texts: Synchronizing SPI ports for higher data rate

texts:
I am designing a new board which uses the NXP LPC4330 (Cortex M4 microcontroller) with a XESS Xula2 FPGA development board. In this design, the Xula 2 has limited I/O pins since it is designed to fit into a DIP-40 form factor. The primary form of communication between the micro and the FPGA is through SPI.

I would like the bus to be fairly high speed, on the order of 80 to 100 Mbps. It might be enough to run a single SPI port at 80 MHz, but since the main clock on the FPGA is only running at 120 MHz (and it drives the SPI interface), I'm not sure that the SPI would work at such a high data rate. The LPC4330 has multiple SPI ports, and one idea I have is to use 2 SPI ports so that each can run at a slower bit rate. There is plenty of room on the Spartan 6 FPGA, but I do not have the I/O pins on the development board to have 2 sets of all 3 of MOSI/MISO/SCK (plus a single CS).

Therefore, I am wondering if it is possible to synchronize the ports on the LPC such that they share a SPI clock. The fast communication only has to happen in a single direction, so I would only need to double up the MISO pin (the micro needs to read quickly from the FPGA, not vice versa). There doesn't appear to be a special mode to synchronize the SPI ports, but I assume that they would be on the same clock domain due to the clocking architecture of the micro.

I realize there is also a multi-port SPIFI (spi-flash memory interface) on the NXP. Has anyone had an experience creating a block on the FPGA which basically emulates a SPI flash?

So my questions are a) do you think this will work? and b) is there a better way to do this?


texts: physics behind the impedance matching performed in this case

texts:
On the website here: basic impedence matching, I found a way one would pick the right value for your coaxial cable given the generator's impedance and load impedance.

I've always been told to just make everything 50 ohms but now I'm curious to know where they got the math here.

I am also familiar with the way you calculate reflection coefficient \$ \Gamma = \frac{Z_0 - Z_L}{Z_0 + Z_L}\$

What is the math/physics behind taking \$\sqrt{Z_0 Z_L}\$


texts: Turning on and off car ignition - created two pulses?

texts:
I'm building a car DVR using a GoPro. The GoPro can be turned on by shorting out two pins on the gopro bus and then turned off by shorting out the same two pins.

So when the car's ignition is turned on I need a 3 second pulse (555 timer probably) then when the cars ignition goes off I need another pulse - this is where I am struggling to come up with a solution. I need some type of edge triggering right?  going from 0-12v fires off one pulse / triggers the 555 then dropping from 12 to 0v fires off another timer.

Any suggestions, I think I just need to set up two 555 to be positive edge and negative edge trigged right - how do I do that? Been a while since I dabbled in electronic so I'm a little rusty :)


texts:
I am doing my best to make a portable charger.
Here is the link with the schematic of the circuit I am working on:Voltage regulator question
.I was told that the 9 V battery I was using didn't have enough capacity to charge any device,so I decided to connect 5 1,2 rechargeable batteries(NiMh and one NiCd) is series in its place,the lowest capacity one having 800 mAh.Here are the questions:
1)Will these batteries perform better?If not,what kind of battery would I need(mAh and voltage)?
2)I suspect that the device,when connected to my circuit may be losing  energy at the same time while it charges.Would I need a diode somewhere to prevent this?
3)I would appreciate a few examples of how to make this charger better(without changing the battery's parameters).


texts: Control the door release function of an apartment intercom

texts:
I have a Aiphone GT-1C system and am trying to see if its possible to trigger the door release feature for my apartments intercom system.

The pinout reads:

    IN  | OUT | IN | OUT |
    ----+-----+----+-----+
    R R |R R  |B B |B B  |
    1 2 |1 2  |1 2 |1 2  |
   23.4v|23.4v| 0v | 0v  |

I measured the In and Out for R1/2 at 23.4v and 0v for In and out of B1/2. When I press the door release button (when its off not being called) all the pins go to 23.4v high. This leads me to believe that they are sending data over wire. I do have an oscilloscope that I could use but I feel like if it got to that point it would be over my head.

I emailed tech support asking if they had a dedicated door release pin and they responded with this:

  An option switch dry contact closure can be used when connecting a
  dedicated strike circuit to the gray and black wires of the 6-pin
  option cable.

  The door release button on the GT-1C triggers the Form C contact built
  into the back of the speaker module of the entrance. The tenant would
  need to press the Option button (the icon looks like a laptop monitor)
  to unlock their own unique door.

I was confused by the response. From what I understand dry contact just means it's volt free meaning its a secondary relay or something. But I don't understand the part about the dedicate strike circuit.

With the information would it be possible to trigger the door release using a some kind of hardware (microcontroller, switch, etc.)


texts: 8051 behaves differently with two similar programs

texts:
I am trying to drive relays with a 8051. For this, P2 is connected to Darlington array ULN2803A, and relays are connected to the corresponding outputs of ULN2803A.

First, I tried to test if the circuit is working, with this very simple code:

#include <at89c51cc03.h>

void main()
{
    P2 = 0xFF;
    while (1)
    {
    }
}

Nothing happened. Then I found this code on Keil's website, to drive relays again:

#include <reg52.h>

#define relayport P2

void Delay_ms(int);

void main()
{
  do
  {
    relayport = 0xFF; //All relays On
    Delay_ms(1000);
    relayport = 0x00; //All relays Off
    Delay_ms(1000);
  }while(1);
}

void Delay_ms(int k)
{
  int j;
  int i;
  for(i=0;i<k;i++)
  {
    for(j=0;j<100;j++)
    {
    }
  }
}

This worked, for some reason... the relays started ticking on and off.

Question is, why didn't the first code work? I expected the first code to turn and keep the relays on. The variant is AT89C51CC03.

Edit: The same faulty behavior is observed when I did the following, intending to turn the relays on and off once:

void main(){
    relayport = 0xFF; //All relays On
    Delay_ms(1000);
    relayport = 0x00; //All relays Off
    Delay_ms(1000);
  while(1);
}

Very weird... Does anybody know what should be done in the case which I want to toggle the relays once, then enter the superloop?

Edit 2: It looks like it is a very specific bug, because the program is also behaving normally on software debugger. I will report to Keil.


texts: Reasons for and against choosing input and output capacitors for a regulator with more capacitance than called for in the datasheet

texts:
The regulator in question: NCP161AFCT330T2G. We use it in a USB device to convert 5V to 3V. The device will only be used at room temperature.
It says in the datasheet: “The value of the input capacitor should be 1 µF or greater to ensure the best dynamic performance.” About the output capacitor however it says: “The recommended capacitor value is 1 µF.”
Is there a reason to not explicitly recommend values higher than 1 µF for the output capacitor? I am asking because we use a lot of 10 µF capacitors (MLCC imperial 0402) on the PCB and I would like to just use 10 µF capacitors for the input and output capacitors of the regulator as well (would simplify the BOM), instead of the 1 µF capacitors the regulator datasheet is calling for (for those 1 µF capacitors I would use MLCC imperial 0402 as well by the way). Are there any drawbacks of using 10 µF capacitors instead of 1 µF capacitors when literally the only difference is the capacitance?


texts: How to make a VGA monitor display a white screen at all time?

texts:
I am hacking around with an old (CRT) VGA monitor. Trying to make an oscilloscope.

What I want is to make the monitor display a blank white screen at all time, when the power is connected of course. I do not care if I cannot use my monitor for its normal job anymore.

Is it possible to short some pins of the VGA connector to mimic a blank white screen?


texts: LTspice error reading a downloaded model

texts:
I'm downloading a model for an n-channel MOSFET, the DMG6968U-7.  This is the SPICE code:

*SRC=DMG6968U;DI_DMG6968U;MOSFETs N;Enh;20.0V 6.50A 25.0mohms  Diodes Inc MOSFET
*SYM=POWMOSN
.SUBCKT DMG6968U   10 20 30
*     TERMINALS:  D  G  S
M1   1  2  3  3  DMOS L=1U W=1U
RD  10  1  10.9m
RS  40  3  1.62m
RG  20  2  33.7
CGS  2  3  119p
EGD 12  0  2  1  1
VFB 14  0  0
FFB  2  1  VFB  1
CGD 13 14  226p
R1  13  0  1.00
D1  12 13  DLIM
DDG 15 14  DCGD
R2  12 15  1.00
D2  15  0  DLIM
DSD  3 10  DSUB
LS  30 40  7.50n
.MODEL DMOS NMOS(LEVEL=3 VMAX=41.7k THETA=80.0m
+ ETA=2.00m VTO=0.900 KP=31.8)
.MODEL DCGD D (CJO=226p VJ=0.600 M=0.680)
.MODEL DSUB D (IS=27.0n N=1.50 RS=55.4m BV=20.0
+ CJO=176p VJ=0.800 M=0.420 TT=247n)
.MODEL DLIM D (IS=100U)
.ENDS

I cannot open the file with LTspice (if I try opening it from within LTspice, it does absolutely nothing;  if I drag-n-drop the file into the LTspice workspace, it gives me an "Encountered an Improper Argument" error).  Please help!

Actually, the above is not exactly the downloaded code — all of the .model directives were missing the closing bracket (parenthesis), so I added them, but I'm still getting the same error.


texts: Preventing Raspberry Pi Zero from rebooting due to inrush when device plugged in

texts:
I have a Raspberry Pi Zero 1.3 and a standard USB OTG unpowered hub. When I plug in certain USB devices, the RPi reboots instantly. I believe this is due to "inrush":
https://www.raspberrypi.org/forums/viewtopic.php?t=25803
What is the correct way to modify the system to prevent this inrush problem (eg. can I just solder a large electrolytic capacitor across the supply rails)?


texts: Solid State Relay Either Stuck on or not Running

texts:
So I've wired up a relatively simple circuit where an Arduino controls a solid state relay that is connected to a 12V 30A power supply which runs a solenoid valve. I'm using the an Arduino Mega 2560 a Gem Sensors solenoid valve and a Broadcom Limited ASSR-1511-001E solid state relay.

On the input side I have:

Arduino 5V --> SSR Pin 1 --> Out SSR Pin 2 --> 500 ohm resistor --> Arduino ground

And then on the load side I have:

Power supply positive terminal --> SSR Pin 6 (labeled as the positive pin) --> Out SSR Pin 5 --> Solenoid Valve --> Power supply negative terminal

So with that all in mind I find that when I power it all on it doesn't do anything. I've checked the voltage going through the input side and it is 5V on the dot but nothing on the load side. When I switch the connections on the load side it turns on and always stays on even with power turned off on the Arduino side and then my load side looks like:

Power supply negative terminal --> Solenoid Valve --> SSR Pin 6 (labeled as the positive pin) --> Out SSR Pin 5 --> Power supply negative terminal

Do you have any thoughts on what I'm doing incorrectly and what I can check to get this circuit running properly? I've got it prototyped on a perf board but it is pretty easy to switch everything around.

For some additional info:

The SSR input side has a max suggested amperage of 20mA. I have the 500ohm resistor on that line so at 5V (subtract the 1.65 voltage drop) that is 6.7mA on that line.
The SSR load side has a max of 2A and my solenoid valve has 20ohms of resistance so at 12V we're running around 0.5A.


texts: Connecting different Sensors / Actuators

texts:
I have a fairly general problem in understanding, I guess, "bus systems":
Take the following scenario:
We aim to create a motherboard-type of board, it shall use some kind of CPU that is able (assuming the right software is supplied) to control (write) and sense (read) from several periphery devices like sensors (thermo sensors etc.) and actuators (like stepper motors).

Obviously we cannot wire each component directly to the CPU. Instead we use a system bus to connect things together.
We can use Encoding and Decoding (Multiplexing) to address certain devices and send data to them or read a certain register value.

But how does the electronic implementation detail look like?
Decoding and Encoding should require some sort of additional processor that en-/decodes data according to the bus specification including timing requirements, right?
But this in turn means that we simply connect several processors together using a common interface language, i.e. protocol.
Moreover, in the end, each periphery device class has a dedicated processor, for example a USB serializer.

Glad for any hints and clarifications!
Thanks!


texts:
I messed up my PCB design when I made a change of FET-model. Now the Drain and the Source pins are swapped and it seems that there are no TO-220 models made this way (1-Gate, 2-Source, 3-Drain). Are there any pinouts like this, or do you have any other solution? Making a new PCB is too expensive, since many other components where soldered before discovering this mistake.

simulate this circuit – Schematic created using CircuitLab


texts: Source/Drain terminals in a MOSFET Sampling circuit

texts: In a simple sampling circuit consisting of a MOS as the switch and a capacitor, how does one decide which of the terminals are source/drain? Thanks.


texts: What is this electric thing, hanging on an electric pole?

texts:
Recently I found this plastic thing on a pillar in the village:

Looks like it is not finally connected yet, just attached with tape to the pillar.

What is it's purpose?

4 cables go down to this thing:


texts: How does the resistance-capacitance oscillator shift voltage by 180 degrees?

texts:
I'm trying to wrap my head around how the resistance-capacitance oscillator shifts voltage by 180 degrees.
As far as understand, a capacitor shifts phase for current, not voltage.
What am I missing here?


texts: How important is the gate threshold voltage on a MOSFET

texts:
I am using several MOSFETs (STP16NF06 datasheet here) controlled by a shift register (74HC595 datasheet here) which is controlled by a microcontoller.
The spec sheet says the gate threshold voltage is between 2V and 4V. When controlling directly via the MCU, the voltage on the pin is 3.3V. However, I have switched to a shift register (to save pins) which is connected to the same 5V source  that the microcontroller uses for power. That means the output pins of the shift register are 5V, which is 1V higher than the maximum of the MOSFET gate.
My multimeter reads 5V across the shift register Vcc and GND, and 5V at the shift register pin out/MOSFET gate pin.
Is this something I should correct?
I am going to run the whole thing off of a 24V power supply, so I already plan to use a boost/buck converter that will convert it to 5V for the microcontroller and shift registers, while the 24V will be used for the solenoid valves. I don't really want to add another boost/buck converter just to power the shift registers; while they are not large, they still take a fair bit of space (5cm x 2.5cm). (The shift register works with 2V minimum to 6V maximum and 5V typical.)
The MOSFETs seem to be running fine at the moment, powering a simple LEDs off the same 5V power source. But once I wired it up, I realised the shift register was outputting 5V and not the 3.3V of the microcontroller. Do I need to worry about being over the maximum voltage? If I do, is there a better way to get the 4V and 5V other than a boost/buck converter?


texts:
I was thinking of having a ceiling fan come on when my furnace came on.
I used to dabble in electronics but it's been a long while and I know there are new and innovative approaches to accomplish the task. But, I'm kind of out of date on ideas.

Does someone have an idea to start with?


texts:
Given this circuit, I have to find \$\frac{V_2}{V_1}\$ as well as the magnitude of hysteresis.

I don't need a full solution. Any hints to approach this problem would suffice.

So far, I know the left op-amp is a Schmitt trigger and the right one has unity gain.

Edit update:
Now I know that in case Schmitt trigger outputs 5V Inverting op-amp makes it -5V
applying voltage divider in this case with 5 at one side and -5 at the other.
I get two values either 7.5 or 2.5, 2.5 seems the correct answer but if I take 0.75R as the voltage drop for V+ then it's not correct why?
Is it that the V+ automatically thinks that taking 7.5 as the reference Overshoots the saturation Voltage of the op-amp itself?
update: V2/V1 graph looks like this,

Inference: I tried to apply Voltage divider in the case where negative/positive potential was present instead of ground and I failed terribly.


texts: ARM Cortex-M3 Interrupts and Interrupt service routine &interrupt handler

texts:
I am trying to understand arm architecture and i got stuck with one concept, i.e, INTERRUPT SERVICE ROUTINE. I had gone NVIC structure for HARDWARE &  SOFTWARE interrupts. But at some point i got confused how that particular function is called when an interrupt occurs. All those functions are already defined like for TIMER-6, TIM6_IRQHandler(). How can i update this particular function with user defined function (means any function).

Any reference document or link will be appreciated.
Working IDE is EWARM.
Testing Controller STM32L152RE.


texts: Find electric field due to point charge +Q under given condition

texts:
As shown in the image, there are four conditions given:

Electric field in figure:1 at point 'P' let = E_P,
Electric field in figure:2 at point 'M' let = E_M,
Electric field in figure:3 at point 'R' let = E_R,
Electric field in figure:4 at point 'S' let = E_S,

we can say: E_P < E_M
but
E_P = E_R {why}
and
E_R < E_S


texts: Can we calculate the upper bound of needed power from some information from datasheet?

texts:
This is a energy harvester product data sheet, and we can know some information below

https://www.powercastco.com/wp-content/uploads/2016/12/P1110B-Datasheet-Rev-4.pdf

1.\$V_{out} \$ current = 100mA

2.\$V_{out} \$ voltage = 4.3V

First,we all know that we need some energy to start up the circuit,if this circuit is "off",it can't work,i mean,it can't harvest energy to charge itself.So we can know that this device has to have some energy to let itself in "on" state,then it can begin working!

I assume this device wants to harvest the energy to charge its battery,and this battery is also the device's power supply,if there isn't a power supply,the harvested circuit won't work.So the power supply needs to has some energy,\$E_{ini}\$,first to startup the circuit.And what i want to know is that what is the upper bound value or lower bound value of that \$E_{ini}\$

Is there anyway that can calculate  the upper bound value or lower bound value of \$E_{ini}\$ when we only have some information from its datasheet?


texts: Why does my FXAS21002 gyrometer return a faulty WHO_AM_I?

texts:
I'm trying to use the FXAS21002C gyroscope on BRKT-STBC-AGM04 breakout board.

As a first test I tried to read the WHO_AM_I register at 0x0C, which is supposed to give 0xD7 as a result according to the documentation. But instead I am reading 0x00.

I monitored the I2C communication and I'm not noticing any irregularities there. The FXAS21002C is responsing with ACK's. etc

(Upper line is SCL; lower line is SDA; both pulled to 3.3V)

The conversation here is:
010000000 000011000  010000010 000000001

And I'm running the following code on my Arduino Uno:

#include <Wire.h>
#include <math.h>
#include "Arduino.h"

#define GyrAddress 0x20

#define pullupPin 4

#define gyr_WHO_AM_I 0x0C
#define gyr_WHO_AM_I_RSP 0xD7

#define I2C_address GyrAddress
#define WHO_AM_I gyr_WHO_AM_I
#define WHO_AM_I_RSP gyr_WHO_AM_I_RSP

uint8_t readRegister(uint8_t address) {
    uint8_t output;

    Wire.beginTransmission(I2C_address);
    Wire.write(address);
    Wire.endTransmission();

    delayMicroseconds(4);

    Wire.requestFrom(I2C_address, 1);
    while (Wire.available()) {
        Serial.println("reading a thing");
        output = Wire.read();
    }

    return output;
}

void writeRegister(uint8_t address, uint8_t value){
    Wire.beginTransmission(I2C_address);
    Wire.write(address);
    Wire.write(value);
    Wire.endTransmission();
}

bool initialize() {
    Wire.begin();
    Wire.setClock(400000);        // I2C fast mode, 400kHz
    uint8_t reg;
    if ((reg = readRegister(WHO_AM_I)) != WHO_AM_I_RSP) { //Could not find MAG3110

        Serial.println(reg);
        Serial.println(WHO_AM_I_RSP);
        Serial.println("Could not find gyro connected!");
        return false;
    } else //Successfully initialized
    {
        Serial.println("found gyro!");
        return true;
    }
}

void setup() {
    pinMode(pullupPin, INPUT_PULLUP);
    Serial.begin(57600);

    Serial.println("begun");

    Serial.println(initialize());
}

int pullup;
void loop() {
    // test code to rerun when I press a button.
    int input = digitalRead(pullupPin);
    if(input ^ pullup){
      pullup = input;
      if(input){
        Serial.println(initialize());
      }
    }
}

Schematic of my current setup:

Does someone know why the FXAS21002C is not returning the WHO_AM_I response that is listed in the documentation?


texts: How do I modify pin assignments to use my signal names in Quartus Prime?

texts:
I am working through the Quartus Prime Introduction Using Schematic Diagrams tutorial for Quartus Prime Lite 16. (I am using version 16.0.2 on Windows.) Because I have a DE1-SoC board, I specified that board and the corresponding device when creating the project:

My circuit includes inputs named x1 and x2 and an output named f. In the assignment editor, I renamed SW[0] and SW[1] and the output pins LEDR[0], respectively, to my signal names. I ended up with:

The pin assignments are shown in my circuit diagram:

However, the assignments don't seem to be working correctly. I get these messages when I compile:

  Warning (15714): Some pins have incomplete I/O assignments. Refer to
  the I/O Assignment Warnings report for details

  Critical Warning
  (169085): No exact pin location assignment(s) for 3 pins of 241 total
  pins. For the list of pins please refer to the I/O Assignment Warnings
  table in the fitter report.

The fitter report includes:

  210 LEDR[0]   Missing location assignment

  211 SW[0]     Missing location assignment

  212 SW[1]       Missing location assignment

How do I assign signal names to pins correctly?

UPDATE

Here is the list of files for the project:

DE1_SOC_golden_top.sdc [which I did not manually create]
light.bdf
Waveform.vwf

When I double-click on DE1_SOC_golden_top.sdc, I get an error:

  Can't open file DE1_SOC_golden_top.sdc -- file does not exist

I also see these messages when I compile:

  Info (12021): Found 1 design units, including 1 entities, in source file light.bdf

    Info (12023): Found entity 1: light

  Warning (12125): Using design file de1_soc_golden_top.v, which is not specified as a design file for the current project, but contains definitions for 1 design units and 1 entities in project

    Info (12023): Found entity 1: DE1_SOC_golden_top

  Info (12127): Elaborating entity "DE1_SOC_golden_top" for the top level hierarchy


texts: I don't know how to choose an adequate antenna

texts:
I need to choose an antenna for a long range free space communication (~10km), and I currently have a receiving antenna, but I don't understand enough to be able to pick an adequate emitter.

The receiver is a 900Mhz antenna, with 14dBi gain. I learned about the Friis equation, but there are a few things which I do not understand.

Of course, if you increase the electrical power in your emitter, the signal will be stronger, but is there a direct link between those two values or is it different for each antenna ?
With this formula you can calculate what will be the theorical strength of the received signal, but what is the minimum required to have a correct transmission ?

Thank you


texts: Where to put the unused states in synchronous counter that counts Even numbers?

texts:
Suppose if we have a counter that counts only Even numbers and the unused states(odd numbers) treated as don't-care condition.

Current state           Next State
A  B  C  D              A  B  C  D
0  0  0  0              0  0  1  0
0  0  1  0              0  1  0  0
0  1  0  0              1  0  0  0
1  0  0  0              1  0  1  0
1  0  1  0              1  1  1  0
1  1  1  0              0  0  0  0

0  0  0  1              x  x  x  x
0  0  1  1              x  x  x  x
0  1  0  1              x  x  x  x
0  1  1  1              x  x  x  x
1  0  0  1              x  x  x  x
1  0  1  1              x  x  x  x
1  1  0  1              x  x  x  x
1  1  1  1              x  x  x  x

Above; I put the all unused states at the end.

Does this a right way? OR I must put them as normally as it's, like :

   Current state            Next State
    A  B  C  D              A  B  C  D
    0  0  0  0              0  0  1  0
    0  0  0  1              x  x  x  x
    0  0  1  0              0  1  0  0
    ........


texts:
I want to built solar panel system and i rather to buy system parts and assemble them by myself, but i don't know the calculation :

1- How to calculate what kind of solar panel(How many Watt and Ampere) is suitable for my location ? some of theme is define by watt and other define by Amp and Volt,so i get confuse.

(I found gaisma.com but i don't know how to use it in calculation, we have 12 hour sunshine).

2- I know i can use 12.v car battery but How many of theme i can use compare to my panel (Is there any formula to calculate that)?

3- How to i find suitable Controllers and Inverters for battery (volt & amps) ? (I heard if i don't use proper Inverter, it might explode).

PS : Big vendors like ebay and alibaba services is not available in my country(Iraq) as i know,so if you be more general about the range of option which i can use, i will be appreciated.

PS2 : I don't want to apply it in the facility power grid, i just want it to  charge the batteries and inverter give me an output.


texts: What values for current and voltage are considered "relatively small" or "relatively large"?

texts:
Background

I am working with a Yokogawa WT310 power analyzer. A section of their getting started guide, available here, has this diagram:

I understand the purpose of these diagrams, and they make sense individually. However, I'm having trouble deciding which wiring scheme I should use, because I don't know what ratios of current to voltage would be considered large and small.

The Question

I am trying to measure power on DC devices with voltages of 18V-25V, and currents of 500mA - 10A. Which wiring scheme would be appropriate for these devices? What ratios of current to voltage are considered "large" and "small"?


texts:
I'm trying to understand this circuit.
I can see that BW1 is a low pass filter and BW3 removes any DC from the output signal, but what does BW2 do?
If it is acting as a filter, is it a high pass filter or a low pass filter?


texts: How to drive MOSFET switches in a cascaded hybrid modular multilevel converter using a half-bridge driver "IR2103S"

texts:
I am trying to drive the MOSFET switches in a cascaded hybrid modular multi-level converter as shown in Fig. 1. Fig. 2 is used here to simplify the circuit and to present the problem (let's focus on Fig.2 instead of Fig.1). The type of the MOSFET used is "IRF530N"https://www.alldatasheet.com/datasheet-pdf/pdf/68169/IRF/IRF530N.html. Each cell is integrated with half-bridge (called a sub-module) while each pack of sub-modules is integrated with full-bridge (called a module). Each module is connected to the next module (cascaded). The type of the Half-bridge driver used is "IR2103S" [https://www.alldatasheet.com/datasheet-pdf/pdf/84683/IRF/IR2103S.html] 2. A single IR2103S is used to drive each half-bridge while two of IR2103S are used to drive each full-bridge as shown in Fig. 3 and Fig. 4, respectively. Note that in Proteus software, I have used IR2104S instead of IR2103S (both of them are able to achieve the same function). For each half-bridge (except the last half-bridge used), the wire between the COM pin of "IR2103S" and the source pin of the low-side MOSFET switch is lifted as shown in Fig. 5. Cell voltage=3.4V, Rg=47ohm, a capacitor with 22uf/25V, and  DC/DC isolated is used for each half-bridge.
The circuit is operating correctly when I am using only one module (only one full-bridge is used) (i am able to measure the positive and the negative output voltage across the full-bridge).
The problem appears when using two modules in a cascade way (see Fig.5). Connecting the load is necessary in this case to complete the circuit. I noted that I can measure the positive output voltage across the two H-bridges correctly (9.7 to 10.1V) while I can't measure the correct negative output voltage (I got -8.42 V).
I have tested the circuit in the lab and by Proteus software and I got the same results.
I have two questions:

Am I able to use the half-bridge driver (IR2103S) to drive the MOSFETs or I should use an individual driver (such as TLP351H) for each MOSFET?
If I can use IR2103S, is there anybody who can help me to figure out where is my mistake and how to connect the circuit correctly?

Thanks in advance


texts: What's the RMS voltage of this asymmetric rectangle function?

texts:
I recorded this asymmetric rectangle function:

I calculated the RMS voltage to be equal to the amplitude (4,10 V in this case)
However when I measured this exact signal with a TrueRMS multimeter, it showed 3,54 V.
Where is my error?


texts: I2C ADC IC for many components located separately?

texts:
my first question in this page :)

The sensors I use give analog signals, so I want to translate them all to I2C, but I can't find IC's that allow me to give them any desired address, I find only with very limited possibilities.

My idea is to have few cables in my system, so I would want to have these ADC ICs very near of each sensor and make the communication through I2C. Thank you for your help, and excuse me if the question has an easy answer, I'm still an student and just couldn't find anything that fitted my concept.

Maybe there is another way to do this... I saw multiplexors, which don't help me, because all the analog signals should go to it, so, at the end, I have the same quantity of cables going around. Then, I saw IC's with 3 address bits, but I need more address, like 15 or even more.

Thank you again for your help.


texts:
Power supplies often accept an input range of 90-264Vac. I am wondering where the 264 comes from.

A couple of random examples from power supplies available:

85 - 264 Vac input range (100 - 240 Vac nominal)
Takes universal inputs (90-264 Vac, 47/63 Hz)
External Power Supply 90 to 264 VAC
Input voltage 90-264Vac

I understand that large parts of the world are 220-230V. I also understand that 277V may be available, as well as 208V.

But where exactly is the 264Vac limit from?


texts: Electronics to select every third pulse from Ti-sapphire laser

texts:
I'm currently building an optical imaging system and have run into some difficulty. The optical source is a Ti-sapphire laser which outputs pulses at 80 MHz and I'm using a photomultipler tube as a detector. I would like to trigger my sampling based on every third pulse from the Ti-sapphire (in other words I would like to sample at 80/3 MHz). I have already setup a fast photodiode that can detect each pulse. Is there a way I can easily pick off every third pulse?

Thanks for any help.


texts: I am using no-clean flux paste for assembling the PCB board. Although it is 'no-clean', I need to clean it. Can anyone please suggest on cleaning the 'no-clean' flux? What do I need? And how to clean?


texts: Is it possible to phase shift a single harmonic rank without shifting the rest of the distored signal?

texts:
Let's suppose I have a voltage of 60 Hz, containing distortion due to 3rd, 5th and 7th harmonics (180Hz, 300Hz and 420Hz).

Is it possible to phase shift the 3rd harmonic (for example) without shifting the rest of the signal ? If yes, how and using what ?

EDIT : Adding more information just like Sean Asked

i read this article : Harmonic interactions of multiple distributed energy resources in power distribution networks, ELSEVIER Journal

basically what they did, is taking under consideration the phases of the harmonics :

  In a systems with multi harmonic sources, the injected harmonic
  current from each source add vectorally. Therefore, it is crucial to
  study the impact of each harmonic source phase angle on the total
  harmonic distortion.

Here is the network Model they used :

So a number of harmonic simulations were performed with the phase angles steps for both harmonic sources (1 & 2) being varied as follows: (0◦, 15◦, 30◦, 45◦, 60◦, 75◦, 90◦) to the : 3rd, 5th, 7th, 9th and 11th harmonics. the result of the THD according to each combination is in the following Graph :

Now, i saw that for some combination of Phases (ex :75° to Source 2 & 45° to Source 1) the THD is reduced because the harmonics canceled each other, without any harmonics mitigation technique, so i was wondering if it is possible to create an algorithm to compute the right combination of phases for N harmonics sources in a way they cancel each other and than apply those phases to each harmonics in each source, to obtain a minimum THD without any effort of mitigation. of course in the real life not all harmonics have the same phase, so the phase shifting must be different for each harmonics rank, and this is why i asked my question at the first place


texts: Why are thresholds for energy detection and preamble detection different in 802.11 standard?

texts:
Assuming a 20 MHz band, it is -62 dBm for the data and -82 dBm for the preamble.
Source: August 2013 doc.: IEEE 802.11-13/0994r0


texts:
How can one determine the maximal cable length an Opamp can drive without getting unstable? The thing which leads me to this question is that the impedance of a cable changes over frequency. Means, a cable can be seen capacitive and/or inductive over frequency. What is the procedure and what parameters are important to look at in the datasheet of an Amplifier? Cable is NOT impedance matched. Cable end terminates in high input impedance.
See the following LTSpice Simulation of a 5m long Coaxial Cable:

It can be seen that in the first plot that the phase alternates between -90 (capacitive) and +90 (Inductive)


texts:
In order to drive pass transistors (MOSFETs) located between two non-zero voltage points, one can use a resistor divider followed by a MOSFET as seen here where V2 is high enough to drive the top MOSFET:

simulate this circuit – Schematic created using CircuitLab

This works, but I hardly think it's ideal. This has the drawback of taking time to turn on and off as you now have a potentially hefty RC time constants between the R's and the capacitance of the top NMOS. To counter that slowness, you could burn more current during the off time by reducing the resistances. Either way, there's a balance that must be had that may not be anywhere near ideal.

Is there a better way drive a pass transistor at some very different voltage than the driving signal (0-5V). I can see opto-isolators working for this. There would obviously be pros and cons to each of these options. Anything better?

Also, assume that the mosfets have between 10-20V max \$V_{GS}\$ and can have very high (200-400V) max \$V_{DS}\$. Equivalent PMOS devices could be used as well if using some kind of complementary logic.

EDIT: Changed V2 to V1+Vt and added notation for the schematic to have Q1 and Q2.

Andy has pointed to some chips with internal capabilities to do what I'm after. My question is, what's in level shifters or buffer elements of the datasheet he gave. Here's the block diagram of the LTC4444:


texts: Optoisolator Long term Reliability at HVDC

texts: Most optocouplers spend most of thier time isolating mains voltages.They are reliable doing this and they are cheap and simple.How would things go if the same garden variety opto was isolating a DC potential ? A work associate did a HVDC supply in a previous life and found opto failure despite using the opto well below its ratings .He said that this was due to electromigration,he started life as a chemical engineer         .Is this true ? Does this mean that optos should be derated for DC isolation? What would be a reasonable derating factor? Should one not use optos period for HVDC ?  Would isolating a negative voltage be better than isolating a positive voltage due to electrochemical reasoning ?


texts: Trying to identify SMD with morse coded? markings

texts:
New here and first question:

Any idea what this component is and it's specs? Markings look like morse code which reads "XTK" and what looks like .A. It is part of a circuit for LED, back lit, press buttons. I need to source a replacement as one of them came broken out the box.

I'm not well versed in the electronics arts, so please excuse my ignorance.


texts:
For my job, I was tasked with creating a board to interface with a 2.5V device we've made. So, to keep things simple, I decided to interface it with an ATmega328P-PU running the Arduino firmware at 2.5V. All the specifications say the chip has an operating voltage of 1.8V-5.5V, so I didn't bother testing any circuit at 2.5V until today. That was a dumb mistake.

I was testing the low voltage setup by running the simple blink sketch on a breadboard and found it would stop working just below 2.7V. The power supply would also show 0mA current draw as opposed to the 2mA it was showing before. I checked the pin with a DMM and the LED unplugged to confirm that no output was coming from the pin.

After some research, I found a site that seemed to say that, at lower voltages, it needs to run at a slower speed. So, I burned the bootloader to have the chip used the 8Mhz internal oscillator. However, it still turns off below 2.7V.

How can I get access to these lower voltages? I am guessing that this has to do with some internal fuse setting, but can't find anything about it. I'm well within the operating voltage for both the I/O pins and Supply rail. I know it can run at 2.5V as the Arduino BT can have an input voltage as low as 2.5V. Is there something I'm forgetting?


texts: Using a N-Mosfet to switch a common cathode ledstrip

texts:
I am trying to drive a RGB-ledstrip using the following circuit: http://learn.adafruit.com/rgb-led-strips/usage

As I am using a Common Cathode led-strip instead of a Common Anode one as used in the above link thus I came up with this 'modified circuit'. Because my experience with FETs was nihil this didn't actually work as I would need at least a voltage => Vcc to saturate the MOSFET.

                                   VCC
                                    +
                       STP50N06FI   |
                        N-MOSFET    |
                                 ||-+
                  ___            ||<-
                 |   \_----------||-+
                 |___/              |
             Logic 5V (PWM)         |    Ledstrip
                                    V -> (Common
                                    -    Cathode)
                                    |
                                    |
                                   ===
                                   GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Is it possible to use a N-channel MOSFET at all for this application? and if so, what do I need to do to make this work (Control the LED-strip brightness with a PWM signal, logic 5v).


texts: I'm not sure in this schematic if the left and right audio inputs are connected by ground, or if the ground of the audio input goes straight to ground.


texts: Is there a circuit simulator out there that has latching relays?

texts:
Okay, I'm at my wits end with this one. Having tried a dozen or so free/semi-free circuit simulators, I can't find any that include latching relays. This surprises me as they're one of the most common components I use.

Am I missing something obvious like another naming convention, or is there a decent simulator out there that does include them that I just haven't found yet?

I'm giving thought to coding one for Falstad's simulator, but can't do this in the office as I don't have the software...

The functionality I need is a single momentary switch latching the relay on, then latching it off again on the next press. I imagine I'm missing something fairly obvious in making this happen, so will keep playing, but felt it couldn't hurt to ask for an extra prod in the right direction please?


texts: Do I need an accurate clock for an accelerometer?

texts:
I am working on a project where I want to get very accurate data from an accelerometer. I plan on sending my data over bluetooth to be interpreted by a computer.

I am assuming that bluetooth will have some unknown delays that come from things such as how Windows handles the data.

So, since the accelerometer data is time depended, would I be benefited by using a clock that can easily create time in some even divisor of seconds? Or possibly add a RTC? I would then be able to "time-stamp" my data before sending it over bluetooth.

Is this worth it or am I just over thinking how accurate I can actually get my data to be?

Clarification:

I will be pulling in data based off of a timer interrupt. I am wondering if my timer needs to be something like 0.5ms. I would go ahead and "time-stamp" the messages I am sending so I know if I loose a message for some reason.

Also, I am using a digital accelerometer, so I am not doing an ADC, instead I am getting the measurements over I2C.


texts: How does Solar Cell efficiency relate to Band Gap/ Isc/ Voc?

texts:
I am trying to understand how does the band gap Eg relating to the solar cell efficiency.
Efficiency is defined as VocIscFF/ Input power. if we have the same Voc * Isc product , that will translate to the same efficiency.
This is the case for below curve where we have the same Voc*Isc product.
In this case, does A and B has the same efficiency? or how does this relate to Eg?
Please help me to understand it.


texts: Thevenins theorem + two diodes and a resistor using graphical solution

texts: I've got a homework to solve this circuit by a thevenin's theorem and get a current and tension of the diodes using graph. I've looked all around the Internet and couldn't find one single video that does the same thing. Can anyone help me please ? Things that I know : U=10V,R1=10Ω,R2=20Ω, R3=30Ω


texts: Efficient Power Supply from CR2032 button cell

texts:
Continuing my weighing scale experiments...

From a single CR2032 button cell I would like to drive a PIC but also provide a voltage reference, 3.7v, to excite the load cell bridge.

Please could you suggest an efficient way to up the voltage to stable 3.7v from the cell voltage which will vary from say 3v to 2v during the lifetime of the battery.


texts:
Here are some representations of simple VHDL statements.

Synthesizing

        Y <= A and B ;

results in

Synthesizing

         A <= B or C ;
         D <= A and E ;

results in:

OR gate inputting to AND gate http://www.takeprint.com/wp-content/uploads/2011/01/221.jpg.

What are the representations of the following keywords ?

<=
:=
process
entity
wait
if-then
case
while
for

VHDL is a hardware based language. Thus, all of the keyword must have one representation in real life.

For example, after synthesizing:

          <=

what will be the result - just a wire ?

For a more complex synthesis, what will be the result of

for index in 1 to 32 loop
    if product_register(0) = '1' then
        product_register(63 downto 32) := produce_register(63 downto 32) + multiplicand_register(31 downto 0) ;
    end if ;
    product_register(63 downto 0) := '0' product_register(63 downto 1) ;
end loop ;

When we use for or while, after synthesizing what is the representation?


texts: Do class D headphone amplifier ICs typically contain integrated step-down converters?

texts:
Headphones can range in impedance from 8 ohms to a couple hundred ohms, and many only require a few milliwatts. This means that - for a low impedance headphone - only a few hundred mV RMS will be needed at the output.
Typically a class D headphone amplifier IC will be used with a supply voltage of 1.8V to 3.3V. I'm confused about how this high supply voltage is used to drive an appropriate voltage level on the headphones without making one of 2 concessions:

The headphone amp includes a voltage regulator inside of it that will supply the voltage rail for the output driver with a lower voltage.
Less than 100% of the available "duty cycle swing" is used in the amplifier.

My questions:

Is something ACTUALLY being done inside the class D amplifiers to bring down the voltage delivered to the headphones, or is it not that high?
If the voltage does need to be brought down, am I correct in assuming that at least one of these 2 things has to be done internally inside the headphone amp IC to bring it down, or are there other ways?

I'm not asking for information about how to use a headphone amplifier IC; I want to know how a class D amplifier designer would practically deal with a super-low power output requirement that a low-impedance in-ear earbud would present.


texts: Characterising an Audio Isolation Transformer

texts:
Rummaging around the junkbox in an effort to find a 600:600 ohm audio isolation transformer, I found a possible candidate rescued from a store closure some time back.  It's basically a cheap, low power unit that looks something like this:

Unfortunately, it came without a datasheet, but I had marked it 1:1 (probably after some quick measurements).  Now the 600 ohm termination resistances are significant and I'm wondering how I might determine if this is actually a 600:600 audio isolation transformer.  The inductance of both primary and secondary are both around 395mH, whilst the winding resistances are 40 ohms and 50 ohms (oddly, not quite the same).

What's the best way to determine if this audio transformer is designed with 600 ohm terminations in mind?


texts: DC voltages at long distance from battery

texts:
I have 12 volt and 135 ampere battery. Now I want to connect a device approximately 300 feet away from the battery.

When I connect it at this distance, my device does not work. When I connect the same device to the same battery at a shorter distance, the device does work.

What can I do?


texts: Why are JFET transistors used in circuits with high input impedances?

texts: I read an introductory textbook to understand this but it doesn't tell the reason behind it. Is that because the JFETs require much less voltage to operate comparing to BJTs and one needs to drop voltage at the input? I'm a bit confused.


texts: Are sealed lead-acid batteries safe to use indoors?

texts:
I have a small, 12V sealed lead-acid battery. I know regular lead-acid batteries can be dangerous to use or charge indoors, due to the fumes they release and the potential for acid to leak out or spill. A sealed lead-acid battery wont release fumes or spill though, correct? Does this make it safe to use/charge indoors?

Thank you!


texts:
In several designs I've come across the following setup. Design -> RC Network (High Pass) -> Oscilloscope Input:

Where SK2 is the SMA connector from the PCB that goes into an oscilloscope.

Some questions:

What is the purpose for having two RC networks? I can understand that the 2.2uF cap will allow frequencies above 1.45kHz (fc= 1/(2πRC)) and the 100nF cap will allow 31.85kHz. But why not just use the 100nF cap? Is there some limitations that the 100nF cap would normally have that would require a 2.2uF cap?
Or am I mistaken and this is actually just a simple RC circuit where the time constant t=RC is the importance of this setup?
If the latter is true, why would you need an RC network before an oscilloscope input? I understand you need 50ohm resistor for impedance matching, but then why the capacitors?


texts:
I am having trouble working with OLA(online arithmetic addition) radix 2 SD(signed digit) addition MSDF(most significant digit first).

If I have an 8 bits range unsigned number and a redundant and symmetric set of \$\left\{ {-1, 0, +1}\right\}\$
with the following table:

+1 ---> 01
 0 ---> 00
 0 ---> 11
-1 ---> 10

If I want to make \$a-b=c\$, I do not understand how the operation of \$a-b\$ is performed in binary.

If we have \$25-10=15\$,

$$25_{10}=0001 1001_2$$
$$10_{10}=0000 1010_2$$

If we map each two consecutive digits to the those in the table, how do I perform the computation so that I could implement it in hardware?


texts: For UART, should I use parity on a board level?

texts:
I am considering whether to use parity or not with my UART. It is a board level high speed (upwards of 115,200 baud) signal. The traces are very short (less than 2 cm), MCU to DSP, but they could pick up noise. During a logic analysing session using my logic sniffer I noticed one byte was captured incorrectly, it was just a single error. I couldn't replicate it. Now I'm wondering whether I should include parity.

My application is somewhat safety critical in that a failure would lead to a graphical error on a HUD/OSD which could provide incorrect information to someone piloting a model aircraft. However, the HUD is updated at 30 frames per second, so any glitch would be temporary. One problem that could happen is it could send a command which put the OSD into an incorrect state where it did not display anything, leaving the pilot blind about 25 km away from home... which is not good.

Will including parity protect me against common glitches or will it just make the protocol slower? Why is it that most UART protocols do not have parity? And is there a reason to select odd or even parity over each other?


texts: variable voltage divider using transistors

texts:
I found this schematic for a water level indicator:
sensor schematic

I would like to modify it some.  Namely, instead of illuminating LEDs I would like to make it a variable resistor (aka make a voltage divider circuit out of it).  I would be using it in the same application though (i.e. stainless screws in a PVC pipe to sense water level by contact method).

Here is the application this schematic came from: sensor application

In my application I want to supply Vcc with 5VDC and have the circuit divide that to an analog input on an Arduino.

I redlined the schematic to what I think might work, but I'm not an analog circuits expert.  I would appreciate any guidance or links or ??? whatever can help me out.  Here is my redline (PS the R value of the resistor(s) i've added is TBD):


texts: Difference in conductivities of metals and semiconductors based on quantum theory

texts: According to Fermi-Dirac statistics, in a metal, only certain number of valence electrons take part in conduction when they acquire an energy equivalent to KT for some temperature. Now my questions is: How is this different from conduction in a semiconductor where the concentration of conduction electrons also depends on the temperature due to breakage of covalent bonds? Why should resistivity due to electronic vibrations play a larger role in a metal than in a semiconductor? Note: I have just finished an undergrad course on quantum mechanics where we dealt with conduction in metals.


texts:
I'm going to use a DG403 analog switch, supplied with +/-15V, to switch an audio signal below that range.

datasheet

The logic signal would be 0V/5V, so I need 5V on the VL pin of the switch. The logic signal is coming from another PCB, and there is no 5V source on the board with the switch.

I'm trying to understand if I can simply use a voltage divider from +15V (which is already stable and regulated) to provide 5V to the switch, or do I actually need to use a 5V regulator?


texts: Why is it that most ADC have even number of bit resolution like 8, 10, 12, 14 bits etc. Odd numbers are not available.


texts: I am working with an home made PXIe card. The PXie controller is a PEX8311. The EEPROM used to save name and configuration registers is a 93C66. I need more user space to save calibration data and replaced that unit with a 93C86 (same as the '66 but with more bits) but when I turn on the PXI chassis I don't see my card on device manager and then I cannot use it to work... somebody has an idea why?


texts:
I originally planned to use ISOW7841 digital isolator with Isolated power to interface part of my circuit. But Having the power and signals on one IC, is causing me problems. This is because I need to have a 5v on my isolated circuit, and the digitals signals are on 3.3v logic. Meaning For me to have 5viso i have to have 5vin meaning that the digital signal level would also be 5v and therefor i have to place level shifters on both sides of the isolator.
So I decided to split it into signal and power. So that the digital signals can be at 3.3v while still having the 5v power. As for digital signals it pretty easy to find an IC like the ISO7741. What im having trouble looking for is the Isolated power IC. What would they be called using terms like power isolators just brings me back to digital isolators the category ISOW7841 belongs Or being brought to those really expensive modules. My load is not high and will consume less than 100mA at 5v.


texts: ICSP Circuit: Vpp (13V) and Vdd (5V) on Pic microcontroller MCLR pin

texts:
When hooking up ICSP, is it safe to connect Vpp to MCLR while the +5V from ICSP is also going to the MCLR pin though a pulldown resistor and Vdd of the microcontroller?

I'd suspect this to be unsafe as you would get 5V and 13V from two different voltage sources at the MCLR pin momentarily.

How can you correctly design an ICSP circuit?


texts: I'm familiar with the idea that RX means receive, and TX means transmit. Therefore, if I'm wiring two IC's together, feeding the TX of the sending chip into the RX of the receiving chip makes sense. How does this labeling standard extend to other devices that aren't either the source or termination of the signal? For example, I have a USB connector that has certain pins labeled RX and TX. It seems like the RX pin could mean "receiving from the cable" or "receiving from the device" - so the meaning is not as clear. Obviously I can check the standards for USB to determine the answer to this particular question, but I am curious if there is a more general labeling system that applies in these non-obvious cases. And, is there ever a case where an IC would have a pin labeled RX that isn't a receive input (ie. trying to imply that it is driving a receiver or something)?


texts: Profet Smart Highside Power Switch Output Always 'High'

texts:
I bought the Infineon Smart Highside Power Switch - PROFET BTS442E2, in order to switch a ~16V supply using a logic level PIR sensor.

BTS442E2: http://www.mouser.com/ds/2/196/Infineon-BTS442E2-DS-v01_01-en-785251.pdf
PIR Sensor: https://www.jaycar.com.au/medias/sys_master/images/9229257965598/XC4444-dataSheetMain.pdf

The switch has 5 pins:
1. Logic GND - Connected to GND
2. Input - Connected to PIR output
3. Vbb - Connected 16V
4. Diagnostic Feedback - Not connected
5. Output to the load - Connected to input of NAND gate

I would have imagined that the switches output should be 0V when its input from the sensor was low. However, when PIR is LOW - Switch output is ~9V. When PIR is HIGH - Switch output is ~ 16V.

Have I misunderstood how this device works or is this how it should behave?


texts: Is upping the voltage on a multiplexed LED display an appropriate response for dimness?

texts: I have a 10 character x 16 segment display that I'm driving using multiplexing off a PIC. The problem is, however, that with each display only being on 1/10th of the time, the display appears much dimmer than it normally would. Currently the LED's are getting their recommended voltage - 2.2 volts across each red segment. Would increasing the voltage across the display be a safe way to make it brighter? Is there a way to do this in software?


texts: When doing the DC analysis of a common emitter amplifier, why can we disconnect the parts involving capacitors?

texts: I don't understand why the components involving the bypass capacitors and the coupling capacitors need to "disappear" when we are doing the DC analysis.


texts:
I have a question about direction of vectoral line integral in formula of electric potential and electric field.

In electrostatic I assumed \$B\$ is positive potential and \$A\$ is negative potential so the boundary of the integral is negative to positive and also there is a minus sign outside the integral, and also \$d\ell\$ direction is always positive. This approach was always true in my electromagnetic 1 class.  For example if electric field is negative in the y-direction it means that the upper side is more positive and the lower side is more negative through the y-axis.

-But In electromagnetic 2 according to Faraday's law, time varying magnetic fields create emf. But this time the line integral is closed loop and I am very confused, what should I choose?  Which direction is positive and negative and where is the minus sign of the integral? For example if path is a circular loop
between 0 to 2\$\pi\$ how can I decide the positive and negative direction 0 to 2\$\pi\$ or 2\$\pi\$ to 0 and where is the minus sign?


texts: How does verilog evaluate conflicting assignments?

texts:
Is code like the following legal or would this give undefined behavior in case reset is set?  Would the compiler turn the initial assignment into a conditional or first increment the counter, then reset to 0? If this is executed sequentially, how are these sequential relationships represented in hardware?

always @ (posedge clk) begin
  counter <= counter + 1;

  if (reset)
    counter <= 0;
end


texts: Main Stack Pointer(MSP) vs Process Stack Pointer(PSP)

texts: I was reading the STM32 Programming manual and somewhere on "page 18 " i see these two kind of stack pointers. I always think that there is only ONE stack and therefore only ONE stack pointer to that exists in MCUs and now i'm confused of what these pointers are and what's the difference between theme and each of these is used for what?


texts: Suppression capacitors? What type should I use?

texts:
I'm building a digital power base for a Scalextric slot car track using the schema provided here (you might have to click the "Powerbase Circuit" tab).

Now, my question is, what type of capacitors should be used for C7 and C8 (the right-most ones next to U3 & U4). What is said about the caps in the text is only "Output protection is provided by suppression capacitors C7 & C8", but nothing about their type.

At my local electronics shop, the only bipolar capacitors they had was 1,5uF of the following type: "Visaton elko glatt 1,5uF 10%". It also reads "For high quality speaker networks". See this link for a pic.

Can I use these caps for this purpose or should I get another type with correct rating (of 1uF)? In that case, which type should I use?


texts: The program doesn't work correctly when I toggle the pin via Set and Reset register

texts:
I have two program to do the same task. the both should toggle GPIOB0. the first program is this:

#include "stm32f10x.h"

/* Private functions ---------------------------------------------------------*/

GPIO_InitTypeDef GPIO_InitStructure;

void GPIO_Configuration(void);

int main(void)
{
    GPIO_Configuration();

    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;
    GPIOB->ODR ^= GPIO_Pin_0;

    /* Infinite loop */
    while (1)
    {

  }
}

/*******************************************************************************
* Function Name  : GPIO_Configuration
* Description    : Configure GPIO Pin
* Input          : None
* Output         : None
* Return         : None
* Attention      : None
*******************************************************************************/
void GPIO_Configuration(void)
{
  RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB , ENABLE);
/**
 *  LED1 -> PB0
 */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
  GPIO_Init(GPIOB, &GPIO_InitStructure);

}

And the output:

Ok, five pulse as I expected. another program is this:

#include "stm32f10x.h"

/* Private functions ---------------------------------------------------------*/

GPIO_InitTypeDef GPIO_InitStructure;

void GPIO_Configuration(void);

int main(void)
{
    GPIO_Configuration();

    GPIOB->BSRR = GPIO_Pin_0;
    GPIOB->BRR  = GPIO_Pin_0;
    GPIOB->BSRR = GPIO_Pin_0;
    GPIOB->BRR  = GPIO_Pin_0;
    GPIOB->BSRR = GPIO_Pin_0;
    GPIOB->BRR  = GPIO_Pin_0;
    GPIOB->BSRR = GPIO_Pin_0;
    GPIOB->BRR  = GPIO_Pin_0;
    GPIOB->BSRR = GPIO_Pin_0;
    GPIOB->BRR  = GPIO_Pin_0;

    /* Infinite loop */
    while (1)
    {

  }
}

/*******************************************************************************
* Function Name  : GPIO_Configuration
* Description    : Configure GPIO Pin
* Input          : None
* Output         : None
* Return         : None
* Attention      : None
*******************************************************************************/
void GPIO_Configuration(void)
{
  RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB , ENABLE);
/**
 *  LED1 -> PB0
 */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
  GPIO_Init(GPIOB, &GPIO_InitStructure);

}

And output:

As you can see, there is just one pulse. Why? looks like it cannot make four next pulse. but why?

Edit1: the MCU is STM32F103RET6.

Edit2: all explanations you can see in the reference manual for these three registers:


texts: Directly Using a Smart Charger with An Old Vector Hunting Spotlight?

texts:
I have an old hunting spotlight (http://documents.dewalt.com/documents/English/Instruction%20Manual/Vector/VEC184POB.pdf) which has a small 12V sealed lead-acid battery.

The chargers that come with it aren't smart chargers (And may overcharge the battery/not trickle charge it), but I have a modern smart charger and would like to use it with it.

The battery terminals aren't exposed though. The charger uses a typical 12V cigarette lighter which I can wire my smart charger to.

Can I just use the smart charger, or is it likely that this will damage the internal circuitry?

Judging by the wording of the manual, I would assume that the 12V DC source just directly charges the battery.


texts: Measure delay of sound in wood with piezo sensor without an oscilloscope

texts:
First of all, excuse my layman terminology but electrical engineering is not my speciality.

I am currently trying to measure the delay of a sound wave travelling through different pieces of wood. I have already read on here that this is obviously possible with two piezo sensors (and a knocking device, e.g. a hammer) and an oscilloscope. Since I'm on a tight budget I am not willing to buy one just for this experiment.

Now I was wondering if I would get accurate measurements if I was to use a Raspberry Pi and an ADC (I have a MCP3008 lying around) as well as two piezo sensors. Is the sampling rate high enough to measure delays in the µs range?

If this is not possible, I would appreciate other low-budget suggestions. I was maybe thinking of a circuit which first subtracts the two signals which I can then convert via my ADC.


texts: How much current does this Opto isolator output (HCPL-3180)?

texts: I wanted to use it like this in this configuration][How much current does this Opto isolator output (HCPL-3180) ?


texts: Dip switch or rolling code garage door opener?

texts:
I'm a total noob in electronics field and want to begin. (I'm an IT engineer).
I'm trying to use my remote garage door opener (868 MHz HF) to create a system with my Raspberry Pi so I can replicate the signal when I use an Android application (by contacting a web server on my Raspberry).
I did some research and found there are two different remotes: DIP switch ones and ones with rolling code where we can't replicate the signal as the code is changing every time.
I opened my remote to check and as I'm a total noob, I don't really know how to know which system it's using.

Is it easy to replicate?


texts: Why are different currents through the TVS diode or 8-20 us and 10-1000 us

texts:
In datasheet you can see that the currents are different.

For any TVS diodes, Ipp(8-20)> Ipp(10-1000). For an example, see datasheet SM15TY

I do not understand why the current depends on the overvoltage time?


texts: Bridge rectifier as load for an SSR circuit

texts:
I wanted to control the power to a bridge rectifier. I had two ideas in my mind:

Using a PCB mounted power relay driven by a transistor (is isolation maintained?)
Using an SSR, i.e, a power triac driven by a optotriac, as shown below

In both cases, I would have to place a NTC thermistor to limit the inrush.
The idea I chose was the SSR, which I haven't tested yet. But, someone told me:

Zero crossing will work for the first 1/4 cycle, but then:

There will be no current flow to the "zero-volt switch" IC for it to know when the zero-cross happens, because "2200uF" is charged to 170V & all bridge diodes are reverse biased.
Even if a firing pulse is given to triac @ zero-cross, it will not latch-on, because the available current is below "hold-on" current for Triac*

I would like to hear your viewpoints.


texts:
I'd like to know if it is theoretically and/or practically possible to enable a smartphone (iOS or Android) to communicate with another device via IrDA (IrCOMM) using a simple infrared transceiver that's plugged into the 1/8" audio jack.

The IR transceiver would be as minimal as possible: just an IR LED and IR receiver soldered to a typical 4-conductor 1/8" audio plug.

The basic idea is that the app would read/write to the audio port to control the IR transceiver to talk to another IrDA device. We're assuming the IrDA protocol stack is implemented in the app.

Are there any physical limitations of an audio port, such as the frequency range, timing precision, power output, mic sensitivity, etc., that would prohibit controlling an IR transceiver to the extent necessary to communicate via the IrDA protocol?

We've seen the simple DIY television remote controls for iPhones, but they are only transmitters at specific frequencies (and even in those simple cases there were complexities involved in producing the 38kHz carrier frequency). In our case we're interested in two-way complete support for IrDA.

Any insight would be most appreciated!

EDIT

Just to clarify, in my understanding there are two ways to approach this: (1) IrDA stack in hardware, or (2) IrDA stack in software.

In case (1) you would use an IrDA transceiver (e.g. IRMS6118) with an IrDA encoder/decoder (e.g. MCP2150) connected to a microcontroller with a modem plugged into the audio port and the smartphone app would use FSK modulation via the audio API's to talk to the modem. So:

App > FSK > Audio Port > Modem > Controller > IrDA Coder > IrDA Transceiver

In case (2) you would skip the digital conversion altogether and the app would use the audio API's to directly control an LED and IR receiver (in which case the app would be responsible for implementing the lower levels of the IrDA stack for handshaking, etc.). In this case the IR LED and receiver would simply be soldered directly onto a 4-connector 1/8" audio plug (no circuit boards or IC's or power source or anything).

App > Audio Port > IR LED/Receiver

I've done quite a bit of searching online but haven't found any mention of either of these as working prototypes.

For case 1, some folks have the audio-to-modem part working (e.g. softmodem) and others have the IrDA-to-controller working (e.g. sor) so putting them together seems reasonable.

But I have not found any mention of case 2, and I'm wondering if it is because (a) it's just not possible for the audio API's of a smartphone to control an IR LED/receiver via an audio port well enough to implement the IrDA protocol, or (b) there are no software implementations of the IrDA stack available, or (c) it would be too much work to port the software stack over to the mobile platforms, or (d) some other reason.


texts:
I'm solving previous' years exams problems and i'm having trouble understanding one part of the problem. So I solve the first part and I have the truth table which is:

I did elimination with Karnaugh and I've got that output D is (A'B + C). Now, the second part says that I've got decoders of all combinations and OR chips. It wants me to implement the circuit with the simplest possible way.

Now, I know that with decoders I can implement all circuits and when I've got functions in format of sums (Σ1,2,3,5,7 in this case) I can use a decoder but I've got only one output function and all the exercises i've seen have 2+ outputs. What do i do? I create one 3x8 Decoder and a 5-input OR gate?


texts: Is this BJT reverse \$\beta\$ believable?

texts:
Looking at the manufacturer's spice model for the Rohm 2SC4713 BJT, I was struck by the high reverse \$\beta\$:

BR=123.13

Is a value this high believable or an obvious misprint?  Typically BJTs have a reverse \$\beta\$ value somewhere in the range 1 to 10.
Possibly the best way to find out is buy a device and test it!


texts: How to protect my DIY bench power supply from reverse polarity?

texts: I have been playing with arrays of 18650 batteries for the last 10 months, charging and discharging them all the time with my LM338K based power supply, that, until tonight, where I inadvertently connected (backwards) a semi charged array (pack) of 2P3S delivering 10v and who knows how many amperes in shortcircuit, and it looks like I fried the LM338K, I know I can avoid that with just a single beefy diode in series, my question is: is there any other way where I don't lose the 0.7V voltage drop in the diode? Should the regulator have survived? The circuit for the regulator is the one in the datasheet and surely it does have overload protection and overcurrent/thermal and whatnot, but I think hooking my battery pack in reverse was just too much and unexpected.


texts: Puzzlement on Evaluating the Datasheets of a GLCD

texts:
I have decided to use an LCD display for my project. In order to learn how to use one, I have consulted its and its drivers' datasheets. Here are the links for them:

Link for the LCD display's datasheet: WDG0151-TMI-V#N00.

Link for the LCD display's segment drivers' datasheet: NT7108C.

Link for the LCD display's com driver's datasheet: NT7107C.

If you would excuse, I would like to ask a couple of questions regarding them.

1) First of all, why aren't pin numbers of the drivers shown at the block diagram in the LCD display's datasheet which is at p.10? Also, not every signal's name is shown as well. Am I supposed to be able to extract a meaning out of a block diagram without knowing which signal goes to where?

2) Another puzzling point is as follows: In the p.10 of the LCD display's datasheet, there is a block diagram. In that diagram, there are 8+6 lines connected to the MPU. Also, there is an application circuit provided in p.20 of LCD display's segment drivers' datasheet. In the application circuit, there are 8+7 lines connected to the MPU. Now what does that mean?

3) In the p.6 of the datasheet of NT7108C, pins; CS1B, CS2B and CS3 are defined as follows:

  Chip selection

  In order to interface data for input or output, the terminals have to
  be CS1B=L, CS2B=L, and CS3=H.

and throughout the entire document, only that given combination of CS1B, CS2B and CS3 is mentioned. My question is: If only a single combination is being used, why are there 3 pins provided for a single task, instead of just 1?

4) As my last question, in this page, there is an application provided using the same LCD display. In that page, there is a figure given which explains how the display is structured. My question is: How are the authors of the page were able to come up with that figure? More precisely, which points in the datasheets helped the authors of the page to come up with that figure?

Thank you very much in advance.


texts: Troubleshooting wien bridge oscillator circuit with 741 op amp

texts:
I built the standard Wien bridge oscillator circuit using the UA741CN op amp IC, however I am not getting any oscillation.

I am powering this circuit with two 9V batteries. I'm using the values R1=R2=10KΩ, C1=C2=100nF, R3 = 1KΩ, R4 = 470Ω. The oscilloscope just shows a flat line, no matter what values I try. I also tried hooking up a 8 Ohm speaker to V_OUT and circuit ground, since the oscillation amplitude and expected frequency are sufficient to make the wave audible. But there is only static.

I have tried a number of things to troubleshoot the circuit:

Using different resistor values, consistent with the circuit requirements.
Built a working comparator circuit using the op amp chip to ensure that the chip is good.
Checked all voltages.

I'm very new to electronics, so I might be missing something simple. I am wondering if somebody could provide a step-by-step guide that would eliminate any common problems with this circuit.


texts:
I'm having trouble interpreting the results of my spectrum analyzer, concerning noise generated with an AWG. So, step 1. The AWG generates gaussian noise with mean 0 and variance A at a sampling rate of 1.2GSamples. I will look at the noise in the 50 - 150 MHz band, so it should still be produced relatively well there. For A I chose for example 0.2, with a Vpp of 4.5, which means that the entire time trace of 3 million points should be produced by the AWG without too much trouble; no clipping or anything.

Now, I then hook up the AWG to the spectrum analyzer, which has a 50 Ohm input. I pick a 100MHz center frequency, 100 MHz span, and set my RBW to 1 MHz. I take about 1000 points. Now, the amplitudes are in dBm so I convert them to watts and divide by the RBW (so Watts per Hertz), and go back to dBm/Hz. This should be a proper power spectral density; moreover the inbuilt function of the spectrum analyzer that calculates the PSD gets me the same values.

However, this does not work out with the theory. In theory, the spectral density of white noise with variance A can be calculated through the autocorrelation function:

$$
\begin{array}
RR_{xx}[\tau] &=& E\left[ x[t] x[t+\tau] \right]\\
&=& \left \{ \begin{array} EE \left[ x[t]^2 \right], {\rm if\ }\tau=0 \\ 0, {\rm otherwise} \end{array} \right.
\\
&=& A \delta[\tau]
\end{array}
$$
where the last delta is the Kronecker delta. By the Wiener Khinchin theorem the power spectral density is then simply given by the Fourier transform of the above, which is rather nicely equal to just A.

Linking this to my measured power spectral density, I divide by the 50 Ohm resistance and go to the dBm/Hz units. Great; except the numbers I get are completely different. From the above considerations I expect a power spectral density of around -24 dBm/Hz, and I measure -78 dBm/Hz. Clearly something is terribly off, but I simply do not know what.

So this is my question; what am I doing wrong to measure such a different power spectral density?

As for the amplitude calibration of the spectrum analyzer, I checked by using a signal generator at 54 MHz with a power of -50 and -60 dBm; it reports these values quite nicely; that is probably not the issue.


texts: Input and Output Voltage of a Full bridge rectifier

texts: I know If we provide a sinusoidal AC Voltage across the Inputs of a full bridge rectifier we get a fluctuating DC Voltage (more or less) with the peaks of source AC Voltage. But what would be the peak voltage after smoothing the Output DC with Capacitors if we hypotactically provide 220VAC RMS?


texts: Can I trust in visual inspection to identify LED terminals?

texts:
In the figure above, LED A is a regular 5mm LED and the visual identification of its terminals polarity is well known.

As you can see, on LED B the anode is identified by the longer leg, but the other rules for visual identification are inverted.

I've confirmed the situation above with a multimeter.

I have no datasheet or reference for LED B.

I never saw an LED with these issues before.
Is LED B the result of a manufacturing error?

Thanks in advance.


texts: read from uint32_t in flash is zero STM32F1

texts:
I am working on an STM32F103RBT6 program and at some point I need to store values in the FLASH.

Writing in Flash is working as a charm, if I parse through the memory of my microcontroller, I see that the data has been written at the expected spot.

However, if I try to read the data I stored on a word (uint32_t), I read 0.

__attribute__((__section__(".nb_Frames"))) const uint32_t nb_Frames_Flash;
uint8_t CAN_nb_Frames_Tx_cc = 0;

[...]

CAN_nb_Frames_Tx_cc = (nb_Frames_Flash & 0x000000FF);

For example here, I want to get the low byte of the value stored in nb_Frames_Flash (0x01 for example), but CAN_nb_Frames_Tx_cc stays = 0.

I am sure that nb_Frames_Flash != 0 because If I go through these lines step by step thanks to the debugger, I can see that nb_Frames_Flash = 0x00010101 (which is the value I wrote in the Flash). The assignement just feels like it's not going through ...

I have tried to change the assignement : CAN_nb_Frames_Tx_cc = (nb_Frames_Flash & 0x000000FF); by adding casts, changing the definition of CAN_nb_Frames_Tx_cc (uint32_t for instance), going through an intermediate variable ... But it just won't work ...

I am really stuck here and I don't know why it is not properly working.

The thing that makes me go nuts is that reading in Flash is completely working for structures. I stored structures in Flash, and I have no issue to read them and store them in a RAM variable ...

In advance, thank you for your help !

EDIT : Here is my linker script :

{
RAM (xrw)      : ORIGIN = 0x20000000, LENGTH = 20K
FLASH (rx)      : ORIGIN = 0x8000000, LENGTH = 128K - 5K
Erases (RW)     : ORIGIN = 0x801EC00, LENGTH = 4
Frames (RW)     : ORIGIN = 0x801EC04, LENGTH = 4
TRAMESTx (RW)   : ORIGIN = 0x801EC08, LENGTH = 1400
TRAMESRx (RW)   : ORIGIN = 0x801F180, LENGTH = 1800
TRAMESADC(RW)   : ORIGIN = 0x801F888, LENGTH = 800
TRAMESOP (RW)   : ORIGIN = 0x801FBA8, LENGTH = 800
}

/* Define output sections */
SECTIONS
{
  /* The startup code goes first into FLASH */
  .isr_vector :
  {
    . = ALIGN(4);
    KEEP(*(.isr_vector)) /* Startup code */
    . = ALIGN(4);
  } >FLASH

 .nb_Erases :
 {
    . = ALIGN(4);

    *(.nb_Erases)

    . = ALIGN(4);
    } > Erases

 .nb_Frames :
 {
    . = ALIGN(4);

    *(.nb_Frames)

    . = ALIGN(4);
    } > Frames

 .user_TramesTx :
 {
    . = ALIGN(4);

    *(.user_TramesTx)

    . = ALIGN(4);
    } > TRAMESTx

 .user_TramesRx :
 {
    . = ALIGN(4);

    *(.user_TramesRx)

    . = ALIGN(4);
    } > TRAMESRx

 .user_TramesADC :
 {
    . = ALIGN(4);

    *(.user_TramesADC)

    . = ALIGN(4);
    } > TRAMESADC

 .user_TramesOp :
 {
    . = ALIGN(4);

    *(.user_TramesOp)

    . = ALIGN(4);
    } > TRAMESOP


texts: Output Voltage Formula verification of Operational Amplifier circuit

texts:
I'm trying to built an op-amp circuit for a PT100 temperature sensor.
I've found the following circuit diagram online (from a polish website):

And I'm trying to find the formula for the output voltage as a function of the input voltage.
I came up with the following formula (sorry, it's an image, no Latex here):

Can someone please help me verify that the last formula expressing Vout as a function of Vin is correct?
Thanks in advance

EDIT1: at the beginning of the demonstration, R1 and R2's values have been switched.

EDIT2: Please, this question IS NOT a duplicate of a previous question I've posted. In this question, I'm trying to verify that my computations are OK. In the other question I was trying to ask if it was common for Proteus to present results that slightly differ from the electric model.


texts: Rules and guidelines for drawing good schematics

texts:
There are a lot of poorly drawn schematics here. A few times people have actually asked for critiques of their schematics. This question is intended as a single repository on schematic drawing rules and guidelines can point people to. The question is

What are the rules and guidelines for drawing good schematics?

  Note: This is about schematics themselves, not about the circuits they represent.


texts: High side MOSFET Driver component selection

texts:
I'd like to drive high side and low side MOSFET for buck converter, so I have used IR2184s,(the image bellow) to do the job,

The frequency of oscillation is 1Mhz, so DRVR is a square wave signal of 1MHz frequency and 5V peak.
VBATT=23V
and the other components are shown in the image,
The duty cycle is 50% and the mosfet used to be driven id IRF540

My circuit doesn't work as expected, (ie: I do not get a squar wave at bothe HO and LO)

I have recalculated the value of C6 but this  doesn't solve the problem, and I don't know why ??


texts: why electric motor or alternator have stack of plates?

texts:
i have noticed that all of the transformer/motor/alternator/electric actuator have a stack of metal for stator ( or where winding is done. ). why is that needed ? can same thing not achieve by using a block of metal ? i guess its because of performance. how much performance can possibly lost ?

why motor or  alternator has stack of metal plates instead of simple block of metal ? what is the difference between the two ?


texts: Does whole house surge protection device (SPD) protect from Ground (PE) surges?

texts:
I've been researching on whole house surge protection devices and came across an Illustration of lightning current flow from a direct strike near
the (protected) structure.

From my understanding Type 2 residential SPDs divert surges from L-N, L-PE and N-PE. But the above illustration shows a Type 2 surge I never considered before, where inductance from a nearby lightning strike to the ground causes surge in the Ground (PE) wire. Can a normal type 2 SPD protect from this type of surge event?

P.S. I have a type 3 SPD (to protect terminal equipment) which I currently use and a whole house type 2 SPD which I haven't installed. It is my understanding that both essentially divert surges to Ground (PE) but I honestly have no idea what they'd do when it is the ground wire that causes the surge.


texts:
I've searched and searched and can't figure out what this thing is. The trace on the bottom is going to a GPIO pin on a micro controller. The top trace goes out to a serial communications line. As best I can tell, the line is a half-duplex open drain serial connection. I think the comms itself is just bit-banged in the MCU.
Partially out of the image is a 5v zener diode. That Zener is being used as a voltage regulator and is connected to a 47.3k resistor, pulling up the comms line. I'm not sure what the resistor between the comms and the second line on the IC is doing, nor the other resistor on the right. All the resistors are 47.3k
Bottom left of the IC goes to ground. I assume bottom right is VDD.
I believe the writing is N14D4 written both directions. Google gives nothing for various combinations.


texts:
I have a couple Attiny85 based USB development boards (or rather, cheap Digispark clones from Ebay). The pin 5 seems to be always at high, no matter what I do. I am suspecting the manufacturer didn't disabled the reset. And hence it is pulled up internally.

Can someone please confirm this? I am tempted to lock the reset bit, but this means I can no longer program with over ISP. So I am hesitent.


texts: Choosing an appropriate voltage regulator to limit power consumption

texts:
I am new to the electronics world and trying to figure out how to choose the battery for the circuit.

The circuit consists of an ATMega328P-PU, a DS2321 RTC and a PIR motion detector sensor. It needs 5 volts to operate normally.

Initially, when a button is pressed the circuit has access to power input which automatically starts the RTC, sets the time and powers the PIR sensor through a transistor for a specific duration. During which, the sensor is trying to detect motion (with small delay) and lights up an LED for a duration different than the former. After the detection period is over, the controller enters in deep power down state until a trigger from the RTC wakes it up and from there the controller cycles between detection and sleeping state.

By implementing the above, i was able to reduce power consumption as much as i could.

The circuit for the controller already has a 5V voltage regulator which I can use to power the whole circuit, however, my problem is here, as i am not supposed to go below 5V, i have to use a higher voltage as input but as you guys are pointing out: using a voltage regulator will eat up the battery and then the battery size won't even matter. Thank you for pointing it out since i didn't know about regulators, i only compared schematics and decided accordingly.

If i measure the current draw of the circuit and its in the milliAmps range then would it be safe to use voltage regulator with a drop out voltage of 3-6V?

I updated this post to ask help about choosing a regulator without dramatically compromising the circuit's power consumption.

Sorry for the inconvenience.


texts:
I have a very specific need.
I need to avoid a VFD due to its square waves - my research requires exact sinwave frequencies of electrical current.

With that said
I have a Tesla turbine which powers a AC Generator. The tesla turbine is powered via heavy water - For reasons I can't go into the power is collected, transformed a number of times and then fed back into the water apparatus to 'push' down on the water which then goes back into the tesla turbine.

I need a way to generate AC from the turbine, convert it into D.C.for storage, the the D.C. Needs to be able to be fed back into a reliable AC sinewave for reuse. Probably by a AC gen...

What I was thinking is to have the AC generator which is being driven by the turbine ->feed to a battery stack, have that power stored as D.C.- Then have the D.C. Which is stored to Power a AC generator ...
The catch - I need the AC frequency to be modular - as in I need to be able to change the final AC frequency at will...

A VFD produces square waves - so I thought the second AC gen would be ideal.

Any thoughts, problems I'm going to have and solutions?


texts: What language to write USB 3.0 application for ADC demo board?

texts:
I need some suggestion/guidance on which language/setup to use to create an application with USB 3.0 connectivity that processes 1.6Gbps of data in real-time.

The application collects data from an ADC and plots it on a chart in the application. Basically, it is a high-speed data acquisition board I am designing, and need software to pair with the board.

Target operating system is Windows, but eventually support for OS X and Linux will be needed.

I have experience using FTDI USB 2.0 serial-mode chips, but not sure if USB 3.0 will be the same for speeds at 1.6Gbps.

Any comments/suggestions welcome.

Thanks!


texts:
I am using heater circuit for bio-medical application ( to achieve 37 degree Celsius for blood samples ). I am using opto-isolator P781F to isolate control circuit ( Micro-controller I/O pins - H1G shown in schematic) and heater.

Link for opto datasheet:
http://www.farnell.com/datasheets/90914.pdf

My schematic is as shown below:

H1G= I/O pin from LPC2138 controller

Heater = 12V,23 Ohms Silicon Heater

But, I am little worried as I have connected controller I/O pin directly to cathode of LED of opto. So, is there any loading issue I can face, what parameter will come in picture to check I/O pin source/sink capacity with OPTO pin.

Will this cause any loading or impedance problem? Do I need any buffer circuitry from controller I/O to opto circuit.

Thank you in advance.


texts: How does the CMRR of a fully differential amplifier change with input impedance imbalance?

texts:
Most pro-audio microphones provide a balanced output -- this is intended to provide improved noise rejection, and provided the output and line impedances are appropriately balanced, it does.  However, with conventional differential-to-single-ended conversion stages, source and line impedance imbalances degrade the noise rejection ability of the system.  Transformers don't suffer from this, but have problems of their own (magnetic coupling, size/weight, low frequency response), so the Whitlock bootstrapped topology has come into use for differential-to-single-ended conversion, at least at line levels:

Unfortunately, though, no microphone amp yet has adopted the Whitlock bootstrap for an internal differential-to-single-ended conversion function.  However, at least some pro-audio microphone amplifiers are designed to be fully differential -- i.e. they have a differential input and a differential output.  The intuitive thinking is that since a fully differential amplifier doesn't have a CMRR, it would not impact the ability of a downstream stage to reject the common mode signal, so cascading a fully differential microphone preamp with a line receiver is used to provide a high-CMRR balanced microphone input.

However, assuming a Whitlock bootstrapped line receiver (such as a THAT120x) is used for the differential-to-single-ended conversion function, does putting a fully differential preamp in front of it negate the ability of the Whitlock bootstrapped topology to maintain a high CMRR in the face of inbalanced input and line impedances?


texts: Detect aluminum using an inductive sensor

texts: I was wondering if you can use an inductive proximity sensor to detect aluminum or if a capacitive sensor must be used? I wasn't sure if inductive sensors were reserved for ferrous metals only.


texts:
my circuit is not giving me the expected voltage. This is used to measure the current flowing trought the shunt.

For example: if I expect 1.3, I get about 1,15V out. Anyone knows what I did wrong?

edit: the resistor is 5k of course, not 5000k

The voltage was measured with a multimeter.


texts: What track does this bias current loop through?

texts:
Please see the edit.

A source is coupled to a diff-amplifier circuit as sown below:

The 10k R1 provides a path for base currents to return.

But Im confused about the loop taken by ib2.

For ib1 I can say it loops through A-->B-->C(GND)-->D-->E--F

Is this loop for ib1 correct?

Im confused about ib2's track

Does ib2 loop through F-->G-->C(GND)-->D-->E-->F

But this doesn't make sense because current cannot loop back to the same terminal.

I put those capital letters for nodes as A, B, C ect.

What is the correct track for ib2?

EDIT:

Let me ask this way:

simulate this circuit – Schematic created using CircuitLab

In the above conceptual schematics Rb providing return path.

What are the loops for the input bias currents in terms of nodes for ib1 and ib2? I named all nodes with capital letters. An answer would be like A-->B--> ect. easy to demonstrate.


texts:
Background
I'm working on a PLL based frequency synthesizer for the 20m amateur radio band.  For reference, I've asked questions in relation to this project before (see here).  It uses the idea of an offset mixer in the loop to allow fine tuning, while keeping the course steps relatively large (5KHz) to achieve a higher loop bandwidth (around 400Hz).  I should add up-front, that this is mainly an educational exercise to discover how PLLs work.  If I can get the loop to lock, I'll be more than happy.  I'm not looking for
the lowest jitter loop or anything like that at this stage.
Here is the block diagram of what I have so far:

and here it is on the breadboard (if I can get the concept to work, I'd consider a more professional layout with a smaller number of boards):

Since I'm using an Analog Devices PLL IC (ADF4002), I've used the ADISimPLL application to suggest a loop filter design. The advise I've received on this site and elsewhere is to keep the loop filter as simple as possible to start.  I've settled on a simple active filter (shown below) and I can get the loop to lock if I simply have the PLL drive the VCO.  So, if I leave out the mixer, LPF and amps the loop will lock using the filter suggested by ADISimPLL.  However, adding back the offset components obviously changes aspects of the loop and the filter no longer keeps the loop stable.  I can play around with the phase margin in ADISimPLL to try to take account of the phase effects of other components in the loop.  Here's the design that allows a 70deg phase margin:

I believe I've successfully reverse engineered the loop gain equation used by ADISimPLL and I can reproduce the open and closed gain bode plots for the loop filter suggested (see my previous question).
The loop equation has the following format (for this type of charge-pump PLL): \$\frac{\frac{{I_{{cp}}}}{2 {\pi} } \frac{2 {\pi}  {K_o}}{s} {F}(s)}{N}\$ and the loop filter shown above has the following transfer function: \$\frac{{R_2} s\, {C_2}+1}{s\, {C_2} \left( {R_1} s\, {C_1}+1\right) }\$.  What I think I need to do, is alter this equation to account for the extra gain components in my loop and this is where I'm struggling.
Question
By my reasoning, I can ignore the lowpass filter, since it should have negligible effect on phase at the loop bandwidth.  I'm not quite sure about the effect of the mixer, but I think the amplifiers will be a problem.  Here's the amplifier following the LPF (called Offset Amp on the breadboard):

I chose this amp because it has broadband gain (the previous amp I designed was non-inverting and had practically no gain at the loop BW).  Here is the frequency response:

You can see that at the loop bandwidth, it has a lagging phase of approx -18deg and a gain of 11dB.
So, finally to my question: is there any easy way to account for the amplifiers (and mixer??) in the loop apart from working out the transfer function and including that in the loop equation?
I'm thinking, can I take the response given in LTspice and factor that into the ADISimPLL margin allowance or is that just not going to work?  Thanks for all your assistance and apologies for the (yet another) long-winded post!
P.S.  I feel I'm very close on this since despite the VCO signal hopping around on the scope, I can actually tune it coarsely (somehow the hardware frequency counter in the scope is picking up the changes in frequency but the jitter is really bad).


texts:
I intend on building a small robot with a DC motor that operates with voltage of 3V-6V. The website provides the no-load rpm, no-load current, stall current and torque all when it is at 3V. My first question is how can i determine this at 6V.

My second question is that from there, how do i determine the load on the motor in order to calculate if it is too much. Along with that i also need to know how to get the rpm at that load to calculate efficiency.

The motor is a TAMIYA 70167. Thanks in advance.


texts: Practicality of Logic Gates for a newcomer

texts: For my project, I was thinking of making a password lock using logic circuits. I have a basic understanding of logic gates and have a few designs. However, I have very little experience in how to actually put together a working circuit. I wanted to know if it was practical or even possible for a novice to make something like this. How hard is it to make the transition from paper to physical electronics?


texts:
I have a few 0603 LEDs that come with the instruction to bake them if they had the chance to draw moisture. What is the best way to do that?

Can I leave them in the tape, so I don't lose the orientation?
Alternatively, can I just run the entire board through a cycle with 24h at 50 degrees, followed by the normal reflow process?


texts:
This is an extension to the question "Safely housing a power supply" asked by Harry Braviner.
I plan to use a very similar power suppy as the main compnent:

In my case the need is to power a 24v 130w motor to drive a clockmaker / watchmaker 8mm lathe. A speed controller will be separate and not contained within the power unit housing. The lathe will be mounted on a stand which is about 4" deep and has a central slide out drawer, but that will leave an underside compartment ether side of the central area, which might be large enough to house the power supply subject to the answers I receive. Alternatively I'll build the supply as an external power brick with a fly lead that plugs into a socket on the lathe cabinet. A controller for the motor speed will be mounted on (or beneath) the lathe stand.
My questions are:

The answer to the original question recommended a metal junction box. Could a rigid plastic box be a safe alternative if the heat from the power supply is fairly low (or is it best to play safe and use a metal box)?
Is a ventilation fan likely to be needed, or can that be determined only by experiment?
If the power block is kept exernal (like a laptop) wth a fly lead to a socket on the lathe base, what style plug and socket would be appropriate to use that can take the likely current?

many thanks in aniciption,


texts: Building a power supply, want to stay alive

texts:
I am building a power supply for a very old laptop. The circuit uses a transformer (220 V primary to 15 V secondary, 33 VA) and that worries me a little. (Please note that I an enthusiast and so far I have been running microprocessors at low voltage and current.)

Since I already had the opportunity to experience how it feels to be a resistor during a power accident at our house last summer, I am considered with my safety a little, not to mention my other fears.

Can 2.2 A of output current cause serious harm to my person or anyone else around?
What happens if I short-circuit the secondary branch by accident?
Is it a proper thing to do to use a 2.5 A fuse given that the laptop is 15  V / 1.8 A? Should I place it:

(a) between the transformer and the rest of the circuit, or
(b) between the circuit of the power supply and the laptop?

What does it mean when they say the laptop requires a rated power supply? Does it mean the power supply should employ a stabilizer?

My answers, which I would like you to verify:

Hope not.
Sparks, buzz and the transformer dancing, but nothing after all.
It is, but it will burn immediately, because the filtering capacitors will load so eagerly they will burn it. And (a) is right.
It does.


texts: Insulation resistance and leakage current in capacitor

texts:
I am using the capacitor in a battery powered device but unable to find the leakage current. They have mentioned the insulation resistance minimum as 10 GOhms.
Can I take this into ohms law to find out the leakage current?

Capacitor link