texts: Is it important that vias are plated on a PCB?

texts:
As in the title. I've noticed several PCBs of mine have vias which are not plated - they do not have a characteristic "gold" shine to them. I suspect this is because I was pushing the limits of drill sizes - my fab specifies 12 mil and I used 15 mil (20 mil including plating.) I've checked a few with a multimeter and they do have continuity, which is good, but I've only checked a few, so have no idea if there might be a few dodgy connections because of this. Is it something to be concerned about? Board passes DRC as specified by fab.

I've seen quite a few high density boards like motherboards and graphics cards without plated vias.

Here's an older board of mine which shows a similar problem to my newer boards. Note that some vias look gold, while others don't look plated at all.


texts: DIY reference clock jitter / Allan deviation measurement

texts:
I am considering doing some recreational timing. I have few OCXO's, GPSDO, Rb source - but no way to compare their stability / jitter. Majority of sources are around 10Mhz.
Is there any DIY-friendly way via some publicly available / open source hardware & software to measure jitter / Allan deviation?
For example, I think it should be possible to compare clock1 vs clock2 (OCXO) using phase comparator feed into soundcard or ADC. Then some software might analyze it and build a graph. Maybe signal could be compared to 2 independent OCXO and even better measurement extracted with very simple measurement setup. Or some DDS-based approach could be used.
Is it possible? Can you suggest where too look for previous DIY-friendly developments in the area?
Example image by @LeoBodnar:


texts: Dealing with bidirectional communication over 1 pin

texts:
I am writing a Verilog driver for a simple temperature sensor connected to an FPGA. (The temperature sensor datasheet is available here.) Communications occur over one pin, the sda pin, where the slave or master sends a byte, which is then "acknowledged" by the other at the end of the byte (between the clock cycles 9 and 1).

I imagine that the best way to model this is making sda an inout wire, where both the master and the slave drive sda using an assign statement. It is unclear to me how collisions can be avoided.

What happens when the same inout wire is driven by both the source and the master? What is the best way to model send-acknowledge cycles over one pin in Verilog?


texts: Amplifying photodiode current with BJT transistor

texts:
I'm trying to develop a kind of light detector. To do that, I'm going to use a photodiode and a bjt transistor to amplify its current. I found a circuit in this tutorial:

which explains how the phototransistors work. It is pretty simple, but I'm not able to understand two things:

It is said that Rb is optional. But the photodiode needs bias to work in that way. How on Earth it will be biased? Maybe due to base-emitter junction, but how exactly does it work?
What if the Rl resistor would be connected to collector? I tried such circuit with  this photodiode and this transistor. The Rb and Rl was both 100K. I expected Rb voltage to be about 1,2V because of the 12uA current produced by the diode, but actually it was about 0.7V and the circuit was extremely unstable - it turns off and on for unexplainable reason.

I guess I'm missing something obvious, but just can't get, what exactly.


texts:
I am not sure this is the right place to ask this question, but did not see any communities dedicated to Atmel chips.

I used a scope to look at my atmega328 clock signal (pin 14) and got the following result.

I expected a square wave, not a notched sine wave, but I have no basis for that expectation.  So, is this what the signal should look like, or do I have some problems with my clock setup (noise, wrong caps, etc).  I am using a 16MHz crystal with 22pF caps to ground wired to XTAL1/2 (9 and 10).  The clock frequency looks dead-on at 16MHz, 62.3ns which you can see on the scope.  Supply voltage is coming from a 7805 (fed from a 12V wall wart)  Does this indicate a noise problem (need additional capacitors perhaps) or maybe this is actually what the signal looks like?

Second question this made me think of, what generates the clock signal anyway? (If I need to ask that as a separate question I will).

EDIT:

The probe is a 10x probe, 100 MHz.  It was not calibrated when I measured the above signal, so I calibrated it per Stratton's instruction.  The probe is now compensated as can be seen here (820 microsec period = approx. 1.22kHz which is what it should be)

Now when I hook everything up, I get the following, it looks worse...

Could the notching be strictly from no bypass capacitor at the chip?  I find that hard to believe, but I have never done this experiment, so I am out of my league!!  I know every thing I have read and learned says to use them, it would just be amazing.

Also, I included a picture of the setup just for clarification.  Maybe you can see something you don't like (besides my poor ability to build a test board!!)


texts: Is "Forward Voltage @ 1A" equivalent to "Internal Voltage Drop"

texts: I have a problem for an Electrical Engineering 1 subject with information given as "LED Light Internal Series Resistance" = 15.1Ω and "LED Light Internal Voltage Drop" = 9.5V. When attempting to model this circuit in Falstad or other circuit simulators I'm not sure how to correctly configure this information. The only input option for LEDs in Falstad (Circuit Simulator) are "Forward Voltage @ 1A". I have put a resistor in series with an LED with a resistance value of 15.1 Ohm and set "Forward Voltage Drop @ 1A" of the LED to 9.5V but I'm not sure this is correct. Can somebody explain how these two terms are related?


texts:
I am having 100% failure rate trying to get this high side driver to operate.  The failure happens as soon as the 5v logic signal is turned on. I have had straight shorts from VDD to GND, and I have had burnt smoking chips.  I am clearly doing something incorrectly.

Following the schematic i made:

The driver datasheet is: Fan7371

https://www.onsemi.com/pub/Collateral/FAN73711-D.pdf

Diode data sheet: c3d04065A

https://www.wolfspeed.com/downloads/dl/file/id/841/product/46/c3d04065a.pdf

Power supplies used:

tektronix PWS2323  DC power Supply 0-32V, 3A

IGBT data sheet: IXXH110N65C4

https://www.littelfuse.com/~/media/electronics/datasheets/discrete_igbts/littelfuse_discrete_igbts_xpt_ixxh110n65c4_datasheet.pdf.pdf

last circuit the 10ohm Rboot (replaced with 100 ohm in picture) burnt out and then the driver when I was noticing that the capacitors were discharging when VDD was turned off. Pretty sure this should not happen.

EDIT:

The circuit will eventually be run at much higher voltage which is why the overkill on some of the parts.

The pins are correct on the IGBT. orange wire going to 1 (G) and blue going to 3 (S)

In response to the answer:

Similar to this typical setup from the data sheet.

If i add a diode from source to ground would that provide a better result?  It was my thinking that CB was able to find the off time charge path through the load ground.  when i turn the first supply on it has no trouble charging to 15 volts, but CB does discharge immediately if i turn it off as well.


texts:
Maybe this is little bit off-topic, but I wanted to try to find out here what's the name of this connector?

I tried googling like "6 pin connector", "6 pin flat connector" but nothing like this comes out.


texts:
How do you find out what voltage is being used on a data bus for the high signal?

On a small electronics I guess you can assume it will be 3.3v or 5v but what about other circuits, say in a car or on the side of a TV or some old random electrical equipment without knowing the spec of a port.

If I wanted to connect say a logic analyser to some digital bus, not knowing anything about it, how would I first find out the voltage to make sure I don't blow up my logic analyser and then, once I know what the peek voltage will be, so I'll not blow up my logic analyser by connecting it, how do I bring the voltage down to the right level (Some sort of Attenuator?) so that I can see the data on the bus?


texts: Switching two contacts with 24VDC potential difference

texts:
This question relates mainly to the means of operating a relay module using a PC parallel port. I have outlined the application that this is to be used with but that is provided for background so users can get an overall picture - it is not part of my actual question.

I want to join two interface connections to an existing electronic device in order to actuate it. One pin (I'll call it P_ground) is grounded and the other (= P_operate) is at +24 VDC above ground. The device (an entrance turnstyle) is actuated by grounding the P_operate (24V potential) pin.   I do not know the turnstyle's internal circuitry, but grounding P_operate is the standard method of actuation.

I have a +5VDC powered relay module that I wish to use to ground pin Poperate when required.

I wish to use the LPT (printer) port of a computer to operate the relay module. I bought a relay module that triggers with logic 0.
I have been unable to make the relay switch.

[[RM:]] This is the heart o the problem - the referenced relay module requires a high (not low)level to operate. ]]

I connect Vcc to +5v of adapter, GND to Negative(-) pin of the adapter...when I connect In pin to GND it should switch but it does not.   How could I make it to work?

_______________________________________________

This is NOT the actual turnstile used but shows the general sort of device that I am referring to:


texts:
I used to have a Motorola Milestone which used magnets to detect car and desktop docks.

I've now got an HTC One X and am looking for dock options. The standard ones look pretty expensive, but there are some products on the market which suggest it's probably just resistors between some of the lines like the iPhone?

Does anyone know what the magical combination is for the desktop and car docks?


texts:
module ram_reg;
parameter SIZE = 4;

reg [2:0] address;
reg [SIZE-1:0] data_in;
wire [7:0] connector;

reg clk;
reg rstn;
reg wr_rd;

output reg[SIZE-1:0] data_out; //LINE IN QUESTION
wire [SIZE-1:0] reg_out[7:0];

register #(SIZE) reg0 (.clk(clk), .data(data_in), .load(connector[0]), .rstn(rstn), .out(reg_out[0]));
register #(SIZE) reg1 (.clk(clk), .data(data_in), .load(connector[1]), .rstn(rstn), .out(reg_out[1]));
register #(SIZE) reg2 (.clk(clk), .data(data_in), .load(connector[2]), .rstn(rstn), .out(reg_out[2]));
register #(SIZE) reg3 (.clk(clk), .data(data_in), .load(connector[3]), .rstn(rstn), .out(reg_out[3]));
register #(SIZE) reg4 (.clk(clk), .data(data_in), .load(connector[4]), .rstn(rstn), .out(reg_out[4]));
register #(SIZE) reg5 (.clk(clk), .data(data_in), .load(connector[5]), .rstn(rstn), .out(reg_out[5]));
register #(SIZE) reg6 (.clk(clk), .data(data_in), .load(connector[6]), .rstn(rstn), .out(reg_out[6]));
register #(SIZE) reg7 (.clk(clk), .data(data_in), .load(connector[7]), .rstn(rstn), .out(reg_out[7]));

mux8 #(SIZE) mux_1 (.in0(reg_out[0]),.in1(reg_out[1]),.in2(reg_out[2]),.in3(reg_out[3]),.in4(reg_out[4]),.in5(reg_out[5]),.in6(reg_out[6]),.in7(reg_out[7]),.sel(address),.out(data_out));

//sevenSegment ss (.B(address), .segment(data_out));

up_counter uc (.clk(clk), .enable(wr_rd), .rstn(rstn));

endmodule

I am doing this in quartus, and it tells me "Top module port 'data_out' is not found in port list. The Quartus site just tells me   Edit the design to make sure the port name appears in the list of ports in top-level module's Module Declaration, which I don't know how to do. I also tried writing it as just reg and just output and I get the same error.


texts: How long would a 5v battery power supply run a 5v LED strip for

texts:
I have an LED strip which requires a 5v input, to run from a portable power supply. The power supply has a capacity of 2200mAh with maximum output of 1A.

How long would the power supply be able to power the LED's before it needed replacing?


texts: dual ramp voltmeter meaningfully displaying the microvolt digit

texts: How can a common dual ramp voltmeter meaningfully display the microvolt digit when measuring a DC voltage ridden by a 50 Hz signal of several millivolts captured from the power distribution network.


texts: How do I get started in C using avr-gcc on the mega2560

texts:
I've program the arduino using tools before (on windows) and using C++ but never with c++ without tools nor done it on linux
I have a (at)mega2560 and want to do a simple blink program like the below
int LED_BUILTIN=13
void setup() {
    pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
    digitalWrite(LED_BUILTIN, HIGH);
    delay(1000);
    digitalWrite(LED_BUILTIN, LOW);
    delay(1000);
}

I'm completely clueless how to implement this. The only thing I figured out is _delay_ms and the command line args I should be using (which may be wrong)

avr-gcc src.c -DF_CPU=16000000 -mmcu=atmega2560 -Wall -Werror -Wextra -Os
avr-objcopy -j .text -j .data -O ihex a.out my.hex
avrdude -patmega2560 -cwiring -P/dev/ttyACM0 -b115200 -D -Uflash:w:my.hex:i

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

int led = 13;

inline void digitalWrite(int led, bool isHigh)
{
    //No idea
}

int main()
{
    //pinMode(led, 1);
    DDRB &= ~(1<<led); //I doubt this is right
    for(;;)
    {
        digitalWrite(led, 1);
        _delay_ms(1000);
        digitalWrite(led, 0);
        _delay_ms(1000);
    }
}


texts: Gaussian function power spectrum (Matlab)

texts:
I am trying to plot the power spectrum (\$|FT(f)|^2\$) of a Gaussian function, and overlap it with the theoretically expected spectrum calculated from the Fourier transform pair:

\$e^{-\alpha t^2} \iff \sqrt{\frac{\pi}{\alpha}} e^{-\pi^2 \nu^2 / \alpha}.\$

But when I do this in Matlab they look completely different:

So, what is wrong here? I am very confused but I think it has something to do with the differences in the normalization of FT used here with that of the DFT of Matlab. What exactly do I need to change in the code in order for the plots to match?

Any help would be greatly appreciated.

Here is my code:

clear; clf; clc;
a=0.05;
n=50; % length of DFT
k=[-n:1:n];

x=exp(-a.*k.^2); % Gaussian function

nu=[0:1:2*n];
xx=fft(x); % DFT calculation
y=(sqrt(pi/a)).*exp((-pi^2*nu.^2)./a); % Theoretical
yy=(abs(y)).^2; % Power spectrum

% subplot(2,1,1) % Power spectrum plot
plot(nu, yy, '-om'); hold on;
hold on; plot(nu,(abs(fftshift(xx))).^2,'-o'); grid;xlabel('Frequency');
title('Power Spectrum')
hold off;

% subplot(2,1,2) % Temporal waveform plot
% plot(k,x);grid;
% xlabel('Time');
% title('Data waveform');
% hold on; plot(k,x,'o'); hold off;

figure(gcf);


texts: Confused about Eagle libraries (can't add parts I see in control panel to schematic)

texts:
I want to add a diode with an SOD80 package to a schematic. In the Eagle control panel under diodes.lbr, I see a part named SOD80C:

Question 1: I'm confused at this point. Am I looking at a device or a package?

I right clicked on the library, clicked on "Use," went back to my schematic, clicked to add a new part, and there's no part named SOD80C in the diode's library:

Question 2: Why isn't the part showing up in the ADD dialog, when it does show in the control panel?


texts: calculate the cutoff frequency of a low pass filter

texts:
Given that R = 12kΩ and C = 3.3nF, calculate the cutoff frequency (fc), unit in Hz.

The frequency response of Vo/Vi is 1/(1+j ω RC).
Therefore,cut off radian frequency(Wc) is equal to 1/RC.
Then, cut off frequency  ω = ωc, isn't the frequency just the 1/RC which is equal to 25252.5252 .


texts:
If we use a controller and wanted to send data via UART to PC. I trust serial data will be displayed on the software and is there any way you can display real values on the software apart from collecting the bytes and makes appropriate data type in PC software.

I am using PIC and I needed to send data via UART. And I ended up reading this question:

Sending integers via PIC's USART

Is there any software where we can send the data serially and the values will be displayed according to the data type?

How do we fix such problems? Can you suggest free software to monitor serial data and can be later used to view real values also.


texts: Inductor Core Loss: Volt-uS vs. Irms vs. Switcher Frequency

texts:
For DC to DC application, I see these charts often for inductors, but I don't understand what they actually mean. What does this chart mean, and how does it relate Volt-uS, Irms, & Freq?

Edit:

This image was taken from this inductor's datasheet. Full Datasheet Here.


texts:
I've been using STMCUBE combined with Keil for some time now. For most part I like the HAL library and the documentation for STM32f1xx drivers is quite good.

I'm doing a project where I am using STM32f103rb Nucleo card combined with an MPU6050 gyro/accelerometer.
I use code generation tool STM32CubeMX in order to generate initiation function. However when I want to implement I2C I have a strange problem. STM32Cube generates all necessary initiation steps, handle is set up then GPIO pins set as OD, then finally the clock is enabled using the macro __HAL_RCC_I2C1_CLK_ENABLE(), however when this macro is run within the HAL_I2C_MspInit, the I2C busy flag seems to be set, and is not cleared, hence I can't communicate with the MPU6050 device.

I noticed that if I put something (for example a measuring probe) on the SDA line while macro __HAL_RCC_I2C1_CLK_ENABLE() is run, the busy flag is not set and my I2C communication works until I reset the micro controller.

Another(better than putting a physical probe?) way that seems to work is that after macro __HAL_RCC_I2C1_CLK_ENABLE() is run, I use macros __HAL_RCC_I2C1_FORCE_RESET() and __HAL_RCC_I2C1_RELEASE_RESET(). This way my I2C communication works fine.

I think it's strange and I can't really explain the behaviour. But since I added the force reset and release reset macros, I haven't had any I2C problem, it works perfectly.

Let me know if I need to share some more code.


texts: Meaning of 'Scatterer' and 'point scatterer' as opposed to just using the word 'target'?

texts:
https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/ers/instruments/sar/applications/radar-courses/content-3/-/asset_publisher/mQ9R7ZVkKg5P/content/radar-course-3-the-radar-equation

"The geometry of scattering from an isolated radar target (scatterer) is shown in the figure, along with the parameters that are involved in the radar equation."

I'm a bit confused about usage of the words "scatterer" and "point scatterer" in radar. The above makes it sound like 'scatterer' is exactly synonymous with target. That can't be right- then we would just say "target." There must be some connotation with the above that makes us use the word scattterer.

My googling efforts:

I searched "scattering" on wikipedia but am confused how it relates to the above
https://en.wikipedia.org/wiki/Scattering
"The types of non-uniformities which can cause scattering, sometimes known as scatterers or scattering centers, are too numerous to list, but a small sample includes particles, bubbles, droplets, density" <- this doesn't sound like anything related to radar. A scatterer in wikipedia seems to be anything that can deflect radiation

There is also the term "backscatter" (something to do with bouncing according to this site http://www.radartutorial.eu/07.waves/wa51.en.html "“bouncing” or “backscattering” radio waves off the ionosphere"
)  but I can't tell if it is related to "scatterer"


texts: convert step down to step up transformer?

texts:
I have step down 12-0-12 1Amp transformer input volts 220V and output 12V. As it is step up transformer Np > Ns. I was wondering if I can change it to step up transformer by reversing the input to secondary coil and output at primary coil.

Problem :

There are 3 wire at secondary coil. how do I connect those wire so that I can use 2 wire as input?(or 12V to both end)

My questions:

1.step down can change into step up transformer?

2.is there any power loss?(compare to step up transformer,actually I see there is some thin and thick copper wire binding in  the transformer.  Will this     affect the power loss?

update:
I have 12V(Two 6V acid lead battery connected in series) I=16A(8A each battery) and i will add some resistor to get I=1A  still working on the inverter part for AC current. The load is 9W CFL 100-300VAC.


texts:
I have a circuit board with STM32L433 that has around 320uA of baseline current draw in STOP 2 mode. Only LSE with a 32kHz crystal is active.

The board has separate analog Vdda power which is disabled for the stop mode. (tied to ground). Before disabling Vdda, ADC, DAC and OPAMP are disabled and their pins put into an OD low mode.

The configuration was done using the STM32CubeMX software.

Any ideas how to debug this? I disconnected and measured pretty much every external peripheral to see what is drawing current, but it seems like the STM32L433 is the culprit.

I'm measuring current with an oscilloscope using a 2ohm resistor in series with the battery. The LDO could be responsible for 20uA of it, which still leaves 300uA unaccounted for.

EDIT:

~ 120uA of it was using STOP 0 instead of STOP 2. This was left over from some experimentation.  Now I'm at 200uA.
I've also disconnected both the BMI160 and DRV2603 chips. And they aren't the problem.

EDIT2

I've soldered another board with just an STM32L433 and an LDO LP5907-3.0 and a couple of decoupling capacitors. SAME PROBLEM.

This is the minimal code I used to set the GPIOs

GPIO_InitTypeDef GPIO_InitStruct;

/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE()
;
__HAL_RCC_GPIOH_CLK_ENABLE()
;
__HAL_RCC_GPIOA_CLK_ENABLE()
;
__HAL_RCC_GPIOB_CLK_ENABLE()
;

GPIO_InitStruct.Pin = 0xFFFFFFFF;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOA, GPIO_InitStruct.Pin, GPIO_PIN_SET);

GPIO_InitStruct.Pin = 0xFFFFFFFF;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOB, GPIO_InitStruct.Pin, GPIO_PIN_SET);

GPIO_InitStruct.Pin = 0xFFFFFFFF;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOC, GPIO_InitStruct.Pin, GPIO_PIN_SET);

GPIO_InitStruct.Pin = 0xFFFFFFFF;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOH, &GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOH, GPIO_InitStruct.Pin, GPIO_PIN_SET);

//BOOT0 PIN
GPIO_InitStruct.Pin = GPIO_PIN_3;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOH, &GPIO_InitStruct);

HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);

EDIT3

USB DM pin floats when USB in is low power mode. This caused the seen 200uA current drow. Pulling this pin down externally removes the 200uA. Now i'm trying to find a way around this in firmware.


texts: How to prevent PA system from interference of 4G signal

texts:
I apologize if this is not the right place to post this.

I am working on a small PA system for a weekly gathering. It catches the signal from wireless mics and output it to the speakers. I am pretty sure that the machine itself is not damaged.

Recently, I've found that there are very sharp digital noise coming out from the speakers and it is so annoying that it masks the voices and songs. I've done some investigation and found out that it could be caused by 4G cell phone signal. So I tried some experiments and the observations seem proved the theory.

I've learned from my online research that I can either ask everyone to turn off the 4G signal (which is unlikely since the population is around 100), or replace my PA system.

Is there another way out? Such as a 4G signal filter or jammer? If so, my concern is, will these filters and jammers also get rid of the signal from the wireless mics?

Thanks.

Update 1:

Thank you all for your advice. Unfortunately, I cannot get access to the equipment until this weekend. I'll mark the models of the gears and post them here then. I'll also try to upload a sample noise for your analysis.


texts:
For someone with no knowledge in electrical engineering, is there a way to check if a device is "grounded" (?) and safe to use?

It is not uncommon when shopping for appliances online (eg. lamps), mainly with those imported from China, to find reviews warning about a missing "grounding" and the associated dangers. The danger behind it seems to be that in the case of an internal failure, a live wire could come in contact with the metal chassis and electrocute the next person to touch the device. This also means that in a device built to safety specifications, there is some sort of failsafe guarding against this danger.

If one were to receive an electrical appliance with unknown safety mechanics and potentially missing/forged certifications, how could one reasonably check the product regarding safety?
Does this process differ depending on the outlet it's built for (US vs EU etc)?
Can this check be done without disassembling the device, wherein a layman could inadvertently destroy the safety features?


texts: I have an LED with no specs, but it does have a resistor. I want to double the voltage

texts:
It's one of those "stick anywhere" lights that look like a household switch.
It's powered by 4 AAA batteries and has two-2 inch LED strips connected in series with a 3 ohm resistor(looks like a 1 watt).
I want to cannibalize the parts and reassemble into a ceiling fixture I bought at the thrift store. That way I can use it in my 12 volt system I'm installing in my house.
I'm having a heck of a time figuring out what resistance to use so I can up the voltage to 12 volts. I'm probably just looking at it wrong, I normally have the specs on the LEDs.
Thanks in advance for any help with this.


texts: Is there a difference between PIO and GPIO pins?

texts:
GPIO = digital + analog pins;
PIO = only digital ?

EDIT: PIO defined in datasheet as "Programmable input/output, also known as general-purpose I/O"


texts: DP83848C: DP83848 stops working after few month on field

texts:
In a product we designed, the LAN drive circuit(MII mode) is composed of LPC1768 and DP83848CVV. The function is very normal. There are no problems with factory testing. After using it in the hands of customers for 2-3 months, the product does not work one after another. Not even the computer. Analyzing the returned products, it was found that the RESET PIN of the DP83848C was short-circuited to the ground, and the LPC1768 could not be started. The RESET foot of DP83848 is directly connected to the RESET PIN of LPC1768 and then grounded by a 0.1uF capacitor.

on damaged PCB, if i desolder DP83848, LPC1768 works fine.

I have attached the Schematic PDF for reference.

We also have applied ESD protection as shown in LINK , we applied Basic ESD Protection, from PDF link , we used SP3002 for same. But that also didnt work. Now we are deadlock and we have to resolve this, we would like to know if anymore data is required from my end .we would like to receive some guidance to resolve this issue


texts:
I am looking for a "cheap" => Less than $60 way to measure the amount of fog. It doesn't have to be an exact calculation.

I basically need to be able to differentiate between different amounts of fog.

Now I was wondering if a particle / dust sensor would do the job in my case: https://publiclab.org/notes/donblair/05-03-2014/how-do-we-measure-particulate-stuff-in-the-air or https://www.sgbotic.com/products/datasheets/sensors/datasheet-SM-PWM-01C.pdf

It seems like the perfect solution, but I'm not sure whether it filters out fog particles because they're not big enough.

The second datasheet states a minimum particle size of 1 um.

Now by googling "Fog particle size" it says "Most typical fog machines create a fog particle size of 1-5 micron."

That should be detected by the sensor module, but are real fog particles of the same size? And I assume these particles are only that big when the fog is really thick?


texts: differential input overvoltage protection

texts:
some suggestions to protect an RS485 from differential input overvoltage?
I want protect the transceiver RS485 if the differential input voltage is below -7V or above +12V.
Someone does anyone know any device or IC that do this?


texts: why do i have to add a capacitor to observe AM output

texts:
so our TA asked us to simulate this modulator in lTspice but told us to add a capacitor that has a value of 0.1 uF at the output and record the result and confirm the envelope shape from message signal and bandwidth etc..
then he told us to use this demodulator and connect to extract the message signal from the AM  signal
can anyone explain what the sets of resistors and capacitors do in these circuits i know that the carrier null is adjustable so that it produces a DSB signal im really confused


texts:
I am a graduate math student and I want to design some electrical circuits for a math games workshop. I know physics only at a high-school level.
At first, let's explain the game and its rules,
suppose that we have a \$3 \times 3\$ board,
and there is a light on each square,
when we press the corresponding switch of each light,
the status of that light and all other adjacent lights will change.
For example, let's consider this example:

If we press the corresponding switch of the blue signed square, then the status of the blue signed square and all red signed squares will change.
At the next step,
if we press the corresponding switch of the pink signed square, then the status of the pink signed square and all orange signed squares will change.

How should I design such a circuit?

We want to replace the \$3 \times 3\$ board, with other boards like:

But the rules are the same as the above example.

  How should I design the circuits corresponding to
  \$(4 \times 4)\$ or \$(\star \star \star)\$?


texts: Can I use an LM324 as a buffer amplifier or voltage follower for ADC reading with an ATmega328?

texts:
I am looking to read an analogue voltage from a pressure sensor. For that application, I don't want to connect the pressure sensor directly to Atmega328P ADC input as it might alter the original signal.
Which operational amplifier should I choose to work as a buffer between an analogue device and a microcontroller?


texts: What is the best way to charge phone's lithium-polymer batteries to optimize battery life?

texts:
I was looking for tips on how to best charge a phone which comes with a lithium-polymer battery, but most articles online talk about lithium-ion batteries.
Can the same tips, for example those in this article, be applied to lithium-polymer batteries?


texts: I'm a beginner in electronics and I was studying when I had a question, how to calculate the voltage after passing by a resistor. Ex: there is a circuit of 10mA with a 5V voltage, what is the voltage in an LED, after the current pass by a resistor of 100 ohms?


texts:
I am looking for high capacity eeprom(I2C compatible) IC as an alternative to 1gb or 2gb micro SD card (data storage segment in my project) just in case I fail to interface Sdcard with pic32 mcu..

Suggestions are welcomed..

Thanks in advance..


texts:
First of all, sorry, I missed the links / images where I have found the solutions mentioned below (I hope, if you are familiar with this topic, you know them):
I have to design an ECG / EEG analog amplifier with a gain around 1000. Sigma-Delta is the preferred AD converter architecture. As I search trough the net, I see some implementation, where:

the input is AC coupled trough RC high pass filter
the instrumental amplifier's reference pin is driven by an integrator (servo feedback)
after that an active high pass filter is realized

The design tread off that I cannot decide / I don't understand (we know, every components add noise to the signal present on the output):

as the input should be AC coupled due to electrode offset cancellation, why should I apply servo drive and HP filter?
some designs throw away the AC coupling, but requires lower instrumental amplifier gain, that reduce CMRR
some another designs left the servo drive and connect the instrumental amplifier's reference to a predefined potential

Can somebody help me to decide about these solutions / constraints?
Regards
Edit:
This is my concept design:

User69795 said:

The problem with the high pass filter in this application is due to the very slow response time of the filter ... When the input is overdriven, ... the filter takes a really long time to settle, so the signal output is not visible to the doctors, so they don’t know if the patient is still in fibrillation or is dead or is OK.
Overcoming this response time problem while still providing the correct high pass filtering leads to the different ways of implementing the high pass function that you have noticed. A good solution calls for clever design.

As I understand you correctly, the C15 R13 U4A HP filter should be removed due to the large settling time?
And what about the AC coupled input and the common to differential mode transformation caused by the component mismatch?


texts: Making a voltage drop while providing high current - how does this work?

texts:
I have a USB power source at 5V which needs to power a chip at ideally 4V (4.4V max) - but I need to be able to supply 2A of current for the "spike" current draws for the chip.  In general the chip will probably only be drawing 200mA.

A simple voltage divider can get me the 4V, however I am not quite sure how to calculate the resistor values when it could draw anywhere from 10uA to 2A - the current draws could have wildly different resistance values.

I might be overthinking this myself, but does this still work as a simple voltage divider equation?  You'd need resistors rated to handle the current, but is that all there is to it?

-- Yes, I've considered other circuit options for this kind of thing, I'm specifically wondering whether this could be done with a simple voltage divider.


texts:
I'm using a microcontroller to simply turn on and off an LED, but I want it to fade in and out. I set up the circuit in this way:

When the pin goes high, the capacitor would instantaneously draw a large amount of current as it starts to charge up, and the pin can only source up to 25mA.

I was wondering whether this is still safe to do or could it possibly damage the pin?


texts: Component connected in series in a block diagram of a control system

texts: I am given the following block diagram of a control system (I think it also applies to electrical circuits as well with linear components. Correct me if I'm wrong). My textbook says that C(s) is connected in series with the system characterized by input v(t) and output y(t). Why is it that?


texts: Thinest insulator between metal case and PCB?

texts:
For a miniature product, I want the smallest possible product enclosure around the PCB. I figure I can get away with a 1mm thick metal sheet enclosure.

But I (probably) also need an insulator between the circuit board and the case, so nothing shorts out. What's the thinnest way I can make the inside of the metal case insulative? Paint? Powder coat? Paper?


texts:
I am studying space vector modulation but every time i read i get confused. I hope i will get some clarification here. I am referring to the following document SVPWM Document

I am mainly referring to the Figure 24 to 29 pwm waveforms. Fig 24 says first changes in voltage combination. What that statement exactly means? Why should it be (100) and (110) I know 000 and 111 null vectors and we have to apply for some time. Similarly what is second, third, fourth, fifth, sixth changes in voltage combinations? And the Table III
 how it is arrived?


texts: Questions regarding transistor audio amplifier circuit

texts:
I have a few concerns with the audio amplifier part of my circuit which I hope somebody can help me with...
It's part of a larger circuit but the schematic below shows the parts of the circuit which I'm concerned about.

Short Version:

Does the headphone socket need a capacitor and if so where?
Does the speaker need a separate capacitor?
Does a value of 10 Ohms for R10 seem suitable?
Could this part of the circuit be responsible for draining the
battery so quickly?
And for a bonus point, am I within the 20ma continuous current limit
of the MCU pin?

Longer Version
As it is, the circuit appears to be working fine, and I get reasonable audio from both the speaker and headphones. However, I have two devices on my bench. One which I've made myself and has a 250mah battery, and an off-the-shelf solution which has an 80mah battery. The off-the-shelf solution will run on it's battery for about 7 days. Whereas mine, with a substantially larger battery will only run for about 4 hours. I've ruled out everything else I can that might be consuming power so now I'm looking at the audio part of the circuit. Looking at my schematic, I made my best attempt at doing some calculations and came up with a value of 10 Ohms for R10. Does this seem correct?
My second concern is that I understand speakers don't like DC current so normal practice is to include a capacitor. As it stands, the headphone socket is receiving DC current. I tried putting a series capacitor between the digital potentiometer and the headphone socket but the circuit stopped working.
Datasheets
Speaker
Transistor
I've got no attachments to this model of transistor so am perfectly happy to swap it for a different one. However, I must use this specific speaker.


texts: How to calculate Doppler Shift for multipaths from moving objects?

texts:
Let's say we have a radar where the transmitter and receiver are placed together, and form an angle theta with a target object moving with velocity v.

I understand that the Doppler shift in this case is given by:

where c is speed of light, and fs is source of frequency. My question is what happens when we receive a multi-path reflection instead of a direct reflection back from the target.

My thinking is that the Doppler shift will now depend on the signal from TX to the moving target, and then from moving target to the wall, and so the observed frequency will now look something like this:

Is this expression correct?


texts: Power loss in an equally distributed parallel solenoid circuit

texts:
I have 12 solenoids (12v rated) connected in parallel to two Darlington arrays (ULN2803A). Each solenoid has 88-ohm impedance. The power supply can provide a stable 12V with up to 2A current draw. (See below)

The solenoids are controlled with 20ms impulses. When all solenoids are activated, the current draw does not exceed the maximum (2A) and voltage stays stable (slightly above 12V).

All solenoids are connected with 0.5mm wires with up to 2-meter length.

The problem:

When each of the solenoids is activated, they perform as intended. However, when 6 are enabled at the same time, one of them does not work.

As the solenoid works when activated on its own, there should not be mechanical issues and is rather a lack of power to activate it.

Why would it lack power if the operational voltage is supplied and the power supply maximum current draw is not reached?

EDIT:

The inputs to Darlington IC are driven by 3.3V signals from an MCU.
It is the same solenoid that fails.
If 12 are driven at the same time, then multiple solenoids fail.
All of them are relatively same distance from GND.
(When 6 are driven, #2 fails)

EDIT2:
After re-measuring voltages across the solenoids:

When 12 are active - voltage across each is 10.8V
When 6 are active - voltage across each is 11.1V
When 1 is active - voltage across it is 11.4V

The voltage supplied by the power supply is 12.3V

simulate this circuit – Schematic created using CircuitLab


texts:
I intend run a 6V Dc motor with a 7.4A current rating using a motor driver with an output current of 15Amax. I am told that the motor will utilize the current it requires so it wont be a problem.
Do I need to limit the current flowing through to the motor? I know a higher voltage will damage the motor, but will a higher current be damaging?


texts:
Upfront, I apologize if this may be a terribly obvious question. I don't have all of the background to understand it confidently.

I'm trying to apply a voltage for an electrophoresis experiment across a glass capillary, which eventually meets a silicon microchip that serves as an optical detector. I need to be able to ground the capillary voltage either before or at the microchip surface in order to avoid having a floating chip, which generates signal that is difficult to interpret.

My question is whether or not I can ground my microchip by applying a piece of conductive tape to the bottom, which would lead to my grounding electrode. The high voltage electrode would be placed on the other end of my capillary, in solution. My concern is that because the chip is technically silicon-on-insulator, the circuit may be incomplete. The capillary is filled with the same liquid, so there should be a conductive path from chip surface to HV electrode.  But I wonder if it'll just happen to work anyway, or if I'm missing something that would allow it to work.

Here's a very rough schematic of what I'm looking at.

Thank you very much for your help.


texts:
When engineers are designing an instruction set architecture, by what procedure or protocol, if any, do they follow when designating certain binary codes as instructions. For example, if I have an ISA that says 10110 is a load instruction, where did that binary number come from? Was it modeled from a state table for a finite state machine representing a load operation?

Edit:
After doing more research, I believe what I'm trying to ask concerns how the opcodes for the various CPU instructions are assigned. ADD might be designated with an opcode of 10011; a load instruction might be designated as 10110. What thought process goes in to assigning these binary opcodes for the instruction set?


texts:
I am making an ADC circuit using ADS1115. It is 4 channels which I will be using to measure 2 signals in differential mode. On the Layout and Examples section of the datasheet it says:

  Analog inputs with differential connections must have a capacitor placed differentially across the inputs.

In the layout example it basically is following this circuit:

What are these components for? It is in the guidelines so I assume they are important components. And most importantly how do I calculate their values?


texts: What is wrong with this voltage shifter?

texts:
I need to do voltage shifting (3.3V Papilio FPGA <--> 5V RAM chip).

Most of the pins are output 3.3V -> input 5V, and 3.3V qualifies as "high" to a 5V device, so I can connect them directly.

The databus is bidirectional, so that won't work - the spec sheet for the FPGA says up to 0.8V for low, and 2V to 4.1V for high; the SRAM takes less than 0.8V for low and above 2.2V for high.

I worked out this very simple voltage shifter, which seems like it would do the trick, and is within the tolerance of each device, but then I found various circuits online, and they all seem to be an order of magnitude more complicated. This says to me that there is something wrong with my design, but I can't figure out what.

simulate this circuit – Schematic created using CircuitLab

This either makes a voltage divider between +5V and the FPGA-out, or between SRAM out and 0V.

Some experimentation with a spreadsheet shows that ratios of 2:1:15 for the 3 resistors (e.g 2MΩ, 1MΩ, 3MΩ) give numbers within the allowed tolerances (the FPGA would get 0V for low and 3.3V for high, and the SRAM would get 0.31V for low and 3.41V for high).

So what did I miss? It seems easier and cheaper than all the other examples.

The only thing I could find was that it might affect the rise & fall speed, but I couldn't follow the maths as to how much. The SRAM I have is rated at 100ns, and I hope to read/write it at 2Mhz, so I do have a little leeway. The control signals will be direct, so would end up a little ahead of the databus, which would work in my favour.


texts:
I have been using PIC microcontrollers and have been using MikroC for the programming but I am little bit confused about the ports. On a PIC16F84A the port is defined in mikroC as TRISA = 0xFF, and a bit of the port can be accessed by PORTA.f0. But for other microcontrollers in the series a different code is used. For example, TRISIO = 0xFF.

Can you please explain to me how I can know the code for accessing the ports that applies for every microcontroller out there? Also the input for a PIC is 1 and output is 0, and for Atmel the input 0 and output 1 which I found confusing if someone can explain?


texts: Plotting High Pass Transfer Function in Matlab

texts:
I've been trying to practice using Matlab for circuit analysis and am trying to create a transfer function plot of a high pass filter where the gain is in volts/volts not in dB.

This is the information I am given:

R = 10,
C = 0.3e-3, 0.45e-3, and 1e-3
w = 0.01:0.1:4000 rad/sec

I've been trying to use the bode() in Matlab returns a transfer function in dB and I was wondering how I could plot it with volts/volt unit and plot all four outputs for each capacitor on the same plot.


texts: Pitfalls of using only two diodes in a "full wave rectifier"?

texts:
Scenario:
I have a small signal from a Piezo element which I am amplifying using a fully differential amplifier. Thus, my gained output from this In-amp are "two" (sine) waves inverse of each other (or 180 out of phase). These are not shown on the schematic as it exceeds the scope of the question.
To complicate matters, I am designing the system to use only positive voltage references. Thus, my output from the diff amp is centered around +2.5V.
Size is a huge portion of this project so I am trying to use as few components as possible.
I put together a "rectifier" of sorts using only 2 high-speed schottky diodes. Basically simple concept(s) as a regular full bridge. Obviously simulation only holds so much water--but the early results seem promising. Though, this "seem too simple" am I missing something?


texts: Have some queries about Fourier Transform?

texts:
I am fond of Fourier Transform. I have some queries about Fourier Transform

In most of the cases,the Fourier transform of a signal is symmetric about positive and negative axis.I think the computational complexity increases because only half part of symmetric spectrum (i.e. spectrum except on negative axis) is  of use. Also,while calculating  in frequency domain we could get wrong value of energy /power due to the spectrum on negative axis .

In the Fourier transform formula the limits of integration are from -infinity to +infinity .But for a signal which is continuously or exponentially increasing with time,one can't compute it's Fourier transform.

After computation of Fourier transform of a signal, we get Phase and Frequency spectrum of the whole signal which is localised in frequency domain only . But from both these spectrums,we don't get any spatial component features like which frequency component is present at which time (and same with the phase value ).

If we think practically ,concept of negative frequency doesn't exists. But after computation of Fourier transform of signal,with dc and positive frequencies we also get unnecessary negative frequency components. I think concept of negative frequency doestn't exists practically.

So can anybody give explanation on any of the above doubts?


texts: Understanding motor constants Kt and Kemf for comparing brushless DC motors

texts:
So for a practical definition, the torque constant Kt specifies how many Nm of torque you'll get from the motor at a certain current?  Is a bigger Kt always better?

I am more confused about the backemf constant Kemf.  This is the amount of back EMF produced by the motor running at a certain speed.  Does the back EMF limit the voltage the motor can accept and hence it's speed?

Would an ideal motor have a very high Kt and very low Kemf?

What happens if the back emf voltage reaches the input voltage, does the motor stop running?

Thank you for any answers,
Fred


texts: What relation is valid for the voltage U6 in the adjacent circuit?

texts: I have problem with the question, I always come to other results. Can you help me with this task.


texts: How can I attach a heat-sink to legacy ICs?

texts:
I work (play) with some legacy chips like the mighty TMS9918.  Which, if you didn't know, doesn't require a heat-sink but the thing does get really hot.  Amazing they don't fail more often.

Anyway, I actually have a heat-sink for it that is the perfect size (came out of an old Colecovision) but I don't know how to attach it.

Modern CPU and heat-sinks have the mounting holes in the motherboard that clamp it on top of the CPU.  This heat-sink or motherboard has nothing like that.  It's literally a piece of metal that sits on top of the chip.

I have thermal paste but that isn't glue.  In fact, the reason I have this is because it was glued (I'm guessing) to the chip but over time fell off.

So my question is, is there a thermal paste that can also act as glue to hold this on?  I want to protect these legacy chips as much as possible.

Thanks.


texts: PIC H-Bridge: PWM doesn't ground on 0 Duty cycle

texts:
Good day everyone,

I am following this guide to build an H-Bridge: http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-use.html.
I finished building it and it works, exept if I want to use a PWM Pulse. I connected the ENA cable to the PWM port on the PIC. However, when I output a 0% duty cycle, the PWM port still has an voltage on it (1V), thus the DC Motor will not turn, because the PWM port doesn't ground the ENA signal.

Is there a flaw in the design? Should I use an extra NPN transistor connected to ground, with the base connected to ENA?


texts: How should I use a static-shielding bag prior to opening, and why?

texts:
After grounding the ESD mat and wearing the properly grounded anti-static wrist strap, what is the correct process to take the contents out of the static-shielding bag and take it onto the antistatic work surface (ESD mat) and why?

(The content of the bag I have in mind is a pcb, in specific a single-board computer).


texts: How to calculate primary, secondary, and auxiliary inductance of this transfromer?

texts: I am wondering how to calculate/find out the inductance values for primary, secondary, and auxiliary windings of a Würth Electronik 750310742 transformer. The main reason is so that I can attempt to model the transformer in LTspice.


texts:
I have,

AA5620 camera , http://electronics123.net/amazon/datasheet/OV5620_CLCC_DS%20%281.3%29.pdf
http://electronics123.net/amazon/datasheet/AA5620.pdf
STM32VL Discovery board
http://www.st.com/internet/evalboard/product/250863.jsp
Generic MicroSD Card

AIM: Need to take a color image from the camera and store it onto the SD Card.

So, i was able to enable the camera and then write onto the internal registers of the camera, and get a image out to the SD Card in bmp format.

I am currently taking a greyscale image for test purposes, will be implementing color later.

The problem is: This is the image i get...

This is where i am stuck for quite some time now. I have tried using both horizontal and blanking lines. Nothing seems to change.

Any pointers ?

thanks!


texts: STM32 16bits ADC oversampling and 2^n values noise and glitch problem

texts:
I work on project using STM32H753VIT6 and its internal ADC. When I increase the sample rate some strange glitch/artifact with values around 2^n begin to appear into my signal after 48kHz. and I know I don't understand why.
A microphone and opamp analog toolchain are connected to the internal ADC in differential mode. The STM32 do the acquisition and send data to PC application which record wav file. I permanently check the ADC input signal with oscilloscope and it's about good. (no glitch or artifact)
Glitch are not completely random in time domaine, there is no frequency so FFT not help that much but I will post anyway
Here is the signal (without no microphone excitation) at different sample rate with ADC configuration.
@48kHz
All seem about good, random noise that I used to see

@96kHz
Glitch begin to appear, I can see the levels of those glitch samples create some "floor" or "stage" effect

@192kHz
Glitch are here to with the same "stair" affect

DISTRIBUTION / VALUES DENSITY
So I take a look on the distribution off the sample values on the different signal (all wav file are 10s)

We can see the good half gaussian curve for sample rate lower or equal than 48kHz, but greater than 48kHz, gaussian is destroy by abnormal density of value at 2^6, 2^7, 2^8, etc...
I don't understand what append, and how I can correct this to increase my sample rate and get a clean signal without those glitches at 96 or 192 kHz...
Can you help me ?
EDIT 2021-05-26
Ok, I play with the oversampling ratio, when I stay lower than x16 signal is really good at any sample rate, equal or more than x16 glitch arrive. (I use 3.072MHz oversampling frequency)


texts: Will the resistance of the certain valued resistor decrease or increase at cryogenic temperature?

texts: I tried to measure resistance of 332k Ω while dipping in liquid Nitrogen (cryogenic temperature) I got the resistance value near about 458k Ω, doesn't it contradicting "Resistance should increase and decrease with increase and decrease respectively with surrounding temperature"?


texts: I2C get stuck on busy with DMA interrupt

texts:
I'm trying to interface with NXP device using I2C.
I'm initializing it that way

/* I2C3 init function */
static void MX_I2C3_Init(void)
{

    hi2c3.Instance = I2C3;
    hi2c3.Init.ClockSpeed = 100000;
    hi2c3.Init.DutyCycle = I2C_DUTYCYCLE_2;
    hi2c3.Init.OwnAddress1 = 0;
    hi2c3.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
    hi2c3.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
    hi2c3.Init.OwnAddress2 = 0;
    hi2c3.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
    hi2c3.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
    if (HAL_I2C_Init(&hi2c3) != HAL_OK)
    {
      Error_Handler();
    }

}

I'm using DMA RX for I2C.

unsigned int axI2CWriteRead(unsigned char bus_unused_param, unsigned char addr,
                            unsigned char *pTx, unsigned short txLen,
                            unsigned char *pRx, unsigned short *pRxLen)
{
    extern I2C_HandleTypeDef hi2c3;
    bool recv_length = false;
    HAL_StatusTypeDef status;

    *pRxLen = 0;
    memset(pRx, 0, 2);
    uint8_t rxData[255] = {0};

    status = HAL_I2C_Master_Sequential_Transmit_IT(&hi2c3, 0x90, pTx, txLen, I2C_FIRST_FRAME);

    if (status != HAL_OK)
        return I2C_FAILED;

    while (HAL_I2C_GetState(&hi2c3) != HAL_I2C_STATE_READY)
        ;

    readblock = true;
    readblock_length = 0;
    status = HAL_I2C_Master_Sequential_Receive_IT(&hi2c3, 0x90, rxData, 255, I2C_LAST_FRAME);

The problem it gets stuck in that line:

while (HAL_I2C_GetState(&hi2c3) != HAL_I2C_STATE_READY)
            ;

I have defined the interrupt handelers here

/**
  * @brief This function handles DMA1 stream2 global interrupt.
  */
void DMA1_Stream2_IRQHandler(void)
{
  /* USER CODE BEGIN DMA1_Stream2_IRQn 0 */

  /* USER CODE END DMA1_Stream2_IRQn 0 */
  HAL_DMA_IRQHandler(&hdma_i2c3_rx);
  /* USER CODE BEGIN DMA1_Stream2_IRQn 1 */

  /* USER CODE END DMA1_Stream2_IRQn 1 */
}

    void I2C3_EV_IRQHandler(void)
    {
      /* USER CODE BEGIN I2C3_EV_IRQn 0 */

      /* USER CODE END I2C3_EV_IRQn 0 */
      HAL_I2C_EV_IRQHandler(&hi2c3);
      /* USER CODE BEGIN I2C3_EV_IRQn 1 */

      /* USER CODE END I2C3_EV_IRQn 1 */
    }

    /**
    * @brief This function handles I2C3 error interrupt.
    */
    void I2C3_ER_IRQHandler(void)
    {
      /* USER CODE BEGIN I2C3_ER_IRQn 0 */

      /* USER CODE END I2C3_ER_IRQn 0 */
      HAL_I2C_ER_IRQHandler(&hi2c3);
      /* USER CODE BEGIN I2C3_ER_IRQn 1 */

      /* USER CODE END I2C3_ER_IRQn 1 */
    }

The interrupt request I2C3_EV_IRQHandler is getting fired, but after it the DMA interrupt is not called at all.


texts: Can a flyback diode work on the "ground" side of a transistor?

texts: In every flyback diode setup I see, the relay coils are on the drain side of the transistor (if my terminology is wrong, I mean the top), so the flyback diode sends current back toward the power source. I'm curious if it can also be setup like this, with the load and flyback on the "grounded" source side of the transistor. I think it should work, but I'm not sure. As an aside, how would I test this for myself?


texts:
I'm looking to build a timing system base on passive RFID transponder. This is how I see it :

An antenna to "question" the tag
An antenna to receive tag unique ID
A tag with unique ID

I would like to buy a lot of transponders on internet (like this one). My question is :

If I want to build my own antenna, is this reasonable possible to do? From there, where should I start looking for technical information about those system?

What about the "questioning" antenna? It doesn't seem to be really complicated. How is it working?

My question may be too evasive for some of you, but is still relate to circuit designing. Any answer will help me to identify more precise questions.

Edit

The timing system would be for running event. So, I won't need a system really fast for this


texts: Why is the inductor necessary in an LC filter?

texts: I am using an LC filter for the output of a buck converter. Dont both the inductor and capacitor just attenuate high frequency signals? Does having the inductor affect the output voltage or does it just affect the noise of it?


texts: How to limit current consumption for integrated class D amp?

texts:
I have a small amplifier IC, rated at about 2.5 - 3W output going into a 3W rated 8 Ohm speaker. The input signal is going through a pot. and than into the amp though a cap and resistor in series, as shown below - only pot. not shown.

I only have 1 speaker connected to pins 1 & 3, the other output is currently not connected.

Normally the amp. uses under 5mA current which is fine, as I turn the pot. the volume goes up as well as the current consumption. When it reaches about 30mA my batteries can't hold the voltage which causes the source device to reset.

Can I limit the current consumption somehow? Perhaps attenuating the input with even larger input resistors. Right now I have 50 Ohms in series with the 100nF caps.

I have this for a datasheet: How is your Chinese?

The circuit:

simulate this circuit – Schematic created using CircuitLab

The NCN pin seems to be doing some limiting or compression to the signal. The datasheet does not give a formula to calculate it however it gives a short table with some examples.

Update

I've tried swapping the input resistor from 50 Ohms to 150 Ohms but that made things much worse - distortion is much higher. I swapped it again to 68K (that's what I had around) and it works very well.

New problem - I can hear a high pitched sound from the speaker, going to use my scope with FFT to find out at what freq. this is at and going to need to filter it out.

Update II

Looks like this IC is a clone or similar to this one


texts:
What is the maximum number of nested functions in PIC16F628A?
ex. [NEW CODE, should be more explanatory]

int main(){
    function1();
}

void function1(){
    function2();
}

void function2(){
    function3();
}

void function3(){
    function4();
}
// And so on
void functionX-1(){
    functionX();
}

ex. [OLD CODE, not so clear for the question]

int main(){
     function1(); //PIC goes in function 1
      function2(); //Function 2 is inside function1, PIC goes in function 2
       function3(); //Function 3 is inside function2,  PIC goes in function 3
                    //...
         functionX(); //Function X is inside functionX-1
                      //^^^PIC goes in function X where it ends executing the code
                    //a lot of } here
    }

Does main() count as function?
In the datasheet it says 8-level deep hardware stack. Does that mean X=8? If not, then X=?


texts:
I'm attempting to put an HC-05 module into command mode in order to change the PIN and default baud rate etc. According to the datasheet, PIO11 needs to be high to do this, so I connect it to 3.3v, remove power and power it back up.

Using an FT232 interface and a level converter, I send the AT command to it via Putty. I can observe the command on the RX pin of the HC-05 module but I don't see anything come back. I've tried various combinations of baud rates and flow control settings.

For the record, I can pair with the module and receive data sent to it in my Putty window via the FT232/level converter.


texts:
I have an old clock radio from the 90s that worked great until recently. Suddenly it stared running fast and every day it gets about 10m ahead. I am curious what could be going upon under the hood to cause this and how I might diagnose and fix it. Obviously easier to just buy a new one but I don’t want to throw it out and think I might learn something by fixing
Thx


texts: How to accommodate a range of input voltages

texts:
How does a designer generally accommodate for a range of input voltages in their circuit? For example, my design needs to be able to accept 12-24V where it uses 12V and 9V at seperate areas as shown below. Current no more than 200mA.

The 12V supply does not need to be very accurate as it is being used for two things:

A power supply for a 4-20mA sensor transmitter (As far as I know, the sensor has its own regulation to maintain a constant current)
A supply for the 9V regulator. The 9V supply needs to be precise, say under ±1% but a regulator will be able to step down a slightly noisy/innacurate 12V supply if needed so i'm not concerned.

simulate this circuit – Schematic created using CircuitLab

Is there an IC that output a regulated 12V with a range of input voltages from 12V up to 24V. I've found a buck boost converter that seems to do the job (TPS55165-Q1). Will it do well in a 12V - 12V situation scenario?


texts:
I've looked around for the answer to this question, so I'll only ask the new questions.

I am designing a PC board that has some need for circuits carrying 2 amps and some that are very low power micro-controller (micro-amp) circuits.

I want to use a 4 layer circuit board. The board house I want to use supplies boards with 1oz copper on the top and bottom layers and 1/2oz copper on the inner layers.

My board has a lot of surface mount components, and a small amount of through hole components.

There are DC-DC buck and boost converters on the board, operating around 1 - 2 Mhz (using shielded inductors). There is a microcontroller running a 20mhz crystal as well as a 32.768khz crystal and a USB connector. That's about as fast as my circuit gets.

I am mounting my board into a grounded cast aluminum box to avoid noise.

I see a lot of texts recommending me to use my top layer for power buses and the bottom layer for ground. They say to use the inner two layers for signal routing and low current needs.

I am guessing that is to also provide some noise suppression for the faster circuity in the inner layers.

Because my board and components are fairly dense, (1000+ pins in DipTrace in 4 x 3 inch board) and because they are mostly surface mount components, my question is that I'm finding it easier (and my plan) to route small signal traces on the top layer layer, high speed signal traces on the 3rd (from the top) layer, and use the 2nd layer for Power and the bottom one for ground. I have no high current ground circuits. All of the high current circuits I have are Power circuits.

Is doing this OK or will I run into gotchas (like needing to make sure the traces on the power circuits are double wide because the 1/2oz copper)

And would it be smarter to use the 2nd layer for ground and the bottom (1oz copper) for power? I don't think I need the shielding of the ground being on the bottom since my entire board will be going into the metallic enclosure which will also be ground.


texts:
I am working on a robotics project. Using timers in ATmega16, I am controlling servo motors.
By incrementing the value of OCR1A I am manipulating the servo motor. After getting the desired position of servo, I want to store the value of OCR1A for that position so that I can use it afterwards to get the same position.

OCR1A is a 16 bit register. How can I store this value? Will variables do the job?


texts: Potentiometer at 0 resistance + arduino = smoke

texts:
I had connected a pot to my arduino and i cross check the wiring before switch on.
Everything went well but when I turned the pot to zero resistance, It started to release smoke and the arduino got disconnected .

When i turned the pot back to the other end, it got connected. (resistance = 10k ohm)

Now everything is working fine. But why did it happen?. What precaution should i take from next time?

Thank you


texts: Reflection on a matched transmission line

texts:
A matched load with source using a transmission line (assume real load and matched using quarter wave transformer) should not have any reflection ideally.

But we can see that the load impedance is not same as characteristic impedance of the quarter wave transformer, so when we calculate Gamma L (ΓL)  at the load, it shows there is reflection.

I would like to understand what's the difference between load reflection coefficient and the actual reflection on the line.


texts: Difference op amp with imperfections -- maximum dc offset

texts:
How may I find the maximum dc offset due to the imperfections listed in this question?

For \$I_B\$:

I know \$I_{b1}=0.5\mu A+0.1\mu/2=0.55\mu A,I_{b2}=0.5\mu A-0.1\mu/2=0.45\mu A\$

This yielded \$v_+=-0.45mV\$

Hence,

\$0.45mV/R_1-(-0.45mV-v_o)/R_2=0.55\mu A\$

Which yielded \$v_o=0.505V\$

For \$V_{OS}\$:

\$v_+=4mV\$

Hence,

\$-4mV/R_1=(4mV-v_o)/R_2\$

Which yielded \$v_o=0.4V\$

For \$I_{OS}\$:

\$v_+=-0.99mV\$

Hence,

\$-0.99mV/R_1=(-0.99mV-v_o)/R_2\$

Which yielded \$v_o=0.098V\$

Does this make sense? If it doesn't, where am I erring?


texts: Why does this dual summing op amp have this equation?

texts: I understand the voltage input at Rb gives the first two additions of the equations. But why is this subtracted from R3 and R4?


texts: How to plot dy/dx versus x of a given y=f(x) plot in LTspice?

texts:
Below is a plot of a sweep which shows how  Vo changes versus Vi in LTspice:

How can I plot the "derivative of Vo" i.e dVo/dVi versus Vi?
How can I plot the "integral of Vo" versus Vi?

Edit:
I was trying to see how the voltage gain for a transistor changes with input.
I tried to plot -dVout/dVin versus Vin below which is the plot of voltage gain:

For 10mV change in Vin causes very different gain in the middle of active region. "Change in Vin" must be around 1mV or less for a stable gain.


texts: STM32 External Interrupt via GPIO cannot be triggered after waking up from STOP mode

texts: I have a problem with a project based on an STM32L051. I want to use the stop mode and wake up on an external (GPIO based) IRQ. This all works great but after the MCU woke up once, no IRQs seem to work. I have a very simple IRQ handler which just outputs some debug info for now. Naturally I do hal-initialize again after I woke up. Also the whole thing works when I use stand-by mode instead of stop mode. I tried to enable the related IRQ via HAL_NVIC_EnableIRQ(EXTI0_1_IRQn); explicitly but it did not help. Any idea what could be missing?


texts: How to calculate resultant of 32 bit CRCs

texts:
Im working on automotive controller and I have following question
I have list(about 6) of 32 bit CRCs and I want to combine them to get a resultant one
can I 'OR' or 'XOR' them to get resultant one?
Have gone through CRC32(a,b) function but could not understand its definition or how it is combining two CRCs. Is it combining the normal way of finding CRC of a number?
Suggestions will be helpful .Thanks in prior.


texts:
Is this a good circuit to use as a air condition switch with a help of microcontrollers 5V? What relay to use in this situation?

What parameters should I take into consideration when choosing relay?


texts: Microcontroller shutting off because of brief loss of power, can a capacitor fix this?

texts:
I have a microcontroller hooked up to a 5v supply which goes through a voltage regulator stepped down from 12v.

I'm assuming that it's rebooting because it's possible that the voltage drops quickly for a small fraction of time, which is enough to cause the chip to reboot.

Is this assumption correct?

Could adding a capacitor to the circuit solve this issue?


texts: ARM Cortex M3 (ATSAM3N4B) IACCVIOL Hard Fault

texts:
The ATSAM3N4B is an ARM Cortex M3 microcontroller from Atmel. I wanted to ask if anyone can help clarify the IACCVIOL Hard Fault processing.

What I want is the infringing instruction address which the datasheet explains in 10.21.11.1 (pg 182) as:

  IACCVIOL

  Instruction access violation flag:

  0 = no instruction access violation fault

  1 = the processor attempted an instruction fetch from a location that does not permit execution.

  When this bit is 1, the PC value stacked for the exception return points to the faulting instruction. The processor has not written a fault address to the MMAR.

What I want help with is the stacked for the exception return? I don't understand what this refers to.

Is anyone able to help?


texts:
In a load supply using P-MOS, the input to source is 25V. We found unfortunately that the MOSFET we chose and soldered has only 20V maximum gate-source voltage. Although there are voltage dividers consisting of R1 and R2, we are not sure upon the sudden turning on of NMOS, whether VGS could temporarily reach 25V, and whether the P-MOSFET Q1 could stand it.
We haven’t yet found MOSFETs having rated VGS>20V yet.
Questions:

http://www.diodes.com/datasheets/ZXMP6A17G.pdf

Could someone recommend PMOS having larger maximum VGS?
The application of using PMOS for high voltage switch should be common and VCC=25V is unlikely to be at the high end of typical applications. So how do applications typically handle voltage exceeding maximum VGS?

Matt


texts:
I am looking at creating a device within regulations for a medical environment with two Txing antennas, BLE (cypress FCC certified module) and 915MHz ST Spirit1 FCC certified module.

I have found multiple sources on the usage of the 915MHz band and other ISM bands. But I believe there is/are regulation(s) about the distance required between these two ‘co-located’ antennas, ie 915&2.4GHz in this case, but I cannot find the specific regulation. Has anyone had any experience with this or able to point me in the right direction?

Any help would be greatly appreciated!

Edit ****

Think what I may be after is ‘Section 15.212, Modules, Module Certification’

This is to do with modules, which will probably be used but a custom PCB config. maybe be used.


texts: What is meant by this statement about op-amps?

texts:
I am trying to understand the inverting negative feedback how it stabilizes the op-amp circuit. As the book is explaining this I came across the highlighted sentence:

Thus the voltage vo will not depend on the value of the current that might be supplied to a load impedance connected between terminal 3 and ground.

If I understand correctly what he is trying to say, is that if I have the below circuit, then, io = always regardless of the output resistance. Why?

The book:
Microelectronic Circuits SEVENTH EDITION
Adel S. Sedra
University of Waterloo
Kenneth C. Smith
University of Toronto
ISBN 978–0–19–933913–6


texts:
During the last days I've been working on driving multiple stepper motors (28BYJ-48 – 5V) with SparkCore and Stepper.h arduino library. I'm trying to drive some stepper motors, but without having to move them at the same time. I mean, stepper1 moves 100 steps, once finished, stepper2 moves 30 steps, and so on.

In the explanation I'll use two steppers.

The point is that I have some doubts of how to do it using the less ICs and easier as possible.

Option 1 (it works)

The first try was using a CD54/74HC137 (3-to-8 Line Decoder Demultiplexer with address Latches) and a CD4508B ( CMOS Dual 4-Bit Latch).

Workflow:

Stepper.h library is configured to work with D0-D3 pins.

D0 to D3 pins are connected in series to both CD4508B input pins (dual latch).
The decoder enables or disables the input pins of CD4508B, in order to choose the stepper that I want to move.
In Stepper.cpp library, each time that sends an step, I enable the two strobes of the CD4508B.
The outputs of CD4508B are connected to ULN2003A  IC (darlington transistor array) that will drive the stepper.

So, every CD4508B can drive 2 stepper motors. All CD4508B input ports recieve the same inputs and the same strobe (they are in series) and using the demultiplexer I enable/disable one or the other input port and I move one or the other stepper.

I've tried it and works perfect, but I think that it could be easier and could be done without CD4508B. So here is my second option.

Option 2

I'm thinking in connecting directly D0-D3 to both ULN2003A (or similiars) input in series and using the CD74HC237 demultiplexer enable/disable the ULN2003A.

The point is that ULN2003A has not enable/disable pin so I'm afraid it won't be so easy. I've found a darlington transistor array IC with a latch that could do it well: TLC59213

I've phoned some electronic shops and do not have it. They said it's a strange IC.

So, what to do you think is the best choice? I think that option2 could do the job, but the TLC59213 is not easy to find, perhaps another IC that could do it as well. Any suggestions will help.

Thanks.


texts:
How can I configure an XBee-PRO module in broadcast mode?

We are using an AT8051 controller.


texts:
Here is the Following circuit :

I don't know how the application note can assert that the voltage after the capacitor is equal to Vdrv-Vcl or -Vcl according to the driver output as there is a resistor Rgs ? Even with the clamp circuit it is just an RC circuit. Where is my error ?

The picture is extracted from this application note written by TI. http://www.ti.com/lit/ml/slua618a/slua618a.pdf

Thank you very much,


texts:
I'm trying to make a PCB where I have USB connectors, but I'm really new into this and I'm trying to solve a few questions online about the theme, if you could guide me online through the theme that would be great. For this purpose, this systems is a USB sensor with 2 USB connectors (one male for PC connection and a female for bus extension) and, besides the sensor and MCU, will have switches to let us cut the VCC line of USB.

The main issues in my mind are:

What's the difference between the several USB connectors materials? I found some that say they have shield, others are gold plated and there are so many that I just quit looking online for everything
For mechanical resistance, is there any special type of connector? (this board will have switches and one of the connectors could be connected to the PC USB).
Is it cheaper (this is for a school project, but we might try to sell it after) to make a USB Male connector using only PCB (like this) or buy and solder a connector?

Basically I'm trying to find some kind of "USB connectors in PCB for dummies" guide, but Google isn't helping me that much.

EDIT

The "bus extension" will be for VCC and GND and that's just for sharing the power switches that I talked above, there is no hubs involved in this.


texts: Determining the Maximum Gate Voltage for an N-Channel MOSFET

texts:
What considerations should be made when selecting a MOSFET for a switching application? I have a project that I have been working on and I'm trying to wrap my head around FETs.

Essentially what I am trying to do is create a barrier using an N-Channel MOSFET between the 5V from a USB connector, and the necessary 3.3V input for one of the digital pins on an MCU.

I'm doing this because I would like to be notified via an interrupt whenever the USB is connected or disconnected. The Gate of the MOSFET is pulled to ground, so when the USB is unplugged my input isn't floating. This is basically what my MOSFET circuit looks like:

I know that \$V_{gs}\$ and \$V_{ds}\$ are the two main voltages when it comes to MOSFETs, but I have no idea how to calculate them. I think that \$V_{gs}\$ must be 5V (the USB to MCU) and my \$V_{ds}\$ must be 3.3V (drain to MCU). Is that right? If these numbers are correct, how can I determine whether this MOSFET can handle these voltages?

Also, should I be including any current limiting resistors for this MOSFET, the IRLM2402? I chose this MOSFET because we have them in stock.

I know I could achieve the same result by using a voltage divider or a level translator, but I would really like to use a MOSFET.


texts:
I'm trying to simulate for Phase Frequency Detector with the following implementation:

and inside NAND_PFD:

NOTE: the triangles on the right are inverters and not amplifiers.

I'm currently getting a \$Clk_{ref}\rightarrow{Up}\$ delays which are represented in this sumulation:

same for \$Clk_{Vco}\rightarrow{Down}\$.

\$Clk_{Vco}\$ is the voltage that should come out of the VCO in a general PLL. here I picked a frequency just for simulation.

looking at the sate machine:

when \$ Up = Down = 0 \$ and \$ Clk_{Vco} \$ goes up, \$ Down \$ should go up.
in most articles that I've read, this change appears exactly in the area of phase difference, which appears that the change is immediate and without delay.like in this image:

how can we interpret this delay in terms of phase detection?
should the phase detection appear exactly at the same time \$ Up/Down \$ change? or we just need the information of the widths of change and deliver that to the PLL to do it's job and it doesn't matter when we detected the change?

here is a longer simulation of which I'm trying to verify that the pattern of phase detecting right:

the transistors sizing was done as the following:

by using ESDnfet, and ESDpfet transistors in 28n technology, with a library called cmos32lp. (in virtuoso).

Note: I still don't know what ESDnfet and ESDpfet mean, and I randomly picked them and I would be glad if someone knows this library can tell me if picking other kind of transistors would make a difference.

\$ Clk_{Vco} \$ and \$ Clk_{ref} \$ were defined as the following:

enter image description here


texts:
As per the TI document I came across which compares narrow band sub-1 usage vs wide band sub-1 usage mentions a concept called coding gain and its disadvantages.
Because of my lack of understanding in S1G I do not understand certain statements made in this document. e.g.

"Using coding gain does not improve the sensitivity nor range, it simply is another way of representing data"

"Given the same net data rate/throughput, narrowband and coding gain systems will have similar range." How come?

" Adding more coding gain will not help, as then you need to either reduce the net data rate or increase the RXBW to fit the signal. "

"Trading higher receive sensitivity for less spectrum efficiency (higher bandwidth) by spread spectrum" How can we achieve higher receive sensitivity using code gain?

I would appreciate help to better understand such statements made on this document. Your explanatory answers and time are much appreciated.


texts: Transformer Power Rating for CCFL Inverter

texts:
I'm trying to design an CCFL inverter using the UCCx972/3 but I am a bit confused about the power rating for the transformer
The lamp I'm using has the same operating voltage and striking voltage of the lamp specifications they use in the Design Procedure. The only difference being that for the lamp I want to use, the full rated current is 15mA RMS and the full rated power is 4.7W
I follow the design procedure but then I get confused starting after equation 2 where the resulting secondary voltage is 820V - I understand where this comes from, but does this mean that this is the voltage I should use when calculating power rating for the CCFL transformer ? With the lamp in series with the transformer secondary side, that would mean that the transformer would need to have a power rating greater than 820V*15mA = 12.3W, and that only 4.7W of that is dissipated by the lamp ?
Is there a mistake in the way I'm trying to determine the transformer power rating ? The inefficiency seems to indicate to me that I may be understanding something wrong (only 4.7W of the 12.3W being used by the lamp).
In addition, using the calculated 12.3W I was not able to find a suitable CCFL transformer. In the UCCx972/3 datasheet as well as many other CCFL inverter application notes, many of them seem to use the CTX series from Eaton which was discontinued with no replacement. The only reliable source I've found for CCFL transformers is the FL series from Coilcraft but the max output is 6W and the max secondary current is only 11mA which is too little for the 15mA lamp current. The obsolete CTX series had a 14W version but I have not been able to find anything on Digikey/Mouser other than the Coilcraft FL series.


texts: Capacitor value in schematic with "mk" units

texts:
I've got a schematic that originated in Brazil that generally uses European symbols rather then US.  But some values for capacitors are confusing me.

There are several that are marked 100n and so forth, which I take as being 100 nF; but there are also a bunch of electrolytics marked with "mk", such as 1mk and 10mk.  Is 'mk" the same as µF?  Just want to make sure.  Where does mk come from?  I'm guessing the "m" probably stands for micro, but what about the "k"?

The markings are not very consistent, as they use n by itself instead of nF; but smaller values are shown as pf.


texts: volt management for a big circuits (mother board if you will)

texts:
I've to have a 2 Ardunio and 1 Netduino in a board, they are connected to +100 component. All I need is less than 5A so I bought a 12v 6A power supply and need to ask some questions so I avoid doing anything stupid.

Is it safe to take a 5V (after passing the 12V to 7805 or some other way to get 5V) and give it to the 2 Arduino and the 1 Netduino?
Is it better to give each component it's own fuse or should I just use fuses for major parts?
I can give each component it's rated voltage and the current will be given to each component as it needs from the power supply knowing that I should not take more than 40mA from the Arduino pins, am I right ?

Sorry but this project is major and I'm more of programmer than electrical engineer :)


texts: Generate N pulse with a fix frequency STM32f107

texts:
I need to know how to generate N pulse with STM32f107 without any external sampling.
Could you provide me any good reference?
Thanks


texts: Why Do We Need Flash In Bluetooth Module

texts:
I understand that flash memory is used to store some program in microcontroller, it's erase programmable. But after look at HC-05 bluetooth module, there are 2 chips on the board. One chip is CSR bluetooth core-4 and one chip is for flash 2Mbit (seen on datasheet here!).

My Questions are:

What is flash usage here? is every bluetooth module had to have a flash chip? is it for writing and erasing data spread tranceived by bluetooth over and over?
On the datasheet it is stated that 2Mbit flash . From my prior knowledge bit usually bit referencing for speed not for storage (byte). or is it typo?


texts: Tiny speakers, used in headphones - what are these called?

texts:
After having searched Mouser and a general search for "tiny speaker", "small speaker", "headphone speaker", and not having found what I am looking for, wanted to see if someone here can help me find the correct term, part-number of the tiny speakers used in headphones (s.a. handsfree kit for mobile phones, mp3 players etc.)

If required I can crack open one of the several damaged handsfree sets and share a pic, but just being lazy.

Edit:
Please note that I am looking for the tiny speaker, as a component - that is housed inside the ear-plugs, head-sets etc., not the whole finished product.

Also, I am looking for speakers that have a diaphragm that vibrates with enough power to push airwaves through an air-tube for a short distance, like 5-6 inches, yet be small enough, light enough to be put behind a lapel pin.


texts: Op - Amp and Unbalanced Input Differential Signal

texts:
Let's consider for instance an Open Loop Op-Amp (for instance with double power supply: VDD and -VDD), which is a good comparator circuit.

The sign of its input differential signal (Va - Vb) determines if its output will be VDD or - VDD.

Surely it works if Va and Vb are voltage sources connected between, respectively + and - of Op-Amp, and GND.

But what does it happen if we put a source of value Va - Vb between + and -? The difference is that it is not balanced with respect to GND. It is something like putting a battery between + and -.

I'd say that the circuit will not work, since the base - emitter (or gate - source) part of each transistor of the differential pair at the input stage wants a signal referred to GND.

The circuit may work if at the input of the op-amp is present a sort of BALUN, is there it?


texts: Formula to calculate power from a solar panel?

texts:
I am currently working on a project that works with solar panels on Mars and I am trying to calculate how much power I would get from a solar panel on the surface. I have values such as solar irradiance, the area of the solar panel, and the efficiency of the panel. I found one formula: Power=area x efficiency x solar irradiance x performance ratio

However, I cannot find a standard value for performance ratio anywhere and I don't have a reliable source on this equation either, so I can't use it on a paper.

So, does anyone know formula out there that allows me to calculate the power delivered from a solar panel? If so, I would greatly appreciate it and if there is a reliable source (like scholarly paper), please leave a name for that as well.


texts: What is the name of this connector type? I have tried searching pretty much everywhere, but I can't find it. Please help.


texts:
I'am developing a simple badge with a fading led.
My idea was a LMC555 timer powered by a cr1025 battery, these batteries have a nominal voltage of 3v. I chose the LMC555 for its low operating voltage.
https://www.ti.com/lit/ds/symlink/lmc555.pdf

I have ordered my parts and made the circuit following this instructable:
https://www.instructables.com/id/LED-fading-with-a-555-timer/ and this schematic.

I used these parts:

LMC555 timer
220uf electrolytic capacitor
2N2222 npn transistor
two 1206 red LED's 1.7V forward voltage
1.5k resistor instead of 20k for better timing

Powered by a my lab bench powersupply set to 3V.
The circuit starts only working above 4.5V, I tried changing the current limiting resistor to a higher and lower value and changing the npn transistor for a ao3402 mosfet http://aosmd.com/res/data_sheets/ao3402.pdf , but that did not help. I even tried removing the current limiting resistor so that there is no voltage drop over the resistor.

Because the fading is to fast to be measured with my multimeter and my oscilloscope stopt working last month I tried to simulate the circuit in LTspice.

Here you can see the LMC555 is giving the full 3V on the output, but on the end the led gets only 700mV. What did I do wrong, is it even possible? I hope somebody can help me solving this problem.


texts: What parts do I need in order to connect a light to my netduino?

texts: I'm software engineer trying to get a little electronics project working. I have a netduino plus. I want to hook up a huge light like this and make it turn on and off. Where do I start? What would it take to make this happen? I'm not worried about the programming side I'm just curious what components I would need to get going. I'm a total noob so be nice. Thanks in advance.


texts: Connecting push button to a controller pin

texts:
This problem is decades old but I do not see a direct answer to it on this site. I want the following:

This circuit just allows to check the state of the button from inside the micro-controller. Nothing fancy. My questions:

Is there anything better than this simple design?
Is the value of 100 kilo ohms resistor adequate for our days CMOS devices, like dsPIC30FXXXX and not a high power application?


texts: Need understanding of a LED/Lamp question

texts:
I have recently received a problem statement and need help understanding it.
Problem Statement
Proposed hardware must be able to support 10 White LEDs such that it provides a minimum of 450
“warm” lumens total.
It is preferred to have all 10 LED elements in series.
Operational Voltage is 8.0V to 19.95V but must be able to handle an overvoltage of up to 26V for at least 60 seconds. Start/Stop functionality is not expected for this system (not expected to operate below 6V)
The lamp will be driven directly from the power line and must incorporate basic ESD/decoupling
protective countermeasures for power input lines as well as LED elements.
Recommended Devices
Regulator: TI TPS92692-Q1
Question:
As mentioned the lamp is driven directly from power line and then it is mentioned that the operational voltage is 8 to 19.95V. I need a little clarification there. Does that mean there is a AC to DC block which is giving a variable output of 8 to 19.95V ? And will that be used to drive the LED controller?


texts: Soldering iron thermocouple measurement HELP

texts:
I'm working on a relatively simple soldering iron circuit. I'm using a T12 tip, which consists of a resistor and thermocouple in series.

I'm driving the gate of the N channel mosfet with 20V via a NPN transistor. The base of the transistor is directly connected to a digital pin of an Arduino.
First I run current through the soldering tip so it heats up. In order to measure the electricity produced on the thermocouple aka the temperature, I want to turn off the power supply or at least its path to ground and just measure the differential voltage generated between the two connections on the soldering tip.
Because I'm using a N type mosfet, with its source connected to GND and its drain connected to one of the soldering tip connections, I included an opamp as a differential amplifier to measure the generated voltage between the two connectors of the soldering iron/thermocouple.
I didn't want to have problems with the GND of the power supply, PC and oscilloscope, so I put a display on the Arduino which displays the generated voltageX50, so instead of getting 0.02V I should get 1.00V.
I also powered the Arduino via its Vin pin, but I used a buck converter in between the PSU and the Arduino Vin pin to lower the voltage to 5V.
The code is pretty simple, so I won't include it. It basically turns ON the NPN transistor, thus turning OFF the mosfet. It waits 2seconds, then measures the amplified voltage. After that, it turns the transistor OFF, thus turning the mosfet ON and heating the soldering tip. It does this over and over.
I'm also powering the opamp (rail to rail) with the Vin and GND.
I'm not using any filters, since I just wanted to see if the circuit works well enough to keep working on it.
The issue is that while I do get a voltage reading, it's always around 0.60-0.90V
I'm not sure what I should test or what the possible issues could be. Am I missing something obvious?

I've simulated the circuit in LTSpice and it works fine, but the real world is a whole different story.

I'm using an 2222 npn transistor, an IRF44N mosfet and an LM324N opamp in a differential amplifier configuration.

Here is the circuit I'm talking about. The right part of the circuit should be flipped, because the Vout=k*(V2-V1)

EDIT:I've tested it by heating the soldering tip with a lighter and the voltage measurement works fine. Problems only happen when I shut off the heating via the mosfet.


texts: 12v to 5v buck converter to power rasberry pi on parallel circuit

texts:
Main question: will oversupplying current to a raspberry pi damage it? For example, will providing 5a at 5v be damaging when the pi requires only (up to) 2.5a at 5v?

Here is my backstory, assumptions, and sub-questions:

I am trying to power a raspberry pi in parallel with a 12v led lamp on the same circuit. My power supply for the lamp is a 1.5a, 12v wall wart. (The LEDs require 12v). The raspberry pi 3 power requirements are 5v and up to 2.5a.

I would prefer to use a buck converter to step down voltage to 5v for the pi rather than a linear regulator, such as the LM7805, so that I don't have to deal with a lot of heat output (and hopefully don't have to end up needing a high current power supply).

Therefore, my design has the LEDs on one branch and a buck converter + pi on the opposite branch of the parallel circuit.

I am considering using the 12v to 5v, 5a buck converter here:
https://www.pololu.com/product/2851/specs

I think power is conserved over the buck converter, and power = voltage * current.

Based on my ammeter, the LEDs of the lamp only require 0.5a of the 1.5a. I'm not sure how the remaining 1a will be divided on the two branches circuit.

Could I just stick a high resistance resistor on the LED side to push the remaining current over to the buck converter and pi?

If so, the power to the buck converter will be:

Power1 = voltage1 * current1

Power1 = 12v * 1a = 12w

The graph Pololu provides appears to indicate that the converter efficiency will be about 92% at Vin=12v and 2

0.92(Power2) = voltage2 * current2

0.92(12w) = 5v * current2

current2 = 2.2a

However, I'm guessing I should supply more current to the pi to be safe. If I got a 2a, 12v power supply I end up "pushing" 3.3 amps at the pi using the above assumptions.

Will this damage the pi or is it completely safe to oversupply current?

I am only a beginner, so let my know if my assumption are off. Thanks!


texts: Why the torque of single-phase(split-phase induction motor) is not zero?

texts: In single-phase motor, the torque developed is equal to sin a , where 'a' is the phase difference between the two currents ( one through starting winding and the other through main winding). After the motor attains the 75% of the full speed, the starting winding is cut out. So does it mean that 'a' is zero? And why the torque is not zero?


texts: Use microprocessor with arduino / ESP32 WROVER

texts:
I was looking through some of the atmel microprocessors, and I was wondering if you could use a microprocessor (say, the atsam91) as a coprocessor for a microcontroller (say, an esp32 wrover (240Mhz)), so if the microcontroller needed to do any processing-heavy arithmetic, it could simply send through the instructions to the ATSAM.

Is this possible?

And if so, how would the microcontroller send through the instructions and in what format?


texts: Murata NCS6D1215C DC/DC converter for +15V and -15V

texts:
I would like to know if I can use a Murata NCS6D1215C DC/DC converter with a 12V battery to provide the necessary +15V and -15V for a power supply and amplifier that together require 200mA.

The last page, page 9, show the pin connections 14 and 16 as +Vout and -Vout;
For this unit the data sheet says the outputs are +15V and -15V.  So, does that mean that there is a potential difference of 30V between these two, pins 14 and 16?  If so, what do I use as the "ground" or zero voltage reference to get the +15V and -15V outputs from these pins?  Is it the negative terminal of the battery?

Does this IC require a current limiting resister to the inputs?  If so, should I place it at the positive or negative battery terminal, and how big a resistor should I use?


texts:
I have seen many a toys using just discrete components and IC's to produce songs (with words and everything!). I want to gift someone a piece of electronic art in which I want to use such a circuit. Does anyone know of these? I don't think those toys use uControllers to produce speech so there has to be some cheap alternative. What can it be? Please suggest.

Edit

For anyone who reads this question afterwards, I found all the answers very much doable and these are great options. The reason I had marked Leon Heller's answer as my accepted answer is just that it was very very easy to do. And can be implemented using the cute little Attiny uControllers.


texts: To what extent to I need to be concerned about PCB punch-through when dealing with AC mains?

texts:
I'm working on a project that deals with AC mains directly.

I know about maintaining proper creepage distances for adjacent tracks, and that you can add isolation slots if you lack the space to provide proper creepage.

However, is punch-through between overlapping copper layers a concern at all?

Basically, If I have a two-layer board, with a horizontal trace on the top layer carrying AC Hot, and a vertical trace on the bottom layer that is grounded, do I even need to worry about the point where they overlap, insulated only by the dielectric strength of the FR4?

What if I had a PCB where the entire top layer was a copper pour that was connected to AC hot, and the entire bottom layer is grounded? Where is the threshold of concern?

What rules of thumb (or actual standards) are used to evaluate this sort of layout?


texts: I've made a triangular wave by ICL8038 and it works perfectly at 15kHz with 15Vpp. I need to drive a 4 ohm load by that triangular wave. Could you please show me a solution/circuit to do that?


texts:
https://electrical-engineering-portal.com/the-real-truth-behind-household-power-savers
concludes

Power factor correction devices improve power quality but do not
generally improve energy efficiency (meaning they would not reduce
your energy bill). There are several reasons why their energy
efficiency claims could be exaggerated.
First, residential customers are not charged for KVA – hour usage, but
by kilowatt-hour usage. This means that any savings in energy demand
will not directly result in lowering a residential user’s utility
bill.

yet some reviewers such as on http://amazon.com/dp/B07FSQTBTQ claim that it has saved them money.
What could be the reason? Is it that some electricity meters measure kVA, or that people who want to reduce their bills adopt other measures and incorrectly attribute savings to the device?


texts: Diode characteristic measurement - initial tester settings

texts: While doing the diode characteristics experiment I was instructed to keep the voltage at zero and current at max before starting the power supply. Can I know the reason why?