texts: What happens to the steady state of the series RC circuit if changes happen to any circuit element?

texts:
The question that I'm trying to understand is the following:

In any series RC circuit that is in steady state, WHEN any of the
elements changes (R, C, or applied voltage), the following will happen to the
circuit:
(A) The circuit will briefly operate in steady state then gradually go
on a transient state.
(B) The circuit will immediately go on a
transient state then reach a steady state.
(C) The circuit will
immediately go to a transient state.

My answer is B since, according to the textbook, the transient response is a circuit's temporary response that will die out with time and the steady-state response stays for a long time after an external excitation is applied. Now, is that external excitation include changes in any of the circuit elements?


texts: How isolation is achieved in isolated channel oscilloscopes?

texts:
I tried to search something about this but found only a small amount of information.

What confuses me is that all isolation amplifiers, optocouplers etc. I could find usually work at much lower frequencies than hundreds of MHz. So it is a mystery to me how the oscilloscopes work.

For example, here is some photos of Hantek DSO1152S
https://www.eevblog.com/forum/testgear/hantek-dso1152s-wont-boot-after-firmware-update/100/
and DSO1122S
http://www.davidefabbri.net/files/foto/SANY0116.JPG

It is very difficult to understand from those photos how the isolation works. I only could find about DC-DC converters that seemingly used there
https://lib.chipdip.ru/503/DOC001503388.pdf


texts:
Cascode devices used in power systems are assigned values for Ciss, Coss and Crss in the datasheet, for example the UF3C120150K4S ( https://unitedsic.com/datasheets/DS_UF3C120150K4S.pdf )

What does this mean in terms of the capacitances of the low voltage mosfet and high voltage jfet used within the cascode?

Below is a description of the capacitances I found at 2 different operating conditions, would the datasheet values be a description at one of these conditions? If so which one?


texts:
The question asks to compute the convolution of x(t) and h(t). While I know how to do this mathematically, using a combination of derivatives and integrals, I don't know how to convolve the two using the graphical approach.

Either method should work, but I want to know the specifics of the graphical approach.


texts: Are I2C Transactions with no data (SDA H->L->H with SCLK high) legal?

texts:
I have a legacy expansion connector on an MCU board that I am looking to use in a new mode.  I have full firmware control over all the pins going to the connector.
The interface has I2C SCL/SDA pins which are currently used.  It also has currently unused SPI pins. However, when the board was first designed, only three SPI pins were defined: MOSI, MISO, and SCK, i.e. there is no chip select.
Since I can guarantee in the firmware that I2C and SPI transactions never overlap, I am considering re-purposing the SDA line as a chip select during SPI transactions.
To do this, at the start of the SPI transaction I would force the SDA line low through the GPIO control registers, run the transaction, and then reconnect the SDA line to the I2C controller so that it goes high again.
A side effect of using SDA to enable the SPI interface is that for every SPI transaction you  generate a START condition (SDA H->L with SCL high) followed by a STOP condition (SDA L->H with SCL high), but with no data in between.
Does anyone know if START followed by STOP with nothing in between is a legal sequence of states on I2C?


texts:
After recently acquiring an MSP430 Launchpad I've been playing with various microcontroller projects. Unfortunately, the MSP430G2553 only has 512 bytes of RAM, so doing anything complex requires external storage.

After looking at SPI and I2C SRAM and EEPROM chips, I discovered FRAM.

It looks perfect. Available in large sizes (the one linked to above is a 2Mb part), low power, byte addressable and programmable, nonvolatile, no wear issues, no need to explicitly erase anything, and actually cheaper than serial SRAM (comparing against Microchip's parts).

In fact, it looks too perfect, and that makes me suspicious. If this stuff is so much better than serial SRAM and flash EEPROM, why isn't it everywhere? Should I stick with SRAM, or is FRAM a good choice for experimentation?


texts: Voltage Divider Configuration of Transistor

texts:
I have a voltage divider configuration for biasing my transistor. The gain of transistor is lets say 150 which is typical value for BC547.

What I want is limit the current flowing through the base to be 10 micro amps.

Doing the Thevenin's analysis gives me the Thevenin Voltage(Vth) of 6V and the Thevenin resistance (Rth) of 500 ohms. So I redraw the circuit with Rth in series with the transistor and the input voltage being Vth=6V. The B-E on voltage is 0.7V. So doing the calculations gave me the current of 10.6 milli amps.

Instead, I choose to go with the design in figure 2. Since I know that the voltage divider produces the voltage of 6V, keeping a resistor of 530 kohms does the job of limiting the current through the base to 10 micro amps.

simulate this circuit – Schematic created using CircuitLab

So  my questions are:

Why do we calculate the Thevenin's resistance and keep it in series with the transistor? We can create a voltage divider to create a voltage of 0.7V and feed it directly into the base. Why don't we do that?
Can't we just calculate the voltage from voltage divider(since the current going into the base is very less) and place the resistor of our choice in series? This would enable me to change the current going into the base just by applying Ohm's law and changing the resistor accordingly. Why bother with Thevenin when Ohm's law is simple enough?

Looking for conceptual explanation rather than mathematical one.


texts:
I ordered several LMC6482IN opamp without reading the datasheet details! I want to measure high side current with mA accuracy, for that I need the opamp output to go all the way to ground 0V. in the datasheet it says:

So basically if supply voltage is 5V having a rail-to-rail output should be "guaranteed" and powering opamp with higher than that means we get some voltage swing (up to 20mV), right? but the output doesn't go below ~9mV!

Why opamp doesn't behave as datasheet "guaranteed"?
How can I achieve 0V output with this opamp?
If I connect opamp ground to -1V it would work?


texts: Can anyone tell me why my game buzzer isn't working?

texts:
As you can see bellow I have designed a "somewhat" simple latching relay game buzzer.

For some reason I have just finished building it and it will not work, as it sits, there are no LED's even though I have them in the diagram they're actually globes. The speaker is just a buzzer.

A few things I have tested:

All globes work
All buzzers work
All relays work switch and latch
My 6V battery is charged and running
All momentary switches work

When I press the button it does nothing, and when I hold the button it does nothing.


texts: Why is there 84.5 volts AC between two grounds? Is this dangerous?

texts:
I have a laptop, connected to the wall socket.
A separate USB charger is also connected to the (same) wall socket.
I have noticed, when my arm touched the USB ground, it hurt a little bit.
When I measure the difference between my laptop aluminium plate, and my USB charger ground, the difference is 84.5V AC. AC uA measurement is 76 uA.
Why does this happen?
Is this dangerous?
Do I need to do anything to alleviate this "issue"?


texts: Is there any relationship between frequency of signal and distance it travels?

texts: I'm currently researching 5G technology. Many videos/articles on this topic claim that 5G is designed for communicating on lower distances (than 4G), because of higher (than 4G) frequency. So to build a network we need more dense grid of access points. Is this some general rule, that the higher frequency means less range, or is it connected to this exact frequency range, specific to 5G?


texts: Does the TI CC2540 support Bluetooth High Speed protocol?

texts:
The Bluetooth High Speed (HS) protocol is included in the Bluetooth 4.0 spec, but I can't find whether or not standard Bluetooth 4.0 modules such as the TI CC2540 support the high speed part of the spec.  Most of them focus on the "low energy" feature of the spec.  Are there any modules that support the "high speed" protocol?  How would I find out?

In addition, do Bluetooth 4.0 devices such as the iPhone 4S support the "high speed" part of the Bluetooth 4.0 spec?


texts: Using an IGBT with a small ESC for large BLDC

texts:
I think I have a modest understanding of how an ESC for RC hobby crafts works, and how a BLDC motor works.  I've been wondering about how to make an ESC that could run a motor with large current required like a motor for an ebike when the motor is not spinning fast like a quadcopter motor.  Could a circuit like the one in https://www.instructables.com/id/Make-Your-Own-ESC/ be used in conjunction with an IGBT on each output?  That way it could handle higher loads than the ESC could normally.

Edit: I've been trying to do some basic calculations on sizing a motor that would accomplish my desired acceleration, and top speed of an ebike, and I anticipate using a 72V 18S lithium battery.  I think I would be looking at about 150A during peak acceleration to about 60 mph.


texts: What are the main characteristics of high reactive power RF capacitors?

texts:
This question is related to this one.

I have to design a high quality factor RF parallel resonant circuit, to be placed in parallel to the output of a medium to high power RF generator.
Precisely, the design data are the following ones

\$Q_F\approx 10\$, where \$Q_F\$ is the resonant circuit quality factor,
\$f_\max=(1.0\div 4.0)\, \mathrm{MHz}\$: the resonant frequency is fixed but its value should be varied if needed,
\$P_o\ge 100\mathrm{W}\iff Q_c\approx 1\mathrm{kVAR}\$ where \$P_o\$ is the output power of the generator and \$Q_c\$ is the reactive power flowing in the circuit
The load will not be directly placed in parallel to the resonant circuit, but it will be coupled by the use of a multi winding transformer where a secondary winding inductance will be part of the resonant circuit, so I have some freedom in choosing the voltage and current of the resonant circuit. From the schematics point of view, the situation is this one (the multi winding transformer is shown as two separated transformers just because Circuit Lab does not offer a symbol for such devices).

simulate this circuit – Schematic created using CircuitLab

I have some experience in the design and construction of low to medium power resonant circuits, say up to \$60\mathrm{W}\$: in those circuit I used nice low loss, low \$TC\$ ceramic RF capacitors, and all worked fine (apart from a couple of high Q SMD capacitors floating on a pool of melted tin in a quick and dirt prototype, and an ETD coil former literally burned by the winding it carried). However, a look at the size and structure of common high power RF capacitors makes me think that there's more than low dielectric loss: and this motivates my questions

  Are low dielectric losses and low connection resistance the only key parameters (jointly with the maximum working voltage) in the choice of RF power capacitors? Or are there other second order effects arising and influencing capacitor performance at high power levels (for example dielectric hysteresis)?
  If only contact an dielectric resistances are the only phenomena to be accounted for power dissipation, would it be possible in principle to construct \$C_r\$ as a plane capacitor made by two copper layers on a board of appropriate material (for example the standard FR4) connected to the circuit by short and large copper strips?


texts: What can cause an oscillator output voltage to go higher than expected?

texts:
I am currently testing a 50MHz 3.3V CMOS oscillator in my circuit, which is connected to two pins/loads - MCU pin and Ethernet PHY pin. The oscillator is rated for 15pF output load, which I could be exceeding by a few pF perhaps. Things are working fine in my circuit and so is the Ethernet Communication.

Now, the oscillator Vcc is supplied by 3.3V. When I am observing the waveform at the output pin of the oscillator, I am getting a 4V high, 0.8V low 50MHz sine waveform. I am wondering what is causing the voltage to go to 4V when my supply vltage is 3.3V? I have a 10R resistor at the oscillator output which is provided for termination adjustment.

Note: I am testing the waveform using an oscilloscope of 100MHz bandwidth, because I don't have any other oscilloscope at hand. But I think that should actually result in lesser amplitude.

Diagram:

simulate this circuit – Schematic created using CircuitLab

Could anyone please help me in identifying the reasons for this higher output voltage?

Let me know if I missed providing any important information required for the analysis.

Thank you.

EDIT: The higher voltage is irrespective of Ethernet cable connection.


texts: How to design a 3V3 device to be safely programmed by 5V ISP

texts:
I'm designing my first 3V3 circuit with ATmega8. While the uC itself supports both 5V and 3V3, some of components do not. I'm going to place ISP socket on board and I'm wondering how to ensure that a 5V programmer won't damage lower voltage components. My first idea is:

route Vcc from ISP through 3V3 low-drop regulator (already available on board) and add a diode to protect the programmer from being powered backwards with 12V which appears on board "before" the regulator,
add voltage dividers on MOSI and SCK lines which, if I understand well, are always programmer's outputs and circuit's inputs.

Does it make sense?

In case someone connects a programmer already working with 3V3, the dividers will drop it to approx. 2.18V. Won't that be too low to maintain correct logic levels?


texts: Top layer vs mid layer for high speed ADC signal routing

texts:
Assuming we have an analog differential signal trace that we must route from the connector to,say, an ADC (24 bit or 32 bit kind as I don't think lower resolution ones are affected by this.) What we would like to happen is to preserve the signal as much as possible so that our ADC can read as accurately as possible.
I have read that in order for traces to be least likely to be affected by external interference it is best to surround the traces by ground planes above, below and beside. In order to execute this on a PCB (lets not factor external shielding) we must have a lot of vias.

From what I know, adding vias adds capacitance which we might not want especially at high frequencies. At what frequency do you think 4-6 vias will start being a problem? Is 50kHz still in the clear? How about 1MHz or 100MHz?
At what point do you think that the added EMI protection is not worth it due to signal being affected too much by the vias and the traces should be all be brought back up to the top layer?


texts: Synchronization mechanism suitable for bare metal applications

texts:
I have been developing a bare metal control application on dsPIC33EP256MC506. My application consists of infinite loop in the background and three foreground "application" interrupt service routines (isr). Besides those application isrs there is also let's say system isr which services the SPI end of transaction interrupt requests. In each SPI interrupt new status of the remote digital inputs (state of contactors) is being read. This information is then used for the calculations (logic expressions determining when to close or open individual contactors) done in the background loop.
My problem is that I am not sure how to ensure that during one pass through the background loop the state of the remote digital inputs will be consistent. Better saying I have been looking for a mechanism how to avoid following situation

Can anybody recommend me a simple and robust solution for this kind of problem?.
EDIT:
Below given answers inspired me to following possible solution. I will define SPI driver:

The update function will be executed in the background loop and it will do following
if(new_data_ready){
    new_data_ready = false;
    transferDataToMirror();
}
startTransaction();

The SPI end of transaction interrupt will be serviced in following simple manner:
new_data_ready = true;

The client's code from the SPI driver point of view will access to the digital_ inputs_mirror via getInputsState function call. The digital_ inputs_mirror will be updated in synchronous manner in the background loop via transferDataToMirror() which will retrieve data from the SPI peripheral registers.


texts: Is PWM or voltage control the most efficient way to control a heating element?

texts:
I am thinking about a heating controller for my electrically heated motorcycle coat.  It draws about 6 amps at 14V on my motorcycle.
My question is whether it is more efficient to drive a heating element by pulsing full power or just lower the voltage so that a constant but small current is drawn.

I am trying to determine whether it would be better to build a circuit (for example a 555 driving a FET) with which I could vary the duty cycle or just buy a variable buck converter from Ebay.
Not all of my motorcycles have that much spare generating capacity, so I would like to maximise how long I could run this for at a given level of heat output.

Apart from efficiency, could there be other issues such radio interference? I wouldn't think that higher frequencies would be helpful in this application, so a few Hertz would be all that is needed.

I know that I may be over-complicating this, but I am the kind of person that bores aluminium bolts for the weight saving; it adds up if you can do enough of it.

I am a beginner with electronics, have I missed a power control technique that would be more suitable?

Regards

Otto


texts:
I have a board in which there's two chips connected to I2C bus. I have tried to keep a distance and a ground plane between scl and sda lines. The routing topology is: mcu in the center and the two chips at the opposite directions (chip1-mcu-chip2) . The total length of SCL line is measured by altium about 100mm and SDA about 80mm.

My question is if there will be any problem due to length difference?


texts:
I am trying to implement one of the ciphers in VHDL.

I have 2 entities:  Main and  block_cipher

The Main entity also have a parameter named mode which is of type : std_logic

So from main entity I want to call block_cipher on the basis of the mode value.

e.g.

blk_cipher_prc : process(mode)
begin
 if(mode = 0) then
    block_cipher_0 : block_cipher port map (text, key,output);
 end if;
end process;

But it gives me an error: ERROR:HDLCompiler:806    Syntax error near "port".

My only motive is to call the other entity on the basis of the mode value, If someone can help with my code or can provide some alternative way to do it.


texts: Which microcontroller and transistors can I use to control these switches?

texts:
I have a SATA HDD case (product details) with switches that toggle the power supply for each HDD.

My aim is to control each switch individually via software.

(My background: I'm a total novice to applied electronics, but I have a good grasp of the underlying physics.)

Edit:

I've measured the resistance between all pairs of switch pins and found out that each switch is equivalent to the following circuit:

Luckily, it suffices to connect pins A and B (or any equivalent pair) to enable
the HDD power supply as if the button were pressed. The top pins are ignored.

When a HDD is attached and the switch is off, the voltage between A and B is 12V. The current, when connecting A and B, is < 1mA.

My idea is now to add a transistor to each A-B pair of pins and route a wire from each transistor base to a microcontroller that's attached to the same ground potential
as the HDD case.
Is this approach feasible and safe?

Can you recommend a simple, low-power microcontroller that can be attached to a consumer motherboard, preferably via
USB? It should have at least 15 output pins which are only needed to toggle the
transistors.

The software interface that the MC should be able to implement is trivial: set_pin_voltage(PIN_INDEX, on|off). Maybe a simple IC is enough?
What type of transistor would be appropriate? The default switch state should be off, so the transistor should only conduct when a voltage is applied to its base.
What type of cable would you recommend?

Since posting my original question, I've read a good amount of The Art of
Electronics, but I nonetheless feel very insecure about real-life component
selection for my first electronics project.
I'd love to hear your expert advice.

Detail view. These are 6-pin alternate action switches (push for on, push again for off). D5 is a status LED

Overview. The case is partly disassembled.


texts: Difference between analog and digital rpm controller

texts:
I was doing some research into RPM governors for diesel engines and could essentially find two different approaches. One was based on some NE555 based PWM circuit that based on the input RPM from a hall sensor creates more or less current in a solenoid that will actuate the throttle of the engine. It was usually rather complicated circuits with a lot of elements.
On the other hand I also found quite a few approaches where an arduino was used that took the signal from the hall sensor and essentially controls a servo that increases or decreases the throttle. It ended up being pretty much "Take arduino X, connect hall sensor to pin Y, servo to pins XYZ and run this code".
Objectively this is much simpler than a circuit with roughly 30 elements. So I was wondering, are there any downsides of using a "digital" approach for an RPM governance device compared to the purely "analog" version with just ICs and some RC components? Or is just about costs?


texts: Reading EEPROM memory (Winbond W25M02GV) with FT4222H USB bridge

texts:
I would like to read an EEPROM Memory (SPI Flash Winbond) using an FTDI USB/SPI bridge (FT4222H).
I developed a c++ application that connects to the FTDI and reads data from the memory(and using the FTDI library).
I am using the continuous mode read because it's much faster than the buffer read.
The problem is that the FTDI transfer limit is 64Kbytes and the total memory is 256MBytes so I have to read 64Kbyte in a loop of 4096 times and then save it in a file.
The problem is that each time you have to send the OpCode of reading memory followed by 7 Dummy Bytes, which I lost each time 8Bytes in each 64Kbyte.
I tried to read less then 64Kbye (for example 60Kbyte +8Byte) but I realize that the data was corrupted and is not properly read.
Also, I tried to fix the starting reading page in each 60Kbyte but the same, the data was corrupted.
Does anyone have an Idea about that or he reads data through an FT4222 bridge?
And Thank you very much :)
Here the code bellow:
uint8* FTDIQuodSendRecieve(uint8 *Tx, uint16 *byteToread){

uint8 R[80535];
uint8 *Rx=R;
uint16 sizeTransfered;
uint32 sizeOfRead;
ft4222Status = FT4222_SPIMaster_MultiReadWrite(ftHandle, Rx, Tx, 1, 6, *byteToread, &sizeOfRead);

if((ft4222Status!=FT4222_OK) )
{
    // single read write failed
    std::cout <<"single read write failed "<<ft4222Status;
    return 0;
}
return Rx;
}

int ftdiQuadConfig(){

ft4222Status = FT4222_SetClock(ftHandle, SYS_CLK_60);
if (FT4222_OK != ft4222Status){

    // set clock failed
    std::cout<< "set clock failed";
    return 0;
}

ft4222Status = FT4222_SPIMaster_Init(ftHandle, SPI_IO_QUAD, CLK_DIV_2, CLK_IDLE_LOW, CLK_LEADING, 0x01);
if (FT4222_OK != ft4222Status){

    std::cout<< "spi master init failed";
    return 0;
}
return 1;
}

void saveFile(QTextStream *outStream,uint8 *Rx){

for (unsigned int i=7; i<32772; i++){ // all data was shefted with 8 bytes

   if ((i-7)%2048 ==0){
       *outStream << "\nPage "<< Page++ <<": ";
   }

   *outStream <<hex<< Rx[i]<<" ";
}
*outStream << "\n";
}

void continiousRead(QTextStream *outStream){

QElapsedTimer timer, total;
uint8 Tx[4];
uint8 Tx1[65535];
uint8 Rx= new uint8 [65535];
uint16 bytestoRead=3;

/*Memory reset*/
Tx[0]=0xFF;Tx[1]=0xB0;Tx[2]=0x00;
ft4222Status = FT4222_SPIMaster_SingleReadWrite(ftHandle, Rx, Tx, 3, &bytestoRead, true);
FtdiError(ft4222Status);

/*Set page data Read*/
bytestoRead=4;
Tx[0]=0x13;Tx[1]=0x00;Tx[2]=0x00;Tx[3]=0x00;
ft4222Status = FT4222_SPIMaster_SingleReadWrite(ftHandle, Rx, Tx, 4, &bytestoRead, true);
FtdiError(ft4222Status);

/*Set continous Read*/
bytestoRead=3;
Tx[0]=0x01;Tx[1]=0xB0;Tx[2]=0x00;
ft4222Status = FT4222_SPIMaster_SingleReadWrite(ftHandle, Rx, Tx, 3, &bytestoRead, true);
FtdiError(ft4222Status);

/*Verify continous Read*/
bytestoRead=5;
Tx[0]=0x0f;Tx[1]=0xB0;
Rx= FTDISingleSendRecieve(Tx, &bytestoRead);
std::cout <<  std::hex <<Rx[3]<<"\n";

/*Set FTDI to Quad Mode*/
ftdiQuadConfig();

Tx1[0]=0xec; Tx1[1]=0x00;Tx1[2]=0x00;Tx1[3]=0x00; bytestoRead=32775;//32775 =32Kb +8Byte

/*If Continious Mode Then start reading */
if (Rx[3]==0x00){

    total.start();
    for (unsigned int i=0; i<8192 ;i++){

        timer.start();
        Rx= FTDIQuodSendRecieve(Tx1, &bytestoRead);
        std::cout << "64Kbyte took " << timer.elapsed() << " milliseconds\n";
        saveFile(outStream, Rx);

    }
}
else {

    std::cout<< "\n\nERROR Continious read not fixed";
}
std::cout << "64Kbyte *10 Time is: " << total.elapsed() << " milliseconds\n";
}


texts: Splitting a power supply between two circuits

texts: I have two separate circuit boards (clock & radio) that I'd like to place within the same enclosure. One takes 12V, and the other needs 3V. How can I utilize one AC adapter to power both boards appropriately?


texts: Help with DFRobot ACS758 50A Current Sensor

texts:
I bought this sensor from DFRobot to measure DC current using my 5v Trinket Pro. I followed the wiring setup and code samples from their website. Seems to be working fine once everything is setup, but I'm wondering why is it that once I disconnect the lines from the IN and OUT connections, I still would get a reading? My understanding is that I should be getting a value of 0A once I disconnect them. Am I missing something?

Attached are the photos of my setup below:

Update: Here is the code from sketch

// include the library code:
#include <LiquidCrystal.h>

int RS = 3;
int EN = 4;
int D4 = 9;
int D5 = 10;
int D6 = 11;
int D7 = 12;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(RS, EN, D4, D5, D6, D7);

const int numReadings = 30;
float readings[numReadings];      // the readings from the analog input
int index = 0;                  // the index of the current reading
float total = 0;                  // the running total
float average = 0;                // the average
float currentValue = 0;

// the setup function runs once when you press reset or power the board
void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
    for (int thisReading = 0; thisReading < numReadings; thisReading++)
      readings[thisReading] = 0;
}

// the loop function runs over and over again forever
void loop() {
    total= total - readings[index];
    readings[index] = analogRead(0); //Raw data reading

    lcd.setCursor(0, 1);
    lcd.print("Orig: ");
    lcd.print(readings[index]);

    //Data processing:510-raw data from analogRead when the input is 0;
    // 5-5v; the first 0.04-0.04V/A(sensitivity); the second 0.04-offset val;
    readings[index] = (readings[index]-512)*5/1024/0.04-0.04;
    total= total + readings[index];
    index = index + 1;
    if (index >= numReadings)
      index = 0;
    average = total/numReadings;   //Smoothing algorithm (http://www.arduino.cc/en/Tutorial/Smoothing)
    currentValue= average;

    lcd.setCursor(0, 0);
    lcd.print("A0: ");
    lcd.print(currentValue);
    delay(10);
}

Please bear with me as I am still new at electronics.


texts: Does reactive power cause extra fuel use in a Diesel UPS?

texts:
It is a bit of a theoretical thing, of little practical use, but I just want to understand the physics behind it. I am aware that I'm simplifying things quite a bit.

In electric power we differentiate Real, Reactive and Apparent power and of course we want the reactive part small, but with practical loads this is rarely the case.

The other day, a colleague of mine and I, were discussing a multi-MW Rotary Diesel UPS (demo takes a while to load) in one of our datacenters and the following question came to mind, which we weren't able to answer ourselves:

Say that the load on the UPS causes a non-ideal \$\text{cos(}\varphi\text{)}\$ on that UPS, causing Reactive Power \$Q > 0\$ being transported through the power lines back and forth. Would the Diesel engine still use fuel just for the Real power part or does Reactive power have its impact on fuel consumption too? Theoretically reactive power is not consumed, but it feels weird once grid power is replaced by a Diesel engine. Does Reactive power exist in the mechanical world?


texts: I am working on driving an 8 ohms speaker. I am currently modelling(in Ltspice) it just as an 8 ohms resistor. However this is probably far from being realistic. I don't want/need too much precision however.  So how can I model a speaker with minimum complexity but also better than one single resistor?


texts: How do I find these transformers? Please help me identify

texts:
I'm trying to buy components for these simple capacitor chargers but I don't know how to find the transformers. I've looked all over Mouser and other websites but their specifications are confusing and I can only find huge 110V-24V type transformers.

Are these called flyback transformers, or maybe audio transformers?
What is the ratio? I'm guessing that's 6 turns to 1750 turns.
What is the #25 and #45?

I would really appreciate the help, I just need a simple camera flash circuit for a project.
Also, how would I calculate a different transformer if I wanted 5V input and 300V output?
I'm really running out of time with this project.


texts: Some question about understanding the electrical data of a manual

texts:
I need to wire a servo motor system by using this manual for the model x00606.

Page 79 and 82 shows explicitly the wiring of this driver as below:

(left-click to enlarge)

I've read the entire manual but I have some short questions regarding it.

1-) At page 35 under Electrical Data, the manual says I need to use a 24V power supply which is PELV type. Is this 24V supply needed for break? And what can be the reason that PELV is required?

2-) Again at page 35 under Electrical Data, What is meant by:

-current B, P, T types without/with motor brake ?

3-) At page 42 for the regenerative resistor, the following is recommended:

Does that mean a 33 Ohm 1.5kW resistor is adequate? Can it be any type of resistor like wire wound or Aluminium Enclosure Resistor? How important is to install this resistor?

4-) Is the "drive cut-out" in the figure I added at the beginning a contactor switch or a circuit breaker?


texts: powered led generator works but with other power source with voltage divider at same volts don't

texts:
As the title say I have a small motor used as generator that generates 0.5ma at 1v that power up my led (slighty). I don't have the data sheets from led(it's a 5mm red led), I suppose the forward voltage is around 1.7v that's why the led is slighty lighting up. The problem is that I want to try to run the led with same voltage from other power supply (0.5ma at 5v). So I made a voltage divider to get same volts as generator but the led didn't turn on.So I tried with 2.2k and 1.2k resistors to get around the led forward voltage and it works just slighty as with generator. So why Can I light up the led with generator at 1v and can't with the voltage divider at same volts?

PS: sorry for my english


texts: RF PCB design: right angles in components?

texts:
For RF pcb design, it's common knowledge there shouldn't be any right-angle traces, because capacitance increases in the corner, changing the impedance and causing signal reflections. Less clear (to me at least) is what happens when a right-angle is formed by a passive component, like so:

Pad 10 is the output of a voltage-variable attenuator--the signal is anywhere 50MHz-1GHz and can be up to 20dBm here, and it is traveling from right to left, then up through C8 on to U2.  Notice that capacitor C8 is oriented at 90 degrees with respect to the trace.

Is this even a problem? Should I move that cap up and bend the trace to it? Or am I being overly-fastidious and this doesn't matter?


texts: Why a Transistor is considered to be an active device?

texts: How it a Transistor an active device? Because it it not producing energy. We just feed it with energy and it amplifies it and that too not on his own but using a bias battery. So how it is considered to be an active device? Please can anyone provide full explanation?


texts: Can a grounded static-shielding antistatic bag be used as a circuitry work surface to protect from ESD?

texts:
Basically, I have looked around about how to take proper care with respect to ESD and I am quite confused. I know an antistatic bag of any type would not provide additional protection from ESD if used as a work surface but, if I understand the principles correctly, then wrapping a static-shielding antistatic bag to an antistatic wrist bracelet and connecting it to proper ground would do provide additional ESD protection for placing ESD sensitive devices and anything on it and working with them (while also having properly grounded oneself of course), because technically, the bag would shield from the underlying surface in terms of static, and it would also be grounded, so as to provide a safe dissipation route for static.

Is this reasoning correct? If not, I would appreciate it if someone could explain what makes it wrong from a theoretical perspective.

EDIT: It's probably not going to be ok for some serious work on PCBs, I am mostly asking from a theoretical perspective. Also another reason I am asking is because all I want to do is take this Single-Board Computer, put a 30mm fan on the heatsink, add this m.2 ssd drive and put it in either this acrylic case, or this metal case. What are the minimum precautions I have to take? Can I simply ground the static-shielding bag somehow and drop everything on it (screws, spacers, ssd and SBC) and assemble the thing? Otherwise, will it be ok if I only do it without letting anything touch any surface other than my (grounded) hands (I know it takes a bit of juggling)?


texts: Proof of concept - converting block diagram in US patent 5,159,703 to functional schematic

texts:
I am reading US patent number 5,159,703 titled "SILENT SUBLIMINAL PRESENTATION SYSTEM". I'm making this for a proof of concept project for a research paper I'm doing on subliminal messaging. I'm very good at assembling circuits from a schematic, but not at making the circuit.

Below, I put a block diagram of this system, which is figure 3 from the patent. Some of this I can figure out on my own like 31 in this diagram (and 11 on figure 1 in the patent) is a normal microphone; 32 in this diagram (and 12 on figure 1 in the patent) can be an LM741. As for everything else, I'm having trouble with no one to ask.

Please help me with making a schematic and I'll assemble it and put up pictures of the finished project.


texts: Why are n-channel MOSFETs at high-side position and p-channel MOSFETs at low-side position on many push-pull circuits?

texts:
Like in this example Common drain stage/Source follower circuit analysis there are many MOSFET push-pull circuits that show n-channel MOSFET on high-side position and p-channel MOSFET on low-side position being connected through their source connectors.
From testing a circuit with p-channel MOSFET on high-side and n-channel on low-side position (gate -> 10K -> GND), connected through their drain connector, my experience was, this would be a more stable and reliable circuit (on 5V VCC and 5V/0V gate voltages). (Example circuit for this complementary MOSFETs (P/N) circuit would be https://en.wikipedia.org/wiki/File:CMOS_inverter.svg)
What are difficulties with MOSFET source pins connected first version on biasing and why are drain connected MOSFETs not recommended (https://stackoverflow.com/questions/39116524/why-push-pull-can-not-work-in-this-manner - similar, but no explanation for MOSFET circuit) for power push-pull tasks?


texts: Redundant Battery and Chargers Behaviour

texts:
I am designing a circuit for a high powered LED that needs to have a redundant battery power supply. The LED is around 380W and nominal 24v so draws around 16A when lit. The LED will flash for up to a second, every 5sec so no fast switching but it is pulsing.
The below image shows what I am testing with but I am not 100% how it should be behaving. V1 and V2 are 24v 100Ah AGM batteries. V3 and V4 are 250W battery chargers that output 27.6v. D1 and D2 are Schottky diodes used to isolate the redundant power supplies and so there is no equalization between the batteries.

I was expecting the load to sink current from the batteries primarily as the batteries should have a lower series resistance than the chargers however my measurements are not reflecting that. I can measure with a clamp meter, 16A going to the LED and proportionally more current coming from the chargers than the batteries.
Can someone explain why more current would be sourced from the battery chargers? Will it also cause issues for the chargers if they are sourcing the bulk of the current every time the LED flashes? If one half of the redundant circuit fails then the LED sinks more current than the remaining charger can source which could cause damage and the battery will not charge properly at all?


texts: 230V/230V AC with center tap alternative

texts:
I'm currently disassembling an old (1960's) tube radio and trying to reproduce parts of the circuit. When i come to the power supply part, i found this:

I wonder about some things:

Is it a 230V/460V transformer or a 230V/230V transformer?
What is the purpose of this "center tap"?
Is there an alternative to achieve the exact same thing with "modern parts"?
Isn't this exact the same thing like using P1 and P2 as P3 and P4? If no, why?


texts: Thevenin generator of circuit with coupled coils

texts:
All i need to do here is to find equivalent thenenin U12 generator with it's impedance.Known values are: \$\ E, L_1 , L_2 , k, \omega\$ This is what i have so far:

\$\ \frac{E}{j\omega L1}j\omega\ L_{12}=U_{12}=E_T  \Rightarrow \frac{E}{L1}k\sqrt{L1L2} = E_T\$

i believe that this is correct since i don't know what else could i do here.

But i don't know how to find equivalent impedance. Any ideas?


texts: How long will 4x 0.16A Computer Fans running off a 15000mAh Battery Last?

texts:
I am making my own Bill-tong box to dry meats.
I have 4 fans which are 0.16A each
Running at 5V from a battery pack that is 15000mAh

I have tried doing the math myself online but the answers I am getting back are crazy!

I would like to know how many hours this battery pack will run these fans for when fully charged


texts: digital current monitor/sensor for monitoring ~0.1 uA to mA current from a MCU and sensor

texts:
Hello I am in need of a current monitor/sensor like INA219 for monitoring current in the range of 0.1 uA to ~ mA. Kindly suggest a way to monitor current in such lower range.
I have a microcontroller and a Accelerometer. I need to monitor the current consumption over a time using a current monitor and Arduino.


texts: How do I calculate how much power a servo consumes for specific degrees of turns?

texts:
I have an FS5103B servo with a stall current of 780mA at 4.8V. So say I am calculating power for the stall current as P=UI^2, I get 2.92W. What does that mean, like is it for a one-degree turn or does it depend on how fast it did the turn? And also how do I go about calculating how much power it consumes for a specific degree of turn.
Thank you very much in advance.


texts: Current mirror not depending on power supply (BANDGAP design)

texts:
is there any topology that allows a current to stay constant on a current mirror when the power supply of the transistor is varied?

I simulated a bandgap and the PTAT varies a lot when I the power supply is varied. Especially at -40 degrees.
Instead of the direct output I used also a current mirror (2 pmos transistors) that is driven by the output of the opamp to get a higher current to be able to drive the resistive output.

The green selected curve is the derivative for the lowest voltage: 1.62V.

Is is possible to improve the linearity of the ptat with respect to power supply sweep?


texts:
I have a task to drive four LEDs from a 4-20mA loop. I have 24V for the LED side so I need to convert the current into something that can drive the LEDs.

I know I can use a 250\$\Omega\$ resistor as the converter in the loop which will give me 1-5V from 4-20mA respectively, now I need to get this voltage to drive the LEDs.

Do I simply connect a transistor base to the 1-5V point, ground the emitter and drive the LEDs from the 24V via dropping resistors via the collector??

It needs to be a variable drive as the brightness of the LEDs must vary with the 4-20mA signal.


texts:
I know it is really stupid question, but I can’t understand.

I have a picture with dipole antenna (different length). If I have the current distribution along the length, that it is easy to determine L, I mean number of lambda/2. But if I don’t have this distribution, how to determine?

In this case for example: why the first was determined as lambda/4?


texts: Continuous, frequency-domain digital equalizer

texts:
I'm facing a real case of DSP application. I have a basic knowledge of digital filtering and telecommunication issues.

The input of my "black-box" is a digital audio signal (say a common WAV file, stereo 44100 Hz, 16-bit). I need to develop a digital equalizer and create the output audio samples.

The computation has to be done in real-time, i.e. with a live-stream.
I'm aware that it means I have to define a buffer large enough to feed the filters.

The basic approach is to create several pass-band digital filters to change the gain of the frequencies in each band.
Because the requested bands are a lot (> 16) I'm going to work in the frequency-domain.

My thought:

convert the signal in frequency-domain (DFT)
define a shape of the desired response
process the input samples with this shape
revert back to time-domain to retrieve the actual audio samples

Questions:

what is the technical name of this method?
do you think this approach is better(*) than use a lot of steep pass-band filters?

(*) better here is not just an opinion: I'm talking about code complexity, latency and accuracy


texts: Max power draw on voltage rails of mini PCIe Card

texts: I am designing a custom mini PCIe card.  What is the max power I can draw from the 1v5 rail, and the 3v3 rail?


texts: Calculating pitch and roll from gyro data

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Does anyone know if it's possible to calculate pitch and roll angles from gyro data (without an accelerometer)? I'm trying to use a L3GD20 to measure pitch and roll. I can read the angular rates, but how should these values be converter to pitch and roll angles?

Any help appreciated.


texts:
Say we have this cmos circuit any advice how you would size up the transistors assuming that the gate is minimum-sized. Ive done some reading and I am struggling to understand. Is there an definition to define this?? I feel like it is really simple.
Thanks


texts:
Is it appropriate to trim signal offset to an op-amp using only a divider and a trim-pot? For stable operation would it be preferable to connect drive the potentiometer from precision references or use zener diode shunts to keep the reference voltage independent of supply fluctuations.

Is the 1uF filter cap a good idea to keep this a stable DC reference and filter noise introduced by the divider resistors?

I use this circuit very often and I want to make sure this is the best approach for precision circuitry.


texts: How to control the amount of current I drain from a lipo? U=I*R and I know R but how do I control the values of U and I? If the battery has 1000mAh, 10C and 10 V (I made this up), does the battery constantly drain 10 A at 10 V and I have to increase the resistance to lower the current?


texts: How does magnetic flux affects the speed of a DC motor

texts:
I'm doing a high school physics project where we need to investigate
the relationship between the speed and magnetic flux of a DC motor.

We built a simple DC motor which basically looks like this, with brushes and a split-ring commutator. So our observation is that the further apart the magnets, i.e. the smaller the flux density, the lower the rpm.

We are given the torque equation t=nIABsinΘ so it seems like torque has decreased in this case. But everywhere on the internet is saying that a DC motor's speed is inversely proportional to torque and that higher flux gives lower speed, e.g. on wikipedia, which all contradict our result.

There must be some flaws in our understanding so can someone please explain to me what it is? Any help would be appreciated.


texts:
I have understood that this is a bad way to do it:

Since some LED can draw more current than others.

So lets say I would power some high powered LEDs, like say 10 x 3W LED with a DC forward voltage on 600mA @ 3.2V. This is just an example so I'm not going to look up a specific LED, this is only to learning.

Which is the best way to secure that all LEDs get the same voltage and current?

Additional questions

Let's say I have a power supply that delivers 2A at 3.6VDC, and I have a LED with forward current 350mA at 3.6VDC, can I connect the LED directly to the power supply without resistor, since the power supply delivers 3.6VDC?


texts: Difference between ultrasonic transmitter sensor and ultrasonic receiver sensor?

texts:
What is the difference between ultrasonic transmitter sensor and ultrasonic receiver sensor?
Can an ultrasonic receiver sensor be used as an ultrasonic transmitter sensor or vice versa?


texts: When looking through a datasheet for a connector how do I find out which pin on the part does what?

texts:
I was shopping for some aux connectors and when I found one that should suit my purpose I checked the data sheet.
Now I am unsure how I can figure out which pin on the part does what.
I looked at some other data sheets and was unable to find which pins do what.
Here my question, how do I find out which pin on the part is for example used for ground?
Here is the data sheet of one of the aux connectors I was looking at.
Here is the link to the data sheet: https://www.farnell.com/datasheets/3164267.pdf


texts:
I'm trying to fix an AC-DC line regulator that I have build and doesn't work as expected.
I'm trying to convert AC 220V mains to DC 5V 10mA without a transformer. To do this I'm using an 1uF 250VAC Polypropylene Film cap like in the schematics bellow, followed by a voltage regulator with TL431.
When I simulate the circuit in Proteus, I get 5V at output with/without C3.
In real circuit with C3 I get 5V output (not sure how noisy though; no oscilloscope), but if I remove C3 I get 2.5V, which clearly indicates that the shunt regulator TL431 oscillates.
I tried putting a 22p cap between the cathode pin and ref of TL431 (pin 1-2), but no dice.I have also tried removing D4.
Any thoughts?
WARNING: - The output of this circuit is not "isolated"from AC mains and should be treated as being at mains potential at all times. [RM]

Notes:
Failure of C1 or reversal of Vac connections or other conditions will result in mains live (Phase) voltage appearing at output.
C1 MUST be an "X rated" capacitor designed and certified for use on 230 VAC AC mains by its manufacturer.
[RM]


texts: How can I hardware protect a microSD from writing to

texts:
I have a beagle bone black board and I want to make the card read-only so no modifications go to the microSD card. How can I achieve that?

I have searched over internet for this. SD card have a switch to do this, however microSD does not.

I am thinking that there must be a pin through which the info is written to the card. Is it possbile to make the card read-only by blocking that pin, or is there another, better, way to make the card read-only?

Edit: I want a non software way of blocking. I am trying to install a small os on it, and want that someone who could hack into, not to be able to add anything on that microSD card.


texts: Correct usage of 74LCX245 logic level converter IC

texts:
I am designing a PCB where I need to convert some 5v logic signals from a Wiegand reader into 3.3v logic that a Raspberry Pi can understand.
I have been using a resistor-based voltage divider before, but that was too slow for the Wiegand data so now I am looking at using a dedicated IC for this purpose, namely the 74LCX245MTR
Here is the schematic I have created. The WG*-* nets are the 5v Wiegand D0/D1 pins from 2 readers, the H1P** nets are pins on the Raspberry Pi header.

The datasheet for the IC is here.
Does this look correctly designed? Anything obvious missing?


texts:
I am trying to understand the hardware difference between the sensored and sensorless FOC 3-phase Induction Motor Drive circuit.

So far what I understand is that FOC require following sensors:
1. Quadrature encoder on the motor shaft.
2. Phase Current sensors on 2-legs of the 3-phase H-bridge.

Please tell me about the above hardware. If it is sensored FOC circuit then what will be sensorless circuit and how will that work?

Your help is highly appreciated.


texts: Simulating IP core (i.e ALT_FP_DIV) on Altera modelSim gives "z" (high impedance) as output

texts:
I'm trying to simulate (functional Test) a project that contains both my own codes and some instances of Altera Floating Point IP Core generated using MegaWizard on ModelSim.

All the instantiated IP blocks such as ALTFP_DIV, ALTFP_LOG, ALTFP_ADD_SUB are producing no outputs (result being "z"). The input signals for these blocks such as clock, clk_en and aclr are set properly.

I'm not sure if i'm missing any special steps here simulating the IP blocks.

My procedure in setting up this simulation is as the following:

Turn on modelSim
Create new project under a new arbitrary directory
Add existing files from my own project that is written in Verilog (a bunch of .v files including the IP core instances)
Compile on modelSim, all files get green checks (indicating fine)
Start simulating by choosing the top level module -- loads and I can view the waveforms of some signals. My own code tend to have expected values but the connections to the output of these IP core modules give "z".

Final point: There are files associated with the creation of these IP core through megaWizard. names such as ADD_SUB_BB, ADD_SUB_INST. They core_name_bb.v files are green checked in compilation on modelSim while the core_name_INST.v files don't go through so I just excluded these files from the project tab listing on modelSim (not sure if that's the factor).

Any pointer would be much appreciated!


texts:
I am a newbie in the world of circuits and electronics. But we all started somewhere.

I have this idea about a street sign that should be used as an instrument. All most like a Theremin. Touching it high gives a high note, and touching it low, low note.

So is there a way that I could measure where on the steel rod/sign I am touching it? I have been surfing around for awhile, and I came up with something like a comparison of a capacitor in each end of the rod/sign.

So, am I totally off, or is there a smarter way to do this?


texts: Battery pack charging port reverse diode | voltage over charging port pins

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I'm planning on building a diy battery out of 18650s, which has a BMS, for a Onewheel. The voltage will be 63v and max load +10A so it will be 15s. There will be an XT90 where the load will be connected and I want to have a separate charging port.
I want to prevent shorting over the charging port pins, if dirt or mud gets in it. What kind of diode do I need or how would a mosfet be wired if I were to use one? I've tried Googling a lot but really hard to find anything specific. And I dont want to use a 3 state switch that has modes for use and charging.


texts: I've been looking into making my own pcbs and was thinking I may try printing the circuit on to the fr4 with carbon and electroplate the circuit on. After a while on google I havent found any info on this. Obviously I'm not the first person to think of this. Can any of you kind and intelligent folks tell me why etching seems favored over deposition?


texts: How can we visualize active reactive and apparent power as areas in time domain?

texts:
Regarding AC power feeding an impedance, is it possible to plot an example of V and I versus time for an inductive load R+jwL and especially the instantaneous power on the same plot where we can mark/paint three different areas for a power period where one area will show the active power the other reactive and the other apparent power?

Instead of using phasors, I would like to see in time the areas corresponding to three types of powers namely active reactive and apparent.


texts: How can I evaluate on-chip bypass-capacitor's capacity based on the topology?

texts:
The transmitter I designed has been showing lots of jitter.I think there's something wrong with the layout topology.Pad of the power supply is a little far away from the circuits by connection through thin metals,thus producing a resistance as large as 2 ohms,which would lead to IR-Drop.It will not do much harm if bypass-capacitor for the power is large enough to compensate for that.But I feel since the mesh-structure capacitor(green part in the pic) mostly sprawls over the chip distant from the current path, its capacity on providing the transients must have been weakened than if it is "properly" placed.I really want to know if it can be turned to some actual,smaller-value one so I can see its effect through simulation on Spectre?

Also:It seems to me that the inductance is large because of the loop,but how can I estimate it?


texts:
I have an issue which I think maybe related to internal timing issues.

I know that crossing clock domains can cause metastability, because setup and hold timing not being kept.

But I was thinking that this could also be an issue with the internal signals (within same clock domain).

If ex. an signal to an FF is passed through some logic, and thereby delay an amount that will cause the sampling FF to sample on transition.

Or will the tool given the timing constraints always warn / catch this?


texts: Overheating/insulation destruction of Transformers

texts:
Let's say you have a very critical circuit (for example special GFCI, hospital emergency equipment, airplane wing motors, etc.) that shouldn't allow the transformer fuse/breaker to nuisance trip. So you don't use any fuse/breaker, not even slow blow or thermal fuse at all.

If there is accidental shorting that can overheat and destroy the transformer insulation. Would the winding just explode? Or would the transformer caught fire? Or perhaps the core itself blowing up into smithereens?

What have you actually witnessed?

This is for small 1000va transformer and below. And not those power lines transformer.


texts:
I have already been searching for this but couldn't find something reasonable

I want to know that when  will be the value of back emf maximum in a dc motor?
At no load or full load or half load?


texts: Verilog: How to perform Logical operations on a vector with single bit

texts:
Like an enable logic, I want to perform a logic operation on the whole vector like so:
input en;
input [7:0] a;

wire [7:0] enabledA;

assign enabledA = en & a;

where enabledA[i] = en[i] & a


texts:
I have some doubts about a magnetometer application.
I am trying to get YAW angle value from magnetometer data and so I am doing the following:
mag_x_data

mag_y_data

    yaw=arctang(mag_y_data / mag_x_data);
    yaw=yaw * (Rad_to_degree)

After successfully calibrating it, if I work in the xy plane without moving it, I get successful results.
The problem arises when, for example, I move the magenetometer in the x axis (rotating the magnetometer in x axis - ROLL angle)
and leaving YAW still, the result of the YAW changes. I understand that this should not happen.
Am I getting it wrong?
What should I do to obtain the YAW values, independent of the position of the X and Y axis, with the magnetometer data?
When I refer to YAW I am talking about rotations in the z axis. Assuming the xy plane corresponds to the surface plane, and the z axis is colinear to Earth's gravity.


texts: Hand-cranked vs hydro-turbine generator for single potential energy (no continuos flow)

texts:
Let's say you have a certain amount of water at a height; think a bucket with 3 liters of water in it on a 4 meters tall wall. By letting this water to fall, we'd have an opportunity to convert some of this potential energy into electricity.

By using cheap commercial gadgets, one could achieve this by:

Hand-cranked generator, using the falling mass of the full bucket to do the cranking (using pulleys to get the right torque). example
Micro water turbine, letting the water flow from top to bottom, where the turbine would be located. example

There are many options on the market for each strategy. Some are more expensive, some have very specific limitations in terms of working pressure, minimum rpm, etc.

My question is: is there a preferred method between these two from a purely conceptual point of view? Should one of these methods achieve higher efficiency in most cases under similar limitations?


texts: Darn you V=IR, you are wrong (does V really equal IR?)

texts:
Here is my simple reasoning. We apply a potential difference across a resistor. All the electrons begin responding. Since it takes time for electrons to respond, our current is not yet fully established. In fact, immediately after we apply the voltage, the current is zero! And yet we have a non-zero V and R. So am I wrong here, or does V sometimes not equal IR?

EDIT:
I'm having a bit of an issue here. People want to say that an inductance of zero will allow for instantaneous current initiation, but I wonder. Is it ever possible to accelerate an object with mass infinitely quickly with nothing but an electric field? Sounds impossible more than likely. I feel that an instantaneous acceleration can only be caused by an infinite amount of energy given.


texts:
I'm looking at options to build an IoT system where we can trace the integrity of the data from any device i.e. we know that the data came from a particular device and it hasn't been tampered with.
Can you please let me know resources to understand ways to do this. For example is this possible with the Crypto line of ICs from Microchip https://www.microchip.com/en-us/products/security-ics


texts: Single Fault Pulls up Both AND Gate Inputs

texts:
I have a situation where I have 2 inputs to an AND gate coming from 2 sensors (passing through a comparator before). If both signals exceed some predetermined value (let's say 2.5 V for sensor 1, and 1.8 V for sensor 2) then the AND gate should open (and the rest of the circuit should be triggered).
However, if either signal/sensor is disconnected or gives an out of range signal, then the rest of the circuit should still be triggered. I though I could artifically make both signals high if one is faulty and feed them into the gate.
I was thinking of using a pull-up resistor that is somehow "connected" to both signals (so if either is disconnected, then I pull both signals up). I am not sure if this even makes sense or is possible, so any advice would be helpful (or alternative pathways, other than checking if the signal is out of range using 2 comparators per sensor)


texts:
Im currently using STM32F4'S built in 12 bit ADC. When I get my measures, it varies wildly at +- 40 numeric range. Is there a way to eliminate this? I have tried software filtering with no luck.

Also, when I put this mcu in an IP67 EMI filtered box, would it behave smooth? How much of this noise is coming from EMI?


texts: Connect large number of MPU 6050 I2C devices

texts:
I am quite new to electronics , in my project I am trying to connect large number of MPU6050s(about 10 sensors) I2C devices and try to get the reading 'simultaneously'.

Some questions that I am not very clear:

Someone suggested that the device address will be problem but someone doesn't, which only two device address is possible to use (HIGH and LOW).If device address won't be a problem how I connect them?

I have search the solution online but I am still not quite clear of how to do it, and I got an simple (might be silly) idea of how to approach it however I thought it's not the best solution.

Here is my idea:

I am using two multiplexer MUX-A and MUX-B.
I use MUX-A C0-C15 slot
to connect each individual MPU6050's AD0 slot , so when I select one
of these MUX-A will pass 5V to it .
I use MUX-B C0-C15 slot to
connect each individual MPU6050'S INT slot , since if I connect them
serially FIFO buffer will be overflow.
I connect I2C buses serially ,ASA VCC and GND.
I control both MUX-A and MUX-B together by using S0-S3 slot, for
example if I try to connect device-0 then I will pass 0000 to both
MUX-A and MUX-B, MUX-A will pass AD0 a HIGH voltage which marks it as
an 0x69 ;MUX-B will make it connect to GND; and rest of other devices
will remain disconnected .
I loop through every device from 0000 to 1111 as fast as possible, and using Jeff Rowberg's MPU6050 DMP code to fetch the data ,and stored.
Which means it's not perfectly 'simultaneous' but asynchronised, however if my requirement data only need to be lower frequency like 50Hz which means I probably could fetch all of these device's data in the same time.

Here is the requirements of my project :

My project involve with machine learning so I should gathering data as synchronised as I can otherwise I will be worry about the accuracy issues.

And my question:

Is there any better idea to approach my target?

I will be so appreciated for any helps ..

=========Intresting Picture I found online==========


texts: Simple generator to light a series of LEDs question

texts:
Playing around with a simple circuit idea with friends but none of us have really worked with circuits since college so we need a little guidance. The thought is to have a small generator (someone said a stepping generator) being turned by a wheel. Then we connect some sort of rectifier then to SOMETHING (the part we can't remember) that will pass current to about 8 LEDs but divert any excess current to either a battery or capacitor to store until the wheel stops being turned then the battery/capacitor will discharge to the LEDs.

Guys I know this is a very simple circuit so sorry I can't remember my electronics from college. Any assistance is appreciated.


texts: What are some ways I can modulate the duty cycle of SPWM with mixed signals?

texts:
I'd like to experiment with SPWM, as used in motor control applications. But instead of modulating the duty cycle with a single frequency, I'd like to use a mix of frequencies.
I've been searching for a examples of this and a place to start, but I haven't been able to find any. In fact, I'm not even sure what terminology to use. Internet searches presented me with many examples which use the PWM output of a microcontroller, but I think they wouldn't have the power needed to create a mixed signal. A DSP chip like the Microchip dspic33 series seems like a good possibility, but that would present me with a steep learning curve of learning DSP programming.
I think the place I would like to start is generating the signal in analog form and then converting that to SPWM. It would kind of be like an FM signal generator, where the input signal modulates the frequency of the carrier, but in my case it would be the duty cycle of a square wave. But...I can't find any examples of that to study, and I don't even know if that's possible or if anyone has done it.
Does anyone have any thoughts on this, or can point me to some examples? Would my analog-first idea even work, or is DSP the way to go? Or are there other ways?


texts: What is this yellow "liquid" on the graphic card?

texts:
Currently I've been assigned the task to try to fix a laptop.

The problem was a malfunctioning graphic card.

It has no image what-so-ever.

I've looked all over the circuit and found no burn marks or blown capacitors and resistors, but I've found this yellow "stuff" everywhere:

(Excuse my mad Paint skills)

The yellow "stuff" is marked with the red circle.

What is that thing?

Can it be the reason why the graphic card doesn't work?


texts: How does the GPS scale and deal with potentially millions of requests per second and respond in real time?

texts:
Nowadays almost everyone who have owned a smartphone or some type of GPS device somewhere. These devices also seemly update in real time. How is the GPS satellite capable of responding to potentially millions of requests from millions of different devices, and update all the millions of devices in real time without lag.

As I understand it, websites which get traffic even in the thousands gets slowed if it's not properly prepared for it, how does the GPS cope with amounts of traffic that is seemly impossible to deal with, even difficult for a super computer.


texts: Waveforms from a Function Generator, What is Good Enough?

texts: I got an HP3311A function generator. The Sine wave forms below looks pretty bad to my eyes. Is it normal?


texts: Transistor Push Pull Stage to drive Mosfet

texts:
simulate this circuit – Schematic created using CircuitLab

Hi,

I want to make a Transistor based Push Pull Stage to drive a 30V Mosfet.

uC GPIO drives the transistor stage with 3.3V and GND to Turn On and Turn Off the Mosfet.

In datasheet, Mosfet has a 1.5V to 2V Threshhold voltage range.

The Problem is:

When GPIO turns the NPN Transistor ON to Turn ON the Mosfet, Gate has maximum 2.7V because of base-emitter diode and this 2.7V is not sufficient to drive Mosfet in Saturation region to allow sufficient current through Load.

I suspect it could also raise the Temperature of Mosfet being driven in Ohmic Region.

My question is:

how could I have more voltage on Gate ? or should I search another Mosfet with very low threshhold voltage ?

Thanks for your suggestions.

EDIT:

Mosfet replaced with that of one with lower threshold voltage.

NPN and PNP transistors changed with those having integrated biasing resistors as well.


texts: Understanding Oscillation in Power Amplifier

texts:
I have been modeling this circuit in LTSpice and it has a tendency to oscillate. The transistors are chattering on and off resulting and a square wave output at ~8 kHz depending but the precise frequency depends on the inductance of the various transformer coils.

What is the source of oscillation in a circuit like this?

I want to understand where the coupling is and not just how to "fix" it.

UPDATE 1:

This circuit simulates very well:

In general I think the problem was just impedance mismatching. So adding series resistance with the transistor bases helped. But what I think was more important was the inductance of the output transformer was too high. If I use a ratio like Hammond 106T which is 100R : 8R and pick low inductance values, it behaved much better. So basically it was not loading the transistors enough. As soon as the transistors started to turn on, they would just stall because they couldn't pull current.

The simulation runs pretty quick and the FFT is flat:

The feedback capacitor also helps to significantly reduce the peak at 48kHz which is where the oscillation actually was:

So the above shows the FFT without feedback. You can see from the first FFT that the feedback significantly tightens the response.

UPDATE 2:

It seems the biggest factor of all in this simulation is leakage inductance which is defined by the transformer coupling factor. I started with 0.98 and then 0.99 and changing this to 1 often completely eliminates oscillations.

The question is - what is the typical leakage inductance of an audio transformer like the interstage and transistor output transformers shown (eg Hammond 106H / 106T)? Is it ok to assume a coupling of 1? Or is 0.99 more realistic. Believe it or not the difference between 0.99 and 0.999 is significant to my simulation. So I need to figure out what this coupling constant would be in practice.


texts: usually common mode chokes are used on AC lines to take care of common mode noise.  If I am using a CMC on a DC line ..would the inductance degrade ?


texts:
I am looking for an Arduino-compatible RFID reader supporting ISO 11784 & 11785, in order to read tags used for animals (mostly cats and dogs) identification.

I found both RMD660 and and Sniffer Nano v2.0 from ITead Studio, but they are out of stock. Is there any alternative?

The final goal is to build an intelligent cat door, that does not require adding a new RFID tag to my cat (he already had one implanted, and doesn't wear a collar).


texts: Can capacitively coupled voltages on mains cables harm devices?

texts:
In my bedroom, I have a ceiling LED light with three switches. One at the door, and one at each side of the bed.

The LED light contains a constant current supply (simple switching supply), which failed these days. Until the new one arrives, I have replaced the light with  a simple fluorescent light bulb in a simple socket.

Now, I hear a quite ticking at 25Hz from the bulb when the light is OFF. Further investigation shows that the neutral line and earth is OK, there is no voltage between them. But the hot gives 40V with the bulb connected, and 70V without. (And yes, the switches act on the hot wire!)

So OK, this clearly indicates some capacitive coupling from other cables in the walls.

My question is:
Can those low voltages harm power supplies or other devices over time? It's already enough to let the fluorescent light tick at 25Hz. I could imagine that this has also caused the death of my LED light, though this could also be just by chance.


texts: Using Visual Studio as IDE for mbed developement

texts:
I am aware that is has been looked at / done in the past, but I was wondering if there is anyone who has experience / understands how I could use Visual Studio 2015 Professional to develop mbed code in C/C++. As VS can already handle C++, I think the two main barriers are getting the mbed platform's libraries into and working with VS and getting an ARM enabled build engine.

Mbed now has a range of offline export options, so I wonder if any of those can be utilised? I have downloaded my project as a .zip and added main.cpp to a new blank C++ project in VS, but of course it is riddled with errors and I am not having much luck getting the libraries into the project. All thoughts are much appreciated. Many Thanks.


texts:
I recently bought a UART WiFi module (this one) and configured it (wireless configuration method) with right SSID but wrong password (and I don't know what it is).

The problem is that I can't reset this module to its manufacturer settings and I can't connect to this module via serial port to configure it with some wire or cable. But I'm sure that my module is trying to connect my access point but with wrong WPA2-PSK based network key (because in logs of my access point I can see my module's MAC address that trying to connect but it can't)

So my questions:

Why I can't connect my module to my PC using a USB to Serial Converter ? (something like this one) I tested this module (I mean USB-SERIAL converter) and I'm sure that it works pretty well with my atmega8 microcontroller. And I checked baud rates, stop bits. When sending commands via some terminal debugging applications (like hyper terminal or code vision's terminal program) it responds nothing.
How can I reset this module to its manufacturer settings without connecting it to any PC using serial port? There is nothing in datasheet but a command that needs a serial connection to some PCs.
How can I see what password this module trying to connect to my access point (that cause "wrong password" failure)? Is there anyway to find out?
Is there anyway to create or configure a WiFi network that accepts any WPA2 network key? I tried to create an open wireless network without any security but this module fails to connect to it either. It skips non-WPA2-PSK based networks.

First of all I should send 3 plus "+++" via serial port and after that it should respond with "+OK" but nothing happens when doing this. What's the problem ?


texts:
I am doing a study on Improvements in biasing and compensation of CMOS opamp.

Do you guys know how to come up with the equation for RDS4C ?


texts: Trying to identify a battery and its controller

texts:
Attached are two images of the inside of one of those devices to extend the battery life of your phone. This one was a promotional giveaway and only had their logo on the outside. I tried searching for the text in the second image, but nothing that comes up is likely. I'm hoping there is something I am not realizing in the image that would help my research.

!! Update !! I found another one. The little chip reads ETA9640 / 5486B.


texts: LCD screen: can this problem be caused by the inverter?

texts:
I'm repairing a HP 530 laptop with bad screen image. The image does not flicker, the corruption pattern is static.

If I connect an external monitor through the VGA port the image is fine, therefore I rule out the motherboard/GPU and I'm left with three components as the only suspects:

Flat cable
LCD inverter
LCD panel

Do you think I can rule out the inverter too? If I understand correctly what it does, if it fails I get no image at all, therefore a kind of on/off failure type.

I would rule out the flat cable too, I replaced it a million times on another laptop and it also causes a blank screen issue. Moreover, flat cable problems cause intermittent failure which depends on LCD hinge position too.

I could replace the inverter first and see what happens (it's cheaper than the screen) but I don't want to waste money if you can explain me how such failure cannot be caused by the inverter

Thank you


texts:
In all example circuits using a transistor to power something (say, a motor), it seems to always be an NPN transistor (or NFET) with the something/motor connected to V+ and the collector/drain.

This leaves the powered component ungrounded, connected only to V+ while not powered. So (in the case of a motor) the ungrounded chassis cannot touch any other ground. So if its mounted to a grounded frame, next to another motor perhaps, turning one on will turn on both, so they must both be isolated and be sure no ground can touch the motor's ground.

Am I missing somthing? Is this really how circuits are designed or is there something (multiple things) basic examples omit for simplicity? Do I just need to get over this and accept a less-than-ideal world where everything doesn't actually work the way I wish it did?


texts: Some questions about a low frequency reed switch interface circuit

texts:
I need to wire this reed-switch rain-meter sensor to a counter input or to an isolated analog input channel of a data acquisition board. The sensor will be around 30 meters far away from the data acquisition board. The counter input has Schmitt trigger and below is the counter's properties:

The interface circuit I used at first yielded the following output to counter:

I basically poured a glass of water into the bucket(since there is no rain) and it seems like from the above plot the maximum frequency is around 3Hz. And the switching time is around 0.03 sec i.e 30ms. I used 4.7k resistor and 4.7u cap for low pass filtering for debouncing. I only used 1 meter of cable. In real it will be 30 meters.

But with this interface I'm not happy with couple of things: The first is the curvy rising edge and the second is I want the output to be voltage ON when the switch is ON. But above it is inverted.

So I decided to use the following circuit instead:

I didn't implement this in real but I have some questions regarding this:

1-) I don't know the contact bounce time of this switch and it is neither given in the data sheet:

Since I don't know this contact bounce period, I cannot decide about the LP filter R and C values. I know from experiment is that this switch when I pour water has around 3Hz frequency and the switch ON time is around min around 30ms from my MATLAB plot above. I also dont want too slow rising edges. What R C values can be optimum or fine for this interface?

2-) I came across some examples using the diode but I don't really know the purpose of that diode. What could be the reason it is used sometimes? Is there any fundamental mistake in the circuit?(If I don't use R4 it causes current spikes in simulation ect.)

edit:

I forgot to mention that the sampling rate for that MATLAB plot was 500Hz. But the counter input has like MHz level freq.

edit 2:

debouncing switch with 20 cycle 1ms debouncing:

this is tested with the suggested circuit:

C1 is increased to 2.2u:


texts: Driving a 6v 250ma motor by using 12v 2A adapter

texts: I am trying to use 4 motors(3-6V 250ma) controlled through 2 L293D Motor drivers. I have a 12V 2A adapter to supply VCC to the motor drivers. I am looking for a way to power my motors without damaging them. I guess using a Voltage regulator(7805) to convert 12v to 5V. I am afraid if 2A will damage my motors. How can I regulate both voltage and current to operate the motors without damaging them? I will be running only one motor at a time.


texts: Why is there a textile thread in some cables

texts:
Here is a photo:

I have seen many cables with a single textile thread in them and I always wondered why it is there.

Does anyone know?


texts: Looking for help on why my n-channel mosfet is getting destroyed

texts:
I've got a design that I've inherited with a pretty standard n-channel mosfet driving a relay that controls a motor and actuator.

On a recent build we started getting a 50% failure rate on the n-channel mosfet. Previously we had no failures of the mosfet. The only differences I've been able to find so far are different date codes on the relay and mosfet. Otherwise nothing has changed.

The mosfet is an ON Semiconductor 2N7002LT1G

The relay is a Omron Electronics G6RL-1-ASI-DC24

The flyback diode is a ON semiconductor MRA4003T3G

The mosfet was examined by ON semiconductor and it was found that it was most likely destroyed by excessive voltage. But I've not been able see a voltage spike on the mosfet above 30V so far.

Here is the part of the circuit with the mosfet/relay/diode.


texts: Oscilloscope causes a problem with my envelope demodulator

texts:
In the circuit below I expect to derive a periodic signal in frequency of 31 Hz at TP13. The output is read by a microcontroller and if the signal changes to zero it will be detected by the micro. Regarding this I expected that the output will become zero for 1 ms periodically, which is proved correct based on the micro's response.

But when I just connect the oscilloscope's ground to my circuit's ground the output remains at 3.3 V which again can be recognized by the micro's action. I think it may happen due to the oscilloscope's internal circuit. I need a way to offset the effect so that I can follow my circuit's behavior using the scope. Does anybody know how I can do this or if there any other reasons the scope ground may interfere with the circuit?

Note that the output is correct as it is expected at TP11.


texts: How to measure voltage drop along silver foil with nanovolt precision, using Arduino's ADC?

texts:
For a project I am doing, it would be useful to measure voltage fluctuations in the microvolt/nanovolt area. The scenario is the following: I have a voltage divider circuit set up with R1 being a 4 Ω resistor and R2 being a 5cm pure silver foil with dimensions 5cm length and 1cm width (presumably having a resistance in the milliohms range). These R1 and R2 are connected in series using jumper wires in the breadboard.

So I am taking the Vout from this divider i.e. the drop across the silver foil (R2) (I know the jumper wire resistance will contribute to this drop as well) and then amplifying it using an opamp set to 100 gain.
The Arduino ADC gives an output, visualized with the serial monitor.

When the silver foil will be mixed with some chemicals, its electrical properties will change slightly and hence its conductivity as well. I am only interested in measuring the difference i.e. voltage drop across silver foil before the solution is mixed and after the solution is mixed (does not have to be accurate).

Is the current method I am using valid?
Can I measure nanovolt differences using this method?
Is there any other more effective and reliable methods of measuring differences with nanovolt resolution?


texts:
I'm trying to obtain a high impedance, several decades current pump for charging a capacitor from 1uA to 10mA, swing +/-5V.

I arranged two current mirrors like this and is working acceptable for simplicity, cost, etc.

The problem is that I need a precise unified control (voltage) to set the output current, instead of R5/R6.

Two options I tried so far:

1) Controlled FETs, but due to P/N mismatches, control curves are completely different :) I guess worse solution.

2) Using OA's to drive voltages across R5/R6 based on the fact that when approaches +5/-5, mirrors will be "disabled" and maximum charge time will be achieved.

Still not the best deal, OA's needs to be matched and control curve will be most of the time effective at 90% of voltage (near rail) due to log effect of linear charging the cap.

So I wonder if there is a brilliant idea here :))

Thank you in advance!


texts: Simulating all transient solutions for RLC series circuits

texts:
I am reading this page that contains the transient solutions for RLC series circuits: over-damped, critically damped and under-dumped.

This site presents these graphics for the 3 cases:

Then I have decided to create a simulation using multisim, at https://www.multisim.com/content/LzLcDKNVvCzQeRUc6B9GTU/rlc/open/

My simulations are far from giving me these curves.

If I understood the theory correctly, these are my values:

Over damped = R^2 > 4L/C... I choose R = 10Ω, C = 1C, L = 2.25H
critically dumped = R^2 = 4L/C... I choose R = 3Ω, C = 1C, L = 2.25H
under damped = R^2 < 4L/C... I choose R = 1, C = 1C, L = 2.25H

These are the curves I get:

OVER

UNDER

CRITICALLY

My curves are completely off.

Solid curves are voltage across capacitor. Dashed curve = current. V1 is a pulse, 10 VDC amplitude, 1ms.

What am I missing?


texts: switching voltage rail to lower relay voltage

texts:
I would need to lower the power of my relay after it has been closed.
To do this ( I'm switching AC with this relay) I intercept the relay output with a db107 bridge rectifier and isolate the signal with ltv816 optocouplers.
This first part seems to work.
then signal arrive then to SN74LVC1G3157 that should activate the output when receive the signal from the switch and activate 5v or 12v rail. rail are controlled by 2 2n2222A.
This unfortunately not works, the power remain always at 12v, seems the transistor not open.
Do you have some easier suggestions or see the error ?
here the schematics:


texts: P-channel MOSFET with variable resistance on the drain

texts:
I would like to switch a variable resistance using a P-channel MOSFET as a high-side switch. I asked a similar question here using PNP BJT; however, it appears as though a BJT would be inappropriate for my problem.

General information:
After doing research on using a PNP transistor to switch a load with an unknown resistance, it appears that a PNP BJT isn't appropriate. From my limited understanding, I need to know the resistance on the collector side of a PNP BJT in order to calculate the correct base resistor using the transistor's β value. In my circuit, the resistance of R4 can vary from 0Ω to infinity and will be read from an ADC (not shown). This means that the range of resistance on the collector side can go from 1000Ω to INF because of R3. This appears to cause issues with the BJT switching on and off correctly.

It appears as though MOSFETS do not require such base resistors. I've seen MOSFETS being pulled up if P-type and down if N-type such as in the answers to a similar question here and here.

The datasheet to the LP0701 MOSFET I found is here.

Questions:
My first question is, will the MOSFET (M1) be able to switch the circuit on and off as I have diagrammed it? I should note that the digital pin is 3.3V as well. Second, is my logic of choosing a MOSFET over a BJT correct in this case?

Bonus:
Should another resistor be added between the digital pin and the gate for added protection?

Thanks.

simulate this circuit – Schematic created using CircuitLab


texts: How to replace relay with N-Channel Mosfet

texts:
I have this simple circuit which uses a relay to charge and discharge a capacitor.
Now instead of a mechanical switch, I want to use an electronic switch such as a N-Channel Mosfet.

How can I replace the relay with a N-Channel Mosfet?

My proposed solution so far:


texts: What's the relationship between susceptance and reactance?

texts:
I was trying to find the relationship between these two online, but I found out two completely opposite answers, and I'm wondering which one is the right one.

Is B = -1/X or is B = 1/X ?


texts: Measuring Power Consumption of a Mixed-Voltage Device

texts:
TL;DR

How can I measure the power consumption of a system that uses power supplies with multiple voltage outputs?

 Background

I need to perform some power consumption tests on a desktop computer. I will be running various workloads on it, and want to measure the power response at the board level. It uses a standard 24-pin ATX connector, which supplies voltages of +3.3V, +5.0V, +12.0V, and -12.0V. I want to run both active and passive workloads, and record the power consumption while the system is asleep, if possible.

I know there are numerous components on a desktop system that can affect power measurements, such as WiFi cards, SSD/HDD, PCH, etc. Most of these effects are actually desirable, because I want to see when the system's power management features don't reduce their power consumption properly in various S-, P-, and C-states. I have determined that the most significant source of error remaining in my test infrastructure is the power supply. I am seeking to eliminate the power supply as a source of error.

I can freely open up and modify the supply as needed, including cutting and splicing the wires.

Here are a few characteristics of an ideal solution:

Starting measurement, stopping measurement, and collecting results can be automated with Python scripts
<25mW measurement error when the system is drawing <1A
As low-cost as possible
Can switch out the system under test easily
Measures the power consumption of the whole motherboard and everything attached to it, excluding the supply itself if possible

Possible Solutions

Use multiple power meters
I could  wire up four discrete power meters to the outputs of the power supply, one for each voltage.

Pros:

Probably the most accurate of the options
Usable in all system sleep/wake states

Cons:

Four power meters is very large cost investment to measure just one system at a time
Difficult to switch out the system under test

Test Target Software
Both Windows and Linux (I don't care about MacOS) have the ability to tap into hardware registers that track power consumption. I could read these registers to estimate power consumption.

Pros:

No hardware requirements
Easy to replicate on multiple test systems
Free

Cons:

Can't measure power during sleep states
Cannot give accurate total-system power measurements, only system components that have registers configured for this

Measure the PSU input instead
There are tools like Watts Up? power meters that measure power consumption, as seen by the wall outlet.

Pros:

Much lower cost than four power meters
Easy to switch out the system under test

Cons:

Includes power consumption of PSU
Haven't found one yet that is accurate enough while providing a programmable interface and the ability to measure both current and voltage at the same time (or power directly)

The Question

Are there other solutions or techniques that I have left off of this list, or aspects to the included ideas that I should consider? Is there an industry-standard approach to measuring power consumption on mixed-voltage devices, or are they generally custom to each application?

Note
I have taken a look at these other related questions from EESE, but they haven't been helpful for this question:
Power consumption of my device
Measuring power consumption
Measuring Output Amps From a Power Supply
Multiple voltage output power supply
Measuring precisely the efficiency of a power converter


texts: 3 axis accelerometer for detection of cutting a fence

texts: I am currently working on a project and would appreciate your help. So i have this fence (eg. 3m x 3m) on which my 3 axis accelerometer is mounted in the geometrical center. It can detect whether someone is trying to climb upon it, or if someone's  hitting or trying to break it using brute force. The deal is, suppose a person tries to cut the fence at the bottom left corner. Assuming that this will produce much smaller vibrations, how could one detect whether someone has cut the fence or not, using the accelerometer or any other sensor ?


texts: Dynamically pushing instructions to SRAM IC

texts:
Sorry if this isn't the right place to ask this.  Coming from a programming background, and I'm not 100% sure how to read some of these data sheets.

I'm looking at using IC 628512LP-70 CMOS SRAM" (or comparable) in a "computer", on breadboards, that I'd like to build.  However, I'm wondering if this chip does what I'm understanding.

To my understanding, we've got 11 pins we can use to input memory to a buffer, which is then decoded, and placed into RAM.  We can then request that data by giving it the "buffer" (which I'd assumed would be its location in memory), and the RAM module gives us a "peek" at the data, which still remains in memory.

It would then be the microprocessor's job to manage that data and null them out if need be.

Is this the correct interpretation?  Am I using the correct chip?  Thank you very much in advance for your help


texts:
Does the L298N have a minimum output voltage? I want to control it such that the output varies from -Vs to +Vs, does it go linearly near 0, or is there a threshold that it passes? I can't tell what value I am supposed to read from the data sheet.
So far it seems that it drops to 0V after reaching .66V, but this might just be my multimeter playing up.


texts:
After 40+ years you would think I would know this, somehow it never came up, but for the life of me I don't see it.

Typical transistors specs list a plethora of values but one that always seems to be missing is \$I_{b_{MAX}}\$. That is, the maximum current you can pass through the base emitter junction.

Obviously you can't exceed the power rating across the base-emitter diode forward drop, so 626mW/0.7V ~ 900mA, but I have a feeling there is a fusing number for the bonding wire. Perhaps it is the same as the max collector current.. 200mA.

What number is the right one, if any?


texts:
I am trying to understand the main purpose of backup fuse used in SPD (Surge Protection device). Is this used to protect the SPD from high AC current but still allowing surge current to pass or does it has different reason. I tried searching but with no luck I am positing it here.

I also found following picture which explains about the Fuse F1 and F2 but cant figure out much.

Can anyone explain me about this or provide some links where I can read more about it.


texts: Is there a variable forward voltage diode-like device or circuit construction?

texts:
I need to make a test PCB for an LED drive circuit that can drive a variety of different single LEDs.  The forward voltage (Vf) of the LED could be anywhere from ~2.2V up to ~6.5V.  I'd like the test PCB to be able to simulate the range of possible Vf.

Rather than using switches (likely FETs) and putting a variety of LEDs on the test PCB, it would be great to find something (a device, a circuit) that is a "variable Vf diode" or "voltage controlled diode."  Does such a thing exist?

My searching and (limited) EE knowledge so far suggests that an PN junction (a diode) gives a constant Vf, that adding another junction (BJT transistor) allows for current but not Vf control, and that adding a 4th junction (thyristors, SCRs, triacs, ...) doesn't help either.  A FET can be thought of as a voltage controlled resistor and a Varicap is a voltage controlled capacitor, both of which are close but not what I need.

For what little I know about device construction, it seems like there should be a device that uses a voltage or current to bias up a PN junction, changing the width of the depletion region and therefore changing the bias required (Vf) to "punch through" with carriers into conduction.  Then again, this sounds a lot like a BJT, which I don't think will work.

I guess putting a heater under a diode could give some Vf control, but that seems like it would have poor control (and be inefficient and sort of silly).

It feels like I'm missing something obvious here.  Any thoughts on devices or circuits that can function as a voltage-controlled, forward-voltage diode?


texts:
I'm designing a small battery powered circuit which will draw around 50mA for a millisecond every couple of seconds. I was planning on using a CR2032 coin cell but have recently learned that a coin cell has a rather low peak current of a couple of milliamps at best.

Are there any alternatives in a similar form factor which can be used?


texts: Can you desalinate or distill water with a Peltier module?

texts: Can you use both sides of a Peltier module to distill water? Using one side for heating and the other side for cooling. If so what type of Peltier module do you need and can you make it solar powered? Also do you need heatsinks, and how should it be placed? Do you need anything else besides the module? What type of power supply do you need?


texts: Bypass Capacitors - Why do they not provide voltage spikes back down the line?

texts:
I am new to electrical engineering. Please excuse me if I use the wrong terms. (Welcome to correct me tho ;-) )

I am learning about capacitors, and I have been studying a circuit diagram explaining how capacitors can "stand-in" as a power source if the power drops. This article also mentioned that it can help with spikes. Upon researching spikes, I learned that a cap can handle a percentage more voltage than what it is rated for. This is useful in a voltage spike because the cap can "absorb" some of that voltage, decreasing the spike to let's say an IC.

I understand this. BUT. Won't the 5V capacitor now sit at lets say 6 volts? What happens when the power dips and the cap is supplying current to the circuit? Won't it supply that current at 6V instead of 5V because of the previous overvoltage it accepted?

Thanks


texts: Can I increase short circuit protection shutdown delay?

texts:
I recently built a simple audio amp based on the TPA2005D1. The schematic is identical to the one that Sparkfun implemented in their Mono Audio Amp breakout board, minus the power LED circuitry.

https://www.sparkfun.com/products/11044

I wired this up to a headphone jack and a speaker. The headphone jack is a traditional switched jack that diverts audio to the speaker when there is no jack plugged in, the diagram below is for the exact jack I'm using.

Vo+ is hooked up to pins 2 and 3, Vo- is hooked up to pin 4, the speaker is hooked up to pins 5 and 6 on the positive speaker terminal and pin 4 on the negative speaker terminal.The sleeve is not hooked up to anything at this point.

The problem I'm having is when I plug or unplug headphones, the Vo- and Vo+ pins short together momentarily inside the jack and trigger the short circuit detection built into the TPA2005D1. I have to power cycle the amp or pulse the shutdown line to get it to work again. The short circuit protection can be seen in the bottom right corner of the TPA2005D1 functional block diagram.

Is there any way to increase the amount of time a short circuit can occur? Maybe up to a quarter second? Is there a simple way to pulse the shutdown line every time I plug/unplug headphones?


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I am building a diode detector circuit in order to detect ASK signal with 125 KHz carrier frequency and 8 KHz data rate. However, I realized I would say a strange behaviour and discharging of capacitor.
The setup is following:
Function generator set to sine wave 3 Vp-p and f=125 KHz.
Function generator is connected to anode (1N4001. From kathode goes C=1nF to ground as well as 330k ohm resistor. This value is for sure not correct but it was an experiment. Here is schematic:

The generator has 50 ohm input impedance.
So, here is the waveform:

As you can see, capacitor is charging, but then suddenly discharges really fast until certain DC level at capacitor is reached. I would at least expect that charging stops as soon as capacitor is charged to the voltage that can't any more provide forward voltage for diode. In that moment it should start to discharge via resistor which should be pretty much slower than shown.

So, my question is why this happens and is there any feature of the diode that comes into game near the point of shutting off?

So, you were all right guys. I changed to 1n4148 and now it works fine, although I cant realize how can this voltage drop.


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I am doing my first steps in designing an FPGA project with NIOS and RS-485 interface. I have looked through a bunch of tutorials and books, but haven't found useful info about how to add RS-485 interface in an FPGA with NIOS. I know there is an option in QSYS to add "UART(RS-232 Serial Port)" but can i use it to get my 485's with an appropriate coverter ic ?

I am using Quartus.
FPGA is 5CEBA4F23.


texts: How to check output after FPGA Implementation?

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I have 10 numbers saved in RAM. I sorted it using Verilog code and  saved output in another RAM. I did simulation and it was doing correct sorting. I synthesized it and generate bit file. Now i want to see whether it performing logically fine after FPGA Implementation or not.But i am confused how will i get output sorted data after FPGA implementation.

Please suggest me how will I get output data after FPGA implementation so that i can check it manually and sure that my CODE is right with FPGA too.
Thanks