texts: Mains to low voltage seperation between FR4 PCB layers

texts:
I cannot find clear information on running mains and low voltage on adjacent layers on FR4 PCBs. I understand how much creepage distance to allow, but for example, can I run - 50Vdc, 240Vac, 0Vac, ground, on a 4 layer 1.6mm FR4 PCB. Would it be more appropriate to use a 6layer pcb, leaving blank layers between 50V/240Vac/0Vac?

Could someone point me to a standard on this? I have had not much luck with Kervill's Low Voltage Directive.


texts: How to design a boost converter? And how to specify the inductor and capacitor values?

texts:
I want to design a boost converter with input of 48V and need to get to a voltage of 100V.
How to select the inductor and capacitor values in it?


texts: Maximum data rate that can be achieved between PIC and FPGA

texts:
We are looking at PIC24FJ256GA705 here. It is connected to an FPGA and the FPGA must transfer a few kB of data as fast as possible. I assume that parallel transfer is the best option here, parallel transfer of 16-bits at a time. Some handshake signals must be worked out here since the PIC and FPGA operate in unrelated clock domains.
Lets assume a simple operation where the PIC reads the two 8-bit words and then stores it in RAM. The PIC is operating at 32MHz. How many clock cycles will this simple operation take? I think this is a 16-bit PIC which means that this reading should be possible in a single instruction actually. I want to then also consider the hand-shake signals and see what is the maximum data rate that can be achieved.


texts:
On the RaspberryPi.SE it was suggested that one can use MOSFET BS170 to switch a USB device on and off by a GPIO pin (3.3V). I need to get 500mA to power a GSM dongle; the voltage drop should preferrably be minimal since USB is quite strict on voltage).

I'm not sure if I did the right thing. I cut the power wire of the USB cable, and connected the MOSFET to it in the following way:

simulate this circuit – Schematic created using CircuitLab

(I use a speaker in the schematic to represent my USB device, and a switch to represent a pin of the GPIO.)

The problem is that:

I'm not sure that the two grounds are actually connected.
According to a scheme on RPi's elinux page, I should have cut the GND wire instead of the PWR one.
The official gate voltage is 3V and I supplied 3.3V to it.

I think I demaged the transistor I bought. I can buy a new one (even couple of them, they're really cheap), but I would prefer to know what to do before I experiment again or cut some more wires.

EDIT:

I did some more search, and I found a schematic by bretth on sparkfun.com, which seems to do what I want, using a P-MOSFET instead of N-MOSFET. Is this schematic angood way to go? It is a problem that GPIO provides 3.3V and maximal V_GS is 3V for N-FET and (minus) 2.4V for P-FET?

simulate this circuit


texts: Can One hook up several displays on the same RGB parallel interface?

texts:
I am working with a 800*480 24-bit parallel RGB LCD display. The required clock for the RGB interface has to be between 23 and 27 MHz (typ. 25 MHz).
For testing purposes, I need to display "something" on a large number of displays (e.g. 20), the update rate of "something" not being an issue (it can be a color changing every minute for example). I do not have any piece of information regarding the current sourced/drawn by the interface pins.
The backlight of the display is not an issue here as it can be totally independant from the control interface for each display.
Normally, we are successfully driving one display with a STM32H7 and the suitable LTDC peripheral.
Can I hook up more than one display on the same parallel RGB interface ? The idea here is to test all of the displays (or at least several of them) with only one STM32H7.
My guess is that it should be possible, however at some point the current sourced/drawn by each display on each line, as little as it is, will overcome the current source/draw capabilities of the STM32 (20mA per pin, 140 mA being the maximul output current sourced by sum of all I/Os and control pins). Without the information of the current sourced/drawn by the display I don't know how I can figure out the number of display I can hook up to one STM32.
Another issue I am thinking of and that I cannot evaluate is that by hooking several displays to the same data lines, this will increase capacitance of the line and as a result, rise and fall times of signal might increase to a point where it will no longer be possible to meet proper timing requirements.
Does anybody have any experience in this kind of setup ? There is maybe some kind of dedicated IC for multiplexing that I am not aware of ?
Thank you for your help.


texts: PSpice OrCAD Adding Diode and Unknown Source

texts: On the PSPice OrCAD, how do you add a diode with a 0.7V forward bias and a unknown voltage source?


texts: Proper capacitors for ESP8266-12F?, resetting at high current peak

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When using the ESP8266-12F on a PCB I designed myself it keeps resetting after a high current spike of another module (Sim800L). I ofcourse tried to solve this using capacitors but I seem to have made a miscalculation.
My calculation is as follows \$C = \frac{I * \Delta t}{\Delta V}\$
With a max ripple current of 0.35 V with a current spike of 2 Amps for 0.6 ms this results in: \$\frac{2 * 0.0006}{0.35} = 3400\$ µF which seems excessive.

Context
I have a total of 1410 µF of capacitance which should only give a
The SIM800L is connected to a 700 mAh LiPo battery, its ground is regulated through a IRLZ34N mosfet. The ESP12F is controlling this mosfet by supplying 3.3V to it's gate programmatically.
The Sim800 has a SMD tantalum capacitor of 470 µF and 2 other electrolytic caps of 470 µF.
The ESP12F gets 3.3V through a HT7333A LDO and has it's own 220µF electrolytic capacitor. The ESP has a operating voltage of 3.3V to 3V (but 2.6V also worked for me)
The LDO is powered with the battery.

Problem
The problem is not the Sim module resetting but the ESP module doing so. Should I add ceramic capacitors to filter noise or do something else? Space is of concern so I prefer something small.
I do not have a working scope yet but will have soon (In case I can fix it)
(when I charge the battery everything works just fine so it isn't RF interference)
Some schematics


texts:
I would like to connect an electric toothbrush motor (Braun Oral-B Type 4729) directly to external power supply. So far I have been trying at least 3 different DC power supply unit with appropriate voltage (1-5 V) but nothing happened. However motor works perfectly fine when connected just to a regular battery (AA, 1.5V)...what is happening? The only guess I have is some impedance mismatch between the source and the motor...can anyone confirm this and/or provide any solution how to connect this motor to regular DC power unit?
Thank you very much!


texts: Running vacuum tube without grid or bias voltage

texts:
First some context: I am considering building a decoration out of a old RF power vacuum tube (like a Eimec 3-400Z, Telefunken RS630,...) with direct heated tungsten filament. I plan to get a appropriate SMPS to power only the filament for a nice glow in the living room & already know what to look out for as to not burn down things (already built a tube audio amp from scratch).

Since I don't want to actually drive the tube with a signal, no high voltage is necessary (plus I wouldn't put 3kV into my living room).
This also means I likely don't need to worry about heat, e.g. the 3-400Z would have a plate dissipation of typically 400W when used in a power amplifier.

My question: I found that there are claims of tubes decaying faster if only the filament is heated an excessive amount of time; I wonder if this will cause the "light" to break quickly, or if it doesn't matter since it will only degrade the characteristics (German "Kennlinie")?

I found the similar question I need a basic primer on interpreting vacuum tube datasheets - but even if I only would turn the "tube light" on for decoration a few hours per week, I suppose I will operate it way longer than they shot that movie.


texts: Synthesis timing summary in Xilinx tool (ISE)

texts:
I'm getting the following timing summary from the synthesis:

Timing Summary:
---------------
Speed Grade: -1

   Minimum period: 9.982ns (Maximum Frequency: 100.180MHz)

   Minimum input arrival time before clock: 4.597ns

   Maximum output required time after clock: 4.364ns

   Maximum combinational path delay: 2.788ns

I want to improve that, is there a way to find the critical path and maybe buffer it up a bit?

I don't know what is the bottleneck..


texts: Why would high-voltage cables have semiconductive layers in their design?

texts:
Turns out a high voltage cable can have semiconductive layers in its design. For example here's a rather old patent covering some specific way of producing such cable.

This doesn't make much sense. Yes, insulating layers are obvious and also a cable can contain a conductive screen to reduce dielectric losses.

What's the need for a semiconductive layer?


texts: How do we design a control system with a mix of single-phase and three-phase electrical loads from a three-phase supply?

texts:
I have connected a three-phase incoming power to a MCCB, MCCB will distribute to a 3-phase transformer as well as few single phase equipment, which is means outgoing of MCCB L1, L2 & L3 to transformer, L1 and N (neutral is from incoming distribution) to a 1–5A single phase AC-DC power supply, L3 and N to a 10–15A single phase heater. The problem is, is the wiring correct and safe to use?

Purpose of using transformer is to supply 3 phase 230VAC to servo motor as servo motor support only 3 phase 230VAC instead of 3 phase 415VAC. Besides, that's means I am safe to use two MCCBs (one for transformer another one for single phase equipment) from incoming power supply (from factory distribution board)? Will it damage the 3 pole MCB in the factory distribution board which supply to my two MCCBs?


texts: Differentiate Value of Unmarked Potentiometers

texts:
I am constructing a signal generator using a kit. Upon soldering it together, I have encountered a problem. The board is marked with two potentiometer slots, identical except for the values named on the board: 50K for the amplitude control and 1K for the offset control. I have two potentiometers, nearly identical. One of them is completely unmarked. The other has B503 etched on the back. How can I tell which one is 50K and which is 1K?

Thanks.


texts:
Whenever I come across crystals used in any of MCU or Processor, whether it be 32.768 kHz responsible for Real Time Clock or 25 MHz crystal required for clocking different interfaces connected with the MCU or processor. There are always two capacitors connected with the Quartz Crystal as shown in the fig.

I have few questions here:

What will happen if don't connect capacitors with the crystal?
How is the value of these capacitors decided?
While checking crystals datasheetI will come across a specification like stability +/-5ppm or +/-10ppm. what is the significance of this term?
And what are 2nd overtone and 3 overtone crystals?


texts: How do I externally protect a driver FET on a device from load short circuit

texts: I am trying to find a way to protect the output FET in an LED driver. Unfortunately someone else manufactures the LED driver so I don’t have access to the inside of the box or any way to modify the FET drive inside the box.  The LED driver is being powered by a  25 Amp , 24 volt DC external power supply. The FET is rated for fairly high current .It is a STP100N8F6 100 Amp N Channel MOSFET .  Both the driver and the output load is being driven by the same 24 volt power supply. I want to protect the driver against shorts across the load. I have tried various traditional circuit breakers and PTCs. Unfortunately it appears non are fast enough as the output FET keeps failing.  I am not sure if it may be partially because when the load is shorted this effectively shorts the power supply through the FET. This probably causes the drive to drop to the FET so that there is a high current through the FET while a high VDS is forced across the FET putting it outside of it’s SOA (Safe Operating Range) as specified in the datasheet. Does anyone have any clever ideas as to how I can protect this FET from a load short circuit externally without modifying the drive circuit?


texts:
My next project requires me to have energy-efficient wireless sensor modules. Basically, these modules read sensor data and transmits it over a wireless transceiver.

Currently, my setup includes an Arduino Microcontroller and XBee modules. I have been considering using an MSP430 Launchpad instead, as its low power mode uses much less than the Arduino.

However, the XBee modules are crucial as they provide a 2 mile range which for my project is important. If you have suggestions of another transceiver around the same price that provide the same range and considerably lower power consumption, please comment on it below.

I would like this module to run for a year or at least six months, but the current prototype I have with an Arduino chip and an XBee module sending data every minute cleans out a 9V battery in an hour. I have read a lot about this problem and wanted to know if XBee's are out of question. Am I doing something wrong here? Is this a software or hardware problem. Maybe one of you guys have more experience than me so your opinion will definitely help here. Has anyone else tried this same design?


texts: What's the conduction angle for a full wave rectifier with filter capacitor?

texts:
Shouldn't the conduction angle for a full wave rectifier with filter capacitor be twice that of a half wave rectifier with filter capacitor? The conduction angle for a half wave rectifier with filter capacitor is:

$$\sqrt{2V_r/V_p}$$

Since the frequency of the output wave in case of a full wave rectifier is twice as that of a half wave one the conduction angle should be twice as well, but we've already taken the above into account while calculating it's Vr, so should we take it into account again?


texts: What action is responsible for speed changes in a brushless DC motor?

texts:
Hi and thanks for looking!
Background
As a hobby, I enjoy tinkering with basic circuit building (often using Arduino) and lately I have mixed this hobby with another hobby of mine: building RC multicopters.
In the multicopter world, you need to eliminate as much weight as possible so lately I have been wondering if the need for traditional electronic speed controllers (ESC), which account for about 10-15% of total aircraft weight, could be eliminated.
I realize that the ESC is taking a PWM signal from the RC receiver and then converting that to something that tells the motor to change speed.
QUESTION
What is actually changing the motor's speed?  Is it delta in voltage or is it a delta in frequency of the polarity change?
I may be completely off track, but it seems to me that if it is simply a matter of changing the frequency at which the polarity of the electromagnets change, then some of this could be handled in code via the Arduino thus eliminating some of the needed hardware.  You would--of course--still at least need a transistor as the Arduino can't directly handle the 11-12 volts needed to drive the motor.


texts: the . hex file we burn goes to flash memory or RAM or EEPROM of Atmega8?

texts:
The flash memory of atmega8 is 8Kb.

Is this the maximum size for the .hex file, or it the max memory which i can allocate to variables in my code?

If none of the above is true, than what is memory allocation structure of Atmega8? To which memory does .hex file goes to?


texts: Transfer Function of Non-Ideal Transformer

texts:
What is the mathematical relationship between primary and secondary windings?

It can be either in the s-domain, or a time domain expression.

This expression must contain all realistic parameters, like core losses, hysteresis losses, winding inductances, mutual inductance between windings, effect of frequency, etc.


texts:
I am writing a reset for a vhdl statemachine that has an integer signal, which is initialized in the second state of the statemachine. However for completeness (assign every signal to avoid latches) I would like to assign a don't care value to the signal, so the synthesis tool has the most room for optimization.

Is there any way to assign a don't care value to a signal of the type integer?
(I know I could convert it to signed/unsigned and assign (others => '-' ) however it feels more natural to write this code with integer, since this allows to write if var=3 ... instead of if to_integer(var)=3 ... or if var=to_(un)signed(3, var'Length)... which feels uncomfortable.

Of I can not assign don't care, what is the best practice, assign the value, that I will assign in the second state, leave it unassigned or others? (I would go with assigning the value from the second state early)


texts: LiFePo4 battery charging for maximum cycle life with solar panels

texts:
The problem is charging lithium iron batteries for "maximum cycles" with a solar charge controller wile using loads.
I have a PowerSonic 45 amp hour LiFePo4 battery for my Caravan house battery.  I am powering it with a 100 watt solar panel and a pulse width modulation "PWM" charge controller.
My loads are a small multi-voltage refrigerator that draws about 2.5 amps at 13.5V with appx 50% duty cycle, a Sony car stereo, some LED lights and other small 5 VOLT USB loads, phone and tablet charging.
Currently I am using a factory programmed PWM charge controller that should limit the bulk charging voltage to 14.2 volts but it doesn't and the voltage rises to 16 volts where the battery management system takes over and cuts the voltage to battery bank to 13.7V.  The load low voltage cut out is set to 12.1V, the maximum solar output is theoretically 7.1 amperes at 14 volts but because it's not a maximum power point controller realistically it's approximately 5.6 amperes maximum which is well below the recommended 20 ampere maximum charge rate.
I have ordered an EP solar Landstar programmable PWM charge controller for the solar panel and plan to set the bulk charging rate at 14.1 volts and the trickle charge rate to 13.3 volts and the load low voltage cut out to 12.5 volts.
I have also ordered a buck boost converter and plan to connect it to the Caravans auxiliary output set to 13.7 volts at 8 amperes for supplemental charging while driving.  I hope this will give me a charge profile to extend the maximum charge cycles for my LiFePo4 battery's application.
It's my understanding that deep discharging and charging too high reduces the cycle lifespan of lithium iron batteries.
What bulk-charge and float-trickle charge voltages should the charge controller and buck-boost be set to for maximum cycle life?


texts: I have a code block (multiple files) in Systemverilog. I am using the Xilinx tool flow that does not understand SystemVerilog (an old part). Is there a tool (or a rule book) I can use to convert the SystemVerilog to standard Verilog-2001 code ?


texts: Which topology is best to design a DC DC 120W Power Supply? Kindly go through details

texts:
My requirement is as follows:

Input Supply 110+-30% VDC i.e., 77VDC to 138VDC.
output need to be 24VDC 5A.
All the basic protections like short circuit, Reverse polarity.
No power consumption when no load.
Rugged design to sustain harsh climatic condition.

I have thought to use Half Bridge LLC topology. using infenion IC IRS27952.
Suggest me better high Efficiency topology or another equivalent Transistor drive IC that can surve my purpose.


texts: I2C interfacing with ATmega32 and ArduinoMega2560 failed

texts:
I'm trying out I2C interfacing the ATmega32 with Arduino Mega2560 Board without success.

The Arduino Board is configured to be the Master Read.
The Atmega32 is configured to be the Slave Write.

I have connected the wires like in the Image below:

The Code for ATmega32 in Atmel 6:

#include <avr/io.h>

#include "I2C_slave.h"

void i2c_initSlave(unsigned char slaveAddress)
    {
        TWCR = 0x04;
        TWAR = slaveAddress;
        TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
    }

    //*************************************************

    void i2c_send(unsigned char data)
    {
        TWDR = data;
        TWCR = (1<<TWINT) | (1<<TWEN);
        while ((TWCR & (1<<TWINT))== 0);
    }

    //*************************************************

    void i2c_listen()
    {
        while ((TWCR & (1<<TWINT)) == 0);
    }

int main(void)
{
    int PIN = 0x02;
    DDRC &= ~PIN;

    i2c_initSlave(0x90);

    i2c_listen();
    i2c_send("G");

    while(1)
    {
        return 0;
    }
}

The Code for Arduino Board:

#include <Wire.h>

#define TRANCEIVER_ADDRESS 0x90

void setup()
{
  Wire.begin(TRANCEIVER_ADDRESS);  // join i2c bus (address optional for master)
  Serial.begin(115200);  // start serial for output
}

void loop()
{
  Serial.println("HALLO");

  Wire.requestFrom(TRANCEIVER_ADDRESS, 2);

  while(Wire.available())    // slave may send less than requested
  {
    char c = Wire.read(); // receive a byte as character
    Serial.print(c);         // print the character
  }

  delay(500);
}

As described in the code, I use Address 0x90 to establish the connection and send the character "G" from ATmega32 to Arduino. The output i got in the SerialCommand Window in Arduino IDE is like in the image below:

That means NO CONNACTION !!!

Could someone spot the problem? I think the problem is in the ATmega32 code.

Is the DDRC and PORTC configured correct to the MASTER READ?

DDRC=0xFF;
PORTC=0x00;

I'am not sure. Or should the PORTC be

PORTC=0xFF;

Could someone explain me?


texts: Display of set current on a variable bench power supply

texts:
I'm making a bench power supply, which will go from 0 to 17VDC and up to 30ADC at the output, which will have a voltage and current regulation (with potentiometers).

I am wondering, is it okay to use a push-button to short-circuit the Vcc and the GND pin, current going through the shunt resistor (enough for 30A or 50A)?

And the second part of this question here is, can I use (instead of 30A push button) a smaller push-button and few of MOSFET transistors, where I'd connect the current to the Emittor, some smaller voltage (I have stabilized +5 and +12VDC from the circuit) connect to the Base of MOSFET and the Colector to the shunt (where the other pin of shunt goes to GND)?

The thing (as I imagined) would work such as: I set the voltage, then I press the button. While the button is pressed, through the shunt goes max. current, as my circuit let's it through. While I'm measuring the current going through the shunt, I can regulate it and set it to desired value.

EDIT: Is okay to use shunt in series as this schematic applies?


texts: Should you always band limit a signal into an opamp when you are trying to control noise - even at DC?

texts:
Saw a Youtube video from TI talk about opamp noise and one of the points they made was limit  your bandwidth. TI:How to select an op amp based on datasheet noise specs

While I do understand the reason for limiting the bandwidth, I've seen a lot of schematics where there is no input filter. And in DC signals, I don't think I've seen any filter.

Is it good practice to put input filters (passive or active) to any opamp circuit if board space and cost can be neglected ? Or is purely driven by requirements and anything more than what is required (even if the signal looks cleaner) is just "over engineering" ?

A dramatic analogy would be taking a helicopter to the grocery store, simply because you can vs doing the minimum required that gets you there in a reasonable amount of time like car, taxi, bus or walk.


texts: What is needed to power a netgear switch with an ATX style PSU?

texts: I'm hoping to power a couple 8 port netgear switches from an ATX style PSU.  The netgear switches require 12v 1amp DC power.  I'm hoping to create a few cables which convert the 2.5mm coaxial power connector from the netgear switch to a molex style connector for the PSU's 12v power.  In theory, this sounds relatively easy but I want to be sure I don't need some type of protection for the switches, such as a fuse.  Reading about the netgear power adapters it sounds like they have over voltage protection and short circuit protection.  Is this something I need to worry about?


texts: How to convert between G and mV/g of sensitivity?

texts: I cannot for the life of me understand how mV/g or LSB/g can be related to the g sensitivity. For example, how can I find 0.0025 G sensitivity accelerometer given the sensitivity in mV/g? I haven't found resources online to explain this clearly to me. Can someone please enlighten me? Thanks!


texts: Storage bit in OSF and best way to detect falling edge

texts:
I was looking for a way to detect falling edges and I encounter two ways:

|--XIO---ONS------------OTE--|

and

|--XIC------------------OSF--|

|--OSF.OB---------------OTE--|

My colleagues told me that the 1st way is better, mainly cause you save one tag (being the storage bit). My question is why does the OSF need a storage bit and are those two methods equivalent ?


texts:
Consider the following circuit

Capacitor C2 is charged up to 1V from an external source before-hand. The top plate of C2 is connected to the bottom plate of C1. The top plate of C1 is at a voltage of 0.25V

Now, let's say we increased 0.25V to 0.35V:

Due to the increase in voltage across C1, the charge on it must increase according to Q = CV. This is fine for the top plate of C1 which can get it's +Q charge from the 0.35V source, the bottom plate however must receive the increased (-Q) charge from the C2 capacitor.

Thus, negative charge flows from top plate of C2 to bottom plate of C1, hence conventional current flows to C2, charging it up further and increasing it's voltage to 1.1V (random chosen value to illustrate).

Is this correct? It seems wrong to me.
I know I can calculate this with maths, but I really want to understand intuitively how charge is moving. I can't find any resources online that talk about charge moving in detail. I don't care about exact values, I just want to understand roughly what's happening.


texts:
I have a very simple question, I want to learn how to build E-bike (Battery / Controller / BLDC)
I want to understand first the system model and what's needed to be learned to build one.
I searched google but i didn't something clear about that.
Would you please help me .
Thanks in advance


texts: DC-DC converter bypass for VIN = VOUT question

texts:
I need to develop a device that requires 5V power. The device must be powered from 5V (USB) or 12V. I need such a system that will bypass the DC-DC converter when it works from USB and enable the DC-DC converter when it works from 12V.

Will my solution work?

I want to use a voltage comparator with some voltage dividers and voltage reference, so it can short the input and output of a DC-DC converter when the VIN is (let's say) <6V with a P-MOSFET, thus disabling the DC-DC converter and providing the power to the device.

I want to use TPS54331. What will happen if I feed 5V to the DC-DC converter when it configured to output 5V? Will there be a drop? I haven't found this info in the datasheet.


texts: How to measure and plot the voltage of a capacitor over time?

texts:
Hi,
I tried searching and could not find anything (this might honestly be so basic of a question that I couldn't find it). How do I measure the voltage of this capacitor and plot it over time? My circuits class literally just told us to download LT Spice and use it to simulate stuff and has given us no information on how to actually do that. Would very much appreciate any help right now.
Thank you
PS: On a Mac running Catalina and using version XVII of LT Spice


texts:
Hoping this is the correct exchange. At the moment I'm currently renting my house in Canada (120V), and it seems the landlord has attempted to try pull a fast one. From what I understand, or possibly before the previous tenant, there were only two prong outlets installed in the house. The landlord decided to install three prong outlets with of course not having a ground connected.

This is obviously terrible for pretty much everything in my house, but unfortunately the rental board won't do anything about it and I can't afford to do anything myself for the entire house, so instead I'd like to attempt to ground a single outlet or atleast myself (then possibly move on to the rest of the house slowly).

I'm putting together a recording studio in the basement, only to find I get zapped by my instruments and can hear popping and the "sound" of electrical current on my tracks. Would anyone happen to have a suggestion to help clear this up? I used to build computer for a living, so wiring I can get away with, but this I'm a bit stuck on. Any help is appreciated!

EDIT:

Just to make sure I'm not crazy, here's a few images of one of my outlets. Got hot and neutral, but no ground.

https://i.imgur.com/TX7Lyxc.jpg

https://i.imgur.com/IKBMANe.jpg

https://i.imgur.com/zXc9fyc.jpg


texts: Can powered speakers actually send any Power/audio OUT of the input port?

texts: Thanks in advance for reading .So is there any chance that reverse current is sent back by old speakers,from speakers power adapter (which fell down few times on ground) to motherboard's green audio port and affecting/damaging the system.


texts: Current draw and voltage drop of DALI bus line

texts:
I am starting with the DALI protocol and already was able to send/receive commands based on this project. With comments from a related question I improved my circuit and the quality of my signal.
The current circuit follows following schematic and wiring guide and the library for Arduino NANO

In the power line two 100_Ohm resistors are needed in series. This however will drop my bus voltage from 15V to 7.8V and the DALI-line shows the broadcasted signal on the osci, but the command is not recognized. This is probably because the bus line should be between 12-24V.
Increasing the supply voltage to 40V also increases the line voltage >12V. Here the commands are recognized, but the circuit draws almost 350mA and the standard metal resistors are over their limit. I was also able to detect all channels (1.driver-> 3 Channels, 2.driver->1 Channel)
What is the reason of the 100\$\Omega\$ resistors?
They act as voltage dividers, where I would understand that I need a current limiter to supply the bus with max 250mA. I also tried removing the resistors and the current limit of the power-supply was triggered (1A) where the voltage dropped to 2.5V. (Only for <1s, the circuit is not damaged).


texts: In some boards, like Papilio, spi flash connected only to fpga. As I can understand the firmware writes to flash through fpga. How does it works? Doesnt fpga need firmware first to work? If so, how it goes through fpga before any firmware was written in flash?


texts: Difference between spectral efficiency and bit rate

texts: I am reading articles about error correcting codes, facing to a term "spectral efficiency". Due to the context, I guessed that it means "bit rate", but I wonder are these two terms equivalent or not? I will be thankful if you guide me


texts: How to calculate lithium-ion battery energy density

texts:
According to this battery comparison sheet, lithium-ion batteries should have an energy density around 110-160 Wh/kg. Wikipedia cites it may be around 100–265 Wh/kg, although it refers to it as "specific energy" and uses "energy density" to refer to a measurement based on physical volume.

I'm thinking of buying a lithium-ion battery pack rated for 12V @ 6800mAh, giving it 81.6 Wh, and it weights 162 grams, meaning its energy density is 503.70 Wh/kg. Since that level is nearly twice the documented energy density for lithium-ion, is my math wrong? Or are the battery's specs incorrect?

This is somewhat related to this question, but I'm trying to calculate it from a real battery's specs, not the technology's theoretical limits.


texts:
In a project, I am using the PTN78020H power supply, and it has a recommended circuit (from the datasheet linked above) that looks like this:

Now on the input, it requests a massive 4 x 4.7uF ceramic capacitors. I've had a look around and haven't found any place selling through whole ceramic capacitors in values anywhere near that.

Typically a ceramic cap is used to filter high frequencies, and electrolytic have much worse performance, so I don't want to switch all the input caps to electrolytic, but would it be feasible to, say, use 10uF electrolytic and 1uF ceramic?
Tantalum caps come in the 4.7uF capacitance range, and I believe have better performance than electrolytic?

My question is pretty much: Assuming I can't get hold of 4.7uF ceramic capacitors, what should I do?


texts: raspberry pi 3.3 to 5v level shift for led rgb strip

texts: I'm working on my first electronics project. Basically I'm trying to control an rgb led strip from a raspberry pi's gpio pins. I'm trying to convert the raspberry pi's 3.3v up to the 5v required for the led strip. I bought these level converters https://www.amazon.com/gp/product/B0148BLZGE/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1. The docs for the level converters say both 3.3v and 5v need to be supplied at all times. Does this mean I need a seperate 3.3v power supply in addition to the led strips 5v power supply? This is assuming the GPIO pins should be sent through the channel pins on level converter and not through the 3.3v pin.


texts: Op amp voltage follower saturates (high-rail) at 0V

texts:
I have 3 op amps, and they perform in two different ways, but I am not sure why.  I want to buy another op amp that behaves a specific way, but I'm not sure what spec causes it to behave like this.

Here are the 3 op amps I'm using.  I will refer to them as A, B, and C respectively from now on.

A) NJM072CAG-TE2 - Acts Strange

B) RC4558P - Acts strange

C) LM324DR - Acts Ideal

After a lot of hassle, I decided to use them in a very basic way to test their properties using a voltage follower circuit with supplies (V-)=0V and (V+)=5V (now we won't have to deal with gain and such).

I hooked up Vin to a variable power supply (0-5V), and I measured Vout with an arduino and made graphs.  As I increased the voltage from 0->5V and back down, here's what the output looked like for each of the three op amps.  Red=Vin, Blue=Vout

A) NJM072CAG-TE2

B) RC4558P

C) LM324DR

Notice how A and B output a high voltage when the input is 0 (it stays this way until about 1.0V).

So my overall question is: How can I know if an op amp will "Saturate" or not at 0V (Like A & B) instead of following the voltage properly (Like C)?

Thanks in advance!


texts: Does a Breadboard Compatible DC Barrel Jack Have to be Connected to Positive and Ground to Receive Power from an Outlet?

texts:
I am using an Arduino to control an electric lock strike but I don't know how to power the lock with sufficient power. To control the lock from the Arduino, I am using a TIP31 transistor (It is NPN). The transistor will be getting the signal from pin 9 on the arduino and will connect to the ground wire of the lock strike. Since I will only need the DC barrel jack for positive (since the ground wire of the strike will be connected to pin 9 via transistor), I need to know whether this barrel jack will draw power from a power source even though it will not be connected to ground.

P.S. The lock strike needs 12VDC.


texts: PC shares memory with external microcontroller

texts:
I'm looking for a PC hardware interface that matches these needs-

The PC will constantly be busy performing calculations. Each time there is a calculation result (every ~1ms) I want it to share it with an external micro-controller that is attached to another (closed) unit via RS232, the unit will use a predefined protocol to request the result when it wishes to do so (undetermined timings).

so-

PC <-> micro-controller <-> unit

Theoretically I could connect the PC directly to the unit via RS232 (mux, cause I need around 6 units), but I did not want to interrupt the PC with too much I/O, I want it to be focused on the calculations.

On the PC<->micro interface I want something fast, so PCI seemed like a good idea - I can have the micro-controller sit on a pci card and 'share' memory (mapped) with the PC to transfer calculations result, and also communicate with the unit.

There are many FPGA cards on PCI out there, but I'm looking for something like ARM or even something more simple on the card, does anyone know some good product for that?
Is the PCI a good idea for my setup? Do you suggest something else? I really want this interface to act like a shared memory.

Thanks

Elad


texts: Failure of Bourns Common Mode Chokes, Series SRF2012

texts:
I work for a company that designs and manufactures electromagnetic flow meters.  One component, a Bourns common mode choke, PN SRF2012-361YA, seems to have a failure rate in the field of approximately 1 per 1000.

Since the meter is already assembled and installed, the entire meter becomes inoperable.  The most common failure mode is shorting of the two coils.  It is almost impossible to exceed the rated voltage or current in the circuit application.

What is a likey failure mode of this simple electical component?


texts:
I have a switched capacitor circuit that looks like below:

It operates at 80MHz to realize a 625k resistor. It works fine in the circuit. I tested with VDAC(input)=1.8V and the voltage at the right is 1.5V. Average current of 0.46uA flows in the circuit.

However, I am very much concerned about the practical implementation problems (noise). When I found the noise voltage of this circuit at 100kHz bandwidth, it comes out as:
$$\frac{K.T}{C}.100kHz = 0.0207$$ which is -33dB.

The input referred noise requirement of my circuit is around -110 dB. Am i doing something wrong or its just that the switched capacitor is not feasible?

Even if I try to add bigger capacitor in parallel, it can improve the accuracy, however, the noise voltage still cannot match to -110 dB.

Any guidance would be helpful.

Thank you.


texts: Net-Zero Magnetic Fields in a Three-Phase Motor

texts:
When a three phase motor in running and you clamp an amp-meter around all three of the phase wires, you should expect to read zero because the magnetic fields cancel each other out.

I'm having trouble visualizing the process of fields canceling each other out in this scenario. It makes sense to me for two wires carrying AC current in opposite directions that are lying parallel to each other. But for three phases, I don't understand how all three fields are canceled.

Some insight into this would be appreciated!


texts: Powering a constant current strip with a constant voltage supply

texts:
I have an application where I have the following components installed.
277 Vac to 48 Vdc Constant Voltage Driver (MeanWell) -> 48 Vdc CV PWM dimming interface controlled by 0-10 V -> constant current strip (44-48 V and can be run at 40, 50 or 60 mA per segment)
It appears to work correctly, but are there any long term issues with running a constant current strip with a constant voltage supply, as long as the current draw (maximum current available by driver is less than the combined segment maximums) and voltage are within range for the strip?
Is there an issue with the PWM function on the constant current strip?


texts: I am new to PCB design. My circuit contain a voltage of 3.3V, maximum signal frequency of 400 kHz and less than 10 components connected to ground. Do I really need a ground plane in my PCB? Or to be precise: When should I use a ground plane?


texts:
I need to be able to simulate communications with a sensor device over a large length of wire (0-10km).  This is for quite low-speed comms (10khz max, usually 1-2khz though). This would be FSK... but at some point I may have to handle a low baud RS232-like signal as well.

Mostly, I'm looking for voltage drop and signal distortions.  Delay doesn't matter much.

How would you go about it?

EDIT:

I've been able to determine the cable is indeed a (fairly nonstandard) type of coax. I now know resistance and capacitance per unit length, cross section geometry, and that the insulation resistance is high enough not to matter. It wasn't initially clear if the return line was a separate run or not.

This would be a test setup for multiple target devices. Most are FSK of various frequency choices under 10khz, some are ASK (you could almost use a standard UART after bandpass/filtering). All are riding on a high DC offset (comms over power).

In the past, I've seen people build a simple rotary switch that swaps in resistors, capacitors, and maybe inductors to simulate a given line length. Could that be good enough?

I'm currently trying to build a few simulations in LTspice.

EDIT 2:

Okay, if I go with just adding resistors, caps, and inductors... what does the model look like?  The RLGC network below is assuming the grounds are at the same potential I believe (a safe assumption on PCBs w/ground planes). The return in this case is through the outer shell, and it's resistance is probably 3 times higher than the inner conductor. Does that change things significantly? Do I just add another resistor on the bottom rail, and split the capacitance on both sides of it?


texts:
I am designing a 4 layers PCB with the following stack-up:

Signal flooded with GND
Solid GND plane
POWER plane
Signal flooded with GND

For the top Layer I want to divide the GND plane (flooded) into 3 parts and connect them to the solid GND plane through vias.
Can this decrease the noise from the digital circuits (digital sensors) and the power supply that can affect the analog circuit? {J6, J13 } (ADC + PASSIVE FILTER)
Would it be better to connect all the GND pads to the solid GND plane directly or should I split the ground plane?


texts: Thevenin Equivalent Circuit of Two-Port (Transmission Matrix)

texts:
The question is to calculate the thevevin equivalent of the following two port network described by the transmission matrix
[A B]
[C D]

The way I approached this was from the transmission matrix we know that
$$
V_1 =AV_{th} - BI_2
$$
$$
I_1 =CV_{th} -DI_2
$$

Now, to find open circuit thevenin voltage source, we open circuit right side, making
$$I_2 = 0$$
Subbing this back in to the first equations,
$$ V_1 = AV_{th}$$
$$ I_1 = CV_{th}$$

I'm not sure where to go with this now?


texts: Getting a small voltage when it is meant to be 0V in a schmitt trigger circuit?

texts:
PR1 is floating between 10V and 81.3mV. I am finding it difficult to explain why PR1 is not floating between 10V and 0V...

I tried to read about it, but it feels as if I'm getting voltage out of no where. Is there always tiny voltage associated with schmitt trigger..?


texts: "Disconnecting" an opamp from a potentiometer circuit

texts:
Last time I asked about changing a sensor (which is a potentiometer) output in various ways. I've decided to go with an opamp and circuit like this:

Now I'm looking for some device that will disconnect the opamp from the potentiometer output based on an ON/OFF (3.3V) signal.
Right now the options I see are:

Relay - does exactly that, but I don't want any mechanical parts, also the dimensions are an issue.
MOSFET or MOSFET relay - the opamp output must be always higher than Vgs of the particular MOSFET.
Bipolar analog switch like the MAX4541 - it has low I/O current and I need higher current capability because of the resistor and potentiometer values.

What else can be used?
Also can anyone tell me about a good alternative to AD8244 unity gain quad buffer? I need only one buffer circuit with a smaller and easier to hand-solder footprint (SOT23-5 maybe.)
@EDIT
I will use MOSFET SSR as suggested in comments. Question regarding AD8244 alternative remains.


texts: Problems with Infrared circuit on a PCB - Is it the board or schematic?

texts: I am using the toner transfer method to apply my circuit for 6 sets of infrared emitters and collectors connected to an RJ15 cable on a PCB for use with a Raspberry Pi B+ board (connected via IDE cable).  The circuit for a single emitter and collector works (82 ohm resistor to ground on emitter, and GPIO on power in front of a 10k resistor for the collector).  I created the schematic and board in Eagle and then created the physical PCB.  To my confusion, it did not work with a single RJ15 plugged in to one of the 6 jacks.  I didn't wire them in series.  I used an LED between traces on the board to find that there is power, but no signal from the IR collector.  Is it possible that I've somehow made a mistake in my schematic or final .brd file?  If not, I guess the problem is with the physical board.


texts:
Our TDS2014 o-scope is measuring signal from a 33210A waveform generator. The signal out of the generator is a 1VPk-Pk sine wave. But the o-scope is reading the signal as 2VPK-PK. Is there something wrong with this?

We checked the multiplication of the probe and o-scope . Their multiplication were the same.

Has anyone encounter this problem?


texts: How far does reforming a capacitor help? Does it have any adverse effect on using such a capacitor on components?

texts:
I read a few articles on the internet about reforming capacitors. Does this actually apply only to a capacitor that was stored during a certain period of time or can it be used on any electrolytic capacitor? I know about the capacitance and ESR measurements, but lets say if these are within okay range.

I've a bunch of old capacitors as shown in the picture. I was thinking maybe use the leakage tester of my Eico 950B and use it to form the capacitor as mentioned in a military article I'd read.But I also read on some forums people say the these old capacitors on some circuits with transformers can cause it to give "magic smoke!". How true is this?

In the order of make:

**Japanese:**SMC 16V 2200uF,

European: Philips 385V 22uF,

US: Nippon (Chemi-con) 15V 64000uF, Mallory 25V 15000uF, General Instruments Can type 450-350-250V 40-40-30uF & Astron 150-150-150V 100-100-100uF.


texts: CC430 circuit isn't working like an almost exact copy

texts:
So I have two PCBs(They are Kicksats) with the following schematics:

This is the bad one.

This is the good one

The cutoff in the schematic is just the irrelevant solar panels and the block to the right is just an accelerometer which has nothing to do with the radio.
I get the second one that produces a signal like this:

and the first one to produce a screaming signal like this:

So I'm sure it's the hardware because I used the same code on both(the results are the above you see). I've tried basically everything to get the bad one to work. I've changed gauges of wires for the antennae, tried changing the lengths to the half wave length and quarter wavelength(I'm working with 868 MHz). I've repopulated the board. I've made another one entirely again. I put on an LED just to make sure that I put on the microcontroller the right way and no luck.
 Here is what each looks like: The Good one:

The Bad one:

Any suggestions are welcome.

This is the schematic for the bad

This is the schematic for the good not including the solar panels(which I've detached.)


texts:
The title says it all. I'm doing a project with a spinning HDD disk with a slot cut in it, RGB LEDs,  and precise turning on and off of the colors.

I'm planning to glue a magnet and use a hall effect sensor, but just opened another HDD and this one has 4 pins instead of 3. I applied voltage to all 4 pins (5V)so I hope I didn't fry the sensor, but I've identified 3 that have 8 ohms, 1 has 4 ohms. So I want to know, can I forget using a magnet and use the sensor already in the motor?

If so how would I wire it to receive pulses on each rotation, or magnetic pole switch?

Any insight on this is greatly appreciated as I've googled and cannot find one example of how to wire it.


texts:
I was developing a footwell controller for my car, using RGB LEDs for the lights, an Arduino Nano for RGB controlling and an auxiliary PWM generator
(pure white lights) when the Arduino is off. The two signal sources are complementary.
The problem arises at the end stage when the two signals have to merge to drive the MOSFETs (PWMR, PWMG and PWMB comes from the Arduino):

simulate this circuit – Schematic created using CircuitLab

The square wave coming from AUXPWM after it passes the 1N4148 is completely destroyed, it isn't able to drive the MOSFET anymore. The LTSpice simulation produces this graph from the schematic above:

It's possible to see how the signal is almost flat after passing through the diode. I really cannot understand what is happening here, so am I missing some underlying knowledge or is the simulation plain wrong?

Edit: the MOSFET are N-Channel I did the schematic wrong, sorry


texts: N-Channel MOSFET as on-off switch between battery and load

texts: I'd like to use 3v microcontroller to activate a small fan after the microcontroller wakes from sleep. I'm not quite clear on the placement of the load (i.e. fan) and the LiPo battery in a MOSEFT schematic. My understanding is that I can use an N-chanel MOSFET to create a closed circuit between the LiPo and fan by supplying voltage via GPIO to the gate. Am I correctly understanding this? Below is my circuit diagram. Thanks for any feedback.


texts: Full wave AC Voltmeter Vs True Rms Voltmeter

texts: Does a full-wave rectification AC Voltmeter give the same indication as a true rms voltmeter when you measure a 50 Hz sine wave?what happens if the the sine wave is clipped by an inadequate transformer?


texts: Where is the flash memory for this IP camera board?

texts:
I just opened an Escam IP camera and this is the main board.
You can see the HI3516 SoC + H5TQ1G63EFR RAM + that thing with adhesive that in the second photo I took off and you can see it's a TMS1102NL which according to https://www.yoycart.com/Product/628493863187/ is a network transformer. That MK24C16A looks like a small EEPROM.
On the other side we have 2 small microcontrollers: 8041NL 1625SA4T and 25Q128FVSG but I couldn't find anything about them on google.
So where is the flash memory?


texts: How to modulate Transceiver module for use with ATmega164PA

texts:
I am using a transceiver TFDU4101-TR3 to communicate with another device which has exactly the same transceiver. I bought this thinking I can communicate with the transceiver using my microcontroller ATmega164PA running at 8 MHz at 3.3V. Turns out I cannot use serial without the endec which I cannot buy because of budget constraints.

So I was looking to use the RxD and TxD pins on the transceiver to somehow modulate the signal. I made my PCB ages ago and the transceiver connects to the microcontroller through RX and TX lines. Can I still modulate the signal using RX and TX pins on the micro as GPIOs?

I was looking into pulse width modulation but for that do I need to connect the transceiver pins to OCxA and OCxB pins on the micro? Can I still make do with RX and TX pins on the micro used as GPIOs and somehow use that in conjunction with PWM?


texts: I have a 4x4 LED matrix multiplexed, meaning that I can control individual LEDs with just 8 lines rather than 16. I am interested in finding the power consumption of the grid. The LED has forward voltage drop of 1.8 V and I am using 330 ohm resistor with each LED. The power supply is 5 volts. Appreciate any help!


texts:
I need a little help with some electronic components:

From my RC system a I get a signal which is 3.3V PWM, 5 volt and GND.

I need to make a 5V PWM out of this for my camera.
PWM values are 1-32ms and need to be identical (3.3V input PWM= 5V output PWM)

I was thinking of a relay or transistor but I'm not sure about that.

Can somebody help me with a schematic and shopping list?


texts: To amplify the output of a linear Hall Effect device for the purpose of driving a voice coil

texts:
I am working on an invention that is 99% mechanical in nature. However, it requires a closed loop servo, consisting of a linear Hall Effect sensor, whose output is amplified to drive a voice coil. I have come up with the circuit shown below but can't quite figure out how to make it perform correctly. The output of the Hall Effect sensor varies from 0V to 2.5V and in response to that I would like to see R7 (which represents the voice coil) to conduct from 20mA to 100mA. Which resistor values do I have to change to accomplish that?   https://www.circuitlab.com/circuit/42gc63byzs44/complete/

**Edit in response to Neil, UK:**The output of the Hall Effect sensor is controlled by a magnet attached to a mechanical slide. The voice coil acts as a mechanical forcer. The voice coil consists of a re-purposed actuator arm from a hard drive. Currently I am controlling the voice coil with a potentiometer and it requires 20mA to 100mA to work correctly.


texts:
During my journey to electronics I came across several questions about capacitors.

If we connect an empty capacitor to a fully charged re-chargeable battery, after the battery charged the capacitor, it then became empty (wires still connected and never touched), what will happen in this situation? Will the capacitor re-charge the battery? Or will its charge drop due to the battery’s internal resistance without charging it?
If we replaced the battery with a charged capacitor (empty capacitor and charged capacitor with same values) what will happen in this situation?
If we connect a charged capacitor and an empty capacitor and a charged battery all in parallel, what will happen?

Any help to clear my doubts is preciously appreciated.


texts:
I am trying to simulate an IR sensor circuit as described here:

https://circuitdigest.com/electronic-circuits/ir-sensor-circuit-diagram

I am using EasyEDA for this purpose, and the following is my first attempt:

After making this circuit, I wanted to know voltages at few points and I have added the probes as can be seen in the schematics.

Then I started simulation ("simulate this sheet"). But I got the following error:

Circuit: gooduntitled

Doing analysis at TEMP = 27.000000 and TNOM = 27.000000

Warning: singular matrix:  check nodes u1_7 and u1_7

Note: Starting dynamic gmin stepping
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Warning: singular matrix:  check nodes u1_7 and u1_7

Warning: Dynamic gmin stepping failed
Note: Starting source stepping
Warning: singular matrix:  check nodes u1_7 and u1_7

Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful gmin step
Note: One successful source step
Warning: singular matrix:  check nodes u1_7 and u1_7

Warning: singular matrix:  check nodes u1_7 and u1_7

Warning: source stepping failed

DC solution failed -

Last Node Voltages
------------------

Node                                   Last Voltage        Previous Iter
----                                   ------------        -------------
u1_7                                              0                    0
volprobe2                                         0                    0
volprobe1                                         0                    0
led1_2                                            0                    0
gnd                                               0                    0
+5v                                               0                    0
led1#branch                                       0                    0
led2#branch                                       0                    0

doAnalyses: iteration limit reached

op simulation(s) aborted
Error(parse.c--checkvalid): volprobe1: no such vector.
ngspice-26 done

I  am unable to understand  why I am getting 0 values for volprobe1 and volprobe2, and what is the meaning of the errors.


texts: Using shift registers with ws2812-b (or c) leds and how to treat the DO signal

texts:
Hello  Community Newbie here.
I had a query i would like help  with. I have 8 chains of ws2812c leds (12 leds in each chain)  which I would like to turn into a matrix.
Inorder to do this I was thinking to send each of the DIn at the start of each chain to 74hc595 (pins Q0-Q7 respectivley and each of the led DO at the end of the chains to 744hc165 shift register.
Would this work??
Especially if i wanted to stack each matrix via pin 9 and 14 of the hc74595  and pin 7 an pin 10 of the 74hc165 to create a larger matrix.
I ask as I am struggling to find out how to treat the D0 signal once you get to the end of each chain.
ANY help or direction to resources that might help me would be greatly appreciated .
Power is comming from  7.4V 7400mAh 54Wh battery which will be attenuated to supply the STM32F4 which will supply the SR chips the battery will also supply all the leds approx 3.4 amps drawn;
if all leds are on and at full power.(there will be 672 leds in theproject or 56 chains of 12 leds).
Thankyou in advance for any pearls of wisdom.


texts: digital logic - positive edge-triggered d flip flop triggers when input is on the decreasing edge

texts:
I have this scheme from my lecturer of digital logic. It is supposed to be an edge-triggered D type flip-flop, with a reset so there's no undefined zone at the start of the simulation of this schematic. We're using Lattice Diamond to make these schematics and Active-HDL to simulate them.

Now everything's well except for one thing, which is what happens when my clock is rising and my D (which is input), is decreasing?

I've read on these forums that this is because of metastability and the inability to determine exactly what should be done. So I made this schematic and my simulation returns these results:

Where C is the Clock, D is input and Dinaminis is the output

You see the output rising on 30ns, when the Clock is increasing and D is decreasing. Then at 50ns, C is rising and D is rising too, but the flip-flop stops.
Are these results okay or am I wrong somewhere? Does this flip flop use previous output to determine which output to choose? Thank you for all your answers


texts: How to build a simple transistor switch?

texts:
How to build the following:

A simple Transistor turn-OFF switch.
A simple transistors circuit that has its own power source, but when I apply a second alternate power source then it will switch to the second power source. (power sources are two 9V batteries). I don't want to use a relay!


texts: There is the presence of noise(High frequency) at simulation (post-synthesis and post-implementation)

texts:
I am using verilog in VIVADO(XILINX) design tool, at simulation(post-synthesis and post-implementation) of my design i am getting a noise(High frequency-even greater then actual board clock) at near both edges of my derived(slow) clock. Can anyone tell me how to remove this unwanted noise.

the snapshot of simulation as follows:

The verilog code for this as follows:

module counter(
input clk,            //Actual clock(100Mhz ->Artix-7)
input rst,
output reg[7:0] out,
output reg nc         //New clock(slow)
);

reg [25:0]temp;
reg slow;

             initial
                       begin
                           temp=26'd0;
                           slow=1'b0;
                           out=0;
                       end

    always@(posedge clk)
        temp<=temp+1;
    always @(temp)
    begin
       if(temp==26'b10111110101111000010000000)//clock divided by 50Mhz
        slow<=slow+1;
     end

     always @(slow)
             begin
               nc<=slow;
             end

    always @(posedge slow)
    begin
      if(rst==1'b1)
       out<=0;
    else

       out<=out+1;
     end
 endmodule


texts: I fried my Raspberry Pi while using L298N but I don't understand why

texts:
Everything seems to indicate that I fried my raspberry pi: the green light wouldn't turn on, I changed the SD card for a new one but it still didn't work.  That is a shame because I was having a lot of fun! So I will definitely get another one, but I really would like to understand how it happened first (so I don't make the same mistake again.)

My understanding is that there are 2 main ways of frying it:

Using it to power something that requires too much energy (like a motor.)
Input more voltage than it can handle to one of its pins.

I have always been aware of that and always tried to be very careful with both things, always double checking and such.

When my Raspberry Pi stopped working I was trying to get this to work:

Before running anything I triple checked the whole connection (which is very simple but I still checked wire by wire more than once) and I'm 100% sure that the ground and the 3 pins (23, 24, 25) were connected correctly.

When it stopped working I had the circuit connected but I wasn't running any code (I did it a few times before it) the code also only has outputs:

import RPi.GPIO as GPIO
from time import sleep

in1 = 24
in2 = 23
en = 25
temp1=1

GPIO.setmode(GPIO.BCM)
GPIO.setup(in1,GPIO.OUT)
GPIO.setup(in2,GPIO.OUT)
GPIO.setup(en,GPIO.OUT)
GPIO.output(in1,GPIO.LOW)
GPIO.output(in2,GPIO.LOW)
p=GPIO.PWM(en,1000)

In that scenario, what kind of mistake could I have made to have my Raspberry Pi stop working?

I did play with the L298N quite a lot to get to understand it, at some point I even put 24V into it (but when it stopped working I had that aforementioned exact configuration.) Still, can you blow up a Raspberry Pi with everything connected as "output?"

My understanding is that the voltage would never "go in."

Could you guys advise if there are more common "blow up" scenarios that I didn't mention?

Edit:

To add more clarity based on comments:

I was following this tutorial
I see people asking why nothing is connected to the +5V of the L298N. My understanding is that the orange wire of the image (connected to the pin 25 on the Raspberry Pi and the "Enable A" of the L298N) would make that unnecessary. In any case I was just following the instructions of the aforementioned tutorial. Could someone clarify where would that +5v be connected and why wouldn't it be mentioned/used in there if it is necessary?
I bought my L298N on Amazon.

I have a Raspberry Pi 4 arriving today and would hate to be in the same situation (I sure cannot afford this hobby if I keep breaking them) so I'm reading every comment and suggestion with huge interest.


texts: Addition and subtraction of binary digits

texts:
I have to solve the following exercise :

Extend the circuit of the first part (the first part was an adder of integer numbers of 2 binary digits) in order to execute addition and subtraction of integers numbers of 2 binary digits (AB+-CD). Considering that numbers AB, CD are in 2's complement arithmetic. What does 2's complement mean and how I create the truth table?


texts: problem with printing function return value

texts:
I am new to programming. I have small doubt, I know this is simple question but I am confused. I have the following function:

void ReadAdConfReg(void)
{
    SPCR = 0x5D;
    ADC_CS = 0;
    while (MISO_PIN != 0) ;
    spi(0x50);
    adcConfig = spi(0xFF);
    adcConfig = (adcConfig << 8) | spi(0xFF);
    ADC_CS = 1;
}

I have declared adcConfig as global variable: unsigned int adcConfig.

How can I print the adcConfig value. Because this is a void function, it doesn't return any value.

I have tried like this:

ReadAdConfReg();
printf("configreg:%d",adcConfig);

Is it wrong? Or how can I print adcConfig value.

Controller is ATMega32A, compiler CodeVisionAVR.


texts: What does "the resistance looking into" mean?

texts:
See this circuit, from Sedra & Smith microelectronics, 6th edition, page 287:

It says that the resistance between the gate and source looking into the source is 1/gm, but that the resistance between the gate and source looking into the gate is infinite. Why? What does "looking into" even mean and what difference does it make?

According to my understanding, whether you look into the source or into the gate, the resistance between G and S is 1/gm. If you put apply a voltage between G and S and measure the current with Ohm's law, you would find that R is 1/gm.

There must be something I don't understand.

EDIT: Here's another related thing I don't understand. See this circuit:

It says that Rin is vi/-i. I can kind of see where does this expression come from but I don't know the formal definition of Rin. Why is there a - in front of the i?


texts: A 1USD 11W led bulb circuit and parts analysis

texts:
I know this is not a huge deal, but still I want to do it because for Three reasons: 1, it only costs 1 usd. Yep, this is a very cheap led bulb, and I need to take it apart to see if it's trust worthy. 2, It's a great opportunity to learn something new and exciting. 3, I need some parts for my Led project.

(Update: I actually found out that this $1 bulb is made by uninex. A comparable 8 watts costs $7 usd in their website, so I think I got a good deal here. It's probably being subsidized like one commenter has said.)

With that being said, I took apart the thing, and my first impression is impressively surprising. This bulb use better parts than all those other more expensive bulbs that I have took apart over the years. I am super skeptical whether this is really a 11w led bulb or not because counting all those SMT leds doesn't really add up to 11w anyway, and that the outer case is actually plastic, the only heat sink is that Aluminium disc. See photo below, Q1: Can this really dissipate 11 watts?

Other than that, the manual soldering connectors are crude. Not really complaining here, it should works fine. The PCB looks very nice and the parts look New and high quality to me.

I also notice there are few parallel resistors pairs, like a lot of them, which is a very cool design that I probably will be copying soon in my future project.

The One part that I don't really know, but I am sure that I have seen them in other PSU before, is that green round thing. Q2: what is that?

Finally, There is my trace circuit for this LED bulb. Other than that green thing (I assume it's some kind of fuse for the moment), the top part is easily understood, but the bottom part is more than confusing. I know the bottom part is a high frequency switch, but Q3: how does it really work? (Note: I am not too sure if B is C or C is B, but E for the NPN is correct.) There is also a 63v 330uf capacitor between the 473 resistor. The circuit seems very simple, but I don't really get it. It's not an isolated design, So how does it step down a  120v to 65v and less?

Update with corrections and voltage read-out:
One of the diode is actually a 51 voltage zener if I am not wrong. The transformer measures 0.4:3 while in the PCB. So for Q3: How does it drop down from 104vdc (Point B) to 50vdc (Point LED-)? I don't really see a current path here. (The leds are 6 in series and 3 pairs in parallel, total 3x6=18. 3.6vX6=21.6v, but voltage read out is 50v, very strange.)

To aid discussion:


texts: I want to build a automatic agricultural robot for my final year diploma project. The basic idea is to program 8051 to drive the robot in a fixed path in farm for ploughing the farm which i am planning to do by setting a particular distance till which it will go straight and then take a U turn and plough in next lane. Width of the farm will also be set so when it completes full farm it'll stop and go back to starting point. the only catch is to reprogram it as per size of the farm of the person who uses it. So i want to add a number pad with which he can set the length and width of the farm as well as width of each lane as per his needs without professional help. Can this be done using 8051 or should i go for AVR or PIC microcontrollers. I have just started studying programming and interfacing of 8051 so I am not that good in programming. If its possible how do i do it. can someone please help me with circuit diagram for this project. After everything i said i need in my project if i still get an empty port in microcontroller I would love to add a fertilizer sprayer or water irrigation system and a GSM module so that a farmer can simply ask the robot to start working using his mobile phone. As I am making just a prototype i want it to be as small as possible. Suggestions are welcomed.


texts: Why Collector-to-Base currents ratio in a BJT transistor is always greater than 1?

texts:
In fact, this question has been asked on the EE site, but it's not well-answered. I suppose it might be more on-topic here.

According to this answer:

  Note that the holes injected into Emitter are supplied from Base
  electrode (Base current), whereas the electrons injected into the Base
  are supplied from Emitter electrode (Emitter current). The ratio
  between these currents is what makes BJT a current amplifying device -
  small current at Base terminal can cause a much higher current at
  Emitter terminal. The conventional current amplification is defined as
  Collector-to-Base currents ratio, but it is the ratio between the
  above currents which makes any current amplification possible.

First off, Why collector current increases as base current increase? Is the former causes the later, or the later causes the former, or something else (voltage on electrodes, maybe) causes both?

And here is my question, Why collector current always increases more than the increment of base current? Say after something changes, a extra holes are "injected into" emitter region, and b extra electrons are injected into base region. Then why b is greater to a?


texts: Which N channel mofoset should i use for PIR sensor to turn on LED strip 12v 6A

texts:
As i am not a graduate of electronics i have no idea about the transistor that i need to use. Can anyone suggest which N channel MOFOSET should I use to turn on my 12V 6A LED strip. The output given by PIR is 3.3v 1A. Source given to PIR is 12v 6A. I was suggested to use RFP30N06LE but its not available and it doesn't fully open at 3.3v instead it fully opens at 5v.
Kindly help


texts: 6 Volt Futaba Servo controlled by a 5V Arduino

texts:
I've been able to hook up a Futaba S3003 servo directly to my Arduino and it works perfectly. However, when I power it with an external 6 volt DC power supply (instead of the Arduino's onboard 5V) it fails to work.

I'm assuming I need to translate the 5v "language" of the Arduino to the 6v "language" that the servo now uses. Pretty new to this. Any and all help is greatly appreciated.

EDIT: My question, generalized, is how do I use an external power supply, that's more than 5V, with a servo and control it with an Arduino?

Here's a photo of how it's setup (and working).


texts:
I have some question about programming options for ICE40HX8K-BG121
These are some facts I’ve collected which are causing some confusion:

The iCE40HX-8K Breakout Board uses an FTDI USB-to-SPI chip to program either SPI flash or the ICE40 device directly.
The documentation for programming cable HW-USBN-2B indicates the FTDI drivers are needed.
The programming cable support JTAG, but the connection table for ICE40 devices indicate SPI not Jtag.
The open-source project TinyFPGA appears to use the ICE40 device to program the flash, then reads it again at power on.

So my conclusion generally is that the SPI Flash needs to be programmed by Lattice Programmer running an FTDI USB-to-SPI chip, then this is read back by the iCE40 at boot.
Is this correct?
So I have these questions:

Does ICE40 support Jtag?  The Programming Cables User Guide suggests no; ICE40 appears to use SPI only
When using SPI flash with iCE40, is it expected that the external SPI master (not the jtag-controlled iCE40) program the flash?
Does Lattice Programmer support only FTDI vendor specific USB-to-SPI chips, or can SiLabs chips be used?
In my design can I use FT4232H Hi Speed Quad USB UART IC?
If I use FT4232H to program SPI Flash, does this mean I can avoid using the HW-USBN-2B cable?
Does Lattice Diamond support iCE40, or must I use only iCE Cube?
Is there a command-line tool chain for ICE40?  I’d like to use something like a makefile or build script to rebuild and program.


texts: Waterproofing my pulse width modulator board

texts: I want to use a pulse width modulator to replace the on- off switch on my modified electric trolling motors. (I take disabled vets out on motorized kayaks).  The modulator works great but, I need to water proof it somehow. What's the best way to do this? What  material should I use ?  How do I apply it and what should I not apply it to?  From my research, I understand some of the issues such as using an epoxy for instance that is thermally but not electrically conductive and that has minimal shrinkage when it dries.


texts: How to make a USB 3.0 slave that can draw 900 mA?

texts:
I have a simple electronics project where I need to build a device powered by a USB 3.0 port. The device controls some motors, so it needs quite some power. I need nearly 900 mA, which as far as I know, is the max. USB 3.0 port can provide.

However, I don't understand what should be there on the slave side for the USB port to supply such current. Would it be enough to put some specific USB bridge IC, such as FTDI? If so, could you recommend one? Or maybe I can use some simple USB hub for example?


texts: Via in Pad (Does Via Count Affect Cost?)

texts:
I have never gotten a good answer from board houses, but once you require a via in pad process (IPC 4761 Type V) you might as well do as many as you want right?
Effectively 1 vs 100 vias is going to be the same amount of work, and thus a similar price? I find I typically try to user them as little as possible, but in reality if I need an IC that requires it for route out, I might as well use them all over and maximize board density (if desired)?


texts: Can I draw 2,2A current at 9V with AA batteries?

texts:
I am new to electrical engineering aand I need a battery for a project of mine. To power the whole system I need 2.2A of current (that is the max current the motors will need, though they will not be running constantly) on 9V voltage.

Can I even draw that much current from AA batteries? And can you also tell me how the batteries should be allinged to be as least space consuming and what will the capacity of all batteries be?


texts: How to choose a low power Microcontroller?

texts:
Cortex-M0+ from NXP and Freescale claim they have world leading energy efficiency.

TI Wolverine also claim they cuts power consumption in half and have the lowest power in memory, peripheral, standby and active.

In some data logging application which platform consume less lower?
I have 3 channel sensor with a sampling rate about 3200hz.


texts: Is it possible to specify a script that should be executed as soon as synthesis starts in Synopsys Synplify?

texts:
The Synopsys Synplify Pro is used internally to carry out synthesis in Libero and probably other places. Is there a method to assign a tcl or python script to be executed just before or just after synthesis?
A script that runs just before synthesis can be used to generated compile date and time into a VHDL file that will then be compiled into the project.


texts: CE-compliant Schuko mains power switch: do I need to switch both poles?

texts: I am currently revising a plug-in power meter (i.e. a power meter that you plug into mains, then plug the DUT into it) for CE compliance. It features power switching using a latching relay, only on one pole. Because Schuko is reversible, do I need to add an extra relay so that both poles are switched?


texts: Summing amplifier - output voltage and power supply

texts:
I have to solve a problem where a summing amplifier has AC and DC as inputs.
I calculated the output voltage min and max with the formula:

$$
V_{output} = \frac{R_{f}}{R}(V_{1}+V_{2})
$$

So I have values of V=-30 V=+10.

Now, my problem is that the question states that the amplifier is powered by a ±10 volt supply.

Does it mean that my two output voltages can be only V=-10 and V=+10?

Or how do I calculate the fact that the power supply is ±15 volts?


texts: How would I use an oscilloscope to measure sound signals?

texts: I want to detect an audio frequency, something about 10 kHz in order to observe the doppler effect. How would I do it? Do you guys have any recommended reading about it?


texts: BeagleBone Black - power supply sensitivity

texts:
I've bought a AC/DC adapter which per its specifications should output 5VDC and deliver 3A. I was going to use this adapter to power my BeagleBone Black (BBB) with. However, when I'm measuring the output from the adapter while it's idle (not powering anything) with a good-quality multimeter, it reads 5.24V.

The BBB System Reference Manual (Rev. C) states the following:

  The board requires a regulated 5VDC +/-.25V supply at 1A. A higher
  current rating may be needed if capes are plugged into the expansion
  headers. Using a higher current power supply will not damage the
  board.

As one can see, my adapter outputs a voltage that's pretty close to the upper limit of 5.25V that the manual says is the maximum supplied voltage for the BBB. Is it still safe to use it to power my BBB with?


texts: What power supply do I need to power 4 peltier plates with 5A 12V each?

texts:
I need to power 4 peltier plates (tec1-12706) with 12V and 5A for a thermoelectric cooler project.
I wish to have maximum cooling. Also I need to attach a few(4) computer cooling fans to dissipate the heat from all 4 peltier plates.

Please let me know what will be the best power supply to power all those altogether?
(Excuse me if I have asked a very basic question because I don't have an electrical background)
(I found some articles on computer power supply but not sure if it will give me enough power to power all 4 peltiers if so how to connect them parallel or series)


texts: Will back emf damage a lithium ion battery?

texts:
I am prototyping a battery-operated toy containing a couple of motors - these motors are driven by a pair of h-bridges which are controlled by a micro controller.

I'm running this whole thing from a lithium ion battery, and I happen also to need 5v and 3.3v logic rails.

So I have a boost circuit giving me the 5v from the lithium ion (it's for some of those dinky little ultrasonic sensors), and I'm linearly regulating that down to 3.3v for the micro controller.

So far, so good.

Of course, when the motor runs and/or changes direction, we see voltage spikes on the battery of anything up to about 8v. I have lowpass filters on the logic supply rails, and they survive (for now...), but will that voltage do any damage to the lithium ion battery, and if so how do I mitigate that?

Also - when the voltage spikes happen on the battery, and thus the regulated supplies, I see a voltage drop after the lowpass filters. Is this something to do with phase? It just seems so counter-intuitive.


texts: How to draw constant current independent of voltage for capacitor testing

texts:
I have a 150 farad 2.7 volt super-capacitor. I want to test the cap under various loads, .1 amps, .5 amps, and 1 amp. I will be creating a graph of the voltage over time.

How can I constantly draw the specified currents independent of the voltage? Schematics/explanations for beginners help a lot.

I know I can probably just figure out calculations, but I would have a lot more fun doing a hands-on experiment.


texts: MOSFET is overheating when running on a 20A load

texts:
I'm trying to build a controllable switch for a heavy load (3D printer), controlled by a microcomputer.
I don't want to use relay because of slowness, sound and durability. So I've built a switch based on MOSFET IRLB3034 datasheet.
And here is my circuit diagram:

The main issue is, the transistor getting more than 150 °C after 20 sec of working at full power.

Vgs = 4.5v or even 11v (that makes no difference) of constant DC
Vds = 1v and rising
Current is about 15A (max of power supply is 20A)

What could be my possible mistake?


texts: How to avoid shorting the boards while using Probe or Multimeter?

texts:
I have been working on multi layer boards at my work. Occasionally I short the boards because of probe hits a wrong spot. I measure various power rails and most of the output capacitors are 0201 and 1005 size.

Can people here provide some tips on avoiding shorts while probing?


texts: What do you call a device that reverses polarity?

texts:
I am replacing a DC power supply used in a lab experiment. We need to be able to choose a positive or negative current. Bipolar power supplies in our power range (around 1 kW) are expensive, so I am planning to buy two separate units: a unipolar supply, and another unit that will allow us to switch between the two polarities.

What is the name of that second component? Can I reasonably expect to get both from the same supplier?


texts: How to interface MIPI DSI with a microcontroller

texts:
I'd like to learn about interfacing a TFT LCD with a microcontroller via the MIPI DSI protocol and writing a program for it.
Both have suitable number of pins, some microcontrollers support MIPI DSI while others don't.
Where can I start and what should I do?


texts: Can I use different package inductor in impedance matching circuit of NRF52832 design

texts:
I am designing a custom PCB with NRF52832 IC. According to datsheet, required specification of inductor L1 are:3.9nH, 0402 package, 5% and a High-frequecy chip inductor. Can I use other package inductor(other than 0402) with same specifications?

L1 is a part of impedance matching circuit. Can changing its package impact the circuit perforamce?

Circuit diagram:


texts:
How would one mount a fuse that is 3,6mm in diameter and 10mm in length  on a  PCB?  I can't seem to find a method to do this, browsing through the electronic components suppliers.

Datasheet: http://datasheet.octopart.com/MCPDS-004-Multicomp-datasheet-10027002.pdf


texts: Circuit completes whether base current applied or not - transistor

texts:
My fourth electronics project ever. The most challenging yet.

I've wired up this project (Project 4 - Short Circuits project kit Jaycar Electronics). After much research, it doesn't do what I expected. I complete the circuit by touching the two probe wires together and the LED flashes - so far so good.

I then disconnected the wire running from the emitter to the 100k resistor and connected the two probe wires again. The LED still flashed. I expected it not to flash because the base current can't flow through a circuit (out of the base) due to the fact the circuit was broken by me disconnecting the wire.

My expectation was that no current can flow between the collector and the emitter until a base current was supplied. Perhaps the calculation of the impedance was understated and a current would flow from the collector through to the emitter anyway because the current is simply to big for the transistor to resist, base current applied or not!

simulate this circuit – Schematic created using CircuitLab

I think I'm missing something quite fundamental here. I'm not experienced enough in electronics to accuse a textbook of being incorrect.


texts:
I hope some one have an answer for me.
We have a 2600 HP synch motor driving two generators this feeds a mine winder typical ward leonard system.
The synch motor starts up through a korndorf starter and starts up normal. Currents balanced in the correct vector diagram. It reaches synch speed switches from star to run and then the excitation gets applied, the vector starts to go all over the place.
Typical VA and IA are correct but IB and IC flips to the other quadrant.  See attached picture. This effects the operation in running the Synch motor with DC excitation.
Have any one seen this before.
Why would this happen
At start up

After excitation applied

It is the first time I have seen something like this happen.


texts:
I am building circuit to control some LED strips.  I will be using APA102 strips. https://cdn-shop.adafruit.com/datasheets/APA102.pdf

I am using an Arduino to control the strips.  The strips will have approximately 100 rgb LEDs, and so the maximum current is 60mA x 100 = 6A.  They will normally be at near maximum brightness, including when turned on.

I have been reading a fair bit about inrush current.  I am strictly amateur, so please excuse my ignorance and poor terminology. My impression so far is that from a cold start, a 6A circuit can have a significant inrush current, especially if I include a 1000uF smoothing capacitor across the power supply, as advised by the LED suppliers, to protect the LEDs:

https://learn.adafruit.com/adafruit-neopixel-uberguide/power : "Before connecting a NeoPixel strip to ANY source of power, we very strongly recommend adding a large capacitor (1000 µF, 6.3V or higher) across the + and – terminals. This prevents the initial onrush of current from damaging the pixels."

https://github.com/ManiacalLabs/AllPixel/wiki/Installing-Optional-Components#21mm-dc-barrel-jack : "1000uF Capacitor - This capacitor sits over the strip V+ and Ground lines and helps smooth out the power for the LEDs. Some strips are more sensitive to power rail conditions and recommend such a capacitor be installed for reliable use. Regardless of the strip type, there isn't any harm in installing this capacitor."

https://github.com/ManiacalLabs/AllPixel/wiki/Assembling-the-PowerTap also suggests a 1000uF cap.

From my reading, the large cap will result in an even larger inrush current, exacerbating the problem.  Is this correct? Is the cap really necessary?

How can I measure the inrush current?

Can this inrush damage the PSU?

How can I deal with the inrush current.  I am thinking of using a NTC thermistor, specifically the NTC 5D-15
https://www.icbanq.com/data/ICBShop/board/00000000-NTC-POWER.pdf

Are there better ways to deal with the inrush current?

Also, I would like to use a mechanical switch to turn the circuit on and off.  Should this go before or after the cap and thermister?

I know this is a lot of questions, but the more I read about this, the more confused I get.  Thank you for your help in advance.


texts: Dual AC feed to power a DC unit (Raspberry Pi) with Diode and Polyfuse for protection

texts:
I wish to place some Raspberry Pi's in remote locations (data centres) for telemetry and other services like serial OOB access.

Typically dual AC feeds are presented to customers in a data centre which come from completely separate feeds from the local power grid. Raspberry Pi's take a single DC 5v 1mA input. In the event that one of the power feeds in the data centre goes down I want the Pi to stay up (and in the event they both go, it will have a battery pack).

This isn't a natural feature of the Rasp Pi (two power supplies) so I need to design a safe and fault tolerant system that will do this. My knowledge of electronics is limited and I will be consulting others and testing in a lab style environment; As a basic premise though, does the following sound sane or a have I grossly misunderstood electronics and risk exploding all the kit in my rack and potentially others;

Dual 16A or 32A feeds per rack (A and B feed)
Attach a regular 5v DC  Rasp Pi transformer to each feed to present two 5v DC feeds
Attach a diode to each feed to stop any current passing back towards the source A or B feed
Attach a polyfuse in case of a surge coming in from the source A or B feed
Attach A feed to Rasp Pi battery pack, then to Pi 5v inpit
Attach B feed as the power supply to a powered USB hub, which is then connected to Rasp Pi USB port (A Rasp Pi can be powered by either it's main USB mini power input, or voltage coming from a powered USB hub, both together as far as I have read, won't harm it)

  A Feed                    B Feed
     |                         |
    DC                        DC
Transformer               Transformer
     |                         |
   Diode                     Diode
     |                         |
  Polyfuse                  Polyfuse
     |                         |
 5V DC 1mA                  USB Hub
Battery Pack               Power Input
     |                         |
  Rasp Pi                   Rasp Pi
  5V Input_________________USB Socket

I understand this question is somewhat Rasp Pi specific, but in terms of general electronics, would this work? What should I be looking out for on the Rasp Pi that could cause this plan to fail?

My main concern is that I will connect the A and B feeds directly together and blow everything attached to both feeds. Also, what if the A and B feeds are out of phase as they are coming from two different sources?; I assume this doesn't matter as they are both being converted to DC?

Many thanks and sorry if this seems silly, my knowledge of electronics is very limited.


texts: What is the DC component of the sum of phasors?

texts:
I am preparing for the written test conducted by IISc Bangalore for admission into their graduate program. I happened to come across a sample paper from 2016, I think.

I am struggling to understand the 11th question,

Since phasors are sinusoids, I think the answer is 0. But, here they called it a "time signal" and specified a finite time range.

So even if I considered a windowed version of the periodic signal, then since the Fourier transform of the signal at 0 frequency is finite, I can conclude the time average value is still 0.

So my question is, what is the answer? which of my interpretation would be correct? Also how can complex signals be "time signals", is there any physical interpretation of "dc component" of sum of spinning phasors?


texts: Arduino: programmatic disable crystal/change system clock prescaler

texts:
I have a ATtiny2313 board which does not have a crystal installed. According to documentation it looks like it then runs by default on 1MHz. Because this board only allows ISP programming I thought about first testing the timer-related code on Arduino (with ATmega 328, but using only features which would also be available on the ATtiny2313).

Questions:

How to disable the Arduino crystal (temporarily) without having to set fuses (don't want to send my AVR to hell)?
Is it possible to change the system clock prescaler by code, e.g. to change the system clock of the ATtiny2313 from 1MHz to 8MHz?


texts: Program speed with and without JTAG debugger

texts:
I have some custom boards with an ARM processor (marvell78100, armv5 compliant), some SDRAM and some Flash. I'm trying to investigate timings problem with the SDRAM, since it seems the layout was not done correctly, which causes program crashes on some boards, every couple of hours.

Unfortunately, it's a typical situation of heisenbug, where observing the bug makes it disappear: when I run the program on gdb with a peedi JTAG debugger, the amount of errors seems to be extremely reduced.

What is the speed of a program running in a JTAG debugger compared to the normal speed?

I think I could find this information in the specifications for the ARM JTAG debug cells, but I didn't manage to find those specs.


texts: Can the Kalman gain matrix contain negative values or absolute values greater than 1?

texts:
I have implemented an EKF in a power systems application. When I run a simulation in Matlab, in some iterations of the filter I get a Kalman gain matrix (K) with negative values and/or absolute values greater than 1. In some books I have read that the Kalman gain is a real value between 0 an1.

Is this correct ? Or is it an indication that something wrong with the Kalman filter?


texts: Is my battery really fully charged? Should I use the "pulse repair" button of my charger?

texts:
I have a 12V lead-acid battery that is detected at 0.8V when I use a multimeter:

When I plug my charger it says "fully charged":

Should I use the "repair" button of my charger (I don't know what it does)?
Is my battery dead?
How can I charge it with the charger I have?

I have no knowledge about this kind of things.


texts: SPST Power Switch with LED for Guitar Amplifier

texts: I would like to have a power switch for the solid state guitar amp I am building, but I would like an LED indicator to know when it is on. I know how to do this using a dpdt on-off, but would it be possible to use an spst and still have the LED?


texts: Can any BJT be used for temperature sensing?

texts:
I'm looking for a cheap and easy way to monitor temperatures and came across the Microchip EMC1403 which interfaces to general purpose diodes (or transistors with their base tied to collector/emitter respectively).

This fits my application quite nicely as the sensing points are at close distance but outside the PCB and only two wires are needed per sensor. Also, I expect leaded transistor packages (such as TO-126) to be resonably easy to handle and thermally bondable to the components to be monitored.

However, the datasheet does not go into much detail on which diodes/transitors are suitable and only mentions 2N3904 NPN or 2N3906 PNP general purpose transistors.

I wonder whether there are any specific characteristics that make up a good temperature-sensing transistor/diodes? I'm especially interested in higher-power devices because they come in cases which I expect to give better thermal-bonding.

Is there a reason for using transistors instead of simple diodes?


texts:
I have a prototype board like this, on which I plan to add some solder traces (the black lines).

I plan to place a BNO055 on top of this same prototype board and solder it in place without using header like this:

It is intended that there is a connection from the Pads to A8,A6,A5,A4 to coincide with Vin, GND, SDA and SCL.

I was wondering if I need to place some insulating material like tape between rows B-G to insulate the breakout board from the PCB ? I intend to have a connection from 3vo (A7) to ADR (H4), and intend to place a connector on K(4-7).

Is insulation tape necessary ? Or is the breakout board already insulated, and the traces being in contact with the board shouldn't matter ? Any other suggestions about what is wrong with this approach ?

The reason for my approach is:
1. I don't have access to any parts or tools to place all the individual components on the prototype board itself, so as a quick hack I'm trying to just place the breakout board on the prototype board without headers (through-hole soldering).
2. I would like to minimize height and footprint.

Thanks.


texts: Understanding on frequency compensation on driving capacitive loads with an op-amp

texts:
I am trying to understand an example circuit of frequency compensation on driving capacitive loads with an op-amp from:
https://www.allaboutcircuits.com/technical-articles/how-to-drive-large-capacitive-loads-op-amp-circuit/
I understand how the capacitive loads cause the stability issue and the idea of using a capacitor to neutralize the phase lag caused by the capacitive load.
It is just very confusing to me how the value of compensation capacitor Cf is determined in the below example.

The second condition imposes:

to make the phase lead introduced by Cf exactly neutralize the phase lag caused by CL. I tried to figure out how this condition was derived but still got no clue. Anyone can help on this? many thanks.


texts: Powering an old train crossing gate (semaphore) with a PC power supply and Arduino

texts:
I recently found an old part of a train crossing gate (semaphore) in the weeds and mud near a train crossing.

I cleaned it up, and want to make it flash when I get a notification, so I'll be using one of my Arduino Unos.

I have an old PC power supply that should do the trick for powering it, and it works, so I think I'll just wire the Arduino to control the power supply by switching it on and off using the on/off pins (14/15)

Anyways, would using the Arduino to rapidly (1-2 seconds) toggle the power for the power supply be safe or alright thing to do? Would it be over-taxing on the supply? It'd only flash until I clear my notification, though that could be hours' time, if I'm away.


texts:
I don't normally allow vias on regular SMT pads, but for test points there's no real need to go out of your way to avoid them. As long as the bed-o-nails will make good contact anyways.

Now I can write a clearance rule like this:

(Component Like 'TP*')

which matches Same Net Only and

IsVia OR IsTrack

This will allow you to plop down a via (p v) on top of the testpoint - It'll show a violation before you drop the via (since it's not connected to any net) but it disappears when it gets connected to the pad.

However, when routing, adding a via on TP pad, no go, nuh-uh. It'll get pushed outside the pad. I've tried adding a high speed rule about vias on SMD pads but it had no effect..

Is this just a limitation of the online DRC?


texts:
Im bit struggling with PAM question. I've been trying to solve this for few hours but I am stuck at the stage where I need to sample \$m(t)\$.
Could you please help me with detailed answers and workings.
Thank you :D
1st Question
The sinusoidal signal \$ m(t) = A_{m} cos(2\pi f_{m}t) \$is PAM modulated to produce the signal \$s(t)\$. Assume that \$A_{m} = 5V\$, \$f_{m} = 3Hz\$. the sampling period \$T_{s} = 0.1s\$  and the PAM pulses are of duration \$T = 0.02s\$.
*PAM -> Pulse Amplitude Modulation.
(a) Derive an expression for the spectrum of \$s(t)\$ and plot this over the frequency range \$±2f_{s}\$, where \$f_{s} = \frac{1}{T} s\$.
(b) Assuming an ideal reconstruction filter, plot the spectrum of the filter output, \$g(t)\$. Compare this spectrum with the output that would occur if there was no aperture effect.
2nd Question
Prove that the PAM generator, \$h(t)\$, is a linear process, where \$h(t)\$ is square wave between 0 and T with amplitude of 1.


texts: Why are lithium-ion batteries typically used if they’re so flammable?

texts: It’s no secret that lithium-ion batteries are volatile - just look at hoverboards, Samsung Galaxy Note 7’s, and even some iPhone models which have exploded. Granted that these are not so common occurrences, but the fact that they happen at all is still troublesome. Lithium-ion batteries are not the only type of rechargeable battery out there; why don’t electronics companies try a different type of battery, like nickel-cadmium, or nickel-metal hydride? Is there a benefit in using a lithium-ion battery, or does it just come down to what’s easier to mass-produce?