texts: Getting fast performance from a STM32 MCU

texts:
I am working with the STM32F303VC discovery kit and I am slightly puzzled by its performance. To get acquainted with the system, I've written a very simple program simply to test out the bit-banging speed of this MCU. The code can be broken down as follows:

HSI clock (8 MHz) is turned on;
PLL is initiated with the with the prescaler of 16 to achieve HSI / 2 * 16 = 64 MHz;
PLL is designated as the SYSCLK;
SYSCLK is monitored on the MCO pin (PA8), and one of the pins (PE10) is constantly toggled in the infinite loop.

The source code for this program is presented below:

#include "stm32f3xx.h"

int main(void)
{
      // Initialize the HSI:
      RCC->CR |= RCC_CR_HSION;
      while(!(RCC->CR&RCC_CR_HSIRDY));

      // Initialize the LSI:
      // RCC->CSR |= RCC_CSR_LSION;
      // while(!(RCC->CSR & RCC_CSR_LSIRDY));

      // PLL configuration:
      RCC->CFGR &= ~RCC_CFGR_PLLSRC;     // HSI / 2 selected as the PLL input clock.
      RCC->CFGR |= RCC_CFGR_PLLMUL16;   // HSI / 2 * 16 = 64 MHz
      RCC->CR |= RCC_CR_PLLON;          // Enable PLL
      while(!(RCC->CR&RCC_CR_PLLRDY));  // Wait until PLL is ready

      // Flash configuration:
      FLASH->ACR |= FLASH_ACR_PRFTBE;
      FLASH->ACR |= FLASH_ACR_LATENCY_1;

      // Main clock output (MCO):
      RCC->AHBENR |= RCC_AHBENR_GPIOAEN;
      GPIOA->MODER |= GPIO_MODER_MODER8_1;
      GPIOA->OTYPER &= ~GPIO_OTYPER_OT_8;
      GPIOA->PUPDR &= ~GPIO_PUPDR_PUPDR8;
      GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR8;
      GPIOA->AFR[0] &= ~GPIO_AFRL_AFRL0;

      // Output on the MCO pin:
      //RCC->CFGR |= RCC_CFGR_MCO_HSI;
      //RCC->CFGR |= RCC_CFGR_MCO_LSI;
      //RCC->CFGR |= RCC_CFGR_MCO_PLL;
      RCC->CFGR |= RCC_CFGR_MCO_SYSCLK;

      // PLL as the system clock
      RCC->CFGR &= ~RCC_CFGR_SW;    // Clear the SW bits
      RCC->CFGR |= RCC_CFGR_SW_PLL; //Select PLL as the system clock
      while ((RCC->CFGR & RCC_CFGR_SWS_PLL) != RCC_CFGR_SWS_PLL); //Wait until PLL is used

      // Bit-bang monitoring:
      RCC->AHBENR |= RCC_AHBENR_GPIOEEN;
      GPIOE->MODER |= GPIO_MODER_MODER10_0;
      GPIOE->OTYPER &= ~GPIO_OTYPER_OT_10;
      GPIOE->PUPDR &= ~GPIO_PUPDR_PUPDR10;
      GPIOE->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR10;

      while(1)
      {
          GPIOE->BSRRL |= GPIO_BSRR_BS_10;
          GPIOE->BRR |= GPIO_BRR_BR_10;

      }
}

The code was compiled with CoIDE V2 with the GNU ARM Embedded Toolchain using  -O1 optimization. The signals on pins PA8 (MCO) and PE10, examined with an oscilloscope, look like this:

The SYSCLK appears to be configured correctly, as the MCO (orange curve) exhibits an oscillation of nearly 64 MHz (considering the error margin of the internal clock). The weird part for me is the behavior on PE10 (blue curve). In the infinite while(1) loop it takes 4 + 4 + 5 = 13 clock cycles to perform an elementary 3-step operation (i.e. bit-set/bit-reset/return). It gets even worse on other optimization levels (e.g. -O2, -O3, ar -Os): several additional clock cycles are added to the LOW part of the signal, i.e. between the falling and rising edges of PE10 (enabling the LSI somehow seems to remedy this situation).

Is this behavior expected from this MCU? I would imagine a task as simple as setting and resetting a bit ought to be 2-4 times faster. Is there a way to speed things up?


texts: Is there a Kicad Library loader for Linux?

texts:
I am using Designspark pcb with Library loader for years now. Library loader lets me import and use any footprint instantly once I download it.
But I want to switch to Linux with KiCad, and I want an alternative for Library loader, since I do not want to manually replace my files for footprints, I would love it to be automatic.
Even if there is a plugin would help.
EDIT:
Regarding the plugin The closest thing i could achive was to use SnapEda's Kicad Plugin, but it looks like it only works on windows. Trying to use it in linux (Ubuntu) after installing sudo apt-get install python3-tk, which is needed, I ended up with a gray screen of the plugin saying Nothing (it is supposedly installing but it just freezes there)


texts:
I have modeled an ideal diode rectifier fed from a 230V/50Hz grid with a slim DC link capacitor and a constant power load (1kW) coupled with a small resistive load. For Cdc=14uF i get a phase input current that oscillates between 0A and 8A while it is dampened. However for Cdc=15uF (or 16uF, 19uF, 20uF) the current never gets to zero (which actually greatly improves the harmonic content and also the power factor).

The only reason I can think of for the input line current to become 0A is diode commutation. However, apparently this does not happen for certain Cdc, Lg value combinations. Why could that be?

The schematic of my system:

simulate this circuit – Schematic created using CircuitLab

Pictures of the different input currents are presented below (V(n001) is the upper diode to earth voltage).

The netlist of the model is given below.

Lgra L1 N001 {Lg} Rpar=100k
Lgrb L2 N002 {Lg} Rpar=100k
Lgrc L3 N003 {Lg} Rpar=100k
XX1 N001 N002 N003 Vdc 0 diode_rectifier
R2 Vdc 0 {Rload}
Vga2 L1 COM SINE(0 {Vac} {fg} 0 0 0) AC 1 0
Vgb2 L2 COM SINE(0 {Vac} {fg} 0 0 120) AC 1 120
Vgc2 L3 COM SINE(0 {Vac} {fg} 0 0 -120) AC 1 -120
R3 COM 0 10Meg
B1 Vdc 0 I={1000/V(Vdc)}
C1 Vdc 0 {Cdc} Rser=14m

* block symbol definitions
.subckt diode_rectifier Va Vb Vc V+ V-
D1 Va V+ D
D2 Vb V+ D
D3 Vc V+ D
D4 V- Vc D
D5 V- Va D
D6 V- Vb D
.ends diode_rectifier

.model D D
.lib C:\Users\NVA\Documents\LTspiceXVII\lib\cmp\standard.dio
.param Vac = 230V
.param fg=50Hz
.param Lg =100u
.param Rg =1m
.param Cdc =15u


texts: Meaning of TLC59281 LED supply voltage rating

texts:
TL;DR: Does the max VO of 17V refer to the LED supply voltage or only to what's left after the diode drops?

TI's TLC59281 is more or less a device that combines two 74HC595-like shift registers with constant-current LED drivers.

The datasheet advertises the feature "LED Power-Supply Voltage up to 17V"; in the stats, this seems to correspond to VO, "Voltage applied to output", which is 17V max.

Ignoring LED failure modes, which I'll admit I may not have considered thoroughly, these sound like conflicting figures: the full LED supply voltage is never actually applied to the driver output. The max LED supply voltage seems like it should be 17V plus the sum of all of the LED drops. For example, if I have a string of 10 white LEDs with Vf of around 3.6V each, it should be perfectly acceptable to supply them with 48V (because 48 - (3.6 × 10) = 12 < 17).

(A string driver that only supports 4 LEDs per string doesn't seem all that useful…)


texts: Unlimited electrons?Can a conductor cancel a very strong field?

texts:
I started studying about how a conductor behaves once placed inside an electric field E0 . The electrons will move inside the conductor according to the electric filed's direction gathering at one side of the conductor leaving the other positive.

This is what that looks like

After this process the electric field inside the conductor will be zero. How am I sure that the object has enough electrons to create the required field E1 to cancel the outside field E0.
That field could be huge and the object definitely has finite electrons.


texts: New to using PIDs. When normalizing a range, we would need to know the maximum and minimum of that range. Since a PID is summing the error in the I portion wouldn't the range be potentially infinite? How would we limit the output to the expected range, (-1 to 1 in my case). Would we also need to normalize the error that is passed in?


texts: Eagle keyboard shortcuts getting deleted

texts:
Every time I open Eagle, all of the keyboard shortcuts that I had previously assigned are lost.

A web search on how to fix this, or other people reporting this problem has turned up null.

Anyone have this problem too?  If so, anyone know how to fix it?


texts: DS1307 RTC not working with rweather library

texts:
I'm using the DS1307 RTC together with arduino and this library
http://rweather.github.com/arduinolibs/classDS1307RTC.html

When i power the chip directly from the 5V and GND outputs from my arduino UNO all works well.

When i power the chip using a digital pin with output set to HIGH for voltage input and/or a digital pin with output set to LOW for GND the library is unable to read the time from the RTC.

This exact same configuration does work with library provided by adafruit
http://learn.adafruit.com/ds1307-real-time-clock-breakout-board-kit/understanding-the-code

But i would like to use the rweather library because it provides more features ( like easier access to the RAM and an alarm convenience function ), it's also much better written and well documented.

The following code works with both libraries but only fails with the rweather library when not using 5V and GND directly. When starting with 5V and then switching to an output pin the library can read the time, so it seems that this is related to a start up issue of some sort.

#include <Wire.h>
#include <RTC.h>
#include <SoftI2C.h>
#include <DS1307RTC.h>

void setup()
{
    pinMode(7, OUTPUT);
    pinMode(6, OUTPUT);
    // provide power for the RTC module
    Serial.begin(9600);
    Serial.print("Setting output\n");
    digitalWrite(7, HIGH);
    digitalWrite(6, LOW);
    Serial.print("output Set\n");
    delay(2000);
    Serial.print("delay over\n");

    SoftI2C bus(5, 4);
    DS1307RTC controller(bus, 3);

    Serial.print(controller.isRealTime() ? "controller is realtime" : "controller is simulating");
    Serial.println();

    RTCTime theTime;
    controller.readTime(&theTime);

    Serial.print("startup time");
    Serial.println();
    Serial.print(theTime.hour);
    Serial.print(":");
    Serial.print(theTime.minute);
    Serial.print(":");
    Serial.print(theTime.second);
}

void loop()
{

}


texts: Does several PIC12F683 pull-ups cause short circuit

texts: I am connecting several PICs together by GP4 and GP5 pins, and I used their internal pull-ups to make pins high by default. If in all PICs pull-ups are enabled. Does connecting a lot of PICs together (i.e. 25 PICs) makes a low pull-up that causes short circuit when one pin in one PIC became low? Do I need to disable pull-up and simply use two resistors for all PICs?


texts: Simple Theory question about Circuit Analysis

texts:
I have the following circuit.

I calculated it's transfer function, in the common way, to be: \$ \frac{Vo(s)}{E(s)} = \frac{-R_3}{s\ R_2R_4C + R_2} \$

Then i thought something else. Since there's only one current flowing in the circuit (ideal Op-Amp) from \$R_2\$, to \$R_3\$ to \$R_4\$ to \$C\$ and down to earth, if i apply Kirchoff's current Law at the \$Vo\$ node i get: \$ \frac{E(s)-V_o(s)}{R_2+R_3+R_4} = s\ C(V_o - 0) \$ which gives the transfer function: \$ \frac{Vo(s)}{E(s)} = \frac{1}{s\ C(R_2+R_3+R_4) + 1} \$

Now i'm confused with this second method, because something doesn't feel right. Also the Op-Amp introduces a phase difference so there should definitely be a minus sign in the transfer function. This second transfer function should be wrong but i don't understand why exactly. Can someone tell me your thoughts and what do you think about mine? What is wrong? Thanks in advance!


texts:
ServoDatabase lists various different servo motors, and describes some as "analog" (e.g. SG90) and some as "digital" (SG92R).

"Digital" servo motors are apparently better (they seem to cost more, anyway).

I've read a number of sources that dismiss the label as "marketing". Even if there is an actual technical difference, what could I check in the devices' specifications sheets that would confirm that motors described as "digital" do indeed enjoy those technical advantages?

What is the difference between "analog" and "digital" servos?
What difference should this make to me when I am using them - can for example SG92R motors simply be treated as drop-in replacements for SG90 motors in the same sort of application?
When I'm driving them (directly from the GPIO pins of a Raspberry Pi) should I treat them any differently - for example, if I have been using a 50Hz pulse to drive them, should I change this or any other parameters for a digital servo?
Are digital servos more or less easily damaged (by excess load, electrical errors, etc) than analog servos?


texts: Can I create paths to two external GPS antennae but use only one

texts:
I am making a PCB for a SIM968 GSM/GPS device. Printing PCBs in my country is expensive.

I am making this PCB for two different purposes. One is to work in an open environment where there is enough GNSS satellite signal is evident. In this case size has to be minimal and I wish to solder the GNSS antenna on to the PCB and let the signals flow in to the RF in of the SIM968 GPS engine.

In the second scenario, I wish to connect an external active GNSS antenna because of the harsh environment problem. At this time there will be no PCB GNSS antenna soldered to the PCB.

In both situations, I will only have one antenna connected to the SIM968 at a time. Therefore there will surely be no out of the phase cancellation or reduction of signal strength due to signals from both antennae.

However I wish to divide my 50 Ohm characteristic impedance line into two to accommodate space to fix both antennae. I made my self more clear through the image below.

I do not want to accommodate another antenna switching IC.

Please be kind enough to let me know if this approach  is flawed. I would so much appreciate your design views and any other information I should keep in my mind while I am designing the PCB. All PCB paths to antennae will of 50 ohm characteristic impedance.


texts: Connecting to motor controller input ground drops system voltage

texts:
I am currently working on installing photoelectric sensors into motor controller inputs. The inputs to the motor controller are 24V open ended inputs. The supply source is a 48/24 V buck chopper. When I connect the signal of the sensor into the input with without running a ground wire connecting the cold wire of sensor (connected to system 0V) to the micro controller the inputs see 24V when sensor is on and the motors perform exactly as expected when they reach their physical limits (stop moving). When I connect the ground wire the whole 24 volt system (of 3 other motors on same 24V line as well as 24V lighting system all fed from buck chopper) drops to 18V.

There is a serious hole in my understanding of grounding, as I would have figured ground reference would be necessary for the input to know what 24V is. Furthermore why is the system voltage dropping? The entire system is quite complicated and the 0V of different systems are connected interchangeably as opposed to each system has own return route to 0V. Is the 24V likely not grounded properly and by properly connecting the 0V to the motor controller GND the system 0V changes its reference to the 24 or am I likely introducing a ground fault somehow? Any assistance or links to reference material / good textbooks would be appreciated. Thank you.


texts: How to increase the range of BLE chip RN4871

texts:
I have an RN4871 Bluetooth chip and integrated it with my micro. The chip is scanning for nearby BLE devices and reporting them to the host micro via UART. However, I see that the range of this chip is just 10 m. I could buy RN4870 and increase the range to 50m, but that's still not enough.
I see that the power output of the chip is 0dBm (1mW) and the max transmit power is 100mW (20dBm) for BLE 5.1. Apparently there is no way to increase this. Lame, I know.
So my only option is to find an antenna that has a higher gain compared to the built-in antenna (5dBm) of the chip and replace it with it. Can somebody back me up on my idea?
Also, is there a better way to increase the range of the chip?
Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/RN4870-71-Bluetooth-Low-Energy-Module-Data-Sheet-DS50002489D.pdf


texts:
I don't have much AC knowledge, but I am willing to learn. I've been surfing the web to find out more about outlet grounding. I still want to know more, that is why I am asking this here.

Grounding an outlet means to connect a third wire (apart from hot and neutral) to the earth by some conductive objects(pipes). This, I understand, helps prevent electrical shocks.

Now the questions:

How is the ground wire connected to the outlet?
If the ground wire is a path for electicity that protects you from becoming one, how does the outlet provide power at all?
Why doesn't the entire current go through the ground wire?


texts:
I would like to make an inverter from 12Vdc to 45Vac.

I am trying to simulate it into LTSpice but I can't get a Frequency of 60 Hz.

Here is the Schematic:

BOM:

Q1 & Q2 : 2N5877

R1 & R2 : 220ohm 2 W

Source : 12V+

TFO: ?

The question:
How can I figure what kind of transformer I need ?

Presently here is the output:


texts: Using a diode to lower supply voltage to nrf24l01+?

texts:
I was wondering if I could use a IN40007 diode (or Zener diode) instead of a 3.3V voltage regulator. I plan to power the module using a 3.7V LiPo. Since the battery would be 4.2V when fully charged, my understanding is with the diode voltage drop the voltage at the Vcc pin of the nrf24l01+ module would be ~3.3V.

I've also tried using a voltage divider instead of a diode but found that this setup wasn't stable. So my question is whether using a diode over the voltage regulator would suffice?

Thanks.


texts:
I have a LCD driver board and it uses LM2576 for voltage regulation/step-down. As being cheap ebay/aliexpress purchase the instructions state 12V DC input without specifying range. Datasheets I found for LM2576 state unregulated input voltage can be up to 40V.

So the question is whether the LCD driver would work in car environment where 12V is really something like noisy 12-15V. Any recommendations for extra components like capacitor before the board?

Edit: Managed to find more specifications of the board (PCB800099 was the keyword) and there 5-24V is mentioned.


texts:
The Idea
When I heard about Mirasol and Electrowetting the first time, I considered this techniques to be useful for building a wall-hung touch screen where you can show notes, calendarings, drawings and so forth.
The advantage would be that you can leave this notes visible, but without wattage or display lightening (like on LCD).
Such a display has to satisfy the following requirements:

not shining
small wattage
one big screen or multiple small screens combinable to a big screen
color picture, if possible
overall less than - let's say - approximately 600 $
the ability the show pictures rendered by a computer

My Problem
I even after intensive searching I wasn't able to find a screen suitable for such a use-case or - more precisely - I wasn't able to find a display with a acceptable resolution at all for retail selling. It seems like there aren't any new e-paper products coming onto the market at all (expect for cheap and small grayscale e-readers).
I also thought about demounting displays from Mirasol readers, but all these readers are currently out of sale, very expensive compared to their screen size and I don't really have the know-how to assemble a display wall from small E-Ink displays.
My Questions

Does anybody know where to get such E-Ink displays?
Any ideas how to build such display walls yourself?

Thanks for your help - if anything's unclear, please leave a comment.


texts:
simulate this circuit – Schematic created using CircuitLab

When finding Req between M and N i can't understand why current isn't flowing in R3 and R4.


texts:
What is the difference between a H11L1 and H11L1M opto coupler?
(I want to use it for MIDI).

Datasheets

H11L1
H11L1M

If I check the data sheets, I see some different values, but for me it is unclear to know if these will affect the usage for MIDI ...

I want to buy it actually from AliExpress (either the H11L1 or H11L1M), which do not specify a datasheet, but I assume I can consider all H11L1's having the same specs and all H11L1M's (?)

(also I always thought the H would be the manufacturer's 'code'), but H11L1 seems to be from Motorola and H11L1M from Fairchild).


texts: 12VDC power adapter to power Arduino Uno and another device?

texts:
I have a RHINO 12VDC power adapter (500mA). My goal is to use this power adapter to power an Arduino Uno and another device that is powered through a DB9 serial cable and takes an input voltage of 6 to 16VDC. I have a M/F Micro Connectors serial cable as well. My thought process is to...

1) Cut off the 2.1mm x 5.5mm jack 3-4 inches back

2) Strip both ends (exposing the ground and power on the adapter and now independent 2.1mm jack)

3) Cut the serial cable in half and strip it exposing all the wires on the Male end

4) Find the power and ground wires

5) Solder the power wires from the power adapter, serial cable, and 2.1mm jack together and wrap in electrical tape; do the same for the ground

Would this work safely for the devices?

Any advice would be appreciated. I just want to be able to power both devices with the one power adapter. Thanks.


texts: SystemVerilog: copy a slice from a vector to another vector of different size

texts:
as per title, I want to copy a slice of fixed size from one vector to another, starting from a variable location.
Example:
logic[19:0]            in_vector;
logic[$clog2(20)-1:0]  in_vector_index;
logic[2:0]             in_vector_size;
logic[3:0]             out_vector;
logic[
...
always_comb begin
    out_vector = out_vector_r;
    // if the input is telling me that in_vector has something useful...
    if(in_vector_size > 0)begin

        // ...copy from in_vector at the specified position the max amount of data...
        // This may access the in_vector outside the range, copying X into out_vector, but I will clear them.
        out_vector = in_vector[in_vector_index +: 4];

        // ...maybe only a portion of data was valid and not all 4 bits.
        // So, "clear" to 0 out_vector from the specified position (decided by the size).
        // This may access the vector outside the range, but I don't care of what happens: I only care up to the max size of out_vector.
        if(in_vector_size[1:0] != 0)begin
            out_vector[in_vector_size[1:0] +: 4] = 0;
        end
     end
end

Now, this code works well in simulation. I wonder if there is a better way to code this, and if so which one. Also, do you see any criticality from the synthesis point of view?
I see I can access vectors outside of the range, but:

when I access the input vector outside of the range, I clear to 0 the possible X. I expect the same to happen after synthesis (??)
when I access the output vector outside of the range, I don't care what happens to the "extra" locations (that don't exist), I will not use them.

Thanks!


texts: Interfacing switches with microcontroller

texts:
Im trying to interface momentary push-button switches to my Stellaris EK-LM4F120XL.

Im using a positive logic interface, to momentarily set pin as HIGH if the button is pressed. A 10K resistor is connected to GND from the switch, which is then connected to Vcc, 5V. The selected pin is connected to this junction, setting the pin as LOW when no current flows and a 0V signal is at the pin. Then when current flows the voltage at the pin is Vcc and is set HIGH.

Using a multimeter this works flawlessly.. Although, when debugging - the output isnt triggered as desired..

My activation code in main is as follows..

if ((GPIOX_DATA & 0xXX) == 1) // IF THE PORTS' DATA REGISTER, AT PIN, IS HIGH,
    GPIOX_DATA |= 0xXX;       // SET THIS PORTS' DATA REGISTER, AT PIN, TO HIGH

(The control of setting the pin via the data-register works fine, eg on-board LEDs..)

It is my understanding that you cannot write to an input pin - therefore its value is set by its logic-level. If it has a threshold voltage similar to TTL or CMOS, the active 5V on the pin should be setting it as HIGH - therefore == 1.

My init code sets the input pin as -
DIR as input
AFSEL to regular
DEN to digital..

Ive even tried adding disable analog thru AMSEL, clear port control thru PCTL..
Just to test the control, I want to turn on an on-board LED while button is depressed..

Am I missing something..?


texts:
I'm working on implementing an audio amplifier into a circuit design, and I am trying to understand the output configuration for the speaker using the TPA0253. I will be using a 8 ohm, 1W speaker for my design. For my project, I plan on using only a mono speaker with the input being stereo. So I chose this IC because I wanted something that would easily convert stereo to mono.
From what I understand, the output to the speaker uses a highpass filter. If I was to use a single speaker without a headphone connection, how would I draw the schematic, and would I need a highpass filter on both the mono+ and mono- pins?


texts: Is it possible to store a large enough amount of power to supply a house?

texts:
Say I want to provide power to my house off the grid (i.e. without relying on utility companies). Say I have a method of generating power elsewhere (e.g. wind power).

Is it possible to "farm" the power, save it in a large enough "battery" (I'm imagining something the size of a barrel here) and have it power a conventional house for, say, a week?

I would very much like to learn about the feasibility of this proposition.


texts:
Say I've got a peltier block that is rated at 15.2V and 6A, providing 90W of cooling power to one side.

Will I be able to operate it at 5V, and will it draw 2A, providing 30W of cooling power?

EDIT: sorry, error above. :P brain was not working. 5V and 2A would indeed be 10W instead of 30W above.


texts: water leakage alarm consumption in stand by mode?

texts:
Hello.
This is a pcb of water leakage alarm,which works with 9v battery and
activates the piezo speaker when the three metal legs(on the bottom of the plastic)came in contact with water.The unit is working.
I had been told that the consumption of this unit in stand-by(the battery is connected,but the speaker is not activated)is about 0.1 mA.
I measured the current consumption with digital ammeter in order to check
it(even in micro amper scale),but there wasn't any readind,as it is open circuit.So,my question is:
According to my description and the attached pcb photos,Is this pcb consumption,in stand-by,zero or it actually consume some current?
Thanks.


texts:
In Eagle (v9.6.2), the routes fill the holes of my pads. hence when I want to print it, the pads are all black, no drill holes.
What am I missing?
I know this is similar to Eagle Ground Pour Fills Drill Hole, but the answer did not work for me...
Edit:
I've changed the images, I'm expecting all the pads to show a white hole like the second column:


texts: LED restricted minimum current (do not use below 10mA)

texts:
I was looking into the datasheet of this LED by OSRAM (GW JTLPS1.CM, page 15), and can't understand why would an LED not be "allowed" to be used below 10mA?

I can understand if the performance is not guaranteed below a given current but why such strict warning?

My interpretation would be that a not guaranteed performance would be drastically less efficient or some color drift, while "do not use below 10mA" sounds like something bad might happen (damage, lower lifetime).

Some other GW CSSRM1.EC OSRAM LEDs have even higher restrictions, 200mA for example.

While some others have no restrictions: LUW CN7N. Both the latter ones are from the OSLON family, if that means anything, and the one without restriction seems to be an older model.

Can someone shed some light on this?

p.s.: I'll probably buy a few of those an test it out anyway, but it would be great to have some information.


texts:
I have DC-UPS
http://www.mercury-pc.com/product-detail.php?link=p-ups&subtitle=UPS&productid=1255

I want to make this ups bypass battery(by using a switch),
the switch connect and disconnect battery from ups,
when main power off the ups will use the battery if the switch on, and not use battery when the switch off

i try to do that and its work.
but i wonder , disconnecting battery by this way a good idea? is it possible to damage the UPS?


texts: What will it take to build a DIY 2km (city conditions) RF transmitter (433Mhz)?

texts:
This is my first question on this site. I am not an electronics/electrical engineer so pardon my depth of knowledge.

I am trying to build an RF transmitter/receiver. These are my end goals :

a text (bytes) transmission. (Voice not required)
1.5 - 2km range (Line of sight independent, in city conditions)
as short antenna as possible
as small circuit in size as possible
use of free unlicensed spectrum

after reading a bit I figured out 433Mhz is one of the most used for such purposes but I am not sure if it checks all the above conditions.

Qs :

Am I using the right frequency or there are other options?
How much battery power will be required to send the signal upto 2 kms? Is it even possible to broadcast that far? I am ok if the the whole battery gets drained in 1 or 2 transmissions (don't ask why :)) but the battery has to be really small to make the whole circuit small.
How big will the transmitter antenna be if all the above are achievable?

A desired ideal solution would be something like remote car-door lock/unlock circuit with a greater range and no line of sight limitation.

I'll be so thankful to you guys if you can provide me these answers and any pointers for circuits or similar projects on the internet.

P.S. : I am located in India (for license reference)


texts: I've got a 8 year old pair of powered studio monitors that have recently started hissing for about 5-10 minutes after being powered on from being completely off. The culprit was some bad caps that I am replacing. While I was at it, I noticed that there are two large resistors coming from a bridge rectifier that are positioned in such a way that they are 1cm vertical from the board. I was wondering, is there any reason for resistors, or other components for that matter, to be soldered in such a manner?


texts:
I am trying to switch a SPST-NO relay that is rated to handle up to 227VAC. The coil is powered by 5V, has a 100 Ohm coil resistance, and its contacts are rated for 16A max.

I would be using the GPIO pin to power the base of the transistor, which is 3.3v and the 5Vout to power the relay coil.

To make your life easier I will list the relevant data from the 2n3904's datasheet:

Ic(max)  = 200mA
Vce(sat) = .2v      with 50mA Ic & 5mA Ib
Vbe(sat) = .65-.95v with 50mA Ic & 5mA Ib
hFE      = 60       with 50mA Ic & 1v Vce

Relay can be found here:
http://www.newark.com/panasonic-electric-works/adj23005/relay-spst-no-277vac-16a/dp/12N3389

I have the base resistor at 520 Ohms:
R = V / I
  = 3.3v - .7v / 5mA
  = 2.6v / 5mA
  = 520 Ohms

The Ic is found by multiplying the current gain(hFE) by Ib. The test case for Vbe(sat) shows Ib should be 5mA:

Ic = hFE * Ib
   = 60 * 5mA
   = 300mA

The 2n3904 can only handle 200mA max. I need Ic to be at 50mA according to the datasheet if I want to saturate the base. I would need a resistor to retard the current a whole 250mA.

Am I missing anything? Does this all look good?? Meaning will it work? Please explain anything I am missing conceptually or anything at all I would very much appreciate it!

EDIT: I have researched this topic as best as I could and these are just concepts and question I need help wrapping my head around.Ultimately I would like to be able to do this with out the help of this forum/group and move to mosfets next.


texts:
I am interested in the following compressor, which I reverse-engineered from a pcb (there might be some mistakes, but I don't think so)

(open the schematic in a separate window to see the small text). The lightning sign is +9V DC and Vin is only AC, with frequencies 20 Hz < f < 800 Hz. The chip is a TL074CN quad op-amp, and there's a jfet which says K192A.

I guessed this is a compressor because it makes sense in this application to have one (e.g. make the bass more rich), but I am otherwise clueless as to what this part of the circuit actually does.

I suspect it does amplify the signal a bit, could you tell me how much? I am in principle only interested in the linear range of the compressor, as my point is to bypass it, but I need to match the input and the output's magnitude.
Of course, if you want to tell me exactly what the circuit does, please by all means, go ahead :)

EDIT: To clarify: In my previous question (see Short circuit or disconnect to bypass a compressor), I wanted to bypass this compressor. In this question, I am interested in its response, particularly in the linear range.


texts: Switch between 3V battery and 5V USB as power source

texts:
I know there are several other threads with similar questions, but my requirements are different. So far I couldn't find a solution even though I read through several of these topics.

My circuit is normally powered with a 3V coin cell battery. I would like the circuit to be powered by USB as soon as a 5V USB power source is connected to my circuit - to save power from the coin cell.

Obviously I was looking at the well known diode-or setup but in my case I cannot use diodes, because even Schottky diodes would have a voltage drop of around 0.3V. Thats too much when running on the coin cell. I cannot accept any voltage drop on the coin cell rail and max. 0.1v drop on the 5V USB rail.

Then I was trying to experiment with a p-channel mosfet, but I'm not sure, if my solution works out in reality. I'm just a maker, not an electronics guy :-( Attached is the schmeatic.

Beside using a power mux ic (which would cause quiescent current), is there any other discrete solution with high energy efficiency I could use?

Thanks!


texts: 16x2 LCD operating in 4-bit mode. At first, I tried initializing the LCD in 4-bit mode using software. Did not work. After repeated tries however, LCD started working. But for some reason I had to reset the microcontroller 2 or 3 times for it to properly function. On the first reset, it shows garbled values, but on repeated resets, it started displaying properly. Then I switched the project to STM32F030R8 and again the LCD wouldn't work. Sometimes when I connect and disconnect the ground jumper it goes into 4 bit mode and displays some random things. When the power is turned on and off, it'll be back to square one.


texts: Will this design for an XHP70.2 LED Driver with arduino control work to the params specified?

texts:
I am making a driver PCB to drive an XHP70.2 LED at 15A (~7v) Continuous, Controlled from an Arduino. I am new to OpAmp's so I would like to know:

Does this circuit look as though it would function as intended (as a
current source for 15A@7v from a 2S Li-ion, controlled by an Arduino
PWM pin)?
Would 1.5mOhm (1W 2512 [6432 Metric] Thick Film) be a suitable value
for RSENSE?
What OpAmp would be best?
What values would be needed for R1, R2,...R8? (& C1)
Would (CSD16340Q3)'s be suitable for U1 & U2?

CSD16340Q3 - http://www.ti.com/lit/ds/symlink/csd16340q3.pdf

NCP3420 - https://www.onsemi.com/pub/Collateral/NCP3420-D.PDF

LTC6992 - https://www.analog.com/media/en/technical-documentation/data-sheets/LTC6992-1-6992-2-6992-3-6992-4.pdf

If it will work, are there any possible improvements? i.e. reducing the number of components

Thank you in advance


texts: SD card sector address vs. physical location

texts:
I'm curious as to how SD cards map the supplied sectors for read/write to physical locations in the flash memory. Is this the real physical address, or is it just a virtual address that the SD controller then maps to the physical location?

I've read that SD cards have a controller which will manipulate writes in such a way that the wear of flash sectors is spread out as much as possible.

The main concern I have is if I have a micro-controller dealing with low-level IO where I read/write to a SD card using the SPI interface (mainly writes). I'm planning on using a PC program to pre-allocate sectors/clusters in a FAT16 formatted SD card at pre-known locations that my micro-controller can use. However, I don't want these sectors/clusters to magically be moved by the SD controller in such a way I have to re-parse the FAT16 file system in order to find where they are. I also don't want to accidentally repeatedly write to the same physical flash sector causing a failure in that one portion of the SD card.


texts:
In my application, I need to find true north direction, for reference purpose.
I am having a GPS enabled drone.
I have searched over Internet and found that moving in the north direction while keeping your Longitude constant, the path followed will be the direction of true north.
However, I don't know how much accurate this method is.

Can anyone please explain the best way to find the true north direction in a Drone/UAV?


texts: LM393N with hysteresis and potentiometer

texts:
I am having a bit of a problem with this next circuit:

The problem is, when there is 0V at the base of Q1 and when the potentiometer is set close to 100 kOhm. Because of the hysteresis set on LM393N, I belive something like this happens:

Meaning the voltage on comparator will never pass ~3.4V to switch its output to high.
My question is, how can I avoid this from happening? How do I have to construct this circuit to work with a potentiometer?

How the circuit should work:

The base of Q1 is connected to IR receiver. When the IR beam is gets broken, the voltage on the base falls down to 0V and C1 starts to fill up through R1, R6 and R2. When voltage on C1 passes ~3.4V interrupt (rising edge) on AVR gets triggered. When the IR beam gets closed, the voltage on the base of Q1 rises to 5V, the capacitor discharges through R2 (which will be replaced by potentiometer in the future). And when the voltage on C1 goes below ~3.4V a second interrupt (falling edge) gets fired.
The capacitor is added to avoid false triggering, and the potentiomter is there to allow the "sensitivity" to be set.

Any help is greately appreciated!


texts:
I'm trying to make a DIY smart socket. Is it possible to control the relay with an Arduino? Maybe replace the controller with the Arduino?

Can I use the ribbon cable Out, Ground and VCC pins do to that?
Model: EMT757

The Timer Controller Board With the OUT pin, VCC and GND:

Relay board where the VCC, GND and OUT go from, the controller:

Behind the relay board:


texts: Bidirectional TVS supressor instead of Snubber for Triac

texts:
I am planning on building my own smart home socket and I want to mainly control LED lamps. But of course I can't make sure that someone is not plugging in let's say a toaster into the socket. (Yes I know that I could warn everyone since it is only for private use but this seems to be not the right approach).
Of course I know that dimming capabilities using phase cutting is not suitable for most LED bulbs but it suffices to just turn them on and off at this point.
Now my problem is that by using a snubber circuit I can protect the Triac from voltage spikes caused by the cut-off of an inductive load but this is also mostly a problem when switching LED Lamps since the capacitor charge is often enough to let the lamp flicker once in a while (depending on the lamp circuit).
Therefore I would like to know if it possible to use a bidirectional TVS Diode instead of a snubber and if it still offers enough protection.
Here are some of my circuit parameters:
Voltage (Load) 230 VAC
Triac BT136 600E
MOC 3021
TVS Diode 1,5KE250CA


texts:
I have the following circuit and I want to process the output of the op-amp through an ADC. However, as you can see in the picture the signal is clipping at 1.89 Volts, rather than 3Volts. Why is it doing that? Does it have to do with the biasing of the amplifier?? The signal I applied was a 19 kHz sine wave.

Circuit diagram:

Output capture:


texts: How to wire a switch to change the speed of a motor?

texts: I wanted to create a switch mechanism, using a three position switch that would allow me to change the speed of the motor in the picture. I know that the motor's speed can be changed by switching the ground wire from low to high but how would I use a switch to make this switch, electronically, instead of manually?


texts: Direct Coupling and No bias on JFET guitar preamp's

texts:
Why some of JFET preamp's for guitars don't bias the gate to Vgs(off)/2 and just reference it to ground? (Setting Zi)

This also lead to just direct coupling the guitar output to the gate.

As far as I understand with N-JFET's one should apply a negative voltage up to Vgs(off) to control the current the channel. And that on the ohmic region near to Vgs=0 the transfer curve becomes more non-linear.

The direct coupling non-biased design would mean the preamp or voltage buffer would be working on the Vgs=0 non-linear zone and that on the positive semi-cycle of the input sine wave the gate will be forward biased and would not make the channel less resistive (since Ids is already max and the channel saturated) then the output would be quite different from the original.

One example of these designs:

Ruby: MPF102 input buffer for a LM386

Explanations like this one has a DC bias on the gate (that doesn't matters on the AC analysis though).

As far I have figured out if we put our reference on the Source, Rs is biasing both Source and Gate, making the Source more positive than the gate, and the Gate as negative as Vs.

But then on the Ruby circuit, taking the Source as reference, the Gate would be at -9V above the -8V needed to reach cut-off voltage on a MPF102 and -6V with a 2N5457. A positive semicycle above 1V should make a difference but a negative semicycle won't.

My approach is wrong?
I know that DC and AC analysis should be done way different from this, but I don't understand the physics mechanics that are working here.

EDIT:

Setting aside that learn how things work is a good thing, I wanted to understand this to replace that MPF102 with an 2N2302 with smaller specs than the MPF102: Idss=5mA; Vto=-4V. (MPF102 and 2N5457 are not available here)
I was worried if I would have to change values to achieve a proper polarization since my signal in a worst case scenario goes as high as 2Vpp and the MPF102 Vto is -8V. I understood that it was a voltage follower but failed to understand the inner workings so these questions came up.


texts: Quarter-wave impedance transformer working principle

texts:
consider the following scheme:

A transmission line of length lambda/4 has been put before the load ZL in order to get an impedance matching. But, I do not understand how it works. Precisely, by the following formula (suppose for instance a purely resistive load):

we get that:

Zin = (RL)^2/Z0, and this means that there is reflection at the input port, since we know that the reflection coefficient there is equal to the ratio:

(Zin - Z0) / (Zin + Z0).


texts:
I'm working on a project and I need to know where the information taken by the barometer sensor are stored.
I think in the eeprom, but exactly where? Is there a specific address or register memory?

My goal is doing the ROP attack on the system.

I compiled the ArduPlane code (just the part of Ardupilot relative to the plane and not ground station), then found the .elf and I did the command

avr-objdump -S arduplane.elf > arduplane.lss

and now I have the istruction of all the arduplane.
In the section of the sensor I found the function

static int32_t read_barometer(void){
   barometer.read();
   return altitude_filter.apply(barometer.get_atitude()*100.0);
}

that in the lss became:

static void init_barometer(void)
{
    697e:   cf 93           push    r28
    6980:   df 93           push    r29
    barometer.calibrate(mavlink_delay);
    6982:   cc e8           ldi r28, 0x8C   ; 140
    6984:   dc e0           ldi r29, 0x0C   ; 12
    6986:   ce 01           movw    r24, r28
    6988:   6b e5           ldi r22, 0x5B   ; 91
    698a:   7e e4           ldi r23, 0x4E   ; 78
    698c:   0e 94 f6 8d     call    0x11bec ; 0x11bec <_ZN7AP_Baro9calibrateEPFvmE>
    }
    void            set_compass(Compass *compass) {
        _compass = compass;
    }
    void            set_barometer(AP_Baro *barometer) {
        _barometer = barometer;
    6990:   d0 93 8b 07     sts 0x078B, r29
    6994:   c0 93 8a 07     sts 0x078A, r28
    ahrs.set_barometer(&barometer);
    gcs_send_text_P(SEVERITY_LOW, PSTR("barometer calibration complete"));
    6998:   81 e0           ldi r24, 0x01   ; 1
    699a:   90 e0           ldi r25, 0x00   ; 0
    699c:   64 ec           ldi r22, 0xC4   ; 196
    699e:   7f e0           ldi r23, 0x0F   ; 15
    69a0:   0e 94 a4 34     call    0x6948  ; 0x6948 <_ZL15gcs_send_text_P12gcs_severityPK11prog_char_t>
}
    69a4:   df 91           pop r29
    69a6:   cf 91           pop r28
    69a8:   08 95           ret

Are r29 and r28 registers dedicated to the barometer?

Are 0x078B  and 0x78A the stack addresses for the information?


texts: Can a NFC tag be read over a large flat area

texts:
Was wondering if I could create a large flat area that could detect the position of NFC tag (or similar preferably powerless technology) and if possible the direction the chip is facing. Say if you had a chessboard and placed a pawn that had a nfc tag on it, could a computer recognize this as a pawn and where it's going and facing. There wouldn't be much vertical distance but a lot of horizontal area.

It would also be great if you could point to subreddits or other resources with similar technologies if this is not feasable.


texts: Find the power dissipated by the controller source

texts: I am confused about the controller source. How can we define the controller source? I cannot figure out which one is the controller source.


texts: Removing digital noise on quadrature encoder signals

texts:
I am using a quadrature encoder with 3 lines to track the rotary position of a shaft attached to a BLDC motor(through a planetary gearbox).

When I rotate the shaft, the A, B and Z lines always have an erratic digital noise(observed using a logic analyzer), which always messes up the position readings. The picture of the digital signal is as follows
 The order of the signals is A, B and the last one being Z(index)

The noise is always seen on all 3 lines together and compared to the actual encoder pulses, it is of a very short duration.

What could be the source of this noise? How can i remove the noise from the signals? Preferably through a minimal hardware solution.

My position data is processed by a controller who's code I cannot change, hence the option of compensating for the noise in software does not exist for me.

A closer view at the noise

EDIT: I am using a CUI AMT11-3S encoder, which is a capacitive encoder Link
 & Datasheet


texts: How to figure out how much time you have for writing to flash when voltage source breaks down?

texts:
I try to figure out how I can make sure, that my controller (STM32F030K6) is always able to save a 16 bit integer to the flash when the power is breaking down rapidly.

This controller has an Analog Watchdog that fires an interrupt when it detects a value below a certain threshold.

The ADC runs in continious mode and multiplexes 4 channels of which one is the critical and is used for the Analog Watchdog. So I figured I get a new value for this channel every 350 cycles ( 87.5*4, to scan and convert 1 channel the adc needs 71+12.5 = 87.5 cycles). When the IRQ fires it runs this function:

uint16_t data=...;
...

void ADC1_IRQHandler(void)
{
    HAL_FLASH_Unlock();
    HAL_FLASH_Program(TYPEPROGRAM_HALFWORD,0x8007C00, data);
    HAL_FLASH_Lock();

    HAL_ADC_IRQHandler(&hadc);
}

According to the data sheet, it takes this chip ~50µs to program a 16 bit value to the flash.

My set up is a PCB with a 24V supply, an LM317 generating 3,3V and a charge pump for a MOSFET, which takes the clock from the controller. I thought about shutting everything down before writing to flash, to save some power, but shutting down costs cycles...

I've got 100nF on the 24V input and 1µ on the input and output of the LM317 voltage regulator.

How can I make sure I can always save that value, even if the voltage on the input breaks down immidiately?


texts: Extend linearity range of this opamp circuit

texts:
Sorry if my question is too naive, I'm new to this. I am trying to design a controlled current source for currents up to about 1A (diagram below). My requirement is that the current depend only on the value of a single voltage source and a single resistance (which I can precisely choose).

simulate this circuit – Schematic created using CircuitLab

The problem is that the output voltage of the op-amp = gate voltage of MOSFET is becoming equal to the rail voltage, causing saturation at about 300mA itself (i.e. before reaching 1A). Is there a way I can improve the above circuit to prevent the op-amp from saturating and getting a 1A current?

EDIT: I've changed the design following τεκ's answer and swapped the FET and Load. This should ensure that FET's source voltage doesn't go above 5V, but the gate voltage still goes to 14V and saturates the op-amp.
Thanks in advance.


texts: Constancy of gain bandwidth product for amplifiers

texts:
I've seen the assumption of gain-bandwidth product being constant for some amplifiers. More specifically for a compensated op-amp.
Is there any mathematical proof to establish why the product is constant?


texts: Help identifying a possible connector for these unterminated contacts on my HP Stream 14 motherbard

texts:
I'm trying to identify the appropriate connector for this bundle of unterminated contacts, from my HP Stream 14 motherboard.

I'm talking about the red circled part of the motherboard:

Here's a close up:

The number of contacts are:

\$4 \qquad\qquad 29\$

\$5 \qquad\qquad 29\$

The first picture, with unsoldered contacts, was pulled from the internet. The second picture is of my actual motherboard.

The reason for asking is that the Intel Celeron embedded on this motherboard (https://ark.intel.com/products/91832/Intel-Celeron-Processor-N3060-2M-Cache-up-to-2_48-GHz) supposedly has

4 PCIe lanes
1 DisplayPort/HDMI (integrated graphics in CPU)
5 USB ports (some 2.0, some 3.0)
2 SATA
1 UART
1 GPIO.

\$\$

The screen uses the DisplayPort/eDP.
The physical HDMI port is most likely in dual-mode with the DisplayPort above.
There are physically 2 USB 3.0 and 1 USB 2.0 ports
The keyboard might take up either a USB or the UART or the GPIO.
The trackpad might also take up  a USB or the UART or the GPIO.
The M.2 slot uses 2 of the PCIe lane.

So really, there are more or less:

2 PCIe lanes made unavailable
0 to 2 USB ports (some 2.0, some 3.0) made unavailable
2 SATA made unavailable
0 to 1 UART made unavailable
0 to 1 GPIO made unavailable

So perhaps some of the unavailable lanes above are on the unterminated contacts?

How do I test?

But really, the easier way of going about this is identifying the connector.


texts: Trouble with first part of Experiment 11 (Make: Electronics) when using multimeter

texts: Here is my circuit. It works well, as described in a book, but I want to understand it better, so I want to check voltage on capacitor. But when I do it, LED doesn't blink and voltage goes up to 4V. When I turn off multimeter - it works again. Мultimeter is connected to capacitor directly. What did I do wrong?


texts:
I think I have a challenge for you smart souls on here, who donate your time by answering all of my terrible questions.

I have to design a switch that completely shuts off a system when it is engaged, then turns the system on only after five seconds have elapsed from when the switch is closed.

That is,

switch is open, system is completely off
switch is closed
five seconds pass
system is on

By open I mean the switch is touching the top terminal in the junction labeled U3 in the schematic. By closed I mean its touching the bottom terminal.

If the switch is re-opened at any time during the 5 seconds in 3., the system goes back to 1. and the switch must be closed for another five seconds.

Even more complicated, once the five seconds have passed and the system is on, I'd really like it if this whole switch-circuit apparatus didn't change the system state any more, unless I unplug the power source. That is, after the system turns on, it's always on, and toggling the switch can't turn it off.

I've made a test circuit using a p-channel mosfet and a tiny45. The idea is that, when the switch is open, the mosfet's gate is pulled high by the voltage source (a 3.7V LiPo) supplying the power to the system. When the switch is closed, the attiny45 is turned on, and the MISO pin pulls the FET's gate high for another 5 seconds, then low, allowing charge to flow through the FET.

Only problem is, when I close the switch, the system turns on momentarily, I assume because the 45 hasn't started up yet. I can't have the 45 be on, since it will draw power from the battery and perhaps drain it before it gets a chance to power the system. Is there a way to smooth that transition so that the MOSFET gate continues to be high for the few microseconds required for the 45 to turn on?

Thanks!


texts:
I am trying to make a motor driver, similar to a H-bridge using four tip 121 (the label in the schematic below is wring because I could not find a tip 121 at my B2 simulator) the schematic is this:
B2 and the switches represents my arduino's pins.

The problem is that I only get 5V at the motor... even when the power supply is 12V! It does happen in the simulator, but I have no clue about why it happens...

Googling I found that the schematic of the L298 (the IC used in many arduino shileds/motor drivers) is quite similar to mine... But I do not understand why I only get 5V at my motor... As far as I understand the voltage drop at the collector-emitter of a transistor is constant...

What (and why) is wrong with my design?


texts: How do I control two 240v water pumps with float switches connected to one outlet pipe so that only one pump is switched on at a time

texts: The pumps are in two different 1m deep wells that collect rain water to stop flooding they have float switches but because they use the same discharge pipe if both pumps tried to pump at the same time it would take a long time to lower the level. Need a relay to only allow one pump to operate at a time.


texts: What is this communication standard I'm seeing? It looks like UART but with a third line

texts:
What the title says. I looked into flow control, as that seems like the obvious answer to "what are these extra lines in my UART communication?" But what I'm seeing doesn't really look like flow control, even if we assume that one line is tied to gnd. Also, I didn't see any other data moving across other lines. As far as I can tell, what I'm seeing is a standard UART TX/RX arrangement, except that there's this third line which is controlled (it seems like) by the master.

It looks like it "ticks" (pulses) every time the master finishes sending a byte, and then it also pulses to indicate that the slave is clear to communicate. I've attached some pictures below of traces that I've taken with a logic analyzer. This is this mighty gecko development board driving communication with the smaller mighty gecko module (EFR32MG12).

EDIT: for detail, this is a mighty gecko dev board talking to the mighty gecko chip/module (EFR32MG12). The lines are unlabeled because they're not listed in the schematic of the device that I'm talking to (the gecko), so I basically went around tapping lines while it talked until I found something. I'm assuming that host TX is the top/black line, as it talks first, and that host RX is the second/brown line, as it's clearly another serial comm line. That leaves the red line as the mystery line.

EDIT 2: changed beaglebone black to mighty gecko dev board. Apologies for the confusion.


texts: What is non-characteristics harmonics and inter-harmonics in HVDC?

texts: I have only heard about harmonics in AC power, but in the HVDC system, these terms are used. How do they affect the system?


texts:
I have a signal which toggles between 7v and 0v up to 100 million/sec. The receiving IC only accepts voltage levels up to 3.3v.

What would be the best way to lower the voltage from 7 to 3.3? I considered a voltage divider, but wondered whether the resistors would distort the signal at such high frequencies.


texts: Using FTDI with AtMega328P@3v3,8MHz and RFM69

texts:
I am running an AtMega328P-PU at 3v3, 8MHz with external crystal successfully. I am able to burn the bootloader using ISP and flash the chip using FTDI and the clock seems right.

The mega is connected to a RFM69HCW, which uses the SPI interface and thus occupies the SCK, MISO, MOSI and SS along with int0 for RFM DIO0 and PD4 for RFM reset.

I am facing a problem where the FTDI interface does not work most of the time when the RFM is connected to the mega. There does not seem to be a pattern to when it works and when it does not, so I guess it might be something with timing (I do not have a scope, so I cannot verify this).

When the FTDI interface does not work (I cannot establish a serial connection - either using a monitor or uploading a program) the TX LED (red) on the USB-2-FTDI board is very dimly lit. I am using a Sparkfun FTDI Basic with the voltage jumper cut and soldered to 3v3. This board has auto-reset, no no need to reset the mega manually during programming (doing so does not change anything).

The FTDI interface works perfectly and reliably if I disconnect the RFM from the mega, so I suppose that it has something to do with this.

I have attached a schematic of my setup (it contains a few more components than my setup, so please disregard connection labels that have no match).

Any help will be much appreciated!


texts:
I ordered an STM32F4xx board to use it in an embedded systems class a couple months ago. It has arrived yesterday and I figured out it does not have the ST Link module included.

How can I program it? I understand I can get an STLink module, but i would like to know if there is another way.


texts: Step-up transformers with varying voltage outputs in parallel on single line?

texts:
Just curious if this is possible.  I also know this is very simplistic.
Say I have an AC generator that outputs 24V.  I have three separate devices that each require a different, increased voltage to operate.  Can I put three separate step-up transformers in parallel, each stepping up different voltages?
I drew this diagram to help explain what I mean.  The "G" is the generator, "T" is the transformer, and "D" is the device.


texts:
After running power flow solution using Newton Raphson, I have been trying to vary the voltage of a PQ bus by adjusting the reactive power at bus.
If my desired voltage is higher than actual, then I am increasing the net reactive power flow (Q=Qg-Qd; I increase Q) and vice versa.
Normally to boost voltage, I must supply leading reactive power. And so far what I have seen is, leading reactive power has negative sign. But here in my scenario, I am increasing Q (Q=Qg-Qd) to boost voltage.
So what is the sign convention used here for the reactive power?
Could someone please share me a link or if possible explain me the sign convention used for reactive power? I am so confused that I am not even able to frame this question clearly. Sorry for such a lengthy and improperly framed question.


texts: Potentiometer Range in Speaker Frequency Response Curves

texts:
In several speaker spec sheets from CUI a frequency response curve is given, such as in the CLS0231MA-1:

Notice the two y-axes:  one for the potentiometer (0 dB to 50 dB) and one for the DUT (0 dB to 25 dB).

The latter is self-explanatory, but what is this potentiometer range?  Is there a standard test setup that this refers to?  Does the potentiometer range use the same 60 dB zero level as the DUT?

EDIT: Seems like this 'Potentiometer Range' shows up in other companys' datasheets, too.  This one is from Soberton's SP-3205:


texts: Why do you need a conductive layer with conductivity of \$~10^4\$ S/cm in a capacitance touchscreen?

texts:
ITO has has conductivity of \$~10^4\$ S/cm. A capacitive touchscreen measures the change in capacitance or electric field.

1) Why do you need a conductive layer in a capacitance touchscreen in the first place, if you just measure the capacitance or electric field?

2a) Does it really need to be as low as \$10^4\$ S/cm or can it also be something like \$10^3\$ S/cm or \$10^2\$ S/cm?

2b) What happens when the conductivity gets lower?


texts: Electromagnetic 7-segment flip display: H-Bridge alternatives?

texts:
I have an electromagnetic 7-segment flip display which has 28 electromagnets for 4 digits.

They run on 20V, have a 7.5W power rating and need alternate polarity applied to switch between the 'on' and 'off' states.

I tried using a Raspberry Pi with 14 x L298N Dual H-Bridge Driver Modules to run the electromagnets and it usually works, but there's a lot of wiring involved with the H-Bridge modules, making fault-finding tricky, and I've had a few fail on me already.

Is there a better/tidier way of controlling them that I haven't come across? I've done research online but can only really find these H-Bridge modules as being the answer.

Thanks.


texts:
Short version: What might be breaking the first sensitive component connected to an ungrounded 14cm UHF dipole antenna mounted 30' above the ground? Could it be related to static electricity?

I have designed a built a few simple weather stations that I have installed in my region. The system consists of an atmega MCU that monitors wind and temperature, and sends a message over LoRa every few seconds to a receiver at my house.
All good, except after a few months in the field the signal cuts out. I take a replacement out and bring the broken unit home to find out what went wrong. What I have found is that the most of the circuitry is still working fine, but the radio has stopped transmitting. Further investigation revealed that RF switch (PE4259) of the broken units is inserting 30dB+ of attenuation (This was determined by soldering some thin coax cable at various places along the radio signal path and measuring with a spectrum analyser).
The units are mounted 30' above the ground, solar powered, transmitting +22dBm at 424.8MHz (w/ ham license).
The radio units I use are small devices based on the SX1268 chip, and encompass all of the hard RF stuff into a simple package that I just attach to my board: http://www.dorji.com/products-detail.php?ProId=64. I have opened them up on broken units (necessary to troubleshoot) and they pretty much follow the reference design from Semtech:
The signal path is: Tranceiver RFO -> Filter & Impedance matching -> RF Switch -> More impedance matching -> U.fl connector -> Coax -> SMA Connector -> Coax -> Antenna.
The antenna is a home-made dipole antenna from ~13cm long aluminium bar on the end of a plastic arm. It is mounted about 1' below sensor units, which are at the top of the pole (See this image of an assembled unit, not yet mounted on a pole).
The station has no connection to any sort of real ground - the entire thing is floating.
While I am not completely familiar with the internals of the radio unit, I assume the manufacturer has done a decent job of impedance matching along the signal path. I have tested the part of the signal path that I am responsible for (from where the signal leaves the radio units to the antenna) and measured a SWR of 2.2 - not ideal, but low enough that I wouldn't expect it to damage the components.
So - getting back to the problem - I am at a bit of a loss as to what is causing the RF switch to fail, and how to prevent it. A recent thought that occurred to me is that the switch is the first 'sensitive' component any signal from the antenna will see. Perhaps this is caused by large voltages from the antenna? This article / video and its comments have me wondering if it may be caused by static electricity developing on the antenna. The stations are mounted at ridge-top locations, sometimes in snow, sometimes in cloud, sometimes in dust. I assume that lightning is not to blame because I would expect much more significant and widespread damage.
If it is static, what would be a way I could confirm that? What would be a suitable fix? A sufficiently large inductor or resistor between the antenna elements?
Sorry about the rambling details, but my problem here is I'm not even sure if I'm looking at the right factors.


texts: Using an open-collector output from one IC to trigger a level change on the input pin of another IC?

texts:
So my problem is simple: I have an IC that provides an output pin to alert you when some condition is met.  The output pin is open-collector, high-impedance when active.  I want to monitor this output on another IC (a microcontroller, specifically).

Is this as simple as having a pull-up on the output so when it's "on"... the level goes low and I just monitor for the high-to-low transition?  I feel like I'm overthinking this, but it's not immediately setting off a light-bulb in my head.


texts: I have a hypothetical question about running a DC motor on lower voltage than it is designed for.  Lets say I have a 2hp 100VDC (yes, Direct Current) motor that I want run on 12 VDC. The motor is 2hp = ~1500 Watts, so I'd have to supply 125 Amps at 12 VDC.  This would require some big wires, and result in some efficiency and heat losses. Would it burn out the wires in the windings of the motor?  Would that be entirely dependent on the load?  Would the motor turn at a lower speed? Lets say the rated speed of the motor is 4400rpm, what would the speed be with a 12VDC input?


texts:
I have following wire as shown below, one end has male USB connector and other end has four wires. I know, when connected to laptop, the RED one acts as voltage source and BLACK as ground. If I give 2 bits data input to GREEN and YELLOW one, is there any software or API for (Python, C or any other language) to know about state of those two wires ? I mean to check if GREEN or YELLOW one have a voltage or not.

Please guide me if I am asking the wrong question.


texts: Burning graphite with 9V battery vs. Arduino's 5V

texts:
First off, I'd like to say that I am completely new to electronics and the way circuits work, so this may be a really dumb question.

I've tried searching Google but I can't really find what I'm looking for since I'm new to all this.

Basically, I'm trying to get a pencil graphite to produce some smoke.

When I connect one part of graphite to the +5V Arduino pin and other to ground, it smokes for a bit before Arduino's short-circuit protection kicks in.

The above works as expected, but when I connect it the same to the 9V battery as the source, the graphite barely warms up.

So my question is - why does Arduino's 5V make graphite smoke while the 9V battery doesn't?


texts: The best way to bring drop 700VDC to 12VDC?

texts:
I am currently working on a PCB design that will be using 12VDC to power all of its components. It will be mounted on a vehicle, which is powered by an external power supply, which supplies the average voltage of 375VDC. I want to make the board bullet proof, and design it so that it can take up to 700VDC before bad things happen, and using the flyback converters is not an option. Most of buck converters have the maximum input lower than 100VDC.

The only solution I can think of, within my knowledge, is to use a voltage divider to bring the voltage down first, and then use a buck converter chip to get 12VDC. Would it be a valid option? Could anyone suggest better ways to solve this problem?


texts: Is plunging in an ESD strap to a batter backup like a UPS or APC reasonable? I have a simple ESD cable that terminated in a 3 prong wall outlet where only the earth ground prong is metal. There is a 1MEG ohm resistor between the contact on the strap and the earth ground prong. Will the strap discharge me to earth ground through the backup? Is there a way to tell if power strips are isolated from earth ground?


texts:
I'm trying to work on a reactive lighting project and I'm confused about a couple topics when it comes to sampling audio.

I want to be able to have RGB reactive lighting controlled by a microcontroller sampling audio from a standard audio jack (such as from a phone). I'm planning to just use a mono sound audio jack to simplify everything.

My main concern is how to actually sample the audio. My understanding is that from a phone audio jack the signal is already in analog form, and needs to be sampled again at the microcontroller, and I figure I would need a sampling rate of around 20kHz to capture most of the frequencies in the audio.

In the past I've used Arduinos for projects that sample at ~8kHz with the standard audioread() function. I was able to use a library I previously had and  interrupts in C to achieve a sampling rate of around ~10kHz which isn't much better. Would I just need to purchase faster hardware or is there a way to increase the sampling rate on cheaper microcontrollers?

I'm also worried that even if I can sample the signal fast enough, that the processing for my reactive lighting may take too long and slow the sampling down. I plan on using FFT and calculate a dominant frequency from the last X samples (to be determined based on sampling rate) and quantize it into different colors. What sort of timing limitations are there here? If I know the sampling rate I can calculate the time between samples, but is there a way to calculate the time it takes to execute a loop of the reactive lighting algorithm? If I could do that I would be able to see if my algorithim is fast enough to keep up.

I'm trying to sort all this out before I go and purchase any parts for this project, so any help is appreciated.


texts:
You always learn in school that you should never short terminals of a battery because the wires overheat from the large current.

If you look at a brushless motor, you'll see that its nothing but coils of wire.  So why don't these motors "short" the power leads?  How is this any different than shorting terminals of a battery?  How is the current being regulated when the motor is operating?


texts: Unsual sizes of TFT, LCD or OLED panels?

texts:
On Stackoverflow there was a question about a round TFT display, but that answer was difficult and pricey.

What is the possibility of finding rectangular LCD/TFT/OLED displays that are small in height, or long in width? Like a LED strip banner display, but then in either color or monochrome. Like one third the height of a normal 16:9 monitor. So 16:3.


texts: How to connect MP3 player to TV using RCA?

texts:
I have a personal MP3 player with 3.5mm stereo socket for output.
I have made a 3.5mm to RCA stereo cable by connecting the shorter inputs to the centers of each of the Left and Right RCA jacks and the ground is split up between them.
Even with full volume in the player, I'm unable to hear any sound from the TV speakers in the AV Receiver mode.
How do I get this to work?


texts: Question related to the interference seen at the spectrum analyzer's receiver

texts:
I am preparing for the RF course exam. I have an old question on hand that I am trying to solve. Please review my attempt.

  Question:

  A simple spectrum analyzer with superheterodyne receiver having 10.7 MHz  intermediate frequency is given. It works well unless the analyzer is used to analyze a signal on 318.6 MHz by setting the analyzer to 318.6 MHz center frequency, 5 MHz span, and 10 kHz RBW. Before we switch on the desired transmitter, the analyzer detects a clear signal at the center frequency. Later, when we learn that there is a 340 MHz transmitter in the same antenna tower you immediately realize what happened.

  1) Explain the "issue".

  2) Improve the design of the spectrum analyzer that protects against this kind of problem.

My attempt

Does the below arguments make sense to you? Thanks.

a) The adjacent channel interference generated by the carrier at 340 MHz frequency could be leaked to the spectrum analyzer receiver at 318.6 MHz.

b) The IF bandwidth of the receiver can be narrower in order to reject the adjacent channel interferences.


texts:
I am measuring the phase voltage of a BLDC motor as shown in the figure below.
As the motor doesn't have neutral point, a virtual neutral point(VN) is created by the resistor network and three-phase voltage are measured with oscilloscope Probe A, Probe B and Probe C. First let me know if my measurement setup is correct!!!

simulate this circuit – Schematic created using CircuitLab

I want to understand why there is a spike in the back EMF as shown in the figure below. As described in theory the Back EMF of floating phase ant any instant should ramp up or down but why there is a huge spike? How to reduce the spike?

My second question is at lower rpm why there are so much noise in back EMF? Is it actually happening to the back EMF or it is just an oscilloscope trigger visualisation.?


texts: What are some cheap, reliable methods of water-proofing switches and buttons?

texts:
I'm working on a project to put together a custom bike light from some LED flashers and a battery pack. I'm looking at two different options, one which comes with a built-in switch, and another where I would be wiring up my own switch.

If I build my own switching mechanism, I will purchase waterproof switches. If I buy the system with the built-in switch (it's actually cheaper than making my own, but there are other considerations), then it will not be water proof.

With the pre-built switch I would need a way to waterproof the whole thing; with the self-built I would need a way to waterproof the contacts on the backside, where the wires get attached. In either case, I must protect the battery from the elements. Most suggestions I have seen are to put the battery inside of a water bottle, which is then easy to put on the bike, and simple to add/remove.

What are some low-cost ($20 max, preferably cheaper) ways to water-proof switches and contacts? I'm not looking for a specific product, so much as a method for protecting them. Is it best to build some sort of cover? Use some sort of shrink-wrap? I've seen suggestions online to just put the finger of a latex glove over the switch, and seal that off. Would that be sufficien protection?

Note: this application will be using 12v DC and a max of 3 amps (likely more like 1.5A).


texts:
I am using PIC16F886/ 4MHz external Frequency/ timer 1 (100ms)/prescaler is 1. I am trying to turn on off LED for every 100ms.
In below code I need to change any setting to get exact value. or my formula is wrong.

If I do reverse calculation me getting 20Mhz

  Count=65536-((Time*FOSC)/4*Prescalar))
  3A98(hex)=15000
  15000=65536-(time*4XMhz)/4*1
  time=0.050s

OR

  Count =65536-(100mS*4Mhz)/4*1
  count=34464

#include <htc.h>
#define _XTAL_FREQ 4000000
__CONFIG(FOSC_HS & WDTE_ON& PWRTE_ON & CP_OFF & BOREN_ON & LVP_OFF & CPD_OFF  & DEBUG_OFF&MCLRE_ON &BOREN_ON&FCMEN_ON &WRT_OFF);
#define LED_RX RC7
unsigned char Counter=0;

void InitController() {

//  OSCCON=0X08;
    //OSCTUNE = 0x00;
    WREN=0;
    WDTCON = 0b00010111;
    PORTA    = 0b00000000;
    TRISA    = 0b00111000;
    TRISB =0b00001000;
    PORTB = 0b00000000;
    WPUB    = 0b00000000;
    ANSEL  = 0b00000000;
    ADCON0  = 0b00000000;
    TRISC = 0X00;
    PORTC = 0b00000000;
    ANSELH = 0b00000000;
    ADDEN  = 0;
    //T1OSCEN = 0;
    //INTEDG = 0; //falling edge
    //INTF = 0;
    //INTE = 1;
    PIE1=0b00000001;
    PIR1=0x01;
    INTCON = 0;
    //T1CON  = 0b00000101;
    T1CON=0X15;
    TMR1IE = 1;
    PEIE   = 1;
    GIE    = 1;

}
//===========================================================================
//                              Main program starts here.
//===========================================================================
void main(void) {
    unsigned char value;
    unsigned char conter = 0;
    InitController();

    while(1) {
    }
}

//==========================================================================
//                              Timer Interrupt - 5mSec
//==========================================================================
void interrupt isr(void) {

    asm("clrwdt");

    if (TMR1IF) {
        TMR1IF = 0;
        //  TMR1H = 0x3A;
        //  TMR1L = 0x98;
        TMR1H = 0x0B;
        TMR1L = 0xDB;
        Counter++;
        if(Counter>1) {
            Counter=0;
            LED_RX=!LED_RX;
        }
    }

}


texts: Wiring up 5+ meters of LED strips powered through USB

texts:
I am trying to power on about 5 meters of LED strips together with my ESP8266. The LEDs are called WS2812 and each LED is addressable.

After about 3.5-4 meters, the LEDs' colors starts to fade out (they start as white but end as yellow/orange). There are about 130-150 LEDs total and the voltage ranges from 2.8V (at the top where they are white) to 2.5V (at the bottom where they are orange).

The current I read out when all LEDs are powered on is about 1.08-1.1A at 5.1V, which means a total of ~5.6 watt. That is a lot for a regular USB port, but it doesn't matter if I plug it into an USB 2.0 or 3.0 port (the cable is only 2.0).

I'm looking for a better way to power this, so there's no voltage drop near the end, so my thought was to use two USB cables instead. One acting as power and data, while the other is simply used for power (need to split them up).

I would have to hook it up in parallel, right? Is that just a matter of slicing up the USB cables, then join the two wires for power?

Is there a better way to do this? Grabbing an USB 3.0 cable might be able to solve this, but I really have no clue about that.


texts: Control AC load with microcontroller. TRIAC behaviour problem

texts:
As per the title of this question i'm trying to control an ac resistive load. So far i had little success and i'm experiencing "strange", to me at least, behaviour from the triac(s) i tried. first of all i post a schematic of my test circuit (bare with it, it's not a complete schematic, it represents only the control part)

as you can see it's sized for a 220v ac line
missing in the schematic is a quadrature encoder input used to control the delay of the firing pulse to the opto.
What i did is take the zero cross signal and compute a delay based on the encoder input (ie if the input was 5 out of 10 i'd start a timer on ZCD and once it reaches 5 it would trigger the opto led thus triggering the BTA10 triac)
So far so good, the ZCD outputs a nice spike which is read by the pic and the output to the MOC is perfectly timed. Now comes the problems. Just to test the circuit i tried first with 15vAC (sizing the resistors accordingly and using a couple of car tail lights as a load) and i experienced this problem

ok, i don't draw very well...what was happening was that the triac switched nicely in the green region and won't turn on at all in the red one. i was puzzled but i thought it could be a voltage problem so i went from 15v to 110vAC (again changing the resistors and load). Now the triac switched on only at the very beginning of each half wave right after ZC. Sometimes switching only one half of the full wave. As soon as i delay my triggering signal more than a few hundreds uS or so the triac just stops working. I also changed the load to a beefier one (a heater) to increase current but nothing happened. I also tried playing with the resistors a bit to see if i can get some changes but had no luck. Now reading some forums I thought I may get rid of the transformer i used to supply my circuit with 15vAC first and 110vAC after and connect everything directly to the mains as it will eventually be. But maybe someone can point me directly to the correct answer! May the transformer be the culprit? If not what can it be?
I don't have much experience with TRIACS so my knowledge is surely lacking something and i may have forgot something important in the description of what I'm doing that can be helpful to get the answer right...
Just to be sure i link here the datasheets of the triac, optocoupler and optotriac. And an app note with some of the calculations i've used.

www.vishay.com/docs/83608/h11aa1.pdf

www.fairchildsemi.com/ds/MO/MOC3023M.pdf

www.fairchildsemi.com/an/AN/AN-3003.pdf

www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00004894.pdf?s_searchtype=keyword


texts: I have an application that calls for a "12V battery 120AH/1000A (EN)". I want to be sure I'm reading it correctly in that the 120AH is the battery capacity and the 1000A is probably CCA? And the EN is some European standard. Does anyone know what the actual EN standard is?


texts: Tapping energy from high voltage AC transmission lines

texts:
The details are hazy as I recollect this from my nipper days.Many, many years ago.

“Persons were charged with stealing electricity by placing a large coil, somehow, near high voltage AC transmission lines.”

Is this feasible or was it perhaps an April fool’s article that I swallowed hook line and sinker in my youthful naivety.

There is a modern reason for this question.

Due to country wide cable and transmission tower spar actual theft. We are looking at placing modules with a gyroscope and Wifi module to form a mesh that will report if a tower is being “attacked”. Of course I will still have to test if the electronic gyroscope is sensitive enough for this. But one of the problems is going to be, how to power the unit? Solar will require an extra solar panel and battery. If I could tap into the radiated energy from the actual transmission line, great. Many modern SOCs don’t require much power and can sleep most of the time.

To clarify our needs. We are looking at building a device to sense if parts of the metal tower are being removed by scrap metal thieves. If too many parts are removed from the tower. It will buckle and earth the line. This is still at the feasibility stage.


texts:
I am using the AEDR-8300 as a simple optical encoder solution. The part seems simple enough:

An LED emitter
Photodiodes that pick up the light that is reflected from a codewheel or black/white strip

The current part I have is the AEDR-8300-P, which has a minimum and maximum LPI of 150. I can understand why there is a maximum LPI but why is there a minimum LPI?

PS: I am not getting any output on either output channel on my test circuit and I am trying to understand if I need an improved black/white strip or if my circuit is not right. I've also tried using pull ups/pull downs but there was no difference.


texts: What would be a good language interpreter to implement into a Microcontroller

texts:
For beginners it is always a problem getting started with microcontrollers.
The biggest problem is getting the whole system running and then programming it with C. C is a great language but it has its pitfalls.

A solution for this problem would be running an interpreter of a high-level language on the microcontroller. Another advantage for the user would be that he can directly see what a command did.

In detail we want to use the atsam4s16b controller from atmel.
We developed a board and now want it for the users to be as easy programmable as possible.

At the moment we are thinking of implementing the lua interpreter or porting the elua interpreter.

But before we get started I want to ask if there could be other interesting solutions and what are the pros and cons.

For an embedded lua interpreter I would say you have of course some performance losses as for every other interpreter you run.
But on the positive side lua is a simple language which can be learned quite easily and you can communicate in an easy way with c code.

So the features of the language must be:

Easy communication with C
interpreted
Easy to learn
modern concepts (object oriented, maybe functional)
fit in the ATSAM4S16B
widely used would be good
and the interpreter should not be in an experimental state


texts: Selecting infrared non-contact temperature sensor

texts:
I want to select non-contact infrared temperature sensor for measuring temperature
I have following question regarding its selection:

My basic doubt is whether i am using Glass-container or metal container will it give me different reading of temp. ? Though the same material in both the container

2.Can anybody give me a hint/idea that which parameter's i should keep in
mind in selecting this sensor to detect the temperature of the material kept inside either Glass/Metal container of different thickness with non-contact distance of 2cm.

My last question is does the emissivity of metal body or glass body changes while change in their thickness ?


texts: In AC circuit will there be a voltage drop or current drop

texts: For reference purpose consider an AC voltage source of 240v 1amp and there are 3 loads connected to same 240v line one consuming 600 milliamps and another one consuming 300 milliamps.now if i add another load which consumes 200 milliamps will there be a voltage drop or current drop across the supply line. And if I connect the 600 milliamps load and 300 milliamps load (excluding the third load as I mentioned above ) to the same 240 v line will the voltage drop on the 300 milliamps load or does the it remain same as 240 v, if yes when to know if the voltage or current drops at a particular point if we keep on adding loads.i am new to electrical stuff


texts:
So I have a circuit shown below, that looks to me likes it's a CMOS inverter circuit. In this question, we're asked to find the current and voltage across drain-source voltage of the NMOS component.

The values given for the PMOS are as follows:
VDD = 5.003V
VT,pmos = -509mV
µpCox = 101µV/A2
W/L = 2µm/1µm
Lambda = 0V-1

Likewise for the NMOS:
VT,nmos505mV
µpCox = 209µV/A2
W/L = 9µm/1µm
Lambda = 0V-1

Here's the schematic:

So in my attempt to figure this out on my own, I got this:
Clearly, VS of the PMOS = 5.003V
Now after this is where I start to really question myself, and end up going in circles.If I assume that VG = VD based on the circuit diagram, then VGS and VDS are going to give the same value. Won't that then mean the PMOS is cut off?

I've also simulated the circuit in LTSpice. This gives VGSDS as the same value. Which appears to approximately be the source voltage minus the threshold voltage, but a little different. Here's that diagram and the related info it obtains.

Any help is appreciated. Especially in any conceptional mistakes or general assumption methods for the future!


texts: Specs on an AC-DC adapter that has two outputs

texts:
I have a custom adapter with 2 outputs that are the same in each output.  Based on the below specs what are the outputs of each of the cables coming from my adapter?

Input: 100-120V~3A
Output:12V-12.5A
Positive polarity

And I know the output in each is 75w.  So what is it?

6V and 12.5A

or

12v and 6.25A

Oh and this powers an external Graphics card for a laptop.  One plug is for the Graphics card the other is for the housing device. I already tried looking up the input specs for the card with no luck.


texts:
I would like to have three led lights on the front and rear of a locomotive (garden railways) so 6 leds in total. These are (LED, bi-colour, 5 mm, red + yellow 3 Pins - L-59EYW).

The part I'm struggling with is when the current reverses (direction of locomotive changes) I need the lamps to change, so the rear would go all red and the front all yellow, and vice versa. The voltage is a maximum of 12VDC and and the leds are 2.1V in one direction and 2.4V in the other. Would anyone be able to draw a diagram that I can follow to make this work?


texts:
Hai I'm doing the project on J1939 Periodic Group Broadcast (PGB) protocol.
I had an document where it mentions the word "INTERLOCK".
I didnt get what is an INTERLOCK,First INTERLOCK,Second INTERLOCK actually does it means in the PGB protocol.
so can help me in understanding what INTERLOCK actually means in the J1939 protocol.
Thanks in Advance


texts: How to show the VSS and VDD pins in 4033 IC (7 segement decoder)

texts: I am trying to make a stopwatch circuit by watching a circuit diagram (Right one is my proteus and left one is from internet) you can see on the left image that second has all the pins which are connected to other jumper wires and i dont have those pins in my proteus


texts: High current from an op amp with or without transistors?

texts:
I have a 30Vppk signal (under 1MHz) which terminated to a 50 Ohm resistor. This is the output of the system. It can be optionally terminated by a 50 Ohm load or ** higher ** Z loads.

With 50 Ohm load the system need to push a lot of current. More of what is available from a 20 - 40 mA op amp I'll have in there. What kind of stage should be included to have unity gain without adding almost any distortion or DC offset that will be able to provide 200mA easily (transistor based I guess) ?

I also looked into paralleling op amps but I don't know if this is recommended.


texts: Add aux input to Audio Amplifier circuit

texts:
I have bought a ready Audio Amplifier using TDA7498 chip and now I need some AUX input other than default one. Is there any circuit for this?

https://www.st.com/en/audio-ics/tda7498.html

https://handsontec.com/index.php/product/tda7498-2x100w-class-d-audio-amplifier/


texts:
I'm building a portable measurement device, that internally uses a CMOS sensor hooked up to an ADC converter. It's normally powered from battery, but I also allow it to run when hooked up to USB port (for both charging and debug data output). This is realized by MCP73871 chip that does power path control.
The device itself needs a bunch of different voltages, so the voltage from the above chip is first boosted to ~7.7V with a boost regulator (MCP1665) and then dropped to 5.0V by an LDO (LM1117). These five volts drive the sensor itself and the ADC converter plus a bunch of op-amps for buffering the analog signal etc.
The problem is that the voltage coming out of the 5V LDO is actually slightly different when powered from battery vs USB.
The voltage coming of the switching regulator does change slightly depending on the source and that's something that I get - it's a switching regulator, the line regulation guarantees certain precision of the feedback voltage, which can result in slightly different output from the regulator - since the switch has different on/off periods etc. The difference I'm seeing here is 7.722V (RMS 2mV) when on battery vs 7.737V (RMS 26mV) when on USB.
There's a bit of unevenness in that signal, but it goes into that LDO, which smooths it nicely out, however when on battery, that LDO generates 5.024V (RMS 1mV) and 5.005v (RMS 1mV) when hooked up to USB. It's still totally within the tolerances, but doesn't really match the "line regulation" characteristics from the datasheet of LM1117.
While that difference is small, less than half percent, it actually gets propagated to the sensor, which boosts it up a bit (because of the gain settings on the sensor) and in the end I'm seeing 1% of a difference in the measurement. It's not a disaster, I can correct for it in the software, but is there anything that could be done about it in the design itself? What's causing this difference? Is there any point in using a different voltage regulator to drop the voltage to 5V? Maybe some high precision one or with a different architecture (like the LT3080 with the constant current reference)?


texts: What connector to use to non-permanently fix wires to large switch terminals?

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I have a rather old rotary switch I want to use in a project. I want to connect wires to the terminals but would prefer not to solder directly to the switch. What connector is good for this?

The switch (the terminals are about 2.5mm)


texts: Accuracy of manufactured photocells (LDR) with respect to light intensity

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I was looking through photocell (photoresistors) datasheets, like for instance the NORPS-12, especially the graphic on resistance value versus light intensity.
In no datasheet could I find information on the accuracy, due to the manufacturing process (that is between different single component of the same type, say different NORPS-12 photocells.)
The only information I found from a blog was: "can vary quite a bit from photocell to photocell (perhaps as much as 50%.)"  That is quite a lot.

Why is this information never(?) provided?
What is the typical variation between single components? 50% variation of the resistor values for the same light intensity, really?
Are there photocell types whose variability is less than others?
Does it imply that each photocell has to be calibrated for each device with respect to light measurement applications?

Thank you very much fo sharing your experience and knowledge about this issue.


texts: What material can be used to connect nichrome heaters in series

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I would like to run 3 heaters (26 awg straight nichrome wire with slightly different lengths) in series to form one continuous heater with 3 different temperature zones.

All of the sections are connected using spot welds. I have tried connecting the sections with larger diameter 22awg nichrome and stainless steel wire, but the sections are not operating completely independently of one another. Of course, I could operate the 3 sections in parallel, but for my application it would be much better if the heater sections were run in series.

What could I use as a connection material between the sections so that each acts independently of the other 2 sections?


texts: Dc power supply outputting sine wave at both terminals

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I connected a DC power supply (set to 706mV) to a 1kohm resistor as this:

The semantic is like:

However, strange things happen when I use the oscilloscope to view the voltage waveform at point A and B.
Below is what is shown on the oscilloscope - cyan wave for point A and yellow for B:

As you see the two points are all sine waves. The voltage difference between the two waves are always kept at 706mV.
I know the dc power supply is floating (not grounded to real Earth) and the oscilloscope here is (separately) measuring the voltage of the two points relating to the real Earth (because the oscilloscope is natively grounded)
And I know that a floating circuit’s voltage related to the real Earth cannot be determined.
Yeh, this way truly the 706mV DC voltage is outputted between the two terminals of the dc supply - But, why is the dc power supply outputting two sine waves (relative to the Earth, one higher and one lower) to maintain a dc voltage? Why not straight output plain DC voltages? Is this for safety? As you can see in the oscilloscope picture above - the two sine waves are having much higher magnitudes related to the 706 mV desired voltage, which looks relatively unsafe though...
Also, I don't understand how a floating equipment can make such a voltage referring to the real Earth - previously I always thought there is a voltage difference from an object that does not touch the Earth to the Earth only when there is static electricity or an unequal amount of + - particles in the object.. Now I'm confused about this too...


texts: How to draw schematic and set values for transformer with auxiliary winding in LTSpice simulation software?

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I have drawn the schematic in LTSpice for dc to dc buck converter in LTSpice. I want transformer with auxiliary winding.At the secondary side , I want Vout=5V and Iout=2A . The auxiliary winding is required to supply 5V to the UCC28C40. Winding ratio is given as \$\sqrt{L1}\$:\$\sqrt{L2} =N1:N2\$ .

I think that N1=120 and N2=7, N3=6. So values of inductor should be L1=14400 ,L2=49 and L3=36 .Also, I have set the values of peak current of L1 as 0.387A and L2 as 8.18A. But when I click on RUN button ,It gives error as  "missing value for I1". So  are values written using spice directive i.e. "k1 L2 L1 L3 1"  right or wrong? Also, what changes should I do in the schematic ?


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I was looking for a way to drive the gate of a power NMOS. Since I've already have a small FPGA available at a independent backup-3V3 rail, I was thinking I could use it's internal oscillator to build a simple charge-pump.

The following should be a charge-pump relative to the NMOS source (load-side). It is stepped-up 3x3.3V from the independent 3V3 supply.

simulate this circuit – Schematic created using CircuitLab

I've simulated above circuit in LTSpice and got a nice ~13V/ms rise at the load with a final Vgs around 7V. The FPGA outputs are modelled as Push-Pull drivers and switching frequency is at 100kHz.

I can increase the rise-time by increasing C1 or lowering R2-R4.

I noticed that when charging a capacitive load, the current trough M1 is oscillating with the frequency of the charge pump. Does this matter? How can I avoid it?

Please help me understand how a gate driver is usually build, or point me to a suitable integrated circuit.


texts: I've heard of those things that tesla was trying to do by sending power into the earth using a 1 conductor transmission technique. Can the earth be used to send modulated signals of voice to be recieved somewhere else on earth like under the sea in a submarine?


texts: Why does the voltage decrease across resistors in series?

texts: I've read a lot of anologies about voltage and how is a type of "water pressure" but i can't understand why when 2 or more resistors are in series there is a voltage drop but when the 2 resistors are in parallel the voltage keeps the same.


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In my assignment I have the following question:

The processor has a clock rate of 1 GHZ.
The miss rate in the instruction cache is 1.5%.
The miss rate in the data cache is 4%.
30% of the instruction access the data.
The miss time for the data and instructions is 70ns.

A. Assuming we don't have any more stalls, what is the CPI of this processor?
B. I have to choose between two options:
  1. Use a processor with 2 GHZ while the cache stays the same.
  2. Use a better cache, which in it the miss time for data and instructions go down to 35 ns, while the clock rate remains 1 GHZ.

Which improvement is better?

What I don't understand here, is how can I calculate the CPI if I don't have the base cpi?

Let's assume the base cpi is X, then the memory stalls as I thought is:

4%*30%*70+1.5%*70=1.89

So the CPI is:

1.89 + X

What am I missing? is it possible to calculate A part as a number?

And for part B, how does the improvement in GHZ affects the performance? What I know is that if we improve the clock rate, the miss penalty goes up

*We don't have to take into account the hit time, for this question.

Your help is much appriciated.


texts: I am used to arcs, where the electricity wants to go to ground, or negative, but here, I saw the electricity going up into the air just like a flame from a candle. How does this work and how can this effect be achieved?