texts: I'm trying to implement interrupt from RB pins. But it doesn't work

texts:
I'm new to PIC programming. I made a program to get interrupt from RB pins. but it doesn't work. My code is as follows:

int flag=0;
unsigned short temp = 0;

void interrupt(void)
{
    if(flag==2)
    flag=0 ;
    else
    flag++;

    if (INTCON.RBIF==1)
    {
        flag=9;
        temp = PORTB;
        PORTB = temp;
        INTCON.RBIF = 0;
    }

    INTCON.INTF = 0;
}

int i,j,k,mina,minb,seca,secb,hra,hrb;
void main()
{
    IOCB=1111110;
    TRISA=0  ;
    TRISC=0  ;
    PORTB=0;
    ADCON0=0;
    TRISB=1;
    ANSELB=0;
    INTCON=1;
    INTCON.RBIE=1;
    INTCON.RBIE = 1;

    INTCON.RBIF = 0;

    INTCON.GIE = 1;
    INTCON.INTE = 1;
    INTCON.PEIE = 0;
    OPTION_REG.INTEDG = 1;
    while(1)
    {
        for(i=0;i&lt;59;i++)
        for(j=0;j&lt;59;j++)
        for(k=0;k&lt;59;k++)
        {
            seca=k/10;
            secb=k%10;
            mina=j/10;
            minb=j%10;
            hra=i/10;
            hrb=i%10;

            if(flag==0)
            {
                PORTA=mask(seca);
                PORTC=mask(secb);
            }
            else if(flag==1)
            {
                PORTA=mask(mina);
                PORTC=mask(minb);
            }
            else if(flag==2)
            {
                PORTA=mask(hra);
                PORTC=mask(hrb);
            }

            Delay_ms(100);
        }
    }
}

All other sections are working, RB0 int is working too.. But the button from other inputs (RB4..RB7) are not working. The MCU I'm using is PIC16F722A.


texts:
I need to take power from ebike's battery (30–60VDC) for a datalogger (3V3) based on STM32 with almost no consumption.
My question is what is the most efective conversion from 60V to 3v3?
Is it good to use one DC-DC Converter from 60V to 3v3 or is it better to use more converters for example from 60V to 12V and second from 12 to 3v3? Maybe there is any better solution...?


texts: Finding the resistance of a practical inductor having its reactive power

texts:
Suppose I have a simple practical inductor as such:

simulate this circuit – Schematic created using CircuitLab

L is known. R is unknown and we need to find it. The supply frequency (say \$f\$) is known. Also the reactive power on the whole inductor (say \$Q_i\$) is known.

Here's my approach. The reactance on the inductive part would be (say \$\chi\$ )

$$\chi = \omega L$$

(where \$ \omega = 2*\pi*f\$). So the impedance triangle and the power triangle would be something like this:

that angle a is equivalent in both triangles. so this would mean that:

$$\frac{\chi}{R} = \frac{Q_i}{P_i}$$

We don't have \$P_i\$ ...however I have a source that says that the equation is just

$$\frac{\chi}{R} = Q_i$$

and that we can get R. The source doesn't provide steps. Just the equation. What am I doing wrong??

Actually I need to solve (the first part) of a question. Here's a screenshot of the question and the part of the solution of concern.


texts:
I'd like to use SIMtrix/Simplis Simulator for simulation of SMPS design, and I'm about to start building a peak current mode buck converter like the one shown below from richtek.com:

but unfortunately I did not find the current sensor device, please does anyone used this software and know where I can find this component in order to continue my simulation ?


texts: How is this crystal / ferrite bead / ground shield connected?

texts:
This is part of the schematic for a TI TAS1020B USB Streaming Controller MCU that I don't quite understand. Obviously the shield connects to one end of the ferrite bead, but what else? Are the XTAL pins connected the shield as well? And, does the shield have to be tied to other ground planes at a single point elsewhere (the way you usually do with isolated grounds) or is the connection through the ferrite bead the single point of connection? Does the shield have to wrap the components and traces exactly as shown?

From Figure 4-1 on page 71 of the linked datasheet:


texts: TimeQuest Timing Analyzer: What is the difference between post fit and post map timing netlists?

texts:
When we wish to add timing constraints to our design in TimeQuest Timing Analyzer, we have two options. We can use either a post fit netlist or post map netlist. Post map netlist is available after mere design synthesis, however the post fit netlist is only available after fitting.

Now my question is which is used when?

Is it true that post fit netlist has timing information but post map does not? Besides that, when comiling an FPGA design, is post map netlist defined using the "atoms" of the FPGA?


texts: Need to increase the amplitude of op-amp output

texts:
I'm using this circuit to measure the RPM of a DISC rotating at 24000 rpm. This circuit is working fine. But the problem is with amplitude. It should be of 4.2V, but actually is of 2V as shown in picture below. The question is how to increase the amplitude upto 4.2V.
The op. amp. is an LM324A


texts: Mixer LO to IF Isolation vs. 1*LO - 0RF Spur

texts:
I am working on a simple digital radio receiver and am confused by the difference between the LO to IF leakage vs. the 1LO - 0RF spur. These two tables in the datasheet of the Analog Devices HMC218B passive mixer are the source of my confusion.

The "Spurious Outputs" table lists the 1LO-0RF as being 3.4 dBc. Working from the test conditions at the bottom of the table, this means that the mixer would have an output spur at a frequency of 5.25 GHz 3.4 dBc below the power of the desired IF output, in this case 100 MHz. If the conversion loss of the mixer is 7 db (as is specified in the 2nd "Electrical Specifications" table), then for a RF power of -10 dBm the IF power at 100 MHz should be -17 dBm, so the power of the 1LO-0RF spur at 5.25 GHz should be -20.4 dBm.
If the LO to IF isolation given in the "Electrical Specifications" table is used to find the power of the LO signal at the IF port, one finds that the power of this unwanted LO at the IF port is -19 dBm. This calculation uses the specified LO to IF isolation from 4-6 GHz to be consistent with the frequencies used in the "Spurious Outputs" table.
The 1.4 dBm difference in 5.25GHz power at the IF port given by the "Spurious Outputs" table and the "Electrical Specifications" table is minor, but in my case the input RF power is around -50 dBm (@ 5.8GHz), not the -10 dBm that is used in these tables. This decrease in RF power significantly changes the calculated LO power at IF depending on which table is used to find the LO at IF power. For example, if the "Spurious Outputs" table is used in conjunction with the conversion loss from 4-6 GHz in the "Electrical Characteristics table" I find that the 1LO-0RF spur should be -60.4 dBm, 3.4 dBc below the -57 dBm IF output at the desired IF. However, if I use an LO power of 13 dBm (the LO power used throughout the datasheet), and I calculate the LO power at IF using the LO to IF isolation given in the "Electrical Specifications" Table, I find that the LO power at IF would be -19 dBm. Which method should I used to find the LO power at IF? Is there a fundamental difference between LO to IF isolation and the 1LO-0RF spur? Perhaps my understanding of dBc is wrong and is throwing off my calculations.
Thanks for your help.


texts: LED tests. Don't quite understand the math

texts:
I'm trying to understand the behaviour I'm seeing with some high power (apparently 5 watt) leds I purchased for some basic testing. I have one led plugged into a constant current 350ma power supply (using a Meanwell LDD-350HW to regulate current).

I'm measuring voltage across the LED at 20.32v which means I'm significantly over driving the LED at around 7 watts. It also means that I must have around 57 ohms of resistance somewhere from what I understand.

I'm assuming I'm missing pretty obvious here. Some advice would be much appreciated.


texts: On a schematic I have, some resistors read as R16, 0.025R, 3W. Some read as R60, 33R. I guessed that R16 or R60 are the labels, and 3W is the power. But what does 0.025R or 30R mean? Google search did not help much. Thanks.


texts: Can't upload sketch to my custom designed arduino Uno

texts:
I'm having problems uploading sketches to my custom arduino uno design. I have a ttl to usb based on the ch340 and at the same time I have a RS485 transcriber both conected to the atmega328 serial port, since I know I can't use both devices at the same time I added a jumper (J11) to enable or disable the RS485 part of the circuit when I want to upload sketches or use the USB port to debug my code, following the arduino uno design I added two 1K resistor in series on the RX and TX (R29 and R30) see https://electronics.stackexchange.com/a/213167/123482 so the RS485 takes preference over the USB when selected with the jumpers.

I have tracked down the issue to my USB part of the design, if R15 and R16 are 320k like on my schematic the arduino IDE can't upload code to the board, avrdude timeouts, if I change the resistor values from 320K to 1K most of the times the upload works as expected but fails when it tries to read back the flash memory, if I remove the resistors it always work as expected. Obviously the problem is there but why?

Note: Added 328 pinout


texts: Analogue encoder / multi-throw infinite-turn "potentiometer" from two-axis potentiometer/joystick

texts:
For an analogue multichannel audio-panner I essentially want to create something like an infinite-turn multi-throw potentiometer. The idea is to have one input which is distributed to 4-8 outputs through a resistor/opamp network where the "panning" is supposed to be continuous. You can imagine it like a surround panner where you can let a sound circle you if you have a symmetric speaker setup (ex octaphonic).

And I want it to be as cheap and simple a module as possible which is why I am avoiding VCAs/multipliers and try to route the audio signal directly through the panner instead of using it for control input only.

My current approach to be tested is based on using conductive materials (for now GRAPHIT 33, or a plastic-graphite mix) to create such an analogue "potentiometer" (because I did not find a ready-made component and for the fun of it) by creating a conductive ring or circle with evenly-spread taps/throws.

But my question here is more regarding an alternative:

Using a two-axis potentiometer (ie a joystick controller with two unconnected potentiometers placed in an 90 degree angle w.r.t. each other), is there a (simple) (linear) way to route (voltage) signals in a similar way as above mentioned approach would do? Ie, depending on position there would be an electrical connection to every (circular arranged) output but the further the output is from the input the higher the resistance which is something like a 2d potentiometer without separated axis.

Using the potentiometers as staged elements that distribute the signal to two outputs and then connecting this to another stage (with doubled amount of potentiometers) might some way or other work to single out individual outputs, but there problem is, there would be no "bleeding" to neighbouring outputs, but this does not seem very viable..

I am aware, using an encoder and digital potentiometers would be a plausible solution that would also allow for more possibilities (or panning/control behaviours) - but would need the necessary controller unit. I'm just curious if there is a simple solution using a (readymade) joystick..

ps. I'm afraid my electronics knowledge is rather rudimentary..


texts: Are there "female" 2.54mm screw terminals?

texts:
There are a variety of male screw terminals with pins one can solder into a PCB.  Are there female screw terminals that fit directly over the 2.54mm pitch/spaced "jumper" pins that small boards like the Teensy stick into breakout boards?

I've found boards that do 2.54mm, but they're huge. I've also found 3.5mm pitch female pluggable screw terminals.  Yet, nothing small and 2.54mm so far.


texts:
I would like to use the smallest component to control the power of a component (nano motor).
I have seen on the web two main possibilities:

DC converter : LTC3127 for example, I change the value of the resistor and I can get the 3.7 power supply I am looking for.
The MOSFET :  This technology looks really small and I am interested to make a simple montage but I don't know which component should I use.

Information:
* Power In = 3.7 to 4.2
* Power out = 3.7 to 6V
* Switch on = fast and last only 10 seconds
* Power = Extremely low power component please
* Motor Intensity = 160 mA pic to pic

If you could advise me, it would be very nice.


texts: Does noise increase when using connectors with lower pitch?

texts:
I'm building an EEG circuit and as such there are approximately 128 channel leads. At the moment I'm just running standard wires but to improve space and neatness I'm going to print these on a flex PCB which will terminate in a board-to-board connector. When looking at the pitch sizes I'm tempted to use the 0.35 mm, however I am concerned due to the lower space between traces this will lead to a decreased signal-to-noise ratio and convolution.

Would it be less risk to go with a higher pitch i.e. a 0.5 mm or even a 1 mm or should a 0.35 mm be fine?


texts: Using a Small Signal Relay in Automotive Application

texts:
I want to implement a 12V relay (https://www.mouser.com/ProductDetail/Panasonic-Industrial-Devices/TX2SA-12V?qs=HLLy2pIPwuuBcCVwky7PWw%3D%3D)
in an automotive application.

I will be using the car's 12V battery power to control the relay coil. The signal I am switching is battery 12V going into a high impedance input, so very little current will flow through the contacts, necessitating the use of a small signal relay.

Using a transistor is not possible as there would be no voltage drop between gate and source since this is not a low/high side switch.

I am concerned because I cannot find a small signal relay rated for automotive use, particularly vibration. I am also concerned how the relay coil will respond to the noisy battery power, and whether I will experience unexpected switching under conditions such as load dump or starting.

Is this a valid concern, and if so, what measures should I take to prevent issues?


texts: What is this electronic symbol labelled "Current Source"?

texts:
What is this electronic symbol?  How do I physically implement this?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to connect 4 ultrasonic sensors HC-SR04 to Arduino UNO using a NXP's PCF8574P chip. If 4 sensors are connected to Arduino pins, everything's fine.

The problem appears when I try co bind them throught PCF8574P. The speed of response falls dramatically: almost 4 seconds to send signals and read response from the all 4 sensors.

What really takes time is pulseIn(). This is the place where I see the most of time being spent...

Here's the code:

#include <Wire.h>
#include "PCF8574.h"

PCF8574 pcf_us; //Ultrasonic sensors

//The matrix of pin assignments for the ultrasonic sensors (trig (OUTPUT), echo (INPUT))
int usPinMatrix[4][2] = {
  {0, 4}, //0 (pin for trig), 4 (pin for echo)
  {1, 5}, //1 (pin for trig), 5 (pin for echo)
  {2, 6}, //2 (pin for trig), 6 (pin for echo)
  {3, 7}  //3 (pin for trig), 7 (pin for echo)
};

void setup() {
  Serial.begin (9600);
  Serial.println("Initializing device...");

  Wire.begin();

  //PCF8574P I2C address
  /*
    A0 A1 A2 address
    -  -  -  0x20
    +  -  -  0x21
    -  +  -  0x22
    +  +  -  0x23
    -  -  +  0x24
    +  -  +  0x25
    -  +  +  0x26
    +  +  +  0x27
  */
  pcf_us.begin(0x21);

  for (int i = 0; i <= 3; i++){
      pcf_us.pinMode(usPinMatrix[i][0], OUTPUT);
      pcf_us.pinMode(usPinMatrix[i][1], INPUT);
  };

};

void loop() {

  int us_pin, trigPin, echoPin, duration, distance;

  for (int i = 0; i <= 3; i++){

    Serial.print(usPinMatrix[i][0]);
    Serial.print(") ");
    Serial.print("Send sound...   ");

    pcf_us.digitalWrite(usPinMatrix[i][0], HIGH);

    pcf_us.digitalWrite(usPinMatrix[i][0], LOW);

    Serial.print("Switch off...   Reading from ");
    Serial.print(usPinMatrix[i][1]);
    Serial.print("...   ");

    duration = pulseIn(usPinMatrix[i][1], HIGH);
    distance = duration / 2 / 29.1;

    Serial.print("Duration: ");
    Serial.print(duration);
    Serial.print(" s   ");
    Serial.print(distance);
    Serial.println(" cm");

    if (usPinMatrix[i][0] == 3) Serial.println("");

  };

};

This is what I get when I run the code:

0) Send sound...   Switch off...   Reading from 4...   [Waiting] Duration: 0 s   0 cm
1) Send sound...   Switch off...   Reading from 5...   [Waiting] Duration: 0 s   0 cm
2) Send sound...   Switch off...   Reading from 6...   [Waiting] Duration: 0 s   0 cm
3) Send sound...   Switch off...   Reading from 7...   [Waiting] Duration: 0 s   0 cm

What am I doing wrong?


texts: Problem Using An 9 degree of freedom IMU with Ubuntu terminal?

texts:
I am using an IMU from sparkfun that posses an atmega328p.
I upload the source code and everything works fine when using the Arduino IDE.
 I created a .sh script to read from the terminal in ubuntu.

When I read the scripts to initialize the communication with the arduino using the stty command it works, but when I try to retrieve the data the process keeps running until I hit ctrl+z to stop the process and I get trash data.
In order for the scripts to work I need to open the serial monitor in arduino and send one command. Then I can use the .sh file that I created to run and read the data from the IMU from the terminal without problem. I want to be able to run everything without having to use the arduino since the system is going to be running in a computer and everything will be called from a Linux terminal.

If someone has an idea and can help me to solve this problem I will be grateful.


texts: Connect multiple in/outputs in predefined order (beginner question)

texts:
I want to create a device for my guitar pedals which can rearrange my pedals in any given order. I have the following: At the beginning of the device I have an input for my guitar. For each pedal I have an ouput from which the signal goes to the pedal, and an input, which receives the output of the pedal. Usually these pedals are linked in a predefined order, which can't be changed without rewiring. I want to be able to change to do that without rewiring. Also, the device has to be able to work with ~20 pedals max.

The first solution I came up with is to use (a lot of) rotary switches. However, this requires to change all the switches when I want to change the order in which the pedals are linked, so this isn't really useful on stage. As far as I could find there is also no way to control a rotary switch from an electric circuit.

Another solution I came up with is to use (ss) relays. I can control these from a microprocessor, so I can predefine the order of the pedals. However, I can't come up with a solution which doesn't use many dozens of relays.

Can someone help me with a solution?


texts: What precautions should I take to setup a home electronics lab? (Living in the UK)

texts:
I'm soon to be buying a house in the UK and would like to setup an electronics lab in the garage (attached to the house).The type of equipment I'll be using is nothing out of the ordinary:

Oscilloscope
Soldering Iron (up to 400C)
Triple output 10A 30V power supply
Signal generators
PC Equipment

The types of projects I want undertake will range from low voltage embedded systems designs to high power tube amp designs. All projects will be for my own use - nothing commercial

What safety devices are essential for a home lab?


texts:
I am trying to send audio from a microphone such as this over Ethernet to a computer. My first idea was to connect the mic to an arduino's ADC and send the data using an ethernet module such as the ENC28J60 but some people say that the micro controller can only send about 5kb/s.

Has anyone tried a similar setup where raw data is sent from an analog pin and measured the throughput?

(any ideas on a better way to send the data are also welcome)


texts: Analysing circuit for digital filter design

texts:
I have a hard time understanding how one would come up with \$H(j\omega )\$
 given a circuit for an unknown filter.

The circuit looks like this:

I know that: \$H(j\omega ) = \frac{Y(j\omega )}{X(j\omega )}\$ ,   \$\delta = \frac{R}{2L}\$  , \$\omega _{0} = \frac{1}{\sqrt{LC}} \rightarrow \omega _{0}^{2} = \frac{1}{LC}\$ also \$\underline{P} = j\Omega = \frac{j\omega }{\omega _{0}}\$

I'm not expecting spoonfeed since i want to learn, but general direction at what i should look at or hints would be appreciated.


texts:
The datasheet is here http://www.ssousa.com/pdf/SLC800.pdf . I need help on the following:

Where is the maximum operating DC voltage is specified? It appears to be 500VDC but I am not sure.
I need to wire it to a battery bank of maximum 1050VDC, across a shunt of 1miliohm with a full scale deflection of 200mV.

Can it handle common mode voltage or do I need some margin? Can someone more experienced with this guide me?


texts:
I have an input signal with an amplitude of a few mV that I want to filter, amplify and then feed to an ADC ("Analog Signal").

The input signal (Coming though C1) is lifted at 2.5V and the range of the ADC is 0-1.25V. The ADC has a reference voltage pin of 1.25V (it's the LTC2470).

Until now I was using the Adjustable resistor R4 to center the output signal of the opamp by hand. But this solution is not elegant. I would like to remove R3, R4 and the +5V input and manage to center the output without external intervention.

How would you proceed to center the output signal of the opamp to about 1.25/2?


texts: Thermocouple chip & CJC compensation under 0°C

texts:
We are currently designing a "conditioning" module that takes a couple of sensors (T°, Pressure but also via digital bus) and repeats over CAN / also outputs them in nice and clean analog signals (0-5V) when needed.

Problem is : we are trying to find an analog (the detail is imporant) thermocouple conditioning chip that carries a serious Cold Junction Compensation mechanism.

N.B : we've obviously found the AD595/59x series but they only specify (and guarantee, we've contacted them) for Cold Junction Temperatures above freezing point (0°C). They might work below but we have no firsthand experience with them out of the datasheet so we can't legitimately integrate them.

The other option being to use a Tk-to-digital but we want to avoid that for various reasons.

Is our only option to use discrete Op-Amps with a CJC mechanism based
on discretes?
Have any of you any experience on using these integrated-CJC out of
specs? the +50°C is fine by us but we need to go below 0°C. What we are really asking ourselves is : what happens when we go below the minimum (0°) ? Does the CJC stop working altogether or does it compensate based on a temperature of 0°?

Thanks for the help,

M


texts: When should we NOT simplify a digital signal in an expression?

texts:
When we do a simplification in a Boolean expression, sometimes we eradicate some Boolean variables, either from part of the expression or entirely if it's not needed.
Is there a case in digital design where we would instruct the tools NOT to simplify a specific variable (or more than one)? If so, why?


texts: How to add DC offset to a sine wave (so from -2.5V - 2.5V to 0V - 5V)?

texts:
I have a sine wave with a minimum peak of -2.5V and a maximum peak of 2.5V. I want to add a DC offset of 2.5V (using a separate power supply so no positive clamper) in order to get a sine wave between 0V-5V.

Can I somehow use the LM324N by any chance since I have that one available? If not, any other IC is also fine...


texts: Calculating the time constant for an RC circuit

texts:
I have this circuit where \$C1 = 2~\mu F, C2 = 4~\mu F, R1 = R2 = 1~\Omega \$. Here, I want to calculate the time constant of the following circuit.

I calculated the equivalence resistance and equivalence capacitance as \$R = 0.5~\Omega \$ and \$ C = \frac{4}{3}~\mu F\$. Now, time constant of RC circuit is:
$$t = C \cdot R = 0.5 \cdot \frac{4}{3} = \frac{2}{3}~\mu s \approx 0.667~\mu S$$
But my textbook says that the time constant is \$\frac{8}{9}~\mu s\$. So, where exactly am I going wrong?


texts: How to efficiently implement a single output pulse from a long input on Altera?

texts:
I have a fast clock and a switch called 'ready'. When the switch is flipped (ready goes HIGH), I would like the output pcEn to produce a pulse that lasts only for one clock cycle. pcEn will only output another pulse the next time ready goes HIGH again.

The following code simulates correctly, but is unfortunately not synthesizable. Note that space is an important consideration, so I was wondering if it's possible to implement it without using a state machine (which uses a lot of logic elements).

module control
(
    output logic pcEn,
    input clock, ready
);

always_ff @(negedge clock)
    pcEn <= 1'b0;

always_ff @(posedge ready)
    pcEn <= 1'b1;

endmodule


texts: Scaling an electrical motor to open my door knob

texts:
I have a round door knob, which allows opening the door.

To release the door bolt, one must pull the door knob to make it translate horizontally for about 10 centimeters.

Once you stop pulling, a spring bring it back to its normal position.

I've tried measuring how much force is needed to pull the knob. I've to figure that out using a weight I could measure, tying a metal cable to my door knob, and trying to make the weight pull it. Here is a scheme of what I've tried.

I don't need gram precision, I've calculated the weight necessary is 1.3kg, being about 13N.

Knowing that, I've bought a motor which has a couple of 800g.cm.
I've bound its main axis to a 10cm diameter pulley, to which I've attached a metal cable. Then, I've loosely attached another pulley to the door knob, and I've passed the metal cable through it. The metal cable then is attached to a fix point on the wall. Here is a scheme.

Currently, when I plug in my motor, it just tries to turn and blocks immediately, without even pulling a little on the door knob.

What could I try to demultiply the force of my motor so I could open that door knob ?


texts: Ground layout between two data acquisition boards

texts:
I'm designing a two-board data acquisition system for resistive and capacitive environmental sensors.
Board 1 hosts the sensors on a mezzanine daughter board (dashed lines) and contains the ADC for the resistive sensors. The sensors must be physically as close together as possible so their traces run very close to each other for about 3 cm and go through the same connector.
Board 2 is optional and contains the ADC (AD7745) for the capacitive sensor (P14, pdf), which is floating (not grounded) and connected as per AN-1585.
For various reasons it's desirable to keep boards 1 and 2 separate for the first prototype, although they may be merged later.

How should I connect (if at all) the ground planes of board 1 and board 2 to minimise ground loops and coupling of the AC signal into the DC paths?

not at all?
directly at the connector ?
with a capacitor, at the connector?
extend the ground plane of board 2 as a guard around the blue traces up to the sensors' mezzanine connector?


texts:
I'm pretty new to using transistors and I'm trying to make nfc doorlock. My electoric doorlock is working on 9V and 280-530mA, and have resistance about 20 Ohms. I'm powering it from external 9V power supply. I have transistor BC557 datasheet. I'm connecting output pin to base of transistor and putting between them 200 Ohm resistor. But tranistor won't go into active state. I'm using arduino uno r3, and voltage on output pin is almost 5V and can provide 20mA. What am I doing wrong? How do i calculate correct resistance?

I made schematic in paint :)


texts:
I have a "problem" while trying to measure the external voltage from a coin cell. I have simplified my circuit, but basically I have a DS1307 real time clock powered by the Arduino 5v output, and a coin cell connected to vBat to keep the clock alive while the Arduino is shutdown. My idea was to measure the battery level with Arduino by connecting its positive to an analog input and read the voltage level. So, I thought, as the max voltage is 3v, I can use the 3v3 as AREF and set analog reference to external and then read accurate results. The result is pretty cool and the readings from Arduino are the same as reading the battery voltage from my multimeter. The problem comes when I disconnect the source power from Arduino (an USB connection). For my surprise, the Arduino does not shutdown (some leds keep turned on), and seems to be powered by the 3V input (at the moment not a coin cell, but two AA batteries) connected to Analog pin.

Why is this happening? How is the Arduino taking current from the Analog Pin? Is this little circuit an electronic aberration?


texts: Why buy protocol analyzer modules for an oscilloscope?

texts:
Scopes with logic analyzer inputs often have optional add-on modules that let them decode various serial protocols: SPI, RS-232, I²C, CAN, etc. Tek and Agilent want around
US $700 per protocol family for theirs.

My question is, why would I want to buy a software module more expensive than Photoshop to do this when there are many PC-based protocol analyzers on the market at a fraction of that cost, many of which decode multiple protocol families? Are Tek, Agilent, et al just soaking EEs, or do these modules have features you don't get with a US $150-400 PC-based protocol analyzer?


texts: how big my track should be to handle this current

texts:
I've read before that each 1 mm\$^2\$ of copper can handle up to 1 A. Is that true? Is there an easier formula than the one used on online calculators that requires temperature and such?

To give more details, I have 3 main points in my circuit where current is going to be at most 500 mA which are now unrelated (to make 1.5 A in total). My tracks' width is 0.02 in which is 0.5 mm. My width is going to be most likely 1 mm (or maybe less, depending on the etching equality which I cannot guarantee) so with my calculations I'll have around 0.5 A with no factor of safety.

My questions are:

Are my calculations correct? Is there a better way to do them?
Any tips or suggestions?


texts: Does an Ideal voltage source with current flow from negative terminal absorb power?

texts:
I had a question during a physics tutorial today and it has left me quite confused.

One of the questions was to find the power delivered by the 6V source. I figured that P=VI, I is negative with respect to the voltage source, so therefore power is negative. So the voltage source must be absorbing power?

This didn't make much sense, and my tutor assured me that voltage sources can only supply power, and that I should just forget about the negative sign. Is this correct, or is there something wrong with the circuit?

Thank you for any feedback.


texts: This connector is part of a home built current controller I found. It is 20 years old. I know it's a long shot, but I am wondering if anyone can identify it, as I would like to use it. The only markings I can see on it are one the back side, it says "CXA" then it enumerates the pins 1 to 6. The outer diameter of the barrel appears to be about 0.7 inches.


texts:
I think I might need different pixels or an additional power supply.
I bought 10 strings of 50 (12mm, 12v) pixels (aka WS2811 12mm 12V LED)  to do my first matrix project.  It says that is uses 22awg wire.  I am planning on doing a 21 pixel x 16 pixel display which will be a total of 336 pixels.  The power supply is a 12VDC/350 Watts.
I am worried that the wiring in the strings is not a high enough gauge.
Using the RGB Pixel Light Power Calculator (http://spikerlights.com/calcpower.aspx) it shows an amp load of 16.8.  I was planning on doing power injection every 100 pixels to keep the volatge drop low across the entire run.
I am worried that this load is to much for the 22awg wire.
Will this be okay to run on a single string?  Also I am using the Picap as the controller.  If so, what size wire should I be running power to the strings.
Edit:
Link to LEDs (https://www.amazon.com/gp/product/B071R5HKDR/)


texts: I'm writing a simple verilog code, having little trouble

texts: In the image shown below, there says a syntax error at line 10. Its a basic If statement, i dont know why the syntax error shows up. Please advise


texts: Calculating the current needed to drive an N-MOSFET

texts:
Given the partial datasheet below (I do have the entire thing) I am unsure how to use these numbers to drive the mosfet.

I am sure that I am misunderstanding some basic concepts here and pardon my ignorance,  but here are my assumptions..

Qg (total gate charge ) is 71nC at 10V.
So if i divide 71nC by 10V i should get an equivalent capacitor at the gate. At least that is what I think. (and if this is wrong everything that follows consequently is also wrong)

However further down the datasheet input capacitance is given at 1960 pF.

Why is that not equal to the value I calculated above..After all the gate is the input so given a certain charge and voltage i can calculate the equivalent capacitance.

Further more is states in a grpah that Ciss is Cgd + Cgs.... but when i calculate those capacitance from the given Qgs and Qgd the numbers are not even close.

My guess is that I am calculating those capacitance from the given charge completely wrong .

Furthermore the datasheet stats 71nC at Vgs 10V but this graph below does not come even close to representing that...


texts: Generate flip-flops using only combinational logic

texts:
Just for fun, I wanted to design and simulate D-type flip-flops using only combinational logic in Verilog (or SystemVerilog).  I am using using Verilator for the simulation.

My initial attempt, which uses a classical six-NAND design, seems to work fine -- and has passed all tests.  My second attempt, based on a four-NAND JK-type, is not working.  The output doesn't stay latched during the positive level of the clock, and for some tests the simulation doesn't even converge.

Q: I know it isn't normal or optimal, but is it reasonable to design flip-flops using combinational logic in Verilog?  If so, is there something wrong with my second design?

This one works:

module dff( input clk, input D, output Q );

   wire a, sn, rn, b, Qn;

always_comb // captures D @( posedge clk )
   begin
   a = !(b&sn);
   sn = !(a&clk);
   rn = !(sn&b&clk);
   b = !(rn&D);
   Q = !(sn&Qn);
   Qn = !(rn&Q);
   end

endmodule

This one does not work:

module dff( input clk, input D, output Q );

   wire J=D, K=!D;
   wire sn, rn, qn;

always_comb // captures D @( posedge clk ), but fails to hold
   begin
   sn = !(J&clk&qn);
   rn = !(K&clk&Q);
   Q  = !(sn&qn);
   qn = !(rn&Q);
   end

endmodule

In an effort to eliminate blocking assignment and sensitivity lists, I reimplemented the JK-based approach as follows, but the output waveforms were not affected by this difference.

module dff( input clk, input D, output Q );

   wire J=D, K=!D;
   wire sn, rn, qn;

   assign sn = !(J&clk&qn);
   assign rn = !(K&clk&Q);
   assign Q  = !(sn&qn);
   assign qn = !(rn&Q);

endmodule

Note: I based the design of these on the descriptions and diagrams here.


texts: Power Supply for Stepper Motor Stop Motion Camera Rig

texts:
Apologies in advance for this being a somewhat meandering question. I've read all the forums I can find on this and other sites but still feel I need a little direct assistance; if you feel this is redundant or too broad a question, I understand if you can't respond.
I'm working on building a camera slider to use for stop motion animation and need help understanding the power supply I'll need for the stepper motor(s). I'm going to base the project on this slider system from OpenBuilds:

https://openbuildspartstore.com/v-slot-nema-17-linear-actuator-bundle-belt-driven/

which optionally includes this nema 17 stepper motor:

https://openbuildspartstore.com/nema-17-stepper-motor/

with the following specs:

2 phase
Peak Current is 1.68A/phase
1.65 ohm/phase
12-24VDC (Recommended)

I'll be connecting it to an Arduino Uno and an A4998 (or similar) driver. My initial build will only need one motor, but I'd like to be able to add 2 or 3 additional motors/drivers down the line. As this is for stop motion animation, the motors needs to be able to move precisely, but not quickly.
My (admittedly limited) understanding is that for one motor, a 12 volt 5A power supply should be sufficient (and safe for me to handle), and that if I were to run 3 identical motors off the same supply I would need a 12 volt 15A supply. For whatever reason a 15A circuit makes me a bit nervous. In truth, the motor above might be overkill for what I need. There are other motors with lower amperage (and lower torque) that might suffice, like this one:

https://tinkersphere.com/3d-printer-parts/1885-nema-17-stepper-motor-with-detachable-wires-48v.html

which is rated at

12 volt
0.4 A (I'm not sure from the specs if this is per phase or total)
30 ohm

I gather three of those motors could run off a 12v 3A supply. It's also my understanding that there is no issue providing excess amperage to a build, only excess voltage. I also understand that the stepper driver will control the amount of current delivered to the motor.
So, my question boils down to: am I doing this math correctly? Am I significantly better off or safer using the lower amp motors and a smaller circuit? Have I missed anything crucial?


texts: How to select an appropriate capacitor for input voltage stabilization

texts: I have a design where I have some high speed ICs and need to put a capacitor on the input voltage line to stabilize the voltage and protect from spikes or dips. I am operating at 5v and between 300 and 500 mA. My research indicates that I need an electrolytic capacitor for this application but I have no idea how to select the appropriate capacitance value. Also, why couldn't I just use a regulator for this purpose? The datasheet for my IC indicates that I should use a capacitor but wouldn't a VR do a better job?


texts: how to measure power of a sound wave produced by a whistle?

texts:
i have a galtons whistle producing frequency of 10khz.
I have no idea how to measure the power aassociated with it.
Also if i say (10khz,10w) what does it mean?
is it even possible to link mechanical sound waves with energy?
other gadgets have voltage and current which will give the power but how can we estimate power with a whistle?
we blow the whistle using an air compressor.


texts:
Quick two part question on PCB manufacturing. I am looking to order a prototype PCB and all the manufactures I've gotten a quote from all offer to include a Laser stencil, some charge for the stencil some are given free with the board. After looking online to me it looks like the laser stencil just shows the outlines of the pads.

So 1. Why have a laser stencil? what advantages do you get from having one?

and 2. Why do some manufactures charge and some are free for what looks like the pad outline?


texts: Custom push-to-talk button on a handheld two-way radio

texts:
I want to make my own PTT for this two-way radio.

How can I determine how it is realized?

I've figured out that the two "potential rings" with the biggest diameter on the 3.5mm and 2.5mm plug are shorted when the push to talk button is pressed. But I'm not sure if that is all I have to do to realize a reliable push to talk button.

Is there a norm for how PTT is realized on two-way radios, or is there an overview of the various methods used? I couldn't find it, and there is no good datasheet for my specific radio.


texts:
I'm wondering what determines the polarity conditions in a JFET - is it that this transistor can only operate when the p-n junction is in reverse biased polarization? If so, what about the states of operation that the transistor can be in? There are three of them, and the polarization mode is only one. Don't they result from additional polarity conditions?
While browsing through various books as well as websites, I came across a statement that says:
"JFET Transistors can only operate with a reverse bias of the p-n junction, so there is only one way of polarization":
-n-type junction
\$ U_{DS} > 0, U_{GS} < 0 \$
-p-type junction
\$ U_{DS} < 0, U_{GS} > 0 \$
But I have also encountered the definition that:
"Depending on how the unipolar transistor is polarized, it can operate in three different areas:

in the cut-off area - when \$ |U_{GS}| > |U_{P}|, U_{DS} \$  - any

in the active region - when \$ |U_{GS}| < |U_{P}|\$  and \$ |U_{DS}|\$  <= \$ |U_{DS} SAT| \$

in the saturation area - when \$ |U_{GS}| \$  < \$ |U_{P}| \$ and \$ |U_{DS}| \$ > \$ |U_{DS} SAT| \$ "

And it says that these areas of operation are methods of polarity at the same time (or more precisely, areas of operation are associated with different methods of polarity, but there is, after all, one) - I completely don't get that!
These definitions are confusing to me. So which one of them is correct? Is there one way to polarize as in the first definition? Does the second definition fit more with the ways of polarity? Could someone please clarify this for me?


texts:
I was flying next week from one US to London tomorrow. I was curious about how much electronic parts can I carry in the checkin luggage with me ?

I can say its for a university project, but its a lot of stuff(Almost like 8 kgs)..
Things like(uboards, Transmitters/Receivers, PSOC's, couple of arduinos, FPGA Boards, few capacitors(uncharged-No Electrolytic). However, I am not carrying any batteries.

Have you guys faced any problems in the past with carrying similar things on an aeroplane.


texts: Does it matter which 2 nodes on a CAN bus you terminate?

texts:
I know you need to terminate the 'ends' on a high speed CAN bus but what if you know nothing about the topology of the network or where the bus will go. For my application i have designed a data acquisition unit for a vechile and want the ability to add nodes to the network as i please. The location of the devices that may be used is unknown so in that sense im finding it difficult to define what the ends of the bus are.

Can i terminate the bus on the same circuit and have connections to the bus through that device

                    [node1]      [node2]
                       |             |
  ------------------(connection to unit)----------------------
                       |             |
        [Termination]===================[termination]
                             |
                       [internal node]


texts: The real supplied energy for some device is not equal to the energy of a battery, right?

texts:
These are some informations about the Lithium-ion button battery LIR2032:

Voltage: 3.6 V.
Capacity 35 mAh.

So its full energy is \$3.6 \times 35m \times 3600\ \text s=453.6 \ \text J\$

But if this battery is used in a device,which minimum working voltage is 3 V, I mean when the voltage of battery is less than 3 V, the device won't work.

So the real supplied energy for this device is \$(3.6-3) \times 35m \times 3600 \ \text s=75.6 \ \text J\$, not \$453.6 \ \text J \$, right?


texts: digital electronics circuit delay- how to find setup time?

texts:
How to find setup time for this 'd' register?

In my opinion, Tsetup=T_I5+T_I6+T_T1+T_I1 but not sure if to include T_T3 next of T_I2 next? which path would we take?


texts: Similarities/differences/Interfacing between ESP32 and RaspberryPi

texts:
I am new to the field of micro-controllers and stuck with some basic understanding wrt ESP32.
I referred a few documentations but I am not able to figure out following things:

In RaspberryPi we make use of micro-SD card to install linux based debian OS.
Likewise, where do we install OS in ESP32?

To interact with RaspberryPi, we make use of VNC/Putty to access the RPi through our laptop. Likewise how do we interact with ESP32.

How do I ensure that data recorded by ESP32 gets transefred to RaspberryPi in a csv/txt or any other file format?

If somebody could please clarify my doubts, I would be very much thankful!


texts: I had difficulty in evaluating following circuit's node analysis to find the transfer function. I had difficulty because of the ground in the middle of the circuit and the way the source voltage is attached to circuit. I would be very happy if you can show how i should evaluate the node equations. Thank you very much.


texts:
I'm facing a strange behaviour of DMA which I cannot explain myself. I just want DMA to send a data block (i.e. one 32bit word) to the SAI peripherie and quit then and give a "transfer complete callback". The normal/blocking mode sends data block and exits then. But in DMA transfer mode, DMA sends the data block continuously so SAI peripherie outputs the word in loop. No exit, no callbacks...

What am I doing / configuring or understanding wrong?

Here's a simplified code, which outputs the looped signal above:

//main function
uint32_t buf=0b10101010101010101100110011001100;
HAL_SAI_Transmit_DMA2(&hsai_BlockA1, (uint8_t*)&buf, 1);

//DMA Transmit Funktion

HAL_StatusTypeDef HAL_SAI_Transmit_DMA2(SAI_HandleTypeDef *hsai, uint8_t *pData, uint16_t Size){

    HAL_DMA_Start(hsai->hdmatx, (uint32_t)pData, (uint32_t)&hsai->Instance->DR, Size);

    // Enable SAI
    __HAL_SAI_ENABLE(hsai);

    /* Enable SAI Tx DMA Request */
    hsai->Instance->CR1 |= SAI_xCR1_DMAEN;

    return HAL_OK;

}

Configurations

//Configuration SAI

  hsai_BlockA1.Instance = SAI1_Block_A;
  hsai_BlockA1.Init.AudioMode = SAI_MODEMASTER_TX;
  hsai_BlockA1.Init.Synchro = SAI_ASYNCHRONOUS;
  hsai_BlockA1.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;
  hsai_BlockA1.Init.NoDivider = SAI_MASTERDIVIDER_ENABLE;
  hsai_BlockA1.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_HF;
  hsai_BlockA1.Init.AudioFrequency = SAI_AUDIO_FREQUENCY_8K;
  hsai_BlockA1.Init.SynchroExt = SAI_SYNCEXT_DISABLE;
  hsai_BlockA1.Init.MonoStereoMode = SAI_STEREOMODE;
  hsai_BlockA1.Init.CompandingMode = SAI_NOCOMPANDING;
  hsai_BlockA1.Init.TriState = SAI_OUTPUT_NOTRELEASED;
  HAL_SAI_InitProtocol(&hsai_BlockA1, SAI_I2S_MSBJUSTIFIED, SAI_PROTOCOL_DATASIZE_32BIT, 2);

//Configuration DMA

__HAL_RCC_DMA2_CLK_ENABLE();

 hdma_sai1_a.Instance=DMA2_Stream1;
 hdma_sai1_a.Init.Channel = DMA_CHANNEL_0;// Channel 0, Stream 0
 hdma_sai1_a.Init.Direction=DMA_PERIPH_TO_MEMORY;
 hdma_sai1_a.Init.PeriphInc=DMA_PINC_DISABLE;
 hdma_sai1_a.Init.MemInc=DMA_MINC_DISABLE;
 hdma_sai1_a.Init.PeriphDataAlignment=DMA_PDATAALIGN_HALFWORD;
 hdma_sai1_a.Init.MemDataAlignment=DMA_MDATAALIGN_HALFWORD;
 hdma_sai1_a.Init.Mode=DMA_NORMAL;
 hdma_sai1_a.Init.Priority=DMA_PRIORITY_HIGH;
 hdma_sai1_a.Init.FIFOMode=DMA_FIFOMODE_DISABLE;
 hdma_sai1_a.Init.FIFOThreshold=DMA_FIFO_THRESHOLD_HALFFULL;
 hdma_sai1_a.Init.MemBurst=DMA_MBURST_SINGLE;
 hdma_sai1_a.Init.PeriphBurst=DMA_PBURST_SINGLE;
 hdma_sai1_a.XferCpltCallback  = HAL_DMA_XFER_HALFCPLT_CB_ID;

//Initialize DMA
HAL_DMA_Init(&hdma_sai1_a);


texts: How does this circuit given with diode works different from the standard current mirror circuit or will it work in the same way?

texts:
This question had already been asked here by someone else few years ago but I could not see any satisfactory answer so I am asking it again.

All I can see relevant in that post was the image attached here. Now I want to know how the circuit with diode are working.
I am attaching the link of that thread so you can reach there and see the answer given there.

replacing diode connected BJTs by simple diodes in a current mirror circuit2


texts: My Chua's Circuit is flatlining (i.e., malfunctioning)

texts:
I tried to build a Chua Circuit, but it doesn't appear to be working as expected.

The problem is that, while it's supposed to be an oscillatory circuit, I see no oscillations. Refering to the diagram below, capacitor \$k\$ gets charged up a good deal, capacitor \$c\$ gets charged up a little bit, and the current through \$l\$ appears to be zero. These values are constant in time after the initial charge-up. The capacitors will discharge to zero when the power is disconnected.

Fiddling with \$r\$ will move the capacitor voltages up and down a bit, over certain ranges, but fiddling with the inductor value doesn't seem to do anything.

Also of note, I'm trying to prototype this on a protoboard before soldering, so it's still on the protoboard now.

On the diagram: the op-amp and diodes to the left are part of a Chua Diode, and and the op-amp and capacitor to the right form a gyrator, which is simulating an inductor of about \$19\$ mH.

The component values in the middle of the diagram diagram are:
\$r \approx 1.7\$ k, part potentiometer (\$1\$ k).
\$k = 10\$ nF
\$c = 100\$ nF

In the Chua Diode:
\$s = 1\$ k
\$\sigma = 2\$ k

In the gyrator:
\$\kappa = 10\$ nF
\$\tau = 10\$ \$\Omega\$
\$t \approx 19\$ k, part potentiometer (\$10\$ k)

The op-amps (\$411\$s) are supplied with about \$12\$ V; it's supposed to be \$15\$ V, but I measured the supply and apparently the output is pretty crappy.

The diodes are just regular silicon diodes.

Every element in the circuit is working qualitatively like I would expect it to.

The negative impedance converter in the Chua Diode is sourcing current at its input when supplied a positive voltage (\$\sim 5\$ mA @ \$5\$ V), and it's doing the same with the diodes attached, just with a smaller response (\$\sim 3\$ mA @ \$5\$ V).

The voltage across the gyrator, when a sinusoid is input into it, is a sinusoid. The voltage drop shrinks as the frequency of the sinusoid decreases.

I've measured all the resistances with a DMM, and they stand up to within \$1\$%. They are of the ordinary carbon film variety (I think that that's the ordinary variety, at any rate . . . ).

I've checked the labels on the capacitors to make sure they're good (two \$103\$s and one \$104\$). They have rather short leads, but I've checked each with a sinusoid to make sure that they're connecting soundly with the protoboard. They look like blobs of blue stuff stuck on their leads; I think that that might mean metal film, but I'm not really sure.

I've tried these values in a simulation, where they produce oscillations just fine. I can assume either a \$0.6\$ V or \$0.7\$ V drop across the diodes; it doesn't seem to sensitive to this particular quantity.

Thank you very much for any ideas you have here; I would be more than happy to supply any information that you might find useful. I can't get back to the circuit for about 16 hours (from time of posting), what with sleeping and going to classes and all, but after that I can run as many tests on the circuit as desired. I have access to (I think) pretty high-quality DMMs and oscilloscopes, as well as a large array of components.

simulate this circuit – Schematic created using CircuitLab

Below are some pictures of my physical circuit. The top one is a global view of the whole thing, the next is a close-up on the Chua Diode, the next of the gyrator, and the last on the middle section with the capacitors \$k\$ and \$c\$, and the resistance \$r\$. Note that the op-amp in the Chua diode is pointing down, whereas the op-amp in the gyrator is pointing up.

The red wires indicate common, the green ones indicate high voltage, and the yellow one indicate low voltage. Brown wires are used to make connections within the circuit, and white wires are easy probe-points for the oscilloscope. The confusing colors are 'cause the longest pre-cut wires in the teaching lab I'm working in are green and yellow for some reason, and the HV and LV wires need to reach more places than the ground wires.


texts:
I am pretty new to EE. I'm trying to make an oscillator similar to this one:

In order to run it from a single 5V supply, I've selected a low voltage op-amp (TLV 2324) and am using a resistor divider to create a virtual ground as described here:

I've got a pot in place of R1 to adjust the frequency of the circuit, and all of this is on a breadboard.

I've got a cheap multimeter with a frequency mode. It detects a sane, measurable frequency on the square wave output (albeit ~477Hz instead of the calculated/expected 1527Hz), but nothing on the triangle output.

When I insert a small piezo speaker between ground and the outputs, I hear nothing -- unless I also use the freq meter at the same time, in which case I do hear an audible tone at a frequency controlled by the pot, which fades out in about 1/2 sec when the probes are removed. Again this only works on the square wave side, not the triangle side.

In voltmeter mode, I see ~2.4V on the square out and ~1.4V on the triangle from a very tired 9V battery giving 5.1V. I got similar results driving the circuit from the 5V line of an Arduino.

I see there are caveats about the voltage divider circuit I'm using, but I don't fully understand them.

My questions:

Is it feasible to make simple op-amp oscillators like this on a ~5V supply?

Is the voltage divider inadequate for producing audible output, or do I need a separate amplifier circuit, or is there some other problem?


texts: AT+CSQ without Disconnecting PPP Connection in ARCH Linux

texts:
I have a Telit GL865 GSM/GPRS module which is connected to a SBC (running ARCH Linux.) via Serial Port. For GPRS connection, PPP connection as indicaten on this page.

I want to read Cell Tower Signal Strength by the following AT Command:
AT+CSQ?

But I can not use AT commands (AT+CSQ?) if PPP connection is active. First I detach/release PPP connection. Than I can use AT commands. Reconnection to the GPRS tooks about 2-3 minutes. But I do not want to wait for this delay.

Is there any way to check Cell Signal Strength Level or running this AT command (AT+CSQ?) without closing/disconnecting the PPP Connection?


texts: Boost converter capacitor charging question

texts: I don't understand this part. When the inductor is charging, the capacitor current should be decreasing because its supplying the load. When the inductor is discharging (after DT), the capacitor should be charging and hence the current should be increasing, but in the figure its decreasing, why is that so ?


texts: I had a problem finding the Thevenin equivalent resistance of this circuit. If anyone could help me, I would be very thankful.


texts: Where can I find good documentation about memories?

texts:
I'm learning about the different kinds and functionalities of electronic memories (i.e. RAM, flash, etc) but I'm a little confused because all the sources show something different and I don't know which of them is correct.
What manuals or documents are accurate?
Documentation about micro-controllers would be good too. The purpose of this is only learning. I'm not looking for documentation about a specific device.


texts: I have been doing some research into synchros and I know the base equations from to determine the voltage difference between phases. Those equations can be used to determine the angular position from sin and cos, but is there a way to determine the angular position if one of the phases is connected to that same ground as the rotor? This would have 2 phases 120 degrees apart and I was thinking that if I shift the remaining phase to 90 degrees it could be done.


texts: Error on Lattice Diamond: "core0 incorrect response (Write: 512 != Read:0) ... Problem cause is sample clock too slow or not continuous".

texts:
Question for persons experienced on Lattice Diamond, I'm trying to test a previously developed project on Lattice Diamond. The project initially shouldn't have any problems because it was implemented and is running fine.

However, after opening the project in my own computer,  when I'm intending to run the reveal analyzer it gives me the following error message.

"Error: core0 incorrect response (Write: 512 != Read:0) See Reveal Troubleshooting Guide for more details. Problem cause is sample clock too slow or not continuous".

Anyone has any idea what's the problem about? and how to fix it?


texts: Accurately measuring distance using ultrasonic rangefinder

texts:
I need to measure the distance to an unknown object, which can be made out of any material. The solution should be low-cost, so I assumed using a HC-SR04 sensor would be a good choice.

Would an ultrasonic sensor like that be able to measure the distance to any object accurately (with a maximum error of 1cm) without knowing what material that object is made out of?

The distance I have to measure is approximately a range of 0-0.5m.

As an alternative, I could possibly also settle for the ability to detect if an object is present between the sensor and a known background pane for example. Measuring the distance would be preferable, but that might also work.


texts: I'm a newbie to communication systems and circuitry. I was going through superhet receivers while trying to undertand AM/FM/DAB receiver architecture. For FM, IF is fixed to 10.7 MHz and AM 455 KHz. Once the carrier wave is shifted to this IF frequency, it is amplified and filtered. In DAB, it is mentioned that IF is 0 (Source). So, is it possible to set IF frequency as 0?


texts: In TI reference design, why the gnd1 and gnd2 of isolater connect with a cap?

texts: In this circuit, the gnd1 and gnd2 connected with a cap c27, why?


texts: Is there a way of dividing 2 DC voltages? ie Vout = V1/V2

texts:
I need to take the ratio of two filter outputs as part of a project. I converted them to DC voltage values using a rectifier and a smoothing capacitor thinking that this would make division easier. But I'm stuck for what to do now.

A guitar signal will eventually be used as the input of the system as this is intended to be a guitar tuning tool. So the frequencies used will be in the range of 30-600Hz. The input signal is fed into two filters, one high pass filter and one low pass filter. These both encompass the 30-600Hz frequency range. I want to perform division of VoutHPF/VoutLPF and feed the resultant voltage into a flash ADC and drive a strip of LEDs, ie. higher frequency means higher voltage.

Also, both voltages (VoutHPF and VoutLPF) should never equal 0. They will lie within the range of (0.5-2.5V). Any help would be greatly appreciated.


texts: Difference between external event mode versus external interrupt mode for stm32

texts: I am configuring GPIOs for stm32f0 MCU using CubeMX. I encountered this "GPIO mode" setting. It seems that GPIO mode can be triggered by "External event mode" or "External interrupt mode". See image below. What is the difference between "External event mode" and "External interrupt mode"? Under what situation should one use "External event mode" versus "External interrupt mode"?


texts:
I am using an Allegro Microsystems A4935 3-phase MOSFET driver in a brushless speed controller. I recently got the motor spinning, but when I began increasing the voltage, my commutation started to become jerky, for reasons I suspect to be in software.

What I'm confused about is that, when this happens, both my MOSFETs and MOSFET driver heat up. At one point I released the magic smoke in the driver, and eventually the VBB trace (high voltage, supply for gate driver circuitry) going into the MOSFET driver even burned and broke! I understand that whenever the motor gets stuck, it causes large amounts of current through the MOSFETs, but why does this cause the MOSFET driver to heat up also?

The resistors I have at the gates of my IRFS7530 MOSFETs are 4.7Ω, and I'm driving the PWM at 25kHz. The driver only gets a little warm at no load driving the capacitance of the MOSFETs. My question is, what causes this stress on the driver when there is a load? Why does sudden high current flowing through the MOSFETs cause the MOSFET driver to need lots of current? Isn't the only load on the driver due to charging the gates, which is independent of the current through the MOSFETs?

Here is the schematic for the relevant part of the circuit:


texts: How can I route 2 inner pins on this USB-C component?

texts:
This is my first time trying to use a USB-C component.  Luckily, just for a personal project.  Anyway, I want to use this particular USB-C component that cuts out the board slightly, in order to reduce total height of the connector.

I've googled how to route USB-C connectors, but I haven't found anything on this particular style of USB-C..

I am in luck because I am merely configuring my USB-C to act as a USB 2.0, but I want the USB-C form-factor and current capabilities (only using 1 amp for now)

So the connector I am using looks like this,

Noting that it cuts out the board..  The cut out area is usually marked as a "no pattern zone" anyway.

Here's another view of such connector on the bottom:

So it's half SMD, half through hole.

Now all is well, it's kind of like having automatic via's for the pins in the back row..  but!  I don't know how to escape the 2 pins in the middle, furthest row back (or forward?)

Here:

There's plenty of room for a via.. but that doesn't help because that pin is surrounded by through holes.
The board house I'm using can go down to 0.2mm (7.874mil) between the outline and the trace.  I'd prefer not to adjust my DRC, but I can if the only way to route this is towards the edge of the board.

Any ideas?

Thanks!

The connector I am using is:

Amphenol UC-31PFFH-QF7001


texts: Switching between multiple high voltage outputs

texts:
I need to verify 15 outputs from a product. All of the outputs are 230V. I want to automate this test so my idea is to connect all outputs to a PCB and then connect a multimeter and an electronic load to it. Because I have one connection to the multimeter I need to switch between the outputs to measure.

What is the best way to switch the outputs on the PCB to the multimeter?


texts: Are usb ESD protection like the PRTR5V must have?

texts:
I am making a custom pcb basing on Arduino's open source schematics and i noticed that their newer products always have a PRTR5V0U2X USB ESD protection wired like this:

Are they a must have if you are dealing with usb lines? Also how do they protect from electrostatic discharge ? judging from its diagram it is several diodes in a certain configuration

Its Ground pin and the usb shielding also does not directly go to ground they pass through C18 and R10 first.


texts: I am mounting multiple devices (TO-247) on a large rectangular heat sink. What difference does it make to mount them on the edge of the heat sink vs. the middle?


texts: computing Impedance related with Voltage Vx

texts:
I have a circuit like:

How do you get Thevenin ( \$V_x = I_x  * R\$) circuit?

I have these formulas, but I am a little stucked...

\$\ I_0 + Ix = (\frac{V\pi}{r\pi}) + gmV\pi \$   --- 1
\$VR_1 - VR_2 = Vx\$                  --- 2
\$\ I_0 = (\frac{VR_2}{R_2})\$                  --- 3

How do you get \$V_{R_1}\$?


texts: Why is the bandwidth for a matched filter twice the normal nyquist theorem one?

texts:
Why is the needed channel bandwidth for a matched filter higher than the normal bandwidth derived by the nyquist theorem (2B=R, assuming L=2)?

After some digging I found this source that states the following:

  Overcome the practical difficulties encountered with the ideal
  Nyquist channel by extending the bandwidth from the minimum value W =
  R_b/2 to an adjustable value between W and 2W.

What are these practical difficulties and how does increasing the channel bandwidth overcome them? Why do these difficulties only occur when using a matched filter?

edit 1:
In response to "not specific to matched filter" comments, I realize that in practice 2.2 (or more) times the highest f is used instead of 2 to overcome imperfections. However, in my handbook B=R is used for matched filters (both in theory as in exercises) and 2B=R is used in every other context.

F.e. my handbook states the following for a matched filter:
$$
BER = Q(\sqrt{\frac{(A_1 - A_0)^2 T_s}{4N_0/2}}) = Q(\sqrt{\frac{(A_1 - A_0)^2}{2N_0 B}})$$
which implies R=B, does it not?

edit 2:
My question was inherently flawed. Unluckily, in my handbook it just happened to be so that both the relevant exercise and the theory section about matched filters used a (flawed) sampling method at the middle of the bit puls merely as an example. The usage of B=R stemmed from this coincidence, not from the fact that a matched filter was used.


texts: EEPROM in Simulator for Microchip Pic18f

texts:
When programming a Microcontroller from Microchip using Pic18F and using XC8 Compiler, can i use Simulator to test / verify it ?

eeprom_write(0, 1);
unsigned char value = eeprom_read (0);

always returns 0

Note : I Am Starting at Address 0, is the starting address correct ?

Regards


texts: Why is the rectifier necessary in this circuit?

texts:
I asked a previous question about this circuit:

I am fairly confident that I understand why the transformer coil only sees something like 2V. What I am now unsure about is why the rectifier is needed in the first place.

From what I understand, if the rectifier is removed, there will still be a small voltage drop over the coil of the transformer, with the rest going to the load.

So what does the rectifier actually do here?


texts: How to detect several agents within a radius, what is the best and easiest way to do it?

texts:
I have a room with 30 objects which may or not be present, and I want to be able to detect which objects are in the room.

My first idea was to attach a RFID tag to each one of these objects and have a sensor detecting them, but then I have frequency collision problems and since the room is quite large, I also cannot activate tags which are further away. Or I may be missing something...

I would also want to have objects not carrying an active radio transmitter, i.e., no batteries wandering around, just RFID tags or resonant metal pieces.

I could use cameras but image processing would require an Arduino on steroids.

This is for a hobby project since I need an excuse to use my Arduino again :P

How would you solve such challenge?


texts:
I am making a PCB and I want the ability to have multiple power sources for it. One is a DC barrel jack and another is a transformer/rectifier.

In the past I would use jumpers to allow one power circuit to be totally disconnected while the other connects, or vice versa. I'm wondering if this is necessary though because I will need to break up some power planes and have less optimal routing on my current design to accomplish this.

My board has a separate regulator for each power source. I would like to have the outputs of each regulator tied together and have either one or the other  power the circuit. Is it bad for a simple linear regulator or LDO to have voltage present at its output while the regulator input is left floating/disconnected?

I have seen some other designs use Schottky diodes in series with the outputs, but I'd rather not lose the 0.3V after the regulator output.

I will never have a situation where it is powered by both sources at once, so one regulator will always be off (its input floating). Is it bad to tie the regulator outputs together in this situation or should I use jumpers to totally isolate them from each other?

Edit: Initial searches only led to discussions of paralleling regulators for increased current, but I recently saw this post:
Can the outputs of 3 different voltage regulators be tied together?

It has been stated in that thread that the regulators could be damaged, but not much explanation why.

Thanks in advance,
Pansy


texts: Small relay with no coil (or reversed) polarity

texts:
Due to a wrong design I'm searching for a relay with the same footprint of the AGN THT family:

http://www.mouser.com/ds/2/315/mech_eng_gn-1075921.pdf

but with no coil polarity or, at least, with a reversed one.
It seems all the relays as small as this have the coil polarized.

Is there a reason for this or I just did a wrong search?


texts: Does a battery powered resistor have Johnson Noise?

texts:
The mean noise voltage for Johnson (Thermal) Noise is given by the formula:
\$ v_n = \sqrt{4kTR\Delta{f}} \$.
The bigger the resistance of a resistor or the higher the frequency of a voltage supply, the higher the thermal noise the resistor will have. Does the formula also indicate if the voltage is supplied by a battery (DC, or a voltage of 0Hz frequency), any noise you measured on the resistor cannot be due to thermal noise because:
\$ v_n = \sqrt{4kTR \cdot 0} = 0V \$ ?

[Edit]
The question should be - what is \$ \Delta f? \$


texts: RF help, difference between using 12V and 5V as power supply voltage

texts:
I am currently looking into building a custom RF transmitter. The commercial ones built for Arduinos usually operate at 5V. I was also looking into some RF remotes, and found that they usually use 12V. I am wondering if this creates a difference in terms of RF output power?
It kind of makes sense for Arduino modules to run on 5V since that is a voltage the Arduino can supply, but would using a 12V circuit improve the output power?


texts: When to monitor UxSTAbits.TRMT and UxSTAbits.UTXBF

texts:
According to the reference manual on UART for PIC here(page 7), the UxSTA register have two read-only bits; TRMT and UTXBF. While writing a simple transmission program over UART, I didn't notice any change if I include

while(UxSTAbits.TMRT != 1);

or

while(UxSTAbits.UTXBF);

before I send anything with the UxTXREG buffer. In what case is each of these bit relevant?


texts:
I was recently reading a technical article from AllAboutCircuits by Robert Keim about Op-amp Stability, https://www.allaboutcircuits.com/technical-articles/negative-feedback-part-8-analyzing-transimpedance-amplifier-stability/

I am simulating the LTSpice circuit, as seen below, of the transimpedance amplifier using the LT6015 Op-Amp as depicted in the article.

However when I run the simulation I am not able to get the same Open-loop frequency response as stated in the article.

I obtain a max open-loop gain of ~145dB, whereas he has ~102dB. Furthermore I created some matlab code to check the open-loop gain using the approximation of the op-amp as a first-order low-pass filter. Taken from the datasheet of the LT6015 the open-loop gain is 3,000,000 and the open-loop bandwidth is therefore 1.1Hz (calculated from the gain bandwidth product, with a value of 3.2MHz). However this outputs a open-loop gain of ~129dB.

Here is the code of my matlab program:

    Ao = 3000*10^3 %Open-loop gain
    Wb = 1.1 %Open-loop bandwidth of op-amp

    w = .1:.1:100000;
    h = 20*log10(Ao*(abs(1./(1+(j*w)/(Wb)))))

    figure
    semilogx(w,h) %% Plot on log scale
    hold on
    xlabel('\omega(rad/s)')
    ylabel('|H(j\omega)|dB')
    legend('1','2')

I am unable to see what I am doing wrong to create the discrepancy between these three plots, with the primary focus being the former two, the last one acts as check. Perhaps the last one is incorrect because the LT6015 cannot be modelled as first-order low-pass filter?

Any help would be greatly appreciated!


texts: Why does the high Side Current Shunt monitor fault as soon as power is on

texts: The high side current shunt monitor fault goes high as soon as power is turned on preventing the P-MOSFET from turning on, its not faulting because of over current but as soon as the Enable signal goes high the Fault also goes high with it. the 3.3V is the first signal that comes on after the 18V.


texts: RS422 Receiver Not Reporting Errors When Too Few Stop Bits

texts:
I am interfacing with a device (the transmitter) which configures its serial settings to 8 data bits, no parity, 1 stop bit at a baud rate of 115200.  These are known values and fixed values I can't edit or change.

The transmitter is connected to a computer via an FTDI USB-COM422-PLUS4 which uses the FTDI FT4232H chip to decode serial into USB and present it as a virtual com or TTY device.

For fun and my own understanding of both serial communication and the Linux driver, I've been experimenting with connecting to the transmitter at incorrect serial settings and looking at what errors are reported (framing, parity).

When I connect to the transmitter with 8 data bits, no parity and 2 stop bits, I would expect to see some sort of error, likely framing, since the transmitter only sending 1 stop bit.  But there are no errors of any time I can find reported.  Data is received normally.  I can confirm the transmitter is 1 stop bit via a logic analyzer.

Are most receivers going to ignore a missing stop bit like this?  Any reasons this wouldn't be presented as an frame error?  Or could it be a quirk in the FTDI chip that it ignores this kind of error?


texts: How is the bias current reference value determined for CMOS circuit design?

texts:
In the few textbooks I'm reading on CMOS analog design, they all seem to have reference currents of \$10 \mu A\$ or similar that get mirrored, and there doesn't seem to be any discussion on how this reference value was arrived at.

Is there any science to choosing these bias current numbers? Why is it not \$1\mu A\$, or \$200nA\$ or something to save power?


texts: Time to Digital Converter using FPGA with Coarse Counter in Verilog

texts:
I am currently using Verilog to program an FPGA and create a time-to-digital converter. What I am trying to do is measure the time interval when a square wave is high and then convert this to a binary output.
The general steps are:

Once the positive edge of the inputted wave is detected, a counter will start that is based off a 100MHz clock.
The counter will then stop once the input goes back to zero and the number of counts will be multiplied by the period of the clock (10ns) to get the time interval.
This time interval is stored or assigned to another variable, and the counter will be reset to zero so the next pulse can be measured.
The stored time interval from the last pulse will be converted to binary and then reset back to zero so it is ready for the next pulse.

What I am not sure of is how to quickly store the previous time interval, convert it and then reset back to zero all before the next pulse.
Any suggestions or examples of time-to-digital converters would be appreciated.
Thank you!


texts:
i'm taking a course in Switched-mode power supplies and I am a bit confused about the theoretical explanation of what is happening in increasing voltage using a bootstrapped capacitor.

You connect a capacitor with a +Vdd. This places a charge +Q on one side and -Q on the other side of the capacitor. You then apply +Vdd to the other plate and use a diode on the other to stop the current flowing.
1)

You've then surely got +Q on both plates now. Or is that even right?
This confuses me a little further, if the equation for a capacitor is Q = CV, is Q in this equation the amount of charge that can be placed on one plate, i.e. +Q, or the total difference +Q and -Q, i.e. equal to a difference of 2Q?
I read in multiple sources that a capacitor is the same as an inductor and it's voltage cannot change instaneously, in a similar way an inductor's current cannot change instaneously. However the latter's is due to the magnetic field collapsing, And I do not see anything happening to the electric field?

I think my problem probably lies in the definition's of these quantities and what is happening to the charge on the capacitor's plates and the electric field between them but cannot figure out what.

Please see an example circuit below of where this is applied.


texts:
Can anyone recommend a cheap ( less than $4 ) driver chip capable of driving a 4 digit, 7 segment display with the center colon? I'm very familiar with the likes of the MAX7219 and similar but they are WAY too expensive for my project. Also, the chip MUST be a DIP package.

Thoughts?


texts: IXDP 20N60B IGBT reversed biased conductive

texts:
I am using the  IXDP 20N60B IGBT as an AC switch. This IGBT has no internal diode. When the Gate Emitter voltage is ~10V the device is on and conducts in the forward biased region as expected, shown below.

However when the Gate Emitter voltage is set to 0V the device is off but there is some reasonable voltage in the reversed biased region as shown below.

Why is this the case? The voltage should be 0V when the device is off.

Thanks.


texts:
I am doing part a in this homework:

Doing nodal analysis of two op amps and came to these two equations:

$$\frac{V_1-V_{ref}}{R_2} + \frac{V_1-V_{x}}{R_1} + \frac{V_1-V_{2}}{R_f} = 0 $$
$$ \frac{V_2-V_{x}}{R_3} + \frac{V_2-V_{1}}{R_f} + \frac{V_2-V_{out}}{R_4} = 0 $$
$$ where: R_3 = R_1 and R_2 = R_4$$
I am trying to simply these two equations down and get it in this form: $$V_{out} = A_d(V_2-V_1)+V_{const}$$

I simplified down to get
$$V_x = R_1(\frac{v_1-V_{ref}}{R_2} + \frac{V_1-V_2}{R_f}) + V_1 $$
$$V_out = R_4(\frac{V_2-V_x}{R_3} + \frac{V_2-V_1}{R_f}) + V_2 $$

So I try to plug in Vx into Vout and get this monster:
$$ V_out = R_4(\frac{V_2-[R_1(\frac{v_1-V_{ref}}{R_2} + \frac{V_1-V_2}{R_f} + V_1)]}{R_3} + \frac{V_2-V_1}{R_f}) + V_2 $$
and then try to simplify using R3=R1 and R2=R4 but get nowhere.

Any hints on how to simply this circuit down to the required form?


texts:
I'm using LM3478 converter to convert 12V to 30V in standard circuit for 456kHz.

Circuit was working perfectly but when I was measuring something I demaged probably LM3478. I replaced it with new IC but it did not help. I can see after power cycle full current to R4 sensing resitor because Q1 transistor is opened via DR pin. But IC keeps it opened forever. Seems as oscillator does not work or so. I can see 2V at COMP pin (which is output of err comparator but thats all). Q1 seems correct, when I force 0V at gate it closes transistor. D1 seems correct too. FB voltage is supposed too. L1 is 6A inductor, it's heating but I don't think it's broken.

Rarely I can see that oscillator starts (I cannot repeat it) but any load causes it falls back to error state above.

Does anybody have an idea what might be wrong or what focus on? Replacing blindly IC over and over trail&error is rather strange approach.


texts: How can I effectively reduce the voltage needed to activate a transistor?

texts:
I have built a circuit which basically connects the line out (audio output) of a music playing device to a set of LEDs (actually a huge strip of around 200 LEDs), so they flash in time with the music (from internet tutorials - I'm a bit of beginner).

simulate this circuit – Schematic created using CircuitLab

My circuit works very well using my laptop as the audio device (connecting my circuit to the headphone jack on it). But when I use something smaller such as an iPod, the lights barely turn on at all.

I've tried using a Darlington Pair (below), but that makes the issue worse. This is why I think the issue is that the audio line out is not reaching the 0.7 volts across the base and emitter that the TIP31C transistor needs to activate (the Darlington Pair means it now needs 1.4 volts to activate).

simulate this circuit

From my research, it looks like using an op amp might be the way forward, to amplify the audio line out signal before the TIP31C transistor. Would somebody be able to suggest one, and which inputs I should connect to?

I've also read that Germanium transistors only need 0.3v across the base and emitter to activate, would that be useful?


texts: How to use IV characteristics of a diode in calculations

texts:
In the following question they have asked to calculate the negative and postitive peaks of the output voltage across load resistor and to determine the peak load current and the diode power dissipation

The peak values can be calculated as 49.3V and 0V

Hence the peak load current and power dissipation can be calculated

But they have also provided the IV characteristic of the diode also

How does that helps me in this question
Or is there any errors in my method because i haven't used the characteristic curve


texts: Technique to trigger oscilloscope on peak to peak value

texts:
I have a 4.5Khz bi-phasic square wave signal that ramps down from an amplitude of 20v peak to peak to 0v over 500ms. I would like to trigger in the middle of that amplitude ramp to 0v in order to zoom in and inspect the timing and details of the ramp. I've tried to get lucky and take a single sequence but I never catch it, not to mention I feel like a fool for trying! :) I'm imaging a technique where I can trigger when the peak to peak value is <= 10v, if anything like that is possible.

I'm using a Tektronix TDS 3032. I'm not an engineer, I'm not even really a hobbyist, just trying to help someone with a question and would like to learn an advanced triggering technique, if there is one.


texts: Toggle between two colors in a common-cathode RGB LED using a SPST switch

texts:
I'm working on a switching circuit for a guitar amplifier that uses one DPDT relay which is powered by 12V DC supply. A SPST switch (panel mount or footswitch) will power the relay and switch to a second amplifier channel.

Is it possible to wire a common-cathode RGB LED to glow one color (red) when relay is off and other color (blue) when relay is on?

The closest circuit I could find is this Alternating between two LEDS using BJTs
but it has common anodes.

Is it possible to rework the circuit to use common cathodes?

If that's possible, I could bring a positive voltage to R4 when I turn the relay on.


texts: Burn bootloader from Arduino Nano to Atmega chip

texts:
As seen from the above question, I need to know how to use an Arduino Nano to burn the bootloader onto an Atmega chip. The Arduino website only shows how to do it from an Arduino Uno chip configuration.

Does anyone know what I can do?


texts: Designing a simple circuit with a Parallel Port and Leds

texts:
I am designing a simple circuit to control 80 LEDs using the parallel port.

I am a software engineer and I barely remember the basics of hardware design. I already implemented the software to control the circuit. However now I would appreciate if someone can guide me how to build the hardware.

The following components are used for designing the circuit (a parallel port, 5 4x16 decoders, 80 resistors and 80 LEDs).

Questions:

The power required to turn on all 80 leds at the same time will not be enough, right ? so I guess I need a power supply, how can the power supply be connected to the circuit ?
From what I read, the resistors are used to prevent burning the leds (since I have an output of +5 voltage), this might sound stupid but is it possible to connect the resistor before the decoders ?


texts:
I don't recognize this component, maybe some of you will. I measure 10.6 ohms across it. I believe it might be an inductor or filter bead, but i need to be sure.
As you can see in the picture, it says 105K , 4083, and that is it.

I'll point out that this board is no longer working, and i'm looking for a faulty component, so the measurment i took (10.6 ohms) could be the result of measuring a component that no longer works as it should.

Note: in the circuit, there are no parallel components with this item, so i believe the measurement to be accurate


texts: Connecting to sensors a few meters away from the microcontroller

texts:
Usually sensors would be close the a microcontroller so it is possible to use SPI or I2C or someother means to read/write them for communication. This is still true even if they are on another board connected to the backplane.

However, how would one get data from sensors that are more than a meter away. This will require one to use long cables that will have a lot of capacitance that will limit the data rate of transmission and make it more susceptible to corruption via noise.

How is this type of problem usually solved?


texts: Transistor question and is my circuit safe for Raspberry-Pi?

texts:
This is my first circuit designed from scratch (that actually does something interesting), so please be patient with the beginner's mistakes (and maybe point them to me).

My circuit is the following:

What the circuit does is:

When switch SW1 is open, the D2 LED turns ON and the D1 led turns OFF
When switch SW1 is closed, the D2 LED turns OFF and the D1 led turns ON (they switch state)

Most probably this circuit has a common name (astable ?) but I don't know it.

I've tested the circuit at 9V (with R1 & R2 at 470 ohms) and it workes like a charm.

This circuit will be used with Raspberry-Pi's GPIO. Basically, the SW1 will be replaced by a GPIO pin.

My questions are:

Is it ok what I did there with Q2 by not using any resistor for the base ?
Considering that the GPIO pin will create a -3.3V drop when ON and the GPIO on Rasperry-Pi has no protection (AFAIK) and the 3.3V is supplied by the Raspbery-Pi itself: is this circuit safe for my Raspberry-Pi ? I've read in some place that by drawing to much current from GPIO may brake the device, but I still didn't wrap my head around how a circuit may draw more current than what it's given :(

Thank you!


texts: Powering up MC34063 circuit with transformer

texts:
I am having an issue with the circuits that I am working on in Multisim.
The first one is supposed to convert 24VDC into 27VDC/200mA. And it is working just fine.
When I substitute VDC source with 220VAC and a transformer the result is almost the same.

The second circuit that gives 12VDC/50mA output also works with this configuration.
But when I attach it to the same 220VAC source it gives rather strange results. During the first few milliseconds of simulation Iin shows value of ~-2A.

My questions are as follows:

How do I fix the negative Iin current in beginning in the fourth scheme?
Is there a simpler way to connect MC34063 to the transformer?
How can I connect both step-up and step-down converters to the same 24VDC source?


texts: PCB Design: What is the minimum value of Via Dia and Via Drill size?

texts:
I am using KiCad and I am new in PCB design.
I want to use Fusion PCB service (SeeedStudio) for the boards.
In their forum, they say that the minimum Via Drill size is 0.03 mm.
But in SeeedStudio's site is written:

Drilling Hole(Mechanical) 0.3 - 6.35 mm
Finish Hole(Mechanical) 0.8 - 6.35 mm

And in tinyosshop's site it is written (just for comparing):

Minimum vias specifications:   pad:20mil(0.5mm)/hole size:12mil(0.3mm)

I thought that the Via Diameter was equivalent to the Finish Hole and the via Drill Size was equivalent of the Drilling Hole, but I think I got it wrong. Then which are the parameters I should look at?
I was using 0.8 mm, as it was the biggest number, but I just realize that they are almost as the same size of the drill of a 100 mil header (it seems to big)
I'd appreciate if someone could help me understand this.
Thanks.


texts: Consistently assigning electrode nodes in random resistor networks

texts:
In the context of random resistor networks, the general question of interest is often "what is the effective resistance between two arbitrarily chosen nodes?"
But more specifically about the nodes we choose to assign as electrodes, along which we would measure/compute the resistance, are there generally accepted ways or definitions for how to assign the electrodes?

To be more precise, this can be easily relevant as soon as we have two networks (maybe one is a transformed version of the other), and we are interested in comparing the conductivity (or equivalently) the resistance of the two networks. Then depending on how we proceed to choose the electrode-nodes, we will obtain different results and not be able to meaningfully compare the two networks.

To resolve this, one might adopt some of the following, natural looking, definitions, given a network of \$n\$ nodes and \$m\$ edges (resistors, either uniformly valued or according to another known distribution):

Using the graph diameter nodes: We assign the nodes $i,j$ that are furthest apart as electrodes, i.e., furthest in the sense of the graph distance between them.
We choose the nodes \$i,j\$ randomly and average over \$x\$ such realizations.
We choose the nodes \$i,j\$ that are exactly a distance \$d\$ apart, and obtain the resistance as a function of graph distance.

Either of these definitions have an arbitrary aspect to them. For example, if we choose the first definition, then the two networks may have very different diameters, and therefore, we'd be comparing resistances at different distances.

My questions are:

How does one consistently compare the resistance of two networks either by factoring out effect of the choice of electrodes, or by adopting a generally accepted definition for how to assign the electrode nodes?
Is the dependence of resistance on choice of electrode placement a well studied problem? I haven't been able to pinpoint works that directly tackle this aspect of random resistor networks.


texts:
I want to make a steampunk type table lamp. I want to use a dimmer switch and an old fashioned analogue AC voltmeter to display the "voltage" as a feature/gimmick.
This displayed voltage doesn't need to be accurate.
So my question is:

Would the needle display a varying voltage as the dimmer switch is varied?


texts: How to create bipolar power supplying from Powerbank 5V 3A

texts: I have 2 ADS1299 analog to digital converters(https://datasheet.octopart.com/ADS1299IPAG-Texas-Instruments-datasheet-17020782.pdf). I need to give them bipolar mode supplying but I must use a powerbank of 5V 3A. I wonder how can I create a bipolar supply of +2.5v -2.5v as mention in the datasheet from the 5V of the powerbank. I am new in this field. Thank you


texts: Drop input voltage for a boost converter

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I have a 21V DC solar panel power source, that feeds a DC-DC boost converter. I set the output voltage of the boost converter to 19.5V to charge my laptop, but since the input voltage is higher than that, the output voltage is also 21V. I cannot use a buck converter, because when I draw current from the boost converter, input voltage drops below 19.5V, so it must be boosted to stay at 19.5V. How can I prevent the initial (when first plugged in) voltage to be below 19.5V?
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On mains power, the laptop draws about 1.5A of current at 19.5V, and that is about 30W. My solar panel is 50W under direct full sunlight.
The PV panel's Voc is 21.46V, Isc is 3.21A,
Vmp is 17.46V, Imp is 2.98A.
Is does not have a part number.


texts: What's the purpose of this diode in this level-shifter?

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look at this circuit:

I don't get that what's the usage/purpose of the BAS316 in this circuit?


texts: How do I choose my optocoupler to drive a solenoid with a MOSFET?

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I need to drive a solenoid with a MOSFET. The solenoid is an 8W solenoid and it will be connected to a +12V voltage.

And this drive command have to be isolated with an optocoupler but I don't know how to choose it.

What characteristics do I need to watch in the datasheet? What is important? Are there some good brands and some bad ones?


texts: Lead acid battery cutoff voltage circuit

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I've developed a device that runs on a 12V lead acid battery. The device will be deployed at a location where we cannot have physical contact with it. It is therefor not possible for us to detect the battery's voltage.

I want the battery to last as long as possible, but I don't want it to deep discharge. For this reason I wanted to implement a low current voltage cutoff circuit, but I am having trouble finding any. There are several that 50-100 mA, which already is too much.

What are low current cutoff devices or how can I make one?


texts: Understanding the operation of LM219 Comparator

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I'm trying to use the LM219 (equivalently LM119 or LM319) comparator in a project I am working on (I chose this over other comparators because it has a fast response time for the desired supply voltages). I am using supply voltages of +-12 volts, and I am generating a square wave output from a triangle wave input (+1 to -1) and DC bias (for duty cycle control). Essentially if the difference in the inputs are greater than 0, it should rail to +12, and rail to -12 otherwise.

However, all of the datasheets for the LM219 I have looked at don't have a simple comparator application circuit (all typical application circuits don't intuitively explain how the comparator works), and I don't completely understand how to wire it up. How does the part decide whether to rail to +12 or -12 based on the connections? Would the circuit below suffice for my application?

A related question, all SPICE models for the part I found online don't seem to work well. Who can I contact to find a SPICE or TINA-TI model for this part?


texts: 8Mbps power line communication with PLC \ Homeplug

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I'm trying to design a circuit to transmit data over the power lines. The data I'm trying to send is real time FFT of about 100k samples per second, for 32bit data this comes to about 3.2Mbit data per second.
I have found various ICs that implement a PLC communication front-end but the maximum speed they can deliver is about 500k baud/sec. Now I know there are various Ethernet power line communication modules available commercially, so my question is: how is this implemented if not with a dedicated IC.
I was unable to find any specific information about this on the web. Have not searched for books yet though. Do they use specialized ICs not available to the general public?


texts: Why is the output resistance of Common Collector mode low while that of Common Emitter mode is high ? I think this is true for static resistance.


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How are dopants chosen for producing semiconductor devices? I've heard that boron and phosphorus are some common dopant elements, but you'd want different ones for different semiconductors, right? They need to be compatible with the crystal structure. Could you dope a compound semiconductor by altering the ratio of its component elements?

Is there any advantage to using different dopants, in different devices or within the same device? What if, for example, you made a silicon BJT where the collector was doped with nitrogen, the base doped with boron, and the emitter doped with phosphorus? Would that have significantly different properties to a device using phosphorus on both the emitter and collector?


texts: IEC60950-1 - Does soldermask reduce creepage to pollution degree 1?

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Since creepage distance requirements across a PCB are at least partially due to the potential of conductive pollution, is soldermask a sufficient coating to reduce fully covered traces to pollution degree 1 for determination of required creepage?

I'm wondering about the creepage requirements between the heatsink trace and the copper pours on the top and bottom layers under CN4. Since the heatsink trace will be covered with soldermask, as will the copper pours closest to that trace, can I apply the creepage requirements for pollution degree 1, or do the requirements of pollution degree 2 still apply since it's not a conformally coated board?


texts: What determines how much power the motor 'draws'?

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I'm new to electrical engineering, and probably asking the wrong question. Not sure how else to phrase it.

For the question, I'm going to use an example layout of simply a 9v battery attached to a toy DC motor.

From my understanding of my previous question, the voltage coming from the battery through the motor will be around 9v. The current will be from 0amps to however much the battery can supply without frying. What decides how much current goes through the motor?


texts: Controlling a 3 speed AC ceiling fan motor with a Raspberry Pi

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I have been trying to reverse engineer a ceiling fan remote control receiver to work with a Raspberry Pi Zero W. The light portion of the fan was easy enough to control, but I can't figure out how to control the motor. From what I've been able to figure out, the motor has 3 speeds and runs on 120v AC at 60hz. Here is a picture of the motor controller that I've extracted from the motor:

Here is the cover in higher resolution:

Here is my current schematic:

What should I use to control the motor that can be controlled by a Pi? It could either be pre-built (as long as it's not too expensive) or hand-built.


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I am looking a replacement of this diode BAV99W Datasheet.I have a confusion about Average Rectified Forward Current,Forward Rectified Output current and Forward Continuous Current ratings.What is a difference between all this terms,because in this datasheet I got Forward continuous current ratings but there is no Average Rectified Forward Current or Forward Rectified Output current ratings.

While I found this diode 1N4007 Datasheet it have Average Rectified Forward Current rating and this one BAV99W Datasheet have both Forward continuous current and Average Rectified Output current ratings.


texts: 9V battery is not able to power 2 sensors. How can I do it?

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I wanto to power

an IR sensor
an ultrasonic sensor (HC SR04)
and a sound module APR33A3 IC

through a 9V battery connected with a LM7805.

When I connect my atmega32 to the computer and power the ultrasonic sensor and the sound module using only the atmega while powering the IR sensor through an external battery everything works well.

But the moment I connect the ultrasonic sensor, sound module and atmega32 to a 9V battery while keeping the IR sensor connceted in the same way, then something stops working.

What changes should I make?


texts: Circuit for charging RC car battery with solar

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For my high school engineering course I have to make a project that involves solar panels. I have chosen to convert an RC car to recharge the battery while driving with solar panels, because I realize it wouldn't be possible to fully power the car with solar. Now I need help on the circuit. The car has a 6 volt 700 mAh Nickel Cadmium battery, meaning it is five 1.2V cells in series. This battery of course powers the DC motor - of which I do not know the power consumption etc. Now my question is how exactly I should make the circuit to charge the battery while in use. I have already purchased three 2V, 240mA solar panels, which I planned to place in series to meet the voltage of the battery and thus be able to fully charge it.

My plan is to place wiring from the negative terminal of the battery to the negative terminal of the solar cell array (the 3 in series), and from the positive terminal to the positive terminal, this would be parallel. Would I need to place a diode in between either of the poles? And would this diode mean I need a greater voltage than the 6 volt of the battery? Also, is this a dangerous thing to do, should I use charge controller such as http://www.maximintegrated.com/datasheet/index.mvp/id/1666.

Also, if I do this, would I be charging the battery while it is being discharged, or does the current from the solar panels go straight to the DC motor, with additional current being pulled from the battery?