texts: Internal oscilator vs external and Serial port question

texts:
I've been thinking about getting into using some pic microcontrollers, and I found the below two things to help get me started. But, on the product page for the microcontroller, it says 20 mhz, but then in the description it says it has an 8mhz internal oscillator. Which is right? Also, with the programmer below, it says usb to serial adapters don't work, but I don't have any serial ports on my computer, is there anything I can do about that?

http://www.sparkfun.com/products/8
http://www.sparkfun.com/products/228


texts: How to incorporate voltage controlled current limitation

texts:
This is part of a lab PSU and programmable load, for generic lab use including e.g. battery charging/discharging. This question is about the desgin of the current limiter in the psu part.

It must be controllable from a computer. This part will be achieved with an arduino and/or raspberry pi inside the device.
The current limitation could be implemented in software, but I don't trust this to react fast enough.

I have seen many designs that use potentiometers to adjust the current limit, but I want to use the microcontroller gpio/dac outputs to set reference voltages that control the output voltage and current limit.

My idea so far is based mainly on opamps. The voltage regulation is simple enough with a voltage follower with some current amplification, e.g.:

I'm thinking the current could be limited by manipulating either the feedback line or the Vref line, based on sensing the current with a shunt resistor. However, my attempts at this all sort of feel unnecessarily complicated.

Not sure if there is any rationality behind this, but it also bothers me that the output has a different ground than the internal circuitry. Should I care?

Attempts at addressing the different ground levels issue
(Would these even work?)

I'm sure this can be achieved simpler and more elegantly, probably by using more suitable techniquies and principles. I appreciate your suggestions.


texts: Testing a circuit systematically and efficiently

texts:
I need to determine a circuit's response to variations in component values. What are common go-to methods for this?

Background: I'm a growing novice in electronics design. So, my question is about common, de facto strategies accepted by experienced hobbyists and professionals alike. What for? To analyze how a circuit behaves for different combinations of its components' values (and other parameters). And to do so in a structured, systematic, efficient way.

My first thought is a SPICE simulation. But I would like to confirm whether this is 'it' or whether there are other approaches that I'm unaware of.

Context: I have a simple optocoupler circuit as shown below. The left side (1) operates on a different potential than the right (2). And a MCU on the right needs to read an analog signal on the left (V_ana_1). Hence the optocoupler. I use it to convert V_ana_1 to V_ana_2 which then is fed to the MCU.

Now the optocoupler's response is not linear. So I would like to choose R1 and R2 such that V_ana_2's range falls within the sensitive (as opposed to the saturated) region of this response for a given V_ana_1 range of, say, 2-3 V.

What's a good way to go about doing this without physically and manually trying out different resistor values? (Which is what I did, which is why I'm asking this question - that was a pain.)

simulate this circuit – Schematic created using CircuitLab


texts:
I am looking for some advice.

I understand that LED drivers transform a supply from AC to DC as well as the amount of volts from input to output, for this reason i believe they are classed as inductive loads.( these are not inductive, these are non-linear resistive loads)

Will there be an increase in efficiency using LEDS on a site with voltage optimisation and if so what would the average increase in efficiency be. Just so you know there will be a lot of 22w LED tubes.

I want to say they voltage optimisation will increase effiency but im not sure if it will be worth it considering the buy back time and the fact there are minimal inductive loads on site.

Thank you in advance for any replies

Liam

ps. £60,000 for voltage optimiser
    2000 LED lamps on site average 22w


texts: Which is good method for step down 50Hz, 230V AC

texts:
Which is low cost and safe for step down 50Hz 230V AC into 12V?

Transformer or reactance or Regulator IC ?

simulate this circuit – Schematic created using CircuitLab


texts: How does higher amperes NOT affect a DC motor for example?

texts:
I'm shocked that no one has asked this question on the whole internet. So the question is mindblowing and frustrating.
If I have a 12V DC supply with say 500 milliampere, I can for example short circuit the supply without any issue.
But if I use my car battery with 12V that has incredibly high amount of amperes and short circuit it, it would generate an insane amount of sparks and could cause fire. I get why this is happening, so here on everything is clear in my head. But these two points are important to keep in mind for the question itself.
But now for the mindblowing question.
How can a 12V DC motor run just as well on both the weak power supply and the car battery that's incredibly powerful? I get that "a motor/component only draws as much current as it needs" and "ampere is the size of the water pipe" concept. But, whatever you put on the circuit. once that something is connected you are essentially going from open to closed circuit, which is similar to a short circuit with a component/resistance/DC motor in middle, so if we have the car battery with super high amps and connect it with the DC motor in the circuit why doesn't it burn up everything from the battery terminals to the dc motor?
Essentially we ARE short circuiting it with just a resistance (DC motor) in the middle.


texts:
I am trying to design the following.
My Android device (and the applications processor on board) has a limitation of a single USB PHY only.

Here is my goal.
I have to support the Android box in USB-OTG mode.
I have to support simultaneous operation of Keyboard/mouse and also to a PC so that I can do a file transfer to the Android box.

Adding the USB-Hub is the easy part.
But I don't think there are existing solutions to hacks that I am aware of doing Android Host to PC Host and emulating Mass storage for file transfer.

Can somebody help? If there are possible solutions.

I have googled around, and found that I can add in a microcontroller bridge in between the Hub and the PC to emulate this.
However I am not understanding how this works, i.e. wouldn't the Microcontroller still be a USB downstream??


texts:
I am reading JEDEC DDR3 specification, and so many other documents on DDR3 guidelines.
Before I move to pcb prototyping, I just need a confirmation.
I connected all my lines, respected the grouping, length matching, impedance matching, via size. My DDR3 type is 1333.
Question:
If I keep the CPU and Memory IC close (less than 2 cm), do I need to take care of trace length (I mean their absolute length, not their matching)?

My opinion is that it doesn't matter because the current travels at half the speed of light on a FR4 pcb board. Even 1cm more should not matter much. And my SDRAM controller will take care of the rest of the details for me.


texts:
Is it possible to control a bicolor LED with just one pin of a microcontroller?

Instinct says NO, because you can have one end grounded and the other going to the micro's pin, allowing you to turn it on or off but not change its color.

But maybe someone has a better idea?


texts:
Well I'm struggling hard with this, been at it for 2 hours so far.  I should have stuck to my TI parts :)

Anyway I have a board and I'm trying configure the PPS to bring the SPI peripheral out to the pins.  Actually I'll use it in I2S mode.

So the part is a PIC32MX210F016B and the SCK pin is this: SCK2_PRB15 Physically connected to pin26.   I can see that in the datasheet this is the SCK2 pin.

I've been trying to follow these plib examples I've found like so:

PPSOutput(3, RPB15, REFCLKO);

But it's not working.  I understand that there are different peripheral groups, but I don't get how to find the group number from the datasheet.  I have been reading it tonight and reading table 11-2 about port settings.  I'm still not clear.

I'm also reading the PPS.h header file to try to understand the settings but I can't find anything about SCK in there.  I did finally figure out by looking at the macro expansion what the PPSOutput function is trying to do, but I just don't know how to figure out the parameters for my part.

Anyone have any ideas?


texts: Why port B5 on ATMEGA64A-AU mailfunction after enabling USART function?

texts:
I've wire up ATMEGA64A-AU based on this schematic from here:

I've tried to program a blink on pin B5 which has a LED on it:
#define F_CPU 16000000UL

#include <inttypes.h>
#include <avr/interrupt.h>
#include <avr/io.h>
#include <util/delay.h>
#include <stdlib.h>

void main( void )
{
    DDRB |= (1 << PB5);
    PORTB |= (1 << PB5);

    while(1){
        _delay_ms(1000);
        PORTB ^= (1 << PB5);
    }

}

It works actually fine but when I tried to enable USART on the chip by adding these:
#define FOSC 1843200 // Clock Speed
#define BAUD 9600
#define MYUBRR FOSC/16/BAUD-1

void USART_Init( unsigned int ubrr )
{
    UBRR0H = (unsigned char) (ubrr >> 8);
    UBRR0L = (unsigned char) ubrr;
    UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);
    // Set frame format: 8data, 1stop bit
    UCSR0C = (1 << USBS0) | (3 << UCSZ00);
}

It still works but when I add this code to main function:
USART_Init(MYUBRR);

Toggling stops! Why this happen? I couldn't found any thing on its datasheet PB5 hasn't any thing to do with USART to my understanding.
PS:
This chip has some weird property like this but it comes with two UART and it is cheaper than the others! that is why I choose it.
Update1:
ATMEGA64A has two fuse bit which was new to me :
1-ATmega103 compatibility mode fuse which was set as default and shouldn't be in my casse.
2-Jtag fuse which I don't have a device to use it! I use ISP programmer. so it shouldn't be set.
It start blinking after setting them, But still I don't understand how they got PB% involve, they use other pins!


texts:
This is a Board off a 8tb WD Hard Drive. I plug in the wrong power and i believe the little thing with the S on it is bad. I do not know what it is call or where i could find another, any help would be appreciated. The power coming in from the sata is 12v
Thanks


texts:
How to evaluate magnetic energy when only vectors of magnetic induction B, and vector of magnetic field, H are known?

We know that in general,
$$W_m=\int w_mdV$$

where wm is the density of magnetic energy that is defined as
$$w_m=\int HdB$$

My question is, is it possible to evaluate magnetic energy Wm when only vectors B,H are known? If yes, what is the expression for magnetic energy in function of only B,H?


texts: How to determine total tolerance of a ceramic capacitor?

texts:
For the sake of this question (as an example only) lets consider MLCC X7R ceramic capacitor. Such a component among others is characterized by a number of tolerances.  Temperature dependeant tolerance, DC bias voltage tolerance or aging tolerance as a few of them might be listed. Ommitting the problem of determining tolerances themselves (assuming knowledge of particular tolerances values), how to calculate total tolerance of a capacitor?

Is it just a sum of all tolerances or it is more complicated (e.g. there exists some sort of tolerance "propagation")?


texts: Would a ground plane/traces impact NFC antenna performance?

texts:
I am building a PCB business card with an NFC chip and a WS2812B LED display (powered by a USB-C port, NFC is not connected to the LEDs). Right now I have a ground plane on the side of the antenna (not connected to either the NFC chip nor the antenna), and a +5V plane on the opposite side of the antenna (also not connected to the NFC circuit). Here are screenshots from both sides:

Would the planes interfere with the antenna in any significant way? And should I change the grid pattern to a normal plane? (The grid was a cosmetic choice)
I am using this chip for NFC, and the antenna is the same as the antenna from this tutorial.


texts: Running a load off a solar panel connected to 2x 12V batteries.

texts:
I am having trouble figuring out what relay I should be using for my solar panel set up.

I have a solar panel running to a solar charge controller. I then have the controller running into a relay. The purpose of the relay is to allow the panel to charge one of the 12V batteries while letting the load run off the other 12V battery. I then have a 12V timer switch that is connected to the relay to flip the direction of current from one battery to the other.

I have attached an illustration of my current set up that does not work. When the timer switch activates or deactivates, it does not change what battery is running the system.

I really do apologize for being a total noob, my normal work is with fish :)

If anyone is wondering this is for a Passive Integrated Transponder system used to monitor salmon movement.


texts: Is a Zener and a fuse enough protection?

texts:
We have a power chain that runs from an alternator, to a 24->12 dc regulator, to a battery charging circuit, to a 12 v battery.

We were thinking of using this circuit minus the ac-dc converter part for the charging circuit. http://www.circuitsgallery.com/2013/04/automatic-battery-charger-controller.html
And this regulator:
http://www.amazon.com/HOSSEN%C2%AE-Converter-Regulator-Step-Down/dp/B00BWKXTUU

From what I've heard, the battery should be charged at somewhere between 2 and 10 amps?

Is it enough protection for the battery/regulator to stick a 10 amp fuse and a 24v zener to ground between then alternator and the regulator? Also, do we need filtering circuitry or will the regulator take care of most of the noise?

Thank you!


texts:
This was my first topic, RS485 Tutorial Issue. I referanced because of the schematics.
I solved the problem in above topic, I forgot to pin settings for DE and RE pins.
I have a different problem now.
I have two device on the Rs485 line, one of them transmit the data, another receiving the data.
Transmitter, transmit rs485TxBuffer, it is include uint8_t rs485TxBuffer[2]={0xAA,0xBB}.I expect the receiver fill the receive buffer with these data. But I have a problem in here.
My problem is:
I get receiver side very interesting printing value, I get rxbuffer like this:
Received Message From Rs485 line : aa, 00
Received Message From Rs485 line : bb, 00
Received Message From Rs485 line : aa, 00
Received Message From Rs485 line : bb, 00
Received Message From Rs485 line : aa, 00

But I expected the message get like this
 aa,bb

These are my codes:
uint8_t rs485TxBuffer[2]={0xAA,0xBB};
uint8_t rs485RxBuffer[2] ={0x00, 0x00};

Transmitter codes:
while(1){

        RS485_Set_Transmit_Mode();
         while(HAL_UART_Transmit_IT(&huart2, (uint8_t*)rs485TxBuffer, 2) != HAL_OK)
         {
             // ...
         }
         uartReady = RESET;
        while (uartReady != RESET);
}
void RS485_Set_Transmit_Mode(void)
{
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_4, SET); // DE pin
}

void RS485_Set_Receive_Mode(void)
{
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_3, RESET); // RE pin
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_4, RESET); // DE pin

}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *UartHandle)
{

uartReady = SET;
}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandle)
{

uartReady = SET;

}

Receiver codes:
    while (1)
    {
            RS485_Set_Receive_Mode();
            HAL_Delay(1);
            while (HAL_UART_Receive_IT(&huart2, (uint8_t*)rs485RxBuffer, 2) != HAL_OK)
            {
                  // ...
            }
            SerialPrint("Received Message From Rs485 line : %02x, %02x\n",rs485RxBuffer[0],rs485RxBuffer[1]);
    }
void RS485_Set_Transmit_Mode(void)
{
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_4, SET); // DE pin
}

void RS485_Set_Receive_Mode(void)
{
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_3, RESET); // RE pin
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_4, RESET); // DE pin

}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *UartHandle)
{

uartReady = SET;
}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandle)
{

uartReady = SET;

}

When I didnt use the delay in my function, I didnt get correct values.
How can I solve the receiving values?
/* USART2 init function */
static void MX_USART2_UART_Init(void)
{

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
}


texts:
I am trying to identify these components, and I couldn't find anything with just the marking. Any help is appreciated.
The first picture I thought is Passive crystal/oscillator!!!

This one is marked 2058


texts: Can LED be used for both light emission and sensing

texts: I have read about LED in Wikipedia, and it says that LED can be used for both light emission and sensing. Is it possible to achieve this and how?


texts:
I'm trying to wrap my head around following library:
http://rweather.github.com/arduinolibs/classDS1307RTC.html

I can see that the DS1307RTC has a writeAlarm and readAlarm function.
I'm not sure how I should use these functions, do I need to manually check if the alarm has passed in my loop function?
Or should I use this in a different way?


texts:
I'm having a problem with my constant current sink circuit [see below].
As I increase the variable voltage, the Voltage across my 22 Ohm resistor remains relatively constant (0.7V). However, the voltage across my LED increases as the source voltage increases, well past 5V and even 6V (I did not want to take it further as these values would be damaging the LED). That indicates that the current across the LED is not limited by my constant current circuit as I believed it should be [see question: 'Leftover' voltage when using constant current

My question is this, what is the path for this excess current, and how do I actually implement the current limiting I want?

simulate this circuit – Schematic created using CircuitLab


texts: How to set threshold above or below which the signal turns zero

texts: In simulink, I have a signal. Sometimes it is positive but sometimes it is negative. When the signal is positive, I want to turn it to zero when it is above a specific threshold. Similarly, when the signal is negative, I want to turn it to zero when it is below a specific threshold. Can you please let me know how to do it? Thanks


texts: Common mode error formula from TI seems counter intuitive

texts: I'm working on an application to measure current in a buck converter using a current sense amplifier. According to this video from Texas instriment, the equation for common mode error is same as eqn 1 below, Where Vcm_pds is the common mode voltage used when during device testing and Vcm_sys is the actual common mode voltage in the application.The formula just doesn't look right. Looks to me like all you have to do to eliminate the common mode error is to make Vcm_pds=Vcm_sys ecmrr(%)=0 . It cant be that simple to eliminate common mode error can it?


texts:
I have some questions regarding ideal transformers, similar to the one seen below:

When talking about 'ideal transformers', can I calculate the current on the primary side by finding the complex impedance of the primary side, then divided by the primary supply voltage. OR do I need to reflect the secondary impedance over to the primary winding taking the turns ratio into account?
If the secondary winding was open circuit or had no series impedance, am I  right in saying that the secondary winding will have no effect on the primary current? Hence the primary complex impedance over the supply voltage would give the correct primary current?
In order to find Vout in a case like this where the primary supply voltage obviously doesn't equal V1, am I correct in saying I need to find V1 first in order to find V2. And the output voltage is simply V2 minus the voltage drop over the secondary series impedance?

Sorry for the questions, would just like some clarification before I move on

Thanks


texts:
I'm designing a Lead Acid battery charger with 3 stages. For the 2nd stage (constant voltage stage) as it is written in literature: the voltage applied on the battery must be dependent on temperature. So I thought of making a buck converter. The mosfet is controlled by IR2111 driver via a PIC Microcontroller PWM (Look at the circuit). Input = 18 V.

When I used a resistive load (R = 3 Ohm or 10 Ohm) the circuit worked very well: The driver worked, the output voltage is flat (no ripples) and up to 15.5V (with a duty cycle of 95%), the current is up to 5 amps with the 3 Ohm load (without overheating) ...

Now when I use the battery as a load to charge it (I have a discharged battery of 12V and its voltage is 9V) it doesn't work at all :( The output voltage is imposed by the battery so I find Vout = 9V. !!! Even if I change the duty cycle nothing will happen, the driver can not drive the mosfet and (Vgs is not square and equals 9V: seems that is related to battery voltage)

It seems that I must add something or .. I don't know ..
I you can help me I will be very thankful :)

This is the circuit that I used:


texts: Setting bit value and loading register with same push button

texts:
I am building a circuit to send 8 bits to a serial bus. bits A to E must go high depending on what push button is pressed. Only one button is pressed at the time. Once the pressed button is released, the 8 bits should be loaded into the register so they can shifted to the tx bus.
I'm struggling to figure it out how to properly load the register. In my current approach, the circuit is loosing the push button high signal as I am using the same signal to load the register so the bit of the pressed button goes back to low at the same time that the load pin of the register is set to high

I'd assume this is a common application but I have limited experience. Any help to know how to load the register when a push button is released would be appreciated


texts: Why does my in-wheel BLDC motor have sinusoidal back emf (line to line) when rotated by external system?

texts:
I have an in-wheel BLDC motor with 46 poles (permanent magnet) on the rotor and 51 slots in the stator. When I used an external machine to rotate my in-wheel BLDC motor, then measuring across two phase back EMF I got sinusoidal back EMF instead of trapezoidal.

Can any one explain why this happened?

For the measurement of back EMF constant, how one can calculate if back EMF is sinusoidal?


texts:
I understand that with proportional only control you have to have error or the control output goes to zero.  The answer to this question
Proportional controller was very informative.  Mr. Lathrop gives the the example of a car that you desire to go 50mph.  Everything makes sense to me until this:

  However, the problem now is that you won't ever get to your desired speed. If you were at 50 MPH, then I-S would be 0, and you'd let off the gas completely, which clearly won't maintain 50 MPH. This simple proportional-only controller always requires some error to maintain a non-zero output. For example, let's say to maintain 50 MPH would require a 25% control output (step on the gas 1/4 of the way), and that steady state speed is linear with throttle setting. In that case, the system would asymptotically approach 40 MPH and stay there. K(I - S) is 20, which is the control output required to maintain 40 MPH.

My question is: Why does the system asymptotically approach 40mph and stay there given a 25% controller output?  Given C = K(I - S), where I is the control input to the system, S the actual system response, C the control output that drives the system, and K the proportionality constant, .25 = 2(50 - S), so S would approach 49.875mph?  I sure I'm missing something real simple here.


texts: How to connect the PHY crystal for RMII?

texts:
I'm attempting to implement Ethernet communication for the first time and have run into an issue with my PHY. I'm using the KSZ8091RNBCA. According to the datasheet, when running in RMII mode, the XO pin is supposed to be left unconnected (Tables 2-3, 3-2). Figure 3-4, shown below,  shows that my external 50MHz crystal needs to be connected to both the XI pin on the PHY and the REF_CLK line.

Since both paths are shown coming out of the crystal, does REF_CLK come off the same pin as XI, or does it come off of the other pin, where the XO would normally go?

simulate this circuit – Schematic created using CircuitLab


texts: How to choose resistor values in op-amps

texts: Ok so my question is what resistor values should I choose for this amplifier. Vin is 0.5Vpp, 50kHz and the desired Vout is 25Vpp, so the overall voltage gain is 50. I know that the voltage gain for an inverting amplifier is -Rf/Rin. What's the difference between choosing resistor values like 50ohms and 1ohm or like let's say 50kohm and 1kohm. Also, what should my +-Vcc supply voltage to the amplifier be? The 2nd picture below is the op-amp's(LF351) datasheet Wondering if that could affect anything. Any help is much appreciated, thanks.


texts: Build two independent circuits with one switch

texts:
I have 2 DC sources 12V and 5V, I want to switch them using one switch as shown on scheme. I used here 2 diodes to isolate circuits and it works fine on simulation, but in real scheme 5V (actually rather 4.7V from USB) becomes 5.4V. How can I make circuits run independent (ie. they do not affect each other) in this case?

Simulation with open/closed switch - works fine on simulation but not in reality


texts:
I've a problem where I for the moment can't use my ESD shoes because off ergonomic reasons. So I wonder if anyone have a good temporary suggestion on how to add ESD protection to some normal shoes for ESD protection?

The floor I walk on is concrete.

I've thought a bit on how it could be done.
My own idea is to strap some conductive material to the leg and then attach it to a resistor which later on is connected to a pad I attach under the sole of my normal shoes. I have no clue on what material to use though if this now is an eligible solution.

I hope someone can give me some tips
Best regards


texts: Altium: create a component that expands to multiple footprints

texts: I am using a component that requires two headers to connect to it. I currently have a single footprint for this component that simply includes two copies of the connecting header. The problem I'm running into now is that our company is moving to streamline our process for creating files for our pick and place machine. Currently, I use the "Generate pick and place files" option from Altium to create the files, and then manually edit it to expand the single component into the two headers, but my bosses want to remove any manual steps from the process. Is there a way to get this single component to expand into two placements in Altium?


texts: Clap relay using 555timer - not sure about voltages around transistor

texts:
Hello!

I am working on a clap relay project and I want to do my own clap relay using timer 555 but I am not sure how the circuit works in details.
I am familiar with the 555 timer and I know that the trigger voltage has to be lower than 1/3 of Vcc (in this circuit 4.3/3=1.43, so lower than that). Electret microphone M1 is also included.

I have posted a part of a clap relay circuit which I found it on the internet and this circuit makes the led turn on(not on the picture). I marked points A and B because I am want to know the potential in those two points.

My assumption how it works(please correct me, because I am not sure!):

before any sound is made:

electret mic is biased with 4.3V voltage and it acts like a capacitor because of its internal structure
current flows through 470k resistor and base of NPN, so that the potential in point B is around 0.7V and the transistor conducts current
if the transistor is in active/linear mode and Ic=beta*Ib is valid in active region, therefore potential is calculated to be around 2.6V

But that means that 2.6V>1.43V and the 555timer is not triggered.

When sound is produced

the 4.3V biased electret mic vibrates which changes the voltage on a microphone and therefore changes current through 220n capacitor and at the same time also changes base current.
because the base current is changed and the transistor is in linear/active region, that also changes the collector current and also potential in point A.

Please correct me if I am wrong. I would like to make this circuit but before I make it I would like to know if I am understanding it correctly!

Thank you in advance.

EDIT: I have made a circuit on a breadboard and measured voltage across microphone to be around 2.9V. Apparently my knowledge about electret microphone is a problem :) Potential at point A was 0.2V and in point B around 0.7V.
I will experiment further and post what I found out, maybe it will help someone else :)


texts:
I'm planning to use a set of daisy chained 74HC595s to control a set of 108 mosfets, 3 of them are geographically in the same area (couple of mm apart) and for the sake of modularity should each use their own register. That would mean I will use 36 74HC595s and chain them together. They are all on one board and the distance between the groups of 3 is around 2-5cm.

Questions:

How do I calculate the minimum time it takes to to write the whole set of serial instructions to 36 74HC595? I figured I need to add clock rise times and propagation times, but I'm not sure exactly how.
Is there anything else I need to add for this to work? Do I need additonal buffers or delay components? There's gonna be some noise made by high currents (through the mosfet).


texts: Why is this projection in a draftsman document incomplete?

texts:
I am working on generating a draftsman document. 3 components have a line going through them, as shown below, as if the footprint outline is incomplete.
The draftsman document is using the BodyProjectionSimple as the geometry source for the components, and the line is still there when I use BodyProjection. Below I have included the 3d View of the same component, as well as a picture of the layer stack.
The footprint was generated using Altium's built in IPC Compliant Footprint Wizard.

Any clue what might be causing this to happen? or how I can go about fixing it?


texts: How to increase voltage rise time for micro controller?

texts:
I am working with a micro controller which has this written in its data sheet:

"A step increase in supply voltage of 300 mV or more, with rise time of 300 ms or less, within the valid supply range, may result in a system reset."

In my application, the supply voltage may in the worst case scenario rise from 2v to 3v, how can I prolong this rise time?

I have looked at an RC circuit which seems like it may do the job, however I don't want to add too much series resistance to the supply voltage.

If anyone has any suggestions it would be greatly appreciated!


texts: wrong bode plot of closed -loop converter

texts:
I made a simulation of a closed-loop buck converter with simplis.
the basic parameters of the open-loop circuit are listed below:
\$V_g=12V,V_{out}=5V\$
\$D=0.52\$
\$C=100\mu F,ESR=5m\Omega; L=30\mu H,ESR=5m\Omega\$
Then I made the compensation of the open-loop circuit.
The closed-loop circuit is this:

I derived the both the ideal tf of the buck converter and the closed-loop tf.
Using matlab, I got the ideal closed-loop bode like this
It is weird that when I build up the compensation circuit in simplis, the bode plot totally went wrong.
Neither the gain graph nor the phase graph suits the ideal bode plot of matlab.

However the transient result looks good.

I think the derivation and the result of matlab are correct and there should be some mistakes in simplis simulation. I really appreciate your help if you can explain it for me.


texts: Power supply failing when turned on, but doesn't fail if voltage is slowly applied?

texts:
I have a dual output PSU that take 9-36VDC in, and outputs +/-12V. This PSU is powered by my DC bench supply. This PSU is powering 2 amplifiers for signal processing, and a HV supply. The HV supply takes in 0-12V, and outputs 0-1000V. I need 900V, so I put a linear voltage regulator in to step down the 12V to 9V.
When powered separately, the LVR/HV supply function properly, and I get the 900V output. Same with the 2 amplifiers. However, when all are powered together, the PSU enters its short-protection mode, and will not power on. I noticed that if I start my DC bench supply at 0V, and slowly go up to the 24V I need, the PSU powers on and everything works properly. If I power off the bench supply while it is set at 24V, then turn it back on, the short-protection of the PSU engages.
The data sheet for this PSU states it has a max load of 298 mA before the short-protection engages. However, when all components are powered on and functioning properly, my bench supply reads only 150mA at 24V. More interesting is if I ramp up the bench supply from 0V to ~10V, it reads 400mA of current! Shouldn't the PSU shut off?
I would like to simply turn the bench supply on/off while set at 24V. Is there some way to automate the slow 0V to 24V ramp up via some circuit? Any advice would be greatly appreciated.


texts:
I'm investigating battery monitors and I'm looking at TI's BQ76930 to take care of an 8 cell 24V LiIon. They provide the datasheet for their evaluation module (PDF warning) which includes the board schematic on Page 29. What I'm trying to figure out is the shunt regulators they've put in between the cells, which stack on top of each other. Here it is redrawn:

If the design works properly, the PFET should kick on and drain the overcharged cell into the 100ohm load. I don't see how their design can do that. Supposing that D1 can be reverse biased, there's nowhere for the current to go; the ADC pin is high impedance and the TVS diodes shouldn't kick in under normal operation. From what it looks like here, the PFET will always be firmly off.

Secondly, 5.6V is crazy high for a LiIon and the battery will have long since exploded.

So, what's up with TI's design here?


texts:
Could you explain to me the differences between a tachometer and a tachogenerator? For example, is a tachometer just a  tachogenerator attached to a dial to display RPM rather than voltage or are they two completely different devices?

Thank you.


texts:
So I have "built" a voltage sensor for an Arduino by using two resistors. The current setup is as shown in the schismatic and the Arduino pins are only 5V tolerant.

The accuracy of the sensor is alright when there is little current draw on the battery. But when the battery is powering motors, the voltage tends to jump around a lot. The first thing I will do to this setup is to increase the value of R2 from 100K to 330K. This will lower the max voltage from 55V to 20V, but I should never be pushing more than 20V anyway. That will increase the resolution at which I can measure the battery, but I believe to get very accurate data that I should add smoothing capacitors somewhere in the circuit to make sure the voltage doesn't "jump" around as much. Any thoughts?

EDIT:
So after hearing some recommendations in this post I decided to run some tests. I decided to switch out the 1M and 100K resistor with a 10K and 1K respectively. I then used a fully charged 2 cell lipo battery and ran 4 motors on it continuously for about 25 minutes until that battery ran out of juice. The data was recorded in the Serial Mointor and graphed in Excel. I did not start the motors until 20 seconds have passed for recording. Here are my findings.

As you can see from the graphs, the data in the first two is all over the place. The "stability" of the signal being recorded does not seem to be dependent on the impedance of that signal (At least for the Atmega32u4). Averaging 20 samples at a time did show usable data that seems consistent with other lipo battery discharge curves.

The following graphs stability could be improved by lowering the ratio of R1 and R2, and I suspect adding a filtering Cap across R2 would also increase accuracy of the measurement.


texts:
I want to create a LED Matrix circuit with 74HC595 shift register and 2n7000 mosfet.

The schematic is as follows. I have mentioned voltage levels at various points.

All the control signals of 74HC595 IC are connected to PIC18 mcu. and gate pin of mosfets (CON_RED and CON_YELLOW) is also connected to mcu's GPIO pin. i have tested the shifting operation of 74HC595 and it is working properly.

The Problem: To turn ON yellow LED and to keep red LED OFF, Positive voltage is provided at anode of both LEDs. The mosfet attached to yellow LED (Q2) is turned ON by providing 2.55 v at its gate and the mosfet attached to red LED (Q3) is kept OFF by providing 0~0.01 V to its gate. Yellow LED glows as expected, but red LED also glows with very low brightness (visible by observation).

I thought one solution by providing pull-up resistors at kethod of both LEDs. but, when both LEDs required to turn OFF, the voltage at pin 15 of 74hc595 should be kept at 0 voltage. In that case, the LEDs are in reverse bias mode and this might damage the LEDs.
(Actually i have tried this method and many LEDs in matrix were damaged)

Any solution to this problem ?


texts: Oblique incidence over a stratified medium - the transfer matrix is not unitary?

texts:
As you've read on the title, my problem is about an oblique incidence problem over a stratified electrical medium.
I've made a quick sketch with the incidence on the first layer. Let's suppose that I have a TE incidence, even if it is not important to my question.

I tried to solve the problem using the transfer matrices. For the first interface between layer 1 and 2, for example, I have:
$$
\left[\begin{matrix}
 E_1^+ \\ E_1^-
\end{matrix}\right]
= \underbrace{\frac{1}{t_{12}}\left[ \begin{matrix} 1 & r_{12} \\ r_{12} & 1 \end{matrix} \right]}_{M_{12}} \left[\begin{matrix}
 E_2^+ \\ E_2^-
\end{matrix}\right]
$$
with
$$r_{12}, t_{12} \in \mathbb{C} \quad \mathrm{and} \quad M_{12}\in \mathbb{C}^{2 \times 2}$$
The coefficients \$t_{12} \$ and \$r_{12}\$ are computed using the Fresnel equations.
Obviously before I can add a second interface matrix, I should add a propagation matrix:
$$
P_2 = \left[
\begin{matrix} e^{-j \beta_2 \ell_2} & 0 \\ 0 &  e^{j \beta_2 \ell_2} \end{matrix}
\right]
$$
Where \$\beta_2 \$is the propagation constant in layer 2 in the axis orthogonal to the interfaces and \$l_2\$ is the thickness of layer 2.
For N layers I have:
$$
\left[\begin{matrix}
 E_1^+ \\ E_1^-
\end{matrix}\right] = \underbrace{M_{12} P_2 M_{23} P_3 \cdots M_{N-1, N}}_{M_\mathrm{tot}}
\left[\begin{matrix}
 E_N^+ \\ E_N^-
\end{matrix}\right]
$$
I numerically computed:
$$
M_\mathrm{tot} = \left[ \begin{matrix} m_{11} & m_{12} \\ m_{21} & m_{22} \end{matrix} \right] = \left[ \begin{matrix} 1/t & r/t \\ r/t & 1/r \end{matrix} \right] \qquad \mathrm{and \ I \ plotted \ how} \ |r|^2= \left|\frac{m_{21}}{m_{11}}\right|^2 \ \mathrm{ varies \ with} \ \theta
$$
Where \$|r|^2\$ is the reflection coefficient.
This gave me nonsense results: I have for some angles a reflection coefficient greater than one.
I think that the main problem is that the propagation matrices are not unitary.
If I compute the determinant for \$M_{12}\$, I get:
$$
\det(M_{12}) = \frac{1}{t_{12}^2}(1-r_{12}^2),
$$
Using the definition \$t = 1+r\$, then:
$$
\det(M_{12}) = \frac{1-r_{12}^2}{(1+r_{12})^2} = \frac{1-r_{12}}{1+r_{12}} = \frac{1-(t_{12}-1)}{t_{12}} = \frac{2}{t_{12}}-1.
$$
This means that the determinant of these matrices can be also greater than one with certain angles.
I am doing something wrong, but I can't see it.
I've also thought to use the scattering coefficient S21 instead of transmissivity t, but the transfer matrix requires the use of Fresnel coefficients.


texts: I2C Level translator 5 V to 1.8 V using MOSFET, output look weird

texts:
I am designing an I2C level translator using MOSFET. I am using BSS138 DATA SHEET. My clock can go up to 1 MHz. The output is not coming properly for fast mode plus (CLK = 1 MHz, RISE TIME = FALL TIME = 120 ns). The 1.8 V output is peaking to 2.1 V and slowly settles to 1.8 V.Please find the attached circuit diagram and waveforms. Is it a pull-up resistor issue?
May I know what is wrong with my circuit?


texts: PIC MCU: Reliably Capture and Measure Drum Transients with ADC

texts:
I'm seeking advice to help my circuit/code/mcu work more reliably and accurately. What I've got right now is almost there, but I'm just missing the know-how to get me consistent readings. I've tried to paint a good picture of what I'm doing and why so bear with me to explain.
The goal of my design is really straightforward, it's just to capture the volume of a drum. I'm doing this through a Electret mic, into a preamp, into the ADC onboard of the PIC18F2620. My goal in capturing the volume of drums is to display the loudest reading over a given sampling period, so the user knows how loud they're playing. The sampling period is set to about 500ms, which gives the user time to read it properly.
Where it gets a little complicated and where I'm struggling is trying to capture the loudest point of the transients of a drum hit. The problem with these transients is that they're come and gone so fast, that sometimes when I give it a good whack, it displays a value no-where near how loud it should have been. Below is what the transient of a drum looks like, showing how brief that loudest point is.

My instinct is that then I need more samples per second, but then I wonder if having less but longer samples would solve this problem (I just don't know).
Ok, hopefully I've been able to paint a picture of the context, here's how I've been doing it.
It all begins with an electret condenser capsule (rated up to 130dB SPL) and the preamp design from this answer, except I'm using the LMC6484IMX. I've included this detail in case you can see this preamp isn't fit for what I'm trying to do.
The output of that then feeds into the ADC input of my PIC18F2620. I decided to run the whole ADC workflow with interrupts to avoid polling and wasting time.
It begins with running the sampling as a high priority interrupt, by grabbing and keeping the largest sample:
void __interrupt(high_priority) ISRs(void)
{
    if(PIR1bits.ADIF == 1)
    {
        ADC = (ADRESH << 8) | (ADRESL);     // Get ADC value from registers
        if(ADC > ADCpeak)                   // Check if volume result is greater than existing temp
        {
            ADCpeak = ADC;                  // If it is then make that new temp peak
        }
        else{}                              // If it isn't then do nothing
        ADCON0bits.GODONE = 1;              // Start ADC again
        PIR1bits.ADIF = 0;                  // Clear interrupt flag
    }
}

Then, once timer 0 runs out, the rest is managed as a low priority interrupt. It's designed to run at the rate of user display refresh (~500ms). I plan to process the results through formulas, so am happy for it to be interrupted by more sampling/other high priority interrupts while the maths churns in the background:
void __interrupt(low_priority) adcISR(void)
{
    if(INTCONbits.TMR0IF == 1)
    {
        float adcr = (float)((ADCpeak*100)/1024);    // Convert ADC reading to percentage
        volume = adcr;                               // New volume int ready for displaying
        ADCpeak = 0;                                 // Reset ADC peak
        TMR0 = 61618;                                // Reload timer
        INTCONbits.TMR0IF = 0;                       // Clear flag
    }
}

Right now, I have been setting the ADC acquisition time to 12Tad and the conversion clock to Fosc/8, and it's been working ok. Clock speed is 8Mhz too. As previously mentioned though, it still sometimes misses loud hits, and hits roughly the same volume are sometimes displayed as vastly different numbers.
I know there's things I can do to make it capture samples more accurately and faster, but I don't know how. I guess ideally, I'm just looking for someone to tell me my kind of preamp isn't quick enough, or I should change my aquisition time etc...
Would greatly appreciate all input/suggestions.


texts: Bidirectional logic level converter with voltage regulator and 5 volt microcontroller

texts: I have to use an N-channel enhancement mode Mosfet based Bidirectional logic level converter along with a fixed 3.3 voltage regulator along with 5 volt micro controller. I am powering the low voltage side from 3.3 volt regulator and high voltage side from the 5 volt supply of micro controller board. I am not able to drive the 3.3 volt I2C sensor with this arrangement. I am getting strange results some times i get 3.3 volt from level shifter and some times i get 1.8 volt on the level shifter chanels on changing the loads.


texts:
what book titles would you recommend to get started with FPGAs and VHDL?

edit
I noticed that a few of the recommended books date back from 1996. I can imagine that the devices referred to will be seriously outdated, but has VHDL also much evolved since?


texts: Retrieving samples from an FPGA using Ethernet

texts:
I have a Spartan 3 FPGA for implementing a specific kind of digital modulation. I read the output signal by UART and RS232 but the rate is too slow for following high frequency signals.

It was suggested that I could read the output using Ethernet. How can I read the output from my Spartan 3 by Ethernet?


texts: Is there any way to modify the output voltage of a laptop adapter from 18.5V to say 7V or 13.6V?

texts: I have an old 18.6V 6.5A adapter from an old HP docking station. I tried to open the adapter and saw an small pot inside it, tried turning it but the out just remained constant and there was no change. How can I change the output with minimal components. I had previously tried with an LM2596 Buck converter to step down the voltage unfortunately I accidentally shorted the leads and it blew up though it did work for a while, also since the input was capable of upto 6.5A if the current draw exceeded @A it could heat up pretty quic. So, my first option would be to get a similar buck conv with a 75W or 100W capability(around 5A) or I need to get the above mentioned fixed voltage or  a variable one by adding say a pot? Also is it safe? I've seen people mentioning its dangerous trying to modify ATX PSUs.


texts: Circuit changes, what is the input high and low given when the circuit is lit and not!

texts:
One change in the circuit, the R1 is not 4300 ohms but instead 4700 ohms.
The voltmeter is the input into the raspberry pi GPIO board. What would be the input (voltage) when light gets to the phototransistor and when not?
PT0 is the ir phototransistor (my real circuit has no base, only two leads.)
For any more information please ask for clarification. Thanks


texts:
Common through-hole power semiconductor devices, like TO-220 and TO-247, can be mounted to a heatsink by running a screw through the hole in the device. However, on TO-220 the hole is often electrically connected to one pins of the device. TO-247 often isolates the hole from the device backplate, but this isolation is not guaranteed, and often fails below 1500VDC. I frequently need 3kV withstands.

We often use clips to hold the device to the sink, which can help the problem, but makes construction more problematic, and may still have insulation problems. Shoulder washers are also used occasionally, but again, that makes construction more complex. Life would be simpler if we could use insulated screws. The only ones I'm aware of are nylon, and good luck getting any torque out of those!

Are there any screws (M3, M4, #6, #8, or similar) which are made of an insulating material, but which still have sufficient mechanical strength to hold a device to a heatsink? Especially in high-vibration environments?


texts: I purchased a dayton 1/3 hp 1725rpm and am wondering how to use it with a VFD. It says continuious as duty. I only have 220 at my house so I am wondering if i can set it up with a VFD and use it to make a stone cutter and polisher out of it. What type of VFD will work. I see that there are many to chose from


texts: Unclear RF Schematic Reference for Power Amplifier Connection and Matching Network Properties

texts:
Background
I'm trying to design a device with an STM32WL series MCU using the UFBGA-73 package. There is only one reference circuit given for the RF portion of the MCU in an application note (pg. 6) and the examples given in the document use the same package, so the pins are identical.
There are 4 RF signal I/O pins, 2 for RX and 2 for TX:

RFI_P: Positive differential input (RX+, 100Ω).
RFI_N: Negative differential input (RX-, 100Ω).
RFO_HP: Low power output (TX, 50Ω).
RFO_LP: High power output (TX, 50Ω).

There is an internal "power amplifier" supplying from pin VR_PA which itself is supplied from external input to the VDDPA pin. The external supply for VDDPA is required to be full voltage (e.g. 3.3V) when using high power (RFO_HP) but when using low power VDDPA must be connected to a different supply (SMPS feedback, 1.55V).
The VR_PA pin appears to be connected via an "inductor" (no value ever given in any document) to either RFO_HP or RFO_LP depending on the chosen TX power level, but another application note (pg. 8) shows a configuration for using both power levels is shown in this image:

The sole reference image of the schematic for the RF circuit used in an unreleased MB1552B reference board can be seen below. This board uses an RF switch for choosing either TX or RX to the antenna connector from an external input and is configured for using RFO_HP but can be switched to RFO_LP via "permanent" solder connections, assumed to be for testing purposes.

Questions
I have two issues, one about the power amplifier connection to the TX line and one about the general content of the reference circuit.
1. Component Function
Most of the components don't have values, so it feels like an educated guessing game to figure out what they're for. I've included a rough interpretation of what I think they might be for.

2. PA connection to TX (choke?)
I plan to target 915 MHz operation, so if the inductor L3 in the reference is acting as a choke to block noise from the PA I should theoretically be able to use the same inductor for both of the two transmission lines because the blocking properties would not be related to power level (assuming it can handle the power). I am using an RF switch for selecting the power level as shown below, using the same signal as changing the two other switches (i.e. control input at each "LP" into a switch in the image). Can I use a single inductor to connect the currently active PA to the currently active RFO?.
As a side note I have seen guidelines for the choke impedance to be 10x the impedance to 10x50 = 500Ω, please let me know if this is appropriate/correct.


texts:
I'm new to electronics and I don't fully understand how short circuiting works. For example I have this battery LiMn 3000mAh, it states:

 Nominal Voltage: 3.6V
 Standard Charge: 2A
 Continuous discharge current: 20A

First thing I don't understand is if I connect a wire between the positive and negative terminal, it would create a short circuit, correct?  Can the battery blow up?

My goal is to simply make a hot wire, but I don't understand how will the wire 'determinate' how much current it needs or will it draw full 2A or even 20A from the battery?

If I use resistors, what's their purpose? to protect the battery from all the 'unused' electrons or to protect the wire?

What about taser gun? is it 'short circuiting' and what effect does it have on the power source?


texts:
I've started studying assembly, and I've been tryign to solve this problem:

For the following C statement, what is the corresponding MIPS assembly
code? Assume that the variables f, g, h, i, and j are assigned to
registers $s0, $s1, $s2, $s3, and $s4, respectively. Assume that the
base address of the arrays A and B are in registers $s6 and $s7,
respectively:
B[8] = A[i−j];

Source: Computer Organization and Design 5th Edition.
So, I did this:
sub $t0, $s3, $s4 // temp = i - j
sll $t0, $t0, 2   // temp = temp*2^2= 4*temp
add $t0, $t0, $s6 // temp = &A[i-j]
lw  $t1, 0($t0) //   t1 = temp
sw $t1, 32 ($s7) // B[8] = t1 = temp = A[i-j]

But looking at the book's solution manual to verify that my answer is correct, I got this:
sub $t0, $s3, $s4
add $t0, $s6, $t0
lw $t1, 16($t0)
sw $t1, 32($s7)

I am confused. How did they come up with the third statement lw $t1, 16($t0) ?


texts: Is a ground/common needed for proper CAN bus communication?

texts:
Since CAN Bus is a differential signalling system, what is the significance of GND/COM signal? Can I get by without it?

I've got a very simple 2-node system that has some weird happenings going on. (see here for that issue, if you're interested) The two nodes are my device and a USB-CAN monitor; both have 120ohm termination resistors, and the wire run between them is <1m.

I just remembered that in my earlier tests I only had the CAN_H and CAN_L signals connected between the nodes; I did not have anything connecting the CAN_COM of my device to the ground pin on the USB-CAN monitor.

A (the?) point of differential signaling is to be much less (not?) effected by common mode noise. So by not having the ground connected, I would guess we lose the absolute reference for CAN_H and CAN_L... but does that make a difference?


texts: How to tell the lumen output of these LED's

texts:
I'm trying to build a light fixture for my aquarium, but I'm having difficulty understanding the various way manufacturers represent light output.

I'm trying to compare the output of CREEXPE-ROY-3 and CREEXTE-ROY-3 and I am just completely lost.

How can I figure out the lumen output of these LEDs? Assume they are both driven at 350mA (per LED).


texts: SMD capacitor package size and high frequency performance

texts:
I am designing a circuit with a Spartan6 FPGA and the documentation for the FPGA specifies 4.7uF (0805) and 0.47uF (0402) capacitors for decoupling. As I really do not want to solder 0402 capacitors if I can avoid that, I would like to use 0805 or 1210 size capacitors for this. Would their performance at high frequencies be different from those that have smaller packages?

The max in/out frequency is ~300MHz


texts: Can the volts and\or amps in a repalcement DC power cord vary without problems?

texts:
In general I've always wondered about this but now I have lost the DC power cord to my portable speakers.  The manufacture does not have a replacement or at least one I can find.  The specs are 12.5 V --- 2.5a.

Questions:

1) If I buy a generic replacement which of the voltage and amps need to match and\or if I can't get an exact match how can I vary the volts\amps ... which can I go higher or lower on.

So for example would 12 volts and 5 amps work, be harmful, or not work\not work well?

2) Do voltage\amps have some standardization on the input adapter into the device?  That is, will I also need to ensure a generic replacement also matches the portable speakers or should it just match if the voltage\amps match?

GB

p.s. I think this is the stack exchange I should be  posting this to if not please advise.


texts: RC circuit and HEX SCHMITT-TRIGGER INVERTERS

texts:
I have a complex circuit, and I am dealing with a problem that appears. I have a RC circuit followed by
a 7414 Trigger inverter. My input voltage is 90mV and after the simulation the output looks like this.(see first picture). And the circuit (see last picture.). So the question is why my Output at C27 isn't almost at the input voltage value like it should?


texts: Not seeing set_address packet using USBTrace

texts:
I'm currently exploring the wonderous world of the USB Stack. I'm using a PIC18F2550 and the USB IO example available at www.moty22.co.uk. The code works as expected, but when using USBTrace (or any other USB sniffer) I fail to see the set_address setup packet. I see it ask for each descriptor and receive them, but nowhere in the log do I see a setup packet to set the address.

I fail to see this packet even when using other usb devices like my mouse, keyboard, and flash drives. Which got me to thinking if I would even be able to see these packets using USBTrace? Or would I need to be using an oscilloscope and debugging at the bus level?

I can post log output from USBTrace if neccessary, but I don't think it'll help much.


texts: What does a 5.5 VDC rating on a super capacitor imply?

texts:
I'm confused as to what a 5.5 VDC rating on super capacitor implies.  Is this with respect to 5.5 VDC tolerance, impedance, or feedthrough?

You can find the product details at:
https://www.mouser.com/ProductDetail/80-FC0H105ZFTBR44-SS

Thanks.


texts: Differential gain of an op-amp and feedback

texts:
In an op-amp, we know from basic electronic courses that

vo = A(v1 - v2)

Assuming large differential gain and finite output, we get that (v1-v2) is very very small, ideally zero.

In a university course I'm studying what's inside of an op-amp. The first stage is a differential stage (2 mosfets with sources in common and a current generator under them). We're studying it by using small signal analysis, I suppose because in future there will be negative feedback and thus a very very small differential input.

Now the question, assuming that the following reasoning is correct: negative feedback reduces the differential input (it becomes a small signal) and the small signal differential gain coincides with the A gain of basic electronic courses (that "A" we use when op-amp is simply a 3 terminal object). But when the circuit "switches on", feedback is still not working, I mean: in the exact moment the circuit switches on, some signal (not necessarily a small signal) arrives to inverting and non-inverting terminals of the op-amp; the op-amp amplifies this signal (the signal is not yet small, so the gain is not yet A) and only now some output signal is brought to the input, thus making the differential input small. Which is the expression of the gain when the signal is not yet small?


texts: github example analisys of clock definitions for efr32fg14

texts:
in the link bellow we have I2C example  of efr32.
There are 3 components that i am having trouble to seehow they work together.
The only clock diagram i found is in page 281 of reference manual shown bellow.
i cant see where the CORE_FREQUENCY   goes?
why we enable HFLE LFXO I2c gpio ?
how its all allowing the final line i2cInit.freq = I2C_FREQ_FAST_MAX
I cant see the big picture behind it.
I'll be glad to have some intuition i could use to understand this mechanism.
Thanks.
https://github.com/SiliconLabs/peripheral_examples/blob/master/series1/i2c/i2c/src/main_efr.c
https://www.silabs.com/documents/public/reference-manuals/efr32xg14-rm.pdf
1.
#define CORE_FREQUENCY              14000000
2.
// Enabling clock to the I2C, GPIO, LE
CMU_ClockEnable(cmuClock_I2C0, true);
CMU_ClockEnable(cmuClock_GPIO, true);
CMU_ClockEnable(cmuClock_HFLE, true);
// Starting LFXO and waiting until it is stable
CMU_OscillatorEnable(cmuOsc_LFXO, true, true);
3.
i2cInit.freq = I2C_FREQ_FAST_MAX


texts: Delivered energy of a RLC circuit - proof

texts:
I have an RLC circuit with two resistances \$R \$ and \$R_i \$ in serie.
On my book there is the expression of the stored energy (\$C \$ capacitance, \$E \$ voltage on the capacitor):

$$W_s = \frac{1}{2} C E^2$$

and the delivered energy:

$$W_d = W_s \frac{R}{R+R_i}$$

How can I get the latter expression?

Thank you for your time.


texts:
I have following truth Table :

F(w,x,y,z) = Σ(0,2,5,7,8,10,12,13,14);

    Truth Table
    W   X   Y   Z   F
0   0   0   0   0   1
1   0   0   0   1   0
2   0   0   1   0   1
3   0   0   1   1   0
4   0   1   0   0   0
5   0   1   0   1   1
6   0   1   1   0   0
7   0   1   1   1   1
8   1   0   0   0   1
9   1   0   0   1   0
10  1   0   1   0   1
11  1   0   1   1   0
12  1   1   0   0   1
13  1   1   0   1   1
14  1   1   1   0   1
15  1   1   1   1   0

With the following Karnaugh Map

  W  X
Y
Z

I'm able to reduce this to the following SOP

 ~x~z + w~z + x~yz + ~wxy

My Professor explicitly told me that this function can be reduced to 2 SOP terms, but he doesn't have the time to demonstrate this as finals start this week.

I want to trust my professor on this, but I do not see how this can be reduced any more than it is.

How to prove that this can be reduced to 2 terms or prove that it can not be reduced to less than 4 ?


texts: Is it reasonable for a potentiometer to have a minimum of 1.3Ω?

texts:
I purchased a 25Ω linear potentiometer, and found that the minimum resistance is 1.3Ω 0.9Ω.  I expected that the minimum would be closer to 0Ω.  Is this typical?  Should I return the potentiometer as faulty?  Is there a spec for this?

EDIT: I originally said 1.3Ω, but several people correctly guessed that I did not account for the meter's resistance of 0.4Ω.


texts: Minimum connections needed between stm32 MCU and the st-link programmer?

texts:
My MCU is stm32L432kc. I've concluded that we need a minimum of 4 connections: SWCLK, SWIO, vcc and gnd. Can someone from here confirm that?

And another question is I'm confused how to connect the Vdda/Vref+ pin 5 and the NRST pin4. Do I have to connect them? I have the schematic of nucleo board for my MCU attached. Should I just connect them the same way?


texts: Does frequency need to be an integer in order for a signal to be periodic?

texts:
Please help me understand periodicity. Why can \$T=\frac{1}{3}\$ be periodic but \$T=\frac{1}{\sqrt{3}}\$ be aperiodic?

For example:

$$\cos(2\pi\times 3\times n) \Rightarrow \mathrm{periodic}$$

$$\cos(2\pi\times\sqrt{3}\times n) \Rightarrow \mathrm{aperiodic}$$

I understand that in order for a signal to be periodic, \$f=\frac{k}{n}\$ (frequency must be rational), but why is \$f=\frac{\sqrt{3}}{1}\$ not considered to be periodic?

Is it because \$\sqrt{3}=1.73205...\$ is not an integer?


texts: Is this a correct way to do a low voltage cutoff for motorcycle use? (Zener diode + relay)

texts:
I want to design an electrical component that I would connect to my motorcycle battery. As I do not want it to fully discharge my battery and I want it to run only when my motorcycle alternator is "ON", I want to implement an automatic cutoff when the voltage is below 14V.
In order to do it I use a transistor, a 14V Zener diode and a relay.
Is this a good way to do it? Will the circuit will be completely "off" when the voltage is below 14V (no drain on the battery?)


texts:
I intend to use an STM32F401RE (on a nucleo board) to capture some time based data.

I am new to ARM and have an 8bit uC (AVR) background. I have a toolchain set up (using gcc as part of AC6 SW4STM32) and have used the HAL Library provided by ST to do simple binking LEDs etc.

I have been importing CubeMX projects into SW4STM32.

I am looking at measuring voltage at 10kS/s for a period if 3 seconds. I want to use the full 12bit ADC.

I would be great full if anyone could help me with the high level code structure before I invest the time learning the functions etc and get bogged down in the coding...

I have something like the below in my head, the interupt being triggered every time a sample is required...

ISR every 1/10000s
    if measure > 0
        read ADC and ouptut to UART
        measure++
        if measure == 30000
            measure = 0

main
    loop forever
        if measure==0
            if start_button == 1
                measure = 1

How does this look as a starting point? Also, what is the general opinion on the use of libraries? In 8bit a 'library' is little more than some labels for registers, they seem much more commonly used in ARM... Should I  just accept using the HAL from ST, try and restrict to the CMSIS or really try and continue to poke memory as in 8bit?

Any guidance is greatly received...


texts: emitter follower biased by input signal?

texts:
For the standard emitter follower you typically need input coupling capacitors and a DC bias of roughly half the supply voltage however what if the input signal itself swings around half the supply voltage?

e.g if the previous stage to an emitter follower is a standard op amp non-inverting amp with a split supply (+12V,-12V) with the input referenced to centre point but the succeeding emitter follower is referenced to -12V (i.e +24V, 0V),
so The op amp output is referenced to ''+12v'' relative to the emitter follower?
Could this replace the input coupling cap and resistor biasing or would it not work?

Load would be a pair of headphones (50 to 300 ohm)

example of circuit is attached below

Differential emitter follower?

Inverting amp?


texts: Can I use the 1.8 inch TFT LCD SD slot for other purposes other than displaying images on the display? For example, storing text files on that SD card (that's on the display's SD slot)? Can I use that display SD card slot like a normal SD card slot (no images, no bitmaps). Something like this:


texts: Creating an isolated power supply to prevent effects of lightning

texts:
Transformers isolate the load completely from the primary power source. Does that mean that I can connect two or more transformers one after the other and expect my Linear Power Supply to have better safety than having the isolation of one transformer?

For example, lets assume I need 12V AC out. The situation I am trying to imagine here is having 230V/50V and 50V/12V transformers.

Would this make my system more immune to lightning?

Are there better ways of doing the same?


texts: timing constraint for bus synchronizer circuits

texts:
I've a bus synchronizer circuit for passing a wide register across clock domains.

I'll provide a simplified description, omitting asynchronous reset logic.

The data is generated on one clock.  Updates are many (at least a dozen) clock edges apart:

PROCESS (src_clk)
BEGIN
   IF RISING_EDGE(clock) THEN
      IF computation_done THEN
          data <= computation;
          ready_spin <= NOT ready_spin;
      END IF;
   END IF;
END PROCESS;

The control signal for fresh data, which is NRZI encoded (so a valid word on the bus corresponds to a transition on the control signal).  The control signal passes through a DFF chain acting as a synchronizer.

PROCESS (dest_clk)
BEGIN
   IF RISING_EDGE(dest_clk) THEN
      ready_spin_q3 <= ready_spin_q2;
      ready_spin_q2 <= ready_spin_q1;
      ready_spin_q1 <= ready_spin;
   END IF;
END PROCESS;

The synchronizer circuit introduces a short delay, which provides plenty of time for the data bus to stabilize; the data bus is sampled directly without a risk of metastability:

PROCESS (dest_clk)
BEGIN
   IF RISING_EDGE(dest_clk) THEN
      IF ready_spin_q3 /= ready_spin_q2 THEN
         rx_data <= data;
      END IF;
   END IF;
END PROCESS;

This compiles, and works well when synthesized into a Cyclone II FPGA.  However, TimeQuest reports setup and hold time violations, because it doesn't recognize the synchronizer.  Worse, the Quartus manual says

  Focus on improving the paths that show the worst slack. The Fitter works hardest on
  paths with the worst slack. If you fix these paths, the Fitter might be able to improve
  the other failing timing paths in the design.

So I want to add the right timing constraints to my project so that Quartus will spend its Fitter effort on other areas of the design.

I'm pretty sure that set_multicycle_path is the proper SDC (Synopsis Design Constraint) command, since the data lines will have multiple cycles of the destination clock to stabilize, but I can't find any complete examples using this command to describe clock domain crossing logic.

I'd really appreciate some guidance on writing SDC timing constraints for synchronizers.  If you see a problem with this approach, please also let me know that.

Clock detail:

External clock generator: Two channels, refclk = 20 MHz, refclk2 = refclk/2 (10 MHz, and related).

Altera PLL: src_clk = refclk * 9/5 = 36 MHz

Altera PLL: dest_clk = refclk2 * 10 = 100 MHz

I also have data going the other direction, with 100 MHz src_clk and 36 MHz dest_clk.

TL;DR: What are the correct SDC timing constraints for the above code?


texts:
I'm looking for reference or manufacturer of such THT Board connector. It comes from Automotive module.
Note the PIN-Holes are elongated:


texts: How do I implement Lights-Out game using logic gates or flip flops?

texts:
First, for those unfamiliar with the game, this is how the game works,

The goal of the game is to turn off all the lights, hence called "Lights Out", and each press of the button/light inverses its state as well as its north/south/east/west adjacent neighbors, and that's pretty much it.

Now, what I could think of is by using SR flip-flops, or JK flip flops. This is due to its ability to act as storage element (the initial state and next state). But I can't seem to think of ways to actually implement them.

Another idea is that each set of button and its adjacent (NSEW)button/lights will have its own truth table, like this:

but, is it possible to have the input variables be the same as the output variables? Are there any other ways to do this?


texts:
I am designing a relay circuit with MOC3021 and BT136 from this datasheet.

I know the importance of snubber circut(39ohm resistance and 0.01uf capacitor). But I have no idea why 360,470 ohm resistance and 0.05uF cap is required (may be low pass filter). what its importance ?
Any article/blog is also helpful.
PS: I refereed many blogs but they are only explaining the importance of snubber circuit


texts: Confusion regarding the Q point of a transistor

texts:
Many standard text books define the Q point as follows :

"Q point or the operating point of a device, also known as a bias point, or quiescent point is the steady-state DC voltage or current at a specified terminal of an active device such as a diode or transistor with no input signal applied".

Now let me explain why it is confusing to me.
As we know the signal is supposed to apply at the base of the transistor, "with no input signal applied" means the base voltage is zero at some point, but that means the transistor is off at that point and as a consequence, there will not any collector current, missing something?


texts:
I am trying to understand the construction of an RGB TFT LCD that has brightness control in it.

I could not understand how does the TFT color LCD pixels glow? Does each of the pixel has its own light that it emits just like an LED or is it that there is a backlight bulb behind the TFT LCD screen and that bulb gives out the light that is passed through the transparent pixels while blocked by the opaque pixels?

If this is the case then how does the colors come on the TFT LCD? Are the colors due to the backlight bulb or the colors are in each of the individual pixels?

Edit:
For example this LCD:
https://www.alibaba.com/product-detail/High-brightness-1000cd-m2-5-inch_60312509314.html

Is there a single backlight bulb behind its screen?


texts: I have been using the schematic of MCB1700 Evaluation board in my customized ARM Powered board. I planned to use RS 232 communication on my board. When I go through the schematic, I am stuck with the  #4 pin of DB9 connector which is a DTR Pin for RS 232. My confusion is, that #4 pin is connected to NPN transistor as given in the image. Why is that pin used there? Thanks in advance for the help!


texts: All power factor improvment controller has a setting c/k ratio. Their manual says it is the lowest step of capacitor bank. It controls switching threshold. But how what is its significance?


texts:
Context:

I want to extend a wire that hooks up to the power momentary switch of a PC ( which has a built in LED). This extension will be about 10 meters long. While this distance might be that long to matter, I want to make sure that there is no voltage drop so I have read that thickening the wire will help.

A cat5 cable has 6 wires. I'd like to use this cable as it looks nicer and is easier to route.

Question:

Does soldering three of the cat5 cables to each terminal on the momentary switch effectively thicken the wire (thus preventing a drop in voltage)? Or am I misled in thinking this would work?

More information on the switch:
-The switch is rated up to 3A/250VAC, but the LED is rated for 1.8-2.8V, if you want the switch and LED to work under 12V, you need to add the resistor


texts: Control LED states (on/off/brightness) through multiple clicks of push button

texts:
I would like to learn how to build a standalone circuit that allows me to flick through several LED states (on/high/low/off, etc.) without something like an Arduino.
I'm new to electronics and have decided to learn by examining simple, existing circuits. Today I opened up a cheap LED tent lamp. It has a single button to control it. Each click cycles through various states. From the off state, these are:

First click: White LED On - Max Brightness
Second click: White LED On - Half Brightness
Third click: Red LED On (White LED off)
Fourth click: Off

I've attached a picture of the circuit board inside the lamp. It's hard to tell if pins 1-3 of the IC are connected to anything, which just adds to my difficulty understanding what's going on here.
The bit I'm holding on to is the push switch. Pin 1 of the IC is in the top right corner. The transistors are J3Y transistors. The component right beside pin 4 is a diode with the cathode on pin 4 side.

If you could please advise:

how this circuit works;
what the IC is or could be (it's unlabelled so I couldn't find a datasheet anywhere); or
any other options I might have in replicating the functionality described above!

Thanks!


texts: How to shift resistance range of Linear Potentiometers by X ohms in the Positive or Negative direction?

texts:
For example, I have a 10k ohm (linear) Thumbwheel Potentiometer. This POT will produce values from 0 to 10k when reading its resistance.

Positive Shift

How do I shift resistance range values by X ohms in the
positive direction?  E.g. a 10k POT will yield a new range of: 10 to 10,010 ohm, shifted by 10 ohms?

Since I am using an Arduino, I could programmatically scale the resistance value. But I do not want to do that.

Negative Shift

How do I shift resistance value range by X ohms in the negative
direction? E.g. a 10k POT will yield a new range of: -10 to 9990 ohm,
shifted by 10 ohms?


texts: Can the outputs of 3 different voltage regulators be tied together?

texts: I'm working on a variable power supply board. It will take 9-35VDC input and output either 3.3V, 5V or an adjustable output that's jumper-selected. If I hook the outputs of all 3 regulators together will that cause problems? Only one regulator will have input power at a time (via the previous jumper).


texts: Can a surface-mount ceramic capacitor fail partially and intermittently?

texts:
My focus is on surface-mount ceramic capacitors. The obvious failure extremes are open and short. Other than these extremes, can the failure be that the effective value of the capacitor is either higher or lower than the spec? Can this failure be intermittent in that it disappears when the technician eventually comes around to examining the circuit? I don't mean intermittent in the sense that it lasts seconds or less but that the failure lasts minutes but only at random time of day and random day of week.

If yes then I'm curious as to what the failure mechanism could be. Also, is there a test to confirm such a bad installed capacitor?


texts:
Motorized potentiometers are easy to find and often used e.g. in music studio equipment, but I could need a similarly motorized rotary switch for a project. I am either searching for the wrong term (are such switches known under a specific name?) or they are very hard to find. The rotary switch will be used as an input device to a micro controller, but I need the micro controller to be able under specific circumstances to kind of 'override' the user input and choose one of the other selections. The microcontroller can of course simply ignore the user input and do whatever it likes, but it would make operating the device much easies and intuitive, if the micro controller was able to actually move the switch, so that the knob position could also be used as a visual feedback to the operator.

The switch should ideally have a 15° turn between each position. I will likely only need 7 positions, but due to panel design, these should be in reach within a ¼ rotation or so. As long as I somehow can drive the motor from a micro controller, the type of control interface is of less importance. If it is necessary, I could also drive a 4-wire stepper motor directly.

I do not have any specific requirements for the switch regarding voltage, current or behaviour (bouncing, break before make etc). It should only provide control signals to the micro controller and any behaviour sanitation can be made in software.

The only ready-to-use product I have found is from the Swiss company Elma. They have several different rotary switches which are compatible with a motor driver they call 'Remote Audio Plus'. The motor driver comes complete with a micro controller, IR receiver and can be operated with a standard IR remote control, as it is primarily targeted for use in audio amplifiers. I don't need the remote control functionality, but the controller also has an input interface and can be controlled independent of the IR receiver using a simple protocol. This product would cover all my requirements, but it is not exactly cheap. The motor drive alone retails at around €350 and that is not just slightly outside my budget.

I realize that I with some effort probably could adapt any stepper motor to operate a rotary switch, but I don't have the tools or knowledge to make the necessary fittings, brackets or whatever is needed to combine a motor and a switch, so a ready-to-use product will very much be preferred.

Do anyone of you know of a product, which at least comes close to my requirements?

Answers to comments:

Are alternatives viable? If not a must-have, this is at least a want-very-much. I have tried to consider other options as well, but not found anything making sense. The motorized switch is indeed not crucial for the thing to work, but there will be several rotary switches and potentiometers on the same panel and only one of the switches and one of the potentiometers should be motorized/automated. If I replace just the switch with e.g. a rotary encoder and display combination (or some other type of input and feedback mechanism), I ought to do that with all the other inputs as well for consistency and that would compicate things a lot and also IMHO mess up the visual design. Having knobs with a notch indicating the position would be preferrable, because all switches and potentiometers then would look the same.

Have I considered to have anything custom made? Not really. I can't believe that a custom made device is any cheaper than the Elma system I already mentioned and the price is the reason why I am searching for alternatives.


texts: Effect of placing components under a magnetic component (transformer, inductor)

texts:
I recently had my eyes on the the tear-down of onboard charger from Tesla, and saw that they have placed the control circuitry under the major magnetic components (PFC boost inductor (toroidal), phase-shifted full-bridge transformer). The control circuitry were placed on the other side of the PCB, but directly under these large magnetic components.

Wouldn't the magnetic field generated by, e.g. unshielded inductor, effects the control signal of the circuit? Or the shielding of the magnetic field with just a PCB enough?


texts: Calculate field strength for shielded isotropic transmitter

texts:
How to calculate the field strength of a shielded theoretical isotropic transmitter, if there is a hole in the shield for example.

I am looking for a complex formula that also takes into account the hole in the shield and possibly the skin depth of the shield if possible.

If we have a simple transmitter/receiver system, then the field strenght can be both calculated at the source (EIRP) or at the Pr which is the receiver.

Pr= Pt / (4* PI * r^2)

Pt= (E^2*r^2)/30

What I need is a formula for this scenario:

Where we have an isotropic transmitter inside a shield. The shield has a hole, or perhaps multiple holes (if there is formula for that) with a diameter z, and also if possible to take into account the skin depth where the thickness of the shield is x. Let's say the material of the shield is a variable so that we can calculate the skin depth for this formula for different materials.

What I need is the field strength at Pr in V/m or dBμV/m units that is emmitted from the shielded environment. Or vice-versa the EIRP of the transmitted signal outside the shield (obviously different than the original transmitter power inside the shield), measured in W.

Obviously z and x and all other variables are in SI units.


texts: Conduction angle in three-phase rectifier

texts: In a standard three-phase bridge rectifier, which consists of 6 diodes, each diode (or thyristor) conducts 120º of the full 360º period. I have built a synchronous rectifier (for research purposes), which is controlled by microcontroller, and found out that I can extend this angle by 15º, so each MOSFET now conducts 135º. For example, upper leg MOSFET of the phase 1 now conducts from 22.5º to 157.5º, instead of the usual range from 30º to 150º). However, past this point (wider angle) the system goes into a short-circuit. Can someone explain how is this limit determined?


texts: why does a potencial coil in wattmetter influences the pointer rotation

texts:
can somebody tell me,
why does a potential coil in wattmetter influences the pointer rotation.
if the ideal potential coil doesn't have current, it would not generate a magnetic field and it would not exerced ana kind of force.

But for the wattmeter to work, the force experienced by the pointer as to be proportional to the current passing the current coil and the voltage across the potential coil.

Can you try to explain me this, (interaction between voltage coli and current coil).

thanks


texts: How come PC/laptop power suppliers have much higher wattages per physical size than laboratory switching power suppliers?

texts:
This 2.2 kg 1000W BeQuiet BN213 ATX power supply is able to provide 12V 83A (no typo. Eighty-three.), which is around 1000 W.

This huge PS900W (60V15A 30V30A 15V60A) bench power supply weighs 5 kg already, reaches 900 W, but is significantly larger.

This ~2.4kg PS-3010DF variable laboratory SMPS has 0–30V with up to 10A, which maxes out at 300W. It's housing is significantly larger than the 1000W ATX power supply.

This 230W 19.5V 11.8A laptop power supply is significantly more compact, weighs lighter and does not require any external passive/active cooling (heatsink or fan):

All of them are switching-mode power supplies.

How come the PC and laptop power supplies deliver much higher performances per same volume? What are the technical reasons?

Is it because the bench power supplies have a variable, adjustable output voltage while the PC/laptop power supplies deliver a fixed voltage? But most PC/laptop power supplies usually have a current control mode when voltage controlled is no longer possible due to overcurrent. (also known as “current limiting”)

Is it maybe because of voltage ripple filtering or something similar?


texts:
I'm trying to do my first PCB in KiCad and came across a few problems. Here is how far I got:

My questions are:

1) The LM358 socket and the capacitors I put do not have holes. Only the resistors do. I checked this by looking at the 3D model of the
board. How can I make the holes appear?

2) Why do the resistors have a yellow part (which a believe are the holes) and a red one (those that seem like parallelograms)? What are they?

3) I need to put some pins in the board. For example, I need a pin to measure the OUT signal, and a pin to connect the circuit to VCC and GND. How can I insert these in the board?

4) When I export the image to print it and make the board at home, I get this

and there are no holes there whatsoever. I mean, I was expecting to see small circles with no cupper on them to know where to use the drill and to make the process of hole-making easier. How can I make them appear?


texts: LTSpice: how do I pass to a function a component name as parameter?

texts:
Good morning all.
I am implementing a subcircuit in LTspice, and I want also to modify the plot.defs to calculate some quantities with the voltages/currents inside the subcircuit. Thus, I will have a function like:

  .func A(x) V(x:Vo)/V(x:Vin)

where the function "A" should take the instance name of the subcircuit as parameter, in order to access to its nodes (labelled Vo and Vin in the subcircuit, using a behavioral voltage source to make the node name always the same).

The syntax written above doesn't work, I get the error:

  undefined symbol in: "A(<>)"

Where of course "X1" is the name given by spice to the instance of my subcircuit.
What could be the problem? Please note that by explicitly writing the expression of "A" in the plot panel, everything works fine, so it is a matter of how to pass the instance name as parameter.

Thanks all in advance!


texts: System Generator. Estandard exception in FFT block

texts:
I am trying to generate a bitstream file from a the FFTv4 block, but I get errors, one of the errors is about a file called 'fftv4_cw.ise'
This is the error message I get:

  standard exception: XNetlistEngine: An
  exception was raised:
  com.xilinx.sysgen.netlist.NetlistInternal:
  Could not copy 'C:/My Dropbox/Archivos
  sobre mi PFC/Files_Matlab/System
  Generator/Mis
  pruebas/bitstream/FFTv4/sysgen/fftv4_cw.ise'
  to 'C:\My Dropbox\Archivos sobre mi
  PFC\Files_Matlab\System Generator\Mis
  pruebas\bitstream\FFTv4/fftv4_cw.ise':
  No such file or directory at
  C:/Xilinx/dsptools/9.2.01.1028/sysgen/scripts/SgPass2Netlist.pm
  line 150

Does anyone have any idea of what to do?
Does anyone could me give the file called 'fftv4_cw.ise?

By the way the link to my file is:
https://www.dropbox.com/s/gpoeuefmbrpg5n9/FFTv4.mdl

Thank you for your help.


texts: Little DC Power Supply As Charger: Why Not?

texts:
I have several BB Battery BP4.5-6 Batteries that I want to charge (these are 6V batteries).

To do so, I connected three of them in series.  Then, I connect the positive end to the positive output of a V-Infinity (Model EPS180033) 18V 0.33A power supply, and the negative end to the negative end of that same power supply.

At some point over the night, the power supply quits working (I have done this a couple of times, replacing the supply each time) and will no longer put out any voltage whatsoever.

Is this a totally illegitimate way to charge lead-acid batteries?

Thanks!


texts: Send simple signal over AC power line for Arduino / ESP8266

texts:
I am looking for the simplest electronic solution to be contained in boxes B1 and B2 so that when the switch SW is toggled, a signal (free choice) should be carried across the AC power lines (residential 110/220V) to B2 where it should be detected and converted to a small voltage meant to feed some input GPIO pin of a microcontroller.

In other words, the uC should be aware whenever the switch gets toggled, provided the configuration. B1 and B2 are some feet apart and the circuit is also used for other consumers, therefore no huge voltage or current spikes can be used unless filtered by B2. The carried signal can be of any kind as far as B1 can generate it and B2 can detect (and further cancel) it. I hope for an easy solution, not involving additional uC or heavy signal modulation processing, if possible.

LE: based on the provided answers I want to stress out the need of the simplest solution to send/receive a "sign" of any kind over the power lines. I don't need to de/modulate data, a fair voltage spike generated by B1 that can be detected and filtered out in B2 would be enough for the "sign" I need, if possible. I'd rather avoid uC and heavy processing in B1, maybe just in B2.


texts: I Can't find DTMF Decoder HT9170B IC in Proteus

texts:
So I'm trying build a project that is based on the DTMF decoding IC.
Obviously I want to simulate my project first on Proteus.
Unfortunately, I can't find the DTMF IC mentioned above. Is there any library out there that I can use? or maybe a an equivalent element functionally?

Thanks in advance


texts:
I've constructed a basic dual op-amp LFO as in the below circuit

simulate this circuit – Schematic created using CircuitLab

The variable resistor R5 is used to alter the rate of the LFO, I'm unsure of the exact frequencies, but this is used in an audio application to control a VCA. It runs on a dual rail power supply at +/-9V, and uses 0V as VR. It works fine.

What I would like to do is control the rate of the LFO (currently done by R5) with another, similar LFO running at a different speed, so the overall rate of the LFO is not constant, and some randomness is added, as if a potentiometer were being constantly adjusted.

My question is - assuming I had another LFO as above, how would I use that to control the rate of the first LFO? My first thought was to use a standard BJT transistor, but I am unsure how to implement this. Can anyone give some pointers?


texts: Best sensor to measure light intensity in open room

texts:
I am working on a project to understand how robot localization is effected by light levels. I am wanting to build a circuit which can be mounted on a small robot near the camera and can determine lux levels. I am spec'ing which sensor type to use for this.

I have come across LDRs but by the looks of them, they can only take granular measurements for light a couple feet in front of them. If I am looking to characterize a whole room, what's the best sensor to use?

Thanks


texts: Driving an RFID device from a presumably noisy boost step-up converter

texts: I'm building a circuit that will be powered by six AA batteries producing 9V at full charge.  Part of the circuit powers an RFID device that works at 9V and probably somewhat less than that.  I'd like to keep it working all the way to the point where the battery pack voltage has fallen to about 4V or so at which point other parts of circuit operating at 3.3V would be approaching failure.  The RFID device is an implant transponder (134.2kHz) whose range is reduced by the presence of line noise, which consumes 150mA at 9V and will need to continuously operate for a period of about 5 seconds or so.  To get 9V from 4V will require a step-up boost converter, which is bound to be noisy.  I'm wondering if charging up a large capacitor, turning off the converter and driving the RFID from the quiet battery for those 5 seconds would be a viable strategy and if anyone has any recommendations for doing so.  Thanks.


texts:
Let's say I am simulating something as simple as BFSK. It has two symbols, one entirely on the real plane, and one entirely on the complex plane for representing let's say zero. That is how the constellation of BFSK looks like. Now let's say we added AWGN (N) and Rayleigh fading (h) as well.  Rx= h*x + N;

Now when I tried to detect it on the receiving side I will have to divide this entire Rx by an h, makes sense. Now my entire graphs for BER matches non-coherent detection for FSK. It exactly matches with theory. Now how to do the same for non-coherent detection?  If I didn't divide ****Rx/h**** I get very bad results and that doesn't match anything. Theory tells us that in non-coherent detection, prior knowledge of the channel impulse response is not known at the receiver.

In coherent systems, the receiver needs phase information of the transmitter (the carrier phase) to recover the transmitted data at the receiver side. Is there any phase information in FSK? I haven't use any such thing but still simulation results for BER matches theory for Coherent FSK, may be dividing by channel response did some magic?
Some books tell us that NON COHERENT In this technique we use signals of two different frequencies for encoding and decoding, Should we do same? how?
While some say non-coherent systems do not need carrier phase information and use methods like square law to recover the data. Well I am simply simulating it,  I don't think so they are going to make a difference.

Can someone here help me with this?


texts: Converting 5 volts to 12 volts using a photocoupler

texts: i have an arduino and i need to convert 5 volts to 12 volts in order to trigger a 12 volt Rele, i am considering to use the circuit that i attached here (below), if the "input" square is 5 volts, what is the square "output" voltage according to the image below, how is the math calculus of voltages of this circuit taking into account that +12 source voltage is applied at the final part (above 4.7k ohms), thank you very much, anyhelp is appreciated


texts:
I bought a SIM808 module to use it with a PIC microcontroller. Everything works great but now I'm trying to reduce the module power consumption. The module I have is this one from DFRobot. When the module is in power down mode it draws about 60mA!

The datasheet says it should draw 50uA at max in power down mode. I know I'm in power down mode because the network activity LED is off and I haven't powered it up using the PWRKEY. I removed all the LEDs from the board and the active GPS antenna that also draws current. I even removed the buck converter and powered it from a 4V power supply! But I can't go lower than 60mA. The same happens when I put the module in sleep mode, 60mA is the lowest current.

Do I have a faulty module or I'm missing something on the schematic that is drawing so much current? You can download the schematic from here.


texts: Understanding power dissipation of a diode in a datasheet chart

texts:
According to this chart of a diode's power dissipation over temperature, the power dissipation would decrease as temperature goes up.

But wouldn't it be the exact opposite and even more power be dissipated as heat, when the temperature goes up ?


texts: How do you choose a diode for a 5v to 3.3v clamping circuit

texts:
I have a logic input that is 3.3v and I want to be able to allow it to interface with either 3.3v or 5v input signals w/o worrying about it being damaged.  I would like to use a resistor with a clamping diode but I'm unsure how to choose an appropriate diode or even what specific type of diode is the right one to use.

What are the relevant specifications I should look for when choosing a diode to clamp an input signal to 3.3v?


texts: Is grounding needed when using adapter to phone?

texts:
I am doing research on an audio plug. I wonder, is it a must to connect grounding circuit from handphone to the earphone if we use an adapter (image 1). Or can I do the connection like in image 2?

Image 1

Image 2


texts:
I'm using a PIC24F to interface with an SD card in SPI mode. When the card is idle, the device still draws ~200 uA of current which is unacceptable for this device's purpose. To correct this, I am using a bit-enabled Linear Regulator (NCP694H33HT1GOSCT-ND) to kill power to the SD card's power rail. However, the leakage current remained at ~200 uA even when the SD card's power was cut off. Then I realized that upon physically disconnecting the wires for the SPI clock and Data In to the SD card from the PIC, the current drops down to ~10 uA, which is very acceptable.

So, I am assuming that power is somehow leaking through the PIC24F and the signal lines to the SD card. I have tried reconfiguring those pins as digital outputs set to 0 and as digital inputs, but neither methods have had the same results as physically disconnecting those two lines.

Is there something I'm missing here? I would think that being set as a digital inputs would result in those pins becoming high impedance and thus blocking out the excessive leakage current, but it doesn't seem to be working. Any help would be appreciated.


texts: Best place to place a decoupling capacitor

texts:
See this image which gives four options to place decoupling capacitors:

(from http://www.learnemc.com/tutorials/Decoupling/decoupling01.html)

I would say option (d) isn't good - I would recommend someone to place the capacitor near VDD instead of VSS. Is this right? The same goes for (c).

Generally: what's the best place to place a decoupling capacitor? Where would it have the most effect? And, more important, why? I'd like a theoretical explanation.


texts: Single Section Branch Line Coupler at 73 GHz

texts:
SE,
I am having trouble making sense of my simulation charts for a branch-line coupler tuned to
73.5 GHz.
I followed Keysight's tutorial given by the link below.
https://www.keysight.com/us/en/assets/7018-05295/technical-overviews/5992-1629.pdf
I finished this correctly and started using this template for my own. However I did change the substrate parameters to Rogers 5880 as seen in the schematic.

Figure 1: Schematic
However, I cannot replicate the (theoretical) 3dB insertion loss and 90 degrees phase shift.
I am getting -200 dB loss (pretty much all the power) and a fluctuation in phase and I don't know where I am going wrong. All the components are right for the theoretical model.
I read somewhere since the width of the microstrip is much larger than the length then the coupling is thrown off.
If that is the case, then is a microstrip branch-line coupler at this frequency possible to design?

Figure 2: Simulations of S21, S31, S41 and Phase


texts: How to wire up a single-phase electric blower motor

texts:
I have an Electro ADDA C80M-2 0.75kW single-phase blower motor that I need to hook up, switched, to power a cyclonic dust separator that I've built. I thought it would be a piece of cake: pop off the wiring cover and red-to-red, blue-to-blue, green to earth. But this is what I found:

The dark world of electric motor schematics with Z2, U1, Cr (switch?) et cetera. Bit much to expect line and neutral marked, I suppose?

If I'm reading the schematic correctly, it's currently set up to rotate in the clockwise direction and I've attached the earth terminal, thanks to the nice symbol on the casing, but I'm afraid I don't have confidence in which terminal to take live and neutral to.

Please help if you can.