texts:
As I understand it a balun is something that converts a line with a signal into 2 lines with mirrored signal to reject the noise like showed in this picture :

I am trying to understand the balun of the CC1101 circuit :
.
As I understand it, the balun is usefull to reject common mode noise picked up by the RF cable.

1)I don't understand how the capacitors and inductors showed in the yellow circle create the signal and a mirror copy of it like showed in the first picture.

2) Why is the balun locate just before entering the IC? It will receive alrady plenty of RF noise before no? I(In meander antenna, in the matching network,...)?


texts:
I'm trying to understand how the leakage current of D1 will affect the above circuit. From point A to point B I have a lengthy cable whose characteristic impedance is unknown. Because of the length of the cable the falling edges often undershoot and go down to as much as -1.5V (and sometimes more).

To counter this I'm using a clamping diode to cut off the excess voltage. However, the PMEG1020EA has a leakage current of upto 2 mA @ 5V. My question is, how would this affect my circuit?

The diode will be reversed biased when the signal settles down to 3.3V. Let's assume the leakage current is 2 mA at 3.3V as well. When the signal settles to 3.3 V, the diode will draw 2 mA. But if the diode draws 2 mA it means that the voltage across R1 is 2 V and so the voltage at X is just 1.3 V. So this scheme clearly doesn't work with a diode which has a large leakage current. Would I be correct in that conclusion?

But because the voltage at X is just 1.3 V now, wouldn't the leakage current now decrease?


texts: Vias direct connect better than thermal relief ? Ground/Thermal

texts:
I am thinking about if there is a positive point on having vias which have a thermal relief connection to their respective planes?
I know that for soldering pads it makes sense having less copper. BUT on simple vias, which are there to connect a ground plane on top to the on on bottom, I don't see any pros having those vias with a thermal relief, as there is no soldering on those vias to be done?! I rather see cons having thermal relief as it only increase the electrical resistance between those ground planes..
Same also for having planes which acts as a thermal sink, the thermal relief would only increase thermal resistance.
Am I right about this? Would be happy to hear a few thoughts on this

cheers


texts: How can I convert binary into multiple 7 segment displays

texts: I've been trying to make a decimal calculator using binary adders that feed into 3 x 7 segment displays. I cant find an efficient way to do this. If someone could point me to the correct resources, or maybe show a circuit that you made that is similar, that would be greatly appreciated.


texts: Overvoltage protection for DC controlled Device

texts:
i've designed this schematic using a simple buck converter (LM2596) for my board that powers up some leds and board peripherals.
The board will work at 5V with maximum current draw of 2.5A.
Now, as you can see in the schematic, i've already added a reverse voltage protection using SS34 (D6) diode (Datasheet here), what i want to implement is the overvoltage protection, i want that if there is a voltage input of more than 15V the external peripheral (marked with netflag +12V-POE) will not start blowing up (as the external peripheral maximum voltage rating is 15V).
What i can use? a Zener (in this case what part you recommend) or something different?


texts:
For an medium-high speed ADC converter, my FPGA is currently receiving 16-bit samples at 54 MHz over an LVDS interface (4 differential signal lines plus 1 differential clock signal). These are video/camera signals.

Now, I need to consider how I can get the image from the FPGA to the PC. I have a micro-controller and a USB-OTG interface. But USB is 480 Mbit/s, and probably down to 35 MB/s effectively (or less), which is not high enough for 16 bits 1.5 MPixels @ 54 frames/sec. That would be 162 MB/sec, far too high for USB 2.0. Am I forced to use USB 3.0? I really did want to get the raw images out to the PC. I also could conceivably perform loss-less compression on the FPGA.

The second question is how to stream this data out of the FPGA. I could buffer the ADC-data in external RAM, or I could set up an interface to the micro-controller, or even directly drive output signals on a port. Either way, what options do I have w.r.t. large streams of data?

Any help would be appreciated!


texts:
For years I programmed PIC controllers in assembler, but let it drop.  Now I want to get back to where I was, and - so help me - I can't find out where to start.
Downloaded MPLAB-X-IDE and it says I must buy a C compiler, although I have no interest in C. Found a page that says I can use assembler (MPASM) if I  just click the link.  No link.  (Do I need a C compiler to not use it?)
I called Microchip and a robovoice said to fill out an online question form.  Did so. No response 5 days later.
All I want to know is just how to bring up the first screen - y'know, where I type in the source code and assemble it to a hex file.  That's it.  And I am getting nowhere fast.
Yeah, I feel like an idiot, but I am at wits end.


texts:
I want to make a ZVS flyback driver, but all the sites say to use 2 n-channel MOSFETs and I only have one powerful n-channel MOSFET. I have a bunch of p-channel MOSFETs, specifically, 2 of powerful Fairchild SFH9154 MOSFETs. I am wondering if there is a way to make a ZVS driver or at least some type of reliable flyback driver with a p-channel MOSFET and how I would do it. Also, does putting MOSFETs in parallel increase the "Tolerance" or make the Amperage rating higher?

Additional information: If one n-channel could be used in combination with p-channel, I have an IRFP450.

I also have about 15 IRF9450 p-channel transistors and a couple IRF610 n-channel (although I don't think they are great for high current applications).


texts: How much time needs a 1.5 kW solar panel to charge a car electric battery?

texts:
Tesla car battery has about 6000 li-ion batteries. Each rated 3.7 V and 3500 mAh.

I asume ten 1m2 solar panel, each gives 150 W at 12 V (this gives about 12.5 A). For this problem, I put them in parallel, so together they give 1500 W, 12 V and 125 A.

The li-ion batteries will be in 3s, so they will behave like 2000 batteries in parallel, each 3s group will have 12 V (aprox.), and 3500 mAh capacity.

The total capacity of the battery group is 2000 cells x 3500 mAh = 7 ∗ 10^6 mAh = 7000 Ah.
The time the solar array needs to charge the batteries is: 7000 Ah / 125 A= 56h of good sunlight.

In a sunny location, lets say that you have 8h of good sunlight per day, so 56h / 8h/day = 7 days to charge the battery.

Have I missed something important? This is not homework, just curiosity. I think the solar panels are not really used in parallel because taking 125 A from them seems like a bad idea (very hot and melts everything). What else?


texts: dropping a signal voltage proportional to signal

texts:
Basically i have a car that im installing at aftermarket ecu in,
The tps signal is normally a 0-5v signal (varible resistor on a 5v output from the ecu) that the ecu uses for various things,
However on this car the factory ecu also would output a 0-3v signal for the tps signal to send to the awd control module in the car,

I was thinking could i splice into the main tps signal (0-5v) that goes to the ecu and send it to the awd control module, and if i did this and used resistors to drop the signal using a voltage divider circuit with r1 = 1400 ohms and r2 = 2200 ohms, this should give me a 0-3v signal thats proportional to the original 0-5 signal correct?
also would this effect the signal voltage before r1, as the aftermarket ecu still needs the 0-5v signal ?

Thanks

Scott


texts:
First of all, sorry to ask such a simple and uninteresting question, but I'm a very beginner into electrical engineering.

I have got an exercise to do, with a simple RC circuit, where I need to determine some voltages at given times. The following image is the exercise (where E is a low frequencies generator) and the values I found:

Even if I applied what I thought to be the good techniques, my circuit is equivalent at t=0 and t=oo . So Uc is the same.

Did I made a mistake somewhere?


texts:
My car radio doesn't support Bluetooth and I am wondering how to solve this problem so I can play songs from my phone.
The first idea that came to my mind is obviously just to buy a new radio.
However, I am wondering, just for the sake of having fun with electronics, if it was possible to somehow generate radio waves in the frequency range of the car receiver so I could for example connect my phone with an Arduino (e.g. via Bluetooth) and transmit audio in a custom frequency so the car would receive it as if it were regular radio station.
Is this, in theory, possible?


texts: If one plays too loud of a sound through a speaker, it can blow - i.e. become visibly torn or stop working entirely. However is it possible that the loud sound will damage it partly and result in the speaker operating at a less loud level; can a speaker blow just a bit?


texts: Does biasing of address pins require a resistor?

texts:
I'm a total newbie fooling around with a project of mine.

I want to use an MCP23017 I2C port extender (Data sheet) for my Arduino project.

The chip has three hardware pins that must be externally biased.

I apologize if the question is silly, but, can I just connect the pins to V+ or GND, or do I need to put a resistor in series to limit the current? I looked around a bit but I wasn't able to find an answer.


texts:
I have included a LTC4054 IC in my project and here is how the circuit is. I purchased it from here

The schematic is uploaded on github.

The chip has 5 pins

Pin 1 CHRG- connected in series to a resistor (1kohm) and a red LED to 5v pin of micro USB connector

Pin 2 is connected to GND

Pin 3 is connected to the Li Ion battery positive terminal.

Pin 4 is connected to the positive +5V pin of the micro USB. A 47uF capacitor is also connected from this pin to GND.

Pin 5 PROG pin is connected to GND through a 5.1kohm resistor. This gives the charger a maximum charging current of 200mA.

According to the datasheet, the CHRG pin will be connected to a low 20uA pulldown once charging completes. I am expecting the LED to turn off, because 20uA shouldn't be enough to make it glow.  The open circuit voltage of my Li Ion battery is currently 4.21 volts, which I think has reached the level of charge expected.

Also, my battery has a charge protection circuit built inside it, which prevents over discharge, overcharging and short circuit protection.

My only question is- Why doesnt the LED turn off to denote that charging has completed?


texts: What does pre-damped mean in the pre-damped switched-inductor piezoelectric energy-harvesting charger

texts:
There is a paper from the IEEE,title:Optimally Pre-Damped Switched-Inductor Piezoelectric Energy-Harvesting Charger,and the author show two kind of pre-damped: symmetry and asymmetry,shown as fig 1 and fig 2.

And now i want to ask what does "pre-damped" mean in his pre-damped switched-inductor piezoelectric energy-harvesting charger?i know the damp  means that any vibration system in vibration, due to external effects or the system itself is inherently caused by the gradual decrease in vibration amplitude characteristics,but what is "pre"-damp ?


texts: Filter Design (Low Pass Prototype Method)

texts:
In the Low Pass Prototype Method for filter design, after choosing the order N and the tolerance of the filter according to the design specifications, we have to look at some tables with the normalized impedances gk, with k = 1,...,N+1.

My doubt is about g0 and gN+1. Do you know what they represent and how to choose their values?


texts: My BeagleBone Black does not turn on other than power LED turns on for a second

texts: The power LED just turns on for a second and turns off. I again tried with power adapter (5V 1A) and the mini USB cable but nothing else happens.


texts: PIC understanding the sign of the integer that is in the register

texts:
I am getting current data from CANBus, they send me the value as a signed number. The problem is even if the number is supposed to be negative if(current<0) is always true and it never becomes if(current<0). So I think that I cannot check the sign of the number in the register like that. So is there way to check if the number is positive or negative?
I declared current as an integer number and I directly put register value in it like that:

int current;
current = RXB0D0;
if(current>0){
    led1=1;}
if(current<0){
    led2=1;}

Edit: This is the battery spec I am following : datasheet

On page 59 current() section.


texts: Measuring nanoamp range current consumption

texts:
I am looking to buy one of Joulescope, ZS-2102-A (angler circuits) or Otii (QOITech) to measure power consumption and get graphs of current consumption for some low power BLE/WiFi devices. Does any one have experience with these devices?
Circuit under test consumes between a few nanoamps to 400 mA @ 7.4 V input.
I have looked at EEVblog microcurrent etc., I really need the software which graphs consumption in real time without the use of a scope.  I would appreciate any suggestions.


texts:
I assume this an already known "bug" but I'm unsure if this could be fixed or not.

Straight to the problem:

I feed my RIGOL DS1054Z a 20MHz sinusoidal waveform and set the timescale to 200ms/div. The output is the following:

(Sorry for the bad quality picture but the scope just don't want read my USB Stick for some reason.)

It is displaying the waveform just wrong! I know some other scopes have this problem as well but can this be fixed?

Note: My KEYSIGHT MSO 3000 Series displays the waveform as I would expect:


texts: Why should a UPS fail if the battery fails but the power from the wall outlet is still good?

texts:
Sounds to me like a design flaw.

Why wouldn't this work?  No switching transient and the power supply to the servers (or whatever) fails only if both battery and AC power fail.

simulate this circuit – Schematic created using CircuitLab

Over the weekend, some server in the server room died because of a UPS battery failure while the AC power remained fine.

I don't see the reason for why this failure is inherent to the problem.

Revision: It finally occurred to me to look it up in Wikipedia, and they say there are 3 different designs, and the seamless switching design I might have been looking for is the Online/double-conversion design.  All other designs have a hard switch from the AC mains to the output of the inverter.

So it just occurred to me, similar to how the power-generator with the power company is put online to the grid by carefully aligning the phase of the generator to the phase of the AC on the grid and then throwing the switch, can't they make an energy-efficient UPS that has the UPS output connected directly to the AC mains in parallel to the inverter where the amplitude and phase/frequency of the inverter output is adjusted with a control system very similar to a phase-lock loop so that the power contribution to the output from the inverter is zero or very small during normal operation.  It's an AC source that is phase-locked to the mains with amplitude adjusted from fiddling with the switching transistors on the primary of the inverter output transformer.  The amplitude is increased so that the net AC current is never delivering power to the inverter's output transformer but there is only a trickle of current coming out, under normal operating conditions.

Then, when the AC power main goes out, the inverter is taking over the load and the battery is supplying a lot more current to the switching transistors on the primary of the transformer.  There would have to be a disconnect of the output from the mains, because when the power comes back at any random moment, we don't know that the inverter phase is in phase with the mains.  Then the controller of the inverter would slowly adjust the phase of the output of the inverter to be in phase with now-energized mains, the output voltage would be adjusted to be the same as the mains, then the disconnect switch would be reconnected and the system would go back to "normal operation".

Does that make any sense?

Tim, what do you think of that?


texts: Reverse polarity protection for battery powered application

texts:
Im designing battery powered application and need reverse polarity protection.

My system specs: 4.5v(3x AA batteries) in and system running on 3.3v. Im using MCP1711T-33I/OT LDO to convert 4.5v to 3.3v. My system will take about 50 milliamps maximum. Therefore i can't obviously use any diodes since voltage drop and power waste will be too big. I read some threads and people tend to suggest P-channel MOSFET. I was looking for low rds(on) MOSFETS and all their packages seem so huge. Like this one:

http://www.farnell.com/datasheets/2049687.pdf

Size isn't too big problem though(sot23 package would be perfect though). Can you suggest me anything else than P-channel MOSFET? If not, can you suggest me some decent P-channel MOSFET for my needs? Thanks in advance.


texts:
I have an ADC signal, how do I shrink it to 1V from a 5V sensor like Hall IC for example. Of course, a resistor divider is one method, but will it work reliably as the output is expected between 0 to 1V, so I am assuming, the margin of error would be high.
I have also seen some of the low voltage op amps like: LMV951 but the cost is pretty high, instead for that cost, I would choose a separate ADC chip.
Is there a way to reliably do the level conversion at the minimum cost, high accuracy is really not required. The micro controller can do 10 bit ADC, but I may be interested in only 8 bit accuracy.


texts: I need help with this problem. Some numerical answers would also be very helpful.


texts: Finding a solution to make a decent batterypack, that I can install and charge/discharge without having to remove it

texts:
I have a problem with a power delivery circuit for my bluetooth speaker I am planning to build.
I am unable to find a BMS for 4 Cells that would allow me to charge and discharge it through different terminals.
Here is what I initially bought
But these BMSs only have 2 Terminals for Charging/Discharging. What I want is a BMS that can charge and discharge, but through different outputs, so I dont have to flip switches all the time when going from use to charging. I have been recommended the BQ24753A Microcontroller in a schematic a fellow user designed.
I am no electrical engineer and just a beginner. As far as i understand I would have to buy the chip and build the other necessary components for it to actually work.I have been told the chip could also help downregulate the voltage from the PCB, but I thought I could just use a dc voltage step-down regulator, since thats more beginner friendly imo. I couldn't find a PCB with the chip that would cover my needs. Maybe I am just looking in the wrong spots.
Is there anything that would help in my specific case?
Thanks in advance for your answers!


texts: How do I find the right resistor for an LED panel?

texts:
I purchased one of these cheap LED panels to light a room.  One review suggested that it's important to put a resistor on it, to keep it from frying itself.  But, he didn't list what resistor to use.

I've searched around and found a lot of discussions of resistors for individual LEDs.  But, I haven't stumbled onto the right page for this situation.

I have a UNI-T multimeter.  I saw "Easy way to figure out a LED's Vf in order to pick an appropriate resistor", but putting my multimeter into what I think is diode mode stayed stuck at 0L.  (I was careful about polarity.)

This is my first encounter with "forward voltage" so, it's a bit overwhelming.

Thanks.

----- Edit

I understand that you can't give me a definitive answer.  But, does anyone have a Scientific Wild Ass Guess?  Something along the lines of, probably higher than this.  I'd be surprised if higher than that.  And, likely around here?  Just a ballpark number that has a reasonable chance of being safe?

And, I haven't ever bought something like this.  A suggestion or two on a source would help me out.

I appreciate everyone's input.  I understand that not having a data sheet makes this a pain.  But, this is just a DYI thing, and they're so inexpensive that it's hard for me to pass them up.


texts: Restoration of time-shifted audio file using matlab

texts:
The two stereo channels of audio file are time shifted. Which is the easy model to restore the file to the original?
I have a partial solution something like:

Loading file like, [data,fs]=audioread('xyz.wav');
Calculating the power spectrum of each channel using fft, fourier1 = fft(data(:,1),1024);
Get power spectrum channel 1 and channel, Powspec_1 = fourier1.*conj(fourier1)/1024;
Normalizing the spectrum
Then compute cross correlation between these pair of signals

I can't understand the next steps to get original file or may be a simple model could help me to solve it.
Regards,
Lalit


texts: STM32L4's Temperature Calculation Equation shows improper results

texts:
While using STM32L4's ADC to measure its internal temperature sensor data, I am facing an issue.

The equation provided in STM32L4's reference manual, seems to showing improper results.

The equation is:

*Temperature = ((110-30) * (TS_DATA - TS_CAL_1) / (TS_CAL_2 - TS_CAL_1)) + 30*

where,
TS_DATA = 945 (raw ADC data for temperature),
TS_CAL_1 = 1035 (calibration point read from predefined memory address),
TS_CAL_2 = 1373 (calibration point read from predefined memory address)

This results in 'Temperature = 8.69' at room temperature (about 26 Celsius), which is clearly incorrect.

My Code for the same is:

#define TS30    ((uint16_t*)((uint32_t)0x1FFF75A8))
#define TS110   ((uint16_t*)((uint32_t)0x1FFF75CA))
uint32_t ADC_Value;
double temperature;
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc){
   ADC_Value = HAL_ADC_GetValue(&hadc1);
   temperature = (double)ADC_Value - (uint32_t)*TS30;
   temperature *= (double)((uint32_t)110 - (uint32_t)30);
   temperature /= (double)(int32_t)((uint32_t)*TS110 - (uint32_t)*TS30);
   temperature += 30;
}
int main(){           /**Main Loop**/
 MX_ADC1_Init();
   HAL_ADCEx_Calibration_Start(&hadc1, ADC_SINGLE_ENDED);
   HAL_ADC_Start_IT(&hadc1);

   while(1) {
     HAL_Delay(400);
     HAL_ADC_Start_IT(&hadc1);
   }
}
static void MX_ADC1_Init(void)
{
  ADC_ChannelConfTypeDef sConfig;
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc1.Init.LowPowerAutoWait = DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.NbrOfDiscConversion = 1;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc1.Init.OversamplingMode = DISABLE;
  if (HAL_ADC_Init(&hadc1) != HAL_OK){
    _Error_Handler(__FILE__, __LINE__);
  }

  /**Configure Regular Channel**/
  sConfig.Channel = ADC_CHANNEL_TEMPSENSOR;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_640CYCLES_5;
  sConfig.SingleDiff = ADC_SINGLE_ENDED;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 0;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK){
   _Error_Handler(__FILE__, __LINE__);
  }
}

Please review the code and help me.


texts: With harmony how to implement printf to uart?

texts:
I setup a project using harmony v2 for a pic32mx470f512l. In drivers -> USART i configured the UART (strange its called USART in harmony in datasheet says its a UART):

Now i want to use the function printf, like we can easily use in MCC.
How can it be implement in harmony?

I seem to have made it work after

but i get wrong chars on termite:

The configs i made in device configuration:


texts: Is a cigarette lighter battery voltage meter accurate?

texts: Recently, I bought a USB car charger that shows my batter voltage at about 13.7v when the car is running.  Is it possible that this is accurate?  Since you can get a lot of gimmicks on eBay, I want to be sure if this is even possible.


texts:
There is a famous paper from Milton Dishal called 'Two New Equations on the Design of Filters'. The paper was published in the journal 'electrical communication' and can be found here

http://www.americanradiohistory.com/Archive-ITT/50s/ITT-Vol-30-1953-04.pdf

on page 65. The equations 10A and 10B as well as Figure 7 allow to calculate the normalised coupling coefficients of Butterworth and Chebyshev filters. What I don't understand is the following: using the K and Q values, I would like to create the coupling matrix as it is shown in many papers on filter theory. I found out (by try and error), that the coupling matrix must be (say, for a filter having 3 poles) as follows:

$$
M = \begin{pmatrix}
0 & \sqrt{1/q} & 0 & 0 & 0 \\
\sqrt{1/q} & 0 & k_{12} & 0 & 0 \\
0 & k_{12} & 0 & k_{23} & 0 \\
0 & 0 & k_{23} & 0 & \sqrt{1/q} \\
0 & 0 & 0 & \sqrt{1/q} & 0
\end{pmatrix} $$

Then, from this, I calculate the frequency response of the filter as follows:

$$ Y = G + s\,L + j\,M $$

with the abbreviations:

$$ G = \begin{pmatrix}
1 & 0 & 0 & \ldots \\
0 & 0 & 0 & \ldots \\
\vdots \\
0 & 0 & \ldots & 1 \end{pmatrix}  \text{,}\quad
L = \begin{pmatrix} 0 & 0 & 0 & \ldots \\ 0 & 1 & 0 & \ldots \\
0 & 0 & 1 & \ldots \\
\vdots \\
0 & 0 & \ldots & 0 \\ \end{pmatrix}$$

For a bandpass filter, the frequency transformation

$$ s = \frac{1}{FBW} \cdot \left( \frac{j\omega}{\omega_0} + \frac{\omega_0}{j\omega} \right) $$

is used. The scattering parameters are then found with
$$ S_{11} = \left(Y^{-1}\right)_{1, 1} $$ and $$ S_{21} = \left( Y^{-1} \right)_{N+2,1} $$.

However, in many books and papers, the coupling matrix M has completely different values in it; it is kind of denormalized with the coupling coefficients being multiplied with 1/FBW. Why is this, and what is the difference to the coupling coefficients found with dishals equations? And why is S11 and S21 found with these equations, how can this be derived?


texts: Why is the only way to make this device work to manually unplug and re-plug the supply wire while the master is on?

texts:
Context
I'm reading acceleration from an ADXL355 in the evaluation board EVAL_ADXL355Z to an ESP32-WROVER on the ttgo evaluation board.
Wiring
ADXL345 Pin name (number) -------- ESP32 Pin name (number)
VDD (P1-3) -----------------------------> 3v3
GND (P1-5) -----------------------------> GND
CS/SCL (P2-2) -------------------------> vspi cs (D5)
SCLK/VSSIO (P2-4)  ------------------> vspi scl (D18)
MISO/SDA (P2-5)  ---------------------> vspi miso (D19)
MOSI/SD6 (P2-6)  ---------------------> vspi mosi (D23)
Note: the accelerometer arrived with STBY-1 (VDDIO) connected to STBY-2 (RESERVED). I removed this connection because it seemed strange to me to connect something to a reserved pin, I didn't try yet to reproduce the problem with those pins tied and nothing about the usage of those pins is present in any datasheet.
Question
I got stuck with a problem that seems very similar to that described here.: I can read/write everything from/to the device but the acceleration data are stuck to -2g. That is the lowest boundary of the measurement range. It happens that by chance I tried unplugging and re-plugging the wire that supply power from the master to the accelerometer while the master is on after that operation acceleration data are correct. What surprises me is that simply turning off and on the whole system (powering down the master but not removing the supply wire that connects the accelerometer to the master) doesn't solve the problem, and at following restart the problem persists
What can be causing this? How could I fix it so that I dont have to manually act on the system to make it work?


texts:
I have this sheet for practice but I can't figure out how to find the outputs of it:

To fill out the first part: EQ[n](equal so far?)

yes(4) yes(3) no(2) no(1) no(0)

So, what is EQout going to be for each case? I don't understand that part at all. Also, it asks for a building block circuit? I have not learned about those yet.

There seems to be a lot of terms that I do not understand yet, maybe this sheet is too advanced.

Anyway, if someone could help me understand that would be very great. I really appreciate any help, thank you.

EDIT:

The X's represent "don't care terms" but I'm not sure if that is valid here.

EDIT: Tried to solve my question below: https://electronics.stackexchange.com/a/358585/175939 please reply with any criticisms.


texts:
I'm working on a mixed signal PCB that has some high-speed interfaces (HDMI, DDR, etc) I'm having some EMI issues on the HDMI that causes the product to fail radiated emission when the load is connected to the port via HDMI cable. While looking at the layout I noticed the CLK and data pairs each go through 3 vias between the connector and the uP.

Let's assume I have to use the number of vias I currently have due to space constraint. How important is via impedance to maintaining good signal integrity when dealing with high-speed interfaces?
What are typically the most important via parameters that can significantly affect signal integrity?

Signal goes from inner-layer1 to TopLayer to inner-Layer4 to TopLayer


texts: How do get the proving FREQUENCY-TIME graph by using oscilloscope?

texts:
Now I'm trying to prove the Sawtooth Ramp wave output of ADF4159 with tektronix oscilloscope as the below.
But as you can see the below image, it's FREQUENCY-TIME graph.
So I want to know how to prove the Sawtooth Ramp wave output of ADF4159 with tektronix oscilloscope.
Would you please help me?


texts:
After rectifying an AC sine wave (full-wave or half-wave), we get Vdc, Idc, V Rms and I Rms.
However, if we want to calculate the power dissipated in a load, we use the RMS values, so why we used the RMS values instead of the DC values?? and what the difference between AC and DC power??
And the definition of the efficiency is not clear, what's the meaning of the ratio between DC power and AC power??


texts:
I have an analog sensor, a resistance temperature thermometer, which is essentially just a resistor (~50 Ω) which I apply a constant current to (10 mA) and measure the voltage of in order to detect temperature changes.

The temperature changes of interest are extremely small, and so it is extremely sensitive to electrical interference, and nearby there are many pumps and stepper motors. I have been told conflicting information about how the cable should be shielded.

The two options are: (diagram attached also)

A: COAXIAL CABLE
I have up to now been using a coaxial cable. The outer of the cable is connected to ground at the oscilloscope I use to record data. The outer is carrying the return current, which I have been told is bad.

B: SHIELDED TWISTED PAIR
The constant current is carried in the internal twisted pair with a shield connected to ground at the oscilloscope end.


texts: How can I model a circuit for this noise coupling phenomenon

texts:
A shielded Wheatstone type force transducer FT is mounted on a metallic structure and through its cable is connected to an industrial amplifier module Amp(I gave the names in the below illustration). The end of the cable has several wires which is connected to the amplifier. One of the wire is shield SW which is connected to the transducer shield K. The amplifier is powered by an SMPS power supply whose DC negative terminal is galvanically isolated from mains earth.

The outpuut of the amplifier vi a BNC coaxial cable goes to a DAQ board which is a single ended earth grounded board. The shiled wire was floating i.e was not connected to anywhere.

I tried to illustrate this below:

If the force transducer is completely isolated from the metallic structure the output is fine. On the other hand, if it touches to the metallic structure there is 50Hz noise appears on that particular DAQ channel. Obviously some noise is coupling through the metallic structure either magnetically or overcapacity.

But by a wire I wired/shorted a point on the shield K directly to the AIGND and even if the transducer touches to the metallic structure the noise disappeared. If the metallic structure was earthed I would expect some ground loops but the 50 Hz disappeared.

So for some reason tying the shield directly to the AIGND solved the 50Hz pickup problem even the transducer is mounted on the metallic structure.

I tried to simulate this scenario but failed. How can we model what happens with a basic circuit model? I mean I want to simulate a representative circuit modelling when the shield is wired to the AIGND the noise disappears and when the shield is floating the noise appears.


texts: How to read the position of the decimal point with this multimeter?

texts:
Note (edit): This cheap multimeter has a bad serigraphy, confirmed by comments of other buyers. The top range should probably be 200 µA.

I rarely use my multimeter in current mode (I usually it in voltage mode), but here I did a measurement:

I understand that the current is probably 220 mA (thus 0.22) but what is the signification of 02.2 (see the 3rd picture)? Which unit is it using to write 02.2?

If the unit when used in 200mA mode is 1=100mA (which I could understand), why wouldn't it be 1=10mA in 20mA mode (then it should display 022. in 20mA mode)?


texts: In my digital circuits class I have a project as shown in the picture. I am having trouble because I cannot get the led's to light up in sequence(left to right) I don't know why the lines are red. Any help would be great.


texts:
I have a diode where forward voltage is 3.5V and forward current is 25 mA. I supply it with 5V so I calculate a value of resistor in the following way:

R = (5V - 3.5V)/25mA = 60 Ohm

However I see that most times bigger resistors are used, like 220 Ohm or 330 Ohm. Why is it better to use bigger resistors then to stick with the calculated values?


texts:
Please help me to find the answer for the following question from Flyod 9th Ed.

Determine the voltage across the diode in the following figure, using the complete diode model with r'd = 10 Ohms and r'R = 100 Ohms.

Since the lower point is grounded, voltage at upper node is -10 V. Hence diode is forward biased. Then in complete diode model we can consider the diode as a closed switch with a DC source and resister inside.

Is this explanation is right and if so how may I proceed from here?


texts: Where to place a capacitor to prevent arcing in a brushed DC motor?

texts:
I always thought that if you want to reduce arcing in a motor commutator, you should put some capacitance across the motor terminals. But recently, while reading application note AN905 from Microchip, I saw this:

Here, capacitors are placed across mosfets. Microchip says that the purpose of these capacitors is the same: to reduce the RF radiation that is produced by the arching of the commutators. So what's the difference between one capacitor in parallel with a motor and four capacitors like on the picture above?


texts: The output of the amplifier changes depending on my distance

texts:
I made this circuit to amplify the output of a load cell.

simulate this circuit – Schematic created using CircuitLab

The instrumental amplifier has a Gain = 750.
I use a dedicated voltage regulator (LM350) because I want an output of max 5V.

The circuit seems to work well (there's a bit of background noise), but when I'm close to the circuit the output is greater than before.

The Output change a lot when I move my arms in the air.

The cable from Load Cell to circuit are close in an aluminum foil connected to GND.

Is this the correct way to read data form load Cell?
Do you know how to remove the influence of a body?

More details:
Thanks everyone for suggestion (it's only the second time I use electronics.stakexchange)

The schematic shows only a single part of the PCB circuit of my project.
In the real circuit, between load cells and amplifier, there are two demultiplexers.
They switch signal from 8 Load Cells to 1 amplifier. (1 demux manage the +In and the other the -In).
On PCB there aren't capacitors. I tried to add capacitors in the breadboard version.

The circuit and the load cells are mounted into a big aluminum case, not yet completely closed.

In this picture the cables are uncovered, but during tests they are covered with silver foil.
Every part of the aluminum case is connected to GND.

For @ANDY AKA
This is what the oscilloscope sees when I put my head near to the circuit in Breadboard version.

If I set AREF to 1V and move my arm near to the wires, you are right, the output do the opposite: it decreases.


texts:
I want to purchase this new GPS on sparkfun, but I have no idea how to get the correct supply voltage (1.8vdc) for it from the Arduino.

48 Channel GP-2106 SiRF IV GPS Receiver

Datasheet


texts: Will Open Collector Output of 0~12V damage 0~5V input DAQ?

texts:
In my lab configuration, I am using open-collector with 2K Ohm pull-up resistor to 12V.

The data aquisition card I am using is from national instrument.

If I look at the Low and High voltage of open collector output when not connected to input of DAQ, i get 0.2 ~ 12V.

However, If I connect to the input of DAQ, the voltage becomes 0.2~5.6V.

Will DAQ input be safe from over voltage since 12V is not directly connected to the input, but through 2K Ohm resistor?


texts: SMD transistor identification - top marking ARRL 1S

texts: I have an SMD transistor. As I tested it, I know it's a MOSFET, but the top code is ARRL 1S. All 1S are NPN transistors and I know it's surely a MOSFET. Please help find the correct part number.


texts: Conceptualizing an analog input pin on a microcontroller?

texts:
As I am trying to learn basic circuit design I would like to build and simulate simple models to test my conceptual understanding. One of the first designs I am trying to tackle is to use an analog input pin on a microcontroller, but it is not clear to me how the pin itself should be modeled (and indeed thus how it behaves in a real circuit).

Can I think of an analog input pin as behaving like a multimeter set to read DC voltage, with the negative lead attached to ground? And does it, like a multimeter, have some large internal resistance?


texts: finding output resistance of CB amplifier with ro

texts:
I have this CB amplifier circuit below

This is the small signal equivalent circuit arranged to find the output resistance R_out with the r_o included

Here is my analysis below to find the output resistance R_out

\begin{equation}
v_x\:=\:r_o\left(i_x-g_mv_{\pi }\right)+R_e\left(i_x+\frac{v_{\pi }}{r_{\pi }}\right)
\end{equation}
\begin{equation}
v_x\:=\:i_x\left(r_o+R_e\right)+\left(\frac{R_e}{r_{\pi }}-g_mr_o\right)v_{\pi }
\end{equation}
\begin{equation}
v_{\pi }+R_e\left(i_x+\frac{v_{\pi }}{r_{\pi }}\right)\:=\:0
\end{equation}
\begin{equation}
therefore\:\:v_{\pi }\:=\:-\frac{r_{\pi }}{r_{\pi }+1}R_ei_x
\end{equation}
after some rearragements
\begin{equation}
\frac{v_x}{i_x}\:=\:R_{out}\:=\:r_o+R_e+\left(g_mr_o-\frac{R_e}{r_{\pi }}\right)\left(\frac{r_{\pi }R_e}{r_{\pi }+1}\right)
\end{equation}
I tried to manipulate my results but it does not come out to the same formula in the book which is below:
\begin{equation}
\frac{v_x}{i_x}\:=\:R_{out}\:=\:r_o+R_e\backslash \backslash r_{\pi }+\left(R_e\backslash \:\backslash \:r_{\pi \:}\right)g_mr_o
\end{equation}

can somebody please tell what am doing wrong?? thanks in advance for all the help.


texts:
I'm analyzing a circuit (USB game console.)
Three identical ferrite beads (805 or 603 package) are used in the circuit.
It was working but I tried something on circuit. Now it is not working.
I measured the ferrite beads, they are short circuit. I did not measur to ferrite beads when it was working.
Could this be the reason why it is not working?


texts: acs71020 Connecting and reading voltage properly

texts:
I am using an ACS71020 3.3V I2C version hooked up to ESP32. I have connected the IC as proposed in the datasheet. Rsense used is 1.8k ohm as proposed in the evaluation board user manual for 230-240 VRMS. With connected load i get reasonable results for Irms when reading register 0x20, but Vrms are much lower than expected, and i guess as a result the P rms is also not correct.

*Above is my implementation (I2C pull-ups are present)
It is also stated that maximum voltage for the VINP pin is 0.275.
I measured Rsense with multi meter and got something around 0.100 V rms(Which will not be close to 0.275 V in aplitude). So i thought that might be an issue and tried to recreate the scenario in LtSpice . And indeed it shows that the the voltage across R5 would be around 0.100 Vrms. Was not sure of the role of R3 and R5 , therefore tried to remove them and got ~0.290 V max amplitude , changing Rsense to 1.7k would yield ~0.275 V max amplitude exactly. I have removed R3 and R5 from my PCB, but i still get results pretty similar as with them.(will attach result later,when i get my hands on test pcb again)

Regarding the code, maybe i am doing something wrong as well. But as far as I understand the basic flow would be. Read the values from VRMS IRMS registers.
Transform them from Q number() format to Float and then Multiply Vrms by 325(Full scale voltage,or should it by 230 ? ) and Irms by 30 as i have a 30 amps AC71020 version. I expect that the values would oscillate based on which time of cycle they are being read by ESP32,therefore they should by averaged.

Code snippet :

void acs171020_read_2_15Bytes(byte address) {
  uint16_t Irms;
  uint16_t Vrms;
  byte buff[4];
  Wire.beginTransmission(0x66);
  Wire.write( 0x20);
  Wire.endTransmission();
  Wire.requestFrom(0x66, 4);
  int nrrr = 0;
  while (Wire.available())   // slave may send less than requested
  {
    char c = Wire.read();    // receive a byte as character
    buff[nrrr++] = c;
  }

  Vrms = (buff[1] << 8) + buff[0];
  bitClear(Vrms, 15);
  Irms = (buff[3] << 8) + buff[2];
  bitClear(Irms, 15);

  float testVRM =  ((float)Vrms) * 0.00003051757; //or /32768.0
  float testVRMMM = qToFloat<uint16_t>(Vrms, 15);

  // both give same value
 testVRMMM = testVRMMM *325;

 float testIRM = qToFloat<uint16_t>(Irms, 14);// ((float)Irms) * 0.00006103515;

  float testIRMS =  ((float)Irms) * 0.00006103515; //or /32768.0
  testIRMS = testIRMS * 30;

To sum up :
Are 2 1 mega ohm resistors really needed on the VINN line ?
Am I missing something crucial in the code part?

UPDATE:
Ok, in order to improve improve performance a bit and let the IC to actualy do it's job, I have enabled the customer mode and set in the register 0x1C to make an average of 62 samples per minute. Then I read 0x27 once a second. The Q to float value is now ~0.3121337891 so to get 230 the full scale voltage should be then considered 736.86351184 V. Where does this number come from, how can i verify it ?


texts: Reusing heatsink vias for ground plane connection

texts:
This a more elaborate phrasing of my previous question on the subject, which did not get much love. I would appreciate a clear and thorough answer since it is my last question (after a long journey) before I finally send the PCB for manufacturing (cross fingers).

I have 4-layer PCB (signal, ground plane, power plane, signal). On the top side, there is a QFN-76 IC which has a heatsink pad on the bottom. According to the datasheet, it is connected to the ground and should be connected to the ground plane by vias, which I have done so as you may see:

As said, those vias, and consequently the pad, are connected to the ground plane. On the other side of the PCB, I have placed the required decoupling caps physically as closer as I could near the corresponding power pins and I have used the vias of the heatsink pad in order to connect them with the ground plane, as depicted below:

My Questions

Is this a bad practice? Is it possible to cause any problems? If so, what is the proper way to do?
On the first image, top of the PCB, I have also connected some of the IC ground traces to the pad. Is this, also, a bad practice?
One thought of mine was to create an identical pad on the bottom of the PCB, using the same vias to ground as well, for the caps to connect. What do you think of that?

As always, all your recommendations and guidelines are more than welcome. Thanks in advance.


texts: Long term effect of over-voltage on clamping diodes and ADC reference voltage

texts:
I am contemplating building a small voltage/current monitoring circuit that needs to monitor a wide range of voltages and currents.  Currents will just be a single low-side shunt.

Monitoring will be done by a number of ADC inputs on an MCU at 3.3V.

Input voltages for both voltage monitoring and current shunt will be 0-24V.

Now, not only do I want to measure the 0-24V (through simple voltage divider), but also the lower portion of that same voltage range (0-3.3V) in greater resolution, so directly connected without the voltage divider.  Similar arrangement for the current shunt - different voltage dividers to measure different current ranges at different resolutions.

So I am thinking the simplest input stage for the over-voltage inputs will be a simple resistor and clamping diodes to +3.3V:

simulate this circuit – Schematic created using CircuitLab

Now the 10KΩ will limit the diode current to a maximum of around 2mA, so the diodes won't care much about it.  My question is, what will happen to the power supply voltage and, more importantly, the ADC reference voltage (I could use an external reference, but for this I will probably just use Vdd) when 24V is applied for an extended period of time (I'm talking hours or even days here).

Should I be considering adding extra decoupling to the input of the MCU? Maybe an additional small resistance?  To the input of the MCU (A), or to the diode->Vdd connection (B)?

simulate this circuit

Would either of those be recommended, necessary, or pointless?  Given the small (2mA) current, would there even be an issue to worry about?

(The simulations I have run, though crude [falstad], have all shown Vdd staying at 3.3V, but I don't trust it, and I don't have PSpice).


texts: What problems could occur when chaining 40 shift registers?

texts:
I'm planning on chaining together 40 x 74HC595 shift registers. The whole chain of 74HC595s will be controlled by a 5 V microcontroller, which will generate the SDI, CLOCK & LATCH signals.

Each shift register and the microcontroller will have its own PCB, as illustrated in the diagram below:

Because of mechanical constrains, the distance between each shift register will be of about 30 cm (12 in), so the control signals will travel along a distance of aprox. 12 m (40 ft). Besides that, the whole system will be mounted in a very noisy environment (near fluorescent lights, mains wires etc.)

My concern is that the control signals will be very noisy and the shift registers might output the wrong things. I was thinking of:

Using a buffer IC on each board, to buffer the control signals. Which one would you recommend?
Using shielded cables between the boards for the signals
Lowering the CLOCK frequency as much as possible. I only need to update the registers' content a few times a day.

Are the above solutions a good thing to do? What else can I do to keep the (potential) noise in the signal wires to a minimum?


texts: Current mirror configuration analysis in LM393

texts:
I've been trying to figure out how this comparator (LM393) works.

So far I can recognize the sections:

Q8, Q9, Q10, Q12 form the differential amplifier.
Q15 and Q16 are the output transistors.
Q1, F1 and Q2 turn off Q3, so they work as a current limiter?
And Q3, Q4, Q5, Q6 and Q14 are the current mirror.

I'm having problems trying to figure out how this current mirror works. The current through Q3 is mirrored in Q4, Q5, Q6 and Q14. Still, I can't figure out what is the role of R4. I've never seen a resistor connected in that way to the base of the transistor; it's different from R2 which balances the current mirrored in Q5. Any help would be appreciated, thank you.


texts: Does a DC isolator smooth the voltage as well as a regulator?

texts:
I'm designing a power supply for multiple guitar pedals. To minimise noise I'd like the output voltage to be smooth when it's up and running. (I don't mind about small transient fluctuations when plugging in). I also want to eliminate ground loops by isolating each pedal's supply.

My design involves a toroidal transformer, bridge rectifier, smoothing capacitor, and an optional voltage regulator. This supplies multiple isolator assemblies.

The isolator assembly will include a DC/DC isolator plus the recommended inductor (in series) and capacitor (in parallel) to accompany it.

To ensure smooth output from the isolator assembly, should I add a regulator before the load?

A possible final regulator would be: Texas Instruments LM2940CT-9.0/NOPB, LDO Regulator, 1A, 9 V, 10.5 → 26 Vin 3-Pin, TO-220.

Otherwise, the isolator would be: Murata Power Solutions NMG 2W Isolated DC-DC Converter Through Hole, Vin 10.8 → 13.2 V dc, Vout 9V dc. (I know that wouldn't work in front of the TI regulator because it requires 10.5V in.)


texts: Q: Whats the schematic of this Potentiometer

texts:
Just wondering what's the wiring, kinda confused on how this actually looks on a schematic.

Does this look correct?

simulate this circuit – Schematic created using CircuitLab


texts:
To measure Beta (hFe) of the transistor you should zero u_ce (voltage across CE for the AC component in signal). To zero that component you put capacitor in parallel with transistor AND as shown on the picture "b" a source of amplified (varying) signal ("e_g") in series with U_CC.

If I use my DC power supply to set Q point of the transistor, I plug it to black and red terminals on my little test board, then I should have "e_g" plugged right before a switch, so that pressing the button would apply DC + AC signal.

I know you can't do just that, as the voltage sources will eat each other, so how do I achieve that? Is the best option to use an op-amp, are there any possibilities available which do not involve op-amps?


texts:
In the current market, the chargers are only 40-50% efficient.

How much is the conversion and flux losses during transmission?
Is there any way to improve the overall efficiency?
Can a ferrite core help to reduce the losses?


texts:
I have a generator stopper which works on 220 volt AC (in India 220 volt AC is normal supply) and has an electromagnet which pulls up a lever and the generator is stopped.
It works perfectly when the mains supply is given, but when I give supply thorough my UPS it doesn't work, while the same voltage is given from UPS also.
I opened up the stopper and tried to check what final voltage it supplies to the electromagnet after passing the circuit, as the mains wire first goes to a circuit and then to the magnet and I got reading from multimeter in both AC and DC.  In AC it read as 80 volts and in DC it read around 150 volts.
How is this possible? My multimeter is also fine as I tested it in other things.


texts: Solutions to store GUI elements in an embedded systems

texts:
I have a project in mind to create a GUI using a STM32F4 microcontroller. I am currently working/playing with a STM32F469I-DISCO board that embeds a MIPI Display. I understood how to display images and others stuffs but I was wondering what are the solutions to store icons more "efficiently". What solutions are commonly used.

For now when I want, for example, display a specific icon, I create two files :

a source file icon.c that contains an array in which each element describes a pixel ;
a header file icon.h that simply contains the array prototype.

Then I include the header and use my icon when I need it. But I noticed that icons are not negligible in terms of space requirements (depends of course on the icon size, color format...).

Anyway, generally, in an embedded system (using a STM32 for example), what are the most "efficient" solutions to store everything that is related to the GUI itself ? Is an EEPROM correct ? SD Card or something else ?

Thank you !

EDIT : By efficient I mean a solution that takes the less space possible (physically). I don't have any requirements on the power consumptions side.


texts: Perpetual machine from a PN-junction diode

texts:
Consider a PN junction diode

Now, this system will naturally form a depletion region due to diffusion and will convert into this:

Now, I wish to connect the ends of this diode with a conducting wire and resistance like this:

Thus, I expect the electric field in this space to be aligned as follows (indicated dim green:)

This will make the charges in the wire accumulate in the following way:

Finally, this system will end up neutralizing all the charges so that no electric field remains inside and outside the diode; creating equilibrium state for the free charges. So, we are going to be back on a simple P-N junction diode with no depletion region and no electric fields.
However, this will again create a difference in electron concentration between N and P sides; these high-speed free electron will naturally flow from N-side to P-side creating an electric field which would later be balanced by the conducting wire.
I thus expect this cycle to go on and on leading to continuous charge flow through the resistance. Overall, the diode will be taking up heat from the surroundings, while the resistance would be releasing heat there.
Obviously I expect this analysis to be wrong, but I am not able to figure out where did I made any mistake.
PS: I asked this question originally at the Physics StackExchange, but they consider it to be similar to (https://physics.stackexchange.com/questions/108314/why-isnt-there-a-potential-difference-across-a-disconnected-diode). However, I am still not satisfied because I am not finding where I am going wrong. Simply stating that there is no potential difference across the diode is of no help.
Here, I have used basic core principles of electrodynamics only.
I would be grateful if someone points out the exact step where I am making the blunder.


texts: What does "lower" reactance (higher susceptance) mean for a physical system, and when is it "good"? I see that it has less opposition to a change in voltage or current, but what does that mean? Lower resistance makes sense to me in that current can travel more easily, but what about reactance?


texts: My ESD diodes on some specific lines are dying inconsistently

texts:
I made a PCB with 2 connectors for display connection. On one connector are fast signals (SPI + some more signal for display control (reset, A0,...)) and the second connector has signals for 4x buttons and RGB backlight control. Saving money, I have used the same ESD/TVS diode for all line protection, PESD5V0X1UB,135 (datasheet). All signals are 3,3V.
Now the diodes on the connector with SPI are always OK. But the diodes on the buttons signal lines are sometimes dying. Recently I have ordered several PCBs and on 3 of them is one or more diodes shorted after the very first power up(PCB not yet build inside the unit, just lying on ESD-safe table in room without EMI disturbances).    Edit: I am not sure if the power up is killing them. I should have said "the buttons signal lines are not working on a completely new PCB". The power up may killed them, the first button press or they were damaged before (that would be a lot of bad luck).
On the other hand there are also PCB running for 1+ year without any problems with the same configuration (which puzzles me). The PCB batch (10 PCB) I ordered a year ago had 1 PCB with this issue (I assumed I touched it and killed with it static discharge).
The buttons are switching the signal to GND. The connection and PCB layout (4-layer) is shown below. The only difference between the button line signals and the other signals line are the capacitors and pull-ups. Are they causing the issue? I find it very hard to debug as the issue is not always present + it is really hard to replace the 0402 diode placed so close to the connector. Am I using the diodes wrong?
I used oscilloscope, trying to find if there are any transients on power up or on a button press. I have not found any overshoots/undershoots or disturbance coming from the RGB control. The signal lines are always between -0V and ~3,6V and nice and smooth.

Edit 1:
Screenshot from the diode datasheet:

Edit 2:
Adding power distribution network (project names censored). On the connected PCB with the display there is R-78E9.0-0.5 datasheet generating 9V for the display.


texts: Altera Quartus Design Assistant Critical Warnings

texts:
I get a number of Critical Warnings with respect to lpm_ff and
lpm_counter:

Below are few:

Rule A102: Register output should not drive its own control signal
directly or through combinational logic - Structure 1

App:inst1|Exp_Box:inst2|lpm_ff:ff_Last_Image|dffs[0]
App:inst1|Exp_Box:inst2|_~3
App:inst1|Exp_Box:inst2|lpm_ff:ff_event_HStrig|dffs[0]

App:inst1|Expe_Box:inst2|lpm_counter:cnt_ext_HStrig|cntr_6ik:auto_generated|cout_actual

Can these warnings be ignored? Moreover I am using Altera Quartus 11.1
Web Edition. Could it be because of Open Core Plus?

ff_event_HStrig.clock       =   System_Clock;
ff_event_HStrig.data[]      =   B"1";
ff_event_HStrig.enable      =   (red_HS_trigger OR (dl_enabled AND HS_trig_deglitch)) AND (SW_Con_en OR
                                                    SW_KK_en     OR
                                                    SW_KK_ro_en OR
                                                    SW_Ser_en);
ff_event_HStrig.aclr        =   !n_Reset OR !HS_trig_deglitch OR fed_gen_ready OR !HW_Con_en_LIHext;    -- reset HS trigger signal
HS_trigger                  =   ff_event_HStrig.q[0];

cnt_ext_HStrig.clock            =   System_Clock;
cnt_ext_HStrig.cnt_en       =   10kHz_Pulse AND !cnt_ext_HStrig.cout;
cnt_ext_HStrig.aclr         =   !n_Reset OR !ff_ext_HStrig.q[0];
---------------------------------------------------------------------------
ff_ext_HStrig.clock         =   System_Clock;
ff_ext_HStrig.data[]        =   B"1";
ff_ext_HStrig.enable        =   red_HS_trigger;
ff_ext_HStrig.aclr          =   !n_Reset OR cnt_ext_HStrig.cout;

HS_trig_activated               =   ff_ext_HStrig.q[0];
---------------------------------------------------------------------------
cnt_Last_Image.clock        =   System_Clock;
cnt_Last_Image.cnt_en       =   100Hz_Pulse AND ff_Last_Image.q[0] AND !cnt_Last_Image.cout;
cnt_Last_Image.aclr     =   !n_Reset OR HW_Con_en;

ff_cnt_LIH_out.clock        =   System_Clock;
ff_cnt_LIH_out.data[0]      =   cnt_Last_Image.cout;
ff_cnt_LIH_out.enable       =   B"1";
ff_cnt_LIH_out.aclr         =   !n_Reset OR HW_Con_en;

cnt_Last_Image_fix.clock        =   System_Clock;
cnt_Last_Image_fix.cnt_en   =   100Hz_Pulse AND ff_Last_Image.q[0] AND !cnt_Last_Image_fix.cout;
cnt_Last_Image_fix.aclr     =   !n_Reset OR HW_Con_en;

ff_Last_Image.clock         =   System_Clock;
ff_Last_Image.data[0]       =   B"1";
ff_Last_Image.enable        =   fed_HW_Con_en AND LIH_en;
ff_Last_Image.aclr          =   !n_Reset OR (cnt_Last_Image.cout AND (!HS_trigger OR LIH_ro)) OR !LIH_en OR HW_Con_en OR cnt_Last_Image_fix.cout;

LIH_active                          =   ff_Last_Image.q[0];
LIH_activated                       =   LIH_active;

Regards!


texts: Energising Electrostatic Charge Into Nylon Ribbons? Is it possible?

texts:
Forgive me for how high level this is but this is the goal I'm trying to achieve here:

I want to build a device that has dangling ribbons of a material (lets say nylon for now) that can be actuated to turn electrostatic attraction on and off. The idea here is that these ribbons will be collecting floating pollen in the air using the electrostatic, and later released by turning the electrostatic off. The device would resemble something of a wind chime, just nylon ribbons instead of pipes.

My question is then: how (if at all possible) do I apply and then remove electrostatic charge from a collection of ribbons?

EDIT: This will be an aerial project (from a drone) using an onboard 12 V distribution board from a 3 cell 75 C lipo battery.


texts:
I'm trying to build a very simple headphone amplifier for my bass guitar. The bass has a built-in amplifier, meaning that unity-gain is sufficient for my amplifier, I essentially only need a voltage buffer.

To this end, I've used an LM358 (because that's what I had laying around) and a BC547 / BC557 push-pull output stage. Supply voltage is 9V which is overkill, since my signal is no more than 2 Vpp.

The problem is, that the output signal that I'm hearing is quite distorted. I can hear the clean signal but there are some undesired high-frequency components as well. Using an oscilloscope I was able to verify that the distortion is not due to clipping. However, I don't have a function generator, so I can't test if the culprit is cross-over distortion (shouldn't be though, since I've added biasing) or if there's some parasitic oscillation going on.

Anybody see a problem with the circuit right away?

simulate this circuit – Schematic created using CircuitLab

Thanks

Edit: I've been able to get a hold of a function generator. Here's a new scope screen capture (10kHz sinusoidal input) which seems to show some funny business around the zero-crossing. Blue = input, purple = output


texts: WatchDog control (MAX6369KA+T) with a Microcontroller (Atmega328P)

texts:
There is a hardware watchdog MAX6369KA+T, which has the functions of setting the standby time and enable / disable via contacts (SET0 / SET1 / SET2).

At the moment, I control them using external transistors S9018.

Using transistors slightly increases the size of the circuit.

Tell me, will it be the right decision to remove the transistors and connect the control pins directly to the microcontroller? The maximum current of each contact of the microcontroller is 25 mA. Are any limiting resistors needed for this purpose?


texts: Reducing noise in microphone amplifier circuit at higher gains

texts:
I am using the below circuit to amplify the signal from an electret condenser microphone for analysis by a microcontroller to detect short bursts of sound. The circuit runs off a ~4.5V supply from 3 AA batteries, so options for opamps are limited. I am using an NJM4580D. Datasheets for microphone and opamp linked below:
https://www.cuidevices.com/product/resource/cma-4544pf-w.pdf
https://www.njr.com/electronic_device/PDF/NJM4580_E.pdf

Circuit includes a potentiometer to adjust gain on second stage. The circuit is working fine at low gains with louder sound bursts, but I am having an issue with the noise at the higher gains required to detect fainter sound bursts.
Low Gain

Higher Gain

The noise appears to be approx 580Hz. The room is quiet prior to sound bursts. The circuit is built on protoboard, and size is somewhat limited. Photo below:

So, given the limitations on power supply and construction, is there anything I could do to reduce the amplitude of the noise while maintaining the signal strength at higher gains?
Appreciate any feedback.
EDIT 1
Brian appears to be correct. I removed the microphone circuit board and powered directly from 4.5V batteries. At max gain, the noise was acceptable:

The rest of the circuit board that this device is connected to is fairly straightforward. I don't have a presentable schematic at the moment but it is constructed in a manner similar to the microphone circuitand made up of the following components:
The microcontroller is an ATMEGA328P
https://ww1.microchip.com/downloads/en/DeviceDoc/ATmega48A-PA-88A-PA-168A-PA-328-P-DS-DS40002061B.pdf
MAX7219 driven 8-digit segmented display
https://datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdf
Pair of SN74HC165N shift registers for keypad input (momentary pushbutton array)
https://www.ti.com/lit/ds/symlink/sn74hc165.pdf?ts=1607932478460
SN74HC125N buffer on SPI MISO line
https://www.ti.com/lit/ds/scls104e/scls104e.pdf?ts=1608013220070
100nF decoupling is provided at each IC power pin and I have a couple of 100uF electrolytic capacitors on the power rails.
Any thoughts as to what might be causing instability/interference?
EDIT 2
As suggested by Andy, I tried a different op-amp, the MCP6022, which I was able to drop into the existing circuit and the difference in output range is remarkable:

In addition to this, I took Brian's advice and added a 470uF capacitor to the power rails at on the mic board, which also helped significantly:

Finally, I added a 10ohm resistor in series with the power supply to the mic board and it also produced a noticeable reduction:

Original op-amp with the additional capacitor and resistor, for reference:


texts: Mounting BGA package on PCB with force without reflow

texts:
I was searching for a method to use a BGA based MCU on PCB which could be easier to change frequently. There are sockets for this purpose but I want to ask what if I simply put MCU on the right place and then hold it with a 3D printed holder with some force. This idea is storming in my mind but a question is raising frequently if it is possible or not, will it work??
Any help with this??
Thank you.


texts: Which one is more dangerous to human body among high voltage or current and their AC and DC versions?

texts:
I have already gone through many similar questions but none seems to quench my thirst to know.
Take the example two different sources A and B, as -

A = 1000 V & 1A

B = 1 V & 1000A

Note - Consider the given parameters that are fixed(constant) using circuits.

So which one is more lethal to the human body?
Looking to have a clear and crisp explanation.


texts: Modular multilevel converter (MMC) - effect of 3rd order injection on circulating current

texts: In a typical MMC as shown here, how can I mathematically prove that a sine-triangular PWM with 3rd order harmonic injection will cause 4th order harmonics in the circulating current? The MMC consists of submodules of half-bridge DC-AC converter as shown in the picture.


texts:
Possible Duplicate:
  I'd like to learn how to make my own USB gadgets
  How to build a USB controller having knobs, sliders, and switches

I need to activate a relay via USB, using a program made with any language.

Someone have simple schematics to show me, or some information on how this works?


texts: Can UHF rfid pass thorugh few layers of clothes in a smart shopping system?

texts: I am working on a smart shopping system and would like to know if a UHF rfid signal can pass through few layers of clothes in a bag as multiple clothes would be present in a bag and system has to detect it correctly.


texts: What is the best way to filter out noise on data line?

texts:
I am working on a product that has a controller connected to a device via an 8 conductor cable (an ethernet cable). The cable length varies depending on where the device is installed but the length varies from 15 to 30 feet. The device being controlled consists of a stepper motor, a digital temperature sensor and a limit switch. The controller outputs pulses to the four stepper motor wires to move the motor. The temperature sensor outputs a 0 to 5V square-ish wave that has a variable duty cycle proportional to the current temperature. The temperature sensor signal has a nominal frequency of about 50Hz. The controller monitors this signal to compute the current temperature at the device. The stepper motor driver is a constant current driver which means it pulses the motor on and off very quickly to keep the current through the coil at a set amount. This pulsing can occur upwards of 100kHz and the voltage switches from 0 to 12 Volts.

There are several problems occurring. Fist of all, the signal from output of the temperature sensor is being induced on the 5VDC supply voltage for the temperature sensor. This makes the supply voltage very inconsistent and noisy. I have tried putting a 10uF capacitor, and smaller ones, between this signal and ground inside the controlled device and that helps a bit but I can still see ripple. Is there a better way to get rid of this ripple that is at about 50Hz?

The next problem occurs when the stepper controller is pulsing the motor to provide holding torque. The controller pulses the motor at around 100KHz and this also causes noise on the temperature probe signal, the 5VDC signal, and the ground when measured at the controlled device.

The controlled device does have a small circuit board inside it so I do have some room to play with filtering techniques there. Do you have any suggestions? I would think that sending stepper motor controls and other digital data down the same cable is a rather common thing to do so there must be an intelligent way to get rid of the noise.

NOTE: I don't think changing the cable type is an option because of backward compatibility issues.


texts: This circuit is in a vintage electric car. The 12 volt circuit works perfectly alone. The 36 volt circuit works perfectly alone. When both circuits are activated the contactor points bounce open and closed open and closed and the lights go on and off on and off.  What can I do to make this system function properly?  Thanks.  John


texts: Chattering relay on microcontroller power supply

texts:
I am working with a device that has a relay on the 12v power supply to the micro controller that runs the device. Under certain unplanned circumstances this relay can chatter.

What is the potential for memory corruption/unpredictable operation of the micro controller, and
if the chattering relay causes problems for the micro controller, what is the most likely nature and effects of those problems.

The micro controller operates numerous other subsystems and has many digital inputs from sensors. The relay is located within inches of the micro-controller and its exposed I/O wiring.


texts: LED mixing: 2 off-line drivers vs 1 powersupply + 2 buck converters

texts:
I want to drive two sets of 3 LEDs. They are all 35V but the two sets differ in color spectra and current: the first set needs 900mA the other 500mA.

I want to freely mix the two sets using PWM, so that the total power consumption always stays between 72W and 100W.

One easy way  to do this would be to connect each set in series and use two dimmable drivers (e.g. ELG-100-C).
But this seems to be quite a waste in terms of cost and size; and probably also efficiency considering one of the drivers might be much less utilized at any given time.

It seems to me a cleaner way is to use a 100W power supply and 2 buck converters.

But I have trouble finding an off the shelf constant current buck converter that supports PWM dimming and the 105V needed. Nor any reference design for such a thing.

Using boost converters seems to be more common - but this is likely to be less efficient. Another possibility around this would be to drive the sets in parallel and use a current mirror (or a more fancy LED balancer) - not sure how this fares efficiency wise.

My main questions are:

Is using 2 buck converters a good idea worth investigating further? (Any pointers would be nice!)
Is there another easy solution I'm missing?
Am I in way over my head? I had some EE classes during my Computer Engineering Bachelor, and now again skimmed Chapter 9 of the Art of Electronics.

I am willing to dive into the material but want to avoid to find out I spent months working on an idea that was doomed from the start - because I won't be able to match (or exceed) the efficiency of two professional 100W LED drivers.


texts: What cap value to use for window “box” fan?

texts:
Two years ago a 3-speed 19” (50 cm) 120vac window “box” fan stopped turning. I guessed the cap died so sourced a replacement and installed it. This didn’t fix the problem.
Now I’m getting back to diagnosing it. With the blade removed I now see that the motor hums and if I spin it, it will run fast (can’t say if this is the rated speed). This is when powering the motor’s high-speed leads, bypassing the 3-speed switch.
It’s not a mechanical issue—with power off the armature spins freely.
I don’t remember the original cap markings but this one is marked “PMS405J” and measures 4 uF. I’m usually good at looking up markings and matching replacement components but there’s always the possibility I couldn’t find the exact one and tried a different value.
Should I sub 2, 1.5, 1.2 uF caps and just see what works? How will I know when the value is correct? I presume torque and speed are max at one value and reduced at others?
I’ve watched countless videos of repairs of 120v fans and they used caps from 7 to 1.2 uF, so no joy looking for statistical help.
Suggestions welcome.
Thanks.
EDIT: I realize I’m going on the premise that the original cause IS a failed cap. Other ideas welcome.


texts: Advice/ techniques in non-invasive nA-range current reading

texts:
My current (perhaps outdated) knowledge tells me that portable current clamp meters are meant for high current readings only. Can portable current clamp meters measure down to uA-range, or even nA-range readings?
I've measured pA and nA currents through lab equipment before, but bringing them out in the field is not an option this time.
To add, the wires from which the measurement are to be taken are short and rigidly mounted. As such, current magnification through looping is not possible. For this, I'd like to ask for techniques in non-invasive nA-range current (expecting 10nA minimum reading)using a plain current clamp meter with a minimum measurement capability of 10mA.


texts:
I'm a safe engineer and have little to no idea regarding electrical engineering,  however I'm more than capable of soldering components and very willing to learn but also begrudge spending £300 for a sound amplification system (again!!)

I've seen a couple systems that people have made themselfs but not inquired further as to ask for a component list etc.
I understand the basics (very basic) I realise I'll need mic's to pick up the sound and that the circuit will need to amplify the sound into a pair of earphones in order for me to deduce what is going on through a couple inches of steel!!

Advice on components required etc etc. I have looked into it in some detail but as yet I'm at a loss. What I can say is they seem to be  similar in construction to covert listening devices ie the ones that listen through walls etc but still would not know where to begin So I thought I would come to the experts.


texts: Modeling magnetic levitation system with current as the input signal

texts:
I am exploring magnetic levitation system as a part of studying control system. The height of the ball levitating in a magnetic field is described by the following differential equation
$$ m\frac{d^2H}{dt^2} = mg-K\frac{I^2}{H^2} $$
And I got the following non-linear state-space equations for the system
$$\begin{bmatrix}\dot{x_1} \\ \dot{x_2} \\ \dot{x_3}\end{bmatrix} = \begin{bmatrix}x_2 \\ g-\frac{K}{m}(\frac{x_3}{x_1})^2 \\ -\frac{R}{L}x_3+\frac{2K}{L}\frac{x_2x_3}{x_1^2}\end{bmatrix}$$
And upon linearization, I got the following state-space paramters.
$$ A = \begin{bmatrix}0 & 1 & 0\\\frac{Kx_{03}^2}{mx_{01}^3} & 0 & \frac{-2Kx_{03}}{mx_{01}^2}\\0 & \frac{2Kx_{03}}{Lx_{01}^3} & -\frac{R}{L}\end{bmatrix}
$$
$$
B = \begin{bmatrix}0 \\ 0 \\ \frac{1}{L}\end{bmatrix}
$$
$$
C = \begin{bmatrix}1 & 0 & 0 \\ \end{bmatrix}
$$
$$
D = \begin{bmatrix}0 \end{bmatrix}
$$
In the above equation $$ x_{01},x_{02},x_{03} = H, v, I $$ at equilibrium. H is the height of the ball and v is the velocity and I is the current.
However, in the above equations, current is not treated as the input signal but the voltage provided to electromagnet is taken as the input signal and the inductance and resistance of the electromagnets are also taken into account.
My doubt is how do I find the state-space equations and A, B, C, D when parameters like input voltage, inductance and resistance are ignored and the current is taken as input signal. How will each of the above steps change in such a case?
The above values of A, B, C, D will result in a transfer function with a cubic polynomial in denominator. What I basically want is a simplified one with transfer function of the form $$ \frac{A}{s^2-b^2}$$


texts:
Suppose I have a fixed voltage supply of 10 V and I need to get 20 amp-turns from my solenoid coil but my solenoid coil with 10 turns is 10 ohms, so I am getting 10V/10 ohms = 1A,  1A * 10 turns = 10 amp turns.

Can I take my coil and instead take the wire and cut it in half and wind both halves at the same time.  So now I have two 5 turn coils in parallel, each with 5 ohms resistance.  So I do the calculation and get
10V/5 ohms = 2A for each coil, 2A * 5 turns = 10 amp-turns for each coil,
So now I have 20 amp-turns total on my coil.

Therefore making my solenoid 4 times stronger?

Is this right or am I missing some fundamental law of electromagnetism?

Thank you


texts: Why is an H bridge needed in a bidirectional motor control circuit?

texts:
I'm trying to understand figure IV in this article about controlling motors, and I do not see why the H bridge is needed. As best as I can tell, this is so that if the motor is stopped (by making the two inputs equal) then the back EMF can be snubbed and avoid damage to the IC. Is this right?

If so, I do not understand the comment that says the diodes must be able to pass the full current of the motor, because it seems they would only be used when the motor is stopped, which would produce only a transient current through the H bridge, and not pass current while the motor is being run.

Would another way of avoiding such damage be to slowly wind the motor down by reducing the PWM duty cycle on the enable line?

Would another way be to turn off the enable line? I guess in that case, you get coasting stop (which might not be what you want)?


texts: Why do most of the non-volatile memories have logical 1 as the default state?

texts:
I have used non volatile memory, like EEPROM and FLASH memory, in embedded applications and I have always found that unused memory (EEPROM/FLASH) bit locations are always set to 1 by default. Why is this used instead of 0?

For example an address, say 0th address (first byte of memory), if not written to by the user, always stores 0xff and not 0x00. Why is it that people who built the memory chips kept it that way? I'm sure keeping the default memory location as 0xff would provide some advantage or something important for the manufacturer.

What is the reason behind this structure in memory chips?


texts: What is the COM terminal on a DC Power Supply?

texts:
We have a HP E3631A power supply at my university's lab. There are 6 ports. My questions are as follows.

What is the green port titled 240VDC Max? I was explained to an extent that it was the ground associated with the ground of the building. I'm just not understanding it completely and why there is such an option.

Under the 25V option there is a black port titled "COM" between the two red ports. Why is it titled COM? What does this mean? I know this is the port I ground to everyday when I use this but don't know why it's called "COM".

Under the 25V option there are two red ports and the black port titled "COM" as I mentioned above. I'm confused why one of the red ports is titled "-". Does this have something to do with polarity? Could someone explain the definition or use behind this red port titled "-"?

Thanks for any help.


texts:
I saw XL6009 Link for XL6009, DC DC Converter buck boost converter module. After seeing the circuit diagram XL6009 Circuit diagram, I see the output voltage is controlled by using the Pot over there.
Can we control the output by designing our own control system using current sensors, voltage sensors and MCU for varying duty cycle using PWM.


texts: ESP8266 Wifi for http server: What are pros and cons with different libraries/approaches?

texts:
I have found the following options so far for getting an http server running on an ESP8266:

NodeMCU exemplified by e.g. this tutorial
Arduino ESP8266 library exemplified by e.g Adafruit here
mbed ESP8266 library
ESP-HTTPD
Sparkfun's hookup guide

What are pros and cons with the different libraries/approaches? E.g. performance, ease of use (for programmer) available storage left for "web content".

Are there other good options?


texts: Switching between low voltage recording of biologic signal, to high voltage stimulation

texts:
I am recording a biopotential signals (EEG ~microvolts), which I pass to a digital amplifier circuit (ADS1299). I am recording 8 channels. I would like to switch channels, one by one, with a voltage-controlled stimulation source.
I'm wondering if I could use an analog switch, to switch between the two inputs. I'm not sure if an analog multiplex would work. I'm worried about noise, since the signals are so small before the amplifier. I made a picture if it helps. It's supposed to show that channel 1 is connected to the stimulator, while channels 2-8 are connected to the amplifier.


texts: What are some 'gotchas' of high-frequency board design?

texts:
I'd like to design a PCB for an analog loop controller.. something with an A/D, D/A, and processor on board.  (Either DSP or FPGA, I haven't decided.)  Since this should modulate analog signals at 10 kHz, it needs to be quite a fast processor.

From what I understand, designing a board for processors running above 150 MHz or so can be very challenging due to RF problems.  What are some advice you can provide in designing such a board?  What problems due to layout can occur?  Are there any good online resources that have knowledge bases for this?

Thanks.


texts:
I'm having trouble configuring the USART6 in my STM32F746NG. I am setting up the USART6 to enable UART comunication, using the code below to initiate it and also create an echo function.

    __USART6_CLK_ENABLE();

GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.Pin = GPIO_PIN_7;
GPIO_InitStructure.Mode = GPIO_MODE_AF_PP;
GPIO_InitStructure.Alternate = GPIO_AF8_USART6;
GPIO_InitStructure.Speed = GPIO_SPEED_HIGH;
GPIO_InitStructure.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOC, &GPIO_InitStructure);

GPIO_InitStructure.Pin = GPIO_PIN_6;
GPIO_InitStructure.Mode = GPIO_MODE_AF_OD;
HAL_GPIO_Init(GPIOC, &GPIO_InitStructure);

static UART_HandleTypeDef s_UARTHandle;

s_UARTHandle.Instance        = USART6;
s_UARTHandle.Init.BaudRate   = 115200;
s_UARTHandle.Init.WordLength = UART_WORDLENGTH_8B;
s_UARTHandle.Init.StopBits   = UART_STOPBITS_1;
s_UARTHandle.Init.Parity     = UART_PARITY_NONE;
s_UARTHandle.Init.HwFlowCtl  = UART_HWCONTROL_NONE;
s_UARTHandle.Init.Mode       = UART_MODE_TX_RX;
HAL_USART_Init(&s_UARTHandle);

  char generic_buffer;

    for (;;)
{
  HAL_UART_Receive(&s_UARTHandle,generic_buffer,1, HAL_MAX_DELAY);
  HAL_UART_Transmit(&s_UARTHandle,generic_buffer, sizeof(generic_buffer), HAL_MAX_DELAY);

}

But the code is not working, is there something missing in the configuration? I'm using the same code that worked in my STM32F407VG, changing the USART name and pins.


texts:
I'm trying to build a FM transmitter, but without sucess. The current schematic I'm using is this one:

The alternating current at the (+) of the op amp is the P2 output of my phone.
V3 and V4 are 2 switching power supplies connected into the AC outlet.
I am trying to calculate the inductor with this site: https://m0ukd.com/calculators/air-cored-inductor-calculator/
The wire I'm using to build the inductor is from an UTP cable. The multimeter that I have is very simple, and I can't measure the inductance of the coil. I'm trying to tune this on the radio of my other phone, and can't get it to work. I'm building this on a breadboard. I would appreciate it if someone could help me.


texts: Quartz oscillator using a large irregular (natural) piece of quartz crystal for maximum Q?

texts:
Background

Based on helpful comments and links here and also from my question on the physics stackexchange, I have learned that the quartz crystals are nature's transducers of energy, allowing electrical energy to be converted into mechanical energy (and vice-versa). Furthermore, the Piezoelectrical properties of quartz crystals used in circuitry are best utilized by slicing (or growing) the quartz crystal in precise planes in order to facilitate the electrical conductivity across the physical lattice structure perfectly (even though energy is lost in this conversion). Lastly, "twinning" describes the natural "irregularity" from the divergent growth of crystalline structures in natural quartz that causes an inherent dampening of electrical potential, and consequently, less Q or oscillations. Therefore, as I understand the subject so far, hooking up electrodes to opposite "polar" ends of a natural quartz crystal without consideration for the physical internal lattice structure is possible to achieve low frequency oscillations, but electrically inefficient and unpredictable in the amount of amplification needed to overcome the low induction potential for piezoelectric oscillations.

Question

How do I build a quartz oscillator for a large pieces of quartz crystal ranging from a gram in weight up to several grams in weight (palm-sized and larger) for maximum Q? I would like to know what circuitry, components, voltages, amperage, and current to use to achieve some range of safe oscillation frequency for vibrating a large, irregular (natural) piece of quartz. I imagine that hooking up cathode and anode leads of hot current to a large crystal could be quite dangerous to experiment around with, from risk of electric fire to even the crystal exploding. I imagine that I would use a amplifier dial-in the desired oscillations. The oscillations do not have to be regular or precise in form, but should be maximally efficient.

Here is the best video on Youtube that I could find showing a computer simulation of my basic intention at 2:20: https://www.youtube.com/watch?v=1pM6uD8nePo

Here is the best link on physics.stackexchange that I could find:
https://physics.stackexchange.com/questions/187604/vibration-of-quartz-crystal

Update

I am not attempting to make my own crystal by slicing, cutting, or grinding raw quartz, although I appreciate the interest and resources provided by the community in this direction. My sister question from the physics stackexchange is about oscillating a chunk of quartz by overcoming the known piezoelectric limitations of irregularly-structured natural quartz, and my question here is about the practical implementation of safely and efficiently applying voltage to a piece of tectosilicate mineral formation for maximum Q. Based on the answers so far, it appears that placing the electrodes on the sides of the crystal (versus the polar ends) will allow for better piezoelectric coupling. Additionally, my local Radioshack does not sell circuit amplifiers (just audio amplifiers). Any direction or help on building an amplifier (or safely modifying an audio amplifier) to adjust the amplitude of raw voltage going to the crystal would be greatly appreciated (I'm not sure if this should be a separate question). In conclusion, this questions is less about circuits and more about how a layperson should get a chunk of quartz safely between two electrodes.


texts: Need to know battery configuration for a 250 watts inverter

texts:
I have  a 12 Volt inverter which have ability to produce 250 W output. I would like to purchase a battery for this. can any one tell me the configuration of battery ?
eg: Minimum AH


texts: Selecting potentiometer for adjusting Vo in DC-DC step down

texts:
I am trying to figure out the correct value of a potentiomenter for trimming Vo in a step-down DC/DC converter. I am using a 150W 12V output DC/DC from murata. From the datasheet, equations are given to build a resistive network to adjust the DC/DC. Also from the datasheet, option to use a potentiometer is suggested. The problem is that it is not clear if the equations for the resistive network are also valid when using a potentiometer.

These equations can be seen in page 33 of the datasheet:
http://power.murata.com/datasheet?/data/power/uee150w.pdf

From the equations, I have calculated that a 20% trim down can be achieved with a resistor of 15k33 Ohm, and a 10% trim up with a resistor of 488K Ohm.

Many manufacturers offer the same equations for resistive networks for different step-down converters, though none specify an appropiate value for a potentiometer.

I thought of using a 2M potentiometer, but I suspect a much lower value could be used. Am I right?
Thank you very much.


texts: 75 Ohm Coaxial Cable Used On a 600 Ohm Output

texts:
I'm working on restoring an HP 211A square-wave generator and I'm looking to add a shielded cable to the 600 ohm output. I've got some spare 75 ohm RG59 cabling and I was wanting to know if using that would have any detrimental effects on the output such as signal loss due to the impedance mismatching. The length of cable will be 10" - 12", the output will be between 1Hz and 1MHz and mostly used on loads like oscilloscopes and maybe stereo receivers.
To clarify, the RG59 cabling would run from the V10 and V11 plates to the wiper on R71, and then another cable from the non-grounded pin of R71 to the output screw post. I'd likely use 75 ohm cabling to run to any devices on the output though anyways.
Thank you.


texts: Purpose of resistors on SDIO lines and antenna matching circuit?

texts:
What is the purpose of R40....R45 and pull-up resistors R46....R50 on SDIO lines as shown below?

Is it really necessary to have L51, C52 & C53 matching circuit for antenna?


texts: Can water condensation appear on PCB in IP67 enclosure box?

texts:
Does IP67 box protect PCB from moisture?

If not, is it OK to have an outdoor air humidity sensor soldered on PCB in IP67 housing?

Also if it doesn't block moisture, is there any reason to use IP65/IP66/IP67 housing, if there isn't chance for water to directly come inside box?

Thank you.

Edit: It's a weight scale, it only works few seconds per day so there isn't heating inside the box.


texts: electronic device to manage power demand

texts:
I want to start let's say 20 motors (110V, starting current 40A) for 5 seconds in the same time but my power supply can't handle more than 10 motors. There is any electronic device who can manage my power so I can run these 20 motors for 5 seconds in minimum amount of time: 10 seconds?

Thank you


texts: How to properly use the 4N25 Optocoupler

texts:
I am using a 4N25 (datasheet) in my project and just had a few questions about it. First what I do not understand is that pin 6 is a base pin, but whenever I look up a tutorial for how to use it online they just ignore it. I was wondering what the purpose of that is and how to use it (and if I need to use it). Secondly, if I do ignore it, will I be able to control 12V 70mA with an Arduino digital pin?

TLDR; What is the base pin for? Can I use an arduino to control 12V 70mA load?

Thanks in advance!


texts: Why is the PCB part number traditionally on a copper layer?

texts: I'm an experienced board designer, having designed 100+ boards over the past decade, and I have yet to hear a good answer for why the PCB part number is traditionally on an external copper layer, and the PCBA part number is on a silkscreen layer. To me copper is always "sacred" and should not have anything unnecessary on it, as this can screw up voltage isolation, RF performance, etc. But for some reason designs tend to have the bare PCB part number in copper instead of silkscreen. Why?


texts: Recommend motor type to turn baby rocker, into auto-rocker

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Would like to convert a baby bouncer (like this one), which requires continuous manual effort to rock it, into one that use electro-mechanical means to auto-bounce. However, my aim is to make these on the cheap (as all of my other projects so far have). So I am on the look out for alternative design approaches or parts.

My idea is to place a low RPM, high torque (unable to quantify, since I've not work with DC motors, beyond the ones found in small toy cars etc.), DC motor (brushless?), which periodically winds (like a winch) pulling the bouncer seat to the low-position, and then (here is where, I am not sure, it is right or feasible to do with standard DC brushless motor), just de-energise the motor, for the bouncer to bounce up, and have few naturally dampened oscillations (bounces), and then repeat the process.

Is the above approach correct ? Will de-energising the motor, and the rapid unwinding in opposite direction, make it act like a dynamo and feed current back into the circuit ? Can that harm the motor ? Will stepper motor be a better approach ?


texts: Understanding Phase frequency detector logic

texts:
I have one of these common digital phase lock loops which compares the frequency and phase with a VCO (local oscillator) via a phase lock loop. I failed to understand why Figure (2) (A) and Figure (2)(B) seems to follow very different logic despite they are the same device.

How does one know what OUT look like given the form of signal from +IN and -IN?


texts: What to use for the high-side (anode) drivers of a common anode LED matrix?

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I'd like to multiplex rows of LEDs with a constant current sink driver. Should I just use BJTs to switch current into the rows of anodes, or is it better to use FETs, an array of FETs, or the same packaged into a convenient IC? It's easy to find current sinking ICs but I'm not sure what to search for on the sourcing side.

I would like to build something substantially similar to the Rainbowduino, http://nkcelectronics.com/rainbowduino-led-driver-platform.html . The Rainbowduino lights 24 LEDs at once with 24 current sinks and one current source using a Darlington array as the so-called "Super Source Driver", then it lights the next row of 24 and so on for 8 rows. Very standard. I would like to find a substitute for their unavailable-in-the-USA Darlington array. What do I need search for on digikey/Mouser to find an IC containing an array of current sources?


texts: Trying to understand what I'm seeing on my oscilloscope

texts:
I've been working on this project on and off for some months now and am really at a loss as to the nature of the signal I'm seeing - really hoping someone can help me out with this.

Let me start off by saying that I have much more experience with software than hardware - no EE degree, total hobbyist/hack, but I have been so for over 40 years, so I've got a certain level of experience.

A few months ago, I started playing around with a type of preexisting metal detector circuit board, used to detect the metal in cars. Connected to the circuit board is a large loop of wire, coming out of the circuit is a very simple NO/NC relay. As far as the contents of the circuit go, I don't really know, although it does contain a 16F628A PIC microcontroller, which is significant for several reasons (more on this later). It also contains a two pair transformer, where one pair goes to the coil that detects the car, and the other coil goes into the circuit on the board. I'm fairly certain that the circuit implements a Colpitt's oscillator, which is what is actually performing the detection.

Anyway, I have found two important things poking around on the board with an oscilloscope, while the device is running;

A 0.1 second pulse (approximate) is generated by the PIC chip and
used to excite the loop of wire.
A modified pulse comes back into the PIC chip that appears to give
the PIC the information it needs to make the decision if a car is
there or not.

All of the other pins on the PIC are fairly uninteresting - ground, power, clock, relay output, etc.

Good so far - as I said, I believe that second pin contains the key to the decision making process (car or no car). Here's where my problem starts. I've attached two photographs to this post - one showing the waveform of that modified pulse when no metal is present, and the other one showing the waveform when there is metal. I can see the difference - in fact, I can see the difference when I start approaching the loop with my metal object (toolbox) even before the relay clicks. But I can't seem to measure, or even understand the nature of, the change in the waveform! As can be seen in the images, the change is slight - it's some sort of characteristic of the pulse train, just can't understand what it is though.

So, here's what I did next - I attached the two lines to a simple Raspberry pi circuit. My plan was to perform maybe an A/D conversion and also try to examine the frequency of the signal, along with the pulse width. I mean, the information must be buried in there somewhere, right? It does work...and quite well!

But I have found nothing - the A/D showed that the signal is binary in nature (which was expected, because the PIC chip has no built in A/D converter ), and I don't see the pulse width or frequency changing with respect to the presense or absence of metal. I just can't figure this one out!

So, back to the scope - I feel like if I just understood what I was seeing on the screen, I could know how to measure what was there.

Anyway, take a look at the images I've attached and ask me questions - I am certain I've left some huge holes in my description. I will do my best to get you answers! Thank you so much in advance! This problem is just killing me!!!!

Respectfully,
Marshall

No metal

Metal


texts:
For example 8x8 small image stored on eeprom will get corrupt over time?
I've seen somewhere eeproms losing their data over time like vhs tapes.


texts:
We have a newborn and rely on hand sanitizer when changing diapers, and we ran out at an inopportune moment in history. By some stroke of luck, I managed to snag one of those "industrial" touchless foaming hand sanitizer dispensers and a couple of refill bags off an office supply site. The bags are Purell branded and the dispenser is branded by the office supply store and made by a company called Brighton. The form factor of both the bags and the dispenser is something called LTX (1200ml).

Unbeknownst to me at the time of purchase, the bags are somehow incompatible with the dispenser. Namely, there is what seems to be a little RFID wand embedded in each bag, and the dispenser refuses to use the bags unless they are of the same brand. The wands on my bags are marked "LBL 9214" (photo attached).

Does anyone know anything about this system? Can it be hacked? Online searches turn up absolutely nothing. I'd really like to be able to sanitize my hands, and buying the right/matching equipment is simply impossible right now.