texts: Have I worked out the correct AC power draw for this power supply?

texts:
I've purchased this power supply (480watt, 40amp, 220v AC to 12V DC).

From my (very limited) understanding, the maximum AC current drawn from my home circuit (assuming maximum load on the power supply) would be calculated as:

Have I got that right?

Secondly, if I expect a max load of 36Amps on the power supply, is the expected AC current draw +-1.9Amps?

The circuit breakers in my house are sitting at 20Amps, so I would like to understand how many of these 36Amp setups I can run on a single circuit.

Thanks


texts: Why aren’t the magnitude comparators cascaded the “more efficient” way?

texts:
In Practical Electronics for Inventors, Paul shows the following cascading of two \$ 74HC85 \$’s to build an 8-bit magnitude comparator.

Question: Why doesn’t he cascade them in the apparently more efficient way where the higher order bits are compared first?


texts: Any Cortex-M3(LPC1768) compilers for Linux?

texts:
Are there any uVision alternatives for Ubuntu/Linux?, i know about LPCxpresso, but i just don't like it and its only for LPC MCUs.

i tried Googling and it didn't help, I only saw results about LPCXpresso.


texts: How do I active the relays on this relay bank?

texts:
I purchased 2 "Mechanical Relay Board, 8 gang, 10A 220VAC, 24VAC 30ma coil" relay banks that I am trying to control from a raspberry Pi. To do this I've built out 2 595 shift registers and I'm using an external power source, not the power from the pi.

Testing on LED's everything is ok but for the life of me I cannot get the relays to activate. I figured that maybe the input was too small, not enough mA to activate it.

I'm supplying 12v DV from a 12v 1A transformer to power the relay bank and I tried to activate the relays using 5v from USB, 5v from 9v battery running through a 5v regulator, 9v directly from battery and also 12v directly (from the transformer used to power it).

Nothing. I notice that when I test the voltage across the input power terminals, it reads very low (0.10v) but when I unplug the adapter from the relay bank, it reads 12v. So when the power is plugged in to the relay bank, I'm imagining that the bank is causing a fault in the transformer? I noticed that when I had the 9v battery plugged in to the bank as the power source it got really hot.

What am I doing wrong? I changed the jumpers to both positions and tried the same tests on both setups.

Datasheet


texts: Smart vs Intelligent vs Adaptive vs Advance (etc) Embedded Devices

texts:
I hope my question is not off-topic here. I am asking it here because it is directly related to the hardware devices which are primarily based on MCU's. These Embedded System devices are used every where everyday.

Let us say the device is a 'Time Attendance Device".
https://www.alibaba.com/showroom/face-recognition-time-attendance-system.html

Unlike what the Device manual says about its capabilities I want to know when to say that a device is:

Intelligent
Smart
Adaptive
Advance
Fault-tolerant
Self-healing/repairing
Innovative
etc.

These days I see these words are used without knowledge of their exact technical meanings in the devices marketing manuals.

I wonder when to attribute the above properties with a certain device? Are these attributes related to the Firmware design or Hardware design of an Embedded system device or both?

What could be the minimum requirement to say that a specific device has one of the above attributes in it?

Edit:
I want to know when it will be "technically" correct to attribute any of the above properties to an Embedded system device.


texts: Is there any memory cell that can store more than one bit?

texts: SRAM, DRAM, Flash, EPROM - all of the memory cells contain one bit of data each. Is there any memory cell that can store more than one bit, e.g. 2 bits/4bits?


texts: digitalRead sampling rate for Arduino Uno

texts:
I am attempting to send a character across the serial port when I press an external button the button is attached to the digital IO pin 3, I used the code from the SerialCallResponse example, and replaced the "sensor" stuff it was doing in the main loop with the following:

void loop()
{
 // if we get a valid byte, read button in:
  if (Serial.available() > 0) {
   // read the state of the pushbutton value:
   buttonState = digitalRead(3);
   if (buttonState == HIGH) {
     // print B on serial port:
      Serial.print('B', BYTE);   // send a T
    }
  }
}

However I get multiple B's sent out, so I tried putting a while loop in the if buttonState==HIGH section to wait until buttonState==LOW, however if I press the button, and then release then press again, it doesn't respond as quickly as I would have expected seemed to be a second to a second and a half response (although not accurately timed).

Is there a certain amount of time that has to happen between the digitalRead's where it will changeover to another value? Is there a form of an internal "debouncing" of a signal on the Digital IO?

This is my first Arduino and I got it two days ago, it's already much further along in my project then I was able to get with my Pic due to the full dev board fortunately.

EDIT: So I was browsing adafruits tutorials earlier trying to figure out if she mentions anything about what I'm seeing, I tried this code as an additional test:

int switchPin = 3;              // Switch connected to digital pin 2

void setup()                    // run once, when the sketch starts
{
  Serial.begin(115200);           // set up Serial library at 9600 bps
  pinMode(switchPin, INPUT);    // sets the digital pin as input to read     switch
}

void loop()                     // run over and over again
{
  Serial.print("Read switch input: ");
  Serial.println(digitalRead(switchPin));    // Read the pin and display the value
  delay(300);
}

I press the button, after I have released it, roughly 15 1's came across still, which tells me that even if I call digitalRead it's really only reading a buffer (or something like this) that samples the digital IO port at some rate, is this expected, any ideas where I can figure out where this number is? Where it came from (as in why that number)?

Would using an interrupt would make more sense? This way you would only be "notified" of when a new event occurs.

EDIT #2: So I decided to try interrupts, I changed my code to the following:

int switchPin = 3;              // Switch connected to digital pin 2

void setup()                    // run once, when the sketch starts
{
  Serial.begin(115200);           // set up Serial library at 9600 bps
  pinMode(switchPin, INPUT);    // sets the digital pin as input to read switch
  attachInterrupt(1,handle_button,FALLING);
}

void loop()                     // run over and over again
{
}

void handle_button()
{
  Serial.print("Read switch input: ");
  Serial.println(digitalRead(switchPin));    // Read the pin and display the value
}

This change now only displays anything on the serial port when an interrupt is triggered. I pressed the button and got "Read switch input: 1", however if I press the button anytime before 30 seconds has elapsed (rough count to 30 that is) it doesn't seem to trigger the interrupt. I wait for a count of 30, and I get the "Read switch input: 1" message. Again this continues to tell me that the digital IO isn't polled at a very fast rate, I find this surprising, I have messed with Pics in the past and haven't noticed this problem, and this is my first "real" program with the Arduino, I'm wondering if there is something I need to setup maybe?

The problem still is and remains that I am wondering what the rate the arduino uno (and more exactly the atmel atmega 328P) polls the digital IO ports.

EDIT #3 To be more specific, it's about 12 seconds (used an online timer and kept an eye on it). If I press a second time in 11 seconds it doesn't trigger it and I still have to wait another 12 seconds from the second press.


texts:
I'm new to verilog and modelsim. I'm having trouble with my AND and OR modules in this particular testbench. The output is always Z(hi impedance)

    module mux2to1_tb();
  reg[1:0] r0,r1;
  reg r2;
  wire[1:0] out;

  initial
  begin
    r0=1;
    r1=3;
    r2=0;
    #10;
    r2=1;
    #10;
  end

  mux tm(r0,r1,r2,out);

endmodule

here is the mux module

module mux(d0,d1,s0,out);
  input[1:0]d0,d1;
  input s0;
  output[1:0] out;
  wire [1:0]w1,w2,w3,w4;

  assign w4[0]=s0;
  assign w4[1]=s0;

  inv2bit M0(w4,w3);
  and2bit M1(d0,w3,w1);
  and2bit M2(d1,w4,w2);
  or2bit M3(w1,w2,out);

endmodule

  /*assign w3= ~w4;
  assign w1= d0&w3;
  assign w2= d1&w4;
  assign out= w1|w2;*/

this is the or module

module or2bit(iA,iB,out);

  input iA,iB;
  output out;

  assign out= iA|iB;

endmodule

this is the inverter module

module inv2bit(i1,out);

input i1;
output out;

  assign out= ~i1;

endmodule


texts: Can EEPROMs have feedback networks to make state machines?

texts:
I have imagined a simple system that detects in which direction a stepper is going based on the voltages across the windings, and which emulates from that two end switches relying only on one single switch activated at either end. This solution is solely based on a single 64kB 8-bit EEPROM (11 bits adresses used out of 13), but it requires something fundamental:
Is it possible to tie the output of an EEPROM to its inputs in the following way, to effectively use the EEPROM as some sort of Flip Flop with unit delay for a state machine? In this example, B has dummy values but it really is the useful output of the EEPROM.

I have done the following exercise which seems to validate this: assuming A mem is initially 0, and A now is 1, A mem becomes 1 and stays at 1. This seems to work for all states.


texts: Maximise Q factor in low pass Sallen and Key Filter

texts:
How do I maximise the Q-factor of the low pass sallen and key design.

I have this equation: \$Q = \sqrt{ \frac {(R1 \times R2 \times C1 \times C2)} {R1 \times C1 \times (1-A) + (R1 \times C2) + (R2 \times C2)}} \$

but I'm not sure of the best way to maximise it!


texts: Is building a DC-DC PSU PWM controller from discrete components a terrible idea?

texts:
I am building a 1kW PSU that is controlled with DSP MCU. It requires a lot of features such as synchronous rectification, bidirectionality, current regulation. Those features make the PSU very exotic and I was unable to find any suitable PWM control IC. My current problem is that the PSU is unable to regulate current quickly enough and I need to find a solution for that.

It is quite easy to build an analog CMC PWM controller model using ideal analog components and switches. But  I've never seen anyone do that in practice and that suggests me that it might be a terrible idea. There might be complicated problems such as noise pickup or timings mismatches.

Does anyone knows if it is a useful practice to build a PWM controller from discrete components or not and why?


texts:
I read a research paper that explains why permanent-magnet synchronous motors (PMSMs) are better suited for high-precision position control than brushless DC motors (BLDCs). I'd like to buy one, but the only PMSMs I can find are very large and expensive.

Does anyone know a good source of PMSMs suitable for servomotor control?

Thanks.


texts: Why are my net names not corectly exported to a SPICE netlist?

texts:
I have a schematic:

When I export this with the "Export Netlist" feature...

The SPICE netlist has renamed my Hello and World nets to NC_01 and NC_02...

.title KiCad schematic
F1 HelloWorld NC_01 Net-_F1-Pad3_ FET
R1 VDD HelloWorld 10Meg
F2 Net-_F1-Pad3_ NC_02 GND FET
.end

What am I doing wrong to make KiCad ignore the net names?


texts: Differential measurements with high voltage oscilloscope probes

texts:
This interesting post about differential measurements with a scope has raised a few questions in my mind.

I have read about true differential scope probes and they seem to be very expensive. Would two high-voltage 1:100 probes with the following derating curve still be safe/suitable to perform A-B differential voltage measurements on mains-connected appliances?

If the ground alligator clips cannot be removed from the probes during the measurement, would clipping them together adversely affect the measurement?
What about safety and accuracy of differential measurements at the frequencies at which switchmode power supplies operate (10Khz - 1MHz)?
Apart from common mode noise, is there anything else that could affect measurement accuracy?


texts: USB 2.0 termination. Single ended vs Differential

texts: why are usb 2.0 differential traces terminated with 45ohms each to ground, instead of being terminated with a 90ohm resistor across the pair? and if it is equivalent, why would we choose one way over the other?


texts: Non-systematic (7, 4) Hamming code encoder

texts:
I have to do the scheme of the non-systematic Hamming code encoder (not cyclic but classic). But I have not found any source where it would be written how to build a generating matrix and create a system of linear equations for finding symbols of code combinations. How is this done?

Once again, I consider the non-systematic classical (n, k) Hamming code. For example, (7, 4) Hamming code.

Thank you in advance for your detailed answers.


texts: Output from TD100 with instrumentation amplifier not as expected

texts:
I've been having trouble with my TD100 circuit for a few days now and I cannot understand why the output isn't as I expect.
This is the process:

simulate this circuit – Schematic created using CircuitLab
I get around 3.105V at the output for room temperature, but I'm expecting ~500mV. The Wheatstone bridge and op-amps share the voltage source from the Arduino Uno. I'm using an LM324 and a 1.1V reference from the Arduino (currently 5V for the unexpected voltages of >3V.)
The Wheatstone bridge outputs the expected ~40.95mV, the instrumentation amplifier has a gain of 10 - so I'm confused why I'm not getting ~409.5mV at the end.
Note: The resistors aren't exactly these values but they are the same to ~10ohms e.g. R5=R7=R9=R11=9.84k


texts: I am quite new to ac small signal analysis of transistor amplifiers. I do not understand why a different model (like re) is required in the analysis while the DC analysis seems to work without them.


texts: How does the compensating resistor act in op amp

texts:
Figure above is an integrator which has a compensating resistor

Hi there and I have a question about the compensating resistor, which is connected to the positive input in above circuits.
I know the 'compensating resistor' to compensate input bias currents b/w two inputs in Op and that this is for making voltage drop to be zero.
But I cannot understand the principle of this, and why the resistor should be same as the resistor which is in serial connection with V_in?


texts: This question may sound senseless but I am novice, just looking for clarification. My Cordless phone has a Wall wart AC Power Adapter rated at 9v 500mAh. As far as replacement is concerned, does output power only matters or we have to be specific with ratings also? Like a 4.5V 1A adapter output will also be 4.5W as original rating. I have read in this forum that higher current rating may not matter but higher voltage may damage. Also, I have heard that SMPS based supplies senses the actual load and outputs accordingly. Please correct me.


texts: How to determine Vds(on) and Vds(off) for switching loss calculation?

texts:
In the Infineon Application Note, two of the parameters they've used to calculate the switching loss of the MOSFET are Vds(on) and Vds(off).

Is the Vds(off) the blocking voltage?
Where do they obtain the Vds(on) and Vds(off) values from? Are they:

arbitrarily chosen
taken directly from the datasheet
dependent on the converter it's used in

If it's the third option, how to calculate the Vds(off) specifically?

Reference:
Application Note: https://www.infineon.com/dgdl/Infineon-ApplicationNote_MOSFET_CoolMOS_How_to_select_the_right_CoolMOS-AN-v01_00-EN.pdf?fileId=db3a304412b407950112b40acf580693
MOSFET Datasheet: https://www.datasheetarchive.com/pdf/download.php?id=76cd77451b2171be9a0ed7cbcf732382c7b37e&type=M&term=SPP04N60C3


texts:
I am looking at FM radio receiver designs others have created with gnuradio.  There are a couple of signals questions I have after looking at these designs.

The source (e.g. rtl-sdr) samples at a high rate, for example 2.4M samples/second.  After this the signal is decimated by 4 or 5 times.  Why is that?  Since the hardware samples > 2*highest frequency of the signal (music), why not just use that?  Also, what is the relationship between the WBFM receiver 'quadrature rate' and the sampling rate?

Finally, low pass filter blocks include a decimation parameter.  Is this the same as decimation in the resampler block?


texts: Using timer to power on/off a high current circuit

texts:
I'm working on a Arduino project that takes measurements from the environment and sends them to a remote server over WiFi. The circuit should be battery powered and I've measured that what I have at the moment takes about 160mA of current, which makes it impossible to run on battery longer than couple days. The good thing is that it is enough to power the circuit once an hour and run it for approximately one minute and then power it off.

So I was thinking of creating a very low power timer circuit that would power my main circuit for one minute every hour. Unfortunately I don't have any idea how to do that :). I tried to research and I think it might be possible with IC 555, but if I understood the data sheet correctly it draws around 3-6mA of current which is little bit too much.

Does anyone have any ideas to point me to right direction?


texts: Altium Designer, using signal layers as power planes

texts:
In cases when a 4-layer board is space limited, and there's a lot signal traces in the whole board, "power plane layers" is not very usefull to distribute power rails. Because it is used only to draw solid regions in a negative format. Therefore it is very hard to place some signal traces along the power plane.

I've been thinking, what's the difference to use a "signal-layer" instead of "power plane layer" which offer the capability of non negative format? You can also draw as solid region as you want but you are still able to put a few traces that they are difficult to stand on the external layers due to complexity.


texts: What does the "D/V" marking on small DC motors mean?

texts:
I have noticed with the large amount of optical drives and CD/DVD players I have taken apart that most of the spindle motors (RF-300, RF-310, RF-400, etc.) have the somewhat cryptic marking "D/V 5.9" on them along with the standard part number. This appears to be mainly found on spindle motors, and very rarely on the sled or eject motors. It also appears to be a fairly standard marking, as I have seen it on motors dating back to 1985. It could be the recommended voltage, although Mabuchi's information on the RF-300 says the voltage range is 1.5-6 volts and 3 volts is nominal. Some motors I have seen write "D/V" as if it were a fraction. All but 2 of the motors I have seen this on are made by Mabuchi, and on the ones that are not there is nothing after the "D/V" marking. I have been looking for an authoritative source on this for a while, and it seems there is none.

Any ideas about what it means or why it seems to be found only on spindle motors?


texts: My transfomer says "O/P 9v .2A" what does that mean?

texts: I understand what a transfomer does. I guess O/P means it delivers 9V as output voltage. But, what is the meaning of .2A? Will it burn if I connect a load greater than .2A?


texts: How often should I have to set oscilloscope probe's capacitance?

texts:
I got a new Owon SDS7102 oscilloscope and I'm using the included oscilloscope probes with it.

The manual says that the proper calibration procedure is to let the oscilloscope work at constant outside temperature for 25 minutes, do the oscilloscope's internal calibration routine and then set the probe capacitance using the included tool. The manual also says that the correct capacitance should be checked often and corrected if necessary. What the manual didn't mention is how often often is.

I expect that checking probes before each important measurement would be needed, but I'm looking for some "rule of thumb" for general use. From my current experience, several hours are enough to see small loss of sharpness of the calibration signal.


texts: Replacement power relay for convection oven

texts:
I looking to replace a blown power relay on a convection oven.  The part is no longer available.  I can't conceive of replacing such an expensive asset just because I can't find a $30.00 part.  (Thanks, GE!)

I'm looking for a suitable replacement relay.  The switched power is 240V with two output poles feeding (from the same switch) a 21A /5000W cleaning circuit and a 14A / 3000W heating circuit.  Existing relay is a SPST-NO (single pole, single throw, normally open) configuration.  I'm trying to determine the correct coil amperage.  The coil is on a 120V circuit.

Questions:
1) without a published spec, how can I determine the correct coil amperage requirement?
2) the existing relay has the typical diode across the coil terminals -- how do I calculate the correct diode on the new coil?  I think I can calculate the impedance of the coil solenoid -- is there a typical adjustment factor that is used to figure out the diode?  Would rather not experiment too much with this.  There is a diode on the existing relay, but I think I'm correct in assuming that IT'S capacity is irrelevant since it's unique to the old relay's solenoid impedance.
3) This seems like a dumb question, but which way should the diode point?

Just an aside, my local appliance tech will help with the replacement.  I'm wary of messing with 220V.


texts: How can I realize this nonlinear resistor?

texts:
I want to know if it's possible to realize a circuit described by the equation

$$I = \sin(w V)$$

where \$I\$ is the current, \$V\$ the potential and \$w\$ a variable which characterizes the single circuit.


texts: LM317 Constant Current Battery Charger Question

texts:
LM317 constant current charger are quite popular as it seems. I made one for my 12v 7Ah Lead Acid battery. I used  a 2.2 ohm 10 watt resistor and calculated that it would give a decent amount of constant current to charge my battery. To my surprise, I noticed that the battery is drawing only 20 - 30mA current when charging. Currently the battery is little over-discharged to 11.8v.

I had an impression that LM317 Constant current mode pumps constant amount of current, no matter what the load is. Was my understanding wrong?
If so, should the constant current value, i.e 1.25/R is actually the max current value? Because when I sorted the output terminals of the power supply, it reached upto desired current level, i.e (1.25/2.2) * 1000 mA

And if my understanding of LM317  constant current supply is correct, why is the  battery drawing only 20mA  current?

My circuit is as simple as following.

simulate this circuit – Schematic created using CircuitLab


texts:
I am designing a Chevyshev filter of order \$n=2\$, and I the terminant resistances to be equal (since when performing the denormalization of a low-pass circuit for an even order in Chevychev this never happens) and I can use an ideal transformer. My circuit is the following:

and I need the following one:

but my problem is that I don't know how to compute the turn ratio \$n_p:n_s\$ for the 133 ohm resistor to be 50 ohm, does somebody know how to achieve this? Also, the voltage of the sources is not specified (I don't know if that is relevant)

Thank you


texts: What MOSFET circuit replaces a diode in a 48V 40A escooter?

texts:
I want to use a 1kW generator and convert my eScooter to a hybrid.

The scooter uses a 48V SLA battery bank of 4x22Ah SLA batteries in series.

I used a transformer from a 1200W microwave oven and rewired the secondary to give me 54V.

Made a bridge rectifiers by placing 20x2A 100V diodes in parallel for a total of 80 diodes (didn't have a big diode).

I also series/paralleled 1000uF@16V caps to give me 8000uF, @96V.

My scooter uses 40 Amps to start moving and depending on the speed switch, will draw 25A (medium speed) or 30A (high speed).

If I connect an 80A diode from the generator's output to the battery, it should prevent the back feed from when I apply the brakes and the regeneration kicks in. Which is about 65-70V at 30A.

The diode will not work as there is too much power lose.
I need a circuit that will use MOSFETs to do the job.

Ideally, the circuit will chose the higher voltage source and prevent the regenerative current to flow back into the generator part of the source.

Can anyone help me?

More info on request.

Thanks.


texts: transfer function of electrical circuit (Beginner)

texts:
What is the correct way to find the transfer function of this circuit using the Laplace transform?

Can I add the impedance values of \$R\$ and \$C\$ (\$R\$ and \$1/(Cs)\$)?


texts:
From an article by an engineer at Cisco Systems:

  An RF signal can have the same frequency as a sound wave, and most people can hear a 5 kHz audio tone. No one can hear a 5 kHz RF signal.

Why not?


texts: Dual output/dual input canceling 12v trigger

texts:
I have a video projector with two 12V trigger outputs (output impedance: 4.7 kilohms). It is attached to two separate motorized screens. Unfortunately the projector software makes the second trigger additive to the first, but I need them to operate exclusively.

So, I think need to construct a gate according to the following truth table:

| i1 | i2 | o1 | o2 |
|----|----|----|----|
| F  | F  | F  | F  |
| T  | F  | T  | F  |
| F  | T  | F  | T  |
| T  | T  | F  | T  |

I don't remember any of my high school EE, but I can solder, so I would like a recommendation for a simple circuit to accomplish this.

Thanks in advance.


texts: Faulty mechanical keyboard: Identifying "defective" ground connection on PCB

texts:
So, I got a mechanical keyboard (Ajazz AK33) which had a problem since the start: a row of keys was either unresponsive or typing on its own; after reconnecting it a few times and restating my PC it started working fine, and it did for about three days.

Then I desoldered all the mechanical switches and LEDs, and soldered some other switches in, while the soldering/desoldering process was a bit rough I don't believe I damaged anything on the PCB. Now, after reconnecting it the same row which didn't work the first time started not working again.

After some snooping around on the PCB with a multimeter I figured out what might be the problem (or at least something is different on the non working row compared to the others): the upper switch contact of every key in the non working row is directly connected to ground on the mini usb connector. Here is a picture of the PCB:

All the little red dots are connected to each other (which I believe is normal, since all of the working rows are connected the same way and the keys are read in a matrix by the microcontroller) and to the same pin on the microcontroller (also normal), however they are all directly connected to ground on the mini USB connector, the bigger red dot, which I believe is not normal since all other rows seem to be connected to ground through a diode (my multimeter gives me a ~.580 to ~.640 one way reading on diode/continuity mode)

This also means that the pin of the non working row is directly connected to ground on the microcontroller, that can't be good, right?

Also, each diode seems to be connected from the cathode to ground, and the same thing happens in the non working row: each key in the non working row gives me a ~.580 to ~.640 one way reading if I measure it from cathode to ground. However, if I measure it from the upper contact of the switch to ground it gives me a direct connection while all the other working rows give me the same ~.580 to ~.640 one way reading.

There seems to be some kind of connection to ground on the non working row which should not be there; what would be the best way to identify it, and/or possibly get rid of it? I tried following the traces on the PCB but they are not clear at all.

EDIT: Did some voltage testing while the board was on measuring the voltage on the switches' contacts: the working keys stay at a ~2.15v when not pressed and drop to 0.00v when pressed. The non working keys, on the other hand, stay at ~0.08v when not pressed and drop to 0.00v when pressed.


texts: Writing code for new microcontroller/module without examples

texts:
I started learning embedded systems programming(after a long time when I stopped) and I see that most microcontroller boards/modules come with some set of example codes which can be used a base to create new projects.
my goal is to get job in embedded systems programming and I would like to know, do developers in the industry also use examples code as base ? If not, what is the industry practice?


texts:
Hi I am building an USB sound card circuit for raspberry pi. It involves a button, LED and Sound card IC PCM2912A (TI).

I am mounting raspberry pi over the 2 sided pcb on top (top has full digital ground). All analog components are in bottom but the wires to and from mic/speaker are in open. Bottom have both digital and analog ground which are connected at only single point (as power supply is one). I am also using PAM8403 to amplify the speaker output. (see below)

Basically i am building 2 way audio video system enclosed in a 5 face 'metal' box. 6th face is ABS plastic. Wifi connected to router is working perfectly inside box.

My problem is that when i start communication I hear a noise (most likely EMI noise). I have tested power supply to amplifier and it does have little spikes but thing is when I keep system inside but take just raspberry pi outside (wifi out) the noise is significantly reduced and when i keep pi out and  keep wifi parallel to body, noise is zero percent.
So the inference i have drawn is that noise is not from power supply but from RF waves.

I have tried to shield top of pcb, connectors for mic and speaker and camera circuit with aluminium shield inside electric tape but noise is still there. Also i have found out that if i keep my direct hand over antenna for raspberry pi noise is reduced to 0 but if i shield the inductors of antenna with foil (yes wifi still works) noise is slightly reduced. I have tried shielding various parts but not able to find perfect solution that works not sometimes but always.

Question: What may be the cause for noise? How touching wifi antenna makes noise zero? How to reduce the noise effectively?

Additional info: There is also NRF24L01+ in system but it is in power down mode most of the time and is only transmitting for less than a second. Also I am not grounding the shield at the moment.


texts: What is the meaning of the caution in hardware manual of a microcontroller

texts:
I am trying to understand the hardware manual of a microcontroller. Here is one caution in this manual:

"The behavior and performance are not guaranteed when the alternative functions are not assigned to the register"

This caution appears with a table describing the alternative functions of several pins in a register.
Here is the image of the caution in the hardware manual:

I don't understand the meaning of this caution. If an alternative function is not assigned to the register, we just simply can not use this register as the alternative function. Why do they say that behavior and performance are not guaranteed?

Does it mean that we can still use a register as an alternative function even when the alternative function is not assigned to the register? The only problem is the performance is not ensured?


texts: Non overlapped implication(|=>) used in system verilog assertion

texts:
I know that if I use

s1 |=> s2

the consequent sequence expression s2 will be evaluated on the next clock tick. However, if there is no clock(combinational circuit) how will the assertion be evaluated?Will the simulator wait for 1 time period and check s2 or is it something else?


texts: What is the difference between 'x' and 'plus' symbol in the block diagram

texts:
Generally speaking, what is the difference between the 'x' and the 'plus' symbol in a closed loop block diagram?

For example, in

(https://ieeexplore.ieee.org/document/6983570)

, what's the difference between the 'cross' sign and the 'plus' sign?


texts: In a vacuum triode, what prevents the grid from acting as another anode?

texts:
A triode vacuum tube has three electrodes, namely an anode, a cathode and a control grid in between of those.
Assuming that the filament is hot, current would readily flow from the cathode into the anode when no bias voltage is applied to the grid, like a diode valve.

But doesn't the grid also have the ability to capture electrons? Would there be a non-negligible current path between the cathode and the grid?


texts: Use a TVS device to protect meter from live capacitors, workable or not?

texts:
I've been working on a LCR/Impedence meter and want to protect my inputs from possible damage if I forget to discharge a large cap.

I know I've seen various types of diodes and relays used for that purpose.  But from what I've read and experienced, the larger diodes can cause degradation and relays would be a pain in the ass.

Then I remembered using a TVS array from TI(TPD2E2U06-Q1) to protect my usb signal lines on a prior project.  With a minimum break down voltage of 6.5VDC and a stand off voltage of 5.5VDC, I thought it would be perfect.  It has what looks like a 0Db insertion loss out past 100Mhz(I'll be using a max of 500Khz, and more likely 100Khz and below).  The line capacitance is only 15pF, I'll have more than this in parasitics. This thing is mostly being built to deal with small impedances/resistances, miliohms and the like(I have a VNA that can handle larger stuff/higher testing signals) and a 5.5VDC cutoff will be plenty for this.  I will also be putting two of them in parallel.

Now the question, did I interpret the data sheet correctly?  Meaning will it protect my inputs(my front end AD630's are powered at +/- 12VDC, so they are safe until 13VDC) from a live cap and not greatly effect the measurements?  If it comes down to it, I don't care if these things act like popcorn, at $.60, they are a LOT cheaper than my AD630s...

Here is another question, would adding a 2 or 5 watt resister in the TVS's ground leg help out here?  If They


texts: How to choose a PM motor for its generation charcterstics?

texts:
I have to run a device that consumes 250Watt at 36V and now I have to power it using a generator.
Now I have 2 options for this:
1-BLDC motor (permanent magnet) which consumes at 24V @ 250Watt, max 360rpm
-https://robu.in/product/ebike-my1016z2-250w-360rpm-geared-dc-motor/
2-BLDC motor (permanent magnet) which consumes at 36V @ 240Watt, max 328rpm
-https://robu.in/product/240w-36v-brushless-hub-motor-for-e-bike/
Now which between the two options is more suitable option to be used as generator in the given condition of 36V @ 250Watt and why?
Links for both the motor provided if you want any other information.
I am not looking for the fact if it will produce less or more or somewhere near this. I just want to know which of the following will produce more power in comparison to each other.
Also one of them produce the same power at lower voltage and hence will it be difficult to consume the lower volt power at the condition which is higher provided above.
I am just looking for comparison and what basis this comparison is done.


texts: Is there a database on internet for LTspice models?

texts: LTSpice doesn't have many components as default. One has to download the spesific model component and integrate it. Is there a website where I can look for it?


texts: Maintaining a current in a circuit connected to multiple DC motors (3.0V) that turn on and off arbitrarily

texts:
I have a circuit that is connected to multiple DRV8833 motor drivers. Each motor driver is connected to two 3.0V DC motors. The timing of when they run and stop and how many rotations they perform is very important for this purpose. When I try to run two or more motors at the same time, only a few actually turn and others are delayed by a lot. This is likely due to the sudden voltage drop caused by the first motor that runs without a problem.
Is it possible to solve this i.e. by using a buck converter like this one? At the moment I am simply using a USB wire directly connected to a power outlet, which is also not ideal for the 3V motors.


texts: Sallen Key topology input and output impedance

texts:
Ideal Operational amplifier
Zi=(R1+R2)||Zc2
Zo=0
741 Operational amplifier
Zi=(R1+R2)||Zc2
Zo=0 (at DC)
For the input impedance when using a 741 I am not sure if I should consider the Fairchild version of the 741 graph showing input resistance vs frequency impedance (at DC is about 6Mohm) so It would be Zi=((Zc2||R_OA)+R2))||Zc1+R1


texts:
My fish at a part of the insulation on my filter. What is the best way to fix the insulation and also make sure that it remains waterproof?
The best option I came across is silicon gum. Can I apply it directly over the naked wire and pray for it to work?


texts: low power rfid on objects to aid in mapping

texts: Is there a means / method to using rfid on objects placed in a field and then using a fixed point receiver to plot the objects relative to the know position of the receiver?


texts: Performing measurement on a function of a waveform in NGSPICE

texts:
I am trying to perform a simple measurement of the absolute value of a waveform (measuring the waveform itself is working). See source file:
*First simple simulation
V0 IN 0 PWL ( 0 0 ) ( 5e-9 3) (10e-9 1)
R1 IN 0 500
.TRAN 1P 20N
.MEAS tRAN sample find I(V0) AT=10n
.CONTROL
listing e
destroy all
SAVE V(IN) I(V0)
let abs_cur_vin = abs(i(V0))
RUN
MEAS TRAN sample_abs find abs_cur_vin AT=10n
display
PLOT V(IN)
display
plot I(V0)
.ENDC
.END

The error I get is:
Error No such vector as abs_cur_vin

Thanks.


texts: Switching between battery and external power sources with reverse polarity protection

texts:
In my design, I will use AA batteries to power the electronics board.
As a requirement, also it should accept the power from external power supply (12V) - The board should automatically switch from battery to external source.
- The board should have reverse polarity protection for both battery and external source.

I found this solution from Maxim Integrated..

FET switch can reduce the drop to less than 0.1V instead of diode.

My Question:
The FET (FDN340P) and diode (1N4001) work as reverse polarity protection for board?


texts:
I am working on a remote-controlled (IR) lightswitch. This is pretty easy with an Arduino; you just do serial I/O with an IR receiver/transmitter to read "ON" and "OFF" signals.

I want to know if this kind of thing is possible without a microcontroller. Do there exist IC's that send/receive a pre-defined pattern (and then activate a pin if one of those patterns is recognized?)

I want something similar to a multiplexer; if I activate a set of pins, how can I output that pattern, like morse code, to my LED? Similarly, how could I read in such a pattern?

Is there a category of IC's, pertaining to logic or communication, that I might want to be aware of?

The reason I ask is:

I am a software guy. So "just programming it" is really easy, and I would like to learn more about ICs and using them.
I plan to make a few of these, to give to my buddies and put in different rooms of the house. It would be cool if I could use standard parts, rather than having to program a chip every time I wanted a new one!


texts: What kind of diode package/case is "case-17"?

texts:
The Russian company asked me to purchase several elements for the production of the device.

Among the elements in the BOM there were two "5 watts" zener diodes

1N5342B at 6.8 Volts
1N5349B at 12 Volts

For both diodes in the column "Case Type" was written "DO-СASE17".

Seeing this name of the type of case, I am a little surprised, because I have always used diodes in cases with names like "DO-15" or "DO-204AC". At first, I decided that it was just a mistake and started looking for a diode by its parameters - but it turned out that some manufacturers, for example, "ON Semiconductor", do not write standard types of coruses in the documentation for diodes, but on 7 page - write such lines in the header of the case type description:

  SURMETIC 40, AXIAL LEAD

  CASE 017AA

  ISSUE O

Link to the Datasheet "1N53xx(B, G) Series":
>>>>> HERE <<<<<

Screenshot this page:

Actually my questions:

1) What kind of case is this "CASE-17", is it another name for a particular manufacturer?

2) How is this case different from "DO-xx" type cases?

3) What does the line "SURMETIC 40" mean, is SURMETIC a company producing packaging or something else?

4) What does the line "ISSUE O" mean?

==========================================================

============ As a result of proceedings on this issue: ============

SURMETIC is a trademark specifically "ON-Semiconductor" - for example, in my document >>>>>HERE<<<<< is written on the last page, quote:

  SURMETIC is a trademark of Semiconductor Components Industries, LLC (SCILLC).

Now it remains to figure it out

1) What do the other lines mean

2) What actually write in the BOM, in the column "type of housing", instead of the short and well-known DO-15 and DO-204AS

All together "SURMETIC 40, AXIAL LEAD, CASE 017AA, ISSUE O"
Or just "017AA." But in this case, not everyone will understand what kind of case it is.

3) Why did ON-Semiconductor come up with their new name for the long-known case.


texts: What does the common terminal (COM) do in PLC

texts: What does the "COM" (common terminal) hook up to on the input of PLC (i.e. Omron CP1L). There are 10 NO input points, one COM and one ground, and two for power AC power supply. Am I supposed to connect the "+" input to NO input point, and "-" to COM?


texts: Automated test for pushing a pcb mounted mini push button

texts:
We have a test that checks whether or a push button works or not, and as of now the test is done manually by hand. My question is how to do this automatically?

We have considered using a solenoid to push the button but have some hesitations on whether this might damage the somewhat delicate button or the PCB itself. The button is similar to this but mounted perpendicular to the PCB.

Some solutions I thought of:

Using a small solenoid with a damper so it doesn't accelerate quite as aggressive
Adding a spring between the button and the solenoid
Using a small linear actuator
Using a servmotor to actuate the button

I would prefer if the "buttonpusher" would revert back when the power is removed so I am somewhat biased against using a linear actuator or the servomotor.


texts: Why is the soldering surface of this pogo pin slightly rounded?

texts: I was curious as to why the bottom of these SMT pogo pins are slightly rounded. Wouldn't it cause them to fall over before they are reflowed ? It seems that a completly flat bottom would make sense like most SMD pads.


texts: Positive and negative terminal of a Tesla Coil

texts: I'm trying to build a Tesla coil, I'm using it as a large voltage multiplier, though I can't figure out where is the output positive and negative terminal. thanks!


texts:
I have created a small product using Sim800 and the product uses only GPRS. I am told by the testing company, that I need to create a test firmware which will continuously transmit.
The confusion is, that in order to continuously transmit, I need to know which IP and port to connect, but the testing house says, it will be simulated...and I don't understand what does that mean.
Even after 3 calls, the testing house keeps repeating the same requirement.

Maybe, either I'm not asking the right question or the testing house is not giving me right answer.

Therefore, the exact question is - I need to write a firmware which will use AT commands of Sim800, connect to the internet and simply ping a website in a loop. Since this will be inside a simulator, what IP/Port combination is required OR how is this simulated.

The testing house does not say anything and is not very co-operative in this regard.

Any pointer in this area would be of great help.


texts: Can an ML2032 battery be used in place of a CR2032 battery?

texts:
I discovered this battery existed earlier when I looked into replacing the battery in my logitech K750 solar charging keyboard. In fact, searching for the ML2032 battery comes up with many specific references to this keyboard.

Given the name and form factor, I assume it has other uses as well, but information on it is surprisingly lacking. One website said that this battery was not for public sale, but only sold directly to OEMs.

I ordered a replacement battery for my K750, but it wasn't possible to order a single one, so I will be receiving a pack of two.

I'm wondering if it's possible to use the other battery in place of a CR2032, as I frequently have to replace the one in my doorbell and other appliances. It might actually be cost-effective to buy an ML2032 recharger given how often I seem to replace it, and perhaps nicer for the environment as well? But I digress.

Anyway, my question is simply, can I use the ML2032 in place of the CR2032?


texts: Ferrite beads as power rail in opamp breakout analog input circuit

texts:
i'm designing a small breakout boards that is used to interface some external sensors (voltage and current) to a MCU.
In order to get better results, i'm using an external dedicated ADC, the ADS1115, i've seen the implementation of Adafruit in this breakout: here and here there are the schematic and pcb design.
My question is pretty simple: can i use the output GND and VDD from ferrite beads in order to power up my circuit? it is a bad choice? it will generate some issue power the opamp's from the output of ferrite beads? consider that the analog inputs are only 0...20mA and 0...10V inputs from sensors.
Here is the circuit schematic, very simple and effective:

And here it's the Ferrite bead electrical characteristics used (MMZ2012Y152B):


texts: Eliminate transient loss of power due to inverter (UPS) transfer time

texts:
I have a 120V AV receiver (amplifier) connected to a step down transformer for converting from 230V mains. This is the only electronic equipment in my home to completely lose power and turn off/on when the inverter (UPS) switches to battery and back to mains when there is loss of mains power. The inverter is pure sine wave and has a transfer time of <= 15ms. As you can imagine, this is very annoying and I have been trying to find a solution short of buying a very expensive double conversion online UPS.
My knowledge in electronics is very lacking so I would be very grateful if someone could answer my questions here:

Why does connecting an equipment (driven by an SMPS, same as everything else) to a step down transformer cause it to completely lose power when the inverter switches?
What can be done to prevent this? Could a capacitor be used at the input/output of the step down transformer?

Thank you


texts: How to protect GPIO from back current? Diode?

texts:
After frying a Rpi with this montage 6 months ago:

I followed advice from kind users here and modified the wiring to this back in February:

It has been working fine for 6 months and suddenly yesterday, this montage fried a Rpi again, probably due to a short circuit or maybe PWM failure pushing back current in GPIO.
Now looking for advice on how to protect GPIO on the Rpi.  Diode or any other economic solution...
PLEASE BE EXPLICIT AND VISUAL IN YOUR ANSWER as I'm a visual learner.  If it requires rewiring please draw it or a particular component added, then please name it.
PWM module I'm using:

The Rpi is powered/grounded via a 12V to USB (5V/3A) converter module, which is wired directly to the 12V battery:

Now thinking of replacing the above PWM modules with OPTOCOUPLER isolated ones like the LR7843 (max 30V/161A) which seems to address the flash back current problem that I suspect is happening with the current cheap PWM modules (which do not have an optocoupling feature).


texts:
I want to learn about the raw serial communication protocol (The one that uses the Rx and Tx pins of a microcontroller).

I want to be able to send bits of data without using a microcontroller.

How would you go about to send the letter "a"  (I guess you send the ASCII character) but how do you do that??

Is there a predefined way the pins flash?

I want to know everything there is to know about the serial communication protocol.

It would be great if anybody sent me links to learn this in a very in depth way.

further clarification
Here's what I want to do..... I want to build a circuit (probably using a 555 timer and yes it's gonna be ridiculously slow) that will send the character "a" repeatedly.

Why am I doing this??? Well...by doing this I will get a a really good understanding about this whole serial communication thing


texts:
I'm studying feedback amplifier and I stumbled upon these slides from Jaeger-Blalock book.

However, I just cannot understand what happens in slide 2. Two R_F resistances appears: but why? I thought of Miller theorem, but the Z1,Z2 values aren't close to the original 100kOhm value. Could you explain me what is the circuit transformation?

EDIT: Just to clarify: this is how I'd draw the schematic in slide 2. Apparently it isn't equivalent to the one in the slides. Why Rf is being doubled and grounded? I don't fully understand the explanation "it needs to be considered both in input and output parts".

simulate this circuit – Schematic created using CircuitLab


texts:
I am having problems with this ADC. Here is the datasheet:

http://ww1.microchip.com/downloads/en/DeviceDoc/22072a.pdf

I connected it in Single-Ended Input, so I have 15-bits from 0v (0x0000) to 2.048v (0x7FFF).

According to the page 8 of the datasheet, the output code is (max code + 1)*((Vin+ - Vin-)/2.048)

So if I measure 0.994v (Vin+ - Vin-) I should get 15904 (decimal), but I get 7957 instead. This rule of the "half part" is always true.

Any idea of what I am doing wrong?

Thank you.


texts:
I built a very simple circuit from a schematic I found online, but it is not working. It is a touch switch circuit in which I touch a metal object connected to the circuit, and the LED2 connected at the output glows. When touch is removed, the terminal is pulled back to ground, thus lighting up LED1.

NOTE: LED 2's direction has to be reversed. I have already reversed it!

What could be wrong? I am using a LM324 Operational Amplifier, two 10k resistors and one 100 ohm resistor, 6V battery, and two LED's. Since the LM324 chip has 4 op amps within it, I tried using the another op amp, but that did not work. The LED's are not burned out, and I have checked multiple times that I set my circuit up right. Thanks for any help!


texts: How do I generate a schematic block diagram from Verilog with Quartus Prime?

texts: The answers to this question say that Altera Quartus will generate block diagrams from Verilog files. I'm a user of Quartus Prime Lite Edition. How do I generate block diagrams?


texts: I am possibly getting a problem with variation in performance between batches of boards that contain one area which is very current sensitive (to sub nanoamp). Could it be due to manufacturing residue or the board being inadequately washed? If the latter, how would I go about washing the board to check?


texts: How does a RCBO trip from a vapourised PCB trace?

texts:
I was replacing a power board with a new (plastic insulated) one, which resulted in a trip of the 20A 30mA RCBO on the circuit instantly upon turning on one of the board outlets. The built-in 10A breaker on the power board did not trip.
Since all loads previously worked fine on the old power board, I assumed something was wrong with the new power board and begun to investigate.
I found that inside the power board, both active and neutral is routed through a PCB, and a trace ~1mm wide on the active side of the outlet had vapourised and covered the area in a thin layer of black dust.
A 1mm wide trace is clearly too narrow to carry the rated 10A of current of this board, so it doesn't surprise me that it blew up. (The rest of the trace was 5mm wide, but the 1mm part was next to a slot. So I assume it was a misalignment during manufacturing, where the slot cut into the trace more than intended)
However, how did it trip the RCBO?
As far as I know, the RCBO should only trip instantly on either ~30mA of leakage current, or >100A of overcurrent.
So I considered the options:

Ground fault in outlet: The trace that blew up was nowhere near the ground line (~10cm of separation). I also checked the continuity around the blown-up trace (active) and ground line, and it was definitely open. Neutral to ground was also open.
Short in outlet: Area around blown up trace (active) to neutral was also open. And the 10A breaker on the board did not trip.
Fault in load: The load that was connected to it previously worked on the old power board, and continues to work in a different outlet.

So right now, I'm guessing that as the 1mm trace got vapourised, it greatly lowered the ionisation potential of the air inside the board, and formed a conductive path between active and ground (via arc or corona discharge), causing a ground fault and tripping the RCBO. After the dust settled, the conductive path disappeared.
Does that even sound possible? Is there a less outlandish explanation of why the RCBO tripped?

EDIT: I've now repaired the blown-up trace with a thick solder bridge, and now all outlets on the board work as normal. Which is more evidence that the trace vapourisation was what caused the trip

Actual sequence of events for context:

Switched off all outlets on both old and new power boards, and at the wall
Replaced the old power board with the new, and plugged everything in
Switched on the outlet at the wall, and on the board slowly one-by-one (downstream devices automatically start drawing power)
RCBO trips instantly upon switching on the last and highest downstream load (~1A continuous; unknown inrush) outlet
Leaving outlets on the on position, I try to reset the RCBO, but it continues to trip
Switched off the "offending" outlet on the power board and reset the RCBO, and it now stays on
Try switching on the "offending" outlet again, and the RCBO doesn't trip, but there appears to be no power coming from the port anymore (vapourised trace is no longer conductive now)
Moved the "offending" load to a different outlet on the board, and switch it on, and this time everything works with no problems
Disconnected everything, opened up the power board, and found the vapourised trace
Cleaned the black dust off, reverse engineered the board, and started probing around


texts: Is it possible to select a whole net class and change its track width?


texts: Will one pic programmer program all pic chips?

texts: If yes which one and where could i buy it and is there an inexpensive programmer for the chips?


texts:
I am building a Crowbar circuit for one of my sensor which is power supplied through a Recom Power R-785.0-0.5 (datasheet).
The crowbar SCR is controlled by this IC.

I am having troubles in selecting the right SCR because:

I don't understand what happen at the output of the R-785.0-0.5 when the CC happens. The datasheet says that it has short circuit protection, but what does that mean?
What is the maximal current which will go through the SCR when short circuited?
What is the output current limit of the R-785.0-0.5 of 2000mA in the datasheet?

Any suggestion for a correct SCR?


texts: Transparent epoxy covering component on logic board

texts:
While performing CPR on a MacBook Pro exposed to water, I accidentally removed a piece of glue/epoxy from the logic board. It is a strip of glue covering two components with blank metal surfaces.

It is visible here near the ethernet port:

I found similar applications on the back-side of the logic board, more easily visible.

Do you have any idea what its purpose is? If removal may have caused damage and if it needs reapplication?


texts: Will a HCMOS output TCXO work with LPC1114?

texts:
I am planning to use the output from a FOX924B 10 MHz TCXO with HCMOS output as an input to the 32 bit counter of LPC 1114 (not the XTAL input, but to CT32B0_CAP0 pin). I have the following questions:

(1) The datasheet for FOX924B just says HCMOS output. Does it imply square wave output?
(2) Can I directly route the output from the TCXO to the CT32B0_CAP0 pin of LPC1114?

Would much appreciate your replies!
Abhishek


texts:
I wanted to avoid using a soldered usb plug, and add copper pads directly onto my board to act as a usb plug.

Now I wanted to know how thick the board should be, in order to have a snug fit in any USB port.


texts:
This is a schematic for the an internal input/output pins of an uln2003a and other such array transistor.

From what I understand, when no voltage is present on the first transistor, the current will flow from Ouput C to E or Ground. Here I'm, not exactly sure why we have a ground in the schematic as E should be connected to the ground itself.

Now the things I really don't understand is why is there a diode from ground to input. Wouldn't it allow current to flow from OutputC to Input? I guess if such thing would happen, the transistors would stop the current from flowing back to the input.

All output pins should be connected to some kind of positive voltage, so when the input is activated, the electron will be sunk into the output C.

Second thing, it looks like all inputs are connected together to the ground which makes it possible to actually trigger all inputs at once. The resistance between any pair of input is always around 18.88K ohm. Which makes me believe that if I put too much current on one input, it's enough to activate all inputs at once.

By looking at the diagram, we can see there is no diode to prevent current from flowing back from one input to an other.

The reason I'm asking is because I'm unable to understand how to wire this thing to a stepper motor. Most of the tutorial simply wire the input from an arduino for example and it just works. In my case, it seems to be pushing either too much current through the input or not enough because the output do not seem to be activated independently of the input.

I only have a digital analyzer so It's a bit hard to understand what's going on. I can see in the analyzer that the voltage is rising up or down for all channels.

I was trying to add some resistance on one wire to check how the output would change, after I got around 100k for a "clean" rise and fall for one single channel, I tried to connect the other channels but once the four channels were connected with each of them with 100k resistor before the input. I still got messed signals.

It's just a guess, but since I added resistor on each channel, it might prevent electron to flow back to each inputs. Like all of the connected input leak a bit of voltage to ground so it's technically not possible to flow back... With one channel used, it might be simply flowing through the diode below...

Anyone could clear this up... How is it possible 1 input drive multiple output?

Voltage put on input is 5v and on COM 12v. When a stepper motor is connected, I'd expect 12v to flow through the output ports that are open.

Here's the shematic of what I'm have right now:

simulate this circuit – Schematic created using CircuitLab


texts:
so I plan to build a house (at some point in future) and I'd like to implement some sort of home automation. Now one of the things I'd like to have is PWMed lighting. Most of the lights would be 12V LED lights which consume around 0.3A each.

I plan to have Arduino (under plasterboard ceiling accessible via a revision door) in each room which would (among other things) control the lights via TLC5940 + TLP250 + MOSFETs. This is just for illustration how it might look like in a room:

Each red line represents a pair of wires. I estimate that the longest wire could be 8m (26ft) and for that I need to use 20 AWG wire to be under 3% of voltage drop. Each light would be dimmable (provided by TLC5940 at PWM frequency of 1kHz) and powered from a single 12V power source (per room).

This all works fine on a breadboard with short cables and couple of lights but I am not sure how well it will behave with long wires and lots of lights (like 20). I already bought some wire so I can test a few lights on long wire. And it even might seemingly work well but I am trying to design it so I don't have to replace parts every month.

So here are things that I would like to ask:

Will PWM work reasonably well at such a long distance? Such long wires have not negligible capacitance, inductance and resistance so I know that I am not gonna get a square signal at the other end of the cable (far from it) but I am not trying to communicate with the light, just trying to light it up. Will the lack of square cause any ill-effects on the brightness or the LED itself?
Long wires are antennas. Could a lightning storm induct such a high voltage on those wires that would damage either the lights or the MOSFETs? Arduino will be opto-isolated via TLP250 so there should be no harm. Also if there will be any power lines (230V) crossing those wires e.g. for controlling electrical jalousies, will switching the jalousies cause the lights to flicker?
Do I need any protection for the lights or the MOSFETs? I mean like a flyback diode...
20 lights PWMing at 1kHz on 8m long wire...Will that generate lots of EMI that could distract other devices in home? Btw. there will also be dimmable LED strips (12V, 4-5A) but hopefully not on a very long wire. As I have mentioned I plan to use 20 AWG cable (might use smaller diameter cables for shorter distances) for the lights and there seem to be lack of (or more an absence of) a twisted and shielded 20 AWG cable. On the other hand 20 AWG speaker cable is available everywhere. How much of a difference  is there going to be between a speaker cable and twisted and/or shielded cable (if I can get hold of some)?
Anything else that might cause problems of any kind you can think of?

Btw. I did not state it explicitly in the questions but I am not only looking for the answers but also for solutions. If you know how a particular issue might be fixed that is. I welcome and thank you for any comments/feedback.


texts: Understanding volatile class fields in AVR C++ programs

texts:
I'm having some confusion about what members to declare volatile in a program I'm writing in C++ for an AVR microcontroller, with interrupts. When it's plain C it makes sense - the compiler doesn't know that interrupt ISR's can modify variables at any time, so those variables need to be declared volatile. But I have an architecture that's somewhat like the following (distilled example):

class FifoBuffer {
    public:
    int Size;
    int BeginIndex;
    void Push() {
        Size++;
        // ...
    }
}

class RadioInterface {
    public:
    FifoBuffer RxBuffer;
    void HandleInterrupts() {
        RxBuffer.Push( 123 );
        // ...
    }
    int GetPacket() {
        RxBuffer.Pop();
        // ...
    }
};

RadioInterface g_Radio;

ISR( INT0_vect ) {
    g_Radio.HandleInterrupts();
};

void main() {
    while ( true ) {
        g_Radio.GetPacket();
    }
}

My basic question - what needs to be volatile here?

When the ISR calls RadioInterface::HandleInterrupts(), are we back into a safe non-volatile context that the compiler can figure out and optimize? Or do I need to recurse down the call tree and figure out everything that could potentially get touched from main() and from ISR(...) and make it volatile?


texts:
simulate this circuit – Schematic created using CircuitLab
I am trying to design a buffer only using NMOS and resistor as this picture shows. The goal is to get the CLK signal as much amplitude as possible. My questions are maybe little too basic, so

How can I ensure that?
Generally speaking, how to design a good buffer? What kind of aspects should I be concerned about?


texts: Adding a potentiometer to an LM4910 as a volume control

texts:
Can someone tell me  where I need to place a potentiometer to control the volume in this LM4910 amplifier circuit?

Does the shutdown pin need a pull up resistor  to enable the IC?


texts: 74161N 4-bit counter not counting properly

texts:
As further issues arise I see myself stuck once more with a dysfunctional circuit. Whenever I press the clock button I get all of the leds on except maybe one or two, with some flashing during the button press. I have added a debounce circuit, but still to avail.

simulate this circuit – Schematic created using CircuitLab

Debounce Circuit: http://www.labbookpages.co.uk/electronics/debounce.html#what
Datasheet for 74161N: http://www.jameco.com/Jameco/Products/ProdDS/49664.pdf


texts: The step transient response of a parallel RLC circuit

texts:
Let's say an inductor is connected in parallel to a resistor and in parallel to a capacitor. At time t=0 the circuit is connected to a DC current source.The initial stored energy is zero. I have the solution in the text book under the section "The Step Response of a Parallel Circuit".

The current through the inductor is equal to the current of the current source plus a negative exponential multiplied to a sinusoidal function.

I understand that an inductor acts as a short for DC. But for the transient response the current through it will be zero and the current goes through the capacitor and resistor.

My question is where does the sinusoidal term comes from? Are there any physics behind it, or we just get it from analyzing the circuit?

What I am looking for is an answer like this:

When the DC current source is connected to a parallel RLC circuit,  the capacitor acts as an open circuit, the inductor acts as short so all the current goes thorough the inductor but this the steady state response. For the instance that we close the switch(transient response) .....???...I am not sure what happens. It seems that the inductor becomes an open circuit(not sure why)and the capacitor and resistor current is negative exponential times sinusoidal (I don't understand this part either)


texts: Designing a MOSFET current mirror circuit

texts:
This is the design problem:

This is a brief of my design for W and L of the transistors and R:

I've connected the upper voltage source to ground and made the lower one equal to 0.4 V to make sure that N2 operates in the saturation region.

I don't know what to do with the condition (ro >= 5k ohm) in my design. Is it for simulator stage not for the design stage?
ro is considered only for P2 and N2. Right?
Please give advices and notes on my design especially if there is something wrong.


texts: Black box on Arduino unsoldered itself due to overheating

texts:
Okay, so I was following this tutorial to control an RGB led strip with Arduino Uno R3:
http://learn.adafruit.com/rgb-led-strips/usage

And the LED strip wasn't lighting, so I tried plugging the other end of the LED strip into ground. Then I realized I was using the wrong pin for ground, so I switched that and then the lights were working, but the Arduino began to overheat, and the black box next to the 12v power supply and IOREF pin became unsoldered before I had a chance to unplug the power supply. USB power works at the moment, but not 12V.

What exactly happened to cause this? Should I have not plugged in the other side of the strip into ground? What is the black box that fell off, and is there any way to solder it back on?

Edit: The part is shown here: https://www.dropbox.com/s/xu7fbycufhlq9fl/arduinopart.png?m=


texts:
I developed a board and I like to measure the power for each block. Power can be a few micro amps to a few hundred mAs. (Depending on the block). I have zero ohm resistors at the input of each block so I can insert a DMM.  I don't have the budget for a nice Scope Current probe. What would be a good way to measure individual currents on each block? (I tried to connect the DMM in between but it changes the total load on that block it is not as effective. Shunt resistor is also not preferred since at low currents, I need to put a high value resistor and that impacts the circuits).

If the method could provide measurements up to 10KHz, it would be great.

Are there low cost home-grown measurement probes that are sold that I can use?


texts: meanwell psu inrush current and temperature sensor

texts:
I want to use a Meanwell PCB mounted power supply on my next project.

https://www.meanwell.com/Upload/PDF/IRM-20/IRM-20-SPEC.PDF

The spec sheet says that it has an inrush current of 20A/115VAC (I'm in the US so this is these are the numbers applicable to me).

Now, the device seems to have a great deal of protection, however, it doesn't say anything about a thermal shutoff; rather just that the device output is derated.

I wanted to incorporate a re-settable thermal fuse like: https://www.digikey.com/product-detail/en/F20A070053600060/317-1321-ND/1287335/?itemSeq=305616349

Such that the fuse is in series with the LINE/HOT side of the AC input to the PSU.

The thermostat is rated at 1.6A/250VAC. Under normal operation, the PSU is only drawing 0.6A/115VAC so this thermostat should be more than enough. However I am worried about the in-rush current blowing it. Should I be? If so, how would I go about mitigating it? I have read that an NTC is the way to go to limit in-rush current.

I'm not a professional electrical engineer, just a hobbyist so please keep that in mind when answering.


texts: When I add a wire segment to a wire that's turned on, it turns red (even though I'm not connecting it to anything else). In fact, any wire passing over that particular dot in the schematic turns red. Is this a bug? What can I do to fix this?


texts: Does opto-isolation matter when there's only one power supply?

texts:
Optoisolators are often encouraged for isolating signals controlling higher voltage loads. The typical example is a low-voltage microcontroller controlling a motor or solenoid operating at a higher voltage. In this hypothetical scenario, the power supply for the microcontroller and the power supply for the high voltage load are entirely separate. In a lot of real cases, though, the microcontroller is actually being powered by the same power supply, just via a voltage regulation circuit. So this is my question:

Let's say there's a single 10 V power supply. One subcircuit regulates the 10V down to 5V that powers a microcontroller. The microcontroller sends a signal that controls a solenoid operating directly from the 10V supply. Does putting an optoisolator between the microcontroller and the solenoid control circuit serve any purpose or is it pointless because, ultimately, the two power supplies are connected anyway?


texts: Why an does an offset on the reference electrode create an offset on the measure electrode of a pH probe?

texts:
I am making an analog front end for a pH probe.  I encountered a design where creating an offset on the reference electrode creates an offset on the measure electrode.
How does that work? Does the charge go through water?
Based on TI application notes: https://www.ti.com/lit/an/snoa529a/snoa529a.pdf?ts=1619613280868&ref_url=https%253A%252F%252Fwww.qwant.com%252F

(The temp circuit can be overlooked.)
This circuit basically creates a voltage of 512 mV between the reference electrode and the ground, thus adding an offset of 512 mV on the measure electrode, allowing it to have positive voltage.
I don't understand how the potential of the reference electrode translates to the measure electrode.
I have made a similar circuit and I can indeed observe an offset at the output.


texts: Aim TTi EL302RT PSU : understanding the specs, and comparing

texts:
I'm considering to dump some $ on a desk power supply for myself. I'm looking Aim TTI EL302RT, with data sheet here:
EL302RT

Few questions I have:

Are all the 3 channels isolated, have their own ground? Even that middle one which goes upto 5V?
The measured or displayed voltages, spec says resolution is 10mV, but the output regulation performance I'm not sure I understand it is spec'ed : it says, Line regulation "< 0.01% for of maximum output for 10% line change". So does this mean, for a 30V line (max V output), if I do a 10% change on the dial knob(s) , the output V will change by 30000 mV * 0.001 = 30 mV ..?   It doesn't , it seems, say anything about the smallest change I can make - can I make only a 1% change with Fine knob ?   If 30mV is 10%,  I hope then if I can change by 1% that's a 3mV change..?
And also I wanted to ask for your experienced opinion, do you think EL302RT is much better than Rigol DP-832 or other way? Spec for this Rigol here : Rigol DP-832. This Rigol seems very popular here for home-lab / semi-professional, and good reviews.  But at least on line voltage regulation, if I understand it correct, might be slightly less accurate - <0.01% + 2mV - but, it's digital, so perhaps I can sure step in 1% adjustments, unlike on the knobs on the EL302RT...
Also this Rigol has only 2 isolated channels I think, 2 share ground.

So I was about to commit to DP-832, but then I saw this EL302RT, and, I remembered as one of my employers had it in their lab.  So now I'm not sure.

Your answers would really help me out.


texts: I have to use some Test Points on my PCB (shown in the Figure), do they need to be solder to the pcb? or is just by applying pressure?


texts: Which components should be checked on a faulty tv power supply?

texts:
So, I'm new to working with electronics and I didn't study electrical engineering or anything related.
I've collected some dead tvs and monitors over time hoping that I'm gonna fix them.
I managed to fix a dead monitor by replacing some capacitors on the power board. Now I'm stuck with a dead tv. I don't have the 5V stand by to the main board and by looking at the power board's schematics I should have some 12V lanes as well to the main board which I don't have either. I checked all the electrolytic capacitors and they're all fine.
Now, the question is.. how do I proceed with the troubleshooting? Which components should I check or what should I look for now?
I can provide more details if needed.
Here's the board schematics.. I only have it as a pdf:
https://drive.google.com/file/d/16dITYFEr1YRkQZ55OlUVdLGzwtFrczkv/view?usp=sharing


texts:
In this circuit can any one tell me complete working of ic cd 4093. Mean how schmitt triggering occur in this circuit?
And how to draw square wave in different steps of gates? What is the purpose of transisters in this circuit??
I will be thank full ....


texts: How can I use a generic doorknob as a capacitive touch sensor?

texts:
I would like to use a generic doorknob that's installed in a typical wooden exterior door as a capacitive touch sensor. I have found various references for the circuit, but I have some questions about the sensor itself.

First, the doorknob in question seems to be non-ferrous (as a magnet doesn't stick to it), but it's still conductive. The "back-plate" that the doorknob rotates in is ferrous (and conductive also).

The image below shows the two options I am considering for fashioning the sensor foil. The option that I am most confident will work without interference from the doorknob itself is a copper ring that surrounds the backplate of the doorknob, but doesn't touch it anywhere. The obvious drawback is this will require some visible modifications to the surface of the door.

The cosmetically preferable option would be to conceal the copper sensor foil beneath / behind the backplate of the doorknob, as in the illustration of the inner copper ring below. But will the sensor function there, with a plate of ferrous metal between it and the hand it is supposed to sense?


texts: LTspice .param variable component selection

texts:
Update:  In case I could not explain myself clearly, I am reparaphrasing what I want to achieve. Let's say I will have 8 opAmps. Their symbol is opamp2 and their values will be LM741 with ".lib lm741.sub" attached. Now, consider I want to change all those opAmps at the same time to being TL082 which is another model and I have also included it with ".lib tl082.sub". For now, I do that by changing all LM741s with TL082 manually. So, I want to give a variable to all those opAmps which will be a string of the model name. So just by changing the value of that parameter, I can get all opAmps changed. As seen, I don't try to change things during simulation. I just need to do it before simulation.. Thus, if the situation was I could not explain my goal, I hope this time it is clear.

Can I use .param to change the model of a component in LTspice? I am talking about  something like that:

Apparently, this style does not work, I wonder is there a way to do this. The reason why I want to be able to do it is, to be able to change multiple components with one modification.


texts: Looking for advice how to correctly configure PWM dimming with Mean Well LDH-45A-1050 device

texts:
I am looking to use a Mean Well LDH-45A-1050 DC/DC LED driver with a an LED matrix but crucially to use PWM dimming. Already have perfectly working led  with this driver, just looking now to figure out how to use the dimming function. Have tried with a couple PWM devices but either a no-go (no effect) or else dimming can only be gotten by wiring the dimmer direct to the dc input which I guess is only going to cause problems even though the result is fair (some flicker). Some of the dimmer units have an actual PWM output (in addition to direct output for led strip etc) but this does not work with the LDH unit.
This particular device is PWM and analogue dimable.  See link:
Link to Mean Well LDH driver unit document
Mean Well themselves decline to comment or recommend any particular dimmer that is a known match for such a unit. Anyone here have any suggestions?

Any feedback would be much appreciated.
Cheers,
Ken


texts:
I am looking to detect 12+V from a car wire using an Arduino.

I have found the following schematic:

I know how crazy automotive voltage can get so I just want to make sure the schematic I found above will accommodate the crazy random currents that the car could produce.

Also, wouldn't I need some type of heat sink taken that I am stepping down a +12V to 5V or less? That, in my mind, would produce a pretty good amount of heat?


texts: Per unit solution gives different result

texts:
We have a 200MVA , 15kV , Xs=1.62pu synchronous generator feeding a load of 15kV and 100MVA with an inductive power factor of 0.8. I'm asked to find the generator's voltage (along with its phase angle).

I did solve the problem turning everything into per unit values using the nominal values of the generator as bases. However, trying to convert the reactance to its real value(multiplying it by the base impedence) I can't get the right result. Why is that? I get a different value and angle for the voltage.

$$I=\frac{100\cdot 10^6}{\sqrt3\cdot15\cdot10^3}=3849\angle-36,87$$$$=>I=3079,2-2309,5j$$ $$X=1.62\cdot V^2/S=1.62\cdot1,125=1,8225j$$
$$E=V_L+X\cdot I=15000+4208,88+5611,842j$$$$=19208,88+5611,842j$$$$=20011\angle16.29$$

Now with the pu values:
$$E=V_L+X\cdot I=1\angle0 +j(1,62)(0.5\angle-36,87)$$
$$=1\angle0+j(1.62)(0.4-0.3j)$$$$=1\angle0+0.648j+0.486=1.486+0.648j=
$$$$=1,621\angle23,56$$$$=24315\angle23,56$$


texts: What are the adavantages of neutral vs. isolated grounding?

texts:
While studying "Neutral grounding" I've come to know that advantage of neutral grounding is

Voltage to ground are limited to phase voltage.
The high Voltages due to arching faults or transient line to ground faults are eliminated.

And some advantages of isolated neutral

Possibility of maintaining a supply even with fault on one line.

Can anybody explain me clearly these advantages of neutral and isolated grounding. I don't understand these at all.

I am attaching images of source thorough I've read these concept for reference:

.


texts: Selecting different impedances then 50 ohm in DDR3

texts:
I've worked with DDR2 and DDR3 memories and usually stuck to 50 ohm impedance for traces. But i do see that SoCs and DDR2/3 memories seem to support other impedances such as 30, 60 and 150 ohms.

Now if using other impedances allows for a cheaper layer stackup then i guess i should have the option of going for it as long as i'm willing to accept the downsides of higher or lower impedances regarding EMC suspectibility and radiation.

Are there any other specific downsides to this ?


texts: Picking a capacitor for HCMS-29xx display

texts:
I've got a HCMS-3972 LED display, and I'd like to play with it from Arduino following this tutorial. The diagram and schematics show a capacitor, but does not specify any details. The data sheet says the following:

The value of the capacitor depends on the series resistance from the ground back to the power supply and the range of frequencies that need to be suppressed. It is also advantageous to use the largest ground plane possible.

I'm a complete beginner and can't decipher what that means. How should I pick the capacitor to use for this project?


texts: Microcontroller incapable of driving MOSFET

texts:
I am using attiny45 microcontroller for switching MOSFET at 40kHz. I have the following circuit set up:

simulate this circuit – Schematic created using CircuitLab

If I measure the signal coming out of the uC without anything connected to it, I can see the modulated 40kHz signal. But as soon as I connect the circuit to it, I get unusual single spike with length anywhere between 1us to 20us and it looks something like this:

What could be the problem? Is it maybe a faulty microcntroller?

EDIT:

If I use function generator at 40kHz and some modulation, the MOSFET is switching correctly.

EDIT2:

I have this assembled on a breadboard and the uC is running from 16MHz external crystal, do you think this could be the cause?

I used a new attiny85 and added a series resistor as was suggested but now, if I connect the MOSFET driving circuit to the uC I get gibberish from the uC although it does slightly resemble the wanted signal.

And again if I disconnect the driving circuit, the signal coming out is exactly what is wanted.


texts: Measuring amperes, what the reading mean?

texts:
I am new to electronics, but I don't know what the readings mean. I took measurements with a digital multimeter, the power source is a 9V battery and I have a load a LED.

Setting    Reading
20          0.05
200m        00.5
20m         0.6
2m         .600

Which setting on the A range indicates the milliamps?

I did the measurement correctly in series, on DC. The manual doesn't say, it was made in China

Here is the image of the multimeter:


texts:
This is how the book explains the process:

Let me consider the first 90° of the input, the capacitor charges up to the peak voltage less the diode drop of D1, D1 is forward biased and D2 is reverse biased, that's ok, but what I don't understand is, right after 90° to 180°, why isn't D2 forward biased? Shouldn't the cathode of D2 be negative with respect to the anode because of the capacitor's polarity (C1)? Likewise D1 should be reverse biased because of the capacitor, so why isn't current flowing through D2?

.


texts: Convert Electret Microphone output to digital data for transmition

texts:
I might be asking a stupid question but....

I was wondering about whether or not there is a circuit to convert the output of an electret microphone to 1s and 0s for transmission. And then we can use the reverse method to convert the data back to voice to play on a speaker.

I have read this webpage, and I found out that we can transmit ons and offs at 27Mhz. So I was thinking about using a microphone to convert real time data from the microphone to 1s and 0s and then to send them out to the receiver to be played.

But the problem is, I don't see a way to convert the output of the electret microphone (for example this one from sparkfun) to 1s and 0s, WITHOUT any special parts.

Any suggestions?
Thanks in advance

EDIT: Define Special Parts: Pre-made complex circuits counts as special parts. Something like the arduino and raspberry pi all counts as pre made parts. Bluetooth moduels counts too. However, something like an h-bridge motor driver. The 555 Time doesn't count too. Furthermore, diodes, capacitators, resistors and etc. don't count.


texts: Plotting G(t) of an oscillator in Cadence

texts:
I have a cross-coupled NMOS-only oscillator that has its bias voltage changing so its transconductance is also changing over time. I want to plot its transconductance (G(t)=G0-gm/2) over time in Cadence. G0 is the tank loss and -gm/2 is the negative transconductance introduced by the cross-coupled NMOS transistors. How can this be done in Cadence? I tried to plot only gm of transistors using oppoint in transient analysis. but it's showing a plot that's always positive which is wrong.
any comments would be appreciated.


texts: Why does a speed-controlled computer fan require 4 pins?

texts:
A "standard" computer fan has two pins; one for power, one for ground. A three-pin fan adds an additional pin used for the signal from the hall-effect sensor. A speed-controlled fan generally uses a four-pin connector, and is commonly referred to as a "PWM" fan.

It is my understanding that any DC motor can be driven with PWM instead of a steady signal, so I am confused why there is a need for an additional pin for the PWM signal. Is the PWM signal fed into a MOSFET or some similar switching component on the fan itself in order to control the speed of the fan?


texts: Can you interface 2 gigabit ethernet ports via one rgmii interface?

texts:
Can we use the KSZ9893RNXC from Microchip as the Ethernet PHY chip, and interface the 2 gigabit ports to Allwinner H6, which has only one RGMII interface. Also please note that we are aiming at using the 2 gigabit ports simultaneously.
KSZ9893RNXC
https://www.mouser.com/ProductDetail/Microchip-Technology/KSZ9893RNXC?qs=qpJ%252B%252B%252Bdg6p1h38Qq3AER7g%3D%3D
Allwinner H6
https://linux-sunxi.org/H6


texts: Replacing RJ45 connector with another type connector

texts:
I am looking for a replacement for an RJ45 panel mount connector. Can I use any standard connector (picture below) for connecting Ethernet networks?

I know about cable impedance matching but I was wondering if the connector's contacts have any effect on the line's impedance. So I searched dozens of RJ45 panel mount connectors datasheets(such as this datasheet) to find that the impedance is not even mentioned.

Edit:

Since people are asking questions about the reasons for replacing the RJ45 connector:

There is another RJ45 connector and I want to prevent plugging the cable into the wrong connector
I listed the mini DIN as an example (We use this connector so its stocked and really cheap) but the question is generally about using a non modular connector to connect an Ethernet network.

Some Conflicting answers:

The connector has a matched impedance even though its not stated in the datasheet because it's so obvious

VS

Its meaningless to ask for the impedance for a connector. It has no capacitance or inductance

Correct me if I'm wrong but I think The second answer is correct. I will surely use a CAT5e cable and shorten the mini-DIN connector's wires minimizing the length of the unraveled cable. I guess this should work...


texts: Questions about connecting a passive infra-red sensor to the USB port

texts:
So, we are linking a sensor to a computer via USB, using a female USB connector and male USB wires. The sensor is connected to a circuit with 3 pins, vcc, ground, output signal. If I would want the signal to be processed by the computer to output " I sense someone" when ever the sensor fires, what would I need to do? basic questions to answer are:

How would the computer understand the signal from the usb? Using a device driver? or something else(please specify)
I read that the usb can burnout if you are careless about the energy you input on it, so what is this healthy energy( Vcc , Amps) range? ( and how do I achieve this?)

P.S.: my professor told me that the device driver is only used for driving a certain device... idk if he is right or not :\ this totally contradicts my knowledge about device drivers, I know that everything you insert to a computer that has an input to be understand needs a device driver( ei, mouse, keyboard) it's hard for me to believe that the computer controls the mouse since, it can't because that is senseless(because the standard mouse is only for input :)

P.S.: the sensor is a Passive infrared sensor, with 2 jumper modes, to fire only once every X time while their is movement. and to fire constantly which there is movement.


texts: Why the integrations of left and right domain are not done and be said enough to calculate the composed capacitance of 2 capacitors?

texts:
\$
\theta ~~\text{is assumed to be small}
\$
The conductive rectangle exists which depth is \$a\$ and the length is \$2l\$ and it has been bent and grounded as the above diagram.
And the conductive rectangle KL exists which depth is \$a\$ and the length of it is \$b\$
The distance between the origin and the leftmost side of KL is \$x\$
We can assume that there is 2 capacitors are connected parallelly in the diagram.
\$  C=2 \int_{x }^{x+b } \frac{   \epsilon_{0} a   }{ x \tan \left( \theta  \right)   }  \,dx  ~~ \leftarrow~~ \text{composed capacitance}  \$
Currently I can't get the above equation.
Firslty I introduce you the below formula which calculate the capacitance which each plate is not parallel(size and form is same) using infinitesimal capacitors.
This formula assuming that the plate is seperated by infinitesimal plates and the composed capacitance is calculated connecting the each infinitesimal capacitors parallely.
\$  C=\int_{0 }^{a } \frac{  \epsilon_{0} b   }{ y(x)   }  \,dx   \$
\$  a:= \text{width of the plate of capacitor}  \$
\$  b:= \text{depth of the plate of capacitor}  \$
\$  y(x):=\text{function which returns the distance between the plates as }x ~\text{proceeded from the leftmost side of the plate}   \$

\$ ~ \$
So bringing back
\$  C=2 \int_{x }^{x+b } \frac{   \epsilon_{0} a   }{ x \tan \left( \theta  \right)   }  \,dx   \$
and think appyling the formula to it.
The current problem for me is that of the denominator \$x \tan \left( \theta  \right)  \$
Since the range of integration \$ \left[ x,x+b \right] \$,I guess that this integration only summing up the infinitesimal capacitors of range between the each edge of the capacitor KL
Is this integration really calculating the composed capacitance?
Why the integrations of left part( left from KL) and the right domain(right from KL)
are not done?
What I've been missing?


texts: Boundary scan functionality of JTAG for onboard Flash programming

texts:
I would like to know whether we can use the Boundary Scan functionality of JTAG for programming an onboard Flash device without initializing the core CPU/processor (JTAG compliant Processor).

During the initial board bring up, we need to program the onboard empty flash using the JTAG interface.
But we don't want to use the processor core logic for programming flash, since after initial assembly we will not be sure if it is working correctly.

So, is it possible to program onboard (boot & Code) flash(NAND/NOR/SPI) using the JTAG interface on the processor, without initializing processor core logic?


texts: Connecting balanced output with unbalaned input using adaptor

texts:
I want to connect my audio interface (balanced TRS jack output) with guitar pedal (unbalanced TS jack input) and I wonder if this kind of adapter will work:
https://www.amazon.com/dp/B001JYSMV0/ref=psdc_172544_t1_B000068O4M

I'd plug TRS male to my output in interface and then connect TS cable to female input of this adapter, then the other end of TS cable would go to the guitar pedal.
Can that adaptor I linked above be used interchangeably with the one below?
https://www.amazon.com/Hosa-GPP-290-TRS-TS-Adaptor/dp/B000068O4M

The first one (female TS to male TRS) I'd plug on the output side of my audio interface and then go to guitar pedal with TS cable.

The second one (female TRS to male TS) I'd plug on the input side of my guitar pedal and use TRS cable to connect it to audio interface.

So are they interchangeable and will either of them work for sending signal from my audio interface to guitar pedal?


texts: What type of wire does transmission tower use?

texts:
I learn form a more than 20years old book(South Korea text book) that high voltage transmission towers take Bare wire into service. But I saw some company take Insulated wire into service.
Question : What type of wire is using in high voltage transmission-wire?


texts:
As far as I know, current division for spesific place's formula is:
Ix=(Req/Rx)*Isource   However, here,the solution is 3/(3+2+4)*6. How is this a current division ? Can you explain this to me


texts:
I am trying to make a pcb using the toner transfer method. The problem I have is that the toner does not transfer completely so i cannot proceed to etch it.

I am using glossy paper, a laser printer, and I have polished and cleaned the pcb before ironing it.

I add some pictures to see if anyone cal help me out.

There are parts that the toner doesent stick at all:

And some parts where it sticks poorly:


texts: Confusion about the meaning of Bandwidth-limited pulse

texts:
I am quoting Wikipedia: “A bandwidth-limited pulse (also known as Fourier-transform-limited pulse, or more commonly, transform-limited pulse) is a pulse of a wave that has the minimum possible duration for a given spectral bandwidth.”
But every pulse has minimum possible duration, so does that mean all pulses are bandwidth limited? Im superconfused here. Can you give me an example which illustrates the difference between bandwidth limited and not bandwidth limited pulse?


texts:
I have create project witch has an "counter" counter = Integer. I need to increase/decrease an integer value by pressing the buttons. the progress has 2 entitys, entity 1 should increase
the value and  entity 2 should decrease the value, Im not allow to do so with component how to do this?

-- component 1 -------------------------------
entity MyCounter is
 port(
    clock: in std_logic;
    KEY: in std_logic;
    counter: in integer range 0 to 15;
    clk_out: out std_logic
  );
end MyCounter;

architecture arch of MyCounter is

component decrease
    port(

    clock: in std_logic;
    KEY: in std_logic;
    counter: in integer range 0 to 15;
    clk_out: out std_logic

        );
end component;

begin
    p1: process(clock, KEY)
     variable counter : integer;
       begin
         if KEY = '1' then
          counter <= counter + 1;
         end if;
end process;

end arch;

-- component 2 -------------------------------
entity decrease is
 port(
    clock: in std_logic;
    KEY: in std_logic;
    counter: in integer range 0 to 15;
    clk_out: out std_logic
  );
end decrease ;

architecture arch of decrease is
begin

    p1: process(clock, KEY)
     begin
      if KEY = '1' then
        counter <= counter - 1;
    end if;
end process;

end arch;


texts: Disconnecting system load during charging

texts:
I'm designing a charging circuit for a single-cell li-ion battery that powers a PCB with high-power LEDs. For safety, I want to disconnect the PCB and the high-power LEDs during charging. Therefore, I need a circuit that has the following properties:

If the charging voltage is applied to A, the circuit disconnects B and C and connects A and C
If A is ground, the circuit connects B and C and disconnects A and C

A is the output of the charger, B the positive terminal of the PCB and the high-power LEDs and C is the positive terminal of the battery.

I tried to implement this with a MOSFET, but I think it's not possible using a single one.

Do you have an idea?

simulate this circuit – Schematic created using CircuitLab


texts: MicroSD card on Beagleboard A6 white is only 70 MB?

texts:
I have one of the older A6 revision beagleboard. They advertise that it comes with a 4GB microSD card. I plugged the card to the beagleboard, then plugged the beagleboard to my ubuntu computer via USB. Then I ran

sudo fdisk -l

as well as

lsblk

to list the block devices that the system sees. It reported "sdb" drive, size of which is only 70MB, though. I also tried GParted. It also sees only 70MB. Why can't I see the 4GB as advertised? I am trying to install ubuntu on it, but I need more disk space.

EDIT:

The output of: sudo fdisk -l

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xe1892732

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *      409600   302864678   151227539+   7  HPFS/NTFS/exFAT
/dev/sda2       302866430   976771071   336952321    5  Extended
/dev/sda5       302866432   508022783   102578176   83  Linux
/dev/sda6       508024832   515835903     3905536   82  Linux swap / Solaris
/dev/sda7       515837952   976771071   230466560    7  HPFS/NTFS/exFAT

Disk /dev/sdb: 73 MB, 73995264 bytes
3 heads, 48 sectors/track, 1003 cylinders, total 144522 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System

The relevant part is /dev/sdb

Output of: lsblk

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 465.8G  0 disk
├─sda1   8:1    0 144.2G  0 part /media/windows
├─sda2   8:2    0     1K  0 part
├─sda5   8:5    0  97.8G  0 part /
├─sda6   8:6    0   3.7G  0 part [SWAP]
└─sda7   8:7    0 219.8G  0 part /media/data
sr0     11:0    1  1024M  0 rom
sdb      8:16   1  70.6M  0 disk


texts: Which integrated circuit can I use instead of multiple MOSFET?

texts:
I have designed a circuit using a combination of NAND, NOT, AND and OR gates:

I know how to build this circuit with MOSFET using CMOS technology but it requires 18 MOSFET. I would like to know how can I build the same circuit using an integrated circuit in order to reduce its size:

I looked at some catalogs of electronics components and I didn't find any integrated circuit that embeds these four gates in one chip.
Does this kind of integrated circuit exists? If yes, how can I easily find them? If no, how can I reduce the size of my circuit?