texts: Replacing electric Ice Machine Motor with a resistor in a Samsung Refrigerator

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We bought a house 3 years ago and it came with a Samsung Refrigerator. For some reason the previous owner bought a fridge with an ice maker and never hooked it up. Well you cannot disable this feature without causing an error that will not go away.

I've replaced the motor in the unit with a resistor but I just want to make a reality check as I am not an engineer.

The motor is a Mabuchi model RF-370CB-13490. I could not find the specs for this exact model but I found the series spec sheet here

So I went with the high side for both voltage (16V) and amps (0.011) with no load which would give me 0.176 watts. I measured the resistance through the motor at 20 ohms. So I installed a 56 ohm 1/2 watt resistor that I had laying around. Now obviously ohm's law says the resistance should be around 1455. Should I install a resistor with a value near 1455 or is the 56 ohm ok? I just don't want to cause a fire.


texts: Soldering breadboard wires onto a small chip

texts: I have some DWM1000's that I need to use for a project. One will be connected to a raspberry pi 3 B+ as the tag and 1-4 others will be connected to arduino's as the anchors. I am having trouble though with soldering wires to these chips. I want to use these breadboard wires I have and just remove the plastic covers on one end. I already took off the connectors on one chip, making it useless. Is there a better way to go about this? My background is in computer science so I'm a total noob with soldering stuff like this. Pic provided. Thank you.


texts: Voltage rating for switch with high voltage but very low current

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I'm building a small circuit for measuring high(ish) voltages with an oscilloscope. It's based on an isolation amplifier that measures the voltage across a measurement resistor (r3 below), attenuated by dividing with R1 or R1+R2, depending on the range selection. I've scribbled down a picture of the relevant part of the circuit below.

I'm planning to use a toggle switch for SW1, but notice that they have maximum AC and DC voltage ratings. Now, I understand the difference between the two ratings (arcs self-quench more easily with AC), but I'm not sure what properties I need from SW1 for my example.

Specifically, R1 is a series chain of resistors adding to about 450kOhm and R2 is much larger. I want to be able to measure 700V pk-to-pk AC (British line voltage if the probes are out of phase). I'm more ambivalent about DC ratings: I don't think I have a 500V DC source lying around... (Incidentally, I'll be using a panel-mount switch for SW1, so the terminals on the PCB can be well separated.)

The question (finally) is what ratings I need for SW1. I assume I'll need ≥1kV insulation strength to protect the user, but how do I characterise the AC/DC voltage rating? I mean, if SW1 is fully open, it will have almost the entire input voltage across it (because R2 >> R1), but R1 = 450k means that, even if V is 1kV, the maximum current that can flow is about 2mA: I assume that arcing won't be a huge problem...

However, I'm not sure how to express that in terms of switch ratings: can anyone tell me what I'm missing?

simulate this circuit – Schematic created using CircuitLab


texts:
I have an antenna I made with about 2 feet of insulated copper wire, stripped at one end.  The antenna is connected to the positive side of a 1000uF capacitor, using this circuit.  I am using a 741 op-amp.  The negative voltage for it comes from a separate battery with its positive lead connected to ground, and its negative lead connected to the op-amp.  When I test the voltage of the output of this op-amp, it is constant.  It has no frequency.  This leads me to believe that my antenna has absolutely no signals coming from it.  How can I fix my antenna?

I am also using a silicon diode.


texts: Photodiode scintillation detector for gamma spectroscopy

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I'm trying to build a basic detector for x-ray or low energy gamma spectroscopy. I have a big photodiode with a CsI(Tl) scintillation crystal glued on top (Hamamatsu S8559 for x-ray detection [1]) and want to detect for example gamma radiation from a ~1uCi Am-241 source.

To do spectroscopy and being able to discern the pulses by energy I would first have to be able to measure single pulses coming from radiation hitting the detector. So I tried to calculate the charge of these pulses:
The CsI(Tl) scintillation crystal [2] has a light yield of 54 photons/keV and Am-241 decays partly via gamma decay with an energy of 59.541keV, therefore I calculate the number of 550nm photons produced by the crystal after being hit with a gamma photon to be 54 photons/keV * 59.541keV = 3215.2 photons.
Quantum efficiency has been calculated to be about 0.586 for my photodiode at 550nm, so I would expect 3215.2 photons * 0.586 = 1884.1 electrons being generated by the photodiode, which equals a charge of about 0.3 femtocoulombs.

This seems really low, so my questions are:

I realize this is not the physics stackexchange, but can someone check if my calculations are realistic?
If this is really the charge I have to detect, how would I do this? Should I use a charge amplifier circuit with a tiny feedback capacitance, for example with an LMC662? [3]
Is this photodiode + crystal combination even usable for this application or would I have to use a silicon photomultiplier?
Sadly my photodiode has a huge junction capacitance of over 500pF even with the highest allowed reverse bias. Can I use photodiode bootstrapping to reduce the capacitance? [4]

I found a circuit that seems close to what I need in [5], but it uses a photodiode without scintillation crystal that is also much lower capacitance than mine, so I'm not sure it would work.

[1] https://www.hamamatsu.com/resources/pdf/ssd/s8559_kspd1051e.pdf
[2] https://www.crystals.saint-gobain.com/sites/imdf.crystals.com/files/documents/csitl-and-na-material-data-sheet.pdf
[3] http://www.ti.com/lit/ds/symlink/lmc662.pdf
[4] http://www.analog.com/en/design-center/reference-designs/circuit-collections/large-area-photodiode-bootstrapping.html
[5] http://einstlab.web.fc2.com/Gamma/spectroscopy.html


texts: Why are the transformer windings in series with line and load in this circuit?

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I came across this switching power supply circuit and I noticed the transformer is connected in a way I had never seen before.
What is the benefit of connecting it like that? And why does the circuit use a capacitor voltage divider?


texts: What factors affect the voltage drop in a basic ac generator when an additional load is added in parallel

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As a preface, I am in school to become an engineer on a ship so my question relates to a self-contained circuit/grid and not a home.
We are going over generator theory and how an automatic voltage regulation circuit is used to control voltage. I know ac gen voltage is proportional to the magnetic field and relative speed between the magnetic field and the armature (output) winding. I get this and how the voltage regulation works. What I don't understand is how adding a parallel load to an otherwise steady state generator without a voltage regulator causes a noticeable voltage drop.
One of the laws in a parallel circuits is that the voltage drop across loads in parallel is constant. So if you add a load in parallel the resistance goes down, resulting in current going up. And therefore wattage goes up. Voltage isn't affected. This is an ideal circuit so let's take it a step further.
Say you have a engine turning a permanent magnet next to a coil of wire. This is the most basic generator I can think of. Now if I have that generator operating in steady state with an electrical load where everything is constant and if I add a load in parallel then my total resistance goes down again, and this would cause current to go up again. But winding/coil impedance is a thing and Lenz's law would would result in a counter force to slow down the engine and reduce the RPM and thus hertz. But, engine feedback will correct this returning to steady state RPM and hertz. Therefore, neither the speed nor magnetic field of the generator has changed. Generator current has gone up and therefore power has too, but I still can't see how this would drop voltage.
Finally I know the generator coil windings will have some kind of resistance, but this is always called out as conductor resistance is effectively zero.
Effectively zero is not zero though, and an increase in current would result in an increased voltage drop for internal resistance. The actual voltage drop seems too large for this alone to account for the change. Is it this internal resistance causing the noticeable voltage drop at output, or is there some other factor, law, or equation that I am missing that would account for a generators output voltage dropping?


texts:
The circuit below contains a battery light-bulb circuit connected to Earth.

If the distance between points A and B where relatively small, then one could see that the earth would be acting as a sort of resistor (practically speaking, as soil has some resistance) and the lightbulb could be potentially lit.

If we however put A and B at large seperation, is current flow still possible? I say this because if the earth is considered an infinite electron source/sink, there would then be reason for current to flow with a battery as a voltage potential, thus lighting our light bulb

Reasons I don't think it will flow.
The potential over the battery is 12 volts, but as far as I know there isn't a relationship between any terminal and the earth, as voltage is relative.There doesn't appear to be a voltage difference, yet I still can't reconcile this thought with earth as an electron source/sink


texts:
Below is the datasheet of the IGBT
https://www.semikron.com/dl/service-support/downloads/download/semikron-datasheet-skm75gb063d-22890050

It has 4 Control Pins , Number 4,5,6,7 . Generally a MOSFET has a single gate which is used to trigger the saturation mode (Short Circuit Collector and Emitter).

I'am confused here , can someone help me out on how to perform ON , OFF switching with these 4 pins available .

Thanks


texts:
During a recent job interview of mine, one of the panel asked me the following question
Q) Why is the transmission voltage of overhead lines in our country in the multiples of 11?
Some background information, I am from India where the transmission voltages are 11,33,66kV etc.
I have found 2 answers on google one of them stating that it's due to form factor and other to account for some kind of losses, I don't feel convinced by both these answers.
What is the actual technical reason?


texts:
I built the following circuit, a reference VIPer22A circuit.

It works fine but I have a little problem. It gives an electric shock on the secondary side. It's not a "line" shock (sticking your fingers into an outlet), but rather, a "tingly" shock if you touch the device while you're grounded.

It's the same thing that happens when you have an PC power supply not connected to mains earth.

The obvious solution would be, of course, to connect the secondary GND to Earth. The problem I have with this is that this is an audio amplifier, so I'd rather leave GND floating.

Is there a way to eliminate this shock? Capacitively connecting GND to EARTH? Or should I just connect my circuit's ground to Earth?


texts:
I have made this 4-bit binary multiplier circuit, but the product of, for example: B3B2B1B0 (1100) x A3A2A1A0 (0001) = P7P6P5P4P3P2P1P0 (00101000) and not 1100,

What have I done  wrong?


texts: Problem with digital potentiometer [MCP41010] in Op-amp Amplifier

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I'm using two potentiometer in amplifier design for controlling gain and offset.
the potentiometer that used in offset control works perfect. but that one used in amplifier resistor have a big problem. When it joined to circuit, output signal become too noisy.

My circuit design in this section as follows:

I changed the potentiometer in feedback path, but result is same. Also I cut the offset path and test gain section separate, but output don't changed.

can I help me or explain this problem?

thank you,


texts: fastest B field rise time in an inductor/electromagnet

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What is the fastest attainable pulse rise time for either

a pulse or
a square wave

using a iron core aka transformer steel laminated core, assuming the laminations are of the best possible quality for the task.

I know that this is largely dependent on the inductance of the inductor.

For me there are multiple smaller paralleled inductors all driven with the same signal, so the inductance will be very low.

Is it possible to get ns or maybe even pico second rise times for a pulse in a core that is not air core?

Do Ferrites have better parameters with regards to this.

My need is to get a B field in an airgap that increases from zero to its maximum value as fast as possible.

Does the B field rise curve follow the coil current rise?


texts: Need help finding out whether this my circuit will work as intended (new to electronics)

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This is my first time designing a simple circuit. I made one that enables an Arduino Uno to control a step motor by turning on various coils. It has 4 inputs that go to the Arduino, and as each coil is turned on, an LED should light up as an indicator for this. I am using the IC 'ULN2003APG' as the central IC.

The section that is circled is the 5 pins for the 28BYJ-48 motor.

Does/will this circuit work as intended?


texts: Numerical value in decimal of the 32-bit word stored at address 1000H

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I'm a little confused how to tackle these three questions.

Assuming two's complement arithmetic and operand alignment, give the numerical value in decimal of the 32-bit word stored at address 1000H and of each 16-bit half-word stored at addresses 1000H and 1002H under (1) Little Endian and (2) Big Endia storing conventions.

1000H:  23H
1001H:  F7H
1002H:  32H
1003H:  AB

Questions:

For the first question, we have 23H at 1000H. Is this a hex word? What is the H for? 23 would be 35 in decimal
But two's complement would assume binary? 35 in binary would be 11011101. I also understand big vs little endian, but I'm missing something here.


texts: Importance of constant collector current (BJT)

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I was reading these notes and I have a couple of questions.

What is the importance of the constant collector current in varying voltages across collector and emitter? How does it really relate/help amplification?

Also, why don't we want a varying collector current? What is so important in the linear region?


texts:
For the circuit above $$Vc=16V, β=200,
VT =25mV \quad and\quad |VBE|=0.6V $$ are given. I want to design a circuit with following conditions

The current on \$R_1\$ will be 0.1*Ic1. Pmax (DC maximum power consumption) =10mW
there will be no resistance value higher than 600kΩ

I tried to solve it using KVL and KCL but each time I got stucked with voltage drop across BJT's itself because I could not find \$I_{B}\$. Are there any suggestions for how could I find it?

P.S: I do not ask for anybody to solve whole problem. I just want suggestions to solve by myself. So please just guidance, no complete solution.


texts: When incorporating the STM32F7 MCU onto your own board design, is it necessary to connect supporting circuitry (analogue supply filtering etc) to the VDDA, VCAP pins if not using any of the analogue parts of the chip?


texts: Generate hamming code-words with given minimum distance

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My understanding of hamming code (adding this as it might help someone in future):

Description: Hamming code is basically an extended parity check code. Message is divided into blocks, and multiple parity bits are added in each block of message (by the transmitter) in a way that these bits indicate the position of the error bit in that block.

Code-word: Each block (message + parity bits) forms a code word. The list of valid code words is known both to the transmitter and the receiver. Whenever a block is found not to match the list of code words, it is considered as error, and a correction is applied.

Hamming distance: It is the number of bits that differ between a pair of valid codewords. The minimal distance among the all possible pairs of valid codes is called the minimal hamming distance.

Questions:

Currently am using parity method to generate hamming codes. As an an example, I will do the following to generate a (7,4) hamming code

Define positions 1-7 for the  7 bits of block.
Designate position {1,2,4} , which are powers of 2, for parity bits.
Designate other positions {3,5,6,7} for data bits
Compute parity bits which will be a function of data bits present in the subset of the above positions and form the code.

Will the above algorithm guarantee the code-words generated will  have a minimal hamming distance of 3? If not which algorithm I should use to solve the problem of generating hamming codes with the given (or specified) minimal distance?

Note: Since it was a laborious task to find the minimal distance of the generated 7 bit code-words, I am posting this question here to know the general procedure for generating hamming codes with the given (or specified) minimal distance


texts: Controlling digital potentiometer as feedback resistor in transimpedance amplifier

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Main Idea: I have designed a transimpedance amplifier for current-to-voltage conversion application. To increase the dynamic range of the input current that can be measured, I have integrated the digital potentiometer as the feedback resisitor and controlling the resistance value on Arduino microcontroller. Problem: The transimpedance output voltage is being compared to another voltage signal and then the TIA output is being levelized to be within the same range of the other voltage signal by varying the potentiometer values. But, the output value is keep on increasing and until it reaches a certain value and then starting back from zero again like a loop. How do stop and stabilize the output value once it reaches a certain point. I have attached the schematic& code below:

#include <LiquidCrystal.h>
#include <SPI.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 9, 5, 4, 3, 2);
int CS1= 10;
int pot= 1;

void setup() {
  // setup the dig. pot.
  pinMode (CS1, OUTPUT);
  SPI.begin();
  pinMode(0, OUTPUT);
  pinMode(1, OUTPUT);
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
}

void loop() {
  int sensorValue = analogRead(A0);
  int sensorValue2= analogRead(A1);
  // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
  float voltage = (sensorValue-sensorValue2) * (5.0 / 1023.0);

  lcd.begin(16, 2);
  lcd.print(voltage);
  float voltage2 = analogRead(A2)* (5.0 / 1023.0);

  while(voltage >= voltage2 - 0.05){
    pot++;
    digitalPotWriteRed(pot);
  }

}

void digitalPotWriteRed(int value){
  SPI.beginTransaction(SPISettings(14000000, MSBFIRST, SPI_MODE0));
  digitalWrite(CS1, LOW);
  SPI.transfer(B00010001);
  SPI.transfer(value);
  digitalWrite(CS1, HIGH);
  SPI.endTransaction();}


texts: What was used to detect light before the invention of photodiodes/phototransistors?

texts: Were there technologies before photodiodes/phototransistors or similar semiconductors, which could be used to start or stop machinery based on the amount (or presence/absence) of light falling on them?


texts:
I bought the IAR Kickstarter kit to work with the SM470R1B1M-HT (Texas Instruments) microcontroller. I would like to implement CAN communication between the microcontroller and a PC. I need to send commands from the PC and get some response from the controller.

CAN document for SM470R1B1M-HT.

I am a little bit confused about my CAN connection termination.

I have the IAR kick starter kit with a CAN connection, and I am trying to PC via CANUSB (CANUSB). I have terminated CAN_H and CAN_L with a 120 ohm resistor after the CAN transceiver and then connected to a DB9 male connector. I have connected the DB9 male connector to the CANUSB device using a DB9 female connector. I have checked the connections, and everything seems right.

I am confused about termination at the other end of CAN network which is on the CANUSB connection side. Do I need termination with 120 ohm at the DB9 connector to CANUSB?

Please have a look at the images about my connections:

I have terminated with a 120 ohm resistor after the CAN transceiver on the board. Please have a look at the termination at the board side:

I have closed that open connection to terminate.


texts: How do I test an xbox 360 slim power brick?

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I've looked everywhere and I just want an answer to a simple question. I have an xbox 360 slim and 2 power bricks I am trying to fix. I also have a multimeter. I know the power supply is meant to output 5 volts and 12 volts but with both of the power bricks I only get a 5 volt readying, the 12 volt line doesn't even register. and I am wondering, seeing as this is the case with both power bricks, does the 12 volt line not activate until it is plugged into the xbox?

No matter where I look no one seems to be able to help me so lets see if i can get some responses here.


texts: Why is my zero and pole frequency of this transfer function wrong?

texts:
So I have this transfer function:
$$\begin{align}
\dfrac{g_m-sC_{gd}}{s(C_{gs}+C_{gd})}=\dfrac{-C_{gd}\left(s-\dfrac{g_m}{C_{gd}}\right)}{(C_{gd}+C_{gs})\left(s-\dfrac{0}{C_{gd}+C_{gs}}\right)}=-\dfrac{C_{gd}}{C_{gd}+C_{gs}}\dfrac{s-\dfrac{g_m}{C_{gd}}}{s}
\end{align}$$
Then im supposed to find the zero and pole frequency expression based from my transfer function and this is what I got:
$$  ω_{z} = \frac{-gm}{C_{gd}} $$
$$  ω_{p} = \frac{1}{C_{gd} + C_{gs}} $$
But then that two is wrong. But I dont understand why. Then we are asked for the gain to when ω = ωz and this is my formula:
$$ A_{v},dB = 20\log\left|\frac{C_{gd}*\sqrt{1+(\frac{\omega_{z}}{\omega_{z}})^2}}{ \sqrt{(-\frac{ω_{z}}{w_{p}})^2}}\right| $$
The above formula for my gain is also wrong but i guess thats because my formula for the zero and pole frequency is also wrong. So where are my mistakes here? Help would be much appreaciated!


texts: Calculating currents with a current source in series

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Is this circuit correct? I am not sure if I can consider I5 as a  current source. I remember that current sources cannot be in series.

Or is this as easy as it looks. Specifically I am getting I1=0.8232 I2=0.5488 I3 = 0.5875 I4 = 0.783 A.
The confusion is caused by I5 which I believe is a current source.


texts:
I want to control a lot of LEDs via a Raspberry Pi. My current idea is to use MCP23017 chips together with optocouplers to protect the Raspberry Pi and the chips. This is the schematics I have in my head, I've drawn only 4 of the 16 optocouplers and LEDs:

This should work fine. But it takes a lot of space on my breadboard and I have to place a lot of wires. So I thought, maybe there is a port expanding chip that has opcouplers built-in. Because in my schematic all the transistor emitters are connected to each other, such a port expander would only need one more pin than a port expander without optocouplers.

Does a port expander with built-in optocouplers exist? Or any other ideas to reduce the amount of chips and wires?


texts: What is the physical significance of a complete boolean function

texts:
As per the definition,

A boolean function is said to be complete if

It derived all the basic operations
It reduces to another function that is already known to be functionally complete.

What inferences can be draw in light of this definition and what exactly do we mean by a functionally complete boolean function.


texts: Show Pad Nets Seemingly Not Working in Altium

texts:
For some reason, the PCB is not showing net names on the pads

I have all connections (rats nests) visible
I have checked the "Show Pad Nets" and "Show Via Nets" under the View Configurations > View Options Panel

I have checked layer colors and everything is on

What other setting might there be which is preventing the net names from displaying within the pads/vias on the PCB layout?

I am running AD15 on Windows 8.1 and this is really bugging me!

This is an example screen shot of the PCB environment, you can see that despite the option for "show pad nets" being enabled, they are not showing.

Thanks for the help

This question is not the same as another related question "Show Pads with their Name on PCB altium " which discussed adding silkscreen designators. It is about why the Altium feature "show pad nets" does not seem to be working to show the 'virtual' net names in the PCB tool within the pads


texts: Modern piezo microphone impedance-matching circuit

texts:
I want to record sound with a piezo transducer. I am connecting it to my sound card's input which has a good mic pre-amp. The levels are quite good and the sound seems quite clear but there's a lack of low end.

I want to build an impedance-matching circuit to improve the sound, to make it full range.

My priorities are:

Full frequency range and good quality sound.
Simple to build, because I have very little experience in electronics.
Must not cost a lot.

I've seen some options on the internet, but they are old and most include the functionality I don't need, introducing additional undesirable complexity.

I was wondering if there are now better and possibly simpler, modern solutions to this problem, possibly making use of the newer elements of better quality.

What would be a good approach to solving this, considering all of the above?


texts: Controlling piezoelectric-actuated mirror wth arduino

texts:
I would like to know where I can purchase a piezoelectric-actuated mirror device, such as those used in a single-colour laser pattern (not scanning) projector eg. the kinds used at music venues/concerts.. I'm assuming these devices reflect a single laser beam with the piezo mirror according to some coordinates/defined rotations.

Is anyone familiar with these devices? I'm not sure where to read more about them, apart form supplier websites, etc.. I would like to control my own laser projector, creating patterns etc, using an arduino for prototyping.

What other kind of device can achieve high speed movements (>120Hz) for a move-pause-move-pause... type action.

Hope that makes sense.


texts: Can I combine step-up and step-down designs for switched DC-DC convertor?

texts:
I need to generate 5 volts from unstable source. The voltage on input will be between 2 to 7 volts. The source is hand-crafted dynamo, which I'm doing as an experiment.

I found LT1173CN8-5 DIP8 integrated circuit. In the datasheet (written for all LT1173 series circuits) they show these two examples on page 13:

I'll be going with the left design, since my input voltage is most likely to be less than 5V - random peaks above can be handled by capacitors.

But is it possible to combine designs? Would that cost me efficiency?

Why is the diode on the images above actually placed completely differently?


texts: Eliminating Thermal Isolation Pads in Eagle

texts:
When creating a ground plane in Eagle, Eagle automatically creates a thermal isolation for the pad.

My first question is, does this isolation limit the current compared to a pad that is "completely" connected to the plane?

My second question is, is there a way to make Eagle not automatically create a thermal via? I know one work-around: I can connect the pad with a thick wire then make that same wire on the ground plane. Unfortunately this is hard to do and can introduce errors.


texts: How to drive a 555 timer with pwm input?

texts: I'd like to create a square wave generator with variable frequency that is determined by the presence of a 0-5 volt input signal. I have a very sketchy understanding of electronics - but I know what an RC network is. I'm thinking that I would need to replace the resistor in the rc network with a transistor, and bias the gate such that 0-5v input would give me 0-x output frequency? The reason for the pwm input is I want to drive it with an Arduino analog out pin. The frequency range needed is 0-60khz.


texts: Turn OFF a PUSH ON/PUSH OFF circuit from NodeMCU

texts: I have a PUSH ON/PUSH OFF circuit using one momentary button. I want to turn it off using a command from NodeMCU. In the image/gif below, I did manage to turn it off from the simulator. In reality it will toast the NodeMCU by the time I pressed SW2 because 12v will enter to the NodeMCU. I also tried placing a diode after SW2 but it did not worked.


texts: why does high speed current follows the path of least inductance? and how are the shape of lines are different at low and high speed?

texts: Does anybody know why the lines of electromagnetic field at high speed are bent and exactly following the shape of line, while in the low speed device the electromagnetic lines are in the usual propagation shape.


texts:
I have designed a PMOS (FDN306) based power on off switch. When I turn off the switch by connecting gate and source (via Schmitt Trigger), I see a output voltage of 50mV. This is with 3.9V Source voltage. If I increase the source voltage to 5V, the output voltage goes down to 20mV. I check the Gate and Source voltage and I see them identical.

I don't have the schematic in this computer but it is essentially a super simple switch. It sounds like, I didn't choose the right PMOS.

What type of PMOS I should choose? Why there is a significant leakage out of PMOS in this case?


texts: Identifying and finding a replacement audio signal transformer 50 ohm / 0.5 ohm

texts:
I am trying to identify and find a replacement for the attached transformer.  The green/white leads with the red center tap have a 50 ohm resistance.  The side without the center tap has a 0.5 ohm resistance.
Can anyone identify what this transformer would be used for?  I am thinking it is an audio signal transformer, but that is not the application it is used on currently.  It is currently in an analog signal processing application.
I also cannot find anything close to the 100x impedance ratio, so I am not sure if I have classified it correctly.
Thank you for your help,
Tom


texts: Why the difference between the RSSI and Rx Level measurements is so big?

texts:
I'm new in Telecom. Today, I downloaded the Android APK called "Network Cell Info Lite".

In my house, I got this measures:

RSSI: -51

RXLEV: 60

I know this measurements represents the received signal. I mean... the greater the value, the higher is the power received by the phone.

I would like to understand which are the differences between  two measurements and why they have so different values?


texts: DAC output is completely dependent on Vreff?

texts:
I want to generate unipolar and bipolar output voltages 0-10V and +/-10V respectively.

I am thinking of using AD5752R for this purpose, my requirements meets with this particular DAC.

My doubt is that in test conditions he has mentioned with Vreff=2.5V the DAC can produce 0-10V and +/-10.3V.

Can we Produce higher outputs than the Vreff ?

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/AD5722R_5732R_5752R.pdf


texts: How to actuate a solenoid for maximum power without damaging it?

texts:
I want to activate the solenoid. See specs for 34 AWG solenoid here:

I am powering the solenoid with 12V. Which of the following two ways would give the most power?

Powering the solenoid for 100ms without PWM, and off for a very long time
Powering the solenoid for 100ms with 100Hz PWM signal of duty cycle 25%, and off for a very long time

I think the first one is the most powerful, but could it damage the solenoid? 100ms is below the maximum on time of 5s so I don't think it will damage it. Could some one please confirm that my thought process is correct?


texts: What's the correlation between spectral graphs produced using near field probes and ones produced using an antenna?

texts:
I've been looking at getting some equipment for EMC-precompliance on a budget (about £5k). I understand that I can get a spectrum analyser with some EMI options and some near-field probes (about £2k) and together these can be used to highlight points on my product that are generating EMI and show me if my attempts at fixing them have made a difference.

If I wanted to go a step further for radiated emissions, I could purchase a bilog antenna + preamp + reference source for calibration (about £2.5k), use our car park as an OATS, and hook that up to the spectrum analyser and perform some measurements with that. Presumably, depending on how close my test setup is to what the standards specify, those measurements should be more easily comparable to the test limits and give me greater confidence as to whether or not the device has passed that test.

How far can you go using just near-field probes? Are they only good for identifying trouble spots and getting an indication of whether or not modifications have made a difference, or can you also use them to determine whether you're above/below limits? How about with an antenna and our own car park as an OATS?

Naturally, these will not replace our local test house, but will using an antenna/preamp and an OATS test give me much higher level of confidence than using just the near field probes?


texts:
So I have a control panel which controls the speed and direction of a motor in a sliding mechanism. the direction can be inverted using a tri-state selector on the panel. the selector input is a COMMON signal coming from the drive and the output is P1 "direction 1" and P2 "direction 2" which are going back to the drive. what I want to do is to add 2 limit switches on the mechanism and allow the drive to revert direction either by the selector or the limit switches. knowing that in order to the drive to be able to reverse the direction, the signal (P1 or P2) has to be continuously active high, So I will add a relay to achieve that with the limit switches "Latch Circuit". but the problem is how to link the selector and the limit switches without the need to add more components rather than the relay.
These are the available components that can be used:


texts:
I'm currently looking for some MOSFET's to do some RGB LED lighting with using PWM. I found the 2N7002 in SOT-23 packaging (datasheet). According to the datasheet the MOSFET can handle a continuous drain of 300mA. My current draw will be about 200mA. I'm also seeing elsewhere though on the internet that typical current draw should be 115mA.

Now I really don't understand most of the datasheet but the basics; so am I ok to use these for my application?


texts:
I am planning to measure the voltage of an rgb LED pulsed with an ADC. The pulse is around 20ms long. The pulse is necessary so the self-heating is within reason so it won´t affect the any characteristics.
My Question is now what properties my ADC should have like Sampeling Rate, Bits, etc. so my measurement will be good.


texts: UARTs often let you choose between 1, 1.5 and 2 stop bits. With 1 stop bit payload efficiency is 80% (8/10), with 2 stop bits that drops to 72.7% (8/11). So what's the advantage of the second stop bit?


texts:
Here is Wien Oscillator circuit:

Amplitude of oscillations, Vout, is about 10V. If I put step up transformer on output with appropriate primary/secondary ratio, I can get 220V AC voltage, and it would be some basic DC to AC inverter, right? But because of small output current of LM741, it can't be used to power bulb for example?


texts:
I am designing a flyback converter.
Input = 180-240 Vac
Output = 15 V, 0.4 A
The secondary output seems to be oscillating when the diode is turns on. Oscillating frequency is around 27 MHz.
I am using TNY267 Ic for the converter.
Primary inductance = 3.3 mH.
Secondary  = 19.526 uH
I have used a RCD clamp on the drain. R = 47k. C = 2nF.
Yellow - secondary , Blue - Drain voltage waveform

The drain voltage rings at 3.77 MHz but reflected secondary voltage rings at 27.7 MHz.
I have come to understand that the ringing in the secondary is caused by the capacitance of output diode oscillating with the leakage inductance of the secondary winding.
There are many sources related to design of primary snubber.
But I cannot find any design procedure for secondary side snubber. I need a solid design procedure to damp out the ringing.


texts: Lead-acid battery charging fixed current stage specification

texts:
This post doesn't question the charging process or its theory. I seek to understand how to read the battery manufacturer's requirement of fixed current stage.

They prescribe a current to be held at specific value, let's call it I_fixed. I am assuming that to be a true DC current, which would be easy to comply with.

Now for reasons not important to discuss here, many chargers just rectify transformer output and give pulsating DC voltage. I control this with thyristors for each half-wave, thus current is pulsating. In order to measure the charging current, I decided to use RMS calculation from 256 samples I take each half-wave.

In short: Am I following correctly the manufacturer's specification to control the RMS current value to match their value? Is I_rms == I_fixed?

EDIT:
Note that I have no choice with the hardware, I can only modify the software. The battery is lead-acid 36V 215Ah, voltage after thyristors is 36Vrms = 51Vpeak, pulsating 120 times for 60Hz AC. I control the pulse width for each half-wave pulse. The Irms I use now to charge goes from 0...21.5A

Pardon for hand-made chart... I noted this down during one test cycle. the current is what I calculated form the above described RMS current. Voltage is measured every 16th half-wave with no charge current present in 64 samples then averaged.


texts: How can I split a 5v power supply into 4 isolated (no shared ground or live) channels?

texts:
I need to power a number of tp4056's with the battery outputs in series (using tp4056's because I have a bunch already, and because I want to be able to add more cells in series later).  If I do this normally It will short out the cells so my options are to either charge in parallel then have a 4-6pdt switch that can take >5 amps of current (pretty damn hard to find and wouldn't allow usage and charging at the same time, or as I saw in a tutorial use isolation on multiple tp4056's with some B0505S IC's.  These apparently cannot take alot of current and I would like to charge quickly so I need another option.

-edit: I may be an idiot but I just thought about the fact that I could just use two B0505S 's in parallel for each battery and charger.


texts: A question on PWM frequency of a DC motor

texts:
I'm planning to pwm-control four of the following motors by a single ArduinoUno:
http://uk.rs-online.com/web/p/axial-fans/8179151/

For some reason the nearest pwm frequency I can set is 31kHz.

The other options are: 244, 488, 976, 3096, 7812 and 62500 Hz

In the data-sheet of this motor: http://docs-europe.electrocomponents.com/webdocs/13cc/0900766b813ccfde.pdf
it is written "※PWM Frequency：25kHz"

Would that be an issue if I use 31kHz or one of the other frequancies?
Which one would work or none?


texts: What do these passive components do in this microphone amplifier circuit?

texts:
I have this circuit I built long ago to amplify 2mV signal from speaker and phase shift it by 2.5V.

Now the question is, what does C2, C4, R5, and R6 exactly do?


texts: Proof of type for Current mirror and Early effect (Mosfet transistors)

texts: Can anyone explain me how I can prove this equation below (4.19).I know that \$V_{GS1}=V_{GS2}\$ and assuming that M1,M2 is in saturation then \$ID=0.5kn(vov)^2(1+\frac{V_{DS}}{V_{A}})\$


texts: How large is the address decoder to select an address in RAM? Is the address decoder just a bunch of multiplexers?

texts:
I have recently started building simple computing devices using logic gates inside of Minecraft. What I'm trying to build right now is some RAM, and an address decoder for this RAM. I want to build a machine that will enable you to select a bit in RAM, and then turn it on or off.

So, I would input something like 10 (This is the address) and 1 (This is the value), and it would turn the second bit on. Right now, my address decoder is designed very similarly like this Wikipedia demultiplexer example.

My machine works perfectly. But I have come to realize something: Computers nowadays have billions of bytes in RAM. Assuming computers use the strategy that is shown in that Wikipedia image to do address decoding, the address decoder must be huge, must contain billions and billions of demuxes.

So my question:

When I first began researching how I should build an address decoder, I expected there would be much more elegant way instead of billions of demuxes.
Is this strategy shown in the Wikipedia image how computers do address decoding, and therefore have computers gigantic address decoders? Or do they decode it in a better way that I do not know about?

PS. I apologize if some people think that this is a LMGTFY question. I understand that this probably could be answered on google, but I'm completely new to EE concepts, I hardly know any terms, so I don't exactly know what it is I should google.


texts: Is it a PI controller always a good solution for speed control in treadmills?

texts:
This topic got me confused again. I'm trying to regulate the speed of a treadmill, i.e, maintain the desired speed with load variations (the person on the tread). It's a PMDC motor. I have two scenarios:

First scenario:

A simple algorithm that samples speed of the motor, compares it with setpoint and increases/decreases duty cycle at a certain rate to avoid sudden changes in speed until the setpoint (desired speed) is reached. No computations for PI controller here.

Second scenario : A PI Controller

Record the speed step response of the motor, then find the best PI parameters for the task. But here's the point.

Let's put an example. Say that a setpoint of 340 RPM is given.

The first sceneario will then increase duty cycle slowly (due to duty cycle ramping) until 340 RPM is reached, since I'm continuously reading the speed.

For the second scenario to respond like the first one, I have to tune PI parameters for slow response. But I think that load compensation should be fast, right?

What's the right way to go?


texts: IMU (gyro + accelerometer) breakout board with integrated Kalman filtering?

texts:
I am in need of a reliable gyro/accelerometer combo, that already has built-in motion processing (don't want to deal with Kalman filters in software). It seems that there are breakout boards out there (like IMU Fusion Board – ADXL345 & IMU3000), offering built-in motion processing, but the online comments sections reveal that that is not the case, or that it is rather hard to achieve. The MPU-6050 sounds more reliable, yet there is no official breakout board available yet.

The whole project will consist of ~25 sensors, that will all be connected to a desktop computer. I want to avoid having to do the heavy Kalman filtering for all sensors in software on the computer. Therefore i am looking for a sensor-board that already integrates the filtering.

DOF: I actually only need 1 DOF as the project has just one rotation point (think of a swing). But all available boards seem to have the maximum DOF.
Range: >= 150 degree/second
Frequency Response:  >= 100 Hz
Noise: I am really hoping for a quite noise-free signal, to avoid heavy interpolation-filters later on (on the desktop computer)
A plus would be if i could daisy-chain those boards together. If not i'll have to add another hardware piece that chains them together.

Any recommendations or comments would be appreciated!
Thanks!

EDIT:
I found this MPU-6050 breakout board at drotek.fr, looking for some experience reports now.

EDIT2:
I opted for the Razor IMU in the end, even though it was a bit pricey. There is pretty good firmware around.


texts:
I designed a really simple circuit that's supposed to detect when my car is running.

simulate this circuit – Schematic created using CircuitLab

I expect while the engine is off output to be 0V and when running to switch to ~4.5V or something. What I observe is about right when running but when turned off the output does not drop to 0 but rather stays at between 1.8 and 2.0 volts.

Looking at reasons not to use LM741 I'm suspecting any combination of those may be the cause of this.

Given that my above statement is correct and I haven't made any mistakes in my design, what is a good and also cheap op-amp that I can replace the LM741 with?


texts: Interface of XBee module with ATMEGA 168

texts:
I have configured 2 xbee series 1 modules such that one will receive serial data from any other module of same pan ID and the other will send data to the previous mentioned one.

Now when I use a terminal software (XCTU) to check data transmission its fine.
I want to send data serially using a ATMEGA 168 using xbee as transmitter. And another xbee will receive the data and send it to an ATMEGA 2560 based platform. I do not have any platform for atmega 168 so I kinda built a burner (bootloader circuit). The bootloader works.
I have connected pin 3 (TXD of USART0) of atmega 168 with data in (pin 3) of xbee module. I have made necessary power connections as well (Vcc=3.3V & GND ). But the xbee does not seem to send anything. Is there something I am missing ? Please help, as you may already figured out I am a complete newbie.

PS : before reducing my reputation please let me know what I am doing wrong so I may rectify that.

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

void uart0_init(void)
{
 UCSR0B = 0x00; //disable while setting baud rate
 UCSR0A = 0x00;
 UCSR0C = 0x06;
 UBRR0L = 0x5F; //set baud rate lo
 UBRR0H = 0x00; //set baud rate hi
 UCSR0B = 0x98;
}

void init_devices()
{
 cli();
 uart0_init();
 sei();
}

 int main(void)
{
 unsigned char data;
 init_devices();
 data =1;

 while(1)
 {
     data =0x21;
     UDR0 = data;
    _delay_ms(2000);
    data =0x55;
     UDR0 = data;
    _delay_ms(2000);

 }

}
}

This is the code I used.


texts: I'm playing with I2C on an AVR. I need the devices separated, and each device has its own battery. For the I2C I'm not clear if it is OK to have the pull up resistor within the source device, then share on a connection cable: ground, SCL and SDA?


texts: Help identifying thread locking adhesive

texts:
I've opened some old electronic device and in many cases, I've come across some adhesive coating the screws, which are in different colors and are easy to break or scratch, I think it's safe to guess they have some sort of thread-locking duties.

For instance, check out this image depicting the internal view of a Grundig TK46 recorder, which by the way I took from here.

So my questions are:

What is the specification or part number of these adhesives?
What are the alternatives for them in our days? I know the answer is probably is thread-locking fluid, But I want to know if there is any sort of adhesive to be applied to the components and screws and are similarly easy to break and scratch.


texts: Is this the correct circuit for a Sourcing Digital Output

texts:
My objective is simple:

Let the user connect any reasonable voltage to SOURCE0 (3.3-48V) and get that voltage at OUTPUT0 when BACKUP0 goes high from my MCU (3.3V signal)

I've seen some examples including an additional transistor placed after the emitter of the opto, is this necessary?

Also should the grounds on each side of the opto be different?

This circuit will be used in an industrial setting. Thanks so much


texts: LTSpice - envelope detector LPF behaving like buffer

texts:
I have an issue with an LTSpice simulation and I'm not sure if the issue lies in the simulation setup or somewhere more basic.

The simulation is as follows:

The system is as follows: on the left, there is a Class E amplifier. In the center is an inductive link which I've used the T-model for (so instead of a transformer, I have that LM). On the right is a full wave rectifier, voltage doubler, and "load". The part that I'm interested in is middle-top: a buffer and envelope detector.

The issue is this: the signal entering and leaving that first order active LPF are identical. I don't know how this can be the case, as the carrier is 1 Mhz, the modulation is 50 kHz, and the LPF rolloff is ~110 kHz. See image below:

Can someone see how I've misconfigured the envelope detector? Thanks!


texts:
I am making a dc motor vehicle, it will have 2 drive wheels each powered by a separate motor. For a desired speed and acceleration, how would I go about calculating the gear ratio needed?

Info I have obtained:
- Torque vs. Angular Speed Curve equation: y = -6E-6x + 0.0059
- Therefore Theoretical Torque Max = 0.0059 Nm and theoretical angular speed max =983.33 rad/s.
- Mass of Vehicle ~ 1.150kg
- Desired Speed 0.3 m/s
- Desired acceleration  =0.1m/s^2

I am unsure which equations to use to get a proper gear ratio as to get the desired speed without overworking the motor. Note: the voltage applied is constant at about 4.5 V, it cannot be changed.
Wheel radius is 37.5mm


texts: Arduino and GSM Module running on Li-primary batteries for years

texts:
For one of our projects we need to run an Arduino board + GSM module (SIM800C for example) for many years on batteries without recharging.

The Arduino should be in power down mode for 99,99% of the time and only wake up once a day, read a sensor (an ultrasonic sensor) and send data to our cloud server using the GSM Module.

I am using a 3.3V Arduino.
The input voltage for the GSM module is between 3,4 to 4,4V but it needs a high pulse current when transmitting — up to 2A. The transmission is short (I guess less than 1 second).

Now my issue is that I don´t know how to power these two.
Would a 3,6V Li-SoCl2 battery be the best solution? Should I power the Arduino from the Li-SoCl2 battery and then the GSM module from the Arduino?

Someone recommended a FET level converter but the ones I found online are converting from 3.3V to 5V and the GSM module seem to operate at lower than 5V though. The GSM module does not have any regulator on the board.

The battery manufacturer recommended to use a super capacitator too?
They also suggested a boost converter as they say in high pulse (2A) the voltage will be lower than 3,6V so it might affect the running of Arduino and GSM module..

At first I though using a 2-battery pack (7,2V) and drop down the current A DC/DC converter is not a viable option as it has a high quiescent consumption and we must eliminate any power consumer.
I know there are very low quiescent regulators like TPS61222-EP from Texas Instruments or others from Microchip, but these can only be used on a break board right? I cannot install them on wires directly, right?

I would welcome any suggestion.

Many thanks.
Razvan


texts: How can I design a finite state machine that counts according to this sequence?

texts:
when X is equal to 0

and

when X is equal to 1

I don't understand how to write the truth table. I understand that when X=1, it means that the machine counts in the following order: 1,3,2,6,4,C,8,9 and when X=0 it counts in the following order 9,8,C,4,6,2,3,1. But I really can't understand how to write the truth table when using D-flip-flop for example.

[edit]
Here's the final result


texts:
I'm working with an 8051 (Cypress FX2LP) that doesn't have jtag/bdm capability. Typically, developers on this project have been using ad-hoc serial printfs for debugging. I'm looking into options for serial debug monitors such as Keil's Mon51, Isd51 or IAR's generic ROM-monitor.

I'll need to modify/configure this debug monitor to write to code RAM (to set software breakpoints). I'd guess that most 8051 debug monitors offer the ability for such modifications in order to support Harvard architecture or bank switching.

The Keil tools come with Mon51 and Isd51. The Isd51 is very small and comes as source that can optionally be embedded in the application. C:/Keil/C51/ISD51/Examples/Generic_8052 works as-is on the Cypress eval board. This can all be done with the free Keil eval (subject to the eval size limitations).

This pdf 'MSC1210 Debugging Strategies'  from TI, explains some strategies for serial debugging on an 8051.

If this Cypress part had jtag/bdm - it would be a no-brainer - I'd use that.

Does anybody have recommendations for serial debuggers for 8051 or similar processors?

Have you had to modify it to write to Harvard code RAM or flash etc?


texts:
There is 5 kilometers long cable with numerous (possibly many) central stop buttons in series. The cable is laid around machinery and other cabling at a production plant. The buttons are SPST-NC (normally closed).

As it usually is with production plants it can never stop unless somebody actually pushed the button.

The problem is to design interface at the terminals of the cable that will detect the central stop request. The solution must be sufficiently robust so no false detection occurs during lifetime of the device and, as usually, one needs to keep the costs as low as possible.

How would you solve this? My take is described below.

I use a current-sensing loop. There is current source that feeds the cable with constant current (10mA) from one end and a shunt resistor connected to an ADC at the other end.

The ADC is connected via passive, first order low-pass filter. The microcontroller implements high-order numerical low-pass filter (NRDF type) with settling time of about 75ms. The protection circuitry includes transils and filtering capacitors.


texts: Powering Multiple devices off one battery backup

texts:
I have a 12v3a battery backup with 1 dc barrel connector on the end.

How can I power multiple 12v devices without needing to solder them, thus opening them and voiding the warranty.

One device is 12v1a the other is 12v1.5a.

I would rather not buy 2 of these backups.

Keep in mind I have never touched a soldering iron in my life.


texts: FSM for predesignated process (How to draw the state diagram)

texts:
let me start by saying this involves some homework problems so if you could help guide me a bit I would greatly appreciate it.

I have been working with finite state machines for a bit in my course and have always dealt with designs that required user input. As of recently we have dealt with a few designs which involved predetermined jumps from one state to another, as in an order of lights to be switched on.

For instance a stop light scenario where after a certain amount of clock cycles green goes to yellow, after more predefined clock cycles onto red, after more clock cycles back to green. This cycle then repeats forever.

Another example involves a shift register with outputs wired to 8 leds, upon start lighting led 1, next clock cycle led 2 and so on until reaching the last led (led 8) at which point the 7th led is lit and the the sequence is reversed until reaching the first led and the sequence flips yet again and so on. The cycle repeats forever.

I had no issues in the past designing finite state machines when they were based off of user input but I feel a bit lost now that the cycles will repeat forever in a known cycle. Any information or resources would be greatly appreciated.


texts: Does STM32 USB OTG support all USB 2.0 flash memories?

texts:
I'm using STM32F105 USB OTG standard libraries to drive USB flash in mass storage mode. It works fine with some USB memories models but not with all models. In the ST documents is written "Complies with the On-The-Go Supplement to the USB 2.0 Specification (Revision 1.0a)".

I have problem with the most of USB 2.0 flash memories that I've bought recently. Is it about "Revision 1.0a"? and is there a way to modify the library to support newest models?


texts:
I've developed a prototype using the STM NUCLEO (NUCLEO-F411RE) board and now that I am happy with design I am now in the process of testing everything together on my own PCB. All the other components designed for on my PCB are working great except for the new bare STM32F411RE (LQFP4 package) I have integrated onto the board. I am unable to connect to the board via the SWD interface to upload any program and am now completely stumped after many debug attempts! I followed all the hardware design recommendations provided in the STM32 application notes, (https://www.st.com/content/ccc/resource/technical/document/application_note/76/f9/c8/10/8a/33/4b/f0/DM00115714.pdf/files/DM00115714.pdf/jcr:content/translations/en.DM00115714.pdf).

I tried using two different programmers to communicate with the board;
1) ST-Link/V2-ISOL
2) The ST-Link that can be broken of the NUCLEO board

I verified that both of the programmers work when connecting to the correct pins on the NUCLEO-F4llRE breakout board which is VDD/SWCLK(PA14)/GND/SWDIO(PA13)/NRST/SWO(PB3). The connection verification is done with the STM32 ST-Link Utility software. The settings for the ST-Link utility are; connection settings = SWD, freq = 480kHZ (I have tried other frequencies), mode = connect under reset and reset mode is Hardware reset.

When trying to connect I get the "can not connect to target!" error from the the ST-Link utility as well as a FAIL.txt from the ST-Link V2 which contains "the interface firmware FAILED to reset/halt the target MCU". I hooked up my oscilloscope to analyze the NRST pin which I have pulled high with a 10Kohm resistor along with a cap to ground near the STM32F4 reset pin. I see that the ST-Link is sending a reset pulse but the MCU but no connection I guess. I then tried connecting to the board by pulling NRST to low with a 10k pull-down resistor and still no connection... I checked the continuity between the STM32f4 pins on the PCB and the connector pins and everything is okay in terms of soldering I guess? I believe the layout and placement of the controller is correct as I followed the ST datasheet as well as NUCLEO board layout. Maybe if someone could verify that would be great! Also I am new to PCB dev with mcu's so this very well could be a stupid mistake I am not seeing :)

Also, I have my board powered from a separate power supply before connecting the ST-LINK V2 programmer. Any help/recommendations would be much appreciated as I am stuck! Here are some photos of my setup


texts: Circuit for stabilizing the mini - 3 phase wind turbine output to 5 Volt using 7805 IC

texts:
I am trying to get some stable output from a Brushless power generator/motor/turbine which i purchased from Aliexpress

Mini Micro Small 3 Phase Turbine

To check if it works i tried to rotate it and LED blinks.

Added some toys gears in front of it and running it fast i am able to run over 7 3/5 mm leds so looks like it is generating around 10 Volts with a current of around 150+ milli amperes.

Now i want to get a stable voltage something like 5 Volt so i added a Voltage IC 7805 and then added couple of LEDS. I still didn't added a capacitor as was not sure how much value of capacitor i really needed.

So it is like this Turbine -> 7805 -> 5 mm Led - no other electronic component

In this case when i run the motor - the LEDs just blink for once (0.5 seconds) and then unless the motor fully stops then didn't blink at all.
And if it run it again it again just blink for a second.

Is i am missing only the capacitor and what about what value? or something else is needed more to prevent damage to IC/Motor like some diodes etc?

I am also curious that my cheap Multimeter (under $10) does not show any voltage out of the IC and of motor but works for AAA/AA etc.

Any ideas are appreciated


texts: Solution for EMI on signals in a connector?

texts:
I have PWM signal and PSU signals coming from switch mode PSU to our machine.
The motor drive boards that run the stepper motors in the machine are located in the PSU.
At the moment the outputs to motor windings are on separate connector but I need one connector for everything now.
To avoid any interference I need a D sub connector that filters any interference from signals and power on different pins of connector.
The frequency of PWM is 50 KHz (taken from the stepper drive datasheet) and based on that the capacitance of load (motor) is 1.6 nF and 10 nF for max operation voltage and min operating voltage respectively.
I have been looking for EMI filtered connectors but they are rare and expensive and maximum capacitance they have is 4000 PF. I am told that the attenuation still is very low for the 50Khz frequency that I want to filter out.
These are a notch filter so you don’t want to also filter out high frequency data as well.
Is there a way to supress motor noise?
Or are power line filters relevant?
I do need cable screening as well.
Has anyone worked out this kind of situation and has any advice about how to have one connector without any noise/interference issue?
Thanks


texts:
I designed this circuit, put V1 as sinusoidal source and output was good at oscilloscope.However when I changed V1 to pulse signal there was no output on oscilloscope.

Thanks to tell me if pulse signal can be superimposed with this kind of circuit.

It would be much appreciated if you can guide me to some IC that can transmit VHF(tv signals) at 3v to 9v.This will help me to proceed without designing such circuits.


texts: What does it mean to send CAN messages at 10Hz or 100Hz? Is this configurable on Linux SocketCAN

texts:
I understand the meaning of message transfer speed, i.e. a theoretical maximum of 1Mbit/second, and the 8Mbit/second in the CAN FD.

That's essentially the rate at which bits are travelling on the copper for a lack of better description.

What I don't understand is the 10Hz and 100Hz that I see in some links like this.  I looked at the Linux kernel docs for SocketCAN where it talks about the device properties, such as Clock Frequency.

It seems that this message rate is somehow configurable but I am not sure how to go about that.


texts:
I would like to make sure that I understood p JFET (https://electronics.stackexchange.com/a/97350/78253) right:

With SWitch1 in its current position, there is voltage at the gate of the J1 p JFET, the depletion layer is large, current through J1 is blocked, D1 is dark.

With SWitch1 closing to the ground, there is no voltage at the gate of the J1 p JFET, the depletion layer is very small or not there at all, current can flow through J1, D1 is shining (correct voltage V1 and resistance R1 provided).

Correct or what did I make wrong?


texts: Calculating values for a DC step-up circuit

texts:
As a learning exercise, I am attempting to make a step-up DC converter (5V to 12V). The basic design I'm following is this:

Source: http://www.daycounter.com/LabBook/BoostConverter/Boost-Converter-Equations.phtml

From the source above, I've derived an equation for a value of L1 which will avoid an unstable output voltage (I'm ignoring Vtransistor since it seems to be negligible for my components):

$$
L \ge {V_{in} (V_{out} + V_{diode} - V_{in}) \over {f (V_{out} + V_{diode}) \min(I_{load})}}
$$

I'm using an IRF520 MOSFET and an IN4007 diode, with an Arduino providing the PWM source (running at 62.5kHz), so I believe this fills in as:

$$
L \ge {5\text{V} \times (12\text{V} + 1.1\text{V} - 5\text{V}) \over {62500\text{Hz} \times (12\text{V} + 1.1\text{V}) \times 0.0001\text{A}}} = {40.5\text{V}^2 \over {81.875 \text{V} \text{A} / \text{s}}} = 0.495\text{H}
$$

(to guarantee the 100µA minimum load, I'm putting a 100kΩ resistor in series with the diode, although I'm not sure this is the right thing to do since it will be dividing the output voltage. I guess that once I have something for this to drive I'll have to recalculate the value for the specific circuit)

So that gives me a number, but 0.495H seems like a huge value, and I'd rather not accidentally produce 100V if I mess up the PWM duty cycle.

I have two questions: does this look at all reasonable? and is there some way I can calculate the maximum obtainable voltage from a given inductor in this setup?


texts: LiPo battery charger using only analogue components

texts:
I am trying to build a 1 cell LiPo battery charger using only analog components. That is, I don't want to use a specific LiPo battery charging IC. (I know it would be simpler and better with this method.) Instead I want to use op-amps, voltage regulators etc. I want to know if it is possible to build a constant current-constant voltage charging circuit using this method, since while I was researching most people were using specific ICs or only doing constant current charging.
If you think it's possible, can you guys give me some ideas? I was thinking of using a Howland current source, but I don't know how I would set the max voltage using this method.
Any help is greatly appreciated :)


texts: Convert expanded boolean function into a switching matrix

texts:
I am given a boolean function f(x) that I have to develop them according certain variables, let's call them a0 and a1, using Boole's Expansion Theorem. From the result I have to construct a "switching array". I have developed my function according to the variables but I'm not sure how to develop them into a switching matrix.
PS - I can't post the function because it's a homework exercise but I would just like some general help in deriving a switching matrix from a function


texts: Why did these two ethernet switches die (again)?

texts:
For the second time in four months I find that the two ethernet switches in my family room are dead. These are Netgear GS105 unmanaged switches labeled SW1 and SW2 in the attached figure. By dead I mean that at least the ports connecting them have failed although last time all ports had failed.

The first time this happened, in early September, I had just returned from a trip and assumed there was a lightning strike or other outside surge that lead to the failure. Netgear was good about honoring their warranty and I got two replacement devices in short order. There are several devices (PC, TV, Roku, PS3) connected to SW2 but none showed any sign of damage. The rest of my networkd (SW3, SW4) runs downstream of SW1 and I did not detect a problem on those devices either.

Recently I was on the laptop in the basement connected thru Wi-Fi to WAP2 when I lost network connection. I went upstairs to investigate and saw that one of our house cleaners was vacuuming in the family room. Her vacuum was plugged into a different outlet than either of SW1 or SW2. After the cleaning crew left I checked and sure enough SW1 and SW2 no longer work. I swapped in SW4 where SW1 sat and was able to get network downstream to SW3. Also, I have no problems on my router or WAP1. I have not had a chance to go thru and check each port on these two switches.

SW2 plugs into a Panamax M8-EX with good RFI/EMI filtering and over/under voltage control. SW1 plugs into a no-name surge protector power strip with a couple USB outlets. Both outlets appear to be grounded. Specifically, the Panamax does not report a bad ground and both outlets pass a basic outlet tester. Could be it's a crappy ground but not an open ground for sure. There is a 10 ft span of UTP cat5e cable between SW1 and SW2 (? in diagram). The ethernet cable runs tightly along the bottom of the baseboard up against the carpet.

I assume that the vacuum cleaner had something to do with the failing switches but I'm not sure how. First theory: the vacuum cleaner causes a substantial dip/spike in the mains voltage and this messed up the switches. Seems unlikely as each switch is plugged into a surge suppressor and there are several electrical components plugged into the same surge suppressor as SW2 with no problems. Second theory: The ethernet cable between SW1 and SW2 picked up EMI noise from the vacuum when they vacuumed along the wall where it runs. This EMI noise was enough to bust ports on SW1 and SW2 but nothing downstream (although I have some reason to believe that SW3 is now dropping packets).

Do either of these theories make sense? If so, what should I do to avoid a three-peat? (1) I will replace the no-name power strip with a high quality noise-filtering surge suppressor such as an ISOBAR4ULTRA or another M8-EX. (2) I may replace the UTP cable between SW1 and SW2 with an STP cable. Also, I can run it above the baseboard rather than at the bottom of the baseboard to keep it away from vacuum cleaners. If I do install STP it will be a factory patch cable. Do I need to do anything special at the ends to ground the shield? Do I just plug it into the switches? (3) I have considered to install ethernet surge suppressors on either end of this cable. Is that overkill?

Any comments or suggestions are appreciated.


texts: Do PWM Half-Bridge Gate-Drive ICs allow 100% DC?

texts:
I read in other questions that is not possible to use 100% DC as PWM input for drivers that use a bootstrap/charge pump to shift the gate levels.
I'm talking about common brush DC motor gate drivers, like these:

FAN73832
HIP4081
UCC27710
...

I don't find in the datasheets any requirement for the PWM input signal.
Which parameter should I check to find out if I can reach 100% PWM?


texts:
I have been trying to run the following code:

void reset();

int board[8][8];
int i,switcher,j,k;

void main() {
    TRISB = 0X00;
    TRISD = 0X00;
    TRISC = 0X00;
    reset();
    ADCON1 = 0X06;
    TRISA =0X11;
    while(1)
    {
        for( i=0;i<16;i++)
        {
            switcher = i;
            PORTB.F0  = switcher%2;
            switcher /= 2;
            PORTB.F1 = switcher%2;
            switcher /= 2;
            PORTB.F2 = switcher%2;
            switcher /= 2;
            PORTB.F3 = switcher%2 ;
            if (!PORTA.F0 == board[i/8][i%8])
                break;
            delay_ms(1000);
       }
       switcher = i;
       PORTC.F0   =  switcher%2;
       switcher /= 2;
       PORTC.F1 = switcher%2;
       switcher /= 2;
       PORTC.F2 = switcher%2;
       switcher /= 2;
       PORTC.F3 = switcher%2 ;
       switcher /= 2;
       PORTC.F4 = switcher%2;
       switcher /= 2;
       PORTC.F5 = switcher%2 ;
       break;
   }
}

void reset()
{
    PORTB = 0;
    PORTD = 0;
    PORTC= 0;
}

On running this code, it's showing

  "Not enough RAM" error.

However on running this code :

void reset();

int board[80][80];

void main() {
    TRISB = 0X00;
    TRISD = 0X00;
    TRISC = 0X00;
    reset();
    ADCON1 = 0X06;
    TRISA =0X11;
}

void reset()
{
    PORTB = 0;
    PORTD = 0;
    PORTC= 0;
}

It runs successfully with no errors (Note that I am creating a multidimensional array of 80x80 whereas for the previous one it's only 8x8). Can someone help me in identifying the cause for the problem? And if possible then also the proper solution for the problem ?


texts: How do I maintain an active list of ZigBee devices in a HAN?

texts:
ZigBee as a standard doesn't believe in direct connectivity of devices, its more of a floating network. But if I am to have a network of devices in a HAN (Home Automation Network), I need to know if these devices are still discoverable.

Each device has a neighbour table of devices that are in physical proximity of itself. I can query this table for each device using an LQI request, however, as many of the devices contain similar devices in their neighbour tables, I would be checking each device against an increasingly large list. It is also entierly possible that some devices may not be on this network.

If I had (lets say) 200 devices in my network, this is a **** load of requests and comparisons to do on a uController.

I can create a list of devices as they join the network and store them in eeprom, but is this actually the best idea?

I am working with the Atmel Bitcloud stack on an 8-bit AVR, however these are standard requests specified in the ZigBee specifications.

I need to know this in order to see if any device in my network is faulty.


texts: How to implement a three-input LUT if I have a lot of two-input LUTs?

texts:
I have gone through various sources... But I am not quite sure what it is.
For example, I have three input variables: A, B and C. Now I have to use two 2-input LUTs such that their input lines are connected to variables A and B. Then connect their outputs to a 2x1 multiplexer whose select line is the input variable C.
But in this problem, I'm not allowed to use the MUX, only two 2-input LUTs. How can it be?
The configuration of LUTs would depend upon the particular Boolean function that you wish to realise. Can you cite an example, please?


texts: DDS238 AC Power Meter: how to calculate current power consumption using pulses

texts:
I have a DDS238 AC power meter with 2000 pulses/KWh (1p/0.5Wh) and I want to calculate the real-time power consumption and play an alarm if the value exceed a specific value.
I'm using an ESP8266 by now, and I tried two different approaches:

calculating pulses count (with an ISR) in the last 5 seconds
calculating the time interval between two pulses

I tested it with a hot air blower and both method give me bad results compared with a plug power meter, sometimes I got a difference above 200W.
In addiction to this the method (2) may hang if no pulses detected.

So I would ask you how can I calculate the power consumption in a better way?
I need a wide interval in the method 1) for example?


texts: Estimate minimum detectable light pulse in a photodiode (5 ms, 44 kHz modulated)?

texts:
I'll use an IR LED modulated at 44 kHz to illuminate particles in air or water, and will use a silicon photodiode to detect weak pulses of scattered light as they pass through the LED's collimated beam.

Photodiode is shielded from direct light, so it will exhibit only dark current except for say roughly 5 ms pulses, when light scattered by the particle illuminates the detector.

An example of a detector's specs are shown below, it needs to be a large area detector for geometrical reasons.

I'm trying to make a ballpark estimate of how weak of a pulse I can reliably detect without getting a lot of false positives from noise.

I'll amplify the signal then use a simple diode + bandpass filter (say 100 Hz to 1 kHz) to remove the 44 kHz but pass the envelope of the 5 ms pulses.

With a bandwidth of ~1 kHz, detectors dark current of 200 pA means every 5 milliseconds there will be about 6 million electrons, with an RMS (shot noise) of about 2500 e-. So if my 5 ms light pulses produce say 10,000 or 20,000 e-h pairs and I set a threshold there, I'm in the right ballpark.

The 0.55 A/W at 850nm means each photon has about an 80% chance of making an e-h pair.

However, I haven't used the capacitance of the photodiode at all, nor the NEP (1.5E-14 W/Hz^1/2 @ 1550 nm) which curiously is specified at a wavelength for which silicon is blind. In other words, I haven't designed an amplifier and threshold discriminator yet.

Is disaster waiting for me around the bend, or is this likely to work with a reasonable low nose amplifier and bandpass filter?

Some spec data for an example 10x10mm PIN photodiode: https://www.thorlabs.com/thorproduct.cfm?partnumber=FDS10X10


texts: Reducing surge current in 5V High Side Switch

texts:
Re-visiting a prior question I asked a while back. I have a circuit that looks like the following:

simulate this circuit – Schematic created using CircuitLab

... and from what I surmised from my previous question, a possible way for me to reduce power-on surge current from my downstream sensor module would be to add an RC filter on the P-FET gate, and maybe a (e.g. 5.6V) zener diode in parallel with the load (though I doubt I need a Zener diode in this application).

simulate this circuit

Have I correctly understood the guidance in the previously reference question?
Is a  10k x 0.1uF = 1ms RC time constant a useful / good choice of values to limit in-rush current?


texts: How to run Xilinx ISim simulater faster?

texts:
I have started to write serious test benches with lots of loops which have inner loops to check all the possible input conditions of a design.

Some of the test benches takes hour to finish. I am just wondering how people run these test benches faster? Do they use supercomputers?


texts: Delay a clock to give time for the input to settle?

texts:
I have a numerical keypad that I want to feed into a shift register to display the last three numbers I have pushed. My numeric keypad has ten lines, each of which connects to a common on a button press, which feeds into a 10 line -> BCD encoder.

The problem is, how do I clock the shift register? If I clock it with the keypad itself, the input hasn't yet settled and it gets inconsistent results. What I need is to clock the shift register with a delay. How can I do this with the fewest components? I don't want to use a microcontroller as this device needs to be field supportable by a tech without microcontroller knowledge.


texts: Voltage divider before the input of an LM324N used as a comparator

texts:
simulate this circuit – Schematic created using CircuitLab

I am designing a driving system to control some servomotors, and since my microcontroller can not drive enough current, I had thought in do this with some LM324 as comparators.

The thing is that I have a fixed 5 VDC source, and I want the negative input of the opamp being 1V. This way I can source the LM324 with 5 VDC being sure it will not switch.

I have two questions:

It is correct if I just put a voltage divider between my DC Source and the input of LM324N?
Since the input impedance of LM324N is very high, I was thinking of using only one voltage divider instead of one for each input, is this correct?

EDIT: As you can see in the schematic, my idea was to drive the servomotor with the lm324. Output current of this operational amplifier is about 20mA acording datasheet. My servomotor is the famous sg90 towerpro, there is a lot of missunderstanding about how many current does it draw. As @Peter Bennet commented, I thought lm324n does not source too much current, so I did an experiment and it worked fine. So I thought it would be enough.

However, your solution is great @Arturas Jonkus, I did not think about it, so I think I will go around it. It makes much more sense than using a logic component.

Thank you very much to all of you, What a great community!

EDIT2: I have been wrong in my questions, so I was wrong in my concepts from the very beginning. My servomotor has 3 pins: VCC (current comes from here), GND, and PWM. So it was perfectly ok with using a logic device such as a comparator to control the servomotor because it draws the current from VCC, not from the PWM pin.
I want you to IGNORE my question because I was completly wrong. I am very sorry.


texts: How to produce a certain amount of volts and amps?

texts: I assembled this mini tesla coil kit and the instructions say to plug it into a power source that's 15-20v 2amps. I'm just wondering how do I do that? As in how do I make something that produces this specific current? All I have is batteries. I tried looking it up but it mostly comes up with calculators for amps and things


texts:
I am pretty new to circuits analysis and I have the following problem as homework:

ig2(t) = 4sin(ωt + π/4),
e3(t) = 12sin(ωt + π/4),
R1 = 10 Ω,
ωL1 = 4 Ω,
ωL3 = 3 Ω,
1/(ωC2) = 6 Ω
I have to calculate Ee and Ze with the equivalent generator method (Thevenin). I managed to calculate the impendace Ze but I don't know how to continue from there. I hope you understand the problem statement.
My attempt to solve it:

I don't think that the system is correct and I don't know how to continue from here.


texts: Small powerbank, li-ion cell charging voltage problem

texts:
While ordering a replacement for an 18650 cell from a small powerbank, I've overlooked an important property of the battery. The old, broken one had 4.35 charging voltage and this is what the internal charger delivers. The new one, however, has typical 4.2 V charging voltage.
Is there anything I can do with the charger board to reduce the output voltage? Or is there no way and I just need to find a proper li-ion cell (with 4.35 V)? I do not consider using the existing combination as a good idea.
Models:
Old one -> Samsung ICR18650 30B
New one -> Samsung INR18650 30Q
Thanks in advance for any pragmatic hints!


texts: Amplifying heavily filtered attenuated stopband signal

texts:
The picture is of a noise analysis, but a signal that may be present in V1 would be filtered in the same way as the noise.

At 100 KHz, the noise is attenuated by about 42 dB, from 568 uV to 4.7 uV. Suppose there is a signal a few times stronger than the noise that is attenuated in the same way by the filter.

The capacitor C1 is an approximation for the parasitic capacitance that may be present at the input of an amplifier or it could be the capacitance of a wire. There may be some capacitance to the positive supply voltage as well. A better representation would be with a distributed model. I am only approximating these with the capacitor.

The amplifier would have a low input bias current, in the pA range, so the main problem is capacitance. In the real world, inductance or electromagnetic shielding for example, could be problematic.

The questions are:

Is there really any signal in the stopband, as simulated for a first order filter?
Is it possible to recover (equalize) such a signal?

Edit: I actually need a flat frequency response, so the signal in the stopband must be amplified to the initial value. The phase shift could be done digitally, but the signal should be equalized before amplification.

I've found some similar cases: https://en.wikipedia.org/wiki/Equalization_(communications)

For example: http://www.ti.com/lit/an/sboa125/sboa125.pdf

So these equalizers are widely used for copper cables, like cat5e cable or video signals. I haven't seen any equalizing of signal from the stopband, however.

Later edit: the gain of 120 V/V seems very achievable with a large number of low input bias operational amplifiers. However, some single transistor amplifiers can have lower noise it seems ( https://www.ncbi.nlm.nih.gov/pubmed/23020394). The other challenge is tuning the response of the amplifier so it will output the original signal. After some thought, it actually looks achievable.

Later edit 2: some sources say that the feedback capacitor in a noninverting opamp can tune out the input stray capacitance. without going into further detail, these are some examples:

Negative Capacitance – Using Positive Feedback to Compensate for Microelectrode Capacitance

https://en.wikibooks.org/wiki/Circuit_Idea/Revealing_the_Mystery_of_Negative_Impedance#Op-amp_implementation


texts: Signal line current estimation and impedance matching

texts:
As far as I know, the input pins to ICs are typically just the gate of a MOSFET. I have always just take stuff for granted (like if you want to control a logic pin, just put a source voltage on it), but recently I have been thinking about how these things actual connect.

How do I estimate the current level going through the signal line? For example,if I have a driver outputing a high frequency control signal to an IC, how do I estimate the instanteous or effective current going through this path so I can size my PCB trace appropiately? In my mind, the MOSFET will ask for as much current possible to charge and discharge the gate, so it could be pretty bad if the driver is capable of high current (1 A) but the trace is not sized properly. If the driver is limited, I don't think it is available in all IC datasheet so I want to understand what people do to ensure the signal trace is appropiately sized for power. I know some people will put a gate resistor to limit current and therefore transition time, but it is not the best to minimize FET power lost.
For signal lines, would the general design consideration is that you want to match impedance for signal integrity while making sure the trace can handle the required current?

Let me know if I am understanding it correctly!

Thanks!


texts:
simulate this circuit – Schematic created using CircuitLab

I am working on a binary calculator using 2n3904 NPN transistors. I noticed when using a NOT gate the voltage gets divided when running the ouput of the NOT gate to a 10K resistor that controls the base pin of another transistor. Is there any way to avoid this?


texts: Why are some AC outlets and plugs polarized?

texts:
This will show my naivety when it comes to alternating current... but why are some plugs and sockets on AC outlets polarized (one prong is taller than the other)?

(See this question on DIY.) (Or this one.)

My thought is that if the current is alternating that the hot and neutral effectively switch roles every 60th of a second. (50 if you're in Europe!)

I can't seem to wrap my head around why any device would care which line is hot or neutral, since the current coming into the device might come from either side. Wouldn't the safest option for implementing an on/off switch be to disconnect both sides for off?

Phrased differently, if I connect only neutral to a device, why doesn't it conduct to ground in the same manner as the hot line?


texts: Suggestions solutions for high current bed of nails style testing

texts:
I'm trying to create a tester board that will hold some power path components (DC input caps, IGBTs, current sensors) that are normally on the Unit Under Test (UUT).

I'd like to connect these components to the UUT through some spring-loaded probes. Are spring-loaded pins even a good way to do this? Should I be looking into alternate methods? Additionally, are high-current, PCB mount, spring loaded probes a common component or should I expect to not find very many?

This probe is an example of what I'd like to place on the baord SHE-5-B-18.7-G. Unfortunately it's not high enough current.


texts: LED radio display - How to control multiple segments at a time?

texts:
I have a display from an old radio (I think it was a Watson).

Now, there are different wires connected to it: Let's call the first two A and B and one of the others (it seems to be not so important which you choose) C.

If I connect A to the (+) of a power source and C to the (-), LED M lights up. If I connect B to the (+) of a power source and C to the (-), LED N lights up. Using that technique, I can light up any LED on the display. (Connecting A or B to (-) and C to (+) yields no results). Also note that the display does not need a binary encoding (i.e., voltages LLHL -> number 2 on display); I am able to light up an arbitrary segment.

However, I can only light up one arbitrary LED; If I wanted to choose two arbitrary LEDs, I would have to connect for example A and B to (+) and the other wires C and D to (-). As one might expect, four LEDs light up, as a current flows from C to A but also from C to B and from D to B and also from D to A. Therefore, four LEDs light up.

Does anybody have an idea about how to control this type of display correctly?

There are also some notes on the back: AV-923A8Y, SB 98 IHB, E228731. However, I did not find any suitable (and free) data sheet.


texts: AC transient analysis for LR series circuit for a given AC source?

texts:
How can we formulate the current for an LR series circuit which has an AC sine source? The current formula must include both transient current and steady state current. So the i(t) function should give us the instantaneous current for any t. The equation should also make sense when R is set to zero. Some suggested superposition of transient response and steady state. I just want to see the right equation and see how R and L effect the settling time to steady stage.

edit1: Here is how I would put it. But Im not sure:

transient current: i_tr(t) = V/R*(1-exp(-Rt/L))

steady state current: i_s(t) = V/sqrt(R^2 + w^2*L^2)*sin(wt + arctan(wL/R))

total current after superposition:

i(t) = i_tr(t) + i_s(t)

i(t) = V/R*(1-exp(-Rt/L)) + V/sqrt(R^2 + w^2*L^2)*sin(wt + arctan(wL/R))

And if R = 0;

I cannot understand this because V/R goes to infinity and parenthesis goes to zero.

edit2: Here is LTspice simulation for 10V 60Hz AC sine source 10mH inductor:

Unfortunately LTpice puts some resistor even-though you don't have any resistor in circuit.

And here is LTspice simulation for 10V 60Hz AC cosine source 10mH inductor:

As you see when the source is cosine, the current starts from 10KA. I guess this is actually infinity for pure inductive circuit? In my formula setting R = 0 leads infinity*zero so I cannot relate it and be sure.

And if the source is sine it is like there is no sudden voltage jump at t = 0 unlike in cosine case. But still it takes time for the current to settle to steady state and again I cannot relate it to my formula when R = 0:;

Do you agree that if R = 0 theoretically(which cannot be achieved in simulation) and the source is AC sine, current would never go to negative and oscillate above zero? I cannot see that both in LTspice and from the equation.

I hope I could express my problem.


texts: Heat dissipation through ground plane and other thermal considerations for 3W LED

texts:
In designing my first PCB ever to mount a 3W white led (shown above) thermal dissipation is a concern.

It is a simple PCB and I don't have the ability to add any heat sink beyond the ground plane of the PCB to which the led will be soldered. Here's what the PCB will look like :

The lighter green you see all over the place is the ground plane and in the center of the PCB is the foot print of the led with the round center piece being the heatsinking pad. Overall the PCB is 6x6 cm, the copper is 1 oz / ft2  or 305 g/m2 and the board is 1.6mm thick. The led is the only sensitive thing on there.

How much power do you think this board can take before the led starts cooking itself? Do you think it will survive the full 3W ? Or even 0.5W ?


texts: Am I calculating the V(t) and I(t) of all of the elements in this RC circuit incorrectly? (two resitors and 1 cap connected to 10V DC)

texts:
Am I doing something wrong calculating the current and voltages at time t for the RC circuit? I put these equations on google sheets and the voltage across all of the elements passes 10V between 4 and 5 seconds. Then it goes all the way to 35V around 20 seconds!

Super thanks


texts:
I have a sensor which generates signal in range of 240mV to 940mv.
Now, I use amplifier of voltage for my sensor, which generates output signal in range 350mV to 1000mV. I used rail-to-rail operational amplifier.

simulate this circuit – Schematic created using CircuitLab

But I need switch which can quickly toggle between original signal and signal amplifier.
Switch must act quickly, because signal below 240mV is not allowed and signal above 1000mV is also not allowed.

Additionally, I have one +12V signal that I can use to control of switch.

How do I design switch for this circuit?


texts: Why would you set the reset at the input state of FSM to 1?

texts: I am trying to find the answers online but without any luck. The FSM is a moore machine and there is a reset that is set to 1. What is the function of a reset? Thanks


texts:
I am trying to model a transformer of 1:100 ration in Ltspice, here is the picture of it

The above circuit is stepping up the input voltage by 100 times but I see something strange which is when I am providing SINE 1V input with series resistance of 0.1ohm and freq of 1MEG then I am observing the following 1mV at input

and output voltage as 100mV which makes sense when the input voltage is 1mV

My question is why is the input voltage 1mV when I am providing 1V at the input? Can anyone please answer this question.


texts: How to disable arduino Hardware Serial Rx Interrupt Properly

texts:
Intro:

I have an Arduino mega doing multiple tasks , from which A function Reads data from a sensor using SPI . Every like 10,000 read or something , i get 1 error bit in the SPI data . and I have narrowed down the problem to the Interrupt generated by the Serial Receive library.

So : I want to disable the RX1 interrupt while i deal with the SPI sensor ( about 10us) , then re-enable the RX1 back to normal .

Questions:

1- Shall i use Serial1.end() then Serial1.begin() (source code shown below from arduino GitHub), my assumption is that these functions take too long to perform ( in millis seconds ). and the data in the already received and prepared to be sent in the Hardware buffer gets lost !

void HardwareSerial::begin(unsigned long baud, byte config)
{
  // Try u2x mode first
  uint16_t baud_setting = (F_CPU / 4 / baud - 1) / 2;
  *_ucsra = 1 << U2X0;

  // hardcoded exception for 57600 for compatibility with the bootloader
  // shipped with the Duemilanove and previous boards and the firmware
  // on the 8U2 on the Uno and Mega 2560. Also, The baud_setting cannot
  // be > 4095, so switch back to non-u2x mode if the baud rate is too
  // low.
  if (((F_CPU == 16000000UL) && (baud == 57600)) || (baud_setting >4095))
  {
    *_ucsra = 0;
    baud_setting = (F_CPU / 8 / baud - 1) / 2;
  }

  // assign the baud_setting, a.k.a. ubrr (USART Baud Rate Register)
  *_ubrrh = baud_setting >> 8;
  *_ubrrl = baud_setting;

  _written = false;

  //set the data bits, parity, and stop bits
#if defined(__AVR_ATmega8__)
  config |= 0x80; // select UCSRC register (shared with UBRRH)
#endif
  *_ucsrc = config;

  sbi(*_ucsrb, RXEN0);
  sbi(*_ucsrb, TXEN0);
  sbi(*_ucsrb, RXCIE0);
  cbi(*_ucsrb, UDRIE0);
}

void HardwareSerial::end()
{
  // wait for transmission of outgoing data
  flush();

  cbi(*_ucsrb, RXEN0);
  cbi(*_ucsrb, TXEN0);
  cbi(*_ucsrb, RXCIE0);
  cbi(*_ucsrb, UDRIE0);

  // clear any received data
  _rx_buffer_head = _rx_buffer_tail;
}

2- Or shall i disable serial1 interrupts manually (as shown below) , then re-enabling them . is this safe from a microcontroller standpoint ?? what happens to data in hardware and software buffer ?

 //disable Interrupts
cbi(*_ucsrb, RXEN1);
cbi(*_ucsrb, TXEN1);
cbi(*_ucsrb, RXCIE1);
cbi(*_ucsrb, UDRIE1);
//Do the SPI routine //
//enable interrupts
sbi(*_ucsrb, RXEN1);
sbi(*_ucsrb, TXEN1);
sbi(*_ucsrb, RXCIE1);
cbi(*_ucsrb, UDRIE1);

Option 3:

Disable global Interrupts CLI()

do SPI routine

Enable global intruupts SEI()


texts: Small-signal voltage gain of P-type common-gate circuit

texts:
Given the following p-type common-gate circuit, I'd like to try and calculate the voltage gain \$A_v=V_o/V_i\$. Given the following information: \$V^+=5V\$, \$V^-=-5V\$,\$V_{TP}=-0.8V\$,\$\lambda=0\$, \$K_p=0.001mA/V^2\$

I began by doing a DC analysis. This means that the capacitors are seen as open circuits to DC and all AC sources are switched off, leaving only the independent DC sources. The simplified circuit therefore looks like this:

simulate this circuit – Schematic created using CircuitLab

The drain current can be given by the equation \$I_{DQ}=K_p(V_{GS} +V_{TP})^2\$

The gate resistor is tied to ground directly and therefore no current flows into the gate. Then the gate to source voltage can be written with KVL as:

\$-V^+ + R_sI_D + V_{SG}=0 \implies V_{SG} = V^+-R_sI_D\$

Substituting this back into the equation for the drain current:

\$I_{DQ}=K_p(V^+-R_sI_D +VTP)^2\$

Solving for \$I_D\$ gives two values for \$I_{DQ}\$. \$I_{DQ} = 0.0008A\$ or \$I_{DQ} = 0.001339A\$. Choosing \$I_{DQ} = 0.001339A\$, the transconductance value \$g_m\$ can be solved for:

\$g_m = 2\sqrt{K_pI_{DQ}}\$

which gives \$2.314mA/V\$

The voltage gain \$A_v\$ for a common-gate configuration is given as:

\$A_v = \frac{gmR_D}{1+g_mR_{si}}\$

In this case \$R_{si}\$ was not given so I assume it simply falls away in the equation. I calculate \$A_v = 4.617 \frac{V}{V}\$

\$A_v = \frac{0.002314(2000)}{1+0.002314} = 4.617 \frac{V}{V}\$

The answer is given as \$A_v = 2.41\$. What did I forget to include or where were my assumptions wrong?


texts: What exactly is Characteristic impedence in transmission lines?

texts: Please help me to understand what does a characteristic impedance mean. I am unable to get the exact idea of what does it actually mean and its physical significance.


texts: Designing a low power wireless temperature transmitter

texts:
I'm going to work on a project in which I need to take your experience into consideration to which path should I go to.

I need to design a wireless circuit at max size 5x2 cm, that has a thermostat and a MCU. I need to cover an area of 1km, so I would go for the ZigBee approach. There is also a design problem with battery life, so I need also to have the least power consumption that can be done.

Do you think with that design specs, is it possible or no?

So in general I would care about:

Low power
Size
Cost
Transmission range

Update:

I have found this chip, the CC2543/44. How do you like it and is it suitable for my design?


texts: Splitting an Analog Signal Without Adding Noise

texts:
I am trying to take a current measurement, run it into a PCB that splits the signal, and then output the signal in two places. One of the destinations is a RIO being used for feedback control, the other is a higher sample rate data logger.

When splitting the signal from the RIO into an oscilloscope there was a lot of added noise on the signal. This has me concerned that the data logger will see the same messy signal instead of the actual current.

What is the best practice method to take a single analog input to a PCB and use it to provide two separate outputs, without the two outputs introducing noise to one another?


texts: DALI Slave not responding to short address

texts:
I'm creating customized DALI Master from scratch. The problem is, that no matter what I do, none of the devices responds to short addressing.

Let's start from the beginning.

After connecting single device to DALI bus, it works as expected for all commands if using BROADCAST addressing (first byte equal to 0xFF). Transmission goes both ways reliably, including 'direct arc', 'off' and 'query status' commands. As expected the device responds with dec 64 for 'query status', which means no short address is set.
In the next step I tried performing binary search sequence, to assign short address to the device:

Initialize command is sent (x2) - 0b10100101 0b00000000
Randomise commands is sent (x2) - 0b10100111 0b00000000
Binary search is performed, device is detected as expected.
Program short address is sent (x1) 0b10110111 0b00000001 (to set short address 0)
Verify short address returns 'YES', Query short address returns 0b00000001. Works like charm.
Terminate command is sent (x1) - 0b10100001 0b00000000

After trying to execute any command with short address (for example querying status) using 0b00000001 0b10010000 device won't respond.
What is even more interesting, if broadcast is used again, device responds to 'query status' with status 0, meaning that short address is set...
What is more interesting again, sending this command to all short addresses gives no response to any of them.

I already tried 2 different DALI slaves from different manufacturer, both with exactly same result.