texts: Photodiode - Modes of Operation, Currents and Voltages

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Problem Statement

Consider a pin-Photodiode, whose depletion region, space charge profile and electric field profile can be visualized as follows (screenshot of the Semiconductor Applet Service by Prof. Chu-Ryang Wie):

The Voltage-Current-Characteristics can be approximated as shown in the following diagram:

Questions

First Question: Is the following classification of the modes of operation including the explanations correct?

1st Quadrant: Photoemissive Mode - Light Emitting Diode (ger.: Lichtemitter)

Voltage, Current and Power:
Passive Element Power-Absorbing Element
$$V_D > 0, I_D > 0 \rightarrow P_D = V_D \cdot I_D > 0$$
We apply a (positive) external forward bias voltage and force a positive current through the diode. As a consequence, the diode emitts light.
In summary, externally supplied electrical energy is converted into photons, i.e. light.

3rd Quadrant: Photoconductive Mode / Photodiode Mode - Light Sensor / (Reverse) Voltage Bias Operating Mode (ger.: Diodenbetrieb)

General Case

Voltage, Current and Power:
Passive Element Power-Absorbing Element
$$V_D \leq 0, I_D < 0 \rightarrow P_D = V_D \cdot I_D \geq 0$$
We apply a (negative) external reverse bias voltage. The negative current through the diode is now a function of the light it is subjected to. By measuring the current we can calculate the light intensity.
In summary, externally supplied electrical energy is modified by the diode proportionally to light it is subjected to.

Special Case \$V = 0\$: Short Circuit Mode (ger.: Kurzschlussbetrieb)

Voltage, Current and Power:
Neutral Element
$$V_D = 0, I_D < 0 \rightarrow P_D = V_D \cdot I_D = 0$$
No external power is applied. Instead, the current developed by the diode while being subjected to light is measured to determine the light intensity.
The current is (almost) a linear function of the light intensity.

4th Quadrant: Photovoltaic Mode - Solar Cell (ger.: Elementbetrieb)

General Case

Voltage, Current and Power:
Active Element Power-Generating Element
$$V_D > 0, I_D \leq 0 \rightarrow P_D = V_D \cdot I_D \leq 0$$
No external power is applied. Instead, light energy is converted by the diode into negative voltage and negative current, which is then forced through a load (e.g. a resistor).

Special Case \$I = 0\$: Photovoltaic Mode / Open Circuit Mode (ger.: Leerlaufbetrieb)

Voltage, Current and Power:
Neutral Element
$$V_D > 0, I_D = 0 \rightarrow P_D = V_D \cdot I_D = 0$$
No external power is applied. Instead, the voltage developed by the diode while being subjected to light is measured to determine the light intensity.
The voltage is a highly nonlinear function of the light intensity.

Second Question: How do the generated electron-hole-pairs in the depletion region behave for different modes of operation?
The only thing I found is that, due to the electric field in the depletion region, holes are always sucked into the neutral p-zone and electrones are always sucked into the neutral n-zone.
Is this true for both forward and reverse bias voltage, whether it is internal or external? What does happen next?


texts: I've mistakenly purchase an unwired battery pack, I'm unsure about how to wire this, never done anything like this but I thought if try and understand wiring a bit better. I have a 3xAA battery pack that I bought from Maplin but I don't know how to wire it, all the tutorials I see already has the wires protruding from it. Sorry for the basic question


texts:
I tried to plot the magnitude of transfer function using Matlab.

\$
H(\omega) = \frac{V_0}{V_i} = \frac{R}{R + j\omega L + 1/j\omega C} = \frac{R}{R + j(\omega L - 1/\omega C)}
\$

simulate this circuit – Schematic created using CircuitLab

Matlab code:

%% Band-pass filter

R = 1;
C = 1;
L = .02;
w = 0:.01:10;
H = R ./ (R + 1i*(w * L - 1./(w * C)));
mag = abs(H);

% plot magnitude
figure(3), clf
plot(w, mag);
title('Frequency response of RLC series resonent circuit')
xlabel('\omega'), ylabel('|H(\omega)|')
hold on
% plot center frequency
w_center = 1 / sqrt(L*C);
plot([w_center w_center], get(gca, 'ylim'), 'r--')
plot(get(gca, 'xlim'), [.7071 .7071], 'r--')

How do I choose the value of R, L and C that can plot the actual curve below as same as possible.


texts: DC-DC Half Bridge Converter Capacitor Selection?

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For the  shown in figure. How do I decide on the capacitor values C4 and C3? I know they should have a balanced voltage across them. Do I go with the regular capacitor equation to determine the value? Do I need to keep anything else in mind?

Please let me know. Thanks!


texts: Clock Divider IC, Using Series or Parallel Termination

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I am using a 542MILF in a design.

The datasheet says the output impedance is 20Ω (not low output impedance)

Would I have to use series termination e.i. 30Ω resistor followed by 50Ω transmission line because this IC has a fairly high output impedance?

If the clock signal is going to a HiZ input could I still use parallel termination instead?

Thanks


texts: Why did the Intel bubble memory chips have a hexadecimal label on them?

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Such as in this image:
I guess some sort of configuration, am I right?


texts: 5-pin SMD device identification - top marking CaC9A

texts: Please help me to find the name of this SMD device with top marking CaC9A


texts:
Hi everyone I've done a fair bit of googling but please let me know if this question is a duplicate or answered in altium design documents.
I have a hierarchical design and I needed to separate two sections of a circuit that have a lot of nets connected between them, as you can see.

Altium in its infinite wisdom appears to have named all of these nets N000-1 by default.

Now, so far I've been going around this issue by adding net labels, and maybe that's what I should do, but it seems a bit tedious and redundant. Is that the only solution to this? This issue hasn't come up for me when I'm wiring schematic symbols together, just when I'm wiring together sheet entries from ports as shown. I'm pretty new to this top level hierarchy stuff. Thanks for any help.

I found a similar question, but the consensus was that this one was caused by poor choice of net names and the way they were wired together. As far as I can tell, this doesn't apply to my question.
Altium Hierarchical design error


texts:
I have found this problem in my textbook.

The system has 3 inputs. The first two, A and B,
represent a number in the range 0 to 2 (3 is not used).
The third input, C represents a second number in the
range 0 to 1. The output, f, is to be 1 if and only if the
two numbers equal to each other.

(1) Create the truth table of the system.

(2) Create the k-maps of the system

(3) Get the express f(A, B, C) in minimum SOP form.

(4) Get the express f(A, B, C) in minimum POS form.

I have tried this way:

c   A   B   f

0   0   0   1

0   0   1   0

0   1   0   0

0   1   1   x

1   0   0   0

1   0   1   0

1   1   0   0

1   1   1   x

As f=1 when AB == C .

What does it mean by "The output, f, is to be 1 if and only if the
two numbers equal to each other." ? What will be the truth table?


texts: Original motherboard component + redesigned PCB = Well working?

texts:
Well I bought my laptop about 3 years ago, and I want to replace motherboard.

I have a nice Micro-ATX board, but as I know, this desktop motherboard cannot fit in laptop.

So I'm planning to figure out all the connections in original motherboard, re-design PCB to

make it fit in my laptop, and then transplant all the components.

Is there any possible problems in this plan? (except problems about soldering)


texts:
I have a Xilinx/Digilent Spartan 3E starter board, UG230. I'm designing a PCB for an ADC/DAC board. I'm quite new to FPGAs (with some experience), but I don't want to make any silly mistakes using the Hirose FX2 connector (J3) - see board datasheet pg. 115. I have 2 questions:

1) The board clock is 50 MHz. Can I also output that same 50 MHz onto an IO pin to clock the ADC? I know this will work in theory, I just want to know if the FPGA will be able to do this? I'm used to MCUs where the IO speed can only be a fraction of the master clock.

2) Some of the pins on the Hirose FX2 connector are IO and others are INPUT only. The ADC I have is a 16 bit parallel bus, and I'd like to keep the IO pins for user input/output (display, etc). So the INPUT only pins would be good for the ADC. Are there any tricks to using the input pins (D12, C12, A15, B15, C15)? I would like to clock the ADC at 50 MHz (see Q1).

All advice greatly appreciated. Just don't want to get a board make and have to junk it for a silly mistake because I've miss-understood something trivial.

Cheers folks.


texts: With reference to the circuit on attached -- the zobel/ impedance equalization circuit. If we don't know the value of L, Is there any ways to calculate C' without knowing the value of L? I believe this story might be involved in the frequency-domain. Therefore, if we have the data of frequency response, in this case it is a loudspeaker's, such as cut-off frequency or the point where frequency starts to rise, can we use it instead? Please anyone help to explain.


texts: Industrial product wires soldering to pads

texts: I'm designing a board for an industrial product that has a lifetime of more than 20 years, the product housing is sealed. which is better for ultrasonic transceivers connection to the board, to use connectors or solder the sensor wires directly to pads on the board?


texts:
I'm applying a 3.3V signal with my Raspberry Pi to the base of an NPN transistor to activate a SPDT 6V relay (relay data sheet, model G2R-1-S-DC6(S)). The relay pickup/dropoff voltage is 4.4/0.9V.  The transistor activates the circuit like it should when the signal is applied, but it does not turn off when the signal is removed.

The relay coil resistance is 68.7 ohms, as shown in the simulation. The 161 ohm resistor was added to dissipate some power because the transistor is rated for 600 mW.  When adding the emitter resistance, I calculated that it needed to be under 40.7 ohms. I used a 33 ohm because that is what I had on hand.  The 24Vdc supply is used here because it is what is available in the system. I am using a 2N2222 transistor from Radio Shack with a Beta=200.  The 3.3V ground and 24V ground were tied together when the circuit was constructed.

I've experimented with adding a resistor from base to ground; I tried this with 10k, 33k, and 100k resistances. I have tried a diode in parallel with the relay pointing up. I used a new transistor every time I tried a new circuit to ensure the transistor was not burned up from the previous test. I also tried multiple different combinations of Rb and Rc with the same result. The strange part is, when experimenting with Rc values, the Beta calculated from test measurements ranged from 50-500, which is very odd. In all trials, the current through the relay was as calculated in the simulation; it did not change upon application and after removal of the signal.

I saw another post where someone used a small capacitor in parallel with Rb to sweep voltage off the base emitter, we also tried this but it didn't work (link - it is the third diagram from the top).

Any advice will be will be greatly appreciated.


texts: Understanding some mistakes, when trying to find the Thevenin equivalent

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I was asked to find the Thevenin-Norton equivelant, and I got stuck on some things that I can't quite understand. I don't know if i need to be more specific.

What's wrong with the following?

And why isn't this allowed?


texts: headphone input to arduino for FFT usage

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I am building a FFT audio-reactive project with an Arduino that I would like to add a line-in input to. I am most likely to be using a ATTiny84 or ATTiny85 as the sampling device, which is running at 3.3 volts with the AREF set to VCC (also 3.3V).

What sort of schematic would I use to ensure that I can read the full range of the audio input while not harming the device? I am aware that the audio signal is likely to vary based on what the input device is, so please try to make any suggestions as flexible as possible with simple passive components. The target source device (not perhaps the only source, but a reasonable average) is an MP3 player with a 3.5 mm audio jack that can power headphones or a reasonable unpowered PC speaker (Sandisk Clip) or a PC headphone-out jack.

(Note: I have only a limited selection of capacitors, so knowing what ones aren't too specific would be helpful. I have a bunch of 0.1uF, and three or four 10uF, but I'm not sure I have enough to make two of these. I also have a number of ceramics of varying values. I have a large assortment of most common resistors, however.)

It may be possible to use the system at 5V levels if I can disable the internal i2c pullups on the ATTiny (how?), but I am communicating with a 3.3V host device, so those MUST be disabled if I am to do this. If you can confirm how to do that (or to disable them again fast enough that it won't be noticed on the line), a 5V system and AREF can be assumed, if that would simplify the design.

Similar designs I am aware of (but that I don't know the voltage ranges for):
https://forum.arduino.cc/index.php?topic=476900.0,
https://github.com/PaulStoffregen/Audio

For further information, I would ideally like this to be interchangeable with the microphone breakout here in terms of functionality:
https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814/
(Offset at 1.25V with AC signal. Note that this microphone is thus for 3.3V as well, but I'm fairly sure that the FFT library I use won't care too much about where the resting value is, so a different DC offset is fine if building for 5V.)


texts: How do you level-shift a sawtooth signal?

texts:
I am designing a sawtooth generator for an integrated PWM mode buck converter. I have built a constant current source (a simple PMOS current mirror) which linearly charges a capacitor. There is a switch that discharges the capacitor as the desired height is obtained. The value of capacitance, current and the time for which the switch is OFF, determine the voltage across capacitor. This could generate a signal that ramps up from 0 V to a certain height and in a short time, falls back to zero.

This signal is fed to a comparator whose common mode range is around 1 V. I have to add a DC shift of 1 V to the signal so that comparator is properly biased. I tried adding a resistor in series with the capacitor, so that I get a DC shift even when the switch shorts the capacitor terminals.It does work well but fails as process, temperature and voltage/current variations are considered. Is there any other way I could do this?

EDIT

Here's the schematic: I have added a resistor of 650 K and the current is 2 uA which gives a shift of 1.3 V. The signal VP controls the switch M3. M3 is OFF for 249 ns and is ON for 1 ns during which capacitor discharges. The voltage across capacitor changes from 0 V to 0.5 V while that tapped from upper terminal of resistor changes from 1.3 to 1.8 V.


texts: I can't get out from interrupt driven serial communication

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program  works correctly but after receiving '#' it has to come out from while loop and print "Exit" on lcd but it doesn't.program still in while loop.

#define F_CPU 14745600
#include<avr/io.h>
#include<avr/interrupt.h>
#include<util/delay.h>
char data;
int ser=1;
void uart2_init(void)
{
   UCSR2B = 0x00; //disable while setting baud rate
   UCSR2A = 0x00;
   UCSR2C = 0x06;
   UBRR2L = 0x5F; //set baud rate lo
   UBRR2H = 0x00; //set baud rate hi
   UCSR2B = 0x98;
}

ISR(USART2_RX_vect)         // ISR for receive complete interrupt
{
  data = UDR2;
  lcd_wr_char(data);

  if(data=='#')
  {
    ser=0;
  }
}

void init_devices()
{
   cli(); //Clears the global interrupts

   lcd_port_config();
   uart2_init();

   sei();   //Enables the global interrupts
 }

//Main Function
int main(void)
{
  init_devices();
  lcd_set_4bit();
  lcd_init();
  while(ser);
  lcd_string("Exit");
}


texts:
I was trying to look for the answer of what I think it should be quite a simple question but I haven't found any nice answer (at least any that has convinced me).
Here it is:

Through a cable (reflectometry) or even a in a RADAR, in order to detect small defects/objects, you usually use high frequencies, because the resolution will be better; my questions is why? I have always assumed instinctively that the object must be bigger than the wavelength in order to be detected but I would like to know why... Does the reflection coefficient get bigger with frequency? Is the reflected energy the same but as the reflected pulse would be wider with low frequencies, it is just more difficult to detect?


texts:
I using STM32F103C8, I want to use PC13 in GPIO mode (RTC is active).
The register ODR13 changes, but the logical value of the PIN does not change.

static void MX_GPIO_Init(void)
{

     GPIO_InitTypeDef GPIO_InitStruct;

     /* GPIO Ports Clock Enable */
     __HAL_RCC_GPIOC_CLK_ENABLE();
     __HAL_RCC_GPIOD_CLK_ENABLE();
     __HAL_RCC_GPIOA_CLK_ENABLE();

     /*Configure GPIO pin Output Level */
     HAL_GPIO_WritePin(LED_GPIO_Port, LED_Pin, GPIO_PIN_SET);

     /*Configure GPIO pin : LED_Pin */
     GPIO_InitStruct.Pin = LED_Pin;
     GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
     GPIO_InitStruct.Pull = GPIO_PULLUP;
     GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
     HAL_GPIO_Init(LED_GPIO_Port, &GPIO_InitStruct);

 }

I read manual this chip, This pin current limited

  PC13, PC14 and PC15 are supplied through the power switch. Since the switch only sinks a limited amount of current (3 mA), the use of
  GPIOs PC13 to PC15 in output mode is limited: the speed should not
  exceed 2 MHz with a maximum load of 30 pF and these IOs must not be
  used as a current source (e.g. to drive an LED).

But I did not connect to the place


texts: For electrical outlets that have on/off switches, is energy sent to the socket when nothing is connected to it but the switch is on?

texts: In several countries, electrical outlets have physical on/off switches used to control the energy flow sent to the connected appliance. If the switch is set to the on position but nothing is connected to the socket, will any energy be used/wasted?


texts: Buck converter - Spikes on output at switching frequency

texts:
I've been using LT1158 to make a step down switching regulator.
I have an input frequency of 50kHz and this is my circuit

I put 22 Ohm 50 Watt resistor on CON1 as a load.
I got this output measured from CON1

its 5us/div

VIN = 24V

input = 3.3V 50% duty cycle

Can you help me why there are reoccurring spikes at every beginning of the switching frequency?


texts: Why do electrolytic capacitors have terminals of different length unlike ceramic capacitors

texts: Electrolytic capacitors have 2 terminals of different length to indicate polarities, but ceramic capacitors have terminals of same length having no polarities. Why is there a difference between these two types of capacitors?


texts: Decoupling capacitor placements and ratings - how to choose?

texts:
I am building a circuit with 2 hybrid stepper motors each powered by a stepper motor driver A4988 and both drivers are connected to an Arduino UNO R3.

Before soldering the components together on a PCB, I would like to clear my doubts, confirm what I'm doing and prevent any disasters or improve it, if possible.

I have done some research about the importance of using capacitors, but I still have some unanswered questions.

Here are the specs for each hybrid stepper motor:

Rated current (Amps/Phase): 1.68

Recommended voltage: 12 - 24 V

Holding torque (kg.cm): 4.4

Resistance (Ohms/Phase): 1.65

Inductance (mH/Phase): 3.6

Here are two variants of the section of the circuit schematic relating to the stepper motors and drivers:

I have a few questions since during the circuit design, I've been puzzling over several aspects of the decoupling capacitor placements and their respective capacitance and voltage ratings.

I have made two versions of the schematic in the picture above but I can't figure out which one is better.  And why? In design B, I have placed a 100nF ceramic capacitor between the 5V and GND of each stepper driver - is it better from a design perspective? Although design B uses one extra 100nF capacitor compared to design A, I am trying to make the best practical circuit possible and explain it coherently.
Why connect a 35 V electrolytic capacitor when only a 9V supply is used to power the motors? How is this 35 V calculated? I found this in a schematic during my search but I want to understand why that value was chosen before i build it.
I have read that as a good rule of thumb to always use a small 100nF ceramic capacitor and a bigger 100uF electrolytic capacitor in parallel to the supply and ground. But in this schematic, there is only a 100 uF between the MV and GND, so should I add a 100nF ceramic capacitor in parallel to improve this design??
Why is a 100nF ceramic capacitor used between the logic voltage 5V (supplied from the 5V output from the Arduino UNO R3) and GND? I read that it filters out high frequency signals. But shouldn't the voltage output from the 5 V pin on the Arduino already be stable??
The recommended voltage for the motor is 12 V, so if I were to use a 12 V DC power supply instead of 9 V, what capacitor voltage ratings should i use? How do I calculate this?
I have set the current limit to each stepper motor to about 500 mA (from my online search, I read that a limit of 500 mA is safe so as not to damage the wires,) so is that something to be considered when choosing the capacitor ratings?

At this point, I am just blindly using what I found in my search online going through several schematics without really understanding why. I would really appreciate some clarifications. Maybe someone with PCB design experience can enlighten me on these issues.


texts: Calculate the direct voltage common mode rejection ratio for an instrument in which a common mode voltage of 100V produces an error in reading of 5mV

texts:
Dv/dt = 5/100 =0.05V
V * 100 =0.05 * 100= 5V
This is what I did. I can't get it right.  It's a measurement and instrumentation course, specifically an electronic engineering course.


texts: What happens the transistors in a chip as the temperature increases?

texts:
If the chip stop operating properly, then as it gets hotter the transistors fail, eventually to the point where the silicon in the transistor melts.

I'm after the whole process of how a temperature increase affects the chip, until the chip is destroyed.


texts: Use one or two transistors to switch an LED from PIC

texts:
I'm fairly new to electronics - I've had a reasonable amount of success with getting PCBs made using Eagle, but it was mostly wiring together breakouts and fairly simple stuff. I've spend the last two days learning about mosfets, resistors and transistors though, and one part of an existing circuit I'm using has me confused.

The LED being driven is a 5mm white 20mA. The existing schematic is here:

The PIC that is feeding "Torch" has an absolute maximum rating of 0.025A @ 3.3V [CORRECTED - previously stated 0.25A] on an IO pin (PIC16F1513). I don't understand why this simpler layout (on the right) wasn't used instead:

(picture taken from here: http://forum.allaboutcircuits.com/attachments/transistor-and-led-png.39778)

The question is: does the first circuit with two transistors have some advantage over the circuit with one transistor, given that the control is from a PIC?

[EDIT 2] The PIC datasheet is here: http://ww1.microchip.com/downloads/en/DeviceDoc/40001452D.pdf


texts: why do most sensors have an electrical output, regardless of the physical nature of the variable being measured

texts: I have been trying to figure out a explanation to this question, can someone explain this ?


texts: DIN Rail with In-Rail Bus - GND/PE design question

texts:
We are designing a system that consists of several modules that are mounted on a DIN rail. They are connected to each other using an In-Rail Bus system like this:

System design:
The 5 bus line currently are used like this: GND | SIGNAL | 12V | SIGNAL | GND

We use a third party AC/DC supply that is mounted on the DIN rail as well, but without In-Rail connection. So we have one module that only acts as an interface where the 12V and GND from the power supply are connected and then go to the In-Rail. The DIN rail itself will be connected to PE.

Due to the isolated output of the AC/DC supply, the GND/12V are currently floating with respect to PE.

All our modules are enclosed in plastic casings. Several of them expose some kind of connection interfaces that are susceptible for ESD testing. There is a SUB-D connector for example, where the metal casing of the connector is currently connected to GND. Then there are some high impedance connections where push-buttons can be connected to. We used TVS diodes to GND to protect those exposed contacts.

The In-Rail bus lines are protected by a plastic cap after installation, but we put ESD protection there as well.

ESD testing
During ESD testing the functionality of our modules was occasionally disrupted but went back to normal afterwards. Since we only need to pass "criteria B" this would still pass the test since nothing was damaged. However, we though about improving on that.

(Another somewhat strange behavior we observed was some kind of "ESD related voltage build-up", where we only had a actual contact discharge (as indicated by the ESD pistol) every 4 or 5 ESD pulses.)

Potential improvements?!
We thought about using one of the two GND in-rail lines for PE. We could then connect the SUB-D casing to PE and maybe even the TSV diodes, instead of connecting them to GND. This would prevent the discharge moving through the whole whole GND system.
We probably would have to connect PE/GND right where we interface the power supply with the DIN rail to get it to the same potential.

Any thoughts about this or a totally different approach are welcome!


texts: Keeping SMPS output above the post-regulator by a certain amount

texts:
I have some components here to make an SMPS from mains for a CV/CC power supply for my workshop, and I decided to add a linear post-regulator to smooth the output. To avoid big heatsinks I wanted the SMPS voltage to follow the post-regulator voltage when I adjust it, and I've found a possible solution from this question. However my simulations showed better results while using an OpAmp (image below).
As you can see, I set up the comparator of the SMPS in a way that the output voltage of the post-regulator will determine the output voltage of the SMPS (keeping it always 5V more then the post-regulator output for example, precision is not a problem). The circuit works fine on simulation, however I wanted to know if ripple, noises or imperfections of hardware that doesn't exist in my simulation might make this a bad idea, and what filters should I study to put on the output of this OpAmp (if any) to avoid any problems with this "follower" circuit before I buy the components I need.
I have another comparator not shown in the image that is doing the current sensing.


texts: How to connect RS485 Device to computer in Modbus RTU

texts: How to physically connect a voltage monitoring meter device(ND20) with RS485 out, to a computer with Modbus RTU? Should I use a converter to RS232 and connect to serial COM port of computer? Should I use RS485 to USB converter to connect? Can I connect directly to serial COM port from A,B and Ground of RS485 using D9 connector pin? Then A,B and Ground to which pins of D9 in Modbus RTU?


texts: I am using an attiny85 coupled to a mosfet and a water valve to water my plants at a regular interval. I want to water it every day. I programmed it to turn on every 24h, and today it is not on time. I expected a drift, but watering can occur 4 hours earlier or later, no problem. When should I expect there to be a problem in my setup? In other words, given that I use the internal clock of the attiny85 (which I run at 1MHz), what is the time bracket I can expect the water to turn on if I target 24h of delay between two waterings? Also, is it always going to be biased in the same way, i.e. is the bias systematic or random?


texts: Why Circuit Breaker has neutral and no ground?

texts:
My understanding is circuit breaker only need to trip when the hot end current jumps up (e.g. short circuit), but I have seen circuit breaker has dual (two) poles with both red cable and blue cable going in and out - what is the reason of connecting neutral to circuit breaker? Also I do not see anywhere around the circuit breaker where there are cables connected to the ground - without ground, how could any voltage have a reference?

Sorry for the newbie question, but I have read a few on circuit breaker but did not find the answer.


texts: Negative Voltage Ccfl Inverter from AC Adapter

texts:
I have a CXA M10M-L ccfl inverter and I need negative voltage from its output, for anode ground scheme of a photomultiplier tube. I am confused because most discussions of this topic use batteries to explain, but I would likely use a 24v AC adapter. I read a post where grounding the positive leaves the ground pin at the same voltage but is then negative, but wouldn't the ground pin already be grounded via the AC adapter's negative wire? I will have full wave rectification right after the positive pin, before any other circuitry, because this has to be DC.... or do I put it somewhere else for negative?

http://www.tpub.com/neets/book1/chapter3/1-38.htm
-I understand this topology but would the center ground need to have a shorter path to the actual ground wire in the earth?


texts:
I have made a reverse engineering about some medical devices nowadays that has pressure sensor. What is the purpose of extra excitation (Q2). When is Q2 on out rise about 150mV.
Best Regards


texts: Corroded PCB from Rechargeable NiMH battery

texts:
This NiMH battery began to leak battery acid onto the circuit board / PCB below it. Some of that acid ran down one of the wires connected to the battery and pooled up at the foot of the plug where it connects to the PCB.

Here's a closeup image of the black wire with battery acid gunk running down it onto the PCB below.

Here's what the PCB looked like after I sprayed some WD-40® Specialist® Electrical Contact Cleaner Spray and wiped with a Q-tip.

Is this exposed copper something I should worry about? Is there some means I can use to protect the copper?

For instance is it safe to dab some 100% silicone caulking on it or anything like that?


texts: Monolithic and Hybrid Integrated circuits

texts: I was told by my professor that ICs can be of two types, monolithic and hybrid and then she went on to explain technologies of fabrication. What is the difference between a monolithic IC and a hybrid IC?


texts: Beginning arm cortex Ax hardware development

texts:
Where can one find information on how to put together a minimal linux bootable board based on the cortex A family (like the beagleboard)? Programming information is plentyfull, but hardware knowledge appear more arcane. I'm especially curious about:

What external components are needed and why.
Why dev boards seems to end up around 200$, even though I could get an omap3517 for 15$?
What kind of equipment is needed to create prototypes around a chip such as the omap3517?


texts: I'm trying to connect some 18250 lithium ion battery. 3.7v and has a 2700mAh capacity. I'll like to connect twenty of the batteries which I guess will be 54A at 3.7v in series to boost the valtage to 12v or 24v. My question is how much Amp will the twenty batteries derive in both 12v and 24v connections. Thanks


texts:
In some datasheet (two example in links below) I see only this information, about production date, in marking code explanation:

Date code (A : 1997.1)

If there was a further value I could think per induction but only with this information I can't figure out how to interpret the letters.

My capacitor (Matsuo type 553) have the second row: 63VM. The "63V" means rating 63V but the M what date mean? Maybe it is one date among  1998.1, 2000.3,  2002.5, 2004.7, 2006.9, 2008.11, 2011.1, 2013.3 and so on?
Or there is another way to count?

This is what say the datasheet:

(from: NCC-Matsuo metallized pet film capacitor - My capacitor)

And there it's another example:

(from: Jaro Components Tantalum Cap)


texts: Why SPI transmit not happening in EFR32FG14

texts:
I have made a standart SPI transmit of EFR32fg14 using USART1 ,i used manual chip select and using a starter kit manual shown bellow and LOCATIONS from the data sheet.I defined my code as shown in the photos bellow.
and when i connect the probe to my board as shown bellow nothing being transmitted as shown in the scope photo bellow.
Tha full code is shown bellow.
Where did i go wrong?
Thanks.
https://www.silabs.com/documents/public/data-sheets/efr32fg14-datasheet.pdf
https://www.silabs.com/documents/public/user-guides/ug318-brd4257b-user-guide.pdf

#include "em_device.h"
#include "em_chip.h"
#include "em_cmu.h"
#include "em_gpio.h"
#include "em_usart.h"
#include "em_ldma.h"

uint8_t com1[4] = {0x03,0x0F,0xFF,0xF0};

/**************************************************************************//**
 * @brief Initialize USART1
 *****************************************************************************/
void initUSART1 (void)
{
    CMU_ClockEnable(cmuClock_GPIO, true);
    CMU_ClockEnable(cmuClock_USART1, true);

    // Configure GPIO mode
    GPIO_PinModeSet(gpioPortC, 8, gpioModePushPull, 0); // US1_CLK is push pull
    GPIO_PinModeSet(gpioPortC, 9, gpioModePushPull, 1); // US1_CS is push pull
    GPIO_PinModeSet(gpioPortC, 6, gpioModePushPull, 1); // US1_TX (MOSI) is push pull
    GPIO_PinModeSet(gpioPortC, 7, gpioModeInput, 1);    // US1_RX (MISO) is input
    GPIO_PinModeSet(gpioPortF, 7, gpioModeInput, 1);    // delay gpio

    // Start with default config, then modify as necessary
    USART_InitSync_TypeDef config = USART_INITSYNC_DEFAULT;
    config.master       = true;            // master mode
    config.baudrate     = 1000000;         // CLK freq is 1 MHz
    config.autoCsEnable = true;            // CS pin controlled by hardware, not firmware
    config.clockMode    = usartClockMode0; // clock idle low, sample on rising/first edge
    config.autoCsEnable = false;            // CS pin controlled by hardware, not firmware
    config.msbf         = true;            // send MSB first
    config.enable       = usartDisable;    // Make sure to keep USART disabled until it's all set up
    USART_InitSync(USART1, &config);

    // Set USART pin locations
    USART1->ROUTELOC0 = (USART_ROUTELOC0_CLKLOC_LOC11) | // US1_CLK       on location 11 = PC8 per datasheet section 6.4 = EXP Header pin 8
                        (USART_ROUTELOC0_CSLOC_LOC11)  | // US1_CS        on location 11 = PC9 per datasheet section 6.4 = EXP Header pin 10
                        (USART_ROUTELOC0_TXLOC_LOC11)  | // US1_TX (MOSI) on location 11 = PC6 per datasheet section 6.4 = EXP Header pin 4
                        (USART_ROUTELOC0_RXLOC_LOC11);   // US1_RX (MISO) on location 11 = PC7 per datasheet section 6.4 = EXP Header pin 6

    // Enable USART pins
    USART1->ROUTEPEN = USART_ROUTEPEN_CLKPEN | USART_ROUTEPEN_CSPEN | USART_ROUTEPEN_TXPEN | USART_ROUTEPEN_RXPEN;

    // Enable USART1
    USART_Enable(USART1, usartEnable);
}

/**************************************************************************//**
 * @brief Main function
 *****************************************************************************/
int main(void)
{
    int i;
  // Initialize chip
  CHIP_Init();

  // Initialize USART1 as SPI master
  initUSART1();

  while(1)
  {

        GPIO_PinOutClear(gpioPortC,9);
            USART_SpiTransfer(USART1,com1[0]);
            USART_SpiTransfer(USART1,com1[1]);
            USART_SpiTransfer(USART1,com1[2]);
            USART_SpiTransfer(USART1,com1[3]);
          GPIO_PinOutSet(gpioPortC,9);
          for(i=0;i<115;i++)//delay loop
          {
           GPIO_PinOutSet(gpioPortF,7);
           GPIO_PinOutClear(gpioPortF,7);
           }
  }
  }//end main


texts:
Can you produce max waves, adding them, creating massive spikes like it showed in this video with water, but with multi antennas. Can you do this with electromagnetic wave in air with some complex mathematics, if you can, how can you measure it? I am only interested, if you can create massive wave, spike shown in minute 2:50-3:10 and if you can capture it? Can you create this massive "spike" anywhere in space? Is this even possible, does anyone know if someone already done this?

https://youtu.be/ewIr4lO4408?t=2m50s


texts:
In equivalent circuit  of a transformer, there are two inductances, \$L_p\$ and \$L_s\$. These are called Leakage inductances, as the name suggests due to the leakage flux from both the coils.

1) Are these self inductance?
Cause, when we calculate the voltage  across an inductor we include two components, one is due to self induction, \$-L \frac{di}{dt}\$ and the other due  to mutual \$M \frac{di}{dt}\$. Are \$L_p\$ and  \$L_s\$ only due  to leakage  flux or they generally represent self inductances of both the coils? If yes, what about the rest of the  flux, won't  that induce  emf?

2) In the book I'm following,

  In an ideal transformer, assuming there's no leakage of flux, the
  induced emf in the primary coil will be given by $$e_1 = \dfrac{d\lambda_1}{dt} = N_1\dfrac{d\phi}{dt}$$ and for an ideal
  transformer $$v_1=e_1$$and thus \$e_1\$ and therefore \$\phi_1\$ must be
  sinusoidal of frequency \$f\$ Hz, the same as that of the voltage
  source. So, $$\phi = \phi_{max} \sin\omega t \implies
 e_1=N_1\dfrac{d\phi}{dt}=N_1\omega\phi_{max} \cos\omega t$$ Therefore,
  induced emf leads the flux by \$90^\circ\$

How can the induced emf lead the flux by \$90^\circ\$? An induced emf is created only when there's a change in the flux, which is produced only when there's a current flow, which means the flux has to be produced first to create an induced emf.

3) Why does resistor reduce the lag in a RL circuit? I understand why current lags by 90° with the voltage across the inductor.  (After watching this) But I don't understand why that lag, would be diminished by the presence of a resistor,
 the resistor would just decrease the amplitude of the current.
I thought that, there would be lesser voltage across the inductor in a RL circuit, as some would fall across the R, and hence the change would also be less which produces smaller opposition. But then if I apply that reduced voltage across L alone in a separate circuit, there's a solid 90° lag, it's not reduced. If there were a capacitor, it would push the current more, and therefore it would reduce the lag, by why does the resistor reduce the lag in a RL circuit?


texts: What do I do with the FLG pin on the static mic3975

texts:
I'm messing with using the mic3975-1.8ymm (http://ww1.microchip.com/downloads/en/DeviceDoc/mic3975.pdf) The problem I'm having is I'm not sure what to do with the FLG pin's output if I'm not going to monitor it.

Do I do the pull-up, then send it to ground? Can I leave it floating (my reading of the doc says "no")?

I've spent most of the day trying to find an answer, but all I have found is about what to do with unused input.


texts:
For my robotics project I am powering the arduino with a 12v 250mA source. I am using a DC motor l298 breakout board by iTead that allows a power supply of 5v to around 46v for DC motors. I am also using a geared DC motor that has operating voltage between 3v and 7.5v.

I drew this up (imagine the bulbs are the arduino and breakout, couldnt get them on circuits.io) Can I use a 6v regulator for breakout without any issues? And also I see people use capacitors alongside regulators to reduce spikes or something but I did not know what to implement so could someone explain that as well? cheers.

Update:
This Is what the circuit is of on circuits.io
Also there is no 6v regulator in it so i used a 5v


texts: Why do measurements displayed in multimeter inconsistently vary by factors of 1000 depending on range?

texts:
For my science fair project, I am measuring the resistance of a 100 foot piece of 32 gauge Nichrome wire. Using a Innova 3300 digital multimeter, I get the following results for each resistance range value:

200 ohms: 1 (to far left, indicating over range)
2000 ohms: 1025-1030
20k ohms: 1.02-1.03
200k ohms: 01.0
20M ohms:  0.00

I understand that precision varies based on the range value, so the right-most digits makes sense to me. However, I don't understand the scale of the left-most digits?  Why aren't they all in the 1000 range if actual resistance doesn't change.

I have read the manual several times but it just says:

  Plug the RED test lead into the "Ω" jack of the multimeter; plug the BLACK test lead into the "COM" jack.
  Set the meter’s Function/Range Selector Switch to the OHM "Ω" range function.
  Place the RED test lead onto one side of the item being tested and the BLACK test lead onto the other side of the item. (Polarity does
  not matter when checking resistance).
  Read the results on the display

There is no mention of what the results mean. After thinking about this with my dad and searching the internet, I think I have an answer: The units of the display value are in the units of the range.  For example, 200 and 2000 are in ohms, 20k and 200k are in kilo-ohms, and 20M is in mega-ohms.

Is my hypothesis correct?  And what about the leading zero in the 200k range?


texts: Practical way to splitting CAT5 for 1wire?

texts:
I'm planning Raspberry Pi system using One-Wire with thermometers (ca 10 pcs). My electrical skills are basic. I'm looking for a good way connecting stubs to main line.

.

The main line (green) 1 planned to use CAT5 with shielding, expected length 10m.

The stubs (blue) with thermometers cable is not decided yet, but thinking about 3 conductors with shielding. Stub lengths max 0.5-1m.

My question is about connecting stubs to main line - what could be most practical way doing it? I don't want to solder them as I consider it too monolithic. Would screw terminals be good idea for this? I would like to build it by extending it piece by piece.


texts: Moving to ARM from 8 bit AVR - how to take the 1st step?

texts:
I've written code for AVRs for several years now and it seems like my needs are calling for a more powerful processor. Since Atmel Studio is the IDE I'm already using and my debugger also works with ARM MCUs, going with an Atmel device seemed like a no-brainer. The troubles began when I tried to actually start and write some code. AVRs have an endless amount of tutorials on forums such as avrfreaks.net but the Atmel ARM MCUs do not. To make things worse, Atmel offers, almost exclusively, code that is written with its ASF software framework which means that if I want to use it I have to adopt a pretty high level approach which I don't like in coding, as I am not entirely aware of what goes on under the hood.

My question is: if someone went through a similar path, what was the correct place to start and learn how to use these M3 MCUs without the ASF!


texts: Could a resistor work as well as a signal diode in this level-shifting circuit?

texts:
The following hackish circuit uses the internal circuitry of one "sacrificial" WS2811 LED to level up the logic voltage to 5V for the remaining strip by placing a signal diode in series with the power supply input of that first WS2811 circuit.

Since all we're trying to do is drop the voltage by 0.7V, could we conceivably have found a resistor to be used in place of the diode to drop the voltage by a comparable amount? If so, are there any considerations that make the diode the better choice? If not, why not?

(I'm sure that to veterans this very question exposes a deep lack of understanding of electronic basics on my part. You probably don't need to point that out - I'm here to learn.)


texts: relay or switch that remember previous power status after power failure

texts:
I have application which need a push button on/off switch feature. But i need to do something buy which it can remember or store in memory the previous status after power failure. same like home air conditioner which save previous status if power cut and return. One of my suggest do it with IC 555 but i don't think it can remember the previous status if power cut... please give me a cheap solution.. my application consume only 12V and 2A.

Edited:
Purpose of this solution is to power on/off remote application which dose not have a UPS or power backup. I am using Arduino with Ethernet module to remotely on/off system power but the problem during long power outage.. application shutdown and i am needed to power on it again.. I looking for a Solution to store state of application even if power reset.


texts:
These are some lecture notes for MOSFET amplifier.
Why has he chosen Q point using Vd?
Shouldn't Vds = 1/2(Vdd + Vgs - Vt) ?


texts: What does this dash mark in a DIP 4-bit counter IC indicate?

texts: I have seen a dash mark in 74LS193 4-bit counter IC while working with it in a project. What does this dash mark indicate?


texts: Drive MOSFET by a 24V input signal of an industrial controller

texts:
I want to drive this n-type MOSFET by a 24V input Signal. Because of the max being Vgs=20V I want to set Vgs to 10V.

simulate this circuit – Schematic created using CircuitLab

Is this ok for building the circuit or do you have any other suggestions?

(Switching frequency <2Hz)

An alternative for the MOSFET presented above is this one.


texts: How do you block a signal with a tank circuit?

texts:
I have a signal generator outputting 60 hz AC. I've connected the output to a capacitor (922uf) and inductor (0.0076H) which are in parallel with each other creating a tank circuit. These two values will have resonance at approximately 60hz. However by the loud squeel my signal generator is making, I can tell it's shorting out. I also connected two parallel diodes in series to the tank to indicate if there is current going through and it lit up like Christmas. Isn't it supposed to have  a net current of zero??

Here are my sources:
http://www.deephaven.co.uk/lc.html

http://www.allaboutcircuits.com/textbook/alternating-current/chpt-6/parallel-tank-circuit-resonance/

Can someone explain how to make the tank circuit work? I want to achieve a net current of zero by blocking out the 60hz signsl from my signal generator.

Thanks.


texts: Why is the voltage across the capacitor unbound?

texts:
Consider:

Why does this circuit represent an unstable system? That is, the voltage across the capacitor is increasing with respect to time.

If this is the case, what is the energy stored in the capacitor?


texts: What are UL Contact Ratings in a Relay Datasheet?

texts:
These UL contact ratings are listed in the datasheet for a Tyco relay: T90 Series, 30A PCB Relay.

(Note: the link will ask you to download the PDF, as do most Tyco PDF links)

The contact life is different for different loads and this is as expected. However, if you look at the ratings for the 'ballast' load type notice that at 6A it's specified to 100,000 cycles yet at 3A it's only 6,000. Why so?

Don't lower currents usually increase contact life? Furthermore, for CFLs, should I be looking at "ballast" load-type?


texts:
The most common idea on 'new age' embedded devices - IoT Devices is using an Arm Cortex (Mostly M Series) processor as Central Unit and some Sensors and Peripherals for acquiring data and metrics (Correct me if i am wrong please).

I was wondering, if and how much efficient is, in a more complex embedded device, the idea of using more SoCs for different purposes, (for example, for a device which is logging 3 different cases, for each case using a different SoC developed for this specific case) and finally all the processed data sent to Cortex and from there to a hub or to a mobile device.

Is this a feasible 'Architecture' ? If not, what You would propose to a similar Use Case.


texts: Is there a master list of LG TV RS232 commands available somewhere?

texts: I have a LG OLED65C7P TV and for aesthetics reasons, I'm trying to force the TV to use the analog audio input (multiplexed with composite video input on a 3.5mm jack) for direct analog audio playback through the internal speakers (no matter what is going on with HDMI, ARC, or internal app audio.)  I'm hoping there is some way to do this through the RS232 input.  Maybe there is a way to do this with settings menu but I cannot find it.  Thinking that there is a "SERVICE" description on the RS232, I'm hoping I can force the TV to play analog audio to the internal speakers in a special forced mode.  Anyway to do this?


texts: What is right or left alignment of data in ADC?

texts: I am using a STM32F407 discovery board for ADC and I found that the DR or the data register of the ADC can be configured in left or right alignment. What does this mean? Also, what are the advantage/disadvantages of each alignment?


texts: What dielectric liquids can be used as coolants?

texts:
I've seen some interesting videos of people putting their computers in containers with sunflower oil, where they continue to work normal.

Are there any other dielectric liquids that can be used to cool a technical device which is fully submerged in it, possibly without hazard for people, or in a sealed container?

I'm mostly after dielectric liquids that won't deteriorate too fast (in under a month) and lose cooling qualities or become conducting for whatever reason (liquid blooming, though not sure how).


texts: What's the usage of two NPN transistors with their bases and collectors tied together?

texts:
I'm thinking to know what is the usage of these parts of this circuit.

Source

It's the schematic of UT70C Digital multimeter.


texts:
I'm interested to know what this assembly code do knowing that X1 is full of zeroes.
ori  X2, X0, 0xFFF
slli X2, X2, 12
ori  X2, X2, 0xFFF
slli X2, X2, 8
ori  X2, X2, 0xFF
xor  X2, X2, X1
addi X2, X2, 1
and  X2, X2, X1

The problem is that I don't understand what 0xFFF and 0xFF are. How am I supposed to know their values at all?


texts:
I just started learning vhdl code and i wrote this code for a D type asynch flip flop. How should i modify my code so that it has a second D-type, with the input to the second being fed from the output of the first?.

library ieee;
use ieee.std_logic_1164.all;

entity FLIPFLOP is
port (
  clk : in  std_logic ;
  clr : in  std_logic ;
  D   : in  std_logic ;
  Q   : out  std_logic
  );
end FLIPFLOP;

architecture behav of FLIPFLOP is
begin
process (clk,clr,D)
begin
if clr = '1' then
Q<= '0';
elsif rising_edge (clk) then
Q<= D;
end if;
end process;
end behav;


texts: How to connect a flex ribbon cable to a screw terminal block?

texts:
Does anyone have ideas on how to mate a flex PCB with a screw terminal block?
Some background:
At my workplace, we're using the following Keysight DAQM900A Datalogger MUX cards:

In the past we've placed the flying leads of our cables into each slot directly. However, because this requires some labor time, there's been a push to modify the cards. Specifically, we want some circuit designed that can easily be placed inside the MUX card to interface with the screw terminal blocks instead of using flying leads; on the other end, we want to add a connector with a standard pinout so we can easily purchase cables from assembly houses.
What I've done:
So far, I've decided to remove the strain relief slots, drill mounting holes at the entry for a D-Sub PCB connector (for strain relief), and run flex ribbons from the PCB to all 4 screw terminal blocks (see image with basic idea drawn for 2 of the 4 terminals):

However, I can't seem to find any connectors that work between flex ribbons and screw terminals. Originally, I considered using FPC connectors with vertical leads: if done right, the leads could mate with the screw terminals. However, I can't seem to find anything with the right pitch for these terminals. Most FPCs have a 1mm pitch, but I'm looking for something with ~3.25 mm pitch and 5mm lead length.
Does anyone have any other connector suggestions? Or even a suggestion on a different way of going about this?
Thanks in advance for the help!


texts: Embedded Linux Project on Qualcomm Snapdragon S2 (MSM8655)

texts:
I have my old blackberry 9900 device, I am interested to start a project of modifying and installing linux inside.
To do so I need user manual of the processor (which is turning out hard to find) even with well supported Snapdragon family.
Question: Assuming the SoC doesn't have a memory controller, will it still be theoretically possible to install linux inside it?


texts: Some questions on a passive network's transfer function and time domain response

texts:
Before asking my questions I would like to write down briefly about my big picture understanding so far. I will go with an example RLC circuit below:

Above circuit’s transfer function H(s) can be written as H(s)=Vout(s)/Vin(s)

Since all is in series the same current I(s) passes through the components, this circuit can be treated as a voltage divider. So by using relevant Laplace transforms, the voltage across R which is Vout can be written in terms of Vin as:

Vout(s) = Vin(s)*R / (sL+R+1/sC)

So the transfer function H(s) can be simplified as:

H(s) = sR / (s^2*L+sR+1/C)

Now that we have the transfer function, we can find the response of this circuit for a given input in s domain and then transform it by taking inverse Laplace transform to plot it in time domain. One can also find the location of poles and zeros on the s plane.

Before that, first I will start with a step response of this circuit in LTspice to estimate the impulse response in time domain which is the transfer function. Impulse response of an LTI system in time domain is the transfer function. Since I cannot create a real Dirac function I apply a very sharp rising edge step input and see the response in LTspice. I also do the same thing by using MATLAB in s domain.

Since step input X(s)=(1/s) in s domain, the output can be written as:

Y(s) = X(s)*H(s)

Y(s) = R / (s^2*L+sR+1/C)

So taking the inverse Laplace transform of Y(s), L-1[Y(s)] yields a time domain response Vout(t).

And below plots shows the same result is obtained by using LTspice and MATLAB:

Ok so if we look at the above plots we can see that the circuit response to a sharp step input is a decaying sinusoidal with f=50Hz(ω = 2*pi*f= 314), in other words damped oscillation at a particular frequency.

Now the reason for the question I’m going to ask is about some observations or the relation between the transfer function and the time domain response.

First of all here is the 3D plot of |H(s)| of this circuit above the s plane:

At this point, from  the transfer function H(s) = sR / (s^2*L+sR+1/C) one can already determine the two poles and the zero locations on the s plane.

First I look at the |H(s)| vs imaginary axis as below:

My first observation of the transfer function of the plot above is that the location of the poles are where ω = 314 on the imaginary axis. This value of the ω is exactly the same when we observed the step response or natural frequency of the circuit where it damped with an oscillation at ω = 314. So I think what pole’s imaginary part indicates is the impulse response’s frequency. Is that correct?

Second is that, if we look at the real axis which is σ axis of s=ωj+ σ plane as follows:

And as seen above, σ for the point of the pole is around -100. I think this negative sign indicates the decay rate of the sinusoid as e^-100. Is this correct?

And here is the top view of the s plane:

Now regarding these observations so far,(if you agree with them) my questions are as follows:

From the observations of the s plane, the locations of the poles turned out to be complex numbers which are carrying the knowledge of the time domain input response i.e the natural response. So as you see if it is true one can relate this particular pole points to something in time domain. But what about the other points on the s plane rather than a pole or a zero. Pick a random s point on the s plane and find out what |H(s)| for that point. What does that indicate in time domain?
Another observation is that this RLC circuit’s response is decaying. Does that mean this system is stable? If so, is there a passive network example where the system would be unstable? Or do we need an active component to observe such phenomena?
At the poles |H(s)| mathematically goes to infinity, not in MATLAB not in LTspice. Is that because applying a Dirac delta function is just a theoretical concept?


texts: I'm working on a project in which I'm forced to connect an SD card to a shared SPI bus with some other peripherals. I need to make sure a hot insertion event won't corrupt any ongoing data transfer on the bus, but I can't find any information on the power-up state of the card drivers in the simplified specifications. Does anyone know if the CLK, CMD, and DAT0 pins on an SD card are guaranteed to be high-impedance during a hot insertion?


texts:
Does anybody know the function of the PNP circuit?
The PWM is UC3843 output, and then connected this PNP circuit.
Can anyone tell me how it works?


texts:
I am driving a bipolar hybrid stepper motor rated 1A with a DRV8825 at 12 V.

About current regulation the datasheet says:

  9.2.2.2 Current Regulation

  In a stepper motor, the set full-scale current (IFS) is the maximum current driven through either winding.
  This quantity depends on the xVREF analog voltage and the sense
  resistor value (RSENSE). During stepping, IFS defines the current
  chopping threshold (ITRIP) for the maximum current step. The gain of
  DRV8825 is set for 5 V/V.

  To achieve IFS = 1.25 A with RSENSE of 0.2 Ω, xVREF should be 1.25 V.

In my circuit, RSENSE is 0.1 Ω. Following, in order to get IFS of 1.0 A, xVREF should be 0.5 V.

However, when I set the reference voltage to 0.5 V, I can measure only 0.5 A in both windings in full-step mode.
Through experimentation I found that I get 1.0 A with a reference voltage of 1 V - which should give 2 A following the equation above.

On page 4, the datasheet says the VREF input voltage should be 1 - 3.5 V with the following note:

  (2) Operational at VREF between 0 to 1 V, but accuracy is degraded.

Can it really be so inaccurate just slightly below 1 V, or am I getting something wrong here?


texts: Can switching step-down regulator loaded with idle LDO consume 6mA @ 6V?

texts:
I'm struggling to understand where 5.7mA may be leaking in this very simple circuit based on ST1S10 step-down regulator and LP2985IM5-3.3 LDO:

Link to full size image

Long story short: ST1S10 drops down the voltage to 3.8V to supply the modem and the LDO that in turn drops down the voltage to 3.3V to supply the microcontroller. There is nothing connected to the circuit, the ST1S10 is loaded only with LP2985IM5-3.3 that is turned on but idle (not loaded by anything).

When connected 6V to K1 (left side) I observe the current of 7.4mA. When I connect the voltage in place of the PWR_FLAG near C7 I observe the current of 1.7mA consumed. That would indicate that the LP2985IM5-3.3 consumes this 1.7mA (another question is if it's possible that it consumes that much current doing nothing - I couldn't identify this info in IC's application note).

That is under assumption that no power is consumed by ST1S10 when it has revere voltage applied to SW (pin 7). May not be true.

But anyway, from the simple math comes the conclusion that 5.7mA (7.4 - 1.7) is lost somewhere between PWR input and C7. Is that possible?

Of course the next step is desoldering the circuit to look for the leakage, but maybe there is no point and it just seems correct.


texts: Making an IR transmitter with a range of 3-4 meters

texts: I am designing a vehicle counter in a parking facility. What I have to do is to detect if a vehicle enters the 4 meter wide entering of the parking. I was initially trying to make an IR receiver and transmitter to detect a vehicle but I have no idea how to make it for 3-4 meters. Kindly tell me if already made sensors are available for this purpose or please give another idea how to implement it.


texts: Should I ground the unused pins of an oscillator crystal?

texts:
I have seen in this example circuit of an RTC where the unused legs of an oscillator crystal are grounded. I will be using an ECS EXC SMD crystal and from what I thought the unused pins are better left disconnected to the circuit and are just there for structural connection to the board.

Am I wrong or is this example circuit I am using doing it incorrectly?


texts:
I found this description in a book for a magnitude comparator, and I don't understand the explanation or why it works. I have commented everything I did understand, but that one line there just kills me:

//Behavioral Magnitude Comparator

module MagComp(a,b,gt);

  parameter k = 8;
  input [k-1:0] a,b;
  output gt;
  wire[k-1:0] eqi = a~^b; // returns 1 whenever corresponding bits in a and b are equal
  wire[k-1:0] gti = a&~b; // returns 1 whenever an a-bit is greater than a b-bit
  wire[k:0] gtb = {   (   (eqi[k-1:0] & gtb[k-1:0])  |  gti[k-1:0]   ) , 1'b0   }; // ??
  assign gt = gtb[k]; // returns 1 if a>b

endmodule

It looks like he's assigning gtb recursively. How can this work if gtb isn't even declared in a first instance? Why is he concatenating a 0 in the end? How can there be any sort of recursion if there aren't any sequential commands?


texts: What features give reason for such a wide range of prices for digital multi-meters?

texts:
Ever since high school, I've been using the same multi-meter.  It works well for low voltage purposes, but I'm scared to use it for anything else (high voltage, unless it's a little zap from an electric fence which I think is high voltage) because I purchased it in 1993 or 1994.  It sometimes flashes on/off, and loses its display.

I'm doing some shopping for a new one.  One feature about my current one is that I always need two hands to touch the wires because it has leads at the end of it.  So I'd like a way to keep the multi meter leads on the wire somehow.  I also want one that stands up.  There are SO MANY different kinds!  I'm looking for some electrical engineering advice on why there is such a HUGE range in prices and what I should buy and get my money's worth.  Spending up to a few hundred won't be an issue, but I'd like to know if there is a reason to spend that much.  If you know about features that clearly give reason to buy a more expensive one, please let me know.

It might also be good to explain when you'd pay more for a multi-meter for low voltage (or low current) situations, or vice versa, during high voltage (or high current) examples?

Some time ago, I also remember reading something where some multi-meters prevent the end user from damaging the device.  Say for example, if you have current running through a circuit, and you turn on the Ohm Meter to measure resistance.  In the past, I was always told to turn the power off my circuit when measuring resistance in a circuit because it uses the voltage inside the multi-meter itself for the actual voltage when measuring, and it could be damaged if there was current in the circuit when measuring.  I've never made the mistake of doing this, but I would think the newer ones (or more expensive ones) would prevent you from damaging the multi-meter if this ever happened.  Especially if they need to pass federal electrical regulations, whatever those are.  Seems like a trivial thing to prevent when engineering the product.

Sorry for a loaded question, but I'm sure your answer will result found in plenty of Google search results if you have a good answer.


texts: Appropriate solenoid valve flyback diode

texts:
I control a 24V solenoid valve via PWM controlled MOSFET. I have a 1N4007 diode parallel to the solenoid. If I put a 2.2uF electrolytic capacitor directly next to the solenoid it works properly, without the capacitor it does not.
I am asking if I could get rid of the cap, if I replace the 1N4007 with this 40V Schottky diode instead: 1N5819HW


texts: Does a 4 pin smd crystal need external capacitors to work properly?

texts:
My understanding of how this works is quite poor, I've tried reading many sources but just got even more confused by the terms crystals, crystal resonators, ceramic resonators, oscillators, crystal oscillators.
What I know is that when you have a simple 2 pin crystal you add 2 caps to it so that it resonates properly. And the AVR chip I am connecting it too (Atmega328p) has some other internal circuitry for it to work.
I am looking at using an smd crystal in my design and my question is, for a crystal like this:

Do I still need the external capacitors or not? I originally thought I would but looking at the specs of the parts they all have a label "capacitance". Does that imply it has caps inside? Or is that recommended value for my caps? Or is that some other capacitance?
Sorry if this doesn't make sense I am just really confused.
Thanks in advance!
Edit to include specifics:
I have these crystals https://lcsc.com/product-detail/SMD-Crystal-Resonators_Seiko-Epson-X1E000021011900_C89371.html
But it seems they are quite standard so here is one with English datasheet:
https://www.mouser.co.uk/ProductDetail/ECS/ECS-160-12-37B-CTN-TR?qs=sGAEpiMZZMukHu%252BjC5l7Yb4vS8HZNl%252BL%2F78jMNI6Q2E%3D


texts: I found this answer regarding a good method for soldering TSSOP parts but it doesn't mention what kind of tip would be most appropriate. Is a standard chisel that comes with a decent soldering iron acceptable? Hakko, for example, lists tons of other options but I have no basis for choosing one.


texts: ESP32 using Arduino: Internal Pull-ups don't work on GPIO25 or GPIO32

texts:
I'm programming a custom ESP32 board using Arduino where GPIO25 and GPIO32 are connected to pogo pins via short 5mm traces and to nothing else. The goal is to poll for a short between them as part of an alignment procedure - pretty straightforward.
The issue is, pinMode(X, INPUT_PULLUP) does not actaully turn on the pullup for either pin; the ADC readings are always floating. Whichever pin I'm using still successfully detects a short when intended, but because It is floating and never pulled high, it causes a lot of false flags.  Code below:
    int foo=9999;
    pinMode(25, OUTPUT);
    pinMode(32,INPUT_PULLUP);
    while(foo>0){
        foo=analogRead(32);
        Serial.println(foo);
        //do other stuff
    }


texts:
I did not really found anything on google to accomplish my idea, so try here to find out an answer:

My task is defined as follows: I need to check if the input voltage is in a specific range. Lets say, for example: 5V +/- 10% so Vmin=4.5V and Vmax=5.5V. If the input voltage is in the acceptable range then light up a LED and start a microcontroller else do nothing at all.

The problem: the voltage I want to check is the only voltage available, so I can't compare it to another for example.

I already came up with a solution but I don't think its perfect: use a simple zener diode in reverse and wait until it becomes conductive and then switch a transistor or so.

Is there a better and more professional way to do it?

EDIT:
I just found a Voltage Detector IC (click) with a really low supply voltage, would that be an  acceptable solution?


texts: what are the disadvantages laptop using without battery

texts: i use my lappy without battery.it means i remove the battery and laptop cable join the direct current supply.but laptop is working.can i know through this what happen to my laptop.is it good or bad to my laptop?THANKS.


texts: Decoupling capacitors on the bottom layer?

texts:
I'm using 0.01 uF decoupling capacitors in a 0805 package, on each Vcc/GND pair of my CPLDs. So, around eight capacitors in total). I find it a bit easier to route the board if the decoupling capacitors are placed on the bottom layer and connected to the Vcc and GND pins of the CPLD/MCU using vias.

Is this a good practice? I understand the aim is to minimize the current loop between the chip and the capacitor.

My bottom layer also serves as a ground plane. (it's a two-layer board, so I don't have a Vcc plane), and so I don't need to connect the ground pin of the capacitor using vias. Obviously, the chip's GND pin is connected using a via. Here's a picture that illustrates this better:

The thick trace coming toward the capacitor is Vcc (3.3 V) and it's connected to another thick trace that comes straight from the power source. I provide Vcc to all the capacitors in this way. Is it a good practice to connect all the decoupling capacitors in such a way or will I run into problems down the road?

An alternative way that I've seen being used is that there is a single trace for Vcc and another for GND that runs from the power source. The decoupling capacitors then 'tap' into those traces. I noticed that in that approach there was no ground plane - just thick Vcc and GND traces running from a single point. A bit like my Vcc approach described in the previous paragraph, but also adopted for GND.

Which approach would be better?

Figure 2

Figure 3

Here are some more pictures of the decoupling capacitors. I think out of these the best is the one where the capacitor is at the top layer - do you guys agree?

I'll obviously need one via for the GND pin if I want it to connect to the ground plane. Regarding the value, 0.001 uF to 0.1 uF was specified in Altera's documentation and so I settled at 0.01 uF. Unfortunately, even though I mentally noted that I'll need another capacitor at less 3 cm, I didn't remember to implement it on the schematic. Based on the suggestions here, I'll also add 1 uF capacitor in parallel to each Vdd/GND pair.

Regarding power - I'll be using 100 logic elements for a 100-bit shift register. The frequency of operation is largely dependent on the SPI interface of the MCU that I'll use to read the shift register. I'll be using the slowest frequency that the AVR Mega 128L allows for SPI (i.e. 62.5 kHz). The microcontroller will be at 8 MHz using its internal oscillator.

Reading the answers below, I'm now quite concerned about my ground plane. If I understand Olin's answer, I should not connect the GND pin of each capacitor to the ground plane. Instead, I should connect the GND pins to the main GND net on the top layer and then connect that GND network to the main return. Am I correct here?

If this is the case, should I have a ground plane at all? The only other chips on the board are an MCU and another CLPD (same device, though). Other than that, it's just a bunch of headers, connectors and passive elements.

Here's the CPLD with 1 uF capacitors and a star-network for Vcc. Does this look like a better design?

My worry now is that the star point (or area) will interfere with the ground plane, as they're on the same layer. Also note, I'm connecting Vcc to just the larger capacitors' Vcc pin. Is this good or should I connect Vcc to each capacitor individually?

Oh and please don't mind the illogical capacitor labeling. I'm going to fix it now.


texts: Power Converter Control Platform for Commercial Use

texts:
I'm designing a power converter for commercial use and I've been struggling to find a control platform that meets the typical industrial standards and can be used to do the control of the whole device.

The device should basically have several digital and analog inputs and outputs, along with communication capabilities and the capacity to execute control operations. The actual functions it should perform are the following:

Protection (receive several digital and analog signals and enable/disable the converter depending on their values)
Measurement & control (receive scaled-down analog signals and perform basic PI control)
Synchronization with the grid using PLL
Semiconductor triggering (send turn-on/-off signals to the drivers)
Communicate with the customer's SCADA system so that the operation can be supervised remotely

So far I've found this product from teknocea for about USD 1300 based on TI's F28M36 MCU. I imagine there must be other options available. I'm not considering a PLC because they usually operate at low frequencies, but if you know products from this kind that can do the job, I'm all ears.

Thanks!


texts:
In Decoupling caps, PCB layout, three variants of placing bypass caps are presented:

In the comments, it is mentioned that C19 is the worst approach, C18 slightly better and C13 the best way, which is somewhat contrary to my understanding, so I'd like some clarification.

I'd expect the C19 layout to be close to optimal:

the capacitor is placed in-line between the vias to the supply planes, so high-frequency components can be filtered out optimally
the vias are not too far apart

I'd probably use wider traces between the capacitor and the vias (Altera's AN574 suggests that).

C13 is a bit closer to the IC, but the vias are on the far end of the connection, so I'd expect worse behavior at high frequencies (probably too high to matter, but...)

The C18 layout is the worst:

the vias are far apart, increasing inductive impedance
the loop is fairly large
same issues as C13 with high frequency ripple

Where am I going wrong with my analysis?


texts:
I'm working with STM32F411 Discovery board. I use Atollic TrueStudio and HAL Library. I'm trying to make a simple program that checks when Timer2 overflows and, when it happens, I toggle an LED.

I can configure Timer2 with no problem. The problem is that I can't find a function that returns true when the timer overflows. I have to use __HAL_TIM_GetCounter(&hTim2); to get the timer count, and I can use interrupt. But, what happens if I only want to know when the timer overflows without using interrupts. What should I use?


texts:
I'm just learning about the use of ESD diodes to protect your system.
Although I've read multiple cases on this being more a black box magic than true science, I'm still going to try.
On what 'signals' or 'traces' from my PCB would it be wise to place some diodes? I do not mean a specific PCB but more 'in general.' What's a rule of thumb? Incoming power lines? Only RX/TX pins or all I/O pins?
Also, I have an example as such which is for an isolated connector. Would it make sense to place such a ESD protection on here? Why? Why not? -> My mind says it is isolated so would be rather safe already.


texts: Running VHDL process off an input clock higher than the FPGA clock?

texts:
I have the following dev FPGA board:
Altera Cyclone II EP2C5T144 FPGA Dev Board
This FPGA has a 50mhz clock. However I want to interface with an external FTDI device that runs at 60mhz. I am driving my VHDL process off the 60mhz clock as an input.
My question is can this safely work? I'm thinking its not safe because the FPGA flip flops are running at 50mhz but its being "forced" to run at 60mhz since the process is driven off this input clock pin?
Should I be removing the FPGA oscillator and connecting it to the existing FTDI oscillator? I'm still very new to this so sorry if this is really silly question :).


texts: It is it possible to safely use a 110V variac (variable transformer) at 230V?

texts:
I've come across a variable transformer/variac which is designed to be used with 110V input.  Our line supply here is 230V.

If I was careful not to exceed the VA rating of the transformer (920VA) would it be possible to safely use this with a 230V input?   (I'd expect the output voltage to be twice of course, and I suppose replace the fuses with 1/2 current equivalents)

It's something like this:


texts:
As you can see this a transitor AND gate and yet the LED glows when only one input is high,  passing the current essentially through the base and emitter. I think I fried (I think) my transistor since I'm running the transistor at the absolute maximum (this is a 2n2222a and that is a 7806 voltage regulator) bar voltage.

I need to know the effect of exceeding the each absolute maximum and whether these are salvageable.

Also,  what happens in the transistor when you exceed absolute maximum values (in the NPN junction, in terms of holes and electrons and why the damage is permanent)

[


texts:
I have an Altera Cyclone IV FPGA (for ie) and my question is: is it possible a raw programming of the FPGA?
Is it possible to set "manually" the gates for making experiments?

Thank you


texts: Difference between a Power Plane and a Copper Fill?

texts: What is the (or is there a) practical difference between designating a layer of a printed circuit board as a power plane as compared making a polygon cover the layer and naming it the same as the power net? I'm thinking of EAGLE when I ask this question, but I think there are analogies in other ECAD tools. I know Sunstone Circuits CAM file seems to think of these concepts differently, but I'm not sure how or why.


texts: What are the trade-offs between different values of resistance for a wheatstone bridge?

texts:
I have a loadcell with a bridge resistance of 10k and I've asked the manufacturer for a new design with RTDs and a slight mechanical change, and as a consequence, the manufacturer's proposed new design has a decreased bridge resistance from 10k to 5k (they are modifying the bridge layout and I assume 5k makes the design more achievable, because of reasons).
Nothing else is expected to change, other than a potential drop in sensitivity - perhaps down from 2mV/V to 1.3mV/V.
So far I'm considering self-heating and power consumption; an additional 2.5mW at 5V excitation in my application.
What, if any, are the other trade-offs of changing the bridge resistance (increasing or decreasing)?

Existing design spec:


texts: What does t2-t1 represents in the expression t2-t1 = RC*ln|9|?

texts:
And how do I find t2-t1 with an oscilloscope?

I was given the following problem, I derived the expression in the title of the question and I need to use the oscilloscope to find t2-t1...

  Resistors can be readily measured with most any multimeter, but the
  measurement of capacitors and inductors requires either more
  specialized instruments or techniques. In this lab it is expected that
  a 10% to 90% rise (90% to 10% fall) time for a RC circuit will be
  used. Derive the required 10% to 90% rise time relationship for a
  parallel combination of a square wave source and an RC pair. Note a
  similar approach could be used to measure an inductor in a series RL
  circuit, except here a sinusoidal source and voltage division is
  utilized.

I have the following configuration (I meant to write 220uF but out 220mF) instead

I think t2-t1 is the rising time but is throwing me off that I have to measure them a whole period apart on the oscilloscope to get something close to my ideal values.

here is a screenshot of my oscilloscope


texts: How does a ferrite core wire terminator work to reduce EMC?

texts:
The following question was asked on superuser: What is that cylinder on cables?

How does that cylinder work? As far as I can tell, even if you put one on either end of the cable, any HF signal should travel straight past it.

Is there an equivalent circuit that shows the principles better?

EDIT

I was assuming in my question that the wire passes through a ring made from ferrite. There is of course the other possibility that it loops around the ferrite, creating a (very small, very low inductance) inductor in series with the cable. Is that so?


texts: MOSFET Turns on without voltage on the gate?

texts:
I am using the following transistor to turn a motor on and off:
http://pdf1.alldatasheet.com/datasheet-pdf/view/418991/INFINEON/IPP096N03LG.html

I am applying 12V to the drain and 0V to the gate... but for some reason current is flowing through and the 12V is coming out the other side. I want the transistor to only come on when I apply a 5v signal to the gate.

Any help would be greatly appreciated.


texts:
How to build a complet circuit with the following led in left and the following circuit in the right?

¨


texts: STM32CubeIDE issues with CMSIS-DSP library files

texts:
I have been trying to add the Library file libarm_cortexM4lf_math.a in the Eclipse based STM32CubeIDE as shown in the pictures below.

But the linker is not able to find the library, and drops the following error.

cannot find -llibarm_cortexM4lf_math

The complete error log is as follows

make -j12 all
arm-none-eabi-gcc -o "CMSIS_DSP_PID_Test1.elf" @"objects.list"  -llibarm_cortexM4lf_math -mcpu=cortex-m4 -T"/home/sandhan/Projects/STM32CubeIDE/workspace_1.3.0/[Nucleo-64 STM32G474RE] Projects/CMSIS_DSP_PID_Test1/STM32G474RETX_FLASH.ld" --specs=nosys.specs -Wl,-Map="CMSIS_DSP_PID_Test1.map" -Wl,--gc-sections -static -L"/home/sandhan/STM32Cube/Repository/Packs/ARM/CMSIS/5.5.1/CMSIS/DSP/Lib/GCC" -D ARM_MATH_CM4 -D __FPU_PRESENT=1 --specs=nano.specs -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb -Wl,--start-group -lc -lm -Wl,--end-group
/opt/st/stm32cubeide_1.3.0/plugins/com.st.stm32cube.ide.mcu.externaltools.gnu-tools-for-stm32.7-2018-q2-update.linux64_1.0.0.201904181610/tools/bin/../lib/gcc/arm-none-eabi/7.3.1/../../../../arm-none-eabi/bin/ld: cannot find -llibarm_cortexM4lf_math
collect2: error: ld returned 1 exit status
make: *** [makefile:44: CMSIS_DSP_PID_Test1.elf] Error 1
"make -j12 all" terminated with exit code 2. Build might be incomplete.


texts: Converting a pulse train to a single pulse

texts:
Posting my question with a schematic

I want to detect AC line voltage using an optocoupler. When i feed the optocoupler input with an AC line, i get a 50 Hz pulse train at the output. Usually this scheme is used for a zero cross detection. But my idea is to use this pulses and convert them to a steady DC pulse so that i can feed this pulse at the input of a PCF8574. In that way i would know the status of PCF8574 port pins and hence the presence of an AC voltage as shown in the schematic below

When i close switch SW, a pulse train is generated at output of opto-coupler. I want the "some circuit" block to generate a steady pulse from the opto-coupler output. When the switch SW is open, there is absence of pulse train and want the "some circuit' block to output a zero until the switch SW is turned ON again.

Now my question is:

How can i convert a pulse train to a steady DC? I want the "some circuit" block in above schematic to do the job, so what circuit can replace the "some circuit" block

Also, is it the correct way to interface an opto-coupler with "some circuit" block ? I am getting a pulse train at emitter of the optotransistor Please correct me if i am wrong

Please share any circuits or ideas

Thanking you,

Gaurav

Basically i want to know whether 230V AC Mains is present or not, so if i use HCPL3700 opto-coupler as shown below, will it do the job for me?

I just want a single steady pulse, so i assume if the AC signal crosses a certain threshold, the HCPL3700 will output a HIGH and when AC signal is absent it will output a LOW.

Am i right ? Please suggest


texts: Opamp stability given in not inverting configuration

texts:
If a datasheet (like AD828) says that an opamp is stable at Gain >2 (or reccomends to work with G>2, hence it is clearly not unity gain stable), what can we deduct about its stability in the inverting configuration at G=-1; G=-2 or G<<-2 (like in any transimpedance amplifier configuration)?
Is it always instable in the three above cases if not compensated?


texts:
Pat asks:

Accelerometer Breakout Board - ADXL193 +/-250g

could you tell me if this is correct.

Looking at the data sheet the mid sensitivity is about 8mv/G @ 5volts. If I use a 10bit adc @ 5volts then 5/1024=4.9 mV, so 1g=8mV so in bits 8/4.9=1.63 bits/g. Then if I have a zero adc reading of say 500 and I get a reading of 530, then

530-500- 30/1.63=18 g's.

Is that the way to calculate G's from this Breakout Board.

the data sheet says that voltage as low as 3.5 could be used and I was thinking of trying both 3.7v and see if 3.3v will work. Any idea what this will do for the calculations and that maximum range. I know the sensitivity is ratiometric so that will drop based on a lower input voltage.


texts: how to timestamp packets with CC2420 and MSP430F1611

texts:
I'm working on a sensor project which uses TelosB based on CC2420 and MSP430F1611 running TinyOS. And I want to timestamp each incoming packet, whose reception time is indicated by the SFD pin rising of CC2420. The SFD pin of CC2420 is connected to P4.1/TB1 of MSP430F1611 as seen from the schematic. One straightforward way is to buffer the timestamps: whenever an SFD rising edge is captured (e.g., by channel 1 of TimerB), store the captured timestamp in a queue. When each packet is read out from RXFIFO, a timestamp is dequeued and associated with it. This is actually what the default radio driver does in TinyOS. There are several problems with this approach.

(1) Before a captured timestamp is placed into the queue, another packet arrives and triggers an SFD rising edge, overwriting the previous timestamp. There is no timestamp for the corresponding packet. What's worse, it's unknown which remaining timestamp corresponds to which received packet. The mapping from the packet and timestamp is messed up.

(2) Some packets are dropped by CC2420 (e.g., fail to pass address recognition) and not placed into RXFIFO. Nevertheless, it still generates SFD rising edge. There is no packet for the corresponding timestamp. Again, the mapping is messy.

Can anyone please give me some hint on how to overcome these two issues and timestamp packets correctly, especially under heavy load? My requirement can be relaxed not to timestamp all packets correctly, but a fraction of them. Your help will be sincerely appreciated.


texts: How are blocking statements synthesised? - Verilog

texts:
I understand that with the following Verilog code

always @(posedge i_clock)
begin
    r_Test_1 <= 1'b1;
    r_Test_2 <= r_Test_1;
    r_Test_3 <= r_Test_2;
end

It uses non-blocking statements all in parallel and I understand that when this is synthesised, it's basically 3 registers in series and it takes 3 clock cycles for 1'b1 to reach r_Test_3.

But what about this,

always @(posedge i_clock)
begin
    r_Test_1 = 1'b1;
    r_Test_2 = r_Test_1;
    r_Test_3 = r_Test_2;
end

This uses blocking statements and so, all of this code should be performed in series. How exactly will this be synthesised? I mean will it be the exact same? I'm confused.


texts: A basic question on interpreting a battery ratings

texts:
A phone battery has the following ratings on its plate:

It says 3.8V 7.22Wh. Does that mean the battery can provide 1.9A constant current to a 1 Ohm load for an hour with a little battery voltage change? This 1.9A has nothing to do with how much the battery sources current to the phone in real correct? I cannot find any info about this phone's max current rating so it is something mystery for me.


texts: Create circuit with triggered light and simultaneous output to computer

texts:
I'm doing an experiment and will be collecting voltage data (from strain gauges) which will be inputted to a computer through a conditioning system.

I would also like to collect video footage of the experiment, and be able to synchronize the video footage to the data.

My idea is to have a trigger/button/switch which is connected both to the data acquisition hardware (which can receive as input differential voltage signals) and also to a light. Therefore, when I press the trigger, a signal will be recorded along with my data and I can align this with the point in the video footage when the light turns on.

I'm wondering what this circuit would look like, and how to incorporate a light in it.


texts: How does electric vehicle motors control, torque and speeds beyond base speed?

texts:
I'm currently trying to design a electric vehicle motor controller for a Permanent Magnet Synchronous Motor and simulate it using MATLAB. I have considered using the Field Oriented Control (FOC) mechanism to control the motor.
I'm thinking of controlling motor torque but using fundamental FOC with torque loop only give speeds up to the base speed. I looked into field weakening control for higher speeds, but it would require having a speed loop according to my understanding. Having a speed loop tries to control and maintain a given speed whereas vehicle
How does the electric vehicle switch between torque/ acceleration control and field weakening control to obtain continuous speeds beyond base speed? Are there any other control methods used by electric vehicles other than any of the mentioned that I'm not aware of?
Your time allocated for this will be much appreciated.
Thank you.


texts: Mechanical Model of DC Motor - Damping Coefficient Problem

texts:
I'm trying to develop a mathematical model for a small brushed DC motor that I own. I've been collecting test data for motor parameter identification, and have everything but the damping coefficient for the mechanical model component, which is throwing me off.

Let me start with some theory.

From literature that I have found, the developed unloaded motor torque can be modeled as the sum of the torque due to inertia, and torque due to damping, which can be written as:

(where omega is the motor speed in rad/s, J is the inertia coefficient, B is the damping coefficient, and tm is the product of the torque constant and motor current)

To determine B, I'm applying a constant voltage to the motor such that it rotates at a fixed speed. The inertial term can then be set to zero for constant speeds. Substitution the expression for tm into the expression above, and solving for B yields:

B = (kt * ia) / w

So we can see that B depends on the motor current and motor speed. Here's the problem: the ratio of current and speed is not consistent for the speed range, so B is not a constant value!

Here's some experimentation data to prove my point:

Edit: 7:15pm - added updated table with more information

Since B should be constant (I think), I am led to believe that I'm missing a term in the model expression above.

One thought I had is "start-up torque", which is the torque that keeps the motor from spinning at very low voltages. I was thinking I could subtract the motor current just before the motor begins to spin from the values in the table above, which will cause B to be constant... but not if this is a legitimate strategy.

Any ideas how I can find the value for B?


texts: How do I register polygons as traces in Altium?

texts:
I've used the Place>Soild Region command to create polygon traces for my board. However when I highlight the traces by hovering over and pressing shift. The Net is connected but the highlight does not include the polygon I made. I think I'm doing polygons in the wrong way. If I do Place>FillI can only make rectangles but it does highlight all the correct regions.

Here is an example of Place>Soild Region not being a part of the highlighted trace connections.


texts: Which diode to use on my RC switch debounce circuit?

texts:
I am choosing parts to build an analog RC switch debounce circuit. I plan to implement the circuit described here: http://www.ganssle.com/debouncing-pt2.htm (see "An RC Debouncer").

(source: ganssle.com)
These are the other parts I plan to use for the circuit:

Voltage supply: generic AC/DC wall wort adapter, output 5.0V DC 1A
R1: 82K, 2W - http://www.digikey.ca/product-detail/en/PR02000208202JR500/PPC82KW-2CT-ND/597440
R2: 18K, 2W - http://www.digikey.ca/product-detail/en/PR02000201802JR500/PPC18KW-2CT-ND/597334
C: 1 µF - http://www.digikey.ca/product-detail/en/FK24X7R1H105K/445-8517-ND/2815447
Schmitt Trigger: 74AHCT14 - http://www.digikey.ca/product-detail/en/SN74AHCT14DR/296-1474-1-ND/404972
Switch: http://www.digikey.ca/product-detail/en/40-2390-00/506PB-ND/185671

What part should I buy for the diode?
(Also, please point out any other mistakes I've made if you come across them -- my first time building a circuit. :3 I'm interested to see if it's a mistake to use a 1A AC/DC adapter or if my 2W resisters are correct for this circuit...)


texts:
I'm using the following ESD protection diode:

On the datasheet it says:

  MOUNTING POSITION: Any

Does it mean I can assemble it at any polarity?
(switch cathode and anode connections)


texts:
Below is my attempt to solve for the generator current is it correct?

SOURCE: Electrical Machines, Drives, and Power Systems
by Theodore Wildi. Sixth edition, 2014.
ISBN 10: 1-292-02458-5
ISBN 13: 978-1-292-02458-5
Pearson Education Limited


texts: Arduino Uno R3: Directly supply regulated 5V to 5V pin?

texts:
I'd like to use an Arduino Uno R3 battery powered a datalogger. I want do supply it directly with a Step-Up regulated 5V rechargable battery powersource at power pin 5V.

I don't want to suppy it with 5V at the PowerJack or Vin because it's not necessary an would result in lower voltage when powered with 5V at Vin and unnecessary power dissipation at U1.

Let's take a look at the schematic: http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf

I've edited it, take a look at the green areas and blue paths (ignore the yellow area at first):

Just supplying it at that pin 5V however might destroy the linear regulator U1 that regulates >5V+ Vin down to 5V, I fear.

Question

Is it acceptable and safe to suppy regulated 5V+ to pin 5V?
Should I additionally short it to Vin?

Unfortunately there's no internal schematic for U1 (NCP1117ST50T3G) in the datasheet.

For interest

Take a look at the yellow area: am I wrong or is the protection diode reversed? Shouldn't it have the catode at USBVcc?

Edit 1:

As three answers state that it would be the safest way supplying the Arduino with regulated 5V though USB, let I should clarify my question a bit: I'd like to fit the setup within a small case, so I want to avoid plugging in a USB cable if possible.

Except for testing purposes where this might happen by accident, it's not possible that Vin/VccUSB and Vcc 5V are available at the same time.


texts: why add a resistor parallel to voltage source?

texts:
Sometimes I see a resistor parallel to voltage source (such as image below), isn't it completely useless ?

Edit: I see the other similar question now, but I think it doesn't have the right keyword for this topic (I didn't find it when I searched)


texts:
Hello,
Can anyone help me by telling working of this circuit as i asked my teachers and they were kind of being vague and didn't explain it properly.


texts:
This question on kirchoff's second rule every time I calculate it I get +12V but in my book's answers it's -12V.
Could someone solve it and tell me what I'm doing wrong or is the book itself wrong ? I solve it this way: +V+2 -20 +6 =0  -->thus V =-2+20-6=+12V  ... Thanks!


texts: what do you connect to IN+ and IN- for ADC differential input configuration?

texts:
I was trying to understand how to read analog inputs on a raspberry pi.  I found this video post and I think I understood how it works.
https://www.youtube.com/watch?v=oW0mTwFck_c
This video uses a potentiometer and read its analog outputs through MCP3004 microchip.

In this video, he says to use "1" for the single / diff control bit, and he didn't explain much about the differential input.  I was curious, and after some searches, I found that it was used to reduce noises when to read analog outputs.

Now, when I look at this diagram,
http://i.gyazo.com/f86370f39c199b4b8a4fe345b1486b09.png
I understand how to use CH1, 2, 3, 4 for single input type (you just connect analog sensor output to one of them), but for the differential, it says IN+ or IN-, and this gets me really confused.

What do I need to connect for the + and -?

Can anybody explain what to do when you have a potentiometer to read just like the video example?


texts:
I'm working on a project for school to monitor a 6 and 15 VAC signal coming in at 11KHz for both. I'm trying to find a simple way of recreating that at home for running some tests on circuits I'm developing. I have a simple function generator but it only goes up to 5VAC and has a very low current limiter so that's not an option and I'm poor so I can't afford a lab grade function generator.

Ideally, I just want to breadboard a few components that I can repurpose later if I need to. Reading up on some other posts I found Changing the frequency of an AC supply and the common suggested answer was "a rectifier followed by an inverter".

I found DC-AC Inverter Circuit - Toshiba Semiconductor (PDF) which explained a bit but it's still muddy for be. I understand I need to rectify wall supply 110VAC to a DC voltage then use an inverter to convert it back to an AC voltage. What I'm unclear on is how:

do I convert to 6 and 15 DC
OR
do I convert to a 12 and 30 DC (because the AC will do half positive, half negative)?

then use an inverter to make it AC at 11KHz? would it be PFM?

Any help or examples would be appreciated because most of the circuit examples I've found in my research are for converting 12VDC battery to 220VAC or 110VAC, AC to DC (guess I could just use it backward) but with no mention of frequency modification, or AC to AC but again no mention of frequency modification.


texts: what triggers the PREADY signal in a slave of an APB?

texts:
I was trying to understand the state machine of an APB. I was curious on how the PREADY signal is triggered low so that it can exit from  the ACCESS state?

If anyone could help me with this basic question, it'll be of great help thank you. :)


texts:
I have a Triac that I want to use to control low voltage (~16 V) AC.  The data sheet is found here.  It specifies that the peak gate voltage is 5 V with a peak current rating of 2 A (which seems quite high to me).  The datasheet also lists out the Gate trigger voltage as 0.7 V (typical).

I'll be using this opto-isolator to drive the triac gate, which doesn't seem to have much play in my question (but I could be wrong).

  UPDATE: After some additional research it turns out that I was wrong here.  The opto-isolator's max current is the determining factor for the gate resistor value.  The iosolator used here has a max detector current of 1A.  16VAC has a RMS voltage value of 22.62VAC which leads to a minimum resistor value of 22.6 / 1 = ~22 ohms.

My question is which of these values should I consider when choosing a resistor to place before the triac's gate/opto isolator?  I understand how a Triac and it's associated driver works but I just need a little assistance with reading the datasheet and which of the values I should be considering.

Also, are there any good resources for learning how to read datasheets or is this something that just comes with experience?


texts: Probability of error of 2 identical BPSK channels

texts:
we know probability of error of single BPSK system is \$ Q(\sqrt{\frac{2E}{N}}) \$
then what will be the probability of error when two independent identical channels are connected
and hence what will the value of \$  b \$ ??
i have proceeded like this:
since \$ P_e \$ of single BPSK system is given \$ Q( \sqrt{\gamma} \$ )
therefore \$ \gamma = \frac{2E}{N} \$ ;
now how will i proceed??
please help