texts:
First, I'd like to say i'm not experienced on circuits, but i'm doing my best to learn.

I'm trying to create an audio equalizer which is capable of amplifying low frequencies (20Hz-200Hz), mid frequencies (200Hz-2kHz) and high frequencies (2kHz - 20kHz).

At the same time it should be capable of amplifying the overall output frequency \$\pm10\$ Hz.

I used a high pass filter and a low pass filter connected through a voltage buffer (LM741 Op Amp) to create a band-pass filter with different values of R and C to achieve the desired frequency to the low, mid and high frequencies.

I'm having problems with the LTSpice simulation, which doesn't output frequencies it is supposed to yield.

This is a screenshot of what I did and the output:

I wasn't sure if I had to add every voltage source to the Op Amp, so I just made one for every Op Amp.

V(n002) is for the one on the top (low freq band-pass filter) right before R13.
V(n013) in the middle right before R14.
V(n018) is the one on the bottom (high freq band-pass).

I calculated the high pass filter and low pass filter with the cutoff frequency:

\$f_c=\dfrac{1}{2\pi RC}\$

And checked the results using \$\textit{Mathematica}\$ software which showed the correct band pass filters.

Can any one explain me why it isn't working?

Thank you!!


texts: What is the physical significance of skewness and kurtosis of an eletrical signal?

texts:
I understood the mathematical meanings of the skewness and kurtosis. But when we calculate these quantities for a signal (say an electrical voltage signal), what physical meaning do they convey?
For e.g. I understood mean as the DC component of the signal.
If the mean of the data is made 0, and then if we find the value of variance it is similar to the energy of the signal, the standard deviation is equivalent to the RMS value.
Then what about skewness and kurtosis, what do they physically signify?


texts:
One can create a very cheap and easy to build capacitive galvanic isolator for low freq (audio)?

In+ --||-- Out+

In- --||-- Out-

Adding resistors does not help much (in fact it increases the noise).

Obviously the two sides are galvanically isolated!!!!

There is no DC path between the in and out. Yet why doesn't this work or is used?

(I thought adding a load resistor on both sides would help with DC discharge if necessary)

Basic analysis says this should work! (cap open for DC == block signal DC and ground DC, cap closed allows signals only)

My guess is that capacitive isolation works but since it it still forms an electrical loop rather than an electrical break that one gets with opto's and magnetics, that ground loops still exist. Although it isn't quite as satisfying since there is still galavanic isolation and that, technically, should break any ground loops.


texts: Temperature sensor TMP36 Arduino problem

texts:
I have a TMP36 temp sensor. I already did the programmation of it, tried different settings, different code found on the internet.

The sensor keeps giving me a temperature approximatly 10°C above real temp.
Can it be broken or something ?

Weirdly it reacts when I put it outside the temp is reduced, and changes back when I put it inside.

What am I doing wrong ?


texts: What does cell phone wall adapter specs mean?

texts:
On many (if not all) of my wall charger it says:

INPUT: 100-240V / 0.5A
OUTPUT: 5V / 2A

So, according to my poor knowledge this would mean that the input power is 50-120 W and output power 10 W. But this cannot be right as the efficiency would be super low?


texts: A basic question about opamp buffer offset and input offset voltage

texts:
The definition of "input offset voltage" is the differential voltage which is required to apply between the two terminals of the op-amp such that the output of the op-amp will become zero.

What I want to learn is: Imagine we have an opamp buffer and we apply(at its non-inverting input) a very well known constant precise voltage 1.0000V for instance and we measure 1.0015V meaning that there is 1.5mV offset. What is this offset voltage called? And does it have any relation with "input offset voltage"?

simulate this circuit – Schematic created using CircuitLab


texts: Frequently interrupting the CC charging stage of a Lithium-Polymer battery

texts:
Because of design constraints I need to charge a 2S Li-Po battery over its balance connectors using a single-cell charger IC (e.g LTC4002). In order to allow the user to interrupt the charging process before the battery is fully charged, it makes sense to charge both cells alternately so that they are not significantly unbalanced after the interruption. The switching would not be triggered more often than every few minutes.

How harmful is such behaviour for the particular battery technology? Would you suggest some other charging process under my constraints?

Thanks for your help!


texts: Capacitor selection - effect of reducing size of the MLCC capacitor in an audio application

texts:
We are developing an audio application using the TI TLV320AIC3111 codec and we are referring to the EVM document for the same. On this document, they've used a couple of 47uF 1210 capacitors (pg 23). However, we have a space constraint and are looking to find a smaller package for them.

What parameters do we need to look at before choosing a smaller package? How will the ESR be affected by taking a smaller package?


texts: i am trying to control intensity of a 20-50W halogen lamp operating at 24V through a POT. my concerned is current passing through POT (which would be between 1A to 2.5A). what kind of POT should i look for? also how can i identify the POT's current rating?


texts:
I made the basic IR LED circuit shown to augment the existing system on a night vision security camera.
No datasheet was found for the LEDs so I just measured the current to extract the power of ~0.1W total for the 4 LEDs. The beam angle is 30deg.

Is the calculation below correct to determine the approximate power at a distance of 0.2m from the radiating source?

Specifically want to make sure that power density is within the 'safe' region guideline I was able to find online (~100 W/m2 at a distance of ~0.2 m for up to 1000 sec).
The light emitted seems to be a comparable brightness to the in-built IR camera illuminator when viewed through the IR camera.
Commercial IR arrays for security cameras I was able to find online seem to be in the ~4 W up to 20 W+ so I assume this 0.1 W is in the fairly safe region.

Here is the LED I used: https://www.amazon.com/gp/product/B00BPAS0BA


texts: How can Quartus Prime System Console be used to read/write a whole file?

texts:
I want to find a way to read/write whole file from/to my Intel FPGA design. The file being written provides data to be processed and the file being read shall contain the results of the processing task.
Is there a way to read/write a whole file worth of data into the FPGA design using SystemConsole tool in Quartus? If so, how?
You could say, why not just read/write one byte at a time into some memory block? You are correct. However, what I am trying to get at is, if there is a built in supported way to do file I/O itself via tcl commands.


texts:
I have a keyboard from an old tablet case with a mini-USB connector that I want to read out using a PIC32 microcontroller.

When I apply 5V to the keyboard (completely standalone, no other circuitry around), the keyboard does do something on the data lines when I press some keys, but it doesn't seem to be using the protocol I know:

Here, D+ and D- seem to be each other's inverse most of the time, and D- is low when idle. My keyboard doesn't show the same pattern.

D- is high when idle. D+ is also high when idle, I didn't just swap the lines. I don't have the tools to perform in-depth analysis, but I do know the two lines are not simply the same.

Are there USB keyboards that have a different protocol (for example, D- inverted, or something entirely different)? What could be going on here?


texts: Researching chips and sourcing components

texts:
How do you research and select a chip for a given task? Are there some formalised and centralised databases I should be using? This would go equally for pre-assembled modules.

Following on, where should I be looking to source small batches (1-10) of said components for prototyping. Even if some vague googling finds me an answer to question 1, i'm usually at a loss for step 2. Note: I would require shipping to Australia.

Right now I am looking for a solution to supply 2 x 3-5A @ 5v from 2 x ~3.3-4.2V sources or 6-10A @ 5V from a ~6.6-8.4V source (powering some WS2812B LED's from 18650 batteries - not a terribly uncommon task I would think). My only tighter requirement is that it be able to fit within a 18mm ID tube - given the current (A) requirements I understand this may not necessarily be achievable, in which case the diameter will grow as necessary, though I would like to attempt to meet it if I can. If anyone knows a solution to this specific problem, I'm very happy to hear it. Though in the interest of teach a man to fish... I'm seeking the tools to do my own research (not least of all because the above requirements are still subject to change).


texts: X capacitor selection for SMPS power supply

texts:
Few months back, I designed a switch mode power supply using Viper22A chip. Now, I am trying to improve that design. The new circuit is intended for universal input (85 VAC - 265 VAC). Output will be 5 V 1.5 A.

Here is a part of the circuit:

D4 is a TVS diode. I chose it over MOVs due to it's longer life and quicker response time. NTC to reduce inrush current during start. X3 is a common mode choke (2.2 mH).

C11 and C13 are X caps. However I couldn't find a good article on value selection. Any pointers will be very much appreciated.

Besides this, is there anything else which I should do to improve the reliability of this part of the circuit?


texts: smoke detector for that "burning electronics" smell?

texts:
We all know that characteristic odor of fried electronics... when you "let the magic smoke" out of the chip.

Unfortunately it doesn't seem to set of ordinary smoke detectors, at least not at concentrations anywhere near the level where humans can smell it.  The gas isn't visible, so it's doubtful that an IR or particulate detector would work either.

Is there a different kind of smoke detector that does detect this?  Or a way to make one?

Looking for something to use as the "last line of defense" in a remotely-deployed (unattended) system.


texts: Can opamps marked as single supply be driven from a dual supply?

texts: Can an opamp designated as a single supply opamp be driven from +/- dual supplies as long as it is within the VDD - VSS range? I'm looking at this particular opamp from Microchip.


texts: Calculating load % of AC motors when operated at a frequency less than rated value

texts:
I have a three phase induction motor with name plate details:

frequency = 50 Hz
PF = 0.86
RPM = 1475
efficiency = 94.2
voltage = 415 V
ampere = 77 Amps
HP = 60

Now this motor is operated at 40 Hz and would like to calculate the load % of this motor.

So, I followed this fact sheet page 3, and used this formula to calculate load %.

$$\text{load}_\% = \frac{P_i}{P_n} \cdot 100$$

where: \$P_i\$ - input power, \$P_n\$ - rated power

$$P_n = \frac{\text{HP} \cdot 0.7457}{\eta_{fl}}$$

where: \$\eta_{fl}\$ - efficiency at full load

To find out \$P_n\$, I used the rated value of HP = 60 and \$\eta_{fl}\$ = 0.94. As the motor is operated at 40 Hz, which is less than the rated frequency (50 Hz), is it correct to use 50 Hz motor rated readings to calculate load % which is operated at 40 Hz?

Or do I need to make changes in the calculation?


texts: Why does drain current stop increasing after a certain value of gate voltage is obtained by a MOSFET?

texts:
I recently conducted an experiment where I grounded the source of a MOSFET, connected a voltage source to the gate (vgs)  and connected the drain in series with a voltage source (Vdd) = 10 V and a 1 kohm resistor.

I kept Vdd constant at 10 V and increased vgs from 0 to 10 V, while also monitoring vds. I calculated the drain current i_D as my output.

As I increased vgs from 0 to 10 V, I noticed that iD was 0 until vgs> 1V, which makes sense because 1 V was probably the threshold voltage of the MOSFET.

However, as vgs approached 10 V, the rate of increase drain current began to decline and looked like it was starting to flat-line. I was wondering why this happened.

I thought it might have been because of the MOSFET reaching saturation, but vds decreased as vgs increased, so
vgs-Vth > vds.

I suspect that it may have something to do with the fact that the gate voltage vgs was approaching the constant drain supply voltage Vdd, but I'm not sure why.

Can someone explain?
Thanks.


texts: Design Considerations for comparator with ~1mV accuracy?

texts:
I am working on building an "exploded" analog to digital converter (ADC) (tracking type: up-down counting) for teaching purposes.

I am working with a 0-5V reference, and 12-bits of precision (values 0 to 4095). This range gives me about 1.2-2mV per "step." The design is based on a clock in the range of 10-20kHz.

I was considering using a hysteresis mode on my comparator to set a threshold, except  hysteresis only works for a certain fixed threshold voltage, and obviously the ADC needs a continuous, changing reference from the analog input signal.

What alternative design considerations, instead of a hysteresis, could I incorporate to minimize error (from noise) while accurately detecting these small changes in voltage?


texts: STM32F103C8 + W25Q64 USB Mass Storage Device

texts:
I have problems creating an MSC device.
I made the following functions:

#define STORAGE_BLK_NBR      0x4000
#define STORAGE_BLK_SIZ        0x200

    int8_t STORAGE_Read_FS(uint8_t lun, uint8_t *buf, uint32_t blk_addr,
        uint16_t blk_len) {
    w25qReadPage(buf, blk_addr*2);
    w25qReadPage(buf+256, blk_addr*2 + 1);
    return (USBD_OK);
}

int8_t STORAGE_Write_FS(uint8_t lun, uint8_t *buf, uint32_t blk_addr,
        uint16_t blk_len) {
    w25qWritingByUSB(blk_addr, buf);
    return (USBD_OK);
}

Read, Erase and Write:

void w25qReadPage(uint8_t *page, uint16_t pagenum) {

    uint8_t com[5] = { W25Q_READ_PAGE, (uint8_t) (pagenum >> 8),
            (uint8_t) (pagenum & 0x00FF), 0x00, 0x00 };

    W25Q_CS_LO();

    HAL_SPI_Transmit(W25Q_SPI, com, 5, 100);

    HAL_SPI_Receive(W25Q_SPI, page, W25Q_PAGE_LEN, 100);
    W25Q_CS_HI();
}

void w25qWritePage(uint8_t *page, uint16_t pagenum) {

    uint8_t temp[4] = { W25Q_WRITE_ENABLE, 0x00, 0x00, 0x00 };

    w25qSetBlockProtect(0x00);

    W25Q_CS_LO();
    HAL_SPI_Transmit(W25Q_SPI, temp, 1, 100);
    W25Q_CS_HI();

    temp[0] = W25Q_PAGE_PROGRAM;
    temp[1] = (uint8_t) (pagenum >> 8);
    temp[2] = (uint8_t) (pagenum & 0x00FF);
    temp[3] = 0x00;

    W25Q_CS_LO();
    HAL_SPI_Transmit(W25Q_SPI, temp, 4, 100);
    HAL_SPI_Transmit(W25Q_SPI, page, W25Q_PAGE_LEN, 100);
    W25Q_CS_HI();

    w25qWaitForReady();

    temp[0] = W25Q_WRRITE_DISABLE;

    W25Q_CS_LO();
    HAL_SPI_Transmit(W25Q_SPI, temp, 1, 100);
    W25Q_CS_HI();

    w25qSetBlockProtect(0x0F);

}

void w25qEraseSector(uint16_t sector) {
    w25qSetBlockProtect(0x00);

    sector = (sector << 1);
    uint8_t com = W25Q_WRITE_ENABLE;
    uint8_t temp[4] = { W25Q_SECTOR_ERASE_4, (uint8_t) (sector >> 8),
            (uint8_t) (sector & 0x00FF), 0x00 };
    W25Q_CS_LO();

    HAL_SPI_Transmit(W25Q_SPI, &com, 1, 100);
    W25Q_CS_HI();

    W25Q_CS_LO();

    HAL_SPI_Transmit(W25Q_SPI, temp, 4, 100);
    W25Q_CS_HI();

    w25qWaitForReady();

    temp[0] = W25Q_WRRITE_DISABLE;

    W25Q_CS_LO();
    HAL_SPI_Transmit(W25Q_SPI, temp, 1, 100);
    W25Q_CS_HI();

    w25qSetBlockProtect(0x0F);
}

void w25qWritingByUSB(uint16_t dpagenum, uint8_t *bufByUSB) {

    uint8_t current_sector_buf[4096];
    uint16_t current_sector_addr = dpagenum / 8;
    uint16_t startPage = current_sector_addr * 16;
    int offset = 512 * (dpagenum % 8);

    for (int i = 0; i < 16; i++) {
        w25qReadPage(current_sector_buf + 256 * i, startPage);
        startPage++;
    }

    memcpy(current_sector_buf + offset, bufByUSB, 512);

    w25qEraseSector(current_sector_addr);

    startPage = current_sector_addr * 16;

    for (int i = 0; i < 16; i++) {
        uint8_t buf[256];
        memcpy(buf, current_sector_buf + i * 256, 256);
        w25qWritePage(buf, startPage);
        startPage++;
    }
}

MSC_MEDIA_PACKET 512
USBD_MAX_STR_DESC_SIZ 512

_Min_Heap_Size = 0x400
_Min_Stack_Size = 0x800

I have already despaired and don’t know what the problem is. The flash drive is formatted, but when reconnected, it erases all the data that was on it and again asks for formatting.
Maybe I made a mistake in the functions somewhere and don’t see it? Help me please!


texts: Question about forcing verilog netlist signals in simulation

texts:
I am using ModelSim to simulate a design with verilog netlist and verilog RTL.

My verilog design hierarchy is like this:
tb instantiates inv_dual_tb;
inv_dual_tb instantiates GF_INV_8_tb;

There are several signals in GF_INV_9_tb which I am interested in. There is a signal called c, (c is 2-bit) so I try to force the value in my do file (vsim -do 'force .....'):

force \/tb/inv_dual_tb/GF_INV_8_tb/c\[0\] 0 0ns

This works fine. But there is an other signal in GF_INV_9_tb called /tb/inv_dual_tb/GF_INV_8_tb/\pmul/p (this is 2-bit), so I tried the command below. But ModelSim keeps complaining. I also attached the error information below.

force \/tb/inv_dual_tb/GF_INV_8_tb/\\pmul/p\[0\]\  0 0ns
# ** Error: (vish-4008) Object '/tb/inv_dual_tb/GF_INV_8_tb/\pmul/p[0]' not found.

Note:
Modelsim cannot handle the case I mentioned. But the solution provided by dwikle can handle single bit cases or multiple bit without escaped characters


texts: Differential pair with current mirror - unequal currents

texts:
I designed a basic audio amp for learning purposes and now I'm trying to upgrade the differential stage with current mirror. However, I encountering a problem - the currents on both branches of the differential amp are different beacuse of the additional current from T1's base (the mirror itself works as expected tough)
In fact, I achieved better symmetry with simple resistor rather than a current mirror. Am I doing something wrong?
I've marked the problematic currents in yellow squares on picture below. As You can see, the difference is about \$23µA\$ which is quite high comparing to \$3µA\$ difference I achieved using a simple feeding resistor.
Agreed - this is just a simulation (and not the best one for sure) but still...
The circuit can be found here!


texts: using an ADC under Linux for automated current monitoring setup

texts:
I'm a slightly overchallenged undergrad ee student. I'm working on a project where I'm supposed to build an automated setup to measure hard disk currents over time.

I want to use a Current Shunt Monitor (CSM) connected to an ADC which is connected to a Linux machine.

I've already picked a CSM (AD8211). I need an ADC now but I'm somehow failing to find a proper way to interface it to linux.
I was thinking the EVAL-AD7091R might do.
I found the libiio form analog devices but I'm not sure if it does what I want it to do.
Can I control the eval board by python somehow through libiio? Just tell it to start sampling?
Is there a library that I can use which let me do certain things with the board?

What needs to be done essentially is to plug in a HDD over SATA and run certain operations like start up the disk, read and write and measure the current simultaneously. I want to do this by fio.
Since SDDs are very fast we agreed on a sampling rate of 1Msps. 200ksps is the absolute lower bound, however.

Sorry for my vague language.
If anything is not clear please ask. I try my best to explain better.

Any help is hihgly appreciated.


texts: Problem about circuit with capacitor and switch

texts:
I'm new to circuits. I would like to calculate the current \$i_x(t)\$ at \$t=0^-\$ of the following circuit:

I know that the capacitor acts as open circuit when it is in its steady state at \$t=0^-\$, so I represented the circuit as the following (where in yellow I highlighted the flow of current).

.

My question is why \$v_c(0^-)=\frac{V_S}{3}\$? Also, when the voltage is saturated, should't the voltage across the capacitor be equal to the voltage of the generator? Also why are we doing \$i_x(0^-)=\frac{V_s}{3R_1}\$? I'm surely missing something.


texts:
I was wondering if there was a mathematical way to combine two different types of antenna elements. Let's say that I have an antenna of $$\lambda/2$$ and I want to combine it with an antenna of $$\lambda/4$$. Since the beam pattern, as far as I know, is computed as:
$$BP = R_1(\theta, \phi) \cdot w_1 e^{-jkr_1} + R_2(\theta, \phi) \cdot w_2 e^{-jkr_2} + \ldots + R_n(\theta, \phi) \cdot w_n e^{-jkr_n}$$
with, R being the radiation pattern of one of the elements of the array antenna,
Should I just compute the radiation pattern of the element of lambda/4 and lambda/2, and add them as shown in the equation above?


texts: Matrix of SPST switches and buttons with Arduino

texts:
I have a controller that I made out of SPST switch (the type with the "missile cover" type) and momentary buttons (so the ones that are normally closed, until you push them, and once released go back to the closed position). The matrix is a 7x6 using digital pins.

All works fine, as long as I press them one by one, or activate the switches one by one. but if I start to have the switches enabled, like 3 or 4 of them in the open position; and I press a button; instead of getting only the value of the button pressed, I trigger all the buttons that are in the same column/row of the button pressed.

I understand that I should not use SPST toggle switches for these cases; and just use buttons, but I am using this contraption, to play flight sim games, which require some switches to stay on or off (like engine fuel lines, lights and such; which require for realism purposes, to be either in the on or off position, so I can't use momentary toggle switches).

While reading, I discovered about ghosting and masking; and that a diode is used to fix issues with multiple buttons pressed, although I am not sure that this apply to the SPST; so before take apart the controller, I want to understand better what is the issue that I am experiencing.

My hardware is pretty simple: various switches and SPST connected on a 7x6 matrix; which goes to a teensy 3.1 (using all digital GPIO, not the analog ones). I can post the sketch if needed; it is a slightly modified version from this tutorial: https://www.instructables.com/id/How-to-Make-a-Custom-Control-Panel-for-Elite-Dange/


texts:
We have a 3 phase electronic motor with a 'useful' power 4kW.
Its efficiency is 80%
Currents on the lines are equal in all three phases, and they are lagging behind the voltages by 30 degree.
We need to make a power factor correction in such a way, that the phase difference between the current and voltages becomes less than 10 degree.

And I am totally lost.

Is the efficiency the power factor?
Do we have to do anything by the fact that it is lagging? (Other than it shows that we need to use a capacitor for the correction?)
Why less then 10 degree and not zero?

Tried looking up videos and googling, but that only made me more confused :/

ps: Voltage is 230 Volt and 50 Hz. If the example needs this information.


texts: How can I isolate properly a home made PCB?

texts:
N.B: I'm still a 14 years old boy that is just a beginner in electrical engineering.

I've just finished My first Successful Single Sided PCB Project, which was a Relay controlled wirelessly via an infrared remote, so a part of the PCB must handle a 220Vac.I made the traces which carry 220vac so thick so that it can carry high current and voltage.

My main Problem is that I want to isolate the copper side of the PCB to avoid electrical shock and short circuit but I don't know what is the substances I can use and How ?

And don't forget that these traces can become hot alittle bit.


texts:
I know this is a super elementary question but I am a one day newborn baby in FPGA field!

For years I have worked with AVR and now I am just starting FPGA learning. I want to know if they have an internal oscillator like AVRs for clock source or it should be prepared externally with  something like crystal oscillators?


texts:
I'm new to electronics and I'm learning the basics for a small home project involving LEDs, fiber optics, and microcontrollers.

I'd like to simulate the circuit I plan to build to get a better understanding of the different V drops and I values in each node as I change the structure of the circuit. I've experimented with various free tools and so far 5Spice (Win, desktop) and Circuitlab.com proved to be the best ones for me.

However, I'm stuck when trying to simulate the simple 5mm 24mA LEDs I bought (manufacturer link here). Both tools support adding LEDs, but I need to set values such as N, TT, M_J, I_S, R_S, C_J0, and V_J.

Even after reading the basics of Spice and reading this other StackExchange question, I'm not sure what values I can use, and the procedures described there are beyond my current (basic) understanding, at least for the time being. Can anybody help me providing these values?

My power source will be a constant 4.5V and the LEDs Voltage is in the range 1.9v-3.2v (depending on the color) What values should I use for a basic simulation? I can't find the datasheet in the manufacturer site.

Thanks,


texts: Can mobile cell stations cause interference in audio circuits near them?

texts:
It's a fact that if you put a GSM cell phone near a desktop PC and call it, the phone will interfere with the audio card and cause that noise most of us have heard somewhere.

But is it the case with the stations? I've seen people shoot videos around the antennas, but it doesn't seem like they cause any noticeable audio noise. Is the signal different coming from the antennas?


texts: Beginner soldering help - solder balls/doesn't liquefy and soldering tips blacken

texts:
Very frustrated!! Have gotten into electronics recently and watched many videos about soldering and proper technique. I started out with the iron from this kit:

https://www.amazon.ca/gp/product/B0009Z3JJA/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

It's not variable temperature, just plug in and use. So I waited for it to heat up, tinned the tip with my solder and used as I had seen in all the videos I watched, cleaning it on a wet sponge after every few solders. I thought maybe I had left the iron on for too long as the tip became blackened and the solder wouldn't liquefy when making contact with the iron tip. So I clean it off on the wet sponge a bunch and it starts looking better, but I still can't tin it. So I follow the instructions in this video:

https://www.youtube.com/watch?v=2VlvjdaMARM

I purchase this flux: https://www.amazon.ca/gp/product/B01EYJJEEK/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Get my iron heated and sink it into the flux, but the solder still won't  stick to the tip, it just kind of balls up if i bring it to the edge of the coated part of the iron (the edge opposite of the tip). I think ok maybe it got burned out or something because I left it on too long, also it was part of a $20 kit so maybe it was just a piece of crap.

So I buy this guy here:

https://www.amazon.ca/Elenco-SL-75-Soldering-Station/dp/B002KIYSHQ

Variable heating, I check the manual it says to heat it just beyond the 4th notch to about 700 degrees for lead-free solder. I heat it right where it says to and wait, it tins and everything is fine and dandy. I start using it, this time cleaning between every solder because I'm trying to be extra good to not mess it up, but after 28 solders it stops working

I can't tin it, even while trying after dipping it in the flux. The solder doesn't liquefy at all.

The station came with two tips, the left one is the one I used that no longer works, on the right is what it looked like before:
https://i.imgur.com/0o1Z2Vz.png

This is the tip of the first iron I used that stopped working:
https://i.imgur.com/GzHoOk4.png
https://i.imgur.com/tGIWY87.png


texts: Control the hardware of an old phone using a Raspberry PI

texts:
I have a very old phone (60 years old) and I want to control its part using a Raspberry PI:

Microphone & speaker from the head set
The bell
The dial wheel

I have the electric circuit but don't recognise all of the parts.

My question is now how I can achieve the following using the Raspberry PI:

Detect the signal from the dial wheel
Ring the bell
Use the microphone and the speakerphone from the headset
Detect when the headset was liftet from the hook

Additionally I don't understand all parts in the circuit:

e.g. what is this Pulse Icon is with the caption of 100 between 2 and 6

Update

I tried to decipher the circuit in order to be able to use the hardware of this phone. I used blue for the German color codes of my cables and green for the connectors:

simulate this circuit – Schematic created using CircuitLab

On the phone I have the following connectors:

M1: Microphone (red)
M2: Microphone (pink)
T1: Speaker (dark green)
T2: Speaker (light green)
a: Phone line?
b: Phone line?
E: Phone line?
W1 + W2 (bridged)
W3/1: green cable connected n times with red through J when dialled
2: red
3: blue
4: yellow
5: white

Update 2:

It sais 300 Ohm - 7000 W - 0.13 Ku Em on the two coils, which are used for the bells.

This is the acutal phone on the inside.


texts: Finding phase shift between the voltage and current

texts:
I am trying to find the phase shift \$\phi\$ of this circuit.

I am using the formula:

$$\phi = arctan{\frac{X_{L}-X_{C}}{R}}$$

Substituting in the values:

$$\phi = \arctan{\frac{2000\Omega-4000\Omega}{6000\Omega}}$$

$$\phi = \arctan{\Big(-\frac{1}{3}}\Big) = -0.322 \text{ rad}$$

which does not agree with the correct answer \$0.983 \text{ rad}\$.

Any tips or guidelines would be welcomed, as I still struggle with very fundamental stuff.


texts: What am I doing wrong with this Wheatstone Bridge?

texts:
Experienced experimentalists, be aware that this is probably going to sound like a stupid question:
I am having a LOT of trouble predicting the output of this Wheatstone bridge circuit.

I am trying to predict the third harmonic voltage read by the lock-in amplifier (I am preparing something resembling a 3-omega setup and need to get this figured out first).

I know how to predict the voltage between 1 and 2 (the first harmonic voltage), from what I understand it is

$$\Delta V = V_{source}\left(\frac{R_2}{R_1+R_2} - \frac{R_4}{R_3+R_4}\right).$$

However, here are two plots showing the predictions made for the bridge output when I just change $R_4$ keeping $R_1=R_2=R_3=1K\Omega$. I've compared these to the actual measurements I get with the lock-in (corrected for the fact that it reads rms voltage).

Notice that the predictions are in volts, while I am measuring millivolts!
The relationship between my predictions and the measured values is either linear or quadratic.

Basically, I'm just thoroughly confused about what is happening.

Here are the actual data arrays for reference:

Resistance(Ohms) = $[.32,10,10^2,10^3,10^4,10^5,10^6,10^7,2*10^3,6*10^3,600]$

Prediction(Volts) = [-.499,-.489,-.406,.00605,.412,.491,.5,.501,.172,.361,-.119]

Measured (mV) =
[3.277,3.285,3.454,4.463,6.218,6.732,6.800,6.812,5.053,5.936,4.096]

Picture of the Setup:


texts: Safe to power up the digital circuit for troubleshooting IC chips?

texts:
I have a complex digital circuit board used in Scanning Electron Machine.
In it, there are lot of IC chips, FPGA chips. diode SMD, capacitor SMD and others.
This problematic board produces no image. I am done with all discrete components except IC chips and FPGA. The question is, "Is it safe to power up each IC or other ICs nearby that share supply voltage and ground so that I can test them  with oscilloscope"?

Kindly advise me and thanks in advance.

Clement Yap


texts:
I have a general question regarding the XMEGA384C3 DataSheet. For PORTF, it has a timer 0. Then I can use PF0-PF3 for PWM. Is it possible to have individual PWM duty cycles for each channel simultaneously.

For example PF0 (0C0A) is outputting 50% duty cycle. While PF1 (0C0B) is outputting 75% duty cycle?


texts: Poor man's equalizer with a few digital bandpass filters - how to overlap band edges

texts:
I am trying to implement an equalizer in an FPGA. It's not hifi or anything so 3 or 4 bands should cut it.

So I have a low, band, and high pass filter covering the entire voice spectrum (0-4kHz in this case since my sampling freq is 8kHz. Each of these filters have considerably slow rolloff (around 300Hz to go from stop to pass band) because I want to minimize the number of coeefficients needed for the filter

My question is how much should the rolloff parts of the filters overlap each other so that no frequency is lost or attenuated more than the others. It seems like, assuming the rolloffs are over the same frequency range with the same slope, then their midpoints should be the intersection point, but I cannot prove this rigorously. Are there common methods for this?


texts: What is the optimal protection diode placement driving a relay

texts:
In any circuit where a transistor or FET is driving a DC relay, its common to see a reverse blocking diode added to suppress the inductive spikes, caused by fast current transitions (particularly the "OFF" transition). Over the years Ive seen such diodes placed across the relay coil, or alternately across Transistor. I don't think I've ever seen both in the same circuit, except in the cases of MOSFETs where a diode is often built in. In my own projects I've used both configurations, and both seem to work equally well for protection. I'm aware that putting the diode across the relay coil will slow down the dropout speed, which could be a problem in some designs. But from a pure spike protection perspective, is one diode placement more optimal than the other?

Almost feel foolish asking this, but I've seen both cases so many times, I have to wonder if there is some confusion or disagreement about it.


texts: Designing 60hz antenna to detect electric field

texts:
I am working on designing an antenna to detect 60Hz electric field. I came across the microstrip antenna being used to detect the field. Before designing the antenna I wanted to maek sure this is the right way, So I took a piece of 2 layer PCB(both the patch and ground plane were same size) of 10cmX15cm size and soldered a wire on one side and connected to a 2 Mohm resistor and measure voltage across the resistor through DAQ. I read approx. 1.7V when placed near a plugged heater. When unplugged I didn't read any. So I was positive that I am reading something on 60Hz. My question are as below.

1) Is this the right method? Am I reading 60Hz or some noise, static field, etc.?

2) I connected only one side of the PCB to resistor and measured voltage across the resistor. Do I need to necessarily ground the other plane(which is called ground plane)?

3) If I need to calculate the electric field(I have been researching on this from antenna-theory.com). By calculation, for 60Hz I would need a bigger size patch(like in kilometer range). Is this correct? If so, how come I am reading 60Hz in a small size?

4) I also looked on the other way considering the 2 sides as a plates of capacitor and FR4 material as a dielectric medium and measured the e-field. Is this the right method too? Considering that I have connected only one side of the plate and the other side is left open.


texts: How to add bouncing to a switch in LTspice?

texts:
Is it possible to add bouncing for a switch in LTspice?
Below is a reed relay simulated in LTspice.
I can set the on and off resistances but is there a workaround to create bouncing as well?

With no bouncing, the simulation of the relay outputs the following clean output:

By bouncing I mean something similar to this:

The reason I'm asking this question I want to see if I can implement an RC debouncing circuit in simulation which works before implementing.


texts: Programming 3.3v ATMega328 running at 16MHz

texts:
I know that running the 328 with 3.3v at 16MHz is "overclocking" it and slightly out of spec. Because of limited board space i'd like to do this though as all other components are 3.3v. I need the 16MHz.

I'm using a TQFP 328 and am planning on burning the arduino bootloader to it and then working with FTDI. I know that FTDI cables come in 3.3v, which should be ok, but i'm wondering what the impact on burning the bootloader will be. Will the bootloader burn fine at 3.3v even if it's actually too low? Other concerns or suggestions?


texts: Alternatives to op amps LM307N and TL071CN

texts:
I'am working on an amplifier/driver circuit for a spring reverb bank. The circuit is from the 90s, but still used:

Accutronicsreverb Drive 1 Circuit
My issues are the LM307N and the TL071CN. These are operational amplifiers from the 90s and not cheap to get. I guess, there are more modern and cheaper solutions for op amps.
Can you tell me, which alternatives are recommended and what should I put attention on when choosing?


texts: What is the schematic capture/PCB layout design cycle?

texts: Is there somewhere a description or flow-chart of the process of designing a circuit: Requirements analysis, schematic capture, simulation, PCB layout, etc. as well as various checks? Something especially for PCB design, and not so much about IC layout please.


texts: How do I operate a tuner of digital satellite receiver using a microcontroller?

texts:
I want to operate this tuner of my digital satellite receiver.
This is the tuner:

They wrote some numbers and words around of the tuner:

and the name and model of the receiver is "DigiStar D600 Digital Satellite Receiver".

What MCU or processor is suitable for operating it?
Where can I find information for operating this?
I couldn't find any datasheet.

i seperated the tuner from the pcb and toke two picture, look(i hope these two picture help me for get answer):


texts:
I am looking for some help explaining a dropping voltage reading on a circuit I have built. Details below.

I have built a circuit to experiment with the TS317. The circuit is very similar to the standard application circuit on the data sheet.

R1 = 212 Omhs
R2 = POT makked with 47 Omhs 3W

[[Note that "very similar to" may mean "not the same as". ANY differences should be explained clearly]]

(These resisters are random taken from a lucky dip bag, I'm finding reading resisters very tough from differentiating the colour to working our which end to rad from when there are 6 bands as there is not always a clearly wider band at one end, any tips?)

C1 = 0.1 micro farad I think, labelled A5E104M
C2 = 1 mico farad

I am powering the circuit from a 9V battery and have a small piece of aluminium angle iron attached to TS317 with some non-silicon head sink compound, surface are ~ 1000 mm^2 one side (so double - area of TS317 for total). I am measuring my voltage with a cheap digital multimeter.

When I attach my batter I get a maximum voltage of 3.3 Volts and a minimum of 0.25 volts. Both these voltages slowly drop if I leave the circuit on. This would suggest to me that I am for some reason drawing more and more current resulting in a larger and larger voltage drop.

Could any one please explain to me why this is?

Considering the heat to dissipate per second,

HeatToDissipate_min = (9 - 3.3)*I = 5.7I
HeatToDissapate_max = (9 - 0.25)*I = 8.75I

but being as I have no load and I am just measuring v_out to ground then I should be negligible (volt meters are very high impedance right?).

BUT

I have noticed the pot is getting pretty warm too again suggesting current flowing, heat sink dose not seem too hot.

According to the data sheet formula I should only be getting ~ 1.5 V with R2 = 47 and R1 = 212, with I_adj as I understand limited to 100 micro ohms. Why are the values I'm getting different?

I've obliviously done something pretty wrong but don't know what. New to this electronics game as you can guess.

Thanks.

EDIT:
Thanks. Sorry for the late reply been busy at work. I have not gotten around to trying to draw the schematic with the pot yet. I decided to do away with the pot for now anyway for simplicity.

Figured out my mistake. I was taking the pins on the schematic to be 3-2-1 left to right, not reading properly that they go 3-1-2. Idiot. Sorry.


texts: Improve 134.2kHz PIT tag RFID reader range

texts:
I need to scan 134.2kHz PIT FDX tags from a range of 5cm to 10cm. So far, I have built custom reading circuit. It has the standard R+L+C in series driven by 134.2 kHz square wave and the output is taken across the capacitor and processed. I am only able to read the tag when it is at the center of the coil. I was wondering how I can increase the range:

What all factors does the range depend on? (Current? if yes, how do I increase current? will decreasing impedance by changing L and C work?)
Does range/SNR depend on Lcoil and Ltag. Do I have to do some matching to increase this?

Any help regarding this will be extremely appreciated. Thank you so much for your time!


texts:
I am a computer engineering student with an electronics background (i.e. mandatory circuit design and analog electronic courses) and my degree thesis requires me to design an electronics project.

So now I have this project to get done and of course I have to look for ICs that do this and that. Do I just Google stuff until I find what I need? I feel really lost since my electronics background is just that, a background, so I know how diodes, opamps and transistors work but I have no idea what the various acronyms (like PHY, MIPI, TTL and so on) mean, so what usually happens is I Google "integrated feature 1 feature 2 ", then I click on any results that look related, read datasheets (when I can find them, since many are under NDA), stop to Google any acronym I don't know, which usually gets me to know what it means but not how it works, rinse and repeat.

Some of the time I can actually find what I want, but most of the time I just spend a whole day staring at my screen feeling completely lost and at the end of the day I turn off my computer feeling like I haven't accomplished anything. Most components look like they are not interoperable, have different standards for input and output or actually have the same standards but call them by different names because of copyright!

So my question is: how do I efficiently search for the ICs I need? My project doesn't sound so hard on paper, I have a very good idea of what I have to do but I have a hard time finding the components I need. Am I doing this wrong?


texts: How does a GPS antenna have only two connections yet have all this circuitry inside?

texts: This GPS module I have broke (just gets hot and won't work) so I took it apart and am amazed to see all of this circuitry under the ceramic antenna but only two connections (gnd and signal).  When tested there is ~3v between the signal and ground wires.  So how does it work to send power over the wire and then also get signal back along the same wire ?


texts:
I have one question on the 74HC161 synchronous counter, you can find the datasheet here:

DATASHEET

How can it be used as a downwards counter?
Actually, is it reversible at all?


texts:
My input is an SPST Dry contact with the closure of 0.5 seconds. I can energize the closure by 5 VDC if needed. The PCB runs on 5 VDC. I need to reverse the output voltage of the PCB to run two bistable valves. These valves are triggered by 5 VDC, +5 VDC for ON, and -5 VDC for off for 0.5 seconds.
I am familiar with the DPDT relay type "X" design but I need a solid-state solution. I also believe I need a flip-flop to control the sequencing of the pulses. Unlike other circuits for voltage reversal that control motors that spin and create Back EMF issues, this circuit should be much simpler.
Unfortunately, A little knowledge is a dangerous thing so I need some experienced advice. So 6 wires are needed on PCB, voltage in (5vdc), Trigger -- dry contact closure of 0.5 s and output of 5 VDC that is reversed polarity each time the dry contact is pulsed for 0.5 seconds.
The REVERSIBLE output is ON only on for the same 0.5 seconds and runs a set of valves that consume about 800 mA.


texts: Reading NFC tag from a slightly longer distance

texts:
Presently, my problem is that I have this NFC/RFID Tag, and due to the small antenna on the tag, it needs to make direct contact with the reader (presently tested using both a smartphone w/ NFC capabilities, as well as a cheap HF RFID reader module connected to an Arduino UNO).

My project requires an extremely small NFC/HF RFID tag that can be read from about 1-2mm, through a layer of material.  For an easier visual understanding, it is as if the reader is in your pocket, and it would have to pick up the tag through the material.  Presently, this is just thick enough that I cannot get consistent results.

So my question is - is it physically impossible for me to ever read this tag given my constraints?  Or, would increasing my read range help at all?  Not sure how I would amplify my range on the smartphone, but I'd imagine a different antenna on the HF Reader would do the trick there.

If it is a matter of physical limitations, is there an alternative I am not thinking of?  NFC/RFID is not an absolute requirement, as I am not trying to read data off the tag.  I am using the presence of the tag within the reader's field to trigger an event, and I cannot think of a better technology that could potentially identify something that is so small/discreet nearby without being within a direct line of sight.  So if there are any suggestions for an alternative, I am more than willing to modify my design to accommodate.  Likewise, I am not tied to this particular tag if there exists a better one of comparable dimensions.

Thanks in advance for any suggestions/references!


texts: Timer Interrupt being called everytime - Pic16F877A and CCS PIC C

texts:
I am currently trying the following example

#include <16F877A.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

#INT_TIMER1
void TimerOverflow()
{
    printf("Timer Overflowed\r\n");
}

void main()
{
   long time;
   setup_timer_1(T1_INTERNAL | T1_DIV_BY_1);
   enable_interrupts(GLOBAL);
   enable_interrupts(INT_TIMER1);

   set_timer1(8000); //count till 8000 then overflow
   time = get_timer1();
     while(1)
     {
     }

}

However the interrupt function is supposed to be called after ever (almost) 8 seconds but its being called as if the delay was 0 seconds. What am i doing wrong here?


texts: LED light fixture glows when not turned on

texts:
This past week at Menards I bought 2 Smart Electrician® 3650 Lumens 46" LED Linkable Shop Light Model Number: 0053-0011  |  Menards® SKU: 3481400.

The LED shop light fixture has a glow to it. Looked like the LEDs were turned on, but not all the way. The power switch is turned off. Don’t know why I did this but I took one of those three prong adaptors converters to two prong and to my surprise the light fixture didn’t light up. I unplug the cord with the adaptor and turned it around and it still didn’t light up. The power supply electronics inside the light fixture must be using the earth ground wire somehow. Using my volt meter. I measured to earth ground to the green wire that comes out of the adaptor and to my surprise depending how I plug in the adaptor. I’m getting 112 volts AC. That's because the adaptor isn't keyed and I'm switching the HOT and NEUTRAL around depending how I  plug it in.

I connected the LED light fixture to “Safety Analyzer tester”. When I press the “Open Ground” button, the fixture stops glowing (lightly lite LED’s).  Looks like the power supply circuit inside the fixture has a connection to “Earth Ground”.  I then switched the “Normal” on the polarity switch to “Reverse” and the LED’s were off. Switching the Neutral to open position has no effect. I'm thinking of taking them apart and see inside what's going on or take them back.

I figured out the problem.

In this light fixture you can clearly see the white wire (neutral/common) is connected to the light switch, turning the power off the LED light strip. Commonly we switch off the “HOT” to your light socket so when you change your bulb you have a less of a chance of getting electrocuted (that’s another story for later). Sometimes in Power supply circuits they place capacitors in there to help filter electrical noise out. Also known as suppressers (electronics to reduce unwanted noise or oscillation in a circuit or unwanted frequencies in a signal). Depending on how or where they are placed in the circuit it could possible cause some issue if not installed correctly or if the circuit isn’t designed correctly.

Since the BLACK live wire is connected to the LED PCB all the time, anything connected to that line will potentially be LIVE voltage, that way when I disconnected the earth ground from the socket and measured 112 volts on it. My guess is they have capacitors connected to both LIVE and NEUTRAL to the earth ground wire.

The current is flowing through capacitor C2, just enough to turn the LED’s on slightly. If the switch was on the hot side, this problem wouldn’t be happening. I still may use them just not connect the “earth ground” wire. Because that’s providing the return path for lighting the LED’s.


texts:
I'm trying to charge my laptop through a 12V battery and 12-19V adapter over a long wire but I've noticed that the adapter makes some noise and doesn't work.
On the other hand when I connect it close to the battery it works just fine. Is something wrong with long distance transmitting of 12V DC?

The wire is around .5 mm in diameter and 10 meters long. I believe the current is around 3.5 amps.


texts: What's wrong with the wiring of my multiplexer?

texts:
My circuit is wired as shown above -but with the EN pin I've tried connecting to ground and to power. I don't think its a code problem because when I wire inputs in directly everything reads normal.
I'm using a CD74HC4067 analog multiplexer. The T4 refers to my Teensy4.0 microcontroller, its hooked up to the breadboard ground and I have tried using both the 3.3V and 5V power pins hooked up to the red line on the breadboard and had identical results between either. The signal pins of the mux are routed to my digital pins on my T4 and the signal is hooked up to an analog pin on the board. The larger components in my diagram are B100k/b20k potentiometers and the smaller ones are tactile buttons.
With this wiring hookup, adjusting the first potentiometer from the left appears to change the signal reading for most of the other input channels. Pressing the first button from the left also was effecting the readings on channels 8-11, and one of the buttons was effecting the readings of a channel nowhere near it.
Any help? Thanks


texts: What's the best comunication protocol for a sensor network?

texts:
What's the best comunication protocol for a fast and cheap wirelless sensor network?

Is it one of these?

WirelessHART

IEEE 1451

ZigBee / 802.15.4

ZigBee IP

6LoWPAN

Other


texts: Since heat is such a problem in modern computers, why aren't we using Tofolli gates and reversible computing?

texts:
Today the Tofolli Gate is largely studied for its application to quantum computing, but Tofolli invented it in 1980 to perform reversible computing with electronic circuits in order to address the problem of heat and cooling.

(For those who are unaware, the Tofolli Gate is one of the building blocks of quantum computers, although it was not developed for that purpose.)

Cooling wasn't much of a problem in the 1980s, but it emerged as a serious problem in the 2000s and it remains one today. Given that reversible computation is universal, and given that there's no reason why reversible computers can't be fast, why are EE designers not using reversible computation and Tofolli gates in modern designs?

Here's an article from EE|Times in 2004 which said "a group of researchers at the Department of Computer and Information Science and Engineering (CISE) at the University of Florida is working to make a reality a radical idea for making computers more energy efficient ” as well as smaller and faster."

In September 2017, Peter Denning and Ted Lewis had a big article in American Scientist, saying reversible computing "may be the future of computing"

IEEE Spectrum had a similar article in August 2017, stating "It’s time to embrace reversible computing, which could offer dramatic improvements in energy efficiency"

So why aren't we using Tofolli gates and reversible computing?


texts:
I did finish a circuit, but it is not working. It is a LED thermometer. I assume that is not working, because It doesn't show nothing in the LED display.

To debug i followed the steps:

I turned on my power suppy in 9V (it is recommended something between 7V-18V).
With my multimeter i touched some components, looking for short circuit. So capacitors, resistors, diodes and an ICS switch are, at least receiving energy.

What else can I do to find out why it is not working? Or at least to identify which component is the problematic one? As I wrote before, I did test all components and they are receiving and transfering energy, but how can I debug the IC switch or another specific component?

Photos from circuit and schematics


texts: Calculation of magnetic field saturation inside coil core

texts:
I want to try to make an electromagnet, but I don't have soft-iron available. I've read that ferrite MnZn are suitable as soft-iron to create a high efficiency magnets with the inconvenient of lower magnetic saturation.

I'd like to know If with my specifics I can occur in this saturation range. Magnet will be activated with a frequency of 10 kHz to control and keep current at 1A-1.5A. About 50 turns are applied. Dimensions of core are 10mm diameter and length 30mm Ferrite type is an MnZn. Relative permeability from datasheet 15000µ/µ₀ at 10kHz, permeability µ₀ 0.3*10-3 H/m at 10kHz.

Applying this equation: B = µ₀ * N * I / L

I've

µ₀ 0.3*10-3 H/m
N 50
I 1.5A
L 0.030m

B = 0.6 * 10-4

Can be this value be so low and can I be so far from saturation? Even if I apply 10A I'm very far from saturation. This mean that saturation is something that occur in very particular applications where high current, lengths and number of turn are involved?


texts: Why does dynamic ram need to be 'refreshed'?

texts:
I read this question, but it didn't really answer my question. I also want to preface this question by saying that I'm asking this from the perspective of being a computer science student that took one electrical engineering course.

In my notes on static RAM and dynamic RAM, it says that a single cell of static RAM is built entirely out of transistors, and will hold 1 bit of data as long as power is applied to the cell.

On the other hand, one cell of dynamic RAM is built primarily with a capacitor. I understand intuitively that a capacitor 'leaks' charge until the voltage on either plate is equal, and it says in my notes that this means that dynamic RAM must be refreshed every 10-100 milliseconds.

My question is why the refresh is necessary. What is the difference between power being applied to static RAM and dynamic RAM? Can't power be applied to dynamic RAM the same way as it does for static RAM to maintain the data? Why does it require a specific refresh signal?


texts: how to implement while loop with time condition in matlab?

texts:
I knew how to set a a while loop in Mikrocontroller, but when I tried to Implement it in matlab /simulink, my computer gets stuck and never get out of the while loop and does not do anything.
here is my code:
function [tout,valueP,valueI] = fcn(tin,Vout)

persistent dp;          %local variable
persistent di;          %local variable

if isempty(di)
    di=0;
end
if isempty(dp)
    dp=0;
end

while 1                 % infinite loop

    if tin==30          %at time t=30s, take Vout value
        if Vout==300    %during this time, compare Vout to 300V
            di=10;
            dp=40;
        else
            di=20;
            dp=10;
        end
    end

    if tin==60            % break the loop at time 60s
        break
    end
end

tout=tin;               % output
valueP=dp;
valueI=di;

my objective is: run the model, then watch the Vout and then at time 30s, take the value of Vout, then use it for comparaison that will result in vlaueP,valueI.
here is my model as pic(could not add it)


texts: Derivation of Discharging Current of an Inductor

texts:
Consider the following circuit:

When \$t > 0\$, the inductor \$L\$ begins to discharge. I already know from KVL that the sum of voltage drops in the loop containing the inductor is:
\$L\frac{di(t)}{dt} + Ri(t) = 0\$
From this, how could I derive the equation for the discharged current across the inductor i.e. at any time \$t\$:
\$i(t) = I_s e^{-\frac{t}{\tau}}\$
As I understand, it involves some integration, but I'm a bit stuck so if someone could help derive it for me, that would be much appreciated.
Thanks


texts:
I am trying to run a small fan I had created using 775 motor. There is no rating, mark anything on that motor.
I tried running with a old unused 9V bike battery and it runs too fast.
So I end up using 1 Ampere 9V adapter (cheap 1 dollar) and it runs good enough. Now the adapter seems to heat. I can touch sort of bit warm. Is it safe? I know that the current requirement for 775 motor is high but can it damage the adapter.
As per me I cannot use L298N motor driver as the 775 motor can fry it but does this apply to adapters as well? Some alternative to use less current for 775 motor something like 5watt resistor? But how to guess the resistance of motor?
Apologies for poor understanding about how these things work,


texts: Does the charging cable affect output voltage and amperage?

texts:
My phone charger consists of two parts (like every smartphone charger nowadays); the adapter and the Micro USB cable. Some time ago, it had an accident and the cable has interruption now. So I bought a new cable.
On the adapter, it writes "DC OUTPUT: 5V 2.1A". Does the cable I use affect V and A values? (There is no such information on the packing of the new cable...)
There will probably no problem while charging my phone and making data transfer, but I plan to use this charger with my new (and first) Raspberry Pi. I don't want to accidentally kill it.


texts: Why mosfet have different turn on and turn off time? If I am correct, mosfet have higher turn off time. Why?


texts: Role of the diode in the non-inverting op-amp circuit

texts:
I have a question:

What does the diode and the capacitor do in this circuit? What's their role? And how will \$V_{out}(t)\$ graph look like, if we know, that \$V_C(0)=-5V\ , \ SR=0.5V/\mu s\$ and \$V_{ppOUTmax}=13.5V\$?


texts:
Can someone help me identify what these cables are for?

I'm guessing (and hoping) the one in the bedroom is for a cat 5 wall socket -- and that these corresponds to some of the cables exiting in the basement ceiling.

Bedroom wall

Basement ceiling


texts: Differential and Common currents in EMI Design

texts:
I need some clarifications about an application note from ON Semiconductor I have downloaded form the following site:
http://www.icbase.com/pdf/add/on/AN-106-00003en.pdf
The discription of the differential and common mode given in the application when referred to figure 1b, confused me!

What confused me is the statement encircled (Maybe my English is not good enough)
If we look to the image both DM source and CM1 are sourcing up and yet it has been said that DM is out of phase in each branch and CM is in phase both to the DC rail and ground.

What is it meant by these two statements?
Can someone redraw the direction of both currents through the whole circuit ?


texts: Why do most flyback converters / LED drivers operate under 100 kHz?

texts:
Most of the LED drivers and flyback converters I have come across operate in the 60-100 kHz range. Is there any particular reason behind this - example - ferrite cores not being able to handle higher frequencies, etc.?

Regular buck converters go up to 1-2 MHz switching frequencies and boast about small magnetics that can be used which means smaller size and/or lower costs. Why aren't LED drivers and other flyback ICs coming in higher frequencies?


texts: Choosing inductor to limit inrush current

texts:
I have a 12V DC input to a circuit. There is a 660uF Aluminum cap on the input.

The 12 volt source is not in my control and can come from anywhere. So it could be a noisy source or a high current clean source.

I am wondering if it's worth it to put an inductor in series with the input to limit inrush current? Or even if it's worth limiting the inrush current in this specific case at all?

I know that there are ICL devices and MOSFET devices that can limit the rise time and they are made for this.

One device is the TI TPS22810DBVR. And is pretty cheap in volume.

But, I already have a cheap 4.7uH inductor that can handle my 2Amp max draw from my circuit. And i'm hoping I can use this for 2 reasons:

1) Limit inrush current

2) Help clean up the 12V input.

I have done some simulations.

Cap: 660uF with 130mOhms ESR

Inductor: 4.7uH with 37mOhm resistance.

12V DC input with 1V/uS rise time. (Just guessing on that one since I don't have control over what the source is.

This gives me:

This gives a peak current of 62Amps. Now I may not have control over the 12V input source, but i'm pretty sure it's not going to be from a source that can output 62Amps. Maybe a 12Amp source that can handle 12Amps peak loads for a short time.

So since the peak current allowed (theoretically) is 62Amp, but is limited by the source, I would say there is no point in putting the 4.7uH inductor in there because is still going to allow the same peak current of 12Amps whether it's there or not. Is this a good answer for my questions?

It should still help clean up the 12V input though right? A cutoff frequency of around 2857.6Hz. Maybe get rid of switching noise if it's a SMPS.

Please let me know your thoughts and experience with this situation. I could put a bigger inductor in there, but I am very limited on PCB space.


texts: How to cut power off when a certain voltage from a sensor is reached?

texts:
I've built a simple Ni-Cd charger (basically a 0.1C current source) for some 1300mAh cells, that I want to stop when a certain voltage is reached on the cell. I tried to design the switch with an Op Amp, but all it does is to limit the voltage the current source is applying on the cell, to the voltage that was supposed to trigger the cut off.
I know I could use a relay, that would be driven by the Op Amp, but I'd rather really not use them.

So, how can cut off the power when a certain voltage is reached?

Here is a schematic of what I did, to give you an idea.


texts: Will a battery be damaged when in series with a low frequency AC signal source?

texts:
simulate this circuit – Schematic created using CircuitLab

Imagine the 5V voltage source as a battery. If I place it in series with a signal generator will I ruin the battery? Also is it safe to place the battery and the signal generator in parallel?


texts: Can I switch a transistor "ON" when the base/gate voltage drops?

texts:
I am using a sound board from Adafruit (this one) to play a small sound file.

What I would like to do is to close a transistor while the sound is playing, which will then close the circuit on a few LEDs. This will cause the LEDs to light while the sound is playing, and then turn off.

After finally finding the pin-out explanation there, I see that it has an ACT[ivity] pin which signals when audio is playing. While the board is on, the pin normally sits at roughly 3.35V, and then when the sound plays, the voltage drops by around 2 - 2.5 V. I see no change in amperage across the pin while the sound is playing.

As I understand it though, transistors switch when a positive voltage is applied to the base/gate. So I'm not sure what to do here. Is there a way to switch the transistor in such a way that when the ACT pin is sitting at 3.35V the transistor is open, and then closes when the applied voltage drops?

I tried to google on this, but all the articles and pages coming up have to do with the voltage drop across the transistor, nothing about switching the transistor based upon a voltage drop.

Below is the segment of my circuit I am trying to figure out at this point...

simulate this circuit – Schematic created using CircuitLab

Originally, I was planning on using the second speaker output on the board to switch my transistor, but that seems to have a constant voltage and amperage whether it's playing or not. Then I found the board's pin-out and the ACT pin, so I'm trying to make this work off of that now.


texts:
We would like to have a stable symmetric power supply with ±15 V.

At the moment we use two ICL 7660 to accomplish this (C=10 µF), with ±10 V for now:

The load consumes around 15 mA on + and - each, and through the ground go 30 mA. Without load the output voltage is 9.6 V but under load it drops asymmetrically to -6.5 V / + 7.2 V.

The idea is to power a DIY Scanning Tunnelling microscope. The measurements are performed high sampling rate so the ripple is visible.

It works okay, however there is this 10 kHz ripple, it would be great to get rid of it.

Also it seems that the voltage is unstable sometimes.

Is there a way to make this circuit more stable? I was thinking to use 2 passive low-pass filters (4.7 kΩ, 47 nF). One between +10V and GND, the other between -10V and GND.


texts: How to simulate commercial Double Balanced Mixer in ADS

texts:
I need to simulate ADE-1 from the Mini-circuit in ADS. I use this circuit simulation in ADS.
.
My RF source (P_1Tone) and Lo source, in reality, generate a 2dBm and 10dBm sinewaves. However, in simulating my mixer output I encounter the "No convergence" error. When I changed the RF/Lo sources to -2dBm and -10dBm it works but the result is not acceptable. For simplicity, I used the default harmonics tables  (dbl1.imt) from the ADS library which approximately is as same as my ADE-1 harmonics tables.
I have set ConvGain to "dbpolar(dbmtow(7),0)" or even "dbpolar(dbmtow(-7),0)" but nothing works.
I need to know how to simulate my mixer based on my real RF sources in ADS.


texts: Atmega8 - Max output frequency seems to be devide by 4

texts:
I'm a little bit confuse, and hope that someone here can point me out what I'm missing...
I'm using an Atmega8-16PU,
Flashed the fuse with :

avrdude -b 19200 -c avrisp -P /dev/tty.usbserial-A9IHTRVJ -p atmega8 -U lfuse:w:0xe4:m -U hfuse:w:0xd9:m

which means.. according to http://www.engbedded.com/fusecalc/ that I'm using int. osc 8Mhz.
In my code, I override OSCAL to OSCCAL = 0xFF; in order to work at its max frequency.

nevertheless, in a for loop (also tried with a 'while'), I'm only toggling a pin LED1_STATE^=(1 << LED1_PIN);
and I'm measuring 1.6Mhz ...

I was thinking that AVR where able to execute one instruction per system clock... here it seems that the FCPU is divided by 4..

I also tried using Timer0 and its overflow interrupt with ;

    TCNT0 = 254;
    TIMSK |= (1<<TOIE0); // enable interrupt
    TCCR0 = 0x01; //prescaler = 1
    sei();

ISR(TIMER0_OVF_vect){
    LED1_STATE ^=(1<<LED1_PIN);
    TCNT0 = 254;
}

and here the signal output 200Khz ....

can someone help me figure it out what is going on ? I am not enough considering the necessary 'instructions' time ?
Many thanks internet

Regards


texts: What makes someone "more" or "less" grounded, and how does this make electrocution more dangerous?

texts:
I've read that if someone is electrocuted by the prongs of a plug, that's not usually lethal, but it becomes a lot more dangerous if someone is grounded by touching metal (and also being wet? but that seems like something different entirely).

Does this mean that touching any metal object makes the electrocution significantly more dangerous? For example, if someone was touching car keys sitting on a table and they were electrocuted at the same time, would the car keys make the situation a lot more dangerous? Or is it only more dangerous when touching things that are plugged in, faucets connected to a plumbing system, etc.? Why does the grounding make things more dangerous, and how much more dangerous is this?


texts:
I want to use a current sense from the CR2550 connected to optoisolator LDA 110 and drive the gate of a triac. How do I connect these two systems with out killing either?

Update

Thanks for all the input so far.

What I am trying to do is this, when I turn on a table saw, I want to be able to sense that current and use it to drive a contactor and thus turn on a dust collector. I found this circuit  on the internet and seems to work. I get 3.5 volts from the output. Connecting it to a triac and the contactor shudders. The contactor requires 24 volts ac to run.


texts: How come a charge pump works without a reservoir capacitor?

texts:
I was trying to understand the charge pump which generates a negative voltage. As far as I understood, the basic operation is as follows:

SquareWaveInput is a 0 to 5V, 10kHz square wave. When the input is high, Q1 is ON and Q2 is OFF. Q1 charges C1 through D1 back to supply.
D2 is reverse biased at this time and does not conduct.

When the SquareWaveInput is low, Q1 is OFF and Q2 is ON, supplying a low impedance path to ground. C1 was charged at the previous cycle, and now it will discharge through Q2, ground, C2 and D2. D1 is reverse biased at this time and does not conduct. When the charge at C1 moves through C2, it charges C2 up until both have the same charge, but with the negative voltage. Assume that C1 is in parallel with C2 at this time.

Now, let's look at the schematic below. This circuit is the same as above except for D2 and C2. C1 charges up the same way the above circuit does. But how does C1 get discharged? Will it discharge through D1's reverse leakage current? I was doing a SPICE simulation and it discharged normally, but I don't know how. The current through D1 was very small (about 150nA) when the SquareWaveInput was low. Then I didn't trust SPICE and breadboarded it. It worked! I do not know how. Does it get its way through the oscilloscope probe? The probe was connected to the anode of D1 (Out) and its ground was at circuit ground and when I touched Out node, the oscilloscope showed some weirdness as in the scope-shot below. How did this circuit worked?

Normal operation:

With my hand on Out node:


texts: On/Off Switch driving MOSFET from Battery

texts:
I'm designing a circuit using a small On/Off switch that can't handle much current. It's going to be driven from a battery that'll be able to output a solid chunk of current and don't want to fry the switch by putting it directly inline. Therefore, I'm planning on using a MOSFET which the switch merely acting as a gate.
Is there any reason the circuit below will not end up working? [Please ignore part compatibility and ratings, since this circuit is just illustrative].


texts:
Several times I have seen schematics with a BAT54S, 2 diodes connected in series. The purpose is to protect over or under voltage but i can't fully understand how it works.

For example with an I/O or analog pin of a microcontroller:

Can someone explain this to me?


texts: Parallel Incandescent Bulbs and Resistors

texts:
I have built the circuit in LEDs and high currents and it works well - when the switch is open, the incandescent lamp lights up but the LED doesn't. When the switch is closed, the lamp goes out and the LED (actually an optocoupler) lights up.

I'm now trying to understand how it works, and also what value I should use for R1 below. For this exercise I've omitted D2 from the schematic and am assuming low resistance for D1. The bulb has a cold resistance of around 60Ohm, and I've arbitrarily multiplied that by 15 to get the hot resistance.

I have annotated what I believe to be values for P, I, V (and R where necessary) using my basic high school knowledge:

simulate this circuit – Schematic created using CircuitLab

Here we see the current too low for D1 to fire, which is what was wanted. Total current is 8.5mA, well within the tolerance of the 2A transformer.

simulate this circuit

With the switch closed, the bulb can be ignored.The current at D1 now jumps and is enough to fire the LED. The total current is 0.3A, still way within the capacity of the transformer.

R1 needs to dissipate 2.13W.

I have found that I can use up to 100Ohm for R1 while maintaining adequate illumination in the lamp, and lower values for R2 while maintaining that switching functionality so want to play around with values in order to get R1's power value down - unless there's something fundamental about the circuit that would mean it stays the same.

My question then: I've used simple DC series/parallel formula for this AC circuit. Do those still hold or have I made some bad assumptions?


texts: Does anyone know of a transparent conductive paint? I am creating some home made electroluminescent panels and I need something what would work with water based polyurethane. Ive had some luck with PEDOT:PSS but I don't like the blue tint it gives and it has a tendency to pool over the polyurethane I am using for the layers under the PEDOT:PSS.


texts: Requirements: I would like to design a circuit that uses an in-amp, and it needs dual supply (+/- 3V at least). I want it to use two lipo cells so it can be recharged. The output from the circuit is a headphone (earphone). I can have 32 ohm headphones, but that is the max. (There are 600 ohm phones out there but they are too expensive for this project.) This is an educational project for myself, and I would like to build the output stage using discrete components, or maybe simple opamps. My problem is with the output stage. The 32 ohm speaker at 3.7V would have about 100mA peak current, which is too much for a headphone. I could add a 330 ohm resistor in series, or lower the gain of the amp, but then most of the output power becomes heat - not a very good design for a battery operated device. Using a class D amp would probably solve the problem, but I don't think I capable of designing a class d amp. How others do this?


texts: Can I feed a 5V boost converter with 4xNiMH cells?

texts:
The spec page of my DC-DC boost converter (couldn't find a datasheet) says ”the input voltage should be kept below the output voltage”. And 4x the nominal 1.2V from an NiMH cell is below my 5V output voltage. But a fully charged NiMH battery starts at around 1.4V for a short time, for a total 5.6V.

Is this something I need to worry about in practice? It's a relatively high current application (driving a couple of dozen LEDs), so I'd like the extra capacity/current draw from four cells.


texts:
I have opened a remote and tried to read it.
Quite tricky if I'm honest.

I'm trying to replicate this DIY. On instructabels (Raspberry-Pi-GPIO-home-automation).

http://www.instructables.com/id/Raspberry-Pi-GPIO-home-automation/step8/Home-Automation/#step1

Very simply put, I want to connect my raspberry pi GPIO with this remote and turn my light on and off.
The Tutorial said each button should have 2 connections, I tried to follow each but have been unable to find anything?
How do I read this board?


texts: I have been measuring signals in an oscilloscope and I have stumbled upon a practical exercise of calculating the DC offset of a signal. Basically what I did was turn on the DC coupling, take the maximum voltage (eg. 2.36 volts) then turn on the AC coupling , take the maximum voltage again (e.g., 560mV) and finally DC offset= 2.360-0.560 Volts=1.8 Volts (or so I thought) Though the exercise continues and states that the DC coupling shows us peak-peak 1.04V and the AC coupling 890mV peak-peak. So my question is the following: If the DC offset is responsible for "lifting the signal" , how is it that the peak-peak is different for the same signal in the DC and AC coupling?


texts: Does it matter if a fuse is connected to the negative or positive terminal of a battery?

texts:
I am currently going through the conundrum of where to place a fuse in my DC battery-powered circuit to protect the circuit components and the DC battery. I've been googling for a definitive answer, but I came across diverging opinions... Which one is correct and why?

Connect the fuse to the negative terminal of the battery since it's where the actual flow of electrons originate which is opposite to the conventional flow of current from the positive terminal.
Connect the fuse to the positive terminal.
Connect two fuses, one at the positive and one at the negative battery terminals.

Also, during my research, I came across a post that advised to connect a fuse at the positive terminal since it would protect both circuit and the battery, but if the fuse is connected to the negative battery terminal, then it only protects the battery. Is this true? It doesn't make sense to me.

So, I can't figure out which one is correct and why? I made a simple block diagram to illustrate my question.

So, is it position A or B? Or both? And why?


texts:
For my project, I have a winch motor that takes 12V. I have a 12V battery to power it. I want to be able to set up a remote control system consisting of a receiver, transmitter, and one of those brushed motor speed controllers (ESC). For example, this ESC can be found on HobbyKing.

https://hobbyking.com/en_us/hobbywing-quicrun-60a-2s-3s-waterproof-brushed-esc-for-1-10.html

However, I am confused about the voltage ratings on the ESCs. For the input voltage, it can take up to 3S Lipo, which would be about 4.2 x 3 = 12.6V. That would work with my Lipo battery. But I am confused about the output voltage. There isn't anything written about it.

Do we assume that the output voltage to the motor is the same as the input voltage to the ESC? In my case, that would be 12V. Or will these brushed ESCs drive the motor at a lower voltage?


texts:
Good morning,

I have a design using these magnetics over here to filter and isolate the ethernet signal: https://www.mouser.com/ds/2/336/-515468.pdf

And I have this other component as an alternative:
http://www.bourns.com/docs/Product-Datasheets/sm13072apel.pdf

My question is if they are fully compatible. The only difference I find is the marking on the polarity of the transformers (in the isolation transformer). Package and pinout are compatible


texts:
For Nyquist theorem, for channels without noise the bit rate is:

\$N=2B\log_2(L)\$
N= bit rate, B= bandwidth, L= number of levels

Intuitively I say that it should be:

\$N=B\log_2(L)\$

Indeed if L=2, every signal carries a bit, so the bit rate is equal to the baud rate. I fail to recognize from where does that 2 come from, could someone explain it?


texts: Personal Mobility Device - motor technology?

texts:
I have temporary mobility problems where I can't walk for days. I am inspired by the Kiva robotic distribution system to make a device to transport me around the house, (or perhaps two or more units to pick up my bed and move it).

Basically I want a stool that I can sit on that can spin on the spot and drive in different directions over slightly bumpy flooring - maybe 1 cm level shifts. I will use manual control. Fancy Segway style stuff can come later.

I've looked at different technology including electric wheelchairs (which are far too large and cumbersome and expensive). I've also looked at electric skateboards including adaptations of RC aircraft motors - not for actual transport but for design ideas.

My requirements are two motors, one per road wheel, that have effective torque over the speed ranges required (0 - 1.5 m/s) and that are reversible. They will drive ~ 200mm road wheels via a reduction system and have proportional control.

The questions are what motor technology? And what controller technology? And what battery technology? Cost is an issue so perhaps hobby-grade systems might be the best choice?


texts:
I had some troubles with debouncing on one button, so i searched on Google to find a solution for my debouncing problem.

I found this code:

http://eewiki.net/pages/viewpage.action?pageId=4980758#DebounceLogicCircuit(withVHDLexample)-TheoryofOperation

Which seem to do the trick, but i am having a hard time understanding the code, and it works.

Could someone clarify how this code works, and how/where i can modify it so i turn on and off an LED.

i tried to change it a bit here

LIBRARY ieee;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std.all;

ENTITY debounce IS
  GENERIC(
    counter_size  :  INTEGER := 19); --counter size (19 bits gives 10.5ms with 50MHz clock)
  PORT(
    clk     : IN  STD_LOGIC;  --input clock
    button  : IN  STD_LOGIC;  --input signal to be debounced
    result  : OUT STD_LOGIC; --debounced signal
     LED        : out std_logic_vector(3 downto 0);
     Segment: out std_logic_vector (7 downto 0);
     AN: out std_logic
     );
END debounce;

ARCHITECTURE logic OF debounce IS
  SIGNAL flipflops   : STD_LOGIC_VECTOR(1 DOWNTO 0); --input flip flops
  SIGNAL counter_set : STD_LOGIC;                    --sync reset to zero
  SIGNAL counter_out : STD_LOGIC_VECTOR(counter_size DOWNTO 0) := (OTHERS => '0'); --counter output
  signal counter_10:            integer range 0 to 9 := 0;
  signal counter_10r:  std_logic_vector(7 downto 0);
BEGIN

  counter_set <= flipflops(0) xor flipflops(1);   --determine when to start/reset counter
  An <= '1';

  PROCESS(clk)
BEGIN
        IF(clk'EVENT and clk = '1') THEN
            flipflops(0) <= button;
            flipflops(1) <= flipflops(0);
                If(counter_set = '1') THEN --reset counter because input is changing
                    counter_out <= (OTHERS => '0');
                ELSIF(counter_out(counter_size) = '0') THEN --stable input time is not yet met
                    counter_out <= counter_out + 1;
            ELSE --stable input time is met
                result <= flipflops(1);
                counter_10 <= counter_10 + 1;
                case counter_10 is
                    when 0 => counter_10r <= "01000000";
                    when 1 => counter_10r <= "01111001";
                    when 2 => counter_10r <= "00100100";
                    when 3 => counter_10r <= "00110000";
                    when 4 => counter_10r <= "00011001";
                    when 5 => counter_10r <= "00010010";
                    when 6 => counter_10r <= "00000010";
                    when 7 => counter_10r <= "01111000";
                    when 8 => counter_10r <= "00000000";
                    when 9 => counter_10r <= "00010000";
                    when others => counter_10r <= "00000000";
                end case;
                LEd <= conv_std_logic_vector(counter_10,4);
                segment <= counter_10r;

END IF;
END IF;
END PROCESS;
END logic;

But it does not seem to work, the LED is constantly lid...


texts: Why longer antenna coaxial cable has better efficiency?

texts:
I am not an RF engineer and I don't understand why for the same PCB antenna but with longer cable length can have better return loss and efficiency.  I am comparing W3538B0150 with W3538B0200.  I assume longer cable mean higher cable loss.  Greatly appreciate.

http://www.digikey.co.uk/product-detail/en/pulse-electronics-corporation/W3538B0150/553-2585-ND/2649124


texts: System on Chip (SoC) ARM + FPGA (ZynQ-7xxx) - code design methodology

texts:
So far I've only been working with either ARM processor or FPGA/CPLD device separately. I.e. either I used a dedicated toolchain to generate binaries for a processor system from a C code, or I used a complex synthesis tool to configure a programmable gate system with VHDL code as input.

Now, I have a project in which the sequential part of the system (e.g. state machine logic) should be governed by an ARM processor, and the combinatorial part should be configured on a FPGA.

I have a bunch of already prepared and tested VHDL modules. I'd like to integrate them with ARM code that is currently being developed. Ideally, in one building process.

In other words, I'd like to encapsulate VHDL configuration in a single C-function (e.g. void init_logic(void)) and let ARM configure FPGA during initialization procedure. Could any of you please point me to any documentation/tutorial that deals with such a configuration?


texts: Confusion about conventional current and electron flow and how it runs through and powers a circuit

texts:
My apologies if these questions have already been asked and answered, if it has then I haven't found the thread so please link me to it if it exists.

I've just started learning about electricity as I've just recently started to learn electronic engineering online. Right off the bat I'm hit with confusion. I understand that conventional current is that positive charge runs from the positive end of the battery to the negative and that electron flow runs from the negative end of the battery to the positive, both of which via a conductor such as a copper wire.

A) Am I correct that both flows happen simultaneously?

B) If I place components on the circuit, say a resistor close to the positive end of the battery followed by an LED, e.g.

simulate this circuit – Schematic created using CircuitLab

and if I switch the place of the resistor to be on the other side of the circuit, e.g.

simulate this circuit

do both of these work? If so, how?

In my mind I rationalise that surely electricity can only work by travelling in one direction, linearly through a path, but apparently it happens in both directions? How then do you construct a circuit if your power is coming from both directions? In my first schematic above shouldn't the LED burn out due to the electron flow not passing through a resistor first?

C) Do both positive and negative charges' power provide equal amounts of power to a component?

and finally, D) if current runs from both directions out of the battery then does it matter which direction the battery is facing? Could I just flip it around without any consequences?

I hope my beginner level questions don't frustrate people. I've just been trying to rack my brain around this over the last few days. I unfortunately do not have a teacher to ask these questions to.

Any help would be greatly appreciated.


texts: I imported unity test harness to my project and seperated them from my production codes. As you know, there is a main belongs to my project and there should be another main to run tests. If I try to compile , I am getting duplicate main definition of course. I am currently reading @jamesgreenings book and I came to till chapter 3 and passed two examples. I did not see yet about how to handle this problem.


texts: KiCAD: "Footprint has no courtyard defined" using Arduino shield template

texts:
I made an Arduino shield with KiCAD.
When I finished the board in PCBnew, I ran a design rules check.
I got "Footprint has no courtyard defined" on all the mounting holes in the shield template.
This is a picture of the PCB:

This is a picture of the errors, with the mounting holes:


texts:
In smartening up my doorbell I've been playing with my illuminated pushbutton and have fallen into a bit of a rabbit hole. The doorbell normally:

simulate this circuit – Schematic created using CircuitLab

My understanding of this is that when the switch is open the bulb lights up and there is not enough current to fire the chime. When it is closed the short circuit then provides enough current to the chime to fire its coil. I used my multimeter to discover that the pushbutton lamp has a resistance of 60ohm, and the chime 6ohm. The AC source is 8VAC.

My enterprising idea was to replace the chime/coil with an optocoupler which would trigger something downstream (an ESP32 in my case). First I tried to get it all working with an LED, so to end up with a lit bell that lights the LED when pressed.

Here the lamp is always off, and the LED is always lit. Which is expected - the current is way too low for the lamp due to the now larger resistance. But reducing this resistor will probably burn out the LED. So:

Is what I want to do even possible? That is, to ordinarily have a high enough current pass through the button in order to illuminate the lamp but not the LED, but when pressed, have the short circuit light up the led instead? I guess what I really want is a low resistance optocoupler that can handle a high current. Does that exist, or is it possible to build one from basic components?
If not, what's the mental model here that would show this isn't possible? Is it that the LED requires much less current than the lamp so shortcircuiting the lamp doesn't make sense since by definition the current would increase?

To be clear I'm more interested in learning here than getting a working circuit - aside from solutions using mechanical relays and current sensors I'd probably choose to just use a normal (ie not illuminated) doorbell instead.


texts: So This is my first pcb and for easier traceing and just to correctly make the connections I want to make intersections of 2 traces specifically for where I am  connecting protection diodes to my stepper motor leads. I cannot figure out how to do this on eagle cad, or easyeda another program I use. I have researched it but cannot find anyone else asking the same thing. I'm wondering if this is possible and if so is there simply a button to do this or a method perhaps?


texts: Op Amp summing the circuit is not behaving as desired

texts:
The first op amp's output is 18 V and second's output is 27 V but when I sum those two outputs with a summing op amp, it gives -8.53 V at output. What is the wrong with my circuit? Am I not supposed to read "45 V" at output?

R1 = 1k, R2 = 1k, (non-inverting amplifier)

R3 = 2k, R4 = 1k, (non-inverting amplifier)

R5 = 1k, R6 = 1k, R7=1K (adder)


texts: Is it ok to clip component leads after soldering?

texts: When working with through the hole components, I have read that you should clip leads before soldering so the shock from clipping doesn't break the joint. On the other hand I've seen a ton of instructions for (more or less professional) DIY kits, where the picture depicted all components of a type being installed, then soldered, then clipped. The latter method is much faster and easier of course.


texts: How could a solar panel drain my battery?

texts:
This question is in regards to a 100 Watt solar panel that is less than a year old.

The solar panel was working fine but recently something happened.

Now when I hook the solar panel up to my batteries, the solar panel starts drawing energy from the battery. The panel used to be charging my batteries but now it's pulling energy from them.

There's no broken glass and it doesn't appear damaged at all. Still in nice condition.

What could have happened?


texts: Future-proofing home network cabling in a building with poor WiFi performance

texts:
I have a very frustrating home WiFi network.
The building in which I live is very (over 300 years) old and was long-ago extended on one side so that the (15"-thick) formerly-external wall is now internal; owing to layout, the radio must often penetrate this thick wall with as much as 70° incidence (i.e. direct line passes through 1114mm of solid brick; since 2.4GHz has a wavelength of approximately 125mm, this is almost 9 wavelengths!).
Therefore the only surprising thing is that I get any coverage at all on the other side of the extension from the access point (which I put down to reflection off surfaces around doorways).
I have tried power line communication, but the electrical wiring is also pretty old and not of particularly great quality: connections can be even less reliable than WiFi.
It strikes me that this is a perfect use case for an additional access point or wireless extender, which would normally be my next consideration.
However, since we are about to take up floorboards in a couple of rooms and move some other wiring around, it is a very good opportunity to install some data network cabling (which, whilst perhaps not needed, could provide some good future-proofing against unforeseeable needs over the next 20 years: increased home automation, media distribution, etc).
I want to maintain full WiFi coverage throughout, so will end up connecting at least one additional access point to any new cabling.  Devices that remain fixed can switch to being fully cabled rather than using up the existing WiFi.
My questions are:

I'm thinking two cables to each of sitting room/study/bedroom and a single cable to the kitchen, which would total about 100m in aggregate.  Of course it's hard to say without knowing what requirements I may have in the future, but does that seem adequate to accomodate 20 years of growth (the last thing I want is to pull up floorboards again)?

Cat6 seems like an absolute minimum requirement for adequate tolerance to any future requirements, but for only 100m of cabling it seems churlish to hold back from a higher quality cable whilst undertaking all of this work.
Should I stick with copper, but go all-out with Cat7A (I estimate the additional cost over Cat6 to be maybe £100, which is completely affordable)?  Or would fibre make more sense for true future-proofing (I have no grasp on what the extra cost would be, especially given that media converters will be required at each end of every connection for the time being)?

Is this all overkill for fairly mundane household needs (albeit increasingly streaming video etc over the data network)?


texts: General process for compensating a complex system in the time domain

texts:
Say one has a system with feedback wrapping around some "complicated" system (more complicated than the traditional examples given):

simulate this circuit – Schematic created using CircuitLab

\$A1\$ is a real op amp but with non-trivial (more than one pole) and not analytically known transfer function.   \$A2\$ is a difference amplifier / level shifter and PMOS output stage.  The transfer function for \$A2\$ is also unknown. \$B2\$ is the compensation loop around the first op amp, and B1 is the global feedback loop that sets the global gain.

I understand the concept of how to find B2 and B1 in the frequency domain, however that kind of analysis isn't always possible: I don't have access to a network analyzer, and LT Spice doesn't always give the right AC analysis transfer function.

How do I go about designing B2, and modifying B1 in order to compensate this system in the time domain?


texts: What is the relationship between the RPM, power, and impedance of an induction motor?

texts:
Does an induction motor draw more power at higher RPM?
Increasing the frequency of the AC power supply will increase the RPM of the induction motor. However, that should also increase its impedance (jwL.) If that is the case, then less current would be drawn (due to higher impedance) and consequently less power is consumed at higher RPM.
I must have missed something, what is it?


texts:
I am currently developing a plasma-coating prototype.
As shown in the image, a microwave emits 2.45GHz radiation into an evacuated chamber.
A PET bottle is in chamber, filled with a low pressured gas.
The gas turns into plasma and reacts with the inner surface of the bottle.
To homogenize the plasma reaction with the surface of the bottle, a magnetic field is created inside the chamber (see the two coils inside the chamber).
The resulting magnetic field causes the plasma ions to move on spirals as described in https://en.wikipedia.org/wiki/Magnetic_mirror .
The question: Can microwaves escape the shielded chamber through the coil wires? Or is it possible that the coils absorb some microwaves and re-emit radiation outside of the shielded chamber?


texts: Electro-static potential of a capacitor during a transient?

texts:
How would I calculate the electro-static potential for this simple circuit during the transient (during the time the capacitor charges)? Do I just use Ohm's law?

simulate this circuit – Schematic created using CircuitLab

My thought process was as follows:

We know when the capacitor is charged it will have a "charge" of 1V * 1μF (Psi aka. Q)
So we have a current (I) of the value Psi / Δt during the transient
I = e / R → e = I * R (e is the potential, aka. voltage, of the capacitor and R is the resistance of the conductor)

I wrote down my full thought-process here: http://circuits.icidasset.com/circuits/01-basics/002-capacitor

Does this seem correct, or is there a better way?


texts: How do you calculate the VA of a toroidal transformer core?

texts:
I'm looking for a calculation which can take relative magnetic permeability, toroidal core dimensions and if relevant windings + frequency to give the VA expected.

The purpose is to either build a custom toroidal core or to use a premade core to build a transformer of a desired VA rating with a custom turn ratio.


texts: Is it possible to redesign a magnetron to be a receiving device?

texts:
Magnetron- As a transmitter

A magentron is used to produce microwaves, by oscillating a magnetic field, and an electric field at a specific frequency.
Magnetron- As a receiver

Is it possible to redesign a magnetron to be a receiver of microwaves waves?  By not necessarily splitting the photon into its components, an electric field, and magnetic field?


texts:
First of all, I have absolutely no experience in electrical engineering, so bear with me.
I want to build a chess set in which it can recognize what piece is on which square. Initially, I thought I could do that with RFID transponders, but as far as my layperson's research goes, the lowest read range is about 10cm/~0.4in, which is too wide in order to make sure the reader only recognizes the piece on its square, given that I do not want to make a large chess board. The desired read range would be 2-3cm/~0.8-1.2in.
But, I found this question which is more or less exactly what I want, so maybe I am wrong with the read range or misunderstand RFID-Transponders?
So, my question is, are there (read only) RFID-Transponders with a read range lower than 3cm?
If not, are there any alternatives, given that I need to know what piece is on a square, which means a simple "something is on that square" does not achieve my needs (for example a hall effect sensor)
The board will be roughly 0.5cm thick half-transparent PETG.