texts: Loud pop noise while plugging to a headphones jack

texts:
I have a Panasonic RX-ES29 boombox with a type C plug (ungrounded). I sometimes hear a relatively loud snap/pop sound in the right speaker of my headphones while I completely plug them into the headphones jack of the boombox when it's on. There's a little buzz when the tip of the jack is inserted but the loud pop comes when the jack is completely inserted. My headphones are Audio Technica ATH-AVC500.

I tried to capture that sound using a male to male cable, but after playing the captured one, it's not as loud as the one I hear by physically connecting headphones to it. You can see the pictures I took from Audacity here and there.

Audacity doesn't detect it as an audio clipping, but it looks like it is by the pictures that I linked above.

One of the strange things about it is that it does not always occur, I mean it's not always there; like sometimes when something discharges near your finger. I tried to unplug and plug several times just after hearing the loud sound but it's gone, exactly like when a charged object is discharged and it needs some time to charge up again.

I'm very curious to know an explanation for this weird behavior.


texts: RGB LED strip presets controlled by a switch via 2-pin connector

texts:
First, I apologize if my terminology is incorrect. I am out of my element, but trying to figure this out.

I bought a cheap PC case in Korea, and it included an RGB LED strip on the front of the case which has a cable attached via 4-pin to the strip itself, but on the other end of the cable, it is reduced to two pins. I am guessing that if I were to plug a full RGB cable (4pin to 4pin) to an RGB controller, I could control the RGB strip more precisely. However, the intention of this 2 pin seems to be simply to toggle the RGB LED strip through a series of presets, which is done via a button on the front of the case.

However, I also purchased 6 cheap Korean RGB case fans, which are also controlled by a 2 pin rgb connector. I believe if I plug them individually into the 2 pin connector which goes to the button on the case, they can each individually be cycled through preset patterns.

My goal, and my question, if I were to find a hub or splitters which allowed me to connect all of these 6 fans and LED strip to the button on the case, would I be able to cycle them through the preset patterns simultaneously via one button? I believe they all have some memory system which allows them to remember which part of the cycle they left off on when the system is powered down, so I would need to make sure they are all synchronized before connecting them to each other, but if this would work, where would I be able to purchase a 2-pin RGB hub/splitter?

I believe the answer is more of an electronics one than RGB specific, as the switch is probably sending a very simple message to trigger the RGB LED systems to move onto the next pattern in the cycle rather than sending specific RGB data.

Thank you for your help.


texts: TV screen in still photo: Why are there dark, blackish bands?

texts:
I was trying to capture the scanning process of a CRT TV screen in a photo. It gave me these dark, broad bands, shown below:

Fig. 1 a,b,c

I'm trying to understand the cause for this banding. However, I couldn't understand it clearly in very similar questions here, here, or here. All web sources I visited very briefly explained it as a difference between the scan-rate of the TV and the camera, and none provided a diagram.

Fig. 2 a,b,c

I assume what is going on is in Fig. 2. The blue lines indicate the scan lines where cathode rays hit most recently (phosphorescence occurring), and black lines indicates where the cathode ray has not been in the image, so phosphorescence is all that is left and a dark band appears.

I assumed this, because out of 10 photographs I took, I found only the above 3 types of photos, and none of the type shown in Fig. 3 or Fig. 4:

Fig. 3.  an Fig. 4.

I also assumed that the camera is much faster than the TV scan rate, so it could take picture in an instant.

My question is, Have I assumed correctly? or is something else going on?

Additional information:

TV:     Videocon 120 W colour CRT, Electricity power supply 50 Hz.
Camera: Nikon Coolpix L24 digital camera.

(please also explain other possible situations, such as this one in Fig.5. I didn't experience it myself. It is similar to Fig. 4.

Fig 5. From  this question

I'll be grateful if any explanations use diagrams.

Update:
I've obtained several fig3 conditions, and though they are less frequent, they're not  very rare.

File properties show exposure time for this still-photo is 1/125 second.

I've also took some videos (in PAL and NTSC mode... both gave same result), file properties show frame rate is 30 frame/sec;  and run them on slowest motion. I found similar, but much brighter and quite unclear bandings, and it seemed from slow-motion video that the alternating bright and dark band rising on the upward direction. From that videos I screenshoot some frames as-successive-as-possible.
.
Red small bars added to indicate the margin of each banding


texts: Nano mechanical transistor Colpitts oscillator with logic gate

texts:
I am a university student and I am working on my master thesis. I have worked on nano mechanical transistor using Colpitts oscillator with the logic AND gate.

I have one question: I tried the Colpitts oscillator in Simulink. How do I make the connection of logic gate to oscillator? Could you please help me with it?


texts: Converting a non-electret condenser microphone circuit to electret?

texts:
I'm trying to convert an MXL 603s circuit, which has a non-electret capsule, to an electret version. I'm pretty certain that the only real difference between the two would be the fact that the non-electret capsule needs a polarizing voltage, whereas the electret is already polarized. You can find the schematic for the 603s here.

I'm pretty sure what would need to be removed is the section of the circuit starting from the connection to the capsule, then moving counter-clockwise until you hit R10 (1.5k). I think all of the components in that entire section are for polarizing the capsule properly (although I definitely don't understand the purpose of the 2N5551 transistor and the inductors).

If someone could tell me:

Am I correct in thinking that those components are for polarizing voltage, and can be removed?
How would I need to change the preamplifier components (the ones that will stay) so that they will work with an electret capsule that has an internal FET?  This is the capsule I'll use.

Thanks!


texts: Measuring current consumption of evaluation board

texts: I have an evaluation board and I wanted to measure the current consumed by this device. I usually power it off a USB port so I was thinking of getting one of these. There is a two pin jumper on the board that allows use of power from the USB port. Its closed (connected) so that it can power off of the USB port. What is the right way of hooking up a multimeter between these two pins in order to measure the current consumed?


texts: Help with design a mic preamp with opamps for PGA and ADC

texts:
I want to sample an audio source using an electret microphone and analyze the spectrum of it with a uC. I'm interested in the 100Hz-2.5kHz range, so I calculate with these values when I tried to design the preamp circuit.

One of my try:

When I leave R7, I get ~10nV output! But when R7 isn't used, I get the output pretty well:

I want to ask four questions:

R7 and C1 is for AC coupling with a corner frequency ~50Hz, also C1
and R1 is a HPF too, but if I put away R7 how can I get the -40 dB/d
slope?
If I don't put R7 there, will the opamp's input bias current
charge C1 and cause an offset drift? How can I handle this without
R7?
Will that 1M resistor cause bigger noise?
Is C4 is enough for the output AC coupling? VF1 will be connected to a PGA's input to extend the dynamic range of the sensor.

For the simulation, VG1 generates a 10mV, 440Hz sinusoidal signal.


texts: With this simple op-amp circuit R1 = 3.6k ohms and R2 = 4.7k ohms. With my input at zero (grounded) I am getting an output of 4.5 VDC.  I am trying to get a near zero output with 0 VDC input. Do I need to run the 741 on a split supply ? Should I choose a different opamp?                  The gain should be about 2.3.  With a 5 VDC input the output is near 12VDC as planned.  Can anyone tell me why I am getting 4.5 VDC output with a 0 VDC input?


texts: Cannot use SoftwareSerial and RS485 protocol in the same code

texts:
Could someone help me ?

I want to make 5 nanos communicating through RS485 protocol with my Arduino Uno master.
This part is working great by using the code of http://www.gammon.com.au/forum/?id=11428

Now, I want my Uno to communicate those datas (from nanos) to an ESP32 through UART.

My problem is : when I do my Uno send data to my ESP32, the Uno can no anymore communicate avec Nanos through RS485 protocol.

Would you have an idea of my issue ?

My code:

#include "RS485_protocol.h"
#include <SoftwareSerial.h>
//#include <LedsHorloge.h>
//#include "FastLED.h"
#include "debug.h"

#define TOTAL_NUMBER_RC 5

const byte ENABLE_PIN = 3;
const byte LED_PIN_ERREUR = 10;

byte RCnumberCalled = 1;

SoftwareSerial rs485 (5, 6);

int etatEsclave[TOTAL_NUMBER_RC][2] ;

int flagRedemarrageJeu = 0;

void fWrite (const byte what)
  {
  rs485.write (what);
  }

int fAvailable ()
  {
  return rs485.available ();
  }

int fRead ()
  {
  return rs485.read ();
  }

///////////////////////////////////////////////////////////////////////////
// SET UP
///////////////////////////////////////////////////////////////////////////
void setup()
{
  Serial.begin(9600);

  rs485.begin (28800);
  pinMode (ENABLE_PIN, OUTPUT);
  pinMode (LED_PIN_ERREUR, OUTPUT);

  Serial.println("START");

}  // FIN SET UP

///////////////////////////////////////////////////////////////////////////
// LOOP
///////////////////////////////////////////////////////////////////////////
void loop()
{

  byte msg [] = { RCnumberCalled,
                  flagRedemarrageJeu
                };

  digitalWrite (ENABLE_PIN, HIGH);

  sendMsg (fWrite, msg, sizeof msg);

  // ---- When I add this snippet of code my Uno can no anymore communicate with my Nanos ---
  SoftwareSerial Ardu2Esp (8, 9);
  Ardu2Esp.begin(9600);
  Ardu2Esp.write(0x01);Ardu2Esp.flush();
  Serial.println("Donnees envoyees vers ESP");

  digitalWrite (ENABLE_PIN, LOW);

  byte buf [7];                                   numéro des cartes Arduino

  byte received =  recvMsg (fAvailable, fRead, buf, sizeof buf);

  digitalWrite (LED_PIN_ERREUR, received == 0);    // turn on LED if error

  if ( received && buf[0]==RCnumberCalled )
  {

      Serial.println("Communication succeeded");

  }

  if (RCnumberCalled>TOTAL_NUMBER_RC)
  {
    RCnumberCalled=1;
  }
} // FIN LOOP()

```


texts:
I am doing a project where I need to measure temperature using lm35. I am using arduino's analog A0 to measure,  I light up extra LED on an other pin while measuring. Suddenly the alarm triggers. I set the temperature to trigger an alarm when it rises to like 40 degree. It is not supposed to trigger as I haven't done anything yet.

The method I am using to measure the voltage of the lm35 is by using 5 volt as the reference.

Personally, I guess that the battery which I am using does not able to support as it consumes too much current, causing the ADC to be inccurate. Another thing worth to mention is that the same thing does not happens when I uses USB cable port.

I am a bit curious, if the battery low, shouldn't the temeprature detected be lower? But it triggers, it is mostly due to battery but why?


texts: Why does my BA speaker truncate the negative part of the waveform?

texts:
I'm developing a custom earphone and I'm having some issues with producing a clean sound from my balanced armature (BA) driver (Sonion 31D005/8). I've come up with a pretty standard circuit (see below) that receives a sine wave at three possible frequencies (227,660,1000) from a 12-bit DAC.

When I probe the output of capacitor C2 without the speaker connected, I see a clean wave with a zero volt average, however as soon as I plug in the BA the peak of the negative portion is truncated, and the voltage (p-p) is reduced (see below). This outcome is more prominent for the lower frequencies, ultimately reducing the loudness of my speaker for lower frequencies, contrary to what's shown on the datasheet (should remain relatively constant).

Another important factor is that the BA's impedance decreases for lower frequencies (500Hz:38 ; 1000Hz:66) so I expected the opposite effect, however I'm assuming there's some time constant effect or an inductive feedback that is distorting the waveform. I've confirmed with a microphone that the received waveform is quite distorted in a similar way, and the lower frequencies do not sound very clear. Am I missing a passive component or something that should be considered when designing headphone (high impedance) as opposed to speaker (4-8 ohm) circuits? Perhaps a different amplifier (tried the LT1010 with worse performance)?


texts: Constellation of BPSK doesn't look as expected

texts:
I'm a total novice when it comes to RF beyond basic concepts.
I'm trying to use a HackRF One to pull the data coming off of this transponder, which theoretically transmits data on a 3.59MHz carrier.
I've followed some tutorials on BPSK demodulation, but while I expect the constellation to look like this:

I'm getting points all over the I and Q axis with no consistency whenever it transmits (having trouble getting a screenshot of just when the device is transmitting). Here's my current setup - is there a parameter I have incorrect or am missing?


texts:
I am writing data to the internal flash of a STM32F746 and I'm wondering what the difference between pages and sectors is? And what is the purpose of using sectors instead ? Notice that I'm very new and the reason to why I'm asking is because I have previously written to flash knowing the page size and amount of pages. But now I have 8 sectors instead.

Unless I have missed it somewhere I can't find any reference to pages or page size in any any document to the STM32F746


texts: calculating inclination using accelerometer?

texts:
i have an analogue devices ADXL203 accelerometer on a breadout board and was wanting to use this to measure the inclination of some equipment at a reasonably high frequency (20-30 Hz).  i am hooking it up to a campbells cr3000 logger to do the sensing.  Does anyone have directions on how to interpret the sensor outputs.
thanks


texts: Reading voltage from coil on top of Qi Wireless Charger

texts:
I am a high school student doing a lab report on changing the number of turns of a coil and seeing the effect it has on the output voltage from a wireless charger.

I am trying to take a Qi Wireless Charger and have a coiled copper wire above it with its voltage being read from a multimeter. I have placed the coil on top of the charger and connected both terminals of the coil to a multimeter reading AC voltage. However, when I do this the voltage oscillates from 0 to a random number and back. I am unable to get a stable voltage reading and was wondering if there was a solution to this which does not require a Qi wireless charging transceiver. I have attached a picture of the setup and the inside of the charger.


texts: How to charge a 3cell 11.1V battery pack made out of 3 Nokia BL-5C?

texts:
I connected three Nokia BL-5C 3.7v 800mAh Li-Ion batteries in series for a robot project resulting in 11.1v @ 800mAh capacity. How do i charge the pack?
Should i get a 12v 5A adapter and limit the current or get a dedicated Li-Ion battery charger and just connect the leads?
If i want to make my own, how to do it?


texts: What options exist for a for low-latency (<1ms) photosensor?

texts:
I'm wanting to build a computer keyboard-to-display lag measuring tool using an Ardunio:

User places the photosensor right-up to their computer monitor.
User presses a button on the Ardunio.
The button press starts a high-resolution timer on the Arduino and also sends-out a USB HID mouse-move event to the computer.

Using mouse-move events means the computer would use the hardware cursor which eliminates the frame (16ms) of lag caused by using desktop composition in most modern desktop computer operating-systems.
The mouse cursor on the display itself would be pre-positioned so be directly visible by the photosensor, so when the mouse-move event is handled the color of the pixels where the mouse is would change.

The Arduino then looks for changes in photosensor output that would indicate the mouse cursor (or rather: display pixels) had changed and then report the timer readings to determine end-to-end lag.

My thought was to set my mouse-cursor to be a big black cursor over a white background and use a simple photoresistor, but I learned that photoresistors have a physical lag up to 10ms from dark-to-light and up to 1000ms for light-to-dark which may make it unsuitable for my application where I'd like to reliably measure end-to-end lag within 1ms - so using a photoresistor is probably not appropriate.

My fall-back idea is to use the Ardunio to fire off a USB event while simultaneously lighting an LED directly attached to the Arduino board (so there should be effectively zero latency between pressing the button and the light coming on) and then using my iPhone's 240fps camera (4.2ms resolution) to record the time between the LED being lit and my computer display changing. As I run it at 60Hz, a 4.2ms resolution is (barely) sufficient - but ideally I'd like sub-1ms measurements.

My questions:

Would a photocell like this begin to change its output within 1ms of detecting a change or would the signal be too noisy or meaningless without waiting the 10ms (for dark-to-light changes).
What other sensors could be used to detect any change in light (either light-to-dark, dark-to-light, color changes, etc) with minimal latency such that an Ardunio could detect the change within 1ms of it happening in real-life?


texts: How can I change the project parameters in Altium Designer with a Delphi Script. I already found a script on how to change the Sheet Parameter, but I really need to change the Project Parameters.


texts: Fastest temperature sensor for a bimetallic strip

texts:
What is the best approach or sensor to analyze the temperature of a bimetallic strip?

From experimental data, the temperature swings due to a current flowing into the bimetal, are up to 80°C in a period of 20s which means 4°C/s.
I want to have a high sampling frequency (10Hz minimum, best would be 20-30Hz I guess).
Ultimately I must have high accuracy as well since I want to model the transient dynamics.

Edit: my goal is to have a batch of samples which contains the temperature transient (when the current is flowing) to make a model (for simulation/prediction). My need is to detect the temperature rising as soon as possible when the current is flowing (with no delays due to the kind of sensor being used, or at least to minimize it, in order to capture the dynamics of the physics as close as possible)

The current solution (an unknown thermocouple) has a sampling frequency of 10Hz and it has a variable delay up to 15samples, meaning it takes around 1.5s before detecting a rise in temperature when the current is flowing. My main problem is that I would like to detect the rise in temperature due to the current as soon as possible (closest to the physics).


texts: Electrical Charisteristics of PIC24FJ1024GB610

texts:
I am reading the Electrical characteristics of PIC24FJ1024GB610 from it's Datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/30010074e.pdf
(Page 419/468).

it mentions:

  Maximum output current sunk by any I/O pin    25 mA

  Maximum output current sourced by any I/O pin   25 mA

  Maximum current sunk by all ports     200 mA

  Maximum current sourced by all ports  200 mA

Does it mean that the maximum operational current sourced/sunk to/by the PIC24 is 25 mA, and the max current allowed to/from the I/O pins is 200mA

Thank you in advance


texts: Transfer function for a Passive Second order Low-pass Filter and to determine the components values

texts:
I am working on an assignment about  Passive, second order low-pass filters. Cool little things if you get to know them.

We are  given the placements of the passive components (Inductor(L1), Resistor(R1) and Capacitor(C1)) without their values.

The only given specification is that the cut-off frequency (fc) is 78 kHz.

The circuit is shown below.

If the Photo is unclear here's the Schematic:

simulate this circuit – Schematic created using CircuitLab

My questions are:

1.How to make the  predicted low-pass filter Transfer function for this specific circuit?

(In other words...the expression for the Output Voltage Phasor to Input Voltage Phasor? )
(Using sinusoidal steady-state analysis and answer in modulus argument form)

AND

2.Secondly how do I calculate or choose the component values for the filter? ...

The components must work out so that:

2.1) the Phase Angle between the output voltage and input voltage is -90 degrees at the cut-off frequency (78 kHz).

(A suggestion given to me was to choose a Inductor value and a Capacitor value that is at my disposal and to calculate the required Resistor value to build the circuit after calculations ).

AND

2.2) that the Ratio of the amplitudes of the Output Voltage to the amplitude of the Input Voltage is 0.7079 at the cut-off frequency(fc).

PS: I have a 1mH Inductor at my disposal,- thats why it is the only value I entered on the circuit for now :) - And the Capacitors at my disposal is 1uF, 10uF, 22uF, 100uF or 470uF ).

I can't wait to here from you!


texts:
I moved my kettle just after boiling it yesterday and noticed the live pin was very hot. None of the other pins are hot. It's a bs 1363 type plug and socket. And a <2 year old kettle.
After a full kettle its burning hot!
It's the same even from different sockets.
Is this normal for a 2kW appliance?
Is it indicating a fuse at the end of life, or bad socket wiring, bad plug wiring?


texts:
I made a rotary encoder using a IR sensor and a wheel with printed black and white spokes.  Everything seems to work but I'm wondering if there is a better way to code this.  The IR signal looks ideally like a square wave and I have it looking for the rising edge of each wave.  Then calculate the time between rising edges to calculate the wheel's RPM.

int wheelPin = 11; // I/O pin for encoder
int count = 0; // number of encoder ticks
bool rising = false; // bool for rising edge of encoder signal
double dt; // time between rising edges
long dtStore[2]; // FIFO array holding current and previous rising edge times
float rpm;

void setup(){
  Serial.begin(57600);
}

void loop() {
  int wheelVal = analogRead(wheelPin); // get encoder val

/* check to see if we are at a low spot in the wave.  Set rising (bool) so we know to expect a rising edge */

if (wheelVal < 200) {
  rising = true;
}

/* Check for a rising edge.  Rising is true and a wheelVal above 200 (determined experimentally)*/

if (rising && wheelVal > 200) {
   dtStore[0]=dtStore[1]; // move the current time to the previous time spot
   count++;
   dtStore[1] = millis(); // record the current time of the rising edge
   dt = dtStore[1]-dtStore[0]; // calculate dt between the last and current rising edge time
   rpm = (0.0625)/dt*1000*60; // RPM calculation
   rising = false; // reset flag
 }
Serial.println(rpm);
}


texts: Does this voltage regulator use "on-off" control, or is it a voltage follower?

texts:
In Electronics A2 (GCE), we are currently studying voltage regulators.

An example voltage regulator circuit is provided using an op-amp and a power MOSFET.

I would judge this to be a voltage follower.

The workbook however claims it uses on-off control. In other words, if the output voltage is below the reference, the MOSFET is turned hard-on; otherwise, it is turned off. Since the cap takes time to charge, this causes the circuit to regulate at a voltage.

However, I would have thought that due to the lack of inertia in the circuit (at most the on-resistance of the power MOSFET, around 0.02 ohms) would cause it to constantly overshoot if it did this; instead, it simply regulated normally.

When the gate waveform was checked, it was steady, which further convinces me that it is essentially a power follower for the op-amp.

The teacher claimed that it was probably switching on and off too fast to see at the gate using "only" a 50MHz scope. The time constant to charge the 4.7uF cap (changed from diagram) through the 0.02 ohm RdsON would be on the order of nanoseconds, so this could be true, but I can't see how a general purpose TL071 op amp could possibly do this, especially without a gate driver and high speed PCB layout.

Interestingly, the original circuit used 470nF which worked up to around 40mA load; the cap had to be increased to 4.7uF to maintain a stable output up to 250mA (otherwise, it did appear to exhibit a form of oscillation, around 500mVp-p noise at a few kHz.)


texts:
I have RPR-220 reflective photosensor, which transistor's part I connect to 2v via 10 Kohm resistor. Emitter is then connected to the base of a transistor C547B, which for the test setup uses LED + 1kOhm in collector circuit.

When something reflective appear above the sensor, about 2uA current is raising up to almost 60uA.

The problem is, that transistor is always open and LED on (and it seems the transistor is so sensitive, that it opens even if I touch the base along with some open-end wire!). I guess, the transistor is wrong, but probably the whole approach is not right.

I can't find what is the right way to connect phototransistor to have clear logic signal as an output (2 v or 3.3v is enough)?

(the RPR-220's LED part is not shown)


texts: Transmitting a video stream through a microcontroller's wifi

texts:
I'm working a a project that currently works well but this year we want to expand it by collecting data from it, independent of its current functions. We have set up an iPad App to control an Arduino through Wifi. The next step is transmitting video through Wifi to the iPad.

With this question I would like to focus on how a microcontroller can send a video stream through Wifi. I can't seem to find any way to even start this project.

How do you interface the camera with the microcontroller?

How do you then send that stream over Wifi?


texts: Is there another part number for z1w47 SMT zener diode?

texts: So I need to replace a SMT component that burnt on a board. The part number that I was able to get from the component is Z1W47. A quick google search lead me to CZ1W47. However, I can't find anyone selling this zener diode with this part number. Is there another known or alternate component under a different part number to replace this bad one? Thank you!


texts: How to deal with grounding and the capacitors in this opamp schematic?

texts:
Here is a schematic I'm planning to make (right click on the image and 'open image in new tab' to see it better'):

I have a transformer and AC to DC converter that makes +/-12V.

(1) Does 'power supply 1' correspond to the +12V wire and 'power supply 2' to the -12V wire?

(2) When I see the symbol 'ground' on the schematic does that mean that I need to connect those to the -12V line? I have no 0 volt line in the circuit so what is the ground line?

(3) Why are C3, C5 non-polarized capacitors and why are the other ones polarized? The current flows from negative to positive. Does that mean that the polarized capacitors need to be placed with their positive legs pointing to the left?

I already asked the grounding question but I got only answers that were theory. I would like specifically to know how do I deal with grounding in this circuit and why there is no grounding symbol in an arbitrary "powering an LED with a 9V battery" circuit.

Thank you very much. This will clarify a lot of things for me.


texts:
I want to connect a whole lot of independent sensors (Arduino boards) to the Internet. They are all within 10m of each other.

Should I use XBee's and link them in a mesh network and have one access point (how?) connected to the Internet? Or should I setup each sensor with a WiFi connection that talks to a WiFi access point? The sensors will be powered by a solar panel.


texts:
For an assignment at school I have an op amp circuit where I need to get the Transfer function of. I want to ask if my approach is correct. Because it feels I simplify it too much.(R1,R2 and R3 have the same value)

If I assume the op amp is ideal, I can say that V2 is equal to V+ because V+ and V- are equal and V- is V2.That would mean that I can simplify the circuit to this:

And then in turn to this:

And then I want to use the node voltage method to get the transfer function eventually. Is this simplification correct? Or am i making weird assumptions? (I dont know the answer so I cant check my eventual answer)


texts:
I'm trying to build a circuit that can amplify 5-20 mV DC voltage to around 3-5V. To achieve this, I'm using a standard non-inverting op-amp circuit, with gain
$$\frac{V_\text{out}}{V_\text{in}}=1+\frac{R_f}{R_g}$$
The problem is that the above formula is useless in predicting the gain, and thus the entire circuit is useless. For example,
$$V_\text{in}=0.1V,~~~R_g=10k\Omega,~~~R_f\in [0,10k\Omega]~~\Rightarrow~~~V_\text{out}^\text{theory}\in [0.1,0.2V]$$
However, experimentally, I'm getting
$$V_\text{out}^\text{exp}\in[3.78,3.81V]$$

Question: How does one explain the discrepancy between the value of Vout as predicted by theory, and the value of Vout as measured in experiment?

The circuit that I'm running (theoretically)

The circuit that I'm running (actually):

The op amp data sheet (perhaps the orientation is wrong?):

http://www.ti.com/lit/ds/symlink/tl082-n.pdf


texts:
So I have a small circuit that I made to flash some led's in sync with my music. It's just a signal from my speaker going into the base of my 2N3903 transistor and the ground of the led is being interrupted by the transistor. The circuit works just fine but I was wondering, how and where can I add a capacitor in this circuit to make the lights dim off instead of shut off imeaditly.

Thank you!


texts:
I needed a new screwdriver set and found one called T4741SESD. In the product description it says the following:

Fully ESD compliant for safe use on sensitive electronic components

What is special about these screwdrivers that makes them ESD safe compared to other screwdrivers?

Before putting the screwdrivers in my toolcase I cleaned them off with some denatured alcohol, as this is how I usually clean my tools. While cleaning the blade/shaft I noticed the cloth became brown and the metal more shiny.

Is it possible I have inadvertently destroyed the ESD safe properties of the screwdrivers by removing the brown coating on the blade/shaft, or could this just be some oil to protect them from rusting?


texts: How can I get 17 VDC from 25 VDC with current may up to 10 A?

texts:
I'm new in electronic and electrical circuits, so maybe my question will be naive.
I have an electrical transformer that gets 220VAC as an input and gives 25VAC as an output, and can produce 20amp current.
I connect the 25VAC output to diodes bridge with capacitor(3300uF - 25v) to the positive and negative pins to eventually get 25VDC.
What I want is to reduce the 25VDC to 17VDC, I thought i could build voltage divider with variable resistor to get the volt I want, but it looks like the passed 10amp damaged the resistor.
What can I do ??

Here's what I tried to do:

simulate this circuit – Schematic created using CircuitLab

PS:
This schema is pseudo, it's only to clarify the connections, circuit in real life is working as expected with the right parts.


texts:
This is one of the circuits in the Electronics 9/10 class.

The package did not explain how transistor combination worked and why the capacitor will reverse its current.

Can you explain this circuit? Why I can't make a transistor combination with only two NPNs?


texts: op amp input biasing question: why wouldn't an input sensor draw current and get fried?

texts:
First post here, thank you in advance for all responses!
In a nutshell, my question is, if you bias the input of an op amp, why doesn't current then flow from your biasing mechanism into whatever input device's voltage you are measuring?
I am an amateur considering using an op amp voltage follower to observe from within the vehicle the output of my vehicle's ABS sensors, which I must do without affecting their voltages. I have observed them with a scope to produce 0-2ish volt low frequency sine waves.
I watched this video: https://www.youtube.com/watch?v=MtccB9K09ck&t=306s where this guy uses a variable power supply to bias his input (schematic at 6:45) and also discusses using a resistor divider (schematic at 1:54). In either case I don't see why current can't flow out to the left and start loading up my input sensor (unless I don't reference it to ground?)
Thank you very much for taking the time to try clarifying this for me!


texts: How could I create mixed audio, with a single PWM output?

texts:
Background: I recently made a project which emits pure tones on a speaker, and it got me thinking about how I was restricted to simple pitches. How would I simulate a chord if I can only play one frequency at a time?
The approach that makes the most sense to me would be to take multiple PWM outputs, each at a component frequency, and feed them into a summing amplifier. Perhaps they'd also need to be level shifted first (assuming for example 0V to 5V square waves in the PWM to -2.5V to 2.5V) to avoid it becoming a purely additive process. Either way I believe I understand the concept there.
But consider a scenario where I'm using a system where other PWMs are already allocated and I need to use just 1. This question's answer addresses it but I don't really follow it. I'm not sure where I get lost but to me I feel like this would just result in some other pure tone somewhere between the two. It's not clear to me exactly what the user is calculating when "adding those phases to two phase accumulators, look up their values in the sine table, add them, and set a PWM output to that value." What does adding them actually do? What if they're both at a max value (e.g 1 -> 100%)? You can't PWM more than 100% duty cycle.


texts: GFI Breaker on a three line 240V circuit

texts:
I need to add GFI to an existing 240V 30A circuit your use an electric home brewing system. The system uses an electric heating element that is immersed in a kettle of water. The manufacturer recommends the use of GFIC for safety.

Will a two-pole 30A GFI breaker function correctly on a three line circuit? How should the neutral pigtail be wired?


texts: Hi, I am trying to use non iverting OPAMP configuration with LM324 and I have 3.869mV output which idealy should be 5.3V based on my calculation. I am wondering what is the issue here?


texts: Common ground circuit on Raspberry Pi blew fuse?

texts:
I tried experimenting with transistors for the first time and using my Raspberry Pi to try to control a higher voltage circuit. Using a breadboard, this is the circuit I tried to build (apologies for the poor hand-drawing):

My thought was that the 9V battery would operate the motor, and by having a common ground between it and the Pi, I would be able to use the Pi input to turn the transistor on or off.

About midway through, I realized that the pin voltage from the Pi wouldn't be high enough to flip the PNP transistor, but I went ahead anyway thinking that, in the worst case, the transistor would just be left continueously open. What I did not expect was that the circuit would fry my Pi entirely! (at least I was itching to upgrade it anyway :).

I'm pretty certain that I didn't inadvertantly short any pins or connect the 9V hot to the Pi's GND, so what went wrong in this circuit?


texts: For a voltage divider circuit, why does \$V_{out} = I \times Z_{2}\$?

texts:
For a voltage divider circuit, why does Vout = I*Z2 ?

I understand that Ohm's Law says V = I * R, but I am new to electronics.  Can you explain this better?    Why is Vout not I*Z1?


texts: How to measure AC and DC with oscilloscope

texts:
I'm a newbie with the oscilloscope. I have a digital RIGOL with two probes.

I'm testing a simple 12V AC to 5V DC converter.

I'm trying to measure the effect of the 7805 on the DC signal in output and comparing this signal to the AC signal before the rectifier bridge.

If I connect the probes as you can see in the pictures I see sparkles (short circuit) on the GND probe of the AC line. This make me think that the the two probes of the oscilloscope have common GND.

So now I have two question:

Have I to connect only one GND of the probe to the GND of the circuit to study the signals properly?
What can I look to understand if the output signal is "clean" (no ripple, no big oscillation)? Have I to select AC coupling in the oscilloscope and see Vrms, frequency, ecc...?

Sorry to bother you with this very simple question but I see that using the oscilloscope properly is difficult.

Thanks.


texts: Calculating power drawn or ampere allowance

texts:
I just want to confirm the calculations for the following scenario.

I have an equipment with the following specifications:

POWER SUPPLIES
AC power input Neutrik PowerCON TRUE1 (IP65)
200-240V 50/60 Hz

INPUT POWER
1800 VA

Would it be safe to say that the amp drawn is 1800VA / 240V = 7.5A? Also, my power supply is 240V,64A AC. Does that mean that from that power supply, I am able to power 64A / 7.5A = 8.53 or 8 of the same equipment?

Thank you.


texts: Where the current's emitter BJT Transistor comes from?

texts:
I tried to solve this problem and I could find the answer but i try to look for more attention to the circuit and finding some doubts. Let me try to explain myself.

the question ask about the current through the \$R_L\$ resistor.

I compute this way:

Current though \$R_1\$ and \$R_2\$ resistors:

\$\require{cancel} \dfrac{0-5}{\cancel{10k}} = \dfrac{5-V_E}{\cancel{10k}} \Rightarrow V_E = 10V\$

Current thought \$R_L\$ is:

\$I_L = \dfrac{V_E-0}{200}\Rightarrow \boxed{I_L = 50mA}\$

Ok. Too easy.

My some questions are:

What the operational mode NPN is?

If it would be on saturation region \$V_{ce} = 0V\$, how could it possible if \$V_b\$ (output of ampop) was 0V, so the BJT would be in reversed bias mode due to \$V_{be}\$. And if the \$V_{bc}\$ would be reversed mode the transistor was on Cutt-off region?

If it would be cut-off region where the emitter current had cames from? Because

\$ I_E -\dfrac{5-10}{10k} = 20mA\Rightarrow I_E = 20.5mA\$

I hope my English was a minimum clear.


texts: 18650, charge and supply at the same time

texts:
I am planning to use a NodeMCU with a couple of encoders to determine the position a telescope is pointing at. While running, the device will be connected to wifi all the time since it needs to interact with an app (or maybe on AP mode so a tablet/phone connects to it).

In the future I may also add a barometric pressure (BMP280) and temp/humidity (DHT11) sensors, gps, and a touch lcd. Probably wont have enough pins for this, but maybe using a MCP23017 could work. Anyway these are all just ideas, to start I will only use the 2 encoders. I haven't even received any of the devides yet, so in the meantime I'm reading and thinking of stuff I could do.

The device will have to be mobile since it may be used in places where there's no electricity, so I am thinking on powering it up with some 18650 batteries I have. I want it to work for about 4-6 hours before having to recharge it, and the device itself must have a charging (usb) port. I also need a 5v line since the encoders work with 5-24v (I choose to use the min 5v since it would be easier to use a logic level converter for input in the nodemcu). So I thought of doing something like this:

Pinout is not important right now, just the concept.

Would it even work? What will happen if I turn the switch on while the charging usb port is plugged in? Any simpler solutions? The charger protection board would be this one.


texts: Are 4-wire resistance temperature detectors sensitive to ambient temperature?

texts:
We're using a TI LMP90080 as an ADC to read a 4-wire resistance thermal detector (RTD) in the following circuit:

The problem we are having is that when the ambient temperature changes, especially near R88, a 25ppm/°C 0.10% 1k resistor, the reading is negatively effected, i.e. when heated, the temperature read changes about 20 °C negatively, and vice versa when cooled. This seems to make sense but I'm wondering is there a way to fix this without temperature compensation via an ambient temperature IC?

The RTD is connected via traces and some interconnect wires between PCBs and are terminated as such:

The RTD is well away from the heating or cooling used for testing and looks like this:


texts: Converting Proteus .GBR file to the more conventional Gerber extensions

texts:
I am using a panelizer program used in this video. unfortunatly upon adding the gerber files to the program the program doesnt seem to draw the body in the viewport. This lead me to believe that maybe it doenst understand the file names.

Reading the usage note

.txt or .xln = excellon drill file.
.gko = outline file.
.gml = mill file. MAKE SURE YOU DO NOT INCLUDE THE BOARD OUTLINE IN THE MILL FILE AGAIN!!!
gbl/gbo/gbs/gtl/gto/gts and the above will be used for image generation
all other files (if gerber) will be combined with files with matching extension (case insensitive!)

And Proteus exports with .GBR only

I read that ggerber files are backwards/forward compatible meaning i can rename the extension no problem. The problem is i do not know which extension goes where
and which files should be combined(same extention).


texts:
I have found the basic tutorials on gates and the way they work.
However, I'm not understanding conceptually how a NOT gate, when activated, bypasses the output.

Circuit as follows:

simulate this circuit – Schematic created using CircuitLab

When switch goes on, LED goes off - SIMPLE & Useful.

But, how does this happen?

Why doesn't ANYTHING go through the LED?
Is this because it's a diode?
.. Is the voltage drop across the transistor too much for the LED to be lit up?
What if it was a speaker?
.. Would it emit a very small/quiet noise even while the switch is on?

I can't find a tutorial, or reference online that explains this to me.

Resources or assistance would be greatly appreciated.


texts: PIC32 GPIO pins Hardware Abstraction Layer question

texts:
I am attempting to write a Hardware Abstraction Layer (HAL) for a PIC32 (PIC32MX664F128H to be precise), in which I can use generic defines for the ports in question without having to use the exact port names and port registers. Ideally I would like to only use these defines for the various pins on the PIC, and have a "wrapper" module in which I can specify which pins the defines refer to.

I have read through this forum post, which basically explains exactly what I am trying to achieve. Post #4 (reply #3) is of particular interest here. The basic idea is to use a struct (GPIO_TypeDef) to define a type that contains the 4 registers (TRIS, PORT, LAT and ODC) for each port (note that the forum post was for a PIC24 (16-bit processor), and that I've adapted the code for the PIC32 (32-bit processor)):

typedef struct {
 volatile unsigned int TRIS; //direction register - offset 0x0000
 volatile unsigned int PORT; //input data register
 volatile unsigned int LAT;  //output data register
 volatile unsigned int ODC;  //open drain register
} GPIO_TypeDef;    //gpio type definitions

The entire port is then cast and bound to a define which is used to point to the port address in memory:

#define GPIOA  ((GPIO_TypeDef *) &TRISA)
#define GPIOB  ((GPIO_TypeDef *) &TRISB)
etc...

The TRIS register's address is used for the pointer binding, since it is the first of the four register to occur in memory for each port. This can be seen from the PIC's datasheet (using PORTB as an example):

Using PORTB for the rest of this post, the define GPIOB thus should point to the TRISB register (with base address 0xBF886040), or rather, GPIOB should point to the address of the first element of the TRISB register.

A set of macros is then defined for the port operations:

#define PIN_SET(port, pins) port->LAT |= (pins) //set pins on port
#define PIN_CLR(port, pins) port->LAT &=~(pins) //clear pins on port
#define PIN_FLP(port, pins) port->LAT ^= (pins) //flip pins on port
#define PIN_GET(port, pins) ((port->PORT) & (pins)) //get pins
#define PIN_OUT(port, pins) port->TRIS &=~(pins) //pins as output

In the user code, one would define e.g. a pin that controls an LED as follows (using PORTB instead of PORTC as in the forum post):

#define LED_PORT  GPIOB
#define LED       (1<<4) //led on PORTB.4

The LED can then be turned on/off as follows:

PIN_SET(LED_PORT, LED); //turn LED on
PIN_CLR(LED_PORT, LED); //turn LED off

However, when I use the above code, the corresponding pin in the TRISB register is toggled, instead of the LATB register. Furthermore, attempting to turn the LED off, the corresponding bit that was set in the TRISB register doesn't toggle back to 0. Why is this not working?

What is interesting is if I define seperate structs for each of the four port registers as follows:

typedef struct
{
    volatile unsigned int LAT;
} IO_LAT;

typedef struct
{
    volatile unsigned int PORT;
} IO_PORT;

typedef struct
{
    volatile unsigned int TRIS;
} IO_TRIS;

typedef struct
{
    volatile unsigned int ODC;
} IO_ODC;

#define IO_LATB ((IO_LAT *)&LATB)

and toggle the corresponding bit (bit 4) in each of these registers as follows:

PIN_SET(IO_LATB, LED);
PIN_CLR(IO_LATB, LED);

it works perfectly. The same goes for when I do the same with the TRIS, PORT and ODC registers (and of course modifying the macros accordingly). Why does this work, and not the first method?


texts: Difference between controlled current and constant voltage charging

texts:
Modern charging of lithium and nickel based batteries starts with a constant current, until a certain voltage and then a constant voltage until the current falls to some level that indicates end of charge (e.g. C/10).

In real terms, does the supply to the battery change from a CC to CV, or is the current just adjusted on-the-fly to reach a specific voltage?  And is there a difference, in practice, between applying a constant voltage, or just tweaking the current (progressively downward) to achieve a constant voltage across the battery (to me they would seem to be exactly the same, assuming good control)?


texts: Replacement for 50+ year old solder fuse technology

texts: I am refurbishing an old automotive clock (VDO Kienzle) that uses an internal low-melting point (~120 degrees F) proprietary solder "fuse". Is there a way to calculate or estimate the size of a suitable modern automotive fuse replacement, specified in amperage?


texts: What will be the output/discharge current of a capacitor?

texts:
I am planning on doing an experiment where I want to connect a 2V 500mA solar panel to a 25F 2.7V super capacitor and then I will connect it to a 5V output boost converter. I know the capacitor output current formula is

$$i(t)=C \dfrac{dv}{dt}$$

but I am not sure what will be the output voltage and current of the capacitor would be to the boost converter. Another set up would be to connect 4 25F 2.7V capacitors in series and then in parallel to a 1.2 watt solar panel, what would be output V and I in that case? Also please let me know if its a bad idea.
Thank you, any help would be greatly appreciated.


texts: Can anyone explain what is doing this diode-capacitor branch on a Boost converter?

texts:
I've analized the circuit through capacitor currents to find the transfer function, but I keep getting to the exact same transfer function of the typical Boost converter, is the Diode-Capacitor branch in parallel to the inductor actually doing something?

Switch and diode are ideal, capacitors and inductors are large and on steady state and the converter is operating in continuous conduction mode. Thanks in advance!

P.S. Sorry for any posible mistake on my english, I'm not a native speaker

simulate this circuit – Schematic created using CircuitLab


texts: Does the microcontroller need to support a given filesystem in USB Mass Storage Class scenario?

texts: I've been thinking about designing a small flash drive of sorts with the AT32UC3A3256. I'm planning on using e.MMC managed NAND which I can hook up to the MCU without a problem. Just wondering does the MCU need to support a given filesystem exFAT or FAT32, or is that simply OS based?


texts: Audio spectrum analysis: PC Software vs Hardware Spectrum Analyzer

texts:
I need to do some audio spectrum analysis (basically, listening to a machine and tell if it is properly calibrated).

I will record the sound it makes with a microphone (it sounds differently if it is calibrated correctly than if it is not), and then want to look at the audio spectrum, with plans to automatically tell if a machine is set up correctly (currently, a human operator listens to the machine and does this job manually).

As a first step, this does not need to be real time, i.e., I will just make recordings of the machine (once set up correctly, once not), and compare the audio spectra.

My question is: Aside from the microphone, do I need a hardware spectrum analyzer, or does PC software suffice for this (FFT can of course be done on a computer too...). Particularly, because for a start, I do not need real-time analysis.

I am mainly asking because it seems that spectrum analysers cost quite a lot, and I don't want to purchase such a device if I don't actually need it.


texts:
I'm designing electronics for a time-of-flight sensor that will have an operating distance of 3cm - 1m. I want a distance accuracy of 5cm, like this model:
https://www.pololu.com/file/0J1187/vl53l0x.pdf
To obtain an accuracy of 5cm, we would need a clock speed of
$$t = 0.05m /3\times 10^8 ms^{-1} = 1.6\times 10^{-10}s$$ or 6GHz. However, most op amps i've seen have ~50 nanosecond settling times (20MHz). Do they use better chips, or is there something else I'm missing?


texts:
I want to make my desk surface into a QI charger but I want a large surface so integrating a pd wont work.

Can I disassemble the charger and add multiple coils to it, or do I need to buy several chargers and keep them separate?


texts:
I'd like to make a solar powered USB charger, to charge my phone. I'd ideally like to use (a) solar panel(s) that I can 'mount' onto a canvas messenger bag, and use a pocket to hold my phone. Obviously I need to provide ~5V to charge a phone, therefore I need a solar panel that can provide at least that much voltage, which can thus be used with a 5V regulator to step the voltage down to the appropriate level.

What other criteria do I need a solar panel to meet? Is there a specific current that I need? Or at least a threshold current? What will the correlation be between the power output of the panel be and its ability to be used in this fashion? Just charging times?

In terms of my skills, I'm an Electrical Engineering major, but my knowledge is mostly academic, so I appreciate any real world advice.


texts: In a H-bridge, when the motor is actively braked, why is the supply providing power when kinetic energy decreases?

texts:
In a H-bridge, suppose a brushed DC motor has been provided +24V for some time, such that the winding current has reached +1A and the back-EMF has reached 23V (R=1Ohm in this example and no other losses).

When we supply -24V across the windings from that point, the motor is even more effectively braked than if it had been short-circuited in a freewheeling state: the current decreases rapidly to -(23+24)/1=-47A, so the motor is in generator mode. However, these 47A are also provided by the power supply (same loop) whereas the kinetic energy of the rotor is supposed to decrease...

I understand from this example that the net power is still negative (2.2kW lost in the windings, 1.4kW provided by the power supply), but is there a way to understand intuitively what is the provided power doing/going?

It is difficult to explain, it just sounds counter-intuitive that in order to decrease energy, we need to provide some still, and if so: where is it going?


texts: At what current and voltage should I run my TEC/Peltier modules for max cooling effect?

texts:
I have 8 x TEC modules each with specs 12V, 6A, and I have a power supply of 12V, 10A.

If I connect all them in series, I know current stays the same and voltage increases.

But what I'm unable to understand is that will be voltage divided equally among the modules?
Also, will the cooling effect decrease with low voltage input? What's the relation of cooling effect with voltage and current?
To run all the modules with full effect, what kind of power supply will I need?
Currently, when I run two modules with my power supply, I don't get temp. lower than 10°C. What could be the problem?


texts: Discrete MOSFET Amplifier question: Trouble finding the Overdrive Voltage

texts:
I am working on an exercise problem (5.18) regarding Discrete MOSFET Amplifiers. I have taken pictures of the question material (Disregard the section under the question) and my latest attempt at a solution:

Alright. Keep in mind that the circuit above is from a different question, they are just re-using it in this one, but they changed the value of VDD from +15V to +5V. Also, they remove RL, but I don't think that matters for my specific issue.

Now, I decided to begin with a DC Analysis to find VOV (Overdrive voltage). I know that I can replace the capacitors with open circuits and then use the MOSFET Saturation current equation and KVL for another current equation, equate them, then solve the resulting quadratic.

However, this method yields an answer different from the book. The book provides VOV = 0.319V, whereas I get VOV = 0.83V.

Is my approach correct? I'm pretty sure the math is sound, so I'm not really sure how to proceed. My solution:


texts: How to prevent MOSFET from operating in high resistance part of linear mode?

texts:
I'm using several MOSFETs to control various loads, e.g. pumps, lighting, ventilation etc.

In the implementation, I have several driver circuits on one board (simple emitter follower, which gives good switching speed with a gate voltage of ~5V; using pull-ups were too slow/inefficient), with jumper cables to a board with several MOSFET circuits. Each circuit is like the schematic.

While testing, I touched the signal cable and it caused the MOSFET to turn on, but it got extremely hot in just half a second of on-time.

Now I'm worried that a small failure in the driver circuit, e.g. if MCU is disconnected and the signal wire somehow picks up a small voltage, it will be amplified into the MOSFET gate, causing a meltdown in just a short period of time. Could this start a fire? Or will the device just fail closed?

Ideally the circuit would not even allow the MOSFET to operate in high resistance part of the linear mode. Can I improve my circuit to avoid gate voltages less than, for example, 4V?
Is there a way that I can detect/prevent overheating (besides a complicated setup of sensors).

simulate this circuit – Schematic created using CircuitLab

UPDATE: Pull-down on signal
Adding a 10k pull-down on the base of the BJTs caused the noise to no longer turn on the MOSFET.

QUESTION:
However, it didn't really answer the core of my question, which is more that I'm worried about situations where a MOSFET may turn on ever so slightly, yet able to conduct, causing extreme heat and consequently potentially starting a fire. I can't use a fuse, since the problem is not overcurrent. Perhaps a thermal fuse mounted to the MOSFET, but that seems rather unorthodox.
Is this a non-problem that I'm overthinking?


texts: Using a single pushbutton switch for 2 seperate circuits

texts:
I'm trying to rediscover my technical roots and am in need of some knowledge from experienced hands.

I have two toy sirens for my nephews pedal-cart, but I need them to both sound when a single push button is pressed (double the joy for my brother and his wife :) …).

Each siren has four types of sounds and the steering wheel only has 4 pushbuttons.
Each siren has its own (3Volt) power source so I can't completely take it apart.

I am struggling to apply Kirchoffs and Thevenins laws to this problem and want to ensure that I get enough current to the sirens (in case the voltages from the power sources cancel each other), but without frying the circuits (and ensuring that I've not series linked the batteries and delivered twice the expected voltage).

Hoping anyone can advise on the dilemma I'm having... I'd like to make sure that my nephew's first memory of "driving" is not one of fire and carnage.

Apologies for the simplicity of the problem in comparison to others listed here.

Many thanks.


texts: I'm using an SPI interface in Raspberry Pi for programming platforms. I have a need to use various logic levels (1.8V, 3.3V, 5V). Is there any IC which allows for dynamic switching between logic levels? I would prefer to avoid using a combination of jumpers and transistors.


texts: How to transmit many digital signals between two systems powered by different power supplies

texts:
I’ve run into problems with my project.I have two different power supplies and I’m trying to pass logic signals through the system as you can see in the picture.

I’m looking for an IC that could handle this job but So far I was unsuccessful finding it

I’ve run into parts such as SN74AVC1T45, but such a device connects both grounds together which would cost short circuit in my project.

I could also use digital isolators, But those are terribly expensive especially when I’m trying to make 20 of these bridges.


texts: Difference between Field Oriented Control and Direct Torque Control

texts:
What is the fundamental difference between Field Oriented Control (FOC) and Direct Torque Control (DTC) (say for an induction motor)? Is it really the same as described in https://www.researchgate.net/post/Can_we_express_the_difference_between_DTC_FOC_of_electrical_drives

I actually understand the principle of FOC but unable to do so for DTC. Would be appreciable if somebody could explain DTC or even post some good resource for studying it.


texts: 220 VAC parts controlled via 12 VDC pump

texts:
I have two water elements using 220 VAC, the water to them is supplied by a 12 VDC pump, I am needing to control the 220 VAC to the elements in case the pump quits, is there a way to shut off the 220 V if the 12 V circuit fails.
Thank you


texts: FCC EIRP test results different than other countries

texts:
We have an issue with regulatory testing where our lab reported EIRP varies significantly between separate labs who have tested for FCC and another country.  The test methods are quite different.  The lab that tested for the FCC filing used a radiated method where the DUT power was measured then a signal generator and known value antenna are used to replace the DUT.  Power is adjusted on the signal generator until the same power is read at the RX antenna.  That power setting is reported as the EIRP.  The second method involves a straight radiated measurement without substituting any other equipment.  As a result one of the labs reported 6uW while the other reported just under 2mW.

We are currently working with the labs to see if there was an issue with either test methodology where we could retest.  Has anyone experienced similar issues when using different labs, and how did you ultimately solve the discrepancy?

Thanks


texts: Difference Between The Transisor Denotations V(th) and V(tn)

texts:
I have seen these values V(th) and V(tn) used interchangeably as the transistor 'threshold voltage' but have also seen them used together on the same diagram seemingly representing differnt things. (I do not have such a diagram available to show you).

If these variables are the same, or different in any way, for both BJT and MOSFET transistors, please explain.


texts:
I have a radio controlled power switch (one that you plug in between the wall and a lamp to switch it on and off with a remote), that has an atmel microcontroller on it. I connected the radio switch to an atmel programmer (Gnd, Vcc(3.3v), Miso, Mosi, Clk, Rst). The atmel programmer is connected and powered via USB.

I accidentally left the programmer connected when I plugged in the radio switch and both the switch and the programmer blew up.

Now I wonder why.

The radio switch's power supply is a resistor followed by a 4 diodes (rectifier?) followed by a capacitor (filter?) followed by a VIPer12A switcher (provides lower voltage?).

I assume that somehow there was a voltage difference between Gnd of my USB port and Gnd of the radio switch, but how can that be?


texts: What component (IC) to use for collecting A and !A signals into a single TTL signal?

texts:
I am building a circuit board to listen to quadrature encoder signals from a motor controller and send these signals on to an FPGA that will be used to count the pulses and direction. The signals coming out of my motor controller are:

Phase A: A and !A
Phase B: B and !B
Phase C: C and !C (origin indicator)

In other words, each phase sends out two signals that are the opposite of one another at all times. I have used Quad EIA-422/423 (MC3486) line receivers to convert differential voltage signals into TTL signals, but is this the correct component for converting each phase from two signals to a single TTL signal? If not, is there a similar IC that will do the trick?

Thanks!

EDIT: It looks like I was treating these signals correctly. I was a little confused on the definition of "differential voltage" as it applies to the line receivers I am using (MC3486). Basically when A is high and !A is low, my line receiver outputs a high on the TTL channel. When A is low and !A is high, it outputs a low on the TTL channel. This is what I wanted it to do; I was concerned that I had misinterpreted the meaning of differential voltage.


texts: Understanding alternating current (sine wave)

texts:
I want to study the basics of propagating a periodic signal, i.e. sine waveform, which is a power signal.

Let us consider an alternating current and write its expression as

$$I(t) = I_m \sin(2\pi f t)$$

Let f=50Hz

In physics we have learned that there are mainly two types of energies based on position and based on the motion of particle.

Potential energy (P.E.)
Kinetic energy (K.E.)

Can anybody explain something about the following issues:

If we consider the period from \$0\$ to \$2\pi\$, in what proportions the above 2 energy values vary at following intervals \$0\$,\$\frac \pi 4\$,\$\frac \pi 2\$ ,\$\frac {3\pi} 2\$ ,\$2\pi\$ that make the sine wave keep propagating?
Why the traveling wave is sinusoidal?


texts: Can I use + charge 3 LiPo cells in series with 3 separate charge controllers?

texts: I'm looking at this circuity from SparkFun. It's an mppt + LiPo charger, which is exactly what I need, but I need several cells. I'm actually fairly content to just build 3 of these, and wire each in series, but will that cause any balancing / other issues? I'm assuming as long as each charge controller is grounded correctly (i.e. one's ground is the next one's VCC), it should be fine, but want to confirm


texts:
I did a bistable multivibrator drive NPN mosfet using timer55 and my mosfet drive power LED. Our Load has 3 circuit stage which are emc filter + smps circuit + power Led. I have a problem at that time my mosfet turn off. When mosfet turn off a clicker happens on my Led. Large capacitive loads are discharhing and mosfet behaves like turning on. I dont know how to handle this problem and want to know are there anybody to had this problem ?

simulate this circuit – Schematic created using CircuitLab

I tried you illustrate my circuit in your mind.


texts: Understanding the role of Pole zeros cancellation from the definition of stability

texts:
I have encountered the following theorem in a book.

According to me, I can get an asymptotically stable system even if cancellations exist for the unstable poles. my example,

Then Why does this book definition state "no hidden cancellations of unstable modes" ?
It is implying necessity I understand


texts: What to look for when buying a reliable hobbyist soldering iron

texts: I wanted to buy a soldering iron for some hobby tinkering, ordered one long ago from Wish! For a few quid, but as you must imagine it's awful. Doesn't heat uniformly, overheats and melts plastic. Tips are bad, i could go on, but I'd rather buy something decent without going mad price wise. I've seen prices from £10 - £300. Soldering irons, sets, kits, stations, extras, you name it. They have different settings, Watts and other characteristics. Which one of these characteristics will help me make an informed decision on what to buy for now, what I may need for more serious projects? Do I go by the price, Watts, extras, origin? Any help appreciated.


texts: Why do receivers have a choke but transmitters don't?

texts:
Here's a receiver I found on the web:

And here's a transmitter:

[

Why do receivers have an inductor specifically designated as a choke (RFC) in their circuits but transmitters don't?


texts:
Any suggestions to open a surface mount package (TSOP, QFN etc) to expose the die?

Possibilities tried or considered:

Split the package using wire cutters - sometimes works and sometimes doesn't
Grind the top off with grinder - Some chips have no cavity between the die and the cap.
Soak in MEK - I heard this works but haven't tried it.

Why would I want to do this? To photograph for forensics purposes - to look for damage or to get die numbers. I don't expect the part to function afterward. Electronic forensics labs seem to be able to open chips easily but I'm not sure what tools/techniques they use.


texts:
Updated: I am not sure if the title fits my inquiry here but I will try to explain.

I have this system show in Fig1. It is a simple plant \$\frac{1}{as}\$ (expressed in the frequency domain). Then I use a simple controller such a a proportional controller (Contr) to follow a reference \$x_{ref}\$ (constant). The controller I use is a proportional controller, lets call it \$k\$ (the parameter of my controller could be easily computed by \$k=a/\tau\$, where \$\tau\$ is the time constant of design).

Then I have a modification of the previous system show in the Fig2.

The addition is a delay with a signal adding and subtracting at the beginning and at the end of it, respectively (it is drew in black in the figure). Since \$b\$ is relatively small (in the range of 0.1-0.001) this addition could be neglected, having the first figure as a result. However, I notice that the addition produce high frequency noises in the output \$x\$. Although those noises are not big and therefore cause no much trouble. I would like to know if it would be possible to mitigate completely or reduce the noise by using a PI controller instead of a proportional only?

So far, I have reduce the system, and got a reduced system show in Fig. 3.

Building that system in Matlab and using PID tuner tool, it provides the gains of the PI controller so that the noise in the output \$x\$ is reduced considerebly. But I dont know how to proceed analitically. I would appreciate any help or suggestion you can provide me. Thanks!

Ps: In case it is necessary some values of \$a,b,c\$ are a=27e-6,b=0.002,c=50, and the gain of the PID tool are kp=0.0479, ki=0.5339.


texts: Does the Commutator of a brushed DC motor cause inductive kickback

texts:
I'm new to electricity.

Textbooks on brushed DC motor talk about inductive kickback when we DISCONNECT the power supply from the motor (and the stuff to protect against it e.g. by adding a diode/snubber). While when a motor is operating, only back emf caused by the rotation matters.

But from what I observe, isn't the commutator of a brushed DC Motor already functions as an on/off switch that keeps turning on/off the current from the winding?  Shouldn't there be some inductive kickback due to sudden removal of current from the winding when commutator switches current direction?  Instead of when turning off the power switch, does the inductive kickback issue matter when a dc motor is connected to a power supply and rotating? If yes, what kind of protection is required in the power supply circuit?

Textbooks always model a dc motor's equivalent circuit as 3 electrical components: inductor + resistor + back emf source. Why there is nothing related to inductive kickback caused by the commutator?


texts:
I have been studying different schematics ive found online to try to get a better understandment on the subject. Recently I came a voltage divider across that consisted of a transistor and a resistor, it looked something like this.

I am only familiar with a voltage divider that consists of two resistors where you can apply the voltage divider formula to know the output voltage.

I'm really curious to know whats's the difference in functionality between these two options? Why would you use one type and not the other one? What effect does the transistor have?

Thanks!


texts:
I am using an Arduino Uno to operate a BLDC motor using IR2110 MOSFET driver and IRFZ44N MOSFET. But every time, all the low side MOSFETs and phase 3 driver(IR2110) are burning. In this position my motor is only vibrating but not moving. How do I solve this?

void AH_BL()
{
  PORTB  =  0x04;
  PORTD &= ~0x18;
  PORTD |=  0x20;
  TCCR1A =  0;            // Turn pin 11 (OC2A) PWM ON (pin 9 & pin 10 OFF)
  TCCR2A =  0x81;         //
}
void AH_CL()
{
  PORTB  =  0x02;
  PORTD &= ~0x18;
  PORTD |=  0x20;
  TCCR1A =  0;            // Turn pin 11 (OC2A) PWM ON (pin 9 & pin 10 OFF)
  TCCR2A =  0x81;         //
}
void BH_CL()
{
  PORTB  =  0x02;
  PORTD &= ~0x28;
  PORTD |=  0x10;
  TCCR2A =  0;            // Turn pin 10 (OC1B) PWM ON (pin 9 & pin 11 OFF)
  TCCR1A =  0x21;         //
}
void BH_AL()
{
  PORTB  =  0x08;
  PORTD &= ~0x28;
  PORTD |=  0x10;
  TCCR2A =  0;            // Turn pin 10 (OC1B) PWM ON (pin 9 & pin 11 OFF)
  TCCR1A =  0x21;         //
}
void CH_AL()
{
  PORTB  =  0x08;
  PORTD &= ~0x30;
  PORTD |=  0x08;
  TCCR2A =  0;            // Turn pin 9 (OC1A) PWM ON (pin 10 & pin 11 OFF)
  TCCR1A =  0x81;         //
}
void CH_BL()
{
  PORTB  =  0x04;
  PORTD &= ~0x30;
  PORTD |=  0x08;
  TCCR2A =  0;            // Turn pin 9 (OC1A) PWM ON (pin 10 & pin 11 OFF)
  TCCR1A =  0x81;         //
}


texts: Is there a good practice approach to powering down peripheral devices (SPI, I2C, UART) which use significant power?

texts:
I'm trying to limit the power usage of a system which uses a number of sensors and transceivers on SPI, I2C, and UART buses. I can't easily design around the sensors in use, so selecting devices with explicit shutdown modes or low quiescent current is unfortunately not an option. Some of the devices (an ESP8266 for example) offer low-power modes which are sufficient, but others do not.

The devices are varied in function: voltage/current/power sensing, temperature and humidity sensing, MEMS, transceivers.

In a question discussing unpowered I2C devices, I understand that there are some difficulties with switching off these devices entirely, due to potential parasitic effects on the bus.

One option I looked at is to insert a bidirectional galvanic isolator at the SDA pin of each I2C device that I wish to unpower, though I have concerns about propagation delay - would I need to drive the clock pin through another channel to ensure a delay match? This could quickly become expensive to implement, too, since the isolator ICs aren't the cheapest of ICs.

This still leaves me without much information on potential parasitic effects on SPI and UART buses from unpowered devices. Do these have similar problems? I'm also unsure as to the best way to actually disconnect the device from the power - is a single N-channel MOSFET inline with the device's Vcc (or equivalent) pin appropriate?


texts:
I have a PowerStor Aerogel 5V 1.0F PB SERIES capacitor.

The datasheet specifies a max voltage of 5V and a surge voltage of 6V.

I understand I can safely use this capacitor in a 3.3V system. Will it also work in a 5V system or is it dangerous to run it like that?


texts: How can I identify transistors with a low Vce-sat (collector-emitter saturation voltage)?

texts:
I want minimum voltage drop between collector and emitter as I have very small Vcc voltage to supply the load.

My Vcc is 3.3 volts. I want to use this switch to turn on/off 3 LEDs connected in parallel with 1K ohms resistor in series at the collector. Is it possible to find transistor with low collector voltage?


texts: Differential transistor stage current not changing with temperature

texts:
I asked similar question recently, which also referred to differential transistor pair, but this one is different.

I made this circuit (in real world):

simulate this circuit – Schematic created using CircuitLab

I was only experimenting with DC (no signal applied). Potentiometer was used to adjust I_e1 to equal I_e2. Beta of transistors were around 300 and both of I_e were set to be exactly 1.1 mA.

After everything was connected as shown, I started to observe the I_e of each transistor when one transistor gets heated up. So, I "touched" the Q1 with two fingers for a few seconds - but nothing happened (no changes in current), same happened with the Q2. It seemed a bit strange that nothing happens. Then I took my lighter and heated one transistor to temperature about 100 degree Celsius - the current through both of transistor didn't even blink! At the end I really really heated it up - and only at this level of heating, the currents moved up/down the scale for 4-6 uA (micro amps)!

How is this even possible? When lighter was usually approached, the I_e changed on the scale of mA, if not tens of mA.

I even replaced transistors - same results!

I also reconnected the whole circuit again - same results!

At the end I used different multimeter (in case one wouldn't work properly) - same results!

*This thing could be possible with current mirrors at collectors and constant current source at emitters, but I only used usual passive resistors.

Comparison of multimeter values:


texts: Troubleshooting a power issue on a DIY board

texts:
I built a board that combines a number of sensors, an ATmega2560 and a TPS62125. The board worked, I was able to measure 3.3V coming out of the buck regulator, and was able to program the ATtmega via ISP. Then, trying to fix another issue, I applied flux to all the pins of the ATmega and reheated them all with an iron, trying to clean them up a bit (it's a TQFP package, and I had some bridging that I originally cleaned up with a wick, but it left behind some crap).

After that, it stopped working. I can only measure about 12mV on the power rail now, but the circuit is still drawing 16mA @ 12.3V from the battery (which is about where it was before). The cause and effect seems pretty clear - I either created a short with the iron that I can't see now, or I fried the chip and there's an internal short. That said, is there anything else I can look at to verify this? I'd have thought that a short to ground would at the very least draw more power. The buck regulator is rated for 300mA so I'd expect a short to ground to draw the full watt or so (300 * 3.3V), but it's only drawing about 200mW.

I checked that the enable pin is high on the regulator (it's pulled up to the battery). Anything else I can look at?


texts: If V=IR Why are voltage and current interchangeable through a constant resistance

texts:
I hear people say things like "I only put 5 amps through the circuit but I put a bunch of volts".  I don't understand how this is possible if V=IR.  Lets say you have a circuit with 5 ohms of resistance so V=I(5).  The amount of voltage and current I am allowed to put through it has to be proportional.

Can anyone can give a good intuitive answer (don't go too in depth with math) that is understandable?


texts: Capacitive crosstalk switching frequency vs rise/fall time

texts:
I'm breaking my head over the frequency dependent behaviour of capacitive crosstalk. Time domain analysis seems to conflict with frequency domain analysis, obviously one must be wrong.
Let's assume we have 2 square waves, one of 1MHz and one of 10MHz, both with rise and fall times of 10ns.
1) Frequency analysis will lead me to the conclusion that crosstalk will become worse with increasing frequency. This seems to be wrong (simulation) but I don't know why. If we decompose the square wave into harmonics, the 3rd and 5th harmonics are also 1/3 and 1/5 in amplitude and so on. So the higher harmonics (around 100MHz for example) of the 1MHz square wave are lower in amplitude than the higher harmonics (around 100MHz) of the 10MHz square wave. The lower amplitude of the higher harmonics should result in lower crosstalk as the impedance of the parasitic/coupling capacitance decreases with frequency.
2) According to time domain analysis, the crosstalk only depends on rise and fall times, and not on switching frequency.
I=coupling C*(delta voltage /delta time), delta time is the signal amplitude and delta time is the rise/fall time, hence no frequency dependent behaviour. It's all caused by the rise/fall time here.
'I' will cause a noise voltage over the victims impedance (R1 in simulation).
3) Simulation

As we can see here, the crosstalk amplitude is the same in both cases, so there must be something wrong with my frequency domain analysis.
Can someone help me out here?


texts:
On my previous exam I was given 2 multiple choice questions.

 Define the operation → as:

 A → B = ~A + B. Then, A → (A → A) = ?

 With the correct answer being '1'

Then the next question

 Define the operation → as:

 A → B = ~A + B. Then, (A → A) → A = ?

 With the correct answer being 'A'

That is the entire text of the question. Nothing that looks like this is in the material he provided us, nor is it in any of the homeworks, nor is it in any of my personal notes.

What is this notation supposed to represent? What is it called?


texts: How can I fix Atmel Studio 7 install which is stuck on "initializing environment"?

texts:
Atmel Studio 7 Install Is Stuck

I'm attempting to install Atmel Studio 7.  I've tried both the online install and the download then install option and the installer becomes stuck (shown in the image).

Hardware Shouldn't be A Problem

I'm running Windows 10 on an i7 with 8GB ram and a decent Internet connection (20MBPS).

Possible Issue?

I do have Visual Studio Community 2013 on my machine (not 2015).  Could that be a source of the problem?

Anyone Else Experience This?

Any Advice On How To Diagnose or Resolve?
Do you know of anything to try to diagnose this issue?
Has anyone else had this issue and resolved it?
I've Googled but haven't found any related info.

EDIT
It seems as if numerous people are running into this problem.

  The solution was to simply Cancel the installation and restart the computer.  The
  installation was locked.  After that, when my computer restarted the installation continued and fixed the issue.


texts: Why does wave winding not need a voltage equalizer?

texts:
I understand that lap winding needs a voltage equalizer to balance the voltage at different points. However, I could not understand why wave winding does not need one (according to the textbook "Electric Machinery Fundamentals, fifth edition" written by Stephen J. Chapman). It seems to me since usually wave winding has larger voltage than lap winding, the imbalance of voltage between its two current paths should be more severe than lap winding.
Moreover, on page 351 of the aforementioned book the author also claims that in frog-leg winding, the wave winding can function as voltage equalizers for the lap winding. How does it work and what is the mechanism for wave winding to equalize voltages?


texts: Identify a component inside an RC car. Dual H Bridge?

texts:
I bought a $10 RC car, and I am trying to replace the remote control with an arduino. I have puzzled out what most of the components on the circuit board are, but one of them has me baffled. In the center of the board is what I thought was a Dual H Bridge motor driver. It is apparently taking some sort of AC input signal from the RC antenna, and I cannot make head or tail of it. What is this thing? Do I have any hope of hijacking its inputs with an arduino?

My electronics knowledge is self taught, and quite spotty. It is entirely possible that I have misidentified something fairly basic. I will try to give enough detail so that more experienced people can spot my mistakes. I am sure that most of these details are mostly irrelevant to my question.

Basic function of RC Car
The rear wheels are powered by a single motor. The front wheels have a motor for steering. Both motors have forward, reverse, and off, with no speed control. This is consistent with a Dual H Bridge motor controller.

Description of Circuit Board
The battery power comes in at the top of the image, runs through a switch which sits below the circuit board, and flows from there to the various circuits. There are three AA Batteries, supplying roughly 4.5V. The negative battery terminal is at the bottom of the board. The antenna connects in the top left corner. It immediately runs through an inductor and a coil of wire wrapped around a solid waxy substance (another inductor?). Both of these are attached below the board. They are marked on the picture as "Connected by inductor." From there, the antenna signal runs through a tangle of circuitry, that I have labeled the "antenna signal magic." I cannot identify the components in this area. There are a few types, all either black boxes with numbers written on them, or blank brown boxes. I know next to nothing about AC signals.

The antenna magic zone connects to a black box with 8 pins per side. I believe this box is some sort of Dual H Bridge motor controller. 8 of the 16 pins can be traced to motors, power, or ground. The other 8 connect to the antenna zone.

Input signals to Black Controller

I used my multimeter, and measured the DC and AC voltages between the antenna pins and ground, and then measured again with the rear wheel drive motor on. All of the antenna pins have a DC voltage between 1.3 and 1.4 volts. For 7 of the 8 pins this voltage does not change when the drive motor is engaged; for the fifth pin from the left it drops to 1.1V. The third and fourth pin from the left have an AC voltage of 1V when the drive motor is off. That voltage jumps to 1.5V when the drive motor is turned on. I assume this is the input signal.

I am not sure what exactly an AC voltage reading means. I do not have an oscilloscope to measure its frequency, or phase shift. The car's package said it uses a 24 MHz signal. Does this mean that the AC voltage my multimeter is reading is at 24 MHz? I didn't think my multimeter would even read a signal with a frequency that high.

Writing on Chip
The controller has DK2991 BG0603 written on it. Googling this did not turn anything useful up.

Summary
I have a tiny chip thing that I think is a Dual H Bridge motor controller that works off of AC input signals. What are these input signals? Is it possible to use an arduino to replicate them?

I do not have fancy equipment on hand, but I am more than willing to run more further tests.


texts: How to design capacitance value for a given full wave rectifier

texts:
I have been searching for design equations for 5v regulated power supply but unable to figure it out. Please check the below circuit diagram

Could anyone explain me why 470uf ? why not 2uf? how can we find out the capacitance value? when only Vrms is known? and also help me to understand the need for 0.01uf on both sides of 7805? Actually I want to connect this 5v output to 8051 micro controller. Any help is greatly appreciated.


texts: Calculating the off impedance of a relay output by a multimeter

texts:
I'm trying to calculate the output OFF impedance i.e. the impedance caused by its RC snubber of this SSR.

So I perform the following test:

Zc is the relay's OFF impedance and Zv is the fluke 114 multi-meter's measurement in loZ setting. In this document loZ impedance of the multi-meter is given as: ~3 kΩ < 500 pF. A you see above, for 229V AC mains voltage the rms voltage across Zv is 6.5V.

So I took Zc as 3k to calculate Zv. This yielded Zv as around 102k.
But the datasheet of the relay says "Max. Off state leakage current (rms): 10mA" this requires n OFF impedance of 230/10mA = 23k.

But my measurement yields 102k.

Where am I doing wrong? And what is 500 pF in the multimmeter input impedance? Does that mean multimeter's inout imepdance is |3k + j*(1/2*pi*50*500pF)| or as in my example only 3k at 50Hz?


texts: How to calculate component value of a matching network

texts:
You can already expect my knowledge level In antenna designing (newbie). This may be or may not be a stupid question. The reason is I don't know about this very much.

Iam designing a PCB for ESP32 Pico D4 and Iam using a chip antenna from Johnson technology. The PCB is 3cm X 2cm dimension. Like I already said Iam new to antennas things. So I kept the basic design guidelines like ground clearance via sticking and components clearance. But what Iam stuck with is the matching network, In
esp32 datasheet they are using a PI match network and in the antenna datasheet they were using two inductor which is grounded with feedline. Can anyone explain me which matching network I needed to use and how I determine the component values?

The main confusion that I have is even I got what type of matching network I needed to use. But I don't know how to calculate the values for the matching network components!
Datasheet:datsheet

Thanks in advance!!!


texts: Will Paralleling Bridge rectifiers reduce heat in each rectifier?

texts: So I'm converting an old AC stick welder that only outputs 30 amps into a DC stick welder. I purchased 1000 volt 50 amp Bridge rectifier to do the job but I got two because I thought I might screw one of them up. When they arrived the thought dawned on me to use one per leg of the welder and my thinking on this would be that they was going to be half as much heat in each rectifier because of this. Is that right? is there a reason NOT to split the legs and when I wire it do I need to run ONE AC wire to both terminals on the rectifiers or do I need to split the AC into two pair and wire both rectifiers that way but with only one leg off each rectifier output to the welding clamps. Usually when you see questions about paralleling Bridge rectifiers it has to do with doubling their output but that's not what I want to do at all. I'm definitely going to be below the rating of an individual even if I wired as a single. My thought on this is that I could get away with passive cooling if I'm only putting half the heat out in each spot. Any help you guys have would be great thank you!


texts: INA168 vs INA169 High-side current sensing

texts:
I have read the datasheets of the INA168 and the INA169 and can't see any difference, other than internal resistors value and quiscent current (25uA for INA168, 60uA for INA169). Those two were even made in pretty much the same period.  Does anyone know if there is any differnce and maybe which one is better?

Or maybe I should go with something different for high-side current measurement on a 40V 5A Lab PSU, since there are things like LTC6101 or MAX4080 ?


texts:
I am trying to build an ADC module using the ADS1110 ADC and the TLS2272 op amp. This is more a problem of composition than a filter design problem.

The 16bit ADS1110 runs at the amazing speed of 15 SPS with a range of 0-4.096V. Unfortunately it is not a fully differential ADC and to reach 16bit on the whole range you need to use a Vref of 2.048V on the AIN- pin (see datasheet for more info). To restore the differential feature I am planning of using an opamp in differential mode, with a lp filter (fc=20Hz).

This is the circuit I came up with, but it's wrong, because the op amp is single supply and it can't detect if the signal ground noise ripple goes below 0V. Also note that the cutoff freq of this circuit is 200Hz not 20, ignore it.

I thought about some variations but I don't know which is the better one:

1) Remove the SK, use the freed opamp unit to buffer Vref, sum vref to both inputs of the differential filter

2) Remove the SK, use the freed opamp unit to sum the signal ground to Vref, feed this to the (-) input of the ADC

3) Something else

Please, give advice.

EDIT:

Main goal is to filter noise from both the signal and its ground, make the difference and feed it to the AIN+ of the ADC. Also, "signal" maybe is too much, I just need to read a fixed DC voltage.

Explanation of the Vref trick:

The ADC reads the (+) input within +/- 2V the (-) input. Since my signal ground is probably close to the ADC ground and the ADC can't read negative voltages I need to move the (-) input to 2V to use the full range with full precision.

More info: http://www.ti.com/lit/an/sbaa133a/sbaa133a.pdf


texts: Arduino Mega & LIN Transceiver (MCP2004)

texts:
I am trying to connect an Arduino Mega with another device using a LIN Transceiver. I have decided to use a LIN MCP2004 Transceiver for this.

I am now trying to understand the reference design of MCP2004.
I have come up with the following design but I have a couple of questions:

Should RxD be pulled up to 5 volt or 12 volt?
Are the values for R1 and R2 ok?
I don't understand what to do with the V_REN pin?

Thanks.

PS, please don't suggest other LIN transceivers since I only have access to MPC2004.

simulate this circuit – Schematic created using CircuitLab


texts: Is the wrong antenna worse than no antenna?

texts:
I have a wireless transceiver. It is programmable to allow both transmit and receive from 1-1000MHz with FSK or ASK. The PCB and components have been chosen for transmission at 433MHz. Another PCB variant is available, tuned for 915MHz.

If I attempt to receive 433MHz signals through the 915MHz tuned board or vice versa, how bad will it be? (I am not concerned with transmitting via a mistuned antenna).

How do I quantify this badness and what factors affect its magnitude?

Will signal quality reduce as well as transmission distance?

Will FSK perform better than ASK?

Can it be reasonably expected to work so long as the user "holds it a bit closer"?


texts: Discharge peak hold capacitor with MOSFET

texts:
I'm just thinking how I can discharge the capacitor of a peak hold circuit, by switching a MOSFET and connecting it to a resistor. Could anyone propose simple ideas with pictures/drawings?
Would something like this work?


texts:
In Pcie Gen5 overview, the receiver can detect the eye opening at 10mV. This require sensitive slicers to be design to capture the Eye height as low as 10mV.

Can anybody explain what is sensitive slicers here? Is that the sensitivity of the  receiver.?


texts: How many times can flash be rewritten before an erase is required?

texts:
With flash memory, it's only possible to write by clearing bits from their erased (set) state, and the only way to set a bit is to erase the region containing it.  If you only need to clear bits, then you can hypothetically rewrite a section of flash up to as many times as there are bits in that section before needing to erase it.  However I've noticed that Atmel's SAM-D parts specify a stricter limit on this.  Section 37-12 of the SAM D21/DA1 family datasheet:

Note that on this flash technology, a max number of 8 consecutive write is allowed per row. Once this number is reached, a row erase is mandatory.

I've looked through a few other datasheets for other MCUs and some flash memory ICs, and so far the SAM D21 datasheet is the only place I've seen a limit like this specified. Since the Atmel datasheet gives this only as a note and not as a qualified specification, I'm not sure if this limit is based on worst-case conditions (such as voltage, temperature, or number of cycles).  I suppose that this limit can vary with the specific technology used (hence the mention in the Atmel note), but in that case I don't know what specific characteristics of the D21 flash imposes this limit.
I don't expect it's reasonable to expect that you can actually clear every single bit in a region individually, but if there is a general limit on the number of rewrites before an erase is required I've not been able to find a reference for it.
There is clearly a lower bound on this, which is imposed by the way that flash is generally organized: specifically the fact that the minimum size that can be erased at once is generally a multiple of the minimum size that can be written at once.  For example, the aforementioned SAM D21 writes per "page", but erases per "row", and since there are four pages per row, it must be possible to write to a given row at least four times before an erase is required if all of the flash is going to be used at once.
Beyond this lower bound, in the absence of a clear datasheet specification, is there a general rule or guideline for the minimum or maximum number of times a portion of flash can be safely rewritten between erases? What if any, specific characteristics of the memory technology would influence this limit?
Edit to clarify:  I'm not concerned with overall write/erase endurance here, that's typically well specified and separate from the rewrites-per-erase spec I'm asking for.  And for the purposes of this question, we can assume that any rewrites are within whatever write size the flash supports.


texts: Locating the Origin of 2.4GHz RF Transmissions

texts:
Is it possible? How would it work?

Consider IEEE 802.11 (aka.Wi-Fi); for instance.
There's such an incredible amount of devices out there, measuring and reporting WLAN AP signal strength (RSSI, RCPI, mW, dBm); but I've never actually seen one that was capable of demonstrating any real sense of direction or spatial awareness.


texts: state-space averaging with matrices not same dimension

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Below are procedures for state-space averaging:

Question:

For some circuits, each matrix pair (A1 and A2) or (B1 and B2) doesn't have the same dimension.
To be specific, A1 is not same dimension as A2 or B1 is not same dimension as B2. So it doesn't make sense to add these matrix together.

So how do we use state-space averaging in that case?

I think this paper also talk about the problem. However, it is too complex for me to understand.

Here is a specific example for this problem. Please see the picture.


texts: Part identification: Board mount rotary switch

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I have a CPAP machine whose dial broke off. Was hoping to 3D print a replacement, but I don't see an obvious way to attach it. I figure finding the specification would help.
Has 3 leads on the bottom, 2 on the top (not visible), and one lead on each side.
There's some marking on the bottom, but I can't make them out.
Anyone know the part?


texts: Stepping-down DC voltage (at low current) in the presence of an audio circuit

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I'm trying to add a bluetooth audio receiver to an old 12V battery-powered boombox.  The receiver board takes 5V and shouldn't draw much current, but I'm trying to understand which type of DC-DC converter would introduce the least amount of noise in the audio frequency spectrum.  (And since it will be battery operated, efficiency wouldn't hurt either.)

The reason I ask is that I've noticed a very audible buzz on my car stereo when my phone (connected by an aux in cable) is connected to an automotive USB charger.  I want to avoid this terrible noise.

A voltage divider seems like the simplest and quietest possible option, but certainly not the most efficient, and definitely not the wisest.

I looked at this similar question and I get the sense that both zener circuits and linear regulators are also going to be very inefficient for this application.

This question on buck converters suggests that they are very noisy.

Is SMPS the best approach?  The circuits I've seen online seem like extreme overkill for getting the ~100ma that I'd imagine would be required by the board I have.

Is there a different design that I should be looking at?  Should I be dealing with the noise a different way?  Is the noise that I'm trying to avoid a non-issue given the relatively small load I need to power?


texts: What happens to DC Spindle horsepower at lower voltages?

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I am running a shapeoko2 from inventables and bought a 300 Watt quiet cut DC spindle to run on it. The operating voltage range is 24V to 48V. My power source is adjustable to 48V but can only deliver 8.3 amps. I have currently dialed down the power source to 24V to power the stepper motors via the smoothie board.

I assume then my 300 Watt motor won't be able to run at full efficiency since 300W/24V = 12.5 Amps. What happens when my motor can't pull that current from it's power source. Does that mean my spindle can only produce 199.2 Watts of cutting power if I am running the power supply at 24V, and the stepper motors aren't running? If I am running the spindle off of the same power supply while the motors are running will I see the cutting power vary when the motors are pulling current?


texts: different threshold value of 2 inverters

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What is the meaning of having 2 series inverters, one with the switching threshold at 1.025 V and the other with the threshold at 0.3V?

What does this difference between the switching levels mean?

The circuit has a sine wave at the input of the inverters and it makes a clock signal from 1.8V to 0V.

Thank you!


texts:
I have a RF signal at L-Band, 950-2150 MHz. with bandwidth up to 100 MHz.
this signal needs to be converted to optics.

Does single mode or multi mode fiber have frequency/bandwidth limitations after conversion?