texts: Using a slider potentiometer with an Arduino

texts:
I'm new to electronics and in the process of building a Joystick using an Arduino Leonardo. I am reusing parts from an old Joystick from the 90s https://www.amazon.com/F-15E-HAWK-Tactical-Control-Joystick-Pc/dp/B0012N0EOQ.

This is my sketch to test:

const int X_AXIS_PIN = 0;
const int Y_AXIS_PIN = 1;

int x = 512;       // variable to store the value coming from the sensor
int y = 512;       // variable to store the value coming from the sensor

void setup() {
  Serial.begin(9600);
}

void loop() {
  x = analogRead(X_AXIS_PIN);
  y = analogRead(Y_AXIS_PIN);
  Serial.print("X: ");
  Serial.print(x);
  Serial.print(", ");
  Serial.print("Y: ");
  Serial.print(y);
  Serial.println();
  delay(500);
}

So far, I have hooked up a Joystick component I bought separately (not from old Joystick) to my Arduino to learn the general concepts. And it works well!

GND to GND
+5V to 5V
VRx to A0
VRy to A1
SW not connected

The code prints the correct X and Y values depending on the position of the Joystick.

Now to my problem: Instead of using a Joystick component, I'm trying to re-use the old slider potentiometers from the Joystick, so I don't have to construct a new Joystick rack. The potentiometers seem to be rated at 120k ohm (isn't that a lot?) and look like this:

Rack and potentiometers:
Close-up view:

However, I'm struggling getting it to work with my Arduino.

First question: The joystick component itself does not seem be anything else than two potentiometers, isn't it? Why does the Joystick (or any other normal potentiometer) need three pins connected (GND, 5v, and Out), but the sliding potentiometer that I took off the Joystick only had 2 connected? From Googling, I learned that 3 pins make the potentiometer a voltage divider and 2 pins make it a variable resistor. But I don't fully understand the difference. Don't both reduce the current?

Second question I tried testing the potentiometers to find out if they work at all. I set my multimeter to 200k and probing each of the cables coming off the potentiometer, the resistence would move between 0 and 134k as I move the slider. I also put one in series with an LED and a 220ohm resistor. The LED would dim but not gradually. It would only dim very slightly between 0-99% and be at full brightness when the slider is at 100%. Is that because the 120k potentiometer is too strong? Why would the resistance still not change gradually?

Third Question I tried hooking the potentiometer to the Arduino and see if it generates any data as I move the slider. I connected one end to GND and the other to A0. It doesn't generate any data. Is that because it is missing the third cable?

Fourth question As the potentiometer has three pins on each side, I was wondering if it simply needs a third pin connected. However, none of the pins are labeled so I tried all 6 different combinations to find out which combination makes the potentiometer working as expected (regulating voltage between 0 and 5V) This is how I tested it:

GND to pot (1st pin)
5V to pot (2nd pin)
Multimeter set to DC and 20V (COM + Ohm, V, mA)
Multimeter - to GND
Multimeter + to pot (3rd pin)

I found two combinations where the multimeter would read constant 4.99 (5) volts, no matter where I move the slider. All the other combinations don't read anything, no matter how I move the slider. Did I test this right?


texts: How are led controllers able to switch high power/current without becoming hot?

texts:
I'm quite new to electronics. I'm trying to power a DC 12V 5A (max) led strip from my raspberry pi. I have constructed a (working) schematic where the main component is a IRF3205 MOSFET controlling the high power circuit.The main problem with this kind of circuit is that the MOSFET becomes really hot.

Led strips like these most of the time come with a Led Controller included. Mine for example came with the one below. These led controllers become merely warm, while still claiming to be able to switch a maximum of 24V and 12A.

How are these tiny led controllers able to switch such a high power/current while not becoming (extremely) hot?

The Source-Drain voltage of the circuit as described by the schematic seems to be 0.45V at a Drain current of 1.3 Amps. The Gate has a voltage of 6V or so, but I'm not 100% sure because of my not-always-accurate multimeter.

Note: Unfortunately I can choose only one correct answer, but all of the answers given below are excellent and well-worth reading. The marked answer will be the one that is the most relevant to the original question.


texts: Sound to electrical energy converter (Energy Harvesing)

texts:
Is it possible harvest sound and convert it into a usable electrical energy

Ex. You want to charge your phone using sound energy


texts:
I have a schematic of Ethernet Transformer that supports POE, and 2.5GBT.
I plan on using Ethernet with transformer on my PCB to connect to Network Switch.

Are pin VC12 13, VC36 14, VC45 15, VC78 16 DC signal? Where do this pins connect to ?

What about TRCT1, TRCT 2, TRCT, 3, TRCT 4? Where are they connected to?

Also, what is common mode filter that is displayed on the schematic.
I have heard that ethernet with transformer are used for isolation. Can anyone explain what does the mean?

What else do I need to know before using the Ethernet with Transformer.

Any help is appreciated.


texts: What is the name of this circuit which has Vout = sin(Vin) transfer function?

texts:
I found this on IEEE's page: https://sscs.ieee.org/education/2017-2018-circuit-analysis-design-contest

Is there a name for this circuit or even does this circuit exist? If so, why and what is the circuit structure?


texts: LM385Z-2.5 in series with voltage divider - voltage reference problem

texts:
I'm doing a simple circuit using LM385. In THEORY voltage measured on cathode of D2 should be 5V. And it is so, if R2 and R3 are not present in the circuit. So voltage divider from R2 and R3 across voltage of 5V should give OUT voltage of 3.4V.

However when I measure it, OUT is only 2.5V and voltage measured on cathode of D2 is only 3.7V!

Could someone explain me please what am I missing?

simulate this circuit – Schematic created using CircuitLab


texts: How do non-flowing common mode or bias currents cause common mode range to exceed/float?

texts:
Below is a very simplistic view of differential ended inputs of a data-acquisition channel's inAmp which measures a floating battery voltage V. To make concepts and explanations simpler I use two resistors to mimic the inAmp:

Above R resistances represents the input impedance of the inAmp, and z are representing the line impedances.

Before asking my questions here are my understanding so far:

Differential current id is very small due to the input impedance of the inAmp:

id = V/(2*R+2*z)

Since a diff amplifier will subtract the voltages between the nodes a and b with respect to its own AGND, we can say the voltage across a and b causes by id is:

Va = id*R

Vb = -id*R

Va - Vb = id*(2R)

But due to the common mode currents ic1 and ic2, additional voltages( call it Vad and Vbd) are also created at node a and b as:

Vad = icm1*R

Vbd = icm2*R

Vad - Vbd = (icm1-icm2)*R

The last equation tells us that unbalance in the system(for example if z are not equal) will not reject the common mode voltages entirely.

If my view on the subject correct here is my question:

Another thing I can say is that if icm1 and icm2 large enough so Vad and Vbd becomes large which can exceed the rails of the inAmp. This can cause saturation and erratic readings.

As a remedy a 10k to 100k resistor is suggested to tie between the negative node b to AGND. I guess this is to lower the common mode voltages causes by icm1 and icm2.

But how come a 10k resistor tied between the node b and the AGND solve this issue? How is icm2 reduced by using the resistor? How about icm1? Is it possible to explain this using my circuit example not involving a real inAmp? Could you explain this in a simplistic way possible?

Edit:

I see that there is peculiarity. icm1 and icm2 has no return path, since the source is floating. But why is not having a return path creates big voltages at the inAmp side? If there is no return path for icm1 and icm2 then how does it create a problematic voltage at node a and node b?

Most importantly how does icm1 and icm2 exist at all if there is no return path for these currents to loop?

Btw I'm not sure if my analogy makes sense for id as input currents. Because input bias currents do not loop back to source the way I oriented right?

simulate this circuit – Schematic created using CircuitLab

Why sometimes the circuit in Figure 1 saturates and how does Rbias in Figure 2 fixes this problem? They say Rbias provides a return path to bias currents but why does the absence of return path causes inAmp to go saturate?

Why non flowing input bias currents saturates the inAmp or diff amp?


texts: Choosing and replace capacitors for audio amplifier

texts:
I have an old audio amplifier (JVC A-GX2B) that sometimes produces crackling noises on one of the outputs. So, I opened it and discovered that its two largest capacitors seem to be leaking :

Can I replace it with any capacitor with the same characteristics (4700uF 50V), or should I instead take specific capacitors for audio? If yes, which ones ?

In addition, do I have interest to replace all the capacitors of this amp (not only the 2 largest)?


texts:
Some while ago, while memorising the 74xx series part numbers, I came across the concept of a device with a "3-state" output. The idea, as best as I can tell, is that the device outputs logic low, logic high, or "not connected", basically.

I was quite interested when I read this. It sounds like you can use it to make a multiplexer with fewer gates. For example, it looks like you can take something like this:

simulate this circuit – Schematic created using CircuitLab

And turn it instead into something like this:

simulate this circuit

(Schematic editor doesn't seem to have the symbol for 3-state buffer... unless I'm missing something.)

This uses significantly fewer gates, and appears to do the same job.

...or does it? Looking at it today, knowing what I now know, I see two potential problems:

If Select goes from high to low, the top row of gates immediately stops driving the output, but there's some propogation delay from the NOT gate, so there's a short interval before the second row of gates start driving the output. That means that, for one gate delay, the circuit outputs are left floating.
Worse, if Select goes from low to high, there's potentially a one gate delay were both rows of gates are trying to drive the outputs, probably to different levels.

From browsing this site, I get the strong impression that leaving any gate input floating is a catastrophic disaster, and that such a thing must be avoided at any cost. Perhaps some pull-down resisters would solve that; I'm not sure.

Then there's the fact that if (say) AND2 tries to drive Z1 low and AND5 drives to drive it high, we now have a short circuit. Presumably this will cause instantaneous destruction of the ICs involved. (I don't think it can fry my power supply; it's supposed to have over-current protection. Likewise, I don't think there's a danger of actual fire or explosion...)

In short (haha!), it seems that this circuit can only work if all propogation delays can be exactly 0 attoseconds, which seems unlikely.

But then, if it's not possible to use 3-state gates... why do they exist? Have I fundamentally misunderstood what they're for or something?


texts: What's really the difference between the Cortex-M series and the Cortex-R series?

texts:
It's interesting! I searched for find a clear article, but I couldn't find a clear article for this. Also I found this link: ARM Cortex-R and this link: Cortex-R Series but they are not exactly clear. in the wiki page wrote:

  The cores are intended for robust real-time use

and in the Cortex-R's page wrote:

  The ARM Cortex®-R real-time processors offer high-performance computing solutions for embedded systems where reliability, high availability, fault tolerance, maintainability and real-time responses are required.

and these:

High performance: Fast processing combined with a high clock
frequency
Real-time: Processing meets hard real-time constraints on all
occasions
Safe: Dependable, reliable systems with high error resistance
Cost effective: Features for optimal for performance, power and
area

For number one: For example for the Cortex-M, recently the NXP made the NXP_LPC4XXX series that has 200Mhz clock rate and for the Cortex-R, you can see this: TMS570LS ARM Cortex™-R4 Microcontrollers, it's funny because it has 180Mhz clock rate.

For number two: It's clear.

For number three: It's not clear! what's the mean this sentence? means isn't the Cortex-M safe/Dependable?

For number five: Well, I think it just is a claim!

Who has the experience to work by this series(Cortex-R)? What's your opinion about it?
What's the deeply and exactly difference between the Cortex-M series and the Cortex-R series?


texts:
I am confused about the difference between "power factor" and "cos φ".

Some textbooks state that those two quantities are equal. Other textbooks state that those two quantities are not equal. And only in one internet resource, I have read that power factor equals cos φ plus non-linear distortion factor.

As far as I know, those two quantities are equal when we have ideal sinusoidal current.

Please help me, as I cannot continue my education without understanding.

Also I will be very happy if you can give me a link to some textbook, in which these topics are covered in more detail.


texts:
hi first of all  english is not my  languaje.
im using a SPARTAN 3E as develop board
 i tried to make a FSM that changes
the state with a counter called "T" (somethig like a pseudo-processor) and use a button as pulse to increment, in one case the FSM asign a 4 size std_logic_vector from four switches in the fpga board to "A", then increment the counter and in other time put the value from the same switch in "B", finally it makes the operation C:=A+B and send it to two external displays    the main problem happens when i want to make the adition between A and B, looklike A and B doesnt hold the asigned value and shows a wrong operation when i tested,
im new in vhdl so my knowledge is limited thanks for the help :)

  `PROCESS(T)

   variable A:    std_logic_vector(3 DOWNTO 0);
   variable B:    std_logic_vector(3 DOWNTO 0);
   variable C:    STD_LOGIC_VECTOR(4 DOWNTO 0);
   BEGIN
    IF T="00000" THEN--0
       X0<="00000011";
    END IF;

    IF T="00001" THEN--1
        IF MEM="0001" THEN
           VAL<="00001";
        ELSE
           VAL<="11111";
        END IF;
        X0<="00000110";
    END IF;

    IF T="00010" THEN--2
      X0<="00011010";
    END IF;

    IF T="00011" THEN--3
      X0<="00000011";
    END IF;

    IF T="00100" THEN--4
       VAL<=('0'& MEM);
       X0<="00000110";
    END IF;

    IF T="00101" THEN--5
        A:=MEM;--takes A from the switch
        VAL<=('0' & A);
        X0<="00110010";
    END IF;

    IF T="00110" THEN--6

       X0<="00000011";
    END IF;

    IF T="00111" THEN--7
        B:=MEM;--takes B from the switch
        VAL<=('0' & B);
        X0<="00000110";
    END IF;

    IF T="01000" THEN--8
       X0<="01010010";
    END IF;

    IF T="01001" THEN--9
       C:=STD_LOGIC_VECTOR(UNSIGNED('0' & A)+UNSIGNED('0' & B));
       VAL<=(C);--shows the result
       X0<="10000010";
    END IF;

    IF T="01010" THEN--10
        X0<="00000011";
    END IF;

    IF T="01011" THEN--11
        IF MEM="0001" THEN
           VAL<="00010";
        ELSE
           VAL<="11111";
        END IF;
        X0<="00000110";
    END IF;

    IF T="01100" THEN--12
        X0<="00011010";
    END IF;

    IF T="01101" THEN--13
        X0<="00000011";
    END IF;

    IF T="01110" THEN--14
        VAL<=('0' & MEM);
        X0<="00000110";
    END IF;

    IF T="01111" THEN--15
        A:=MEM;--takes A
        VAL<=('0' & MEM);
        X0<="00110010";
    END IF;

    IF T="10000" THEN--16
        X0<="00000011";
    END IF;

    IF T="10001" THEN--17
        VAL<=('0' & MEM);
        X0<="00000110";
    END IF;

    IF T="10010" THEN--18
        B:=MEM;--takes B
        VAL<=('0' & B);
        X0<="01010010";
    END IF;

    IF T="10011" THEN--19
       C:=STD_LOGIC_VECTOR(UNSIGNED('0' & A)-UNSIGNED('0' & B));
       VAL<=(C);--shows the result
       X0<="00000000";
    END IF;

    if T>"10011" then
       X0<="00000000";
    end if;

END PROCESS;`


texts:
Below is a cutout of the schematic and close up PCB for a detector I've asked several questions about. Specifically pin 6 on U3, R23, and R21.

I've measured voltages higher than 7.5 from pin 5, which should make the output to pin 7 go HIGH. Instead, it stays low. But once I touch the bottom side of R23, R21, or Pin 6, with the oscilloscope pin the signal goes HIGH (IE I get an output from pin 7).

Does this mean there's a cold solder joint somewhere on these 3 pins? I'm having this issue with several other PCB and would seem odd that every one has a bad solder joint here.


texts:
I'm using the ADC of ATMega8 to read the charging and discharging waveforms of a capacitor. However I'm getting an extremely large number of errors when I see the data I get in my laptop. I'm sending the sampled data to the laptop through a USB to TTL converter at 9600 bps. The sampling rate is 15000 samples per second, so there are probably many samples that are lost due to the speed difference. I'm using the default clock of ATMEGA8. The serially transmitted data is received in MATLAB and the plot is shown:

The zoomed version of one of these charge discharge cycles is shown below:

As you can see, there are a large number of errors but we can make out the actual waveform. What is causing this problem? How can I correct this?

Also, I have a problem with the ADC readings. I have set the reference of the SAR ADC as the default internal 2.56 V. As I understand it, the 8 bit ADC is supposed to give me 0 (Ox00) at 0 V and 255 (OxFF) at 5 V. But here I get 124 for 0 V and 255 for 5 V. Why is this happening? As shown, multiplying the values obtained in the ADC by 5/255 does not give me the original voltage values. The 2.5 V 'offset' shown is due to this error of recognizing 0 V as 124. But I don't know why this is happening.

The C code on the microcontroller end is shown. The program also generates two pulses used to activate the charge and discharge cycles of the capacitor (The pulses are fed into the gate of two MOS switches).

#define F_CPU 1000000UL

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

#define USART_BAUDRATE 9600
#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)  //Calculating prescaler for serial communication

int main(void)
{
    uint32_t i;

    UCSRB |= (1 << RXEN) | (1 << TXEN);  //Enable serial transmission and reception
    UCSRC |= (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1); //Set character size (8 bits). When URSEL is 1, we can write data to UBRRH register.
        UBRRH = (BAUD_PRESCALE >> 8);  \\Setting the prescale
        UBRRL = BAUD_PRESCALE;  //Set prescale value
//DDRD = 0xff;   \\Set port D as output (for pulses)
ADMUX = (1<<REFS0) |(1<<ADLAR)|(1<<REFS1); \\Set reference voltage to internal and left adjust result (out of 10 bit result, 8 bits are moved to ADCH register).
ADCSRA = (1<<ADEN)|(1<<ADFR); \\Enable ADC in free running mode
//|(1<<ADPS2) |(1<<ADPS1) |(1<<ADPS0);
//
ADCSRA|=(1<<ADSC); \\Start conversion
DDRB = 0xff;    \\Set port B as output (for pulses)
    while(1)
    {
    for (i = 0; i< 200; ++i)
        {
        PORTB = 0x01; \\First bit of port B will be high pulse for duration of loop.

//      ADCSRA|=(1<<ADSC);
        while ((UCSRA & (1 << UDRE)) == 0) {}; \\a while loop (with no body) that continues as long as the UDRE bit is set. UDRE is set when it is ready to send data
             UDR = ADCH;  \\Read ADC data

//      PORTB = 0x01;
        }

    PORTB = 0x00;  \\Set all ports off for a brief interval (for nonoverlapping of charge and discharge cycles)
    _delay_ms(5);

    for (i = 0; i<400; ++i)
        {
        PORTB = 0x02; \\Setting second bit of port B high. To activate discharge cycle.

//      ADCSRA|=(1<<ADSC);
        while ((UCSRA & (1 << UDRE)) == 0) {}; \\a while loop (with no body) that continues as long as the UDRE bit is set. UDRE is set when it is ready to send data
             UDR = ADCH;

//      PORTB = 0x02;
        }
    }
return 1;
}


texts: Driving inductive load from IC with MOSFET

texts:
I am designing a driver circuit to drive a hydraulic proportional valve from
an IC's PWM output. (IC is ATmega 2560). The coils on the valve draw approx 3Amps
at %100 duty cycle with a power supply of 28v.

MOSFET's seem to be the way to accomplish this, thou I am struggling to find a
'safe' solution. The two primary methods I have so far come up with are;

A logic level MOSFET: (Please note R7 and R10 are the coil)

Or using an op-amp to boost the PWM signal and use a higher Vth MOSFET:

It seems the logic level version has a ~1v drop across Q3 when driving the coil,
and I am concerned about that causing damage (heat, power loss etc)

Which of these (or any other way) would be the best way to provide control of
an inductive load? (Or have I totally ended up with an incorrect design?)

(EDIT: Please note that protecting the IC from any single driver failure is paramount)


texts: Offical Name of Dell/HP Common Laptop Power Jack/Plug

texts:
I have seen this question asked before, but never has it gotten a real answer. With the popularity of this plug I find it hard to believe it does not have a standard name or IEC name.

Does anyone know the real name of this or is it truly just an oddball DC Barrel-jack connector that HP and Dell love to use?

Here is a related question with no good answer:
Question 1
And another here:Question2

Just to clarify I really care about the female jack, not the plug.


texts: stm32f7x2Rx vcap1 finding a suitable low ESR capacitor

texts:
According AN4661

  In the STM32F7x2Rx devices, only the VCAP1 pin is available and must be connected to 4.7 µF low ESR between 0.1Ω and 0.2Ω ceramic capacitor.

So how do I go about finding a suitable capacitor?

After looking through many datasheets of various brands of capacitors, some list an "ESR(Ohm) vs frequency(Hz)"-diagram which sounds like that's what is needed. Most graphs looks similar to this:

Now the ESR value displayed in those diagrams varies wildly over the frequency, which raises the question what frequency do we need to check? I'm guessing the frequency of the HSE clock (8 mhz in my case), but I haven't found anything explicitly stating that.

There is also the Murata LLR-series which is listed as E01 100mΩ (which seems suspiciously consistent), but it's only available in in 1uF.

Can someone point me in the right direction in how to pick a matching capacitor in 0603 package - not sure if that's at all feasible (maybe the above criteria can only be matched in 0402 or 0805)?

Additional info:

Using HSE with a crystal of 8Mhz
Using PLL
Processor running at 168Mhz
USB running at 48Mhz

Drawing in the 0.1-0.2R range (red bar) in the graph for the GRM188R61C475ME11, then as I understand it, the green line marks the valid frequencies, which are from ~0.004Mhz to 0.008Mhz and from ~600Mhz to 1600Mhz.

At the

cpu-clock of 168Mhz the graph shows ~0.05Ohm
usb-clock of 42Mhz the graph shows ~0.03Ohm
HSE frequency of 8Mhz the graph shows ~0.002Ohm

Neither of the three frequencies is within the demanded range of 0.1Ω and 0.2Ω... So either I'm misinterpreting something or all capacitors from various brands and series I looked at are unsuitable.

Unless the datasheet means that anything < 0.1-0.2R is valid, but in that case for mcu's with both vcap1 and vcap2 it says

  When the voltage regulator is enabled, VCAP1 and VCAP2 pins must be connected to 2*2.2 μF low ESR < 2 Ω ceramic capacitor.

So why specifically mention less-than for this case, but mention a very specific range for the only-vcap1 case?


texts: I have bought a 18650 2S protection board on eBay (http://www.ebay.it/itm/222383859919) because I need to use and charge 2 18650 batteries in series for a project (a portable audio system) but, searching the protection board model (fdc-2s-2) on google, I have found this site (http://mklec.com/components/battery-protection/lithium-ion-7.4V-3A-protection-pcb) that says that "This module is NOT a charging circuit!". What does this means? Can't I use this for my project? Waiting for an answer. Thank you for your attention.


texts: Can anyone help me to design a circuit which outputs 0v dc when the input is 2.6v dc and 5v dc when the input is 5v dc?


texts: simplify external I/O memory access with small micro

texts:
I was reading atmel's AT28C256 datasheet and it states for a write operation:

  A low pulse on WE or CE input initiates a write cycle. The address is latched on the falling edge of WE or CE whichever occurs last. The data is latched by the first rising edge of CE or WE.

For a read operation it states:

  When CE and OE are low and WE is high, the data stored at memory location determined by the address pins is asserted on the outputs.

However, I haven't found this kind of literature in the 62256 static ram datasheet.

Does this kind of behavior only work for certain ROM/RAM chips?

and also, would the following circuit be sufficient to access the memory without bus contention?

And here's my code to do I/O on the ram:

For write:

CE equ P3.5
ADDR equ P3.7
MODE equ P1.7
IO equ P1

clr ADDR    ;set high address switch line low
mov IO,#10h ;set high memory address
clr MODE    ;switch to write mode
setb ADDR   ;save high memory address and write decision into 74hc574
clr ADDR    ;turn switch line low again
mov IO,#23h ;set low memory address
clr CE      ;store low address (I'm relying on AT28C256 datasheet here...)
mov IO,#66h ;set data
setb CE     ;store data

For read (where I have a problem):

CE equ P3.5
ADDR equ P3.7
MODE equ P1.7
IO equ P1

clr ADDR    ;set high address switch line low
mov IO,#10h ;set high memory address
setb MODE    ;switch to read mode
setb ADDR   ;save high memory address and write decision into 74hc574
clr ADDR    ;turn switch line low again
mov IO,#23h ;set low memory address
clr CE      ;store low address and request reading
mov IO,#0FFh ;prepare for read within 1uS of lowering CE to prevent bus contention
setb CE     ;disable read

I know the micro in this circuit is incomplete but for simplicity, the crystal I will use is 20Mhz and the micro is not in reset mode.

Would I be able to get away with using this circuit and above code to store and retrieve data from external memory? or do I have no choice but to either add a second set of octal flip-flops or use a bigger microcontroller? I'm trying to keep things small.


texts:
I am going to make HVProg.

Can I use an ATMEGA8 with it?
If yes then how, if no them can we use any other microcontroller ?


texts:
I am new to pic uart communicatioon with PC using RS232.
I have tried the below code and used Hyperterminal to view the output.
But the output gets scrambled here and there each time when I reset pic. I have tried changing stopbits from 1 to 0 in the hyperterminal but the output remains the same.
The settings kept on hyperterminal is

Baudrate 9600
Parity none
Stopbits 1 & 2(for both the output remains the same.)
No. Of bits 8

Am using PIC16F877a and have coded using MPLAB XC8 compiler
The outputs are there in the attachment

Could you please tell where i did the mistake.

void main()

{
TRISC = 0x80;
TXSTA=0x24;
RCSTA=0x90;
SPBRG=0x81;
unsigned int i=0;
char name[]="Sample Output";

while(name[i]!='\0')
{
  TXREG=name[i];
  while(!TXIF);
  __delay_ms(1000);
  i++;

}
while(1);
}


texts: Confusion related to power in series circuit

texts:
Two 100W, 100V lamps are connected in series across 200V supply. The power consumed by each lamp in watts will be?

My attempt - According to me voltage divided half half and each bulb get 100V and produce 100 watt.

I found same question with solution on google. But solution is not clear.

Doubt 1-

When they are finding resistance of each bulb they are using 200V but why not using 100V as voltage of lamp is 100V and we are finding its resistance.

Doubt 2-

I think voltage is divided in series circuits based on voltage of equipments i.e lamps here. So why not 200V is divided into 100-100V in lamps. And on 100V power is 100W for each. So why not answer 100W?


texts:
Recently I designed a circuit to reduce an input signal by 10x. The design uses a resistor-divider network and then a unity op-amp. The signal is appropriately scaled but there appears to be a ton of ripple / noise in the output. The input signal is -1V to 1V @ 100 KHz and output is a motion control DAC.

I am using a TI OPA188 OpAmp with a +12V / -12V power supply. On both power supplies I have a 1uF ceramic, 100 uF electrolytic and 10 uF tantalum capacitor, and then directly next to the OPA188 I have 0.1uF decoupling capacitor. The schematic is this (note the part is OPA188 not OPA140):

Thoughts:

Do I need to do something with the power (filter?) from the switching power supplies (TDK-Lambda LS25-12)?
I do not have a resistor or capacitor on the feedback from op amp output to negative. Does that cause instability? Ditto with the output - I drive the output directly to the remote ADC, no resistor. Error?
Did I make a poor choice - is this op amp not suited to unity gain buffer?

The noise is periodic, at least 200 mV pk-pk (a deal-killer as noise like that is directly picked up by the ADC control circuit). The output cable is a typical BNC 50 Ohm cable, ~3' long, high impedance ADC controller at the other end.

Added - picture of noise (op-amp -> 3' BNC cable -> scope):

Added - picture of -12V power rail and op-amp output


texts: Tips on routing multiple powers(+5/-5/+15/-15/3.3 and etc. ) for a four-layer PCB

texts:
The most tedious thing for me while routing PCBs are the powers. I have made several PCBs of these kind and it seems that I have not learned much from the process. The power connections are always a mess.

Here is the description:  The circuit need multiple powers including \$\pm5\,\mathrm{V},\pm12\,\mathrm{V}, +3.3\,\mathrm{V}\$. The circuit is to measure weak current at \$10\,\mathrm{pA}\$ level. Therefore, the PCB layout is supposed to be very important. And the ICs are placed in different places which may need different voltages. A four layer PCB is used with signal/ground/\$+15\,\mathrm{V}\$/signal. I can give \$+15\$ and GND for ICs directly through vias. However, for \$\pm5\,\mathrm{V}, -12\,\mathrm{V}\$ and \$3.3\,\mathrm{V}\$, the power lines keep messing with each other. Sometimes I have to use several vias in one power line. Further, if a STAR structure is to be used, the condition will be much more complex.

Could I ask for some tips on design of the power lines? And how to improve my PCB skills?

supplement: Many experienced engineers talked about analog ground and digital ground. Here comes a perfect tutorial for me: http://pdfserv.maximintegrated.com/en/an/TUT5450.pdf

And about decoupling techniques for analog IC, here is a very good one: http://www.analog.com/static/imported-files/tutorials/MT-101.pdf


texts: Can Irms be ignored if using Isat of an inductor

texts:
I have got the following parameters for a buck regulator and am attempting to find a suitable inductor:

Vi = 3.6
Vo = 1.8
Imax = 1.5
Fsw = 56000
Iripple = 0.45

Plugging all these into the inductance value formula:

L = ((Vin - Vout) * Vout) / (Vin * Fsw * Iripple)
L = 35.714

I know I've got to consider the current ratings of the inductor (with the peak current of Imax + (Iripple / 2 ) = 1.725A). If I use this 1.725A and ensure the peak saturation of an inductor is above this (by some safety margin as well), do I still have to consider the RMS current of the inductor. If so, what minimum values should I be requiring considering the above parameters and how do I calculate them?


texts: Is a switching power supply likely to fatigue or burn out early if turned on or off quickly?

texts:
I'm working on a design for growing biomass where I need high power LEDs to switch on and off somewhere in the neighborhood of 1-30 times per second, so that they provide light to grow but don't oversaturate the organism's photosynthetic chemicals.

While I would guess that a better approach to powering these would be to directly power them with transistors or something could be guaranteed not to mind switching at that rate, for a quick and dirty prototype, I've got a switching power supply on the way that will provide appropriate DC voltage and amperage to the LEDs.

The question is: if I switch that power supply itself on or off at 1-30 Hz, is it likely to burn anything in it out prematurely?

I assume that this is less an issue with a switching supply than a solid state one since it won't be heating and cooling as much, but I don't know if there are other failure modes I should be looking out for.


texts: Datasheet's frequency vs. real-world frequency for IR LED

texts:
I am very new to calculating frequencies, but here goes...

The datasheet for an infrared LED states that it can handle a current of up to 1A when the voltage is pulsed at 300 pulses per second and a pulse width of 10us:

Am I correct in thinking that this equates to a frequency of 300Hz with a 0.3% duty cycle? I get the frequency by:

 1 second/300 = 0.0033 second = 300Hz

and I get the duty cycle by dividing "on time" by period, if 10 us = 0.00001 seconds

(0.00001 seconds / 0.0033 seconds) = 0.003 = 0.3%.

So then my other question comes when I read this article on Wikipedia that states that many electronics pulse IR at 38 kHz:

http://en.wikipedia.org/wiki/Consumer_IR

And there's a tutorial I read that instructed me to pulse the voltage at about 13 seconds on and 13 seconds off for 38kHz. Isn't that a 50% duty cycle? How can the duty cycle be so much bigger when the pulse "on time" is nearly the same? Is it assuming a much smaller current than 1A?


texts: High current, slow turn-on, low ripple power supply

texts:
I am a hobbyist and I'm trying to make a power supply that withstands a few amps load, that also has a slow turn-on and low ripple. I'm powering up an ESP32-Cam that's pretty sensitive to ripple and voltage drops, so after scavenging the internet for circuits and some documentation, this is what I came up with:

Is this schematic going to work?

C2, C4 and C8 are tantalum caps, would that help with ripple?

Are the transistors properly wired?

I have seen some schematics with and without low 0.1ohm resistors coming out from the emitter

What is the reason of those resistors?

Should I add them?

I don't have proper knowledge on electronics, so any help or guidance would be highly appreciated! Thanks!


texts:
Can someone please review my PCB?  Simply, I'm running 24 IR Leds at medium power, from a 5v arduino MCU pin, all pulsing together (38khz).  Big fat traces, lots of space, SMD components.  The LEDS are in 8 3-serial runs, and I have power/ground traces around.  The "leds" on the board are just 2.54 headers, as I'll be running them off-board.  But I don't know if I've got my head wrapped around the mosfet circuit correctly.  Please be kind (but feel free to talk to me like an idiot, because I am) :)  I'll fab at seeedstudio if it's relevant.

Edit:  I believe this is the schematic for the board as is currently laid out (with the exception of lowering the gate resistor as a commentor suggested).  Also, I do believe I'm an idiot with the leds, as I'm bridging their legs, rather than just the leds, so can remove those trace portions (ie on the top left led, 1 and 2 are the +- legs of an led so ought not be 'traced', but 2 and 3 need the trace to connect led1 to led2.):

simulate this circuit – Schematic created using CircuitLab


texts:
I'm creating an autonomous sailing boat and just looking into how to control the sail and rudder.

The electronics will be low powered with the main brain being an Arduino.

My problem is thinking of what to control the sail and rudder with, I need something that will hold it's position whilst powered down and has a high torque rating for pulling in the main sail in and out.

I've looked around for servos with braking but haven't found much.

I should also point out that the sailing boat is around 2 meters long.


texts: What is the terminal labelled "U" in some autotransformers?

texts:
I'm trying to wire an autotransformer for usage as a speed controller for a brushless motor fan.

The terminals are quite self explanatory:

Pe for ground, L-N are my input, N1-L1 are unregulated output (same as L-N) and U-N are the output to my motor. Having that said, I'm still hesitant to wire this up before I understand the the following:

Q1: What is the U terminal? What does it stand for?
Q2: Do I connect my motor's ground to the common Pe? I'd have imagined that there would be a dedicated terminal for the ground near the output to the motor.

Here's a picture from inside the transformer's case:

Transformer's datasheet https://www.sentera.eu/Product/ViewDocument/ENG/?DocumentId=690814&ArticleID=108450


texts:
I am in the process of designing a device for a uni project. As a requirement, we are required to have a very low power consumption whilst in standby mode. Our plan for this, was to have our 2 x +-5V rails run through some form of IC that would be switchable by our micro controller.

I was originally looking at something to a TPS2085, however they aren't available in PDIP packages (We are restricted to what we can solder ourselves, and I'm not keen on soldering surface/pad mount components).

Is this a good idea (And if so, are there any common place IC's that do this in a PDIP package)? Or would I be better off creating my own "switch" through the use of transistors (And if so, anyone got any good suggestions)?


texts:
I recently bought some global 3G modules from Digi International and wanted to test one of them with the SIM card from my phone.

I was surprised when I saw the module couldn't connect to the network. So I then used a prepaid SIM card from the same carrier and it was able to connect to the network although I had to force a network reset in order to have a data connection because the module would fail to stablish it in the first try.

I contacted the support team and they told me that the problem must be in the SIM card or the carrier not allowing the module to connect. They told me I must use M2M SIM cards, not SIM cards intended for phones/tablets. I've used 2G modules from SIMCOM with any type of SIM card without any problems. This 3G module from Digi is based on the U-Blox 201 modem.

My question is, is actually a difference between M2M SIM cards and normal SIM cards? I know they have other form factors not available on normal SIM cards and they can also have extended temperature range and the carriers usually provide more tools to manage the M2M cards. But do carriers block connections of non-smartphones or non-tablet devices to their networks? Are the M2M cards treated differently by the network?


texts: Trying to build a Wien bridge oscillator, but can't make the oscillations work.

texts:
I built this circuit to have oscillations between 20kHz to 30kHz. Unfortunately the oscillations come out very tiny and very irregular.

What should I modify or add and why to make the oscillations work?


texts: How to solve this task that relates to method of superposition

texts:
The task looks quite simple it says:

  Find the current that ammeter shows. \$ R = X_c = 10 Ω \$ \$ X_L = 20 Ω\$

The picture of circuit:

I tried to solve it using method of superposition:

In first case If I look at just one current source (I plug out another current source from circuit and make short circuit out of voltage source) I will have:

  \$ I_A^, = I* \frac{R- jX_c + jX_l}{R - jX_c + jX_l -jX_c} = 1 + i\$.

How I think current goes for \$I_A^,\$ :https://imgur.com/a/ee8ixi8

The same thing for another voltage source I would have

  \$ I_A^{,,} = 1 + i\$

https://imgur.com/a/JOMsEK5

And for voltage source (when I plug out current sources ) I would have:

  \$I_A^{,,,} = \frac{U}{R - 2jX_c + jX_L} = 1\$

https://imgur.com/a/zj7fWyq

Now by the method of superposition \$ I_A = I_A^, + I _A^{,,} + I_A^{,,,} = 3 + 2 i\$ But in the textbook it says that the solution is 1.

What did I do wrong to get the incorrect solution?


texts: Alternative for the DF Player (mp3 playback module)?

texts:
The DF Player and all it's clones are super cheap on Aliexpress and similar websites, one can be bought under $1.5. The problem is that the low power state of the module is non existing with around 30mA drawn is that state. That makes the module unsuitable for battery usage. Powering the module down using an external MOSFET does work, however the setup time of the module is about 1.5 sec to 3 which is too much.

I am looking for something that could provide high quality playback of mp3 files, possibly more primitive than the DF Player but could go low power & wake up into playback in under 0.5 sec. Cost should also remain about the same. Can be an IC as well as long as I can actually buy it from somewhere.


texts: Amplifier Repair - How can I find a replacement transformer?

texts:
So I'm trying to repair an old Marantz 1040M amplifier, which after being run at high volumes on New Year's(!!) no longer powers on :(

My electronics knowledge is fairly rudimentary, but I think I have identified the problem as being transformer related. The primary winding reads an open circuit on a multimeter, and there is no voltage across any of the secondary terminals when a voltage is applied to the primary.

It has three primary terminals (0v, 210v and 240v for EU/UK use) and four secondary taps.

I want to replace the transformer, however I can find no information online regarding its specifications. Searching for the part number yields zero useful search results.

Some research has revealed that the 1040M is internally identical to the PM-200. I have found the relevant service manual, but that shows little clues as to the transformer specs -

https://www.manualslib.com/manual/691537/Marantz-Pm200.html?page=8#manual

I have contacted Marantz, who say that the company has changed hands so they have no access to specifications of older products! Both of the repair companies Marantz pointed me to are of no help either.

The label on the transformer reads -

TS1662002-0
(ETP66P2E)

and to the side of that -

6931M

So basically the question is, can I repair this amp, or should I sell it for spares and write the whole thing off?

Is there a way of somehow figuring out what voltages the board needs, just using a multimeter? Could I even crack the transformer open and repair the coil? I'm fairly sure the secondary winding is okay. Any advice much appreciated.

Cheers,

Oli


texts: Back EMF protection on bidirectional DC motor controller

texts:
I am trying to design a circuit using the TB67H450FNG,EL motor driver ic to control a 6v dc motor that will be run bidirecitonal and run in 1 second pulses.  due to being bi directional I am unsure of where to handle the back EMF in this circuit included (only included the relevant parts of the total circuit). Could I just put a diode on the output of the regulator inline with the output voltage, or would it need to run to ground? Or would I need to have some kind of back EMF protection motor side instead of supply side? All ground terminates to an external 12v power supply if relevant. Thanks in advance!

simulate this circuit – Schematic created using CircuitLab

DataSheets:
Motor Controller:TB67H450FNG,EL  https://www.mouser.com/datasheet/2/408/TB67H450FNG_datasheet_en_20190401-1604947.pdf
Linear Regulator:L7806CV
https://www.mouser.com/datasheet/2/389/l78-974043.pdf


texts: Cause of skin effect: eddy current inside conductor

texts:
We all know very well that due to eddy current (back EMF) generation within an AC carrying conductor, "skin effect" occurs.

Eddy current density:
Highest at center of conductor core
Lowest at surface of conductor core

Thus source current density:
Highest at surface of conductor core
Lowest at center of conductor core

My question is:
According to Ampere's law, magnetic field intensity increases as we go far from center of conductor to surface, so eddy should be highest at surface instead of core, right?


texts: Earth connection on this single phase AC motor

texts:
I bought a drill press recently that comes equipped with a 0.5HP single phase AC motor. I have wired it up as per the instructions that came pasted on the motor but I do not see a terminal for earth on it. Do I simply connect the earth wire to one of the screws that hold the motor frame?

This is what the instruction label looks like:

This is what the wiring terminals look like:

I wanted to read a little better what's under the A terminal and I temporarily disconnected those leads:


texts: Replacing the capacitor on an old Philips amplifier

texts:
My Philips amplifier broke down (model FA153) and my friend told me it's likely the capicators have worn out (they were produced in West Germany ;))
I am quite the layman in electrical engineering, but I am trying to replace the problem myself.
Current info on the capacitors:

It's the two 2553 and 2554 capacitors. With 6800 microfarad and 50V.  Diameter is 30mm and height is 50mm.
Here is a drawing of the circuit bord where the capacitors are:

It seems the positive contact point has 1 pin. There the capacitor is attached to a ring, which has three negative pins/contact points.
I was unable to remove the capacitor by soldering all contact points, so I forced the body off of the ring. Then I was able to remove the body by soldering the positive contact point. Result:

Currently, I am unsure how to proceed.
Is the ring part of the capacitor and should I remove it?
What would be a replacement capacitor?
Any help would be greatly appreciated!!
EDIT:
extra picture of the other side of the PCB


texts:
I am designing a lamp based on  neopixel leds and arduino. I'm designing the badge on Eagle and I've noticed a problem. I have noticed that with the consumption of the LEDs (5A) when the user tries to program the lamp Will try to turn on the leds of the usb and can be damaged. How can I make the lamp only turn on when the Power supply is connected and if the USB is not alone?

I have thought of a system based on MOSFET


texts: In a 12v automotive system, can a second battery properly sustain charge with a diode?

texts:
I am working on a 12v system where there is a display/computer that requires voltage to stay above 8V to stay on. Problem is during engine crank the voltage momentarily drops to 5V before regaining.
I am trying to investigate a system with a second battery dedicated for the display (common ground) connected to the main battery through a diode:

In such a system would the second battery sustain charge when it is receiving 14-1.2=12.8V because of the diode? Is this system viable?


texts: Is there a .NET IVI library for the Tektronix TBS1052B?

texts:
I have a Tektronix TBS 1052B meter that I would like to control over a USB port, in a Windows/.NET environment. I am looking to use the IVI foundation's interface libraries in order to do this. I am searching through the driver's section on NI's website. Here are the drivers that they have listed for my device:

Will I be able to control the scope, using either of these drivers? I do understand that I may not be able to, because LV and LW are explicitly mentioned. But what I am thinking, is that by installing either one of these drivers, the raw DLL/IVI-driver may also be installed. I am thinking that I would therefore be able to access the IVI library directly. Is that the case?


texts: What is the 'right' way for a 3-Phase Watt Meter to determine import-export Watt-hours?

texts:
What is the correct way for a 3 Phase Watt-Hour meter to measure total import/export watt-hours?

I ask because I have seen this done in 2 different ways both in 'approved' meters:

Assume that:
Red Phase - importing 1kW
White Phase - importing 2kW
Blue Phase - exporting 1.5kW
Assume this is constant for 1 hour.

What should the Watt-Hour register record?
Option A - Add up phases before adding to totaliser:
1 + 2 - 1.5 = 1.5 kWh Imported

Option B - Add import to import, export to export:
1 + 2 = 3 kWh Imported AND 1.5kW Exported

I have seen meters and solar-loggers use option A and more recently meters doing option B.

What is 'right'? I can't seem to find where this calculation is specified in IEC 62053 - but I don't have $1000 to spend getting each part of it, which may or may not have the calculation specified.


texts: interfacing external push button to msp430 using energia

texts:
I am writing code in Energia using the mso430g2553 launchpad and an external pushbutton with a pullup resistor. The code should simply display the state of the button on the serial monitor, 1 for pressed, 0 for unpressed. This is the code I am using:

int pushButton = 5;
void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
// make the pushbutton's pin an input:
// NOTE this is different from the on-board pushbutton
pinMode(pushButton, INPUT);
}

// the loop routine runs over and over again forever:
void loop() {

// read the input pin:
int buttonState = digitalRead(pushButton);
// print out the state of the button:
Serial.println(buttonState);
delay(1);        // delay in between reads for stability
}

This is the circuit configuration I am using:

My problem is that when I run the program, I always get 0 no matter if the button is pressed or not. It seems like the program is not reading the input from the button, or I connected the button wrong way. However I can't seem to find the problem, I tried turning the button for 90 degrees and I connected opposite legs of the button to ground and to the pin. Would a solution be to add a debouncing capacitor maybe? Any help would be much appreciated!


texts: difference between output resistance, ro, and finite output resistance Ro?

texts:
What is the difference between the concept/meaning of output resistance, ro, and finite output resistance Ro in context of a circuit with MOSFETS (ie. a MOS current mirror)?

thanks


texts: Best way to do I2C/TWI over long distance

texts:
I have a project that requires to do I²C/I2C/TWI over a long distance (30 to 40 meters). I've seen some people suggesting lowering the clock-rate to somewhere around 500 Hz, to mitigate the effects of the capacitance of such a long line I assume? The components I'm using require at least the standard 100 kHz clock-rate. I did some further research and found among answers to another question a suggestion to use a P82B96 level shifter. In the datasheet they give examples of using them on lines of even 100 meters:

I've come across another way of shifting levels through a breakout board from adafruit, which is just a mosfet (bss138) with two pull-up resistors (one for each side/voltage). They got the idea from an application note from NXP (AN10441), and two of the channels on there could be used like this:

Now I wonder: which solution is best? Or is there something I have overlooked?
And also, is 5V enough to ensure a good connection? Would there be an advantage to using an even higher voltage like 12V?


texts:
How does one go about creating a board file for a board with both "normal" PCB material, and flex materal? I have a project where I want the PCB and a flex bus to be seamlessly joined, like: http://www.globalsources.com/gsol/I/Rigid-flex-PCB/p/sm/1055505035.htm

Do you suppose that is one board file? Is the bus defined as a separate part, or is it PCB with different attributes?

I realize that different fab houses may take different schemes for doing this in board files, and there are clearly different kinds of flex fabrication, but I'm wondering if there is a typical or obvious way this would be done / not really sure where to start.


texts: I'm trying to create a model of a thyristor in the Altium 16 schematic library. I can't for the life of me figure out how to rotate a pin at 45 Degrees for the gate. My only options are in increments of 90 degrees. Any ideas?


texts: Altium PCB Layout: Does each pcb footprint and trace segment have a unique identifier. Which stores information about at what time it was laid out?

texts:
Is there any information about when an element is placed on the PCB file in Altium?

A unique chronologically generated ID maybe?


texts: Industry Values for Beta (β) in BJT current amplification

texts:
I recently completed a lab involving the use of BJT's and as part of my post-lab analysis I was curious at looking in to the max/min values of β in current amplification (Using formula would obviously yield infinite possibilities)

\$β = {I_{C} \over I_{B}} \$

I was having trouble finding a source on what values are common.


texts: Question about long-term support for legacy board designs

texts:
This question is summarized from a discussion on the Electrical Engineering StackExchange chat.
It is reproduced here in hopes to generate a discussion with long-term value

Question for anyone with experience with long (> 30 years) life cycle product design:
Do you generally design keeping in mind possible obsolescence / discontinuation of key parts within the life-cycle of the product?

Specifically, if a pin-compatible equivalent for a specific IC is no longer made, how is that planned for? Not every semiconductor manufacturer does lifetime buy notifications by package, and some manufacturers simply fold up and disappear.

The context here is of a product for which my client has over 100k PCBs in inventory, and more than 2 million devices deployed over 30 years. A couple of the key parts used on the board no longer exist, and near equivalents are all SMT. All ICs on the original boards are DIP and socketed. Some of the ICs in question are obsolete analog continuous-time signal processing parts, the rest are digital logic and thus easily substituted by equivalents, ASICs or MCUs depending on complexity.

There's a repair workstream (industrial product, 20 to 30 year serviceability warranties), and there is a production workstream (repeat orders, thousands of boards per year).

Respinning the board, while an ideal suggestion, is not an option in this case, as the Purchases department of the end-customer would consider a base PCB change as a "new product", hence requiring evaluation of competing vendors, and renegotiation of the contract - This will trigger a fresh tendering process and potentially loss of 10x millions worth of annual business for my client, to a competitor.

Current repairs of customer-site devices are all done by manual reworking in the field, the device is not allowed to be brought back to a workshop. Replacement of boards does happen, but the "new" replacement board absolutely must be identical in PCB layout to the one being replaced, as the end customer does not take kindly to any changes.

A proposal being considered, though yet to be validated with the end customer's purchases team, is replacement of DIP ICs with identically sized little PCBs with pins, plugged into the DIP sockets on the main board. This is intended to reduce field-work risks and time.

So, back to the question: What are practical EE experiences in planning for such product lifecycles and associated challenges? Great ideas for "next time" are also welcome.


texts: Are BLDC motors permanent magnet motors also?

texts:
I have to buy a BLDC motor and I was expecting it to be a permanent magnet motor and also when I read on internet link
Where it was mentioned that BLDC motor are permanent magnet motor.
But when I contacted the seller if it is a permanent magnet motor or not they said it is BLDC motor not a permanent magnet motor.
I would like to know which between the two is correct.


texts:
So I am basically just trying to figure out how long a battery-powered hair dryer would last to see if this would make sense as a concept project.
The best energy density I found to reasonably fit inside a hair dryer would be using 4x 2170 Lithium cells.
Spec Link
I'm just not sure how to calculate the energy draw on nichrome wire. (Unless there is a better heating element alternative) The specs usually give the highest Watt rating of the wires, but what specs will I need to include in the equation to calculate battery life?
I am assuming that the actual amount of heat generated will depend on the rate in which you draw power from the batteries.. my brain is hurting!


texts: Does the positive pole of an an electrolytic capacitor act as a cathode when discharging?

texts:
As far as I know, the anode of a polarized device is defined as the location where the oxidation occurs. For a galvanic cell, this means that it corresponds to the negative pole, while for an electrolytic cell it should refer to the positive pole.

Since a battery acts as electrolytic cell when being charged and as galvanic cell when being discharged, this definition explains why the relation between poles and electrodes depends on the operating mode.

I would have thought that this could be directly transferred to electrolytic capacitors. In many data sheets I have looked through, however, the anode is simply referred to as the (+) pole without further mentioning of the operating mode.

Usually, it is even stated that the anode is made from some kind of metal, which means that it has to be fixed. Why is this the case? Doesn't the role of electrodes change when switching from charging to discharging?


texts:
I am currently building a bldc motor and am trying to gauge the amount of force the coils in my motor would need to generate. In order to move a desired load - to a particular speed.
Without taking losses or friction into consideration. Can I use the moment of inertia to ball park the amount of force required by the coils to achieve this? For example - I have a 16inch diameter Rotor which will have a 7kg load uniformly distributed to it. The RPM I would like the motor to operate at with this load is 3000 rpm. I am also not to worried if this takes 1second or 60seconds to achieve.
Can I Use...
( 1/2 * m * r^2 ) * angular acceleration = to find this force?
Secondly - if I can use this formula. Would this be the force needed by a coil - a phase - or in sum overall from all coils?
Or is this the wrong formula/way of approaching this type of problem?


texts: Why does the frequency of carrier signal not matter when we impose the original signal on it?

texts: I know we use modulator to change  the frequency of  original wave, thus reducing the size of antenna. As I understand  the frequency of carrier signal does not matter . But I don't understand why.


texts: Strange BJT configuration, working as a diode?

texts:
I was looking at an old schematic and I came across this strange circuit for low voltage detection section of a larger circuit (not shown). The operation of circuit is straightforward, Q1 is normally conducting and the voltage divider R2/R3 set a threshold voltage, above which, Q2 conducts. When Q2 is normally conducting, the Q3 is off due to the voltage divider R1/R5. Upon depletion of power source,R2/R3 can no longer provide the base voltage for Q2 and it turns off. The Q3 turns on and discharges C2 to provide a pulse.
Does anyone know why Q1 is used in this configuration without the emitter connected to anywhere?


texts:
I am just very confsed about how to do these sort of questions where they give you a point in the middle of two charges. The farthest I've gotten in questions relating to coulomb's law, is using the formula \$F = {kq_1q_2 \over d^2}\$ to work out one of the unknowns when given two variables. Can someone please explain how you would do a question like this:

Two point charges of charge -2 µC and -3 µC respectively are separated by a distance of 15 cm. Point X is positioned at an equal distance away from each of the charges.

    a. Determine the net electric field at X.
    b. Find the point of equilibrium between the charges.


texts:
At school I was told "Never use a LED without a resistor (before or after the LED)!".

Why is that?

If I have a 2V LED why can't I simply use a 2V power supply?

Why should I choose a 3V (for example) power supply and put a resistor in front?

And how to calculate the resistor value?


texts: Baseline PIC12F509 BTFSS Instruction Issue

texts:
****Update Scroll Down For More Info****

I've been experimenting with a PIC12F509 and have been writing some simple code in assembly I'm using the internal 4 MHz RC oscillator.

I have set GP3 as an input (MCLR is off) with a 10k pull up resistor connected between GP3 and VDD. A push button switch then pulls GP3 to ground to turn on an LED connected to GP1 which is set as an output the LED is anode switched.

The following code doesn't work as expected for some reason. I would expect the program to loop with the LED off until the push button is pressed and GP3 goes low at which point the LED will turn on but not turn off. Instead it turns on as soon as the PIC is powered.

The btfss instruction should skip the bsf instruction to set GP1 high as long as GP3 is high.

;***** MAIN PROGRAM *****************************************************

;***** Initialisation
start
    movlw   b'111101'       ; configure GP1 (only) as an output
    tris    GPIO            ; (GP3 is an input)

;***** Main loop
main_loop
    btfss   GPIO,3
    bsf     GPIO,1
    goto    main_loop
    END

I thought it was because GPIO was initially undefined but adding clrf GPIO after the tris instruction didn't solve the issue.

Is it because as the PIC is powering up (this small circuit is being powered by the PICkit3 programmer) GP3 is initially below the logic high threshold for a split second which causes the bsf instruction to be executed?

Of course by adding two more lines like this:

main_loop
    btfss   GPIO,3
    bsf     GPIO,1
    btfsc   GPIO,3
    bcf     GPIO,1
    goto    main_loop

The LED will turn on and off with the switch.

While the previous code isn't very useful I'm curious as to why the LED is turning on.

Thanks In Advance.

**** Update ****

I tried some new code that toggles the LED on and off with a 20 ms debounce subroutine as shown. I removed the 10k pull up resistor and enabled the internal weak pullups as seen in the code.

start
movlw   b'111101'
tris    GPIO
movlw   b'10111111'
option

main_loop
waitdn  btfsc   GPIO,3
goto    waitdn

movf    sGPIO,w
xorlw   b'000010'
movwf   sGPIO
movwf   GPIO

movlw   .2
pagesel delay10r
call    delay10r
pagesel $

waitup  btfss   GPIO,3
goto    waitup

movlw   .2
pagesel delay10r
call    delay10r
pagesel $

goto    main_loop

END                       ; directive 'end of program'

This code also behaves in the same peculiar way the LED starts in the on state when the PIC is initially powered on. It can then be toggled on or off with a single press and release of the switch.


texts:
Hi what are the safety precautions of high tension wire during rainy season?

what is the precaution need to do, if the wire get cut and fallen in the road?


texts:
Assume we have a field effect transistor.We connect the source terminal to the anode of a battery and the drain terminal to the cathode of a battery.We connect the gate terminal to cathode of a battery.Now the electrons will start flowing from the gate terminal towards the p type region.

Due to the attraction, the electrons will start flowing towards the insulating material,though creating a bridge for electrons from source to go to drain.

Question:

Will the depletion region of the p type region and the drain be destroyed?

Help appreciated.


texts: Led ON on Spike Guard Even When Switch is OFF

texts: I have this spike guard and it's middle led is ON even when the spike guard switch is off. I can see there are various combinations of the led and their meaning. But I see the middle led on when the switch is OFF. Can anyone tell me if anything is of concern here?


texts: How do I drive a stepper motor using an LM555 timer?

texts:
I'm trying to drive a stepper motor's driver (QuadStepper) with an LM555 timer circuit, however the logic levels are known to be 5v compatible. While the driver has both 3.3 and 5 volt compatibility, I need to use it at 3.3 volts.

How can I use a 555 Timer (or other simmilar IC) to drive the stepper driver with 3.3. volt logic levels?

EDIT: I only need the timer to drive the step input, all other inputs will be driven from a micro controller.


texts: Can't trigger 5V,10A relay using the output from a ESP8266 node MCU?

texts: I'm currently working on a project where I turn off the ac appliances when the input signals of the relay get high. I'm using a 5V 10A relay and ESP8266 node MCU. But the problem is controller is unable to switch the relay. What should I do? Please help.


texts: What happens if I give 5V to the discharge pin, threshold pin and trigger pin of 555 without giving power at pin 8 and grounding at pin 1?


texts: Chosing microcontroller for a sensing project

texts:
I am upon chosing a microcontroller for a PCB board project. MCU collects data from capacitance to digital converter (from a capacitance sensor) via I2C and I would like to pass that data to a host PC - via USB seems to be the most convenient. In the future there may be some filtering done on the data in the MCU, but in my project i focus primarily on the hardware part.

I am fairly new to the whole embedded/hardware design. On my research I found out that MSP430 may fit in my needs but I am not sure, there are so many of them even in msp430 family.

My main concern is programming, because as I understood in many MCUs, additional hardware is required for programming/debugging. And the examples I found all use some kind of development board - I need to develop complete standalone system on PCB board without any unnecessary components. The MCU part of the board should (there are 3 parts - electrodes, cap-to-digital converter, mcu for communication) not cause excessive electromagnetic interference.

I am looking for some guidelines, because I can't seem to find information on what I need.


texts: What components can an FPGA replace/emulate?

texts: I've been under the impression that FPGAs were merely, well, field-programmable gate arrays, but I've seen some example schematics with resistors, capacitors, and such in them. As such, can an FPGA serve only as a replacement for 7400-series ICs, or also for resistors or other passive components?


texts: Calculating the output power from an Amplifier

texts:
This is not based on any particular hardware. I am trying to understand the theory behind it by doing tutorial questions from my uni, I have completed the question but don't understand the approach taken by the worked solutions.

simulate this circuit – Schematic created using CircuitLab

Above schematic is my representation of the circuit, bascially \$i_1(t) = 0.1\cos(2\pi f)\$, f= 10 Mhz and the Amp has a dB gain of 25 (50Ω matched) and the load is 50Ω.

we are asked to calculate the output power, so i simply worked out the RMS current 0.071 and times it by R1 (50Ω) to work out the input power (0.25 W) and using the gain (G=Pout/Pinput) \$P_{out} = P_{input} \times G\$ (316.2 ratio form) making Pout = 79.7 W. However in the answer sheet they do the same steps except for \$P_{input}\$ they use \$P_{input} = (I_{rms} \times R_1)/4\$.

I don't know where this four has come from and why \$P_{input}\$ needs to be divided by four???

Nb: \$P_{out}\$= power out; \$P_{input}\$ = power in


texts: Why embedded systems are called as embedded systems?

texts:
In most of the times we try to guess the meaning of terms from its name or title itself. For example diodes are electronic devices with two (di) electrodes connected together. Resistors are electronic components which resist flow of current.

Likewise I think, microcontrollers or embedded systems should also have meaning hidden within the term itself.

So

-why embedded systems are called as embedded systems?
In oher words, What is required in the system to be termed as Embedded system?


texts: Feedback factor of Op-Amp based Colpitts Oscillator

texts:
Above is the picture of the oscillator for which I am trying to calculate the feedback factor of the oscillator at resonant frequency. The forward path gain is $$A=R_2/R_1$$.

I want to calculate the feedback factor to calculate the loop gain, so that I can derive the condition for oscillation, and set appropriate values of A.

So for analysis purpose I redrew like following:

So the feedback factor can be: $$\beta=V_{out} / V_{test}$$.

But given the values of capacitors, and inductor in the first diagram, and setting frequency at resonant frequency, I am getting an insanely low value of feedback factor (~10E-30). Clearly I am doing something wrong in the analysis phase.

Can someone be kind enough to guide me here. Is this the right way to calculate the feedback factor? For clarity purpose, I have not put the calculation steps here.

Also I will replace 741 with a very high speed Op-Amp during implementation level.


texts: Arduino Nano + L239DNE + external power supply

texts:
I want to build something with arduino and DC motor, so i'm using L239DNE to control speed and direction of the DC motor. Using some tutorial I hooked up everything together, but motor is just not giving out full power, connecting it directly to battery without IC makes it few times stronger.

So thinking that something is wrong with Arduino code or my layout I connected motor to IC using only battery, connected IN1 and ENABLE1 to VCC and IN2 to GND - still with same results, motor spinning much slower than it should.

This is my scheme now:

simulate this circuit – Schematic created using CircuitLab


texts:
I was wondering if a 3 terminals magnetic tunnel junction can be implemented, as in the Figure.
On the bottom I have a normal metal (NM), on the top a magnetic junction (FM = ferromagnet) and I can simultaneously apply a voltage between 1-2 and 2-3. I know there are many experiments on this geometry but they inject a current between 1 and 3 and AFTER that they measure the tunnel resistance. This is how MRAM works.

Basically I would like to have a kind of transistor but with metallic components.

Do you know other references that explain what I would like to do?

Thanks


texts: How exactly does a capacitor discharge its charge?

texts:
When an empty (discharged) capacitor is connected to a battery, it slowly charges up as one plate fills up with electrons, while the other plate has electrons drawn away from it towards the positive terminal of the battery, resulting in one plate having a positive charge and the other having a negative charge.

However, what happens when a capacitor discharges itself? Do I simply assume that the negatively charged plate returns its electrons to the negative terminal of the battery while the positively terminal returns electrons to the positively charged plate, resulting in an end state where both plates of a capacitor are no longer charged (neutral)?

If so, how am I able to power things like an LED with a capacitor, since a LED or any diode only lets electricity flow through it in one direction?

E.g. If I connect a diode to a capacitor (in series), depending on how I place/orient the diode, the capacitor would not be able to charge/discharge?


texts: What would prevent DTMF tones being recognised (modem to modem)?

texts:
A bit of back story: the SEGA Dreamcast had a dial up modem which was used for online play, in the absence of dialup ISPs it's now common practice to directly connect the DC to a USB dial up modem and route the connection through a PC via ppp.

Some revisions of the Dreamcast require a voltage on the line to dial out, and in this case a solution was found by inducing a voltage by wiring a 9v battery and resistor into the phone line. (http://dreamcast.onlineconsoles.com/phpBB2/guides_pcdcwin98.php#10)

However even still it appears some USB modems don't recognise the signals from the Dreamcast. For example if I connect a standard phone to the line in place of the Dreamcast, the tones are recognised by the PC, but the dialling of the DC isn't recognised at all!

What could cause this to happen? Why would one device generate DTMF codes that work, and another device not? If I connect a phone directly to the DC I can hear the tones being dialled but there must be some difference between those generated by the DC and those by the phone.

Also, it seems that even if I blindly answer the Dreamcast (by sending the ATA command to the receiving USB modem) the Dreamcast doesn't recognise the call was answered, perhaps that's related and this is more than just the DTMF tones...

I'd appreciate any suggestions that might help to get these two modems communicating!


texts: Analog circuit to check if an audio signal is present?

texts:
On the project I am working on, I have 3 line-level audio signals, and I need to determine on an arduino if a non-silent signal exists on each line and act appropriately (in my case, "unplugging" a device from mains voltage). My first over-engineered idea is to amplify each signal, add a dc bias, then do some expensive operations on the arduino to determine if an audio signal exists.

Each audio signal is a mono signal consisting of a ground wire and an AC, low voltage, audio wire.

Now I don't remember much from my analog class from university, but my gut instinct is this can be simply done using analog componenets where I can feed the result (an psuedo digital signal where high would be above voltage x and low would be below voltage y) and do much easier computation on the microcontroller to determine if a signal exists.

The frequency of the audio signal is between 10 to 22,000 Hz
The peak to peak voltage (of the consumer level line level) is 894mV, but the circuit should be able to handle as low as 10mV peak to peak

Any ideas?


texts:
First of all, I am new to the area of electronics and I want some help to stuff that may sound to you a little obvious.
I've seen a circuit using transistor that is used as a NOT logic gate, as in the following image

I understand the way the circuit works. But what bothers me is the fact that the analysis of the specific circuit is based on the fact that the output of the circuit(denoted by A with a dash) has no current flowing through it. But when I want to use that NOT gate, I must connect it to an external circuit(like an LED circuit) to see the results, which means that an amount of current will flow through output as well.
I've seen that kind of analysis where you consider the current of the output to be zero in many other circuits. What I thought is that the external circuits that we connect to it's output has infinite input impedance, meaning that current is very small, practically zero. Following that, I found as a solution to the problem the use of a buffer. In other words, we can use the following buffer circuit

which gives us infinite(very high) input impedance.
Combining the two circuits we have the following:

Is that a correct solution to the problem?


texts: A question about timer resolution and frequency range

texts:
In a manual of this data-acquisition hardware the timer output is state as:

"One timer output channel(32-bit)"

If a timer is 32-bit, what else info is needed to calculate the max and min freq. timer can produce(as a PWM output)? Should we need the processor speed?

edit:

I found more info about the timer output:


texts:
I'm building an 18650 phone charger which follows this tutorial.

The 18650 battery is connected to the TP4056 module.  Then I have that connected to a boost converter to step up the 2.8V - 4.2V (from the 18650) to 5V.  The boost module has a USB output which I can then connect to my phone.
My problem is that after connecting my phone, I can confirm a correct 5V but it only draws like 60-80mA (confirmed with my multimeter.)
I initially thought maybe I had high wire resistance but it still doesn't draw much current.
What am I doing wrong here?


texts: Protect N-MOSFET against short circuit and overload

texts:
I want to connect a PWM pin from an ATTiny to a N-Channel MOSFET in order to fade some LEDs, or switch the speed of a motor.Three wires are connected to my board: VIN, a GND and the OUTPUT GND.

Questions:
1) What should I do to make sure that my MOSFET, Micro Controller and the LEDs are protected against short circuit AND voltage overload?
I want to minimize the damage if any of the wires (VIN, GNDs, OUTPUT) are connected accidentally to each other, or if a high voltage/current is flown into the circuit.

2) Also, should I put a pull-down resistor on the PWM pin?


texts: How susceptive is an inductor to frequency and current?

texts: According to Coilcraft - Testing Inductors at Application Frequencies the inductance of a coil changes with frequency and current. Most datasheets don't give a frequency-inductance plot and current-inductance plot. Is there some rule/guideline to estimate the inductance at circuit frequency and circuit current given the test frequency and the max/saturation current?


texts: Send action signal via radio using energy generated by piezo

texts:
I have an idea going on in my mind but I am not sure if it is even feasible, so please be patient!

Here is my problem. I have a set of chairs, say several dozens. I would like to be able to monitor at any time which chairs are occupied (i.e., someone is sitting on them), and I would like to do this in a way that is at the same time cheap and easy to maintain.

After thinking about some complicated and involved heuristics with cameras, proximity sensors etc, I figured that probably my best chance would be to detect pressure under one of the chair's feet. It should be reasonable to do something like this: there is a significative difference between maybe a few kilos of an empty chair and the, say, 50-90 kilos when someone is sitting on them.

I gave it a try with a force sensitive resistor and a Spark Core, and it worked fine. Actually, I was expecting that! When some pressure is detected, the Spark Core will send a signal through WiFi and I can detect if someone is sitting on the chair.

This solution, however, is neither cheap nor maintainable: a Spark Core can cost up to 40$ and I have to power all this! Since I don't want my users to stumble upon power chords, all the chips should be powered by battery, meaning that batteries need to be charged somehow, and so on, and so on.

So I thought: is there a way to make this more simple? Here is what I would like to do:

When someone sits, I generate some energy from the change in pressure (e.g.: piezoelectric?)
I use that energy to just blindly send out a signal (that doesn't need to be as complex as a WiFi signal, it should just be a simple signal since I want just to be able to tell if someone is sitting or standing up).
Some antenna receives that signal. It is sampled by, say, an Arduino or a Spark powered on a desk.

This, however, has some issues. First of all: can I generate enough energy to send out a signal? Moreover, can I make those signals different between each chair without the hassle of using some very complicated or expensive device? And... how could I do that?

I am definitely not an expert in electronics, so if you could make as few assumptions as possible, that would be great.


texts: How to modify a Minecraft ore lamp to be always on?

texts:
Santa was kind enough to bring a really cool diamond ore lamp for Christmas!:)

It's supposed to work by tapping it to turn it on, tap it again - it increases the brightness etc. The problem is that it shuts off really quickly and the tapping is really inconsistent, so I would rather have it just be always on and bypass the whole tapping thing altogether.

It works with 2 AA batteries and there's a switch to turn the thing on. I'd like to wire the switch directly to the LEDs, but if I remember correctly - I need to use resistors as well? Would anyone know what kind I need or maybe I can use the board to somehow utilize its components?..

Thanks and happy holidays everyone!


texts: How to calculate the properties of spiral antena?

texts:
I noticed some articles about analysis of Archimedean spiral antena. My understanding is that the antena of such type is a compact one and it  allows broadband performance.
To be more precise I'd like to understand pros and cons of the spiral antena defined by eq. in polar coordinates \$r'^2+r^2=t^2\$.
The spiral is very similar to Archimedean one at large \$t\$ and it is similar to Galileo spiral at small \$t\$.
You can see the picture at mathcurve web-site.
What would be advantages and disadvantages of the antena? Any possible application for such spiral in electrical engineering?
Please note this is my personal interest/hobby like DIY.


texts: Do 64-bit CPUs consume more power than 32-bit ones?

texts:
In this lecture about efficient computing for deep learning, the benchmarks show a 3-fold increase in power usage between 8-bit and 32-bit addition operations. Between 8-bit and 32-bit multiplication, the factor is 15. The same happens for floating-point operations, with a smaller effect.

Does this mean that 64-bit CPUs consume more power in general than 32-bit ones, or have I misunderstood the results? (It's not clear if these figures are due to larger numbers being manipulated more often in deep learning, or to the operations themselves consuming more energy.) Can we generalize and say that a CPU with a larger word size requires more power?


texts: Maximum AND minimum duty cycle in SPICE converter simulation

texts:
I am modeling a Push-Pull Converter in LTSpice and implemented this for a simple voltage feedback PWM control. This works great and I have added a bit on the end that allows for a maximum duty cycle control, as shown:

What I'm noticing is that when the duty cycle gets set to something low by the feedback control - under 10% - it starts to drive the two switches unequally during periods, e.g. one will be on for 40% and the other on for 7%. I tried putting another voltage source set to 10% pulses connected to each control line via a diode, but LTSpice did not like that.

Is there a better way to implement both maximum and minimum duty cycle control?
Alternatively, if someone can tell me why the switches are being driven unequally that would also be helpful.

EDIT: I've included a screen grab of exactly what I'm talking about:
Sometimes the feedback will drive one switch for 40% and the other for ~7% in the same period and that is not acceptable. I am looking for a way to have the control say "this period the duty cycle will be 10%" for example, and force BOTH switch driving signals to be that duty cycle for the whole period. I have been trying something with the feedback signal as a reset for an SRFlop and "carving out" the off-time, but it's not working correctly.


texts:
How to connect a real external speaker through a classic Jack connecter to the Board of Education?

So that I can send it FREQOUT instructions?

(instead of using the piezo-electric component)


texts:
I have a NCP1117 5V voltage regulator that is on an Arudino Mega. The Arduino Mega, with all of the necessary electronics parts for the project, draws around 200mA when operational. When using a battery that has a maximum voltage of 12.6 Volts, the voltage regulator gets very hot but it works. (Case temperature of 96 degrees Celsius)

The goal of the project is to use a 4S LiPo battery which will have a maximum voltage of 16.8 Volts. This overheats the voltage regulator and it thermally shutdowns (This happens at 175 C according to the datasheet).

Is there a good way to cool these devices. It is a SOT-223 package on an Arduino Mega board. I have attached a small 5mmx5mm heat sink on the top, and it did help the temperature but not enough for the required 4S battery voltage. It also does not make the best contact due to the low surface area on the top of the device.

I don't like the idea of having a fan so is there a good way to passively cool this device? I was thinking of adding an additional heat sink on the bottom of the board underneath the voltage regulator. Just put it on the bottom solder mask. Is that just a dumb idea or is there a better way to cool these?


texts:
I'm a computer science student who is trying to make a portal augmented reality version of the Oculus.

I'm looking for a power source that will is both portable and able to deliver 5V at 1.5A for an extended duration (at least 2 hours). Is this reasonable and where would I be able to find such a power source (I'm in the Netherlands)? I looked online and it said that you can use a USB port to provide 5V, however it warned not to go beyond 0.5A which is not enough for the Oculus (I do hope I went to the right site if not please tell me which one would be correct).

As I will be depleting this battery regularly it would be nice if it was rechargeable.
In this case, portable means a weight limit in the order of 0.5 kg and a size limit mainly in dept of no deeper than 5 cm, longer than 20 cm, or wider then 15 cm.


texts: Can I make a ammeter using a voltmeter and ohmmeter that would work in parallel to the device?

texts:
I had this small question today when working with an ammeter. Since an ammeter must be in series of the circuit, I had to constantly break the circuit to take current readings. Whereas, when using the voltmeter, just placing the probes on the device to take an immediate voltage reading works.

Since all devices follow ohm's law, assuming a purely resistive circuit, can't I place a voltmeter and an ohmmeter in parallel to a device to take its current reading?

If yes, why don't we do this often and use ammeters? If no, well why not?


texts: Why do smd components in eagle have padding?

texts:
I'm new to eagle and I don't understand why there is a small padding to the left and right of some SMD components (for example the 0402 cap in the image).

Having the physical board in my hand ... the padding seems just wasted space.

PS: the library used in the example is SparkFun-Capacitors

Thanks


texts: Advice regarding Remotely Operated Vehicle (ROV) control scheme?

texts:
Please let me know if this question isn't specific enough, I'll be happy to clarify. I am looking at various options for a control scheme for my underwater robot. I am in school and it is my job to design the control systems that the robot It uses 12V bilge pump motors for propulsion. In the past, I had used some relay boards that another member of the team had designed. But s/he is now long gone and to be honest the boards were poorly designed and we had a huge amount of problems using them. So this year, I'd like to use a microcontroller or similar device to control a set of relays (or equivalent) to power the 12V motors. This will make it much easier to change the direction and behavior of the motors without having to physically modify the hardware.

However, I only want to do this if it is practical.
Currently, this is what I am playing with. I have a Beaglebone Black hooked up to a Sainsmart 16 Channel Relay Board. At first this seemed like a good way to do things, there are nice GPIO libraries for the BBB available and I have experience programming shell scripts and Python if I wish to use that GPIO library. However after doing some testing I'm starting to question the idea for a number of reasons. The BBB GPIO pins (some of them at least) seem to float high on boot, so in my script I would need to set all of the pins low upon boot. Then I have the issue of taking input from whatever controller we are using, we have used some generic joysticks for the past few years and these have worked well, but I have no clue as to how to parse the input from these, if the input is say TTL 5V and is not safe for the board, etc. Not only this, but I had to build a seperate driver circuit to trigger the relay as the 3.3V off the GPIO was not sufficient.

TL;DR Joystick/Other Input --> beaglebone --> Relay Driver --> Relay --> Motor seems too complicated , and leaves room for error, leaving me with the same problems I set out to solve. Basically my question is: Does anyone have any constructive ideas or advice on how to implement a software based solution to controlling 12V bilgepump motors and accepting input from some generic joysticks (or another input device if necessary.) I chose the BBB since it has diverse outputs at it's disposal. I am good with moving to another micro controller or input device if it will simplify the control design. Thanks you for your help!


texts:
I know from V=IR that zero current means zero voltage drop, but what if we don't have a resistance?
let's consider the following example (Logical and made with diodes) :

I know that if Va=0 or Vb=0 all the current will flow to the load, and there will be no current that passes to the right (where Vs is) but why will Vs be zero? What is Vs? (Vs is output voltage, doesn't mean a lot to me), can any one help me please?
Thank you


texts: is flip flop a synchronous or an asynchronous sequential circuit?

texts:
i have read in my text book that : " A flip-flop is the simplest synchronous sequential circuit. "

but it is not convincing at all since we cannot analyze or build a flip flop like a synchronous circuit .

even i asked a question about how to design a flip flop with having it's truth table .

designing a sequential circuit by having it's value table?

and the person who answered (Francesco Conti) claimed that flip flops are asynchronous circuits ?

what type are flip flops ?

EDIT
by flip flop i mean an edge triggered D flip flop .

the best definition i could find of synchronous and asynchronous circuits is here:
http://www.ee.usyd.edu.au/tutorials/digital_tutorial/part3/sa-op.htm

it states that :

  Synchronous sequential circuits change their states and output values at discrete instants of time, which are specified by the rising and falling edge of a free-running clock signal

  In asynchronous sequential circuits, the transition from one state to another is initiated by the change in the primary inputs; there is no external synchronization.

After Reading the proper answer i think we can say that :

if you look at a D-flipflop as a whole it's function IS synchronous

BUT since it's the building block of synchronous circuits obviously it's not possible to design it like a synchronous circuit (since then we would use FlipFlops to design FlipFlops) so it's design is like asynchronous circuits and has no algorithm.

to sum it up since the flip flops are the elements that make the transition from asynchronous to synchronous possible ; (in other words they are the building blocks of the synchronous circuits ) then they are some where between synchronous and asynchronous circuits .

their design is asynchronous since they are the first synchronous circuit to be made.(so they must emerge from asynchronous circuits and asynchronous design)

while their function is synchronous .(they change their states and output values at discrete instants of time)


texts: Register 2 peripheral UUID with 1 service, NRF52

texts:
I have 3 nrf52 boards: 2 act as peripheral and 1 as central device.

I want to register 2 different UUID's for the 2 peripheral devices, which contain the same service (0x0001 - NUS for example).
I add UUID's using sd_ble_uuid_vs_add(..) function and set common_enable_params.vs_uuid_count = 2. After that I register service with ble_db_discovery_evt_register(..) function.

The problem is - I get data from only from 1 peripheral (from UUID, that was registered using sd_ble_uuid_vs_add(..) first).

How can I register more than 1 peripheral UUID with the same service?


texts: Calculate the potential and current in the transistor circuit

texts:
I'm stuck on a question where I need to calculate the potential Vx and the current Ix in the circuit below. I have managed to get some equations, but the question does not mention what the amplification factor hFE is, only that it is "high", so I can't solve the question with what I have.

Any help is appreciated!


texts: DDRx Memory: Memory Clock vs I/O Bus Clock?

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When referring to DDR/DDR2/DDR3/DDR4 memories, I am not able to understand the difference between memory clock and I/O clock.

As per: https://en.wikipedia.org/wiki/Double_data_rate

DDR-200 - Memory Clock = 100 MHz, I/O Bus Clock = 100 MHz;
DDR2-800 - Memory Clock = 200 MHz, I/O Bus Clock = 400 MHz;
DDR3-1600 - Memory Clock = 200 MHz, I/O Bus Clock = 800 MHz;
DDR4-3200 - Memory Clock = 400 MHz, I/O Bus Clock = 1600 MHz

Could someone please explain what is memory clock and I/O bus clock here? Because I understand that memory controller provides only a single clock to the memory chip, which is half that of the data rate.

Thank you.


texts: How to reduce sensitivity of a Hall Effect Sensor?

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In a mechanism with strong magnets, I want to use a Hall Effect Sensor to get the position of the magnets. The sensor move between two magnets in inverse polarity, so the field is minimum in on side, Zero in the middle and maximum in the other side.

Hall Effect Sensor

Searching on internet, Hall Effect Sensors goes from around -0.07 to + 0.07T, but that is too sensitive and the sensor is saturated most of the time (0V or 5V). (I made tests with the Honeywell SS495A.)

How could I reduce the sensitivity of the Hall Effect Sensor to record stronger magnetic fields?

Note: Because of the design of the device, it is not easy to move the sensor further away of the magnets.


texts: I understand the purpose of the minimum permissible load (for contact wetting) but I want to know the relationship between the voltage and the current. For instance, the above table states that the minimum load is 100 mA at 5VDC. What if I apply 10 mA but at 220VAC? Does that satisfy this condition?


texts: Very new to all this, however my dumb self touched a live wire, my skin was very dry and it did burn me. The wire was connected to an 18650 battery that says it is "2600mAh 3.7v" I know that even 1 Amp is fatal. However I am not dead, yet. Should I be concerned and visit an ER?


texts: HC-SR04 Distance Sensor Trigger Signal on 2.5V Voltage level gives no reading

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I am using an Arduino on a breadboard setup with an ATMEGA328p MCU. The whole circuit is designed to work in a low-power state and is powered using a 3V (Nominal) voltage Coin Cell. The HC-SR04 is getting a stable Power Supply of 5V from another source (Grounds are already common). However, the issue is that triggering the sensor from the MCU gives no output reading and the distance is returned as 0. I checked the voltage level on the Trigger Pin and found it to be 2.5-2.6V

Since the battery I am using is a coin cell so I suspect that the voltage is being dropped from the nominal value of 3V to 2.5V and the HC-SR04 demands a TTL pulse on the Trigger Pin. Is it not working because it's not being properly triggered by the 2.5V level Pulse? I checked some resources and they mentioned that 2.5V is within the High Level Margin of the TTL signal, so 2.5V level pulse should be able to trigger the sensor or my assumption is wrong?


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Question 5 Part A Only. I tried converting polar form to rectangular form to add the AC voltage sources and converting it back to polar form. I got the angle (10.09 degree) right but not the r-value and I still can't seem to find my mistake.
(I use my calculator for polar to rectangular form conversion vise versa)
My working is on this link:
https://documentcloud.adobe.com/link/track?uri=urn:aaid:scds:US:51d470e1-906c-42f2-8a7c-aae15008c33d
Answer (5a): 23.568∠10.09 degrees


texts: cable losses per meter (voltage > 400 and frequencies [50 Hz ... 60 Hz])

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If I compute

I * I * R

I obtain the loss of the conductor in Watt. Is this per meter similar to the dielectric loss (see IEC 60287-1-1)?

I am also wondering about the loss factor of sheath and screen (see IEC 60287-1-1). Do I multiply this factor with the conductor loss (I * I * R) to obtain the loss of the sheath and screen?


texts: Wiring LED Lights Together and Running off of 3V Power Supply

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I've looked around this forum but not found the answers I'm looking for.  I've found some similar questions being asked, but this project is a bit specific so the answers were not really applicable to my situation.  Also, I am very much a novice at this kind of thing.  Maybe some of you experts will be able to help.  Here's the background then...

I've got four decorative letters (one is actually a heart) which hang on the wall and are lit with white LEDs. Two have 10 LEDs, one has 11 and the other 12, so 43 white LEDs in total.  Each 3V unit is powered by two 1.5V AAA batteries and each has its own on/off switch built into the battery compartment.

However, it's a real faff having to remove each unit separately from the wall twice a night, to switch them on and later to turn them off. The batteries don't last that long either and I seem to be constantly changing them.

So, in a moment of true innovation (for me anyway), I decided to mount them all permanently on a board that's painted the same colour as the wall and to wire the four 3V units in parallel to a 3V 1A mains power supply.

To complicate things slightly, I've also got four switches which are actually 12V car accessories (to switch on/off each of the units) and each switch also has a colored led in the rocker (1 x red, 1 x green, 1 x blue and 1 x yellow). I've tried connecting one switch to 2 x AA batteries as a test and the LED seemed to light up fine.

My questions are then, does this power supply sound like it would work okay with my LEDs and if so, how should I wire the units up?  I'm guessing each 3V unit should be wired to the power supply in parallel. But if that is the case, should I also put some kind of resistor in the circuit for each unit and if so, what value?

Sorry, I'm a bit of a novice at stuff like this so thank you in advance for any advice you can give.


texts: Why isn't derivative control used without proportional or integral control?

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Why isn't derivative control used separately in industrial controller designs?

One answer I read online was that derivative control is not used separately, i.e., without proportional (P) and integral (I) control, in a closed-loop system because:

  If the error is constant and non-zero, then the output of the derivative controller is zero. So it won't work satisfactorily.

Is this the only reason?