit?

texts:
There is the formula \$\frac{1}{2 \pi\sqrt{LC}}\$, which can help find the value of the capacitor or the inductor if one of them is known.
But if them both unknown and i would like to make a parallel tank circuit that will resonate, for example, at 2400Mhz, how can I determine the value of both of them?

EDIT
In the attached graph,it can be noticed that the Q factor value at 2400MHz is higher with 2.2nH and 1nH(1nH is more significant) inductors than the 4.7nH one(also they have lower impendance).So,while they,also,in the practical range that you mentioned before(1nH-10nH)and a capacitor can be connected in parallel to them,What is the reason for choosing,actually,the 4.7nH one?


texts: I hope this question won't be closed as too subjective. I'd like to know best practice - how to make traces on universal PCB's with individual holes without traces (like the following image). My idea is to bend the ends of discrete components and use them to make traces to other components. Is this approach acceptable, or nasty? Although this is called "prototype" PCB, I'd like to use it for my simple final circuits (low frequency, low current applications), because I hope it will save time.


texts: Ground Plane Net Tie - Question about current design

texts:
I am doing net-tie method to separate two different Ground Planes (for noise mitigation purpose), one ground plane is for RF circuitry and MCU, the other ground plane is for power and motor switching. I wonder if this is a good way of laying out net-tie

Here is the preview of the circuit, the net tie is laid at the top right hand corner, far away from power source. It stay on the top layer and I use via to tie to the ground planes that are mostly at the bottom layer.

Here is the closer look at the net

Please let me know if this method works.

Thanks.


texts:
I have 2 shematics of circuits in order to drive a LED
I want to know how exactly these circuits work and what is the reason of using each components and why we need a dc-dc converter
Tnx very much
the link of the image is
http://www.infineon.com/dgdl/LED+Driving+Concepts+and+Infineon+Basic+LED+Drivers_V1.1.pdf?folderId=db3a304314dca389011561889ef01fe7&fileId=db3a30432f91014f012f96084ec339a3


texts:
Looking at my Arduino Uno, I noticed that not all of the pins/headers are labelled.  I know what most of the pins do, but could not figure some of them (most not labelled at all, and one set labelled ICSP, but I don't know what that means).

So, my question is: What purpose do these pins (circled in red) serve?


texts:
A Component in the Library has 11 Parts.
At the moment I get a Description for Component as a whole. Is there a way to change Description of each Part?

What I have: a component have only one description, Descriptions of parts are empty.
What I need: next to each Part of the component to have a description like "Power", "Grounds", "Signals".

Look at the Picture and try to guess what each separate Part of the Component does.


texts:
I have two of these units. The one that looks fried actually worked just with some cleaning, and the other one won't power up. I check all the SMD Transistor and resistors and I am getting power to the unit. The fuse checked good. The only thing left is this that I thought it might be the pulse transformer since it seemed to have some winding underneath it.
On the pictures, the blue arrow points to the power plug or usb. The red arrow points to the unknown to me SMD component.
What is this component and does it do?
How do I verify if it's working fine?
Thank you

I can't post more than 2 links

The picture at the bottom you can see the winding kinda of. I couldn't take any better picture than that.


texts:
Is it possible to design a single-op-amp schematic to attenuate a high impedance signal? The designs that I know have these limitations:

Non-inverting with input directly going into op-amp, has gain ≥1
Inverting op-amp draws current from the input.

The input is a pressure sensor (probably Wheatstone bridge based) but the impedance is in the area of 100kΩ.

The output goes into a low-pass filter (out of my control) which has non-negligible impedance, and ADC, so it needs to be driven hard.

If possible I don't want to use a voltage follower to buffer the signal. My feeling says it should be possible with one op-amp but I can't think of a way, and searching led me to nothing. Inverted-ness doesn't matter.

[Edit]

The resistance of the filter measures 5.1kΩ at DC. The bandwidth is non-existant (pressure changes take multiple seconds). Accuracy is not important as long as it's repeatable, the min and max are defined, and the domain is monotonic. Input min/max ~2V-12V. Output min/max ~1V-5V. Opamp is rail-to-rail, single-rail powered with 0V/12V.

simulate this circuit – Schematic created using CircuitLab


texts:
I am looking at a Delta-Wye with 480 on primary and 208/120 on the secondary. The transformer in question is Schneider's EX30T3HCUNLP. I came across this drawing in the spec sheet but I am not sure what to make of it. What is the significance of the numbers 1 through 7 that are tied to H1, H2 and H3 on the primary. Do terms like "FCBN" and  "2.5% FCAN" play a role in determining what type of load the transformer can supply.

The NLP in the part number implies non-linear loads. This is a 30kVA transformer that will feed a breaker panel with 30 breakers. Although I might have 5 or 6 loads that classify as "non linear", but the remaining 25 breakers will more than likely just feed regular loads. Can this transformer power both linear and non linear loads, or do I need another transformer for normal loads?


texts: Constructing a 12VDC to 230VAC 1-phase inverter

texts:
Can anyone help me check why the inverter circuit I built outputs only 165 V at no load instead of the proposed 230 V. It can't even light a bulb because of that. I tried adjusting values of filter capacitor but output remained low.

The inverter circuit and output voltage wave is attached.  I'm using a 12 V battery, Arduino Uno, IR2110, and a centre-tapped transformer. I notice that each time I switch on the inverter at no load, the battery terminal voltage drops from 13 V to 12.4 V. I think that voltage is still OK to get about 230 V at output.

Is my circuit and components I used OK? Please your suggestion will be highly welcome. Thanks.

NOTE: The scope trace is inverter output voltage which I  measured through a 230v/6v step-down transformer. I expected it to give 8.48v peak (equivalent to 6v RMS), but it rather gave about 6v peak.


texts:
I'm trying to develop a design which involves switching a 5V rail.

The design goals are:

As low cost as possible (i.e. Can't use a fancy integrated solution)
Relatively low current handling ( typically only a few hundred mA)
Trying to keep the overall solution in the 10's of cent
Low drop off on the the 5V when enabled ( > 4.8V )
Protection from reverse voltage when powered off

The problem I'm having is with the last point.

I've used a p-channel MOSFET as the switch, the gate of which is controlled from an op-amp.
Everything is fine except for the "reverse voltage" part.
The problem is that the body diode of the FET is going to conduct if an external power source is present.

I'm looking for a low cost solution to this problem, but I'm having a mental block trying to solve it without using some expensive IC.

Ideally I could just use a diode in series but the the drop-off would kill me there.
I've seen lots of references to using back to back FETs to solve this type of problem but I haven't been able to figure out a configuration which works.

The following is an overview of what I'm describing as it may be easier to visualise.

Update: Based on the feedback from @endolith I now see how the back to back system is configured which I believe is as follows:

Operation as follows:

When gate low
First FET GS voltage causes FET to be on
This places voltage on second FET Drain
Second FET has no GS voltage but the body diode conducts pulling Source high and causing GS voltage, which switches on the second FET

This begs the follow-on question, how much current can the body diode take? Is it safe to use FETs in this manner? (assuming I have understood @endolith correctly)


texts: how to compare each and every element with other element of two multi dimensional arrays in verilog?

texts:
I want to compare two multi dimensional arrays with each element of one array with the other array. What is the procedure to make it possible?

timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company:
// Engineer:
//
// Create Date:    09:21:01 01/08/2015
// Design Name:
// Module Name:    FACTORISING_INTEGER
// Project Name:
// Target Devices:
// Tool versions:
// Description:
//
// Dependencies:
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
//
module FACTORISING_INTEGER(
    input [15:0] f,g,
    //output reg [15:0] b,c,
     output reg [15:0]mem,
     //output reg [15:0]memc[15:0],
    input clk
    );
reg [15:0]memb[15:0];
reg [15:0]memc[15:0];
reg [15:0] b,c ;
integer address;
integer i,j;
always@(posedge clk)
  begin

   for(i=1;i<=f;i=i+1)
     begin
        if(f % i == 0)
         begin
          $display("%b is the factor of f ",i);
          #100;

           b<=i;
            memb[i]<=b;
            end
       end
   for(j=1;j<=g;j=j+1)
     begin
     if(g % j == 0)
         begin
          $display("%b is the factor of g ",j);
          #100;

           c<=j;
            memc[j]<=c;
            end
      end
    end

always@(posedge clk)
   begin
    for(address=0;address<16;address=address+1)
     begin
      if(memc[address]==(memb[address]))
#100
         mem[address]<=memb[address];
        else if(memb[address]>(memc[address]))
        #100
           mem[address]<=memb[address];
        else if(memc[address]>(memb[address]))
        #100
             mem[address]<=memc[address];

         end

      end

endmodule


texts:
does anyone know what is exact name(s) of liquid crystal material used in modern LCD's and how big should be electric field to make it change polarization?

Update for the second bounty: My idea is that I want to make LCD at home. I can get everything except these twisted nematic crystals, and I haven't found any papers or information on how they should be used (like required electric field, preventing electrolysis, required thinkness), or under which names I can buy them.


texts: Decoding a Two-Wire SPI-esque Serial Protocol

texts:
I'm working on a project that involves the optical sensor from a mouse.  I've got the original control PCB (still populated, save for the optical sensor itself), and I've got the optical sensor on my custom PCB, supposed to be controlled by an nrf51822.  I've wired the clock + data pins (it's a two-wire interface) to both boards, driven by the original control board (I've set my clock and data pins as inputs with no pulling resistors).

I'm trying to capture traffic to determine what signals are being sent, but I'm not having a lot of luck - I suspect my clock rate is too low.  As quickly as possible (just inside a while true loop), I'm scanning my clock pin and my data pin, then printing them both to my console output over UART at 1M baud.  Running this loop empty for 5 seconds results in ~4000 cycles, meaning I'm getting >1ms run time for each loop - which I think is my main problem.

As it is, I capture (in roughly 700 scans) 100 groups of alternating "clock 1 and data 1" and "clock 0 and data 0" - each group is 4-9 items (that is, 4-9 "1s" on both, followed by 4-9 "0s" on both).  Then, about 400 scans later (~0.5 seconds) I get the same thing, but 54 groups.  At that point I stopped scanning.

Is there any way to either:
A) Speed up my scan cycle so I can capture the traffic more accurately?
or
B) Decode what I already have (doubtful)?

Do I need to consider an alternate route? I haven't found any access to an oscilloscope, which is... unfortunate.

I'd appreciate any advice.  Thanks.


texts: Is printf debugging over JTAG (not SWD) with STM32 possible?

texts:
The question is very similar to this one:

I'd like to to printf debugging via the ST-LINK adapter and JTAG, not SWD, in IAR Workbench. Is this possible?


texts: Deviation from typical I-V characteristics of a diode in high frequency

texts: Why the diode shows a loop in the I_V characteristics?(Diode part N4003, Frequency was 100k) My instructor told me something regrading the retardation of charge carriers but I couldn't understand/find anything.Will someone please explain it to me?


texts: Why these resistors on the Pololu MC33926 carrier?

texts:
I'm trying to design a motor driver carrier for the DRV8873 chip, and I've been looking at Pololu's motor driver carriers as reference material. I noticed that they have inserted 1k resistors on all of the control lines. The datasheet says nothing about these. Help me understand why these are needed in this application.

Bonus: does the DRV8873 have protection features which would remove the need to insert a reverse polarity protection circuit?


texts: What might be the cause of noise in my audio out on Stereo when connecting computer as the "audio in"?

texts:
This is from a friend. I wasn't sure of the cause.
Perhaps:

Ground Loop
The wire connecting the computer to stereo needs to be shielded?

I have a question about my stereo. I get a hum through my speakers, most pronounced when using an attached computer as a source of Pandora internet radio. I decided the problem was that the receiver wasn't properly grounded. So I got a grounding wire and proceeded to look for an attachment on the back of the receiver. There doesn't seem to be one! It's a Yamaha RX-V663 receiver. Did I mis-diagnose the problem? Is it possible to ground this receiver? How do I find the attachment point?


texts: Can I connect high power LEDs in parallel without resistor?

texts:
I see lots of people connecting high power LEDs in parallel to a single power supply (constant current).
Some of them have powerful knowledge about electronics (example).
So, is it something special about high power LEDs so they can be connected in parallel without resistor?


texts: Help to identify Video Amp IC - 4 channel used for Analogue RGB video buffer

texts: Way back some 10 yrs ago I used a Chip for RGB video buffer amplifier.it only provided some 3dB gain.  It required no external components , had 4 internal video amplifiers in a 14 pin dil package. I lost all documentation and cannot remember the number or brand. Not sure if it was ANxxxx or uPCxxxx or anything else. Can anyone help please?


texts: How to automatically test the audio quality of a telephone line that randomly goes bad?

texts:
I am a computer scientist and I'm working as sysadmin of a small firm where I've been managing also the telephone system that my predecessor put in place.

Albeit I don't really have the skill set for doing this, until now it was enough.

Since the last few months however we are experiencing a strange phenomenon on one of our lines: after a couple of minutes of use (but not every time) the audio quality suddenly deteriorates and the outside party cannot hear us unless we talk very loudly. This usually happens on inbound calls.

A brief description of our setup: we have two dual-channel isdn land lines with two different operators over which we also have an adsl internet line each.

The first operator gives us two POTS numbers on its line and these work perfectly both inbound and outbound.

The second operator instead gives us an ip telephone number on its line and this is the one we are having problems with.

Now, I know what you are thinking, the ip setup is obviously rubbish. Well, I'm quite expert in network administration and I'm relatively sure that it isn't. The line works as it should and the operator confirms it.

Still, while answering calls from the ip lines my users laments poor quality of audio every other day.
I admit that I didn't believe them at first (I've been unable to reproduce the fact myself) but the accounts were too many and they came from independent sources, some of which are highly trusted and unlikely to prank the poor, overworked sysadmin.

So, here's the question for you engineering types: give me a way for me to automatically test a phone line audio quality without having to subject myself to listening in to all the calls of some of my users for a couple of days or two (which would badly impact my already too full todo list).

What I'm hoping for is a way for me to use my android phone to call the ip line and without having to wait for it get a warning the moment the audio quality drops, so that I can draw some reliable statistics on how often this happens and I can demonstrated to the operator technicians that I'm not wasting their time (like they more or less explicitly told me last time I called for help on this).

I hope I'm asking this in the right community. If not, have my apologies and please point me to the right one.


texts: What is the reason behind the mosfet setup in circuits similar to the one shown in the image?

texts:
I searched and since I don't know what to search for I figured I'd rather just ask. I did find various things but nothing explaining why it's setup like that (as shown in the image below). The upper and lower mosfet's.  I would like to understand why it's setup like that and what exactly is happening there. (if possible)
I have seen this type of setup at a few places like even on the laptop charging circuit for the battery. The phase pin would usually run in between two mosfet's similar to the way "TRIGGER" is on the right in the image below.
Thanks

Edit: Added schematic image of a similar circuit, which contains more detail...

Seems like it's not a well known thing... according to the comments...


texts: Start up circuit in power supply independnent biasing

texts:
I simulated the start up circuit in a power supply independent biasing. I know that the start up circuit is there to makes sure that there is current fllowing thought the transistors preventing the degenerated bias condition but how does this actually work ?? and what sense can I make out of the simulation ??

This is my circuit,

and this is my simulation result (And the current is in Pique amps)


texts: Rinnai water heater power and communication interface/protocol

texts:
My Rinnai tankless water heater can be connected to a wifi module that controls the recirculating pump and other functions.
The only connection between the PCB of the water heater and the external wifi modules consists of two wires, not polarized.
This powers the wifi module (which does NOT seem to have any battery inside) and allows the controller to communicate with the heater; I believe comm is half duplex only, but I am not 100% sure.
Note: The Control-R manual says:
"Additional wiring can run up to 300 feet (91 meters) away from the water heater to ensure a strong wireless signal  (18-22 gauge wire is required)" and it's unlikely wireless communication between control box and heater can happen reliably at 91meters.
The only interface I know that uses only two wires for power and comms is 1-wire from Dallas, but I doubt it can deliver enough power for wifi and it is polarized.
What interface/protocol can it be? I am quite surprised
Water heater: Rinnai RUR199i
Wifi Controller: Rinnai Control-R
https://imgur.com/a/5WT6Dzk

It seems input comes through a MDB8S full bridge rectifier to provide power
On top there is also a  MX30LF2GE8AB-TI 2Gbit NAND
The main chip, that also provides wifi, is a MediaTek MT7620
The chip uses external DDR (wow, check the DDR routing on the PCB, so much work) Winbond W971GG6SB-25
The back has a ZigBee section, with SiGe2432L frontend, EM357 chip and MX25L8006E - what is it, memory?; I know there are RINNAI accessories that connect with ZigBee that can connect to this module, like a button, sensors to detect presence; I do not know if this is also used to talk to the heater.
There is also a chip marked R5F101JED that seem to be a microcontroller

EDIT 2:
I checked the PCB again and yes, the inputs are decoupled with some caps, then go to the following "mystery" component (looks like some sort of daughter board?) and finally to the R5F101 microcontroller. Any idea what is the yellowish thing?


texts:
I know a similar question was asked before, but still, it didn't aswer what I'm looking for.
I need to charge a series of 6 Li-ion cells, and maybe 12 in the future for a voltage hungry project. Since a have a bunch of TP4056 modules laying around, i want to use them as my charger.
I have encountered my self with the very wrong idea of connecting them in parallel to 5V, others say to just hook them up in series, but the drivers need a constant 5V input.
What about chaining zener diodes?
Or even better, i have switching regulatos modules, can i chain them as well, intead?
And what about building a multi-output 5V supply? (like a phone charger, but with isolated USBs, for example)
I don't need much correct out of them, 500mA overall per module would be fine.

(Over complicated, i know, but believe me, it's easier for me to get that done instead of getting a proper charger in my country.)
Here's the concept, these regulators could be any style of voltage regultor that fit the requirements. Also, this chain could be as long as needed (in my case, 6 to 12 cells)


texts: Teensy microcontroller showing slow fall time (but fast rise time)

texts:
My Teensy++ 2.0 is showing some slow fall times, around 1ms, when I set a pin to low (via DigitalWrite). It looks like there's capacitance on the line, but the rise time is pretty much zero, so that can't be it.

Has anyone had the same sort of issues? Is it possible that my Teensy is broken? I looked at the AT90USB datasheet but I couldn't find rise time and fall time on general purpose IO.

Thanks for your help!


texts:
Let say

  A 440-V 60Hz three-phase star-connected four-pole induction motor
  developed 10 hp at 1745. The input power is 10kw at 0.85 lagging power
  factor. the no load input power is 0.6kw

My question is that what does the power factor mean in this sentence?
What is this power factor value derived from and the meaning of it ?


texts: Why is the calculated rated current for this motor different from that on the nameplate?

texts:
For a 75 Hp ,380 line voltage PF 0.85 motor when i calculated the rated current P = 1.73*VIPF
i get Rated Current = 98 A
While what is printed on the nameplate is 124 ampere


texts: Power factor correction of predominantly inductive load component with capacitor

texts:
I started preparing for the college next year, and I came across this question:
How can I express the capacitance of a capacitor which needs to be connected parallel to a predominantly inductive load component to fully correct the power factor?
I remember mentioning power factor correction in high school, I think in Physics class. But we just mentioned it. What does power factor mean and how can you correct it?


texts: About BJT, JFET & MOSFET transconductance

texts:
For BJT, the term "gm" refers to base-emitter conductance. But when we are talking about FETs and MOSFETs, where is this "gm"? Between gate-source junction for JFET? Drain to source conductance for MOSFET?

And what "gmb" means when talking about MOSFETs?


texts: How do I read the value of registers in Logism?

texts:
I am designing a CPU in logism. One of the components of the CPU is a register circuit (RegFile), which stores the registers data. The register circuit (RegFile) is shown below:

I am able to write data to the registers as shown below:

However, I am unable to read data from the registers. The following call of the register circuit always returns 0 values for the registers, even when the registers have non-zero data in them:

When I use probes to inspect the value of A_Register and B_Register, it always shows up as 0 and any of the Reg1d, Reg2d, Reg3d, etc. outputs also show up as 0.


texts:
I know that a simple CPU (like Intel or AMD) can consume 45-140 W and that many CPUs operate at 1.2 V, 1.25 V, etc.

So, assuming a CPU operating at 1.25 V and having TDP of 80 W... it uses 64 Amps (a lot of amps).

Why does a CPU need more than 1 A in their circuit (assuming FinFET transistors)? I know that most of the time the CPU is idling, and the 60 A are all "pulses" because the CPU has a clock, but why can't a CPU operate at 1 V and 1 A?
A small and fast FinFET transistor, for example: 14 nm operating at 3.0 GHz needs how many amps (approximately)?
Does higher current make transistors switch on and/or off more quickly?


texts: Sending data over UART when data has been received over I2C on AVR

texts: So I'm receiving data from an ESP module via I2C. I then need to send this data immediately over the UART. Not sure how I should do this. Would it be ok to place the UART sending inside the i2c receive interrupt?


texts: How is it possible to replace a relay with transistors?

texts:
As we all know:

A relay's COM and NO pins have no polarity, they will work fine when polarity is reversed.
A transistor's Collector and Emitter pins have polarity and this polarity must be respected.

So:

how can you replace a 4 pin Normally Open (SPST) relays with transistors when polarity of Emitter and Collector pins are unknown?
Are there any specific components out there that can switch a DC voltage when polarity is unknown?

(I'm a software guy and a noob in hardware world, so, if it is possible, please explain or add an image for better understanding)
Thanks.


texts: Why does my NVR reset when its UPS switches to battery?

texts:
I have a Reolink network video recorder (NVR) that provides 802.3af Power over Ethernet to downstream cameras.  This NVR is plugged into a uninterruptible power supply (UPS).

I have a switch, whose non-PoE uplink port is plugged into one of the PoE-capable ports on the NVR; this switch normally plugs into the wall to supply PoE to other downstream cameras.  For this question, however, there are no cameras plugged in, and the PoE switch is only grounded, not powered. [1]

With this setup, the NVR periodically resets. Furthermore, I can cause the NVR to reset by unplugging the UPS from the wall, especially if I rapidly jiggle the plug, simulating a power "glitch."

If the switch is not grounded, the problem does not occur.  If the switch is instead plugged into a non-PoE port on the NVR, the problem does not occur.

It is my understanding that Ethernet should isolate the various devices from each others' grounding issues.  Which of these devices is at fault, or has a defective design, and what could be causing the NVR to reset?  How can I mitigate the problem?

[1]: The funny ground-only connection of the switch is my attempt to reduce the problem to an MVCE.  Of course, in real life, the switch is powered.


texts: Page table - I don't understand how this table has been made

texts:
CPU has generated this sequence of logic addresses (in decimal):

777, 2047, 1199, 1100, 546, 129, 3201

page size is 512 Byte, CPU generates logic addresses, 12 Bit length, main memory has 4 pages.

I understand the following table: We just converted the decimal addresses to binary. The total address length is 12 Bit. From task we know that page size is 512 Byte, so 2^9 Byte = 9 Bit for offset. 12 Bit - 9 Bit = 3 Bit for page. So first 3 Bits are page and the other remaining 9 Bit are offset. Easy so far.

But here comes the second part of the task and I don't understand how the table was made...

Make a table that illustrates the content of the table above (called MMU) after each finished memory access in the same order shown above. You only need to specify the necessary entries (so if there is same page twice, ignore the duplicate). At the beginning, all page frames are unassigned and they are used with an ascending page number. If all page frames are in use, the LRU replacement takes place.

Here is the solution of the table but I don't understand... That's my question, how was this table created? I don't get the logic.

Edit: For second table I can see task said 4 pages. So we have 00, 01, 10, 11(so in decimal 0, 1, 2, 3) but why they did it in that order in the table? That's what I don't understand.

Edit: I don't understand the order of the second table. Why did we start with 11, then 00, then 10 etc. It doesn't make sense for me...

Here is how I would have filled the table:

What do you think?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to solve a cicuit with using the branch current method. Here is the circuit:

The words after the values are the unit in my language (Ом=Ohm), so both capacitors are 10 Ohms and so on. I have counted 2 nodes, I think the one is where the letter "b" is placed, and the other where "f" is placed. I made 1 equation using KCL, and three using KVL, but when I calculated the system of linear equations, the result was \$ 0=0 \$.

  Equations:
  \$\$\begin{align}
I_1+I_2-I_3-I_4&=0\quad \text{(from KCL for node 1)}\\
I_1*Z_1+I_3*Z_3&=E_1\quad \text{(KVL for circuit I)}\\
I_2*Z_2+I_4*Z_4&=E_2\quad \text{(KVL for circuit II)}\\
I_1*Z_1+I_4*Z_4&=E_1\quad \text{(KVL for circuit III)}\\
>\\
I_1+I_2-I_3-I_4&=0\\
-j10*I_1 + (10-10j)*I_3 &= 20\\
j20*I_2 + 10*I_4 &= 14,14 + j14,14\\
-j10*I_1 + 10*I_4 &= 20\\
\end{align}\$\$


texts: Steady-State DC Analysis: Inductors and voltage sources

texts:
Consider the following circuit. I'm tying together the basic definitions of capacitor and inductors, and how they work when connected to a DC source.

First off, we have the equations for current throuh a capacitor, and voltage across a inductor.

\$i_c(t) = C\frac{dv_c(t)}{dt},\quad v_l(t) = L\frac{di_l(t)}{dt}\$

Analyzing this, we can see, clearly, that if our inductor and capacitor are "empty" at \$t=0\$, that our capacitor acts as a short circuit, as there's no current going through it unless there's a change in voltage across the capacitor.

However, I'm having difficulties seeing how the inductor acts as a short circuit. Because we have the DC voltage source \$10V\$, all we know is that our voltage is constant. What I wonder then is how we can make the statement that our inductor acts as a short circuit.

Also, why do we call direct voltage sources "DC voltage source"? Doesn't is sound a bit strange saying "direct current voltage source"?


texts: Does an RF receiver constantly consume power?

texts: I'm building a battery operated robotic arm and would like to use a cheap, short distance RF transmitter/receiver kit to trigger it. However I would like to know whether the receiver will constantly be consuming power as it listens for the signal. I would prefer to not have to change the batteries more than once or twice a year considering the motor will only be running for a couple seconds per day.


texts:
I have a problem related with a transistor circuit. Please tell me whether my approach is correct or not.

I need to find the current through the 94.6ohms transistor.

My approach (Assuming PN voltage is 0.6V)

Since the NPN transitor has 5.6V between the base and emitter,
it will be biased.
So, the voltage at the base of NPN will be 0.6V with respect to ground.
So, current through 1K resistors will be (15V-0.2V)/2kohms = 7.4mA. (Vce = 0.2V)
Since the voltage at the top of 1k emitter resistor is at 0.6V, , the PNP transistor now, will turn as, the voltage between the base and the emitter is greater than 0.6V (As 15V-0.6V > 0.6V)
So,Current through the 94.6ohms is (15V-0.2V)/94.6Ohms = 156mA.

Is my calculation right?


texts: Would a faraday cage still work if it was part of a circuit?

texts:
Faraday cages protect against EM radiation and charges.
As far as I understand, this effect happens through the induction of an electric field, which produces a current inside of it, which then counteracts any incoming current. So, my question:
If I replaced part of a wire in my circuit with a faraday cage, say + at the feet and - at the top, would the interior still be protected, or would the current, given that the skin effect applies, move through both the outer surface and the inner surface? And are there any differences between DC/AC?


texts: Identification: Is this an 150A fuse? Or something else?

texts: Can anyone else identify this element? What is it? Seems to have 150A stamped on the left side - is it a fuse?


texts:
I'm building my first ESP32 Wrover Breakout PCB.
Now to me it's unclear at the moment what I can omit to get it running
USB connectivity
Now in order to get USB running there seem to be two options:

Use a CH340G chip and hook it up to the TX, RX pins of the wrover.

Use GPIOs and directly connect them to the D- and D+ of the USB port respectively.

Crystal
The second schematic does include a 32kHz crystal for the ESP attached to two GPIOs. The datasheet tells me that the WROVER uses an internal crystal with a frequency of 40 MHz clock rate.
Update: I did find another circuit. The OLIMEX ESP32-S2-DevKit-LiPo which has several differences:

Pull up of the TXD, RXD signals as well as Schottky diodes.

Current limiting resistors for the USB-/+ signals

Also it has a USB OTG Option.


texts: Why is simulation effective bandwidth of LM741CN op-amp wider than calculations says it should be?

texts:
For my electronics course, I have been tasked with creating a circuit that will take a \$10\text{mV AC}\$ input and amplify by a factor 490 using the LM741CN op-amp with an effective bandwidth (attenuation less than 3dB) from \$1\text{ Hz}\$ to at least \$20\text{ kHz}\$. Knowing that its \$f_t = 1.5\text{ MHz}\$, I know I must split the gain into two stages to increase the bandwidth or else
$$f_{-3\text{dB}}=\frac{f_t}{A_{CL-O}}=\frac{1.5\text{ MHz}}{490}=3.06\text{ kHz.}$$
This lead me to having two stages each with the square-root of the original 490 gain (\$7\sqrt{10} \approx 22.13\$). To do this, I used two inverting op-amps configurations so that the gain would simply be \$-\frac{R_2}{R_1}\$ and set \$R_2 = 22.13 \text{ k}\Omega\$ and \$R_1 = 1 \text{ k}\Omega\$. I do this twice and I get the required gain. This also has the added benefit of increasing \$f_{-3\text{dB}}\$ to \$67.8\text{ kHz}\$.
However, I also have to account for the slew rate of the op-amp, which for the LM741CN is \$0.5\text{ V}/\mu s\$. This brings the maximum frequency to:
$$f_m = \frac{\text{SR}}{2\pi\hat{v}_o} = \frac{0.5\text{ V}/\mu s}{2\pi\times 10 \text{ mV} \times 490} = 16.1\text{ kHz}$$
This posed a problem to me so I went on to NI Multisim to simulate the bode plot for the planned circuit. Here is the circuit:

And here is the bode plot for the output vs input:

The most notable piece of information is the fact that the effective bandwidth (as I've described above, the frequency range where attenuation is less than 3dB) reaches past \$20\text{ kHz}\$, all the way above \$24\text{ kHz}\$. The regular gain (gain at 1 Hz) is 53.797 dB so at 50.797 dB, I take that to be ineffective. Yet at \$16.1\text{ kHz}\$, there is only 1.438 dB of attenuation.
My question is why is this happening? Why is the effective bandwidth larger than what my calculations tell me they should be. I can't find out what I did wrong with my calculations, and I am not sure if there are any other equations to consider.
EDIT: Some more info I was informed should be part of the post:
My actual task is described here:

It doesn't say anything specifically regarding 3dB being the point at which frequencies are ineffective, but it does talk about total harmonic distortion, which I assumed would be similar to the 3dB limit since my class still hasn't actually taught anything about calculating it, and I am not sure if it is possible to calculate in a theoretical POV. It also mentions the LM318N, but I got that to work fine in my calculations.


texts: Why the point SS is at lower potential than S in the MOSFET circuit?

texts: I can't understand why the p type(SS) and the n type conductor(S) are said to be in reverse bais.


texts: What are the available options or ways to connect the STM32 discovery board using UART to a PC via USB or the serial port? What is the required hardware/cables?


texts: Return Current Through Split Planes (1.5V, 3.3V, 5V)

texts:
If return path as GND plane, then return current/signal will be ended to GND pin of driver IC. Right?

Similarly, if return path as POWER plane, then the return current/signal will be ended to VDD pin of driver IC. Right?

Consider my VDD pin of driver is 3.3V and return current of signal flows through across split planes (1.5V, 3.3V, 5V). If so what will be the voltage level of return signal in each power planes?

When it flows through 1.5V plane, then return signal voltage level
will be 1.5V.
When it flows through 3.3V plane, then return signal voltage level
will be 3.3V.
When it flows through 5V plane, then return signal voltage level
will be 5V.

My understanding is correct?


texts:
I am a high school student and am making a project on FM receiver for class 11. I am following this circuit diagram:

The L2 in this diagram is a 22µH RF Choke. The part listed in the website has the configuration provided below in its datasheet.

L= 22uH +/-5%
Q= 51
Test Freq.= 2.5 MHz
SRF= 13
DCR Max.=2.28 Ohm
I, DC= 229 mA
Dim. A Max.= 0.16 inch
Dim. B +/-0.03= 0.25 inch
Core Material= iron

I know how to make inductors but some properties such as the thickness of the copper wire (in SWG), whether enameled or not, no. of turns to use and the diameter and length of the inductor is confusing me.

And as an additional note can u please mention the number of turns in the L1 and the thickness of the copper wire to be used that will be suitable for the circuit diagram.


texts: Why do LEDs have/need positive and negative nodes to function whereas say resistors don't?

texts:
I'm very much a beginner experimenting for the first time with electronics, and I'm still trying to grasp the basics. On my breadboard, my LEDs have to be setup in a very specific way for them to work, the positive end being on the positive side and the negative node connecting to the negative side.

I thought the point was to get electricity to flow through the LED thus getting it to light up. Clearly electricity flows through my resistor even though it doesn't have a positive/negative node dichotomy. So why is it so for LEDS? Also if I may ask, what specifically causes one end to be negative and one end to be positive? What is the actual difference between the two nodes chemically?


texts: Do we have equivalent standards for all UL standards under IEC?

texts: As per the image, it looks like there will be an alternative standard in IEC with respect to every UL standard?


texts: How long will it take to completely run out of power for two A23 batties(12volt each) on a serial circuit with 6 leds?

texts:
I'm connecting 6 LEDs serially with two 12volt batteries. Each LED needs 3.2 volt and takes 20mA of current.

I'm using two alkaline max 12 volt batteries(A23 LR23) and ATC is their manufacturer.

I tried to calculate the batteries' lifetime like below(taken from a website):

To find out how much energy I'm going to use I multiplied the Watts times the number of hours to get Watt-hours. So 12v battery rated(?google search) 1.2Ampere-hour then the energy is:

12 volt * 1.2 Ampere-hour(battery) * 2 batteries  = 28.8 Watt-hours

The LEDs run at 3.2v and uses 20mA each. So

3.2 volt  * 6 leds(each needs 3.2 volt and current 20mA) * (20 / 1000)Amp = 0.384 Watt

And finally the battery lasts:

28.8 watt-hour/0.384 watt = 37.5 hours

Is this calculation correct? If not is it possible to help me correct my mistake?


texts: Substitution for 0.1Ω 2W metal film resistor?

texts:
I'm attempting to repair a Pure Sine Wave Inverter.
I need to replace a damaged 0.1Ω 2W metal film resistor. I found the part that should work on digitkey: https://www.digikey.com/en/products/detail/yageo/MFR200FBF73-0R1/9136767
MFR#: MFR200FBF73-0R1
However, the min order qty is 5000. I looked on mouser and couldn't find it there. I only need one for the repair and probably some extra to keep around.
Anyone know of a different place i could search or for good substitution? I'm not certain as to the function of these resistors in this circuit. There are several of them in parallel with each other, all of the same value.
Thanks!


texts: Why capacitor voltage getting low even in open circuit?

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I got two 2.7V 100F supercapacitors. I have wired them in series and applied 5V.

One capacitor I have tried have been about 2V. I put it on my desk without any connection.

A couple of hours later, when I measured the voltage of capacitor, it was about 0.5V.

So, energy formula of a capacitor says that it is proportional with 2nd power of capacitor voltage. In my case, voltage dropped 4 times and rate of energy loss is about 16 times.

I cannot figure out where this energy has gone.


texts: How can the number of clock cycles required to complete an instruction in a pipelined processor less than pipeline latency?

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I am not new to computer architecture but I have only academic experience with micro-architecture implementation.

I have heard and read this many times but never really bothered to understand the statement: Some  instructions complete in 1 or 2 clock cycles while more complex instructions say integer or floating point complete in 2, 4, 6 clock cycles etc or load/store in 80-100 clock cycles because of slow memory.

Now I am sure most processors be it embedded or desktop have few stages of pipelines say from 5 stages upto 30 stages. So the latency for each instruction should be equal to pipeline depth or number of pipeline stages. Also, throughput of a single pipeline scalar processor can be maximum 1 IPC (Instructions per cycle). But how can some instructions finish in 1,2 or 4 clock cycles for a processor with 10 stage or 12 stage pipeline ? Can someone explain me that ?

PS: Only thing I can understand is that maybe some stages are marked as a Multi-Cycle stage as is usually done during STA and timing closure. And that they are trying to say that execution of instruction takes 1cc, 2cc, 4cc etc. in that particular Multi-cycle stage ?


texts: Decimate ADAR7251 Sigma-Delta ADC Output

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I'm working with a Analog Devices ADAR7251 Sigma-Delta ADC. It has multiple sample rates to choose from (1800 kSPS, 1200 kSPS, 900 kSPS, 600 kSPS, 450 kSPS, and 300 kSPS) but my application requires 112.5 kSPS. I plan on using the ADC in 450 kSPS mode and will decimate by a factor of 4 to reach the target sample rate. This ADC can simultaneously sample 4 channels and has a built in LNA+PGA for each channel. These features prevent me from changing to a new device.

I know the proper way to do it is to use a cascade of 2 half band filters. My question is can I do without them and simply take every fourth sample?

I'm aware that this particular ADC oversamples by a factor of 48xFs (21.6 MSPS in 450 kSPS mode) which relaxes the requirement for the anti-alias filter. I'm using a 3rd order Bessel Differential LPF (fPass @ 60 kHz, fStop @ 180 kHz with 20dB of attenuation). Additionally, my sensors are an array of electret microphones with a LPF frequency response rolling off around 20 kHz. I don't think there will be any significant signal power at a high enough frequency to cause aliasing that I have to worry about.


texts: Understanding Plot Showing Impedance, Resistance, and Reactance

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I am looking at part of the datasheet for a hydrophone I am using in a project. It includes this figure, which plots resistance, impedance, and reactance vs. frequency:

Part of my project involves designing a preamplifier for the hydrophone. Because the output of the hydrophone will be in the range of 20kHz to 40kHz, I must make the input impedance of the preamplifier much greater than that of the internal resistance of the hydrophone to maximize voltage transfer between the two. When looking at this chart, I am unsure of which value I need to use for the equivalent series impedance. The parallel capacitance of the hydrophone is 3.4nF, and its datasheet can be found here.


texts: secondary voltage of practical transformer question

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I am working on a practical transformer question as seen below.
My thought process to solve this question was:

1) Calculate the total current supplied by dividing the apparent
power by the voltage.
2) Find the current in the excitation branch and subtract it from the
total current supplied.
3) Use this value to multiply the series impedance to find the
voltage drop across it.
4) subtract this value from the input voltage and use this value with
the turns ratio to find the output voltage of the transformer.

however there seems to be missing information as I cannot move forward with step 2. How do I find the excitation current without the reactive power? There is another question in my assignment with the same information supplied so what am I missing here? Thank you.


texts: Is dram constantly refreshing during windows sleeps?

texts: I know that sram and dram are volatile so even when windows is in sleep mode(not hibernation, in which memory is backed up to secondary storage), but I'm curious whether dram is constantly refreshing. I'm pretty sure about this because otherwise dram wouldn't be able to store information, but I can't find any source regarding this. Also, if so, is dram refeshing mechanism the only part where computer consumes power during sleep mode?