texts: What is this high pitched sound coming from my UPS backup battery?

texts:
I own two of these APC Back UPS Pro BX1500M units that were purchased new. Both of these units have always made this very annoying "booo-eeeep!" sound when plugged into the wall. I've owned backup batteries before and I've never heard this before. Everything works fine otherwise.
This sound stops after switching to battery. It also takes a little bit before the unit will start emitting this sound when plugged back into the wall. Performing a reset on the device by following steps to provided by the manufacturer will cause the sound to stop when plugged back into the wall but resume again after a few minutes.
I've recorded the sound and boosted it to be heard at a normal volume. I have to put my ear to the unit to hear it consistently over the HVAC in my apartment but it it clear as day across a room when it's quiet.
I have recently replaced one of these with a similar APC Back UPS PRO BN1500M2 which does not have this issue. I have owned these for about two years and this sound has always been consistent. I worked around it by placing the units in areas there the sound would not be audible.
I can confirm that this is NOT the sound of any of the relays switching to or from the battery.
What is this sound?
See the following link for the recording I mentioned above:
https://drive.google.com/file/d/1lxMCApKv-wQnd9s6JOufWFPzX_l1f8v0/view?usp=drivesdk
I'd like a confirmation from someone who is electrically inclined and some kind of explanation as to why it's audible. I've been around all kinds of electronics my whole love and this is the first time I've heard this particular sound.
Here is a reference from another APC owner and a response with the possible culprit:

This noise comes from the battery charging circuit, and it's not
necessarily abnormal. The newer APC UPS models use a "switching" or
pulsed approach to charging the battery, and depending upon the pulse
frequency, you might hear a faint hiss, buzz or squeal. (If any of
these noises are really loud, that would strongly indicate a
malfunction.)

https://forums.apc.com/spaces/4/back-ups-surge-protectors/forums/general/11892/high-pitched-squelching-noise-from-back-ups-xs-1500-bx1500lcd


texts: I have tried connecting one feet of Nichrome 80 wire ( 22 g ) with a 9V battery. Is this enough to heat the wire?


texts: A question about using ferrite chokes in a data-acquisition system

texts:
I'm planning to buy [this flat ferrite choke][1] for ribbon cable to suppress suspected EMI on a data acquisition's multiplexer.

I have no experience on signal integrity. Bu the system setup is basically like this(On the right side the system is single-ended earth grounded):

Instead of adding chokes to each BNC I thought it would be easier to use just one flat core for the ribbon cable since it conveys the signals to ADC insdie the PC.

Which would be a better option? To apply chokes to each BNC cables or to use one flat ferrite core around the ribbon cable? I also couldnt find any passive chokes for 50 Ohm coaxial BNC cables in the market until now, neither info how to install them.

I'm having random glitches sometimes. By random I mean 2 or 3 times in 30 minutes acquisition. And this is not every time. By glitch I mean at some point suddenly all the channels are affected. So it is almost impossible to observe this by scope because I don't know when the noise will hit.


texts: A question on aliasing and sampling in a measurement system

texts:
Before asking my question here is the scenario how the voltage signals are used:

Where I work some are performing data acquisition of four DC signals through four channels by a daq device at a particular sampling rate. The DC signals are coming from transducers devices measuring temperature, air pressure, force transducer ect. All of these transducers have calibration certificates which have linear calibration equations for voltage to temperature conversion as Temperature = A*Voltage + B where A and B are the slope and offset of the calibration equation. So by looking at a certificate one can say "I measure this voltage so this corresponds to this temperature" ect. After sampling and logging the data, the engineers use software like MATLAB where they can do several transforms like FFT ect.

Here comes my question:

Imagine an analog DC signal coming from a force transducer in a time interval as below:

And imagine the maximum frequency of interest is 50Hz.
So according to Nyquist theorem the sampling frequency should be at least 100Hz.

But if this signal has many frequency components higher than 50Hz we will be face to face with a situation called aliasing. So we will be undersampling some of the frequency components. So far this is what understand form aliasing.

And below represents this:

I encounter some tutorials which suggest anti-aliasing filters like RC low-pass filters between the transducer and the daq so that we remove high freq. components and avoid undersampling and aliasing.

1-) Do you think in my case this type of filtering is necessary if the tools like MATLAB can do post signal processing like low-pass filtering? Or an analog anti-aliasing filter is still needed?

2-) If they don't do any FFT and filtering, is there a possibility the signal's mean values or low freq. components might be affected significantly by aliasing?

3-) How can I know that if a filter is needed or not? (I know how to use a scope)

My concern is if I use a low pass filter I don't want to affect the calibration equation of the transducer.


texts: Choosing the meshes in a circuit with a given tree

texts: I have to use mesh analysis to write down the independent mesh equations. I already did this with the same circuit but with a different tree. Now I have to do it with this tree, and I have no clue how to take the meshes correctly. Can someone give me a hint?


texts:
I'm looking for a way to monitor the power of several circuits at home: Washer, dryer, freezer etc.

I already have a modbus meter for the heatpump, but I don't have room for an extra meter on the DIN-bar, even if they are available in 1-unit with.

So I'm looking for an unit which have (multiple) input from current transformer and a modbus or other raspberry-compatible output. Wifi would be ok too.

The unit need to calculate the energy itself, I don't want to have to poll regularly for the watt and add it myself.

Suggestions?


texts:
FCC regulations apply to unintentional radiator devices, but provide exceptions for subassemblies, including this one:

CPU boards, as defined in §15.3(bb), other than those used in personal computers, that are marketed without an enclosure or power supply

Would a PCB business card qualify since it has no enclosure? Do batteries qualify as a power supply? The rest of the page references power supplies in relation to personal computers, but the definitions page does not define power supply. I would be giving these away instead of "marketing" them, but I'm not sure that makes a difference. Also, new rules came out in 2017 about testing, which may be relevant here.

The board I would like to build would have a small screen, tactile buttons, and a microcontroller and use 1-2 coin cell batteries. It would run at over 1.7MHz and use more than 6nW, so I don't think it qualifies for any exemptions.

Here are a few similar projects I have found that seem comparable:

PCB Business card

Tiny Tetris on a business card

Business card game console


texts:
I have been reading about grounding in a mixed signal systems. Do I get it correct that it is best to group analog and digital elements and then have a single ground plane, as long as the digital routes do not pass through analog part, and analog routes do not pass through the digital part?

The highlighted part on the left figure shows the analog ground and the right one highlights the digital ground for the same circuit. The component on the right side is a 80 pin MCU with 3 sigma-delta ADC converter.

Is it better to

let the AGND and DGND to be tied on ADC of the MCU
connect the DGND and AGND through an inductor/resistor
have a single ground-plane (DGND = AGND)?

P.S. as I read the aim is to prevent DGND to disturb the AGND, I defined main ground-plane as AGND


texts: Data Collection and storage using Arduino

texts: I want to read data from sensors (both analog and digital sensors) and save it into SD card by using arduino. Is there any basic program that help me out in doing this as this is the first time I am using arduino boards


texts: I am currently doing a project on automatic water level control. I have a solenoid valve and ultrasonic sensor. The solenoid valve needs 12 Volt to operate. So I have used a relay to connect it and used as ESP32 to program it. The problem is, when I am testing the code without connecting the solenoid valve with relay it works perfectly. But when I connect the Solenoid with relay it works when the water level is low. When the water level is full and the relay turns off, my ESP32 get stuck. It doesn't restart and it doesn't go any further and just sit idle! What's wrong here?


texts: Do I need to install Bootloader on my new AtMega32? Can I do it with USBasp?

texts:
I had a Sparkfun Redboard for some time and I liked playing with it, blinking LEDs and writing to an LCD and such. Now I want to design my own similar development board for similar set of applications. I am comfortable with everything except the bootloader. Following are my questions, most of my questions may be very basic but this will be my first electronics project so kindly bear with me.

If I will purchase new Atmega32 from local store will it come with a bootloader?
If no, Is it compulsory to install a bootloader on it?
If not compulsory then why people sometimes install a bootloader? I read somewhere that a bootloader is installed for field programming but I am not sure what that means.
What hardware will I need to install a bootloader? I can see USBasp can be used for programming but can I use it for installing a bootloader also? This is what I'm planning to purchase.
If USBasp can load a bootloader as well as program a microcontroller, why do people sometimes use Atmel ISP MKII or Atmel AVR ISP which are so costly? I don't need to purchase these right?
If I need to install a bootloader where can I find one for my Atmega32? Is these any standard basic bootloader?


texts: Why doesn't connecting a positive terminal of a battery to ground cause current?

texts:
In other words, why do we need to connect the battery positive to the negative to get electron flow? As far as I know, voltage difference is what drives current flow.

From what I understand, there's a surplus of negative charge (electrons) in the positive end of a battery (weird I know, but I guess they do it for mathematical reasons). Between the positive and negative ends of the battery is some kind of wall that prevents the electrons from diffusing, so they have to go the long way (through a wire to the other end of the battery) to diffuse and reach the receiver atoms/molecules.

So why not just have the surplus of electrons on one end go to ground to equalize (e.g. 5 volts to 0 volts should produce current)? Why does it have to be the other end of the battery? I'm sure there's atoms/molecules in the ground that could accept the extra electrons (receivers atoms/molecules for the donors in the battery).


texts: How can I know whether a random "known not TTL" RS232 device will work with any old random USB-RS232 converter?

texts:
I've been hunting around for RS232 converters for a little while now, trying to get my head around the way RS232 works (or at least how it's supposed to), and the way RS232-USB converters (more frequently than not, seem not to) work. Trying to understand the state of things has left me not a little confused, so I'm asking here to try and sort some of my perplexion out :P

To begin with, Wikipedia states the following about RS-232 (emphasis mine):

  The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are either in the range of +3 to +15 volts or the range -3 to -15 volts with respect to the ground/common pin; consequently, the range between -3 to +3 volts is not a valid RS-232 level.  ...

  The standard specifies a maximum open-circuit voltage of 25 volts: signal levels of ±5V, ±10V, ±12V, and ±15V are all commonly seen depending on the voltages available to the line driver circuit. Some RS-232 driver chips have inbuilt circuitry to produce the required voltages from a 3 or 5-volt supply. RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts.

A bit later on, WP also says:

  Other serial signaling standards may not interoperate with standard-compliant RS-232 ports. For example, using the TTL levels of near +5 and 0V puts the mark level in the undefined area of the standard. Such levels are sometimes used with NMEA 0183-compliant GPS receivers and depth finders.

All of that makes sense. But then I enter the rabbithole...

When I search for a USB-RS232 converter module (as an alternative to the $40 stuff out there that's just pure profit) which actually follows this spec, I instead find an Internet full of converters which state their operating voltage as either 3.3V or 5V. I can't find any explicitly 10V, 12V or 15V devices anywhere. This is a little worrying, because I've gotten the impression that if the converter can only tolerate 3.3V or 5V, a "real" (?!) RS232 device with 10V or 12V signalling/output voltages has a reasonably high chance of making the converter spontaneously combust in a bad way (on top of not responding to the converter's out-of-spec 3.3V/5V inputs). Thusly, my first question is, how can I tell/find/figure out/identify/etc what converters/devices will and will not work, without an oscillioscope?

The other disturbing trend I've found is that ZT213/MAXx23x voltage level converters only seem to level-shift TX and RX, and chuck all the ancillary (but in certain situations very important) RS232 signals out the window. My second question is, what do I do if I have a "real" (?!) RS232 device using ≥10V signal levels which needs (for example) a DTR line - and all I've got is a 5V USB-RS232 converter? What level shifter can/do I use then?!

Finally, this probably isn't covered by WP's article on RS-232 because it's so out-of-spec, but my third question is this: I've found a lot of the converters out there being referred to as UARTs. I don't get whether this reference is being used with regard to the converter chipset itself, or whether the implication is that it's a USB-to-UART converter, where the UART is the target device. What's the deal with this?


texts: LTC1775 Buck converter component question

texts:
I am trying to design a 12v,10A buck converter using a with LTC1775 and have gone through the calculations assuming a 40% inductor ripple current and a switching frequency of 150kHz. This gave an inductor value of 10uH and a mosfet with Rds(on) of 0.014ohm. So based on these i have selected IRLR3915 NMOS and 7443558100 inductor.

My main concerns are the following:

Are these two good choices with regards to the output current or they are overkill?
Should i attach a flyback diode across the output incase I have an inductive load like a motor?
Are the Cin and Cout capacitors adequate? Based on datasheet formulas our output voltage ripple is supposedly ~60mv but the simulation only shows ~10mv

here is the circuit schematic:

and here is a inductor current on LTspice, as you can see the current does reach ~15A:

I can attach the calculations if its needed.

Thank you, I really appreciate your guys help.


texts: Ethernet POE voltage measurement to determine Voltage clamping between line ot Ground

texts:
I am planning on using a tvs diode to clamp power peak to protect network switch; the Port is POE. The issue is that when I measure the voltage of ethernet line to ground, I get around 0.6V. When I use a POE measurement device, its shows the Pin 1,2,3,6 and voltage of 54V.
Why can I not get 54V when measuring using Multimeter.
Please help me understand.


texts:
I am trying to put together a model rocket launcher for my son and am having issues with wiring. He wanted it to look "cool" so I have two SPST switches that light when powered, and a single SPST push switch. All are in series, and powered by two 9v batteries in series. One switch powers, then the next arms, and finally the push button is supposed to fire. What happens in reality is when the circuit is closed by the push button the lighted switches turn off and power is lost. I've included a diagram. Do I need resistors after grounds on the switches to limit power flow? I've looked at several designs online and mine seems to be the same.

Examples:

http://www.instructables.com/id/remote-model-rocket-ignitor/
http://www.instructables.com/id/Model-Rocket-Launch-Controller/


texts:
I often need to create a large counter in my projects, mostly to do some timing stuff, which could be to blink an LED every second ect.

I have done this by creating a large counter, as shown in the code below.

sec_proc : process(resety, clk)
    variable cntr : integer range 0 to 54000000;
begin
    if resety = '0' then
        cntr := 0;
        sec_out <= '1';
    elsif rising_edge(clk) then
        if cntr = 54000000 or timein_en = '0' then
            sec_out <= '1';
            cntr := 0;
        else
            sec_out <= '0';
            cntr := cntr + 1;
        end if;
    end if;
end process;

The code above often gives me timing issues, timing not kept, I have negative slack.
How do you implement such counters effective for synthesis in vhdl?


texts: My Square Wave from my PIC24F got twice the intended period

texts:
I am doing a program where I am toggling an LED at a PIC24F Development Board an Explorer 16/32 development board with a PIC24FJ1024GB610 microcontroller attached to it.

Explorer 16/32 got an LED (D3) connected to pin P17, which corresponds to PORTA RA0

The program consists of configuring the clock signal (oscillator source), setting up the 16-bit Timer 1, and initializing the digital output (TRISAbits.TRISA0 = 0)

CLOCK

The clock signal is sourced from OSCFDIV #pragma config FNOSC = OSCFDIV
the Prescaler block got its oscillator source from the FRC (Fast Internal RC oscillator) CLKDIVbits.RCDIV = FRC. The FRC got a frequency of 8MHz
Set the Prescaler to 1/4 OSCDIV = 4where Foscdiv = 2MHz
After the Fosc is divided by 2 by the Postscalar, we shall have Fcy = 1MHz, or Tcy = 1us

The diagram below illustrates how the oscillator was chosen.

TIMER

Timer 1 is a 16 bit Timer.

I have configured the timer's clock signal to be sourced internally (Tcy = 1us).

t = count * Tcy, if t = 50 ms = 50000 us, Tcy = 1 us, then count = 50000

By the logic of the code, when TMR1 = 50000 (50 ms), T1IF will be set then T1IF will be cleared by SW, and LATAbits.LATA0 (LED0) will be toggled, giving us a square wave with Time Period = 100ms.

This is the code of my application

#pragma config FWDTEN = OFF//disable WDT timer
#pragma config ICS = PGD2//allow debugging

#pragma config FNOSC = OSCFDIV//COSC = OSCFDIV

#include "xc.h"

/*
 I would like to make a pin toggle
 * initialize the clock

 *
 * fcy = 1MHz, Tcy = 1us
 * RA0 will toggle every 50 ms
 * hence we get a square pulse of T = 100 ms

 */

#define TMR1_IF IFS0bits.T1IF
#define LED0    LATAbits.LATA0

#define FIFTY_MS 50000
#define FRC (0b000)

void digital_setup (void);
void timer_setup (void);
void clock_setup (void);

int main(void)
{
    clock_setup ();
    digital_setup ();
    timer_setup ();

    while(1)
    {
       if(TMR1_IF == 1)//if Timer 1 Interrupt Flag is set
       {
           TMR1_IF = 0;//clear IF
           LED0 = ~LED0;//toggle PORTA RA0 (P17)
       }

    }

    return 0;
}

void digital_setup (void)
{
    //output RA0
    TRISAbits.TRISA0 = 0;//digital
}

void clock_setup (void)
{
    CLKDIVbits.RCDIV = FRC;
    OSCDIV = 4;
}

void timer_setup (void)
{
    PR1 = FIFTY_MS;

    T1CONbits.TCS = 0;//cs internal
    T1CONbits.TGATE = 0;//gate don't accumulate

    T1CONbits.TON = 1;//start timer
}

However, when I compiled and programmed the code into my development board, I got a square wave with twice the timer period (200 ms)

Not sure if this is related, but I tried debugging it, and when I change the value of TMR1 to 50000, the T1IF bit doesn't get set.

Can someone tell me why I am getting a square wave with twice the period. Any help would be appreciated


texts: PQ core for flyback transformer - Why use a PQ core

texts:
I m actually considering a board with a flyback transformer and it is a PQ core 26/25 for being precised for an output of 50W. However I read from " Inductor and Flyback - Transformer Design " written by TI, the following sentence :

"Pot cores and PQ cores have small window area in relation to core size, and the window shape is not well suited for flyback transfonners or discontinuous mode inductors"

I know that it is better to have a windows as wide as possible to minimize AC resistance. Nevertheless, I m clearly newby in transformer design, and as regards of my experience I would like to have your opinion about PQ core. Why it is interesting to have a PQ in a Flyback transformer ?

"Magnetics" manufacturer says :
"PQ cores are designed specifically for switched-mode power supplies. This design provides an optimized ratio of volume to winding area and surface area. As a result, both maximum inductance and winding area are possible with a minimum core size. The cores provide maximum power output with minimum assembled transformer weight and volume, in addition, to taking up a minimum amount of area on the printed circuit board. This efficient design provides a more uniform cross-sectional area; thus cores tend to operate with fewer hot spots than with other designs. Typical applications include power transformers and power inductors."

Is this only for minimizing space at the price of lower efficiency ? (The board is clearly huge and there is a lot of space)

If you have any advice, it will be a pleasure to hear it !

Thank you very much.


texts: Terminating Transmission Lines with a Resistor

texts:
I have a large, but slow, SPI bus comprising of 8 devices. The frequency of operation is 2 MHz. As I understand, I need to ensure that the bus lines are properly terminated or reflections may cause signal integrity issues. The max. length that my signal can transfer is 1 foot over a standard ribbon cable.

One thing that I'm missing is the rise/fall times of my signal, which would actually determine if I have high frequency components in the signal requiring proper termination. I buffer the signal with a NC7WZ16 IC but was not able to find the rise/fall times in the datasheet.

How can I ensure that the bus is properly terminated to minimize reflections? The load is a CPLD in all cases.


texts: In FPGAs a tristate drive is used to convert a pin from an input to an output or vice versa.  Now this works only in digital circuits.  Is there a way how you could obtain the same functionality of the circuit but that it is able to work for analogue signals?


texts:
I have 3 power supplies all of which are stack-able.

Powermax PM3-100
2× SUPERNIGHT 12V 30A

Do they have to be identical to stack? I can adjust the voltage but would like to get 160amps if possible out of the 3.


texts:
I am struck . Currently working in sedra Smith , I stumbled across this question in BJT differential pairs . now I am confused as to how to determine which transistor will conduct and which will not .
Can anyone help me please


texts: Does a PCB circuit work without soldering the paste?

texts:
So the case is simple. I have to tune a Pi antenna matching network (a simple LC filter). That means I have to place and unplace a couple of pasives back and forth until I find out the right pair of values. Even if I do that operation with hot air gun, I am afraid I can damage the pad due to solder and desolder the component too many times.

I have been wondering if I can test the LC filter without heating the components, that is, I just place the L and C on the pads, as they are 0402, they stick to the pads and I can manipulate the board carefully. They do not fall unless you shake the board, what allows me to test it quickly and swap the components again without using heat.

I realized the paste is sill conductive before being heated but I don't know if the qualities of my LC network will be affected by this and so my tests will be really giving reliable data or not.

Have you people done this before?
Many thanks
Mario


texts: If I change the phase of a current running through a loop of wire, does the magnetic field produced by the loop change its phase by the same amount?

texts: Running a current through a few loops of wire produces a magnetic field. If I change the magnitude and phase of the current, the magnetic field magnitude will scale linearly with the change in magnitude in the current, but will the phase of the field also change linearly with the current? I'm talking about a current with a normal sinusoidal waveform, but does the answer change for a broadband or other type of waveform?


texts: Do accelerometers know when they are moving straight up or straight down?

texts:
I need a sensor that I can only place on top of an object, to count the number of times the object moves up and down.

Would placing an accelerometer on top of the object accomplish this or can it track the transition between moving up and down?

If not what type of sensor(s) would accomplish this?

---------------- EDIT: -------------------------

Ideally I would like a sensor I can set on top of the box outlined below and count the times it goes up and down. It has multiple guide rails that prevent it from twisting. I plan on using an arduino as a microcontroller that does the math, just need a sensor capable of sensing the up/down motion.  All suggestions welcome. thanks.

   +    +
   +    +
   +    +
------------
|   box    |
| moves up |
| and down |
------------
   +    +
   +    +


texts: What kind of component lets me measure distance in a small space?

texts:
I have bought a beautiful old radio, which I'm trying to convert into a DAB radio (there's no future for FM radio in my country).

Of course I could just use a DAB receiver, plug it into the old radio's speakers, and be done, but there's no fun in that. Instead, I want to be able to operate the old radio, turning its knobs and pressing its buttons. So that when I turn the tuning knob, I'm switching between DAB stations instead of tuning between FM frequencies.

The first step (at which I'm stuck) is to translate the position of the tuning knob (A) into a digital value I can use to control a DAB receiver. I'm a programmer, with only limited experience in electronics, so I'm not sure how to best accomplish this.

[]

Originally, the radio displays the frequency with a vertical bar (B) that travels over a frequency band (C). My idea is to attach something to that bar (or to the carriage that the bar is attached to), and measure the distance (D) between the bar (B) and the inside wall of the radio. If I could do that with some electronic component, I could get a signal that I could translate into a number that again could be used to select a DAB station.

The problem is that space inside the radio is limited.

Images

This image shows a horisontal, round bar on which the frequency bar moves along. When the radio is fully assembled, the speakers are located on top of this, leaving about 1cm space between the horisontal bar and the speakers. It must also go clear of two lightbulbs (for illuminating the frequency scale).

The frequency bar is sandwiched between the glass dial scale, and a metal plate. Here's what it looks like from above.

Here's the back of the tuning knob and its shaft. As can be seen, there's not too much space here. The knob is dual shaft - the outer ring is the speaker selector.

Here is a birds-eye view of the interiors, when taken out of the enclosing cabinet. And a close-up of the variable capacitor's shaft, as per Transistor's request.

Oh, and here's the schematics, if there are any Norwegian speaking radio enthusiasts out there.

Here are the options I have investigated/tried so far:

An ultrasonic rangefinder (like http://letsmakerobots.com/node/30209)
These are too big to fit. Also, I doubt I would get any sensible signal from it, as there are many parts inside the radio that would reflect the ultrasonic waves. The same goes for infrared rangefinders.
A slide potentiometer (like these: http://www.potentiometers.com/select_slide.cfm)
The ones I have found are difficult to fit, and there are not many that are longer than 10cm. The radio is ~50cm wide, so that would leave most of the band unused.
A SoftPot (like https://www.sparkfun.com/products/8681)
These works by reacting to mechanical pressure somewhere on the surface. They come with an "actuator", which is basically a screw with a round, plastic tip. This was promising - I attached the actuator to the part moving the bar, and let it travel along the softpot membrane. However, the tuning knob is carefully designed so that when the bar reaches one end of the scale, it stops moving, because the wire (E) that drives it will start slipping on the tuning knob to avoid damage. The pressure needed to activate the softpot was enough to cause too much friction, so that the wire was slipping, and the bar did not move.
A string potentiometer (like these: http://www.unimeasure.com/). I could attach the string to the bar, and the stringpot housing to the inside wall. However, most stringpots I have found seem to be meant for heavy industrial use, and are priced and dimensioned accordingly. The added friction could also be an issue.

What other options do I have?


texts:
I have flash memory that I write assembly code on it.

I know that flash has limit cycle ( read/ write)

If I write a loop that run 100,000,000 times like

X=100,000,000
While x!=0
    X--

That takes 4-5lines on assembly code.

If assembly run on flash, so after 2-3 loops like that ,my flash memory will be damage?


texts:
I want to send char though Atmega2560 to the xbee coordinator(AT mode), and router(which is connected to the computer) should receive that char. I can correctly receive messages
from router -> coordinator -> atmega. Which means UART receive function works correctly. But when I'm trying to send that way atmega -> coordinator -> router, in router I keep getting  messages like that 01 02 03 04 ... 0D... and so on.

UART initiazilation:

void uart_init(int baud_rate){
    UBRR0H = 0x00;
    UBRR0L = baud_rate;                                 //103

    /*Enabling Tx and Rx*/
    UCSR0B = (1<<TXEN0);
    UCSR0B = (1<<RXEN0);

    /*Setting stop 8 bits and non-parity*/
    UCSR0C = (1<<USBS0|3<<UCSZ00);
}

Here is my code for sending messages via UART:

void uart_send(byte data){
    while (!(UCSR0A & (1<<UDRE0)))
    {}
    UDR0 = data;
}

I'm sending messages from the main loop. Data to be sent is '0x73'. Im using sparkfun explorer for router, both of them is xbee series 1. Formula for baud_rate is (F_CPU /(BAUD*16) - 1). I've tried to replace router with coordinator, but nothing changes.

The thing is that even when I'm unpluging this xbee from microcontroller, it keeps sending hexademicals from 0x01 to 0xff.
So I want to know, what causing these problems.


texts: NiMH AAA battery outgassing after two charges? Is it dangerous?

texts: I bought quality Ni-MH batteries of size AAA. I recharged them properly with the charger from the same manufacturer. Now after only two charges when I insert two of the 4 batteries into my flashlight there is outgassing occuring on two of the batteries. Can I still use them? What causes this behavior? I have used these type of batteries for up to 200 cycles and never had an issue before.


texts: LTspice dependent voltage sources circuit

texts:
I am trying to add dependent voltage sources in LTSpice, but I need to make a voltage dependent source whose voltage depends on the average of two voltages. How can I build that in LTspice?

The circuit is like in image,


texts: Precautionary Discharging Capacitor went Terribly Wrong | SMPS

texts:
I wanted to check the fuse of SMPS pictured.

In order to safely conduct the procedure I followed the discharging procedure as provided in many tutorial videos i.e (connecting the end of the capacitor using nose plier). The fuse seemed alright but I while discharging the capacitor, a loud bang occurred (no power cable was attached)! This was quite loud bang. Does it mean the capacitor is bad? None of the videos warned about such bang! The capacitor was 330 mF.

I cleaned up the soot caused by the bang and checked the capacitance and conductance of the capacitor, I seemed fine, the fuse after rechecking was also fine and pretty much other stuff that I check prior seemed also fine (The power supply is still bad though)

Question: Shouldn't the capacitor go bad if a huge bang had occurred followed by soot on the PCB?


texts:
I want to make a small capsule that you can throw in your coffee and keep it warm (not hot, lets say about 40-50C).

In the first place, I don't care about power supply - I will have 2 wire going into my coffee.
However I do care about it being water-resistant

I found wire-wound resistor, will it do the job?

Next, is there any chance to pack the "thing" (resistor) and a battery in cr2032-sized package? I need 1-2 hour lasting battery.

NOTE: I do not want to "heat up" my coffee (from 20C up to 50) but to slow down the heat loss. So lets say my coffee is ~60C and I need to be @~50C 1 hour later.

Final test: I actually ordered 5W 8.2Ohm resistors and in about 30-45' it was able to WARM UP a ceramic cup of water which was about 15C to a warm-like temperature 25-30C which is way more than I expected (I just wanted to slow down the "getting cold" time of my coffee) @5V drawing min 480mA and max 540mA. Temperature measurements done with my finger but that's actually the kind of precision I need (the amp draw was done with an actual precise amp meter and the power supply was a 300W PC PSU so the voltage was very steady 5-5.1 Volts). KUDOS TO THE ANSWER!!! :D

THOUGH: In my test I had the resistor inside the water and it started "dissolving" so there is NO way you can put that in your drink.

I got fed up and just put 5 8.2Ohm resistors under my mug and got done with. It actually works...


texts: Wireless Power transmission. Is it possible to achieve 100-200w (load side) power using off-the shelf components?

texts:
Short introduction! I've recently built electric skateboard (you can look up the commercial ones) and I want to design/get a wireless charging system for it!

The problem is, it seems the current Qi chargers are not capable enough! I would need ideally 50-150w of power to the battery directly.. These little qi ones are only able to output 2.5-5w max per unit.. + There is also a limit on how many devices the charging mat can sustain it seems (+ their power ratings in general are also not great - Samsung has up to 1amp charging power, it looks)

http://www.bestbuy.com/site/samsung-mini-qi-wireless-charging-pad-black/7250019.p?skuId=7250019

--

I found a company, which seems to be related to developing wireless technology exlusively, take a look at them:

Search: Proxy module 100w (the 3rd result should be the one!)

They have a product for 100w output but it is rather bulky.. plus, I believe the price could also be quite steep as it is individually produced model/product and they will probably want some hefty honorarium for developing such product with their intelectual property...

Btw - I also found such a chip called: BQ 51050B you can look it up, it is made by texas instruments, it is not possible for me to post any more links for now, so I cannot give datasheet directly.

Anyways the chip is for receiving power only and charging the batteries, so it still needs a coil, for receiving power!

It looks like it is already designed for this application (the chip), but the question still remains:

Where to get the parts (coil, especially) to build more powerful wireless transmission module / system?

Thanks for answers anyways - I hope I can come up with something using this forum / Q * A site :)

BTW the max coil diameter should be in the 150mm range /  5.905 in, as the boards are not typically more wider than 200-220mm (~8-9inch.

I umderstand that the diameter alone does not play part.. but the wire thickness and count.. but diamater still should be taken into consideration, because as I said, the receiver coil shouldnt be much wider than that!


texts: Why is flux in field winding constant in DC shunt motor, but not series motor?

texts: As titled, why is the field winding constant in DC shunt motor, but not series motor?


texts:
I understand that AC electricity can travel through wires to represent sound. But, to be honest, I can't find a good explanation of it.

Here are my questions:

How exactly is this setup? Does voltage represent decibels or W/m2? Does the frequency of the current have a 1:1 ratio with the frequency of the sound waves (1Hz = 1Hz)? I assume that there are probably different standards. (line level and speaker level, for example).


texts: Why can a feedline be cut randomly when the antenna needs a specific length?

texts:
With a mobile two-way radio you have the radio, an antenna mount kit and the actual whip antenna.

The antenna needs to be trimed to the correct length so to match the freequency you are Tx/Rx on.

When you install the antenna mount kit though, you cut the feedline length without regard to electrical length.  Why can you do that?

I would think that the feedline and base were just an extension of the antenna whip and that any change in the length of the cable would have huge impact to the matched frequency.

What is in the base of the antenna mount that allows for this?


texts: Trying to determine if transformer is safe

texts:
I am building a switching power supply with an isolating step-down transformer. Part numbers:

Controller: LT3798 (http://cds.linear.com/docs/en/datasheet/3798fa.pdf)
Transformer: 750312872 (http://katalog.we-online.de/pbs/datasheet/750312872.pdf)
LTspice asc file: http://pastebin.com/XF5KJk3U (warning - this takes a LONG time to simulate)

NOTE: To run this spice simulation you will need to add the transformer spice files. Download them here: http://www.we-online.com/web/en/index.php/download/media/06_passive_components_-_custom_magnetics/pdf_doc_files_1/LTspiceStandardLib.zip

I have the official Spice model for this transformer, which includes saturation behavior, and the system works in simulations, outputting 28V 2A at about 75% efficiency.

However, the transformer datasheet indicates 20-60VDC input, while I am running it at about 160VDC input (rectified mains). Also, the transformer has 1.5kV isolation. I'm going to add input protection (500V varistor, common mode choke, differential mode choke, fuse), but is that enough isolation? I'm worried that there are factors involved here that I don't know about.

The transformer is rated for 25A saturation current, and I'm not exceeding 14A.

So I guess I'm also wondering, why is this transformer rated for 20-60V input when it appears to work for 160V? What determines that?


texts: Ceramic capacitor value changes after soldering!

texts:
I am debugging a power amplifier circuit and trying several capacitors values to fine tune the design to meet the frequency response specifications. All the 0603 and 0805 ceramic capacitors are experiencing the following issue:

I measure the capacitor (this one for example) using this digital LCR meter which reads 360nF (typical value 390nF with 10% tolerance). When I hand-solder the capacitor, it reads 420nF in-circuit, and when I desolder the cap, it still reads 420nF. What caused this big increase in capacitance?!


texts: Why can't I use lithium batteries in this multimeter?

texts:
I have essentially the same question as this.  In that question, it seems lithium batteries are prohibited for use in the device because it wouldn't adequately warn the user that the batteries need to be changed.  I'm finding the same anti-lithium-battery warning in a cheap multimeter (Gardner Bender GTD-311 if it matters).  It seems to me it wouldn't matter much if thing thing suddenly ran out of battery power and needed a new one.  It's not a device for alerting homeowners of imminent danger.  So, do I really need to seek out alkaline batteries for this device?

These are the type of battery I'm talking about:


texts:
So hello guys I am a first semester student in Computer Science. I have an exam coming up and I couldn't really find an answer whether bubbles affect the delay like inverters.

The bubbles having no delay makes kinda no sense to me since they do basically what inverters do. So I always assumed that there was an invisible inverter where a bubble is. Thanks in advance.


texts: Why is Frequency Conversion Additive in Acoustics Beating, but Multiplicative in Heterodyning?

texts:
In radio electronics, one of the first concept to learn is frequency conversion by using a mixer. And it's strongly emphasized that the mixer is a multiplier, not an adder used in audio circuitry. The description is usually something like the following...
Heterodyning

Adding or summing two sine waves of different frequencies (f1 and f2) combines their amplitudes without affecting their frequencies. Viewed with an oscilloscope, adding two signals appears as a simple superimposition of one signal on the other. Viewed with a spectrum analyzer, adding two signals just sums their spectra.
Multiplying two sine waves of different frequencies produces a new output spectrum. Viewed with an oscilloscope, the result of multiplying two signals is a composite wave that seems to have little in common with its components. A spectrum-analyzer view of the same wave reveals why: The original signals disappear entirely and are replaced by two new signals — at the sum and difference of the original signals’ frequencies. - ARRL Handbook for Radio Communication

And we have,
$$ \sin (2 \pi f_1 t)\sin (2 \pi f_2 t) = \frac{1}{2}\cos [2 \pi (f_1 - f_2) t] - \frac{1}{2}\cos [2 \pi (f_1 + f_2) t] \ $$
Most books also emphasize that

Frequency conversion (or heterodyning, or amplitude modulation) is impossible in a LTI system.

These made perfect sense to me, until I revisit the description of acoustic beats and beating frequency in most physics textbooks... It is said that if you add two sound wave together, the result is an amplitude modulated sound wave due to constructive and destructive interference of waves.
Beating

Suppose [...] that we have two waves, [...] From one source, let us say, we would have \$ \cos{\omega_{1} t} \$, and from the other source, \$ \cos{\omega_{2} t} \$, where the two ω’s are not exactly the same. [...] Let us first take the case where the amplitudes are equal. Then the total amplitude at P is the sum of these two cosines. If we plot the amplitudes of the waves against the time, [...] we see that where the crests coincide we get a strong wave, and where a trough and crest coincide we get practically zero, and then when the crests coincide again we get a strong wave again.
On this basis one could say that the amplitude varies at the frequency \$ \frac{1}{2}(\omega_1−\omega_2) \$, but if we are talking about the intensity of the wave we must think of it as having twice this frequency. That is, the modulation of the amplitude, in the sense of the strength of its intensity, is at frequency \$ \omega_{1}-\omega_{2} \$ - The Feynman Lectures on Physics

And we have,
$$ { \cos(2\pi f_1t)+\cos(2\pi f_2t) } = { 2\cos\left(2\pi\frac{f_1+f_2}{2}t\right)\cos\left(2\pi\frac{f_1-f_2}{2}t\right) } $$

Why is this even possible in the case of beating?
I initially suspect this is the result of being a non-LTI system, the system somehow contains a time-varying element, but I cannot identify it.
On my second thought, it seems that \$ \frac{1}{2}(\omega_1−\omega_2) \$ (or \$ \omega_{1}-\omega_{2} \$) is only a human perception of the change in intensity of two frequencies, and it's not an actual frequency component created by a modulation process, is it the correct interpretation?


texts: Using Op-Amp for attenuation to give input to sound card

texts:
I know there is lot of question asked about this topic before, I read them but there are some limitation on those circuits which make me ask this one.

I want to do analysis of main voltages(220/50Hz) in MATLAB. I want to visualize the harmonics and the change of the wave effect with Inductive and capacitance load. I have expeience in Digital electronics and little knowledge of analogue electronics.

I looked for this circuit from xoscope but this circuit is made for voltages less then 150 volts. I want to attenuate 220 voltages

is it possible? What would be the possible solution for this type of problem. How op-amp can help me in this problem?

and what are the maximum output voltage limitation to give input to sound card? I think max 1 volt but what are possible ranges? -1 to 1 or 0 to 1?
I am little confused and fear to test with my sound card without authentic suggestion.
Is there some good tutorial or some recomended study material with precisely bound to this topic?

This question may seem basic but I am asking this because I am not sure about my experience of sound card and I cannot afford to burn my sound card with making some circuit which I do not know what it does.
Thanks


texts: Can I power and use 4 small voltmeters for 3 12v batteries in series?

texts:
I bought some small voltmeters hoping I could use them with my kid's Razor dirt bike. The bike uses 3 12v lead-acid batteries in series to provide 36 volts to the motor. Ideally, I'd like to use the voltmeters to measure total voltage of the batteries in series, as well as the individual voltages of each of the batteries. I'd also like connect the voltmeters to the power switch, so they only measure voltage when the bike is powered on.
The working voltage of the voltmeters is 4 to 30v, and they can measure 0 to 100v.
The voltmeters have 3 wires. I ran the positive wire to the power switch, I ran the ground to the ground of each battery, and ran the measurement wire to the positive terminal of each battery. This seems to work fine for the first 2 batteries, because they are powered by 12v and 24v. The voltmeters for the last battery and the overall system end up getting 36v, which is too much for my tiny voltmeters.
The power switch is a single throw dual pole switch. Is it possible for me to power the voltmeters with 12v and use them to measure the system as described above?
UPDATE based on great feedback. I didn't know about reducing voltage with a resistor ladder. This is basically what I have now, just without the resistors. Will this work? I was afraid it may cause a short, because it seems like the batteries are both in series and parallel this way.

UPDATE - using 2 470ohm 5W resistors worked to divide the voltage, but the resistors generated too much heat. I measured 190 and rising after a few minutes. That seems dangerous. I'm going to drop back to 1 voltmeter powered by one battery, measuring all 3, and tied to one of the poles in the DPST switch.


texts: LTSPICE Simple MOS-FET Stacked Current Mirror/Cascode saturation threshold less than expected

texts:
I am running a few very rudimentary cmos circuits in LTSPICE.
For some reason, when designing stacked mirrors, I seem to get a much lower
saturation turn on thresholds would be expected. I've tried many different combinations of short/long channel lengths and aspect ratios. In this case, I would expect a min vout of 4*(VGS-Vt) or 4*.5 = 2V, but the current gets saturated at the output at only about < 1.5V. When using smaller lengths, it goes even lower, like 2(VGS-VT) when the current should saturate at 4(VGS-VT).

I'm using very simple level one models VTO = .8 and forced gamma to 0, to ignore the body effect. The spice operating points seem reasonable. The DC sweep saturation point, however, does not.

Several different stacked configurations are saturating way lower than expected.

Note: One device mirror only matches perfectly, it's when the transistors are stacked that the unexpected results occur. Also, the .op VDS are very slightly lower then VGS-VT, but I can tweak up and there's not much difference. I separated the Vdd sources, but results are the same with using only 1 Vdd source and sweeping output voltage. One other point, the number of matched diodes connected sources to the left (4), and the problem does not change at all. Current still saturates much lower than expected. It is understandable that models vary, etc... But the model deck has very simple models that mostly match expected 1st order level 1 calculations.

Here is a cascode stack of 6 devices, vdsat = vgs-vt = 0.5
I would expect 6*.5 = 3V min before devices saturate, but the dc sweep shows
only < 1.5V.


texts: It is pretty standard practice to clamp a signal to Vcc by using a diode and resistor. However, when this happens, some small amount if current (maybe ~50mA) is flowing back into the Vcc line. When using a switching regulator to supply the Vcc line, what implications does introducing this current source have on the system? Is this safe?


texts:
What options would I have for a cheaper alternative to using a micro controller like the Atmega for mass production products?. I just want something cheaper and smaller than an Atmega micro controller.

Because I can get them from China for cheaper price but they maybe fake or something as they are half the price than a authorized dealer. See if I buy from a reseller they cost about $2 each I need for under $1 each. I would prefer 10,000 pcs at 0.80 cents each for example. How can this be done? or could I deal with Atmel direct to get at right price?


texts: Arduino digital input - Read voltage slightly higher then 5V - a power efficient solution

texts:
I need my Arduino to detect the state changes in a device - (ON or OFF).

In order do do this, I have to check the voltage between two points on the PCB of the device. When the device is OFF, the voltage between such points would be 0V; when the device is ON, the voltage between such points would be 7V. When the device is turned on, it stays on for at least 3-4 minutes.

The problem is the that Arduino can only take inputs up to 5V. I have thought about different options for taking down the voltage to 4-4.5V:

a.) use the old good voltage divider, with low resistor values for the purpose of drawing as little current as possible from the original device circuit. The easiest solution, but not the most efficient.

simulate this circuit – Schematic created using CircuitLab

b.) use a classic RC charge/discharge configuration. It's probably the most easy solution; however being the difference between the 7V input and 4-4.5V output very low, I think it may not work that expected.

c.) use a resistor in series with a capacitor - RC. By doing this I would
  i.) detect a voltage higher than 0 both when the capacitor is charging and when it is discharging;
 ii.) avoid drawing current from the device all the time when the device is ON, but only when it is being turned ON and OFF. In this case I would be keeping trace of the state of the device on the Arduino.

simulate this circuit

I think c. is the best option as it is both simple and energy efficient. Being the frequency of the circuit very low, the capacitor resistence is very high. This coupled with a 47kohm resistor draws very litte current. The RC time constant is 4.7 seconds. To me it sounds a good solution, but as it comes from the top of my head and have not seen it anywhere else, I suspect that might be missing something.

Would it be reliable? And would the addition of that affect the functioning of the original circuit of the device?

Please help me thanks.


texts: Is it possible to run 240V 30 amp service over doubled 12wg Romex line wires?

texts: I have some existing Romex 12/2 installed on my machine. If I doubled the conductors used for each of the two line wires needed, would that adequately carry 30amps at 240 volts? This will be in open air at room temperatures.


texts: Having trouble converting an audio signal to be usable by a mic input

texts:
So to start, to say that I'm a little out of my depth would be an understatement.

I have a single channel audio signal coming from a building intercom system (data sheet). This audio signal is connected to a handset inside which has a speaker inside marker "45Ohm 0.25W".

When I connect this to a computer mic input, all I could hear was a loud buzzing noise so I checked the signal with a multimeter and found that it was about 11.4 volts. So, I made a simple voltage divider circuit (R1=10k Ohms, R2=220Ohms) to bring this down to about 0.25 volts. I connected the resultant signal to my computer and still the only thing I can hear is loud buzzing.

Where do I go from here?


texts: Input and Output symbols in EAGLE (perhaps with Labels and XREF)

texts:
I'd like to create arrows in my schematic.  The solution (using XREF) to an older, related post gets me most of the way there:

Arrows on connections in schematics

BUT, with that approach, the net always connects to the pointy part of the label symbol, effectively making all labels look like inputs.  Mirroring the label, or rotating it 180 degrees does not solve this problem.  Does anybody have a work-around?  e.g. is it possible to make a set of devices (INPUT, OUTPUT, INOUT, etc.) that have symbols and a pin to tie to a net, but no associated packages?

Here is an example of what I'd like to have:

And here is what I can do in EAGLE so far (notice that my OUTPUT is a mirrored version of the input, but the net is drawn through the label in order to connect to the vertex.  What I'd like is for the net to connect to flat side of the output label (i.e. on the left side of the label, near the letter "O" in the example below, and as in the CE, CSN, MOSI and SCK labels in the image above).


texts: Is It Posible To Have Step Up Power Supply Without a Transformer?

texts:
I am trying to design a high voltage low current power supply. My purpose is to  design it without a transformer. For example circuit like this :

My input is 220V AC after this circuit I am going to add some current limitter and also voltage rectifier circuit to have it in DC mode. I have seen a lot of design which is with transformer. And I thought that I can have this circuit to fullfil my needs.(which is 220V AC input ~ 800 or 1000V DC output.) Am I have to use transformer or is it just enough?.
Another question is: I couldn't find any step up transformer on the internet. If I step 220 AC down to 12V and after that is it posible to increase 12V to 1000V?


texts:
I am currently working in the simulation of a physics project. One of the detectors inputs a voltage V1:

V1(t)= D+Acos(wt)

and tries to extract the amplitude. I read that a simple  Envelope detector can do the job. The problem is that in my system sometimes D takes really big values and then the detector fails and returns a wrong value. I have very little idea on how to use a circuit in which this doesn't happen, although I guess that a high pass filter before the source could solve the problem.

How do I stop by system from failing to detect and return the wrong value?


texts: Can I measure current with a 0.1Ω shunt?

texts:
I am currently trying to make a game console out of a Raspberry Pi 4 and a hard drive, with an Arduino to control boot, shutdown or reset, plus temperature.

I got a degree in engineering in electronics and embedded systems, however I could not practice my skills for a while (world is governed by code today) and would like to implement some features, such as current monitoring. As far as I know the best way to do that in my case is through a shunt on the 5V line, measure the voltage difference at the sides with an ADC and estimate it.

Would a resistor of 0.1Ω be ok for this? Such as one like this:

I found some limited to 2W, if we consider a current of 3A maximum, that's a voltage drop of 0.3V and power dissipated of 0.9W, I can compensate for the voltage drop so this is fine.

My calculation gives me a step of 5mV with the 10 bits ADC of Arduino, which would mean I can measure current with a 50mA resolution; not very precise but I just need to know if I am in the 200mA or 2A range while using it.

This project is just for fun and practicing, not something serious, so precision or safety is not a big concern.


texts: Error -32 while establishing USB connection

texts:
We are working on a custom board based on STM32F769NI in Ubuntu 16.04 which has an FT232RL chip. We are connecting a micro USB cable from PC to custom board (micro USB port is adjacent to FT232RL chip in our board). When the USB cable is inserted, the following log appears:

I read there is no need to install any ftdi drivers. In Windows 10 also, unknown device descriptor. There is no serial port in Ports is displayed.

lsusb is also displaying only keyboard and mouse only:

$ sudo lsusb
Terminal log : device not accepting address, error -32
Unable to enumerate USB device


texts:
I'm using MCP2515 CAN Bus controller and I'm connecting between two boards successfully.
I have bough a can bus analyzer Ksaver, which allows to playback log files.

I connect the logic analyzer DB9 to one board that is connected to MCP2515 Transciever
I playback the log file
I expect to get a simulated version of a tx can data
I expect to get data on the board that is simulated

The problem is the board is setup as an rx, but I don't get any callbacks fired for getting a message while playing back the can bus.


texts: When Arduino catch interrupt, is noInterrupts() called?

texts:
I read the documentation about interrupts in Arduino and there is this example code:

int pin = 13;
volatile int state = LOW;

void setup() {
  pinMode(pin, OUTPUT);
  attachInterrupt(0, blink, CHANGE);
}

void loop() {
  digitalWrite(pin, state);
}

void blink() {
  state = !state;
}

Well, it is not good example, but for my question is good enough.

What if in function blink() is some non-atomic operation. Let's say, I have to change several variables, call some function, etc. Should I call noInterrupts() before, or are the interrupts disabled automatically?

void blink() {
   noInterrupts(); // Disable interrupts
  // some complex work, here.
  interrupts(); // Enable interrupts
}

I looked into hardware/arduino/cores/arduino/WInterrupts.c in my Arduino IDE directory, but I cannot find any information there.

And one more thing: Why should I declare any variable in interrupt routine as volatile?


texts: I have a 4-1 multiplexer. I am trying to learn how to use it and I understand the logic well enough, but since I have never had any electronics training, my knowledge is somewhat limited and without actual circuit diagrams on any online resource, it is very confusing. what I am confused about is how do you send inputs to the MUX. Do we need to have a full circuit from positive to ground and then have a branch coming out of that circuit going into the MUX? If someone could explain a simple input like say (0 1 0 1) with selectors (1 1) with a circuit diagram (which shows the power supply), that would be great.


texts: Altium 09 Copy Footprint between libraries

texts:
Just starting out on Altium. I want to start my own library and eventually end with a big library. This is Altium 09 and not the new one with access to the vault.

According to the website:

Adding Footprints from Other Sources

You can copy existing footprints into your PCB library.
The copied footprint can then be renamed and modified to match the specifications required.
If you want to copy existing footprints to your PCB library, you can:

select placed footprint(s) in a PCB document and copy ( Edit » Copy )
and paste them into an open PCB library using Edit » Paste Component , or
Select Edit » Copy Component when the footprint to be copied is active in the PCB Library Editor,
change to the open PCB destination library and select Edit » Paste Component ,
or select one or more footprints in the list in the PCB Library panel
using the standard SHIFT + Click or CTRL + Click,
right-click and choose Copy , switch to the target library,
right-click in the list of footprint names and choose Paste ."

My option to copy from the library is greyed out, and I have tried several hours trying to get around it with no avail. Also not really anything other than tutorials to be found on the internet!

EDIT After realizing that I am also not able to manage 3D models I re-investigated @Spehro's comment regarding licensing - that lead to solving my problem!

Does anyone know how to do this?


texts: IR2110 - measuring Vb to Vs kills MOSFET

texts:
I got a new digital oscilloscope as a gift. As a training course, I observed some waveforms of my test 12V full bridge circuit that is driven by TL494 and two IR2110 operate the IRF3710 100V mosfets. During my tests I was running it off a limited 12V 5A floating power supply.

My goal is to observe waveforms generated by possible parasitic elements of my pcb layout that are described in an-978.pdf, in section 5 "How to deal with negative transients on the Vs pin". I observed Vs-COM undershoot successfully.

However I was curious how high goes high side and what's it's rise time. So I hooked oscilloscope GND to Vs and put the probe to HO. I observed waveform, but mosfet it operated died. I did not noticed that immediately because I was running off a limited supply and input current increased only twice. I noticed that only after poweroff, when I touched heatsink, it was warm. And that high side mosfet is died with short.

It's a silly thing what I did? How measure that point safely?

During that test, scope GND was hooked only to Vs and only one channel was used. Scope was not grounded (my building does not have PE wire).


texts: Does a clamping current specification under Absolute Maximum Ratings imply that less current is OK?

texts:
I have an application where I want many small signal relays driven by an I/O expander chip. In this case, I have selected the Microchip MCP23017 (Datasheet) as an I2C to GPIO expander. I have also selected low-current reed relays with the intent that I drive the relays directly from the I/O pin. (5mA coil current, 24mA I/O current). Normally, with a relay, I would expect to use a clamping diode across the coil to protect the output device - this is standard practice. However, I noticed this bit in the datasheet of the expander, where the absolute maximum clamp current is specified:

With my coil current of 5mA, I'm not close to the maximum rating, which to me, suggests that I'm OK with omitting the normal external clamp diode. However, nowhere else in the datasheet is the clamping current mentioned, which (again, to me) suggests that the internal diodes should not be used during normal operation.

Do I play it safe and put in the external clamping diode, or do I assume that if it's less than the Absolute Maximum Ratings, it's safe?


texts: Can't find Step-Down VREG in D2PAK with "strange" pinout

texts:
I'm repairing a device. I have found burned VREG.
Seems like simple adjustable step-down voltage regulator with integrated switch in 5-pin D2PAK/TO-263.
IC package was damaged and label isn't readable. "No problems" – I thought...
But! When I trace nets I have found, that pinout of VREG is "strange".
Look at pic. I noted my pinout with red.

All 99% of such VREGs has same pinout. And other 1%, that I was found – has another pinout, but not needed.
Anyone know such VREG? Ty!


texts: Using different putch() function in a library

texts:
I'm writing a C library for PIC18 microcontrollers that will communicate with the ESP8266 chip over the UART bus. I would like to use the printf() function to send formatted strings to the chip.

In XC8, printf() uses the function putch() which the user should define as output. This way, the user can decide whether to use UART, LCD, ... for stdout.

This gives me a problem. In the library I want to use printf() which relies on putch(), but I can't (shouldn't) declare putch() in the library because that would give a conflict when a user wants to use the ESP8266 in combination with an LCD for which he already defined putch(). How can I solve this problem?

I could use sprintf() to temporarily store the string in the memory and then write my own code to write this byte by byte to the ESP, but I'd rather not because of memory and time inefficiency.

I could also roll my own esp8266_printf() with limited functionality and use that instead, but that doesn't feel that neat either.

Is there a clean(er) solution for this?


texts:
I am confused by the use of these three terms in conjugation with supplies.

I read somewhere that the prime objective of the circuit is to provide power rather than voltage? What exactly does that mean. Isn't \$Power = IV\$? So saying that you're supplying power rather than voltage is another way of saying supplying a large current. If so why not just say so. Why beat around the bush when saying a current supply is far more intuitive than a power supply?

So what does this cryptic sentence mean: "Supplying power to the load." Do they mean a large current or a large voltage?


texts: single board computers sharing a microswitch

texts:
I have two independent single board computers (SBCs) connected to a common ground.

I wish to have an input pin on each (both used concurrently) connected to a microswitch.
When the microswitch closes both SBC pins will go low.

Is this OK?

Haven't been to this board before.  Hope this is the right place to add info.
Not and electrical engineer.

Both SBCs powered by same 12v source.
Both SBCs and all peripherals (switches, etc.) grounded to single point.

Both SBC inputs are +5v.

Thanks for your help!


texts:
I’ve just graduated from the electrical engineering faculty.
So as I  researched, most of the companies required PCB design in Altium/eagle or equivalent...but there is a question in my mind is,  how many layers of PCB should a new grad electrical engineer draw in this software? Or what kind of qualifications do I have to get a job as a new grad engineer? I can use Eagle and draw some of the circuits but some of my friends said “if you cannot draw less than 6 layers, you cannot get a job” so this kinda conversations makes me worried about this. Thanks for your help.


texts: Is it possible to build a computer (Turing complete) using only diode logic without transistors? I know DTL was a thing, but from what I could tell, they used transistors to amplify signals.


texts:
I have a schematic of some electrical components and something is marked +9/7.2V.  What exactly does that mean?  I presume the 7.2V means 7.2 volts, but what about the +9/ part?

It is a PB Board for powering some fans in a plasma television.  The number is for the connection of the fans to a small board.  Since i am not a great expert on these things (hence the possibly simple question), I don't really know how else to explain it.

Any information would be greatly appreciated!


texts: Charge Arduino through Computer but connect to external circuit

texts:
I'll explain what I'm trying to achieve first. I basically want to control a 4 wheeled robot through an Arduino but I need the Arduino to get the commands from a computer. I've already setup the circuitry for controlling the robot motors (H-bridges, encoders, etc) and I just need to send GPIO signals to that circuit. As I need to get the instructions from the laptop, I need to power the Arduino through the USB connection. Now here's where the problem comes in.

If the Arduino gets its source power from the laptop but needs to communicate with an external circuit, what happens to the ground? I'm pretty sure the Arduino will need to have a common ground with the external circuit's power source for this to work. My worry here is what will happen if the battery sends a spike current through the ground connection and fries the Arduino (I've heard this can happen). Is there some way I can protect the Arduino from this or is this some better solution that I'm missing here?


texts: On-grid solar system - how to control power out from solar system to grid?

texts:
If on-grid solar system is connected in parallel with grid,
solar system give power to the grid when local (at house) consume power less than generated power from solar system.

The question is:

When solar system (or any AC source) tied to grid, that means it share the total load connected to that grid, how power of solar system output can be controlled?

Example: if total load connected to the grid is 100 kW, and power of solar system is just 2 kW, how could make solar system give only 2 kW (to not exceed its capacity)?


texts:
I am trying to find the gain for vd/vi and vs/vi. My initial attempt as to find vd in terms of vdd,Rd, and Id. What I obtained was:
Vd=Vdd-(RdId)
I attempted the same thing with Vs and got:
Vs=(RsId)-Vss

My problem is how do I relate them to the gate voltage, vi? Something tells me I did this wrong(the setup) as I think Id has no purpose here.

Note: The problem doesn't tell me what region of the graph the MOSFET is in and doesn't give me numerical values.

Thanks for the help!


texts: How should I model the DC power supply that powers the drain of an LDMOS RF power amplifier?

texts:
We would like to model a switching power supply for an LDMOS RF power amp so we can design the bias tee powering the drain to reflect as much RF as possible to keep RF out of the power supply.  The signal will be around 144MHz.
We wish to keep the power supply model simple (if possible) and represent common 12V switching power supplies like those found in computers. In the picture below "PORT 6" is where the power supply will be attached in another circuit.

What output impedance should we assume that such a power supply might represent?
Are there any other considerations when modeling the DC power for the amp's drain-source?

(This video explains the project in more detail if you need more info or a picture of the whole circuit.)


texts:
How can I get Modelsim to run faster for simulation rather than
something in the picosecond range (time interval)? Are there any other
methods for speeding up simulation? It takes 45 minutes to get to 1ms as
of now. I want the simulation to run for 20 ms to check on certain
counters, timer modules and events. The system clock runs at 50 MHz.

And if there is an option will there be any drawbacks. For example
missing events etc.?


texts: Battery Protection MOSFET 8205A Replacement

texts:
I am planning to add battery protection to a schematic for a project that is using the Panasonic NCR18650B 3400mAh 3.7V 18650 Li-ion Battery.  The protected version of this battery uses the protection circuit outlined in this post

Dual mosfet 8205A - lithium battery protection circuit

I have difficulty sourcing the Dual Mosfet-8025A in the EU with a short lead time. Does anyone know where I can purchase this Mosfet. Have tried the usual suppliers such as Farnel, RS, Mouser, Digikey etc.  Or is anyone aware of a suitable MOSFET for this part available on Farnel, RS, Mouser, Digikey. I am novice when comes to electronics and have struggled to identify a suitable alternative


texts:
I'm working on BL653 project, I have an issue how to left VDD_HV pin unconnected when I'm using USB?
VDD_HV pin must be unconnected because I am using OPTION 1 with USB.
OPTION 1 says that both VDD and VDD_HV pins must be on same voltage suply(in my case 3.3V).


texts:
simulate this circuit – Schematic created using CircuitLab
How R equivalent can be found (without using star delta connection)? the answer said 3/5R


texts: Resistor Coefficient Voltage Matrix Doesn't have a Solution

texts:
Follow the link to the circuit that I need to solve for all the resistor voltage drops.

I have to make 5 linearly independent equations in order to solve for all 5 unknown voltages.

Using the loops as drawn in the image following the link I get the equations:

1. iR1*4000 + iR2*2000 = 8
2. -iR2*2000 + iR3*1000 = 4
3. iR4*6000 + iR5*1000 = -4
4. iR1*4000 + iR3*1000 = 12
5. -iR2*2000 + iR3*1000 + iR4*6000 - iR5*1000 = 0

And the Matrix:

4000  2000     0     0     0     8

   0 -2000  1000     0     0     4

   0     0     0  6000  1000    -4

4000     0  1000     0     0    12

   0 -2000  1000  6000 -1000     0

When I row reduce this matrix, I get a row of all zeros which indicates that there isn't one unique solution to this matrix. I cant figure out what I am doing wrong as this is impossible. I could probably use different loops but I still need to understand why this configuration does not work. I have the understanding that all of my equations are linearly independent.

Note: There are better ways to solve it but the Question asks to solve it with exactly a 5 x 6 Matrix.


texts: Driving a Bar-graph LED Block With a Range of HV

texts: I'm aware that it's possible to use the voltage drop of diodes to act as a step barrier for a rough ADC(?), as is done here (http://www.instructables.com/id/9-Channel-pure-analog-graphic-equalizer/). However, I'd like to drive a bar of LEDs as a voltage meter for a charging capacitor bank. How should I handle level-shifting the capacitor output for the array of LEDs? I'd imagine I'd use an opamp in a positive-feedback setup with very low gain. However, I'm not sure how to efficiently protect the opamp-- I intend to use high-voltage capacitors. Should I connect the capacitor directly to the opamp? Would that kill it? If so, what should I use?


texts:
I have the following circuit:

I have to find the transfer function by using mesh analysis. First of all I used the Laplace transformation.

Although I saw some similar exercises, I don't really see what I can get out of the mesh equations.

1st Mesh
$$V(s) - I_{1}(s)R_1 - V_{L_1}(s) = 0$$

2nd Mesh
$$V_{L_1}(s) - I_{2}(s)R_2 - I_{2}L_{2}s = 0$$

Also I assumed that $$V_{L_1}(s) = sL_{1}(I_{1}(s) - I_{2}(s))$$


texts: How use 'Hierarchical Blocks' in Eagle?.. nesting schematics within schematics?

texts:
I want to design a schematic and board pair (e.g. 'submodule.sch' and 'submodule.brd'), and then use multiple instances of 'submodule' to make a new design:  '8submodules' (which contains 8 instances of 'submodule'). Yes, you can copy and paste, but I desire the ability to change the 'submodule' and it automatically updating all the instances.

Eagle 6 now declares:

  Design Reuse (available for EAGLE Professional and EAGLE Standard)

  Merge board/schematic pairs using the PASTE function with full consistency
     You can copy an already finished design consisting of a consistent pair of Schematic and Layout into another project. Enumeration of components and signals will be exactly the same in board and schematic, so that consistency between schematic and board will be maintained. This supports easy design, for example, of multi-channel devices. You only have to design schematic and layout for one channel and can copy it easily.

How do I do this?

Edit: After looking into this further, I came to the conclusion that @Dave_Tweed is correct - this is not possible with Eagle. However, I am now using the open source KiCad which does support 'Hierarchical Blocks'. IMHO Kicad is generally an excellent EDA, much better than EAGLE.


texts:
I gonna make some 2-speakers Bluetooth PA system, and I chose bi-amping way with active crossover for do it. I have an 60W amp (battery limits) for my woofer. Skipping all the problems on my road to do it, how much power I gonna need for my tweeter? I chose this woofer and this tweeter:
https://www.thomann.de/pl/eminence_emd2002l.htm
https://www.thomann.de/pl/harley_benton_15tb065_b4.htm


texts: If I have a 2cm*2cm square and drill a really small hole in the middle thats    barely visible for the human eye, and I place a photoresistor below , will the photoresistor be able to detect any light that comes from the hole?


texts: Is it possible to use an AVR Timer such as Timer 0 or Timer 1 to time events, but leave the associated pins unaffected by the timer? For example, if you have GPIO connected to the timer pins, they can still be used for GPIO instead of being tied up for its timer?


texts: Digital Compass: Can it be calibrated/shielded to prevent normal operation in the presence of ferromagnetic materials

texts:
I am currently working on a hobby project, for which I would need a reliable compass that should work in as wide a range of environments as possible (i.e.: In a field, in a car, on a train, possibly even on an airplane)

I chose the LSM303DLMTR tilt compensated compass (datasheet here)

It was easy to set it up with an Arduino board and then make a calibration (using a predefined set of steps, using a library. The Arduino periodically prints a heading, but now the problem arises that if there is even a small magnetic field around, it will make the heading reading useless.

Even in my room, which shouldn't have any strong magnetic fields around, the compass only printed junk. This is frustrating, since an ordinary compass isn't nearly as bothered by nearby fields or ferromagnetic materials.

Thus, I have two questions:

Is it possible to shield the compass effectively against minor interference (I realize that a strong, local magnetic field will always ruin the compass functionality) and against ferromagnetic materials nearby? (Ideally, I would like to be able to use the compass in a train, which creates magnetic fields through the electric lines.)

Related to this: Can minor perturbations be avoided by using a "smart" calibration, and does this need to be repeated every time a strong field perturbs the compass?


texts: Finding the logic expressions of a finite state machine that has three possible inputs

texts:
I'm familiar with finite state machines when there are two possible states for input, which I will call w. That is, w = 1 or w = 0. However, what about the situation in which w can equal A, B, or C? In this situation, I believe that I would have to represent the input with two bits, such that A = 00, B = 01, and C = 11.

For example, say I have to detect the sequence ABCB (using a Moore Machine). Below is a picture of the state diagram, state-table, and state-assignment table:

Here, I represent the present state with three bits, and the next state with three bits. Normally, I have no issue finding the required logic expressions using Karnaugh Maps given that w = 1 or 0. However, here w = A, B, or C. Assuming that I let A = 00, B = 01, and C = 11, how would I derive the appropriate logic expressions?

My inclination is to solve a 5-variable Karnaugh Map for each Next State flip-flop (i.e. Y2, Y1, Y0). For instance, Y2 is some function of y1, y2, y3, and w that can be found using a Karnaugh Map.

Am I heading in the right direction with my reasoning here? Any constructive input is appreciated.

Note: This is related to an assignment of mine, but this is not the pattern I'm trying to detect.

Edit: Now that I thought about it some more, it seems like I really have 5 bits to work with in regard to the Karnaugh Map - which it technically four variables because yn represents 1 bit and w represents two bits.


texts: MOSFET Relay (G3VM-21AR/DR) connected to Arduino Digital Pin

texts:
I am trying to figure out how to go about using this Omron MOSFET relay in my project. I will be sending 12V (car voltage) to a radar detector and I want to be able to turn it on/off whenever via the Digital Pin on an Arduino board (max 5V output).

When the digital pin is high it allows 12V to flow to the radar. When the digital pin is low then it shuts out the 12V so no power is going to the radar.

PDF

Do I have the schematic above correct? Am I leaving something out?

Update

Like so:


texts:
I accidentally killed a transistor in my HP Elitebook 820 G3 and need help identifying it. I searched the internet for about an hour and can't find the code that ist printed on the component to buy the correct replacement. It is located near the power connector.
I hope someone can help me by telling me what kind of transistor(?) this is.


texts: I have four op-amps that are each amplifying signals from four different microphones.  All of the microphones are recording a single source, but the location of the source moves, so the outputs from each amp are different magnitudes, based on the distance to the source.  I want to create an AGC circuit or feedback network to automatically adjust the gains of each amplifier so that all the outputs are of equal magnitude. For example, the gain of the closest mic would be lowered, and the gain of the furthest mic would be raised, thus bringing the outputs to an equivalent level.  Are there any existing designs that implement this?


texts: Shielded Ethernet Cables in Office Buildings - Ground Loops?

texts:
I have a question related to shielding and grounding of ethernet cabling in industrial environments, offices and datacentres.

What I assumed as correct so far (please correct me if I’m wrong):

In Consumer PCs the ethernet shield is connected to the case via the
IO-Shield. The case is grounded over the PE-conductor in the PSU.
On a commercial server it is the same (only had one to check).
The ethernet standard specifies signal transformers at each
interface to achieve a galvanic isolation between endpoints.
For a cable shield to be effective (at high frequencies) and not act as an antenna, it
should be grounded at least at both ends. For very long cables more
ground connections may be necessary. To break ground loops this
connection may be capacitive at one end.
The galvanic isolation on the signal line is, I presume, there to
protect the sensitive electronics from a potential voltage
difference between the two endpoints. But
if you use shielded ethernet cables, then you will create a low
impedance connection between the two endpoints and a current will flow
through the shield.

Now to my question:
Industrial interfaces like EtherCat have a capacitive coupling of the shield to the case. And I assume in datacentres and the likes the grounding system is tightly controlled so no potential differences can arise. But how is this handled in office buildings? Is it just assumed that the grounding system is good enough so that there are no, or only very small, balancing currents on the shield between the two endpoints? Or are these currents just no problem in these practical applications?


texts: I need help with probably a simple problem

texts:
I am taking an online course on electronic devices. It is poorly done and I already paid for it.
Yesterday I asked a question similar to this one however I didn't understand the explanation. This time I took a problem from the course, and I hope somebody is willing to explain me in details what to do.


texts: Low power voltage step down for datalogging

texts:
I am trying to design a datalogger that runs off battery power and am trying to maximise runtime.

The logger is infrequently (every 5 minutes) logging 0-30V analog and digital signals.

One of the key current draws at this stage is the voltage dividers required to reduce the signals to the 3.3V or 5V tolerated by the microcontroller. As even loads as high as 1Mohm begin to add up (16 inputs total = approx 0.48 mA).

This seems like a pretty common problem but I haven't been able to turn up an accepted solution.

I have contemplated options such as

Reed Relays - Semi impractical due to the required quantity, possibly more beneficial at even lower sample rates.
Some kind of buffer IC - Haven't been able to turn up any parts that accept a voltage so far out of the supply range


texts: Finding current through an LED in an amplifier using a BJT

texts:
Suppose you have the schematic:

My job is to find \$I_{LED} \$ knowing that the impedance of the capacitor in negligible against \$V_s\$. Here's my attempt:

I intend to do an AC analysis followed by a DC analysis, and get both components of the current that goes by the LED.

Where \$R_A=R_1||R_2\$

For the AC analysis:
I did the schematic in the figure and with the following set of equations I get to the final result:
$$
i_1=i_2+i_B \\v_s-i_1R_B-i_2R_A=0 \\
v_s-i_1R_B-i_ER_E=0 \\
i_C=\beta i_B \\
i_C\approx i_E \\
\therefore i_C=\frac{\frac{v_s}{R_B}}{\frac{1}{\beta}+R_E\bigg(\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_B}\bigg)}$$

For the DC analysis I use the following set, reaching the result:
$$V_cc-I_1R_1-I_2R_2=0 \\
V_cc-I_1R_1-V_{BE}-I_ER_E=0 \\
I_1-I_2=I_B\\
I_B=\frac{I_C}{\beta} \\
I_C \approx I_E \\
\therefore I_C=\frac{\frac{V_{cc}}{R_1}-V_{BE}\bigg(\frac{1}{R_1}+\frac{1}{R_2}\bigg)}{\frac{1}{\beta}+R_E\bigg(\frac{1}{R_1}+\frac{1}{R_2}\bigg)}
$$

Finally I get to:

$$
I_{LED}=I_C+i_c=\frac{\frac{V_{cc}}{R_1}-V_{BE}\bigg(\frac{1}{R_1}+\frac{1}{R_2}\bigg)}{\frac{1}{\beta}+R_E\bigg(\frac{1}{R_1}+\frac{1}{R_2}\bigg)}+\frac{\frac{v_s}{R_B}}{\frac{1}{\beta}+R_E\bigg(\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_B}\bigg)}
$$

However the correct solution is:
$$I_{LED}=\frac{\frac{V_{cc}}{R_1}-V_{BE}\bigg(\frac{1}{R_B}+\frac{1}{R_1}+\frac{1}{R_2}\bigg)}{\frac{1}{\beta}+R_E\bigg(\frac{1}{R_B}+\frac{1}{R_1}+\frac{1}{R_2}\bigg)}+\frac{\frac{v_s}{R_B}}{\frac{1}{\beta}+R_E\bigg(\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_B}\bigg)}$$

I know that this is a very long question and I don't ask for a solution to the problem, because I have one solution that leads to the correct result, however they don't do the DC and AC analysis separately and I was trying to do it because it should work, but I don't know where the mistake is, the answers are really similar and the AC analysis appears to be correct but the DC does not, and I can't find the mistake.

EDIT: I have found the mistake, In the DC analysis schematics I left out the resistance \$R_B\$, and if I leave it in the schematics connected to the ground then I can substitute, in the DC analysis only, all the \$R_2\$´s by the paralel resistance of \$R_B\$ and \$R_2\$ and the answers match. But a new question comes up, why do I have to leave \$R_B\$ connected to the ground? I thought that with a DC analisys capacitors would be replaced by an open circuit, therefore, no current should go through \$R_B\$, and that's why I ignored it. And this is just th case where I have a resistance \$R_B\$ there, if I didn't, but left that branch connected to the ground, then wouldn't it act as a short and we could ignore \$R_2\$?


texts: How to obtain SNR when we have the samples of a non-DC noisy signal in practice?

texts:
This may sound a naive question but I couldn't find an example. Let me begin with what I know about SNR and where I am confused.

Lets say I have a DC like signal with some random noise on it and I have the samples. I can then by using MATLAB or any such a tool subtract the mean value from the samples and obtain the noise floor and calculate the noise rms. So I can eventually find the SNR by dividing the signal power to the noise power.

But if the signal lets say is a sine wave with random noise like below:

in this case how can we calculate the SNR if we have all the samples? To do that we need the noise samples and rms noise. But my problem here I cannot use the same method I was using for the noisy DC input case. What is the convenient way to obtain the noise and SNR for this case?


texts: Controlling a hard drive motor with arduino

texts:
I bought this controller shown in the image below for controlling a hard drive motor. My idea is to replace the speed potentiometer with one controlled by the ardunio using this circuit here: http://www.learningaboutelectronics.com/Articles/MCP4131-digital-potentiometer-circuit.php Is there a way I can desolder the potentiometer and make use of this circuit? The driver board draws around 100mA it seems.

Thanks for the help!


texts: I have an transistor that is used in mist maker circuit, but it's scratched for not understanding its model or numbers. how can I found out what type is this transistor?


texts: How can i prove that the current value (Ids) of two serial transistors (nmos) with equivalent W/L values is equal to the current value of one transistor with W/2L (In linear region)? (Ids1 = Ids2 in the picture)


texts: Powering a stepper motor without a 9v battery

texts:
I need to power a stepper motor in a handheld device. I'm currently using a 9v battery, which has flawed long term usage.
The problem I am finding is that the 9v battery is: (a) expensive; and (b) has a short life. Once the battery falls below 7V, the voltage is insufficient to drive the motor. This occurs after around 150 button presses (activation of the motor). A single activation of the motor lasts less than one second, as it is only stepping it 1/8th of a step. However, I'm more concerned about the cost and time associated with replacing the battery. Are there better battery operated solutions out there? Something rechargeable would be ideal.

The battery is powering a bi-polar stepper motor for tiny bursts. The battery is currently connected to an ATTiny85 and EasyDriver v4.4. The stepper motor is from Alibaba. It is rated for 3.9V and .6A. The datasheet can be found here.

The mechanism of operation is as follows.

Switch turns circuit on
Capacitive switch actives circuit
Circuit drives motor which performs a 1/8 step.
Switch turns circuit back off

Note: The motor is most likely at the maximum load each time it activates.


texts: Modbus: Sensors timed out when plugging another sensor

texts:
I have created an hydroponic system using modbus to communicate between a RaspberryPI server and plug&play arduino sensors. It works but as soon as I plug a sensor on the bus (physically), all the other plugged sensors are timed out for a couple of seconds.

The sensors are connected on the same PSU as the RaspberryPI.

I tried to power a sensor with another power supply (USB of my desktop computer) and everything works well. Other sensors are not timed out.

I tried to see what happens with an oscilloscope (on modbus lines A & B) but I can't interpret the result and I don't know how I could make them work on the main power supply. My electronics skills are very limited.

Here are pictures of the recorded data:

Thanks for your time !!


texts:
How do you go about identifying a female power connector if it doesn't say anywhere on the hardware or where I brought it from?

I have attached an image below, the male connector (battery) doesn't fit the female connector, would it simply be easier to just change them both to a more common connector?


texts:
I'm about to start placing components on my very first 4-Layer PCB (wrapping up schematic and MCU software tested on 2-layer pre-prototype, all runs surprisingly ok, but still 2 layer meh). I've studied a lot of materials, videos from Robert Feranec and Rick Hartley on grounding. While a lot of stuff there is really complicated or assumed understandable, it's pretty damn hard, nevertheless I've learned a lot (even if understood not 100%, but most of it), but I still have a few questions I want to clarify. Several hours of googling brought nothing, and there is nobody I can ask a specific question (or a few).
My design is up to 20MHz MCU system, UART, SPI, I2C, has DAC and ADC, max system current 5V 1A.
Planned stackup: Sig-GND-Vcc(5V)-Sig.
Question 1: GND pours on Sig planes. Yes or no? Most examples actually don't have pours, but explicit answer would be welcome (and short why).
Question 2: the decoupling capacitor should have a via to the POWER layer (3) and the GND layer (2). BUT: I can't have connections to both Vcc and GND planes from Top and Bottom layer: EAGLE was refusing to allow me make vias like that (1 to 4 ok, 1 to 2 ok, 3 to 4 ok, but only EITHER 1 to 3 or 2 to 4, DRC tells me NEIN when I try both; Eagle numerates layers as "1", "2", "15" and "16" respectively). I googled out it was for manufacturing reasons, which made sense now that I think about it. So how do I place decoupling caps for the chips on the bottom? Bottom (layer 4) can't have direct via to GND (2). What do I do about it?
Question 3: I saw a lot of material on impedance and all, but layer switching was only mentioned briefly and kinda "assumed easy and clear" that I need to switch reference plane or something (since I was against GND plane on layer 1, but against Vcc on layer 4). Well, I have actually no clue what any of that means. Say, I have an I2C signal on layer 1. Suppose, I really need to switch it to layer 4. Signal's via goes straight to 4, no problem. What do I do with current return path, which was on GND plane right under I2C trace(right)? And again, Bottom layer can't even have direct via to GND.
Question 4: mechanical one. Internal layers  in JLCPCB guidelines that I looked at as an example, are by default twice thinner than outer layers. So GND and 5V planes are thin. Should I care? (5V 1A max for system)
Unfortunately, the whole thing is very confusing at the moment. 2 Layer board required less brainwork. Pour more, think less. Now I understand why it's bad (I guess, "worse" is the correct word), but I'm stuck between rejecting 2 layer design wishing to make things better and being unable to adopt 4 layer design even if I spend a lot of time researching it. I grasped the key ideas and concepts, but some smaller practical details are omitted wherever I looked.
I would appreciate if you could also share some materials like "4 layer PCB for dummies" or something in addition to specific replies to my questions. Can't have too much information.
Also, maybe someone could give a link to a good simple 4-layer PCB design I could look at in Eagle or Altium (have trial version of that, wish I could work in it always). No DDR stuff, more of my caliber - MCU and peripherals, if possible. Thank you.


texts: Could you please validate this sine to square circuit?

texts:
I need to read the velocity of a universal motor with a microcontroller. The motor is a universal brush motor 230 V AC 50 Hz velocity controlled by a Triac. The motor has a mechanically connected an AC (generator) tachometer that produces a frequency (and voltage) proportional to the motor rotation velocity. I need to read 1 kHz max of sine wave with a variable voltage from 0 to 35V ac peak-to-peak and transform it in a square wave thanks to the BC547 as a switch.

After several experimentations between a comparator circuit with an LM393 and a more "simple" switch circuit, I chose the last because I noticed that in the field of motor & C it is the most used (maybe for better stability under noise?). I simulated the circuit that I found (the original one was with a PNP BJT I don't know why) and modified it a bit, and all seems ok on the PC. I added R7 in order to shift a bit the sine signal and overcome the 0.7 Vb threshold of the BJT, so that when the input signal is <0.7 V RMS I can still read it. The BJT produce a square wave 0-5V that I send to my micro to count the frequency.

I would put this circuit over a PCB with other stuff, so I would like to know some suggestions about it and if I can proceed!

I read about a third harmonic problem with the 230 AC motor that could be induced in the tachometer (motor and tachometer are very close), and a datasheet suggests for a low pass filter. My doubt is that with a low pass filter centred to 100-150 Hz I think I would take off my signal (up to 1 kHz)!  A lot of noise I think will be produced by the 230 AC sine partially due to the TRIAC.

My questions:
1. How to deal with this (supposed) 3rd harmonic problem?
2. What could be the role of R8?
3. Without the C2, can I avoid the R6?
4. The capacitor values could be ok?

Thanks a lot

Update: analogKid, whitout the BJT the total shift with V2=1V seems not 2.08 V but 1.3V about. With V2=100mV the output is 0.66V about. I would capture motor rotation starting when V2>100 mV about. Maybe I need to raise a little bit more the R7 to 150-180 kOhm to avoid a too low trigger compared with noise. I'm in trouble to calculate the impedence of the generator (V2). The tacho resistence is 70 Ohm, but when the AC signal is generated the impedence appears and I don't know the XL (inductive reactance). The Z=R+jXL also change when the frequency change!


texts: PCB layout - part placement note in draftsman drawing

texts:
I am preparing to transfer a schematic project to a layout person. I'd like to include a note in a draftsman drawing detailing an area where a component must go on the PCB to avoid interference from other external parts in the product but not on the PCB. I thought I could make a draftsman document, draw a rectangle in the correct area (that is larger than the part) and then add dimensions from the PCB origin to the vertices of the rectangle. Altium isn't allowing me to dimension to a rectangle or any object that I add in draftsman view.

How do I do it?


texts: Below in right side there is an discrete output signal circuit implementation and as a platform i need to read this signal somehow. I have a discrete input interface. My question is how can use my open/gnd interface to read signal.


texts: Why can we measure current in AC voltages?

texts:
From Wikipedia:

The drift velocity deals with the average velocity of a particle, such as an electron, due to an electric field. In general, an electron will propagate randomly in a conductor at the Fermi velocity.[5] Free electrons in a conductor follow a random path. Without the presence of an electric field, the electrons have no net velocity. When a DC voltage is applied, the electron drift velocity will increase in speed proportionally to the strength of the electric field. The drift velocity is on the order of millimeters per hour. AC voltages cause no net movement; the electrons oscillate back and forth in response to the alternating electric field (over a distance of a few micrometers

This can be found here
If AC voltages are causing no movement how is it that we can measure current, which is defined as - The net rate of flow of electric charge past a region.
What am I missing here? Thanks for your help.


texts: reading data back from lm016l LCD(HD44780)

texts: How to read data back from a lm016l lcd(HD44780 based)?I couldn't find any useful data on reading except writing.I have followed hd44780 datasheet ,but when i try to display what i read back,the whole display clears off.could anyone help me with the reading procedure?


texts: Calculating the "ball-park" range of a transmitter including dBi

texts:
I'm looking to buy a tranceiver that has a LOS range over 100m at minimum 1kbps. (preferred 28kbps).

I've been looking at this device

I'm using this calculator and I'm getting over 180 miles which seems absurd.

These are the assumptions I'm making

Frequency is 915MHz
TX power is 20dBm
RX sensitivity is -121dBm
TX Gain and RX Gain are 0dBi (That's a simple wire right?)
1% of the calculated range is ~3km

What am I doing wrong?