texts: How can there be a current without a voltage?

texts:
Recently while trying to understand inductive AC circuits better, I got very confused with a question.

Let's suppose we have a purely inductive AC circuit with ideal wires and a switch. Let's also suppose that whenever we close the switch of our AC circuit, at time \$t=0\$ our voltage cycle starts from 0 i.e. \$V(0)=V_0\sin\omega (0)=0\$

But generally we are taught that that in a purely inductive AC circuit, the current lags voltage by 90 degrees. That implies even at time \$t=0\$ we have a maximum negative current. We can also have a look at the current equation \$I(t)=I_0\sin\left(\omega t-\dfrac\pi 2\right)\$ which says at \$t=0\$ the current is not 0.

So, my question is that (physically speaking) how can a current exist at t=0 in such a circuit even without a voltage?

Moreover the circuit was previously disconnected so how was the current increased in the first place?

I searched and found this EE SE post but I'm still confused. I understood the energy argument put forward by user Dave Tweed's answer and I'm okay with the fact that at \$t>0\$ it's possible for either \$V\$ or \$I\$ to be 0 at times but what I'm unable to get why is there a current even at t=0 when instantaneous voltage is also 0.

Thank you so much for your help.


texts: How does a desktop charging station decide its output voltage?

texts:
I have this charger:
http://www.shintaro.com.au/product/shintaro-multi-device-charger/
It supports QC3.0 and has:
Output
USB-A DC 3.6-6.5V/9V/12V/14.5V/16V3A/19V/20V3.5A QC3.0
USB-C DC 5V/9V/12V/15V/18V/20V3A

i connected a 2pin 12v computer fan to one of its USB-A port and the multi-meter suggested that the charger is outputting 30v
obviously, a 2 pin fan does not support any kind of charging protocol, why did it still getting a > 5v voltage?
How does the charger decide its output voltage for old device like old iphones(5V 1A), or when D+/D- pins are not connected(like my fan)?
I plan to drive a WS2812B RGB LEDs Strip (60 leds, DC 5V, 18W) with the charger, how can i control its output voltage?
Update:
i think its defaulting at 20V output on USB-A, while everyone is suggesting that the default output should 5V when there is not any negotiation
not connected to any device
Imgur
connected to a fan
Imgur
connected to arduino
Imgur


texts: Why do circuit simulators like LTSpice prefer current sources instead of voltage sources?

texts:
I was having trouble with a "time step too small" error, and came across this post explaining that "stiff" equations gives LTSpice problems. Looking into LTSpice's documentation, they say that:

It can't be stressed enough that stiff voltage sources (especially
nonlinear behavioral types) are problematic because, unlike current
sources and/or resistors, they will not yield to capacitances at small
time steps during convergence difficulties in a transient analysis.

My question is, what is it about the way LTSpice solves circuits that makes pure voltage sources so hard to deal with? In school, EEs learn about node voltage and mesh current methods, so an answer relating to these methods would be appreciated.


texts: Vacuum diode in space charge mode: emission current

texts:
This must be a rater basic question about terminology.

I frequently come across the following statement: when vacuum diode is working in space charge mode (as opposed to saturation mode), the cathode emission current is larger than anode current

Iemission > Ianode

This is is supposedly caused by the potential barrier created by the space charge around cathode, which prevents some emitted electrons from reaching the anode.

I would immediately understand that inequality if we were talking about the initial stages of vacuum diode operation, when the space charge is still being accumulated, i.e. when emitted electrons leave the cathode and just stay in space charge area around it.

However, it seems that the above inequality is also widely applied to vacuum diodes working in well-established mode, when the space charge is already fully formed, i.e. the number of electrons that enter the space charge equals the number of electrons that leave it.

In that case, how it is possible to have such current inequality? Where does the extra emission current "disappear", if it does not reach the anode?

I suspect that the answer is simple: Iemission, by definition, is intended to include only the current that leaves the cathode, but it does not include the current that returns to the cathode from the space charge. If we designate that return current as Ireturn and assume that it has negative value, then the following equality will hold

Iemission + Ireturn = Ianode, where  Ireturn < 0

That would explain the inequality when Ireturn is left out of the picture.

Is this the proper understanding of what is meant by the inequality in question? Or am I missing something else?


texts: What are these coils on transmission lines?

texts:
What are these coils?

This was asked by doetoe in this physics.stackexchange Question

Where I saw them (maybe six or eight pairs) they came in pairs, always on the same two lines, and they were at approximately regular intervals.
It is from Spain, Barcelona area


texts: Why would a large resistor in series cause a different voltage reading?

texts: I'm watching Electroboom and don't understand why the voltage drops when he touches the spoon. He states there must be a large resistance in series. Why would the voltage not already have dropped before touching the spoon if there was a resistor? He states he's putting his body in parallel with it but I don't really understand what the circuit diagram would look like.


texts: Changing microphone's jack to headphone's jack

texts: I was trying to change my microphone's jack into my headphones with mic jack by cutting my microphone's wire and connect it to my headphone jack's wires. But these 4 color coded wires makes me confused, The red, blue, green, and the wire that has a normal color. And also my microphone has 2 separate copper wires. I Think one of those wires is the ground wire. Please help me. Thank you so much.


texts: Analog preprocessing circuit (anti-alias/pre-amp) for driving ADC

texts:
Background

Similarly to what Jeri Ellsworth did in her C64 Bass Guitar hack I am working on an audio-to-midi converter for my bass guitar.

I am also planning to use piezo discs as sensors placed under each string, connected to a Papilio One, using the ADC of the Logic Start MegaWing (an ADC128S102). The ADC reference voltage is hardwired to 3.3. volts.

My problem is that my analog electronics knowledge is pretty bad and I don't have any practical experience (I have given a try to the relevant chapter of the The Data Conversion Handbook but it's a bit too advanced for me).

Question

What circuit should I use to drive the ADC? The circuit should

Implement an anti-aliasing filter. The frequency ranges (excluding harmonics) typically found in each string of a 4-string bass are:

E string: E1 (41.20 Hz) to E3 (164.81 Hz)
A string: A1 (55.00 Hz) to A3 (220.00 Hz)
D string: D2 (73.42 Hz) to D4 (293.66 Hz)
G string: G2 (98.00 Hz) to G4 (392.00 Hz)

Ensure that the input signal voltage matches the expected range of the ADC (0V to 3.3V as I understand it).

I would appreciate as much practical information as possible (e.g. specific circuits and specific op amp parts to use) since, as I have said, I am pretty unexperienced on this. Pointers to books/articles suitable for a newbie like me would also be appreciated.


texts:
What will happen if an amplifier's gain is not stable? I can understand it may drive the amplifier into saturation, any other reason?
What if the gain is changing in such a way that the amplifier stays in active region, in that case will any distortion occur?
Likely not. But then what kind of problem may arise in the second case?


texts: Solving for inductance L in an AC series+parallel circuit is .. quartic?

texts:
This seems like a painfully simple question, but I keep ending up having to solve a quartic equation. So I'm missing something obvious.

Let's say we have a an AC source feeding a load consisting of a series resistor, Rs, and then in parallel a resistor and an inductor, Rp  and L. I know the frequency of the AC source, and I know the series and parallel resistors Rs and Rp. I also know the voltage of the source, \$V_S\$, and the voltage at the divider between Rs and the parallel elements, call this \$V_L\$.

Here's where things go wonky.

I know that the magnitude of the impedance across the parallel elements because it is simply \$V_L \over V_S\$ divided across \$ R_p || L\$. However, when I try to solve the parallel equation for two complex numbers I end up with a horrific quartic expression for the magnitude of the impedence as a function of L.

Here's what I did:

(1) Start with the voltage divider:

\${V_L \over V_S} = { |Z_L| \over |Z_L|+R_s }\$

(2) Solve for \$|Z_L|\$:

\$ \alpha = {V_L \over V_S}, { |Z_L| } = { \alpha R_s \over { 1 - \alpha }} \$

(3) The right side is constant, so let's set up an expression for \$L\$:

\$ { Z_L } = { { R_p j \omega L } \over { R_p + j \omega L } } \$

(4) Since I want to know the magnitude of \$Z_L\$ I need to separate out \$Re\$ and \$Im\$, which means multiplying by the complex conjugate:

\$ { { R_p j \omega L } \over { R_p + j \omega L } } \cdot { { R_p - j \omega L } \over { R_p - j \omega L } } \rightarrow  {{ R_p (\omega L)^2 } \over { R_p^2 + (\omega L)^2}} + j {{ R_p^2 \omega L } \over { R_p^2 + (\omega L)^2}}  \$ ... !!!!

I succeed in creating two expressions for \$Re\$ and \$Im\$, and then solving for the \$ \sqrt { R_p^2 + X_L^2 } \$ is this when reducing to a function of \$L\$:

Let \$ |Z_L|=K \$, so that \$0=(\omega L)^4 (R^2 - K^2) - (\omega L)^2(2R^2K^2 + K^4) - K^2R^4 \$ ...

R, K & omega are all constants, but did I miss something obvious because solving a 4th order seems a bit ridiculous?

EDIT: Some more research and this form appears to be a biquadratic equation which is easy to solve. Still wasn't expecting to see this complexity solving for L.

SOLUTION: I forgot mag(a/b) = mag(a)/mag(b). Applying this to 3 yields a simple quadratic for f(L). Thanks @Barry below.


texts: How do transistors have three legs when there are two circuits going through?

texts:
I keep seeing a not-transistor outlined like this:

(source: waitingforfriday.com)
But every picture of an actual transistor looks like this:

(source: nefarius.at)
I can't help but notice four lines exiting the diagram, but only three legs exiting the physical transistor. The same seems to be the case for all the transistors I've looked at. What's the missing leg?


texts: Question about the output voltage of an op-amp. (ua741)

texts:
When i hook up my opamp to a 9 volt battery (like in the image below), i get 8 volts from the output pin.
It gives the same reading when i attach both the inverting and non-inverting pins to the 9 volt rail.
Shouldn't it be closer to 0 volts or few milli volts?

Why is the opamp behaving like this? Is it broken?

Thanks in Advance.


texts: What can I use to switch a 500mA 12v inductive load from 3.3v Output

texts: I have a ESP8266 that needs to switch a water valve that draws 500mA on 12V. What can I use to switch that load? Right now I think I will use a logic level Mosfet but I am a bit lost with choosing the right one and the right resistors.


texts: My "flash VS RAM" speed test doesn't work. Why?

texts:
In trying to demonstrate that copying information from a string in flash memory to RAM takes longer than copying from the same information in an array in RAM to another, I ran the following code on the PIC32 USB Starter Kit II (PIC32MX795F512L):

// Global variables:
char b[60000] = "Initialized";
char c[] = "Hello";

// In main():
// Version 1: Copying from flash to RAM:
    while(1){
        strcpy(b, "Hello");
         for (i = 0; i < 999; i++){
             strcat(b, "Hello");
         }
         PORTD ^= 1; // Toggle LED

    }

// Version 2: Copying from RAM to RAM:
    while(1){
        strcpy(b, c);
         for (i = 0; i < 999; i++){
             strcat(b, c);
         }
         PORTD ^= 1; // Toggle LED

    }

I expected to see the LED blinking faster in Version 2, but instead Version 1 was a lot faster!  How could this be?

Could it be that instead of copying information from flash, we are using immediate data hardcoded into MIPS machine language?  Maybe I should try to understand the MIPS code.

Thanks in advance!


texts:
Why are constant current mode and constant voltage mode needed when charging Li-ion batteries?

Why do we apply saturation charge even after the cell voltage reaches 4.2V?

What exactly is 'I-sense' in Li-ion Battery charging?

It would be better if anyone can explain the whole charging process in detail.


texts:
I need to display the temperature acquired by my LM35 on a 2 digit 7 segment display. What I have is LTD383-R2 Common Anode Display. Datasheet here.

The display has 1 Anode pin + 14 Cathode pins for he 14 segments.

Any idea on the best way to drive this (with least components)? I am using Atmega328.

The options that came to mind were

Use a decoder. Google search came up with DS8669 from TI, but it seems that IC is now obsolete.
Go the usual route of using a ULN2803 darlington array IC + 74HC595 shift register. But this would mean using 4 IC's in total (2 for each digit of the display)

Thanks !


texts:
I understand from the diagram below that the neutral wire provides a return path to complete the circuit so that the current can flow.
But once the current goes back to the distribution transformer, what happens to it after that? What I'm trying to say, is where does the current go after it reaches the secondary windings of the distribution transformer? Does the same current flow over and over again through the same circuit, in a continuous cycle like fashion?

Also, why is the 240V split as 120V+120V? If I want the full 240V for some appliances, how do I make the connection? The diagram shows 240v across two live wires. Where is the return path for a 240V connection?


texts: Drive a capacitance load with a very large output resistance analog voltage source

texts:
I have a signal source with a very high output resistance. The output of this source is connected to the input of comparator. Actually the input capacitance of comparator is not large (about 20fF). However, the output resistance of the source is very large (10Mohm). So, is there a way to drive a capacitance load with large output resistance source here?
The voltage source is analog signal not digital one.


texts: Accessing stm32 registers via structs in GCC

texts:
I'm trying to roll my own USB device using an STM32F103 blue pill board in C with the GCC arm-none-eabi compiler, but I've run into some strange behavior that I'm trying to understand.

I've created a struct that models the endpoint buffer descriptor tables associated with the USB peripheral:

typedef struct _EP_BUF_DSCR {
    uint32_t ADDR_TX;
    uint32_t COUNT_TX;
    uint32_t ADDR_RX;
    uint32_t COUNT_RX;
} EP_BUF_DSCR;

And I've created a pointer to one of these structs and set it to address the beginning of the USB packet memory area of the MCU:

EP_BUF_DSCR *EP0_DSCR = (EP_BUF_DSCR *) 0x40006000;

So now I can set the ADDR_TX and ADDR_RX fields by just dereferencing the appropriate fields and assigning them values. However, when I try to do this with the COUNT_RX field, it appears to have no effect:

// debugger memory view shows register as set to 0 after running this:
EP0_DSCR->COUNT_RX = 0x8400;

But I am able to change the value in this register by creating a pointer directly to it and dereferencing it:

// debugger memory view shows register set to correct value after running:
*((uint32_t *)(0x40006000 + 12)) = 0x8400;

Could someone provide some insight as to why this happens? Have I done something bone-headed, or am I unintentionally relying on undocumented compiler behavior?


texts: Why are the voltages the way they are in this transistor circuit?

texts:
This question is about what my book calls "transmission voltage" when an nmos is conncted to the power source, or a pmos is connected to ground. It has a hypothetical diagram ass shown:

It also has a text to describe this, I have underscored in red the most relevant part:

It is the details about this I am wondering about:

In the first case when we have 0 volts in A and 0 volts in B. Do we then get 1 volts because there is 0,5 volts over each of the p-types? If so, what is the details that gives us this voltage over the p types?

Do we in the other cases get 0,7 volts, because we are connected to the power supply, but we lose 0,5 volts over the n type? Again, what is the details that causes a (negative) voltage over the n types in this case?


texts:
I am trying to put three solenoids in parallel so that I can connect the shafts together and get more power from them on switching them on at the same time. I see this diagram for one solenoid.

Can someone help me decide what additional components do I need to add two more in parallel to the existing one.
I have a 12V, 3A power supply, three solenoids of 12V and 1A each.

many thanks,
Marc


texts:
The following vhdl code is meant to do the operation as shown in the diagram.But the simulated waveform doesn't seem to be correct, I've spent hours but can't spot the mistake. Can someone help me please?

library ieee;
use ieee.std_logic_1164.all;

entity LU is
port(
CLK       :in  std_logic;                      -- System Clock
RES       :in  std_logic;                      -- Synchronous reset
OPCODE    :in  std_logic_vector(2 downto 0);   -- Logic Unit Opcode
A         :in  std_logic_vector(7 downto 0);   -- A input bus
B         :in  std_logic_vector(7 downto 0);   -- B input bus
Q         :out std_logic_vector(7 downto 0)    -- Q output from Logic Unit
);

end LU;

architecture behavioral of LU is
signal QA,Aa,Bb : std_logic_vector(7 downto 0);

begin

Aa<=A;
Bb<=B;
process(clk)
begin

if RES = '1' then
  QA <= "00000000" ;
elsif rising_edge(clk) then
  case OPCODE is
        when "000" =>
            QA <= not(Aa);
        when "001" =>
            QA <= not( Aa xor Bb);
        when "010" =>
            QA <= not(Aa or Bb);
        when "011" =>
            QA <= not( Aa and Bb);
        when "100" =>
            QA <= Aa;
        when "101" =>
            QA <= ( Aa xor Bb);
        when "110" =>
            QA <= ( Aa or Bb);
        when "111" =>
            QA <= ( Aa and Bb);
        when others =>
            NULL;
    end case;
 Q<= QA ;
 end if ;
 end process ;
 end behavioral;

That's the wave after i tried moving Q <= QA assignment to outside of the process


texts: Why is the gain of an integrator built using op-amp -Rf/R1 till cut-off frequency

texts:
As you can see the gain is constant for the practical op-amp, even though gain is

This shows that it clearly changes for every frequency. Is the one in the graph an approximation, maybe because it does not change much below cut-off frequency ?


texts:
Unipolar transistor basic variable transconductance is commonly marked by:

It is commonly used in calculations where we need drain current, Ugs, rds(on), and similar.

I have also seen many equations for calculating upper variables but here mostly used variable is known as "conduction parameter" (unit: mA/V square).
It says (in the pdf file) that "K" should be given by manufacturer. But none datasheet till now had any value like this one.

Question: Do these two (transconductance & conduction parameter) have something in common? Can one replaced with another (probably not)? Are these equations with conduction parameter even used in practice?


texts: Feedback in Integrator Amplifier of Op-Amp

texts: Why in analog computers for the integrator amplifier the feedback resistor is not applied? So, how to make sure (apart from resistors configuration) that circuit operates in linear phase?


texts:
I am new to PIC. I have found the following circuit:

But the problem is that I don't have a similat USB to Serial Converter. I use the Arduino as the converter, on which I can't find the "RTS", "DTR" and "CTS". I only know about the Rx and Tx pins of the Arduino.

The Question : Can I use the Arduino's Rx and Tx to program the PIC Microcontroller (for the first time, i.e no bootloader, firmware etc installed).

Thanks


texts:
Ok, so I recently have been seeing the name XMOS appear in places. I've looked on their website and searched online but I can't quite figure out what it is? So what is it? It appears to be a cross between a microcontroller and an FPGA?

I've also looked on their site and I wasn't able to see anything I could understand (just example designs and other reference documents) for what XMOS is and what is different about it from other microcontroller lines.


texts: How to get a FPGA design that will definitely work on actual hardware

texts:
I have just started learning digital logic design with FPGA's, and have been building a lot of projects. Most of the times (since I am kind of a noob), I have a design that simulates perfectly (Behavioural simulation) but does not synthesize properly.

So, my question is "what are the design steps that I can incorporate in my workflow, that will ensure that I have a working design that will work right on my FPGA ?"

I have two main areas where I expect advise, but this is absolutely based on a very narrow viewpoint of mine as a beginner, and more are welcome :

What all steps (viewing RTL schematic, post synthesis simulation, ...) should I undertake learning for the best practice.
What all things should I keep in mind while designing my logic (say FSM's or sequential circuits) to avoid any unexpected results.

I am using a Xilinx Spartan 6 FPGA, and Xilinx ISE Design suite for my work.


texts:
The LM3404 is a "Constant Current Buck Regulator for Driving High Power LEDs." One of the features the datasheet boasts is "LED dimming using pulse width modulation (PWM)." My question is, using this chip (and its associated support ciruitry), which of the following accurately reflects the nature of the current delivered to the LEDs?

the LEDs are actually switched on and off (chopped current) at the configured constant current in relation to the PWM input signal
the LED current is proportionately (i.e. in accordance with PWM duty cycle) reduced from the nominal fully bright constant current, but still driven by constant current (i.e. unmodulated).
Something else, if so please explain


texts:
I'm trying to generate a quadrature signal with a L297
http://www.st.com/content/ccc/resource/technical/document/datasheet/f9/35/6e/3f/48/18/48/51/CD00000063.pdf/files/CD00000063.pdf/jcr:content/translations/en.CD00000063.pdf
I use only phase A and C in order to have a 90° offset

Here is my wiring:
// L297 -> MCU
2 GND -> GND
4 A -> read out phase A
7 C -> read out phase C
10 ENABLE -> GPIO Pin 1
12 Vs - +5v
11 Control -> GPIO Pin 5 set to high for phases line ABCD
17 CW/CCW -> GPIO Pin 2 set to high or low depeding the direction
18 Clock -> GPIO Pin 3
19 Half/Full -> GPIO Pin 6 set to low for full step
20 RST -> +5v

According to my understanding, when I want the L297 to run, I write a bit on GPIO Pin 1 (HIGH) to enable the L297
For changing direction, I must put Pin 2 High or Low
And when I want to send a pulse, I write a bit on Pin 3 /Clock
i'm sending pulse to clock but channel A and C stay always low.
Do you have any idea of what could go wrong with my wiring ? or with my understanding ?

Thank you


texts:
I am working on an amplifier for a car radio for a friend of mine. He is away for few weeks so I can't measure the radio output.

That's why I am asking here, does anyone know, what's the peak-to-peak voltage from car radio, that then goes to the amplifier?

Is it universal, if not, how do these amplifiers usually do their preamplifiying?

EDIT:

Is this +-voltage or only positive?


texts: What's the way of passing a pointer from application file to driver HAL file that contains interrupt handler?

texts:
So there's a static pointer inside hal.c that stores a reference to the pointer being passed in from app.c, but having a separate function to do so seems a bit off to me though it works.

// hal.c
static volatile I2C_Struct *i2cHandle_p;

void SetPointer(I2C_Struct *i2cHandle) {
    i2cHandle_p = i2cHandle;
}

int ReadValues_IT() {
  ...
}

void IRQ_Handler(void) {
  ...
}

// app.c
SetPointer(i2cHandle);  // i2cHandle points to I2C_Struct struct in main.c
ReadValues_IT();


texts: Use interrupt to determine a change in IR detector

texts:
I have build a schematic to read a counter. The counter has a white point at one of the digits, that I detect with a IR transmitter-receiver. The voltage at the receiver changes from 2.2 to 2.5 volts (with some noise between) when te white point passes. So I use a opamp diff amplifier to change the voltage range to 1 - 3 volts. That signal goes to opamp comparator that changes at 2.2 volt input. I measured the voltage and indeed, only when the white point passes, the voltage is more than 2.2 volts
The output from the last one goes to a arduino that I programmed to count the signal via a interrupt.
The problem is now that I have false counts, but I cannot find why. I use a software debounce that is sure big enough to avoid false detections caused by bounces.
I think it has something to do with the hardware. Hereby a schematic.
Unfortunatly I have no scoop...

simulate this circuit – Schematic created using CircuitLab


texts: Design of circuit and soldering onto veroboard

texts: I'm new to electronics and I'm required to solder the circuit (2nd picture) onto a veroboard. I am however having trouble in designing it, with reference to the 1st picture, the left side of the circuit is already displayed on the veroboard, and I'm supposed to design the right side of the circuit and paste it on the veroboard. I dont know how to even approach this and where to put the components in the best position. The 1st picture shows shaded rows representing the 0V, 8V and 15V power lines. Can somebody guide me in completing the circuit? I have tried many times on a piece of paper but am not confident


texts:
I am confused with assigning number to a specific port. When I try:

LATA=31;

In this example when I check pins when by one, I get this result = 0b00001010. It is supposed to be 0b00011111. So cannot I assign number to a port? Or isn't it a proper way? Also let's say I want to make a simple communication by 2 PIC's with 8 PINS. Can I use

LATA=number;

From first PIC then

number=LATA;

From the other PIC. Would it work if timing is not a concern?


texts: Is my PSU design safe, what should I change?

texts:
Normally I would just go and breadboard the design out, but since this is using mains power, I would rather ask experienced people first.

I want to build a desktop 170V DC power supply to fiddle around with nixie tubes.
I came up with this circuit:

The Transformers will be(looking at the cheaper end parts, both will be around 7-10 VA):

T1 : 230V -> 9V
T2 : 230V -> 12V but in reverse.

The capacitors will be:

C1 : 1mF 25V
C2 : 47uF 450V

So will this circuit work and how should I improve it?

EDIT:

OK, here is an updated circuit taking into account all the replies.

 I missed a lead on that regulator, also a resistor on the HV warning led, ignore, please

Some highlights of modifications:

7.5k Bleeder resistor, which should dissipate the power in a second or so after turning the HV off
L7805 regulator for keeping the +5V clean
HV on warning LED
Fuses on all positive terminals
It will be in either a plastic or wooden enclosure, to eliminate risk of touching anything inside
All work on the circuit will be done after the HV is turned off, the warning LED unlit and voltmeter reads zero on panel
T2 will be 18V
output terminals will be this kind or similiar:

all connections inside will be maniacally heat-shrink tube wrapped to counter any chance of a short
will probably etch a PCB for that


texts: Concept of a concentric-double-slotted axial flux permanent magnet machine (motor)

texts:
I am after a design of a permanent magnet machine which is very constrained in the axial direction, but basically unrestricted in radial one. I also need significant space for the shaft hole.
The thought of an axial flux machine is pretty obvious, but what about adding a second row of slots 180 degrees apart:

Here the red/blue disks are the permanent magnets, the yellow/green/red bricks represent the slots of the three phases, using concentrated winding. The aspect ratio in the radial direction is close to what I intend to achieve.
The scope of the exercise are:

Reduce the length of the magnetic circuit by having the phases packed together more closely, and therefore cut the thickness of the yokes (not shown in the picture).
Reduce the axial forces on the rotor and the low order vibration modes.
Reduce the cogging torque.

Although these (and possibly other) benefits, I have never encountered this topology before, therefore I would like to know if there are any obvious showstoppers which I am failing to see. In particular I am very sensitive to losses/efficiency.

Here is a minimal configuration which may help to understand the topology. In this case the slot geometry and the winding would likely require separate optimizations for the two circles, but the real case has an aspect ratio much closer to the picture above.


texts: Does Bluetooth LE stack supports A2DP profile?

texts:
Does Bluetooth LE stack supports A2DP profile (audio steaming)? or if there is any dual mode stack which I could use in combination with BLE and classic stack.
Also any information on the hardware which supports this would be great help. Also if anyone knows Android OS supports dual stack?


texts: Interfacing SD card (SDSC) with Arduino Mega 2560 without SD module

texts:
I have just got into the idea of storing multiple scripts in an SD card, and using a custom driver written to the board to execute those scripts on demand.
I have a 2GB SD card, and an Arduino Mega 2560, but I do not have the SD module to create the connections between the SD and the board in the standard way.
Since the SD card only has 9 pins, I thought "maybe I can connect the pins directly to the board and find a way to read the data without the module". Does anyone know if this is even possible? If so, any good resources for me to learn how to do it?


texts: Why exactly do chips start malfunctioning once they overheat?

texts:
Once a chip overheats it can start malfunctioning - for example many programs may start failing once some or all parts in a computer overheat.

What exactly happens that makes chips malfunction when they overheat?


texts:
When using the RTCC module in the PIC24F, we need to use the secondary oscillator (by setting bit #2 of OSCCONL register) and disable the write lock on the RTCC registers. Now the write lock can be done by using the following pattern according the application note:

MOV #NVMKEY, W1 ;move the address of NVMKEY into W1
MOV.b #0x55, W2
MOV.b #0xAA, W3
MOV.b W2, [W1] ;start 55/AA sequence
MOV.b W3, [W1]
BSET RCFGCAL, #13 ;set the RTCWREN bit

Now this pattern does not work. And the cause can be found at the disassebly of these instruction used in C code (asm volatile):

!void enable_RTCWREN()
!{
0x33A: LNK #0x0
!    asm volatile ("MOV   #NVMKEY, W1");
0x33C: MOV #0x766, W1
!    asm volatile ("MOV.b #0x55, W2");
0x33E: MOV.B #0x55, W2
!    asm volatile ("MOV.b #0xAA, W3");
0x340: MOV.B #0xAA, W3
!    asm volatile ("MOV.b W2, [W1]");
0x342: MOV.B W2, [W1]
!    asm volatile ("MOV.b W3, [W1]");
0x344: MOV.B W3, [W1]
!    asm volatile ("BSET RCFGCAL, #13");
0x346: BSET 0x627, #5
!}
0x348: ULNK
0x34A: RETURN

WHY DOES MPLAB X IDE COMPILE THE CONSTANT #13 AS #5! Therefore the RTCC write lock is not disabled and the module won't start at all!!


texts: Stepping down then boosting the voltage, does the battery get drained at a quicker rate?

texts:
I have purchased a circuit that operates in an unusual way. This circuit firstly only as a 5V DC input terminal to power the 5V components. in addition, the 5V DC input voltage is also fed to a 12V DC boost converter. This 12V powers the 12V components.

My problem is this. I am currently running the circuit via the mains (the power supply outputs 5V DC which goes to the input terminals of the circuit). I would also like the option of running this circuit via a portal power supply such as an SLA battery. However, I only have the option of using a 12V 7Ahr DC SLA battery. (the entire circuit pulls about 840mA/hr)

First I would use a buck converter to step down from 12V DC to 5V DC then input to the circuit.

My question is, will the battery get drained quicker if use so many voltage converters i.e. I step down the voltage to 5V using a buck converter, then using the boost converter on the circuit to step the voltage back to 12V DC to power the respective components?


texts: LiPo use while charging: two cells (one charging, one under load)

texts:
I'm trying to figure out how to power my project using LiPo batteries and a solar charging circuit.

The project will draw up to 2A at 3.3V.

I did a search for IC LiPo charging chips that also allow a simultaneous load of 2A, and have only been able to find chips in SMT packages, such as the LTC4155  I can't find any breakout boards or shields that use chips of this caliber, and am hesitant to try and solder an SMT chip to my protoboard.

As an alternative to using a single battery with a charging circuit that allows a load to be applied simultaneously, I am now considering using 2 LiPo batteries.  While one is being charged by the solar charging circuit, the other is powering the main circuit.  When the battery powering the main circuit is low (say 3.4 V), it gets disconnected while the other battery (that has just been charging off the solar) is connected.  The low battery then gets connected to the solar charging circuit and the cycle repeats itself.

Something like this:

simulate this circuit – Schematic created using CircuitLab

Does this makes sense?  Are there any pitfalls to using this approach that anyone can think of?


texts: I came across some very thin coax cable, maybe 34awg,or even 36. Now i am wondering, foe which industry is it used and what connectors are available there. Any ideas?


texts: Are there data connectors designed to fit through small round holes?

texts:
I'm familiar with pin headers, but I have trouble finding a connector type where a 4-lead connector can fit through a 4 mm round hole.

The standard pin headers with a pitch of 2 mm and 2.54 mm are too large, a 2x2 pin connector has a diagonal larger than 4 mm.

The next smallest type, 1.27 mm, would barely fit through and might get stuck in the 4 mm hole.

The next smallest type, 1 mm, would fit, but I couldn't find long enough male pins to reach the top of the casing my PCB is inserted in (pin headers of larger sizes have plenty of "double decker" variants)

So my question is, are there any other connector types (possibly) unrelated to pin headers, which could fit through a 4 mm round hole?

Notes:

To not make this into an X-Y problem, here is my original problem I would like to solve:
A central device is connected to multiple smaller devices, to each with a 4-lead connection (5 V, very few mA). I would like to find a connector, so that for example the male is soldered to the PCB of the central unit, and the females are soldered on cables which are coming from the smaller external devices (or the other way around, with the females on the PCB). However, each cable, with the connector mounted on it, has to fit through a 4 mm diameter round hole, this hole is not on or near the central device. The ideal solution would be for the cables to be plugged into the top of the central unit, this is why I considered a "double decker" pin header, with appropriate square holes on the top of the casing.

A much less optimal solution would be to have holes on the side of the casing, so the pin headers or sockets on the PCB would be angled 90°.

This is when I started thinking: maybe there are completely different connector types which I never heard about, which would solve my problem much better.

I though of audio jacks, there exist some in 4-lead variants, but the plastic casing is much thicker. Also, they are expensive compared with the pin strips.

the problem with most very thin multi-leaded connectors (used in laptop computers, for example), is that although they are very thin, they are also very wide, they are not designed to fit through round holes.


texts: How do I get my Arduino Mega 2560 registered as a game controller?

texts:
I'm tempted to buy an Arduino Leonardo, but I already own an Arduino Mega 2560. I understand that the Leo already has support USB HID.

I'm just wondering if there's a fairly easy way to get my 2560 registered as an HID joystick instead, or should I rather go about getting an Arduino Leonardo?


texts: How to correctly store spare Cell Phone Battery?

texts: I've got a spare battery for my cell phone. I'm wondering what the correct way to store it would be, so as to maximize the battery time. Should I recharge the battery to 100%, then leave it aside, or should I use about 20-30% of the battery before putting it aside?


texts: Why isn't capacitive coupling considered in EMC testing?

texts: It seems like the emissions of interest in EMC testing are radiated and conducted emissions. Is this because capacitive coupling is so weak it doesn't pose a threat to other devices?


texts: I want to construct a peltier cooling system. However, I have limited mathematical skills. Can I ask how to do the maths to calculate how much temperature differential can a specific peltier cool taking heatsinks, fan air flow, volume of liquid, container, etc, into account.Thank you so much.


texts: I want to put a radio transceiver in the seatpost of my bike. Will it work?

texts:
I am a noob regarding electronics. I want to create a device for my bicycle using a GPS with an eByte E32 (a 1W LoRa SX1268 433MHz radio transceiver) and some batteries. The device will be in the seat post.

Will the RF transmitter work or it will create something like a "Faraday cage"?


texts: Can I use the same serial1 port to communicate with two modules?

texts:
My MCU is STM32L432KC, it has two serial ports 1 and 2. But I’m wondering if I can use the same serial port1 only to communicate with two modules (not on the same Tx & Rx pins but 4 different pins ?

Is there anyway I can in the software communicate with one module then disable the communication and communicate with the other?

I tried connecting both but one of them never works unless I remove the Serial definition of the other.

I attached a pic of my MCU with pins functions described


texts:
I'm trying to interface a rotary encoder with my pic18f4550. Just trying to get it to increase/decrease the variable output and then display that value through the LATD pins.

The code does not seem to be working at all, and was just wondering if I could get some help from you guys as to where I'm going wrong.

#include <xc.h>
#include "config.h"

#define _XTAL_FREQ 8000000

unsigned int output;

void main(void)
{
    OSCCON = 0b01110010; // Oscillator setup
    TRISB = 0b00110000; //Set RB4 & RB5 as input
    TRISD = 0x00; //All D pins set as output

    //Port B interrupts
    INTCONbits.RBIE = 1; //Enable port B interrupts; interrupt flag is not cleared so interrupt is triggered instantly, allowing us to record initial value
    INTCONbits.GIE = 1; //Enable general interrupts

    //Port B pull-ups
    INTCON2bits.RBPU = 0;

    while(1)
    {
        if(INTCONbits.RBIF==1)
        {
             static unsigned char prevState = 0xFF;
             unsigned char state = (PORTBbits.RB4 | PORTBbits.RB5 << 1); //Get value 0-3 from rotary encoder bits
             if(prevState != 0xFF)//If this is not the first time we enter the interrupt, process the gray codes
             {
                  if(((prevState == 0b00) && (state == 0b01)) //Turn counterclockwise
                  || ((prevState == 0b01) && (state == 0b11))
                  || ((prevState == 0b11) && (state == 0b10))
                  || ((prevState == 0b10) && (state == 0b00)))
                  {
                      output--;
                  }
                  else if(((prevState == 0b00) && (state == 0b10)) //Turn clockwise
                  || ((prevState == 0b10 && state == 0b11))
                  || ((prevState == 0b11 && state == 0b01))
                  || ((prevState == 0b01 && state == 0b00)))
                  {
                      output++;
                  }
             }
        prevState = state; //Save previous port b state.
        INTCONbits.RBIF=0; //Clear port B interrupts flag
        }
    LATD = output; //Display value on LED's on D pins
    }
 }


texts: The meaning of leads in equivalent resistances

texts:
Following on this question (How to combine two resistors with a voltage source) and faced with a similar example, it would seem the opposite applies. I am given the circuit below:

simulate this circuit – Schematic created using CircuitLab

and told Rth is (R1||R2)+(R3||R4). In this question (How to combine two resistors with a voltage source), it seemed the terminals were implied to be meaningless, implying that here, R1––R2 and R3––R4. What am I missing?

EDIT

In response to some of the answers below, I will redraw the circuit to better illustrate my confusion:

simulate this circuit

What is the role of the red leads? What is the meaning of asking for a resistance between these vs "the whole circuit"?


texts: Does a carrier wave need to be sinusoidal?

texts:
I am trying to AM modulate a song and I have an idea of how I am going to do it, but I need a carrier wave to start with and I've been having trouble creating one with a ceramic resonator because I don't have a CMOS inverter.

So I thought I would go shopping for an IC chip that can give me a carrier wave of 500kHz and one for 700kHz. However, I don't know what I need to buy. I understand the theory behind a carrier wave, but because I plan to use a BJT for the mixer. I have the suspicion that I could use a digital wave from the oscillator on the collector and the signal to modulate on the base.

Note that the diagram is meant to be basic to show my idea.

simulate this circuit – Schematic created using CircuitLab

Anyway, I don't know much about carrier waves besides building an AM radio receiver and I don't know anything about amplitude modulating a signal.

Would my idea work, or am I going to waste my money if I buy a chip that oscillates only square waves? Any part or schematic recommendations?


texts: Why doesn't a passive x1000 oscilloscope probe have 1000M Ohm impedance?

texts: Most of the x1000 high-voltage oscilloscope probes I find seem to have input impedance around 100M Ohm. For example the P6015A from Tektronix (100M Ohm) or the PPE6KV from LeCroy (50M Ohm) or these from North Star (100-400M Ohm). I thought that the passive attenuating probes just have a resistor in them (and a capacitor) which forms a voltage divider with the oscilloscope's internal resistance of 1M Ohm, so I'd expect a 1000M Ohm input impedance for a x1000 probe.


texts:
There are many heatsink calculation Q&A's on SE that I've looked through.  One very reasonable answer tells me that I can calculate heatsink C/W as follows: $$\frac{T_j - T_a}{P_d} - R_{JC} = R_{SA}$$
where Rsa is the C/W that I need to achieve.  In one LDMOS we are considering, the numbers substitute as follows: $$\frac{175 - 25}{272} - 0.55 = 0.00147$$
But 0.00147 C/W is impossibly small!
Another LDMOS we are considering shows the following C/W:
$$\frac{225 - 25}{690} - 0.29 = -0.000145$$
Yes, that is a negative C/W.
What am I doing wrong here?


texts: Microcontroller overheating when sensor is plugged in

texts:
I am building a board based around an STM32L051C6 microcontroller, which will measure a hall effect sensor (AH3362Q) and count the time in between the edges the sensor sees. The sensor is powered from 12V, and the MCU is powered by a 3.3V switching regulator (ROF-78E3.3-0.5SMD-R) which is powered from the same 12V. The sensor's output, being open-drain, is connected directly to the GPIO of the MCU, which is configured with internal pull-up.

I powered up the board without the sensor plugged in, and everything (minus the sensor functionality of course) worked fine. Then I powered the board off, connected the sensor, powered it back on, and observed that the chip began to heat up drastically. The chip is now dead, even when the sensor is unplugged.

My question is: what could be causing the MCU to die when the sensor is plugged in, given that its output is open-drain and shouldn't be driving the MCU pin at high voltage? Originally, in STCubeMX, I noticed that the GPIO mode of the timer pin the sensor is connected to was configured to "Alternate function push-pull" rather than the only other option of "Alternate function open drain". However, since the timer is being used in input mode, shouldn't these options should be irrelevant?

edit: Code used to configure GPIO, generated by STM32CubeMX:

GPIO_InitStruct.Pin = MOTOR_SENSE_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_AF_OD; // This was GPIO_MODE_AF_PP in push-pull mode
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
GPIO_InitStruct.Alternate = GPIO_AF2_TIM2;
HAL_GPIO_Init(MOTOR_SENSE_GPIO_Port, &GPIO_InitStruct);


texts:
I have an RGB Led strip that I want to use for just white light. I currently use an arduino with some transistors to control each colour. I have now no need to have different colours and I think my LED strip is not as bright as it could be due to the transistors I am using.

If I want to just use it as a white LED strip, can I just connect the +12 volt to +12v on the strip and the RGB pins to ground without the transistors or the arduino?


texts: Is there an ideal PWM frequency for DC brush motors?

texts:
I'll be using a microcontroller to create a PWM signal for motor control. I understand how PWM and duty cycle works, however I am unsure about an ideal frequency. I do not have my motor in yet, so I can't just test it and find out.

The picture depicts a graph of RPM vs Voltage. It's linear from 50 RPM @ 8 V to 150 RPM @ 24 V.
I will not be varying voltage, just the time it receives a given voltage. So can I assume a linear response? At a 10% duty and 24 V supply it would run at a speed of 15 RPM?
If it makes a difference, I'll include the setup. I am running 24 V directly to an H-bridge that controls the motor. Obviously I have two PWM pins going from the MCU to the gates of the two enable MOSFETS.


texts: 10 3W RGB LEDs in series control current

texts:
I'm having the following schematics connected to a 5V 25A DC power supply. All LEDs are 3W RGB, additional values are.
R1: 6.8 ohms 1/2W
R2: 4,7 ohms 1/2W
R3: 4,7 ohms 1/2W

I'm using an Arduino Mini and TIP120 to control each channel (R, G, and B). The 10 leds are connected in parallel, and they actually emit light (which is quite important).

During testing, and connecting a single led, this led was drawing about 0.4A for the Red channel. Now I have connected the 10 LEDs in parallel, the Red channel is only drawing 0.8A. I tried placing a resistor between pin 6 and the base of Q1, but the current drawn stays the same. The resistors tried vary between 10 ohms - 10 Kohms.

Could someone help me out? How can I direct more current through my Red channel, to make the LEDs shine brighter?

EDIT1: I've tried connecting all 10 LEDs directly to my 5V power supply. The light up all more brightfull and draw 2A in total. So I assume the problems ly in wiring up my transistors?


texts:
I have this 12V DPST switch that I want to wire, to make or break both Negative and Positive cable to open or close a solenoid valve.

I would say:
3. (+) to battery
4. (-) to battery
2. (+) to load
1. (-) to load

Is that correct? Anything that I should know?

simulate this circuit – Schematic created using CircuitLab


texts: What do I need to do to connect an ADC IC to a Adam 6066??Is it even possible to read the inputs from the ADC chip?

texts:
I am working on a input array that uses a ADC (MCP3208 or something similar) to read in several analog inputs and convert them to Digital signals that go into an ADAM 6066 Module. What would I need to do to communicate the inputs from the Analog to the ADC to the Adam and read the data into a program? I want this to report to a data logger and use the relays to trigger events from the inputs. I know usually read each channel as one thing, or as my experience so far. I kinda new to all this so I am sorry if I am not being clear.

Edit:Added link to datasheet


texts: proof that k-maps give the most minimized result?

texts:
how can i prove that a k-map for n variables gives the most simplified representation of a Boolean function ?

(by simplified i mean we cannot eliminate another variable)


texts:
Can someone please help me find the transfer function of this circuit.

$$
\frac{V_0(s)}{V_i(s)}= \dots
$$

simulate this circuit – Schematic created using CircuitLab

This is what I have done so far.
$$
I_{R1}+I_{R3}=I_{R2}+I_{C1}
$$
$$
I_{R2}+I_{C2}=0
$$
$$
I_{R3}=I_{C2}
$$
By substituting currents I reach the following formula.
$$
\frac{V_i-V_1}{R_1}+2 \cdot S \cdot V_0 \cdot C_2 = S \cdot V_1 \cdot C_1
$$


texts: Has anyone ever seen a (ring oscillator) circuit like this?

texts:
I first designed this using NT Multisim 14 and the simulation worked. Then I built it with breadboard but used NTE101 Germanium transistors instead of 2N3904 silicon transistors. When I tested it I noticed that when the input DC voltage is 10V++, it starts to oscillate continuously with no damping. I used only 1 capacitor placed in a T-bone connection between Q2 and Q3 so that there will be an imbalance in the ring upon startup to keep the oscillations going.

But the bigger question is: How do I reduce the jitter to a level so low that it will be inaudible? This is intended to be part of an audio frequency VCO(still need an amplifier and speaker to hear it).

I'd like some critique of this design; and if any of you have the components please test it and tell me whatcha got!


texts: Loose connection when attaching an Arduino shield with header pins

texts:
I am adding this Spectrum Analyzer shield to my Mega:

Using these header pins:

The square pegs of the header pins are worringly loose inside the holes of the shield.
I know soldering is an option, but I have no experience with it and worry that I may bridge a connection between two adjacent pins with a little runaway solder.

Any ideas for non-soldering fixes?


texts: Stop a DC Motor on a air flap recirculation car

texts:
i have some problems with a DC motor that rotate the flap from air recirculation in the car.
Problem: The ecu gives command when i press the recirculation button to the dc rotor ~10 sec, but the flap is closing in ~ 4,5 sec the rest of seconds the dc motor forces some plastic wheels from the ensemble => it's ruining in time.When i press again the air recirculation button the ECU gives reverse +/- to the dc motor to open or close the flap.

So before changing the broken things, i need an electric scheme to put it between ECU and DC motor when the flap go to the end, to fell the current growth and stop the DC motor.

DC motor voltage = 12v

Current value on free move = 60-70mA

The scheme must work +/- , -/+

I find on internet a scheme but i don't know if will work, i don't kown how to connect the circuit, i don't know the relay model.

Thank you and sorry for bad english.


texts: Why is the timing diagram of combined SAR ADC more efficient?

texts:
In the timing diagram below we have one SAR sampling while the other is proccesing.
If we have a stream of samples which is twice as fast then the rate of each SAR, given data stream of N+1,N,N-1,N-2 at first we give "N+1" to SAR1 and it is proccesing it.
What happens with the second SAR? When do we give it the "N" sample?
As I see it we should give "N+1" to SAR1 and "N" to SAR2 simultaneously,
but in the timing diagram below it is not like that.
Why?


texts: How does this increase the torque of a synchronous motor?

texts:
I'm studying from Wildi's textbook on electrical machines and I came across the following on starting a synchronous motor:

"To limit the voltage induced in the rotor windings during the starting of the machine and to improve the starting torque , we either short-circut the slip-rings or connect them to an auxiliary resistor during the starting period".

I get the part about limiting the voltage but since the current will be less how is the torque greater than before?


texts: how to use TMP87P809N microcontroller with any EEPROM

texts: How to use TMP87P809N with any EEPROM so that I can save timer counting of CMOS RAM in EEPROM for backup, I want to save that counting if electricity get failed and restart.


texts: How to run ATmega328P-PU using 3.7v Lipo 600mAh?

texts:
I want to run bare ATmega328P-PU using 3.7v 600mAh Lipo Battery. The Lipo is used to run Nano Quadcopter. The discharge rate is 20C.

My Question is:
1. Will connecting Lipo to my atmega directly fry up my chip?
2. Do I need any Voltage regulator?


texts: Calculating resistance given capacitance and charge over time

texts:
Given the seconds \$t\$ it takes a capacitor (with farads \$C\$) to discharge from 5 volts (\$V_0\$) to 0 volts (\$V_t\$), how do you calculate the effective ohms of resistance R in a circuit?

Based on the standard capacitor voltage discharge formula \$V_t = V_0(1-e^{-t/RC})\$, would the resistance formula be \$R = \dfrac{-t}{C \cdot log(1-V_t/V_0)}\$?


texts: Why does using Discrete Cosine Transform lead to data compression?

texts:
DCT is used in JPEG standard along with Huffman encoding to further compress the result. I understand that most of the data in spatial domain which is an image is "present in low frequencies". This is because most adjacent pixels change only little in the color value.

An image which is represented numerically in signal processing, with numbers representing the pixel color intensity. When we do a DCT on it we still get numbers in result. Where exactly does data get compressed via DCT?


texts: How to program a microcontroller over another microcontroller?

texts:
I am currently working on a project that requires two separate microcontroller to work together, but since I am still working on the project I generally need to update their programs.

I couldn't find a solution to my problem and that's why I am programming the second microcontroller unplugging UART connections and connecting it to USB to TTL adapter. After programming make those connections again with other microcontroller.

As you see it is long even when I am describing.

I am using two AVRs. (Atmega32 and Atmega328p). Is there a way to program 328p with 32?

NOTE: In operational configuration they are communication via serial communication. I want to program one with another without changing this configuration.


texts: Rewriting Code in Internal Flash in STM32F439

texts:
I am using the STM32F439 and looking to find a way to write code in the internal flash. Is there a protected area for quality assurance and security? It's supposed to be used for company's intellectual property.
I would also like to know if there's a way to rewrite the system memory, I presume that it is the most protected area and couldn't find a way to write the code on it.


texts: Not sure how to replace a blown fuse in a building's fuse box

texts:
One of our fuses in our secondary fuse box just blew. Luckily, there there is a backup. I am not an electrical professional but I know a little 101.

I just want to ask about the correct fuse / amps to install if I have this kind of setup:

As I said, one of the small fuses just blew and I replaced it with a 30 A fuse. Is it safe to use 30 amps? Because when both of my aircon and computer is on, the fuse copper was sparking. I am not sure what's causing it - is it the contact between the fuse holder and the fuse, or is it the fuse itself that just can't handle the current flowing? I noted when I turned off my PC, I don't see any spark.

Anyway the fuse I was using is this:

I am using 30amps, I think those are the big ones installed in our main fuse box.

Can you please give some advice about proper installation and what type of fuse to use?


texts: How to relate Pwm on time to maximum current ratings?

texts:
I will try to make it more explicit with an example. Imagine we have a microcontroller Atmega328P and one of its pin is set as output pin. And when we investigate about it we find that max current a pin can source is 40mA.

Now we also know that the average current through a resistive load is (PW/T)*(V/R) where PW is pulse width T is period of the PWM and V is 5V and R is 62 Ohm.

Now if PW = T the current becomes 80mA. But if PW = 0.2*T the current becomes 16 mA. But in the second case if PWM is 10 seconds and T is 50 seconds, it is still not okay.

So my question is how can we know the max peak current for known duration? I hope it is clear what Im asking. If we take average we conclude 16 mA is fine but it seems if PW is not short enough the current will be 80mA. Is there a relationship between PW and max current ratings?


texts:
Especifically talking, I need to demodulate a low frequency FSK signal( betwen 120 and 140 kHz ). I already have a circuit of antenna that receive the signal and I already can sample it, but I still have a doubt of how could be the best way, faster and reliable, to process the signal.

Basically, I'm using a comparator with interruption to count the number of cicles of the carrier, and a timer to measure the time between a pre-determined number of cicles. Depending on the time to count the pre-determined number of cicles it is decoded as being zero or one.

This is not working very well, it works, but it miss a lot too, so I was wondering an alternative way.

For those who may want to know, I'm using a dsPIC33EP64MC202.

Here is two figures that ilustrate my situation:

Please, if some one has any Idea, I would appreciate very much!
With my bests regards,
Daniel.


texts:
There are some great blogs out there for programmers (Joel on Software, Paul Graham's Essays, etc.). I would love to know about any similar quality content for electronics. Do you have any great blogs or podcasts you love?

(submit one answer for each blog)


texts: Do all common grounds end up to the chassis ground?

texts:
I'm new to electronics, and still wrapping my head around "common" and "ground."  The schematic is:
My question is if ALL the solid black grounds/commons end up at the one going to the cap/resister to chassis?

I keep debating if the power supply grounds/commons get tied together, then all the signal commons/grounds get tied together separately following the cap/resister to chassis ground.

First post here, thanks for your help!


texts: What will it take to build a small bluetooth device?

texts:
I am new to this part of StackExchange. I am doing a project that requires me to keep track of Bluetooth devices. So I want to build a tiny Bluetooth device that can be attached to almost anything; something tiny but effective. What will it cost to build this kind of device? What is the smallest size obtainable and how effective will it be?

Look forward your opinions!

Thanks!


texts:
Since RFID tag reading has poor performance in adverse weather conditions, I've received advice to use RUBEE. But I could not find it being implemented, nor available on a consumer scale. i.e., RFID tag, tag reader etc are readily available in the market. But I could not find any single one for RUBEE.

Even if I'm pursuing after RFID, I have a doubt on its performance at high speed. For example, if the reader is installed in a fast moving vehicle, say 75 mph, can it practically read a stationary tag on the side of the road? If it can't, what may be possible alternatives that function well in such a situation?


texts: IR2110 LTspice simulation weird behaviour

texts:
I am obtaining weird voltage behaviour at the gate of my high side mosfet controlled by IR2110 which is controlled by PWM.

PWM configuration:

Vinitial = 0
Von = 5v
Tdelay = 0
Trise = 7u
Tfall = 7u
Ton = 150u
Tperiod = 200u

For the simulation I use TRTOL = 7 and I am using the "Alternate" solver otherwise timestep is too small.

Here are the schematic and the simulation results:

Larger picture: http://i.stack.imgur.com/npxEB.png

Larger picture: http://i.stack.imgur.com/1CNqv.png

The green result corresponds to the mosfet gate voltage and the blue one corresponds to PWM.
As you see the gate voltage acts very weirdly.

Is this a simulation problem or would this happen in real life ?

EDIT: I just reduced the load resistance to 10R and gate voltage behaves correctly in 100ms simulation. Seems that is has something to do with the current flowing through the mosfet ... When the current is higher it works better and correctly.


texts: How do I put an LED in series with an optotriac?

texts: I have a set of SSRs (Vf=1.3V, If=20mA) that I am using to switch low-voltage AC loads, and I would like to have a set of indicator lights, one for each switch. Is it possible to simply put another LED in series with the SSR input? This LED would certainly not match the LED inside the optotriac, and I may not even have precise information on this LED, so how would I go about calcuating the resistor I need? Is this even possible or advisable?


texts:
In studying the Fundamentals of power electronics by Robert Erickson I do not understand how they arrived at the equations for current and voltage
Link to Book, page 772 is where I am at
https://documentcloud.adobe.com/link/review?uri=urn:aaid:scds:US:029bd239-6e09-4f9e-8992-f7c2b0f5407c#pageNum=1

Can someone help me understand how solving these differential eqn led to the solution below? I have started with applying Kirchoffs voltage law but not sure where to go from there. R0 is the tank characteristic impedance

Initial conditions and current/voltages eqns I am trying to derive

It would be appreciated if any one can help. If more clarification is needed or the book link does not work please let me know
Here is the work Ive done, I hope its clear! Ive chosen my initial conditions to be constants so I could understand better myself how to solve these equations


texts: Microcontroller - Measure Resistance in Circuit

texts:
I am creating circuit that will control power of heater coil.

For controling power I am using Arduino PWM that controls voltage and by Ohm's Law I am calculating desired power.

P = V^2 / R

Now the problem is next:

Heater coil is low resistance (0.3R - 2R), and resistance can vary with coil replacing. Because impedance of coil is used to calculate power I want to read coil resistance with microcontroller.

I am using this circuit:

Battery voltage is 3.2 - 4.2V.

Power from battery directly goes to the heater coil and it is controlled by MOSFET. After that there is DC-DC StepUP that provides enough voltage for Microcontroller and MOSFET.

VBAT is read by Microcontroller, so Microcontroller have info about current battery voltage that will go through LOAD (Heater Coil).

Now my question is how to measure LOAD (R5) Ressistance with microcontroller?


texts: What does the mass term mean in the unit of inductance called the Henry?

texts:
Reduced to base SI units, one henry is the equivalent of one kilogram meter squared per second squared per ampere squared (kg m2 s-2 A-2).

This does not look like the standard F = ma formula for a force but there is a mass term.  What does the mass term represent?  I am trying to understand how the units gel together.


texts: Detect if a CAN node is transmitting or receiving

texts:
I am not an electrical engineer or EE student; I'm a diagnostic technician.  AFAIK, a CAN transceiver receives bits by measuring voltage between the network and its ground/low reference (high impedance, minimal current flow?)

When it transmits it pulls the bus to its dominant or recessive logical voltage levels. This could be 3.5 volts. The CAN high and low lines being connected by 60 ohms of terminating resistance could cause a current flow through the CAN transceiver.

The voltage drop over the line could then indicate a transmission is occurring.

But if the transceiver has a high impedance on the low side the current flow will be extremely minimal. The transceiver has to supply enough current to maintain the logical voltage threshold with as much as 50 other nodes sampling it and a 60 ohm short between the two.

I don't know, I just can't tell if it would work.

It's useful because CAN nodes sometimes fail to communicate or to send a message when an event occurs and without detailed introspection of the bus traffic this is opaque. Even if the traffic was decided there is no source address to most communication, making it further opaque where a failure to transmit occurred.  CAN networks are extremely busy with general chatter even when a node is inactive so it can't be seen when one starts and stops transmitting.


texts:
Request for pointers to a schematic or an useful link for a voltage controlled PWM generator. Maybe with an op amp and a quartz crystal, and the duty cycle=Vinput/Vcc.

I thought this up: an op amp (comparator), with the minus (-) input a sawtooth oscillator and the plus (+) input the Vinput. The output of the opamp would be the output of the generator.

simulate this circuit – Schematic created using CircuitLab

Would that work?


texts: CD4067BE Multiplexer input always observed at all outputs

texts:
i am trying to use CD4067BE to switch an input between to output pins. I used 15V/0V Vdd/Vss for the mux, and connected all selection inputs and inhibit to 0V (Vss). I get the input signal at all output pins. I tried changing one of the selection inputs to (5V),  but I still have the signal at all outputs?

Could you tell me what is wrong?


texts: What are the differences between active bandpass filter topologies?

texts: I want to use a narrow band active bandpass filter but I found generally 2 topologies as seen below. What are the differences between them?


texts: Processor-in-the-loop for the design of a diagnosis system

texts:
I'm studying the development and implementation of a diagnosis system. I would like to understand what is the processor-in-the-loop, but there isn't any Wikipedia page (while there are for hardware-in-the-loop and software-in-the-loop).
Could you explain that to me?


texts: Jlink Commander doesn't find LPC4088 microcontroller on my homemade PCB

texts:
I just finished a homemade PCB with a LPC4088 microcontroller and some other components. When I connected my board to the J-link EDU probe over JTAG connector and start Jlink Commander, Cortex-M4 microprocessor inside LPC4088 isn't found like microprocessor is found in this video.

If everything was correct J-link Commander should find the Cortex-M4 microcontroller so I assume that I made mistake when I was designing the schematics.

I doubt that I made mistake with a power section of the board. The mistake is probably part of JTAG connections which I am quite new to. Yoou might want to open the image in new tab and zoom in in order to better see the schematics.

This is my first MCU board and I really have to make it work...


texts: Why were germanium diodes so fast and germanium transistors so slow?

texts: Germanium diodes were used for Radar during WW2.  Germanium transistors appeared about a decade later.  Most early transistors were only specified for audio use, like the OC71. The specified RF types like the OC44 were only good for a few MHz. Why was there such a speed difference?


texts: How to diagnose transformer failure or expected output

texts:
I have a pcb that takes 5v from a main board on pins 3&6 and takes this current through the T1 Transformer (obsolete, no datasheet S1673305) and should output some voltage (service manual does not say what current).
After the transformer I have two voltage regulators (IC4 & 5) that should output 3v and 1.5v. Both receiving 0v and outputting 0v.
My issue is: I am getting 0v on the transformer output. I checked the coils for continuity and they seem fine.
Not sure where to go from here and what to do to trouble shoot this circuit or if my problem is definitely my transformer.


texts: Effect of submerging a laptop in isopropyl alcohol without removing batteries

texts:
It's common knowledge that water damage on many electronic devices can be mitigated using isopropyl alcohol at a high concentration.

Many guides have mentioned disconnecting the battery before using isopropyl alcohol on the device. It can be tricky to remove the battery of certain electronics devices (such as many apple laptops), so I was wondering whether someone could please inform me about the consequences of submerging the body (not the screen) of a laptop that has been powered down in a tub containing 99.9% isopropyl alcohol without unscrewing any components (i.e. leaving the lithium-ion batteries inside the device)? The amount of isopropyl alcohol will be just enough to cover the keyboard.


texts: How do you null interference with beamforming?

texts:
I am trying to understand a text about beamforing :

  Classic beamforming toy example. Single spatial stream, 2x2.
  With one interferer, receiver alone can null it.
  With two interferers, need to coordinate nulls in both receivers and transmitters. For example, the nulls for the transmitters to receivers are (1,2), (2,3), (3,1) and for the receivers to transmitters are (2,1), (3,2), and (1,3), thus using all six degrees of freedom to cancel the six interference paths.
  With three interferers (four user pairs), we lack sufficient degrees of freedom to cancel interference. Thus, we resort to orthogonalization of channels.

What do we mean by nulling in this case? Are interference coming from the antennas inside the 2x2 system? is the case with two interferes a 3x3 system and the next one a 4x4 system? What is a user pair, is it an antenna in the MIMO setup? What is a degree of freedom in this case and why do we have only six of them?


texts: USB interface to bluetooth interface for digital scale

texts:
I've got a situation where I need to communicate wirelessly between a bluetooth-enabled Android device and a digital scale which can be accessed digitally via USB.

While normally I would be happy to just use one of the new bluetooth human scales, the scale needs to be officially certified and I haven't found any certified bluetooth-enable scales so far... and since it's certified hacking the scale itself is out of the question. So what I'm left with is a certified scale with a USB interface that I need to access via a bluetooth-enabled Android device.

I've very little experience with Arduino but it seems to me I could use something like Sparkfun Arduino Pro Micro + Sparkfun Bluetooth Mate Silver

From what I've understood, I could simply plug my USB into the Arduino and then have it do data i/o via the bluetooth mate.

So my question for those more experienced than I : are things so simple, or am I missing something? will there be a lot of Arduino coding to do or will this work out of the box? with these models can I count on a strong, reliable bluetooth connection? a bluetooth connection that had to be constantly re-established would completely ruin the interest of the project...


texts:
Replace everything in the circuit except the 3 A source by its
Thevenin equivalent circuit and use the result to find V1.

This is my solution but the teacher said it is wrong and i do not know how to fix it.


texts:
I am working on a project to monitor a power meter parameters like voltage, frequency, current and so on and this monitoring for both AC and DC. For DC we are using Cummins diesel generator, now I need to calculate the generator running hours based on the load.

For example, I have a generator with 10 kVA capacity which consumes the diesel as follows:

On 1/4 load the generator will take 1.5 ltr/hour

On 1/2 load the generator will take 2 ltr/hour

On 3/4 load the generator will take 3 ltr/hour

On Full load, the generator will take 5 ltr/hour

How to calculate these 1/4, 1/2, 3/4 and full load from the power meter parameters? And how can I calculate the diesel consumed by the generator using the same parameters?


texts: Using unused pins on an MCU to ease routing

texts:
I'm using a LQFP-64 MCU on a 2 layer board (ground plane plus power/signal plane), and I'm trying very hard to avoid running traces on the ground plane.  Some of them can be routed out the corners of the MCU.  I do have a couple problematic traces, and my solution is route the traces back under the MCU and out other pins.  I'll configure the "secondary" pins as digital inputs to avoid double driving the signal.

Is this a bad idea?  I guess there's extra parasitic capacitance.  FWIW the signals are <=1MHz, probably <=125kHz.  I need to check that the bootloader and reset states don't drive the pins, but otherwise it seems just fine?
Will EMC be a problem?  I have an unbroken ground plane on the far side from the MCU, but there won't be a solid power plane directly under the MCU.  The MCU itself will probably run around 12MHz, maybe 24-48MHz.


texts: What are the challenges involved in using optical interconnects? As they are efficient than copper interconnects in many aspects like power consumption and data rates, what is preventing using from using optical interconnects?


texts: Why does EM radiation travel much further than the magnetic field of an equivalent power electromagnet?

texts: If both fall of as 1/r^2 from the source then why can radio waves travel around the world and still be picked up easily at the right frequency but the field from a powerful electromagnet can not?


texts: I am trying to build a 0-42v Voltage measuring circuit that outputs to a 5v Micro! Failing badly

texts:
I am on to my next project which doesn't seem to be working as planned. At first I thought that I would find a boatload of pages on how to do this, but to my absolute surprise I couldn't find anything without having to resistor swap!
I am trying to read from 9v-42v. Think its easy? Think again!

There are Chinese circuits you can buy online cheaply that do it, but wheres the fun in that, i want to build it!

Can anybody help me?

This is what I am trying to build (and simplify - I don't need all the features), I could buy it but I wont learn! Its a motor controller circuit. It runs 12-60v DC - why didn't he  use a single resistor divider too? is he a fool like me? he obviously knew what he was doing, instead R1 has to be swapped depending on what voltage is running, 12v, 24v, 36v, 48v but this isn't the only circuit I've seen, some have op-amps or A to D converters, but why? dont they know what they are doing? A resistor divider would be just fine? this is why Im asking the question. I didn't want to hear just resistor divider, i was hoping to see something better and then understand why!


texts: Passive Ethernet Hub / Point to Multipoint Ethernet

texts:
I have a device which needs to connect to one of three devices using ethernet. When one device  is connected, the other 2 will be powered down. Power consumption is a factor, so I'd like to use a passive component

Using a RJ45 splitter has failed, I was wondering if anyone has a suggestion for this architecture

Would a single ethernet cable with 4 end terminations work?
Is there anything off the shelf for this situation?

Best regards


texts:
I am going through the book Verilog HDL by Samir Palnitkar.

I see that there are two types of shifting, the normal and the arithmetic.

But I was not able to understand the difference between them.

It was given that for a=0, b=-10,
the output for c= a + (b>>>3) is -2. How is this possible. What is the output if we use normal shifting.


texts:
I want to use AD536 as rms reader. I have no experience on this specific device. According to its datasheet ( page 1 line 21) it is well protected against input over-voltage. In fact, what was interesting for me in this device selection was this statement that means I don' t need input over-voltage protection circuit. But in page 3 of that datasheet and in the Absolute Maximum Ratings Table, the maximum input voltage is 25V peak. What I want to know is this 25 volt is the maximum voltage that device can measure but it can tolerate higher voltages ( for example 110 V) without damage or I need a over-voltage protection circuit also?
Any help appreciated if anyone has experience on this device.


texts:
I need to replace a 3.7V 1400mAh battery.  It has three leads the extra one being a thermal checker one I think.  I've tried hard to find the same one without success. It to fits into a small box 43mx30mmx20mm,  I can find larger mAh batteries but these dont fit.  So my idea is to put three 3,7V 900mAh batteries in parallel,  I want to use two lead batteries, If I connect the thermal check socket to the positive voltage will that be OK?   I read that these thermal leads are often superfluous/redundant and dont understand why the gadget I've got has to have the extra thermal lead.  Other gagets work with two leads and so why is the third thermal one needed?
I can buy two lead lithium batteries easily but the three lead ones are very rare and much more expensive.
Any advice on connecting the Lithium batteries in parallel is welcome.  I'd prefer not to have an explosion as they'll be mounted on my helmet!


texts: How are irrational numbers best represented and processed by computers?

texts:
My question is closely related to this one: How do computers understand decimal numbers?
However, that question deals with rational numbers only. I was wondering if irrational numbers can be represented by computers.
Irrational numbers are numbers with non-repeating and non-terminating decimal expansion. They have an infinite non-repeating sequence of numbers after the decimal point.
A common example where irrational numbers are seen is when calculating the area of a circle. The area of a circle will be an irrational number in most cases.
If the decimal expansion of an irrational number is shortened then the accuracy would reduce. As a simple example, the natural logarithm of e is 1, while the natural log of 2.72 or any approximation of e, is not 1 but a number a close to 1. If I'm writing a program using floating point arithmetic and the computer uses this approximation of e it will lead to errors.
Is it possible to avoid such errors and error propagation? Computations in science and engineering often involve irrational numbers. If this error propagates the final result will be very far from the correct one.


texts: A question about servo motor direction control

texts:
Before asking the question I want to mention the basic two premises I know:

As far as I understand  for direction control, H-bridge inverter is used only for a certain type of DC motor not for an AC motor(?). For example a permanent magnet DC motor direction can be controlled just by reversing the polarity of the supply voltage. So that means by using H-bridge one can both control the direction and the average voltage across the DC motor hence the speed.
Reversing the polarity for an AC motor does not change its direction since there is no "polarity" in alternating current system. In an AC motor, stator windings create a rotating magnetic flux. The direction of the resultant electromagnetic flux determines the direction of the motor shaft. And the stator frequency determines the speed.

Now below is a simplified diagram for an permanent magnet rotor AC servo motor:

I can understand how the inverter stage above generates a sine wave for stator windings at a desired frequency by using PWM technique. So by this way the speed or torque can be controlled.

But I couldn't figure out how in this case the direction of the motor is controlled.

How is the direction controlled in this case? Is the rotating flux reversed? If so how is that done?


texts: Boosting voltage to power a solenoid (pulsing intermittantly)

texts:
I would like feedback on the following circuit design please.  I am powering a solenoid using a 3S LiPo battery but want to increase the voltage to 35v. I am using an XL6009 module to boost the voltage from roughly 12v to 35v. The voltage booster specs say it can safely output 4A.  Do you see any problems with the following approach?

The LiPo battery is connected to the voltage booster input, of course.
The voltage booster output is connected to a 10,000u capacitor. (The solenoid, which has about 3Ω resistance, is firing for only a fraction of a second.)
I am using a resistor to limit the current running from the voltage booster to the capacitor.  I need to keep it under 4A to prevent damaging the voltage booster, especially if something goes wrong like the solenoid is engaged for longer than a pulse. I plan to use a 100W 13Ω (or greater) resistor at 35V, which will allow 2.8A going through the line.

I plan to use a relay between the capacitor and the solenoid to control the firing. I also use a mosfet to engage the relay’s coil from a microcontroller and have tested this circuit. I am using a relay that can handle 10A of current. I gather I might need a relay that can handle about 12A to be safe but figure if I am only firing the solenoid intermittently and for only 50ms, I should be ok. I will use a flyback diode to try to protect the relay from the reverse voltage spike cause by the solenoid’s inductive load.

Does this approach makes sense?

Thanks for the help!


texts: How do I calculate the capacitor value (Farad & Voltage) given the pulse current, pulse duration & maximum tolerable voltage drop?

texts:
I have an electronic component with following characteristics:

Operating voltage: 4.5V
Peak operating current: 2000mA for 600uS every 4000uS.

The device can tolerate voltage drop of upto 400mV during the peak current burst.

I want to use a capacitor (placed close to the component) to supply the entire peak operating current requirements so that the burst current does not have to flow all the way from main source to the component. Also this will give me the option to use a source of lower output current capacity instead of one that can handle peak current requirements.

Assuming the capacitor's ESR to be <= 0.1 ohm. How do I come up with an optimal capacitance and voltage rating of the capacitor?

[I am seeking a theoretical answer, I will add some headroom while actually selecting the component.]


texts: Mosfet amplifier calculate small signal gain

texts:
I try to solve problems in textbook. There is an amplifier which is powered by a +Vs and -Vs power supply,

The problem asks for small signal gain.

According to solution manual solution for VIN is like that :

But shouldn't it be like that.

$$
\large V_I=V_T - V_S - \frac {1} {K  R_L} + \frac {\sqrt {4V_S K R_L - 2 V_T K R_L + 1} } {KRL}
$$

Also I wonder whether the small signal equivalent differs when \$ \large v_I = v_O \$ at the bias point.

Citation :

  Agarwal, Anant, Lang, Jeffrey. Foundations of Analog and Digital
  Electronic Circuits.. [edx].

Note : This is not a part of homework.


texts: After the PCB is designed, what do I need to check in the Gerber files?

texts: As and after the PCB is designed, I check it using the native CAD tools. What do I need to check to make sure the generated Gerber files are ok?


texts: How do I delay MOSFET turn on without slowing down the rise time?

texts:
In a Half bridge MOSFET switching circuit, in order to prevent a "short" circuit through the high and low sides, I need to delay the turn on of the high/Low side until the Low/High side has turned off. I still need the switching speed to be as high as possible.
this is necessary because this is a very high speed switching circuit.

( a half bridge has current flowing from the positive supply through the High side through load to ground, and alternately from ground through the load and Low side to negative supply.)


texts:
In NMOS,
when,
            Vgs = Vth
            Vds < (Vgs - Vth = 0)
            so, Vds is -ve,

so initially I thought in nmos, if Vds is -ve, Id direction reverses and
electron flow from drain to source, in the n channel, so reverse current increases.
I simulated in LTSpice and saw that reverse current is like -617Amps, But why it's that high? (Here I think some conceptually wrong occurred, what's that?)


texts: How does a laptop maintain battery at full?

texts:
I know how a laptop battery becomes charged, however, I am not so sure how the power is maintained when when the battery has been charged to the maximum.

I am unsure whether the laptop would switch to take power solely from the power supply or would the battery be replenished as soon as it is used up.

Can someone who is knowledgeably of how this works explain to me how exactly does a laptop maintain power once the battery has been fully charged?

Is this true for ANY device?


texts: Correct way to ground components for solar panel measurement

texts:
I'm currently doing a project where I'm supposed to measure the current and the voltage from a solar panel and am unsure of how I should ground all the components in the circuit (since electrical engineering is not my field). I'm wondering whether I should connect all my devices' GND (ADC, Arduino, Hall sensor) to the minus side of the solar panel and load, or if I should connect the devices to the Arduino GND and the load plus voltage divider to the minus side of the solar panel (as picture #2 shows).

Since I've seen both versions in different Arduino battery measurement examples, I want to make sure I don't make any big mistakes and ruin components/measurements. Initially, I was going with version 1 (everything using the same GND in order to get the reference voltages correct), but after some googling I'm unsure. I apologize if my question is badly phrased. I'd also be glad if someone could explain why any/both of the measurement circuits are okay/not okay.


texts: How can a fluorescent lamp run without a ballast?

texts:
I have a desk lamp which, sometimes when I start it, causes my computer monitor that is connected to the same outlet to turn off and reset, so I disassembled the lamp to see what could cause this to happen.

The lamp itself is a circular fluorescent tube of this type, and to my surprise I found that, in the armature, there are only two components whatsoever: The power switch and a glow starter, connected in the ordinary way, only there's no ballast. This surprises me because I thought the ballast was critical to fluorescent tube operation, both to regulate the current so as to not blow the tube, and for providing a pulse for striking the arc.

How can the lamp work at all without a ballast? Could the tube be somehow self-regulating? Note that I have removed the little plastic cover over the connector on the tube (as seen in the picture linked above), and there are no active components inside it; there are only leads from the connector to the tube itself. The tube has always been a bit slow to start and often needs to cycle several times; could this be how a tube "normally" starts if there's no ballast?

Also, as a bonus question, I have noted that when the lamp is turned on and I have some comparatively sensitive skin (like my face) close to the armature's bare metal parts, I can feel a slight tingling, as if the armature were faintly electrified. The armature is properly grounded, though, and all active parts are properly isolated as far as I can tell, so I've wondered how this can be. Does a fluorescent tube normally emit a strong enough EM-field that can cause induction in the armature, or something? Could this be connected to the lack of a ballast?


texts: Why AC induction motor is used for high power applications?

texts: I know that in the variable voltage variable frequency you are able to keep the torque constant in various speeds , but i have also read something about them not requiring commutators but i couldn't really understand this part , can someone explain or provide me with some useful sources . thanks


texts:
For research, I want to build a levitation system that can levitate an aluminum sheet. With traditional 3 phase Induction engines you off course get levitation, but it isn't as stable as I want to. I've seen some Transverse Flux machines that are combined with a Linear Induction Engine. I know that Transverse Flux machines are based on an inward traveling magnetic field. But I wasn't able to understand how Professor Laithwaite created this stable levitation in the following video: https://www.youtube.com/watch?v=f5mA4l6xmGs (t=11:20).
There are two rows of (I suggest) coils that are both creating a magnetic field to the inside?
Or is there a magnetic field traveling from row A to row B?
Please help me out! Thank you


texts: What's the hold function on a multimeter for?

texts: All it does on my multimeter is freeze whatever value it was reading at the time. When would I need to use this?


texts: Oddly placed spark gap? Samsung phone charger (ETAOU10)

texts:
I was bored one day so I took apart an old (as in no longer needed, late 2013) phone charger.

Everything looks well designed except for the spark gap between neutral/live and the low-voltage side.   I'd understand if it was placed between live and neutral, but this one makes it look like you could get zapped if you're holding the phone while it's charging and a massive voltage spike occurs.

What good is it doing where it's placed?

The black thing that sticks out on the top left side is two wires for 5V DC out.
AC in is at the bottom fork-looking pads.

Side view

Top view with plastic cover-stuff

Top view without plastic

Attempted to draw a schematic of it


texts: Can I do on-chip debugging on atmega328p with gdb (command line)?

texts:
Is there a way of doing on-chip debugging of Arduino Uno (atmega328p) with gdb on the command line? I'm looking for something simplistic and excluding IDE solutions like Eclipse and Atmel Studio. I use VIM for programming and compile my code with a cmake build system provided by queezythegreat.

I had a look at my options but didn't get a clear answer to what tools I would need. Would gdb alone be enough or do I need something like openOCD?

Thank you for the help!


texts:
To teach myself the basics of power electronics I've been trying to build a circuit, which charges up a capacitor to a voltage higher than the input voltage. Basically it's a boost converter with no load.
I've run a simulation in LTSpice and found that the simulation results during the "switch-open phase" do not match my predictions at all.

simulate this circuit – Schematic created using CircuitLab

Prediction

When the switch is open, the circuit is basically an LC circuit with a superimposed DC voltage source. Therefore I set up and solved a differential equation and ended up with this:

$$
i(t) = I_{L,0} \cdot \cos(\frac{t}{\sqrt{LC}}) - \frac{C(V_{C,0}-V_{in})}{\sqrt{LC}} \sin(\frac{t}{\sqrt{LC}})
$$
\$I_{L,0}\$ is the inductor current when the switch opens
\$V_{C,0}\$ is the capacitor voltage
\$V_{in}\$ is the input voltage

Since there's still a diode in the circuit, of course there won't be any oscillation. Which is why I expected to see only the beginning of an oscillation, as modelled by the above equation, until the current hits zero. I then plugged in my component values and numerically solved for \$t\$.

Result

The simulation yields an almost linear decay of the current. The time that it takes to reach zero is nowhere near the time that my math predicted.
Using the component values from the schematic, the mathematical model yields a time of 1.92ms until the current hits zero.
In LTSpice however, it only took 396 us.

So where did I screw up?
Thanks in advance


texts: How do these modern power buttons on devices work

texts:
In the older days and still now we have buttons where one way is off and the other way is on, its mechanically built to connect or disconnect an electric path physically.

On modern devices like laptops the power buttons work differently. Push once, it's on, Push again, it won't turn off and will go to sleep mode instead. Keep the same button pressed for around 3 seconds and the laptop shuts down as if the power was literally cut off.

These buttons surely have a more complex mechanism than just connecting or disconnecting a wire.

Does anyone know how those circuits have been designed? I am quite curious as to how these power switches work.


texts:
I am working on a sensor based project using STM32 in which I do the following things,

Receive data from sensor
Transmit that data on the CAN bus.

The sensor will send data twice every minute and there is approx 250ms delay between those two data from the sensor. When a data is received from the sensor it is transmitted as a frame on the CAN bus. I also have a MCP2515 attached to a raspberry pi which logs all the data on the CAN bus. There is no other node on the CAN bus except the STM32 CAN and MCP2515. I also checked the termination resistors and they are ok. Initially I has the following settings
  hcan.Init.TTCM = DISABLE;
  hcan.Init.ABOM = DISABLE;
  hcan.Init.AWUM = DISABLE;
  hcan.Init.NART = ENABLE;
  hcan.Init.RFLM = DISABLE;
  hcan.Init.TXFP = DISABLE;

When I used the above settings, my data log showed a lot of data missed in the CAN bus. So I changed the NART to DISABLE and tried again.
   hcan.Init.TTCM = DISABLE;
  hcan.Init.ABOM = DISABLE;
  hcan.Init.AWUM = DISABLE;
  hcan.Init.NART = DISABLE;
  hcan.Init.RFLM = DISABLE;
  hcan.Init.TXFP = DISABLE;

This time I received many additional data in the CAN log. Why is this NART bit causing additional data on the CAN bus. As per my project, I need an exact data count from the sensor. I am pretty sure that the sensor is transmitting the data on regular interval using a oscilloscope.
Please help me out on this.


texts:
For an application in the lab, I need a filter that bumps up the phase around 56 kHz by about 15 degrees, while not causing a big difference in gain at low and high frequencies. Ideally, it should also not reduce the gain by too much.

I came up with the idea that I could use a combination of capacitive and resistive voltage divider to do the job:

I measured its transfer function, and it seems to be working like a charm. Now my question: I currently seem to not be able to wrap my head around why this exactly works to bump the phase. Is this just an artefact of a low pass and highpass behavior, with carefully chosen frequencies, or am I missing something important here?

Any reference to read for myself would be highly appreciated, I have been looking for a while and couldn't find anything that helped me.


texts: How to simulate a DC sine ripple in proteus

texts: I am trying to simulate a DC sine ripple in proteus to emulate power supply noise and see how effective different power supply filtering will be but i could not find a simulation primitives for this The Sine Generator. The Sine Generator generates AC signal the offset also  does nothing that i can see off


texts:
I'm designing a circuit with an ICF (indirect current feedback) amplifier, and am trying to calculate the gain of the resultant circuit.

Using the AD8237 I followed the example here when designing with one modification. Instead of using a voltage follower, I used a resistor divider as the datasheet said I could (the ICF amplifier does not require a low impedance Vref like other 3 amp instrumentation amplifiers). Doing this does affect the gain, as can be seen from the snapshot from the datasheet below:

The gain when Vref = 0 is G = (1 + R2/R1). I tried dusting off some Thevenin equivalent circuit knowledge (it has been quite a while) and calculated the resistance with R1 removed and the voltage sources and calculated it as (R2 + R3||R4). Replacing R2 in the gain equation with this gives G = (1 + (R2 + R3||R4)/R1) which is the same as what is in the datasheet. So far so good!

The challenge comes when adding the next part of the circuit - an offset voltage Vdac and resistor Ra as seen in the circuit below.

Doing the same as before, I calculated the resistance with R1 removed and all voltage sources shorted. From this I calculated it as (R3||R4 + R2||Ra) which when replacing R2 in the gain equation results in a gain of G = (1 + (R3||R4 + R2||Ra)/R1).

Is this the correct way of calculating this? Is the resultant gain I've calculated correct?

Edit: I don't think my math/understanding here is correct. I tried to derive equation (5) from the example as a check on my understanding and didn't have any luck. Can someone help me understand how that gain equation is being derived?

Many thanks!


texts: Sensor range and speed based on resistor

texts:
I have 4 of these sensor circuits and can't quite figure out the optimal resistor value to use.

Here's what I assume (which somewhere I may be wrong):

The datasheet for the IC states leakage current is +/- 1uA which means its a 5 mega ohm resistor in a voltage divider calculation.

So if I made the pull-up a 2 mega ohm resistor, then 5/7 * 5 = 3.57 volts in if photo-transistor doesn't turn on. which is logic 1 input for many gates but I'm not even using that high of resistor.

But then I learned transistors have capacitance in them and I think my photo-transistor has a 15uS turn-on and turn-off time?

So given this circuit, I chose schmitt trigger because I want the signal to be clean and fast.

I made a microcontroller circuit (connected output of this circuit to demultiplexer input then output of that to one micro's GPIO pin through a resistor) to try to sense when light goes on and off.

I gave roughly a 15uS between each sensor before microcontroller selects the next sensor to sense for light.

Then if light is detected within that 15uS then a 1ms timer starts to see if the light turns off. If it does then detection is complete.

So is my choice of 560K a good pull-up resistor value or do I need to increase detection timing? and what about the schmitt triggers? Is that a good idea for cleaning up signals or is there a better reason to replace them with just inverters (74HC04)?

the phototransistor is an everlight pt334-6c


texts:
Please explain me the results of this problem. Here both sources are supplying active and reactive power to the transformer.

So, both sources are creating core flux together ?

Till now the flow was simple for me. Like

Primary source supplies magnetizing current
Magnetizing current sets up the core flux N1I0
As load is connected, load current increases which creates an opposing flux N2I2 decreasing the core flux.
Now as the core flux decreases, E1(induced emf in primary side) decreases.
As E1 decreases. I1=(V1-E1)/Z1 increases. So, N1I1 increases.
N1I0=N1I1-N2I2. Thus, the net flux remains constant in the core.

But I am not able to understand the flow in case of 2 sources.


texts: AVR Time Delay without Arduino Libraries

texts: Trying to figure out how to do something like delay() in Arduino but just for straight AVR code. What's the typical way to do waits and such on AVR chips?