texts: Can eddy current sensors measure through a thin metallic sheet?

texts: I would like to know if it is theoretically and technically possible to measure/detect a metallic object through a thin metal sheet using eddy current sensor. For example copper has a skin depth of 652um at 10kHz. Will it be possible to measure the distance of a metallic object through a thin copper sheet of 100um?


texts: Switch between two low voltage signal sources

texts:
I'm new to this community so I apologize if this isn't posted correctly.

I am looking for a circuit that could switch between two low voltage (1v or less) DC inputs to a single output. Oxygen sensors such as the type used for car engines use a chemical element that generates a small voltage dependent on the amount of oxygen present. While the engine computer for my application only has one o2 sensor channel, I need to supply computer with the signal/voltage from two o2 sensors; switching between the two at least twice per second.

Since even a small variance in the signal output would cause an issue, there would need to be minimum resistance/voltage loss in the circuit. Is this possible, and if so what could the circuit look like?


texts: Using RS flip-flops to solve this problem

texts:
Consider a rail with a wheel mounted on it. The wheel can move from point A to B or B to A. There is a linear sensor to track the position of wheel between A and B. At point A, the linear sensor gives converted digital output 0 and at B it gives 1000. We will consider the wheel to be midway between A and B when the linear sensor gives reading as 500. Lets say this point it C.

Something like>

A___________C___________B

0__________500__________1000

Now to the electronics part:

Button 1 moves the wheel to A by starting motor x.
Button 2 moves the wheel to B by starting moor y.
Button 3 moves the wheel to the center point irrespective of its starting position, that is, A to C or B to C or from anywhere in between towards C.

The same motors x and y are used, based on the direction.

I have solved all 3 conditions above but there is one more that I am not able to implement. Sometimes when pressing button 3 to move point C, it can happen that the wheel may be acted upon by an external force and cross point C rather than stopping at it. In this case, we do not want that our existing logic starts moving the wheel back towards point C. Think of this like a pendulum effect with the wheel oscillating and crossing over point C before eventually coming to a stop.

So, the ideal condition is that if the wheel crosses over C while button 3 is being pressed, the motors x and y both should be shut off after the first time the wheel reaches or crosses C.

My friend suggested that I should use flip-flops to solve this but I havent managed.

Please help!!


texts: How to correctly apply thermal compound to ICs and heatsinks?

texts:
From http://en.wikipedia.org/wiki/Thermal_grease

All these compounds conduct heat far better than air, but far worse than metal. They are intended to fill gaps that would otherwise hold air, not to create a layer between component and heatsink—this will decrease the effectiveness of the heatsink.
Excess grease separating the metal surfaces more than the minimum necessary to exclude air gaps will only degrade conductivity, increasing the risk of overheating.

Our Chinese factory is just sloppily brushing it all over the IC and the heatsink, and I think it's more harmful than helpful.  Is there a recommended procedure for applying it?  Are there machines for applying it quickly in mass production?


texts: PIC - Problem in NEC IR Decoding in PIC12F675

texts:
I'm using PIC12F675 with internal OSC running @ 4MHz. I'm using MikroC Pro compiler version 6.6.2.

To Decode NEC protocol, I'm not using Timer or Interrupt. I used delay command to make the code as simple as possible with time-out property and the code checks the IR signal with resolution of 50Âµs.

I'm using Timer 0 and Pin change interrupt for my work. And I need to decode IR signal with a normal way using the GP3(MCLR) pin.

My program is working fine with PIC16F877A which running with external OSC @ 16MHz. But when I using the same program for PIC12F675 it's not working for me.

I have disabled Pull-ups and MCLR pin function for PIC12F675. And using the GP3 pin as the input for IR receiver.

I'm using the example from here.

Below is my program for PIC16F877A. Please, can someone help me to solve this problem for PIC12F675?

Thank you

Chayan

/* Pin Configuration */
#define IR_PIN                RB0_bit       /**< IR Signal Reception Pin.*/
#define LED_PIN               RC5_bit

unsigned long ir_code;
unsigned int address;
unsigned short command, inv_command;

short nec_remote_read() {

unsigned long count = 0, i;
// Check 9ms pulse (remote control sends logic high)
while ((IR_PIN == 0) && (count < 190)) {
count++;
delay_us(50);
}
if ( (count > 189) || (count < 120))     // NEC protocol?
return 0;

count = 0;
// Check 4.5ms space (remote control sends logic low)
while (IR_PIN && (count < 95)) {
count++;
delay_us(50);
}
if ( (count > 94) || (count < 30))       // NEC protocol?
return 0;

// Read code message (32-bit)
for (i = 0; i < 32; i++) {
count = 0;
while ((IR_PIN == 0) && (count < 14)) {
  count++;
  delay_us(50);
}
if ( (count > 13) || (count < 2))     // NEC protocol?
  return 0;

count = 0;
while (IR_PIN && (count < 40)) {
  count++;
  delay_us(50);
}
if ( (count > 39) || (count < 4))     // NEC protocol?
  return 0;

if ( count > 20)                      // If space width > 1ms
  ir_code |= 1ul << (31 - i);         // Write 1 to bit (31 - i)
else                                  // If space width < 1ms
  ir_code &= ~(1ul << (31 - i));      // Write 0 to bit (31 - i)
}
return 1;
}

void main()
{
TRISB0_bit = 1;
TRISC5_bit = 0;

while(1) { //Loop executed infinite times

//while (IR_PIN);                //Wait until IR pin falls
if (nec_remote_read()) {
address = ir_code >> 16;
command = ir_code >> 8;
inv_command = ir_code;

switch(command){
  case 0x48:
  LED_PIN = 1;
  break;
  case 0x80:
  LED_PIN = 0;
  break;
   }
  }
 }
}


texts: What is the actual capacity & charging current of a given deep cycle lead acid battery?

texts:
Firstly let me say that this is with a view to using a lead acid battery for backup purposes in case of power outage (mains power, a few lightbulbs but with daily outages lasting a few hours)

So let's provide a data sheet for the battery, deep cycle flooded lead acid type:

http://www.trojanbattery.com/pdf/datasheets/SPRE_12_225_DS.pdf

For the given battery, the SPRE 12 225, the open-circuit cell voltage is:

100% charged 2.122V per cell
50% charged 2.017V per cell
20% charged 1.943V per cell (11.66V total)
10% charged 1.918V per cell (11.51V total)

Meanwhile the capacity of the battery is defined based on discharging (at constant current) in 10, 20, 48, 72, or 100 hours until the cell voltage falls to 1.75V (10.5V total).

According to the manufacturer's data, the total lifetime capacity of the battery (number of cycles * depth of discharge) doesn't appear to be significantly different between 20% and 80% DoD.

So if we want to know how much real capacity the battery has, it seems we can use 12V * C * 80%. The C10 figure is 179Ah, C20 is 204Ah and C100 is 225 Ah. So at C10, 17.9A, that's 12 & 179 * 0.8 = 1718.4W.

However, is it possible that the voltage drop due to the current & internal resistance of the battery is distorting the figures? Or is this insignificant?

The manufacturer do not quote below a C10 figure (17.9A, equivalent to around 170W after inverter & distribution losses). Is this the maximum current draw? Or could you go to, say, C5?

I notice from the manufacturer's datasheet for their renewal energy storage range

http://www.trojanbattery.com/pdf/TrojanBattery_ProdSpecGuide_RE.pdf

that the ratio of, say C10 to C100 isn't completely consistent across battery chemistry, however they do quote C5 numbers for some of the AGM & gel batteries. Is there in fact a possibility to use a higher discharge current for gel/AGM vs lead acid? And as such perhaps a better battery chemistry for the deep cycle, fast discharge use case (let's say we we get a 1 hour powercut and want to discharge at, say C2, and have a generator for backup in the case that it goes over 1 hour)?

Secondly in terms of charging the battery, the SPRE 12 225 states 'a maximum charge current of 13% of C20 rate'. Does this mean 13% of the C20 capacity of 204Ah = 26.5 A charging current, and hence we can charge from 20% to 80% (122.4Ah), say, in just over 4.5 hours?


texts: Trick VHDL Synthesizer to synthesize despite no input signals

texts:
I have a circuit I'm trying to debug and I'd like to eliminate the PLD from the root cause investigation. As such, I'd like to hardwire the outputs of the PLD to a 0 or 1 irregardless of the input combination. I've tried a number of things from using an impossible input combination (in my case, all Z), setting the outputs accordingly if the inputs are all don't cares, to simply setting the output to a hard-coded value. While most of these will link and fit in ISPLever, I cannot create a fuse map because I either have too many terms (in the case of all Z's) or I detects no input signal after simplification. I am using a pretty dated PLD (GAL22LV10C-15J), which is probably why it ran out of terms in one of my attempts. The next thing I'm going to try is the following, but I'm sure I'll have the same result:

output <= input and (not input);

I am doing this so as to ensure the outputs are not floating while I debug the rest of the circuit.


texts:
I am trying to read the wiring diagram of an air conditioner. I could not recognize the symbol in the red rectangle.
Any clue?


texts: How to get from 3 phase variable high voltage AC to 230V AC

texts:
I already asked all the electricians in my area (at least 7-8) and nobody could help me, so I am asking you.

I have a Pelton generator - a type of water powered generator.

My output is 3 phase variable between 240-360V.
How do I get them to a stable 230V AC (to use for domestic electric items?)

I once had am item that did exactly that and I could simply attach the three AC wires and attach anything "normal at home" on the other side. And it did cost about 150$.

The company that made this doesn't exist anymore and nobody can tell me where to buy a replaceable item.

Attached an image of my generator.

Could somebody explain me how to do this?


texts: Control Theorie: Drawing Transition Matrix Trajectories

texts:
Given a transition matrix like e.g.

$$  \phi(t)=\begin{bmatrix} e^{-3t} & 0 \\ 0 & e^{-3t} \end{bmatrix} $$

What is the analytical way of drawing x(t) for two given starting points?
I only received this solution, which I can somehow understand in this case:

Since one x2 is at zero for the right point and one therm is decaying, it hast to go to zero. The left point somehow goes on a line to zero because both x1(t) and x2(t) got the same factor. The hint which was given confirms this assumption: $$ x_1(t) =  e^{-3t} \cdot x_1(0)$$ $$ x_2(t) =  e^{-3t} \cdot x_2(0)$$ $$ x_1(t) =  C \cdot x_2(t)$$

The reason I'm questioning my assumption is a second task which was given:
$$  \phi(t)=\begin{bmatrix} e^{2t} & 0 \\ 0 & e^{-2t} \end{bmatrix} $$
With those starting points (and solution in blue)

To solve this exercise I tried to find a connection (like the C before). The equations for $x_1$ and $x_2$ both have difference coefficients. Besides the starting point they have a factor of $e^{4}$ in difference.

The hint in the solution which was given confused me more. As before, it can be written: $$ x_1(t) =  e^{2t} \cdot x_1(0)$$ $$ x_2(t) =  e^{-2t} \cdot x_2(0)$$
but then
$$ x_1(t) \cdot x_2(t) = 1 \cdot x_1(0)\cdot x_2(0) \rightarrow hyperbole $$

Of course the math seems legit, but the same solution could have applied in the exercise before, which would have led to something different. Is there a mistake, or why is this the proper way?


texts: Clear cut thing to do when 18650 Li Ion Cell Has Been Overdischarged

texts:
I think close to everyone knows over-discharge of Lithium ion cells is bad news, creating fire and chemical burn hazards.

These are my cells

I accidentally over-discharged two Lithium Ion cells.
What I would like to know is whether that should be the end of their recycled lives, or whether there is a margin of safety I can rely upon to keep.

I had a 2-cell (in series) unprotected 18650 lithium ion 2000 mAh capacity pack hooked up to some led lights running 2 A last night. I forgot about the need to avoid over-discharge. So I guess the batteries discharged in about an hour and have been sitting with the lights out but batteries connected for 15 hours.

After disconnecting the batteries from the lights, the voltage in the cells measured with a multi meter is 0.65 V these batteries are supposed to be kept at least 2.7 volts.

Is recycling my only good option?
Any hope in restoring these cells?


texts: Arduino : send data via satellite (or other solutions) without GSM

texts:
I'm a researcher.  I'm looking to build a very tiny embedded system with low power consumption. I must send data from the desert and above the ocean. To do that I think that my single option is to use satellite transmission (and not GSM.)
Thus, I found Iridium Satellite (RockBLOCK) but my main issue is that their Arduino module is too big for my project (4cm of length and too heavy.)
Do you know if there is other module to send data via satellite with Arduino? If not, do you know other microcontroller which can do that? (Using Arduino is not mandatory for me.)


texts:
I am familiar with circuit design - Basic Op-Amp Design, concepts like stablity, Phase margin and I am a beginner in Microwave Engineering. I am familiar with some basic ideas and little familiar with devices like pHEMT (High Electron Mobility Transistor) ,mHEMT,HBT and working principles.

I have a task to give a presentation on this Paper (patent) which can be downloaded here.

One of the circuit diagram:

The title of the Patent is Switchable Multiband LNA Design.
This patent talks about designing a Low Noise Amplifier. On the whole I understand the circuit, which consists of a cascode transistors to avoid the miller effect and the feedback (Which also gives some stability problems). I can understand the circuit theory part of it but I wanted to really understand the Radio Frequency Engineering used in this patent - but I am stuck with some basic questions like:

What are the challenges in designing Amplifiers with high frequencies? - Is it not possible with popular technologies like CMOS - why are they using something like Si/Ge or InGaAs?
Above which frequencies does the amplifier design becomes difficult? How far does the normal Op-Amp with Differential stage work? (I usually design it from DC-some MHz)
What basic knowledge is required in LNA Design? Why can't we use the same approach that we do in a normal Amplifier design? Like if we directly connect wires, impedance won't match? What is that 50 Ohms matching anyways? Why can't other others other than 50 Ohms can be used for matching? Its just we need matched resistances right?
What is noise matching?
Why in RF (Radio frequency) -MMIC (monolithic microwave Integrated circuits), few transistors are used and why are they usually big?

I tried to read this paper but concepts were just totally new and wierd to me - like using spiral inductors, biasing for transistors, variable capacitor. ]

If anybody could recommend a text book which could provide a basic knowledge for this given paper, it would be helpful.


texts: Method to find Correlation for a random variable and thereby power spectral density of random signal

texts: I'm trying really hard to understand the segment of text from a standard communication book ( Modern digital and analog communications by B P Lathi). We are trying to find the power spectral density of binary signalling where the value can take random values 1,0,-1 with probabilities given. What I understand is that to find the power spectral density the very first step is to find Correlation of the random values . I'm not able to understand the method . I understood how the mean and variance is found , but not how Correlation for 1 is found and why does Correlation for greater than or 2 be zero. Could someone please explain an alternate simple method or bother to please explain the same method ?


texts:
I am working on a project using a PIC18F26K20. I need to store several value in EEPROM, but it does not store any data, all I evers get back is 0xff.

Here is the code I am using:

 unsigned char ReadEEPROM(unsigned char address){
     EECON1=0;                   //ensure CFGS=0 and EEPGD=0
     EEADR = address;
     EECON1bits.RD = 1;
     return(EEDATA);
 }
void WriteEEPROM(unsigned char address,unsigned char data){
    char SaveInt;
    SaveInt=INTCON;             //save interrupt status
    EECON1=0;                   //ensure CFGS=0 and EEPGD=0
    EECON1bits.WREN = 1;        //enable write to EEPROM
    EEADR = address;            //setup Address
    EEDATA = data;              //and data
    INTCONbits.GIE=0;           //No interrupts
    EECON2 = 0x55;              //required sequence #1
    EECON2 = 0xaa;              //#2
    EECON1bits.WR = 1;          //#3 = actual write
    INTCON=SaveInt;             //restore interrupts
    while(!PIR2bits.EEIF);      //wait until finished
    EECON1bits.WREN = 0;        //disable write to EEPROM
}

Is there something else I need to do to store Data in EEPROM? Or am I doing some thing wrong?


texts: battery backup supply switch over design

texts:
I have an application with two AA/AAA batteries (so total of 3V or less) powering a unit with a micro controller. I want to design a low cost switch over circuit that can disconnect the battery supply when an external supply is connected with 3.3V. I also want to be able to detect with a micro controller when the external cable is connected supplying 3.3V.
I am aware that this can be done with some source selector switch OR controller ICs like LTC4413. But these chips are relatively very expensive and the minimum input volt is only about 2.5V. I would need to go down as much as about 1.8V, as battery can go down to that level.
Looking for some ideas how this can be done, thank you.


texts: Decay rate of Filter and how it relates to transmission speed

texts:
I had a question with regards to the decay rate of filters and how it responds to transmission speed.

Suppose we have implemented a simple BFSK system with two asynchronous receivers and we have a signal applied to one of the filters(doesn't matter which). Before another signal can be applied it seems the initial signals filter response needs to be sufficiently decayed before another signal can be transmitted.

How is this required time calculated? Are the filters drained of energy after each received transmission?

Thank you for the information.


texts:
I know that the output voltage and current of an ideal transformer depends on the number of wounding of the coils. It means that no matter how many resistors I put in a series in my secondary loop, the current would not change and it depends only on N (Number of turns in coil).

I have been thought that resistors define the current that flow through them and it is hard to look at the current independent of the load.

Could someone explain the physics behind v1/v2=N1/N2
So is it safe to assume that the current in secondary coil acts as an ideal current source because if I know the source current I can get the secondary loop current no matter what the load of the secondary circuit is


texts: What is this 20-pin industrial connector?

texts:
I'm upgrading some pretty old (1975) industrial equipment and this exact connector is on the back panel of the control device. It's rectangular in shape, has 20 flat pins and its overall dimensions are 24 mm x 104 mm.
What type/model can it be?


texts:
I am working on a circuit with a AC to DC power supply module and wireless MCU module. The MCU operates at 240MHz and on the power input to the module there are 2 x 0.1uF capacitors and a 22uF capacitor used for bypass. These have been found through trial and error to most limit the noise passed on to the rails. To further reduce noise, a ferrite bead is located on the power side of these capacitors and has worked to reduce the propagated MCU clock noise to acceptable levels.

The remaining problem that I am hitting is that there is a strong "travelling" transient spike (as shown in the spectrum plot below) that starts at about 1MHz and makes its way to about 25MHz before disappearing into the noise. At any given time there is only one spike a specific frequency and it travels from low to higher frequency while reducing in amplitude. The travel time of this transient is about 2 seconds. This transient is strongest near the MCU module but is getting onto power rail (Test Point) and out through the AC/DC module to the power cord.

I have attempted to add more capacitance (1uF, 10uF, 22uF, 47uF) near the MCU module but have seen no measurable effect on this travelling transient spike by doing so. Ignoring the presence of this spike, the noise level is near the floor as seen by the spectrum analyzer. The presence of the ferrite bead mentioned previously has no effect on the amplitude of these lower frequency spikes as its peak impedance is in the 200-400MHz range. If the MCU module is replaced with low value resistor, the spikes are not present.

Based on this, I have a few questions:

For a travelling transient like this, can anyone suggest how this would affected the conducted emissions values versus a fixed frequency spike?
What would the quasi peak of this sort of transient spike look like?
Are there any suggestions on what might be possible to reduce the amplitude of these spikes given that various additional capacitances on the MCU module power input didn't seem to work? I will be trying a ferrite core on the power cord, as well a low frequency ferrite bead on the input to the MCU module and have already tried an inductor on the input to the AC/DC module.

Thanks.


texts:
Here I am trying to move the data at the SRAM location 0x20000010 into the ODR register of the GPIOE of STM32f303. But it is not happening for me(I an not see the data change in the ODR while debugging) . I dont understand why. Can any one help me out in this?

EDIT

int SRAM_ADDRESS __attribute__((section(".ARM.__at_0x20000010")));
volatile Task_S_T *Task;
    Task = LCD_FIFO_Peek();

    SRAM_ADDRESS = Task->Data;

        //initialize source and destination arrays
    uint32_t source = 0x20000010;                               // SRAM Starting address where the LCD Task data is loaded
    uint32_t destination = 0x48001014;
  DMA_InitTypeDef   DMA_InitStructure;

  /* Enable DMA1 clock -------------------------------------------------------*/
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

  DMA_DeInit(DMA1_Channel1);

  DMA_InitStructure.DMA_PeripheralBaseAddr =    (uint32_t)destination;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)source;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize = 16;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Enable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
  DMA_Init(DMA1_Channel1, &DMA_InitStructure);

  DMA_Cmd(DMA1_Channel1, ENABLE);
  LCD_Port_Set_Output();    // Just ensure that the LCD port is in output direction on the appropriate pin masks.
  GPIO_SetBits(LCD_BUS_GPIO_PORT, LCD_E_PIN);                   // Toggle Enable pin on.
  GPIO_ResetBits(LCD_BUS_GPIO_PORT, LCD_E_PIN);                 // Toggle Enable pin off.


texts: 5V UPS design IC/ battery-backup circuit selection

texts:
Im trying to do an UPS for a new proyect with a li-ion battery like cellphones ones, it needs to be reliable as I would like to left it at home without surveillance.
I have found this: answer from and old post.

I would like to know if this works now a days, as the Post is 4 years old now, Mosfet life cycle is in "end of life" so maybe can be replaced for a new one, as far as I understand the load V is going to get determined by the drop in the Mosfet, I need 5v so maybe someone can recommend any other Mosfet with low drop?

I found this IC= BQ24079RGTR, and as far as I understand it does the same function as the circuit above?


texts:
I have a coprocessor that uses some dedicated hardware 65c618 core that starts up in a halted state. Through a dedicated bus I can control the coprocessor I-RAM which is needed to setup the processor state and transfer the program into its onboard SRAM.

I plan on using a 72Mhz STM32F103RB to handle the coprocessor interface but am unsure how to synchronize the common shared bus properly. I know the cycle time of all opcodes and I can drive the coprocessor clock via the STM32F103, do I simply hold all pin changes for 7 STM32 cycles (72 host / 10.28 slave)?

The original design had both CPU's @ 3.58 but the coprocessor can run at 10.74Mhz and I would like to max it out.

The shared bus is a standard A(0:23), D(0:7), /RD, /WR, /SEL, /RESET, IRQ


texts:
I know how to calculate current in delta connection but just for knowledge purpose I wanted to know from basics why this method(in image)  of calculating phase and line current is completely wrong even for balanced load and so for unbalanced load also, so here is a circuit
Of unbalanced load and that is my calculation of phase and line  current  (which is obviously wrong)
So why this method(method of potential difference)  of calculation don't work here, even though in all dc circuits  this method works always so why not here?
And what is best approach to solve these types(varying magnetic flux)  of complex circuits


texts: A question about usage of common mode chokes for USB cables

texts:
There are ferrite chokes, rings to suppress CM EMI and they are also used for USB cables as shown in below example:

But isn't USB differential signaling type of transmission? That means to be the common mode signals at USB receiver end are already subtracted resulting zero. Just like in a differential ended amplifier with a balanced signal transmission.

If my knowledge above is correct I don't quite understand the need for the choke for USB. The only thing comes to my mind is to mitigate the CM signals if the interference is huge. Where am I wrong? I mean why is USB being a differential type of receiver not enough to subtract the CM interferences and needs chokes?


texts:
As shown below the schematic diagram is given.Point B is grounded.

I did take the potential at A is 2V since it is on the same node where the  2V batteries are located , am I correct? . I want to verify the accuracy of my  answer !. What is your opinion?


texts:
I'm using MAX756 as a DC-DC boost converter to provide 3.3V from of a single 1.5 AA battery. I've implemented the circuit on page 1 of datasheet with 1N5819 instead of 1N5817 and 144uF caps between Vin and Gnd instead of 150uF. Also Vin comes from bench power supply.

I've tested three 22uH inductors with different current capabilities (all above the required 1.2A due to datasheet (page 6).

~SHDN and 3/~5 is connected to out. LBO is left open.
The problem is the Vout is 3.3V in no-load. But as soon as I insert the 220Ohm resistors, Vout drops and in Iout = 60mA, the Vout drops below 2V.

Here is the picture of the setup: lower rail in Vin and upper rail is Vout

I've shown the other two inductors that I tested.
Anyone knows where the problem might be?
Thanks in advance.
P.S.
Glenn W9IQ  says:

  Take a bench supply capable of 2 amps output and set it to 7 volts.
  Put a 4.7 ohm, 10 watt non inductive resistor in series with your
  inductor and put this circuit across the supply. Monitor the inductor
  voltage with your scope. You should see a nice exponential, asymptotic
  curve that heads toward zero when power is applied. This will happen
  within 1 us of applying power. If the beginning of the curve has a
  different slope, your inductor is in saturation at less then 1.5 amps.
  But your problem is more likely the ESR of your inductor and
  capacitor. Use the right parts - it makes a difference! –

I've paralleled 5 , 2 Watts 22 Ohms resistor (so 4.4 Ohm in theory and 4.7 due to DMM).
Here is the circuit:

And here is the scope's result immediately after applying the power :


texts: How do I hold a signal high from one high pulse?

texts:
Assuming I send a signal wirelessly to a receiver connected to a fan. if the receiver detects that a pulse is there, it switches on the fan. the fan should stay on until it detects another high pulse, then it should switch the fan off thereafter.
How could I make this happen?


texts: reaches steady-state at \$t = 0^{-} \$, so I am trying to calculate the initial conditions of \$i\$ (current through inductor) and \$v\$ (voltage across capacitor). It is easy to find that \$i(0) = 10A\$, but I am not able to find \$v(0)\$. What am I missing here?


texts: Why do we want higher power factor in ac motors?

texts:
Here is a simplified 3P electric motor below:

This motor is simply combined of three coils facing toward to the rotator (in the center) 120 degree apart to each other.

The user wants his rotator to rotate (real work expected from the motor). Rotation force comes from the magnetic flux. And magnetic flux comes from the current flowing through the coils. So magnetic flux has nothing to do with voltage, only current is its concern. Am I right so far?

If so, look at the graph below:

This is an illustration of the power factor. Current being out of phase to the voltage. Think that I am applying 3 phase AC voltage (120 degrees apart from each other) to ports 1-4, 3-6 and 2-5 in order. In that case, current flowing from the AC voltage source, directly flow through the coil as expected. But, I am going to pay for only real power? Isn't it right? So why do I want power factor to be high?

Secondly, take a look at the equivalent circuit of an inductor(or coil whatever) below. Even if I pay for the negative power, still though, why do I want power factor to be high?

To make power factor high, I have to increase the series resistance on the inductor(or coil whatever), that means, since I can not increase or decrease the voltage, I will get less current to flow on coils. Therefore, I will get less amount of magnetic flux. Therefore, I will get less performance from my motor.

This is maybe a really dumb question. I am aware of that, but please, can someone help me to understand it? I am trying to understand this for almost a month!


texts: In a transmission line, does the real current interact with reactive impedances?

texts:
simulate this circuit – Schematic created using CircuitLab

According to the diagram above, if real currents do not interact with reactive  impedances, then reactive loads should not worry the energy provider since there is no real power loss incurred?


texts:
I have a PCB with incorrectly connected TXB0108 (TSSOP20), VCCa 3V3 > VCCb 1V8, that I wanted to use for UART communication between two ICs. I'm looking into various options for fixing it. Here's the TXB0108 pinout:

One way is to replace it with SN74GTl2003, which allows arbitrary 0.95 V to 5 V translations, and ignore pin 10 OE functionality.

The only question is: do you see any problems with this direct replacement?


texts:
I have to run 8 PWM signals out of an Arduino Mega to motor controllers that are placed anywhere from 25 ft. (7.62 m) away to 150 ft. (45.72 m) away.  I expect the voltage drop will be high.

The alternate solution is to send a serial or ethernet message to 8 different Arduinos placed next to the motor controller.  I can do that, but it's significantly more expensive.

To do it from the Mega, I assume I would need to do something like have a transistor circuit at the Mega which switches a higher voltage to each motor controller... either something like 7.5VDC, which will drop to the required 5 naturally over the distance, or a higher voltage like 12VDC and switch it back down t0 5VDC with another transistor circuit at the motor controller.

I also don't know if there will be noise associated with doing this...

Thoughts?


texts: If we can access (64*4) 256Kb of memory at a time in 8086 and you can move those segments around, what is the use of the remaining memory? Some say that we can move around the segments but what is the benefit of moving around the segments? Still we can't use the whole memory...


texts:
I am trying to create the best PCB possible for my DC Motor controller. I have been looking into the different ways to make my vias for my PCB and I am a little confused on the topic of tenting and plugging and conductivity between the bottom and top layers. The general idea behind the two are:

Tenting - Apply solder mask over the via to decrease exposure to external conductors, cleaner looking but from what I'm reading it does not work for large drills.

Plugging - Vias are entirely filled with a non-conductive material. This ensures 100% of the via is filled so as no complications with tenting can happen, used for larger drills.

Now one thing I am not understanding is doesn't there need to be a wire that is fed through the via and soldered so as to create a conductive path between the bottom and top layers? If so wouldn't tenting/plugging ensure that no wire can be fed through the via as to create a conductive path. The way I see it, in this case, the via would be a useless hole.

Does the annular ring that feeds between the two layers give enough conductance between the two layers? How is the conductive path between the two layers established in these examples?

When would you use one versus the other? Does it have to do with the size of the drill or are there external factors that must also be considered?


texts: What manufacturing process produces resin coated chips in consumer toys?

texts:
I'm looking at high volume manufacturing and I notice that inside some consumer toys, there are chips which seem to be directly placed on the board and covered in resin. I know this has been done a long time because I remember such boards from my childhood in pocket calculators. See the image for a typical example.

What is under this resin? Is it a naked chip directly mounted on the board with bond wires to the pcb?

Can someone enlighten me to the name and type of manufacturing process here and tell me anything about how hard it is to use this approach, in terms of working with a manufacturer,  and the costs and volumes involved, relative to just using a regular surface mount chip?


texts: How should I drain a capacitor in a rectifier circuit?

texts:
I am trying to learn how to drain a capacitor after disconnecting power from a rectifier circuit.
Specifically what I have is a step down transformer from an old wall wart charger that I have modified. Orginally it stepped 120VAC down to about 11.5VAC. I have modified it by removing a few turns from its primary coil resulting in an output of about 14VAC. I then ran it through a full bridge rectifier and added 2 capacitors in parallel (caps are each rated 25v 2200uf). When I read the DC voltage of the output wires I get roughly 21.5VDC.
So in instances when I have no load attached when disconnecting power, how do I ensure the caps drain? My original idea is to add a high value resistor in parallel right after the capacitors. I have a 35k ohm 1/4watt resistor laying around. Would that be adequate for quickly draining the caps without causing a noticeable power loss?
Are there other simple methods that I may be unaware of?
Realistically, the most this power supply will be used for is to power low power test circuits through a step down module.

Note: This is not for any particular purpose or anything of importance. I am simply an at-home hobbyist who is experimenting and tinkering for the sole purpose of learning. I find trying to understand how different circuits work and trying to replicate or alter them, to be extremely intriguing. So feel free to throw out different ideas or point out any flaws in my design, because I am open to any knowledge you can share.


texts:
My understanding is that a basic FF will in general power-up into a meta-stable state that then resolves to either H or L (more or less quickly).

My question is, does this apply to current real-world parts such as the dual D-FF 74AUP2G80, or do these parts contain some circuitry to force them into a predictable state on power-up?


texts:
How do I implement coulomb counting algorithm ?
Once I read the current using a ADC , what processing do I do ?
say for 10ms load draws 1mA, next 5ms it draws 7mA. So am I supposed to just add the current for 15ms i.e 8mC is my charge removed from battery ?
For this do I require a real time clock,other than initial SOC of the battery what other specifications are required, charging current, discharging current ?
Once by battery is plugged in and being used by some applications do I need to integrate throughtout this period ?
could someone just give an example of the equations that need to be implemented


texts: I have a 2.4GHz Wi-Fi design that uses an SMA connector connected to a dipole whip antenna.  The issue is the SMA connector mounts to a metal chassis. This causes a potential issue in where someone could short a power lead to the chassis and the current would flow through the shell of the SMA connector. Can I place a DC blocking capacitor in series between the shell and PCB ground? I was thinking an 0402 RF capacitor somewhere from 1-10pF. I figure an 0402 cap in this range will have a plenty high self resonant frequency and low inductance.  Do you think this will this impact my antenna matching and thus my range? Looking for an RF friend.


texts: Size of SMD pads for components with high tolerances

texts:
I'm building an Eagle component for an LSM115J.

The connectors on this part have fairly large tolerances (1.85-2.21mm width, 0.76-1.52mm length). There is no recommended land pattern.

Should I go for the largest size (so the part will never need to be partially soldered on top of the stop mask), the smallest size (so the part has a well-defined placement) or something in the middle?


texts: Wiring up 3 alternative power supplies for a new system

texts:
A new system requires 3 alternative power supplies:

On-board PSU 110V~ to 12V=
Onboard 12V= battery
External 12V= vehicle battery through cigarette lighter socket.

I am looking out for suggestions on how to wire them up.


texts: When is impedance matching necessary? Isn't it much less efficient on all other aspects?

texts:
I understand that discontinuities of the physical properties of conductors create reflections much like dioptres reflect a bit of light, but :

  in which cases does impedance matching become necessary to avoid that?
  Is there a simple-ish method to decide quantitatively? (1)

My second concern (which probably stems from my limited knowledge of the topic) is about the efficiency of impedance matching:

  if all impedances including the load must be the same, doesn't that
  mean that the overall impedance is extremely small and hence that a
  lot of current is necessary? By "same", is it solely the amplitude or the phase shift as well? (2)

Which implies a higher voltage source because of the voltage drops, and lots of power lost as heat? Is it a tradeoff?

Let's take the following diagram as an application example.


texts: Distortion in output signal in amplifier after connecting load

texts:
I want to design an amplifier which works in 20kHz-100kHz range with 0.1V peak to peak signal.
This is my circuit.
It works fine in the simulation. It works fine without connecting R6 8 ohm load. But when I connect the 8 ohm load output signal get distorted.
How can I solve this problem?


texts:
I am building a simple PM2.5 PM10 station based on PMS5003ST (Plantower) and ESP32 to measure the particles in the air and convert the readings to the Air Quality Index. Everything works fine, but i have noticed that when there is a lot of fog - the readings are realy realy HIGH - (they jump even 300%).

From what i read in the PMS5003ST documentation - the particle sensor is very sensitive when there is a fog - meaning, it can count the fog particles too.

PMS5003ST

Questions:

The PMS5003ST has a Humidity and Temperature sensor built in so i was thinking, is it possible to model the PM2.5 / PM10 based on the humidity and temperature readings so that it avoids getting huge readouts in foggy conditions? (like a humidity compensation?)
How people avoid 'wrong' readouts during foggy conditions with these particle sensors?


texts: Multiple buttons on 1 analog VS one digital per button:Power Consumption

texts:
im working on a bluetooth watch project.
You may have already seen it on hackaday
http://hackaday.com/2011/08/23/bluetooth-wristwatch-based-on-an-arduino/

i kinda need to add some buttons onto the watch
and power efficiency is really important in this project.
So im wonder which method consumes less power?
Multiple buttons on 1 analogRead like here: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267115381
or 1 digitalRead for each button

1 DigitalRead per button:
Cons:
each Pulldown resistor will always be spending power even while the button is not pressed.
Pros:
no hardtime tweaking pwm interval

Multiple buttons on 1 analog:
Cons:
each button pwm has to be defined.
Pros:
Less power consumption "i think"...

im not very good with electronics...
please guide me which method i should use to add buttons onto my watch
Thanks smiley


texts: Help to construct a State space model of a unipolar stepper motor with shorted phases

texts:
I hope to get some help on an interesting task - I cannot seem to get my model to work which is my I ask for help here.
I am trying to construct a model of the unipolar stepper (seen below in the figure). I was hoping to get a model of what would happen if I try to drive a unipolar stepper with a bipolar driver (which is why the "fifth" wire is not modelled as it would be "open"). The unipolar steppers can have a short between phase A and B which I have modelled below. The problem is that my model won't run or is unstable.
I have tried with the "normal" state-space formulation:
M x' = Ax + Bu, where:
A1 = [-R1-R2 R2          0       R1;
R2     -R2-R3-R5    R3      R5;
0      R3          -R3-R4   R4;
R1     R5           R4      -R4-R5-R1]
M=[L1+L2    -L2     0   -L1;
-L2      L2+L3   -L3  0;
0        -L3     L3+L4 -L4
-L1      0       -L4     L4+L1]
inv(M)*A;
B1 = [1 -1 0 0;
0 1 -1 0;
0 0 1 -1;
-1 0 0 1]
x' = inv(M) A x + inv(M)Bu
D = 0
C = [1 0 0 0;
0 1 0 0;
0 0 1 0;
0 0 0 1]
All inductances were just randomly chosen to 0.01H and the resistance are 50 ohm. Disregard the "e" for back-emf as that will be added as an input later.
Why is my model then unstable, any tips or tricks?
Thank you.


texts: How to use analog mode GPIO pin(not ADC input channel) for ADC?

texts:
I want to use a GPIO pin which is configured to be "Analog Mode" for ADC.

I am working on STM32L073 series microcontroller. The pins with ADC input channels
are used already. So I need to choose another pin to use ADC.

I could not find any information about how to use the analog mode gpio pin for ADC.

Is there anyway to configure a GPIO pin other than the pins with ADC input channels for ADC?


texts: pic16f628a timer1 interupt wakeup from sleep

texts:
I have a problem with sleep mode on PIC16F628a.
Configuration:
microcontroller running on 4Mhz internal oscillator.
32kHz external oscillator on T1OSI/T1OSO pins.

Program below works fine (having 1s pulses on RA1) with "SLEEP()" commented out.

I'm also positive, that TIMER1 uses external oscillator, because pulses disappear if I disconnect external crystal.

But when I try to use SLEEP() mode, TIMER1 interrupt does not wake PIC up, I'm getting nothing on RA1.
I think that I do miss something obvious here.

Code below:

#define _XTAL_FREQ 4000000
// CONFIG
#pragma config FOSC = INTOSCIO  // Oscillator Selection bits (INTOSC oscillator: I/O function on RA6/OSC2/CLKOUT pin, I/O function on RA7/OSC1/CLKIN)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = OFF      // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is digital input, MCLR internally tied to VDD)
#pragma config BOREN = OFF      // Brown-out Detect Enable bit (BOD disabled)
#pragma config LVP = OFF        // Low-Voltage Programming Enable bit (RB4/PGM pin has digital I/O function, HV on MCLR must be used for programming)
#pragma config CPD = OFF        // Data EE Memory Code Protection bit (Data memory code protection off)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

#include <xc.h>

void interrupt isr(void){
    if(TMR1IF){
        TMR1ON = 0;
        RA1 =~ RA1;
        TMR1H = 0x80;
        TMR1L = 0x00;
        TMR1IF = 0;
        TMR1ON = 1;
    }
}

void main(void) {
    CMCON = 0x07; // comparators off
    TRISA = 0x00;
    RA0=1;
    RA1=0;
    RA2 = 0;
    __delay_ms(5000);
    RA0 = 0;
    __delay_ms(500);
    T1CKPS0 = 0;
    T1CKPS1 = 0;
    TMR1CS = 1;
    TMR1H = 0x80;
    TMR1L = 0x00;
    T1OSCEN = 1;
    T1CONbits.nT1SYNC = 1;
    TMR1IE = 1;
    GIE = 1;          //Enable Global Interrupt
    PEIE = 1;
    TMR1ON = 1;
    while(1){
        SLEEP();
    }
}

Thank you for your help.


texts: PIC24FJ128GA202 some I/O PortB pins not behaving correctly

texts:
I am working on a small project using a PIC24FJ128GA202, and noticed that my UART wasn't working with every RP pins. I ran the following code :

#include "xc.h"
int main(void) {
    ANSB = 0 ;
    TRISB = 0 ;
    LATB = 0xFFFF ;

    while(1) {} ;
    return 0;
}

Turns out not all the pins are pulled to Vdd as expected. Pins RB4,8,9 and 10 stays at Gnd, while pin 11 is at 2V (tested without anything connected to the pins). Those were the same pins that my uart didn't work with as either input or output.

Tried to use them as open drain, and these pins cannot pull the line to Gnd either. Replacing the microcontroler achieved the same results.

My guess is that some peripherical is controlling them by default but i did not manage to find it in the documentation. Any recommandation ?


texts: How to check earthing using handheld digital multimeter?

texts: I would like to know to how to check for earthing (electrical) ina house using handheld DMM.


texts: Nodal question with current-controlled voltage source connected to independent voltage source

texts:
so i've got a question here

the question is to calculate v1 & iΦ, of course for nodal analysis (v1/24) + ((v1-(60+6iΦ))/3) + ((v1-va)/2) = 0, but (with va as the node left of 2 ohm resistor) how to calculate va? is it 60+6iΦ? 60-6iΦ? 60? or is it something else?


texts:
The datasheet of the MAX7414 low-pass filter shows the OS pin connected to a voltage divider to set the output offset when the IC is used on a single rail supply.
Can the OS pin be supplied by the REF1933 reference IC to set an output offset of 1.65V?
The REF1933 has a low output impedance, while the voltage divider shown in the schematic of the MAX7414 is formed from high value resistors. Will that affect the performance of the filter?


texts:
I'm building a simple analog mute circuit and I need advice on the simplest way to achieve my goal.

I have a GPIO pin that goes high when audio is playing and low when it's not. When audio is not playing, I need to connect AGND to the L & R channels of the audio circuit.

Obviously, I could do this with a transistor if the GPIO pin were reversed, but it's not. Is there an Active-Low component that I can use to achieve this goal? Preferably something in a small form factor.

EDIT: The audio circuit is driven by a PCM5102A DAC. It's a 2.1v RMS single-ended line driver that is ground centered. I do not believe there is DC Bias.


texts: Segment LCD only viewable at extreme angles

texts:
I have a kitchen scale with a segment LCD display. Starting one day, the LCD display is barely legible at all; sometimes the numbers are viewable from an extreme angle, sometimes not at all. Sometimes it helps if I gently press on the glass.

I have very little experience with LCDs. I've cleaned the contacts to the PCB, which made no difference (I didn't seriously expect it to, since the segments look just fine when visible, it's just that they're hard to see).

Any way to fix the LCD? I rather fix this than throw it out and buy a new kitchen scale.


texts:
If we are given the following equation of Vestigial Side-band Modulation, what values will I put in the equation?

$$      H_0(f)=\frac{1}{H_i(f+f_c)+H_i(f-f_c)}                       $$


texts: Effect of cooling a DC power adapter with too few amps?

texts:
I have a device (PC fan) which wants 2.0 amps, and a DC adapter that supplies 1.8 amps; both 12v. As I understand it, using this adapter will cause overheating and reduced voltage.

My probably-foolish theory is that I can cool the adapter (I'm customizing a refrigerator for homebrewing) to make up difference, and prevent either device from failing.

Assuming I keep it safe and dry, what are the effects I should expect from cooling the adapter to ~15ºC? Will the voltage hold at, or move closer to 12? Will either device be damaged?

...is my initial assumption even accurate?

Thanks in advance!


texts: Configuring Atmega32 timer using the oscillator without prescaling gives wrong delay time

texts:
I am using AVR atmega32 microcontroller. The code below is supposed to toggle the LED connected to PORTD. The frequency of the oscillator connected to the microcontroller is \$16\text{MHz}\$.
So I calculated the number of overflows should TCNTO encounter to delay the LED 1 second, using:
$$
T=\frac{1}{F_{CPU}}=62.5*10^{-9}\text{s}
$$
So, number of overflows is :
$$
62.5*10^{-9}*256*n=1\text{s}
$$
So \$n=62500\$, when I simulated that code, the LED toggle every one second, but when I applied that, the LED was toggling every 4 seconds.
Am I using the formula wrong?
How to specify the time I want precisely for the applications that need accuracy in time?
#ifndef F_CPU
#define F_CPU 16000000UL
#endif

#include <avr/io.h>

int main()
{
  uint32_t timeOverFlowCount=0;

  DDRD=0xff; //configure PORTD as output

  /* timer0 */
  TCNT0=0x00;
  TCCR0=1<<CS00;

  while(1){
    while((TIFR & 1<<TOV0)==0); //wait until TCNT0 over flow (reach 255)

    TCNT0=0x00; //begin from 0 again

    TIFR &= 1<<TOV0; //Write 1 to the D0 (TOV0) flag to clear it
    timeOverFlowCount++; // increment one to know how many it reachs 255

    if(timeOverFlowCount==62500){//if it counts 255 five times, toggle the LED
      PORTD ^=(0x01<<PD4); //toggke the led
      timeOverFlowCount=0; //set counter to 0
    }
  }
}
```


texts: Is it safe to "top up" bootstrap capacitors using a charge pump?

texts:
This document from TI describes a method to allow use of bootstrapped N-Channel MOSFETS at high duty-cycles, by keeping the bootstrap capacitor "topped up" with an external charge pump, separate from the gate driver IC.

My question is: wouldn't this present a risk of exceeding the Vgs rating of the MOSFET? For example, say the maximum gate-source voltage on a FET is 16V, and it is being used as a high-side switch on a 12V load. Your average gate driver IC will (approximately) double the 12V to 24V, leading to a Vgs of 12, within the FET's rating. Say one now connects a constantly-running voltage doubler to the high side of the bootstrap capacitor. Now instead of the bootstrap mechanism doubling the 12V, it will double the 24V coming from the external doubler, leading to a Vgs of 36V.

Is this the case, or am I misunderstanding something? Is there an easy way to mitigate this? The only thing I can think of is disabling the charge pump whenever (probably slightly before) the high-side switch turns off, which sounds like a pain.

simulate this circuit – Schematic created using CircuitLab

(Note that the gate driver I am working with has the bootstrap diode built-in, hence its absence form the schematic)

If it helps, here are the specific parts I'm hoping to use:

Gate Driver: Micrel Inc. MIC4606-2YML
Charge Pump: Texas Instruments LM2767M5
FET: Texas Instruments CSD87588N

(Yes, this is for an H-bridge, not just a high-side switch. I am just confused about the bootstrapping part of it.)


texts: How to use high and low naming with negation on Eagle

texts:
I noticed it's possible to give present a negation value by calling a variable the following:

!A

However I'm trying to imitate an existing part where A has the header line, and B doesn't
and it only works if I go at it backwards:

While this is what what I want

B/!A as oppose to !A/B

There might be some sort of syntax I'm unaware of.
I've already tried !{A}/B !(A)/B and !A_/B.


texts:
I read that using fixed capacitors in power factor correction in low voltage has some disadvantages like : Overcompensation (correct past unity)
can someone explain that to me?


texts: Lighting System in terms of its efficiency and consumption

texts:
I'm curious regarding some matters in my experiment session of Efficient Lighting System. There are 4 types of lamps which we measure the data to fill-in the table as in the picture. Correct me if my hypothesis is wrong.

The brighter the lamp, the higher the magnitude of luxes.
Does the higher the neutral current, the more it consumes energy?
CFL does consume more current as it produces brightest light which could be prove based on the lux value in the picture.
Electronic ballast is one type of lamp that can be categorised as energy efficiency because it uses less neutral current but produces higher brightness.

But what indicates the value of real power, reactive power, apparent power and power factor ? What are those powers relatable with this types of lamp? If you have any points to add, please do so.


texts: Can magnetic connectors cause dangerous voltage spikes?

texts:
I have some magnets lying around and thought about puttin them on the ends of a wire to make a magnetic jumper for my perf board. However, I am aware of the effect of magnets on wires, ie induction.
Could moving the magnet around my arduino circuitry induce large voltages and destroy things? I have seen large voltage spikes created when moving a magnet near a coil quickly. If magnet connectors present too much of a risk alone, are there any steps I can take to reduce the risks?


texts:
For some background, most if not all modern charging solutions for lithium ion batteries use a CCCV model for charging:

As the diagram explains, we charge at a constant current, and then "suddenly" switch into a constant voltage mode. This "sudden" transition seems unnatural, and feels like it's more likely to be related to simpler electrical design for chargers rather than "better" charging.
So my question is, are there other charging models? For example:

Could the charger stay at CC for longer and go above the target voltage, and jump into a CV mode at the target voltage, leading to a quicker charge?
I've heard it leads to a lower battery life if batteries are fast charged near 100% of their capacity, could the CC mode start ramping down earlier as the battery gets full?

EDIT: The existing answers have prompted me to do some more research and I've found:

My two suggestions for improvements were indeed "silly", but I had found other alternatives, such as CP-CV charging (constant power, constant voltage).
Temperature is a big killer - there are charging techniques that vary the current during the CC phase to keep within temperature bounds. This allows them to use a higher base current.
This is a fantastic article that also details the chemistry: https://www.sciencedirect.com/science/article/pii/S2590116819300116


texts:
I'm trying to debug that circuit (pic. 2).

The problem is when the input signal is near 2V the output oscilogram looks like in pic. 3 (with gap). What is the nature of that gap? Looks like some of current source don't conduct some time.

How much C3 capacitor (pic. 2) value would be? In original scheme (pic. 1) it was 22pf but with that value the oscilloscope output lag too strong (i. e. output signal is not printing with pauses of different durations)

How much R5 (pic. 2) value must be?

If I'll use the cascode output as in original schema (pic. 1) how much diodes I need (2 or 4)?


texts:
I am building a large water tank. I'm thinking to convert it into a big lead-acid battery. I am interested if exists a formula that could calculate how much will be the capacity of that battery, voltage, energy density, specific power, specific energy and other parameters ...

The volume of the finished tank will be 5 cubic meters.
If we assume that the tank will be filled with an exact mixture of sulphuric acid and water like in the small one battery what will be the battery properties.

Does the dimensions of the battery determines the capacity of one single cell?
Does the dimensions of the battery determines the voltage of one single cell?


texts:
I'm working on dual axis solar tracker project, but the task I was given was to make a solar tracker work with a single LDR (Light Dependent Resistor).
The LDR would be placed in a pipe which is painted black on the inner sides to reflect light from the sun and direct it to LDR.

Is it even possible to make a solar tracker with a single LDR?


texts: Calculating DC motor rotations from current readings

texts:
Situation: I'm using a brushed DC motor to open and close the vents of a greenhouse and I would like to know the exact motor location for more granular temperature control. Motor moves at different speeds depending on wind and whether it moves up or down, so I cannot use time as a reliable unit to infer the motor's position.
However, the revolutions of the motor are fixed in terms of distance, so I would like to know how often the motor has rotated. As installing additional sensors (e.g., hall sensor along motor path) would add to project complexity, I was hoping to achieve this without any extra external sensors.
Here is where I would like to infer the number of motor revolutions by measuring the current ripples, similar to what's described in this paper, but I'm honestly way over my head.
Hardware setup:

Arduino Uno connected to a
ACS712 current sensor to take the readings
24V brushed DC motor with 12 armatures and 2 permanent magnets and 2 brushes, moving at ~3.7 RPM (Pictures below)
bench power supply for testing and
120W 24V meanwell power supply for actual deployment```

Data processing:

Read log file
Truncate data

Here is a plot of the raw readings. Y axis is the current reading from the sensor, x axis is time in 10 millisecond intervals (~14 seconds).

Apply a fast fourier transform
Set cutoff frequency to denoise the readings
Transform back into time dimension

Result of this is shown here:

My questions:
I have no idea whether I am even on the right track with this approach. Specifically:

Is the current sensor sensitive enough?
Is there too much interference to reliably infer motor rotations with this setup?
The paper uses a different specialized MCU for this. Is an Arduino or ESP32-S2 even usable?
If overall approach is appropriate, what am I even looking for in the data? I assume that the armatures are creating current differences as they move along the poles, correct?
If that's the case, should we see 12 * 3.6 spikes per minute?

Raw data:
Here is the raw measuring data that I saved using Putty over serial.
Arduino code:
const float VCC = 5.0;
float sensitivity = 0.185;

const float QOV = 0.5 * VCC;
float voltage;

void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
}

void loop() {
  float voltage_raw = (5.0 / 1023.0)* analogRead(VIN);
  voltage = voltage_raw - QOV + 0.012;
  float current = voltage / sensitivity;
  Serial.print(millis());
  Serial.print(", ");
  Serial.println(current);
  delay(10);        // delay in between reads for stability
}


texts: Custom SOPC Builder Components in Quartus II

texts:
I am trying to understand how to interface with a custom component within SOPC builder. Basically I have a verilog module which creates and outputs a tone to the audio out line on an Altera DE2 development board. I want to interface with this module in SOPC builder so I can control it using C code and the NIOS II processor.

What I am having trouble understanding is the setting of signals when creating a custom component in SOPC builder. I can successfully add my .v files into the component and it gives me a list of top level signals which I need to set to certain values. I am not sure what to set the signals, such as my GPIO and AUD_ADCLRCK, to within the create custom component. All I really want to do is pass a value to my audio module telling it what frequency to output.

Any help would be greatly appreciated.


texts: Anyone have specific examples of how IEEE 1588 is most commonly used in industry?

texts:
I've run into the concept of IEEE 1588 synchronization over Ethernet several times, and am curious what its most common uses are and the details of why it is required. For example, I read that cell phone towers require time synchronization on order of microseconds, but I am not sure exactly why that is the case.

Judging by the amount of support for it, clearly, IEEE 1588 is an important and widely utilized standard. I can think of some relatively obscure cases where I would want microsecond time sync between devices miles apart, but I am not sure what exactly industry does with it.

If anyone has had any experience with it, please share an example or two, or generally talk about what you think are the most important/common applications of it.

PS. Someone please re-tag this appropriately, I don't have enough rep to add tags, and apparently this has been an obscure topic around here.


texts:
My question is about load currents from AC transformers.

If for example, we take a 3 phase step down transformer (11kV to 415V) with an apparent power rating of 100 kVA, the following equation, S = 1.73 x V x I, rearranged to give            I = S / (1.73 x V) means this transformer is ‘rated’ to supply 139 amps per phase.

My questions are:

At what secondary current do we say the transformer is overloaded? Can a transformer safely supply this full load rated current constantly without causing damage or should the secondary current only be a certain percentage of it’s rated current?
What will happen when the transformer supplies more than 139 amps on the secondary? Will the secondary voltage start to drop below the rated value due to excessive voltage drop over the internal impedance of the windings? Or what does happen?
When sizing a transformer, how much larger should the secondary current be compared to the designed full load current that will be drawn under normal conditions?

Thanks everyone.


texts: What factors/parameters shall be considered (or compare with original) while replacing NTC resistor?

texts:
Suppose supplier of NTC shut-down the production for the NTC series. In this case if I am unable to find exactly the same component but rather found close match (by comparing B value @ R25/R100), then what are the parameters I should look in the new component so that it can best fit in my project without any glitch.
I saw in the datasheet R-T curve and temperature coefficient of resistance (alpha). However, I could not understood how alpha values were derived. I made several attempts to calculate alpha based on (https://www.ametherm.com/thermistor/ntc-thermistor-calculating-the-temperature-coefficient-of-a-thermistor) but I failed to get values mentioned in datasheet (NCP03XH103J05RL).
I tried to plot R-T curve using given resistor value and tried to derive ADC value also and compared both but not sure if this is the correct way!
Example of NTC circuit:

simulate this circuit – Schematic created using CircuitLab


texts:
I'm working on a design and am going to source a smaller pcb and solder it to my design.

Before using the sourced board I'm wanting to test it and so I'm trying to design a test fixture similar in concept to the ones described in this Spark Fun Tutorial.

Here's a drawing of the pads along the outside of the board I need to connect to for the test:

The board that I'm sourcing is gold plated. The pads are on both the top and bottom of the board - but larger on the bottom - so I assume it's better to try to go the pogo pin route from either the top or the sides.

Here's a zoomed image of the pads from the bottom. (my apologies for an image that's slightly blurry)

So first off I wonder if I should follow the spark fun tutorial and try to make a board that will connect to the pads from the bottom or perhaps I should try to get some type of pogo pin to try to go into the drilled portion of the pad at say a right angle. (finding a right angle pogo pin at 1.5 mm might be impossible in itself)

Anyway looking at the spark fun pogo pins they have some here but it's head size is 1.3mm so I'm thinking I'm asking for trouble using something with just .2mm clearance between heads.

I was wondering if anyone had experience using a pogo pin for this type of spacing and pads and what you'd recommend?

Thanks in advance.

-J


texts: Is it required that a capacitor is marked X2?

texts:
I want to replace a capacitor in a power supply.
The original is marked: 250V, 0.1, WIMA MP 3. I bought one that says: ERO MKT 1822 0,1 250V. What bothers me is the safety rating X. Is the original one X2 ? What is MP 3? Do I need to buy another one that explicitly says X2 on it? I want to stay on the safe side.


texts:
Specifically, the LTC1150, but have also seen it with another similar opamp.
Powered from +/-9V DC-DC converter with a startup ramp of about 15ms.
It is in unity gain inverting configuration (10K resistors) with non inverting input tied to analog ground. Osc input and output floating.

The problem is that after powerup the virtual ground at the inverting terminal is about 7mV away from analog ground. After a few seconds it sometimes corrects itself to zero. Sometimes not, with the resulting output becoming noisy.

We are using this to invert a 2V5 reference, going into a 24bit ADC. Since we are measuring better than 1ppm this is a serious problem.

Has anyone heard of similar behaviour? Or solutions that do not require a redesign and layout of the board?


texts:
I'm not all that knowledgeable when it comes to advanced electrical engineering, so I'm asking for some advice here.

Here's my problem:

We have several mobile refrigeration units that are powered by batteries (eight 12V AGM batteries wired in series to 48V). The problem is that the built in inverter on this unit won't initiate charging when battery voltage falls to a certain level. It's a design flaw that's not likely to be rectified anytime soon. What I've been doing to temporarily rectify the situation is take two 24V vehicle jump-starters, connect them in series to 48V and connect them to the unit's batteries via jumper cables to effectively "jump start" the system. Once the inverter sees the battery voltage high enough, it will start the charging circuit, I can disconnect the jump starter and go about my day.

What I want to do is design a type of jump starter that doesn't rely on batteries.

I'm looking at using this power-supply for this purpose: MeanWell SE-1500-48

However my concern is the inrush current when first connecting to the discharged batteries. I measured it with an amp-clamp, and with batteries that aren't even fully discharged, I'm seeing a 30amp draw for about 5 or so seconds at which point it begins to ramp down to a nominal 7 amps after about 15 seconds. That's obviously going to exceed the limits of the above power supply. Rather than selecting one that's a lot bigger (and will then require 240VAC input) can I use some sort of inrush current limiter? It seems simple in theory but there's so many to choose from, I have no idea which one to buy.

This one looks like it might work but the rating is 120VAC and up. Would this not work for a lower voltage DC application?


texts:
I am trying to integrate  an off the shelf wifi module with STM32f2 mcu over UART interface.
I need to test the board after laying out the board. Is there a way I can test this UART interface before loading a binary to STM flash that talks to the WIfi module.

Can I do this communication (UART) testing using JTAG?


texts:
I have a Hall element that I want to read by an ADC (MSP430 ADC10).
The Hall element gives me a voltage within 0-Vcc, whereas the ADC can only sample 0-Vcc/2.
In reality, the lowest value to sample is likely somewhere between 0.3V-1.0V.
What would be the simplest circuit that would give me adjustable lower and higher limits?
A simple voltage divider would allow me to adjust the upper limit, but I fail to see how I could also adjust the lower limit.
The circuit below will only work if min = 0.

simulate this circuit – Schematic created using CircuitLab
Edit: Clarified: Vmin -> 0 (or near 0), Vcc -> Vcc/2


texts: Please explain the following integer constant used in verilog

texts:
The integer constant in verilog specified as "size base value".

8'h81 :  I think in this 8 is size h(hexadecimal) 81(value). but I am confused,  it has 8 size. 81 is 2 digit hexadecimal number its size should be 2 .

16'd5

32'h8f_32_ab_f7

The same confusion occurs in the above two integer constants. Can someone please explain?


texts: Low current control of triac speed controller?

texts:
I'm using a cheap Chinese commercial triac speed controller to control a universal motor that pulls considerable amperage (where "considerable" is no more than 15 amps at 117 volts).

I would like to modify the controller so that it will cut all current to the motor, via a small low current micro switch and associated wiring. I do not know the exact circuit and the device would be difficult to preemptively disassemble. I do have easy access to all three triac terminals, however.

It was suggested to me that shorting A1 to G would disable the triac – it does not.

Could I just switch the gate with the micro switch to accomplish what I want?
Is significant current flowing through the gate at any time?


texts:
There are four types of registers in AVR.

\$r_0\$ - \$r_{15}\$ witch used for CPU's calculations.
\$r_{16}\$ - \$r_{31}\$ witch used for user's temporary data storage.
Registers for I/O statements.
And control flags registers.

Are all of these Registers placed in SRAM?

P.N:I am learning AVR micro-controllers. In a learning video told that these registers are separated with SRAM. I thought that SRAM is a block that contains all registers. Because I think the nature of these registers are same. And can be packed in one register block.


texts: Why use a PMOS transistor instead of a diode for ESD protection?

texts:
I am working on updating a PCB design by adding ESD protection to the power supply. I see that an experienced engineer at my company has placed a PMOS transistor rather than a series diode, and I'm not sure why.

The PMOS has the drain connected to the power supply, gate connected to ground, and source connected to the load.

What would be the benefits to doing one over the other (PMOS vs. diode)?

Am I way off base thinking that they are interchangeable?


texts: Raspberry Pi controlled lamp using a relay & mains procedure

texts:
I am trying to turn on and off a lamp I have at home using a relay controlled by my Raspberry Pi. Here are the exact parts I will be using:

Raspberry Pi B+

My lamp:

My relays:

Potential outlets I would be using (mains):

OR:

With all the equipment being listed, my procedure would be:

Peel off the lamp cable and connect the lamp's power supply to the relay so whenever the Pi closes the circuit, the lamp is powered on.

I am aware that there are risks implied when tampering with the "mains" voltage. With that being said, I would like to ask the following questions:

Will it be dangerous to do this with the hardware listed above? Please know that I would place the relay on a surface that does not conduct electricity (potentially wood), and the though of touching any hardware (not even the PI) while the lamp is connected  WOULD NOT EVEN POP IN MY HEAD.
I am aware that the relay may fail since I've read in some forums that this is supposedly a 5V relay (maybe not?). If it were to fail, would it be dangerous? As in, would my whole house be in a blackout or something like that? Any advice for that?

3.If you were to consider this safe, would it make a difference if I cut/tamper with the wire before or after the manual switch my lamp has? (please refer to the switch image above).

How would I be able to identify which wire is positive and which negative if I cut open my lamp's cable?
Would it make a difference to connect the lamp to the black extension cord (please refer to the picture above) rather than directly to the mains outlet?

I am still debating whether to give this a try or not due to security reasons. I am aware of how dangerous tampering with house-level voltage (especially current) is, therefore I need your help to better analyze the situation.

Thank you so much for your help!

QUICK EDIT:

FYI, I currently live in America, therefore I am assuming my mains V supply is 120V...


texts:
I found the upper circuit. Originally it is designed as an output circuit for an audio player with a jack output. I have no transistora lying around, but opamps like the TL074.
I made the lower design.
On the right you see the in (green) and outputs of the circuits.
My questions,

Is the design at the bottom a good substitution for the top circuit?
Is R4 is for impedance matching? (Then I probably should add it.)


texts: What is the meaning of speed grade marking on Xilinx FPGAs?

texts:
According to Xilinx FPGA product datasheets, the numbers on the 5th line as 4C or 5I stand for speed grade and temperature.I have a XC3S400 with 4C speed grade (4= standard speed, 5= High performance).

I want to know what exactly the standard speed grade means ? Can I relate it to a specific bandwidth? For example assume I want to make a high speed counter and want to use the maximum possible speed driven from a crystal oscillator into GCKx pins. Can I use this 4C marking as a guide for crystal oscillator selection?


texts:
This is very similar to how common mode chokes work but can we implement this by using transistors?
Lets assume we have a signal 's' we are trying to amplify.We feed this signal into some linear amplifiers a1, a2 ,a3 . These amplifiers are practical and not ideal and hence add noise to their output signal. Although these are practical conditions but lets assume for the sake of this concept that there is no phase shift in the output signal and hence the output signals say s1, s2, and s3 are all in same phase.
Now the idea is to filter the noise from s1, s2, s3 by passing these through some common mode amplifier. The common mode amplifier will only amplify the portions of the signal found in all three s1, s2 and s3 and will reject any signal found only in one of these i.e.  the noise. The noise generated will be unique for each amplifier and hence this will get rejected.
What kind of filter is this?


texts: polarity of dc power require by electronic device

texts:
How can the polarity required of device marked 7.5V 1.2A dc be determined, i.e. how to know if the center of the plug on the device's box is positive or negative

I do not have the original charger.

There are no markings of polarity on the case, just the rating


texts:
I would like to have something like an LED bar, except that the light emission should not be broken up into separate lights, but be more or less continuous - without much greater light intensity per length.

Finally, it should be used for a thin, flexible rod of 2 m by 3 mm like the one described in
Light LED light?, so it needs to be somewhat flexible, and not very bulky. I think that short sections of inflexible sections would do.

One way to do it would be just using a continuous row of adjacent SMD LEDs, and using a very low current to reduce the emission per length.

It would need to be assembled from a a lot of LEDs.
Also, there is the problem that differences in individual LEDs are much more visible at low current, so it may be that binning LEDs is needed.

There is something very similar to what I need: Filament LED bulbs,
which have LEDs imitating carbon filaments in an old bulb.

These filaments are actually COB LEDs, where the board is a thin inflexible rod, covered with the LED material in some way - maybe tiled separate dies, covered again with the resin.
The filaments are just right, except that they are too brittle to be bent, and too short.
In the product description of a filament bulb, you can find pictures of filaments:

How do filament LED bulbs work, looking very similar to incandescent bulbs?


texts:
I have my own IP block with 24 bits input/output axi stream type.
It is an image processing ip. Thus, it should be connected by VDMA.

I tried to configure VDMA accroding to the example and datasheet.
However, I still cannot configure it correctly.

Could you help me by explain about VDMA?


texts: How do I do the 6 pin RJ11 to RS232 female serial adapter wiring?

texts:
I'm new to wiring and I have this RJ11 to DB9 RS232 adapter, and I'm not sure how to correctly insert the RJ11 wires into the DB9 female end. http://www.blackbox.com/Store/Detail.aspx/DB9-RJ-11-Adapter-Kit-Female/FA067?CAWELAID=414464303

I've searched google but haven't found any clear explanations. It's hard to see which cable is which, but there are six: black, white, green, red, blue, and yellow.


texts: Common collector :current amplifier or voltage follower?

texts:
I want to construct a simple voltage regulator like this one:

simulate this circuit – Schematic created using CircuitLab

However there is something peculiar: the voltage on the emitter is forced to be some value by Vbe and diodes total voltage drop. If then the load changes the voltage will be the same: the current should change to accomodate for the new load. Does this not contradict current gain principle? How can a transistor both supply an amplified current to the emitter and a fixed voltage?

This 'paradox' could be avoided if the load current could change the base current, of course with hFe taken into account.  Is this were the answer lies, on the fact that the current on the diodes can change depending on emitter load thus providing a way for changing the base current?

This may seem a strange question to some but I fundamentally know that the collector current can be changed by the base current by hFE amplification when the transistor in in the active region. If it were true for the collector current to change the base then everything  would in vain.

Question #2  Why does this configuration(common collector) has high input impedance (reffering to the base of the transistor Q1 in the circuit above)? I imagine because the current needed to drive the base is very small and equivalent (taking into account the base voltage) to a very large resistor. Is this correct?


texts: I need a  time circuit to switch off lamps(6 lamps of 16 watt each) after some time. Time should be adjustable(In secs like 30s or 90s).The lamps are fluorescent lamps. The  circuit should also have a beeper to beep after the required time. If it is possible please add a digital clock timer to show time or some audrino or something. Please help me. I am not into electronics but I really need this for a project.


texts: Bode plot acting weird with specific op-amp

texts:
Hello why is the behavior of this op-amp so weird (OP177).I simulated another op-amp(uA741) with the same biasing and the bode plot looks fine(still i dont get the 80dB amplification i would like, yea any advice on that ?).

op177-first image
uA741-second image


texts: Possibility to use SIL connector for USB

texts:
I'm designing a board with a USB port where the user connects its phone though a USB cable. I want the connection between the USB cable and the board to be strong so the user don't accidentally unplug the cable.
So the standard USB port won't work in my case,  neither those expensive sealed USB connectors.

I was thinking to use simple SIL connectors with "bornier" type of connectors. see pictures below.

Will that affect the USB communication ? it is a USB2 communication with small data packet transfert.

Let me know guys what you think about this

Thank you


texts: Push button counter from 0-999, but increment in 1, 4 and 6

texts:
I would like to create a push-button counter from 0-999 using 'BCD Decade Counter' and a 'BCD to 7 segment Decoder/Driver' the total of button presses will be displayed on 3 x 7 segment displays (similar to http://www.iamtechnical.com/digital-counter-schematic-diagram).

I am OK with this.

I would also like to implement 2 additional buttons to:

increment by 4, and,
increment by 6.

I suspect I may need to connect 2 x 555 to do this for each option.
I think it may be something like this:
https://www.circuitlab.com/editor/#?id=48mxga

I would be really grateful if someone could give me a hint or point me in the right direction.

Many thanks.


texts:
Here, all the initial conditions are : i1(0-)=0A and i2(0-)=0A
When t≥0, the current i1(t) and i2(t) starts flowing. From my assumption, steady state value of i1(t) is 10A but what happens to i2(t)? Applying KVL,
10=i1(t)+di1(t)/dt - di2(t)/dt
And i2(t)= di1(t)/dt-di2(t)/dt.
The time constant τ of this Circuit is 2 sec. If at steady state di1(t)/dt =0 then di2(t)/dt=0;then i2(∞)=0A. According to my calculation,
i1(t)=10-10e^(-0.5t) but what about i2(t)?How to figure out the i2(t) equation? Is it all zero? Please help me out with i2(t)?

I simulated the circuit and got these for 60Hz...

Both of them are same in simulation graph. How is it possible? Also this circuit can not be run at very high frequency. Please help me with i2(t).


texts: How to analyze the biasing of the output stage in this amplifier?

texts:
My textbook says that biasing current through Q8 and Q9 is about 20mA and through Q10 and Q11 about 100mA. How can I analyze the circuit to get these values with back-of-the-envelope calculations?

So far I only calculated that biasing voltage provided by Q5, R8 and R7 is 2V, but cannot get any further.


texts: Solder does not stick to iron after cleaning

texts:
I have read many articles regarding this subject and none have worked - otherwise I would not have made a thread that is surely a dupe of many others on this site.

I purchased this 25W soldering iron a few days ago and used it for the first time without any problems. A few days later I tried using the iron again and the solder would not "stick" to the tip when I attempted to tin it.

I read up on this subject and thought that the tip might be dirty. So, I went about cleaning it. I tried to use a wet sponge when the iron was hot. This worked nicely, and the iron looked great! However, the solder still would not stick. So I then tried using a brillo-type pad to clean it. Yet again, the iron came out looking great but nothing would stick to it.

Here is an image of the clean iron:

I am not sure what to do.
Any suggestions?


texts: Now I know that this question might sound silly, that is because apparently I am missing something here. Basically my question is, if ASK works as on/off keying meaning that provided we have an oscillator with fc carrier frequency and binary input to produce the fc signal (using oscillator) when there is 1 in input we just using that one frequency - the carrier frequency! So why we need a range of frequencies (which as I understand it is what bandwidth basically means)?


texts: Confusion on State Space Equation of Buck Converter

texts:
I'm trying to represent a buck converter in terms of state space equations.

I'm assuming CCM operation and I had derived the state space equations for two modes of operations:

Mode 1: Switch is ON (0 < t < dT)
Mode 2: Switch is OFF (dT < t < T)

My workings are displayed below:

The confusion arose when I'm checking my state space equations with my lecture notes. My state space equation for mode 1 is identical with the referred state space model, so I had no problem for that. However, for mode 2, I found that my state space equation is the negative version of the referred state space equations.

After investigation, I found that the assumption on polarity of voltages and direction of current are the key differences of my work and the reference. Based on what I have learnt, I know that after disconnected from the power supply, the polarity of inductor voltage should change to maintain the current in the same direction, and the direction of capacitor current should change to maintain the same voltage polarity.

However, the reference seemed to neglect this phenomena. May I know why is this?

Just in case anyone wonder what is in my lecture note:


texts: Help Identifying Vintage Capacitor Symbol

texts: I am trying to understand a vintage circuit diagram (70s) and came across this symbol of a capacitor with an arrow. Is this a bi-polar capacitor? Why show an arrow?


texts: LM386 guitar practice amp circuit not working, need help finding mistake

texts:
I'm very new to electronics and I built this guitar amp circuit on a breadboard:

and it was working really nicely. Now I've decided to put the circuit on a universal PCB which I'll use in the actual amp. I soldered all the components on but no sound comes out when I play. Because of the different layout of the universal PCB, the circuit's grounds are connected differently than they were on the breadboard, so maybe that's the potential problem since its the only difference I think there is. Sadly I don't remember what it looked like on the breadboard and I didn't take any pics. Heres the layout of the circuit on the universal PCB:

Heres something I don't understand, when I measure the potential between the output and the ground with a voltmeter, it corresponds nicely to the signal from the guitar, it seems like it should work. But when I measure the potential between the wires going into the speaker (which are connected to the output and the ground) I get zero volts between them always. Why is that and how can it be fixed?

Also sometimes when I poke around with the voltmeter at different spots on the ground and output it will randomly start working and sound will come out. I can't really notice any pattern when doing so though.

Heres the pin layout for the LM386 operational amplifier:

Once again I'm very new so I'm sure I'm making a ton of embarrassing mistakes and that my soldering is terrible lol


texts: please help choose mosfet, npn, pnp, diode for my circuit

texts:
I developed a circuit which uses charge pump to supply a current mirror.

Simulation works, I was able to get 40V and constant 10 mA at load < 4k.

I breadboarded each charge pump and current mirror circuit and each worked.

But when I supply charge pump to current mirror, current mirror load became weird.

I think is because my mosfet, pnp, npn cannot handle 40V?

Can anyone choose correct parts for me, or tell me what to look for in datasheet?

Thank you.

actually I am able to get square wave signal with current mirror supplied by charge pump, but signal is really noisy. when I supplied with only 12V, signal was clear.

I think problem is selection of 2n3906 or IRFH530, because I tested with Vsupply = C5 = about 20V, signal was clear.

If Vsupply = C7 = about 27V, signal is noisy.

Then I tested with 27V power supply instead of charge pump, signal disappear.

So I think my current mirror cannot handle Vsupply > 27V.

How can I choose correct pnp and mosfet.

fE is uF


texts: Why do we care about matching the input impedance of receiving RF amps?

texts:
Lets say we have a receiving antenna that intercepts a certain amount of power \$P_r\$ = \$SA_r\$, where \$S\$ is the power flow density of the incoming EM wave, and \$A_r\$ the effective area of the antenna. This power, \$P_r\$, is also called the available power, and is the maximum power that can be delivered to the attached load (i.e. the first stage of an RF amplifier). Maximum power transfer happens when the antenna output impedance is equal to the RF amp input impedance. Thus, we can also express \$P_r\$ the following way: \$P_r = \frac{V_A^2}{8R_A}\$, where \$V_A\$ is the open circuit voltage at the antenna port, and \$R_A\$ the antenna impedance.

The first stage of an RF amplifier can be a common emitter block, which gives us a small signal equivalent like this (under tuned conditions, assuming no feedback):

simulate this circuit – Schematic created using CircuitLab

I think it is quite obvious now, that if we power match at the input side, setting \$R_{in} = R_A\$, then we won't get maximum power transferred to \$R_L\$, since that requires maximum output current, which in turn is dependent on maximum \$V_{in}\$, which is turn is dependent on \$R_{in}\$ being much bigger than \$R_A\$. Nevertheless, I see in a lot of books that they power match the receiving antenna to the input stage of the RF amp, I just can't see why one would do it, because AFAIK doing it doesn't even imply minimum noise.


texts: zero-sequence circuit of the three phase transformer question

texts:
Although I have tried a lot, I cannot draw the zero sequence circuit. Can you help me?

this is my try.I could only come to some


texts: How do two capacitors share the same current?

texts:
I am first trying to find the voltages across two capacitors in this circuit.

So first I found i using current division and got 2mA. But when I went to calculate the two separate capacitor voltages, the equations were

v1 = 2000i and v2 = 4000i

In the image on the left I drew the arrows indicating were the currents would split and be different. How can you calculate the voltage across the capacitors using current i which doesn't travel through either branch?


texts: How to use less Bipolar Stepper-Motor Drivers

texts:
I make a CNC machine with lot of drivers (12) and the quality ones are quite expensives.

As I never use all the motors at the same time, and the fact that the unused/resting motors can be off is not a problem,

I wonder if a good strategy exist for being able to "switch" between groups of drivers (in 24V 4A), for this case I
only need to use 4 at the same time maximum.

In other words, is it possible to control by example 12 bipolar stepper motors with 4 drivers ?

This would be really useful for saving money and also saving micro-controllers pins.


texts:
I have what is surely a classic problem with regard to power supply switching noise and audio but I am unable to sort myth from reality with regard to what I found so far on the topic.

Setup:

I have a notebook with an external power suppy and/or battery
A radio receiver which has its own power supply (i.e. not fed by notebook SMPS)
the radio receiver feeds an audio signal into line-in of the notebook
the radio receiver is controlled by the notebook via RS232 (tuning, etc.)

Problem:

If I unplug the notebook from its power supply and run it from battery everything works perfectly
But if I use the notebook SMPS, I hear a tremendous amount of noise in the audio

Can anybody tell me where the problem is likely to lie? There is a lot of talk about ground loops but I have difficulty believing they really exist in such a small-scale installation.

Am I right to assume that it is likely a problem of a varying ground level in the notebook and the fact that the line-in input of the notebook is non-differential? Or is there a more likely explanation?

What is the best solution? Use an opamp to construct a differential input amplifier and feed its output to the line in? What do I use as ground reference for the opamp?

Proposed solutions in the comments and answers

From the answers it would appear that there are two possible problems: 1. ground loops and 2. RF pickup from the external SMPS in the audio wire.

Suggested solutions are:

Differential amplifier solution. Advantages/Disadvantages?
Kortuk: Combat RF pickup from the SMPS in the audio link with a grounded shield. Advantage: invisible solution; Disadvantage? Question: does not help with any ground loops?
Russell McMahon: Audio transformer in the audio-line. Advantage: Simple; Disadvantage: not easy to source, expensive or poor frequency response. Question: does this help with RF pickup in the audio line?
Russell McMahon: clamp EMC ferrites on the audio line to combat RF pickup. Does not help against ground loops. Question: does this help with noise in the audible range? It was my understanding that ferrites only help to filter very high frequencies.
David Kessner & Mary: Grounding the notebook. This shunts CM noise to ground. Advantage: cheap, simple; Disadvantage: additional wire to handle. Question: combats both RF pickup (if audio-ground is shunted) and avoids ground loops?
Mary: ferrite absorber around the DC line to the notebook and RF CM chokes in the audio line and RS232 lines. Disadvantage: high component count & effort with the RF CM chokes. Does not prevent ground loops.


texts:
I am trying to build an abc to positive/negative/zero components transformation block (in LTspice), I did it, but sometimes I get erroneous behaviour: DC levels seem to be "omitted" at the output for an abc > 120 > abc chain.

The schematic I'm using is this:

and the waveforms are these:

You can see that all waveforms are identical, but b/b* and c/c* have a DC difference between them. Here are the differences:

(in1, in2 and in3 are the a, b and c in the previous screenshots)

The signals are these:

all three phases have unity fundamental + 3rd/3, 5th/5 and 7th/7 all positive harmonics;
phase a has twice the amplitude;
phase b has 0.1Vdc;
phase c has 0.3rad phase lead.

Is this normal? Are DC bias levels "left behind"?

In order to build the schematic for a practical use, I had to maneuver a bit through the equations to avoid the \$\pm \frac{2 \pi}{3} \$ delay, and so I transformed \$e^{\pm j \cdot  \frac {2 \pi}{3}} = -\frac{1}{2} \pm j \frac{\sqrt{3}}{2}\$, which left only \$j\$ to take care of, a minor leap for SPICE-kind.


texts: How to determine watts and ohms for circuit board resistors?

texts:
I am about to embark on my first soldering job to fix a module that is broken inside my truck (compass/temperature display).  It is a well known design deficiency in this particular vehicle brand as the failure has happened a lot.  In most cases, one of the two 51 ohm resistors overheats and for reasons explained in this article, which also, to a fair degree outlines the fix.

What confuses me is how he came up with the idea to replace a single 51 ohm resistor with three 1W 150 ohm resistors (the formula for calculating net resistance):

  A little research told me that the resistors have values of 51 Ohms. Figuring in the 12V power supply, that means they are probably dissipating about 3 Watts each. That equates to a lot of heat in such a small package. No wonder they keep failing. Who thought this design was a good idea? I decided to replace the single resistor with three 1W 150 Ohm resistors in parallel, and extend them off the board and out into the air so they can cool by convection. In my case, it was only one of the two resistors that kept breaking loose. Some people only have trouble with one of them. Others have trouble with both of them. I only replaced the one that has repeatedly failed. If the other one ever fails I will replace it too.

I went to Radio Shack to get the supplies necessary but they didn't have 1W 150 Ohm resistors, only 1/2 W 150 ohm so I got those thinking that in such small wattages (?), it may be okay.

I am looking for an explanation how to, in such parameters (12V DC, small electricity usage, etc), you would calculate what wattage and ohmage is necessary for your resistor.  I haven't done any electronics but have lots of experience with residential electrical work and how electric load is balanced and how circuits should be structured.


texts: Impedance Matching for Short-Low Frequency Traces

texts:
Is it necessary to have impedance matching for short PCB traces if the frequency is lower than say 100MHz ? I've read somewhere that for a trace to be considered a transmission line it should have a length greater than 1/8 of the wavelength of the frequency,  and somewhere else greater than the wavelength, not sure which one is more accurate ?

Anyway, assuming that it's 1/8 of the wavelength, at 100MHz the wavelength is 3000mm so it's not necessary to match the impedance for traces shorter than 375mm (3000/8), am I correct here ?


texts:
i'm starting get into designing some IOT devices for around the house and looking other peoples design on Hackster.io.  I've come across several designs that i'm having a hard time understanding.   The below picture to me doesn't make sense.  My understanding is the the electric flow starts with positive and flows to the negative.  On the below picture for example we see GPIO pin 5 (blue wire) connects to resister then flows to the transistor then to the blue wire though the negative side of the led.

I don't know understand how this works since we would need current to flow through the resister then LED. When the developers code execute whatever on GPIO5, isn't this flowing the wrong way?  I will go out and say i'm starting at the bottom with basic understand if that.


texts: What software was used for drawing this schematic?

texts: I was reading a book on digital electronics and the gates with more than two input are drawn differently. I have seen many books that draw schematic in this style. I was wondering what software did they use. I am specifically talking about the way the OR gate is done here.


texts:
first post here. I'm wiring a DC motor and horn that will go into a small boat I built. I would like to get some help to see if I'm doing this correctly.

-DC motor hooked to a 12v battery (Max draw 30 amps, manual calls for 50a breaker)
-A foot pedal momentary switch turns the motor on.
-A 3 position toggle switch controls if the motor will go clockwise (forward), counterclockwise (reverse), or off.
-There is also a momentary button to power a horn.

I've built it and it works but I want to double check that there are no problems here and that its safe. Since the motor draws a lot of amps above the rating of the switches I'm using 2 relays.

Attached are pictures of how it's wired and also a picture of it wired up.

Thanks!