texts: Why is diode D2 affected by the current of Vin and the choice of R1?

texts: I was wondering why D2 will not always forward voltage drop .6 volts?  Ground is at 0.  What happens if R1 is incorrectly chosen?  Could too much current through D1 push back on D2 and prevent flow from ground through it?  I would think you will always get current through D2, just not as much under some circumstances, and compared to D1.  Since you get current through D2, you should always be .6V at A... so .. why the extra concern with R1..  Thanks for any help


texts:
I've been tasked with showing that the pulse transfer function G(z) of the following plant
 \begin{equation}G_p(s) =  {12\over (s+1)(s+4)} \end{equation} being sampled and held by a zero order hold with a sampling period T = 0.2s is equal to
\begin{equation}G(z) =  {0.1745z^{-1}+0.1249z^{-2}\over1-1.268z^{-1}+0.3678z^{-2} } \end{equation}

I started by combining the plant with the hold to obtain
\begin{equation} {12(1-e^{-sT})\over s(s+4)(s+1)} \end{equation}

I know \begin{equation} {(1-e^{-sT})} \end{equation} is equal to

\begin{equation} {(z-1)/z} \end{equation}

and I split the remaining equation into partial fractions, found the z transform of each, and recombined them to obtain,

\begin{equation}{0.173z^{-1}+0.126z^{-2}\over1-2.27z^{-1}+1.64z^{-2}-0.368z^{-3} } \end{equation}
combined with the z transform of the hold, this equals

\begin{equation}G(z) =  {0.173-0.047z^{-1}-0.126z^{-2}\over z-2.27+1.64z^{-1}-0.368z^{-2} } \end{equation}

This is not equal to the transfer function I am supposed to obtain- Does anyone see what I am doing wrong?


texts:
Now I'm trying to design a circuit which have 2 voltage level (12V and 3.3V). What I want to create is simple switch using 3.3V to turn off 12V. I know there are thousand question about transistor on this site, but after spending some time scrolling, I haven't found what I wanted.

So far, this is what I have designed and simulate it on Proteus.

simulate this circuit – Schematic created using CircuitLab

The question is, do I have a wrong circuit? or perhaps the Proteus simulator is not correct? Thanks in advance. Please ask if this question is not clear. Thanks :D


texts: Why does a p-type conduction band have higher energy then n-type conduction band in a p-n junction?

texts: In an energy band diagram that represents the p-n junction (during equilibrium) the p-type conduction band has greater energy then an n-type conduction band. Why does the p-type have greater energy when the n-type has much more free electrons?


texts: Is this a valid matrix circuit, I've drawn it based on guides and examples online

texts:
I'm trying to build a matrix of

6 toggle switches
6 momentary buttons
4 rotary encoders

I'm going to use a Pro Micro board and I'm wondering if my wiring looks okay, this is my first real electronics project so I'm very unsure and I would love some advice. If there's any more information I should add let me know and I will add it.


texts: Heating and Chilling ICs instantly from 200C to 0C? Does it damage the silicon inside?

texts: I soldered VCXO oscillator and suddenly tried to cool it down with a cooler spray. Do you think that sudden cooling and heating damages the chip. The heating and cooling were well within the spec requirement but I don't know if the sudden change in temperature of the device damages the IC inside the oscillator.


texts: How to get isolated area using Eagle CAD?

texts:
I've created an area using ratsnest and a simple route as you can see in the first example layout. Both belongs to the VIN net. Then I added a GND polygone.

Using the ratsnet function I'm expecting to get an isolated VIN area like it is for the VIN route on the left. But the VIN and GND area seems to get merged.

What am I doing wrong?


texts: Timer0 overflow interrupt does not work on ATtiny10

texts:
I am trying to use the Timer0 overflow interrupt to make a little project.
I used such a timer in the ATtiny45 and it worked, but with ATtiny10 no result.

So I tried an easy LED blinking program and even that didn't work.

Here is the simple code:

#define F_CPU 1000000UL  // 1 MHz

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

volatile uint16_t overflow_val=0;

ISR (TIMER0_OVF_vect){
  overflow_val++;
}

int main(void){
  DDRB = (1<<PB1);
  // Timer0 normal mode
  TCCR0A = 0x00;
  // Start timer with presc 1:1024
  TCCR0B = (1<<CS02) | (1<<CS00);
  TCNT0 = 0;
  TIMSK0 |= (1 << TOIE0);
  sei();

  for(;;){
    if(overflow_val >= 1)
        {
            if(TCNT0 >= 145){
                PORTB ^= (1 << PB1);
                TCNT0 = 0;
                overflow_val = 0;
            }
        }
  }
  return 0;
}

Hope someone can help me. Thanks!

EDIT1:

I changed line

TCCR0B = (1<<CS02) | (1<<CS00);

to line

TCCR0B = (1 << CS01);  // clk/8

in my code to achieve an overflow every 0.524sec. But the LED is not blinking at all.

EDIT2:

Here is the size:

>avr-size test_attiny10_2.ino.elf
   text    data     bss     dec     hex filename
    138       0       2     140      8c test_attiny10_2.ino.elf

EDIT3:

I changed my if statement in the main as follows:

int main(void){

  ...

  TCCR0B = (1 << CS01);

  ...

  for(;;){
    if(TCNT0 >= 0xFFFE)
        {
                PORTB ^= (1 << PB1);
                TCNT0 = 0;
        }
  }
  return 0;
}

Now my LED is flashing all 0.524 seconds as it should!

So something is wrong with my volatile unit16_t variable overflow_val.
Not only i tested it directly on hardware, but did also a simulation with atmelstudio. Also in the simulation the program is never entering the if statement if i use the variable overflow_val to toggle the LED.

EDIT 4

I think something is not right with my ISR fkt. I testet the following code and i never got the LED switched on.

#define F_CPU 1000000UL  // 1 MHz

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

volatile uint8_t ovf_counter = 0;

void ioinit(void){
    // PB1->outputs
    DDRB = (1<<PB1);

    // Start timer with presc 1:64
    TCCR0B = (1<<CS01) | (1<<CS00);
    // Initialize counter Overflow at 0xFFFF
    TCNT0 = 0;

    // Enable global interrupts
    sei();
}

int main(void){
    ioinit();
    TIMSK0 |= (1<<TOIE0);
      while(1){
        if(ovf_counter>=2){
          PORTB = (1<<PB1);
          ovf_counter=0;
        }
      }
}

ISR(TIMER0_OVF_vect){
  ovf_counter++;
  TCNT0 = 0;
}

i dont know what is wrong.

If i check in the while(1) loop the status of the counter register TCNT0 it works. So the counter is overflowing as it should, but it never enters on a overflow event the ISR(TIMER0_OVF_vect) function.


texts: Low power switch input with MCU wake-from-sleep interrupt?

texts:
Im trying to read the falling edge of digital logic input to wake up a microcontroller. Below is the circuit I have used. There is an RC filter to provide a ~5ms debounce time, and a 100K pullup so the circuit doesn't use lots of power while the switch is in its on-state. The switch may be in its on-state for roughly 10% of the circuit operation time.

simulate this circuit – Schematic created using CircuitLab

The problem with my circuit may seem obvious to some but I seem to have overlooked it; The input is pulled low quickly (discharges) just how i wanted it, but it is pulled high (charges) very very slowly due to the 100K pullup.

I don't want the circuit to take a long time to charge up (ideally <20ms) but I also don't want it to draw lots of current when the switch is in its on-state. Are there any engineering tricks i can employ to achieve these two things together? I assume its a classic problem but I cannot find any solutions.


texts: Using Clear Channel Assessment / CSMA in CC1120

texts:
I have two transmitter nodes both running the same firmware, just that the transmitted packet is configured to have a different node ID (you can call MAC address) in it's packet.

I see that the operation works fine if only one node is switched on and the packets are received from that sender at the receiver at the desired rate (I transmit a packet every 100 ms). However when the other node is switched on, reception from one TX node is affected.

Are there frequency channels available like WiFi? (2412 MHz, 2417, 2422, 2427 . . . )?

How do we use Clear Channel Assessment / CSMA in CC1120? I can't find any examples online. The datasheet is located here, and I know it is done through registers. The Git project of my firmware is located here and the transmitter main routine is located here.

How can I use the CARRIER_SENSE register to check for possible ongoing transmissions before transmitting a packet? I can't find an example to that.


texts: Width of Antenna Feed Line for Chip/PCB Antenna?

texts:
I am designing a board having nrf52832 and a chip antenna (2450AT18B100 Johanson Technology) for 2.45 GHz (BLE basically). But I have few questions regarding standard 50 ohm characteristic impedance of Antenna Feed Line.

In my PCB, antenna feed line will be coplanar waveguide with bottom ground plane. As far as I know transmission line will have capacitance, inductance and resistance. But the standard suggests to keep impedance of antenna feed line to be 50 ohm (which is resistive).

Does that mean the transmission line will also resonate at RF frequency (2.45 GHz in my PCB) and it will be resistive at that frequency only?

The chip antenna (2450AT18B100 Johanson Technology) states that it has impedance of 50 ohm. Does that mean if my antenna feed line is of 50 ohm, then I won't need any matching components?


texts: L and N switched, from a functional point of view, what difference does it make for the device being powered?

texts:
Consider a generic single phase AC 240 V (or 125V) device for home use such as a hair dryer.

From a purely functional point of view, what difference does it make if a phase is switched with the neutral on the supply terminals?

From a safety point of view I understand that there are safety implications.


texts: Series isolated DC-DC converters fed by different PV sources

texts:
I would like to have more detail about the description given by Vicor application note http://cdn.vicorpower.com/documents/application_notes/an1_high-vout.pdf:

  In a series array, the positive output of each module requires a series diode (D1 and D2) to prevent the array from being back-driven by load capacitance during turn-off, and to assure proper operation during start-up and dynamic loading. This diode must have a reverse voltage rating greater than the array’s output voltage and a forward current rating greater than the array’s maximum load current.
  In all configurations, diodes D3 and D4 prevent the output from going negative if only one converter is operational.

This is said because I managed to simulate two distributed DC-DC converters fed by different PV panels and if one converter is operated the diode (D3 or D4) will be reverse biased and prevent the current of the other converter to flow.


texts:
I currently have an application that uses a DB25 switch to switch signals between two devices (it's not actually a parallel port - there are analog and digital signals as well as DC power on the DB25). The manual switch box uses a big rotary switch and I would like to miniaturize this on a PCB. However, short of using 25 relays, does anyone have any suggestions on what type of switch I could use? The only caveat is that the solution must be break-before-make.
The signals include:
- -10V to 10V analog waveforms @ 100 KHz
- 0V / 5V TTL logic signals @ 500 KHz
- 5V 12V 24V DC power @ maximum 1A


texts: Why does ATX power supply claim 60a at 12v when it only has two 18awg 12v wires?

texts: I need a power supply that can output 60amps at 12 volts. Based on the sticker on this power supply 12v maxes out at 62 amps. Perfect. Unfortunately the 12 volt wires are 18 gauge, which after some googling seem to safely max out at around 7-10 amps. Even wiring the two together could only support around 20. How would I manage to get 60 amps at 12 volts from a power supply with 18 gauge wires?


texts: SENT (Single edge nibble transmission) signal to analog signal conversion

texts: I'm currently getting a SENT signal output feedback(IC MLX90367 used in the simple actuator) from an actuator. For closed loop control, I have to feed this signal back to the motor controller. Unfortunately, the motor control takes in only Analog values. Is there a way to convert the SENT signal to Analog signal using an Arduino/ RPi with or without a DAC?


texts: Type of wire for high voltage applications

texts:
What kind of wire is most suitable for HV low-current applications, where the allowed maximum is 25 kV and 5 W?

By type of wire I mean core and type of insulation.

As far as I can guess, even if the wire is thin it will not create much heat, because of the very low current and low resistance (especially if copper core is used), but silicone wires will leak static electricity (And that's a problem) if it's not thick and I would prefer thinner wire if possible.
On the other hand PTFE wires aren't usually rated at >15 kV
But perhaps coated wires is what I should be looking for?


texts: Concept of matched filter maximising SNR

texts: The above question is a solved question from Digital Communication by Proakis . The question is about matched filter where I know matched filter is used to maximise the signal to noise ratio at the receiver to 2E/No where E is the energy of the signal which is input to the matched filter , the output is sampled at T, where T is the duration of the input signal. However in the second example SNR by sampling at T would become 0 since the output itself is 0, so in this case how is matched filter maximising the SNR ?


texts:
I have read about OpAmps in openloop configuration where thy output +V,0,-V depending on the inputs.

when the inputs are equal, the output should be 0. My question is, what can be the threshold or difference of inputs so they get evaluated as equal?

For example if pos input is 0.0001V and the neg input is 0.0002V will I get 0V? I think it is not that sensitive...the question is what in the datasheet of the opamp I should look to find this number? what properties affect this?


texts:
I really need some help to figure out whether the ov7670 camera module I bought is with or without FIFO. I bought it from a local market.Can someone please tell me how can I find out whether the camera module I bought is with or without FIFO?? please..  :(

I also want to know what exactly is the role of FIFO here? (all I know is it serves as a buffer to store the image temporarily) and do we need to keep clearing the buffer each time or is it done automatically??

Please help..I am a newbie.

Here is how it looks...


texts: Creating a specific volt/current "test load"

texts:
Working on a complex power supply, but to test its limits I would like to create a set of test loads of specific voltage/current.

There are several devices for creating a set load, but they seem to start in the $300+ level.

I've found a circuit for creating a "dynamic load":

http://www.ko4bb.com/Test_Equipment/DynamicLoad

...but both would only act as a single load at-a-time.

  Question 1:

  If have a specific Voltage/Amp load in mind, can I just use a power resistor AS that load for testing purposes?

I would like to create a set of 5V/2.1A loads.

Using Ohm's Law, that would work out to a: 2.38095Ω 10.5W resistor.  Am I understanding that correctly?

I'm not finding a resistor with those specific stats, but I found:

2.5Ω 10W 1% resistor, which would work out to a 5V 2A load
2.4Ω 10W 5% resistor, which would work out to a 5V 2.08333A load

The second gets me closest to my "target", but when I look at these two different resistors, it seems that the first is a lot "beefier" (heat sink case, etc.), but I lack enough experience to understand which would be best for my purposes.  Instinct is telling me that if I'm using a resistor as a load, and I want to do any extended length of testing (several hours at least) that heat dissipation will be something I need to plan for?

  Question 2:

  Can I place a cheaper ceramic resistor against a heatsink to create a test load for several hours, or would the military spec resistor be a better option for my purpose?


texts: What limits wireless data transfer rates (compared to wired)?

texts: A friend and I were discussing the possibility of wireless video cables and we quickly realized that the bottleneck is the current data transfer rate of wireless technology.  The average wireless router seems to output at roughly 300 Mbps while a standard HDMI cable puts out roughly 10 Gbps.  Does radio frequency interference, distance, and material interference (such as walls) really account for this huge difference in max data transfer rate? Or is there other hardware limiting factors?


texts:
I am thinking to use arduino to generate square wave of various duty cycle and frequency.
the square wave is going to be fed into transistor amplifier.

What options do I have for programmatically controlling the output of transistor?


texts: How to tell if mains voltage is on with microcontroller?

texts:
I want to be able to tell if the mains voltage is on or off with an Arduino.

How could I do this safely with minimal components (or components from Radio Shack)?


texts:
When the positive terminal of the oscilloscope probe touches my skin, I see a 60Hz sine wave. As far as I understood this is the electromagnetic buzz coming from the AC wires in the wall and is being picked up by my body.

I can also see this wave if I grab the ADC input of my ATMEGA328 with my fingers (when the input is floating/not grounded), but it also picks up any hand movements close to it, so as far as I understood I need to ground it as well, but then the signal appears so weak when it's grounded, that the ADC is not picking it up.

I decided to try to amplify the signal with UM741, I seem to be getting a bit rounded square wave on the oscilloscope, so I believe it's working:

But now I face a problem with amplification factor:

I read that the op-amp can amplify the signal up to 80,000x and that the:

amplification rate = 1 + (R2/R1)

But when I replace the R2 with 1M resistor, I would expect for the amplification factor to jump from 2x to 27x, but the output is exactly the same.

PS: My negative input terminal on the op-amp is grounded to the power supplies negative terminal, is this correct or should it be grounded to my body since I'm taking a reading from it?


texts: Under what conditions should we use negative voltage?

texts: As mentioned in the title I'm curious and confused under what circumstances a negative voltage should be used? Does it mean in a negative voltage power supply the current is flowing from ground point to negative terminal of the power supply?


texts:
I don't get how the antenna design on page 8 of the datasheet is suppose to work. I know that the feed trace from VDD works as an inductor at high frequencies, but how do I design an antenna like this on my PCB ?

Do I just draw one, and hope for the best, when I get the PCB back from manufacture, and start to measure the antenna impedance, or is there some design rules that will help me get best possible efficiency ?

https://www.silabs.com/Support%20Documents/TechnicalDocs/Si4012.pdf


texts: How is a reed switch used to charge/discharge a capacitor?

texts:
Ok, so there's no way to disguise this; I admit this is a question I've been set for homework but I can't find a full answer to.

I know that, in brief, a reed switch consists of two metal contacts inside a glass tube and can be operated by a magnetic field, and I've seen lots of experiments involving capacitors and reed switches (most of which also involve a signal generator), but I cannot seem to find any explanations.

Could somebody explain to me how you can charge and discharge a capacitor using a reed switch and the physics behind it please?

By the way, I am studying Physics at A2 level.


texts:
Newbie here, trying to learn electronics (Iam from SW background). Looking for someone to review the initial schematic and advise. Haven't ordered the parts yet, so appreciate any tips in finalising the design.

GOAL:

To build an automatic watering system for indoor potted plants
The potted plants are split into five zones, each zone having its own watering schedule
Watering schedule should be defined by the amount of water to be delivered (in litres) at a specific point in time

DESIGN:

One submersible water pump is installed per zone (total five pumps)
A raspberry pi is used to control the pump according to a preset schedule (coded in software)
Only one pump is to be active at any point in time. This is to ensure that only one manufacturer provided power supply (12v) is used to power the system
Pump specs:
Rated Voltage: DC 12V
Rated Current: 1.2A
Power Consumption: 14.4W
Driven: Brushless Magnetic
Submersible: Yes
Flow Rate: 780L/H
Details: http://www.aliexpress.com/store/product/Brand-New-12V-Micro-Pump-with-DC-Plug-Strong-780LPH-4M-Black-230g-Electric-Power-Drop/912512_1739623777.html
opto-coupler to decouple the 5V and 12V circuits
Combination of transistors and NOT gates to implement the required logic

DESCRIPTION OF SCHEMATICv3:

VCC2 & 3 are wall-adapter DC power supplies
VCC3 is from the pump manufacturer
M1, M2, M3, M4, M5 are pumps as per specs mentioned earlier
U1, U2, U3, U4, U14, U15, U18, U19, U22, U23 are BJT’s
R1 - R11 are resistors
U12, U13, U17, U21 are opto-couplers
U9, U11, U16, U20, U24 are logic NOT gates
D1-D5 are diodes for flyback protection
Color codes:
RPI GPIO output wires are in green,
5V power supply wires are in red,
12V power supply wires are in blue

SCHEMATICv3:
[![schematic][1]][1]
QUESTIONS ON SCHEMATICv3:

Will the high level schematic work? (For e.g. am I missing any components OR are any components wrongly connected)
Please suggest ratings of parts
a. Value of R1, R2, R3, R4, R9 and R11 (resistors protecting the RPI)
b. Part number for the NOT gate that I found is TC7SU04F. Will this work? Alternatives?
c. Value of R5, R6, R7, R8 and R10 (resistors protecting the transistors)
d. Part number for the OPTOCOUPLER I found is TLP621 (U12, U13, U17, U21). Will this work? Alternatives?
e. Part number for the BJT transistor (U1, U2, U3, U4, U14, U15, U18, U19, U22, U23) I found is MPS2222A. Will this work? Alternatives?
f. Part number for the Diodes (D1,D2, D3, D4, D5) I found is 1N5817. Will this work? Alternatives?
Does it make sense to use MOSFET’s instead of OPTOCOUPLER?
Are any pull-down resistors required for the RPI GPIO pins to protect during reboot?
Is this safe HW design? Will the components blow-out due to multiple GPIO pins being held high briefly at RPI boot? For e.g. if GPIO21 and GPIO20 are both held high, then both U12 and U13 will get activated and consequently both M1 & M2 will turn on drawing more than what the 12v power supply can deliver.

Aug 4, 2015:
Updated schematic based on modifications suggested by @WhatRoughBeast
[![Updated Schematic v4.2][1]][1]

Aug 5, 2015:
v4.3, based on modifications suggested by @WhatRoughBeast


texts:
I'm working on a small hobby project - a small (230V wall plugged) coreless induction furnace. I generally know what I'm doing, chosen a topology, calculated inverter and coil parameters, desired resonance frequency etc. Now my problem is - how do you, in reality, measure the very small inductance that the coil would have, on the order of 1-5 microhenrys? Is banging the coil with a voltage step and measuring the time it takes to reach certain current a good idea, and if not - how?

Or am I trying to reinvent the wheel and should I just shop for a LCR meter? I've seen some very reasonably priced models (for examplpe Voltcraft products, ~100 EUR) that are advertised as capable of measuring from 0.1 uH. Are they any good?


texts: Problems simulating MOSFET astable multivibrator circuit

texts:
I am currently trying to simulate an astable multivibrator circuit to drive the MOSFET in a boost converter. I am using MOSFETs instead of BJTs for the multivibrator circuit.
However, my simulation does not seem to work. The output voltage of both the gates of the NMOS are at a constant 1 V. I have attached the picture of my schematic.

This is where I got the schematic from here.


texts:
I am using a dsPIC33E MUC to interface an UART camera(VGA) at 115.2Kbps. The purpose is to save an image to a SD card.

The program I wrote works well except that it's inside a loop checking if the buffer(512 bytes buffer is for one sector) is full or not. If the buffer is full, it will be written to a SD card. I am wondering how I can adapt this code to a time critical data acquisition project. Since it's UART interrupt driven, I am not sure if the best way to save images to a SD card is to use a flag. Here is the code with the loop checking flag to see if the buffer is full.

unsigned char buff[512];//buffer to store bytes comming from the camera
unsigned int bufferPtr=0;//pointer for the buffer. It will be incremented for each byte
while(1){
    if(bufferPtr==512){Write_Sector(SectorNumber,Buff);}//if the buffer is full, Write a it to SD card
    bufferPtr=0;//reset buffer Pointer so next byte will be save to the beginning of the buffer
}

interrupt routine

void ISR(){
    Uart.FlagBit=0;//clear flag bit first
    buffer[bufferPtr++]=UART_Read();//read a byte and put it into the buffer
}

As you can see, the program is kinda waiting for bytes to arrive and save it to a buffer.
It works very well but I have a question about timing. In terms of writing speed, it needs roughly 3.6sec for 2000 sectors(each sector 512 bytes). So writing one sector needs 3600/2000=1.8ms. The baudrate tells me that 115200/10=11520Byte/Sec, which means 11.52 Bytes/ms. How is it possible to write one sector to SD card(needs 1.8ms) without overflowing UART FIFO buffer? During that 1.8ms period, there will be 11.52*1.8=20.736 bytes comming in.


texts:
I've been doing a lot of research into linear actuators, and have come up pretty much empty handed in finding any small sized (lifting force 10-30 newtons)  linear actuators for a doable price (30-50 dollars).  I've seen some diy rack and pinion designs, and while prototyping I ended up turning a servo into a linear actuator with a lift arm, but I'm not much of a machinist, and would much rather a all in one solution.

So does anyone know of anywhere that sells 30-50 dollar linear actuators? Or will I always need to make them myself?


texts: How do I connect 3 audio inputs with a switch?

texts:
I have 3 outputs from different audio sources via aux cable. I'm trying to combine them all into a box and have an easy way to change the audio source. If only one source is going to be used at a time how should I wire everything together?

Should I use a 3 position slide switch like this?

http://www.allelectronics.com/make-a-store/item/ssw-62/on-on-on-3-position-slide-switch/1.html

Or can I just wire them all together without a switch. Would there be interference that way since only 1 of the 3 audio sources will be on?


texts: What makes DSSS a more robust transmission technique compared to FHSS?

texts:
In many textbooks it is stated that DSSS is more robust than FHSS. Especially in terms of interference and delay spread?

What is the exact reason. Lets say we multiply a given bit 1 with a larger bit sequence. How does this make the communication more immune against delay spread & interference?


texts: Would an AC induction motor rotate if the power factor were unity?

texts:
I know about active and reactive power as a big picture. Active power is what really does the job and the reactive power circulates back and forth in and out of the system. I also know the math behind them to some extend and active reactive components ect.

Where Im stuck as is that why power factor is set near unity like 0.8 or 0.9 but never unity. By adding capacitor banks why would power factor not made unity? In other words why is active power needed for inductive loads? I might be askng something foolish but I couldnt prove it to myself.


texts: why doesn't this code receive string ?(it just receive the first character)

texts:
I want to receive a string whit atmega8 that is sent by another atmega8. The sender send string just one time, but in receiver just first character is received. I can't understand what is the problem?
thanks for your help.
this is the code.

// USART Receiver interrupt service routine
interrupt [USART_RXC] void usart_rx_isr(void)
{
   while ( !(UCSRA & (1<<RXC)));

   for (i=0; i<8; i++) {
     data = UDR;
     if (data != '\0') {
       mass[i]=data;
     }

     while ( !(UCSRA & (1<<RXC)));
   }
   lcd_puts(mass);
   delay_ms(500);
   lcd_clear();
}

and while loop is empty . I try to use interrupt to receive.


texts: Transmitting HDMI/DVI over an FPGA with no support for TMDS

texts:
I'm hoping to be able to output HDMI/DVI-D for my next FGPA project but my FPGA doesn't have native support for TMDS outputs. The FPGA is a Spartan 3E and I believe it only has support for LVDS differential signalling.

I read a lot online about differential signalling and I have a general idea of how it works but I am confused about the different standards. I have also gone through the specifications for HDMI but it's very dry and seems to presume a certain familiarity with these concepts beforehand which I don't have.

For example, what exactly is TMDS vs LDVS? Is TMDS just an encoding scheme run over LVDS? Are TMDS and LVDS just standards for differential signalling but with different electrical characteristics? The absence of search results for LVDS to TMDS converter chips suggests my understanding is broken here.

In a practical sense, I am wondering if I can simply wire an HDMI breakout board directly to the input pins of my FPGA, configure those pins to the LVDS IO standard and expect it to work (given that the software side is written correctly). Some websites imply that I can but it seems that their FPGAs all have built in TMDS drivers where mine doesn't. Other sites say that I need TMDS support but then go onto say that LVDS works too. Wikipedia seems to suggest that LVDS is being phased out as a standard for transmitting data over DVI or HDMI.

Can anybody help me clear up any misunderstanding on how all this works?


texts: Voltage divider to measure 12v battery with arduino low consumption

texts:
I want to measure 12v. Car battery with arduino. Three questions:

Is the R1 and R2 the best values? The car battery can go from +10v. To +15v.
How and what can I use to save power between the measure reads? Like a transistor to switch on and off or something like.
Must I add something to protect arduino pin from car battery overvoltage?

I have this:

———————————————— +10v. To 15v. Car battery
         |
         |
    Something here to switch off and save power?
         |
         |
         R1 = 150kOmh
         |
         |——————————- to analog arduino pin to read voltage
         |
         |
         R2 = 470kOmh
         |
         |
——————————————————- GND negative battery

Solved!

———————————————— +10v. To 18v. Car battery
         |
         |
         R1 = 36kOmh
         |
         |———————————————- to analog arduino pin to read voltage
         |            |
         |            |
         R2 = 10kOmh  5.1v Zener diode to protect arduino pin
         |            |
         |            |
—————————————————————————— GND negative battery and arduino


texts: Finding the overhead and distance of an unknown code based on message making algorithm

texts:
for an information word M with m bits that is coded as following:

M is coded into a word A using an unknown code that allows detection of not more than one error.
the code word is the word obtained by a concatenation of A to itself. so A becomes AA and etc..

1)is it possible to know the overhead in the given code?

2)is it possible to know the distance of the code?

my attempt:

after thinking on it again and rereading the text, i began to realize(hopefully i am right now) that the question is about parity bit and not hamming. so if it can detect not more than one error, there's a parity bit, i think. based on that thought i tried to solve it:

1)I began to realize it's not about hamming code. if we can only detect not more than one error, then it's about the parity bit. so i think that if we add a bit to each byte of message, then the overhead will be 9 bytes total. so it can be calculated, i think.

2)since this sub problem is about the concatenation of A to itself, then like @YuvalFilmus said, the minimal distance should be twice now.

is it correct now? would really appreciate your comments and help.

thank you very much


texts: how to choose components by "popularity"

texts:
An example.
I used Intellifet by Diodes Inc.
They are logic level mosfets, with  builtin protections.
There are many components, with slight different ratings.
Let's say many of these components fit my project.
I want to sort them not by their electrical ratings, but by their  "popularity"

selling volumes
availability in Europe from many vendors.

Are there any source of these informatioms ?
Note: I need to find a solution to speedup the choice made by "visiting the distributors web sites".
Small orders : each component, from 10 to 50 pieces.


texts: Why does my LM393N (dual comparator) ignore its inputs completely when used with an LED?

texts:
I have made the following circuit:

Viusalisation (not working):
  https://i.stack.imgur.com/tDA85.png

Circuit (working):

simulate this circuit – Schematic created using CircuitLab

Left to right, the pins on the chip are: vcc out2 in-2 in+2 and ground at the bottom

It always powers the LED with 3.3 V no matter what the inputs are, so the LED is always on. The circuit simply doesn't change, no matter which line or none at all are plugged into the inputs.

It is powered by the 3.3 V and 5 V connections of a Raspberry Pi. The resistor is 10K, but I've tried it with 1K and 100R as well and the circuit still doesn't work.


texts:
Hi I am from computer science background and hence lack any solid foundation in electronics. I am trying to learn some flip flop conversions. Most of them are their online, however I did not found below two. So I made them myselves. But I need to know if I prepared the correct?

SR flipflop to T flipflop

T flipflop to SR flipflop

Are above conversions correct?


texts: OP-Amp self generated negative voltage from Charge Pump?

texts:
My circuit is a "kludge" designed to solve a problem. I have a wireless device that can regulate audio volume levels, and an amplifier whose volume is controlled by a 0-3VDC input. So I created the circuit below from a quad TL084 op amp, and it works well. Basically U1c (upper left) generates a 4khz square wave which is filtered and passed to the wireless volume control device. U1b takes the now "controlled" return signal coming back and adds some gain, rectifies it, and turns it into a filtered DC voltage. U1a then buffers this voltage and feeds it out to the amplifiers voltage controlled volume input point. U1a simply develops a stable 1/2 V Ground reference point.

Now the circuit works well, but it inconveniently needs an isolated supply to work because the amplifier (the one needing the 0-3V volume control input) needs to share the 0V reference with my circuit's 1/2V ground. Well switching wall power adapter supplies are cheap and small, so right now I'm just using such a supply. But that seems a waste. In most cases where I use this circuit, there will more than likely already be an available low voltage positive supply somewhere, and it would be nice if I could use it to power my circuit. The alternative is to use a more complex voltage translation scheme and I don't think that's a good idea. It would mean the current V- must become my 0V reference, so at the very least I'd need a more expensive rail-rail op amp. Seems the easier way, assuming the amplifier DOES have an available positive supply (say 12VDC), would be to add a simple charge pump like this to generate -12VDC...

Now recall that U1C is already being used to generate an audio (4Khz) square wave oscillator. Even though I'm filtering it to use as a mock audio signal, it is still plenty square at the OP-Amp output. So a charge pump would require only a few parts. The question is, how can I make the circuit INITIALLY have its V+ and V- points powered by the available +12V and 0V, but then have its V- rapidly replaced by the -12V developed by the charge pump? I think its simply a balancing act of resistors, and probably an extra isolation diode. But I'm having trouble wrapping my head around it, and am hoping someone can assist me and point out the "gotchas". Please note that I have seen other articles/questions with a similar theme, but none of them had the goal of letting the op amp needing the negative voltage really generate it on its own.


texts:
Why pairs and quad of 1's are not counted as implicants in the given k-map

ref:- https://www.google.com/amp/s/www.geeksforgeeks.org/digital-logic-implicants-k-map/amp/


texts: Why do mobile phone transmissions come in pulses?

texts:
We are all familiar with the phenomenon that mobile phones induce in amplifiers and loudspeakers. The bip bip-da-bip bip-da-bip which happens just before you get a call, or if the phone is just feeling chatty.

I understand how the sound is produced, I don't understand why it has that particular pattern. Why a series of pulses?

I thought at first it might be an attempt to avoid interference, but of course that's nonsense: two x-millisecond transmissions are just as likely to become corrupted as one 2x-millisecond transmission.

So why the pule? Why not send the packet all at once? (Or send several packets in succession without a gap? Same difference -- the expected number of resends is surely the same.)


texts: Torque of motor vs operation as generator

texts:
While trying to work out which motor to use for a wind turbine project, I'm coming across torque numbers for DC motors. I'm mainly looking at a BLDC motor right now.

Clearly, for a smallish turbine that I'm aiming for, I'm looking for low startup torque.

So, is there any relation between motor torque and/or wattage with its generator torque? Or more in general, how does one decide which motor is best for a given set of blades?


texts:
https://learn.adafruit.com/16-channel-pwm-servo-driver/chaining-drivers
The above link says that we can daisy chain up to 62 of these boards together, but once we scroll down below, we see that we have to solder the offset pins for the i2c controller, and there are only 5 bits in that. That must mean that we can connect only controllers 0x40 through 0x71... Right?
But that configuration only allows us to connect 32 of these, how do i add more?
Also, In the future, i may need to add more than 62, so can i daisy chain another 62, and connect it to 2 other analog input pins in my microcontroller?


texts: Why do ICs often have multiples of the same configuration, with different part numbers?

texts:
Take the SN54AHC125/SN74AHC125 tri-state quad buffer, for example. Data sheet is here: http://www.ti.com/lit/ds/symlink/sn74ahc125.pdf

Refer to page 7, and you will see this (snippet):

Click here for a larger version

SN74AHC125DGVR, SN74AHC125DGVRE4, and SN74AHC125DGVRG4 (the TVSOP entries; middle of image) have the same properties according to that chart. What's even weirder is that chips with the same properties, from the same manufacturer, might cost different! I looked through the datasheet to see if it had anything to do with packaging, but I still couldn't find anything.

So why do multiple part numbers exist that reference the same part/configuration?

Real example

The reason I actually asked this question is that I'm interested in buying a small-ish quantity of said buffer chip. I want this one, but I also see a seemingly identical chip (with the addition of G4 at the end of the part number) for a few cents cheaper. I thought there must be a reason it's cheaper, but I (obviously) couldn't figure out why.


texts:
I have a 220V heater which is equipped with a thermistor. Its value at room temperature (20-25 °C) is 10Ω.
I'm trying to read its value with an Arduino but the output voltage is as low as 0.007V. Analog values on Arduino go from 0 to 1023, where 0 is 0V and 1023 is 5V: I need to amplify this value or I won't be able to read it properly.
I bought an operational amplifier (LM358P) and made the following circuit:

simulate this circuit – Schematic created using CircuitLab
It's my first ever time working with OpAmps and I'm not an electrical engineer, so the schematic could be completely wrong. If so, I'm sorry for that, it was produced by various internet searches as I'm not an expert.
A few question you might have:

Why R1 is 10Ω?
Because I seemed to understand that it's easier to read values if the resistor between the thermistor and ground has the same value as the thermistor at room temperature.
Why R2 is 10kΩ and R3 is 2.2MΩ?
Because as far as I understood the amplifier gain is calculated by using the formula 1 + R3 / R2, so in this scenario I should have a gain of nearly 220 (0.007V should become 1.54V).
Why is the circuit like this?
I tried to combine the way I usually read voltage value coming from a sensor with a non-inverting OpAmp circuit I found online, and that was the result. I'm not sure this is the right way to do it though, copy-pasting often leads to errors.

Nothing is exploding at the moment, but the issue with this is that on the Arduino side I get random values between 250 and 300. This also happens if I unplug the analog input, so I believe it's not working at all.
Did I get it completely wrong? How should I modify the circuit to make it work?


texts: Why is there current flow in the sub-circuits?

texts:
I'm struggling with the theory of this(unusual) circuit:

simulate this circuit – Schematic created using CircuitLab

The load receives no power at all, due to the voltages cancelling out, yet the parallel sub-circuits voltages do not cancel out, and enormous current flows in each sub circuit. I dont understand why current in the whole circuit(even in the sub-circuits) is not equal to zero? If the voltage at node Vx is V1 - V4 = 0, likewise with Vy being V4 - V1 = 0.

I'm trying to understand how this is physically possible(for current to flow or shorting out in the sub-circuits) while the potentials are opposing one another, I tried looking at each branch and how it's possible for current to flow there but it's just difficult.

The reason why I think current flows in the sub-circuits, is because of them being shorted.  But still lost with the concept while analyzing.


texts: Trouble getting 555 timer IC circuit to work properly (Make Electronics Book Experiment 18)

texts:
I am currently reading a book titled “Make: Electronics”. This is an electronics book whose target audience is supposed to be complete beginners.

One of the book exercises (Experiment 18) includes a resistor capacitor connection that is giving me some headaches. A picture is worth a thousand words so if you would, please take a moment to check out the partial circuit diagram below paying special attention to the connection between IC7 pin 3 and IC6 pin 4.

EDIT: Per comments request, IC7 and IC6 are 555 timers. Here is the pin-out for the 555 timer (sorry, I can't believe I totally missed calling out the ICs types):

As you can see from the picture above, the IC7 chip is configured as a monostable timer and the IC6 chip is configures as a bistable timer. The connection between IC7 pin 3 and IC6 pin 4 has a capacitor C4 in between. There is also a connection comming out from IC6 pin 4 to a resistor R10 all combined to form what appears to be your typical RC connection.

The gist of how the circuit is supposed to work is like this:  You press the S4 push button, this makes IC7 pin 3 to go high and after a couple of seconds it goes low. The transition between high and low on IC7 pin 3 is supposed to send a signal to IC6 pin 4 that should reset it (vial pin 3 going low).

In case it helps, below is a link to a video that someone made describing this experiment. On the video, the chip all the way to the left is IC7, and the next one to the right is IC6.

https://www.youtube.com/watch?v=iWvHB0lIbK4

Unfortunately, no matter what I do this is not working for me because pin 4 on IC6 never triggers no matter what size capacitor or resistor I use. I would like to get this to work, but before I can attempt to fix this, I need to understand what exactly is supposed to be going on here and this is where I need your help.

So far, what I think is supposed to be happening is the following:

EDIT: If anyone is still reading this post, what I am looking for (as the answer to this question) is for someone to verify whether the four steps listed below accurately describe what is going on in the circuit. If yes then please let me know, if no, then if you don't mind, please let me know were did I go wrong.

When the circuit is first powered on, pin 3 in IC7 is low so capacitors C4 begins to charge via resistor R10.
After some time, C4 charges up and current stops flowing. At this point, pin 4 on IC6 become positive.
When you press S4, pin 3 on IC7 becomes high. This causes the C4 capacitor to discharge via R10 until both sides are equally positive. Here again, pin 4 on IC6 remains positive.
Eventually, IC7 (the monostalbe timer) changes state and its pin 3 goes low and this is where things get interesting (I think). When this happens, the impedance on C4 momentarily drops down to zero making C4 momentarily appear to the circuit as a direct cable connection. It is at this very precise moment that pin 4 on IC6 should be negative and pin 4 should trigger.

Assuming that the logic stated above is sound, the process does not work for me. I think the problem may be that in step 4, pin 3 on IC7 only reaches about 7.7 volts when the pin is high (the source voltage of the circuit is 9 volts by the way). This I think is a problem because step 4 expects pin 3 on IC7 to ideally be 9 volts. If the voltage I lower than 9 volts the transition will not generate a low enough voltage to trigger pin 4 on IC7.

Sorry for the long post. Any help is appriciated.

Thanks.


texts: Why is the gate drain capacitance in a mosfet zero when in saturation?

texts: Suppose I have an NMOS.  In the linear region the gate drain capacitance is modeled as \$C_{ox}\cdot w\cdot l(ov)\$ but it is modeled as zero when in the saturation region.


texts: How does this "CD4069 smooth bargraph" work?

texts:
I saw this schematic and I had problems finding out how it works:

As the voltage increases from zero, the first LED grows in brightness.
Just when that LED is fully lit, the next LED begins to glow slightly.
Each LED represents about 1 volt of change, when the circuit is
operating from 9 volts.

According to the 4069 datasheet, the gates are not Schmidt triggers nor buffered, and the diagram for a gate seems quite simple:

If I'm right, the resistors form a voltage divider and just drive the LEDs.
I have these questions:

How does the circuit work? Why doesn't the next LED light up until the previous one is fully lit?
What does the first gate (left most gate, with two 1Mohm resistors) do?
What kind of modifications do I have to do, to make it work with a 5V supply? The supply would be a constant 5V and the input would be a variable 5V.

regards.


texts: Choosing resistor and capacitor for active filter

texts:
I am new in designing the active filters though I designed Active low, high and bandpass and notch filter successfully (using Opamp, R and C).  But these filters are not actually designed by me :-( I am using the online tool to design them.

When initially I designed a normal active low pass filter by seeing its general diagram and then calculating the value of R and C as per my cut off frequency. This filter works fine when I am seeing its result by using function generator as input. But I wanted to design it for an audio signal so when I gave an audio signal as input then my whole signal is vanished out. Because of this, I moved to the online tool.

So I wanted to know the impact of the resistance and capacitor on the input/output signal. What are the criteria for choosing the values of the components?
For Eg. A cutoff frequency of 500Hz has many pairs of R and C which give 500Hz.

It will be great to hear your thoughts on this. As I wanted to get deep knowledge in the filter design as these are one of the important circuits in the electronics field.

I am attaching this schematic of low pass filter for 500Hz cutoff frequency which I designed by the online tool. But when I take some other random values of R and C then this circuit not works.


texts: What is "Low Pulse Trigger" and how to use it?

texts: I picked up some of these cheap Chinese Bistable relays and I am having trouble understanding how to get them hooked up. Do I put 5vdc + on VCC and 5vdc - on GND then use a low voltage pulse, such as 3.3vdc, to trigger it? I'm trying to use it with a Raspberry Pi.


texts: How does this N-type MOSFET AND-gate work?

texts: The OUTPUT 'F' is completely seperated from the transistors 'a' and 'b.' The MOSFET infront of 'F' seems to be perpetually on. What makes this a logic gate. Shouldn't F always be on?


texts: Solid state circuit to charge caps in parallel then discharge in series?

texts:
Do there exist a solid state design circuit to do the following:

Charge multiple capacitors in parallel for a certain amount of time from a low voltage DC source, then disconnect them completely from the DC source and rearrange them in series to allow them to be discharged in series?

What I want is to charge about 10 capacitors in parallel with 12 V, then discharge them at 120 V in pulses.


texts: Is a neutral wire necessary between 2 circuits

texts:
Suppose I have 2 circuits with their own individual power supply.
Circuit 1 needs to send some sort of signal to circuit 2. Would I need to carry the current back to circuit 1 after the signal has reached circuit 2 (in the form of a neutral wire)? Couldn't I just send the voltage along one wire and then use the ground in the second circuit to complete the circuit, effectively having just one wire between the circuits?


texts:
I'm not entirely sure how to choose power supply for bldc motor. I have 2 80wat motors with controller (black box, i cant find out what inside), but stall current for both of them can be close to 80A. Controller has 3 wires conected directly to motor. Can I buy simple power supply for 24V and install in series diode for 80A like in this article https://www.heliosps.com/dc-power-supplies-dc-motors/? This would be enought for protecting from damage and also make proper condition for this motors? Or maybe use additional shunt regulator?
Thanks for your help.


texts:
I am using a Meanwell LDD 350ma driver with a 12v power supply.

Datasheet has note that output voltage will always step down 3 volts from input. If I understand it correctly that means that output will be 9v in my case.

What happens when I connect led array which requires 13.6v at 350ma?

Will it work and if it does is there any problem with this? Less brightness is not problem, could it damage diodes or driver.


texts:
I am designing a switching circuit for celing fan (max 80W/230VAC). This is basically relay based switching.
I planned to add snubber circuit to reduce the back emf.
I got a resistor value of 100Ω and 0.1µF capacitance when I did a google search.

I have a film capacitor of 1KV DC voltage rating and second one 440AC X2 class rated. Which one will be more suitable?
If I want to add TVS to cap the max voltage, what voltage rating will give the beat results?


texts: Determining value of capacitor, in a opamp ampifier circuit

texts:
I am working on the follwing circuit, and have found all values for the components, except for C3 which i have a hard time finding.

My requirements are that it should be able to handle 40-16k Hz with a flat frequency response, and that i can change the gain of the amplifier.

Because of this i would preferably have a cut off frequency of 160k Hz in the circuit:

where
R3 = 7,3k ohm
R4 = 1k ohm
P1 = 0-242k ohm

The thing is that i see the last part of the circuit as a low pass filter, with the output on the negative terminal of the opamp.
The problem is that R4 is a part of it, and i will always have a gain lover than 1/sqrt(2) and therefor a cut off frequency does not seem to make sense.

How can i determine a value for C3?


texts: How to know exact Decoupling Capacitor values for supply voltages?

texts: When designing circuits using various components such as IC's a lot of the time the data sheets give you an example schematic where they will usually give you some values for decoupling Capacitors. I usually see a 0.1 uF cap in parallel with a 10 uF cap on the supply rail. Sometimes I see other variants where they have several 0.1 uF caps in parallel. How are they determining these values?


texts:
What is the difference of the area calculation for the Dirac delta function when using different limits of integration?

$$\int_{-\infty}^{\infty}\delta(x)dx = 1$$

but

$$\int_{-\infty}^{t}\delta(x)dx = u(t)$$


texts:
What is the F/cm^2 for a commercially available supercapacitor? Much of the literature is on newer types of carbon, such as graphene, but are commercially available supercapacitors based on activated carbon?

http://www.pnas.org/content/suppl/2015/03/22/1420398112.DCSupplemental (Download Supporting Information (PDF))
In this article published on March 23, 2015, the F/cm^2 is 300mF/cm^2 (.3F/cm^2) for activated carbon (Table S1, p.16), yet references the information from an older article. The reference is to:
Simon P, Gogotsi Y (2008) Materials for electrochemical capacitors. Nature Materials 7: 845-854.

http://rsta.royalsocietypublishing.org/content/368/1923/3457
The authors of the older article state, "Double-layer capacitance for carbon materials in liquid electrolytes is in the range of 5 to 20 μF cm−2, depending on the electrolyte." in this different but more up to date 2010 article.

I have not unraveled a supercapacitor, but the range of 5 to 20 μF cm−2 seems rather low compared to the small size of supercapacitors commercially available, but is the .3F/cm^2 stated in the more recent article accurate?


texts:
I have a board which is a PAL CCIR video sync generator card having SAA1043. The IC is accepting external sync signal from pin 15 and generating composite pulse on pin 26 and burst output on pin 1.

This IC is now obsolete and I am planning to replace this card. While searching for sync generator ICs, I mostly find sync separator for example MAX9568.

My questions are:

What is difference between sync generator and separator?  Can I use MAX9568 circuit in place of SAA1043 circuit?  Would that work?
Can I replace this card with a Microcontroller based sync generator card?  Is this doable?  If yes, any article for guidance because I am really confused what exactly sync generation is?

Edit: Schematics attached.


texts: STM32 MCU PCB layout review (crystal & decoupling & ADC)

texts:
Introduction:
I am designing a hobby electronic for first time, using STM32 to control a soldering tip. I read many documents of PCB layout, and also many information from this forum. And this is my first result, I am going to let this design be manufactured by PCB manufacture.
Since this is my first attempt, I would like to have some advice to check whether I'm doing wrong or not, before I send this design out to the factory.
This PCB will be a double layer PCB.
The components are going to be soldered by hand.
I am designing the PCB with EAGLE education version. (2 layers only)
Crystal Layout:
From this document I learned :

To have a GND island in bottom layer and guard ring on top layer to protect the OSC signal.
The isolated ground island should be connected to the nearest MCU ground.
The guard ring should be stitched by via to the ground island.
No signal should run through the isolated ground area.
The signal paths of OSC should be symmetrical as possible.
The signal paths of OSC should be short as possible.
Return paths of load C goes through via to Ground island

My OSC is running in 8 Mhz; load C are 18 pF.
I hope I understood the rule correctly, and also do the layout correct in the range of a hobby board.
Power and Decoupling C:
I am using 0603 cap. I want to keep the ground plane as whole as possible, so I don't want the signal trace go to the bottom layer. But I also can not keep the decoupling C on the top layer. That's why I moved decoupling C to the bottom layer. If any idea can be provided, which can make both traces and decoupling C on the top layer, will be very appreciated.
What I got as rules:

The decoupling C should be placed as close as possible to the VDD/VSS pair.
Power first go through the decoupling C then to the VDD/VSS pins
MCU has local +3V3 and GND. And they are feed from a single point.
Keep the ground plan not be cut.
For the VDDA, a ferrite bead is needed.
If multiple C are needed, place the C with smaller value closer the the VDD/VSS pair.

Please let me know, whether my layout is reasonable.
ADC signal:
for my application a thermocouple signal is needed, which is in the soldering iron tip. The the tip has a heater resistor and a thermocouple inside and the thermocouple and heat resistor are sharing a common return path. The thermocouple voltage is measured in the period, when the heater voltage is not applied.
I am using a very simple non-inverted op amp to amplify the signal. What I am concerning about are:

whether the return current of heater element will give big disturbance to the MCU. (Since the thermocouple voltage is only measured when no heater current flows, it doesn't matter that the current is effecting the op amp)
Is it better to tie the OP amp VSS to the ground plane directly, or tie it to the thermocouple(-) as I did in the design? Or other options?

Schematic:
I am using a STM32F103C8T6. According to datasheet, .1uF and 2x 10uF for VDD/VSS pair. For fast signal I placed resistor for raising edge suppression. A cap is placed for filtering reset line. I am using SWIO for debugging port with SDO tracing.
Following sections is my current PCB design:
-Schematic:

-TOP:
The dash line is the 3V3 cutout for separating VDD pins and +3V3 plane

-BOTTOM:
The dash line is the GND cutout for separating VSS pins and GND plane

-Analog part:

-Soldering Tip construction:

I hope the information I provided is enough to generate some feedback.
And also let me know, whether my understanding of design rules are correct.
Thanks a lot in advance.
Best regards.


texts: How does the stored charge gets decayed when going from forward bias to zero bias?

texts:
In a pn junction diode when forward biased, excess electrons and holes get stored in p and n regions respectively.
If we short the diode by connecting p,n terminals with a wire,

how do these stored charges decay?
do they discharge through depletion region, or through the external wire?
is it identical to a capacitor discharging when shorted?


texts: How to Calculate Complex Low Pass Passive RLC Filters?

texts:
I have designed a FPGA based DDS and now I want to add a low pass filter to its output. Previously I was working on a project based on AD9850 DDS(0-50MHz) and I had a commercial module for it that had a low pass RLC filter which worked excellent ( schematic below). Now I want to use the same design for my own frequency (fc= 70,100 ,120 MHz with different setups) but I can not analyze its values.

I think R1 and R2 serve as parts of two back-to-back RLC+LCR filters (something like  designs in rows 3,5 here ) but I don't know what those small capacitors  C5-C7 are doing there? .

I also don't know why L1 inductance differs from L2,L3 (From answer of Andy Aka in this thread I just can guess it is related to the impedance between steps but can't realize how to calculate them? )

I am looking for a formula or method for calculating these values  ( R1,2 C1-C7, L1-L3) for other frequencies ( for example for fc=70, 90, 100, 110 ,.. MHz).

For example assume we have fc=100MHz. How do you select part values in this design?


texts: U-blox 6 GPS module why does it still display points every second when set to 5 minutes?

texts:
I'm trying to set up a U-blox 6 GPS module with an Arduino.

In order to save power I have tried to reconfigure it using the U center to search for a fix only once every 5 minutes.  I have read the instructions however probably I don't understand them correctly as the GPS still seems to give a reading for latitude and longitude once every second.  I would like to know why this is and what I am doing wrong if someone could tell me.

The settings I used are:

Update Period: 300
Search Period: 150
Grid Offset: 0
Acquisition Timeout: 60
On Time:2

While the GPS itself is actually stationary I get results that are changing slightly e.g. as follows from 10:41:24:

$GPGLL,4119.01373,S,17445.96088,E,104124.00,A,A*71 10:41:25
$GPGLL,4119.01371,S,17445.96091,E,104125.00,A,A*7A 10:41:26
$GPGLL,4119.01373,S,17445.96100,E,104126.00,A,A*72 10:41:27
$GPGLL,4119.01371,S,17445.96102,E,104127.00,A,A*73 10:41:28
$GPGLL,4119.01380,S,17445.96110,E,104128.00,A,A*71 10:41:29
$GPGLL,4119.01380,S,17445.96112,E,104129.00,A,A*72 10:41:30
$GPGLL,4119.01380,S,17445.96112,E,104130.00,A,A*7A 10:41:31
$GPGLL,4119.01392,S,17445.96120,E,104131.00,A,A*79 10:41:32


texts:
This is a quote from ATmega32 datasheet:

By default, the successive approximation circuitry requires an input clock frequency between
50kHz and 200kHz to get maximum resolution. If a lower resolution than 10 bits is needed, the
input clock frequency to the ADC can be higher than 200kHz to get a higher sample rate.

I'm planning to use 8 bits of ADC. The question is: how much higher than 200kHz can I go? I couldn't find any information about this in the datasheet. Is it possible to use a prescaler of 64 or 32 and therefore run ADC at 250kHz or 500kHz respectively without conversion errors when the uC is running at 16MHz? And what are the possible consequences of running ADC out of spec?


texts:
Shown below is the question which is doing my head in.

I'm on part (ii) and I'm struggling. It's only 2 marks so it must be a simple answer but I cant solve what \$V_{ceq}\$ is. Below the question is what I've done. I don't know what \$R(L)\$ is so I cant get the voltage across it. I've been given \$V(A)\$ so I must have to use an equation with that. Any ideas?

Thanks


texts: 5v usb cable to power a 2AA Kitchen Scale

texts:
This is my first question and I'm a total beginner at this, so, please be kind :D

I have a kitchen scale that eats up 2AA batteries every 2-3 days, so I thought to power it via a USB wall charger (for mobile phone) and a phone usb cable soldering the red and black cables to the scale.

Since the scale takes 2AA batteries I suppose it expects 3 volt, but correct me if I'm wrong, the wall charger + usb cable will give 5.

Could this work just like this?


texts: How does adding two Resistors in Series contribute to the sum of its resistances

texts:
I would like to know why by adding two resistors in series we would get a sum of it's resistances.I know by Ohm's Law that since $$R=\frac {V}{I}$$ it's certain that you would attain the equation $$R_t=R_1+R_2$$

But I would like to have a practical definition on how resistances in series produce sum of it's resistances.

For example in the image below the point that confuses me is that how does the first resistor's resistance influences the second resistor's resistance. Because if we would try to find the current through the second resistor what I expect is that it (current) of the second resistor should be found by dividing only the resistance of the second resistor with the voltage through the circuit but unfortunately it is $$I_2=\frac{V}{R_1+R_2}$$

Could anyone help me understand why my expectation is wrong?


texts: Brushless AC generator types and their winding

texts: It is possible to make odd number of poles in the three phase exciter winding of brushless AC generator?


texts: How to calculate the time needed for the UVC to be turned on and disinfect a specific space/location?

texts: I have 3x60W UVC tube with a 254 nm wavelength. I want to know until up to what meter the range will cover and disinfect the area and how to calculate the time needed for these 3 tubes to be turned on and totally disinfect the entire whole area.


texts: Are smartphone PCB designs at the bleeding edge?

texts:
I am working on a board design that is near the limits of the PCB fabricator's capability. It uses 4mil stacked microvias, via in pad, blind and buried vias, 3 mil trace/space, buried capacitance (1mil dielectric), 12 layers, 1mm thickness, controlled impedance, etc. I was wondering if this is standard technology for modern smartphones (iPhone, HTC, Motorola, etc), or are they somehow getting by with looser design rules.

I am just wondering if the industry is making these types of boards by the millions. The reason I'm asking is our customer does not like to use technology on the bleeding edge due to reliability concerns.


texts:
i have this RAM below, i would like to be able to configured it during instantiation
I want to configure the sensitivity list to process(clk) or process(addr)
Is there a way to do this?
My thoughts were to define a generic variable in the sensitivity list then generic map it during instantiation
Thank you
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity RamMemory is

port (
        clk : in std_logic;
        re : in std_logic:='1';
        we: in std_logic:='0';
        addr : in std_logic_vector(3 downto 0);
        di : in std_logic_vector(19 downto 0);
        do : out std_logic_vector(19 downto 0)
    );

end RamMemory;

architecture syn of RamMemory is

    type ram_type is array (15 downto 0) of std_logic_vector (19 downto 0);
    signal RAM : ram_type:= (X"08602", X"08601", "11100000000000000000",
    X"04000", X"08601", X"0233A", X"00300", X"08602", X"02310", X"0203B", X"08300", X"04002", X"08201",
    "11100000000000000010", "11100000000000000001", "11100000000000000000");

begin
    process(addr) begin
        if(we='0' AND re='1') then
            do <= RAM(conv_integer(addr));
            elsif(we='1' and re='0') then
                RAM(conv_integer(addr)) <= di;
        end if;
    end process;
end syn;
```


texts:
i use arduino with a photocell module to count the number of blinks of LED, arduino code :

attachInterrupt(cds, onPulse, FALLING);

sch of CdS module:

the problem is, for each blink of a LED, the counts is double or sometimes triple, first I suspect is the sensitivity of the CdS, I adjust the trim pot, but it doesn't resolve the problem. I also tried to use a torch, when I light up the torch the count is one, but when I tried to remove the torch away from CdS, the count increase to two. So I suspect is it the whole CdS module but not solely the problem of CdS sensitivity? I tried two new modules, both have same problem. Please advise.


texts: Nodal analysis: how can I represent the current i2 in terms of voltage over R2?

texts:
I am doing the nodal analysis of this circuit:

I have successfully wrote the current equations for node A, using nodal analysis, that I found it to be:

i3 = i5 + i7 or

(Vc-Va)/R3 = (Va-Vb)/R5 + i7

where i7 is the current source value of 1A.

That will give me

-9Va + 3Vb + 5Vc = 400

So far, so good...

Now analyzing node C I have a doubt.

The currents for node C would be:

i1 = i3 + i6

where

i1 = (V1-Vc)/R1 = (12-Vc)/20

i3 = (Vc-Va)/R3 = (Vc-Va)/80

but what about i6?

I know that i2 = i6 + i7 resulting on i6 = i2-i7 or substituting the value for i7,

i6 = i2 - 1

The problem here is, how can I declare i2 in terms of voltages and resistors? If the current source was not there I would say i2 = Vc/R2 but with the current source there I don't now.

Any help is welcome. Thanks.


texts:
Great title, I know.
I have a driver board connected to a really small stepper motor. When I run it in step / dir mode it works.
But as soon as I connect either SCLK or MOSI the motor turns at double the rate, TMCs CS is low it turns in full speed and when CS is high the motor acts completely up, turns into the end stops, changes direction half way...
The serial output is always 1, I guess the chip simply does not send any data. With a pull-up I get all ones and when removing it I get either 0 or random nonsense.
I can't for the life of me figure out anything. It simply behaves completely weird and I have no idea whatsoever, why that thing simply does not work with the most basic "hello world" of motion controllers.
Thing I don't get. Why does the motor turn faster when connecting something? Why does the chip don't output any data at all? Why does it turn back and forth wildly?
My connections are all correct, I don't have open signal lines, my connections are not flaky and the power supply is perfectly fine.
I run the show on a Teensy 2.0++ with Arduino, since I want to understand the driver before working with a real language. The Library is TMC2130Stepper
TMC2130 Datasheet
SilentStepStick Datasheet
There is no schematic. It's simply the step interface, power supply and the ISP interface...
Arduino Code
#include <TMC2130Stepper.h>

#define PIN_LED PIN_D6
#define PIN_STP PIN_F0
#define PIN_DIR PIN_F1
#define PIN_EN  PIN_B5
#define PIN_CS  PIN_B4

TMC2130Stepper stepper = TMC2130Stepper(PIN_EN, PIN_DIR, PIN_STP, PIN_CS);

bool dir = true;

void setup() {
  pinMode(PIN_STP, OUTPUT);
  pinMode(PIN_DIR, OUTPUT);
  pinMode(PIN_EN, OUTPUT);
  pinMode(PIN_CS, OUTPUT);
  pinMode(MISO, INPUT);

  Serial.begin(115200);
  while(!Serial);

  stepper.begin();
  stepper.SilentStepStick2130(20);
  stepper.stealthChop(1);

  digitalWrite(PIN_LED, HIGH);
}

void loop() {
  digitalWrite(PIN_STP, HIGH);
  delayMicroseconds(200);
  digitalWrite(PIN_STP, LOW);
  delayMicroseconds(200);

  uint32_t ms = millis();
  static uint32_t last_time = 0;

  if ((ms - last_time) > 2000) {
    if (dir) {
      Serial.println("Dir -> 0");
      //stepper.shaft_dir(0);
      digitalWrite(PIN_DIR, dir);
    } else {
      Serial.println("Dir -> 1");
      //stepper.shaft_dir(1);
      digitalWrite(PIN_DIR, dir);
    }

    dir = !dir;

    Serial.println(stepper.GCONF(), BIN);
    last_time = ms;
  }
}

I'm not the biggest fan of imgur, but it's not too important, just some additional view.
Without SPI, works great
With SPI, obviously does not work


texts: How to have both PCB components and external components in the same KiCad project?

texts:
I am using Kicad (5.1.4) and would like that the schematic contains all the component wiring  required for a PCB board as well as the wiring for components external to the PCB board (such as switches, displays etc.).

Previously I have set up an additional project for the external wiring. However, trying to manage both projects (e.g. ensuring consistency) is error prone.

I have tried not associating footprints with the external components. This seems to work in that Pcbnew does not attempt to layout the external components - meeting my goal - but still comes up with errors about the missing footprints. Secondly, it does not seem to be a “transparent” method in that it is not immediately obvious from the schematic which are the external components.

Is there a better way, for instance using hierarchical schematics?


texts: I want to make completely on my own a keyboard with maximum 6 keys with a USB connection.  Can someone tell me what microcontroller should I buy and what specification should I look for?


texts: Why are there two sets of ENBW correction factors?

texts:
For calculating the equivalent noise bandwidth of a non-brickwall filter, I can find two different sets of numbers, both of which claim they are similar things:

Order   EqNBW
1   1.5708
2   1.1107
3   1.0472
4   1.0262
5   1.0166
6   1.0115
7   1.0084
8   1.0065
9   1.0051
10  1.0041

RF Cafe Filter Equivalent Noise Bandwidth "Butterworth (fco = 3 dB)")
ADC Noise Figure by Walt Kester

Figure 2: Relationship Between Noise Bandwidth and 3-dB Bandwidth for a Butterworth Filter
"will pass the same noise power as the non-ideal filter"

Linear Circuit Design Handbook by Hank Zumbahlen

Figure 6-147 : "Relationship between noise bandwidth and 3 dB bandwidth for Butterworth filter"

The Concepts of Noise Bandwidth and Cumulative Noise

1 1.57
2 1.22
3 1.16
4 1.13
5 1.12

Equivalent Noise Bandwidth by Radio Geek

"have same integrated noise power"

Equivalent Noise Bandwidth by Tim J. Sobering

"a noise power equivalent to the original transfer function"

PGA309 Noise Filtering
Operational Amplifier Noise by Art Kay

"brick wall correction filter"

Which is correct?

Or are they both correct; just used in different calculations?

Update

After figuring this out, I made a chart of the different factors and the types of filters they work for: ENBW Filter correction factors vs order


texts: How to transfer blocks of data into FPGA to aid in testing?

texts:
How can one transfer data from PC to FPGA and read back result for test purpose where the data must not get corrupted i.e  resend if data integrity was lost or use some other error recovery mechanism. The method must be simple to implement so it does not become a whole project on its own.
This scenario can occur where several kB or few MB of data has to be transferred into a digital design to aid in testing. An example is testing of image processing design.
It is true that using the UART is a very simple solution to such a problem. However, UART does not have elaborate error detection and correction mechanism except the parity bit.
One method could to be create a simple mechanism on top of UART where data is transferred in blocks along with CRC bytes. The receiver end can then send an ACK or NAK and the sender will try again if NAK received. Since the data does not need to be transferred in real-time, this could be a satisfactory solution to this problem. Is there something else that I should look into so as not to reinvent the wheel?
My focus is Intel FPGAs for this question but it would be great if this could work with Microsemi FPGAs as well.


texts:
I’m currently a computer engineering student from lorma colleges and we’re currently doing our design project.

Our project is called an advance helmet. A helmet that is capable on creating a communication between the helmet and the motorcycle ignition switch.

My main problem is:

I’m using 3 different sensors which fingerprint scanner uses 3.3V, ultrasonic sensor uses 5V and an alcohol sensor which uses 3.3 V. I also included a Bluetooth module (HC-05) which uses 5 V but I only have three Li-ion batteries which has 3.7 V and 2200 mAh.

Can I power up all of the components using three 3.7 V power source even if their is a difference on the voltages in each components? What kind of component should I use to regulate the voltages or boost up the voltages in every component to meet the required voltage?

I hope someone helps me to solve my problem.


texts: Is it true that FPGAs and DSPs are widely used for modulation and demodulation of signals?

texts:
I have to write a thesis about digital communications, and I don't want to write something stupid in it. I also wrote that "most of the digital modulations and signal processing nowadays are done via software". So, are these sentences true?
Thanks a lot


texts:
Although I've seen numerous recommendations for the use of FBs on the power supply rails of noise-sensitive analog circuitry, the opinions regarding their use with high-speed digital circuitry are conflicting. For instance, this link from TI, discourages their use stating that they block the power supply during peak current draw. They then discredit the use of bypass capacitors as a solution to this problem:

  [T]he impedance of even the best capacitors is too high above about
  200 MHz to supply enough peak power for the processor.

However, if you can't use ferrite beads in this context and bypass capacitors are similarly inadequate for filtering noise at the clocking frequency, how do you prevent the IC's noise from reentering the power supply? I imagine that linear regulators would also be insufficient here since they tend to have poor PSRR above a few hundred kHz (and the good ones I've seen don't do much above a few MHz). Although I know that PSRR deals with preventing input voltage noise from getting to the output, I don't know that it also deals with the reverse direction? Does it? Is there another metric for this?

Can I use ferrite beads and bypass caps for high-speed digital ICs and, if not, what would I use? If they're not suitable for high-speed digital logic, can I use them without issue for lower-speed digital ICs, say below 100MHz or so?


texts: ic relay.. is there any delay for the responz of <İC insıde the circuit

texts: Regarding SPDT ic relay TS5A3157. Do we have a delay responz inside the İc/ do we have a click sound. Because im startıng for a new project that can switch wireless, bluetooth or ir. What i need on my project is an  actual or quick responz with no delay, if we have a delay may i know. How many milli seconds thanks in advance.


texts: Use transistors to amplify a very small voltage

texts: I'm new to electronics and I have a problem. I want to use a LED to detect light but the voltage it provides is very small (30 mV) and I don't think it can open a transistor. How can I amplify this voltage? (I don't want to use op amp) And, I have only NPN transistors. Can you help me?


texts: Can I use any capacitor for a 2 phase AC motor?

texts:
So recently I got my hands on an old pump motor, unfortunately the connection diagram is missing. I have already determined this is a 2 phase motor, and that in order to make it work I need a motor-run capacitor.

However I was wondering can I use any motor-run capacitor or do I need one with a specific capacitance to get the 90 degrees of phase difference? If it would be important I live in a area with 230V AC out of the wall.

Thank you, for any help/tips

ps: i have included photos of the stator;


texts:
I have ON660 Philips transistors, and can not find any datasheet. The label on transistor is:
PH
331XN
m9249
The package is SOT-82.
Maybe it is the equivalent of BD334? But it would be very nice to have a Philips datasheet.


texts: Conceptual question on interpreting magnitude graphs

texts:
I am designing a band pass filter and I am having trouble understanding how to interpret my simulation results.

What I think this is telling me is that when I send a frequency through one of my filters, the magnitude of the output signal is proportional to the dB gain. So on my low pass filter, I get out slightly less than the same signal I put in, and it decreases down to its cutoff at about 200 Hz. Assuming what I stated is correct, then the band pass filters are activating in the right regions, but hardly activating at all.

So to fix this, would I use an amplifier after the band pass filter to bring the signal back up to match the low and high filters? Secondly, would amplifying the signal before I send it through the filter shift the output up, relative to what it is now? I hope I'm making sense.

Thanks for any help!


texts: Why don't commercial metal detectors clearly distinguish between iron and other metals?

texts:
I've read about how metal detectors work, and what I learnt here on EE.SE and other articles, the main principle is that ferrous metal will increase the inductance of the search coil, while non ferrous metal will decrease it.

Changing the inductance changes the frequency of the oscillation, which you can tell by comparing it to some other frequency such as some internal oscillator.

However I do have a metal detector, and it does not indicate the difference between iron and other metals at all. I read that you can learn to distinguish object by sound. But the sound produced will no longer show in which direction has the search coil shifted, this information is lost since phase shift is only a thing if you are comparing two frequencies, not hearing sound that their difference produces.

Is there a technical challenge to filtering out ferrous/non ferrous metal when detecting metals? I was looking into making a simple detector with arduino and if there's such challenge I'd like to be aware of it.


texts: How to read LM35 temperature values on nodemcu when sent by arduino by I2C communication

texts:
ARDUINO SEND CODE

#include <Wire.h>
const int lm35_pin=A1;
int temp_adc_val;
  float temp_val;

void setup() {
  Wire.begin(8);                // join i2c bus with address #8
  Wire.onRequest(requestEvent); // register request event
  Serial.begin(9600);           // start serial for debug
}

void loop() {
  temp_adc_val = analogRead(lm35_pin);  /* Temperature */
  temp_val = (temp_adc_val * 4.88); /* adc value to equivalent voltage */
  temp_val = (temp_val/10); /* LM35  */
  Serial.print("Temperature = ");
  Serial.print(temp_val);
  Serial.print(" Degree Celsius\n");
  delay(1000);
}

// function that executes whenever data is requested from master
void requestEvent() {
  byte* RPMFloatPtr;
  RPMFloatPtr = (byte*) &temp_val;
  Wire.write(RPMFloatPtr,5);
}

NODEMCU RECEIVE CODE

#include <Wire.h>
float data;
void setup() {
  Serial.begin(9600); /* begin serial for debug */
  Wire.begin(D1, D2); /* join i2c bus with SDA=D1 and SCL=D2 of NodeMCU */
}

void loop() {
  tempdata();
}

void tempdata()
{
Wire.requestFrom(8, 5); /* request & read data of size 13 from slave */
while(Wire.available())    // slave may send less than requested
{
    data = Wire.read(); // receive a byte as character
}
Serial.print(data);
Serial.println();
delay(1000);
}

arduino

I have done interfacing of NodeMCU and Arduino Uno by I2C communication.
The Arduino is reading values from a temperature sensor and correctly displaying it on serial monitor.
Now I want the same values to be sent to the NodeMCU by I2C communication and want to read them on the serial monitor of the NodeMCU. However, i can't see the same temperature values. Instead, the values are some random analog values between 0 and 255.


texts: how to simulate a Laplace function of a PID controller in the time domain with LTspice

texts:
I tried to simulate a Laplace function of a PID controller with LTspice in the time domain, but an error message appears "The laplacian is singular at DC".

cs1 is the controller, so I just have a unit jump (Ugen) + controller (cs1)
with KP=0.9995594504821;  KI=0.0000772197554;  KD=0.00540381443834925;  Tp=KD/100


texts:
In this image When calculating the fan out of the TTL circuit
the current in the TTL drive output is 16mA and is divided into the emitters of the load each emitter has 1.6mA because the fan out is 10.
My question is why he makes the current in the base of the load is also equal to 1.6mA, should it be equal to 16uA because we divided 1.6mA of the  load emitter by beta if we assume that beta is 100.


texts: Is it possible to regulate the amount of counter torque in a generator?

texts:
I have a question for a machine I am working on,
The machine is used to pre-tension steel wire ropes for maritime uses, the wire rope sits on a drum with a 2m diameter. The tension has to be adjustable to anywhere between 50 to 200kN. The wire rope will be spooled by a ship winch. The rotational speed of the drum will have to be about 0,3 rad/s but if it's possible to do it faster while still maintaining the tension that would also be an option.
One of my ideas for this was to use a generator coupled to the drum so that the energy taken from the drum's rotation could be converted to power, while simultaneously producing a counter-torque to the drum's rotation. The electric energy I could then maybe find a use for, or just convert it to heat in a resistor bank.
Now my knowledge about electrical systems is very limited and I'm curious if this is even possible? I think this concept relates a lot to regenerative braking systems but I'm uncertain if the counter-torque will be adjustable enough for my application.
Thanks in advance.


texts: Determining closed loop transfer function from an open loop transfer function

texts:
I have an open loop transfer function given by
\begin{equation}  \frac{(s+3)}{s(s+1)(s+5)} \end{equation}

I'm trying to convert it to a closed loop system with a gain of 0.987 and damping ratio of 0.7071 and find the closed loop transfer function. I know open loop transfer functions are given by KG(s)H(s) and closed loop transfer functions are given by KG(s)/1+KG(s)H(s) but I'm not sure how to relate this to the equation I have here.

Can anyone help me find the closed loop transfer function?


texts: How to design/build the electronic part of a hybrid (liquid + electronic) multi tube manometer

texts:
I am in the early stages of designing/building a multi tube manometer for a DIY wind tunnel.

For those not familiar with what a manometer is, it's a pressure measuring device, and looks something similar to this:

I have the hardware part designed, but I want to automate the data collection part. Instead of periodically manually taking readings of heights of the various columns (tubes), I want to be able to able to do that electronically.

In the olden days, the (pressure) data was obtained by taking photographs of the column heights, and then later, plotting that to an aerfoil shape - I want to eliminate that step (since it's too error prone) - and directly fetch the data from the device, using electronics.

I am thinking of using an Arduino board as the microcontroller, but can't yet thing of how to harvest the liquid height information from the device.

What's the best way of electronically capturing the height data from said multi tube manometer?

[[ UPDATE ]]

The fluid inside the tube will be distilled water, and I cannot insert any sensors in the tubes as they may affect the airflow characteristics of the airfoil I'm testing


texts: Inductance Calculation for a Toroid Core?

texts:
I have a Toroid Core listed here: LINK , i have T130-52 .
I have all the values of the core from this sheet. Now i need to build an inductor out of this toroid. How do i determine which wire to wound, and how many turns would give me what inductance?


texts: How much physical damage does dropping electronic devices cause?

texts:
Phones iPads and other modern portable electronics get dropped. Before the screen is broken and damage becomes physically visible beyond a warp in the entire device structure, How much damage is done to the internal circuitry?
What percentage of software errors could be responsible for non-localized damage?


texts: Phase Difference in LTSpice: Op-Amps vs. Voltage Sources

texts:
Below I have two different circuits:

The left circuit takes a sine-wave and buffers it on one path and then inverts it on the second path using universal amps. The 180 deg out-of-phase sine waves bias two capacitors (nodes testA and testB). The capacitors are assigned values of C*V (where C is an oscillatory capacitance set up as Cgaps1 and Cgaps2...and V is represented by x, per LTSpice manual).

The right circuit is the same exact setup except now I'm using voltage sources directly instead of inverting/buffering with amps.

I am taking the output as the node between the capacitors.

Based on theory, I expect that the output signal is a high-frequency sine wave (same frequency as the initial 1Meg bias frequency) that is modulated by the Cgaps frequency of 1000 Hz. This modulation is apparent in the envelope of the output. I also expect that the output is in phase with the bias.
Here's my question. If I compare all of the testing points in the picture (testA with testA2...testB with testB2), they all match. However, out1 and out2 are out of phase very slightly and have a different amplitude. All shown below. Why does this occur? I imagine that it has to do with the universal amp, like the phase margin or something like that, but I hate guessing and not understanding why. Note that the op-amp rails at +/- 10 V, not shown. Thanks in advance.


texts: Parallel Ressonant Circuit transmitting an AM signal

texts:
I was trying to solve a problem of AM modulation, (Communication Systems, 5th edition, Simon Haykin: problem 3.1), but I struggled to reach a reasonable answear. The solution manual available in the internet confused me even more.
The problem statement:
A carrier wave of frequency 1MHz is modulated 50% by a sinusoidal frequency 5kHz. The resulting AM signal is transmitted through the resonant circuit (attached figure) presented, wich is tuned to the carrier frequency and has a Q-factor of 175. Determine the modulated signal after the transmission through this circuit. What is the percentage modulation of this modulated signal?

My development:
The current signal of the font, for AM modulation, is:
$$
s(t) = A_c[1+k_am(t)]cos(2\pi f_c t)
$$
Where:
$$
m(t) = sin(2\pi f_s t)
$$
Substituing m(t) in the first equation:
$$
s(t) = A_c[cos(2\pi f_c t) + k_asin(2\pi f_s t )cos(2\pi f_c t)]
$$
From cossine and sine properties:
$$
s(t) = A_c\{cos(2\pi f_c t) + \frac{k_a}{2}[sin(2\pi(f_c + f_S)t)+sin(2 \pi (f_c - f_s)t)] \}
$$
The parallel ressonant circuit is tuned in the carrier frequency, so the circuit only depends on the resistor (L and C acts as an open loop):
$$
V_{out} = RI
$$
But  \$I=s(t)\$, so:
$$
V_{out} = Rs(t)
$$
My conclusion was that, as \$s(t)\$ is only multiplied by a constant \$R\$, there is no change in the factor \$k_a\$. From the statement: "modulated 50%", so \$k_a = 0.5\$. This conclusion is certainly wrong, but I couldn't progress any further.
One last thought was: utilizing the Q_factor and ressonant frequency provided, one can find that the bandwith of the circuit response is, approximately, 5.7 kHz, and that imply that the sines components of s(t) are filtred, as their frequency are outside of the circuit's response bandwith (\$f_s > \frac{BW}{2}\$ ), and only the carrier remains, but that also lacks of logical sense for me.
How can I progress? There is something wrong on my development?
Development from the solution manual found:

I couldn't figure out how the signal m(t) is in the 3dB zone. Why considerate the ressonant circuit as a filter in the first place? Is this solution correct?


texts: Repeated sheet symbol with bus inputs and outputs

texts:
Is there anyway to do this kind of thing in Circuit Studio/Altium Designer?

This is just an example of the problem I'm having.

Specifically I am trying to use the Repeat command on a Sheet symbol that contains inputs and outputs that are already in bus format.

When I compile I get this error:

[Error] Sheet1.SchDoc   Compiler    Net OUT[1..2] contains multiple Output Sheet Entrys (Sheet Entry Device2-REPEAT(OUT1..2,Sheet Entry Device3-REPEAT(OUT1..2,Sheet Entry Device4-REPEAT(OUT1..2)

I understand that means that the outputs of all the instantiated devices are getting joined together, which is not what I want.

I would actually rather have all the inputs and outputs enumerated together like: IN[1..8] and OUT[1..8], but I couldn't get that to work either.


texts: What are these gray boxy components with R50 written on them? (Photo attached)

texts:
My motherboard came gradually to a complete death and I'm trying to figure out if one can repair it by fixing some capacitors like in the old days.

I went through all the arrays of caps as well as the single ones with my multimeter and all seem fine at the first sight (loaded up with the 'beeper' mode and then showing some voltage, gradually decreasing).

But there are these boxy things with two thoroughly soldered pins, that I can't figure out:

Q: What are these?

They are of perfect cubic shape with side of about 1 cm (about 2/5 of an inch). Written on them is R50, but they show no resistance. There are similar components at various places on the board, labelled 1R2 or 3R3, but none of them have any measurable resistance.

I'll appreciate any help! In case I should supply some more info, I'm ready here with my lousy multimeter...


texts: Trouble initiating I2C communication between Arduino and 3.3V Slave

texts:
I'm trying to get into capacitive sensing and therefore need a stable communication between an Arduino and a TI FDC2114, which is already soldered on an EVM. Both support I2C, and because of the different operating voltage of 5V for the Arduino and 3.3V for the FDC, I'm using an PCA9512A bidirectional level shifter and 10k pullups to 5V (Arduino Mega internal) as well as to 3.3V.

When scanning the address of the FDC, I sometimes get a positive response (ACK on last clock after the requested 7bit address) but mostly a NACK. Even if I receive a ACK, some seconds later the FDC can't pull down the SDA to 0V anymore and I get NACK again. In case of NACK, it may help to unplug SDA and SCL while under voltage and plug them back in, but it doesn't work every time. I've already changed all wires, so it shouldn't be an mechanical problem.
I also observed that the peak Voltage is 3.4V on SCL and more than 3.6V on SDA, but I don't know if this could cause any problems and also where the voltage difference results from.

When using the included MCU of the EVM, there are no problems at all. What am I missing, why doesn't it work reliable?


texts: Use GDTs or MOVs under low frequency over voltage protection

texts:
For power current transformer, the secondary is not allowed to open when the primary is conducting current of several KAs. So I want to design a over voltage protection circuit for this situation, when there is over voltage (several KVs), then short out the secondary of the CT.

I want to use GDT or MOV for this purpose, but all they labeled as "transient". Is it suitable to use them under power frequency?


texts: how would a non inverting op amp tone boost work?

texts:
I'm modifying an audio circuit to add more tone controls, and found a method I want to try.

It involves separating the wanted frequencies into a boost circuit and the less wanted frequencies around the boost circuit.

Instead of filtering them to ground, I've figured out how to do this using a inverting op amp to boost, but the circuit I'm trying to modify uses a non inverting op amp setup and I couldn't find out how to do this.

My idea was to do it using a filter like R4 and C1 in the picture, but I am concerned that this path might create a second feedback loop to the non-inverting input and I dont know what that would cause; So I thought I might ask here.

Is this the way to achieve what I'm looking for?
Am I completely wrong?

The schematic is just for proof of concept, in reality I will be using three parallel filters to separately control low, mid, and high frequencies.

simulate this circuit – Schematic created using CircuitLab


texts: Did TI make a mistake in this video when they tied two mosfet gates together?

texts:
Automotive Front End Protection

The two mosfets have their gates tied together, but that's all they are tied too. Will something like that work or are they missing a connection ?


texts: Program not running on an STM32 microprocessor

texts:
I have a problem with our microprocessor.
I had written several programs and I tested them on a STM32vlDiscovery  (has stm32f100rbt6 microprocessor.) There were no errors and it worked correctly.
Now I programmed the same program on a new STM32F100RBT6 and unfortunately, the program does not work.
The program was completely downloaded on the STM32 and verified but does not work.
In the debug environment, I saw that all registers were zero, as the microprocessor stopped in the first line of the program.
#include <stm32f10x.h>
#include <math.h>
//------------------
volatile short sinArray[20];
volatile int i=0;

//1000 Hz Sine Wave
void TIM2_IRQHandler(void)
{
    TIM2->SR &=~TIM_SR_UIF;
    DAC->DHR8R1=sinArray[i];
    i++;
    if(i==20)i=0;
}

int main()
{
    RCC->APB1ENR |=RCC_APB1ENR_DACEN;
    DAC->CR |=DAC_CR_EN1;
    RCC->APB1ENR |=RCC_APB1ENR_TIM2EN;
    TIM2->CR1 |=TIM_CR1_ARPE;
    TIM2->ARR=199;
    TIM2->PSC=5;
    TIM2->DIER |=TIM_DIER_UIE;
    NVIC_EnableIRQ(TIM2_IRQn);
    TIM2->CR1 |=TIM_CR1_CEN;

    //TIM2->SR &=~TIM_SR_UIF;

    for ( i=0; i<10; i++)
    {
        sinArray[i]=(128*sin(i*3.14/10)+127);
    }
    i=0;

    while(1)
    {
    }
}


texts:
I'm trying to find the expression that describes the auto-correlation of two heaviside functions u(t). I was told that the result must be 1/2, which makes total sense, as the power spectral density of the heaviside function must be a Dirac's delta centered in 0 with 1/2 area (which can be seen using the Fourier Transform).

This is how I thought it:

$$
r_{xx}(\tau) = <u(t+\tau) \cdot u(t)> = \lim_{T\to\infty} \frac{1}{2T} \int\limits_{-T}^{T} u(t+\tau) \cdot u(t) dt = \lim_{T\to\infty} \frac{1}{2T} \left( \int\limits_{0}^{T}dt + \int\limits_{\tau}^{T}dt \right) = \lim_{T\to\infty} \frac{1}{2T}(T+T-\tau) = \lim_{T\to\infty} \frac{1}{2T} (2T - \tau) = 1 - \lim_{T\to\infty} \frac{\tau}{2T} = 1
$$

What am I missing?

Thanks in advanced.


texts: How to identify and check if transformer is working fine?

texts:
I have 3 in 1 SMD rework station and in that Machine veriable DC power supply is not working and I am unable to check if transformer is working correctly or not and if I have to replace how to find similar transformer because I don't know the name. It has two wire on one side and eight wire on another side. Here are image of transformer if some one will help me to identify and let me know to check it that you will be great help

Edit :-
I checked the voltage(AC) and measured as in the below image and It seems that white wire is not giving 12v power and if I short white and purple the it seems that power supply is working but all the voltage at out are different from what it suppose to be.


texts: Arduino ultrasonic sensors in closed spaces

texts:
I am wondering whether or not it is possible to use an Arduino ultrasonic sensor in a closed box (30 cm x 30 cm.)
I have been told that the walls will cause the signal to bounce all over the place and the sensor will get messed up, but I am not sure if this is accurate. Please let me know if this is possible.
Also, if ultrasonic sensors don't work, I believe the best alternative would be a laser sensor.
Unfortunately, I noticed that laser sensors require SDA and SCL pins. My ATmega64 microcontroller only has one of each of these pin types, yet I need three laser sensors. Is there any workaround for this problem?


texts: In which branch of engineering can I learn about display technologies like LCD, LED, OLED?

texts:
I am finishing high school this year and want to pursue a career where I can learn and develop display technologies like LCD, LED, OLED, and flexible displays.

Can somebody please tell me what branch of engineering I should opt for?