texts: How to manage an output to put only one "1" even when entry stay up?

texts:
I'm a beginner with VHDL and electronics, I'm trying to do something like this:

input list: i_button1 : it's the value of the entry button (1,0)

output list : o_button1_sync : it's the value of the output linked with entry (1,0)

The use case is the entry can be 1 all the time so it would send in i_button1 : 1,1,1,1,1 but the output need to send only a single time a 1, so o_button1_sync would send 1,0,0,0,0,0 until the entry go back to 0 and 1 again

entry 1,1,1 -> output 1,0,0 // entry 1,1,0,1,0,1,1 -> output 1,0,0,1,0,1,0

I tried to use a Mealy machine with two state Pressed and noPressure and I think the problem is in the 2nd process

library ieee;
use ieee.std_logic_1164.ALL;
use ieee.std_logic_unsigned.all;

entity Button1_sync is
   port (   i_button1        : in    std_logic;
            i_clk        : in    std_logic;
            i_clk_game        : in    std_logic;
            i_rst      : in    std_logic;
            o_button1_sync  : out   std_logic);
end Button1_sync;

architecture BEHAVIORAL of Button1_sync is
    type stateType is (noPressure, Pressed);
    signal state, nextState : stateType;

begin
    -- 1st process: memorise the state
   process(i_clk_game,i_rst)
      begin
          if (i_rst = '1') then
              state <= noPressure;
          elsif rising_edge(i_clk_game) then
              state <= nextState;
          end if;
   end process;
   -- ---------------------------------------------------
   -- 2nd process: for the futur state
    process (state, i_button1)
    begin
        case state is
            when noPressure =>
                if i_button1 = '1' then
                    nextState <= Pressed;
                else
                    nextState <= noPressure;
                end if;
            when Pressed =>
                if i_button1 = '1' then
                    nextState <= noPressure;
                else
                    nextState <= Pressed;
                end if;
            when others =>
                nextState <= noPressure;
        end case;
    end process;
    -- ----------------------------------------------------
    -- 3rd process: combinatory for the output
    process(state) --, nextState, i_button1
    begin
        --s <= '1' when (state = A and t = '1');
        case state is
            when Pressed =>
                if i_button1 = '1' then
                     o_button1_sync <= '0';
                else
                    o_button1_sync <= '1';
                end if;
            when noPressure=>
                if i_button1 = '1' then
                     o_button1_sync <= '1';
                else
                    o_button1_sync <= '0';
                end if;
            when others => o_button1_sync <= '0';
        end case;
    end process;
 end Behavioral;

When I simulate I have this result :

but it should send instantly on the next i_clk_game rising edge the value "1" in output for one clock period.


texts: Error in turning ON the LED using UART in PIC32

texts:
I have a PIC32 starter Kit & IO Expansion Board. PIC32 Starter Kit has 3 LEDs on baord LED1 LED2 LED3 . I have made a uart program such that if someone presses 1 on the keyboard, this 1 will be send serially to PIC32 and LED1 will be ON and if someone presses 4, LED1 will be OFF. In the same way, 2 & 5 will turn ON & OFF LED2 & 3 & 6 for LED3. Program is running fine and LED1 & LED3 are responding properly but LED2 is always turn ON whether I press the 2 or not. I dont know why is this happening with this LED2. Is there anything which I am missing. I know LEDs are working but I dont know what is happening in this case. Does anyone have any idea about this thing. Please help.

CODE:

#include <plib.h>
#include <string.h>

#pragma config FNOSC = PRIPLL, POSCMOD = HS, FPLLMUL = MUL_18, FPLLIDIV = DIV_2, FPBDIV = DIV_2, FPLLODIV = DIV_1
#pragma config FWDTEN = OFF

#define SYSTEM_FREQUENCY        72000000L
#define BAUDRATE                57600

int main()
{
    int pbFreq;
    TRISDbits.TRISD0 = 0; //output
    TRISDbits.TRISD1 = 0; //output
    TRISDbits.TRISD2 = 0; //output

    char RxBuffer[5];

    pbFreq=SYSTEMConfigPerformance(SYSTEM_FREQUENCY);
    OpenUART2( UART_EN | UART_NO_PAR_8BIT | UART_1STOPBIT, UART_RX_ENABLE | UART_TX_ENABLE, (pbFreq/16/BAUDRATE)-1);

while(1)
    {

        if((U2STAbits.URXDA)!=0)
        {
            getsUART2(5,RxBuffer , 123);

            U2STAbits.URXDA = 0;
            U2STAbits.OERR = 0;

        }

        if(RxBuffer[0] == '1')
        {
            PORTDbits.RD0 = 1;
            putsUART2(">>LED: 1 ON");

           memset(RxBuffer,0,5*sizeof(char));
    }
    else if(RxBuffer[0] == '4')
    {
        PORTDbits.RD0 = 0;
        putsUART2(">>LED: 1 OFF");

        memset(RxBuffer,0,5*sizeof(char));
    }

    if(RxBuffer[0] == '2')
    {
        PORTDbits.RD1 = 1;
        putsUART2(">>LED: 2 ON");
        memset(RxBuffer,0,5*sizeof(char));
    }
    else if(RxBuffer[0] == '5')
    {
        PORTDbits.RD0 = 0;
        putsUART2(">>LED: 2 OFF");
        memset(RxBuffer,0,5*sizeof(char));
    }

    if(RxBuffer[0] == '3')
    {
        PORTDbits.RD2 = 1;
        putsUART2(">>LED: 3 ON");
        memset(RxBuffer,0,5*sizeof(char));
    }
    else if(RxBuffer[0] == '6')
    {
        PORTDbits.RD2 = 0;
        putsUART2(">>LED: 3 OFF");
        memset(RxBuffer,0,5*sizeof(char));
    }
}
}


texts: How to analyze this circuit with resistors and capacitors?

texts:
I have to find out the value of \$V_{o}\$ and \$V_{c}\$ initially and finally of the this circuit when \$S_{1}\$ and \$S_{2}\$ switches are simultaneously closed.

Edit:  \$V_{c}\$ is across the capacitor \$C_{1}\$ and \$V_{o}\$ is across the resistor \$R_{3}\$.

My thought is:
Initially, \$V_{c}=0V\$

Using mesh analysis,
For first loop, \$-25 + I_{1} + 0 +3(I_{1} - I_{2}) - 10 = 0\$ \$or, 4I_{1} - 3I_{2} = 35\$
For second loop, \$ 10 + 3(I_{2} - I_{1}) - 4I_{2} = 0\$ \$or, -3I_{1} + 7I_{2} = -10\$
Solving these two equations,  \$I_{1} = 11.31mA\$ and \$I_{2} = 3.42mA\$
Initially, \$V_{o}=4I_{2}\$ \$or, V_{o} = 13.68V\$

By substituting open circuit equivalent for the capacitor,
steady state value for the capacitor is, \$V_{f} = 25V\$

I am confused that the value of \$ t\$ is not given. Then how i can calculate the voltage that is stored in capacitor. Also, how i can calculate the value of \$RC\$. Or I just have to assume that the capacitor is fully charged?


texts: To what extent does an ADC solve noise along an analog circuit?

texts:
Please note: Although this question involves EEG, I don't expect anyone here to be knowledgeable in this area! This is a simple electronics question!

I'm trying to understand the circuitry devised in this DIY EEG Instructable. One thing that is troublesome to me is the amount of correction done at each component/module/step (and even within certain components):

Two 60Hz notch filters one at each "end" of the circuit, to reduce noise at a particular frequency (do we really need two?!?)
High pass filter for circumventing galvanic skin response
Low pass filter for waves > 30Hz
Yet another high pass filter
Op-Amp

Now it has occurred to me that this is indeed an analog circuit (brain waves generating the initial AC voltage) feeding into 3.5mm headphone cables and then the PC sound card for digitization. To me, it makes sense to digitize the signal upfront via ADC. If I were refactoring this circuit, I might have it look something like:

Medical-grade electrodes read analog signals
Instrumentation amplifier boosts signal to a meaingful range, uses the potentiometer mentioned in Step 7 to account for the range in alpha wave amplitude
Run the signal through an ADC
Perform some final cleanup/transformation on the signal before entry into a surge protector (for safety)
Surge protector feeds signal into the laptop

Although I am interested in the community's general thoughts on signal transformation before/after the ADC, as well as on the surge protector (and I supposed 'bonus points' to anyone with actual EEG/medical system experience here), but my main concern here is with the ADC; specifically:

Where does it make the most sense to place the ADC, and would the use of an ADC reduce the need for all these signal filters/corrections listed above (and if so, how)?

Continuing with this "ADC-as-a-solution to redundant corrections"-premise, the author states in one of his last stages/steps:

  Even with all the previous filtering stages, the data will still at this point contain a good amount of 60 Hz noise...The final data will still have a small amount of noise, but that can be ignored through software once the data is loaded into the computer

...but if we digitize the signal before it gets to the computer, can't we just let software do all the correction/cleanup for us (I'm a software engineer; that prospect makes me happy)?


texts: Which power supply to use for Raspberry Pi? High voltage Low current (10V, 1A) or low voltage high current supply (5V, 2A)? why?

texts:
As far as the official specifications are concerned an rPi can be powered with supplies from 5V to 12 V. Typical current for 5V supply is 2A. Total power required for an rPi is 10W roughly.

Raspberry pi model 2B, 2GB ram

I have two power supplies (5V, 2A) and (10V, 1A)
which one to be used so that the pi dissipates less amount of heat while in operation?
Why?

If in a given scenario, one has a blackbox with a power requirement of 10W irrespective of Voltage & current (lets assume the voltage bracket of 5V to 12V and current bracket of 1A to 3A) then which power supply you would go for? and why?

Any clarification shall be appreciated.

Thanks.


texts:
We are busy designing a large system with around four PCBs slotting into a backplane. Each PCB could contain a DSP as well as a large FPGA. We would like to run 2 JTAG chains through the system, one chain for the DSPs and one for the FPGAs.

My worry is that there are a lot of high frequency comms/data  running through the backplane and that this might interfere with our two JTAG chains. The back plane will be used to transport multiple lvds data signals at around 500MHz.

I would like to be on the safe side with the JTAG chains. The question is if it is possible to run JTAG over a differential standard and if so, are there any pitfalls to watch out for.


texts:
So I'm working on my Senior Design Project currently. We are building a circuit with the ESP8266 Microcontroller that is connected with a Motor Driver to control a motor. The issue that we are facing is that whenever the motor is in use, it will eventually force the microcontroller to reset. Whether if it's on once for 1 second, or five times for 3 seconds, the microcontroller eventually resets.
We have tried adding a inductor in series with the motor to limit the start up current and tried adding a capacitor to the input voltage of the ESP8266, but no success. The only potential issue I can think of is our test set up. We have our setup soldered onto a perfboard. I feel like there may be electromagnetic interferance with all of the wires overlapping with eachother, but I don't know for sure. If that is the case, then it may be better to get a 2 layer PCB.
The motor driver we are using is the TB6612FNG and we are using the breakout variant on Sparkfuns website. Our 5V power source is coming from a wall outlet USB charger. And for the +VM voltage, we are using a 7.4V Lithium Ion Battery Pack. Any advice to help us solve this issue would be great. Thanks!


texts: Eagle Why ground pour is not connected to smd pads of components in a Module

texts:
I have created modules in my schematics, the Gnd pads of components in main schematics are connected to ground pour and does not have air wires.
But SMD pads of components in the module have sir wires and are not connected to ground pour? Why is this happening ?

What I tried:
1) In the module schematics I have GND port and I connected it to GND pin in main sheet. still didn't help.
And thoughts are welcome , Thanks:)


texts: Can carbon film resistors be used as heating element?

texts:
I am doing a project which needs a heating element to produce heat in a 10cm cube when temperature drops below 0C.

I have a 5V DC source that can only provide 100mA or even less. Thus the maximum power is P=IV=0.5W. If I put one or two 0.5W 50Ohm carbon film resistor in the circuit(P=I^2R=0.1^2*50=0.5W), can it be heated up and increase the temperature to 10C?

Is it a good idea to use carbon film resistor as heating element in this case? If not, what kind of heating element should I try?


texts: Why constant slew rate is important in entire Common-input range?

texts:
Almost rail-to-rail amplifier have different slew rate in 1~4V common-input and 0~1V (and 4~5V) common-input.
(Of course this range can control in the amplifier. This range is just example.)
So there is some drawback because of different slew rate. So please teach me what is drawback in these circuit and why constant slew rate is important in entire common-input range.


texts: Circuit for power on switch and self power-off ESP8266?

texts:
I would like to be able to use a switch to power on the ESP8266 (ESP-12F) and then be able to power-off the unit via GPIO pin in software.

I tried using a switch connected to CH_PD, and holding CH_PD high with GPIO#13, however, there is a long (6-10+ sec) power-up delay before I can "latch" CH_PD high with a GPIO pin. Since the switch on/off time would potentially be shorter than this delay, I think I need another circuit to reliably interface with CH_PD to get the functionality I want.

-Voltage source would be ~3.3V
-Ideally state of on-off switch can be checked by the ESP8266 for further control


texts:
Consider the following MIPS instructions:

lw r6, 0(r1)
lw r5, 0(r2)
add r5, r5, r6

Assume I have full forwarding capabilities. I know that when I produce a value, I only "forward" it to another next instruction right before I consume it. With that being said, am I allowed to forward from write back stage to execute stage? I've only seen write back stage do direct forwarding to decode.
Consider the following cycle diagram:

     C1 C2 C3 C4 C5 C6 C7
lw   F  D  X  M  W
lw      F  D  X  M  W
add        F  D  D  X  M  WB

Note: The second occurence of the decode stage signifies a "stall."

Now, in that diagram, I only get r5 after the 2nd lw instruction finishes its MEM stage. So, I have to stall decode. But at that point, the first lw instruction has completed WB stage. So in that case, would I forward from write back to decode or forward to execute?

If I forward from writeback to decode, that seems like convention. However, if I forward from write back to execute, that seems to comply the practice of forwarding right before you consume.


texts: Variable LDO implementation - capacitor size

texts:
I am designing two linear power supplies that will:

Drop 9V DC to 5V DC to power a Raspberry Pi around 2.5A
Drop 9V DC to 7.5V DC to power a DAC under 3A

I plan to use Texas Instruments LDO UCC283-ADJ. An adjustable LDO.

I have been reading the datasheet:

http://www.ti.com/lit/pdf/slus215

Which advises (see page 5) that a timing capacitor, C, is required:

  CT: Short-circuit timing capacitor and shutdown input for the UCC283−ADJ version. Pulling CT below 0.25 V
  turns off the regulator and places it in a low quiescent-current mode. A timing capacitor, C, from CT to GND
  programs the duration of the pulsed short-circuit on-time. On-time, tON, is approximately given by:

  tON = 750 k * C

Whilst the formula is given, I am at a loss as to what size capacitor I should use as C, for each of my implementations.

I was planning R1 to be 50kOhms and R2 to be 10kOhms.

Can anyone advise me on C?

Thanks.


texts: What is a 3-state storage register on a shift register?

texts:
The question lies almost all in the title
I have bought a shift register to play with, and looked at the datasheet.
I don't understand what is the 3 state storage register associated with RCLK.

My understanding is that if there is a high edge on RCLK then something (the 8 bits I guess) is stored in the storage. Is it possible to retrieve this value for some late usage ?

shift register 74HC595 with storage: https://www.sparkfun.com/products/733

datasheet : https://www.sparkfun.com/datasheets/IC/SN74HC595.pdf


texts:
So, we did our lab activity and I don't quite understand the question

"How could the circuit be modified so that the maximum current could be set to a value higher than that achieved by the supply and load resistor alone?"

Here is the circuit diagram:

The voltage supplied is 10V and the potentiometer value is rated 100K ohms. The RL value are 1k and 4.7k ohms.

Here is the data I measured:

My initial thought would be that the total resistance be lowered, since V/R = I.


texts: A conductive ball connected to a capacitor

texts:
I am not asking for a task solution, but rather how to solve a problem.
Say I have a ball of radius R, charged to a voltage of U (relative to the ground).
I also have a flat capacitor with a side area of S, and distance between the plates of d.
Then, I connect one side of the capacitor to the ground, and the other side, with a non-capacitive wire, to the ball.
What will be the potential of the ball and the charge flowing from the ball to the side of the capacitor?

My approach would be:1. Calculate the capacitance of the ball and the capacitor, given the capacitance, calculate the ball's charge 2. Calculate the total capacitance of the connected ball and capacitor while assuming the charge doesn't change and they are connected in parallel
3. Given the total capacitance and the constant charge, calculate the voltage (or potential) which will be the same both for the ball and the capacitor, since they connected in parallel.
4. Using the voltage and the capacitance of the ball, calculate the new charge of the ball
5. Difference of the starting charge and the new charge is the amount of charge flowing through the wire

Is my approach correct?
Also, is the ball really connected in parallel to the capacitor? Logical reasoning would imply they are connected in series, but I can only find a solution to this problem if I assume they are connected in parallel (I must admit it is a blind try). Can someone justify if, and if yes, why are they connected in parallel?


texts: Storing settings/data on microcontrollers non-volatile memory (STM32F103)

texts:
I want to be able to store values in a non-volatile memory so that the microcontroller can load these settings at start up. These settings might change at run-time and it is important for the systems functionality that these settings are stored.

As far as I know the only non-volatile memory on the STM32F103 is the flash. Is it possible to save values on flash someplace at run-time?

I also have the possibility to use a SD card and the SDIO or SPI interface to store the values there, but if possible it would be best if a  SD card can be avoided.

The amount of data is only a few hundred bytes at most.


texts:
I disassembled a Sharp 42" LCD TV power supply board and discovered 3 glass Spark Gap components (Gas Discharge Tube/Surge Absorbers). I haven't worked with them before and I'm curious about the schematic symbols silkscreened on the PCB. Based on the component specs (there are 2 types here: DA38-452MT, DSPL-301N, from Mitsubishi MMC) I presume the symbols refer to high voltage and low voltage. For the high voltage symbol, are we really looking at thunder clouds suggestive of lightning strike surges?

From Sharp Aquos LC-42D69U LCD TV service manual

SG801 = Spark Gap DA38-452MT

SG802 = Spark Gap DSPL-301N


texts:
I have bought a few of these (similar ones, not exactly this offer, just the same boards) TP4056 Li-ion charger boards, and I attached Li-ion cells out of an old laptop battery pack to them. I charged the cells up to 4.2V with these boards, which worked fine and then started using it. So, recently the battery was low, so I wanted to recharge.

I plugged the USB into a 5V phone charger, and left it there. I got back to it a few minutes later and noticed that the charger LED already went off. However the blue charging complete LED did not come on. I measured the voltage on the battery, and well nothing much had changed. However, the board was so hot that it melted the 3D printed enclosure it was in, and also burned my fingers. The battery did not get hot or even warm.

I have two of those with the exact same setup, same project etc. and they do the exact same thing. Start charging, stop ~20sec later and start heating up. Tried different phone chargers, tried my computers USB source... Nothing changed.

It may be noteworthy that I have modified the boards by desoldering the red charging LED and attaching a 3mm red LED to the outside of the 3D printed enclosure, but the LED works fine and I don't think this would make a difference.

What could have happened here?


texts:
I'm looking at analog switches to control 40-50 switches. Since its a prototype, I am looking at DIP packages on breadboard for the analog switches, then resuse them on the PCB when its fabricated.

Why does the quad channel chip cost so much cheaper ($0.43) compared to the octal channel chip ($4.60)? Going from 4 to 8 switches require a 10X increase in cost.

Quad: SN74HC4066N

Octal: MAX395CNG+


texts:
My brother in law bought a Prius recently. He's experiencing something strange with his iPod.
If he has his iPod plugged in via the USB cable to the Prius, everytime he starts up his car, it resets his iPod. If he unplugs his iPod first, starts the car and then plug in the iPod, the iPod is fine.

What can be the problem? Is there some sort of surge in the Prius circuitry that resets the iPod? Is there an electronic hack for the USB cable to fix this?


texts:
I'm attempting to update the firmware on my Arduino Mega 2560. I'm following this tutorial.

However, when I try to use flip, whenever I try to find my device (from USB), it tells me that AtLibUsbDfu.dll cannot be found. I found this on atmel's support site, but since I can't even connect to my device it doesn't help me (and there's nothing in the Jungo section of my device manager). Has anybody had this problem before? If so, how did you fix it?

/e1
I found the AtLibUsbDfu.dll file in the Flip 3.4.5\bin directory. This directory is on the PATH system variable.


texts:
I am currently working on a quite big project and I use Altium to simulate my overall circuit to make everything works as I expect it to.

I have something like 10 sheets linked to each other with feedback loops etc.
I have for the first time tried to simulate the global process today and it takes me 15s in real time to simulate 1 ms of the simulation.

The problem is that I have phenomenons that are happening at differents scales (basically one part is about the ms and the other one at around the second).

So I calculated and it would take me 4 hours to simulate 1s of my circuit and 41 hours to simulate 10 seconds. 10 seconds is the minimum I need to simulate to be able to see what's happening in my project.

Do you know a way to make the simulation faster thant it currently is ?

(I already tried to increase the Transient step time and the transient max step time but they both are now at 10 ms and it doesn't drastically change the simulation time).


texts:
I am curious about the possibilities offered by LEDs to transmit data over a short range (2 or 3 meters), and what maximum data transmission rate can be expected from carefully chosen, but consumer-grade components. I am interested in a minimal hardware + "smart" (micro-controller) software solution.

So I see this as a two-parts design problem:

The "physical medium" (hardware) layer: what would be a good choice of LED and receiver (phototransistor?) for high frequency signaling? What kind of driving circuitry should I use?
The "signal encoding" (software) layer: would a protocol along the line of Manchester code be efficient? Or are other encoding protocols more efficient for this medium?

Things I am ruling out: I know about inexpansive and robust IR5 modules, but they are not designed for fast data transmission. I also understand that using coherent light (a laser diode) may provide better bandwidth. Also, no fiber optics: data would be transmitted through air.

Update:

The motivation for this setup would be as an alternative to power line communication (PLC) or Wifi; so a bandwidth in the 25 to 100Mb/s range would do the trick. This also explains the "no fiber" constraint, but some minimal reflector would be acceptable.

Considering the "across the room" distance I am considering, I think powerful / tightly focused solutions such as Ronja may be overkill (they have actually a much higher "minimal distance").

Considering the hardware part: you are positive in the high bandwidth I can attain with proper, "non phospor" LEDs. Are some colors better than other in this regard? What should I look for in datasheet to ensure they have this characteristic?

Considering the encoding: what would be better than Manchester for this usage? Something more bandwidth-efficient such as an RLL variant? I am more of a programmer than an electronics person, so I am more at ease with software encoding/decoding; but would some ICs help me with the decoding (which, as I understand it, is the hard part)? Should I consider some pre-filtering of the signal before decoding, perhaps by taking advantage of the frequency characteristics of the encoding protocol?


texts:
This IC is on a breakout board for a SIM868 chip. It is on the GPS antenna signal line, just before the U.FL connector.

It has 5 pins, 3 that are connected to ground, 1 to the signal, and 1 (I think) to power.

What is this chip and what does it do?

Zoomed-in photo (IC's markings are visible):

Zoomed-out photo (all connections are visible):


texts: How to connect an Arduino UNO to an LCD 1602

texts:
I got an Arduino UNO and a 16x2 alphanumerical LCD on hand, the LCD looks like this:

I just have no clue about how to connect these two together. I got some Dupont Line, just want to know how to wire it up.


texts:
Im trying to communicate to my pc using my raspberry pi using a software called Docklight. I'm using a serial cable (that i ripped apart) and my breadboard as shown below.

Now, you can also see I also I have a level converter. I thought this would solve the problem becuase i was converting the logic level from the PC to the rasberry pi. But when i was using this software it would display ''. I made sure that in my code my baud rate is 9600, no pairtity and a bytesize is 8.

I was wondering if theres another way I could connect the raspberry pi to my pc using this serial wire.

I didn't make this clear but in my question I was only talking about the TX from the raspberry pi to the RX of the Pc. I hope my new layout makes more sense.


texts:
This may seem like a dumb question, but does anyone have a schematic for a BDCM controller. All I seem to be able to find are partial schematics or schematics that include a micro controller. My customer has specifically requested no micro controllers. The customer is also governed by the FAA and for them to be able to use the controller they are required to show manufacture capabilities. I'd hate to reinvent the wheel if someone already has something.

Their requirements are pretty simple as far as I can tell and are as follows:

They will be driving a 3 phase brushless DC motor pulling a continuous duty of 8 amps, 10 starting amps. They want to be able to push 20-35 Volts DC in to the control circuit and send the same out to the motor. The motor is required to run at 900 RPMs and be reversible.

The current method of running the motor is through a control box that simply has a 24 Volt brushed motor that turns a three leg rotary switch at a constant speed. Because the control box was manufactured in the 1930s for the USAF it's nearly impossible to find parts for it.

All help is greatly appreciated, and if any information is needed on the current control box, or step motor just let me know. Thanks in advanced.

EDIT: Information on current controller.


texts: why emitter is connected to high level and collector to low level?

texts: generally, in all switching circuit, emitter is connected to ground and collector is connected to high level. i am not getting why is it so? is there any special purpose?


texts: Transistor weak current when switched from microcontroller

texts:
I have ATMEGA328 (running on 5V) connected to a C4793 NPN transistor which controls the TEC1-12706 thermal component.

I'm using the code below to turn the transistor on and off:

#define F_CPU 8000000UL

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

void delayms( uint16_t millis )
{
    while ( millis )
    {
        _delay_ms( 1 );
        millis--;
    }
}

int main( void )
{
    DDRD = 0b00000001;

    while ( 1 )
    {
        PORTD = 0b00000001;
        delayms( 10000 );

        PORTD = 0b00000000;
        delayms( 10000 );
    }

    return 0;
}

simulate this circuit – Schematic created using CircuitLab

Everything is working great, except that the thermal module only gets 0.6A of current, even though the datasheet of the C4793 transistor states that it can handle 1A of current.

If I connect the base of the transistor directly to the VCC, I get 1.07A to the thermal module, which is exactly what I need.

I can't understand why I only get 0.6A when doing the same thing from the ATMEGA328. I thought maybe it's because ATMEGA328 puts out only 20mA from the PIN, but isn't the transistor triggered by the voltage instead of current? Any suggestions please? Thanks!


texts: Need help with NOT Gate oscillator circuit

texts: Sorry, if the question seems silly, but I really need someone to help me understand the below oscillator circuit. How can the oscillation begin, if there are no initial conditions? All analysis shown in textbooks assume an initial condition of either '0' or '1' on input/output. But how does it work in real time? When the IC is powered on, the input side should be floating (high Z state), isn't it? What am I missing here? Also, I read somewhere that this circuit has a nasty habit of altering the duty cycle if operated for long? How is this possible? Any help would be appreciated.


texts:
I have an ATX power supply which has got multiple 5v outputs (at a maximum 40 amp current). I am willing to use it to power up a moving mechanical system 5-10 meters away. The problem is that since the current can be so high I need a thick wire which obviously lacks flexibility. I am looking for a way to "carry" the low voltage high current through a() flexible, long but relatively lossless cable(s).

The ATX splits up the outputs to avoid thick wires into multiple 5v header pins.

Should I do something similar? ; split the supply into multiple cables?

I was also thinking of carrying high voltage low current but I find voltage regulators with huge current outputs to be very rare and rather expensive.

What would be the best way to do it?


texts: What is the minimal set of parts for a circut with this AVR microcontroller?

texts:
My Arduino Uno has a ATMEGA328P-PU microcontroller, and bunch of other stuff on the board. I'd like to program the chip without the Arduino software, and only the minimum of other components.  I want to eventually create things without the cost of Arduino, and I want to learn about the other parts on the board and add them back as as needed.  I'm comfortable with C and gcc, so I can probably figure out the software part. But what, if anything, besides these two products below, do I need to have in the breadboard with the microcontroller?

Atmel Programmer
Microcontroller


texts: Why does a nonlinear system cause inter-modulation?

texts:
Can someone answer or point to a link explaining why a nonlinear system causes harmonics.

According to Wikipedia

  ... non-linear systems generate harmonics, meaning that if the input of a non-linear system is a signal of a single frequency, then the output is a signal which includes a number of integer multiples of the input frequency.

but why?

The only explanation that I can come up with is the following.

Let's say we have a frequency fc going through a NLTI system with a span. The upper and lower part of the span, as well as all the other intermediate frequencies will be affected differently than the it's surrounding frequencies due to the NLTI system causing mixing between all different frequencies thus causing harmonics.

If this is true then sending a delta function through a NLTI system will appear to be a LTI system.


texts:
I am given an LTI system and its impulse response:
$$ h\left(t\right)=[te^{-4t}+2e^{-2t}]u\left(t\right) $$
Where
$$ u\left(t\right)=\begin{cases}
0 & t\leq0\\
1 & t>0
\end{cases} $$
And we are told that the system can be represented by a differential equation.
The question is; Can we identify the order of the system (the order of the differential equation) and the differential equation itself?
I thought about it, it seems that the characteristic polynomial has just 2 roots, and I can tell for sure that one of them (-4) has an algebraic multiplicity that is bigger than 1. But can we tell exactly what the differential equation would be?
Thanks in advance.


texts: Schematic symbols: dot or bar to indicate negative logic

texts:
A question of style or consistency: considering below schematic symbol which notation to indicate a pin with inverted logic is preferred:

Dot and bar above pin label (possible double-negation?!)
Dot only, pin label without bar
No dot but bar above pin label


texts: Maximum *charging* voltage for Li-Ion battery

texts:
I'm implementing a CC-CV algorithm for charging a li-ion battery. I'm confused what is the maximum allowed charging voltage during CC (constant current) phase.

All application notes and datasheets, I've found state that charging in the CC mode continues until cell voltage reaches 4.2V per cell. In order to maintain constant current the charging voltage has to be increased as the cell voltage rises.

So, when the cell voltage is close to 4.2V the charging voltage must be higher e.g. 4.5V, and this should not cause any damage to the cell. Is my understanding correct?

I'm asking because the power control module in the battery pack I'm trying to charge seems to cut off the circuit when charging voltage is above 4.5V.

Edit: Some clarification after Russell's comment.

The control algorithm I've implemented is basically taken from Atmel's app note - AVR458: Charging Lithium-Ion Batteries with ATAVRBC100.  A similar algorithm is described in app note AVR450 - AVR450: Battery Charger for SLA, NiCd, NiMH and Li-Ion Batteries. Both are simple buck regulators with PWM controlled by MCU.

Now let's say that we measure two voltages:

Vcell -> this is the voltage measured at battery connection when PWM is OFF
Vchg -> this is the voltage measured at battery connection when PWM is ON

To be clear I've checked the source code implementation of both. During CC charge phase the algorithm periodically checks if the Vcell > Vmax=4.2V. If not then Ichg is regulated, so that it is ~1C. If so, then CV mode starts.

I've asked the question because I see that during charging Vchg is higher than 4.2V, e.g. Vbat=3.9V is and Vchg is 4.3V.

 Edit2: **
I went to check the source code of both app notes again. In fact the above is true for source code of app note AVR450.

The impl in app note AVR458 changes to CV when Vchg >= Vmax (4.2). Since this is consistent with all information I've found and with Russell's answer I think that the algorithm in AVR450 is incorrect.


texts:
In differential signal circuits (specifically, RS-485), there is usually an isolation between the signal processing / generation stage (eg, microprocessor) and the line driver chip (something like a MAX485 or SN75176).

This is usually accomplished with an isolated DC-DC power supply, or a galvanically isolated AC-DC transformer / power supply.

What I don't understand, is why isolating the power between the microprocessor and driver chip is neccesary, if instead the entire circuit is powered by a galvanically isolated power supply.

Does this not achieve the same level of isolation, if there are no other external connections sharing this power supply?

(My understanding is that the isolation is to prevent ground-loops / large voltage potential between the transmitter / receiver - and the isolated power allows the receiver to be grounded (here I'm assuming the trans/rec are connected with d+, d- and ground) at the same level as the transmitter. In my case, the galvanically isolated power supply would also be connected to the transmitter's ground along with the data wires)


texts: Li-ion CR2 / 15270 voltage and charging circuitry

texts:
CR2 / 15270 Li-ion batteries normally come as 3.0v. I thought Li-ion and Lipo batteries were always 3.7v, how is that possible?

Does it require a different charger circuit than normal 3.7v li-ion/lipo batteries?


texts: Why an ideal LC oscillator has a highly damped response in Spectre but not in PSpice?

texts:
I'm just curious about why a ideal LC oscillator (See Figure) has a damped response in Spectre Simulator but not in Ngpsice. In both cases I'm using 5V of initial condition. I'm also using gmin=0 and gmin_in Spectre in order to avoid some energy losses. In Ngspice, I'm using default convergence options.

simulate this circuit – Schematic created using CircuitLab

The Spectre results gives me something like:

Does anyone has a hint about it?

Thanks


texts:
I have a sine signal with Vpp = 5V, DC Offset = 2.5V.

Now I am asking myself how to remove this offset in order to have a DC free transmission.


texts: Increasing arduino PWM signal voltage from 5V to 10V using a transistor

texts:
I have a VEX 29 motor controller (u1 in the schematic) that takes a pwm signal as input to drive a dc motor in forward or reverse (with varying speed). Unfortunately VEX is not very generous with information about it's electronics. I managed to run this controller at 5V from an arduino PWM pin. But the motor controller should be able to run at higher voltages than 5V which would also increase the motor speed. So I want to instead run the motor controller at 10V, where the PWM input signal needs to be 0V-10V. How can I step-up the arduino 5V PWM signal to become a 10V PWM signal?

I was thinking of using a regular NPN bipolar transistor to switch the 10V voltage on and off with the frequency of the PWM signal, translating the 5V pwm signal into a 10V pwm signal. Is this possible? And if so, what is the type of parameters I need to choose the right transistor (I have a bag of various NPN and PNP transistors lying around)? My motor controller only takes around 10 micro-amps or something from the PWM pin when hooked up directly to the arduino (so at 5V).


texts:
One of these black things is burnt and according to the technician it have to be replaced , and when I asked him: what is this he said : IC ????!!!
Well, What are these?
Sorry for bad English

———————————————————————————
Hello everybody.
Thank you very much for your responses.
I meant the surface mount resistor (as it seems to be), well here more clear photo, and it is clear the burnt component is on the right (down circle) and on the above circle there is broken component (It seems the case) , is it transistor?
Thanks


texts: ATMEGA128 & AD7417 Reading first channel using external reference voltage

texts:
I'm doing test work in Proteus ISIS. Where in circuit used External ADC, but there is no modeling module in the proteus. And i can't test it.
This ADC using TWI(I2C) interface. ADC connection circuit:

I use AVRGCC. Starting code:
I2C_StartCondition(); //Start
I2C_SendByte(0b10010010); //AD7417 addr & Write
I2C_SendByte(0x01);//Configuration register addr
I2C_SendByte(0b00100000);//Select 1st MUX channel
I2C_StopCondition();//Стоп

This code should switch MUX to 1 channel - 001

OTI is not used - 0
Fault queue (what is this?) - 00
Cmp / Int (what is this?) - 0
Shutdown, always on - 0

Am I doing right?
How start conversion and get result?
How to set external reference voltage?
For reading byte i useing I2C_ReadByte()
Excuse me for my bad English.


texts: Reverse Current Protection using two PMOS in back to back configuration

texts:
I am working on a circuit that needs reverse current protection. Back to back mosfet configuration has been suggested by many people, and it seems to make sense at the beginning. But after I built my PCB, after fully charged my capacitor, and then turned off the power supply, the current flowed right back to the power supply.
Let me explain my circuit a little bit. I need to charge C1 and use it to run a pulsed (D=10%) circuit that requires every large current. I have a separate circuit that controls the max current to charge the capacitor, so that I do not need to worry about charging current for this circuit. During charging, my intention is to using R4 and R10 to keep Q1 and Q2 on when power supply is turned on; R2 and R8 sets up a node voltage that is always less than the gate voltage at Q1 and Q2 unless Q6 is turned off. When the power supply is on, R7 and R11 keep Q6 on. D2 blocks the current flowing to C1. Everything works on charging my capacitor. During discharging, when Power supply is turned off, R7 and R11 has no current flowing through and Q6 is off, and the gate voltage on Q1 and Q2 is pulled up to something like +49.5V, and Q1 and Q2 shuts off. Here is the problem, Q1 and Q2 were never turned off. My theory is that any parasitic capacitance or slow power supply turn off action that can keep Q6 on for a very small mount of time, Q1 and Q2 will stay on, and current starts to flow back, and then most of the voltage on C1 appears at Vin and keeps Q6 for longer period of time. It creates a positive feedback loop and keep Q1 and Q2 on.
I have done simulation and confirmed that the Q1 and Q2 are on during discharging(Discharging circuit not shown here).
I would love to have some feedback from someone who has gotten this circuit working before or someone who knows what's keeping Q1 and Q2 on when the power supply is turned off.
If you have different ideas on how to block the reverse current, I would love to hear them too. Using diode is not an option because forward current is too high, diode gets too big and consumes a lot of power.

Thanks!


texts: How much current can my 74HC595 handle on each output pin?

texts:
So, I've been checking out the datasheet and I've gotten pretty confused... At the top it claims that 6mA drive at 5V but farther down in the absolute maximum ratings it says that the outputs can be up to 35mA.
So, my question is, how much current can each output pin of the chip take?
I'm using it for a controllable line of LEDs and I need to figure out what resistor value to use.


texts: Inductor Symbol? What does this symbol indicate?

texts:
In the diagram below the symbol labeled L1 is described as:

  1.5mH, Core: SM CM20 x 12 x 10

But what does this symbol show exactly? I have searched thoroughly and cannot find this symbol and am just not sure if this is a EMI/RFI Inductor or a simple Leaded core? or something else. The input voltage is 28 VDC and the two caps are 220uf @ 100V. The DC/DC convertor is an XP Power QSB300 300W isolated DC-DC Convertor.


texts:
I have a very dumb question in understanding p-MOSFET driver. simple BJT voltage divider or totem pole driver.

first i will ask Simple BJT driver.

During turn ON, Q1 is ON, MOSFET gate charges to v1/2 through the path in violet(from V1 current flows to gate to GND).

During Turn OFF, Q1 is OFF, MOSFET gate should discharge. discharge current has to flow in R3. we expect potential difference for current to flow, Here from where to where current flows because only V1 is connected there is no GND connection in discharge path.

Similarly for totem pole driver also. during discharge path upper transistor will be ON for short time which gives path for MOSFET discharge but there also no potential difference.

Please correct if i am not clear..


texts: Is a flyback diode needed if there are only inductive components on the circuit (Ex. solenoids)

texts:
I'm using relays to drive a circuit of solenoids.  Do I really need flyback diodes on the controlled circuit if there are only solenoids on it?  The driving circuit is already protected by flybacks.

simulate this circuit – Schematic created using CircuitLab


texts: Why is feedback required in op-amp circuits?

texts:
I understand that, in order for an op-amp to function correctly, a DC feedback loop from the output to either the inverting or the non-inverting input (depending on the external circuitry) is required.

What is the purpose of DC feedback when using op-amps? Why is it necessary and what would the effects be without it?


texts: Frequency dependence of electrolytic capacitors

texts:
It's said that electrolytic capacitors behave as inductors at high frequencies, which is why we put small ceramic caps in parallel with them:

  Electrolytic, paper, or plastic film
  capacitors are a poor choice for
  decoupling at high frequencies; they
  basically consist of two sheets of
  metal foil separated by sheets of
  plastic or paper dielectric and formed
  into a roll. This kind of structure
  has considerable self inductance and
  acts more like an inductor than a
  capacitor at frequencies exceeding
  just a few MHz.

Capacitor impedance vs. frequency.

Yet I also see a few things like this:

  The "inductance problem" associated with electros is another idiotic myth
  - they have no more inductance than a length of wire the same as the length
  of the cap.

or

  A popular myth is that electros have considerable inductance because
  of the way the foil is wound inside the can. This is nonsense - the
  foils are usually joined at the ends in the much the same way as with
  film caps. High frequency performance usually extends to several MHz,
  even with standard off-the-shelf electros and bipolar
  (non-polarised electrolytic) caps.

What is the exact nature of this effect and in what applications and frequencies do we need to worry about it?  What are the practical implications?


texts: Is the quoted range of an RF module based on two identical modules?

texts:
Take for example this 433MHz transceiver module. It's quoted range is 300m.

What does this value mean? Is this the distance when the signal strength dies down to 0%?

Does this mean if I were to buy two of these (one for transmit, other for receiving), I would get a theoretical range of ~600m?


texts: Conformal coating of shielded RF modules

texts:
What is the best practice to protect a circuit with shielded RF modules?

I have a feeling that conformal coating is difficult since the shield is not sealed.


texts: Is there a limit on the charge that can flow in a wire?

texts: I assume when I hook up a 12V battery to a wire, all the free electrons in the wire move. If I hook up 24V, they move faster so more charge passes a area cross section for i=C/s. But in AC, their movement is constrained. They move at 60Hz. So what happens if I increase the voltage? More electrons have to pass a cross section, so just some electrons move, and then more of them do if I increase the voltage? Maybe I am confusing myself :)


texts: How to access the Pin directly to read or write data? If I want to write data on pin6 how can I do that? Or if I want to read data from a specific pin.


texts: FAN6754 flyback converter-overcurrent problem

texts: I have a design 193V output voltage and 700mA current, but when the current drawn from output, the auxilary winding voltage fall down, and IC shut down PWM gate signal as you can see in the attachment and the output voltage go to zero. And I could not understand, why auxilary voltage is like sawtooth wave, I think the IC try to open PWM but can not start. Can any body help me about that issue?


texts: New alkaline batteries with 10-year shelf life—what's changed?

texts:
I'm finding that some new alkaline batteries, such as the new Duracell Duralock and Energizer Power Seal batteries, have a shelf life of 10 years.  Most other alkaline batteries have a shelf life of 7 years.

How is the chemistry or structure of these new alkaline batteries different, and how does it affect performance and battery life under various loads compared to older batteries?  Google hasn't been very helpful here.


texts: Amplify Shunt Resistor Voltage to an Arduino Using an Op-Amp

texts:
Basically, I want to measure the voltage across a shunt resistor (1.12mOhm) and feed that to an arduino analog input to obtain a measurement of a current drawn from a battery. I would like to obtain a sensitivity of about 0.1A (0.112mV), hence being the lowest readable voltage above zero,  and the maximum expected current is about 40A (44.8mV). What kind of op amp can I use to amplify this shunt voltage with a gain of 70? Basically my worries are: is there a limit to the gain op amps can provide or does it just depend on the resistor? Due to the input voltage offset, will the op amp be able to accurately increase my lowest shunt voltage values (0.112mV) so that the Arduino can read it? Also, are there specific kinds of op amps that would be best suited to my application or anywould work given the right supply voltage?
Thank you very much for your time and help!


texts:
At the moment I want to build a machine that counts money (money counter machine). When the user puts in the money bills, it will scan them, count them and send the results to a program running on a PC.

I really don't know the kind of hardware I need to build this machine. I have been googling for a while but can't seem to find any place that will give me a good answer.

I will also create a software that will receive the counting from the machine. Creating the software is not a problem. What I need now is how to build this machine and where to get the hardware.

My main concern now is which hardware do I need to create this machine and probably where to get it.

If I decide to buy an existing machine without building it myself, is it possible to create one software that will work with any machine or do I have to write the software for each particular machine I may choose (in case I change the machine later).

Where can I buy an existing machine?


texts: How to convert a 10-Watt solar panel into 3v & 3 amp?

texts:
The device I use requires about 3V and 3 amps.

Based on my Google research, I found out that in order to get 3V and 3 amps from a solar panel, the solar panel needs to be at least 9 watts.

So let's say I purchase a solar panel that outputs 10 watts.

Can I simply find an adapter cord, cut its tail, connect the tail to the solar panel directly and then connect the whole thing to the device?

Will it work?


texts: Mapping unused bits of a bus in VHDL to a signal to avoid partial mapping error: Is there an alternative?

texts:
I have a VHDL design containing a module that is reused frequently. This module has an output port that is 32 bits wide. The output of the submodule needs to be connected to other modules with input busses of various widths. To connect the mismatched width buses, I have connected the unused bits of the output bus to a "junk" signal that does nothing else in the design. The bits I want are connected to another signal which goes to the input of another module.
This solution allows me to synthesize the design but it seems like it could be bad practice. Is there another method that is more accepted?


texts: Basic electric/wiring questions resources

texts:
I have a 12V DC motor that I want to power alongside a 40 Watt incandescent bulb (I might find an LED bulb that works aesthetically).  I need to run a single cord to power both.  Preferably with a dimmer and power switch in line.

With almost no wiring background, I find the lack of a Radio shack alarming!

What resources are there to understand basic wiring fundamentals and best practice?

What do you guys recommend in terms of attaching wiring to components, splitting the wire, and possible AC to DC conversion?

Appreciate it!

Edit***

The goal is to have this plugged into a wall outlet. The motor doesn't need to be 12v. It's just I've only found a 12v that turns slow enough. I need 2 - 5 rpm and needs to be smaller than 2 in in Dia, shaft in center of motor. I can do a higher speed motor if I can find a cheap gear reduction.

Why a lower voltage? It's apparently very difficult to find a wall socket adapter to 12v that isn't huge. 5v motor that can do the job should exist.

If anyone knows a good place for that kind of motor I am all ears :)


texts: Datasheet for Keyes IR Transmitter (KY-005) wanted

texts:
Can someone help me find the datasheet for the Keyes IR Transmitter (KY-005)?

I know how the pins work, I just need to figure out its voltage drop and how much current should go through it.

Thanks! :)

Image of the component:


texts: Can I increase torque and Rpm in a DC electric motor safely using outside magnet

texts:
I'm wondering as a layman what would happen if you place a magnet on the outside of a DC motor. This has been documented on YouTube using a small 12v motor. I'm wondering what would happen to a larger DC motor say 500w 24v Would it hurt the motor? I'm thinking of series wiring two of these motors to the back wheels of my sons go kart and trying the outside magnet.If it is safe. Can someone help me out here
Concerned Dad


texts:
I am analyzing the schematic for an audio amp:

https://www.sparkfun.com/datasheets/Kits/STA540%20Audio%20Amp%20v11.pdf

I am interested only in the top left op-amp (JP2 on the left) where it runs into the op-amp, pictured below.

A few simple things that I don't understand.

Why is the audio fed initially through a capacitor? Won't the filter out any audio signal?
If Vcc is much higher than the audio signal, say 12V, won't if feed back into the lower-power audio source and cause problems?
Similar to my first question, why is the output of the op-amp then fed through another capacitor? Again, won't this filter the signal out?


texts: Impedance determination of blackbox circuit

texts:
I've been looking into something and I'm not entirely sure how this is done.

So I was looking at how they determine the parasitic and resistive components in pv panels, it looks like the majority of studies I've found use impedance spectroscopy. Although the general form of the circuit is known, i.e. we know the electrical circuit equivalent of a circuit can be modelled as either the one or two diode model with the parasitic capacitance and inductance added on.

My question is when you have some circuit, where you have no idea what the electrical representation is, how do they determine it? How was say the one diode model of a pv panel determined?

Not sure if this is very basic and I've just completely whoosed something.

Thanks in advance for any help!


texts:
i'm supposed to work on a project that consists on creating a led analyser to test PCB (functional test)
they want me to create a system that can measure the color (R,G,B) and the luminous intensity of the LEDs
i choosed to work with this sensor tcs34725 from adafruit.
and probably i'm going to work with arduino

but i have a problem understanding the concept of this project because i'm a transmission engineer not an electrical engineer
why we use leds to test pcb , what information can one interpret from the color (rgb) and luminous intensity of the LEDs
i know it has a relation with the Power consumption, but i can't find anything on the internet that details this topic


texts:
Are there any commonly accepted algebraic models for vacuum tube operation (triode, tetrode, and pentode)?  In the same way that BJTs have a Gummel-Poon or Ebers-Moll model, and (macroscale) MOSFETs have a cutoff/linear/saturation algebraic model, is there a similar model for vacuum tubes?  A DC-accurate model plus some dynamic components (dominant capacitances) would be excellent, but I'm having trouble finding any references.  Higher order effects (equivalent to something like the Early effect in BJTs) would be good to know about as well, especially if they tend to impact practical designs.

I am one of the developers of CircuitLab and vacuum tubes are one of our most requested features, and I'm investigating whether it'd be practical to implement in our simulator.  Thanks!


texts:
I'm trying to solder 0.1uF capacitors across DC motor terminals to suppress motor noise, as seen here and here, but it's impossible to solder to the motor case. Motor case never holds the solder. Every time I solder the cap to the case, it always breaks off.

Is there anything that I have to do before soldering? I'm using Sn60/Pb40 solder.


texts: How to use the rate of change of frequency equation to calculate frequency drop in a grid based on lost generation

texts:
My question involves calculating the frequency drop in a power grid when a load is lost. The closest question I have found to mine is, Change in frequency in a grid that has lost generation?
Based on my research I have found the following equations.

I am interested in how I use the second equation, which would be the rate of change of the frequency based on how much load is lost. If the equation works the way I believe it does, then the units on the left side are Hz/s and the units on the right side would be MW/s. I am not sure how I can calculate the frequency drop using this equation, especially because each side seems to have different units. Maybe I am looking at the equation wrong, and the right side is supposed to be a sort of "scalar"? I think I am looking at this too much from a number standpoint and not enough from the stand point of what is "physically" happening when a load is lost. Here is the link for the National Grid power point presentation that presents the equation on page 6, the slide is titled, "The maths behind inertia", (https://www.nationalgrid.com/sites/default/files/documents/16890-Meeting%208%20-%20Inertia%20presentation.pdf).
I am trying to apply the equation to the figure below:

I believe in the thesis, the author used a value of 9 seconds for H, as they state that, "It was found that an inertia constant of 9 s gives a good fit and that value was used in subsequent simulations." I obtained the figure from an online article titled "Measuring grid inertia accurately will enable more efficient frequency management" (http://watt-logic.com/2017/10/12/inertia/). The original source for the figure is a thesis titled, "Use of Smart Meters for Frequency and Voltage Control" by Kamalanath Bandara Samarakoon. The figure itself is on page 73 of the thesis, Figure 4.11.
If I am reading the figure correctly, for the first generator loss (345MW), it looks like the time interval is about 25 seconds, 11:33:50 to 11:33:75 (HH:MM:SS), and the frequency drops from what looks like 49.95Hz to 49.8Hz.
Another source I have been using to understand the equation is a NREL paper titled "Grid Frequency Extreme Event Analysis and Modeling" that has similar equations (Equations 2 and 3) to the ones I presented earlier, however, I am still having trouble understanding how the equations were used to produce the figures for frequency drop as a result of lost load, https://www.nrel.gov/docs/fy18osti/70029.pdf
Further Questions

If the equations can be used to calculate frequency drop from a lost load, can they also be used to calculate how the frequency would increase if a load was added? Is it a matter of a positive, or negative sign in front of the delta P?
How does MW*s/MVA (inertia constant) on the right side of the equation "cancel" to just seconds? Why do you have MW over the rating of the machine MVA? I think this is meant to be a "ratio"?

I am hoping someone can give me an example calculation on how much the frequency would drop based on how much generation was lost using the aforementioned equation. And explain how a change of rate in frequency (HZ/s) on the left side can equal a change in power per second (MW/s) on the right side.
If clarification is needed on my question, please let me know. And let me know if I am using the wrong equation for what I am trying to solve.


texts: How do I find the equivalent resistance in this circuit?

texts:
I'm so confused on how to find the equivalent resistance of this circuit. Initially, I calculated it to be R_eq = (1/(42+21)+1/63+1/(84+105))^-1 = 27 Ohms, but I think that's wrong.

I think that the 84 Ohm and 105 Ohm resistors are in series, but I don't know about the others.


texts: What is a good camera to use with a microcontroller?

texts:
I'm trying to build a low energy camera sensor and I need a camera that doesn't have a lot of output pins. I'm currently using the ATtiny85 to do my processing and it only has 3 analog input pins. I don't want to have to use a multiplexer or some hacky method to force this project.

The camera doesn't need to be suffticated because I'm planning on only using three 1 X 128 pixel arrays to detect if an object has passed through the camera's line of vision.

I was planning on use a line scan module like the TSL1401R-LF but it loses too much senstivity at higher speeds. I need at least 30 fps and ideally I'd like 100 fps. Does anyone on here know of a device that I can use?


texts:
I need to check my answers for parts (a) and (c);

a) I got  q(t) = p(t)cos(5pit)

c) i got  y(t) as a rectangle with amplitude 1 from -pi to pi. So, y(t) = 1/8 f(t)

Am I correct for both parts;


texts: Ceramic space heater: Can i cut the wattage in half?

texts: I got a 500w ceramic core space heater that produces to much heat for my project. Is there a easy way to cut the wattage in half and thereby get less effect I.E. heat from the heater?


texts: Rectified DC current measurement using shunt or Current Transformer

texts:
I am working on a project to design a controller for battery charging solution.

A 3 Phase delta power (440 Vrms ph to ph) is given to a 3-phase Variac Transformer ( Variac is operated electromechanically via a single-phase motor). The power output from the Variac is fed to the 3 phase rectifier diodes to convert it into rippled DC wave. (Having Max output requirements of 20A at 600Volts (Vavg)). This ripple current is fed to a series of batteries acting as the load to the primary circuit.

This ripple current has to be sensed and measured digitally, and further its value is fed to a microcontroller ( say, Arduino) using analog input. The Microcontroller controls the Variac using relays to regulate the main DC current.

My queries:

Which method is better for the measurement of this ripple current: using a shunt resistor, current transformer or any other way?
I have tried using WCS1800 (Hall effect-based Linear Current sensor) earlier to measure this current but somehow (maybe due to magnetic coupling from the large coils of the Variac) or anything else, was not able to get good results. Was it the right choice? Was I doing anything wrong?
Is it better to place the current transformer in the DC loop or in the mains AC line?
I have a shunt resistor (20A/70mV), but I am not able to make a circuit around it. I didn't find a way to electrically isolate the differential terminals of the shunt from the controlling circuit.
Most of the difference amplifiers I could get didn't have high common-mode voltage ratings. How can I achieve this?


texts: Differential equation for current driven RC circuit

texts:
I need the differential equation for the following circuit for numerical integration purpose.
It is driven by a time dependent current source.

So the question is:

How can I know \$U(t+dt)\$ given \$i(t)\$ and \$U(t)\$?

simulate this circuit – Schematic created using CircuitLab


texts: Are there any simulator programs for Linux like Proteus for Windows to simulate an AVR microcontroller using .hex file?

texts:
I prefer Linux OS because of many tools I used in it and because it is an open source.

I wonder if there is a simulator program like Proteus for Linux to simulate the microcontrollers?


texts: Current transformer and amplifier + precision rectifier

texts:
I am trying to design a precision rectifier, to detect AC current through a current transformer. With a 22 Ω burden resistor and a test bulb, the CT I have gives me a pretty ugly 20 mV sinusoid with a 5% duty factor, which I have modeled as pulses in the simulation below:

I am trying to use a first non-inverting amplifier stage, followed by a precision half-wave rectifier. Each circuit taken separately in a simulator works fine, but as soon as I combine the two everything breaks down.

This is a snapshot of the amplifier simulation (5 V voltage source on the right, LM324 op-amps):

This is a snapshot of the half-rectifier simulation:

And the complete circuit that doesn't work at all:

For starters the negative rail goes up to 0.8 V and the positive one to 5.8 V :(
What am I missing?


texts:
I found two different formula in my course material, feel doubt which one is correct.

Below is the picture of the formula, need your expertise to help me which one the is the correct formula.

Thank you.


texts: How does widening the frequency band allows us to make faster pulses in a radio link?

texts:
I’m new to radio communication and completely ignorant in the topic. I spent some time writing software which includes calculation of the channel capacity (in bits/second or symbols/second or bauds) for a line-of-sight radio link. There were several methods, and all of them depended linearly on the frequency  bandwidth. The bandwidth and energy (SNR) were always the main constraint on a bit rate. All else being equal, if you need more speed—get more energy or more bandwidth. And reasons for more energy I can intuitively understand, but why more bandwidth?

What I understand about digital modulation is that we change some parameter (or parameters) every specified period of time (a timeframe) and thus transmit one symbol per timeframe. Variable parameters usually are amplitude, phase and frequency (ASK, PSK, FSK, APSK and so on). The number of distinguishable states provides more bits per symbol—this part is clear too. I view it as Morse code or communication via flashlight. In those two the faster you change the parameter, the faster the information flows. I can click my flashlight more vigorously and thus transmit faster provided the receiver can keep up with me. I would expect the constraints would come from the technical characteristics of the equipment such as, for example, the sensitivity of the receiver (how fast can it register the signal's state) and how fast the transmitter can emit those states.

But here it states that “Nyquist determined that the number of independent pulses that could be put through a telegraph channel per unit time is limited to twice the bandwidth of the channel. In symbols,
$${\displaystyle f_{p}\leq 2B}$$
where fp is the pulse frequency (in pulses per second) and B is the bandwidth (in hertz)”.
So we can't puls faster than 20,000,000 times per second with a 10 MHz bandwidth, according to the Nyquist rate. How come? What's the physics of this?

Thank you very much in advance! Directions to an according literature would also work.


texts: Have I understood this solution to the sensor synchronization problem correctly?

texts:
I read a research paper which proposes an algorithm to synchronize sensors in a way that is independent of the sensors.
Beginning with the simplified version which assumes no drift between the sensor p and the host q clocks and assumes p does not send a time with its messages but consistently sends measurements at a rate of 75 Hz for example.
How do I obtain multiple measurements of p's and q's clock based on some starting event?
More specifically, let's say that p is an Ultrasonic Range Sensor, and q is a Raspberry-Pi running Linux.
Assuming p is a higher-end sensor with an ADC and can provide the distance values over SPI but without a timestamp; I realize that's not how these common sensors are but let's simplify things.
I also realize the SPI frequency of the Rpi is approx 3.5 kHz to 125 MHz, but let's again say we set the SPI clock such that we know p is generating measurements at 75 Hz.
Having these equations

where A is the constant offset between clocks, t is the time on the Rpi at which the sensor observed the data, and e is the latency by which the Rpi processes the message.
We cannot observe A or e directly but we know p and q.
If I say that q1 is the epoch time on the Rpi when I start the SPI communication to read one measurement, is the value of p1 simply
q1 + (1/75)

The author says this method is not useful and is illustrative of the basic idea of the approach, and having written it out like this does make that clear.  But I want to verify I've understood it before moving on to the real algorithm.
Let's finally say I am using a common sensor that I have connected to an STM32 blue pill which the Rpi uses SPI to read the measurement, how does that change p1?


texts: Transistor pad layout for efficient use of prober

texts:
As we are a materials company the expertise is not in EE, so I am asking a very simple question.  I tried to search online for this, but could not find an answer.  We are making transistors with our special materials and need to put many on a test chip.  Hooking each one of them up with their own pads we quickly run out of pads and are limited to fewer devices.

What strategies exist to "chain" the structures together to share pads?  What risks are there in doing this?

See the example of the four transistors that use 12 pads to test.  Can the source and/or drain be one common pad and only need to change the tester for the gate?

Any references that would be helpful would be greatly appreciated.

Thanks.


texts:
I'm using an opamp to amplify a 3.5 Vpp (peak to peak) 10 kHz sinewave which seems fine apart from a tiny noise mostly visible at its' peaks which does not particularly concern me much. The blue sinewave is the input and the output is the red sinewave amplified at 6.7 Vpp. There is a distortion and that is at both no-load and loaded conditions. This opamp is meant to be used as a resolver primary coil driver which is the case of my application. The distortion is something that worries me because it could affect the accuracy of the resolver-to-digital converter. My question is what can I do to minimize the distortion as I do not see any reason for it. The datasheet refers to zero crossover distortion and secondly the opamp is "obliged", to a certain extend, to provide an output signal based on the gain factor which is not so great that could drop the BW so low to affect amplification ratio. The BW is 600 kHz and the signal being amplified is 10 kHz.

Can anybody make any suggestions?

Regards

Images:


texts: Is microcontroller power consumption directly related to its operation time?

texts:
I have to decide on a way to measure the efficiency of an algorithm running on a microcontroller/microprocessor.

My thought is that I can use the runtime of the algorithm to complete a certain task as an indirect measure of how the power consumption of that algorithm compares to another algorithm's power consumption. This would only make sense though, if the time spent in operation of the microcontroller was directly related to its power consumption. Is this assumption true?

The microcontroller runs under the exact same conditions with each algorithm, same peripherals etc.


texts:
I am just starting to learn the theory of electronics.

Coming from a probability and statistics background I have a very deeply ingrained idea of the term average.

The average to me is the Arithmetic Mean. In other words, if I was to take a sample from whatever data I calculated my mean from I have a pretty good chance of seeing a value near the mean.

It seems this definition is not the same in electrical engineering. The average current is defined by the change in charge over the change in time. This is similar to the physical velocity. But there is no averaging here being done at all, is there? You aren't summing anything in the numerator, instead you are dividing the change in charge by the change in time. This would give you the amount of charge changed per unit time.

Imagine I was to draw a charge value from a list of charge values measured from a circuit. If I naively assumed average meant the above I would expected any given charge measurement to be dispersed somewhere near the value there. However, in reality the Average Charge defines the slope of a line.

How can I reconcile these two things so I can really understand what average means here?

EDIT:

After sitting with paper for a while justifying it to myself there is a single case that confuses me:

Let's use this data set:

Q = [0, 1, 2, 3, 4]
t = [0, 1, 2, 3, 4]

and we have the following data points

(0, 0), (1, 1), (2, 3), (3, 2), (4, 4)

Finding the average current between t = 0 and t = 4 is:

4 - 0 / 4 - 0 = 1 C/s = 1A

However, using arithmetic mean:

1/5 * (0 + 1 + 3 + 2 + 4) = 2A.

The final value at time t = 4 where Q = 4 is throwing the calculation off.


texts:
In my opinion the voltage source ABSORBS power, since the current direction and source direction are opposite.
Am I right?


texts: Current in CE and CB configurations of a transistor when output voltage is increased?

texts:
The Early Effect seems to play a role when output voltage is increased in a transistor.

1)In the Common Base config, it causes the emitter current to increase,which in turn causes the collector current to increase. What happens to the base current in such a situation and why?

2)In the Common Emitter mode, my textbook says the emitter current increases while the base current decreases. It also says the Emitter current is constant because input voltage is constant. I am not able to follow this and seem to think otherwise.

Any help would be appreciated.


texts: Q: MOSFET not providing correct supply voltage

texts:
I dont work much with mosfets so I dont really know how to go about this.

simulate this circuit – Schematic created using CircuitLab

So pretty much I have the circuit above, What's happening is that the Source of the mosfet is outputing around 3.3V and not close to 5V. I understand there will be resistance as RDS(on) however its 0.200ohms. Shouldn't make it 3.3V.

EDIT:

simulate this circuit

So I tried this configuration, what happens now is that:

I am still not getting ~5V at the Drain
The mosfet gets real hot
Now the gate voltage is not even 5V, but once I take out the mosfet, 5V returns back at the output of the comparator.


texts: Can I use a Buffer Amp to Isolate Probe Loading on my Circuit?

texts:
and thank you in advance for the hand-holding.

I was troubleshooting a very small and noisy signal in a circuit and the concern of probe loading came up...

I only have access to affordable passive probes like the  these ones available from Tektronix so buying a $1K active probe designed specially for measuring small signals isn't feasible. I was instructed to create a simple unity gain amplifier circuit and connect the input to the part of the circuit being measured, and the output to the scope probe to attempt to get a better oscilloscope measurement.

It's sounds reasonable, unity gain buffers should be capable of isolating the impedance of the probe and isolate the effect of probe loading on the circuit I am trying to measure. But I just haven't seen it anywhere on the internet before, as in an engineering blog or troubleshooting app note that says something like: "here's what happens when a simple LM358 is used to improve your small noisy signals on your oscilloscope readings".

Can someone please provide some examples, and that the results are reliable? Tangent question, If it's so easy why don't passive probes already have this as an option?

Thanks again.


texts: Using p-channel mosfet on high side of h-bridge, do I really need a driver chip?

texts:
I know there are fancy h-bridge ic's to drive high side of h-bridge but I guess that is when I have to drive n channel mosfet.

I am planning on using p channel mosfets on high side and n channel ttl mosfets on low side. I will driving the high side with n channel mosfets.

My Vbatt is 12 V and I will be controlling a wheelchair motor which can conduct upto 30A under load.

my concerns:
1. How do I calculate gate drive current for the p-mos since the gate capacitance has to be fully charged for maximum Id? do I just use i=Q/t, where t is charge time and Q is gate charge. But how does the pwm frequency come into play? say if i am using 31khz
2. How can I calculate the values of the resistors (connected from Vbatt to Gate of n-mos)
3. Do I have to worry about gate resistors?

Shoot through won't be a problem since I will put a delay when switching direction. Any help would greatly be appreciated.


texts:
I would like to create a product that has an embedded Android device for the main reason the price. Because it will be embedded into another system it doesn't need all the peripherals; no camera, gps or tilt sensor. Even the 3G is not important, but WiFi and the touchscreen (max 3.5") are.

How would you start developing such product? Buy old cheap Android phones or media players and take them apart or get in touch with a manufacturer and develop custom modules? The cost per unit is important, casing is not important because they are plastic molded.

We are talking about a prototype first but later batches of 50, so some manual labor is alright.


texts:
Is there a pattern out there for a simple menu system in C for a text LCD. I find myself re-writing code a lot for handling simple text LCD menus.
I find most systems have a main menu and some sub-menus that when selected allow you to set a parameter with within some minimum and maximum value.
Ideally this menu system could be navigated with 4 simple keys such as enter, cancel, up, and down. In my application I'm using a 2 line x 16 character text LCD though an ideal solution should be able to be applied to any NxM display.


texts: How does line impedance of a BLDC motor relate to the RPM of its rotor?

texts:
I am curious about the impedance of the three phase BLDC motor when it is in operation. If the speed of the rotor of a BLDC motor is proportional to the frequency of the three phase current, and the reactance of the stator windings is also proportional frequency of the three phase current, then wouldn’t the impedance be proportional to the speed of the rotor (as inductive reactance of the stator windings can be defined as 2*pifL)? In this case, wouldn’t the motor draw less current as the RPM increases, but only due to impedance (not considering back-emf or other effects).

Or is the increase in impedance (with RPM) balanced out by some other factor in the design of a BLDC motor? If so, what exactly balances it out?


texts: Do surface currents (in EM scattering) really exist?

texts:
When an EM wave impinges on a target, it generates surface currents on that target, and these currents radiate the scattered fields.

However, this approach, namely finding the surface currents and calculating the fields, is just a mathematical construction to make the problem easier to solve.  It is either the induction equivalence, or the physical equivalence principle (see Advanced Engineering Electromagnetics, by Balanis, Sections 7.9-7.12).  In other words, to make the problem easier to solve, the object is replaced by surface currents so that the background constitutive parameters (epsilon,mu) remain the same.

So it is my understanding then, that these currents really do not exist. Do surface currents really exist?


texts: Forward converter - How to measure the equivalent leakage inductane of this model?

texts:
Here is the schematic that I found in an old AN from UNITRODE. https://www.smps.us/slup199.pdf

Here is the equivalent schematic showing the magnetizing inductance and the leakage inductances:

This is pretty simple to find the equivalent magnetizing inductance, nevertheless it is a bit more complicated to understand what are the leakage inductances in a real transformer (at least to me). Lp1 is the leakage inductance between the primary and the main secondary V1. L12' is the leakage inductance between the main secondary (V1) and the second secondary (V2). Actually I do not even understand what is in a real transformer what is the leakage inductance between the main secondary (V1) and the second secondary (V2) as the flux leakage has a meaning between primary and secondaries.
Here is the equivalent model of a transformer (unfortunately with one ouptut):

I know that I can measure the leakage inductance of the primary or of the secondary by shorting the primary or the secondary in order to apply 0V across the magnetizing inductance. (Actually this measure do some approximation as we can see. If you know a better method I will be glad to hear it)
In any case, where is Lp1 in the transformer model? How to find Lp1? If we supposed that the output V2 does not exist it seems that Lp1 is equal to the sum of the leakage inductance at the primary and at the secondary.
$$Lp1 = LprimaryLeakage + LmainSecondaryLeakage$$
For L12', I would say that the leakage inductance would be equal to:
$$L12' = \frac{N1²}{N2²}*(LsecondaryLeakage - LmainSecondaryLeakage)$$
What do you think about it?


texts: What is the "Nyquist" rate for sampling the derivative of a signal?

texts:
Background: I'm sampling the current through a capacitor. The signal of interest is the voltage across the capacitor. I will digitally integrate the current measurement to obtain the voltage.

Question: Given that the voltage across the capacitor is bandwidth limited, and I am sampling the derivative of this voltage, what is the minimum sample rate required to perfectly reconstruct the voltage signal from the current samples?

If there is no canned answer to this question, anything that could point me in the right direction would be helpful. Thank you in advance for any help!!


texts:
I currently am working on a battery powered Atmega328 design, using 4 AA batteries, at around 6.5 volts. I am using it to control a single digital servo, HiTec HS-5645MG. This is done using a RF reciever, here, I know this is not an ideal receiver, but it is my only option currently.
I have to have all of these on the single power supply, due to size restraints.

I put them on a solderable "perfboard," and was able to get it to work well, with just a little interference here and there. I used two ceramic decoupling capacitors, 0.1uF and 1uF.

I am working on designing a PCB for this setup, and am quite new to that area altogether, and especially with such a easy to get interference setup like this. I would like to remove the interference I am currently experiencing.

So, my main questions are:

1) Should I take the input voltage directly from the battery's (6.5v) and go to the servo supply? Then the 6.5 will go to the voltage regulator to 5v. Or should I power both with the 5v?

2) Star grounding, or ground plane?

3) For the decoupling capacitors, since the voltage regulators will have two capacitors already, where and what size should the additional decoupling caps go? For the prototype I just used them as close to the input of the chip as possible.

Thank you so much for any/all feedback. Any other suggestions would be much appreciated. There aren't many resources out there for having servo and MCU on the same supply, but I don't have a choice for this project.

EDIT: There will be very little load on the servo, so it should be at the minimum current draw possible for the servo.


texts: STM32F103 stuck in PLL Ready Flag Set Loop forever!

texts:
we working on stm32f103ret ic and using CMSIS library for setting GPIO Ports, so i have debuged program in keil v5.14 so in debugign mode it's stuck in line 1043 of systme_stm32f10x.c file which is this code :

 RCC->CR |= RCC_CR_PLL2ON;
/* Wait till PLL2 is ready */
while((RCC->CR & RCC_CR_PLL2RDY) == 1)//0
{

as you see in this picture:

and it's clock setting here:

So all of main.c code is here:

#include "stm32f10x.h"

void delay(void);

int main(){
    GPIO_InitTypeDef GPIO_Struct;
    uint16_t N;
    int i;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC,ENABLE);

    GPIO_Struct.GPIO_Mode=GPIO_Mode_Out_PP;
    GPIO_Struct.GPIO_Pin=0xFFFF; // Selects All Pins
    GPIO_Struct.GPIO_Speed=GPIO_Speed_50MHz;
    GPIO_Init(GPIOC,&GPIO_Struct);
  GPIO_Write(GPIOC,0xFFFF);

while(1){
    //GPIO_Write(GPIOC,0xAAAA);
    GPIO_Write(GPIOC,0xFFFF);

    for(i=0;i<16;++i){
        N=GPIO_ReadInputData(GPIOC);
        N=N>>1;
        GPIO_Write(GPIOC,N);
        delay();
    }
}
}

void delay(void){
    int i,j;
    for(i=0;i<1000;++i)
        for(j=0;j<1000;++j);
}

and the whole project is here:

keil files

thanks a lot.


texts: Design guidelines for RF castellated edge connections

texts:
I've seen many examples online of castellated vias at board edges used for module connections. However, all of these seem to be for low frequency signals.
When using a castellated via to connect an RF transmission line from a module to a mother PCB, what are the effects on the impedance matching? How feasible is this, and what considerations should be taken into account?
There will surely be some impedance discontinuity arising from the disruption of the transmission line geometry. I'm interested in whether the loss can be managed to be reasonably small, perhaps comparable to inserting a DC blocking capacitor in series on the line.
It's also intuitive that with increasing frequency, this will be more and more difficult.


texts:
I am trying to design a noise source using discrete transistors and a Zener diode in the avalanche breakdown region. Therefore, I have several questions relating to the use of the diode...

How does the quiescent current effect the noise density?
How much will the noise density vary with time and temperature at a given quiescent current? This will likely determine whether I need to incorporate AGC into my design.
What configuration will maximize the avalanche noise produced by the Zener?
Would using a current mirror in place of a resistor to bias the Zener increase or decrease the noise density?
Would a voltage or a transconductance amplifier be more effective at amplifying avalanche noise?

If someone has a good noise model for a Zener diode operating in reverse bias,  many of these questions can likely be answered. However, I haven't been able to find one, and I don't have the equipment perform the necessary measurements myself.

I currently intend to use a 1N4742 12V Zener in my design.


texts: I do not completely understand the intuition behind equivalent sources used in source transformations

texts: My book states that two circuits can be considered equivalent if they produce the same voltage and current in any resistor connected to the two ends of the circuit.  The book then goes about proving how various different circuits are interchangeable because they produce the same voltage and current in a resistor with arbitrary resistance connected to the two ends of said circuit.  However, what is bothering me is that this strategy seems to assume that the rest of the circuit can be reduced to a single resistor.  But clearly this strategy is used when the rest of the circuit cannot be reduced to a single resistor (such as when the rest of the circuit has a voltage or current source).  Could someone please explain to me why this strategy is still valid in said situation?


texts: Simple questions about current flow and superposition

texts:
So I was doing this exercise to prepare (not homework, school hasn't even started yet), and I think I got the math and the logic right, but there are a few things that I didn't understand, and since my teachers are on vacation I was hoping you could help. Below is a picture with the question that I transcribed and all of my work after it, including my questions: what's the best way to find the direction of the current, if it's positive or negative, and a minor uncertainty that I got regarding simple circuit analysis.

Please correct me if you see any errors.

Thank you so much for reading this far, if there is something you don't understand please ask!


texts: Difficulties with capacitor circuit analysis

texts:
I have been given this question by one of my lecturers and have been having difficulty with it. I was wondering if anyone could help me.

In the circuit of Fig. 1, switch SW1 has been closed, and switch SW2 has been open, for a long time. Capacitor C2 has no initial charge.
Now, S1 is opened; then, at time, t = 0, S2 is closed.

a)  Determine the energy stored in C1 for t<0

b)  Derive expressions for the capacitor voltages, v1(t) for C1 and v2(t) for C2, for t>0

c)  Explain if there is any stored energy in the capacitors as t approaches infinity?

simulate this circuit – Schematic created using CircuitLab

Thank you for all your help guys.
The main issue I'm having is deriving the equations for the voltages across each capacitor. I'm unsure of how to draw up an expression for v2(t) as I think it is strongly related to v1(t) but I'm not sure how to how to formulate an expression for it.


texts: Trying to analyze the audio attenuation.. Is this analysis correct?

texts:
I am learning about impedance. So sorry any stupid question here...

Consider this circuit:

I have an audio input, from 20 to 20 kHz.

I want to know how the AC voltage over AB will behave as the frequency increases from 20 to 20 kHz.

If my math is right, the impedance of the branch AB will be:

Zab = 1000 - j/(2πfC)

Plotting the imaginary part for the frequency range I see that the "length of that vector" (I don't know how to call it... I mean sqrt(a^2 + b^2)) of
Zab will fall from 8kΩ to 1kΩ.

Because the RC group is a voltage divider with R1, I imagine that at 20 Hz we will see a volt divider between R1 (100) and 8kΩ and at 20 kHz, we will see a voltage divider between R1 (100) and 1kΩ.

So, will Vab decrease from 8/9 of the input level to 1/2 of the input level as the frequency increases?

Is this what will happen?


texts:
I have two 90w/12v infrared IR bulbs which is put into a r7s sockets. From thes socket goes in total four wires which is connected to our power supply. We have set two of the wires in serial so they pull 45 watts each, in total 90 watts.

The bulb is 90w / 12v

Our power supply is 12v / 8.3 amps

It should be able to power the bulbs since the power supply is 99.6 w and the bulbs are 90w in total.

But they don't, they cannot power the two bulbs.

However, if we put a bigger power supply which is 10a / 12v then it works.

If we then, after having the bigger power supply connected, switch to the smaller 99,6w power supply then it works as well.

It is only if we try to power the two bulbs directly from small one that it doesn't work.

My questions are

why can't the 99.6w power supply power the 90w IR bulbs? (They are in serial so they use 45w each)

is there a way we can lower the wattage of the bulbs? Maybe a resistance? Something else? I just need to lower them by 5 watts and I'm sure it'll work.

Thanks in advance, and thanks for reading my long post!


texts: variation of thickness of dielectric layer for different textile-based capacitive pressure sensors

texts: For my thesis I am working with textile-based capacitive pressure sensors and I am struggling to see how much variation in thickness of the dielectric layer you can have before you have noticeable impact on sensor output.  If I wanted to have my sensors somewhere between 2x2in and 4x4in for the surface area, and I was using nylon 6,6 for my dielectric layer (dielectric constant of 3.4), and I was testing different construction methods for the nylon (different knits and wovens) and I wanted to keep them as close in thickness as possible, how much leeway is there before the variation in thickness would result in a measureable difference?  Since I am using different construction methods for the dielectric layer there is no way I can make them EXACTLY the same thickness, so I am trying to figure out my wiggle room.  If I have a dielectric layer that is 900µm thick and another that is 400µm  thick, is that going to be way too much variation or is that relatively close enough? I've done the capacitance calculation for each thickness using a 3x3in sized sensor and got a capacitance of 194.318pF for 900µm thickness and 435.924pF for 400µm thickness.  I just don't know what is considered a significant difference for capacitance.


texts: How does this astable multivibrator circuit with FETs work?

texts:
I am having trouble understanding this schematic. I do understand that it is pretty simple, but I just can't seem to get my head around part of it.

The schematic is a more complicated version of an astable multivibrator. I understand how an astable multivibrator works, but I just can't understand how part of this works.

From my understanding, the capacitors that are connected to the gate pin of each of the transistors control whether or not the transistor is conducting. However, the part I'm finding hard to understand is how all three of the capacitors charge and discharge. Also, is there an order of which the transistors will turn on and off?

The LEDs represent an LED strip, so don't need to have resistors to limit the current.


texts: Safely connecting an solenoid/electromagnet to a switch-mode supply

texts:
I'm currently working on a project that involves hooking up an arduino, a cellular shield, and an electromagnet (in this case, one of those old fashioned ringer boxes with a bell powered by electromagnets). I need the arduino to be able to power the ringer - presumably via a relay, and the power supply for the arduino and the ringer electromagnet will be the same 9v wall wart.

I know the arduino and the cellular shield have their own regulators, but should I be concerned about effects the inductive load of the electromagnet might have when it's turned on and off? What precautions should I take besides the obvious reverse-biased diodes?

Further, in order to use the ringer effectively, I need to be able to pass current through the electromagnet in both directions (each polarity moves the striker in a corresponding direction). Can anyone suggest a simple circuit that will achieve this with a minimum of external componentry?

Edit: Does this look like a reasonable interface circuit? It seems involved to use two relays to control a third electromagnet, but I can't think of another way to achieve what I need.


texts: How to program PIC 12F629 internal oscilator in C?

texts:
I have some troubles understanding the datasheets when comes to use the internal oscilator in a PIC 12F629, using C (MPLAB X IDE + XC8 compiler). Also I don't have any PICKIT or anything, I use a DIY K150 programmer. I have read that the manufacturer calibration could be erased when I burn the  program. So the specific question is: Which would be the code to use the internal oscilator? (__CONFIG ?) Feel free to recommend a burning procedure.
PS: Sorry for the bad english...


texts: I have an old Soviet personal radiation dosimeter that I broke as a kid by dropping it into water. I opened it up a while ago and the electronics in there were quite simple - mainly a ~10cm Geiger tube and what looked like Soviet variants of standard logic ICs. The tube looked intact - is there a way for me to test if it's worth salvaging, though?


texts: Is an ADC always necessary between 8051 and zero crossing detector?

texts:
I am making a SCR(Thyristor) trigger by using 8051 microcontroller.
I have a here is a zero cross detecting (ZCD) circuit which detects the zero points and this is conveyed to the 8051 which will do further action.

The ZCD circuit is made up of BJT transistor(s) and gives a pulse of 5 V . So is it necessary to add an ADC in between the ZCD and 8051?

PS:I am trying to first simulate in multisim, and its not working (I have directly connected the output of ZCD to pin p1.0 of 8051).

edit(updated problem):sorry for not clarifying the problem.I mistakenly used led word for probe thinking both are same. You can see one round thing connected to pin P2.0(bottom right). It is the probe. What I was trying to do is to detect the pulse from ZCD and convey it to 8051. 8051 will take the input and turn on the probe, and then again go for checking it.
SCR(with optocoupler) will come in place of probe, but thats second part. I am just trying to make the first part work correctly.The probe blinks at first -90 to 0 while it should only blink when the pulse is given to p1.0 port.

$MOD51  ; This includes 8051 definitions for the Metalink assembler
ORG 0000H;
loop:MOV P2,#00H;//make probe off
SETB P1.0;//make the p1.0 as input port
AGAIN:JNB P1.0,AGAIN;//loop here until p1.0 is high
MOV P2,#0FFH;//turn on the probe
sjmp loop;//go for checking the pulse again-infinite loop
END;


texts: How to increase the peak current to 12 kA in my circuit?

texts:
I am simulating a circuit with a capacitor bank.  I am getting maximum peak current to 8.8kA.
I need to know how can I increase the peak current to 12-15 kA without increasing the input voltage. The input voltage must not be larger than 1000 V.
If I use 15 capacitors instead of 10 I am still getting the same results. I don't know why.
I am also posting the photo of my circuit. Please help me and tell me whether I need to change the values of the elements in my circuit.


texts: Why do Bluetooth modules always include the whole protocol stack

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I was looking to add Bluetooth connectivity to some embedded design, and I was surprised to see that all modules available have a complete protocol stack included, that (as I see it) seem to limit you in what you can do with it. Depending on what you want to do, you have to choose the right module implementing the profiles you need, and you'll talk with the module using fairly high-level commands.

I was actually expecting there was some basic modules taking care of only the physical layers (just "sending raw packets" over the air), and with which the upper stack layers would be implemented in software on a MCU (the current design has a powerful one running Linux available). This is what is usually done for USB, ethernet, and pretty much everything else. It seems to me that it would be much more flexible this way (you could even, let's say, create your own proprietary Bluetooth profiles). But unless I missed something, it seems it doesn't exist.

Even though I can accomodate with this, I was wondering why is it this way?


texts: Differences in Metallized Polypropylene Film Capacitors

texts:
I have two capacitors, and they are both Metallized Polypropylene Film Capacitors, but they look pretty diferent to me, one is red, a little bit shiny with round corners like this:

and the other is yellow, opaque, with square corners and has a lot of information written on it:

Why are they so different even if they are in the same category of capacitors? Is it just aesthetics? different manufacturers? or are they used for different applications?