texts: When people say that the line voltage in the US is 120 volts, do they mean amplitude, Vpp or Vrms?


texts:
I have to make an ADC conversion with an ATXmega MCU, in an air quality application.

The input is a voltage divider between a voltage reference. The sensing resistor vary in relation to a gas concentration. I read the voltage between a load resistor and ground. Since the conversion is not high precision (12 bit) we don't want to wast any bit. The sensing resistor can reach the max value of 60 k: in this case the V on the Load Resistor will be at minimum.

The solution we found is to subtract this minimum voltage from the Vin with an op amp.

And now the questions: The voltage divider interact with the resistors of the diff op amp circuit (https://en.wikipedia.org/wiki/Differential_amplifier)?

Will it be useful to place a unity gain buffer on between the Vref_min and the negative input pin of the op amp?

Is this idea is achievable with a normal low noise op amp like this?

http://it.farnell.com/texas-instruments/tl072ip/ic-op-amp-jfet-pdip8/dp/1459704 ?

simulate this circuit – Schematic created using CircuitLab

Here the schematic. I have to put an unity gain buffer instead of "???" node?

Is the circuit ok?


texts:
I would like to make a Peltier project and in order to save a little bit of money I would like to connect couple of Peltier in series directly into the power line. As far as I have read I should treat it as a diode, therefore every element should be paralleled with:

1000uF 25V electrolitic cap
1 MOhm resistor

is this protection enough?


texts:
I'm in the middle of a project that requires writing software that would send some packets over Ethernet every N milliseconds. The ethernet wire would go from a computer to a switch, and then to the rest of the network. There is no back-traffic, so packet only go out, nothing goes in. This "idealized" situation was created to measure jitter (time variability) of the packets. For example, even though we expect a packet to go out every 5ms, it will actually leave the computer every 5ms +- w where w is random uncertainty (i.e. jitter).

I would like to measure this jitter by hooking a scope to the internal wires of an Ethernet extension adapter, recording the waveform and looking at when bursts of data (packets) are transmitted. I'm making lots of naïve assumptions about Ethernet in general and CAT5 specifically, and so far I'm failing to see anything meaningful except of every possible flavor of noise. Therefore, I have questions.

First of all, can I even assume that no signals other than my packets are constantly being transferred back and forth between my laptop and the switch?

Secondly, does my probing scheme work at all? Can I simply connect two CAT5 wires with such adapter, break it open, strip insulation off wires and hook them to a scope? If yes, which wires should I be looking at?

Finally, can my 100MHz scope even handle the stuff that will be sent over my 100 Megabit connection? I only need to see whether a burst is present or not, so I thought it would be fine.

Are there any other suggestions on how I may do this alternatively?

Cheers! = )


texts: Using a Shunt Resistor to measure current

texts:
Usually when we measure current, we have to break the circuit and place the ammeter in series.

However, if we want to make it easy to measure current at various points in a permanent circuit(for whatever reason), can we add very low resistances in the circuit at those points,, measure the voltage across them instead and use Ohm's law to find the current?

If the effect of those resistors is negligible, and they have no effect on the functioning of the circuit, is doing this ok?

edit: I can't think of a suitable title for this question, help on that would be appreciated as well:)


texts: What is the meaning of the difference between the Fourier transforms of a single pulse in these two cases?

texts:
In texts the Fourier transform of a single pulse is explained as below:

They always create the pulse from -T to T, and they always show the sinc function symmetric around the origin.

But in reality there is no -T(there is not negative time on a scope screen) and even when I take the FFT of a single pulse in a circuit simulator I get a sinc function only for positive frequencies not anything symmetric with negative frequencies.

Below the example circuit which outputs a single 1V pulse with a total ON time of 1ms:

And when I take the FFT of the above pulse I obtain the following plot in linear scale:

Mathematical description of the pulse and the Fourier transform is different than what I get in the simulation. What is the difference between these two?


texts: Arduino incorrect readings from analog pin

texts:
One of my analog pins, A0, on my Arduino Uno, is not giving totally accurate results. Where as one of the other pins will do a full 0-1023 in a certain use case, the problem pin only seems to be outputting around 50-730.

Is this pin getting interference somehow, or is it perhaps defective?


texts: Determine Y-parameters for given circuit. [Used Nodal Analysis]

texts:
I am trying to solve this circuit for past 3 hours, no success, so I am posting here.

simulate this circuit – Schematic created using CircuitLab

I used nodal analysis, I will go over the equations I got;

->To find y11 & y21 lets short V2 and apply a current source at V1,also after identifying nodes; we get

simulate this circuit

Now Equation for Vo;

I2-2io = (2/3)Vo - (1/6)V1

At V2, We determine I2 = -(1/2)Vo So Vo becomes;

2io = (7/6)Vo - (1/6)V1 --> EQ-1

Now for node V1; I get ;

I1 - io = (1/2)V1 - (1/6)Vo --> EQ-2

Now that I got these EQ-1 & EQ-2; I am not getting right answers, I got different answers all the time.
Kindly help me solve this circuit for Y parameters using nodal analysis.Any sort of help will be appreciated.

In my book; I get y11=0.625S,since im not getting y11 right so I didnt bother to solve this problem for y21 and so on.


texts: Do you really need all of the sigals for a general RS-232 port?

texts: I know that having TX, RX, GND, RTS, CTS are good. What about all of the others? Do devices these days even make use of the other pins (DSR, RI, DCD, DTR)? Is it safe to generally leave out these pins? It seems to me like these are mostly only used in fully-specified legacy DCE/DTE equipment. FYI I'm asking this question more specifically in the realm of embedded systems, not PCs.


texts: Using a super-cap with a PIC24F to keep time in case of supply failure

texts:
I want to use a 0.1F 5.5V supercap to keep time with a PIC24FJ64GA004 device. Does anyone have any idea on how to implement this?

I was thinking of using the supercap on the +3.3V supply line and monitoring the battery input. When the main supply drops below say 5V I would put the micro into ultra low power sleep mode (~400-500nA with RTCC.)

Does anyone know how long a 0.1F cap lasts with <1µA current draw? It'll be charged up to 3.3V and 2.0V is the terminal voltage, though it would probably work down even lower.


texts: Can I prevent copper traces from delaminating due to soldering heat?

texts:
I'm making a PCB that has a 100pin QFP pacakge microcontroller. After gaining experience with the UV photoresist process and reliably making the small, 0.5mm traces, I have a new problem: the copper traces are delaminating when soldering them. Specifically, they get stuck to the solder tip and peel off the board.

It seems this mostly happen when a large part of the trace is heated simultaneously and kept heated for > 1s. I cleaned my solder tip repeatedly to prevent a big blob of solder from accumulating, but that didn't completely make the problem go away. The boards I'm using have a copper thickness of 1 oz.

I'm also using a Weller WPS18MP, which has a tip temperature of ~900F. Is that too high?

Is there anything I can do besides using sheer soldering discipline?


texts: Are there any consumer-grade waterproofing solutions?

texts:
Is there a common solution to protecting electronics from water by coating conductors in dielectric material?

I figured you could just cover everything in thin layer of hot glue, but there might be a more added mass -effective way, like spraying hot silicone on the electronics.

I heard a few years back some company in the US provided a service of coating Iphone insides with a silicone spray or something, which made them water resistant to some extent. I don't live there, so I didn't have a chance to try it myself, though. Anyway, this is a service, and I'm looking for something I could apply myself.

I don't visit home depot nearly often enough to keep up with the technological advancements, so maybe I just missed it.


texts:
I have a lamp that has LED driver producing 35 V (actually lamp driver says 16 - 28 V, but I've measured 35 V). On the lamp I have 7 LEDs (originally 5 + 2 I've added) with heatsinks that have burned and replaced a couple of times now. All LEDs are connected in sequence.

LEDs specs:

LED Emitter: 3W
Output Lumens: 180-210 Lumens
DC Forward Voltage (VF) : 3.6-3.8Vdc
DC Forward Current (IF) : 700mA
Color Temp: 6000~6500K (white)
Beam Angle: 120 degrees
LifeSpan Time : > 50,000 hours

So I've figured out:

$$R=\frac{V_{Driver}-V_{LED} \times 7}{I_{LED}} = \frac{35\ V-3.7\ V \times 7}{0.7\ A} = 13\   \Omega\  $$

which is nothing. At the same time my LEDs are burned down within a month.
What am I doing wrong?


texts: Can the metal body of a dc motor be used as negative terminal for that motor?

texts:
I need to power a micro DC gearmotor (6V, 0.5A), but due to the position in which it needs to be placed, i can only access the positive terminal (of that motor). It is possible however to connect the negative terminal to the body of the motor (by soldering a wire) prior to placement and then connect another wire to an exposed part of the body, similar to the usage of chassis in automotive circuits.

Is it advisable (or even possible) to do this? Does it affect by any means the normal operation of the motor?


texts: LED Cube - Drain Current Resistor for MOSFET Switch

texts: I'm an electrical engineering student trying to build an 8x8x8 RGB LED cube as a summer project. Currently I'm designing the portion of the driver circuit that controls the anode layers of the cube. I have 8 individual MOSFET Transistors that I'm using as switches and I'm trying to select resistors. So far I've calculated that the transistor will need to be able to supply 3.84A to the LED (20mA per diode * 3 diodes per RGB LED * 64 LEDs per layer). I've selected a 60W power supply (5V, 12A) and am now trying to calculate the values needed for a drain resistor. If I follow the example in my textbook and the few I can find online I need to subtract the maximum voltage across the LED (3.4V for my LED's) from the supply voltage, and then divide this voltage by the maximum drain current ((5V - 3.4V) /3.84A = 0.417Ohm). Given the low value here can I ignore the need for a current limiting resistor on my drain pin? Or am I missing something a bit bigger? Any help is appreciated!


texts:
Image a simple RLC circuit as below:

The source Vs can supply an AC current 40A max., if L1 is absent, the current flows through C1 can achieve 40A. And with the adjustable inductor L1, I wonder if the current flows through C1 can beyond 40A (by adjusting the inductor)?

Maybe this is simple, but now I just can't figure it out!!!


texts:
I recently soldered a ATMega328P in a TQFP package onto a PCB I designed. The conncetions seem to be fine and there are no bridges. I have used 100nF decoupling caps on the power pins. The RESET pin is connected to +5V through a 10k resistor. I use the USBasp for programming. However, the AVR does not respond to the programmer and avrdude issues the following error:

avrdude.exe -c usbasp -p m328p

avrdude.exe: warning: cannot set sck period. please check for usbasp firmware update.
avrdude.exe: error: programm enable: target doesn't answer. 1
avrdude.exe: initialization failed, rc=-1
             Double check connections and try again, or use -F to override
             this check.

avrdude.exe done.  Thank you.

What could be the problem here?. The picture of the connection as well as the board layout is attached.

Also, I have the same IC in a DIP28 package, and that one seems to work fine.

EDIT: After some tinkering around, I found that the MISO pin was connected to GND. The DMM showed a resistance of 1.1Ohms. But I see no possible way in which they can be shorted. Can you suggest some possible reasons and solutions.?


texts: How do I write an ISR greater than 8 bytes which is triggered by INT0?


texts: ATTiny414 inline assembly operand constraints for IO pin parameter

texts:
I'm trying to use the light_ws2812 library to drive WS2812 LEDs from an ATTiny414.
The core of that library is an inline assembly snippet that bitbangs the serial line. here it is with the timing-nops stripped out:

void inline ws2812_sendarray_mask(uint8_t *data,uint16_t datlen,uint8_t maskhi)
{
  uint8_t curbyte,ctr,masklo;
  uint8_t sreg_prev;

  ws2812_DDRREG |= maskhi; // Enable output

  masklo  =~maskhi&ws2812_PORTREG;
  maskhi |=        ws2812_PORTREG;

  sreg_prev=SREG;
  cli();

  while (datlen--) {
    curbyte=*data++;

    asm volatile(
    "       ldi   %0,8  \n\t"
    "loop%=:            \n\t"
    "       out   %2,%3 \n\t"    //  '1' [01] '0' [01] - re
    "       sbrs  %1,7  \n\t"    //  '1' [03] '0' [02]
    "       out   %2,%4 \n\t"    //  '1' [--] '0' [03] - fe-low
    "       lsl   %1    \n\t"    //  '1' [04] '0' [04]
    "       out   %2,%4 \n\t"    //  '1' [+1] '0' [+1] - fe-high

    "       dec   %0    \n\t"    //  '1' [+2] '0' [+2]
    "       brne  loop%=\n\t"    //  '1' [+3] '0' [+4]
    :  "=&d" (ctr)
    :  "r" (curbyte), "I" (_SFR_IO_ADDR(ws2812_PORTREG)), "r" (maskhi), "r" (masklo)
    );
  }

  SREG=sreg_prev;
}

An obvious difference between the 'regular AVR' and the ATTiny*14 series
 C definitions is that the IO registers aren't called DDRx and PORTx but PORTx.DIR and PORTx. I already fixed that in the light_ws2812 header and it seems to work fine.

After this I am however getting an error with the assembly operand 2 ("I" (_SFR_IO_ADDR(ws2812_PORTREG))):

lib/light_ws2812.c: In function 'ws2812_sendarray_mask':
lib/light_ws2812.c:119:5: warning: asm operand 2 probably doesn't match constraints
     asm volatile(
     ^~~
lib/light_ws2812.c:119:5: error: impossible constraint in 'asm'
make: *** [Makefile:28: lib/light_ws2812.o] Error 1

I also tried using a lowercase i as the constraint instead of the I, which changes the error to

/tmp/ccBR4JKE.s:48: Error: operand out of range: 1028

Looking at the datasheet this value makes sense, PORTA starts at 0x400 (1024) and the PORTx.OUT register has an additional offset of 4 bytes, placing PORTA.OUT at 0x404 = 1028.

with a 16-bit register constraint like x or w it compiles but then I get a linker error:

avr-ld: lib/light_ws2812.o: in function `loop32':
light_ws2812.c:(.text+0x38): undefined reference to `r30'

I am compiling this using avr-gcc and avr-ld, with a current avr-libc that I manually added the relevant files from the Atmel ATtiny Series Device Support package to.


texts: I have a project in which we want to place a proximity sensor inside/ on the bottom of a tapered spring in order to track the compression of a plastic material on top of the spring. The distance range would only be 1-10 cm away from the sensor and the plastic would be compressed 80-200 times/minute. We were thinking ultrasound (but the waves bouncing off of the spring may be a problem) or an IR emitter/detector system. Are there any other suggestions or examples of similar devices that can accurately measure the distance from the sensor to the plastic and the rate of movement (compression/minute). Thanks.


texts: Order of operations and rounding for microcontrollers

texts:
I was working on a project where I read a value from a 16-bit ADC and scaled it to obtain the reading of a sensor. For example:
uint16_t reading = sampleSensor();
uint16_t temperature = reading/0xFFFF*2.5*1000*2;

Where the ADC has a full scale value of 2.5 volts with output code 0xFFFF and my sensor has a response of 2 °C/mV output.
Obviously when this code runs, it doesn't work. The value of temperature jumps from 0 to 5000 when reading increases from 65534 to 65535.
So I rewrote it and evaluated the scaling expression to a single multiplication:
uint16_t reading = sampleSensor();
uint16_t temperature = reading*0.076295;

This works as expected and temperature increases by 1 °C when reading has increased by 14 bits. I like writing out the full expression so I can keep track of the ADC bit count, VFS, and sensor gain, and I assumed the compiler would evaluate this arithmetic expression, before performing the operation on the reading variable.
Is this an issue with a compiler (GNU ARM v7.2.1) setting, or do I have a fundamental misunderstanding?


texts: Does the order of components matter when connected on the same track in a PCB?

texts:
In this LT3652 solar charger application:

the BAT pin first connects to a resistor of 30k, then to the Schottky diode's anode, then to a filter capacitor and finally to a current detector resistor and a battery. How crucial is it that we maintain this order while designing the PCB?


texts:
I wired up two MCP4725 DAC's to my Arduino and wrote a little demo sketch to test functionality. The sketch draws a Lissajous curve on my oscilloscope.
The output frequency is a bit disappointing (approx. 1.5kHz sample rate), but the datasheet to the DAC mentions High Speed I2C mode. Does Arduino (Mega1280) support High Speed I2C mode and if 'yes' how?

#include <Wire.h>
#include <math.h>

#define DAC0 ( 0xCC >> 1 )
#define DAC1 ( 0xCE >> 1 )

int sh[ 360 ] , sl[ 360 ];
int ch[ 360 ] , cl[ 360 ];

void setup() {
  Wire.begin();
  for ( int a = 0; a <= 360; a++ ) {
    int s = sin( a * 3.141592 / 180 ) * 2047 + 2048;
    int c = cos( a * 3.141592 / 180 ) * 2047 + 2048;
    sh[ a ] = int( s / 256 );
    sl[ a ] = s - sh[ a ] * 256;
    ch[ a ] = int( c / 256 );
    cl[ a ] = c - sh[ a ] * 256;
  }
}

void loop() {
  for ( int b = 0; b < 360; b++ ) {
      for ( int a = 0; a < 360; a += 6 ) {
      Wire.beginTransmission( DAC0 );
      Wire.send( ch[ a ] );
      Wire.send( cl[ a ] );
      Wire.endTransmission();
      Wire.beginTransmission( DAC1 );
      Wire.send( sh[ ( a * 2 + b ) % 360 ] );
      Wire.send( sl[ ( a * 2 + b ) % 360 ] );
      Wire.endTransmission();
     }
  }
}


texts: Why solar panel voltage remains rather constant while current increases?

texts:
Did an experiment and found that when the light intensity shinning onto the solar panel increases, the measured current increases while the measured voltage remains more or less constant with very little increments.

Anyone is able to explain why?


texts: I was wondering what determines the availability of a phone to support a camera? and if lets say I have an 8MP camera from one phone manufacturer with the same number of pins that would connect to another phone from a different manufacturer would that work?


texts: BJT operation and conservation of charge

texts:
The theory (that I know) goes like:

Two junctions, EBJ and CBJ, EBJ is put in forward bias and CBJ is put in reverse bias to operate the BJT in forward active operation Region.

Now Electrons are injected at Emitter by battery V1, nice, let's say 100 electrons went out of V1.

Now since base is seriously thin, and there is strong electric field of CB junction, we can safely say that only 10 electrons were able to reach the base terminal and finally back to battery V1.

The other 90 electrons were collected by V2 who didn't even give any electrons.

From what I know of batteries, I think that if I take 100 electrons out of -Ve terminal then I also got to give it back 100 electrons at +Ve terminal. Isn't that so?

My question is Where am I going wrong? How can V1 keep losing electrons and V2 keep pirating V1's electrons and the system still works?


texts:
EDIT: Solved, Problem was with not sending "\r\n" at the end of the sentence.

I'm trying to control Adafruit Ultimate GPS through STM32F407, there is an official Arduino Library and this library has a sendCommand() function. I'm trying to implement this sendCommand() function in Keil using HAL library

// arduino command for setting antenna off
GPS.sendCommand("$PGCMD,33,0*6D\n");

In keil I wrote these lines

uint8_t Tx_Buffer[100];
int size;

// Turn off antenna update nuisance data
size = sprintf(Tx_Buffer,"$PGCMD,33,0*6D\n");
HAL_UART_Transmit(&huart1, Tx_Buffer, size, 100);
HAL_Delay(100);

// Set the update speed
size = sprintf(Tx_Buffer,"$PMTK220,500*2B\n");
HAL_UART_Transmit(&huart1, Tx_Buffer, size, 100);
HAL_Delay(100);

// Request RMC and GGA sentences only
size = sprintf(Tx_Buffer,"$PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*28\n");
HAL_UART_Transmit(&huart1, Tx_Buffer ,size, 100);
HAL_Delay(1000);

However, it seems that I am not changing anyting because it is still giving data in defaults settings. UART Baudrate is 9600 (Transmit and receive)

Can you help me with the C code? Thanks in advance.


texts: Initializing a variable with the input of a process

texts:
I have been trying to think of ways to reduce the scope of indexing variables used in a mux. Today I came up with using something like the code below as a strategy:

entity control is
  port (
    sel_slv       : in   std_logic_vector (1 downto 0);
    in0, in1, in2 : in   std_logic_vector (31 downto 0);
    out           : out  std_logic_vector (31 downto 0))
end Control;
architecture rtl of Control is
begin
  mux : process(sel_slv, in0, in1, in2, in3)
    variable sel : integer := to_integer(unsigned(sel_slv));
  begin
    case sel is
      when 0 =>      outp <= in0;
      when 1 =>      outp <= in1;
      when 2 =>      outp <= in2;
      when others => outp <= (others => '-');
    end case;
  end process mux;
end rtl;

I noticed that modelsim gives a warning: Initial value of "sel" depends on value of signal "sel_slv".
I assumed that sel would be initialized every time the process was run.


texts:
I am working on the following series RLC circuit:

Let the circuit have non-zero initial conditions \$I(0^+)= 6\text{A}\$ and a voltage across the capacitor of \$V(0^+)=-12\text{V}\$.

What are \$\frac{dV(0^+)}{dt}\$ and \$\frac{dI(0^+)}{dt}\$?

My solution is different from the text example, and I want to know why.

$$I=\frac{dv}{dt} ~~\rightarrow ~~ \frac{dV(0^+)}{dt}=\frac{1}{C}I(0^+) = \frac{6}{C} $$

and

$$ v = L\frac{dI}{dt} ~~ \rightarrow ~~ \frac{dI(0^+)}{dt} = \frac{1}{L}V(0^+) =- \frac{12}{L}$$

The text, on the other hand, shows:
$$\frac{dI(0^+)}{dt} = -\frac{1}{L}\Big[RI(0^+) + V(0^+)\Big]$$

What is going on here? What am I doing wrong?


texts:
I'm trying to use an industrial camera lens that has two internal motors.  One is for zoom, with DC voltage, reversible for direction.  The other motor is for the shutter.  It is presumably a stepper. it has 6 wires going to it.  Resistances between the wires is 136 Ohm between red and orange, 1.47kOhm blue/black and 760 Ohm brn/red. All other combinations show as open connections. The resistor in the center has a color code of 680 Ohm.
Using 9 Volts, connected to orange / yellow (gnd) opens the aperture fully.  Reversing the voltage makes a noise like it wants to close the aperture further.  Connecting red / brown (gnd) also opens the shutter.  Reversing does not make any noise.  No other combinations do anything.
Is this a stepper motor?  What would a schematic of the motor look like?


texts: Active Energy, Reactive Energy or just Energy?

texts:
I understand the concepts of active power, reactive power and apparent power. I am not sure I am getting the complete concept about the respective energies.

I am using an energy monitor to record only the active power consumption of a CNC machine, as an indication of its power demand.

Can I say that using the active power, I can estimate the active energy consumption of the motor or the active energy is something that is not widely used as a term, especially in an industrial environment?
If I can use the above term, is it OK if I do not consider at all the reactive energy? Is it even meaningful to talk about reactive energy?
What do we generally mean when we talk about electrical energy in a factory? Do we refer to the sum of the active power in kWh? Or do we use the apparent power to calculate the energy in this case?


texts: Lattice LCMXO2-256HC-4SG32C CHECK_SECURITY_PROTECT_KEY error

texts:
Trying to progamm LCMXO2-256HC-4SG32C with this ebay progammer.

The programmer works fine with LCMX02-1200HC-4TG144C, but with LCMXO2-256HC-4SG32C it gives me the following output:

Starting: "pgr_program run"
INFO - Check configuration setup: Start.
INFO - JTAG Chain Verification. No Errors.
INFO - Check configuration setup: Successful.
INFO - Device1 LCMXO2-256HC: FLASH Erase,Program,Verify
ERROR - function CHECK_SECURITY_PROTECT_KEY
ERROR - Process Operation Failed.
INFO - Elapsed time: 00 min : 01 sec
ERROR - Operation: unsuccessful.
ERROR: pgr_program failed.
ERROR - Programming failed.

This is the 3rd chip I'm trying this with with the same result. I had chips ordered from Alibaba and thought the chips had some issue but now I've ordered a couple from Arrow and these give the same error.

The programming does complete successfully with an earlier version of the Lattice Diamond programmer (v3.8) but then a simple test blinky doesn't work, just no output on the pins, they sit a 0V with the current chip, with the previous chip it was more weird where it would allow to output high on one pin but not on the other and would act as if there was no clock input.

I've checked the clock from the 50MHz oscillator and it looks fine.
The soldering also looks fine.

The same simple test works with my other test board with LCMXO2-1200HC-4TG144C.

Have I just fried the chip?
Is this an issue with my programmer?


texts: How to measure Oscilloscope's self random jitter

texts:
I want to measure how much noise is a certain oscilloscope responsible for. Up until now we (my team) have used the approach of inserting a square wave and measuring the random jitter RMS. This method assumes there is no noise from the signal generator (minimal noise), which is not good enough for us.

Other than that is this a correct approach? If not what is wrong with it?
Is there a way to evaluate the random noise generated from within the scope itself without using an external signal?

P.s.
To answer the questions in comments below, we are trying to evaluate an oscilloscope but we have a small noise budget aloud in the system while measuring (I cannot disclose other details). We are currently considering DPO70000SX series with 33GHz and 200Gs/s. Our goal at the moment is to measure the RMS random jitter in the time domain which is the standard deviation on the total jitter distribution.

Any other suggestion on how to evaluate this oscilloscope are most welcome.


texts: Charging a lead acid battery with a lower bulk voltage

texts:
Will a lead-acid battery completely charge when using a bulk voltage below the one indicated on the specs sheets for it, even if it takes longer?

In my case the battery is in a place with temperature fluctuations, and would be safer to have a lower charging voltage when is warm.


texts: how to generate (electronic energy from static energy?

texts:
I'm currently doing a project on micro-power harvesting , so I'd appreciate some help in

How to generate electronic power from contact between two materials?

to be more specific "One common cause of static charge buildup is contact between solid materials , so electrons can move from the former to the latter creating a charge imbalance after the materials are separated , While static electricity can be a nuisance or even a danger, in other cases it can be quite useful.

analogous to how a spring stores mechanical energy. A voltage applied to capacitor creates a charge difference between the plates. If the capacitor is charged , it can retain the charge for some time. This can be useful

so, the circuit will collecting static energy and generating an Electronic power from This sudden discharge which creates a static energy


texts: How can the Arduino Uno support up to 12 servos if it only has 6 digital PWM pins?

texts:
According to this:

  The Servo library supports up to 12 motors on most Arduino boards and
  48 on the Arduino Mega. On boards other than the Mega, use of the
  library disables analogWrite() (PWM) functionality on pins 9 and 10,
  whether or not there is a Servo on those pins. On the Mega, up to 12
  servos can be used without interfering with PWM functionality; use of
  12 to 23 motors will disable PWM on pins 11 and 12.

However, according to this:

  Digital I/O Pins 14 (of which 6 provide PWM output)

So how can the Uno control more than 6 servos if it only has 6 digital I/O pins that can provide PWM output?


texts:
I'm currently working on a 6 layer board that has both an applications processor and a GNSS module (along other things), and I find myself in a certainly puzzling situation. Let me describe:
I have a 6 layer board manufactured by JLCPCB, with prepeg impedance 4.05 and
the following stackup:
-L1: Signal
-L2: GND

L3: Signal + PWR
L4: PWR
L5: GND
L6: Signal

image 1: stackup

The layout of the part is as follows: there's a GNSS module on the bottom (red layer), connected to a THT SMA connector on top. Internal layers (complete planes below this section, hidden for better visibility) have reference plane openings as seen on the saturn PCB toolkit screenshot below.
On the RF path there's a TVS, a bias-T and a DC block capacitor (as recommended on the HW integration manual of the receiver).
image 2: layout

In order to maintain 50Ω path, I used Saturn PCB Toolkit to get the values for the width of the microstrip and the "via" (THT SMA signal pad) dimensions.
Saturn PCB Toolkit and a tool by the manufacturer report very similar values, between ~0.146 to ~0.16mm for a 50Ω microstrip. I settled for 0.15mm.
(Note there's a mismatch on the manufacturer stackup. On the static page they list the prepeg as 0.1mm whereas in the impedance tool it's 0.0889).
image 3: microstrip calculator

Via (connected to "image 2" GNSS_RF signal trace):
image 4: THT SMA center pin calculator

This is the current state of the things. I received and assembled a couple of the boards to try the circuit and now I'm fixing issues for the next revision. Here's where I thought: Let's try to use that expensive toy you have there to figure out if the RF section is properly executed.
Assumption #1:
If the transition between the THT SMA (port 1) and the microstrip + routing to the SMD pad (image 2 pad 2)(port 2) is properly executed, everything should be Z0. So, if I normalize the TG output and then insert the DUT in the middle, there should be no change (ideally) on the amplitude of the signal as seen from port 2.
Test procedure:
Normalized tracking generator
De-soldered C72 and soldered a small SMA to coax cable.
Fed TG output to the THT SMA and connected the RF input to the SMD pad using a botched SMA to U.FL cable.
image 5: Test setup

To my surprise, assumption #1 seems to be wrong. I can observe a "periodic" change in amplitude, whereas I'd have expected a "flat" (-ish) line.
image 6: SA plot (yell normalized, purple image 5 plot)

I repeated the experiment on a blank PCB soldering only the THT SMA and replacing C76 for a 0ohm resistor. I found a ~1dB improvement but the shape of the "ringing is essentially the same.
Looking for some information on this issue I stumbled upon what I consider a very good thread on a similar issue.
Questions:

Is assumption #1 correct?
What other experiments / tests could I perform?
Are calculations of the microstrip and SMA signal properly made?
Is it possible that my pads (passives along the RF trace) and SMD pad of the GNSS module are indeed acting as a capacitor? Should I void the reference planes to reduce this effect?
Would you recommend that I design a PCB with several pad shapes and cutouts to further analyze this behavior?

EDIT 1:
Since I have a directional coupler I can attempt to perform S11 measurements on the DUT (only up to 2GHz). Following Neil_UK recommendation I soldered down a 49.9R 1% 0603 resistor (no 100r at the moment), and did a couple of passes, one with a 50R load and another with the "terminated" DUT.
image 7: Coupler with 50R load attached

image 8: DUT soldered termination

Here's the result. Yellow line is the open load normalized trace, pink is the 50R load (image 7) and blue is the DUT(image 8). I cut away a bit of the SMD pad and got about 0.5 dB of improvement.
image 9: S11 plot

Disclaimer:
I'm a complete noob when it comes to RF design (and frankly I'm still trying to get my head around the most basic concepts, so, apologies if the question or assumptions on my side are plain wrong), so I got myself an SA to play around and learn.


texts: How to calibrate an optical particle sensor (Mie scattering)

texts:
I have a very simple sensor that basically emits infrared light (1 micron wavelength in the infrared range). The light scatters off particles whose diameter is of the same order of magnitude as the wavelength (Mie scattering). The scattering angle is approximately 90 degrees. A photodiode is located diagonally with respect to the sensor ( scatter angle approx. 90 degress)

I am trying to find out how to calibrate my device with respect to particle size. I looked through commercial optical particle counters out there, and they don't really explain how they are calibrated. For example, the following is a plot of scattering intensity as a function of diameter, as you can see, there is not a simple relationship between intensity(or photodiode voltage output/my sensor output) and particle diameter.

Does anyone know how commercial particle counters are scaled?


texts: Do BLDC and Induction motors have the same efficiency vs. load relation?

texts: In induction motor, the efficiency is maximum for rated load. But for lighter loads, efficiency decreases. I wonder if the same principal applies for BLDC motor also?


texts:
I just ordered a 6502, breadboards, eeprom, ...
Now where I bought those things to build my own "Computer" on breadboards, I am afraid of not being able to find errors, because I have no other microcontroller or logic analyzer.
Now my question is what do I need for debugging on my breadboards, I spent around 130$ on the other things, therefore the debugger/logic analyzer/microcontroller shouldn't be to expensive?


texts: Relay noise problem although flyback diode is used

texts:
I've this relay (5V) with 1N4148 as flyback diode across the relay's coil but there's still noise problem. When I switch on/off the relay, the PIC MCU will occasionally reset and false triggered the interrupt-on-change pin (a switch with pull-up resistor) all the time. The problem doesn't happens when the load (an electric lock) is not connected to the relay.

So my question is:

What is the cause of the problem?, I have a flyback diode but the problem still exists. Did I do something wrong?
Does position of the flyback diode in PCB layout matters and where should I place it.


texts: Making 100 microseconds delay for STM32L0

texts:
I need to create 100 microseconds delay for STM32L0 using HAL. I have HSE 12 MHz. APB1 timer clocks 12MHz.

htim6.Instance = TIM6;
htim6.Init.Prescaler = 1199;
htim6.Init.CounterMode = TIM_COUNTERMODE_UP;
htim6.Init.Period = 1;

When I have a loop of 50000 iterations which wraps calls to polling start/stop basic TIM6 timer (HAL_TIM_Base_Start), then I have 10 seconds delay instead of 5 seconds (The outer loop serves just for time scaling). Is it normal? I've expected 50000 * 100 microseconds = 5 seconds. Should I use another timer? I need +-10 microseconds delta. By the way, STM32L0 HAL does not contain "microseconds version" of HAL_delay.


texts: Just wanted to check iv not made any mistakes and this should work ?


texts:
I'm playing with Hall effect sensors and wanted to identify this one. I got it magnified but I've never seen anything like it.

Is it a code for something, or has it been removed off the surface?

I managed to put it in photoshop and draw dots over it and got the following 2d bar code.  Unfortunately it doesn't seem to match anything online.. thoughts?


texts:
I have a circuit with multiple stages and I wanted to number their components differently. For example, for the first stage I want the resistors to be R101, R102, etc. For the second one, R201, R202, and so on.

I know that there is an option related to this in the annotation tool (Annotation Choice states something like using sheet number*100), so I guess that to achieve this I should create multiple sheets. The thing is that I've done this but haven't reached the desired result, it just keeps using 100 and not 200, 300, etc.

So how can this be done properly?


texts: What are the possible problems for slave to not give ACK (pull down SDA line) after 8 bits of data? I can see 8bits (slave address) with osciloscope, but the ACK is high at 9th bit clock pulse, why?


texts: Is the capacity of a capacitor in an RC circuit independent of time? If so why?

texts:
Is the capacity c of a capacitor independent of time in an RC circuit?

In the notes through which I'm working the following step is made:

$$\frac{d}{dt}Q=\frac{d}{dt}(uc)=c\frac{d}{dt}u$$

the final equality is implies that c is independent of time but why?
(I have a very elementary background in circuits...)


texts: How to reduce the voltage dropped in a mosfet used as a switch?

texts:
I'm trying to use a N-channel mosfet as a switch for controlling a LED, but the most of the voltage is dropped in the mosfet itself (drain-source) and the led are not turning ON. The voltage in the gate is 3.3[V] and in the drain is 4.2[V]. What is my problem? I've seen this circuit before for controlling LED's and it works, Should I use a P-channel instead?
The circuit is already done, so I measure the voltages on my board.

Attached is a screenshot of the circuit.

Thanks!


texts: I work for a company that builds electric motors, within the last few years they've started building control boards from brush-less dc motors.  On the incoming power we have an Inrush Current Limiter to limit the draw on start-up from capacitors charging.  I evaluate returns on these motors and have seen these current limiters cracked or crumbling , but there's no evidence of a short on the board.  I'm having a hard time finding information of failure modes/causes for these.  They are either Ametherm or Cantherm.  Hoping someone has seen this or might have some info and what(other than a short) would cause this failure.  Thanks.


texts: Frequency of stator current in induction motors

texts:
I am learning about induction motors.

I have a question about the stator current, especially the rotor induced current.

If the rotor rotates at 1-s of sync frequency, then the emf and current induced in the rotor with respect to rotating magnetic field would be  less than sync frequency.

I understand that the same rotor current is induced at stator.

Does that mean stator would have current of sync frequency and another frequency of s times sync frequency?

Another query on rotor emf.

If the rotor is perfectly conducting with copper rods, I understand that the resistance would be low.

Since induced emf is proportional to rate of change of stator flux, then I believe that same stator voltage (which causes the rate of change of flux in first place) is induced in the rotor rods (ignoring small resistive drop at stator.)

If, for example, the motor is supplied with 400 volts line to line voltage, does it mean than same 400 volts will appear on the rotor? What does it say about the rotor currents?

Would it be ginormous given small resistances?


texts: Is 5V 5A Battery Charging legal with USB and how to signal it?

texts:
According to the USB Battery Charging v1.2 Spec a Dedicated Charging Port (DCP) shall output an average voltage of 4.75V to 5.25V at a current of 0.5A to 5A.
So if I'm reading this correctly, supplying 5V at 5A should be perfectly fine for a DCP.
However I have trouble understanding how to signal a portable device it is connected to a DCP and it may draw up to 5A.
Section 3.2.4.1 of the aforementioned document suggests, that all I really have to do, is short D+ and D- (or ensure a maximum impedance of 200Ω). The portable device shall then simply assume it's fine to draw up to 5A and needs no further communication.
Is the portable device going to simply ramp up the current until it detects the 5A max current?
I'm confused, because places like Wikipedia suggest, that 5V 5A being the available max power.
However the USB spec suggests that a portable device should not draw more than 1.5A at 5V (Allowed PD Current Draw from Charging Port in Table 5-2 of the spec).
So which one is it?
I specifically don't want to implement a smart USB supply at this point, able to supply several different voltages between 5V and 20V. I'm talking about a simple 5V of \$V_{USB}\$ power supply, but one that delivers up to 5A.
The goal is to build a 5V 5A power supply that will be able to supply the maximum of 25W to a device. However I want to make sure the portable device is aware of the available current, and doesn't limit current to below 5A by itself. Hence me asking.
Thanks in advance!


texts: How do integrated charger ICs dissipate differences in VCC and the battery voltage?

texts: I was looking at a couple of charging ICs (BQ2002 for instance) and some of the fast charger ICs can charge up to 2A whilst running of a 5v supply. In this case charging a empty 1v NiMH cell means that 4v * 2A ~ 8w is being dissipated by the IC? Do they use some kind of internal buck converter to step the voltage down?


texts:
A family member's Bose Wave Music System has stopped responding to its remote control. The battery in the remote control has been changed and I've confirmed that it's emitting a signal (using the "cheap cellphone camera" test). This leads me to suspect that the IR receiver has failed.

I'd like to try replacing it given that the Bose otherwise works properly and initially cost the aforementioned family member a fair amount of money. Even if it hadn't, it seems incredibly wasteful to discard the entire, otherwise-functional system due to the failure of one small, cheap part.

Here's a (rather grainy) photo of the receiver:

The package appears identical to this one:

However, I don't know if this package is only used for one particular component or for a family of components with different frequency response characteristics, etc. It matches the package used for Vishay TSOP5038 receiver modules, for example, but is it also used by other manufacturers?

Any information regarding which specific component this might be (perhaps it actually is a TSOP5038) or how I might narrow down the list of possible identities for it would be appreciated!


texts: Using different UART pins on STM32 Nucleo

texts:
I am trying to use the STM32F103RB Nucleo board. I am learning how to do serial comms so started with the classic 'Hello world' printed to a serial monitor.

Eventually, I want to print data to the serial monitor, while receiving data via different UART pins. The Nucleo uses pins 16 & 17 (PA22 & PA3) as the default Tx/Rx pins. I started with them, and had no problem. The code was simple:

#include "mbed.h"

Serial pc(PA_2, PA_3);

int main() {
        pc.printf("Hello World \n");
}

Looking through the DATASHEET I can see that pins 42 & 43 (PA9 & PA10) can also be used for UART, with PA9 Tx, & PA10 Rx. I decided to change the pin definitions for Tx and Rx, so the code now looked like this:

#include "mbed.h"

Serial pc(PA_9, PA_10);

int main() {
        pc.printf("Hello World \n");
}

And this now doesn't work. Looking through THIS PAGE I don't see why that doesn't work. I have used 'Serial', given it a name (pc), then defined the Tx and Rx pins. I am using the mBed online environment if that makes a difference to anything.

Can anyone see if there is some simple mistakle or something I have overlooked when trying to do what should be a simple task?

If there is any more information required, please ask.


texts: Equality of two 8 bit buses in 7400 series logic?

texts:
Is there a simple way to determine whether two 8-bit buses contain the same value?

I'm currently XORing each bit between the buses then feeding those results into a three-level tree of OR gates.  (The top of the tree being a NOR, rather than an OR.)

This is 8x XOR + 6x OR + 1x NOR gates, which is 4x 7400 series chips.


texts: What sensor used in all non-contact body temperature guns?

texts:
With the whole COVID thing happening, there has been a proliferation of these handheld guns on the market. I have been struggling to find out what kind of sensor is actually commonly used in these.
From my research I see its either a thermopile or pyrometer type sensor. Devkits cost more than the actual guns themselves, can anyone advise what low cost commodity sensor or sensors are used in these guns as there are so many of them on the market?


texts: Beginner question - could this cause a short circuit? (picture)

texts:
Hello! I'm very new to electrical engineering and I wanted to ask a question before I attempted something potentially dumb. One word answers are acceptable here! :) I'm eager to learn so any longer explanations are welcome too.
I need to connect this arduino to this slab of metal jewelry so that it's secure enough for me to plug and unplug a USB in without shearing the arduino off the jewelry. I was going to solder it directly on (and probably use a few more pins elsewhere to stabilize). I don't know what type of metal this surface this is, but I know it's non-magnetic (guessing it could be copper of some sort, though potentially it could also brass or bronze I think? I found this jewelry on the side of the road).
Anyway, I was wondering if this could potentially cause a problem - like a short-circuit. In the picture, I have a battery pack and an arduino connected by these 3 pins. The middle pin is the ground, and the right-side pin is the battery input (sending voltage from the battery pack into the arduino), and the left pin sends voltage from the arduino USB to the battery pack. All 3 would be soldered to the metal in this scenario (assuming the soldering goes well!).
Thanks for your help!


texts:
I am experimenting with a circuit for adding two numbers represented by two digital counters and two cascaded 4 bits adders (74HC283). I tested separately with cascaded 74HC163 and with asynchronous 74HC4040 counters and I ended up with the same results.

I feed one of the counters with a 1 kHz com signal and the second counter with 512 Hz signals. All signals are well formed square signals.
I use a 16Hz crystal-controlled time base. The counters count during logic high of the time base that is 1/32 second or about 31 milliseconds. The counters are reset in the second half of the logic-low of the time base.
When I verify the outputs of the first counter, my oscilloscope shows pulses at some of the outputs and I consider them as logic high. The output of the first counter is binary 00011111 to represent the 1kHz clk input, almost as expected. The output of the second counter is binary 00001111 to represent the 512 Hz clk input also during the 1/32 sec. So far so good because I can read the output of the counters correctly.
I feed input a[] of the cascaded adders by the outputs of the first counter and input b[] of the adders by outputs of the second counter. I expect to see the same pulsing output pins of the adders to show the correct sum. My expectation is to see the correct sum as the binary number 00101110 at output s[] of the 8 bits adder, the same way that I see the correct binary numbers at the pulsing pins of the two counters.
Instead, I see binary 00111111 as the sum.
If I change the clk input of the first counter to 2kHz and I leave the clk input of the second counter as it was 512 Hz, I see binary number 01111111 instead of the correct sum 01001110 as sum at outputs s[] of the adder.
If I change the clk input of the first counter to 512kHz like the second counter, I see the correct output of 00011110 as sum at outputs s[] of the adder.
I understand that as the counter is cycling through the addition is performed. My thoughts are that the total propagation delay of the counters and the adders is in the order of hundreds of nanoseconds but the counters are not counting for many milliseconds before they are reset.
My expectation is to see the correct sum at output s[] of the adder at their pulsing output pins while the counters are counting during the logic high of the time base.
I mean, I expect to see the right output of the adders at their pulsing output pins just like I can see the right output of the counters at their pulsing output pins. Is my expectation justified while counters periodically pause counting? If so, why do I get the wrong sum?
Please note that it is not about what kind of counters I am using. It is about the wrong sum no matter which counter I use.


texts: When using AD9850, I can see a very clean and smooth sine wave  but this is not the case by AD9833. In AD9833 multiple steps are visible in the output that gets worse in higher frequencies( > 2MHz) .The output looks as if the DAC never goes under smoothing process. I want to know if this is an inherent nature of this device or I am missing something? Should I use a low pass filter to remove these steps? The output looks like this in 2MHz:


texts: Analysis on the output waveform from LTspice

texts: According to the data sheet of LT6202, it can be amplify frequency up to 100MHz, but when I input 4Mhz,the output become distorted, so any explanation about it?


texts: Amateur designing a quadcopter: is it possible to use Fizzly for remote control?

texts:
I am a total amateur, so forgive me if my question is naive. I am starting to design my quadcopter, and I was wondering if it would be possible to control it via bluetooth using Fizzly. It would be for outdoor use, so maybe the reach could be a problem. My idea is to use the Fizzly to input command to my laptop and then send it to the copter. Basically I would like to control the copter via my arms motion. My final project would involve more than one fizzly to individually control the different motions.

Do you see any obvious limitation to this?

Do you know any source for bluetooth control where I can find useful ideas?


texts: Can someone explain what does it circuit do? Is it some kind of filter? Thanks.


texts: Cloning Keeloq remote keyless entry system

texts:
Our house and a few other share the same gate, which is opened remotely by a 433Mhz transmitter.

Unfortunately, we only get one remote per house, and we have two car. The company operating the gate charges almost 100€ to get another key, I thought it would make a fun project to try to clone our existing remote.

I own a RTL-SDR dongle, and I captured the packets sent by the remote. It seems the gate uses a rolling-code algorithm, as the transmitted code changes after every press on the remote.

66 bits are transmitted, 32 are changing every time and 34 are constant, which seems to indicate it is using KeeLoq according to the rolling code Wikipedia page

So I was wondering if there was any possibility of cloning my remote?

My main assumption was that if I record enough presses on my remote, the transmitted code would cycle back to the first one, so I would have all the different possible codes.

Is this possible? Or would there be too much codes before cycling back to the first one?


texts:
I am working with MAX1771 Step Up converter, from Maxim in the adjustable mode. I would like to have a continous output voltage of 5V so I have used the application circuit that you can find in the datasheet: http://pdfserv.maximintegrated.com/en/ds/MAX1771.pdf (page 13, Figure 5).

But I have some problems with the output because it is not continous and it has a lot of peaks (I attach a capture from the oscilloscope).

Can someone help me with this issue?

update:

When Iconnect a load (in this case, 2 diodes LED in series) the output have the following form:

The leds are working with 20mA.

update:

First at all, thank you for the answers.

I have attached now the capture, sorry for the inconvenences.

I hope it will help you with the possible solutions.


texts:
simulate this circuit – Schematic created using CircuitLab

I am really struggling to understand how this circuit works theoretically. What will be the currents through the resistors? My understanding (which I suspect is wrong) is as follows:
Ir1 = (7-0.7)/100 = 63mA (B-C is forward biased)
Vemitter = 7 + 0.7 = 7.7V
Ir2 = (12 - 7.7)/1k = 4.3mA
Vcollector = 7 - 0.7V = 6.3V
Ir3 = 6.3/1k = 6.3mA

Now, what confuses me the most is the zener diodes. What is their purpose in the circuit? I have not made use of them in my calculations. Could someone please help me understand this circuit? Thanks!


texts: Can I put Li-ion batteries in series and discharge them at different voltages?

texts:
I need to run a pump (drawing 95mA at peak flowrate) at +14V and the rest of my circuit runs on +3.3V.

To save on battery costs, I was thinking of purchasing four 18650s at 3.6V 3500mAh per cell and stacking them in series to produce ~14.4V needed for the pump (it can run between 10-15V and we are going to use PWM to control the voltage i.e. the flowrate).

Could I also run two terminals from one cell (at 3.6V) and regulate that to 3.3V for my lower voltage loads? I understand that this will cause one of the four cells to discharge faster than the other three, but I plan on using a BQ29209 balancing chip to maximize the capacity I can get out of them.

Would it be wiser to just use two buck converters from 14.4V down to 12V and 3.3V respectively?

Ideally, if I had more money, I would put 4x 3.6V in series = 14.4V @ 3500mAh, and then another 2x 3.6V in parallel = 3.6V @ 7000mAh to get more capacity.


texts: How does a push pull CMOS output drive a pin LOW

texts:
Can someone tell me how does a push pull CMOS output drive a pin low?
I am having a microcontroller with push pull CMOS output.
For high drive, the TOP MOSFET is turned ON and drives the line high. But when driving Low, even if the bottom MOSFET is ON, there is no pull-up resistor on the line to make line go low?
What if there's a pull-down resistor on the other side of the CMOS output? How will the microcontroller drive the push pull CMOS output to low?


texts: Isolated DC supply for Bluetooth receiver in car audio

texts:
This question is about the isolated power supply I've put together for a Bluetooth receiver which is going into an old car stereo, replacing the cassette...
The Bluetooth device wants isolated 5vdc, and the supply is of course the 12-13.5vdc from the car.
I have made a regulator unit, which works, but it was just based on info I gleaned from datasheets etc. (The B0505S-1W being the DC-DC isolator.)
This is the circuit...

It works fine on the bench (haven't yet tested it in the car), the Bluetooth unit is well within the power draw specs of the B0505W and the 7805 has a heatsink on it because it was getting hot.
The question is - are these the right cap choices, and, should it have an inductor to further help filter it seeing as it's in a car?
Thanks for looking at this.
[New question to add to this]
I have made some additions to this power supply circuit for protection namely a TVS Diode 16v.
New question: I keep seeing recommendations to add a resistor before the TVS diode, and one after - but I can't find information about what size resistors to use. It's car voltage coming in - eg ~13.5v - and the load is under 1W.


texts: How to setup the NCV7708B h-bridge/double hex driver?

texts:
I am working on a circuit to control an electromechanical display and settled on the NCV7708B Double Hex Driver (datasheet).

I created a minimal setup on breadboard in order to test the chip:

I connected a load R1 (just a resistor) in a H-Bridge configuration similar to the following diagram (Figure 5 from the datasheet) and I expect it to dissipate 1W if OUTH3 and OUTL2 are enabled (or OUTH2 and OUTL3).

The NCV7708B uses SPI with the following frame format (Figure 3 from the datasheet):

And here is what I sent to to the driver as captured by a logic analyzer (MISO is connected to SO):

However, no current is drawn from the +10V power rail and nothing happens. Do you have any idea of what might be causing this issue? Did I misunderstand the datasheet on how to configure the driver? I double-checked the connections and tested this configuration with two different brand-new NCV7708B in case of a defect.


texts:
I have made the following circuit from a few online sources, it is very basic but uses two NPN transistors to make a latching circuit that toggles when either push button goes to ground.

My Falstad Circuit

My question is, how would I make this work if I wanted both latches to be triggered when going high instead of low.

Would I need to use PNP transistors instead?


texts: DIP package: meaning, dimensions and nomenclature

texts:
I'd like to know exactly what DIP means, since googling it gives me several outright contradictory answers.

I used to assume that DIP and DIL mean these guys only:

That is, through-hole packages with two symmetrical rows, 0.1" (2.54mm) spacing between leads and 0.300"~0.325" (about 8mm) spacing between rows. If I wanted to specify the number of pins, I'd call them DIPn, where n is the total number of pins (obviously, n is always even). I call these guys "regular DIPs".

Then I found out these guys exist, and apparently are also DIPs (I call them "big DIPs"):

Then I found out this guy exists: ("mutant middle sized DIP"?)

So, lots of questions: are they really all DIPs? If yes, how do I specify which size I am talking about? And what about acronyms like PDIP, CDIP, SDIP and SPDIP? And finally, when referring to pin number, some sources say DIP8 and others 8-DIP. Is there a difference? Also, can I always use "DIL" and "DIP" interchangeably?

Also, Wikipedia tells me SMD DIPs are a thing. What about that?


texts: Power Isolation generating error in KiCAD

texts:
I've created a ferrite bead part with two passive pins. When I insert it in a power line, it causes an error "ErrType(3): Pin connected to some others pins but no pin to drive it" Changing the pins to bidirectional or unspecified has no effect. Using an inductor provides the same error message. Is the only way to avoid this error to redefine the pins as power in and out?

This is Eeschema version 2013-07-07 BZR 4022 - stable for Windows


texts:
My high and low side gate measurements to GND show a tiny little shoot through spike.

Adding dead time, Zener bypasses over R(g) and from G-S, and TVS diodes does not do anything.

The load is 100K and it's running off 12V supply. Any ideas as to how to get rid of the spike? I'm assuming it's shoot through, but even giving it way more dead time simply just spikes it anyway. It's like it never fully discharges the gate.


texts:
I am currently working on a prototype for an ESP32 retrofit for a home alarm system.  I am an aspiring electrical engineer and will be attending Miami University next year.

I am having trouble getting my computer to recognize my USB connection to the ESP, despite having the correct drivers installed on my Mac.  Even in the device inspector, my computer doesn't show the FT232 as connected.  I have rebuilt the schematic twice on my breadboard with no luck.  I have attached my schematic below which is based off the Sparkfun ESP32 Thing.  Any suggestions?

EDIT: 3.3V is coming from a regulator circuit which is powering the ESP from 12V.


texts:
Although this question is more of an optics than electronics, it strongly involves LEDs so I think it is a good idea to post it here.

I have a simple 3W, RGB LED with a 5deg lens. Everything is connected and and works but when projecting the light on the wall I can easily see the 3 different colors. I tried using a diffuse lens with partial success as the color mix inst 100%.

Is there any way to fully mix the colors of a standard 3W RGB LED?


texts:
I have a simple RC circuit as below :

I'm trying to visualize current curve and voltage curve (Vout and I(R1)) vs Vin using LtSpice and I obtain the result below:

It's OK that the Vout is leading Vin. However, I do not understand why the current curve I(R1) is completely out of phase with Vout. Any one have explanation for that ? Thanks for your support.


texts: Why are standalone MOSFETs and transistors preferred over integrated load switches?

texts:
As a novice to EE concepts who's trying to apply it to Arduino projects, I was doing hours of research on how to electronically switch another higher current (or voltage) device/component/subsystem on and off.
I've read many long questions on lots of forums trying to solve this same problem, but only see different configurations of MOSFETS or transistors or combinations with some resistors recommended as the solutions.
Only this tutorial mentioned another option which was load switches. I then found several articles (example, example, and example) extolling their virtues.  They small, cheap, some are crazy efficient, and they seem way simpler (especially to someone learning the basics) with fewer (or no) extra resistor sizing and other ancilliary components needed.  Appears to just be Vin, Vout, GND, Signal.
The very tricky knots people are trying to unravel with for example Arduino circuits with unexpected current flows down controls pins and being unable to saturate the transistors or wrong sizing the resistors seems way overcomplicated in many cases if these are as simple as advertised.
So what's the catch?
These articles read almost like marketing material.

Main Question:  Why are standalone MOSFETS (and transistors) preferred over IC load switches?
What's the downside of load switches compared to transistors/MOSFETS?
Why aren't they as preferred or recommended?

I am surprised not to see them on the common maker movement beginner electronics stores.


texts:
I'm trying to build a discrete driver to switch a power transistor (Qg=12nC, Vg=0->6V). I want to push the limits to see what is possible with discrete components (so no driver IC) so I'd like it to have a rise/fall time close to 20ns. This comes down to Ig=12nC/20ns = 0.6A of drive current, assuming constant gate current during the switching. I thought of using a typical BJT push-pull circuit but I'm struggling to find the parts.

simulate this circuit – Schematic created using CircuitLab

Am I using wrong specifications? Is using BJTs a bad idea and would MOSFETs (maybe multiple stages) be the better choice here?

The specifications I looked for:

Considering I need at least 0.6A of gate current, but I'd prefer more: Ic>=1A
Vg=0->6V: Vce,br>10V
tr/tf gate <20ns: tprop+tr+tf+tstor BJT < 20ns

The main problem is the BJT time specifications. Some BJTs don't have these spec'ed, and the best BJTs I find have rise/fall times of 30 ns. Not even mentioning storage times (but I know these can be lowered by using baker clamps and speedup caps)... However I know BJT push-pull is often used in commercial drivers. Are these specs just not possible for discrete components or am I looking in the wrong places?

Thanks in advance!


texts:
While going over some notes for the past year, I never really understood why many of the integrals for signals and systems, integrate over \$ [- \frac{T}{2},\frac{T}{2}]\$ rather than just \$[0,T]\$. (The same is can be true for \$ [-T,T]\$ vs \$[0,2T]\$ )

Why is that a common interval ?

Here is an example of what I mean.

Edit:
I corrected the internal from \$ [0, \frac{T}{2}]\$ to \$[0,T] \$. So you may see some answers talk about a range that wasn't in the question.


texts: Placing TVS or MOV or Transzorbs for a very basic protection

texts:
This is a question for a general scenario I encounter. So I will not be specifying much details besides the voltage level, cable length/type and the power supply type.

Imagine a sensor placed outdoors is measuring some air parameter and it is powered from a receiving unit which is far away and indoors. The sensor output(in the diagram signal SG and signal ground SG_GND) is received inside the receiving unit and measured.

When I see such units they always have sort of protection such as MOV or TVS in the receiver box for over voltage protection.

simulate this circuit – Schematic created using CircuitLab

In general I need to use a single dual power supply(which in the diagram is represented with V1 and V2 above) and also in general power ground and the signal ground are connected inside the sensor.

Does anybody have experience with such setup and its TVS or MOV protection? Between which terminals should one place TVS diodes? I have no experience and couldn't find such practical info. Where should I place the TVSs or MOVs for a very basic protection? If we focus on the receiving unit, I named the terminals as A, B, C,D and E for simplicity.


texts: Eagle: library with only common packages

texts:
is there some library with only common packages, but not compsed with devices?
I use components from many sources and either I would end with tons of librarioes, or with tons of differnet models (which I do not have) (usually with much  layers, which are not relevant, but somebody used them somwhere for something once) or I have to copy and re-create everything.

I would like just the pads/holes like 0802 and connect them with only parts I really have


texts: Finding magnetic field inside closed iron bar

texts:
I'am given this picture with the following information

Core's length L=1.8m cross-section area A=(15x17)cm^2 gap δ=5mm winding turns w=72 winding resistance R=150mΩ, μr=1800,
 i(t)=25sin100π
I can answer questions B and C but they require finding question A which asks what is the magnetic field B. Faraday's law comes to mind but we don't have u(t) and also Magnetic potential $$V=LH_{core}+δH_0$$ But again I don't have V.


texts: Interface to numpad in VHDL. Numlock button support

texts:
I need to implement interface to numpad in keyboard. I am totally newbie in Quartus and VHDL language.
I only know that the decoder should return the appropriate key depending on the entered row and column. So if for example the value of the entered row is "3" and the column is "2" then the output should be "5" because it means that the "5" key was pressed.

The layout works properly, but now I need to implement the "numlock" key, which will block reading the keys.
If the "numlock" key is pressed it means that the system should return the correct values from the pressed keys. However, if numlock is off, it means that the whole keyboard should not work and I should get zeros or uninitialized values on the output.

multiplexer.vhd
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity multiplexer is
port(
    columns : in std_logic_vector(3 downto 0);
    rows : in std_logic_vector(3 downto 0);
    output_binary_key : out std_logic_vector(7 downto 0);
    is_key_pressed : out std_logic
);
end multiplexer;

architecture data_flow of multiplexer is
signal binary_key : std_logic_vector(7 downto 0);
signal tmp_numlock : std_logic;
signal flag : unsigned(3 downto 0);
begin
    process(columns, rows)
    begin
        binary_key(7 downto 4) <= rows;
        binary_key(3 downto 0) <= columns;
        if columns = "0000" or rows = "0000" then
            is_key_pressed <= '0';
        else
            is_key_pressed <= '1';
        end if;
    end process;
    output_binary_key <= binary_key;
end data_flow;

converter.vhd
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity converter is
    port(
        hex_key : in std_logic_vector(7 downto 0);
        output : out std_logic_vector(7 downto 0)
    );
end converter;
architecture data_flow of converter is
    begin
    with hex_key select
    output <=       x"2F" when "00010010",  -- /
                    x"2A" when "00010011",  -- *
                    x"2D" when "00010100",  -- -
                    x"37" when "00100001",  -- 7
                    x"38" when "00100010",  -- 8
                    x"39" when "00100011",  -- 9
                    x"2B" when "00100100",  -- +
                    x"34" when "00110001",  -- 4
                    x"35" when "00110010",  -- 5
                    x"36" when "00110011",  -- 6
                    x"31" when "01000001",  -- 1
                    x"32" when "01000010",  -- 2
                    x"33" when "01000011",  -- 3
                    x"0D" when "01000100",  -- enter
                    x"30" when "01010001",  -- 0
                    x"2E" when "01010011",  -- .
                    x"00" when others;
end data_flow;

Can anyone tell me how should I implement this "numlock" key now?

EDIT


texts: How does doping concentration affect MOSFET switching speed?

texts:
I've read that increasing the doping concentration would cause the carrier mobility to decrease, but at the same time, it would lower the threshold voltage. So a few questions come to mind:

When we're talking about doping concentration, say of a PMOS, are we talking about the heavily doped (with p-type impurity) region of drain and source or n-substrate? I'm assuming it's the former since that's what creates the channel.
Which is more dominant in terms of drain current change - the decrease in carrier mobility or the lowered threshold voltage? I suppose we can use the I-V equation in triode region, i.e. a decrease in carrier mobility lowers the current (i.e. lower switching speed) and a decrease in threshold voltage increases the current (i.e. higher switching speed).
When the threshold voltage is lowered, overdrive voltage (Vov) goes up, would this also mean the supply voltage (Vsd) need to be higher for the MOS to go to saturation? When we talk about supply voltage is it Vsd or the gate voltage?

I feel like I have an idea but am not understanding this clearly. Thanks.


texts: Pros and cons of low-power integrated series voltage regulators vs. shunt regulators

texts:
TL431 (and equivalent) shunt regulators are jellybean parts nowadays and quite cheap. The same can be said of TL317 (low-power version of LM317) adjustable series regulator.

When applied to supplying power to light loads (<100mA) they are both quite effective and simple to use. Despite their different internal topology, it seems that they can be used in the same role quite interchangeably.

I was wondering what are the pros and cons of using one or the other, or, more generally, what are the pros and cons of using a low-power shunt vs. series linear regulator. What are the design decision that can make a designer choose one over the other?

I'm aware that, for example, series regulators may have considerable drop-out voltage (2.5V for TL317), something that shunt regulators don't have (but may have higher minimum bias/quiescent current, instead). But taking into account LDOs regulators, this doesn't seem to be so compelling nowadays.

In the end, are there conspicuous advantages of one topology over the other (and in which case), especially when powering low-power loads?

Note: direct comparison of the two jellybean parts I've mentioned is appreciated as well as a more general comparison between topologies. You choose. The important thing is I'd like practical considerations based on actual design experience or knowledge on reasonably current products or systems. In other words "why and when a design engineer would use one over the other".


texts: Problem encountered while amplifying load cell signal with LM358

texts:
I have an S-type load cell to measure weight up to 100 Kg. Its datasheet mentions 3mV/V against full range and excitation voltage.

When no weight is applied, the voltage is 9.9 mV (Excitation is 10 V).
When I press the load cell manually, the voltage rises a few mV (like 14 to 17).

I designed a dual stage amplifier using an LM358 IC to amplify the voltage. The first stage is a differential amplifier with gain of 10 and the second a non-inverting amplifier, with a variable gain of 0 to 50 to achieve an output of around 10 V to feed to a PLC.

The circuit diagram is:

The Problem:

I get a 4 V output at LC2_O/P and doesn't change if I press the sensor.
However, if I apply somewhere between 0 - 0.1 V from my lab bench power supply, it shows a steady range of amplification.

Can someone please help?


texts: Op amp signal processing of an accelerometer output for an ADC

texts:
I have been designing a board which will monitor vibration activity of a machine using MEMS accelerometers. So far, I have connected the unadulterated signal from the accelerometer to the ADC however, I was considering the fact that if there is very little vibration, if I removed the dc bias, amplified the signal and then re-added the bias, I could make better use of the ADC resolution. The bias is 1.65V and the sensitivity is 300mV/g so under normal conditions with no vibration, the output is 1.95V.

From what I have googled, I think I can use a differential amplifier to remove the bias and to amplify the signal followed by a summing amplifier to replace the bias. So I have created the following circuit where V1 is 1.95V and V2 is the accelerometer output. However, I have no idea of what value resistors to use and how to calculate gain. I would like to either use a digi-pot or a MUX to change resistance and control gain from unity, 2X, 4X, 8X, 16X and 32X

Can somebody give me a heads up please? What sort of values should I use, what voltage should I supply to the op amps - is \$\pm 5\text{ V}\$ sufficient for an accelerometer output of 3.3V maximum? Which resistor should be variable and how do I calculate the values to give me the gain I want?


texts:
In the datasheet (http://www.ti.com/lit/gpn/pcm1807) of the Texas Instruments PCM1807 in section ABSOLUTE MAXIMUM RATINGS (page 2) it says

  Analog Input Voltage \$V_{IN}L,V_{IN}R,V_{REF}\$: \$-0.3V \text{ to } (V_{CC} + 0.3V\$)

Ok, that means it's a standard ADC for which an AC signal must be shifted before it's fed to the input pins.  Oh, and there's a convinient \$V_{REF}\$ for the DC offset (aka center voltage) as well.

But the schematic in section TYPICAL CIRCUIT CONNECTION DIAGRAM (page 25) both \$V_{IN}L\ \text{ and } V_{IN}R\$ are connected using a capacitor, which removes the DC offset and makes it an AC signal again, obviously conflicting with the absolute maximum ratings (and the overall logic of level shifting the input voltage to the \$0-V_{CC}\$ range).

What did I overlook?


texts: Is it safe/possible to add a BMS board to a soft pack 3s1p LIPO for charging and discharging?

texts:
i would like to make a 12V battery pack from a soft pack LiPo which can supply 10A for my projects which i can charge from a 12.6V DC wall powersupply. I dont want to use an external big special BMS charger made for charging these soft pack LiPo's, i want to add a small BMS board to the soft pack LiPo for easy charging. This is the first time im working with BMS's and LiPo's so im new to this.
Most tutorials show this being done for 3 x 18650 batteries in series and adding a BMS board which monitors each battery in the 3s1p configuration, supposedly this is safe and one can charge the pack at the terminals from a 12.6V power supply and discharge the pack from the same terminals of the BMS.
I would like to use a soft pack LiPo and add such a BMS and solder it to the XH connectors on the pack.
Is this safe? Would it be any different if done with 3 x 18650 cells?
Many Thanks
The LiPo im planning on using: LiPo link
The BMS: BMS link


texts: How to choose the correct inductor for my application

texts:
I am planning on using induction to power some game pieces in a project I am building.

My plan is to use identical coils in board and piece, so they will be small (2" max diameter).

My problem is that I don't understand the technical terms. As such, I'm at a loss to identify which pieces meet my needs.

The base, ideally, will have a 5v supply. Some of the game pieces will draw upto 20mA and some will draw upto 200mA. The pieces are not interchangeable, so if it's better to use different value inductors for the different pieces to cut the overall power draw to the base, that is the plan.

But I can't work out from the data sheets what units will be able to supply those requirements.

It has been suggested to me to use a frequency of 125kHz.

So the supply values are 5v DC  (current requirements to be determined) and oscillator frequency of 125kHz.

How do I interpret the data sheet specs:

Inductance (Henrys)

DCR typ/max (Ohms)

SRF typ (Hertz)

Isat (Amperes) @ 10/20/30%

Irms (Amperes) @ 20/40°C

With my supply data to work out what would be suitable.

EDIT

Forgot to mention, working distance between transmitting and receiving inductors will be max 15mm, probably less.

There will be the 3-4mm cardboard game board, and then a couple of mm in the plastics (probably 3D printed) for the game piece and the base.

2ND EDIT

Ok.  It's evident that I might not have asked the right question, so I'll try and explain a bit better what I want to achieve, maybe that will help.

Theoretically what I want to do should be achievable.  Whether it's feasible is another matter.  I'm fully aware I can't just magic electricity or off thin air.

Imagine a chess board where the pieces are electric toothbrushes and the squares are the chargers, you should get a kind of picture of what I'm attempting to achieve.

I only need to power 32 squares.

Of these, 16 need to supply enough power via induction to a floating piece so that the internal electrics of the piece get 5v and 20mA (0.1W). Up to ALL 16 of these spaces could be occupied at the same time.

The other 16 spaces need to supply enough power via induction to a floating piece so that the internal electrics get 5v 200mA (1.0W). However only upto 4 of these spaces will ever be occupied at the same time.

This means that the total amount of power required by the pieces is 5v×((16×20mA)+(4×200mA)) = 5v×(320mA+800mA) = 5v×1120mA = 5.6W

The power required by each piece has been over estimated by about 30% to make sure I have plenty of headroom.

The base will have some small circuitry, plus the primary coils/inductors to power the pieces.

At the moment, if I decide to use physical contacts to power the pieces, including the base,I should be able to get away with a 5v 1.5A supply.

Obviously that is going to increase because induction is not a perfect medium for power transfer.

However, I plan to only have power supplied to occupied spaces so that I'm not wasting emery powering coils that are not powering pieces.

So I need to work out what I need to do to supply the 5v 20mA or 200mA to the required pieces. And whether or not it will be possible within a 2 inch square area.

The max distance between the coils would be 10-15mm based on the fact that the game board is 3-4mm thick glossy card plus the 3D printed plastics for the base and the pieces.

The reason I asked about inductors rather than transformers is because I saw an article using an RF choke to power an ATTiny and turn it into an RFID tag (http://hackaday.com/2009/06/27/avr-rfid-tag/). And researching that lead me to power inductors. Which I thought would do what I want and induce power.

I don't mind winding my own coils but would rather use off the shelf parts if available.

I also am open to using slugs of metal to aid the windings.

It has been suggested that I want to use an oscillation frequency of about 125kHz.


texts: What kind of FPGA board for sha-256 algo

texts:
I am newbie in VHDL and FPGA, i was searching for an answer to my question but didn't find any good answer.
In my projet i have a .txt file containing a hexadecimal data, i want to send this data to an FPGA, 256-hash it, and then send the hashed data back to my laptop in another .txt file.
To do this task what kind of FPGA do i need to buy?
PS: I want a speed and not expensive one, if it's possible
Help is appreciated


texts: Does SystemVerilog support conditional compilation based on the tool analysing the file?

texts:
Does SystemVerilog contain a feature whereby it is able to detect what program is compiling the code (for synthesis or simulation) and then include or exclude sections of file for processing?
This feature could be used to declare "simulation only" code blocks and also write portable code whereby a design block instantiates different IP depending on wheather it is being compiled by Quartus, Libero or some other FPGA compiler.


texts:
We are all, or should be, extremely familiar with this graphic.

It is course the magic triangle used to represent Ohm's Law.

We should all also be very familiar with the similar power triangle.

What I find curious is that we all instantly recognize and talk about Ohm's law, yet I wonder exactly how many of us know who is responsible for the power triangle.

Even nice tutorial pages like this one, glibly talks about Ohm's Law and then wander into the power triangle as if it is somehow a part of it. No mention is ever given to the actual originators.

In actuality the P=IV law is from Joule heating,  Joule's first law, also known as the Joule–Lenz law, discovered independently by James Prescott Joule and Emil Lenz @1842.

Why does Georg Ohm get so much credit while Joule and Lenz, with a law that is, in my mind, equally as important as Ohm's Law, are relegated to the back pages of history?

One has to wonder who slept with whom to either get recognized or forgotten.

I do realize that this seems like a discussion question, but I really want to know if there is some reason not to call it what it is. I do understand that Joule's First Law is a much bigger body of work than just the electrical heating part. Perhaps that is the issue.

Without some reason to the contrary, I'm going to make it my mission to use the credited name for the formula in the future, as, perhaps, should we all.

PS: Interestingly there is no tag on here for the law either. Lenz is not even there and the only mention Joule gets is "Joule-Thief".... sigh

PPS: Ohm's law was published in 1827, I wonder how they figured out how big resistors needed to be for the intervening 15 years...


texts: 74HC14 VCC and GND won't connect even with PWR_FLAGs attached to board input connector

texts:
Sorry, new to KiCAD so decided to place a single 74HC14 in schematic and single 4-pin connector with VCC, GND, sig input and sig output. Also threw in 5 resistors and 5 capacitors to build a simple (stupid) delay line. Was intending to take this design through DRC, netlisting and then layout the PCB.
First surprise, VCC and GND didn't connect to hidden pins on HC14. Read about PWR_FLAG and attached a flag to VCC and another to GND. Great, no more DRC errors. However, upon inspecting netlist output, neither GND nor VCC connects to the HC14.
Inspected pin listing for HC14 and both GND (pin 7) and VCC (pin 14) are listed as PWR inputs.
Hide/display hidden pins has no effect.
Any help will be greatly appreciated. Thanks


texts:
Recently I just bought 2 pack of Eneloop pros, and have fully charged it. By using a multimeter I saw that the voltage went up to 1.3 ish after it is fully charged. And I'm planning on using 5 of them (in series) to power 5 different MG996R servos which has an operating voltage of 4.8 to 7.2v

So 1.3v x 5 = 6.5v

Is it possible that I could burn out the servos because I used the voltage closer to 7.2v?


texts: Can not interface with Winbond W25Q16DVSIG over SPI

texts:
I'm trying to attach Winbond W25Q16DVSIG to Atmega 1284P-PU. I've attached SPI bus according to the pinout, CS pin has 10K pullup resistor.

Whenever I'm trying to perform any operation, chip is not responding. I've wrote very simple code to be able to test read of manufacturer / device id using instruction 90h according to the datasheet page 52

Basically it require to send four bytes, one with instruction 90h followed by 24bit address (all zero).

When I'm trying to get response, I'm always getting zeros (two bytes).

Code is very simple and looks like this

    byte data [4];
    data[0] = 0x90;
    data[1] = 0x00;
    data[2] = 0x00;
    data[3] = 0x00;

    digitalWrite(FLASH_CS, LOW);
    SPI.beginTransaction(SPISettings(10000000, MSBFIRST, SPI_MODE0));

    SPI.transfer(data, 4);

    byte data1 = SPI.transfer(0x00);
    byte data2 = SPI.transfer(0x00);

    SPI.endTransaction();
    digitalWrite(FLASH_CS, HIGH);

I've checked transfer with LA, and it looks like chip is not responding at all (there are some strange two spikes). It looks like this:

I've done the same for Winbond W25Q16BVSIG and it is working fine. I'm getting proper response and transmission looks like this:

What am I doing wrong here ? Is there something I'm missing from the datasheet ? SPI Clock is too slow ?

Wiring is the same for both chips. Unfortunately I don't have any programmer to check flash chip directly.


texts:
So, long story short: I'll soon have a PCB which accepts 24v 5a power input and has a 4 pin power plug of this type:

And is wired like this:

My question is: assuming I have a generic AC/DC adapter with the correct voltage and amperage and I cut its plug, if I were to solder its wires on the 4 pin input of the PCB, would it be fine if I soldered the positive wire to both the positive pins and the negative one to both the negative pins? If not, what would be the correct approach?


texts: Why is my LED less bright when activated through a vibration switch? How can I avoid this?

texts:
total noob here. I'm trying to figure out why an LED in a small circuit isn't getting to full brightness, and how to fix that.

It's a simple, pre-bought circuit, seen here http://postimg.org/image/iab6po9c1/ - originally taken from a basic led bike wheel valve light. Circuit like this:

Battery (3 x AG10) > Vibration Switch > LED > Battery.

(before you ask - http://www.electrodragon.com/product/vibration-switch-sensor-sw-18020p/ - but I've no idea of the exact specs of mine, just that I have a few different ones, and they all act the same way).

When the LED (any LED, I also tried a few) is connected directly to the battery, or I manually press the spring against the contact in the vib switch, it lights up at normal brightness.

However when the vibration switch is, well, vibrated and switched, I only ever get around 50% brightness from the LED. I assume the switch only makes contact for a very short period so doesn't let enough power through or whatever. Either way, it's dull.

I'm not sure exactly what to use, but I've seen similar stuff that puts a transistor or 555 timer between the battery and LED, uses the switch to activate the transistor or 555, that then pulls power from the battery and activates the LED:

Battery > Transistor > LED > Battery

| > Vib. Switch >|

Any ideas if this will get the battery to full brightness? If so, what type of transistor would I need (I got as far as NPN - don't wanna use 555 as it's be too big and complex)? And/or is there anything I'm missing (caps, resistors - trying to keep it simple - I have about 5mil of space and would prefer not to even solder). Thanks :)


texts: What standards cover foot prints for standard part packages?

texts:
So far I see some JEDEC standards for part packages, but I need standards for the corresponding footprints. For example MS-026 is a JEDEC standard for a PQFP part, so what would be the standards that covers the foot print for this part?

Just a note, I started looking for this after seeing a few datasheets' recommended layouts that were smaller than the pins on the part.


texts: Will an FPGA get damaged if contention occurs on a bidirectional pin on it?

texts:
I was told in the university that bus contention can cause hardware damage. I am referring to a situation where two pieces of hardware force/drive different logic levels on the same signal.

Taking example of an FPGA that is connected to a PS2 device or any other example where using bidirectional signals is required, what will happen if both the devices on this bidirectional signal drive different logic levels onto it?


texts: Clalculating effective value of square waveform

texts:
I need to calculate the effective value of this signal:

I dont know how to calculate this. Iknow how to calculate the effective value of well known waveforms like square, sin, ..., but this is a mystery for me. I think I should combine it somehow with square waveform, but I don't know how.


texts: View more than 100 worst-case paths in Quartus II

texts:
I am using Quartus II to compile Verilog for my FPGA project. For debug, I use SignalTap, which introduces a lot of timing warnings. When I go to the TimeQuest report, and look at the worst-case timing paths, the top 100 slowest paths are related to SignalTap. All the "real" paths are below those 100 SignalTap paths.

How can I view more than 100 worst-case paths in Quartus II?


texts:
Why do computers only use 0 and 1? Won't the addition of other numbers such as 2 or 3 speed up computers? Also, 2 and 3 can be used to shorten the bit-length of integers (2 and 3 can be used to end an integer, so that the number 1 only needs one two bits.)..

Why is binary computer more preferred?


texts:
I'm looking for examples of how current mirror is used in real life.
Most tutorials cover the circuit itself but don't go into examples. Therefore, I'm still struggling to understand how it's used and what the benefits of it are.
Update: I'm looking for simple enough examples for a newbie to understand, please don't post complete op-amp schematics, etc. Thanks!


texts: Are there any viable sound IC's in older consumer PC sound cards/modems for diy/circuitbending?

texts:
I watched some diy synthesizer vids on youtube, mostly APC's, and I thought since most use the 556/555's, what if we used something different. As fun as buying kits are, sometimes, we are broke, but still inspired. So, I went into my closet and found 7+ modems(mostly ISA) and 6 sound cards (all SB; vibra16 ISA, awe64 value, SB16Pro2, Live value, live platinum and audigy 2 platinum). A little research suggested the vibra 16 was the most outdated and pretty much useless, so it's now wearing a red jumper.

I couldn't find any schematics for any of the boards or IC's.

Am I totally off base thinking I can salvage an IC to use as a simple tone generator like an APC type synthesizer? I included modems in my search because I recall the sounds they made when dialing up, and I thought, hmmm, if that were modulated and probably slowed down it might work as a tone generator. I admit I am new to this, so identifying the correct chip to use and well, which pins do what is a little confusing. Oh, and modems and soundcards are also a good source for jacks (the sbpro2 actually has a volume pot, ha).

ps- this all started last wednesday when my Roland D2 arrived from a stint on ebay and the left channel is out, after running it thru test mode, I don't think it's more serious, theoretically than cold spots that will go away after being reflowed, but wanted to warm up to possibly ruining the piece of gear with a distraction.


texts: Is a hard to turn shaft a sign of a bad DC motor?

texts:
I have a 220V ungeared DC motor and the shaft is very hard to spin when not powered and the two leads are not connected to each other. I have to use pliers to get it to spin. It feels consistently lumpy. I am getting a resistance reading of about 34.5 ohms from the two leads.

I have another 90V motor and although there is some resistance when turning the shaft, it can be turned by hand.  Does this indicate something wrong with the  motor?

NOTES
I disassembled it and put it back together. I was shocked to find the rotor wasn't centered within the housing causing it to stick to the field's strong magnet.  Apparently, there was an extra lock ring on one of the long housing screws causing it to cock towards one side of the stator. I hand to position the end mill precisely using light hammer taps to the end bells.  While holding it in position and checking the rotation, I tightened the long housing screws in an alternating fashion until both were tight.


texts: Divide clock frequency by 3 with 50% duty cycle by using a Karnaugh Map?

texts:
In this document, On semiconductor describe how to design a divide by 3 system using a Karnaugh Map:

Specify, Divide By 3,
50% duty cycle on the output
Synchronous clocking
50% duty cycle clock in
Using D type Flop flips and karnaugh maps we find;
Ad = A*B* and Bd = A
(Note: * indicates BAR function)

From this, they show this schematic:

Afterward, they say:

  Using the technique, we add a gate on the clock to get differential
  Clock and Clock bar, a flip flop that triggers on the Clock Bar rising
  edge (Clock Neg.) to shift the output of ”B” by 90 degrees and a gate
  to AND/OR two FF output to produce the 50% output. We get Figure 2, a
  Divide By 3 that clocks synchronously with 50% output duty cycle.

And they show this schematic:

I was hoping you could show me how they got to this schematic from the Karnaugh Map. I know it's used to simplfy boolean expressions but I didn't know you could design systems with this method.

I'm asking because I have no idea how to even approach such a question, let alone how to solve it. If anyone has a better idea than using a Karnaugh Map, I would love to hear it.

Thank you!


texts: How do I identify the imput side of a transformer

texts:
I have this 2.5VA Split-Bobbin Power Transformer 115/230VAC. According to page 3 of the Data Sheet (PDF) it looks like there is a line on the "DSW" version on the pin 1-4 side. This seems to correspond to a small step down (maybe 1-2 mm or so) on the top of the physical transformer.

Is it safe to assume that is the identifier for the pin 1-4 side? If not, how do I identify which side is the input and which side is the output?


texts: Input Ripple Voltage and Output Ripple Voltage for Capacitors

texts:
I'm working with Buck converters and Boost converters separately.
Can someone tell me the reason why the output ripple voltage (and current) exists in the Output Capacitors and how does the input ripple voltage (and current) occurs in the input capacitors?
I think since the current in the inductor is ramping up and down, this current flows in and out of the output capacitor which is why we get output ripple current in the capacitor. And if its an Electrolytic capacitor, we have its ESR, which gives the Output ripple voltage? Is my understanding correct?
If so, could you provide a formula for it which might help in intuitive understanding?
But I am not able to understand how input ripple voltage and current occurs at the input capacitors? Please help with that.
Any proper references or links to the formulas for their calculation of ripple current and voltage and the input and output of the capacitors?


texts: Is the QI norm about the components or the coil?

texts:
I would like to have induction charging for my smart object and I was looking at QI chargers/receivers

The QI chargers I find on the market are "designed for phones" : they are very flat and offer a good surface.
Also, QI Charge is very good within 2-3 mm distance but after this it drops very quickly.

But my object (I can't say what it is) doesn't have a big flat shape.

Hence I wanted to know if I could make my own QI charger easily or not. The big problem for me is the coil which is around 4cm*3cm : this is too big to fit in my object and I would like to have a smaller coil (1cm diameter).

Question:

Can I use a QI charger and use my own smaller coil ? Or is the coil really part of the norm and changing the coil will cause problems ?


texts:
I need a single-pole circuit breaker for a 200A, 48V DC battery bank powering a solar inverter.  The batteries are LiFePO4 and capable of large short-circuit currents on the order of 10 to 15 kA.  Large molded-case (MCCB) breakers are available with 200A rating and typically 20kA Icu (breaking) rating, but I am having difficulty finding a suitable enclosure.  Can I use a DIN mounted 4-pole 50A interlocked breaker with the 4 poles in parallel?  Even though this seems like a common case, I am unable to find any trustworthy answers.

The 4P breaker has an Icu rating of 6kA, is non-polarized, and is typically used in high voltage solar PV applications where the DC interrupting voltage needs to be up to 1000 VDC, so the breakers are arranged in series.  This means that the breaker has 4x the I2R loss is series.  Parallel power loss through 4 breakers would be 4*1/(4^2) = 25% of the series power loss, so that seems fine from a power dissipation (e.g. thermal) standpoint.  The question likely comes down to the 6 kA Icu rating and how that works in parallel with interlocked breakers.


texts: I designed a circuit that powers on when the car is started (key is in ACC or ON).  The circuit's uC then enables 12V from the battery by setting port PC5 high.  The uC detects when the key is switched off when port PC4 goes high via the opto-isolator and the uC then remains on until it sends port PC5 low removing the 12V battery supply disabling the circuit until the key is switched on again.  There are many previous questions that cover high-side switching but I haven’t seen one quite like this.  The circuit works fine on the breadboard, but I don’t know that it’s the best approach.  Should I consider using a FET rather than the 3906 BJT?  Would a BJT be more appropriate than the opto-isolator?  Any glaring errors with this design (unnecessary or incorrect value components, etc)?


texts:
This is a question of entrance exam for government telecommunications company:

  A complex device used to send and receive serial data over telephone lines is

  A)USART

  B)Modem

  C)SDLC

  D)RS232

The given was USART, but according to me, it is modem that we use over telephone lines. What would be the justification to USART if it is the correct answer?


texts: Unique Serial Number for Atmel SAM Series

texts:
My aim is to acquire a unique serial number for my design and reuse it as an ID in different places for my Radio communication. I have used an Atmel SAM D21 series microcontroller on my design which on the 1st sight seemed to have a serial number when I followed the following path in Atmel Studio.

Menu > Tools > Device Programming > Device Information

But no traces of any serial numbers of any sort. Just a Device Signature which repeats on all the MCUs.

I am aware that we could use a Dallas One Wire Serial chip for this purpose and apparently some AVR series have an accessible serial number in them, but in the favor of reducing the BOM and the choice of MCU I am trying not to go that way.

In the meanwhile, even though that I haven't used the feature myself, I know that SAM D series have an integrated USB module in them. Considering that every USB module should have a unique serial number (unless I am wrong), is there a method to extract that SN?

Please let me know if there are any solutions you have in mind for this purpose.