texts:
I know that static electricity can damage components, even if it does not destroy them or “break them” studies and tests have shown that it could decrease performance even a little if no noticeable damaged happened. Does the same principle apply to the issue below?

While working on a broken air conditioning unit and seeing if it would work (cable was completely cut and unit was dropped from a windows), I was  not going to go through the hassle of putting rubber on them or a coating if I am just testing if it will work, the exposed wires touched by accident and short circuited.

My apartment is small so the bedroom has all my electronics and they were on the same circuit/circuit breaker as the short circuited AC unit. The circuit breaker did go off but I was wondering since the extra amps and electricity caused by the short circuit was on the same circuit as my electronics like TV, router, etc, could of it gotten damaged even a little. Because before the circuit breaker caught it it could of cycled throughout the same circuit.

Also do regular power outlets have some sort of mechanism to burn themselves out or stop the short circuit?


texts: How does an autoradio suppress transient, switching "plop" generated by an external audio source?

texts:
Out of curiosity I'd like to know how an autoradio device works. Maybe it' not how they all work and my case is just an exception but here it is.

I have a car TV tuner that is used to switch between its TV channel and an external source. Switching sources with the TV tuner produces a "plop" when the tuner is connected to a car amplifier. A a matter of fact, I have measured a DC component at the output of the tuner when it switches to the external source, which should not happen.

Out of curiosity, my colleague has connected the tuner's audio output (standard cinch plugs) to an autoradio. Strangely enough there's no more "plop" noise when the tuner switches between sources.

I didn't know autoradio devices could do that. There's no magic, I know. So I wonder how this one implements such a noise suppression. Is the input audio signal delayed so that a pre-processor can detect a potential DC component and suppress it shortly afterwards? Is it some kind of squelch control? Or is it something else?


texts: Simulate Step down chopper circuit using any Electrical Engineering software

texts:
Here's my attempt:

Could someone tell me where is my mistake ? Or simulate answer the question using any other software,please ?


texts:
I am working on an appliance project in which I have been tasked with the design of the power supply. The project specifications hold that from a 230v 50Hz wall supply two voltage rails of 5v (for small dc motors and some ICs) and 3.3v (for micro controllers) are to be supplied to other subsystems. In addition the power subsystem will need to keep a small fully charged battery and be able to detect when mains power is cut and supply the 5v and 3.3v rails from the battery instead. The aim of the project is to do as much of the design with discrete components where possible without being unreasonable (i.e we are allowed to use ICs if it would prove unnecessarily difficult to implement with discrete components.)

I began with a full bridge rectifier to step down 230v wall supply to 12v.

I also found this circuit that makes use of transistors to replace a regulator IC. I was thinking of repeating this circuit twice with different values of the variable resistor (which is R4 in the circuit) in each to adjust the output to the desired 5v and 3.3v from 12v.

I'm now trying to figure out the best way to implement the backup system. I was thinking of using a LiPo 1000 mAh 7.4V battery (https://www.robotics.org.za/603450?search=lipo) together with a charging IC to charge the circuit and then use the same regulator circuits to get 3.3v and 5v. The problem with this is that that R4 resistor is tweaked for a 12v input and not a 7.4v (which would of course get less as the charge dies). I'm not sure what the best approach would be in terms of the regulators although I would like to keep these as low level as possible rather than buying ICs off the shelf.

I will obviously need a way to detect when mains power is cut but I also need to be able to charge the battery from mains when it is connected. I am a very inexperienced designer and so any tips or pointers in the right direction on the best way to do this would be much appreciated.


texts: How to simulate zener and normal silicon diodes in series to obtain IV curve (with icaps or any other simulation packages)?

texts:
I am trying to obtain the resultant IV curve of the combination of several zener diodes and a normal silicon diode in series.

As the zener diode would be working in reversed biased (and it is installed reversed). How do you incorporate that into ICAPS?

Has anyone attempted to do this via simulation? An ICAPS example would help a lot!


texts:
I am a bit confused about the operating voltage of LED's.

I have an RGB led controller that uses 12VDC.

I looked up a RGB led on mouser such as this one:

http://www.mouser.com/ds/2/216/WP154A4SUREQBFZGC-194997.pdf

The datasheet doesn't really say anything about the max voltage I can use on the LED.   The datasheet does say the total current should be around 20mA.

Using Ohm's law if the voltage is 12V and the current is .02A then the resistor should be 600 ohms.    12/.02 = 600

Is this correct?

What I really don't get is what if I was using 36VDC or 1000VDC?  Even if I sized up the resistor appropriately wouldn't the LED be damaged at some voltage?  How do I tell where that voltage is in a datasheet that does not specify?


texts: Voltage Clipping with Two Series-Opposing Zener Diodes

texts:
Theory

Schematic for Voltage Clipping with Two Series-Opposing / Bidirectional Zener Diodes

Consider the following schematic for voltage clipping with two series-opposing/bidirectional Zener Diodes \$D_{1}\$ and \$D_{2}\$:

The non-identical Zener Diodes \$D_{1}\$ and \$D_{2}\$ have the

absolute Zener voltages \$V_{Z,1}\$ and \$V_{Z,2}\$ and the
absolute forward voltages \$V_{F,1}\$ and \$V_{F,2}\$.

\$V_{in}\$ is the input alternating voltage, \$V_{out}\$ the output alternating voltage over the load resistance \$R_{L}\$.
\$R_{V}\$ is the dropping/series resistance.

Voltage Plots

According to a book, this is how the voltages may look:

Note that \$|V_{Out,Max}| \neq |V_{Out,Min}|\$, if \$D_{1} \neq D_{2}\$.

Question

What are the correct values for \$V_{Out,Max}\$ and \$V_{Out,Min}\$, if assuming \$V_{Z,1} = 20V\$, \$V_{F,1} = 0.7V\$; \$V_{Z,2} = 60V\$, \$V_{F,2} = 0.9V\$?

In this picture from this website, in accordance with these three websites and page 62 of this pdf-file, the values are given as

\$V_{Out,Max} = + V_{Z,1} + V_{F,2} = +20.9V\$
\$V_{Out,Min} = - V_{Z,2} - V_{F,1} = -60.7V\$

Are these voltages correct?

Simulations

CircuitLab

Below you can find an attempt to recreate this problem with CircuitLab.

simulate this circuit – Schematic created using CircuitLab

LTSpice IV

As an addition, here are the two possibilities to realize voltage clipping with two series-opposing/bidirectional Zener Diodes, simulated with LTSpice IV:


texts:
I have two 3.7 volt batteries (I can use one or two) and I need 5 volts.
Initially I thought to use the lm7805 but the circuit absorbs 4 amprere.
how can I do? I need the component to be as small as possible.


texts:
I have a Cree LuxDrive LED powered by a 3.7V 750mAh LiPo Battery hooked up in a circuit with a latching switch.

For some reason every time I turned it on, the driver gets really hot and almost starts to melt so I have to immediately shut it off.

The light works but can’t use it if the driver keeps getting so hot. I’ve tried replacing the switch with the new one and still the problem persists. I have to use the type of switch currently pictured because it’s for a very small application. Maybe I’m using the wrong type of switch? It’s a double pole double throw but I’m only using 2 of the 3 pins on each side of the switch.


texts: US Government Export Approval for TI chip

texts:
I hope this isn't off-topic since I think it's a general issue that applies to many ICs.

I'm looking into buying a TI battery charger chip, but the datasheet alone seems to be restricted by the "U.S. Government export approval". Does that mean even buying a few samples would need such an approval?

The form for datasheet on the TI site asks for a name, an email address and an affiliation. How does the US Government conduct a meaningful assessment given the unreliable data? There's no verification involved but it takes 1-2 business days for processing.

To buy larger quantities, would one need special documents?

Thanks


texts: r28=iee what is meaning of iee code of smd resistor?


texts: difference between error control coding and channel coding

texts:
Is there a difference between error control coding (like forward error correction) and channel coding(like convolution coding)? Both of them help in correcting the errors because of the channel.Why is Error control used at the data link layer and channel coding at a lower level(i am referring to CCSDS doc), when only one suffices(if we assume both are same)?

CCSDS recommendation is given in below link.
https://public.ccsds.org/Pubs/132x0b2.pdf


texts: Circuit that can convert current pulses to voltage

texts:
I have an anemometer which outputs current pulses. I can't take it apart but I know there is a phototransistor and LED in parallel shining through holes to it. I was told that with 30m/s wind there will be 3uS long current pulses over the normal current (through the LED).

My problem is to transfer these pulses to an Arduino or convert these pulses to voltage 0/1. Arduino is no problem for me, but I am inexperienced in circuit design.


texts: Why I got very weak signal with my GSM antenna connected to PCB?

texts:
I have designed the below double sided PCB which uses 3 separate SIM900 modules with separate SIM cards (different operators, same band) and GSM antennas. The PCB is housed inside a plastic enclosure which in turn is housed inside an enclosed steel cabinet. The cabinet also houses some other components like an AC-DC adapter (the type with shielding) and an 20x4 character LCD. There is an AC line running through a hole on the cabinet to the adapter. Cabinet is not connected to common ground.

The antenna pin of each module is connected to an SMD GSM antenna connector via a short trace on the PCB (about  10mm). Each connector is then connected to a commercially available GSM antenna (please see photo and link for specs), running though holes on the steel cabinet and attached (by glue) to the outside of the cabinet.

I am having unstable signals with this design. While on my telephone the signal is full, I am reading from 5% to 60% signal strength on these modules, and it is also kind of fluctuating.

I have seen some commercial SIM900 modules which also run the antenna trace directly to the antenna connector just like my design. But I have also seen some others which use a 1K resistor in series with the antenna trace, and some vias around the trace.

My question is that what should be causing the signal fluctuation, and is there anything I should do to improve the signal quality and stability?

Thank you so much in advance for any experience shared!

External antenna specs: https://www.aliexpress.com/item/2dbi-3dbi-gsm-824-960Mhz-1710-1990Mhz-GSM-antenna-SMA-plug-male-connector-Aerial-1-5M/32228127548.html?spm=2114.13010608.0.0.eIRczU

UPDATE:
I based my design upon the Small Breakout for SIM900 GSM Module by Open Electronics (photo below). Now I can see the only difference is that in their layout, the SMD connector is place as near as possible to the ANT pin of the SIM900 module (I think they are just <1mm apart). Should that be what causes my problem?

UPDATE 2:
The (painted) steel cabinet has a lid (also steel) at the back of it. I notice that once I remove the lid (so there is a large opening at the back of the cabinet), the signal strength improves immediately by around 30-40%. And when I put the lid back on the signal drops immediately. So could it be the case that this has something to do with interference?


texts:
i try to make a current 4.2v with the switching regulation methode as you can see in the attached picture.

The problem is that when i ajuste the voltage manualy from the ajustable resistance to 4.5v from a 12v power supply and i unplugged the power source, the voltage change completly in the output to 12v again when i plug the power supply.
Did i miss something ?


texts: I am not able to get any response from ST25RU3993 via arduino SPI

texts:
I ran out of clues of what could be stopping me from driving the ST25RU3993, hopefully I can get some useful directions from here...

I am trying to drive the ST25RU3993 Eval board using SPI, with my Arduino Due (i read an earlier post on that ran at different voltage and solve using 3V arduino board, in my case both devices run on 3.3V) to prototype a quick project. I used the oscilloscope to probe and it seems my spi outputs (sclk, mosi, chipselect, enable) are looking good. However my ST25 board is not responding at all.

Here is a picture of the eval board and here is the link to the data sheet for both evaluation board and the IC: ST25RU3993 IC , ST25RU3993 Eval

my connection from the Arduino Due board is simple SPI connection: MISO to MISO, MOSI to MOSI, CLK to CLK, an output pin(52) as chip-select, an output pin(2) as enable. The eval-board is powered 3.3V via arduino. Here is my Arduino code:

#include <SPI.h>
////////////////////////////////////////////
//set up pins for arudino due
//MOSI:ICSP-4
//MISO:ICSP-1
//SCK:ICSP-3
//NCS:52
//EN:2
//IRQ:22
///////////////////////////////////////////////

const int NCS = 52;
const int EN = 2;
const int IRQ = 7;

//SPI setting
SPISettings settingsA(500000, MSBFIRST, SPI_MODE0);

void setup() {

  pinMode (NCS, OUTPUT);
  pinMode(EN, OUTPUT);
  pinMode(IRQ, INPUT);
  digitalWrite(EN, HIGH);//set enable to high

  Serial.begin(9600);

  SPI.begin();
  SPI.beginTransaction(settingsA); //I wrote to the following 2 main control registers, register description is at the data sheet

  digitalWrite (NCS, LOW);
  SPI.transfer(0b00000000); // write and register addressL: Device staus register
  SPI.transfer(0b00000001); // value for this register: Turn RF-On
  digitalWrite (NCS, HIGH);

  digitalWrite (NCS, LOW);
  SPI.transfer(0b00000001); // write and register addressL: Protocal Selection Register
  SPI.transfer(0b00000000); // value for this register: Choose EPC Gen2
  digitalWrite (NCS, HIGH);
  Serial.print("written");

  SPI.endTransaction();
}

int8_t O;
void loop() {

  for (int i = 0; i <= 200; i++) {

    SPI.beginTransaction(settingsA); //read from my RSSI_Display register
    digitalWrite (NCS, LOW);

    O =   SPI.transfer16(0b0110101100000000);

    digitalWrite (NCS, HIGH);

  }
  Serial.print(O, DEC);
}

I had tried multiple clock rates from 100k to 5M and all SPI modes.

Usually with these kind of simple code I can drive many sensors via SPI but the ST25 RFID is giving me a very hard time. I asked around in ST community and someone ask if I had connected my IRQ. I did but I don't know why IRQ is important in master if all I am looking for right now is simple to turn the chip on and get some kind of response back.

Any one has a clue? or it is just a bad idea to drive the device with Arduino?

Thanks in advance.


texts: Both transistors have to be operating in the saturation region that means both behave as an current source. But does not this contradict with the rule that more than 1 current sources cant be in series? I understand that T2 will have 0 Vgs as both the gate and the source are at the same potential. How will the circuit work? Please give an intuitive answer.


texts: Combine 2 outputs from a single powerbank to increase current for driving leds and controller

texts:
I want to power a led matrix of 256 leds and my controller on the road.
I calculated an approximation of the required current for the leds at 5.1A and the controller at 0.1A making 5.2A @5v together, though I think it will be lower depending on the animations.

I happen to have a 13600 mAh powerbank from Xiaomi lying around which supports quick charge through 2 micro usb outputs. 2.4A @ 5v.

I was thinking if I could combine these  in parallel to increase current that would make 4.8A. Now that is slightly less but I could just dim the leds a little bit to make up for that last little bit.

Do you think that would be possible? I came up with the following circuit but as a starting embedded software engineer my experience is still limited so I might be missing something.

Basically, I just want to put the outputs in parallel and have a diode to protect against current flowing back into an output from another output and use a capacitor for peaks.


texts:
The left side are the test leads to poke around on something on a vehicle. I for the life of me cannot remember what this was used for. I do know 100% that it is used to test something on the electrical system of a motorcycle.
Everything is in parallel except for the diode.

8.2M
224k 100v
224k 110v
2A 224j
104k 100v
diode N1 40?


texts:
I'm working with the Venus 634FLPx GPS chip.

The reference schematic in the datasheetincludes an inductor L1 marked "optional biasing for active antenna":

What is biasing, what makes an antenna active, why is it optional, why would I opt to include or exclude it?

SparkFun supplies a breakout board for this unit which includes this inductor in its schematic. Interestingly, it also includes a 22pF capacitor between the high side of the inductor and the RF ground:

I assume this capacitor is for power supply decoupling? Or does it serve some other purpose?


texts: What is the advantage of the inverting opamp circuit over non-inverting one?

texts:
Op amp circuits are designed to achieve a specific gain regardless of the differences between individual op amps.  One very common circuit has a gain of -R2/R1.  Here's a (corrected) schematic:

Another common configuration has a gain of R2/R1+1 and is non-inverting:

What I can't see is why on earth anyone would use the inverting one, except for the odd case where you actually want inversion. The non-inverting one has high input impedance without an extra input stage, and almost the same gain. Is there any advantage to the first example?

Also, since the first example does not have high input impedance, it can take significant current to drive.  So, often a source follower is placed before the amplifier.  For the second configuration, is there any reason why a source follower would ever be necessary?


texts: Cutting the ground wire in an isolation transformer?

texts: I bought a non-tech isolation transformer (500w), which I planned to cut the earth mains ground from the output, but leave the chassis grounded; however, when I opened it up I found the output outlets were grounded to the chassis and the chassis connected to the mains ground. So I just cut the ground. Now my isolation transformer is floating both on the primary and secondary coils. Naturally this means the outer case is no longer grounded and if there was a short within the transformer, touching the case would be bad. Otherwise, does anyone see if this will lead to a dangerous scenario when I am probing the DUT with a grounded oscilloscope? Assume that I plan to connect the black alligator clip of the oscilloscope to any arbitrary point in the DUT.


texts: How do components on a ground plane of monopole pcb antenna effect radiation/efficiency?

texts:
I am trying to design a 2 layer PCB including two transceivers (GSM module + Zigbee IC) with internal PCB monopole antennas. I managed to have a solid ground plane on non-component side as recommended in general. Now I would like to insert a touch screen display which covers the most of that solid ground plane. Here's a screenshot (GSM only)

I read a ground plane completing a monopole antenna would behave as dipole antenna. Since this ground is covered with a lcd display, the performance would be affected, right?

How do cell phones manage this issue?

Also if a monopole antenna radiates in one direction opposed to ground plane, why no ground plane under antenna is a must?


texts: LiPo battery sparks when used with DC step up convertor

texts:
I'm using a LiPo battery 700mAh 3.7V with MT3608 DC-DC step up boost converter module 2V-24V 2A.
The problem is when I connect these to anything or even the wires just touch each other they produce a spark. I want to hide or remove them so that it doesn't harm my ESP32. Also is there any way with which I can reduce the current of the output from the battery?


texts: 20A or 30A fuse in 200A fuse clips -- is nesting reducers OK?

texts:
So, I am trying to figure out the cleanest way to make a 20A or 30A tap from a 200A circuit (single hot + neutral) that is being run through a fusible safety switch (NEMA style, as this is in the USA), with power sources at both ends of the run.  So far, I have come up with the idea of using a 3-pole fusible switch with a solid neutral and wiring the switch according to the diagram below (neutrals not shown for clarity's sake):

However, this runs into a snag.  A 200A switch, of course, has 200A fuse clips in it, which are far too physically large to accept a 30A fuse.  Fuse reducer clips are a thing, but apparently, nobody makes a reducer that will take a set of 200A Class R fuse clips and adapt them for use with a 30A fuse.  Can I nest two sets of reducers (either 200A->60A and 60A->30A, or 200A->100A and 100A->30A) in order to achieve my goal?  Should I be looking to Class J fusing instead, where the desired reducer is available, albeit at an increased parts/availability cost?  Or am I better off using an appropriately sized fuse block mounted in the switch enclosure, separate from the switch's fuse clips?


texts: Strategy for Cortex M0 Peripheral Clock Speeds?

texts:
I'm starting on learning the Cortex M, and coming from an 8 bit background.

I've got my demo board, blinking an LED and getting a working project out of STM32Cube.

I'm working my way through the system registers, but I'm a bit stymied on what to think about clock speeds for peripherals?  This isn't really a consideration for any 8 bit firmware I've written.

For the ARM Cortex M0 architecture, what are the major considerations when you set clock speeds for APB1 peripherals?

Say I slow down my peripheral clock too much, what happens?

How could I go about calculating what speed I want for the peripherals?

Do the peripheral clock speeds account for much of the overall power consumption of the system?


texts:
Can someone help me with this sort of circuits?

I don't see how it works because the circuit isn't closed like this type


texts: What is ground on a circuit that uses AC?

texts:
Below is a circuit diagram for a circuit that runs off AC voltage. Where do I connect all of the points that connect to ground? Do I just connect them all on the same rail of a piece of Vero board? And does the order I connect them in matter?

(source: electroniq.net)


texts: How to evaluate current in a circuit involving short circuit?

texts:
I am trying to solve this homework question:

I got the short circuit in the middle by removing a voltage source. The problem is to find the current flowing through R6.

What I tried:

Applying Star-Delta transformation on R3, R4 and R5 however it did not lead me anywhere.
I also cannot seem to be able to apply mesh analysis as no voltages are supplied to me.
I cannot convert the current source to a voltage source as there is no resistance in parallel with it.

Can someone please give me a hint as to how I should reduce this circuit?

Edit: Circuit after removing the short-circuited element R2:

Thanks to @Transistor and @MCG: I now was able to apply star-delta

Thanks to @Transistor and @MCG: I now was able to apply star-delta transformation which reduced the circuit to this:

I was able to solve this using current division.

P.S. The answer supplied by LTspice is 6 A for R6.


texts: Displaying bitmap on Arduino touchscreen TFT LCD

texts:
I'm having some problems displaying an image on my TFT screen, when called from within a custom class. I'm using the Adafruit pushColors method to push an array of uint16_t values, which contains the RGB565 hex value to set the color to.

I currently have a splash screen displaying an image correctly. What I'm trying to do display a menu button using the same method as the splash screen image, just from a custom Button class.

The TFT LCD screen is working correctly using the MCUFRIEND library (which is built on the Adafruit lib).

I have used the following website to convert the bitmap images to c++ arrays: https://javl.github.io/image2cpp/

My images are stored in an Images.h file (I'm having trouble loading them from an SD Card using the Arduino MEGA, I can't get the SPI pins working), but that's a separate issue. This is how I've got the images stored in the Images.h file.

// 'logo', 124x80px
const uint16_t logo_img [] PROGMEM = {
  0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145,
// Other values removes, you get the gist
};

// 'ico-batt', 24x24px
const uint16_t ico_batt [] PROGMEM = {
    0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145, 0x2145,
// Other values removes, you get the gist
};

In my .ino file, I reference the Images.h file #include "Images.h"

When I display the splash logo, I use the following code in the .ino file:

MCUFRIEND_kbv tft;

void seetup(void)
{
  // Other init

  showSplash();
}

void showSplash(void)
{
  tft.setAddrWindow(100, 100, 223, 179);
  tft.pushColors((const uint8_t*)logo_img, 124 * 80, 1, false);
  tft.setAddrWindow(0, 0, tft.width() - 1, tft.height() - 1);
}

This works fine, no problems. The issue I have is trying to use a class object to define a "Menu Button" and draw the button.

TMS_UI.h

/// The default UI toogle button
class TMS_Menu_Button : public TMS_Button
{

    public:
        TMS_Menu_Button(void);
        void init(MCUFRIEND_kbv *tft, int16_t x, int16_t y, const uint16_t img);
        void draw();
        // Other stuff
}

TMS_UI.cpp implementation:

void TMS_Menu_Button::init(MCUFRIEND_kbv *tft, int16_t x, int16_t y, const uint16_t img)
{
  _tft = tft;
  _x = x;
  _y = y;
  _w = 40;
  _h = 20;
  _img = img;

  // Default hasReleased to true so we can click it
  _released = true;
}

void TMS_Menu_Button::draw()
{
  _tft->drawRoundRect(_x, _y, _w, _h, 0, TFT_DARKCYAN); // To be removed, just helps show position of button bounds
  _tft->setAddrWindow(5, 5, 24, 24);
  _tft->pushColors((const uint8_t*)_img, 24 * 24, 1, false);
  _tft->setAddrWindow(0, 0, _tft->width() - 1, _tft->height() - 1);
}

In the .ino file, I call the draw method like so:

TMS_Menu_Button mnu_home_btn;
mnu_home_btn.init(&tft, 30, 215, ico_home);
mnu_home_btn.draw();

When I compile and upload the sketch, the image appears in the top left corner of the screen, however it appears the pixel colors are all random position/colors, like colored noise.

I suspect the issue is around how I am passing the const uint16_t img variable, and then it being cast to const uint8_t* in the pushColors method.

I'm wondering if it's in relation to pointers/references between the methods? I'm still pretty new to C++ and don't fully grasp those concepts yet.

Any help would be awesome.

Cheers


texts: What does "max" really mean in gate trigger threshold of a triac?

texts:
I am trying to understand the parameter Vgt (max) for a triac (or any semiconductor with a gate threshold parameter), mainly the max. part of it. For example, on page 2 of the following datasheet:

http://www.littelfuse.com/~/media/electronics/datasheets/switching_thyristors/littelfuse_thyristor_lxx04xx_qxx04xx_datasheet.pdf.pdf

  VGT (VD = 12V RL  = 60 Ω) MAX. 1.3 V

Could anyone please help me understand how to interpret max. here? Does it mean gate threshold can be 1.3V at max. and that we need at least 1.3V to trigger it and allow the current flow?


texts: What are the extra microstrip elements on this RF amplifier board for?

texts:
I am planning to build an amplifier with the HEMT CGH40010. In its datasheet (http://www.wolfspeed.com/downloads/dl/file/id/317/product/117/cgh40010.pdf), there is a picture of a evaluation kit on page 8, and an even better picture is on page 9. There, one can see several small 'copper islands' near the microstrip lines from the connectors to the FET, and near C1 for example is a tuning stub (that one which is bent towards the left hand side) and at the end of this stub, there are also a few of these strange copper islands.

I wonder what the purpose of these small copper pieces is. I guess it is either some kind of resonator, or it is for tuning. But in the 2nd case, how does it work? is the idea to 'scratch off' some of the copper with a scalpel to tune the stub, or what exactly is it?

(Source: wolfspeed.com)

(Source: wolfspeed.com)


texts: How do i make sure that PCB traces or Enclosure unit is not affecting the BLE 4.0 range?

texts:
I am using BLE 4.1 ready module having on chip antenna, according to datasheet i have taken care in PCB layout design that at least there should be 8 mm of distance from Antenna and copper traces from all the side.

but how do i make sure that the ground planes or any other traces (also thick Vcc traces) passing nearby having distance of 8 mm is not affecting the BLE radio signals ? Also the enclosure i have in this prototype is of 2.5 mm thick plastic covering whole module, will it affect the range of BLE radio signal or is there any way to measure this ?


texts: Option to fail Xilinx process if pins are unconstrained

texts:
I am using Xilinx WebPack 13.2 and I recall there being a setting to force the Xilinx process to fail if a top level input/output net isn't constrained to a pin. I would like for the process to fail the design flow instead of automatically assigning a pin and finishing the process. Unfortunately I can't seem to find where that option is in the ISE, where is that option in the Xilinx ISE?

Thanks,


texts: KiCad ErrType(3): The GND PWR_FLAG pin isn't being driven according to ERC

texts:
I'm currently working on my first KiCad project, trying to build a temperature controller device. I am mostly done with my schematic - however, I'm having a bit of trouble with KiCad's ERC, specifically ErrType(3).

The GND for my positive voltage supply to the OP97 is complaining about not being driven, and I'm not sure why. I noticed that the solution for this is usually to add a power flag, but my case is a bit weird since it is the pin on the GND power flag which is complaining about not being driven. I've attached a picture of that part of my circuit below. Would anyone be able to assist me on this?


texts:
Looking for the simple way to protect output pin of microcontroller with VCC 1.8V - 3.3V, from VPP 6.5V that will be applied sometimes, only during high state (1.8V - 3.3V) on pin output. Easiest way will be to put few kohm resistor between, but this is not possible because of high speed on PIO (6 MHz). Driving current on micro pin is few mA. I guess that isolation can be done with some fast low drop diode like MBR0450.

All things that I can find by google are related to ESD, and 3.3V / 5V glue logic.

Regards,
Josh

Edit:

Just for further clarification. This is only output pin / signal, and 6.5 V is applied to line by FET under same micro control. Changing 1.8V / 3.3V to 6.5V must be continuous (logic hi) without glitches. Only solution that I know (lower frequency) is...

but instead of 1G is direct pin connection. However, micro is connected over flat / ribbon cables to other side and with 150R and 1 meter cable length with 6 MHz signal is working just fine. Don't want to be forced to reduce cable length because of VCC/VPP interface, so looking for some better diode than LL103A, or some other design, whatever. Maybe somebody know why on picture 2k7 is used, and not for example 10k. On other side signal is grounded over 50k resistor.


texts: Verilog - instantiation input port not connected in top level design but design is working?

texts:
I want to convert a verilog design into vhdl but i found a verilog module which I see no way to convert it, because the design itself makes no sense to me. The module entity is the following code snippet:

module fifo_mst_dpath (

  // inputs
 input                fifoRstn,
 input                fifoClk,
 input                latch_clk,
 input [31:0]         tc_data,
 input [3:0]          tc_be,
 input                tc_rxf_n,
 input                tc_txe_n,
 input                snd_cmd,
 input [3:0]          bus_cmd,
 input [31:0]         tx_data,
 input [3:0]          tx_be,
 input [2:0]          ep_num,

 // outputs
 output reg [31:0]   tp_data,
 output reg [3:0]    tp_be,
 output reg          rx_rxf_n,
 output reg          rx_txe_n,
 output reg [31:0]   rx_data,
 output reg [3:0]    rx_be
);

The input latch_clk drives the following logic:

 always @(latch_clk or tc_data)
    if (~latch_clk)
       rx_data <= tc_data;

 always @(latch_clk or tc_be)
    if (~latch_clk)
        rx_be <= tc_be;

 always @(latch_clk or tc_rxf_n)
    if (~latch_clk)
        rx_rxf_n <= tc_rxf_n;

 always @(latch_clk or tc_txe_n)
    if (~latch_clk)
        rx_txe_n <= tc_txe_n;

 endmodule

The problem is now, that the top-level design instantiates fifo_mst_dpath without connecting the input port latch_clk:

  fifo_mst_dpath i_fifo_mst_dpath (
    // inputs
   .fifoRstn(tm_rstn),
   .fifoClk(fifoClk),
   .tc_data(tc_data),
   .tc_be(tc_be),
   .tc_txe_n(tc_txe_n),
   .tc_rxf_n(tc_rxf_n),
   .snd_cmd(snd_cmd),
   .bus_cmd(bus_cmd),
   .tx_data(tx_data),
   .tx_be(all_m_wr_be),
   .ep_num(t_ep_num),
   // outputs
   .tp_data(tp_data),
   .tp_be(tp_be),
   .rx_txe_n(rx_txe_n),
   .rx_rxf_n(rx_rxf_n),
   .rx_data(rx_data),
   .rx_be(rx_be)
  );

Simulating the desing with this configuration (missing latch_clk) will always result in rx_be = "XXXX", rx_data = "XXXXXXX" and so on. But these signals are used in the design for other logic and the design itself when synthesized will work. Can you help me understanding this issue? Am I missing something?
How can this be converted to vhdl?
Thank you.


texts: Generally speaking, reactive power in a system is not good in any system (say transmission lines, etc.), but if somehow we decrease the reactive power to zero then will it be a perfect system? Or is decreasing the reactive power in a system to very low not good for that system?


texts: C++ AVR big code size & excess unused symbols in build file

texts:
I'm developing the program for the AVR microcontroller in C++.
I have created a class that contains 8 methods(with constructors) but used only 3.
Class code:
class Pin {
    Pin();
    Pin(PinId pin_id);
    Pin(Port port, uint8_t pin);

    void SetDirection(Direction direction);
    Direction GetDirection() const;

    void Write(Signal signal);
    Signal Read() const;

    void Toggle();
};

I expect that in the build file unused methods won't be, but it will. I use the Ghidra disassembler to disassemble the build file. Pin(Port port, uint8_t pin), SetDirection and Toggle are used only (simple LED flasher).
But there are all of these methods in the build file and there are no references to these methods. So, why compiler/optimizer/linker doesn't remove these methods from the build file? I compile the program with -Os optimization parameter and Release CMake configuration.
For example, the Write method in the Ghidra:

But the Write method isn't used in my code (and in other class' methods too).
How can I optimize it?
Thanks in advance!


texts: decapsulating a MOSFET to create a bulk terminal

texts:
In my project, I would be using NMOS' and it would be very handy for me to have a bulk terminal. Since my choices of NMOS parts don't have bulk terminal, I was wondering if I could somehow decapsulate it (such as the tested method of dipping the epoxy package in nitric acid, etc) and attach a terminal to the bulk.

This really isn't an IC and I'm guessing that the bulk itself is quite thick (having been rated 24V). So, what I'm hoping is that there are no wires that are too thin and fragile that would break. Would this work?

How about ordering a bunch (to take care of overhead) from manufacturers that has not been potted. All they have to do is take it from the assembly line without much problem, right?


texts: multiple mosfets controlling individual circuits sharing one pull up res?

texts:
i'd like to control several individual circuits using an array of MOSFETs and wondered if they have to have individual pull-up resistors or if they can share one connecting them to ground.

Or do the  controlled circuits interfere with each other if they do?

Thanks a lot!
Marcel


texts: Opposite of night light, on in day off at night

texts: Is there any way to make this circuit stay on during the day and off during the night? I want the opposite of a night light, a day light.


texts: uC-adjustable harmonic oscillator circuit @100W

texts:
I'm looking for a circuit that performs a harmonic oscillation while its resonance frequency can be controlled with a microcontroller (preferably via an analog signal). The circuit has to drive a set of ultrasonic transducers with a maximum power of 100 W at ~ 50 V and a maximum frequency of 100 kHz.

Till now I'm using a h-bridge circuit for my low-power setup (using the 0D24K2 transducers) which dissipates most of the power by (dis-)charging the transducers' capacitance. I can't find any datasheet, but it might be similar to  When I now increase power and frequency, power dissipation will increase as well. Another disadvantage is that driving the transducers with a square wave generates unwanted higher harmonics, but I'd like to have a signal with a pure spectrum.

Some solutions that came to my mind are using:

a LC resonant circuit, but right now I'm unsure how to control its frequency with a microcontroller.
an oscillating circuit with operational amplifiers. I guess it might be difficult to generate the needed power and frequency at acceptable cost.


texts: Trying to figure out what resistor I need

texts:
My power source is 4 AAA batteries. The LED I'd like to use is a 2.65v ran at 1000mA. Does this mean a 3.3 ohm is sufficient?
Or a 3.2v ran at 700mA getting me a 4 ohm resistor?


texts: +12V and -12V for supplying Op-Amps in my circuit

texts:
What is the easiest and cheapest method for acquiring +12V and -12V for supplying LM358 Op-Amps? In my school's laboratory we are using Agilent voltage supply but that kind of supplies are really expensive for me. What is the easiest and safest method to obtain these values?
PS: I've tried using 2x9V and 4x1.5V batteries in series with a voltage divider. And making the ground of my circuit their mid point. It was useful until I was dealing with AC signals. All my signals are distorted because of it. I've searched for voltage regulators found +12V voltage regulator circuit from 24V however I can not figure out how to obtain -12V at the same time.
Thank you for your kind helps.


texts: How can I create an Integrated Library from a Vault component?

texts:
I'm pretty new to Altium Designer, so i hope you can help me.

While searching for some special components, I found some of them in the Vault database, but with the wrong footprints. That's why I'd like to convert them to a local Integrated Library, so I can rework them the way needed.

I know how to download the components to a Component Library (CmpLib) and how to find the footprints and symbols linked to it. But as they are on the Vault, I (of course) still can't rework them.

I already spent hours searching for a solution, but all i found were instructions to convert IntLib to CmpLib, not the other way round.

I hope you can help me!


texts: Why would this power mosfet be made in a surface mount package?

texts: I’m looking at the CSD17303Q5 power mosfet which boasts a 100A max drain current. It confuses me why they have it in a VSON surface mount package because most pcbs would not be able to handle that kind of current by a long shot. The width of the drain and source pads are ~3mm and ~5mm. In order to carry the solicited 100A across a 3mm wide trace, you would need a 30oz cu pcb, which is absurdly big. What am I missing here?


texts:
I am looking at this schematic from the TAS5162 datasheet and I have the questions:

Is the "microcontroller" used as an on-off button?
Are the connections inside the red rectangle optional?


texts: How to route Vdd and Vss to CD4011 in Pcbnew

texts:
As first-time KiCAD user, I was able to draw a simple schema with a CD4011 driving 2 relais. The "electrical rules checker" -finally- gives no errors or warnings. After creating the netlist and placing the components on the PCB, there is no way to route a track from the Vdd power-in pin to pin 14 or from the Vss power-in pin to pin 7 of the CD4011. Worse, I can place a track between Pins 7 and 14 . . .

In the standard symbol_dir, pins 7 and 14 are declared as VSS and VDD "power input" :

This is (part) of the schema with "show invisible pins" activated :

No hidden pins at the CD4011 ...

After reading lots of info on various websites, I tried this power-schema :

In Pcbnew highlighting the "GND" net does not include any pin of the CD4011  ...

Even more curious, Pcbnew lets me connect pins 7 and 14 of the CD4011 :

Where oh where did I go wrong ? ? ?


texts: STM32F103C8 SPI1 clock frequency too low (~32kHz)

texts:
I am trying to program SPI1 on STM32F103C8T6 (black pill board).
I have configured it as follows:
enable APB2 IOPA clock in RCC_APB2ENR register
enable APB2 SPI1 clock

configure SPI1 SCK pin as AF_OPENDRAIN, OUTPUT_50MHZ
configure SPI1 MOSI pin as AF_OPENDRAIN, OUTPUT_50MHZ
; no need to read from slave, so MISO not configured

configure SPI_CR1: 11000010 01010100
;1: 1-line bidirectional data mode
;1: Output enabled (transmit-only mode)
;0: CRC calculation disabled
;0: Data phase (no CRC phase)
;0: 8-bit data frame format is selected for transmission/reception
;0: Full duplex (Transmit and receive)
;1: Software slave management enabled
;0: Internal slave select. Has an effect only when the SSM bit is set
;0: MSB transmitted first
;1: Peripheral enabled
;010: fPCLK/8
;1: Master configuration
;0: CK to 0 when idle
;0: The first clock transition is the first data capture edge

configure SPI_CR2: 00000000 00000000

As I try to send data, two strange things happens.

If I start the Saleae Logic with sample rate 16 MS/s, I get a message box 'we're sorry, but the device was not able to keep up with this sample rate ...', and no data captured.

Lowering the sample rate down to 500 kS/s results in data capture, but I can see that the clock frequency is about 32 kHz, not ~8MHz as expected. Changing BR (bits 5:3 in SPI_CR1) brings nothing.

Please some ideas what is here wrong. I have tried to search internet, but it seems that I stay alone with such a problem.
Here is how logic analyser looks like

The captured bytes are correct. Just as sent.


texts:
So let's take a simple cmos circuit like this:

So I get that for DC analysis \$V_G = 12 \frac{R_2}{R_1+R_2} \$ and then \$ V_{GS} \$ makes sense to me...because there is a constant \$ V_G \$ value and there will be a drop....

What doesn't make sense to me is during AC analysis that capacitor becomes a short and \$ V_{in} = v_g \$ and then we have \$ v_{gs} \$, but this value is always changing because \$ V_{in} \$ is a sin wave....so how can we say that \$ v_{gs} \$ is an actual value?

What's more is that \$ v_{GS} = V_{GS} + v_{gs} \$ but again...I'm so lost as to how \$ v_{gs} \$ can be a constant value...any ideas? Thanks


texts: Analyzing discrete odd time signals (coefficients)

texts:
I'm having trouble proceeding with the following homework problem. I have the following clues about a discrete time signal, x[n].

The period of \$x[n]\$ is N = 6.
\$a_k = -a_{N-k}\$
x[1] = 2
\$\sum_{k=0}^{5}|a_k|^2 = 4/3\$

Using these clues, I'm able to derive that \$a_3 = a_{-3}\$ and since it's periodic, every 7th coefficient must be the same. However, how does one deduce, specifically using clue #2, that \$a_k = a_{-k}\$? I have the solution, but I can't figure out the reasoning behind the aforementioned deduction.


texts: How is output power related to input power?

texts:
Please Note: I stumbled upon this forum after considerable googling but was not able to understand the answers I found. Your simplest terms and explanations are appreciated.

I plan to bring a piece of medical equipment to a location where electricity is limited (think - one or two solar panels and a battery).

The medical equipment has four different models. The main differences being the max output power. For simplicity: A) 400W B) 300W C)200W D) 150W.

How is the max output related to the amount of power used?

If electricity is limited, is it best to choose the lowest wattage?

Thanks,
K

Updated with Links:
Catalogue: http://www.buykorea.org/images/namo/files/000024/20170602151711993_J91SJLC8.pdf

Website:
150 & 200 http://www.daiwha.com/bbs/board.php?bo_table=sub1_3_eng&wr_id=1
300 & 400 http://www.daiwha.com/bbs/board.php?bo_table=sub1_3_eng&wr_id=2


texts:
I want to drive a stepper motor which I've extracted from an old Epson printer. I am able to recognize that the motor is bipolar and i found the coil polarity by testing it with a multimeter. However how do I find its voltage rating? I forgot to mention I didn't find any datasheet online which is why I'm asking this question. The stepper motors are em-462 and em-463.
Thank you


texts: Why are inductively coupled RFID systems put in certain frequency bands when there are no EM waves used?

texts:
LF - 125 kHz
HF - 13.56 MHz

Those frequencies refer to the magnetic field that is used to induce a voltage in the transponder. Can the magnetic fields actually interfere with EM waves in the vicinity?


texts:
I have a machine used the motor to drive a press roll(a small roller) that sends power to drum roll (big roller).

I need speed 27 rpm for Drum roll and how many RPM for the motor that drives the Press roll. I have a gear ratio, 2 diameter's roller.

I just need to know the calculation


texts: What could be the reason an ATX PSU triggers OVP?

texts:
I have a broken MARS MP600 PSU that I am trying to repair.

Everything looks good but when I turn it on (grounding PS_ON) the outputs do not maintain the voltage.
The output signals go to the rated voltage, start increasing softly and then everything turns off, this happens in a period of ~350ms. I suspect that the power supply supervisor (P/N WT7502V) is triggering the OVP.

This is what I measured in the WT7502V pins:

12V pin starts in 11.6V a stops at 13.47V (there is an anti-reverse diode because it is also connected to the standby 5V).
5V pin starts in 5.17V and stops at 5.91V
3V pin maintain the 3.3V during this time. (not shown)

The OVP protection for WT7502V are:

12V: min 12.8V typ 13.4V max 13.9V
5V: min 5.7V typ 5.85V max 6V

I also tried to solder capacitors parallel to the ones in the outputs (without removing the originals), it gave me ~50ms extra but it did not solve the problem.

Any idea where could the  problem be or next steps to follow?


texts: How can I measure the torque of a stalled DC motor @ 6V using a torque wrench? I'm trying to test my DC motor with the torque wrench method (regular torque wrench used for cars). Any guidance helps. Thanks


texts: Which PCM data format to choose I2S or Left-Justified?

texts: I can't find any information which PCM data format is better - I2S or Left-Justified and why I should use one format over another. Is there a difference or it doesn't matter which one I'll use?


texts: Electrostatic protection - input and output ESD protection added to op amp w/built-in ESD

texts:
I have an op amp circuit using the OPA2626 that has a built-in input/output ESD protection of +/-3000V human body model.  The circuit is 3.3V single supply, non-inverting, with only an external battery connection.  However, it can have a large electromagnetic input to the amp due to a parallel coil with magnetically induced voltages of 10-40mV in normal operation.  The main threat may be a magnetically induced voltage spike at the sensor, but do not know at what amplitude. The sensor may see some electrostatic spikes also from nearby objects albeit will have some ferrous-like shielding.

The op amp circuit input is low impedance under 100 ohms. The op amp circuit output is clamped with a zener at +3.3V and continues into an AVR (Atmega) digital pin that is pulled down.  The input for the Atmega is between 10 KOhm-100 KOhm.

What add-on ESD should I consider for the input and the output?

Found this excellent post, but still a bit confused about the solution for the op amp w/ESD vs op amp w/out ESD as far as protecting that mA amplitude gap below the ESD's operating range:

"Therefore, the most we would need to do is limit the ESD diode current to <100mA and all will be well. If we suppress the 8kV to about 250V (as shown by the test curves above), then as the supply is negligible relative to that, an input resistance of 250V/100mA = 2.5k would do the job. Note, however, the source of our input bias current:
The amplifier input bias current is the leakage current of these ESD diodes. This leakage is a function of the temperature and common mode voltage of the amplifier, as shown in the Typical Performance Chacteristics."

ESD protection for OpAmp inputs and outputs

Edit:  added the circuit.   L1 will have a ferrous EMI protection from the outside influence.   The output of the op amp is limited to the upside at 3.3V via zener diode.


texts:
I have two flips flops as so. The clocks are connected, even though it is not shown in the picture.

Given this image, I am trying to figure whether the contamination delay or the propagation delay of flip flop 1 would cause a hold time violation of flip flop 2. The correct answer is contamination delay but I am having trouble understanding why.

What I know is: the setup time and hold time are related to the input, contamination/propagation delays are related to the output.

Looking at it more in depth, setup time is the time before the clock edge that the input D must be stable and hold time is the time after the clock edge that the input must be stable.

Similarly, contamination delay is the time after the clock edge that the output might be unstable (i.e. starts to change). Propagation delay is the time after the clock edge that the output is guaranteed to be stable.

Given this knowledge, I am not sure why the contamination delay would cause a hold time violation. If the output changes instantaneously, let's say, before the clock edge (i.e. the contamination delay = 0), then why would that affect the hold time of flip flop2? A comprehensive explanation of this would be very helpful.


texts: How much of a GPU's electrical usage is probably turned into a increase in air temperature?

texts:
I am trying to find a good rough guesstimate of how much of the maximum wattage usage of a graphics card is turned into hot air.

Say a graphics card is rated at using X watts at maximum usage. How much of that is released as heat into the air via the cooling setup, and how much is not (If not where does it go? To ground?)

Yes I know there are a lot of variables here, I am just looking for a guesstimate from someone who would understand better than me. I'm specifically using this GPU as the example (Radeon 6990 375 watts max)


texts: Why does having magnetic material in the middle of a stator help generate a current?

texts: It seems unintuitive to me why putting a stationary hunk or iron or neodynium in the middle of a copper coil generator would increase its conductivity, because the metal could act as its own conducting path and short paths along the copper wires and furthermore cancel out whatever opposite magnetic field is moving around it. So, why does it help?


texts:
I bought a servo that was modified for continuous rotation.

Is it possible to modify it mechanically to behave like a normal servo?

Alternatively, it is possible to drive it as a regular servo?


texts: Is there a technical reason why you might use a two inverting amplifiers instead of a single non-inverting amplifier?

texts:
For example, I found a schematic that uses two inverting opamps to amplify the output of an AD590 with a gain of 1000:

In this case the second opamp appears to be doing nothing but "re-inverting" the amplified voltage as it has a gain of 1. Perhaps this has something specifically to do with the AD590, or the opamp itself (the LT1014), or perhaps it's just to use up an otherwise unneeded fourth opamp in a quad package?

Is it be a safe assumption that it would be possible to replace these two opamps with a single non-inverting opamp with a gain of 1000?

Edit: After probing around (and just looking at the bands on the resistors) it appears that R28 is in fact a 10kΩ resistor.


texts:
I have a clock running at 100Mhz (in Xilinx FPGA).
My scope only runs at 25Mhz.
I suspect I am having a problem measuring it as such.
However I'd like to know how fast the clock actually is.
My co-worker told me it is 100Mhz + PPM.
I haven't found a concise method/explanation on how PPM works on the internet!


texts:
I'm thinking about putting together something simple for my young son's soccer team. I'd like to build a simple circuit that could be placed on/underneath the laces of their shoes and plays a sound when the kids kick the ball on the laces.

Any ideas on what would be the simplest route to do something like this? I'm wondering what kind of contact sensor would work best and how bulky I'd have to make things to produce a sound loud enough for the kids to hear.


texts: How to make multiple GND pours in Altium?

texts:
I have a PCB design that requires two ground pours on the bottom layer, one is AGND and the other is DGND. Most of the board is AGND ('L' shape) and the remaining should be DGND.

I have tried to pour polygon with AGND over the entire board, draw another polygon for cutting a square out of the AGND pour and tried drawing yet another polygon for DGND. I think this is a naive approach and it did not work.

If anyone can enlighten me it would be super!


texts: What is the purpose of coating around heating element in soldering airgun?

texts:
I have disassembled my SMD reworking airgun (to determine the cause of a 5-E error) and in aigun I have found a paper-like coating wrapped around the heating element that totally crumbled to dust and little pieces when I touched it.

What is the purpose of this coating? Could I use the aigun without it or I will get some problem?


texts: Using variable resistor to nullify Cap Bank Droop

texts:
In a high power application I am charging a cap bank to 800V and letting it discharge into a load of about 2 ohms for 2 seconds.   To avoid droop I could overcharge the capacitors and use a buck converter or use some other power converter with PWM control. However, I believe this would create a lot of electrical noise at these current levels.

Is there an electronic load that I could put in series with the current load that would regulate current?  Basically decreasing from something like 1 ohm at the start of the 2 second period to short circuit at the end of the load. I am wondering if there is a strategy or product for doing this, especially for a system requiring 100s of amps.


texts: Differential Probe measurement and Single Ended probe measurement (Using MATH function in scope)

texts:
I am measuring the differential voltage across a resistor connected between the supply (16.5V) and the ground. Below is my Circuit.

Using differential probe (Probe setting 9.96:1), when I measure, I am getting a Pk-Pk voltage across the resistor as 8V.
Using a passive probe (Probe setting 10:1),
Probe Ch-1 at Supply and Prboe Ch-1 at Collector of NPN Transistor.
Applying MATH Function=Ch1-Ch2, I am getting a Pk-Pk voltage across the resistor as 15.78V.
What do I need to check? Where am I going wrong?

Please help.
Thanks


texts: i have a SPDT toggle switch and trying to power two lights when switch is up and only power one light when switch is down, both lights off when switch is in the middle (neutral), how can i achieve this? i am using simple led strip lights, dc powered.


texts: MOC3021 appropriate input resistance value for microcontroller application

texts:
I have this design.
Mounted on "Project Board" and "Universal PCB" it works great.

But soldered in a specially designed PCB only works fine for the first 10 tries, every 2 seconds, high work load.

All 3 versions use same kind of componentes.

So... I tried to cut off the led attached at input (Led1), and the performance increased 20%, but again fails in 14th try.

It looks like a  saturation in moc3021.

I assume:

R5 ( 220Ohms) is to high?
R6 (1.5KOhms) is not needed?


texts:
In the datasheet for TL431, page 26, figure 32, is an example schematic of a crowbar circuit. I've been toying around with this one, since this is the first time I use a TL431. Instead of a TRIAC I use an opamp to catch the trigger (Vref to opamp = ~2.5V).

For Vcc = 5V, setting R1 = 2k4 and R2 = 2k, the "trip" point for TL431 will be at 5.5V. If Vcc goes >5.5V, the opamp will trip and switch its output. Works nice on my breadboard.

But, I just found something that I cannot find an answer/explanation for in the datasheet; if the trip-point is set at 5.5V and the total Vcc load is 0.5A, the actual trip will not occur until Vcc >= 6.1V. Even worse; if the load is 1A, I managed to turn Vcc up to 8V before the current limiter in my lab supply started to choke, and the opamp did not even react.

Why does TL431 not "trip" when there's a fair amount of load? The load current isn't even going through TL431, so what's going on here?

Where in the datasheet can I read about this?

EDIT The original post was very vague. Rewrote it for clarification.


texts: Backup battery enable with microcontroller

texts:
I'm interested in making a battery backup circuit that is operated by a microcontrollersuch that when the main battery gets below a certain voltage, the system switches to the backup battery.

Currently I am using relay to switch between the normal battery and the backup battery (battleswitch from dimension engineering and using servo pulses to turn it on and off) however this requires about a 1000uf tank capacitor on my vin for 5v regulator as the relay has a switching time and this doesn't strike me as the ideal way of doing things.

Is there a way I can accomplish this with transistors/fets/flip flops?

The switching time has to be almost instantaneous (<50ms?) as its powering a microcontroller so supply MUST NOT ever be interupted and a capacitor is used if required to ensure this. But the switching does not have to be done immediately when the power of the normal battery drops beyond a certain threshold as I have a margin (about 6v on the normal battery as my regulator requires a 1 volt difference between VIN and VOUT). Both batteries are 7.2 volt Nimh with a capacity of 2800mah.

Further, would latching be beneficial here?


texts:
I have 20 identical devices (GPS trackers- QStarz BT-1300ST) which are charged by mini-USB cables. I have no need for data transfer, which is done by bluetooth.

I have bought two USB hubs that are powered from the wall and split to 10 USB charging cables.

But I want to build a custom wall-charger that is smaller, and doesn't have 20 ugly cables sticking out of it. Ideally, I'd like either a short, rigid cable which can support the weight of the device (just 22 grams), or an array of 20 mini-USB ports, like this pic, that are embedded or glued on a (3D-printed) structure.

(This is sort of similar to the iPhone Speaker systems, where the phone clips onto the adapter - although I'm looking for 20 smaller devices and no speakers)

My question: If I want to build a 20-device array charger, and each device needs 3-5 Volts of DC, can I take a 5V AC transformer with ~10 Amps, and split the cables 20 times, to get 0.5 Amps per device? I would then solder the power pins on the 20 mini-USB-ports.

Is this in any way dangerous to me or the device, or impracticle because of readily available consumer products?

I see things like this for DC power supplies, but nothing for (mini)USB, which is probably because most people need to also transfer data.

update 1 Device is USB 2.0. Here's the info from the manufactorer.


texts: Output Register and pipeline implementation

texts:
In his book "Finite State Machines in Hardware: Theory and Design (with VHDL and SystemVerilog)" the author said : 'The optional output register can be used to obtain a fully pipelined implementation with better time and higher clock speed predictability ' .

Where the aforementioned output register is indicated in the diagram below :

Question : How does this additional register permit using higher clock speeds ?


texts: Three legged NOT gate? What is this symbol?

texts: I've come across the above schematic in a datasheet for a 4x2:1 bus switch. What exactly does that triangular symbol on S mean? It looks a lot like a NOT gate, but the third leg is confusing me.


texts: Measure low AC Power consumption (oscilloscope? MCU?)

texts:
I would like to measure AC power consumption of devices such as AC/DC charger, AC LED bulb or an electric circuit in the main box of a house.

However, their power consumption are quite low and the cosinus phi is not always usable to compute power consumption while this kind of devices does not have a proper sinus wave form.

How can I measure such consumption? Currently I have AC/AC adapter to have the voltage measurement and a clamp on amperemeter for the current. But I need to perform some calculations to determine the true power.

How can I do that? Is there a dedicated MCU or can I perform this with an oscilloscope?


texts: how to use TO-254 Power MOSFET and DIODE's full current capacity?

texts:
I want to know how I can utilise full current capacity of a TO-254 power MOSFET or diode while using it on a PCB.
Presently I'm not able to utilise it completely, due to the limitation of the number of wires I can connect to the leads when mounting the device on a heat sink.


texts: Building instrumentation amplifier with resistors and op-amps

texts:
According to this question, it is possible to build instrumentation amplifier out of resistors and operational amplifiers. I am more interested in the version where the gain is set by changing Rgain resistance.

The goal here is to build INA125 or INA122 in-amp. Hence, a couple a questions:

Which op-amps could I use in this circuit? Specifically, would LM124 or LM158 be appropriate? Would you recommend some others? Note that the circuit will be used in 5V low-power design at sub-zero temperatures.
What drawbacks can I expect when using this substitute instead of INA125 or INA122?
If this whole idea is silly, is there some other way to amplify the signal coming from a Wheatstone bridge?

Here's some extra information about my question. I am building a weight scale and I'm using four load cells connected in Wheatstone bridge. I get some 2.3 mV for 100 kg and need to amplify this to use with 8-bit Atmel AVR MCU. Unfortunately, where I live, suppliers do not have any kind of instrumentation amplifiers, so my only options are to try to build one or to wait 30+ days to be delivered from online sellers.


texts: Someone told me that if we used something like 1 kHz AC instead of 50 or 60 Hz AC, it would end up being much cheaper and efficient, because we could use smaller transformers. Is this true? It seems like it would probably cost more as the generators would have to spin much faster - also, it could lead to more losses due to the skin effect. (Just out of curiosity.)


texts: How to calculate 50Hz active power measurement accuracy from datasheet?

texts:
The R&S HMC8015 power analyzer datasheet and technical data list:

Range configuration

            CF3      Peak
voltage     600 V    ±1800 V
current     100 mA   ±300 mA

Measurement accuracy (±reading in % ±peak range in %)

Frequency         ActivePower
45Hz < f < 66Hz   0.05 + 0.05

voltage, current: F = frequency in kHz

Additional errors

Power factor < 1 | ±(0.2 + 0.2 *F)%, only for active power

Does this mean that when range is set to 600 V, 100 mA and measuring these values:

Urms = 229.96 V
f    = 49.986 Hz
Irms = 15.33 mA (with peaks to 230mA)
P = 0.064 W
Q = 3.525 var
Lambda = 0.018

That the measurement accuracy for active power can be calculated as follows:

0.05% for reading + 0.2% for power factor < 1 = 0.25% of reading

plus

0.05% for peak range + 0.2*F for power factor < 1 = 0.05 + 0.2 * 0.049986 ≅ 0.06% of peak value for range

resulting in a nett measurement accuracy of:

0.06% of 0.064 W = 0.0000384 W

plus

1800 V x 0.3 A = 600 * 0.06% = 0.36 W

totalling to ≅ ±0.36 W of measurement accuracy?


texts: I am heating up a wire with a current, and I am trying to express the cooling losses. What is the expression of dT/dx over a wire?


texts: Significance of Capacitor Attached to output

texts:
so I have a question about a circuit design for an earpiece.

It seems clear to me that the first op-amp functions as a high pass filter, and I think the second op-amp is a simple inverting loop, but I'm not sure what the function of C2 is. Basically I'm confused as to what it's doing.


texts:
What is the value of Vout if we know the value of Vin in this case?

It is a buffer amplifier, but it has two extra resistors so I think that the gain is smaller than 1, but how small?

(Vin-V3)/R1=0 <=> Vin-V3=0 => Vin=V2=V3

(Vout-V2)/R2=0 <=> Vout-V2=0 => Vout=Vin=V2=V3


texts:
Why when you synthesise some of the IP provided by the FPGA manufacturers, you end up using huge amount of resources? For example Altera's DDR RAM controller synthesises on 5386 logic units on Cyclone iv. This seems absolutely enormous to me.

I have observed this for other IPs as well. Why is that? I reckon I can design most of them in less logic, which I have done for some functions before.


texts:
I need to step up a 9V power supply (from a battery) to (at least) 45V, very small output current (less than 1mA, but it may be much less). My purpose is to drive a Russian rod vacuum tube, which needs 45V on its screen grid, and works best with about 60V on its anode (but the latter request may be reduced a lot). The current drawn by the screen grid is negligible, and the anodic current won't be more than 1mA.

I am thinking about a charge pump voltage multiplier; Maxim has many of them, but I have not been able to locate an IC suitable to multiply the input voltage by a factor greater than 2. I do not want to use boost converters, since I do not want to introduce an inductor in my circuit.

A possible solution would be that of connecting two charge pumps in cascade, but I wonder whether someone has a better and simpler idea.


texts: Is "new" acceptable when using C++ objects in a FreeRTOS application?

texts:
I've read that malloc() should be avoided when designing FreeRTOS applications. Does the same apply when using "new"?

E.g.:

TestObject* test = new TestObject();

On a side note, can the FreeRTOS C files be compiled with a C++ compiler?


texts: Simple soft start for high power mains device

texts:
I have seen, but cannot find again, a really simple implementation of a mains soft start circuit.
The thing I'm thinking of involves a power resister inline of the mains. When the device is started, current is restricted until a relay is energised, which shorts out the resistor allowing full power

The thing is, I can't remember (and so can't decide on) a good way to energise the relay after a second or so.

Does anyone know of a link to a reference implementation for such a circuit?

Cheers


texts: Problem with making an Arduino-like board

texts:
I'm making my own Arduino-like board with an ATmega328p and an FT232RL. After realizing the circuit (making sure everything was correct) I had some prototypes made by JLCPCB. Later I bought the various components on eBay, among them the AtMega328p-PU with bootloader which I hope has the bootloader already loaded. I then proceeded to solder the various components. It was my first time soldering SMD components, using a hot air gun set at 400° Celsius. For soldering, I used the solder paste xg-z40 from mechanic.
After soldering it, I noticed that the USB connector had not adhered properly (especially the pins, as it was partially raised), so I had to reheat the component to make it stick to the board.
Once this process was complete, I connected the board to the computer, but it gives me no signs of life. Unfortunately I have not included the 'ON' LED on the board, to verify the correct switching on of the board, but in fact the computer does not recognize it. I tried to install the drivers (for the serial interface I put the FTDI FT232RLSSOP chip), but nothing. The board, when connected, does not heat up at all. I would not like to have fried the components due to the high temperature during soldering, or that the pins of the USB connector are not soldered well.
I was wondering if it could also be a short circuit problem, always caused by soldering.
I am currently at a standstill and don't know what exactly the problem is.
I await some advice, thanks.
Schematic:

PCB preview:


texts: Voltage mode ethernet driver to current mode ethernet driver connection

texts:
We are trying to connect two ethernet PHYs - KSZ8999 and AR8035. Here is the schematics.

 The schematics comply with the following document (figure 4) - SimpliPHY Transformerless Ethernet Designs - Microsemi
The problem is that in one direction (from AR8035 to KSZ8999) link does not work (we use 100Base-TX). Though the signal is present on the link and looks pretty clear (status LED is on), and activity LED of KSZ8999 is blinking (as if some packets was captured), but they are not going up to the MAC layer (they are probably dropped because of errors).

We are pretty sure the problem is on the link layer. (We did a lot of experiments.) We can't use transformer. What may be wrong? How can we improve the performance of that connection?


texts: Through Hole (Vertically Mounted) SMA Connector on PCB - Feasible for GNSS Application?

texts:
Due to space constraints on a board I am designing, it is ideal to have the GNSS cable connecting vertically onto the top of the board.  I haven't been able to find any edge-mounted connectors that go to a right angle vertically.  Obviously edge-mount would be ideal electrically, but I am wondering if it will introduce too much loss too use a through hole SMA connector mounted vertically on top of the board - the 50ohm trace leading to the GNSS receiver would a top mounted grounded CPW line (signal trace on top with ground planes surrounding trace on top, and ground plane below the signal on the bottom side of board).  I am concerned about 1. since it is TH, it will be soldered on the bottom, so there is a possibility of shorting the signal pin to the grounded housing of the connector; or possibly not getting a good enough connection to the top-side of the plated through-hole - where the trace is connected. 2. Loss due to the right angle bend where the signal pin meets the plated through-hole.  3. The leftover stub of signal pin sticking out of the bottom.

Here is the digikey link to a possible connector:
https://www.digikey.com/product-detail/en/cinch-connectivity-solutions-johnson/142-0701-201/J500-ND/35274

This for GNSS applications, so it is all below 2GHz.

Thanks for the help!


texts:
I read that the optimal charger for smartphone batteries is 3.92v (to reduce degradation). Is it possible to implement a system that allows an external "charger" to cause charging to stop at this point?

Added:  People have pointed out that the external USB power supply is not actually a charger and that the charging is carried out by circuitry inside the phone.

Would it be possible to design and implement a circuit external to the the phone that terminated charging when the battery had reached some 'less than 100% charged' state, that allowed a longer battery cycle lifetime and greater whole of life capacity?.


texts: Potentiometer usage for a 24V 4A pump application

texts:
I have a 24V-4A oil pump that I use for smoke oil in my jet. I currently control the flow by using a needle valve in the oil line which restricts the flow from 2.1 gpm down to .75 gpm.

I am wondering if just reducing the pump speed with a potentiometer is better and easier on the pump, but in one of your articles it appears this will just cause a loss of power and possible heat issue. I was looking at a 100 W potentiometer for this application, but I have an extremely low understanding of if this is smart, and if so... how to connect it for the best results.


texts: Continuous switch with transistors (NOT gate loop)

texts:
Is it possible to build a circuit where it constantly turns a component on and off with transistors? I heard that a NOT gate loop does something similar but I cannot figure out how to build a NOT gate loop that does exactly that.

I've tried with an online circuit simulator and had gotten a LED to turn on but the LED would not turn on and off continuously.

Here's the simulation

Any help will be appreciated

Btw if anyone wants to edit the circuit, after you've finished you have to press file>export as link

Thanks for all the help, turns out I went in the completely wrong direction.

I tried the astable multivibrator circuit and it worked!

The circuit


texts: Questions about earth grounding enclosures

texts:
A text mentions about the importance of connecting the earth wire to an instrument case/enclosure as follows:

  Instruments with ungrounded cases can become lethal devices in the
  event of transformer insulation failure or accidental connection of
  one side of the powerline to the case.

I have couple of questions regarding this practice above:

1-) I can understand that how earth would save the situation for accidental conduction of power line to the case. But what is meant by "transformer insulation failure" and can you give an example scenario how can that be lethal issue?

2-) I sometimes encounter enclosures which are not metallic but plastic(sometimes DIN rails inside the plastic enclosure). In those would earth wire still be connected to the case?(It doesn't make sense to me but just curious to be sure)


texts:
I was trying out different tutorials with an Arduino/LED. I was following this tutorial when I ran into a problem.

I tried two configurations of the wires: one from the tutorial with a wire connecting from the 5V to the push button, and the other using a 330ohm resistor.

Just using a wire worked (see orange):

Using a resistor to replace the orange wire did not work:

I'm confused about why using a resistor in place of the wire does not work. Could anyone explain the main differences between a resistor and a normal wire, and why it didn't work?


texts: RC-LC network equals lowpass filter of third order?

texts: As far as I know only this are two lowpass filters (R-C1, L-C2) of order 1 and 2 respectively. Is it possible to denote this circuit as Low-pass filter of third order? Or is it possible to transform this circuit into a standard RLC-filter form?


texts:
I have a question about the MPC5606S Microcontroller.
I have very minimal software knowledge and only want to understand in hardware perspective.

On page 68 of the MCU datasheet, we have a block diagram which mentioned PD0 Always ON domain.

But in this Reference Manual of the MCU, on page 1235, the block diagram mentions that this Always ON domain have wakeup input pads.

What are the ports/pins of the MCU in the Always ON Domain?
(Are the Always ON domain pins the same as mentioned in Table 41-1 on page 1238?)
Can't we have any output ports in the Always ON domain?
Is it necessary that I have to connect it in one of the pins in PD0 Domains if I want to drive a PWM output during Mircocontroller sleep condition?


texts:
I am trying to download MCU Package of STM32f1 series for stm32CubeMX from the following link:

https://www.st.com/en/embedded-software/stm32cubef1.html

But the given link sends this messege that the package is not available for downloading. Could you please tell what I should do now.

I have been also trying to download it while generating code in STM32CubeMX software but the following error occurred:


texts: What's that metal wounded filament sponge looking thing and what is it used for?

texts:
I'm new to soldering and ordered a cheap starter kit. It included this:

I have no idea what this is. Any hint?


texts: Where do current developments go regarding graphical displays for devices?

texts:
Our company is currently redesigning a piece of measurement equipment. We have looked at what display we have currently (It's a generic 240 by 64 pixel graphic LCD like this one ) and if there is any chance we can get a replacement which runs on 3V3, offers serial input and which is not near its End Of Life. The main problem is that we are switching from a 5V microcontroller to a 3V3 microcontroller and therefore our system voltage drops down to 3V3. It also saves a lot of pins moving from an old 6800 interface to a fast SPI interface.

Unfortunately I don't know where the display industry developments go and which products will be supported for a long time (read: just have been developed and brought to market). I'm aware that this is a very broad question and may not be answerable. I have failed to narrow it down though.

Where do the trends go and which display format has just started to come up? Chip on Glass? Display on Glass?


texts: Proteus/Ares - how to scrap old layout but keep Isis schematic

texts: I have got in a mess on the layout. I want to scrap the existing layout and restart with a new board size. How do I do that without restarting the entire project?


texts: Proving the output voltage of a resistor ladder only with usage of currents

texts:
I got the following problem. I would like to prove the the output voltage \$U_{aus}\$ of the following system.

I only want to prove it by using currents. So I don't want to use the formula for a voltage divider.

I know I can simplify it to the following system if I want to prove it by using the voltage divider formula.

But how do I simplify this system if I only want to use the currents. I know I need a node for that where all currents go in or out. But in the following simplification I got 3 nodes.


texts: Retrofit a Hi-Fi remote with a RF 433 MHz module

texts:
In the past I used a remote for a AIWA Hi-Fi to control a AVR processor and circuit I custom made. I used an infrared receiver from Vishay (tuned on the 38 kHz) to demodulate the signal, then fed to the AVR (custom board, not Arduino).

The remote I have uses NEC protocol (http://www.vishay.com/docs/80071/dataform.pdf and https://techdocs.altium.com/display/FPGA/NEC+Infrared+Transmission+Protocol) that is based on pulse distance encoding.

The circuit controls fluorescent lighting (selection of lamp and intensity)  in the living room and I found that it has some problems with interferences from the fluorescent tubes. The software already discards most of them but I'd like to improve it.

I would like to use the same remote (due to the multiple and nice looking buttons) but retrofit it with a 433 MHz transmitter.

Would one of the cheap 433 MHz emitters accept the signal meant for the IR LED, after a proper low-pass filter to remove the 38 kHz modulation? or would the 38 kHz modulated signal already work with the transmitter?

On the receiving side I have more freedom and I can put a demodulation circuit if needed, only the remote is space and electronics constrained, that is why I would like the simplest possible solution for the transmitter.

Edit

Clarified protocol and encoding


texts: Whats the highest voltage dc motor that my mosfet can control?

texts:
I am using a IRF520N Logic level mosfet to control a dc motor with my Arduiono Uno. What types of DC Motors (i.e 20-24V) can I use without damaging the mosfet?

Datasheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/68160/IRF/IRF520N.html


texts:
I recently started to work on encoder sensors and circuits.

I found one optical encoder sensor from vishay electronics that suits my requirement,

I found a circuit diagram online and it works like a charm ! but i have following questions about its working:

1 : Why do we need MOSFETS on the output terminals of sensor ?  shouldn't we directlyget quadrature output without MOSFETS at points OUT1 and OUT2?

2 : Can we use BJT like BC547 instead of CJ2102 ? Wil it work ?

Attached : schematic

Thank you


texts: Fuses blown and PC backup power ... and a mystéry

texts:
I must admit it, what happened goes beyond my logic, so I need help to understand.
My two computers and the peripheral devices are powered through an UPS (backup power). I use 3 power strips to power all these guys.

This morning I noticed that the loudspeakers of my PC where down. After a few tests, conclusion : the transformer is dead.
So I turned on my two bigger loudspeakers (KRK Rokit 5), ... well I couldn't ...  After a few tests, conclusion : the fuses are blown.
I changed both fuses with the spare fuses, the loudspeaker turned on 10 seconds and then ... blown fuses again. I thought that there was a problem with the loudspeakers.

I found new pc loudspeakers. I plugged their transformer in one of the power strips. It worked, 3 minutes, but the volume was low and an ugly overdrive occurred in my music. Then the transformer blew up too.

I started thinking that these events were connected (I am a fast thinker) ...

I measured the tension : 237 volts (after UPS and before and in several other plugs in the house ... which is normal in France (where I live) The state electricity company told me that tension ins considered normal up to 250 volts.

All the other devices inducing computer work perfectly. ... but I wonder if it is really reasonable to use them.

Anyway I have no explanation (UPS ? power strips ? ) ... and i need to do my work. I know that life would be worse if the Great Plague was back but i will be grateful to any person able to give me a clue.

Thanks,
Nicolas,
France


texts: Run 12v Incandescent Bulbs off Fluorescent Ballast

texts: Can I use a 120v AC to 12v AC electronic transformer to power 12v bulbs?  I have a 150 watt transformer that I tried connecting to a single 10w  incandescent bulb, but the bulb just flickers at a low frequency.


texts: Noise on the PWM signal. What value of capacitor should i add to decrease the noise?

texts:
I have noise on my 60Hz PWM output. The PWM output is going to the ESC to control the motor. Below is the signal with 5V per division. The PWM signal is a 60Hz, 10V signal. The duty cycle can be changed.

What I have noticed is that as i increase the duty cycle, the Brushless Motor suddenly increase and decreases; I believe noise on the PWM signal could be the issue. Below is the signal at 1V per division. What capacitor value should I add to decrease the noise?

Below is the signal when the motor suddenly increases or decrease. This time, it went from 4.1Amps to suddenly 8Amps. I hope someone can explain why this is happening. Some findings: when I increase or decrease the scale on the oscilloscope, it affect the motor. I don't understand why that is happening.


texts:
Would a 20-30cm microSD extension cord suffer any kind of noticeable transmission loss? This is a passive extender - literally, a microsd card with wires coming off of it, and a card slot at the other end. Simple ribbon cable connecting the two ends.

EDIT I'm not making this - it's a store-bought thing. Here's a picture of what I'm talking about:


texts: How does High Purity Lead Solder react with Orthophosphoric acid

texts: I am currently reviewing all processes and chemicals used in my firm and the one I came across this week is that we are using a high purity lead solder with Orthophosphoric acid. Ignoring the CLAW regs on the lead solder, as I am now all over this issue, can anyone explain why Orthophosphoric acid would give a better join/result than not using it?


texts: How to program STM32_F4VE with ST-LINK/V2/01-0

texts:
I am using keil uvision 5. I haveSTM32_F4VE development board and ST-LINK/V2/01-0.
How to program this board with ST-Link v2? If you can suggest some website link also it would be helpful.


texts: How can you guarantee stability of an inverting opamp configuration amplifier?

texts:
I had to design a circuit for measuring the voltage of a negative power supply rail (-15 V) and feeding it into a ADC (0-3 V DC-coupled input range). This measurement is only used for diagnostics and doesn't need very high accuracy for our purposes, so I didn't think twice and just used the inverting-opamp configuration amplifier to apply a gain of -0.15 (not in dB) to get the proper scaling and 180 degree phase shift.

After talking to some colleagues I learned that there is the possibility of having stability issues depending on the opamp. They said that some opamps will explicitly tell you in the datasheet what kind of gains and configurations they will be stable in, but the opamp we currently need in other places (LM833DGK) doesn't mention that kind of data. I also tried doing some analysis using feedback theory, but I couldn't get the results I need with the plots given in the datasheet.

This is driving me nuts because it is something I've never seen mentioned at school, or The Google as far as my search results say, but makes sense.

Can anyone give me advice on how to make sure that this circuit will be stable under all conditions? (It is now, but I can't guarantee for different noise, temperature, time-of-day, etc.).


texts: How are few-nanometer multigate MOSFETs fabricated?

texts:
Intel and IMEC came up with multigate MOSFET designs with channels as narrow as new nanometers. Which methods/techniques/machines are used to pattern/fabricate such small features?

(source)

(source)


texts: What is this two-lead component across an AC input?

texts:
I'm looking at the PCB for a bicycle headlamp. The input power to the headlamp is approximately 6 V RMS AC, from a bicycle generator hub – the same sort from this question. I've identified most of the components on the board, but one has stumped me.

The unknown component is in the red box. The two soldered leads marked with the two blue dots are the AC input from the dynamo generator.

I've searched the internet for all of the numbers on the part, together and separately. There are also a couple of logos on the part, but after looking at a website that lists common IC logos, I came up empty.

If it's worth anything, the diodes immediately around the unknown part form a bridge rectifier for the AC input to drive an LED. The power MOSFETs at the top of the image are used to switch the lights on or off based on ambient light conditions.

Another fact to note is that these sorts of dynamo hubs can generate excessively high voltages at very high speeds (e.g., going downhill), and that early versions of headlights would blow out if you didn't turn them off before going fast. Presumably this circuit must have some sort of protection to prevent this issue, since it cannot be manually turned off.


texts:
I am currently laying out the board for an audio amplifier I am working on. The power requirements aren't very high - there won't be much more than 500mA flowing through any given trace. However, I have ample space on my board, so I was thinking about using wide rectangular fills (40-50mil wide), like the following:

Having wider traces minimizes resistance, an in addition to being much wider than they need to be, I find a layout like this to be aesthetically pleasing. However, could any issues arise from routing like this instead of using thinner traces? In other words, is there a reason why I should only make traces as wide as they need to be?


texts: I need to measure liquid temperature down to -80C

texts:
Building a device that will sit inside a liquid that will be a max of -80C and trying to figure out what my options are for measuring the temperature.

I was thinking a thermocouple but not sure if that's a good approach.

What have you used that you liked?

Thank you


texts: Does the WiFi alliance protect the protocol documentation?

texts:
I was recently studying the IEEE 802.11 standards for WiFi (pretty dry stuff, huh?) and I was wondering this:

Would it be theoretically possible for someone not in the WiFi alliance to develop a chip without a whole lot of reverse engineering? How hard would it be for an individual to develop this without wasting his/her whole life's savings and 10 years of their life? I am a person who likes to innovate, and I would think that it would be cool to figure out how to create a cheap Arduino compatible device for WiFi.

NOW HOLD ON:

I know what you're thinking: "IT CAN'T BE DONE!" I was more looking at about how tied down the information about the devices are. I would never dream of trying to mess around with HDMI and all the patents and such, but I was wondering since WiFi was anything from the first few generations of WiFi left that could be used? Since it is an older technology, I would imagine that information was more freely avaliable back then, and was wondering if it theoretically possible without loosing that persons sanity.


texts:
I got myself scrap laptop batteries for very cheap, only 2 cells out of 60~70 appear to be damaged (0v)
To charge 2 drained batteries, first I used a powerbank circuit that despite being less than a dollar does a very good and careful job at reviving low voltage individual pair of batteries, takes about an hour from 1.5ish voltage to 3.7 but it was taking too long so I put 220ohm resistor in series with whole 3s pack to a good 3s 12v battery, idea is to wait for batteries to hit 9v then take it from there, can anything go wrong with this method?
Then to balance the capacities for the pack, I will have to measure capacity of every pair or atleast 1 pair per pack which can also take very long, is there a quick reliable way to test battery capacity without fully charging and discharging batteries?
Regarding charging/protecting the pack, bms will cost me as much as batteries themselves, what if I use bms of working batteries instead, assigning each bms some extra pairs to charge and put all bms in parallel?


texts: Why is this Type I compensator phase not 270 degrees?

texts:
This is a Type I compensator with a pole at origin. The transfer function between \$V_{in}\$ and \$V_{out}\$ is as follows:

$$ \frac{V_{out}}{V_{in}}= -\frac{R_{2}}{R_{1}+R_{2}} \frac{1}{s (R_{1}|| R_{2})C_{1}} $$

According to this formula, this compensator should always cause a phase delay of \$270^{\circ} \$ at ALL frequencies with \$180^{\circ}\$ from the inverting amplifier and \$90^{\circ}\$ from the origin pole.

However, in the simulation I have set up below, the phase delay at 0.1 Hz is only about \$180^\circ\$.

What is the reason here?

The OpAmp is one-pole model with DC gain of 1000 V/V and pole at 1MHz.
This is the model: https://imgur.com/9DKSk70

And this is simulation file using Multisim: https://ufile.io/p20r4


texts: Does an interrupt signal with 2.8 V high level need a level shifter for a 3.3 V microcontroller?

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So, I am currently working on interfacing a MSP430G2553 and an I2C proximity sensor VL6180X. In order to have consistency in my voltages and hardware design, i choose this I2C device from polulu (https://www.pololu.com/product/2489), that offers level-shifting for I2C pins. For now, everything works well with I2C communication only.

The VL6180X sensor has a GPIO1 pin that can be configured as an interrupt request output. I'd like to connect GPIO1 to my microcontroller and use this function, so that I don't have to poll the sensor for results data.

The GPIO1 pin is not level-shifted, according to the documentation. I tried to make it work by wiring it directly to the micro, but I did not get it to work (maybe I did not try enough).

I am wondering, as my pin is providing 2v8 high level, do I need to level shift it for connection to my 3.3V MSP430 ? If so, what is the smallest circuit that can do this?

Thank you in advance!


texts: I've built dead bug (on steroids) boost converter

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I know it looks sloppy but this is my very own homemade boost converter! It outputs 6watts of power from a 3.7v battery(phone battery)...
It's switched by an astable multivibrator, and the switch is the MN1526 bjt transistor.
Out of curiosity, please enlighten me, is a square inductor ideal, I know a toroidal inductor is the best but due to lack of material, I'm using a square shaped(a sharp edge U with an I super glued on top), so what do you think such an iron core fairs against a toroidal one?


texts: Can a radio transmitter somehow detect the number of receivers in its area?

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During conversation, a colleague proposed that over-the-air television and radio broadcasters can determine the number of viewers or listeners based on the "load" on their signal. This seems to me like total bupkis, but he's piqued my curiosity and I've not been able to find a discernible answer when searching the web to prove him right or wrong.

Is such a thing even possible? Do the number of receivers within the broadcast range of a transmitter put any "load" on that signal? I always thought that the amount of power required for a transmitter simply determined the distance at which the signal could still be reliably received. AFAIK receiving a radio signal does not require any actual power at the listener's end, except to filter and amplify that signal into something useful, and that power is provided locally.

If this were true, it seemed plausible to me that one could place several signal monitors at a fixed radius from the transmitter and measure the signal strength at each. Monitors with weaker signal must have more receivers between that monitor and the transmitter, which could be used to extrapolate the number of receivers within that arc of the radius at, say, -3 dBm per receiver.

What I do know is that obstructions between the transmitter and receiver degrade the strength of the signal, so in that situation, one would have to account for buildings, trees, mountains, birds, precipitation, clouds, airplanes, helicopters, low-flying kayaks, large snowmen, and Santa Claus.


texts: This is circuit is proposed for a thermomether based on the TSP102 sensor (linear PTC). How can I determine the equation for the output voltage? My main question is about the op amp. I know that two voltages dividers are the inputs of the op amp. What would the equation be for the op amp output?


texts: set the delay time for the 6 steps of bldc

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Hi, i am currently working on BLDC motor controller (ESC without Back EMF), i want to know what is the max and the min delay time to switch between the 6 steps to control the speed of the motor . I am using atmega328p (with quartz 16MHZ).
Motor : Turnigy 2627 Brushless Outrunner 3800kv ( 12 v and P = 260 w )


texts: Ultrasonic Sensor Serial Output Grounding Issue

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I have a small circuit which uses a Maxbotix Ultrasonic sensor (Datasheet: https://www.maxbotix.com/documents/HRLV-MaxSonar-EZ_Datasheet.pdf) to take distance measurements and then transmit them over bluetooth with a BLE Nano 2 IC. The circuit is powered by 3 AA batteries. My problem is that the circuit only works when I physically touch the circuit thereby providing (I assume) additional grounding. To be specific, this sensor outputs TTL Serial data; the data is garbage unless I am touching the circuit.

I am a novice when it comes to circuit design. Can anyone please advise how I might go about solving this problem?

Updated Schematic

simulate this circuit – Schematic created using CircuitLab


texts: Identification of common RFI/EMI sources?

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Is there a way of identifying between common continuous household RFI/EMI sources (USB1/2/3, iPhone/iPad wall warts, cable/DSL modem, ethernet 10/100/1G, light bulbs, etc.), (e.g. which one, if any?) just by looking at a (VHF) SDR or other spectrum analyzer waterfall display?

Does the FCC or UL (et.al.) or other public resource keep a database of fingerprints of common RF noise sources?


texts:
I've made a 32kHz crystal oscillator using the CD4060B IC. The IC is powered by a 7805 voltage regulator which in turn is connected to a 12V SMPS.

I've probed the Q5 output (~1024Hz) using an optocoupled MSP432 and had the following waveform:

The large "off" period grows larger and eventually the oscillations stop.
I've noticed that when I placed my finger at the body of the 7805, I had stable 1024Hz oscillations for some seconds, then the "off" period started growing again until the wave collapsed. I thought it could be an overheating problem, so I added a heatsink to the 7805 and probed the current using a multimeter - still had the same result (the current drawn was at most 1.1mA).
Then I've placed much larger decoupling capacitors (220uF and 470uF) - still had the same results.
Then I connected the IC directly to the 12V SMPS and had the same result...
I also tried the original circuit, but with different feedback capacitors and resistor at the crystal filter (15pF, 33pF, 56pF, and 3.3Mohm) - still no improvement...
Finally I've powered the IC directly using the 5V pin from MSP432 and probed using the same optocoupled circuit. Then I had a stable and perfect ~1024Hz square wave.
Could this be a problem with my SMPS or is it a problem with the circuit? What could possibly indicate the fact that my finger at the body of 7805 created a "temporary stable" square wave? Why does it work with the MSP432 as the power source?
Thanks in advance.


texts:
I wanted to know if there is a simulator that could include the model of the capcitive accelerometer NXP MMA7361L, and if there is a tool-box in matlab that could include it or should I find the transfert fonction first to simulate in matlab ?
Thanks in advence.


texts: Why CW radar I-Q signals do not contain Doppler frequency component?

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I have a question about I/Q signals in Doppler radar, but I couldn't find a solution for this.

As far as I understand, the received signal at receiver side will be down-converted by mixing it with the transmit signal (direct conversion). And in order to generate I/Q signals, the received signal is also mixed with a 90degree phase shift of the transmit signal.

I have read several papers, and all of them say that

$$I(t) = \cos(\phi(t))$$
$$Q(t) = \sin(\phi(t))$$

My question is: where is the Doppler frequency component (assume having a moving target, for simplicity I ignore their amplitudes). I expected to see something like:

$$I(t) = \cos(f_D 2\pi t + \phi(t))$$
$$Q(t) = \sin(f_D 2\pi t + \phi(t))$$

Why the Doppler frequency does no more remain in the IQ signals?