texts: Does this Root Locus analysis contradict my understanding of Nyquist stability criteria?

texts:
I have been trying to theoretically analyse the operation of a 741 op-amp from a stability point of view by firstly deriving its open-loop transfer function.

Here is the magnitude plot of a 741 op-amp.

From the above plot, I generated the open-loop transfer function.

From the open-loop transfer function I have derived the closed-loop transfer function and to keep things simple I have assumed that the op-amp is configured as a unity gain buffer ( β = H(s) = 1 ).

\$\$

Now, the Root Locus method plots the loci of the closed-loop poles on the s plane as some parameter is varied from 0 to infinity. I vary the dc open-loop gain k which is set to 100000 for the 741. The values of the poles at various values of dc open-loop gain can be found by equating the denominator of the closed-loop transfer function (the characteristic equation) to zero and solving for s. That is to say, the roots of the characteristic equation are equal to the poles of the closed-loop transfer function.

Here is the characteristic equation which is equated to zero.

By entering a range of values for k into the above equation and solving for s using the following equation….

….I get the pole plot below on the s plane. The arrows represent increasing k values. I’m pretty confident about this plot because I have seen the same plot for a second-order system on various web sites.

My problem is this. I know from fig.1 above and from Nyquist stability criteria that increasing the dc open-loop gain will reduce gain and phase margins. As open-loop gain k increases, the loop gain will get down to unity at a higher frequency where the loop phase lag is nearer -180ᴼ thereby reducing stability margins and moving the op-amp closer to oscillation. (The phase lag should never quite reach -180ᴼ because this is a theoretical 2 pole amplifier). Why then doesn’t the root locus plot converge on the imaginary axis on the s plane as the dc open-loop gain k is increased. The plot is vertical. I think I am misunderstanding something.


texts: Why would an RGB LED still glow with only the cathode side connected?

texts:
The Setup
I have an RGB LED controller that is mostly a black box to me (I assume it's using PWM to produce color transitions). It's connected to an assortment of common anode RGB LEDs (they're all tiny PCBs with the LED chip + a resistor connected to each cathode). They are all connected to the controller in parallel.
The Question
Why is it that when I take one of the LED modules and disconnect only the anode (positive) wire, it will continue to dimly glow?

My beginner-level brain can't figure out how that could ever be possible. What could be happening in the controller that could result in this? Some sort of induced current even though this is a DC circuit? Could it be related to the PWM signals produced by the controller? Magic?


texts: How to build the simplest 12V 2A switching power supply?

texts:
The problem:
I need to learn to build the simplest switching mode power supply. If I succeed, I hope I'll be able to work my way up and make more advanced SMPSs for other applications.

I did my research:
I've been searching everywhere for a tutorial on how to build a simple switching mode power supply, however, the tutorials and solutions I found look super complicated for me. So far I have looked at a few articles and have used the PI Expert and the Power Stage Designer Tool (from Texas Instruments) to get familiar with designing the circuit. I know how an SMPS works, but I'm afraid I need to learn how to set up the "switching" part (i.e. how to set up the IC that is in charge of controlling the MOSFETs).

My Stash:
Includes 5-PC-power-supplies worth of scavenged components, and I was wondering if I can actually build a smaller PCB that only outputs 12V 2A.

The applications:
The simplest one is that I need to supply constant 12V to two fans, mounted on the heatsinks of two 50W LEDs, which are powered by a 100W LED driver. Linear regulation isn't a good idea for obvious reasons.

I would appreciate any help.


texts:
Having the hardest time with this TLC59116 LED Driver IC from Texas Instruments. I have done a crazy amount of debugging and still cannot get it to drive a single LED. I have followed all the instructions on the datasheet, as well as referenced every software library/tutorial I could find to make sure I am doing everything properly, but it still will just not drive an LED.

I have double checked the validity of the chip and can confirm it is stable.

Here is how I currently have it hooked up:

And here is my I2C code:

  void writeRegister(char reg, char data) {
    char buffer[2];
    buffer[0] = reg;
    buffer[1] = data;
    i2c->write(address, buffer, 2);
  }

  writeRegister(MODE1, 0b00000000); // defaults
  writeRegister(MODE2, 0b00000000); // defaults

  writeRegister(GRPPWM, 0xFF);
  writeRegister(GRPFREQ, 0xFF);

  writeRegister(LEDOUT0, 0b11111111); // led "fully on"
  writeRegister(LEDOUT1, 0b11111111);
  writeRegister(LEDOUT2, 0b11111111);
  writeRegister(LEDOUT3, 0b11111111);

  writeRegister(PWM0, 0xFF);   // full brightness
  writeRegister(PWM1, 0xFF);
  writeRegister(PWM2, 0xFF);
  writeRegister(PWM3, 0xFF);
  writeRegister(PWM4, 0xFF);
  writeRegister(PWM5, 0xFF);
  writeRegister(PWM6, 0xFF);
  writeRegister(PWM7, 0xFF);

I have tried several enumerations of this code but it makes zero difference.

Like... am I missing something integral here?


texts:
I'm trying to add second source to an amplifier. It uses TEA6320t sound fader control chip which takes in multiple sources and outputs one.

  The source selector selects one of 4 stereo inputs or the
  mono input.

Currently only one input is used, but the question is how to change form one source to another? Here's the  datasheet of the chip.


texts: Is a bridge rectifier needed to power LED lights from a DC Power Source such as a cordless tool battery? Or can I simply wire direct from the battery to the light?


texts: How can one organize SMT parts prior to/during PCB assembly?

texts:
Suppose one is hand-assembling a board with many SMT components. Unlike THT, SMT components are often not labeled.

This means that having two different kinds of parts "out" at the same time is a serious problem. How might one keep small (<100) quantities of such parts properly organized during assembly? Are there particular tools? Storage devices? Methods?


texts: how to proteus simulation inrush current

texts:
i've a reverse polarity protection , i want to check inrush current simulation , but i don't know how .

i read this , but i tried but doesnt work

How to plot voltage vs current graph on Proteus Software?

update :

i have removed resistor caps , put resistor load ,   and that what i got for simulation  :

update 2 :

i have made sweep analysis : increase battery voltage from 0 to 48 , and monitor it with monitoring resistor voltage

is that simulation right ?

update 3


texts: In an audio circuit, with an LM386 chip - how does the DC electric power and the AC audio work?

texts:
I am currently putting together a simple audio amplifier using an LM386 chip.  In the midst of studying how this chip works, and the proper circuit analysis behind it, I began thinking about how conventional current would flow in this particular case.

I understand that there is an audio input that produces an AC waveform across the copper into the LM386 chip.  There is also a Direct Electric current flowing from a battery into the LM386 chip - utilized for amplification.

It is when these two signals meet that confuses me...  The DC current flows with the Audio Waveform on the output of the chip.  Based on the picture of the circuit below, I noticed that there are two capacitors, one a high pass and the other a low pass.

From what I have gathered, the capacitors are there to block the DC current, but allow the Audio AC waveform to pass through - clipping waves too high or too low.

What I want to know - how does the DC current boost an alternating waveform if the DC current is only pushing in one direction?  When the wave would push one way I would think there would be more power (flows with the current), but then when it pushed the other way, wouldn't it flow up stream?

What does this look like prior to hitting the capacitors?  Would the DC current be in a wave pattern, or would it still be a line with the audio waveform alternating around it?  I would assume that there would be a solid line of DC flow at a voltage level, with the Audio waveform alternating back and forth with the DC voltage at its mid-point.

Finally, I assume when the capacitors are removed you hear that electric hum...  But with the capacitors there, would it not muffle the amplification?

It is a bit of a noob question, and unfortunately I am in the midst of getting an Oscilloscope, but do not have one yet.

I'd appreciate any help on this!  Thank you.


texts: Digitally controlled audio fader circuit?

texts:
I have two audio signals and I want to fade in one signal in just as the other signal fades out and repeat the process backwards and so on... I want to control the circuit using some digital means or voltage control, however the actual circuit should be analog.
Any suggestion for an affordable solution?


texts:
Now, I have already made some progress, I have figured out what the W/L should be and made most of the circuit. Though I am not sure how I should put the MOSFETs for them to get the following output. Below is my circuit.

And here is my goal.

I have only 2 MOSFETs and I don't know where to put the third one.
Please help!


texts: Create multi touch display for full light

texts:
We have been given a project at uni to create a multi touch display.

I've done some research into this and a lot of them call for special film on the glass or use a projector (meaning it needs a certain amount of darkness).

I want to make a multi touch screen that can be used in full daylight (outdoors) and not more than a few cm behind glass - has anyone come across such a project?

It needs to be about a 42" screen size - so not a small pre-made one.


texts: Experimental calculation of dc motor resistance

texts:
I am trying to calculate resistance of DC motor experimentally.

I have measured voltage and current for different voltages applied (from -5V to 5 V). Motor shaft is blocked.

And the question is why resistance is smaller for higher voltages? (resistance according to applied voltage is decreasing)


texts: How to understand V2164 VCA control voltage per dB?

texts:
I'm designing an audio circuit which includes the V2164 VCA IC. This chip is a clone of SSM2164. I take a "Basic VCA Configuration" circuit which is supposed to give a unity gain with 0V control voltage level. The datasheet says the chip has "a ground referenced –33 mV/dB control port". I want to control my VCA in the range of full attenuation to a little above unity gain. Questions:

Am I right that -100dB can be considered "full attenuation"?
Do I understand right that in order to get -100dB attenuation I need   -3.3V control voltage level?
Why is there a minus sign in the "-33mV/dB"?

My input signal is going to be AC 5Vpp level. The signal source is a CODEC with 102dB dynamic range (if it matters), followed by an inverting op amp stage shifting it from 0V..+5V to -2.5V..+2.5V.


texts:
In the following circuit implemented in an FPGA I have a glitch on the OUT1 (due, I guess, to the propagation delay of the upper XOR which causes to have on the lower XOR two input not syncronized).

Here can be seen the waveform simulation. My question is : how to remove the glitch maintaining the same output values?
I think I have to avoid the direct path between the two XOR ports by using some FF but I do not know how precisely.


texts: Unexpected output from astable multivibrator?

texts:
After following an answer to a question I asked here I created this circuit...

simulate this circuit – Schematic created using CircuitLab

This is the output on either of the transistor collectors.

Shouldn't I be getting a pretty crisp square wave with this configuration?


texts:
The question is - is there an inexpensive oscilloscope I can use to measure DC voltage and current to see why my battery pack is failing to power a DSLR?

In order to take long time lapse photos with long (night time) exposures in cold weather, I have built an external camera battery pack.  However, after a period of time (15 minutes to a couple hours) the camera stops.  If for even an instant the camera does not get sufficient power, it stops the series and once stopped, even if it gets restarted manually, the time lapse cannot because of the gap that gets created.

The battery pack initially was a 12v 12Ah AGM battery connected to a buck converter to supply the camera with 8.4v which is the voltage of a fully charged Nikon EN-EL15 battery.  When even this failed, I tried connecting two smaller batteries in case one could not supply the needed current.  (I tried the two in both series and parallel even though creating a 24v battery and then down converting to 8.4v seemed futile.  It was.)  I have also added two small 5W 12V heating pads to keep the battery from getting too cold.

The camera is a Nikon D750. There is not much I can find about power consumption although 2.5A is written on it somewhere or other. Long exposures are the highest energy drain on a camera as the sensor needs to stay on and the mirror needs to be held open.  (I have not yet tested current usage but now that I think of it, I should with a multimeter.)

I was hoping an oscilloscope could be used to determine if it is the voltage that is dropping or the current is insufficient.  My guess is the current is briefly inadequate as the bucks should keep it at 8.4v as even a discharged 12v is around 11v.

Mostly I want to understand the issue.  But if not and my guess it is the current, what about a capacitor in the circuit?  How would I choose the right size capacitor for this?  (I do realize the capacitor would drain the battery when not in use but could be easily disconnected from the power until needed.)


texts:
So i read about the Zener diode voltage regulator circuit in the The Art of Electronics book, it made no sense to me, then I read about it in this article which was helpful but I still don't get it:

simulate this circuit – Schematic created using CircuitLab

How is it reglating the voltage exactly?! and why is the diode "reverse biased" (I guess it means connected in reverse) which doesn't conduct current unless a very high reverse voltage is applied?

If for example the input voltage is 12V, what would be the output voltage and current? and what would be the voltage and current values through the diode?


texts: Load generator for testing power supplies

texts:
I have some DC-DC power supplies that I would like to test. (about 10 or so).

PSU specs:

Input 6-30V DC
Output 8V DC, 2.5 Amps max.

As I don't have the budget for a DC Load generator, I'm looking for a cost effective alternative to test with.

I have salvaged a PC fan from a Dell Workstation. DA15050B12H - AVC 150mm Ball bearing fan, DC12V 1.8 Amps.

Will this fan behave as an analog of an 8 volt 2.4 amp load as I would expect?  I'm about to do some testing and measuring, I don't really care too much about the fan, but I wouldn't want to damage the PSUs.

Are there better load generation tricks I could consider without spending a fortune?


texts: Help understanding remarkable Voltage Controlled Filter

texts:
I'm quite new to electronics and trying to understand how this voltage-controlled filter (VCF) schematic works exactly.

It's a 12db/oct lowpass filter without the use of capacitors but uses the inherent Miller capacitance of the opamp (between the output and inverting input i guess?)

From what I understand, the circuit involving the first op-amp will set the cutoff frequency by applying a DC voltage on the "Effect control in" input pin. It is a voltage controlled filter after all.

Someone online also told me this but I didn't quite understand it yet...:

Those opamps, the К140УД12 ones, are special (by modern standards) because of pin 8. Pin 8 sets the quiescent current of the opamps, which in turn sets the frequency response.

R5 and R8 make sure that the two opamps share the bias current. It's worth noting that the КР140УД8Б opamp is capable of directly outputting a current with the transistor. As long as R5 and R8 match, their value doesn't matter too much; although, they do set a hard limit to the maximum current pulled from the pin8's.
It appears that all the signals other than the output are current-mode.

I found out the КР140УД8Б can be replaced by a TL072

And the К140УД12 can be replaced by: uA776, NTE888, ...

How does this pin 8 work?
How is it exactly filtering the signal?
Is this a 12db/oct filter because there's two op-amp stages in the filter section?

Thanks in advance


texts: FWHM of something which does not reach half of maximum?

texts: There is some curve for which I have find FWHM. But the curve does not reach half maximum i.e., its maximum is 1 and it only reaches .7 (but it does have the bell curved shape the filters have). Right now I am considering half maximum as (1-.7)/2, is this correct? I am confused.


texts: How do/should LiPo low-voltage cutoffs deal with voltage sag in practice?

texts:
I've seen a lot of literature online about low-voltage cutoffs for lithium polymer batteries, but they hardly mention anything about the effects and considerations of voltage sag caused by the battery's internal resistance while under load. This all stems from the internal resistance of the battery.
For high-power applications, the voltage sag can be quite considerable and lead to premature cutoff in a variety of ways. For example, a 20A draw on a 2S lipo with an internal resistance of 10mOhms gives a sag of 0.2VDC, which is 10% of the usable voltage range of the battery! (6.4-8.4VDC).

Do most LVCs implement a low pass filter on the measured pack voltage to avoid a short current spike tripping the LVC prematurely?

Do LVCs simply monitor the raw output voltage of the pack (which may be sagged)? Could they instead use an assumed internal resistance, measure current draw and output voltage, and estimate the true pack voltage?

EDIT: Specs say to not discharge a cell below 3.0VDC. But does this spec apply to the pack output voltage while under load, or the true internal voltage with internal resistance and load accounted for?


texts:
Motor is 0.75Kw, 3Ph, 400V and the rated RPM is 1380.

How much speed I can reduce using the VFD

Can I operate at 300rpm while it is designed for 1380rpm with worm gear assebly.


texts: Why is a datapath in microcontrollers always a power of 2 wide?

texts:
Microcontrollers data paths are always a power of 2 wide: 4 bit, 8, 16, 32 bit, etc. Even PICs which use 12-bit wide instructions are 8-bit controllers. Why? Is there any design advantage to this? What's wrong with a 12-bit databus, or a 7-bit controller?

edit
The 7-bit doesn't make much sense, but it's what made me think of the question. The answers refer to the tradition of 8-bits. But 16-bit isn't 8-bit, and 24-bit can handle 8-bit data as well as 16-bit, right? Why did they skip 24-bit to go to 32-bit?


texts: What material can I lay over a capacitive touch screen that will still make it work?

texts:
So I am trying to build a capacitive touch screen in a table, but since the table is much larger then the touchscreen. I like to put something on top that not only make it easier to clean, but also avoid the feeling of the bevel between the normal table and the touchscreen within and if someone spills a drink that wouldn't be so much a problem.

Does anyone know which material I can put on top that would still allow touches to go through?


texts:
This is the error I see:

This is my Simulation Command. What is the issue here?


texts: Having issues with using simultaneous timers [STM32]

texts:
In my nucleo L432KC, I have set Timer 1 for PWM generation, Timer 15 as a timer based interrupt and Timer 2 as PWM input mode. Timer 1 and Timer 15 works well until a point. My clock frequency is 2MHz. For example, I wanted a 50 kHz update event, so I set Timer 15 Precaler 0 and period 39. In that case, While(1) loop never executes, i.e, the program hangs.

When I start timer 2 as:

HAL_TIM_IC_Start_IT(&htim2, TIM_CHANNEL_3);

HAL_TIM_IC_Start_IT(&htim2, TIM_CHANNEL_4);

My timer 1 misbehaves. The program in general misbehaves. What could be happening here? It's like Timer 15 interrupt is taking all the control? Is something related with interrupts priorities? The purpose of Timer 15 is to fire an interrupt at 50 kHz. During this interrupt, I'm reading SPI data.

Pseudocode of interrupt routine:

Pull chip select down

Read SPI with HAL_SPI_Receive

Pull chip select up


texts:
I'm new using STM32 microcontrollers, I have been trying to use the printf tracing in my code without success, anything is printed on the console. I can start a debug session, I can place breakpoints on my code, inspect variables and all works as expected but not the printf.

My setup :

I have reimplemented the _write method:

int _write(int32_t file, uint8_t *ptr, int32_t len)
{
/* Implement your write code here, this is used by puts and printf for example */
int i=0;
for(i=0 ; i<len ; i++)
ITM_SendChar((*ptr++));
return len;

}

And placed a breakpoint on:

__STATIC_INLINE uint32_t ITM_SendChar (uint32_t ch)
{
  if (((ITM->TCR & ITM_TCR_ITMENA_Msk) != 0UL) &&      /* ITM enabled */
      ((ITM->TER & 1UL               ) != 0UL)   )     /* ITM Port #0 enabled */
  {
    while (ITM->PORT[0U].u32 == 0UL)
    {
      __NOP();
    }
    ITM->PORT[0U].u8 = (uint8_t)ch;
  }
  return (ch);
}

And ITM->PORT[0U].u8 = (uint8_t)ch; is being executed, but no printf ouput in console.


texts:
I want to calculate the input impedance when I am using a Darlington pair and I'm getting a little confused on the appropriate equation to use.

In Electronic Devices by Floyd he gives and example of a Darlington emitter-follower circuit and when he calculates the input impedance he has B^2*(re+Re) where Re is RE||RL and re is the ac emitter resistance.

I was watching a video by David Williams who is explaining the input impedance and goes through the derivation of a emitter follower Darlington pair (which made sense as he went through it) and goes up with the input impedance of B^2(2re+Re).

So my question is when trying to calculate the input impedance, am I supposed to be using 2re or re in the equation? Or if they are both valid is there a rule of thumb when to choose which. Image from the two sources are below


texts:
I Googled a little bit about transistors and I figured out I have a general understanding problem. Can I simply connect the emitter of the transistor to the GND of my microcontroller that controls the transistor but also to the GND of the 12V I try to control with the transistor, to close both circuits?

Would the circuit shown below work?

simulate this circuit – Schematic created using CircuitLab


texts: High current linear PSU capacitor requirements

texts:
Electrolytic caps have rated max ripple current (usually about 2A or so, even the "low ESR" ones). So, if I want to build a high current power supply (say 100A at 12V), I should use a lot of capacitors (more than 50 caps 2A each) in parallel so as not to overload the capacitors. Is this correct?

Does this only apply to the mains frequency power supplies? I have not seen a PC power supply that uses enough caps to satisfy the current requirement.

I want to build a simple unregulated power supply - just a transformer, bridge rectifier and smoothing caps if it turns out that this is cheaper than buying a (good) ATX or similar PSU.


texts: Sinking and Sourcing Current to and from a PIC24F Output Pin

texts: Sinking and sourcing current refers to current going into and out of the MCU (respectively), right? If you configure a GPIO pin as an output, why would current ever go into the pin (since it's configured as an OUTPUT)? I suppose it depends what the output circuit looks like, if it's tied to the voltage supply rail or ground... maybe I just answered my own question...?


texts:
I'm using

Arduino IDE software
Arduino Uno board
GSM SIM800C
BSNL 4g SIM card

Interfacing

RX (of GSM) to PIN 2 (of Arduino)
TX (of GSM) to PIN 3 (of Arduino)
GND to GND

Power supply

For Arduino - laptop through USB cable
For GSM - 3.6 c.v external battery.

Code:
#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3); // RX, TX

void setup()
{
  // Open serial communication
  Serial.begin(9600);

  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);

  delay(1000);
  Serial.println("Testing SIM800C module");
  Serial.println();
  Serial.print("Sizeof(mySerial) = ");
  Serial.println(sizeof(mySerial));
  Serial.println();

}

void loop() // run over and over
{

  if( mySerial.available() )
  {
    char c = mySerial.read();
    Serial.print(c);
  }

output:


texts:
I was repairing a laptop of a friend, and as i was assembling it, i accidentally broke the ffc badly that connects the on button to the motherboard and the signal wasnt getting trough, i broke the wire. I cut the end off of the cable, where the contact pads were, and i tried to scrape off the plastic coating with a knife, but i was scraping off the metal too. Anyone knows how I could expose the metals with home tools so i can plug it in?
I know other solutions to this problem, but I'd not like to do any workaround if i can somehow mana to salvage the situation.


texts: Controling where sound goes (darlington array)

texts:
source of sound (dealing with multiple sources) and six speakers. I want to control to which the sound goes.
The system has a DC offset with both sides of the wave within positive range
Question is can I use a Darlington array like ULN2003AN? (I have ordered bunch, since I often use them as a protection for mine Arduino)

Can I use the Darlington array to control where sound goes with sound positive (high) being connected to COLLECTOR and the arduino switching relevant base to let it through?

Since base is switched for several minutes at a time (usually 1-2 minutes) and
I am not using the IC as amplifier the speed and exactness or amplification does not matter to me.
I am trying to avoid relays for obvious reasons, and will only get solid state relays if needed.
Any other ideas?


texts: I need to find an Integrated Circuit Encoder that converts inputs (push botton) to its corresponding binary code, as in the table. Can anyone tell me any? I found something similar that was the IC 74147, but the same is obsolete.


texts: Can I use a single large capacitor rather than multiple small?

texts:
I'm designing a PCB to hold an array of WS2812B LEDs. The LEDs are in groups of 4, with roughly 1cm gap between them, 60 total LEDs per PCB.
As per the documentation recommends I add a 0.1uF decoupling capacitor to each LED. Which is what I've done in the attached image.
I'm wondering, as I understand it, the capacitors are there to supply current when the LEDs are turning on really fast, to prevent flickering as the power supply cannot provide the current fast enough. Is there a way I can just use a larger capacitor per group of 4, rather than 4 individual capacitors?
To save PCB space and ease of assembly.
Happy to hear any insights, recommendations or corrections if my assumptions are incorrect, thanks!


texts: Cost Effective Solution to using PAM8403 as a headphone amp

texts:
I've just bought a PAM8403 pre-built circuit board for $1 on eBay, I was going to use it to drive a set of headphones but I neglected to consider that this is a Class D amplifier and will not take kindly to connecting the -ve output terminals together (since headphones are typically 3-wire, unless you have a set of very expensive balanced headphones).

So my question is, is there a cheap solution to connecting the two -ve terminals to drive a pair of headphones without rewiring the headphones themselves? In particular is there any arrangement of inductors and capacitors that will allow the negatives to be commoned?

I am aware that I can use two 1:1 Audio Isolation Transformers but the cheapest I can find these are about $5 each which is not ideal.

I have a feeling that it is possible to connect the two negatives together with some sort of LC filter but I'm thinking that it will probably greatly reduce the usable power output of the PAM8403 chip amp which is already quite low. I would like to hear anyone else's thoughts / ideas?


texts: Range of the write protection registers on STM32 (WRP1AR etc)

texts:
I want to enable write protection on the flash pages occupied by the bootloader on an STM32L4 chip. I understand I must set the WRP1AR register to 0xFFXXFFYY where XX is the end page and YY is the start page.

My question is quite simple, but the docs is not really clear. Is the end page also included in the protection or not? So if I write 0 as start and 4 end I get 5 pages protected (0, 1, 2, 3, 4) or only 4 (0,  1, 2, 3)? The way the documentation is worded makes me think it is the first case, but the second way is more usual in programming (at least in C).


texts:
I'm having trouble implementing a DC series motor simulation, and I think this is due to the fact that I do not understand the motor behaviour itself.

Notice that the mechanical part of the simulation is completely functional, so I don't have to bother with this. I have a DC series motor (motor constant G, internal resistance R) which get some voltage V applied on its terminal, and a mechanical load (Torque T, angular speed w) applied on the shaft.

Here's what I currently do:

Evaluate the current in the circuit: that'd be \$I = \dfrac{V - BackEMF}{R}\$
Get the torque from that current: \$T = G \cdot I^2\$
The mechanical simulation spits out the speed based on this torque and the load, and I compute the \$BackEMF = G \cdot I \cdot w\$
Back to 1

The issue is getting to the steady state: I can't see what will prevent my motor to diverge.

The way I see it, when going to steady state, BackEmf gets close to V -> the torque gets very small...But so does the current, which means BackEmf becomes small on the next simulation step -> (V - BackEmf) grows again, the torque increases, etc.

So: what actually prevents that? Is it inherent to my step-by-step simulation? How can I circumvent this?

What I have tried so far, without success:

the magnetic flux is actually not linear but should saturate at some point (when?)
I tried to add a small friction torque so the motor isn't "perfect"

I also have the same (related, I think) instability issues when I reduce the applied voltage V.


texts: What is the minimum number of 2-to-1 muxes needed to implement a 129-to-1 mux?

texts: I understand that if the requirement was to implement a mux that was a power of two there is the trick where you can do do x -1, so for instance if I wanted to implement a 8-to-1 mux, I would use 7 muxes because 8 = 23 and 23 - 1 = 7. But how does that change if you wanted to implemented a mux that is not a clean power of 2?


texts: A question about remote ground sensing and its advantages

texts:
In this article, they are explaining the benefit of using a technique called remote ground sensing by using a single-ended sensor and a differential amplifier or an instrumentation amplifier. Below is the excerpt regarding that part:

But I don't understand what text means here and how does this work better than the following (my own edited drawing) connection below:

In both diagrams above the sources are grounded in the measurement side. The only difference the one in the article uses an extra wire to the ground of the differential amplifier(or instrumentation amplifier).

1-) Can you explain in a an easier way how come in the first case the ground differences is removed? Obviously I don't get the text's explanation.

2-) If first one is using 3-wires like a shielded twisted pair cable, and my drawing is using a 2-wire coaxial cable; would there be any difference in terms of common mode noise rejection? And why/why not? I'm asking this because I'm trying to understand whether the so called "remote ground sensing" only has advantage for ground offset errors but not common mode interference. In other words are both of way of connections unbalanced same amount?

eidt:

Regarding the below drawing representing the original diagram above:

Considering the source impedance is zero or neglectible, and considering the line/wire impedances are equal Z1=Z2 is the diagram above a balanced system?

"The impedance to ground" seen by common mode interference for the first hot wire is:

Z1+Zamp (the path from the + terminal of the source through hot wire and Zamp to GND of the diff amp.)

But what is the path taken by the source's GROUND SENSE?


texts: Explanation of Edge Triggered D type flip flop triggered at positive edge of the clock pulse cycle (from Morris Mano Book)?

texts:
This is from DIGITAL DESIGN by Morris Mano Book!

Can someone help me in explaining the paragraph about fig 5.10. It starts from bottom of former pic to the first two paragraphs of latter pic. This is a D type edge triggered Flip Flop which only responds to a change in transition of clock pulse from logic 0 to 1.

It says in the paragraph that both S and R are maintained at logic 1 when clock is zero and also when Value of D changes to 1 it goes into set state!

What is meaning of maintained here?
How can we logically predict from the logic of NAND gates from the circuit diagram that when Clk = 1 then only possibility is for S to be 0 and R to be 1. Similar for other cases.

Also why this change only observed at transition not during the positive level of pulse?
Understanding Master Slave D flip flop was easy. But this is way too complicated! May someone help!

Update: my book (Morris Mano) says that when the value of D = 0 and Clk is set to 1 then the value of the Reset variable and Set variable are 0 and 1 respectively.

How can it make such a prediction? Clearly, output of NAND4 has to be 1 and lower two inputs of NAND3 have to be 1 but the above input can be either 0 or 1. Also, one input each of NAND 1 and 2 has to be 1. But their outputs can be 0, 1 or 1, 0 respectively. Hence the value of S can be 0 and that of R can be 1. Then why is everyone so sure that R has to be 0 making the output Latch always in a Reset state. This IS The part I fail to understand.

simulate this circuit – Schematic created using CircuitLab


texts: NXP arm microprocessor memory erase - no JTAG

texts:
I am fiddling around with NXP LPC2368. Recently changed the PLL clock control registers, and as a result JTAG stopped working, so I am unable to program or erase the chip.

My question is, is there any way to erase the chip "manually", as in, non-programatically? Any way that dos not involve using JTAG.

Yes, I've searched the user manual, couldn't find the answer.


texts: How to use present and previous value of a signal for this VHDL code?

texts:
We need present and previous value of the signal noisysignal1 to compute certain equations. One of the equations is  y[i] = noisysignal1[i]*w1 + noisysignal1[i-1]*w2;. How can we use the present and previous value of the noisysignal1 at the same time in our VHDL code?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.math_real.all;
use IEEE.STD_LOGIC_Unsigned.ALL;

use IEEE.NUMERIC_STD.ALL;
entity random is
  generic (
    width : integer :=  32;
    nn : natural := 1; -- power of the binomial distribution <16
    m : REAL := 0.0    -- mean output value
  );
  port (
    clk : in std_logic;
    random_num : out std_logic_vector (width-1 downto 0);   --output vector
    RST : in STD_LOGIC;
    DATA_OUT : out REAL := 0.0
  );
end random;

architecture Behavioral of random is
  type arri is array (0 to 15) of integer;
  type arrr is array (0 to 15) of real;
  signal noisysignal1 : real;
begin
  process(clk,rst)
    variable rand_temp : std_logic_vector(width-1 downto 0) := (width-1 => '1',others => '0');
    variable temp : std_logic := '0';

    variable s1 : arri := (3,33,333,3,4,5,6,7,8,9,11,22,33,others=>55);
    variable s2 : arri := (5,55,555,50,6,7,8,9,5,6,7,21,33,others=>22);
    variable r : arrr := (others=>0.0);
    variable s : real := 0.0;

    variable noisysignal : real;
    begin
      if rst='1' then
        DATA_OUT <= 0.0;
      elsif rising_edge(clk) then
        temp := rand_temp(width-1) xor rand_temp(width-2);
        rand_temp(width-1 downto 1) := rand_temp(width-2 downto 0);
        rand_temp(0) := temp;

        s := 0.0;
        for i in 0 to nn-1 loop    -- nn noise generators
          UNIFORM (s1(i),s2(i),r(i));
          s := s+r(i);
        end loop;
        DATA_OUT <= 2.0*(s/real(nn)-0.5) + m;
        noisysignal := real(to_integer(signed(rand_temp))) + ( 2.0 * (s/real(nn)-0.5) + m);
        noisysignal1 <= noisysignal;
      end if;
    random_num <= rand_temp;
  end process;
end Behavioral;


texts:
Is it good to use one UART interface on MCU, RX_UART for receiving data from RS422 receiver and TX_UART for transmitting the same data to the RS232 and RS422 transmitter? I am trying to use UART as "signal splitter", because I want to use my rs422 input signal and forward it to rs232 and other rs422.

EDIT:
I can not ask another question, and don't know how to edit others to be allowed to ask again, but I would like to know this:

Why JTAG connectors use 20, 14 or 10 pins (standard), when only 7 is required (minimum, TDI, TDO, TMS, TCK, NTRS, GND, VDD)?


texts: How to use a solar panel that has 'watts' to power a battery charger that requires: 3v & 2.8 amps?

texts:
I have a battery charger that charges small batteries ( AAA & AA ).
It uses an adapter that gives it 3V and 2.8 amps.

I want to remove the adapter and give it solar energy instead.
There are cheap solar panels out there (small ones) but based on what I see, solar panels only output "watts" for example "5 watts".

What am I supposed to do with "Watts" if what I need is 3 Volts and 2.8 amps ?


texts:
I'm trying to understand the description of a counter in VHDL:
entity counter is port (
    load, reset, clk: in bit;
    input: in integer range 0 to 255;
    output: out integer range 0 to 255);
end counter;

architecture behaviour of counter is
begin
   ctr: process
      variable value: integer range 0 to 256 := 0;
      begin
         --update value
         if(clk'event) and (clk= '1') then
            value := value + 1;
         elsif load= '1' then value := input;
         elsif reset = '1' then value := 0;
         end if;

         if value = 256 then value:= 0; end if;

         --output value
         output <= value;

         --wait on changes in input signals
         wait on clk, load, reset;
   end process;
end behaviour;

but I don't really get it. There are a lot of examples of counters out there but each is one is completely different from the other and meanwhile, I don't know where to get answers.
This entity will be used along with this testcounter:
entity testcounter is end testcounter;

architecture behaviour of testcounter is

   component counter port(
      load, reset, clk: in bit;
      input: in integer range 0 to 255;
      output: out integer range 0 to 255
   );
   end component;

   signal load, reset, clk: bit;
   signal input: integer range 0 to 255;
   signal output: integer range 0 to 255;
   begin DUT: counter port map(load, reset, clk, input, output);

   --Simulation.
   process
   begin
      --Simulation: Load.
      for c in 0 to 255 loop
         input <= c;
         wait for 25 ns;
         load <= '1';
         wait for 50 ns;
         load <= '0';
         wait for 25 ns;
         assert input= output report "Load: output wrong";
      end loop;

      --Simulation: Reset.
      reset <= '1';
      wait for 50 ns;
      reset <= '0';
      wait for 25 ns;
      assert output = 0 report "Reset: output wrong";

      --Simulation: Count.
      for c in 0 to 255 loop
         assert c = output report "Count: output wrong";
         clk <= '0';
         wait for 25 ns;
         clk <= '1';
         wait for 50 ns;
         clk <= '0';
         wait for 25 ns;
      end loop;
      assert output = 0 report "Count: overflow wrong";

      --Simulation: Reset.
      reset <= '1';
      wait for 50 ns;
      reset <= '0';
      assert output = 0 report "Reset: output wrong";

      wait;
  end process;
end behaviour;

but I'm fine if I could get help understanding the counter.
I have seen several descriptions and I think I know how counters work conceptually but lack the knowledge how to implement them. I understand programming itself but I don't get the meaning of the clock, load and reset and their results when the one is zero or one.
Could somebody explain? I'm also glad if you could point me to proper sources where I can look that up!
added gtkwave:


texts: Atmega MCU freezes when nearby VSD starts. Possible causes and solutions

texts:
I have a custom PCB that uses an ATMEGA1280 MCU. The board has a few inputs and a relay output. Inputs are mostly 4-20mA measuring temperature sensors. I also measure VSD current from a VSD mounted next to my board. My board uses LoRa to communicate to a homebase. Everything works fine until the VSD starts. Then my ATMEGA 'hangs up' / freezes. The reset button sometimes doesn't even reset the board. Then I have to remove power and apply power again. I get power from a charge controller connected to a battery and some solar panels. I get 12V in and my circuit runs on 3.3V. I use a linear voltage regulator to go from 12V to 3.3V.
My board is in a seperate steel enclosure that is grounded. What could cause my MCU to freeze? And why does it freeze? Is it in some sort of safety shutdown mode? What could I look at to prevent my MCU from freezing? EMI? Shielding? Grounding?


texts: Converting Power Spectral Density to Power

texts:
I have a vector signal analyzer which is measuring an OFDM signal with a bandwidth of 20MHz.

The spectrum shows "Power Spectral Density [dBm/RBW per 100kHz]" on the Y-axis. The RBW is set for 100kHz. The average power (in time domain) is measured to be 10dBm.

I am trying to understand how to convert the PSD value to average power.

*I have added a few pictures to show my measurement. The first two are from the power spectral density of the 20Mhz signal being measured. The third image show information about the signal, including the average time domain power (sqrt(I^2 + Q^2))


texts: Op-amp offset voltage and capacitive coupling

texts:
About the circuit above, I can't understand from the row "VA=2Vos".
If that's because most of the voltage between 1K ohm resistor and capacitor is on 1K ohm then I can't understand why VA should be double of Vos.
Please help me understand this circuit.


texts: current drawn by led increase with more leds you put in parallel??against V=IR?

texts:
current drawn by led increase with more leds you put which i saw in a video about thyristor ,but more leds means more resistance which means lesser current which is not true as per the video(https://youtu.be/4N1uLth1o9o )1:50-2:00that does not fall true how and why.
PS -the channel is GreatScott's so its reliable


texts:
I need produce an 18 light strand of series connected light, based on a 100 light 2P50S system (2 parallel strands each of 50 series connected lights).
Based on the wiring, I believe the strand is engineered as two 50 light strands in parallel.   The strand is rated for 120 V and consumes 40.8 Watts at 0.34 amps.
That is each strand of 50 lamps in series has a voltage per lamp of 120/50 = 2.4V / lamp, and each lamp draws 0.34A / 2 = 0.17A.
When I shorten the strand I need to adjust for the lost resistance from the bulbs that have been cut away.
ie I will now have a 18 x 2.4V = 43 volt string drawing 0.17A.
If I did my calculations right it seems I would need about 450 Ohms of resistance.

Resistance per lamp = V/I = 2.4/0.17 = 14 Ohms.
Lamps to substitute for = 50-18 = 32 lamps.
Equivalent resistor = 32 x 14 ohms = 448 Ohms.

My problem is I do not know what part to order to achieve this level of resistance and I am not sure if the heat put out by that resistor is realistic to deal with.
Question is, how should I best engineer this adjustment and what parts should I order to construct the solution?


texts: Ammeter with 2 voltage sources without superposition

texts:
I'm studying for the exam of this very basic circuit analysis class that I'm taking, and there is this particular problem in the textbook:

You are supposed to solve this without using the superposition technique. However, no matter what I have tried, I could never get the same result that they provided. If anyone could explain the steps to solving this I'd be very grateful.


texts: STM32F103. How to use PB4 as normal GPIO? NJTRST remap not working

texts:
I need to use PB4 as a normal GPIO digital output pin. I have a custom designed board where this pin is connected to the CS of a SPI device, so just using another pin isn’t possible.

I’m using the HAL for developing the firmware. The code I use for configuring GPIO is:

__HAL_AFIO_REMAP_SWJ_NONJTRST();
__HAL_RCC_GPIOB_CLK_ENABLE();
GPIO_InitTypeDef config_gpio = {0};
config_gpio.Pin = GPIO_PIN_4;
config_gpio.Mode = GPIO_MODE_OUTPUT_PP;
config_gpio.Pull = GPIO_NOPULL;
config_gpio.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB, &config_gpio);
HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, GPIO_PIN_RESET);

After that, PB4 is always pulled high and I can't set it low, probably because it keeps behaving as NJTRST, so I can’t use it as a normal output.

It seems that the macro __HAL_AFIO_REMAP_SWJ_NONJTRST() doesn’t do anything.


texts: Why do I Have 800 pixels in PAL video line

texts:
I have a DCMI peripheral (STM32H7)  that receives video data from TVP5150 with discrete VSYNC/HSYNC.

I have 306 (it should be 305, but there is a chance that this is because of the way I count number of interrupts) active video full line interrupts in one frame, with one line duration of 64 us.
It's all sounds good but it's seems that I have 800 Y values received during one line (monochrome video).

That's seems odd to me,  Is there any explanation why it is that way?


texts:
I have a smithchart created by MATLAB using the following code (the S22 is a 801x1 vector obtained from a file):

n = 801;
fStart = 45*10^6;
fStop = 15*10^9;
f = linspace(fStart,fStop,n);
figure()
smithchart(S22)
title('S22 with 50 $\Omega$ SMD resistor','interpreter','latex')

Is it possible to mark specific frequencies as dots in the diagram?


texts: Do logic families use different type of transistors?

texts:
Do the logic families such as TTL and CMOS represent only different logical structure? Or do they also use different type of transistors? Latest microprocessor chips with millions of components use CMOS. Is that only because CMOS "operating logic" is superior or also because CMOS family use entirely different transistors?

So far I understood is there are transistors which are used in analog circuits and there are tiny ones which are used in IC chips. I guess analog use TTL level transistors?

The transistors in ICs use many different logic families such as TTL and CMOS. So there are different transistor manufacturers for all these?


texts:
I want to measure the input voltage to my circuit. The input voltage is supposed to be anything between 7 to 35 Volts.

I have a micro-controller with 12bit ADC. I am using a simple voltage divider to connect a fraction of input voltage to the ADC pin.

The voltage divider is simply a R1 = 82k on top and R2 = 5.6k resistor on bottom.

According to my calculation, at 35V I should get (never mind the tolerance):

V_IN = (V_SUPPLY * R2) / (R1 + R2) = (V_SUPPLY * 5k6) / (82k + 5k6) = 2.24

And the same calculation at 7 Volts I should get 0.4V into the ADC pin.

Now the question is, how to convert the raw value of the ADC to a voltage?

If I supply my circuit with 12V and if I did the programming of ADC correct, I am reading the raw value of around 840 out of my ADC.

The ADC reference voltage of controller is 3.3 Volts.


texts: Can this 19.5 V/3.33 A/65 W laptop charger power this 12 V/45(maybe) W motor?

texts:
I have two motors from the back wheels of an old Rollin' Rambler kids powered car (https://www.amazon.com/12V-Rollin-Rambler-Ride-On/dp/B00S713PW4). Unfortunately, I didn't get the wiring harness and controls out before it was thrown away. I'm thinking of using one of the motors to make a vibrating parts cleaner, but want a way to power it without having to use the battery. The car had a slow and fast speed, so I'm assuming it supplied maybe 6 or 8 volts to the motors for slow speed and 12 volts for fast speed. However, I don't really know how many amps the motor pulls. I can't find an exact one online using the numbers on the motor housing, but I think this one is similar: https://www.amazon.ca/SODIAL-15000-Electric-Motor-Spare/dp/B078CR3P86

That description has 35-45 W. If I understand it correctly, that equates to 2.9-3.75 A.
I also have an old laptop charger that outputs 19.5 V and is rated for 3.33 A. I'm wondering if there's any reasonable way I could use this charger and a resistor or something to power this motor at 12 V (or even less volts if that will reduce the current to an acceptable level for the charger).
From what I can figure, to use this charger to power the motor at 12 V and 3.75 A (I know it might even pull more amps on startup), I would need a 2 Ohm resistor:
(19.5-12)/3.75 = 2
But then I think that would require the resistor to be rated for almost 30 W:
(19.5-12)*3.75 = 28.125
And that just doesn't seem right/logical to me, but I've only really done anything with lower voltage and small watt resistors.
So, is there a reasonable way to power the motor using the charger, and are my calculations correct?
Here are pictures of the actual motor and charger.


texts: How to set the input impedance of an inverting amplifier

texts:
I want to Design an op-amp inverting amplifier circuit with
Closed-loop voltage gain = -10 and Input impedance = 10k

Since the it's an inverting amplifier then the Closed-loop voltage gain =-Rf/Rin
So if Rf = 100k and Rin = 10k then the Closed-loop voltage gain = -10

But I don't know how to set the input impedance of an inverting amplifier.

the input of this op-amp is 1 volt


texts: Which method or theorem can I use to solve the current across a silicon diode considering the two DC voltage sources?


texts: How to discharge batteries using bench PSU?

texts:
I've heard that if you can have negative current in PSU, you can use that to discharge batteries. Is this true?

If yes, how to design/modify a linear bench PSU (which have transformer with several secondaries) in a way that be able to discharge batteries?

What's the working principle of it, I have no idea where to start.


texts: Pros and cons of centralised vs decentralised power deliver for small devices

texts:
How does compare using one power supply for multiple devices vs each device having its own - regarding efficiency eg. power consumption?

Model situation:
Home automation using low power devices such as sensors with Arduino, Raspberry Pi, Esp8266. Given 5-12V is not smart over long distances in a house, assume 24V power supply.

Choice:

Put low voltage cabling and power devices either directly from 24V or use a voltage converter to step-down to 3, 5, 12V respectively.
Each device will have its own small power supply from mains voltage, such as hi-link or similar.

Is there another aspects to consider aside from obvious like labour and cost of putting separate cabling?


texts:
I am using a relay to control a 230 VDC duct fan. Sometimes when the relay turns off my USB sound card freezes, to get it back I have to toggle the power (pull the USB cable, as it is USB bus powered). I have a lot of computer equipment and nothing else seems to be affected.

I have a diode across my relay and I have moved the relay further away from the USB sound card, the distance now is about 1.5 meter. But it is still happening. I am trying to understand why.

All computer equipment is connected through a UPS, the fan and relay circuit is not. I think that maybe the relay might be affecting the analog speaker signal going from the USB sound card. But I am surprised it is that sensitive, the sound card has never frozen like this until I got the relay installed.

Any thoughts would be appreciated, I am stuck trying to figure out a solution...

Update: After some more testing I can only get the sound card to freeze if the relay is actually controlling the fan. If the relay is controlling nothing, just turning on and off I have not been able to reproduce. But I am also not able to reproduce if I just turn the fan on and off manually with the switch.

Update 2: I disconnected the audio wire from the sound card, thinking that it might have picked up some noise. But the sound card still froze. It is very surprising that it is this sensitive.

Final update: I replaced the relay with a solid state relay as suggested. This not only made my circuit a lot easier, since I can power the solid state relay directly from the Raspberry Pi without a small 5V relay before the load relay, but it also seems to have eliminated my problem.


texts: Offset and scale a DAC output with opamps

texts:
I am trying to make a simple oscillator controller with an arduino and a DAC, to learn electronics.
I need to send a voltage between 12V and 17V to my oscillator to control its frequency. I got a 24V power and a 12V ref voltage. My DAC produce a 0/5V voltage.

I made a really simple circuit with a non inverting summer, which works fine :

(simulation)

Here the op amp is powered between 0V and 24V (I don't have negative voltage).

But my problem is, I need to be able to physically tune it using two variable resistors, for offset and scaling.

I think the process would be, theoretically :

Send lowest value to the DAC
Adjust offset trimmer until the oscillator is in tune for its lowest value
Send highest value to the DAC
Adjust scale trimmer until the oscillator is in tune for its highest value

Now I should have a perfect output range, which may not be exactly 12-17V but maybe something like 12.2V-16.5V or 12.5V-18V.

I tried to simulate many designs - the simplest one being tension divider bridges on the 12V ref and the DAC output. But my main problem is that adjusting one trimmer would impact the second. For example, adjusting the scale would also alter the offset.

I also tried to simulate this synthetizer "CV scale offset" schematic :

I still have the problem of linked scaled/offset but it seems more "linear". Maybe it could be possible to tune the oscillator if I begin by finding the right scale, then offset it.
But unfortunately I could not make it using a single power supply for the op amps. I had to power their negative supplies by -24V (which I have not) to make it work.

Here is a simulation (offset and scale controls in the right column).

Is there a simple solution to my problem ? I may be missing something (maybe the tuning process is not correct ?). Why does the last circuit not work with a single power supply, all my voltages being positive ?

Thank you very much for your help.


texts: Dc to DC converter: "split" one power supply (24V, 5A) into four power sources 5V, max 3A

texts:
I have one DC input 24V, 5A.
I have designed a 4 channel led driver using the PAM2804 for Cree RGBW leds.
I am using 3 of them. So, 3 Rgbw leds, and 3 led drivers.
I need to be able to control individual r,g,b,w channels, and select if I want to use 1,2 o 3 leds.
An arduino supplies the control signal to the PAMs.
My question, is how to convert the 24V, 5A into four 5V, 3A(max) sources.
I hav been using LM2596, or XL6009E1, to convert 24V into one 5V, 3A source.
But connecting several LM2596s in series to a 24v power supply seems not to work, one of them gets almost all the voltage. I have used them both in adjustable and fixed output.
What can I use instead?
EDIT the picture shows 12V 5A; that is not correct, it is 24V 5A; as described in the text description. Thanks for pointing it out.


texts: AC waveform from transformer is clipping

texts:
The transformer with its primary connected to the line and the the following waveform is what I get from the secondary.

Why is the waveform clipping, I suppose it is not in the primary side as I don't think that much clipping would go unnoticed. I have tested with another transformer and it is the same waveform.
Is the transformer core saturating? Whats the reason for the clipping?
PS: We have 50hz line voltage in India.


texts:
I am using small 1 AMP DC motor the speed of which is controlled by a small controller that actually generates a variable V from 3 to 12V. I can change the direction of the motor by using a DPDT switch in the controller out. However, to prevent damage, I want to have some kind of circuity that will not start the motor in the reverse direction immediately. But first stop it with a decay and then start it with a delay.

How can I implement this in place of the DPDT switch?


texts: High power source and low power load (device)

texts:
Can we drive low power load on high power source? For example we have source power 12 volt 60 amp and load power 12 volt 5 amp. Do we need resistor between them? If needed, what value will it be and how do I calculate its right value?
 Can we drive load directly on hight power source ?


texts: Calculating AC power figure using the DC current consumption

texts:
In a system where I have 220V AC recitified/regulated/converted into 3.3V DC through a transformer and a voltage regulator, would the amount of current I will be drawing from the AC line equal to the amount of DC current that I consume plus the inefficiency of the AC-DC conversion?

As an example: if my DC current consumption is 200mA at 3.3V and I know that my hypothetical AC-DC conversion is 80% efficient, would I then say my circuit consumes 52.8 watts? (200mA plus a 20% extra = 240mA, 0.24 * 220 = 52.8W)


texts:
I just bought a DC gear motor- I'm trying to spin a 20 pound disk. I realize I need to hook it up to a power source, but I'm having trouble figuring out the proper source. PS I also got a DC speed controller and I'd like to use the two in conjunction. How do I do that?

Here are the specs on the motor I've got

PM DC Gear
90 vdc
input hp 1/30
full load amps 0.35
47 rpm
26 lb full load torque

Here are the speed controller specs

DC Speed Control

HP 1/50 to 1/6
Voltage Output 90
Input Voltage 115

Thanks


texts: Does an unloaded amplifier use more power at a higher volume?

texts:
Suppose we have a powerful sound amplifier, which is set at 90% of it's power, and nothing is being driven into its inputs.

Is it using more power at this high volume (and producing heat, etc.)?

Is it bad to an leave amplifier at a high volume even if nothing is playing?


texts: Connecting a coin receptor to a key press

texts:
I want to connect a coin receptor to a keyboard press.

I want to have an arcade cabinet with my computer game running. It should only add credits when a specific key is pressed, which can be triggered by the coin receptor.

I'm thinking the coin receptor would trigger a button press via an arm, or through a USB keyboard.

What kind of receptor do I need to make this happen?

I apologise if this is off-topic, I couldn't find a better hardware focused SE.


texts: When implementing something build with flip-flops and logic gates, why do we aim to minimize the number of flip-flops even if it produces more gates? Does it have to do with minimizing the delay, the energy or something else? Could someone explain this?


texts: Relay closes without load connected across its terminals but doesn't work when it's loaded

texts: why would something like that happen? all the relay has to do is to close its contacts, what difference would the load do?


texts: SDIO standard is specifically meant for devices like camera that have an SD card. Still in many of the applications I found that the SDIO is also used to interface with WiFi chips. Why is that so? Can someone help me to understand this?


texts:
Books on the subject of ground penetrating radars provide definitions of pulse and stepped frequency radars, mentioning the structure of their signal and other technical details.

However, I was not able to find a source or comparison on practical results of those designs.

What are the practical differences between pulse and stepped frequency radars? Is there any difference in resolution, the complexity of hardware, attenuation, power consumption, signal processing...?

I'm asking this question because I am asked to design an imaging radar as homework and I cannot choose which method should I use, textbooks that I can find provide only technical background.


texts: How to constrain delay in the circuit without a clock?

texts:
Background:
The image below is, in essence, a simplified schematic of the, so called asynchronous state machine (AM_fsm.v). The design does not have any clock input signal. It contains many SR latches and a lot of combinatorial clouds. (aka OR/AND/MUX gates).

I would like to reduce the delay from the Q of the SR latch to the output m1. In essence, I need to reduce the propagation delay from pk_in to m1. The delay_A and the delay_B are not critical. In short, I need to reduce the delay_C as much as possible. The main reason why the delays A and B are not critical is very simple. The logic gates, selected/calculated by the synthesizer are such that every in-to-out propagation delay is in the range between 15 and 80 ps per gate. On the other side (delay_C), the propagation delay per gate is between 150-350 ps. So, there is still room for improvement I've tried various commands  to convince the 'genus' (CADENCE's synthesis tool) to size the gates to reduce the delay.

set_max_delay -from [get_pins AM_fsm/SR_latch/Q] -to [get_ports m1] 0.2

create_clock -name virtual_clk -period 3 -domain virtual
set_max_delay 0.2 -from [get_ports pk_in] -to [get_ports m1]
set_min_delay 0.0 -from [get_ports pk_in] -to [get_ports m1]

I even tried to put big load on the m1. It did help (slightly).

RESULT:
Nothing from above reduced the delay_C.

Is there some other way to convince 'genus' to  shorten the delay_C.


texts: Can I permently connect the resistant of a coffee machine

texts:
I have a simple coffee machine that has a little "controller" that control the ON/OFF of the heater.
Suddenly, the machine stop heating the water (and the recipient). I have open the base and test with a continuity tester the thermostat and the heater. The two parts pass the test.

I thought that the problem is from the electronic part.

The question is: Can I connect the thermostat-heater directly to power and adding a switch on the AC cable?


texts: How do we determine the roots from a Routh-Hurwitz array?

texts: I know that we can determine the roots on the right-half plane by counting the sign changes in the first column. However, I'm unsure how to find the roots on the left-half plane. Is it the same as the right-half plane due to symmetry or am I missing something here?


texts:
I'm using the MCP4922 as a dac with some different python programs. I am using this python package which has a setVoltage_buffered(channel, value) command. To quote the data sheet:

  The input buffer amplifiers for the MCP4902/4912/4922
  devices provide low offset voltage and low noise. A
  Configuration bit for each DAC allows the VREF input to
  bypass the VREF input buffer amplifiers, achieving a
  Buffered or Unbuffered mode. Buffered mode provides
  a very high input impedance, with only minor limitations
  on the input range and frequency response.
  Unbuffered ( = 0) is the default configuration.
  Unbuffered mode provides a wide input range (0V to
  VDD), with a typical input impedance of 165 \$k\Omega \$ with
  7 pF.

I'm having trouble understanding what exactly the buffered mode does. Does it prevent noise from damaging the part by preventing voltage values that are inputted which are just under the range from exceeding the range due to noise? Also, the documentation for the python package is a bit unclear; what sort of value should I input? I assume it relates to how much of a buffer I want there to be, but I don't know what the range of values should be.

Thank you.


texts:
I am trying to use PMOS SSM3J334R for charging battery. But I notice that my charging mosfet is getting heated even at less then 1A current.

On checking waveform I found very bad off time of MOSFET. Can someone help me to find issues in my circuit.

In plot below: blue - base, red - gate

In plot below: blue - base, red - drain

In plot below: blue - gate, red - drain


texts: How do I charge a commercial lithium battery with solar cells?

texts:
I have a digital camera (Panasonic DMC-FT1) and will be going multi-day hiking with it soon. I'm looking to build a solar charger for it using something like this and strap it to my pack. Does anyone have any experience doing something like this, or any pitfalls in general that I may fall into (ie will my battery explode if I do xyz) ? There will be plenty of sun on my trip.

Battery markings:

Model: DMW-BCF10E
3.6V 940mAh 3.4Wh Li-ion

Charger markings:

Model: DE-A60A
Input: 110-240V~50/60Hz 0.2A
Output: 4.2V 0.65A


texts: How to choose an electromagnet controlled by sound signal

texts:
I've asked here before but I was told to be more specific so here I go.

I would like to build an electromagnet that I can control with sound input, more or less like a speaker but safe and powerfull enough to move things around.

For example: the electromagnet would be attached to bottom of a 10 x 10 cm glass box filled with iron fillings. Based on the sound signal (soft / loud) the electromagnet would have varying strength and those irong fillings would move around based on that.

I was thinking I would just connect the electromagnet to my guitar amplifier

(It has Hammond Manufacturing 125DSE audio trasformator (http://www.digikey.com/product-detail/en/125DSE/125DSE-ND/454501) and has 4 / 8 / 16 ohm outputs. The speaker curently attached to it is 60W, 8ohm)

but I have no idea what should I be making. I was told that only option was AC type of EM but I am not sure about the specifics in order not to destroy the AMP and to have magnet powerfull enough to move those iron fillings and to be able to be on for hours without overheating.

Any advice on the magnet would be greatly appreciated.


texts: Is there any way to make the output voltage waveform in-phase with my input in the emitter-follower circuit?

texts: I created an emitter-follower circuit on a breadboard using TinkerCad. The circuit is based in the LTSpice simulation of the said circuit. According to the simulation, the input and output voltage waveforms should be in phase. But when I tried to construct the same circuit on TinkerCad, the scopes' readings do not seem to show that the waveforms are in-phase. Is there something wrong with the constructed circuit in the TinkerCad version?


texts: Why are leads from the negative terminal considered grounds?

texts:
I'm using a 9V battery with a 5v regulator as a power supply.  What I can't grasp is why I place the regulator in the (+) lead of the battery.  If electricity is electrons flowing, and the excess electrons come from the (-) terminal of the battery, why the heck is the regulator placed in the (+) lead instead of the (-)?  Wouldn't putting it in the (-) regulate the electrons coming through?

To further add to my confusion, when watching a video about using a 9V as a small LED power supply, the guy connects the 470 ohm resistor on the (-) lead to protect the LED.  Why is it that one person regulates the (+) lead, and another the (-)?  I understand that there is probably some difference in function between the regulator and the resister (I'll look it up later, I swear), but the principle seems the same - manipulating the electricity sourced from the battery.

This leads into my other question about grounds and the negative lead.  I'm going to be working with TTL chips on a breadboard:

14 pin => +5v

7 pin (labeled as ground) => (-)

So in this scenario, the (-) lead is being used as a ground?  This seems to conform to the ground black wire used for car batteries and electric guitar pick ups - stuff I am a little more familiar with.  But with my recently acquired knowledge, this leaves me scratching my head as to why the source of the electrons (the negative lead) isn't being connected to the 14 pin instead, which is essentially what I was rambling about in my first questions.

Please!  Enlighten my poor wretched soul!


texts: What equipment and tools can be used to fabricate an 8 layer PCB for a prototype that has a 584-BGA microcontroller

texts:
I am in the process of setting up a small design laboratory and one of our first projects include the use of a 584-BGA microcontroller. This means that we'd have to use an 8 layer design, something that we have never done before, and we are not aware of anyone who does similar stuff locally in our country. You can imagine how this affects our lead-time.

We are looking to find a way of fabricating

Any idea of what equipment would be used in the fabrication process, from the Gerber file to fully assembled PCB.
For clarity, we know that we need a circuit printer with fine-pitch capability, a pick and place machine and a reflow oven. What we don't know is what we should be looking for in all the equipment, save for the pick and place machine.

Arguments against trying to do the PCB assembly ourselves would be very much appreciated.


texts:
hello guys i have 70AH 12V battery and i have triple phase charger can charge from (0 to 140 ah batteries ) the chager turn off automatically when the battery full charge and i have 12V to 220 V inverter the problem is that i play lots of mmo games and in games like League of legend i cant disconnect even for 1 min ( if i did my team will lose and if i disconnect for more then 5 m i will get ban ) my internet is very good but my problem is with the electricity it cut off any time suddenly so can i do what i did in the photo??
i don't want to disconnect when the electricity  cuts off so i want to plug my internet cable to the inverter while I'm playing only is that OK?

the battery was full so it give only about 1 amp (the load is about 90 watt) and i put the charger on the 80ah ( instead of 70ah because of the load is that ok?? ) thx guys a :)

thx alot


texts:
I am repairing an old four band Transistor MW+ SW radio for which a circuit diagram is unavailable. The radio has four RF transistors, four AF transistors and a Germanium detector diode. Suddenly it is unable to receive any stations, neither will it pass a 455 kHz test signal from the external antenna input to the audio stage. It only passes a faint test signal from the base of the second RF transistor to the audio stage, but a  strong one from one terminal of the second IF transformer. However, I am confident that the audio section is working fine as I was able to connect my MP3 player and play it at full volume without distortion.

It was working almost perfectly after replacing old electrolytics and the Ge transistors with new ones and I was even able to measure the IF of 465 kHz at the collector of the last RF transistor. Something went wrong after I tried to fix the intermittent longwave reception. Now the only frequency measurement I get is 1.6 MHz at the collector of the first transistor.

I have a multimeter and signal generator but no oscilloscope.

Are there any tests I can do to help diagnose the fault?


texts: How to calculate the value of the fixed resistor in a light dependent voltage divider?

texts:
I have made, what I thought would be a simple circuit, an LED night light. The power source is 5V@1A. The schematic is below:

simulate this circuit – Schematic created using CircuitLab

The intended goal is to increase the brightness of the LED, as light decreases. The LED should be completely off when the light level is high. When I built the circuit, I was very surprised to find out that it functioned in the COMPLETE OPPOSITE way. When I pointed the LDR towards a light source, it increased the brightness of the LED as it turned closer to the light source. If I put my finger on the LDR so that almost no light can enter, the LED looks as if it is completely off. Why is this happening? I suspect it has something to do with the voltage divider, whose output is connected to the base of the 2n3904.

I have calculated the value of R1 using the voltage divider equation. I will post my calculations soon(within the next couple of hours),  my final result of the inequality that I solved(will post my steps soon)is 1kΩ

I tested the LDR and here is how the resistance changes in different cases:
1.Almost complete darkness-0.83MΩ
2.Dark-0.44MΩ
3.In between-8.66KΩ
4.Kind of Bright- 2.45kΩ
5.Bright-1.23kΩ
6.Very bright-1.21kΩ

The LED has a forward voltage drop of 2V. The peak brightness of the LED is achieved with a current of 9.09mA.

In case 1, full brightness of LED should be achieved.
In case 2. Half brightness of LED should be achieved
In case 3.Very little emission from the LED.
In cases 4-6, the LED should be off.

It seems as if my calculation(which I will post soon) for the fixed resistor of the light dependent voltage divider is wrong. How do I calculate R1 correctly.Sorry if my question is a bit vague, if you need any details please ask. Thanks.

Edit: The positions of the LDR and R1(the 1.1k resistor) are now switched in the actual circuit. After doing this, the LED is always on. I will calculate the value of R1 again.


texts: Is there a difference between PCB trace impedance and transmission line characteristic impedance?

texts:
PCB trace impedance (equations) don't seem to take into account frequency, I have (previously) been considering this to be a characteristic impedance i.e the distributed impedance of the line 'viewed' from a certain point on the line for a given frequency (but not sure if this is valid)
So is the PCB trace impedance an impedance or a resistance?
(Edits awkward wording)


texts: Writing to pins on a port without affecting other pins on that port

texts:
I'm outputting a 6-bit number on PORTA (RA0-RA5), how do I write to those bits without messing up what is already on RA6 and RA7?

For example if I want to output 0x3F on bits RA0-RA5. If I use PORTA = 0x3F; that will output 00111111 effectively wiping what ever was already written to bits RA6 and RA7.

I'm coding in C with MikroC on a PIC18


texts:
I am currently researching into the security of RFID based access control in relation with jammers. For an experiment, I am trying to build a device that can jam 125 kHz RFID cards from like a meter away. I have found products on the internet that can do so passively up to 1cm of distance.

What kind of antenna/technology would I need to achieve lets say 20cm or 50cm or even 1 meter of distance with such a device? It's just for the experiment which is stationary, so input power is not a problem as it does not have to be portable. I also have the receiver on a fixed position, so a directional antenna for more power can be used.

The problem that I faced is that my understading is that the antenna has to have a length of wavelength / 2, which for 125kHz would be well over 2km, which obviously cannot be built. Am I missing something here?

Thank you for your help


texts: Is it possible to make a JTAG interface with an arduino?

texts:
If so, could one direct me to a site that tells how to do this? I believe I may have found a way, but I am unsure as to whether or not it would work yet (need to find something to test it on).

This question is related to a previous question of mine located here.

In case more background information is needed.


texts: Effect on output voltage for buck converter in discontinuous mode

texts:
In a dc-dc switch mode buck converter, why the output voltage is different from the desired value when the inductor current is discontinuous? How can the voltage be adjusted to the required value?
What would be the effect of open-circuiting the load terminals on the output voltage? Will the capacitor keep on charging until it blows out if the load is removed?


texts: A quick way to remember NAND & NOR logic?

texts:
I'm frequently asked in class to create a logic circuit based on some specifications. Building the circuit and deriving the equations is the easy part. We are usually told to implement our circuit using only NAND or only NOR gates (akin to a real-life scenario).

I find myself consulting pages like this once I have my equations an am about to draw the circuit. If memorizing these combinations are the only way to make a NAND or NOR exclusive circuit, then I will. But there ought to be a better way of converting everything quickly and neatly.

Anyone?


texts: Which datasheet CTR value to use in optocoupler circuit?

texts:
I am looking to use the FODM8801C in my circuit: https://www.onsemi.com/pdf/datasheet/fodm8801a-d.pdf

simulate this circuit – Schematic created using CircuitLab
"Vout" node goes into an IC with the following requirements:

Vlow < 0.4V
Vhigh > 2.1V
Max leakage current out of the pin: 8uA

I've chosen the 36k resistor because it provides margin to the 0.4V low threshold when leakage current is taken into account:
8uA * 36k = ~0.29V
Saturation current through Q1 will be:
(12V-0.4V)/36k = 0.32mA
Forward current through D1 is 4.5mA, so the required CTR is
0.32/4.5 = ~7%
When calculating my CTR margin I am confused as to which CTR value I should be taking from the datasheet.
I don't understand what the saturated CTR value means - shouldn't it effectively be 0 since the current is determined by R1 only?
Should I be using the saturated CTR at Vce=0.4V or the linear CTR at Vce=5V?


texts: what is wideband phase shifter in modulator?

texts:
in these days I have been studying communication systems.

and I want to know the role of wideband phase shifter in the picture above.


texts: Real world objects touching reading the same capacitance?

texts:
In my project, I am developing a capacitive sensor based system which attempts to identify if two real world objects(*) get in contact with each other. I have done my homework (some) on Capacitive sensing and I am able to detect simple touch events either via classic charge/discharging-timer or oscillator 555 IC approaches. However, I still don't know exactly which object is in contact with which, and in my project, it is important that I determine this information.

So, the question I have is directly related to capacitance but in a somewhat general framework:

What can be said about two objects touching when it comes to their capacitance?

Are two objects put in contact sharing the same level of capacitance?
At the very least locally speaking, would it be such that if measured by sensors located on either side (the touching object, and the object being touched), we would read similar capacitance or at the very least relatable figures?
If not the actual level of Cap, would the "capacitance profiles" (dC/dt) be similar or relatable?

I would be interested to hear what people know (or think) on this subject and would appreciate any reference or link on existing research taking me in the "right" direction. Thank you.

*: real world objects would be (for example, but not limited to) a metal rod, and a sheet of conductive foil. For this conversation, I aim to remain realistic and so we are NOT talking about a piece of wood and a cut of fabric, but focus on reasonably conductive elements made primarily of metal.


texts:
As many people on the internet I'm trying to add a DC offset to an audio signal. I've amplified it with an LM324 op-amp, using dual supply (+/- 5V).
Afterwards I'd like to input this audio in my MCP3008 ADC, that has a 0 to 5V input voltage range.

For this reason I used a voltage divider, and I supplied one leg of the divider with 5V and the other one to ground.

Sorry for the really basic and trivial question, but is capacitor needed in front of the voltage divider? Because without it the signal isn't affected, so I was wondering whether the problem is somewhere else or if it is in the lack of the capacitor?

Thank you in advance,

Alberto

Edit: I even tried to use the output of the op-amp as input of another one, and I applied 5V to non-inverting input, as shown here, but with no results:


texts:
As a disclaimer, I have a little electronics knowledge, but I'm no expert.  I've been given an old 1940's Hunter fan and I'm working on fixing it up.  I took the base apart and wiring is pretty bad - cracked and bare in places...  I'm going to replace it, but I'd like to understand what is going on -- how the variable speed works.

I've drawn a crappy diagram based on the wiring I see -- can anyone explain it?


texts: Is there a limit to the number of parallel LED if each has its own resistor?

texts:
I am building a circuit with 6 parallel LEDs, powered by 5 volts through a transistor array which can provide 300ma.  If each LED is allowed 20ma (by setting the correct resistance for each), I should be able power each LED without a problem.  I could even power 12... or 45 LEDs with 1 amp.

Is there anything that limits the number of parallel LEDs that I can power in this manner (besides power consumption?)

Will the voltage drop of one LED impact the others at any point (or would this ever be an issue?)

simulate this circuit – Schematic created using CircuitLab


texts:
I just got a currency discriminator (Carnation CR1500) that can be connected to a receipt printer. There is a modular jack on the back of the machine, but I don't know what kind of cable it needs. It won't accept RJ45 or RJ11 connectors. It's taller and thinner than any RJ port I've seen and there's nothing in the manual about it.

Can anyone identify this?


texts: Symmetrical Component Analysis Circulating Current & KVL

texts:
I was reading in John Grainger Power System Analysis and have a question in mind. Below is the delta connection of an unbalaced 3 phase system with unsymmetrical loads $$Z_{\Delta 1} \neq Z_{\Delta 2} \neq Z_{\Delta 3}$$

So my questions are :

1) Can we use "super-position" of the different components and draw such circuit for each component alone?

2) If so then wouldn't that mean that we can write kvl on the delta loop
$$Z_{\Delta 1} I_{ab}^0 + Z_{\Delta 2} I_{ab}^0 +Z_{\Delta 3} I_{ab}^0 =0$$ however the book clearly says that we could have circulating current in the loop which is non-zero but that violates the KVL equation I've written above. This lead me to conclude that probably drawing such circuits is faulty.


texts: Advice on battery circuit for Raspberry Pi Laptop

texts:
Thanks for looking.  I would like some advice on a charging/power circuit for a raspberry pi laptop I would like to make.  It needs to power both the Rpi 3 and an LCD display. The LCD is a 10" 1280x800 with its own controller board.  I am not sure it will run off of 5.2V like the pi so I have a couple of designs.

These are based on the TP4056 board to charge the 18650 Li-ion batteries, and an XL6009 boost converter to get 5v+ from the 3.7V batteries.

Question: could you please look at my three designs below and provide advice on the "best" one? Option 1 (not shown) would run both Rpi and LCD from the same XL6009. Option 2 has two XL6009s from the same battery pack. Option 3 is similar to the Adafruit design I believe. BTW, there will be a toggle switch between the batteries and the XL6009s.

Also, can any of these be charging and running the laptop at the same time?


texts: High-Speed electronics - Reflections in T-intersection

texts: I'm currently attending a course on "experimental problem solving" and we just started talking about TDR (time domain reflectometry). I do understand that reflections occur whenever there is a change of impedance, and that you can terminate them by making sure the load resistance is equal to the impedance of the cable. However, we now got a question to explain why we get reflections in a "T-intersection" (not sure about the real name but basically a dongle to connect three cables together) even though we match the load resistance with each of the cables impedances. Can someone explain why this happens, or some source where you can read about these things?


texts: Open-Delta 3-phase transformer kVA rating

texts: I have a V-V three-phase transformer supplying a 50kVA balanced three-phase load. I know that the apparent power of a three-phase transformer \$S_{3\phi} = 3VI^*\$ and that of an open-delta system is \$S_{V-V} = \sqrt3VI^*\$. I don't understand what the 50kVA represents in this case. How can I proceed to find the kVA rating of each transformer?


texts: Need a little clarification about this BJT common emitter circuit

texts:
Let me start off by saying that this is not homework!  I am several years removed from the fun of college....  However, one of my main hobbies is electronics tinkering and I am referring to an intro ECE text from college.

An example problem in my book deals with the common emitter circuit shown below.  The DC bias point analysis is straightforward.  For the small signal AC analysis, my book teaches a method of approximating the BJT as a resistance and a current controlled current source (not shown).  I understand how all the various gains are then found, but I don't understand how the output voltage can go negative....  The output voltage is Vo and it is across the load resistor RL.

The next figure in my book gives side-by-side graphs of the input signal Vs (given by Vs = 0.001sin(wt) V ) and the output voltage Vo.

I am not seeing how Vo can be negative!  I have seen several other common emitter examples and they all seemed to have an output voltage that stayed positive (riding on a DC bias).  Also, if you need to know, the calculated voltage gain was Av = -106

A paragraph in the book states that the source voltage Vs divides between the internal source resistance Rs and input impedance Zin of the amplifier.  When that calculation is performed, we get that Vo(t) = (Av)Vin = -54.6sin(wt) mV


texts:
I'm thinking about using a very large home made capacitor as an energy storage device for a light duty off grid application, running some led lights and some 500w loads for a few hours each evening. I've done some calculations and I'm surprised by the results, it's been a while since I've done anything like this and I want to make sure I haven't made a silly mistake. So I'm planning on a flat multi plate capacitor made with tin foil and cling film. I have the permittivity of the dielectric at 3 and it is about 10 microns thick. The plates are 2x.3m and there's 21 of them giving 20 actual capacitors. So the calaculation I made is
e0xe1 x number of plates-1 x plate area / dielectric thickness
8.84x10^-12 x 3 x 20 x 0.6 / 1x10^-11 = 31.824F
Is my math correct?


texts: Tying ground planes together with a non-zero Resistor

texts:
I was reviewing the schematic of a motor driver board and noticed that the digital and analog grounds are tied together with a 3.9 ohm 1/4 watt resistor. I am still trying to find the gerber files to see how the ground plains are laid out, but does anyone know why this would be done instead of using a 0-ohm resistor or just connecting them in the copper?

My first thought was that it was an attempt at some sort of noise suppression but this doesn't seem like something that would be very effective at doing that. Feel free to speculate, because for now I'm at a loss.

EDIT: The analog ground feeds back to a 24V supply off the board and the digital ground feeds back to a 5V supply off the board. At each of the power connectors there are several decoupling capacitors. However the resistor is by noneof the connectors and the respective capacitors.


texts:
I am working on a Single phase Welding machine with a input voltage of 230V and Current of 20A and output ( 100 A and 24 V). Now we are supposed to pass it CE certification, as per standard EN 60974-10. We conducted all the test like RE, RS, CE, CS, ESD, EFT, Surge, Voltage Dip, Harmonics and Flicker. All most all our test passed but it gets failed in the RE and CE. In CE it fails in the 25 MHz to 30MHz by some 10 dB and In RE it fails in 30MHz to 50MHzby some 10dB. Basically it fails in both the test in the higher frequency only that after 25MHz to 50MHz.
The switching frequency are as follows
IPS is 50KHz to 200 KHz (Topology Quassi Resonant Converter)
PFC 70KHz ( Topology CCM Boost Converter)
Main Inverter 47KHz (Topology Full Bridge Converter)

Kindly give some suggestion for the RE to pass.


texts: SPI communication using MSP-EXP430FF5529LP

texts:
I am using SPI communication for the first time using Energia IDE (similar to Arduino IDE) to a gas sensor. However I get FF's as output.
I have tried connecting MISO to MOSI line to check what is wrong but MOSI line seems to send 11111's and the MISO line shows FF's.
I have attached the pictures of the read debug register which i want to read from.The output as shown should be 0A1. I have tried reading the value from LabView before which works fine.
Could anyone please tell me what's wrong with my code? How can I display the sensor output in the serial monitor?

#include <SPI.h>
const int chipSelectPin = 33; // P2.0
void setup() {
  Serial.begin(9600);
   SPISettings SettingsA(100000,MSBFIRST,SPI_MODE0);
  SPI.setClockDivider(SPI_CLOCK_DIV8);
}

void loop() {
  byte result;

   pinMode(chipSelectPin, OUTPUT);
   SPI.begin();

    //SPI.setBitOrder(MSBFIRST);
  //SPI.setDataMode(SPI_MODE0);
   digitalWrite(chipSelectPin, LOW);
   //sending command to the debug register
   SPI.transfer(242);
   SPI.transfer(00);
  SPI.transfer(00);
   SPI.transfer(00);
   SPI.transfer(00);
   result=SPI.transfer(00);
   delay(1);
  digitalWrite(chipSelectPin, HIGH);

  Serial.println(result,HEX);

 }


texts: How to offset AC voltage with varying input?

texts:
I want to offset an input sine wave, while being able to adjust the input voltage.

For example a sine wave of +-3 V should be offset by 1.5 V such that the sine wave never goes below 0 V. However I want the same circuit to be able to offset correctly +-2 V by 2 V, such that the lowest point of the negative cycle (-2 V) would remain exactly at 0 V once the offset is introduced. The same goes for +-1 V with an offset of 1 V etc.. I am looking to be able to offset 0 - 3 Vpp input range.

I have thought of connecting a variable resistor as a voltage divider
across a well regulated voltage, and buffer the output by using a follower amplifier, however I do not wish to stay doing this manually.

What would be a good approach to go about implementing the above? Any ideas would be appreciated.


texts: Vacuum cleaner power rating does not match line voltage and current rating

texts:
I have a vacuum cleaner on which is proudly written:

12.0 Amps
1300 W

Assuming a 120 V (RMS) power supply, how would the power consumption of the vacuum cleaner be calculated given the 12.0 A current draw?
It seems that \$120 \mathrm{\,V}\cdot12 \mathrm{\,A}\ne1300 \mathrm{\,W}\$ and \$120 \mathrm{V}\cdot\frac{12 \mathrm{A}}{\sqrt{2}}\ne1300 \mathrm{W}\$, so then where might the power rating "1300 W" come from?


texts: Broadcast traffic issue in PLC Ethernet network

texts:
The setting: network with about 10 PCs and 8 AB RSLogix 5000 PLCs.

The issue: Everything is communicating OK, but I'm seeing what appears to be a lot of broadcast traffic within the network.  It is noticeable because the activity light on every connected port on every network switch flashes in unison.  In normal circumstances, you expect to see each device's activity light flashing randomly to indicate its own activity, and a network switch is supposed to route traffic between sender/recipient to reduce overall network load.

It appears to originate with the PLC side of the network, because disconnecting the switch with the PLCs from the rest of the network stops the synchronized blinking except on the PLC switch.

Four questions:

Is broadcast network traffic common with PLCs?
If so, what is its purpose?
Will this negatively affect network performance?
Suggestions to improve this issue?

I plan to run Wireshark to determine exactly what's going on, but wanted to ask for advice here also, as I'm sure some of you have seen this before.

Thanks!


texts:
Hello. I couldn't seem to get my U1A to work. I understand the open collector logic gates, like 74LS136, require a pull-up resister in its output terminal. An open collector needs to be powered-on. I think it's true from the way the output does not have any ammeter reading unless you provided it with a 5-V DC voltage.
Now, my problem is that the logic gate isn't enabled to the extent that the reading still stays at 0.05A despite its two inputs being 0 (in which I know that isn't the case for a XOR logic).
Any advice?


texts: Programming CC1110 using Easy 8051 Programmer

texts:
I purchased the VT-CC1110PA-433M RF Data Transceiver Module from DigiRF which has a CC1110 module embedded on it. The datasheet for CC1110 from Texas Instruments suggests there is an 8051 CPU inside the module as shown in the block diagram below:

I have an Easy8051 programmer from Mikroelektronika which uses the 8051Flash software as shown below:

I can't seem to figure out which 8051 microcontroller is embedded on the module. How do I program it? Or is CC-Debugger the only device that can program it?


texts: do power amps need regulated power supply

texts: Does a power amplifier needs a voltage regulator since it needs to draw current around 2 A depending on the wattage and speaker impedance. If we try to use a zener regulator, notice that a zener diode's maximum current is only at 200 mA which is way lower than the 2 Ampere current requirement to drive a speaker. Or will a plain unregulated dc supply will work (no more zener but we risk getting variable supply voltage)?


texts: Interpreting IQ Data (as hex) from an RTL-SDR/Hack-RF

texts:
I am wondering if someone can shed some light on how to meaningfully interpret I/Q data that is produced from an RTl-SDR dongle (RTL2832U) using the Osmocom RTL-SDR library.

I have used I/Q data before to calculate power levels of signals, but after taking a computer networking course, and having worked in an internship that revolved around (basic) digital signal processing, I am curious to capture I/Q data from unencrypted 433 Mhz transmissions (or others) and make sense of the data, given that I can correctly deduce the modulation technique.  I am aware of tutorials that reverse engineer 433 Mhz weather stations (as one example of something I'd like to do), but those tutorials often gloss over the I/Q data aspect.

From what I can tell, the I/Q data that comes from the RTL-SDR library is represented in hexadecimal (unsigned), little-endian format.

So to formally state my question: what are some common algorithms, techniques or other resources for processing this I/Q data into meaningful data (i.e. binary strings)?

I am a computer science student, so I apologize ahead of time for naivety concerning these electrical engineering concepts.

Thanks!


texts: Want to know what the +1 in this finite state machine circuit diagram is

texts: Can someone tell me what the +1 that goes into the right side J and K is?


texts: Wireless Home Automation 2.4GHz versus 433MHz

texts:
Project specifications

To make some things clear first(wow that sounds so arrogant):

This is an Arduino project
This is supposed to be internationally applicable
I have experience with 433 MHz modules
I don't have experience with 2.4 GHz modules
I have done quite a lot Arduino projects(I am not a complete starter) which include but are not limited to

433 MHz wireless control
Web control
Connected a keyboard to an Aurduino

I am working on a home automation project which might go into smaller production. The project is wireless and the connections would be managed as followed:

You would have multiple slave nodes, and one master node in the house.
All of these nodes would be transmitting and receiving data. E.G.

Receive: command to switch relay, turn on the AC etc.
Transmit: optocoupler data to see if a light is on, temperature etc.

Bands

I have 2 band options:

2.4 GHz band
433 MHz band

2.4 GHz

Pros:

Big data transfer rate(not really that important)
Cheap transceivers with antennas available here

Cons:

Small range, solved by making each node a repeater. It bounces the signal if it isn't its, but writes down the packet id so if another node bounces the packet the node wouldn't get stuck in an endless loop)
A lot of interference

Questions:

Do any government regulations limit duty cycles for this band?
Would it be that badly affected with other wireless networks?
Would the other signals make the signal hard to read(I have never worked with this band before)?
Would the repeater idea work?

433 MHz

Pros:

Big range
Good wall penetration
Little interference

Cons:

Really freaking expensive transceivers
If I would use no transceivers, but 1 receiver and 1 transmitter(cheaper), I would need 2 antennae, and it would cost me about the same as the 2.4 GHz transceiver w/ antenna

Questions:

Would the 1 receiver + 1 transmitter interfere badly with each other?
Is this band crowded?
Do any government regulations limit duty cycles for this band?

Suggestions

Feel free to give me any suggestions!

I would be pleased if you answer this, I took my time to write it as nice as possible :)


texts: I have 15W of power to feed in the capacitor. how do I calculate charging and discharging time?

texts:
How can I calculate charging and discharging time of capacitor?
The capacitance is 2100F, rated voltage 2.8V, internal resistance .0158 mohm. Let's say I have 15W of power to feed in the capacitor. how do I calculate charging and discharging time for that? The specific energy is 37 Wh/Kg and specific power 5.6 kW/Kg. based on the charging and discharging time I need to determine how many capacitor do I need to feed 15W. Can you please tell me how can I solve that?   Thanks


texts:
I am still a beginner, and I wanted to do this project

which will be fairly easy if I follow the code and the pic, but there is something I don't understand about the relay connection: Why is there a transistor, and why is there a diode, can't I just connect the output pin to a resistor then to the coil pin on the relay?


texts:
I have this AC voltage divider here wish I want to find the exit voltage of. What I've done is I've applied the voltage divider formula:
$$ V_{out} = \frac{Z_2}{Z_1 + Z_2} V_{in}$$
Now that I have got the magnitude of \$ V_{out} \$, I am trying to figure out the sinusoidal function associated with it. But I'm not exactly sure how to do it
Diagram of this scenario:

$$ Z_{R-L} = \sqrt{ R^2 + w^2 L^2}$$
$$ Z_{C} = \frac{1}{wC}$$
hence,
$$ V_{out} = \frac{ V_{in}}{ 1+ wC \sqrt{R^2 + w^2 L^2} } $$
assume \$V_{in}\$ to be some generic sinusoidal function like \$ V_{in} = A sin( \omega t)\$