texts: Passive Normally-Closed Switch For Audio Applications

texts:
I am working on a small, audio device with aux input and output (both headphone-level) that has some interesting requirements:

In passive mode (dead battery) audio needs to go from input to output
In active mode audio will normally go from input to output
In active mode the MCU can block the audio from the input, and pass in audio from a DAC/amplifier
SSRs that I have found are too big for my application. I'm also not sure what effect they could have on audio (quality is important)
This is for a prototype, so working with .4mm BGA is somewhat out of the question

Here is what I have so far:

This IC is pretty much what I think I'm looking for, however I (personally) would not be able to use it: https://www.fairchildsemi.com/products/analog-mixed-signal/switches/analog-switches/FSA550.html#product-availability
The answer from jippie in this question MOSFETs or BJTs for using as switch for audio signals seems like it may work, however I'm concerned about the +6V input - would this need to be there in passive mode? It seems like the answer would be "no" but I'm not confident
This is different from most BT headphone circuits, since in headphones, the aux input usually trumps the BT, whereas here it is not the case.

Can anyone recommend either an IC that performs as a normally-closed analog switch w/o power or a circuit/application through which I can achieve my goal?


texts: What happens if a small Tesla coil is fed with a powerful Neon-sign transformer?

texts:
It is typically recommended to use a big neon-sign transformer (NST) for a physically big spark gap tesla coil.
Assuming the primary and secondary of a small tesla coil are tuned to have resonance on the same frequency, are there any problems associated with feeding a physically small tesla coil with a big NST (like 15kV 60mA)?
Example:
The original secondary has a diameter of 10 cm and a height of 50 cm (1:5 size ratio).
The alternative secondary for the smaller tesla coil has a diameter of 5 cm and a height of only 25 cm. The wire diameter is also put to half the size so the same number of turns can be used for the same height. This should give roughly half the inductance of the first coil (10 mH vs 20 mH).
Since the resonance frequency will be higher, this  must of course be compensated for on the primary side. Let us say this is compensated for in the primary coil only and the capacitor bank remains the same.
Will this blow up? Will the streamer arcs be shorter, the same, or longer than with the bigger coil? (assuming things are optimally tuned).


texts: what is the difference in u-controller processor sampling frequency and the z-domain conversion sampling frequency?

texts:
I have observed a bit confusing behavior of my system response (or may be i am missing something).

I have a transfer function in S domain converted to Z domain with a 1kHz sampling frequency at the time of conversion using matlab, When I embed this discrete version of the transfer function to my system which is also sampling on the same frequency of 1kHz. The system works the way as expected (i.e. the step response is the same as that of the s-domain analogue controller).

But if I increase the sampling frequency of my system while using the SAME discrete transfer function that i just converted from s to z domain with a SAME conversion sampling frequency of 1kHz , the step response gets further faster.

My question is that, why the discrete system gets faster response than the analogue one, despite the transfer functions of the analogue controller and the discrete controller are the same.

What I understand, the step response of any transfer function should remain the same in either case (i.e. either the function is in s-domain or in z-domain) the response should be the same ?

Does this mean the digital controllers have the ability to fast the response of the same transfer function by changing the sampling frequency of the system?

It is important, NOT to confuse the system sampling frequency of my u-controller at which the u-controller is collecting the samples from ADC, with the sampling frequency that I used as a parameter required to convert the s-domain transfer function to z-domain transfer function.

I thank you all for your time.


texts: I2C Address 0x00 not supposed to be showing up

texts:
I am currently trying to check all the sensors on my PCB with an I2C scanner to see that they all acknowledge. One of my coworkers had it over the past week and dropped it. When it was given back, there was another I2C address that has shown up on the I2C reader. There shouldn't be another address, given that all of the other sensors already have their own address and did indeed get acknowledged prior to dropping it.
More specifics on the board: This is controlled by an ATMEGA328, there is a power management unit (PMIC) with no I2C communication inputs, and 6 basic sensors that communicate with I2C to the ATMEGA328.
Does anyone have any ideas of what this address might be? Thanks :)


texts: Nodal analysis question (with supernode)

texts:
I am studying for the exam, and found this question.

Now, I know that you have to apply a supernode, but I don't know how. Any help is appreciated


texts: How different are the eMMC and SD Card protocols?

texts:
The eMMC protocol is freely available on the JEDEC website.
The SD Card (4-bit) protocol is not publicly available.
Many sources imply compatibility between SD Cards and eMMC, apart from differing bus widths.
How different are the protocols?
i.e. If I correctly implemented eMMC and reduced the bus width to 4-bits, would it work with an SD Card at full speed?


texts: Problem Outputting 2.5 Khz Signal ATTiny85 with Digispark

texts:
I am relatively new working with the Digispark IDE and I am having some issues with something that should be really simple.

I am trying to output a 2.5 kHz square wave signal, that will oscillate +/- 500 Hz. So it goes from 2000Hz to 3000 Hz from a micro controller that uses a ATTiny85 with Digispark's IDE.

I found this tutorial online: https://digistump.com/wiki/digispark/tricks which explains what I want to do. As they said, to modify the HW PWM frequency I changed the value from 64 to 8  of the MS_TIMER_TICK_EVERY_X_CYCLES inside wiring.c

Because of this I managed to get a higher frequency value. But I was not able to tune it, that is why I continued with the Software PWM manipulation

I have used this code:

#include <TinySoftPwm.h>
#include <DigiUSB.h>

#define HW_PWM_PIN               0 /* Used to check HW PWM with analogWrite() */
#define SW_PWM_BUILT_IN_LED_PIN  1 /* Digispark Model A (Rev2) built-in LED pin number (Change it to 2 for Model B) */
#define TIME_TEST_PIN            5 /* Used to check with oscilloscope micros(), millis() are still OK */

void setup()
{
   TinySoftPwm_begin(128, 0); /* 128 x TinySoftPwm_process() calls before overlap (Frequency tuning), 0 = PWM init for all declared pins */
   pinMode(TIME_TEST_PIN, OUTPUT);
   DigiUSB.begin();
}

void loop()
{
static uint32_t PwmStartUs=micros();
static uint32_t PwmStartMs=millis();
static uint8_t  Pwm=0;
static int8_t   Dir=1;
static boolean  State=LOW;
static uint32_t BlinkStartMs=millis();

  /***********************************************************/
  /* Call TinySoftPwm_process() with a period of 60 us       */
  /* The PWM frequency = 128 x 60 # 7.7 ms -> F # 130Hz      */
  /* 128 is the first argument passed to TinySoftPwm_begin() */
  /***********************************************************/
  if((micros() - PwmStartUs) >= 60)
  {
    /* We arrive here every 60 microseconds */
    PwmStartUs=micros();
    TinySoftPwm_process(); /* This function shall be called periodically (like here, based on micros(), or in a timer ISR) */
  }

  /*************************************************************/
  /* Increment/decrement PWM on LED Pin with a period of 10 ms */
  /*************************************************************/
  if((millis()-PwmStartMs) >= 10)
  {
    /* We arrived here every 10 milliseconds */
    PwmStartMs=millis();
    Pwm+=Dir; /* increment or decrement PWM depending of sign of Dir */
    TinySoftPwm_analogWrite(SW_PWM_BUILT_IN_LED_PIN, Pwm); /* Software PWM: Update built-in LED for Digispark */
    analogWrite(HW_PWM_PIN, Pwm); /* Copy Pwm duty cycle to Hardware PWM */
    if(Pwm==255) Dir=-1; /* if PWM reaches the maximum: change direction */
    if(Pwm==0)   Dir=+1; /* if PWM reaches the minimum: change direction */
  }

  /* Blink half period = 5 ms */
  if(millis()-BlinkStartMs>=5)
  {
    BlinkStartMs=millis();
    digitalWrite(TIME_TEST_PIN, State);
    State=!State;
  }

  /* Check USB is still working */
  if(DigiUSB.available()) /* Just hit "Enter" in the digiterm to check USB */
  {
    DigiUSB.read(); /* just to clear the Rx buffer */
    DigiUSB.println(F("DigiUSB is still alive!"));
  }
  DigiUSB.refresh();

}

It doesn't matter what I do, I am reading an oscillating 4.065 kHz - 4.049 kHz value.

What am I doing wrong?
Is my oscilloscope broken?
Should I be doing this any other way?


texts: Arduino project. USB+external power source - works fine. No USB - everything goes crazy

texts:
I have this circuit:

It is a simple project - a focus system for a taken lens and anamorphic adaptor. I have three pots. The first one I use as a manipulator. The second is used to get the position of the continuous rotation servo (JX DC6015 Mod) - motor#1. The third pot is used to control the position of the other continuous rotation servo (JX DC6015 Mod) - motor#2. There are also some buttons and diodes for calibration purposes. Motor#1 rotates the taken lens and motor#2 rotates the adaptor.

Well, let's look at the circuit. I also have there a 1N4007 diode and a 47uF cap. I use this scheme because the circuit even didn't turned on when I tried to power it from a battery. Now at least it turns on. But let's leave it aside for a moment.

The main problem is that everything works perfect when I use an external AC-DC adaptor (or battery) with Nano's USB connected to my laptop. As soon as I unplug the USB cable the system goes crazy. In case it is connected to the AC-DC adaptor it just starts rotating servos several turns CW and then backwards. In case it is powered just with a battery the servos just rotates CCW or CW very fast and never stop.

It looks for me like I have a GND loop problem. I tried to decouple my pots by adding 3 caps for each pot connecting a signal pin with GND, but things went even worse. It didn't work even with USB connected to Arduino. Servos rotated CW and CCW changing the direction very fast.

I tried two other Arduino controllers, but it was all the same.

I've tested all the GNDs. They are all connected together.

Then I decided to try to isolate VCC and GND from servo putting NME0505SC between power source and Arduino. But it didn't help as well.

What could be done to make it work just from one power source?


texts: Why Tcd and Tpd is different in combinational ckt?

texts:
In book Harris & Harris , there is a statement that Contamination delay \$T_{cd}\$, and Propagation delay \$T_{pd}\$ are different due to following reasons:
Different rising and falling delays,
Multiple inputs and outputs, some of which are faster than others,
Circuits slow down when hot and speed up when cold.
I understand that these factors will cause delay but, I don't get that , how contamination delay and propagation delay will be different for above reasons.
Please go to basics.


texts: What is the relationship between speed and torque in a separately excited DC motor?

texts: When a DC motor is powered by an external voltage source, as opposed to using shunt, series or compound configuration, how does speed relate to torque?


texts:
I'm a PC software guy, a newbie to electronics.  Recently, I've got a project in which I need to source for a DAQ that can provide dry contact inputs to an interfacing digital output controller.  The controller generates alarm signals.  I've uploaded the system diagram here -

Link to larger image: http://i.stack.imgur.com/KL88h.png

As shown in the diagram, the digital outputs are Form A relays that "are closing contacts with one common terminal (C) and one normally open terminal (NO). The terminals are isolated from signal ground.".  So the digital outputs are normally open and I suppose will close only when there's an alarm.  It is not indicated in the data sheet whether the digital outputs are wet or dry.

Here's how I figure it will work:

If the digital output relays are open, my dry contacts will not form a circuit.  If the digital output relays are close, my dry contacts will become a closed circuit and current will flow because the digital outputs are rated 250VAC/30 VDC, 2A??

But dry contacts are not suppose to have voltage or current? I can't figure how this part works out and will appreciate any pointers.  Thank you.


texts:
I am extremely interested in learning about electrophoretic displays. On their architecture, how they function and also would like to assemble one from the scratch for myself and see how it works (I have a bit of a chemistry background as well). So as you could see I am seriously in to this.

But so far I could not get hold of any good way of doing this after searching the web for some time.

I have a computer science background and my knowledge in electronics is very shallow. Would somebody be able to provide me some guidance on this? (Good online references, books etc. are welcome to be listed). If you think some college course would help, do let me know what type of courses I should be interested in following too.


texts: Finding datasheets for 30+ year old ICs?

texts:
Anyone who can lead me in the right direction for finding datasheet for some old ICs?
I've googled every possible variation of the numbers, which are:
MSM93H002-74 (DIP64, marked OKI/Intel), C1185 (DIP16, marked OKI) and
2904DX (DIP8, marked JRC)
Edit: These are all mounted on the main board of the air condition controller in an old car I'm trying to reverse engineer since some of the caps have spewed their electrolyte and etched away some of the traces.
It doesn't seem to be any clock/xtal sources on the board, so I'm doubting the DIP64 could be a microcontroller?
Thanks


texts: PCB surface finishing for underwater use

texts:
I need to find a very cheap way to detect water ad specific levels. No needs to have a linear measurement of its height.
I'm thinking about a simple FR4 PCB, with several couples of tracks. Each couple has a different length and ends with exposed pads. All the tracks are of course protected with the soldermask, but the exposed pads.
My question is about the rusting of the pads: what surface finishing should I use (if any) ?
Please note the water is for irrigation and is rich of mineral salts and nutrients.
EDIT
The range of measurement is 2 cm to 20 cm and the neck at the top of the container is less than 15 mm.


texts: RS232 and realterm communication problem

texts:
I am not seeing anything on a port in realterm though it is properly sending the data through the port. Anyone run into a similar situation? What am I doing wrong?

I am using a C8051F120 developers kit, a RS232 to USB converter, and realterm.
On the 8051 I have an example program running that mirrors input received on the input.
I have seen the data received then sent on the DB-9 end of the converter using an o-scope, but I haven't seen anything show up on realterm. The converter was working for a different project so it should be good.


texts: IAR EWARM Unknown or ambiguous symbol __probeCmd in .dmac file

texts:
When im  downloading and debugging my firmware to STM32G070 Nucleo board with IAR EWARM, im getting the following error message in the debug log, I tried researching about __probeCmd and .dmac files online, but couldn't gather any information.

Im using ST-LINK onboard debugger connected via PC serial port for debugging and downloading. Even though this error appears i'm still able to download and debug the firmware without any issues. Have anyone encountered this issue.


texts: Controlling a 5V power supply with a 5V signal

texts:
The might sound like a dumb need. Why if I have a 5V control signal would I want to control a 5V load? The issue I am up against is a voltage drop over a long run. In a home automation setup the installer used an extended run from a 5V power supply that is switchable because it is plugged into a wattbox for power cycling in case the end powered device gets locked up. This is a great feature to have but the problem that the long run created is now having an unreliable voltage at the end point device. (In other words, it works most of the time but not all of the time)
Ideally, rather than trying to boost the supply voltage to compensate for the long run, I would like to have this long power supply run become a control signal run rather than power. Then, at the end point use that 5v signal (which is more like 4.2 under load) to control a local 5v 2A power supply. I guess I could easily control the AC power going to the adapter via a solid state relay but then I get into needing to mess around with the high voltage side of things. I thought it would be easier to put a relay on the low voltage side of the local power supply but the SSR I first tried had too much of a voltage drop across the output connection and I was back to square one.
Is there a low voltage relay type solution that would work for this? If so, please call out specifics because I am lost to find anything that makes sense.
Do NOT suggest running a lower gauge number wire. That is not possible in this setup and I need to use what is there. I also want to keep the power management where it is. I just want the power supply to be localized for stability.
If I am going down the wrong road here and the AC side is the best place to control on the local end let me know that too.


texts:
I'm working on a 4 layers project - 2 signal layers (top and bottom), one internal ground plane and a "mixed" power tracks and ground internal plane which is the object of the question and that you can see below with a power plane like this:
In red, 12V, green 3.3V, black is ground.
There are no particular requirements for currents, we can consider that all tracks power small consumption ICs. 0-50mA.

Do you see a particular reason for this design vs "real" power planes roughly like this? I kept some black ground copper because there's an antenna strip on top layer at this location (yellow on the drawing.)


texts: What motion sensor to use for human breathing

texts:
I need a cost sensitive, reliable, durable motion sensor to track if a baby is breathing or not. This is for use in a university challenge project I hope to win. Any advice on my options are very welcome.
[edit]
criteria to be followedMy project should be cost sensitiveshould be low power Should be easy to use by untrained personel


texts: Errors transmitting 10 bit number read with Atmega328 via serial and reading it with "od"

texts:
I have ATMEGA328P-PU and I have hooked up the photocell to it. I'm using the following code to read the analog values and send them back to computer for debugging.

#define F_CPU     800000UL
#define BAUD      11400
#define BRC       ((F_CPU/8/BAUD) - 1)

#include <stdlib.h>

#include <avr/io.h>
#include <avr/interrupt.h>

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

double dutyCycle = 0;

int main(void)
{
    initSerial();

    DDRD = (1 << PORTD6);

    TCCR0A = (1 << COM0A1) | (1 << WGM00) | (1 << WGM01);
    TIMSK0 = (1 << TOIE0);

    setupADC();

    sei();

    TCCR0B = (1 << CS00) | (1 << CS02);

    while(1)
    {
        unsigned int  value = ADCW;
        UDR0 = (value*100/1024) ;
        _delay_ms(1);
    }
}

void initSerial()
{
    UBRR0H = (BRC >> 8);
    UBRR0L = BRC;

    UCSR0B = ( 1 << TXEN0 );
    UCSR0C = ( 1 << UCSZ00 ) | ( 1 << UCSZ01 );

}

void setupADC()
{
    ADMUX = (1 << REFS0) | (1 << MUX0) | (1 << MUX2);
    ADCSRA = (1 << ADEN) | (1 << ADIE) | (1 << ADPS0) | (1 << ADPS1) | (1 << ADPS2);
    DIDR0 = (1 << ADC5D);

    startConversion();
}

void startConversion()
{
    ADCSRA |= (1 << ADSC);
}

ISR(TIMER0_OVF_vect)
{
    OCR0A = dutyCycle;
}

ISR(ADC_vect)
{
    dutyCycle = ADC;
    startConversion();
}

I use the following command to view the sensor output:

od -d /dev/ttyACM3 -w2

I can see the output change based on the amount of the light, but it changes really weird, if I slowly remove the light source from the sensor I get this output:

      3542
      3298
      3142
      2799
      2243
      2142
      1799
      1543
      1542
      1537
      1542
       262
       257
      1542
       262
       257
      1542
       257
      1537
      1542
         1
       256
       257
       262
     65535
       255
         0
     65535
         0
     65278
     65535
     65278
     30969
     30968
     63736
     63993
     63737
     63479
     63992

First half looks great, but then it suddenly jumps to 63k, this happens every 10cm, then goes down from 63k to 0 then again jumps back to to 63k. can anyone please tell me how to convert ADCW to decimal value? I;m expecting number between 0 to 1024 as the output.

The manual says "ADC has a resolution of 10 bits, it requires 10 bits to store the result" doesn't that mean that it's a 10bit (16bit) instead of 8bit?


texts: Generic PIC 40-Pin and 18-pin development boards

texts:
I've looked at Guide in choosing good overall PIC dev board page already, but didn't really find what I'm looking for. I have found some 18-pin, 28-pin, and 40-pin PIC development boards at Sparkfun http://www.sparkfun.com/categories/9 . However, I want to find out whether I can interchange different models PIC chips with the same number of pins onto the board. I'm looking for development boards that have similar level of peripheral support built-in onto the board like the Arduinos or T.I. Launchpads. What do you know of the options?

On a second note, where can I get economical PIC programmers?


texts: RTC Battery Voltage Error; Non-Ideal Op Amp Error?

texts:
First post here from a hobbyist electronics guy so please bear with me.  I'm happy to do whatever I can to improve my question for the community.

For a bit of a backstory, I have a project that requires an RTC for a Raspberry Pi.  I need the RTC to be thin, at least thinner than most modules you can buy, and I want to be able to read the voltage of the battery so I can get a warning if the voltage gets low before it fails.  So, I designed a board using the DS3231M for timekeeping and an ADC with a voltage follower to read the voltage without affecting the battery current draw much.  The Op Amp is an LMC7101BIM5/NOPB and the ADC is an ADC081C027CIMK (see URLs below).

Here is the schematic, board layout, and zip'd eagle folder for reference:

Eagle Files

When the board is attached to the Pi it works great; I can read the clock and can read the voltage from the battery through the ADC/voltage follower.  But when I disconnect it with the battery in, the OSF gets tripped.  I used this basic design for another RTC (without the battery voltage reading) so I'm sure the battery is connected fine.  I used my multimeter and it turns out that while the battery reads ~2.8V when the Pi is on the voltage is <2.4V when power is removed.

My thinking is that it has to do with the Op Amp.  I cut the trace connecting the battery to the voltage-reading circuit and the voltage went back to ~2.8V so my thinking is that it's a problem with the Op Amp implementation.  I assume that it has to do with me operating under the assumption of an ideal Op Amp.  I thought maybe the battery was attempting to power the circuit through the Op Amp, drawing too much current, and dropping the voltage.  So I solder-bridged the trace I cut earlier, cut the trace to the Op Amp supply, and soldered in a diode (I don't care about the voltage drop as long as I can still "see" a voltage drop to give a low-voltage warning).  This helped a little, but the voltage is barely >2.4V and the current is only somewhere around 1 mA.

Any help is appreciated, even if it's just about my schematic/board layout.

Also, it would kind of suck to switch designs at this point, but i think there may be battery ICs that handle this kind of thing.  Would it be worth it to switch to something like that?

I can't post more than two links, so I'll post the component URLs as comments.


texts:
I've got a question regarding the location of the resistors used to configure USB. I'm currently designing a board with an STM32 chip, on the left of the diagram and want to have USB broken out, on the right. My question is, does it matter on the order of the resistors, so for instance, should it be the High speed pull up R11 first, and then the 2 termination resistors, or should it be the other way around or does it not matter at all?

On a side note, is my USB configuration correct? Are the D pins meant to be criss crossed like that?


texts:
I asked a question the other day but am still unsure, I just bought a 0-30v 0-5A dc regulated power supply today and want to use it to play around with various DC motors, I was told I didn't need to worry about a fly back diode with a straight motor one the other question but the store I bought it from still recommended and sold me a 10A07 diode, the data sheet is in this link http://pdf.datasheetcatalog.com/datasheet/mcc/10A07.pdf

My question is, is it really needed?, the guy at the store said its just safer to use one so i figured why not. After looking at the data sheet it seems it can handle up to 1000V reverse voltage so im assuming its good.

The power supply is only a cheap $150 AUD one so im not to sure if it would have the proper protection but I have read that fly back diodes are mainly used with transistors, Is that true and did I get sold something I don't really need or would it still pay to use it anyway? Im completely new to electronics so any help would be appreciated.

Thanks in advance


texts: how to detect variations of small resistances

texts:
I have a load cell whose resistance is varying between 318.0 and 318.8 Ohm. I have used a voltage divider but still the output voltage is rarely changing when the resistance changes.

Is there any electric circuit that I can use in order to model the resistance variation in terms of Voltage variation?


texts: How to determine time needed to stay in a voltage vector state in Space Vector PWM for 3 phase inverter?

texts:
I need some clarifications on how and when to switch between voltage vector states (for the sake of discussion lets take V1 and V2 in the image below).

Below is the image of 6 possible voltage vector states for SVPWM drive.

To modulate Vref at inverter output, we need to apply V1 state and V2 for specific amounts to times. Equations time T1 and T2 are given below

Okay now I know the time, the sector I am in (sector 1 in this case) and angle, Vref magnitude. All is set.

Now lets see the which switch is on for each voltage vector state (i.e V1,V2 and so on). Below is the image for that:

It can be seen that for V1 top 2 switches are on and one bottom switch is on.(lets call them S3,S5,S2 respectively), similarly switches on for all V-states can be interpreted from the image.

Given the following table for switching time for each Switch (S1,S2 and so on):

My Questions:

Q) Lets say Im setting switches on for V1 state (S3,S5,S2), I need to know, do I need to set these switches On simultaneously ?

Q) Relating to question asked before, once all the switches are on, do I also need to turn them off simultaneously ? (By that I mean, adding times for S3,S5,S2 and switch them according to their sum and not by their individual time)

Also please clarify, if we donot need to switch switches on simultaneously then which switch shall be turn on first(For each V-state) ? What will be the precedence ?

Please be explicit when answering my queries, since im coding algorithm for this, I need to know exactly whats going on. Thanks!


texts: Calculating the right size for super capacitor

texts:
I have a circuit that draws a constant 0.15A and it is powered from a 9V power supply which is immediately stepped down to 3.3V through a linear regulator (LM1117T).  My goal is to power the 3.3V portion of the circuit (through the 3.3V regulator if necessary) for 3 seconds after the 9V power is removed.

I used the calculator here and determined that a 0.22F capacitor would power my circuit for 8.25 seconds which is much longer than I need.

Unfortunately when I connect the capacitor it doesn't power the circuit for hardly any time at all.  I added all the capacitors I had to the circuit (three parallel banks of two 5.5v 0.33F capacitors in series) for a total of 0.495F and it only powers my circuit from the 9v side for 1 second.

What am I missing here?


texts:
I have always this mindset that to drive a MOSFET you have to apply a certain voltage to the gate of the mosfet to turn it "on" But it would seem that it not entirely true, you have to apply a certain voltage into the gate with reference to the source pin not necessarily the ground pin (correct me if im wrong).

For situations stated below i will use the two ADVERTISED as LOGIC LEVEL MOSFETS the BUK9134(NMOS) and FDS8935 (PMOS)

When both used as a switch the NMOS is pretty much staight forward, because NMOS is typically used as a low-side switch a logic-level NMOS like mention above will always turn on at logic 5v HIGH because the gate pin is referenced to the SOURCE pin which is connected directly to ground(which the Logic ground is also referenced). So no matter what voltage that im switching the mosfet will turn on and off with my logic singal. (Again correct me when im wrong about something)

Here is where im confused about. PMOS on the other hand Works the same As NMOS but when used as a typical high side switch the Source pin is not connected to ground but to Vcc!.

Now at logic 5v high my mosfet will probably gget destroyed because the voltage at the gate (referenced to source) will be -45v which is waaay past the +- 20. Now thats not ideal since the the highest i can run it with my 5v logic is 20v way below its rated 80v. If that is so why advertise PMOS's as "logic level gate" (Digi-Key) when with common logic levels i wont be able to use it properly on high voltages(or currents). Is there a trick that i dont know off to drive it at logic level ?? Pulling it up to source voltage seems also not ideal because for example of the IC i mention if my source voltage is 50 the voltage at the gate is 50v witch is beyond its capability of +-20v.


texts: Gerber interpretation of "clear" on silkscreen

texts:
I've had some PCBs back from my manufacturer which I haven't used before, and was surprised with some silkscreen printing which I consider to be an error.  The bottom should have had no silkscreen printing at all, but I supplied a Gerber for it to unambiguous.  The boards are well made and the top silkscreen is completely unremarkable and correct.

My question is: with a just single %LPC command and some subsequent D03 flashes, am I correct there should be no printing?

The Gerber was made by LibrePCB, which appears to output the desired silkscreen drawing commands followed by clear flashes where there is no soldermask, to prevent silkscreen printing over pads.  If nothing is desired, all you end up with is %LPC and the "print-nothing-here" flashes.

gerbv, Ucamco's reference viewer, Mayhew Labs' 3d viewer all show a blank image for my file.

Here is that unexciting but correct image (shown with outlines layer):

I believe that something in the manufacturer's preprocessing, perhaps to do with panelisation, has a bug for a Gerber file with only clear flashes.  Their image is as if I'd asked for a solid white rectangle the exact size of the bounding box of my clear flashes, followed by all the clear flashes.

This following is the essence of my Gerber file, with my interpretations from the Gerber standard revision of 2019-06 at Ucamco.

001:%FSLAX66Y66*%                 | Format specification 6.6, 6.6
002:%MOMM*%                       | File is in millimetres
003:G01*                          | Set Linear Interpolation graphics mode
004:G74*                          | Set single-quadrant mode
005:%ADD10C,1.7*%                 | Aperture definition D10 = circle 1.7
... few more aperture definitions
013:%LPC*%                        | Load polarity is 'clear'
014:D10*                          | Set current aperture = D10 (circle 1.7)
015:X15240000Y5080000D03*         | Flash (15.240000, 5.080000) with D10 (circle 1.7)
016:X15240000Y10160000D03*        | Flash (15.240000, 10.160000) with D10 (circle 1.7)
017:D11*                          | Set current aperture = D11 (circle 1.6)
018:X20320000Y-5080000D03*        | Flash (20.320000, -5.080000) with D11 (circle 1.6)
more D1X and X..Y..D03 flashes
078:M02*                          | End of file


texts:
I have an issue with openOCD, I want to flash an : ATSAM4S2CA, and  Iget this error :

SAM4 ChipID 0x28ab07e0 not found in table (perhaps you can ID this chip?)

I just don't know what I should do to solve it, any idea ?
thanks in advance


texts:
I am designing a watchdog circuit to read a number of 15 signals (analog and digital), so I decided to use MPC506AU as shown in the picture.
First of all, can I supply it with +5 volts and leaving the negative voltage supply pin floating? Is it fine to pass different signal types (analog & digital) without affecting the values of these signals? Can I connect the enable pin and Vref pin to the same power supply? Will the signals affect each other while the Mux turned off?


texts: this is just a quick and dirty question. I don't understand the purpose of the  1 \$\mu\$F caps in the MAX232 circuit. What do they do, exactly? Can they be skipped? Can they be swapped with 10 \$\mu\$F caps?


texts:
On my circuit board, I have three different voltage regulators. I have a 5V Buck converter that goes into a 3.3V LDO and then finally 1.8V LDO. When I power the board with a USB and do not use external power, I get a good 1.8 Volts on the output of the 1.8V voltage regulator.

When I use external power, I get 3.26 Volts output on the 1.8V voltage regulator. My design is already extremely noisy, which I will be fixing on the next design. My questions is, can excessive noise on the 3.3V rail cause a voltage regulator to output 3.3 volts? Or is there something else going on here?

I am using the TLV702 Voltage Regulator. DataSheet

I have shown the waveforms on my oscilloscope of both the 1.8V and 3.3V voltages when powered with USB and External Power. I also included the measurements with the probe at 1x and 10x.

I have also included the schematic of the 1.8V Voltage Regulator.

Edit: I have added the schematic for the Buck Converter and the 3.3V Regulator


texts: How many lumens does an incandescent halogen bulb provide?

texts:
I got my hands on an old slide projector (the kind that projects cel slides onto a wall).

The light source, is a 24V, 150W incandescent halogen lamp.

As a little pet project, I'm thinking of converting this projector to LED, using a high power LED. To do that, I need to remove the lamp mirrors, replace the existing lens with a reflector and collimator lens, add a heatsink, etc.

But before even attempting this, I need to know how much light I need.

I've used a conversion table to estimate the number of lumens that I need. My estimation is between 3.6klm to 5250lm  (I've used "tungsten quartz halogen (12–24 V)" and "photographic and projection lamps", I don't really know which one is applicable in my case).

Only once I know how much light I need, I can deduce what kind of high-power LED I need.

I have no experience in photometry as such, is using Lumens as a comparison value even applicable?
Are my estimations correct?

I was looking at getting a 100W LED, which supposedly provides 10klm, and then add a PWM controller to dim it, if necessary. But it seems that a 100W LED is pretty overkill to me.


texts: What is purpose of zener diodes in this circuit?

texts:
I am reading the I2C tutorial: https://learn.sparkfun.com/tutorials/i2c/all

Why wouldn't it work without the zener diodes? What functionality are they adding? They are just there to keep the voltage at a constant level when the logic is 1 right? When the logic is 0, the transistors are on, and the zeners do more or less nothing right?


texts:
I own an arcade crane machine that stores its music on a API840N sound chip and i'd like to change the music that the machine plays, I've taken a look at the data sheet but it doesn't go into detail on how audio is programmed onto it's internal EEPROM.
Could someone explain to me the easiest way I can go about reprogramming this sound chip?
Thanks!


texts: Using a laptop charger with the wrong polarity?

texts:
I just bought a replacement charger for my Fujitsu Lifebook AH532, but it seems like it has the wrong polarity. The backside of the laptop has a label saying it should be like this: https://imgur.com/0IgstAe. That's also how the original charger looks.
The site I ordered from had a picture of an adapter that looks to have the right polarity, although it's kind of blurry. However, the adapter I received had it reversed:
https://imgur.com/a/dWuh4

As I understand it, it could damage the laptop if you use a charger with the wrong polarity, but some places I've read say it could be fine.

Is it possible the adapter I received is mislabelled? And if it's not, what could the consequences of plugging it into my laptop be? I don't have a battery for my laptop anymore, in case that's relevant.


texts:
I have made a PCB with a few minor mistakes which have been fixed by running wires around my micro on my board. This does not look great and I am hesitant to hand it over to my clients with those modifications visible.

Is it possible to create an epoxy blob around my micro at home in order to hide these modifications? Are there other alternative ways of concealing the error?

This is the type of blob that I am referring to: to.


texts: Do pads 6,7,8 have to be connected with pad 12 in this layout?

texts:
In eagle there is a line that says these have to be connected but the data sheet doesn't mention it.

Here is the data sheet in case it helps https://www.mouser.com/datasheet/2/468/RPX_1_0-1903909.pdf


texts: Are nano/cube satellite electronics components special for space?

texts:
I was reading CubeSat 101 (https://www.nasa.gov/sites/default/files/atoms/files/nasa_csli_cubesat_101_508.pdf) wondering if the electronics components needed to be special for space but it says nothing about the actual parts that make up the electronics. I've run into "radiation hardened" FPGAs in the past and I assumed they were for space application but I was just guessing. My question is for regular stuff like resistors, caps (maybe not electrolytic, I assume they'll vent) and MCUs. Like ... can I use a PIC24 or PIC16/18 without issues or are there special MCUs for space applications?
EDIT: I think this post answers the MCU part of my question: (space-grade microcontrollers)
What about the resistors, ceramic caps, inductors, etc?
Do all active components (MCU, transistors, etc) have to be special?


texts: Non-isolated Off-line AC to DC Power Supply

texts:
I found two very similar designs (ignoring the LDO on the first one) of this type of supply and was curious if one is better than the other and if so why.

I guess a 15V zener is slightly more expensive and takes up a bit more space than a 220pF capacitor so I guess the first design takes the lead in those aspects..

Also, what sets the maximum current that can be drawn? Can it easily be modified to provide say around 200mA?

Thanks in advance!
/englund


texts: Are too low/changing voltages damaging (to Arcade PCBs)?

texts:
This is about Arcade PCBs (like a Neo Geo MVS or Sega Naomi) and it might actually be two questions.

An arcade power supply (JAMMA compatible) supplies +5V, +12V and -5V. The +5V line can be dialed up and down a little and for some PCBs it has to be set up right or they won't run at all.

Should I use a "+5V" voltage that is just high enough to get my device to run or should I try to get as close to the specification (if available) as I can? As an example, for a Sega Naomi you will find statements like "use exactly +5.0V" or "just don't go higher than 5.1/5.2V", but I found it might run at 4.85V as well.

And, as I have to measure voltage while the device is running (correct?), is it better to change the voltage while the device is running or to switch the device on and off between changing voltages? I heard arguments against both options, but as far as I know you have to choose one. I am more worried about long term damage, than about comfort. This is about the PCB not the user.

On a related note, there is this notion going around that a device might "get used to" some specific voltage. Is there any truth to that?


texts:
I have a computer outside its case. All the components are attached and working properly, the problem is that fans dont seem to do a good enough cooling when demanding programs such as high end games are run, so the fans go crazy sometimes and the room with the computer gets increasingly warm especially with the door closed. I cant afford a commercial liquid cooling system so I thought I'd try to build my own.

So my plan is to buy these things:

A small refrigerator.
A plastic box big enough to hold the motherboard and the components attached to it.
Enough oil to will the plastic box almost full.

So I'm going to submerge the computer in some form of oil. I'm not sure which kind yet. Since oil is better at absorbing heat than air is, while preventing freezing and water vapour on the electrical components it should be the perfect solution to keep the computer cool and running smoothly. Even if I overclock it as much as I can.

The only two components that need to sit outside the fridge is the cd-rom and the HDD. I'm not sure the cd-rom station is even necessary since the oil computer is going to be on the same network as my main computer so I can just transfer any files or share the cd station in my home network. But the hard drive being the only mechanically moving part might not fare too well in oil so I'll leave it dry on the outside of the fridge.

I'll bore a small hole somewhere in the fridge from where all the cords can come in/out.

Questions: What kind of oil should I use? I saw a video where they used mineral oil, but thats probably too expensive and they thought vegetible oil would go ranchid (which it doesnt even after years in room temperature.) Do you have any tips I should keep in mind to avoid destroying my computer as much as possible?


texts:
I know I posted a question about this circuit before, but I'm running into a problem. I know this is a terrible equalizer design but I'm trying to learn to put in use what I learnt with Op Amps and transfer functions.
I did the following equalizer using 3 band-pass filters with each one made of a high pass filter connected with a low pass filter via a unity gain op amp for low frequencies, mid frequencies and high frequencies.
I used a inversing amplifier with \$V_{out}=\frac{R_2}{R_1}{\cdot}V_{in}\$ for the gain and then solved for: \$Gain=20\log_{10}{(|H(s|)}\$.
The problem is about the gain I'm trying to get in each band pass filter. I tested it with -10 dB gain on the low frequency band pass filter, 0 dB gain on mid frequencies and 10 dB gain on high frequencies based on the resolution of the above equation with \$R_1=1\$ \$k\Omega\$.
The schematics is the following:

And the simulation yields the following for the amplifier at the 3 different band pass filters:

Where the only working gain is the 10 db on the low frequency band pass filter.
For example for the -10 dB gain:
\$20\log_{10}{(\frac{Z_2}{Z_1})}=-10\implies Z_2=Z_1{\cdot}10^{-10/20}\$
So I don't know what's wrong.
Thank you very much!!


texts:
The datasheet says:

POWER-UP SEQUENCE
Because the DAC output voltage is controlled by the voltage
monitor and control block (see Figure 42), it is important to
power the DVCC pin before applying any voltage to the AVDD
and AVSS pins; otherwise, the G1 and G2 transmission gates are at
an undefined state. The ideal power-up sequence is in the
following order: GND, SIG_GND, DAC_GND, DVCC, AVDD,
AVSS, and then the digital inputs. The relative order of powering
AVDD and AVSS is not important, provided that they are powered
up after DVCC.

I can't see in the document any information about how much time after DVCC the other rails should rise up.
My question is: it's ok to power all the rails together (+12V and +3.3V come from LDO, -12V from ICL76660A) minimizing the time when G1 and G2 are in an undefined states, or it's mandatory to delay AVCC/AVSS? In such a case, what's the minimum delay needed?
Figure 43 shows an external circuit to delay AVdd but the text says:

C1, R2, and R3 are the main components that dictates the delay from DVCC enable to AVDD. Adjust the values according for the desired delay.

Well, I really haven't a desired delay... they seem to have one!


texts:
In the ARM Cortex-M3 processor core, the memory map contains: a Code region, SRAM and a RAM. What makes the use of the code region different than the other memories? In addition, what is the nature of the (memory) of the code region?

Thank you.


texts: Choosing the best FM demodulation technique

texts:
I have an FM signal: 200 mVpp, 11.5 MHz carrier, max deviation - 500 kHz, modulating signal frequency range is 40-10000 Hz. And I need to demodulate it with highest SNR possible.

The circuit has to be low voltage (3.3V or lower), low power and low profile (<4mm, so no large inductors or transformers). What are the best ways to demodulate the signal?
I've found this circuit (autodyne frequency converter and pulse counter), it has very low power consumption, can be made in low profile and doesn't require much tuning, which is also great, but I'm not sure about it's noise performance. I also think about multiplying signal frequency 4-5 times with PT7C4511 clock multiplier and then demodulating it with TLC2933 PLL.

UPD: I've found an interesting patent which claims low noise demodulation. What do you think?


texts:
I want to detect objects crossing a line. I decided to use one IR led (with a 555 circuit to generate a 38khz signal) and one 38khz receiver (TSOP1738). But after testing it on a breadboard I found out that TSOP1738 has gain attenuation, if it receives a 38Khz signal for a "long" period it will turn the internal amp gain down. I want to use 38khz signal to avoid interference with possible ambient IR lights.

How can I solve this problem?


texts:
I have an audio mixer which can run on two 9V batteries in series.  I'd like to run it off a single 12V supply.

Can I use two 12V-9V DC-DC converters both running off a 12V battery?
Will the connection to the 12V battery short the 9V series connection?

The mixer is a Behringer 1002b, the AC input adapter is 16V and 3V.
When I test with batteries I get 18V across the power switch


texts: Finding the resistivity of doped silicon sample

texts:
Given that the mobility of electrons and holes in silicon is given by equations 1 and 2, I'm trying to find the resistivity of a sample which has been doped with a donor density of:

$$N_d=2\times 10^{15}cm^{-3}$$
$$(1) \space \space μ_e=92+\frac{1270}{1+(\frac{N_d}{1.3\times 10^{17}})^{0.91}}$$
$$(2) \space \space μ_h=48+\frac{447}{1+(\frac{N_a}{6.3\times 10^{16}})^{0.76}}$$

Here is my attempt:

We know that drift current density is given by the following equation:

$$J=q(nμ_e+pμ_h)E$$

From here, we can easily get the resistivity:
$$(3)\space\spaceσ=\frac{E}{J}=\frac{1}{q(nμ_e+pμ_h)}$$

Here is where I'm stuck:

To apply equation 3 I need the electron density n and the hole density p. We can approximately say that n=Nd since the number of donors is much greater than the intrinsic density of free electrons. However, I still need p which (at least to my knowledge) I can only get from the equation:

$$p=\frac{n_i^2}{N_d}$$

Neither intrinsic density ni nor any information to calculate it are given by the problem. So, I can't find p. Is there any other way ?


texts: Result of increasing number of stages in pipeline processor

texts:
We are learning about singlecycle/multicycle processors and in the book it is said

  Pipeline processor is k(number of  stages) times faster than single cycle processor.

However at a later point it is said that the number of stages doesn't matter, clock's period is the only thing affecting the speedup. Which  one is it I'm confused.


texts: Restart execution from the start without having to reload

texts:
I am using GDB to load and debug my executable. At the moment, each time I want to run my program I first have to load it, and then continue it to start execution.

Apparently the run command starts execution from the start, but when I try to run I get the error:

The "remote" target does not support "run".  Try "help target" or "continue".

My board is an STM32F2. Is there a way to easily start execution from the start of the executable without having the reload the damn thing onto memory again?

EDIT: I have tried Leo's suggestion, but when I do run I get the following error:

(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) [answered Y; input not from terminal]
../../gdb-7.2/gdb/thread.c:79: internal-error: inferior_thread: Assertion `tp' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) [answered Y; input not from terminal]
../../gdb-7.2/gdb/thread.c:79: internal-error: inferior_thread: Assertion `tp' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Create a core file of GDB? (y or n) [answered Y; input not from terminal]

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.


texts: What must be the minimum input voltage of a series regulator?

texts:
I'm designing a series regulator. I need 3.3V in my circuit, the circuit has 5V and 9V available in it.

What should be the minimum input DC voltage in a DC series regulator in general case?
In this particular case, is 5V enough, or should I supply it with 9V?

BD135 Datasheet

EDIT:

Below is an alternative circuit with opamp. You can also discuss on this one.


texts:
I'm working on a servo project. I connected 12 servos to a single Adafruit servo shield and plugged in a 5V 10 amp (http://www.adafruit.com/product/658) switching power supply to the shield. Instantly, the motors became very hot and one of the motor became unresponsive.

What could be the reason for this? The only rational reason would be that a large amount of current went through the motors but physically how could this happen? I thought V = IR, since voltage at 5 V, then current should have been divided evenly across the motors so it would have been very small?


texts:
I'm currently on an adventure into digital electronics. I've built a bunch of logic, but to test it I need a clock source.

Is there a way I can “easily” construct a square-wave oscilator adjustable from 1 Hz to, say, 10 Hz?

Currently I have a big stack of 74HC00 chips, some LEDs and some resistors.

One of my old electronics books had an LED blinking circuit which (from memory) used a NAND gate as in inverter, and put a capacitor across it to slow it down. Those were 74LS00s though. So, TTL. I doubt my CMOS chips would enjoy the very slow rise time of a large capacitor.

I suppose the “standard” solution is to just build a one-transistor oscilator. But from what I've seen, transistor circuits are always an insanely complex network of dozens resistors and capacitors. I'd like something simpler if possible. (Besides, they're usually sinewave oscilators, not square wave.)

I guess maybe I could buy a Schmitt-trigger inverter and use that with a capacitor... It seems a shame to have to buy an entire batch of parts just for the clock. But I think I'm probably going to have to do that anyway. (At the very least, it seems an oscilator requires some kind of energy-storage device, and I currently have none.)

(The other alternative is a crystal — but I don't understand how those work, I suspect you still need lots of additional components, and I highly doubt anybody makes a 10 Hz crystal.)


texts:
In the slides of the following link is expressed the concept I am trying to understand : slides

I am studying control systems. I have seen that if I have a zero in the RHP, by using decoupling I can move the zero from one input/output channel to another, so we can choose where it create less problems.

I have that this concept is not really clear to me. With a decoupler I can transform the transfer matrix into a diagonal matrix, so that the first input influences just the first output and the same for the other channels, but what does it means that I can move the RHP zero?

For example, consider the transfer matrix:

\$G(s)=\begin{pmatrix}
\frac{2}{s+1} & \frac{3}{s+2}\\
 \frac{1}{s+1} & \frac{1}{s+1}
\end{pmatrix}\$

So, I am considering a system with two inputs and two outputs.

I use a decoupler of the type:

\$\begin{pmatrix}
-1 & 1\\
 1 & \frac{-2(s+2)}{3(s+1)}
\end{pmatrix}\$

then the transfer matrix after applying the decoupler will be:

\$\begin{pmatrix}
\frac{s-1}{s^{2}+3s+2} & 0\\
 0 & \frac{0.3s^{2}-0.3}{s^{3}+3s^{2}+3s+1}
\end{pmatrix}\$

It can be seen that the original transfer matrix has a zero in the right half plane, so with positive real part, at \$s=1\$ since \$det(G(s))=0\$ for \$s=1\$ .If I apply the decoupler I have that in both channels I have a zero at \$s=1\$ , so with positive real part, which imposes limitations in the achivable bandwidth in the frequency response.

So, what does it means that with the decoupling it is possible to move the unstable zeros from one channel to the other?


texts: I was looking at an example board schematic provided by TI and I noticed something rather curious: vias were placed directly on SMD pads. Is this a normal/acceptable practice to follow? Or is it recommended/better to put a short trace and then have a via?


texts: Making a magnetic levitation system with arduino

texts: I am planning on making a magnetic levitation system with an arduino that checks the value of a hall's effect sensor twice per second (but I have tried even 1000 times a second though) and turns the electromagnet on or off based on the hall's effect sensor's value. I have managed to check the output voltage of the sensor and turn the electromagnet on/off too but when a magnet is placed below the electromagnet it either sticks to it (then falls) or falls immediately. Now I am starting to believe that my idea is impractical but before I abandon my project, I'd like to know: is my idea practical? Can it be done? If so do you have any advice on what could be wrong? If not what can I do to make it practical?


texts: Can anything be done about this AVRISP mkII or is it dead?

texts:
It seems that my AVRISP mkII programmer died in a strange incident. It was connected to my computer via USB cable and to a custom board which hosts an ATXMEGA32A4U via its 6-pin programming header. The on-board connections for the programmer are according to Atmel's E-Schematic-Checklist (sect. 4).

The AVRISP stopped working (all lights went off) as I connected the board's power supply (an on-board LDO regulates the supply voltage to the 3.3V required by the microcontroller).
Apparently, when the programmer is inactive there is some pull-down on the reset line, therefore the ATXMEGA at first seemed dead too. However, after disconnecting the programming cable the ATXMEGA resumed operation. It still works flawlessly and the LDO delivers 3.3V as expected.

After the incident I had no power on any of my computer's USB ports, therefore I powered down my computer, disconnected and reconnected mains power, which returned power to the USB ports. But as I connected my AVRISP it still showed no reaction (no power loss on the USB ports this time though).
The OS did not even detect connection of a USB device, as dmesg did not report anything (note: this is on Linux).

I switched the programmer's USB cable, but that did not help. I opened the case to see if the AVRISP has any visible traces of damage, but it looks fine, as far as I can tell. Here is a picture of it (USB connector on the left, 6-pin programming header on the right):

Is there anything that can be done about this AVRISP or must I assume that it is damaged beyond repair? And what might be a likely explanation of this strange death?

EDIT: As suggested by Raj I have measured the voltage levels in what seems to be the power supply section of the device. In the above picture, the traces marked in red carry 5.05 V, everything else in the vicinity is at 0 V. It seems that the IC close to the lower left corner is an LDO which is defect. The package reads "BDR 391 ADFX", does anyone have an idea which device this might be?

EDIT 2: As suggested by Tom Carpenter I have bypassed the defective dc-dc converter, however now the supply voltage drops to 4.5 V and the device indicated in the picture quickly gets very hot.


texts: How to change rotation direction of 3-phase electrical machines?

texts: I was taught that if you want to change the direction of a three phase rotating machine that is rotating in forward direction, you interchange the phases. Since the phases has the same features (voltage and current), what is responsible for making the machine to rotate in reverse direction, when the phases are interchanged?


texts: Is there anything I can do to simplify this even further?

texts:
I feel like there is something more I can do, especially with the current source.
The voltage in the voltage source is 4.024 V, and the resistor is 2556 ohms.


texts:
I recently bought a vtech cordless phone, only to discover the adaptor is not 110-220 ac to 6v ac. its almost impossible to find a 220v ac 6v ac in my part of the world.

my question is, can I use a 220v ac 6v dc instead?

thank you for all your response.

I did not realize the vtech phone I bought 4 years ago is also ac/ac and I have been using a 220v ac 6v dc for it. Yikes! should I stop using it? no problem so far.

Is this youtube video to convert AC-DC Adapter To AC-AC accurate?

https://www.youtube.com/watch?v=AnowEUtkUws

thank you

lar


texts: What is specification connectors used in dji manifold 2

texts:
i'm Filipe
I'm looking about what is connectors specification  used in DJI manifold 2, unfortunately in datasheet there is'not information about this specification only it talks about communication port.
Somebody could you help me?
I need to know whatconnectors specification to buy for my search.
1 - RJ 45
2 - USB A
3 - HDMI
4 - Antenna ports
5 - connector XT 30
6 - Power indicator
7 - USB micro B
8 - UART PORT, what is connector specification ?
9 - CAN PORT, what is connector specification ?
10 - I/O PORT, what is connector specification ?


texts: Why doesn't 802.11 based technologies LTE need time sync?

texts:
I have been reading on 802.11p vs C-V2x, the two technologies for vehicular communications. One disadvantage for C-V2x that is frequently mentioned is that C-V2x needs all the UEs to be time-synced which may not be possible in out-of-coverage areas.

My question is why doesn't 802.11 based technologies need the same time sync ? C-V2x is based on LTE and time-sync is needed for resource scheduling.


texts: What are the pins for in this Relay module?

texts:
I am trying to figure out how to use this relay module. There is no datasheet that I could find for the whole module, there however are for individual box.

Here is the picture below, there are three jumper pins which read VCC, VCC, GND. And there are four activator pins (I guess) they read  GND, IN1, IN2, VCC

At the output end, I got current coming in connected to Middle terminal and receiving wire connected to the one showing Isolated line.

To activate it, I am applying 3V DC -ve on the GND (on the activator pins set) and +ve on the IN1.

Am I doing it wrong ? Here is the URL for further info: http://www.miniinthebox.com/2-channel-5v-high-level-trigger-relay-module-for-arduino-works-with-official-arduino-boards_p727426.html


texts: Function of a component in a Ethernet Board

texts:
I want to know what is the component located next to the Ethernet input for. I guess it is for filtering, but I'd like to know it's name and it's main function if possible. Here it is the board:

The component name is Tonyo FM 208L but I can't find the datasheet of it. Any idea of what it could be? Maybe a rectifier? Any help is appreciated!


texts: Electrical problem;maximum power transfer;confusion

texts:
In the network of figure,the maximum power is delivered to \$R_L\$ if its value is ______ \$ ?\$

simulate this circuit – Schematic created using CircuitLab

where, \$ I_1 \$ is the current flowing through \$ AB \$ via \$ A \$ to \$ B \$

My Approach:
we know for maximum power delivered to \$ R_L \$ :
\$ R_L = R_{TH}\$ where \$ R_{TH} \$ is the Thevenin's Resistance
To calculate  \$ R_{TH} \$ :
Process 1:
\$ R_{TH}= \frac{V_{TH}}{I_N} \$ or  \$ R_{TH}= \frac{V_{OC}}{I_{SC}} \$
For \$ V_{OC} \$ :

Applying KCL at node \$A\$ : $$0.5 \times I_1 = \frac{V_{OC}}{20} + I_1$$ $$\implies V_{OC}=- 10I_1$$ and $$I_1=\frac{V_{OC}-50}{40}$$ so,after solving for \$ V_{OC} \$ we get: $$V_{OC}=10V$$
In a similar fashion we calculate \$ I_{SC} \$ by shorting \$ R_L \$ and get $$I_{SC}=0.625A$$  $$\therefore R_{TH}= \frac{10}{0.625}=16\Omega$$
Hence,maximum power is delivered to \$R_L\$ if its value is \$ 16\Omega \$

Process2:

Here, \$ R_{TH}=\frac{V_a}{I_a} \$ where \$ I_a \$ is the current flowing out from \$ V_a \$ voltage source
so, \$ I_1 = \frac{100-50}{40}= \frac{5}{4} \Omega \$
so applying KCL at node \$ A \$ : $$0.5 \times \frac{5}{4} + I_a = \frac{100}{20} + \frac{5}{4}$$ $$\implies I_a=\frac{45}{8} A$$ $$\therefore R_{TH}=\frac{100}{\frac{45}{8}}= 17.78\Omega$$
Hence,maximum power is delivered to \$R_L\$ if its value is \$ 17.78\Omega \$

Thus,which process is right? please help....


texts:
I want to use a current sense resistor (R54 in circuit) for overcurrent sensing. The rated drain current of the MOSFET is 17 A. Bus voltage is to be 100 V. Then would my sense resistor be R = V/I = 100/17 ohm? Or would the sense resistor be decided by the OC pin voltage?

U15 is the gate driver : UCC21732 from TI
For the current R54 value of 350 mOhm, I am getting a huge power rating of $$I^{2}R$$ = $$17^{2}*0.35$$ = $$101.3 W !!$$


texts: Impedance of the circuit between given points

texts:
I am trying to learn one and two port networks and the book introduced Determinants and minors to calculate the impedance of the circuit. Kindly see the following question:

I have managed to do the part (a) but parts (b) and (c) are not making any sense. Here is my working for  part (c).

I included a current source between the indicated points and wrote KVL equations accordingly. Afterwards, calculated the 3x3 determinant for the equations. Now I am stuck and dont know which column to replace to get the required minor.

Kindly explain either one of them.

Thanks!


texts: LT1721 pulse generator manual gives unexpected resistor values?

texts:
I've designed a circuit depending mostly on this LT1721 pulse generator, that's been thought up by the nice people at Analog:

https://www.analog.com/en/design-center/reference-designs/circuit-collections/lt1721-pulse-generator-has-0ns-to-10ns-width-520ps-transitions.html#cc-overview

My goal is to generate 5 ns pulses to feed into the gate of a FET.

The pulse generator works because C2 is initially on, wheras C3 is initially off. Then as the input pulse passes, the 8 pF capacitors are discharged into C1. If the C3 capacitor discharges before the C2 capacitor, there is a brief window of time when both C2 and C3 are on, and the and-gate sends out my pulse.

Of course the larger my C2 resistor, the longer the delay and the longer my pulse will be. I'm trying to settle on resistors such that my pulse will be 5 ns!

Now this article tells me that I need to choose my C2 resistor as 510 Ohms, plus 80 Ohms for each nanosecond delay I want, wheras I need to choose my C3 resistor as 620 Ohms. So this would give me resistor values of 910 and 620 Ohms.

But when calculating the voltage at the C2 and C3 input pins, these resistor values give me a time delay of only about 2.5 ns! In fact, the 5ns pulse I want corresponds to 510 and 1500 Ohm resistor values. See these calculations: https://www.desmos.com/calculator/ca5ykt03je LTSpice agrees with me too, if that's worth anything.

Now my questions are twofold:

The people at Analog are smart. Why do they recommend these resistor values when they are so far from a conventional calculation? Is there some effect I'm not seeing? Some extra capacitance somewhere? For a 1 ns delay, the C2 resistor is lower than the C3 resistor: how could that even work in the first place?
I'm inclined to go with a 510 Ohm and a 1510 Ohm resistor. Would that be okay? The top line would start sinking about 4 mA into C1, the bottom line 10 mA. The datasheet tells me that the output current can sink 20 mA, so I should be fine making these "modifications"?


texts: Any nice way to use unbonded CPLD pins as registers

texts:
Many CPLD product families offer each chip in multiple packages, some of which don't bond all I/O pads out to pins.  Even I/O pads which aren't bonded to pins, however, may be useful if they have bus-keeper circuits.  Enable the bus keeper on a pin and it will behave as a transparent latch which samples its value whenever OE is true.  In some cases, this may allow one to almost double the number of available registers (e.g. a chip with 64 macrocells could be programmed to behave as a 100-bit shift register while still having some macrocells left over).  Use a few bits as a counter, have the shift register output report the state of macrocell N+2, and have macrocell N+1's output enable set while macrocell N is being latched from the data input.

Unfortunately, the only way I know of to use those extra I/O pads is to lie to the chip-design software and say I'm using the larger-footprint device, which then means all the pinouts reported by the software will be wrong for the smaller devices.  Is there any clean way with e.g. a Lattice LC4064ZE-5TN48C to indicate that one is using the smaller device (so the pinouts will be correct) and yet still map functions to the pads which don't have associated pins?


texts: Garbage in SPI RX Buffer with DMA (STM32)

texts:
MCU: STM32f030f4p6

There is garbage in reception buffer, when I use SPI and 2 DMAs (for reception and transmission).

void sendMsg2(uint32_t size, uint8_t* rx, uint8_t* tx){
DMA1_Channel2->CMAR=rx;
DMA1_Channel2->CNDTR=size;
DMA1_Channel2->CCR=DMA_CCR_MINC
        |DMA_CCR_TCIE
        |DMA_CCR_EN;

SCB->SCR=SCB_SCR_SLEEPONEXIT_Msk;
GPIOA->BSRR=GPIO_BSRR_BR_4;

DMA1_Channel3->CMAR=tx;
DMA1_Channel3->CNDTR=size;
DMA1_Channel3->CCR=DMA_CCR_MINC
        |DMA_CCR_DIR
        |DMA_CCR_EN;

__asm volatile("wfi");

DMA1_Channel3->CCR=0;
DMA1_Channel2->CCR=0;
}

But when I use 1 loop and 1 DMA it works.

EX1:

void sendMsg2(uint32_t size, uint8_t* rx, uint8_t* tx){
DMA1_Channel2->CMAR=rx;
DMA1_Channel2->CNDTR=size;
DMA1_Channel2->CCR=DMA_CCR_MINC
        |DMA_CCR_TCIE
        |DMA_CCR_EN;

for(register uint32_t i=0; i<size; i++){
    while(!(SPI1->SR&SPI_SR_RXNE));
    rx[i]=SPI1_DR_8;
}

DMA1_Channel2->CCR=0;
}

EX2:

void sendMsg2(uint32_t size, uint8_t* rx, uint8_t* tx){
DMA1_Channel3->CMAR=tx;
DMA1_Channel3->CNDTR=size;
DMA1_Channel3->CCR=DMA_CCR_MINC
        |DMA_CCR_DIR
        |DMA_CCR_EN;

for(register uint32_t i=0; i<size; i++){
    while(!(SPI1->SR&SPI_SR_TXE));
    SPI1_DR_8=tx[i];
}

DMA1_Channel3->CCR=0;
}


texts:
Is it possible to take a regular dc motor, use it to spin some strong magnets over some coils, and get a higher voltage than what's being used to drive the motor?
I was thinking; if you're able to create a series of coils around the magnet, wouldn't the output voltage eventually surpass the input voltage?


texts: mATX motherboard JFP1 header: Does not require pull-up or pull-down resistors, right?

texts:
As per some of the mATX motherboard specifications, the JFP1 (Front-Panel connector #1 jumper), the purpose of the various pins is as per this graphic:

As per the description of the pins, I get the impression that the motherboard already has the required pull-up resister onboard, and for the 2 LEDs and 2 switches, I need only some LEDs (s.a. 5mm ones) and some momentary PCB-mount push-button momentary to make the circuit , right ?


texts: How to tell a battery's ideal charging voltage with a circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

I've been looking to build a universal charger for my laptop and phone, and I'm wondering; is there a viable way to adjust the input voltage to match the battery's ideal charging voltage by measuring A and B across an arbitrary load?

The scenario is as follows;

0) I've got a universal charger that can output anywhere from 5V to 24V

1) I want to charge my phone, so I plug it into the universal charger

2) Without my interaction, the circuit and it's microcontroller adjusts itself to the required voltage (5V)

3) I now unplug my phone and plug my laptop in for charging

4) Without my interaction, the circuit and it's microcontroller adjusts itself to the required voltage (24V)

How can I measure the required voltage without checking the battery label?


texts:
I'm trying to design a camera system for use in my bike shed.
The bikeshed is in range of wifi but has no power.

First I thought I could use a Raspberry Pi with a Picam, and have video streamed to an endpoint I have set up in Azure.

I quickly realised it consumes a lot of power and after less than a day the battery would be empty.

A few things to note:

I could maybe change the microcontroller, but from what I've heard the Arduino isn't powerful enough to record and stream video.
I can't use solar power or wind power as I don't have access to the roof and I feel this would give away the camera too.
I have no power sockets available so I'm relying on a power pack. Ideally, I don't want to be charging it more than once a week.
I considered using an Arduino to "wake" the raspberry pi. But with a boot time of around 20 seconds, it could miss crucial footage.

Using a raspberry pi seems like overkill to me. But as mentioned my lower power microcontrollers don't seem to be powerful enough to operate the camera.


texts: Reducing power consumption in controlling 40 7-segments

texts:
Following that post here: Designing a large 7-Segment display

To give you the basic approach I did that:

form the uC to shift register followed by ULN2003, then connected 8 7-segments together
Put 8 P-Mosfets to control each 7-segment, turn it on, then send its digit
In 2, all the 8 Mosfets are controlled by a 3 to 8 Decoder.

I managed to do everything and control the 32 7-segments. but the thing is, to control 7-segments using step 3, would require a power consumption of 8*5*120mA, considering 8 segments per row, 5 cols, and each row consumes 120mA, and that requires a very big power supply.

Is there any other idea to have a better design?


texts: Can I use a subwoofer as a linear actuator?

texts:
I need an actuator with a few mm of travel and it has to be very responsive to a very low frequency (DC 10 Hz) sine wave generated by a function generator.

I'm thinking of getting a cheap subwoofer and hooking it up to my function generator via a power amp.

My questions:

Can I use a speaker as a pseudo-linear actuator or is the speaker designed to pull back the membrane?
Will the voice coil blow when it's used at very low frequencies with enough power to actually displace the membrane by a few mms?

Edit:

The load is a PCB assembly weighing around 100 grams. I want to move that assembly up and down in a controlled way at different frequencies which I'm generating with a function generator. I also have linear stages but they are slower and noisy and I've thought about a mechanical contraption with a stepper motor and cam shaft. The actuator solution seems more attractive because I can control the motion more easily and I expect the latency to be better.


texts: Is it mandatory to use AEC qualified component in automotive applications?

texts:
I'm wondering if it's mandatory to use AEC qualified components in an automotive application. Is it restricted to safety related applications?

I talked to a more experienced engineer about some capacitors an he seems to accept Y (non AEC qualified) capacitor in automobile. I find this very confusing.

Also, is it ok to use medical or military in this case?


texts: How to limit power going into a resistive load originally connected to AC mains

texts:
I want to use the excess solar panel energy production in a home installation in electric purely resistive heating. I have the means to measure excess solar power and feed that information into a controller.
The heating element has a rated power in the 2000W ballpark and the utility can track the power transit into and out of the installation with enough precision to measure instantaneous power in and out of the installation. Therefore, a TRIAC based solution gives more instantaneous power on some parts of the cycle than the available excess power produced by the solar panels or cuts a lot of the available power during most of the cycle if the priority is to never output more than the excess power.
As an alternative, I started looking into using multiple winding transformers so I could step down the voltage and control how much power is going to the heating element in discrete steps. Before even searching for multiple winding transformers, I looked into regular double wound transformers for the 2000W rating but I found they weigh around 10kg and was looking at something a bit lighter.
I am familiar with the design of electronic and embedded circuits, but my knowledge is a bit lacking in power electronics. Given these constraints of never giving more power to the heating element instantaneously than the excess power output by the solar panels and having a somewhat light system, should I be looking at building/acquiring a full blown PWM AC-DC converter or am I overlooking other simpler solutions?


texts:
I know that VA is the unit of apparent power (combination of real and reactive power) and Watt is the unit of real power only. So, I think it is more precise and accurate to express electrical power in VAs not in watts. But that does not happen. What is written on some generators is 40 Mega-Watts. And I've heard the president saying that the government added some mega watts to the electrical grid.

Why don't they express electricity in VAs instead of watts?  Is that because the customers pays for the real power only and not for the reactive power?


texts:
I was wondering how this demodulator works. The input voltage is on the left at C2 and the output voltage is on the right before C3.

What is clear: C2 filters out low frequencies at the input, C3 filters out high frequencies at the output, R2 limits the current coming from the reference voltage V+.

What is unclear: the function of the two Schottky diodes D1 and D2.


texts: How to convert fixed point binary numbers to BCD?

texts: I am trying to make a calculator that can do fixed point calculations but I don't know how to display them in decimal (BCD). People have told me to use reverse double dabble but I am looking for another solution. How can I convert fixed point binary numbers to BCD without using reverse double dabble? Help is very appreciated.


texts:
I´m finishing my PCB Design (Carrier Raspberry Compute Module 4 PCB, with an USB 3.0 Controller), and I have a question about routing crystals oscillators. I have read this guide:
http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-8128-Best-Practices-for-the-PCB-Layout-of-Oscillators_ApplicationNote_AVR186.pdf
Adding polygons on top and bottom layers connected to ground is a good practice or the ground island for the crystal should be isolated from the polygon that covers all the layer? On my schematic there is not ground for the capacitors.
Other problem, I can't place them shorter, (I don't have space). On that position it is fine?
Thank you so much!


texts: Possible causes for 7-segment LED flicker

texts:
I'm working with a vendor overseas to revamp an existing product. We're trying to keep cost down.

Currently the product consists of:

4 large buttons
4 double digit 7-segment LEDs. (each button has double digit underneath it)
1 LCD (8 characters...each character display is composed of a 3x8 grid of LCD dots)
a speaker
a microcontroller
LCD driver

In the revamp, the vendor wants to address an issue with the current product. All 4 of the double-digit LEDs have a noticeable flicker.

The vendor is giving us an estimate that includes using a new microcontroller, some circuit redesign, and redoing the whole program! (we just want to swap out audio files and fix the flicker...I don't think that the general logic for the product needs to change at all)

I'm not sure exactly how the previous circuit was designed, but potentially the flickr could be due to the mcu not being fast enough to PWM when lighting the LEDs.

In general, based on experience, what could be some other causes of flickering 7-segment LEDs. I just want to understand the issue so that I can discern whether the vendor is budgeting additional work when it is not needed.


texts: Is my dynamo a BLDC generator or PMSM generator?

texts:
I want to ask you about a problem please.

I have bought an AC dynamo generator (the commercial name). First I don't know is it an AC synchronous generator or a BLDC generator. The dynamo has 12 poles and 9 coils.

I turn the dynamo by an AC drill and I have seen a back EMF not sinusoidal and not trapezoidal. It's between the two. (There's many harmonics.)

I took multiple samples of speed and voltage so I found

\$K_e = 0.004 V/RPM = 0.004 \cdot 60 \cdot 2 \cdot \pi = 1.5 V/rad/sec\$

and so \$K_t = K_e = 1.5\$;

Now I want to calculate what torque I should apply to take 0.5 A current .
The theoretical answer is

In PMSM \$T = 1.5 K_t \cdot i = 1.5 \cdot 1.5 \cdot 0.5 = 1.35 Nm;\$

In BLDC \$T = 2 K_t \cdot i = 2 \cdot 1.5 \cdot 0.5 = 1.5 Nm;\$

So what type of motor should it be?

And what current should I provide, \$I_{rms}\$ or \$I_{max}\$ or \$I_{phasetophase}\$?

Are my calculations right?


texts:
I have trouble connecting a THT HDMI Connector to a pcb:

The HDMI Connector I'm talking about is this.

The holes are too close to go in between them:

(The blue line is 0.15mm thick)

Is this usual (such close and small holes)?
Should I be using a pcb manufacturer who can produce thin pcb traces? (like 0.10mm?)

Or just route the trace other way around?


texts: 3-Phase Induction Motor with winding heating provision

texts:
I have a 3 phase 6 pole 415V induction motor which has 24 VAC applied between the R & Y phases 3 seconds after the main power is removed as a means of preventing condensation by heating the winding. Usually the applied 24 VAC does not cause motor rotation but after a rewind the unloaded motor will now continue  to rotate if 24 VAC is applied before the motor has stopped turning after main power is turned off.

This ability to operate on "single phase" AC at low voltage seems contrary to what we would expect for a 3 phase 415 VAC motor, and not what we have experienced before the rewind.

Can anyone explain why the motor may now operate in this manner and why a rewind was able to change how it operated?

______________

Details:

We have an 08 motor of rating 15KW, 6 Pole, 415V, CGL make installed. these induction motor has anti condensate winding heating provision given of 24V AC(Between R and Y phase) through its power cable lead when motor is in stop condition. there is a timer of 3 sec  installed in control circuit between motor stop and winding heating start.

One motor was overhauled and when it restored without coupled to the load, it runs perfectly fine but when we stop it, within 3 Sec 24V AC between R and Y phase (4.5 Amp current in R & Y phase) gets starts and motor remain in continuous in running state with reduced speed, even its main supply 440V AC) gets isolated through contactor logic.

since the motor is decoupled and its inertia is high it dosent come to zero speed within 3 Sec of stoppage and 24V AC between R & Y phase gets starts and it remain continue in rotation with reduced speed (may be due to required rotating field gets fulfilled with 24V AC only in running condition, and due to the single phasing with 24V AC)

When we remove 24V AC winding heating space heater fuse, motor come down to zero speed.

This seems a unique finding in my career, please share any experience related to this and some theory part.


texts:
In my Lm 393 comparator, my output is not coming proper square wave.picture is shown below. I have described about my circuit.
I am using voltage comparator LM393 for comparing two signals, one signal is my reference signal which is a triangle wave, with voltages 2.08 volt generated by 555 timers above 200kHZ giving to the input terminal of inverting side of LM393 and input signal or modulating signal which voltage is less than 2.08 giving from function generator as a sinusoidal signal in the range of 1 Hz to 20kHz in the noninverting side of LM393.
My question is when I am providing two signals it should be compared and give a square wave, but LM393 only taking triangle wave, sin wave is not going?
In this picture below, I am referring to this circuit, please tell me what 's wrong in this circuit, when I am taking triangle wave from 555 timer ad providing into the comparator and another signal providing from the generator.


texts: Noise addition. Sum of shot and thermal noise

texts:
The situation is as in the picture. I've made the resistance small compared to that of the tunnel junction so the thermal noise of the tunnel junction can be ignored, since the thermal noise in the divider is given by the parallel combination of resistance.

I don't understand how these noise sources add up. They are both Gaussian, centered at zero and if they are not oversampled after being filtered at 1 MHz, they appear as white.

Wikipedia has an article on this: https://en.wikipedia.org/wiki/Sum_of_normally_distributed_random_variables but when I look at a noise waveform, being random as it is, it seems that there may be some cancellation between the two sources. In terms of amplitude, it looks like they can't add up.

I have an idea that two incoherent noise sources of the same power add up to 3 dB and two Gaussian sources produce another Gaussian distribution, but I might be wrong.

My questions:

What would be the RMS value of the combined noise at Vo? Would it have a Gaussian distribution if I sampled it at 10 MS/s after passing it through a brickwall low pass filter at 1 MHz? (the noise is not white anymore)
What if I sampled it at just 2 MS/s after the filter? Would the RMS amplitude be the same as in the oversampling case?

Edit: so the combined noise is 4 mV RMS, or less than 26.4 mV peak-peak for 99.9 % of the time.

Edit 2: There are some assumptions in my calculation:

shot noise is Gaussian, as an approximation for the Poisson discrete distribution that best characterizes it. More exact calculations need to consider the slight skew of the Poisson distribution
the tunnel junction saturates, so it behaves as a current source at the bias point. Most real tunnel junctions don't saturate, but the approximated noise is essentially the same.


texts:
So I went to RadioShack recently because they were having a 40-80% off liquidation/closing sale.  I picked up quite a few things, and one was a 555 timer for a decent discount from its already low price.  Now, I'm about to make an online purchase and I don't know which one it was.  It was either the tlc555cp or the ne555p.  So, two questions arise:  What are the differences in pinout/internal circuitry the would make them different, and are there any such differences?  Thanks!

EDIT I'm home now.  I see it's a TLC555CP.  What are the differences between that and the NE555?


texts: What connector type is this 3 pin connector

texts:
Can anyone help me identify this connector?
It is 3 pin wire-to-wire female connector, distance between center of the pins is 4.5mm, each whole is 4mm. One of the pin holes is square. Looks like some kind of molex connector.


texts: Assemble a 9 * 9 * 0.05 mm steel foil and castellation PCB using standard pick and place

texts:
I have a hybrid PCB where I want to assemble a very thin steel foil on a PCB using standard pick and place SMT process. the picture below describe how the foil is like:

The orange area is only hold by fine traces and therefore can swing, and we want it to swing using a passive placed on a second castellation PCB assembled on top (passive in red).
Is it a standard practice (at least 50% of PCBA facilities can do without problem) to pick and place the castellation PCB while making the orange area move down?

If yes, do you think it,s possible to do standard, or we should use some kind of smt adhesive to hold the castellation PCB and avoid it being pushed up by the orange membrane?


texts: What is incorrect with my 555 LED flasher circuit?

texts:
I have built a circuit to flash an LED using a 555 timer IC, but it doesn't flash... the LED just stays on steadily.

-- I carefully followed the instructions on a common tutorial, which is: http://www.instructables.com/id/Flashing-LED-using-555-Timer/

-- Here you can watch a video where I give a nice clear display of the circuit I built, and what the IC pins and leads all connect to. Video is at: https://youtu.be/qYDeqq9Bua4

-- I have tried it with 9V battery and also 4 AA's.  Same result.   I also tried with different color LEDs in case the draw is different somehow. Same result.

-- My capacitor: I forgot to mention in the video that I am using one that is "Electrolytic Cap 1uF / 50V" ... the instructions called for 1uF capacitor and this seemed to me to fit that specification.

-- I have checked the positive/negative on the LED and the capacitor. And I know that you see exposed leads to resistors around, but nothing is shorting out...

-- Here is a photo of the circuit. I'm sure very hard to see it. The video linked above(even just the first several seconds of it) might be easier to see. Photo is:

-- In the tutorial I followed, linked above, this is the schematic that I I was told that we were following:

-- As you can see, I am clearly novice at building electronics from scratch. I dabble in other IT stuff like Arduino but trying to get smarter on the electronics here.

Giant, huge thanks for your time and any help you can give!

Eric


texts:
I need to build a Geiger counter power supply circuit that will provide a 400V DC output out of one of those 6LR61 9V batteries. I thought about using a 555 timer to produce a square wave, feed it into a 1:45 transformer and then filter out the output, but I have no idea about what frequency and how many primary and secondary windings to use, and whether it would work at all.

update:

OK, thanks everyone for your effort but I guess I'll just go with a 555 inverter circuit like this (sorry for the watermarks), with custom transformer and a filter on the output.


texts:
simulate this circuit – Schematic created using CircuitLab
I've tried solving for Vo in two ways, one is I took V+ by voltage divider getting
V+ = V1(R2/R1+R2) = 0.05V. Since V+ = V-, it follows that V- = 0.05V. But I tried simulating it in the circuit simulator applet but it shows there that its voltage should be 4.99V so i stopped solving there.
Second solution I tried is using nodal analysis. I get
(V+-V3)/R2 + (V+ - V1)/R1 = 0, V3/R3 + (V3-V+/R2) + (V3-V-)/R4 = 0, getting V3 to be 0.05V but again, the applet says that V3 is 9.88V.
Im not sure where I went wrong, maybe its the voltage divider or the way i used nodal analysis. Circuit simulator applet link if you want to try out for yourselves: Falstad.


texts: Determine polarity of crystal oscillator

texts: A two-pinned 13.824 MHz crystal oscillator broke away from the pads on a PCB board.  One pad is labeled + and the other is GND.  Do two-pin crystal oscillators have specific polarity?


texts: Practical considerations when using a large number of capacitors in parallel

texts:
Capacitors can be wired in parallel for higher total capacitance and lower total ESR.

What are some practical constraints/pointers for using many parallel capacitors (for example, 10, 25, 50, or 100)?

Application example: using 30 330 µF aluminum polymer capacitors to replace two 5000 µF wet electrolytic ones inside devices intended for long-life at low-variance operating temperatures (for example, illuminated ocean buoy).


texts: What type of grease could I use to pack in my connector to prevent corrosion?

texts: I am looking to protect a phoenix contact terminal which is exposed to the elements. When the units come back for servicing I can see that they have corrosion on the contact. I recall purchasing wire nuts pre-packed with grease for the very same reason. I'd like to buy a tub/tube of a similar grease to pack inside these connectors.


texts: Why does Macbook (with a alumnum shell) use a 2-prong plug instead of 3-prong plug?

texts:
Here says that devices with metal shells usually use three-prong plugs.

  Three-prong plugs are for appliances that require the ground
  connection for safety. Most appliances that use a metal chassis
  require a separate ground connection.

I am confused about this. My Macbook Pro uses alumnum case, but why it can still use two-prong plugs? Will it increase the risk of electric shock?

Does anyone have ideas about this? Thanks!


texts: Difference in the datapath of Load Upper Immediate to Load Word in a 32 bit MIPS processor

texts:
For the MIPS insturction Load Word I have got the following Datapath:

How does the datapath for the Instruction Load Upper Immediate looks like?


texts:
I am sending data between a master and several slaves with RS485 with bytes (8 bit) messages with a very simple frame inspired on Modbus ASCII:

0x3A 0x30 0x31 0x32 0x3F 0x0D 0x0A

in which the bytes are the frame sections 1) Start 0x3A, 2) Sender ID 0x30, 3) Receiver ID 0x31, 4) Function to execute 0x32, 5) Data 0x3F, and 6) End 0x0D 0x0A.

With one master and multiple slaves, a receiver slave only sends messages when reads a message with its ID, and is silent otherwise, for discarding any collision.

When the master is the last device to be turned on, everything is ok. All slaves read the full message, and reply accordingly.

But if not, some late in wake up slaves will not detect the Start byte correctly, do not read a full frame at some point, and I don't have any way to make them know where to start.

Because the Data part in the message can perfectly include the Start byte 0x3A randomly, I cannot figure a robust way to deal with this.

I feel this problem is like "escaping" an special character inside a string...

How should I program the frame detection for not having this problem?


texts: How to print value of variable on PCB into String feature in Altium Designer?

texts: I'd like to print value of Revision variable that can be set in Project Options - Parameters (not Document Options on Parameters tab) into silkscreen of PCB. How could I do this?


texts: How to connect these two resistors like on the schematic?

texts:
I am trying to connect CAN to the LPC1768, like here

Expect that I don't understand the picture or the meaning of "you need two 120 ohm terminating resistors at either end of the bus".

Does it mean I am suppose to connect a resistor of value 120 ohm between CANL and CANH (between pin 6 and pin 7) on both of the MCP2551s? For me this schematic shows two resistors connected together.


texts: Unknown huge Volatge drop over a resistor

texts:
I am still learing about the basic electrical engineering and here I have a project for my univ and have some problems.

So my problem is rather weird in my opinion maybe because the lack of knowledge. As you can see in my schematic below I have a 16v power source with 68 mA current (measured with multimeter) but then after the resistor it dropped down to 4 voltage so the LP 2950 cant regulate the voltage properly.
Then I remove the resistor just for trial and error purposes and it worked perfectly fine.
Since I was suggested to use the resistor before by my profesor therefore i can't remove it, the reason was the diode will be broken if it is used for a long time.
And here are my questions:

is it true what my professor said? if yes(or no) what is the reason
for it?
What is the possible reason of the resistor's huge voltage drop?
What is the solution to this problem?
will it be any different if it was a schottky diode?

IMPORTANT NOTE

All the components work perfectly (checked everything twice).
All the connection to soldering also works fine.
without the resistor the current i=200 mA
The diode is necessary to avoid mixing signal
The 4700uF capacitor is also necessary

simulate this circuit – Schematic created using CircuitLab

THank you for your time.


texts: Calculation of MOSFET gate drive current

texts:
I know that there have been many posts on this topic, but I'm confused about calculating the gate current of a MOSFET.

I have calculated the gate current as Igs = Qg/t. For example, I want to drive IRF540n with PWM at 100 kHz. It has Qg = 94 nC and 100 kHz = 10000 ns.

If I use Igs = Qg/t then Igs = 94/10000 = 0.0094 A. I think it's quite a small current.

Are my calculations correct or not?


texts:
I'm trying to drive some WS2812 LEDs which require a (400ns high + 800ns low) or (800ns high + 400ns low) signal to indicate a 0 or a 1.

So essentially I'm trying to take an array of data and output it directly to a GPIO at about 2.5MHz. I've never used the DMA before but from what I understand it should be able to output data straight from memory to a GPIO.

Can anyone offer some guidance on how to setup the DMA to do this, or if there are any better ways of outputting data on a GPIO at a consistent clock?


texts: What is an n-by-n matrix in a series-parallel circuit?

texts:
I started reading a textbook about basic electronics and I reached a section about series-parallel circuits. Here is an example of a series-parallel circuit:

simulate this circuit – Schematic created using CircuitLab

According to the book, in a series-parallel circuit all resistances must be the same. In this example each resistor is 100 ohms.

It also says that this example is connected in an n by n matrix. What exactly is this?

The book explains a practical aspect of using series-parallel circuits by saying that a resistive component can be obtained with a large power handling capacity if there is a series-parallel configuration of resistors of the same value(as shown above in the diagram). Is there an explanation for this phenomena? I do know what power is(Power=voltage*current) but what does power really represent? How is knowing the voltage times current useful?

It says that this configuration can dissipate more power than just using a single resistor. What is power dissipation?

I know that my initial question was what is an n by n matrix sorry if I asked too many questions(I am a newbie)   :) .


texts: Odd voltage read in Atmel Studio when manually connecting the pins of a ATMEL ICE - SAM port

texts:
I have an ATMEL ICE, I connected the cable to the SAM port. As a first step to setting up individual programming pin connections, I then connected 4 of the 10 pins of the SAM JTAG interface: the three grounds and the VCC.
I followed the schema provided on the official website to do that: https://microchipdeveloper.com/atmelice:connecting-atmel-ice-to-a-jtag-target

My VCC-GND voltage difference supply-side is 3.3V as measured with a voltmeter.
But, using Atmel Studio to read the "Target Voltage" according to the ATMEL-ICE (Tools > Device programming), I read 0.8V. I expected 3.3V. Did I miss something ? Could I have damaged something doing that ?


texts: Necessary Read Frequency vs PPR of Rotary Encoder

texts:
I am working on a microcontroller (ATMega328) project where I am planning to use a rotary encoder. I plan to have a non-time critical main loop and set up a timer interrupt to handle reading the encoder.

Is there any reference or rule of thumb for the frequency at which I would need the timer interrupt to be called (the read frequency) relative to the PPR of the encoder in order to have it be read accurately?

Thanks!


texts: What will I need to send Video over bluetooth or WiFi to Android phone

texts:
I don't know much about electorics I'm programmer and know some stuff about digital electronics that I learn at school, but I have this idea to send video data from a camera (I found on Alibaba CCD boards you can get bare CCD board or CMOS and buy a lens for it or get it with a lens) to Android app that will allow to take pictures like with native camera.

I want something realy small. something like this Hidden mini dv camera.

What else except CCD board and WiFi or Bluetooth board I will need in order for it to work? (I was thinking about using Arduino but it seams that it's too slow to handle Video).

It will be possible to modify that button camera to send video to a phone?

Or maybe something like this already exists and only need Android App.


texts:
I would like to wire my position sensor (Datasheet) into Arduino. I plan to connect it with Arduino 5V supply and then read analog input values. It is potentiometric sensor and has 3 wires.

After looking at datasheet there are many values for current in uA range, like Recommended operating wiper current (<1uA)??. Can somebody take a look at datasheet and check if I understand it right... Is it normal? ..If, yes, how to wire it to acheave such a low current with 0-5V proportional output signal. Have somebody experience with such a sensors.

I just dont want to burn it...:)


texts: Clamping circuit output dependence on load resistance

texts:
I constructed an unbiased positive clamping circuit with C1 capacitor = 1 uF and load resistances R1 of 100 Ω or 100 kΩ. The input is a triangular wave of 5 V peak-peak, with 0 offset and frequency = 100 kHz.

I noticed that we get a higher peak voltage for R1 = 100 kΩ compared to R1 = 100 Ω. The difference between them is nearly 0.7 V.

Can anyone explain the difference in peak voltages?

Figure 1. Output waveform for R1 = 100 Ω

Figure 2. Output waveform for R1 = 100 kΩ