texts: header file and register configuration settinggs for MSD usb implementation using pic18f4550

texts:
I want to implement USB mass storage device class as well as the human interface device class, the controller I am using is the PIC18F4550.

since I am very new to microcontroller, can anyone please guide me for this?

Here are some of the details of my task, I have used the given code, modified it a bit and had run the simulation, I could just detect my usb device attached with controller.
I am using Proteus 8.0 and MicroC 6.0 for simulation purpose.

I haven't included any header(.h) file yet, I have knowledge of including USBdsc.c i.e. the descriptors file, I don't know yet, which else to include.

//---------------------------------------------------------------------------------------------------
unsigned char readbuff[64] absolute 0x500;   // Buffers should be in USB RAM, please consult datasheet
unsigned char writebuff[64] absolute 0x540;
//---------------------------------------------------------------------------------------------------
void interrupt()
{
   USB_Interrupt_Proc();                   // USB servicing is done inside the interrupt
}

void lcd(char d[64])
{
 char l[63];
 int a=0;
 for(a=0;a<63;a++)
 {
  l[a]=d[a+1];
 }
 lcd_cmd(_lcd_clear);
 lcd_out_cp(l);
}
//////////-------------------------------------------------------------------
int strToInt(char *string)
{
 int output = 0, i = 1, stringLength = strlen(string), temp = 0, numberLength = 0,j;
 char tempCh;

 for(j=0;j<stringLength;j++)
 {
  tempCh = string[j];
  temp = tempCh - 48;
  if (temp >= 0 && temp <= 9)
  {
   numberLength++;
  }
 }

 for(j=0;j<stringLength;j++)
 {
  tempCh = string[j];
  temp = tempCh - 48;
  if (temp >= 0 && temp <= 9)
  {
   output += temp * pow(10, (numberLength-i));
   i++;
  }
 }

 return output;
}
 // pwm function////---------------------
void pwm(char d[64])
{
 char l[3];
 int a=0;
 for(a=0;a<3;a++)
 {
  l[a]=d[a+1];
  }
 for(a=0;a<5;a++)
 {
  portc=~portc;
  vdelay_ms(strtoint(l)*10);
 }
  //pwm1_set_duty(l);
//  pwm1_start();
}
 //---------------------------------------------------------------------------------------------------

void main(void)
{
 int a;
 //-----------------------------------------------variable area--------------------------------------
 trisb=0; // port as output
 portb=0xff;
 trisc=0;
 portc=0xff;
 ADCON1 |= 0x0F;                         // Configure all ports with analog function as digital
 CMCON  |= 7;
 lcd_init();
 lcd_cmd(_lcd_cursor_off);
HID_Enable(readbuff,writebuff);      // Enable HID communication
pwm1_init(5000);// start pwn module and  set on 5 KHz

while(1)
 {
  if(!(hid_read()==0))
  {
    /*usb_read_filter(readbuff);*/
    /*lcd_cmd(_lcd_clear);
    lcd_out_cp(readbuff);*/
    if(readbuff[0]=='0')
    {
     lcd(readbuff);
    }
    else if(readbuff[0]=='1')
    {
         pwm(readbuff);
    }

    while(!hid_write(readbuff,64));
  }// if Data read  endz

 }  // while endz
}


texts: Help selecting zener diode and resistor values (reduce voltage to talk to raspi GPIO)

texts:
Hi i am trying to connect the obstruction sensors on my garage door to the GPIO pins on a raspberry pi computer so i can monitor the state.

Since the garage door sensors runs on 6v and my raspi runs on 5v i was told to use a zener diode tied to ground, and a resistor to connect it to the raspi without frying it.

Is this hardware going to do what i want safely? (drop the 6v down to 5v so i can read the signal on the Pi and do something in software when i see a state change)

thanks


texts: STM32 RTOS2 execuation code failed, it doesn't execute the thread properly

texts:
Here is my first RTOS2 under CMSIS library code. I need to know why it doesn't change the states of my LED.

/*----------------------------------------------------------------------------
 * CMSIS-RTOS 'main' function template
 *---------------------------------------------------------------------------*/
#include <stdio.h>
#include <string.h>
#include "stm32f10x_gpio.h"
#include "stm32f10x_rcc.h"
#include "stm32f10x_usart.h"
#include "RTE_Components.h"
#include "cmsis_os2.h"
#include "rtx_os.h"
#include "rl_net.h"
#include "cmsis_os.h"

/*----------------------------------------------------------------------------
 * Application main thread
 *---------------------------------------------------------------------------*/

char i;

 void CLOCK(void){
    RCC_HSEConfig(RCC_HSE_ON);
    while(RCC_WaitForHSEStartUp()==ERROR);

    RCC_PREDIV2Config(RCC_PREDIV2_Div5);
    RCC_PLL2Config(RCC_PLL2Mul_8);
    RCC_PLL2Cmd(ENABLE);

    while(RCC_GetFlagStatus( RCC_FLAG_PLL2RDY)!=SET);

    RCC_PREDIV1Config(RCC_PREDIV1_Source_PLL2,RCC_PREDIV1_Div5);
    RCC_PLLConfig(RCC_PLLSource_PREDIV1,RCC_PLLMul_9);
    RCC_PLLCmd(ENABLE);

    while(RCC_GetFlagStatus( RCC_FLAG_PLLRDY)!=SET);

    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

    RCC_HCLKConfig(RCC_SYSCLK_Div1);
    RCC_PCLK1Config(RCC_HCLK_Div2);
    RCC_PCLK2Config(RCC_HCLK_Div1);

    while (RCC_GetSYSCLKSource() != 0x08);

}

__NO_RETURN void app_main (void *argument) {

//  osThreadTerminate(osThreadGetId());

    while(1) {
        if(i==0) {
            GPIO_SetBits(GPIOA,GPIO_Pin_4);
            i=1;
        } else {
            GPIO_ResetBits(GPIOA,GPIO_Pin_4);
            i=0;
        }
    }
}

int main (void) {

    GPIO_InitTypeDef GPIOStruc={0};
    CLOCK();

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);//Map

    GPIOStruc.GPIO_Mode=GPIO_Mode_Out_PP;
    GPIOStruc.GPIO_Pin=GPIO_Pin_4;
    GPIOStruc.GPIO_Speed=GPIO_Speed_50MHz;
    GPIO_Init(GPIOA,&GPIOStruc);

    osKernelInitialize();                 // Initialize CMSIS-RTOS
    osThreadNew(app_main, NULL, NULL);    // Create application main thread
    osKernelStart();                      // Start thread execution

    while(1){}

}

In addition, I need to know:

app_main runs repeatedly? it means if I use "   netInitialize ();"
function right after "app_main" it repeats it many times or it just got stuck in "while(1){" loop?
how a thread can be run after a specific time ( for example each 500us)?


texts:
I am using twisted pair cable for LVDS communication between the Host and the display. It was recommended that the differential impedance of cable should be 100ohm (+/-5%).

Let me know how to measure and verify the differential impedance of a twisted pair cable before using it in any system. I want to do only in cable level by not connecting it with host and display.


texts:
What do you call this plug as a whole? It has 2 pins and a grounding/earthing wire protuding out. As i do not know the name of this plug, I do not know how to properly use it or even know that its safe to use. Is it a fire hazard to use this kind of plug?

PS. It came inside the box when I bought a Philips monitor. Its supposed to be the mains cable that connects to the outlet


texts: How to unite three different batteries in to one powerbank

texts:
I'm absolute beginner in electrical engineering and I need help in building a powerbank using three different batteries with different characteristics.

I have a sudden passion to implement this project because it's very interesting to me and I want to create my own powerbank and don't buy a new one branded by Xiaomi etc.

What I have now is 3 batteries:

Biggest one (black color) it is a used battery. I came out of a Asus Nexus 7 2012 and its capacity decreased by big amount of cycles of charging/discharging. It has strange black black yellow white red red wire and I don't know exactly where is + and - and I have no tool with help which I can detect it.  How can I determine its conbections? Its capacity is 4325mAh, 3.7V and 16Wh (as it described on photo below.)
Middle size one (silver color.) It is a new battery (about 5 charges/discharges) and it was used in a case-powerbank for my iPhone (it accidentally crashed and I've extracted the battery.) Its capacity is 5000mAh, 3.7V and unknown Wh (I'll update my question once I get it.)
Small size one (silver color.) It is a new battery (about 10 charges/discharges) and it was  used in powerbank for my iPhone (it accidentally crashed and I have extracted the battery.) Its capacity is 2020mAh, 3.7V and 7.68Wh or 7.88Wh

I want to unite them all sequentially so all capacities will be added (4325+5000+2020.)

Only one my requirement is I need 1 usb port for this powerbank and it should be 1 ampere (non high voltage) because it's completely enough for my iPhone 6s.

I'm going to print a case on 3d printer from plastic.

Is it possible?

Can you give advice me, please, what I have to buy and what I need to learn and may be some blueprint and some voltage balance board(correct me if I'm wrong) and some other boards and where I can buy them (quality board, please.)


texts: Can I somehow use a neon bulb as a switch?

texts: I’m trying to create a timing light. Due to the lockdown I can’t get any other parts. I have a neon bulb which does light up when I hold it next to the spark plug lead but it is too dim to be useful. Is there any way I could somehow use this as a switch so I could light up another LED?


texts:
I understand that decoupling capacitors are small capacitors (often 100nF) used on VCC/VDD on ICs. When are they most required and when is it just silly using them on every IC.

Are they better used at higher operating frequencies?
Are they better used with repetitive signals?
Are they better used with more important parts of a circuit?
Should they always be used on every IC?


texts: High-current capable (±250A) AC power-supply, sine wave/square wave (±20V)

texts:
I hope you will find patience to read my beginner question.

I need to do some test on a diode using a simple setup: AC power supply + load + diode. The problem is that I must generate a sinusoidal or square waveform with 8 periods (the period duration varies from 300us up to 10ms), with amplitude varying between ±10V and ±20V,0V DC Offset (at least ±0.5V steps) and peak current up to ±250A.

These would be the ideal specifications. The minimum would be ±200A, ±10.5V and ±20V, 100Hz and 3Khz, sine or square waveform, 8 periods.

I'm not familiar with such kind of tests and I don't have any experience in this field. I'm asking here hoping someone having more experience in this field can recommend me some an alternative or some instruments.

I've searched on the internet for some instruments but I can't find something which is suitable for my setup. Or maybe I don't know exactly what to search.
I've found some 4-Quadrant Amplifier and AC Sources but always are limited: if they have current capability then they have limited output voltage or vice versa.

For the load I think I can use something from http://www.frizlen.com/en/home/ but I'm not sure. I need a resistive load between 50 and 100 mOhm.

I've also thinked to create an DC-AC Pure Sine Wave inverter without a 220V transformer at the output, and power it from a High Current DC Voltage source.
I've found this document:

https://www.wpi.edu/Pubs/E-project/Available/E-project-042507-092653/unrestricted/MQP_D_1_2.pdf

in which they explain how to design a pure sine wave inverter and I want to ask the community if this idea might work, keeping in mind that my required output frequency are between 100Hz and 3KHz.

Is anyone who can advice me or suggest how to generate these waveforms?
Thank you in advance :)


texts: multi-tap transformer relay for LM317 tips

texts:
Example circuit:

Since LM317 is a linear regulator it will get very hot when i try to draw around 1 amp @1.25v with a 24v input. The transformer i have at home have these taps:
24v
12v
5v

Is it possible to add some kind of relay to make the transformer switch tap when the voltage gets over/under a specific voltage? I would prefer that the transformer automaticly switches tap. But if that is too advanced for me i can go with a manual a way (a switch) that changes the tap.

LM317 Datasheet

Thanks!


texts: Voltage control relays, Should I use separate power supply circuits?

texts:
I have to realize a relays PCB board controlled by a MCU (arduino micro in the first stage) and a ULN2003, as for example in the attached figure I found in Internet with some other components.

What I would like to understand is if I need a separate power supply line to power the ULN2003+Relays. I ask this question because in almost all the industrial application I have seen, they use 3.3/5V to power the MCU and a dedicated 12V line to power the relay control even if they use separate discrete transistor in place of the ULN2003.

In terms of required current, also with 5V type relays I should stay safe, because the ULN2003 can supply up to 500mA (single output) and a generic 5V relay datasheet indicates a nominal current required to switch to about 80-100 mA. A 12V relay requires 30-40 mA to switch.

So, why in this industrial applications they use 12V to control the relays?

I would like to know if they need to isolate the MCU power supply to avoid  some spikes/noise generated from the coil on/off that could reset the MCU (although they use the reverse diode to avoid this).
Or, they need to reduce the current to drive the relay in order to match with their discrete transistor driver (a 12V relay need less current than a 5V type)?

If you suggest to separate the power supply, could I use two separate (with two regulator) 5V line instead of a 5V + 12V? And in this case, I could connect togheter the two grounds of the two power lines in the PCB?


texts: What is meant by soft strap and pin strap (HW strap) in a processor datasheet?

texts:
I was referring the Intel processor datasheet and it mentions about pin strap to configure various functionalities.

Why is it called strap pins? Has it got anything in relation to 'bootstrapper'?
What is exactly meant by soft strap? Is it accessible to the user during BOOT process?

Intel 495 Series Chipset PCH datasheet- Page 46


texts:
I have a ~20 year old Weller station (base: 921ZX-0, iron: 9216, tip: U9960) for which I've lost all but the 9960 tip. Searches for Weller/Ungar 9960 as a starting point for finding compatible tips have proven fruitless. 20-year-old Jensen Tools catalogs are not the sort of thing Google Books ever scanned :)

Which line of modern Weller tips would be compatible with this old beast?


texts: Are all electrical sockets of my house in the same phase?

texts: Most countries use AC power that is supplied to each house. This AC power is in the form of a sine wave. Suppose I have 2 electrical power sockets in two rooms that are at the opposite ends of my house. Will both the electrical sockets provide the same sine wave that is in phase or will the voltage have a constant phase shift between the two?  Which of the two graphs does it resemble?:-


texts: What is a short circuit at the electron level?

texts:
I'm trying to understand when you can say a circuit is being "shorted".

Obviously you are creating a short circuit when you hook up the two ends of a battery with a wire. But the wire does offer some resistance, even though its extremely little.
What if you hook up the two ends of the battery with a 1 ohm resistor? Is it still being shorted?

So where is the line drawn between shorting and well, not shorting?
What is actually happening to the electrons in both cases?

Thanks!


texts: pwm after constant current switching driver

texts:
I have searched, but cant find an answer for my specific setup. I have a Xl4015 switching contant current source for my 10w LED set at 1000mA. I would like to add a pwm dimming circuit to switch a mosfet on the led ground. I am using an arduino to create the pwm signal that connects to the mosfet gate. It does dimm, but I do not have an oscilloscope and cant tell if there are any voltage or current spikes each time the led turns on and off.

Will pwm cause any current spikes in this case? Or could it damage the xl4015 circuit?


texts: Error in simulation results for balanced pi type attenuator

texts:
I wish to design a balanced pi type attenuator to give attenuation of 20dB and characteristic resistance of 500 ohms.

I have found out the necessary resistances required to design the attenuator. However upon simulation on ISIS proteus, the results are not what I expected. For input of 40V, the output is 7.92V instead of 4V. Where am I making a mistake?


texts:
I have built a DDS (0-80MHz) with an FPGA (XC3S400) that I can program it for making almost any wave form (limited frequency by the wave form complexity). After weeks of struggling with making a suitable low pass filter for it, I realized that it is almost impractical to build a near perfect analog filter that can remove all high frequency images (Nyquist) + all low frequency aliases (photos of the results here; hindrances made by low frequency aliases in DDS, figure-1 here).

Now I want to turn into a low pass (or preferably tunable band pass) digital filter but I really have not time for learning DSP from the scratch. I searched some major companies (Analog Devices, Texas Instruments,...) for a dedicated digital filter product but my search always redirects to DSP products.

I want to know if there are dedicated digital filters with a simple interface (for example, frequency selection by a micro-controller interface or something?). For example, sending the desired filter behavior via a serial/parallel word to the device and it works with that.

Edition:

I realized from the answer below that I can use the current FPGA for my purpose. I tried 2 approaches: 1- DDS > DAC > ADC > FIR (FPGA ) > DAC.   this makes again aliases related to the DAC.   2- DDS > FIR ( no external ADC ) > DAC.  This is not bad but the problem with aliases remains to some extend.  I am looking for a good resource / method of thinking for this problem ( the easiest perhaps ! )


texts: What are the practical implications of changing the rolloff factor of a root-raise cosine filter?

texts: This is in regards to digital communications. I have a link I've set up using GNURadio that's sending BPSK modulated data through water via a LED. I can control the roll-off factor, $\beta$, of the root-raise cosine filter. What are the practical implications of this number? It seems that any value should work fine, since it fulfills the nyquist criteria (adjacent symbols have zero energy at the current symbol's sample point) and the energy/frequency is constrained. Is it mostly just a way to control the affects of jitter vs. slight savings in bandwidth?


texts: Using an Audio Signal for a Control Voltage for an Analog Synthesizer

texts:
I have a Moog Sub 37 Analog Synthesizer and a Korg SV-1 keyboard. Can I take the audio out of either the line outs or headphone out of the Korg and plug it into the volume or filter Control Voltage (CV) in of the Sub 37 to affect those controls as a control voltage? Moogs take a +/-5V CV signal. I'd just go ahead and do it but I don't want to damage anything.

If that can't be done directly, is there a way to convert an audio signal into a control voltage signal?


texts:
I had the crazy idea of making a lamp for my soon-to-be-born son. It is a bunch of LEDs (about 205.. yes I know...) representing a picture. The LEDs vary slightly in voltage and current specs, but I don't need all of them to burn full power regardless. So I plan on going with the 'safe' limits that go for all LEDs which are 2,5V and 20mA.
I understand the concept of placing a resistor of 'n' Ohm to make sure to not burn out the LEDs. I also am aware of the concepts of parallel and series set-ups. But... (here it comes)... I am unsure how to hook up these lights and to what power source.
Going by the calculations I have seen, I either end up with a 512,5V (all in series) or 4,1A (all in parallel) power supply. So I reckon I need to split it up a bit in a combination of series and parallel, but this is where I'm stuck at. Any help would be greatly appreciated!


texts: Replacing a magnetic speaker with a non-magnetic one

texts:
I need to mount a speaker next to a magnetic compass. Any suggestions?

I have a becker radio which comes with a traditional 4 ohm moving coil magnetic speaker. Due to space limitations I don't really have much choice about where to mount it, and it's going to be so close to a compass it's likely to interfere with it. So far my research has suggested that a piezo speaker (no magnet!) is NOT a like-for-like swap.

What are my options? I can't really change the design of the radio, is there a driver-circuit or converter that will allow a piezo speaker to be driven off a radio designed for a moving coil magnetic speaker?

My only other option is embark on physically moving the speaker, which (because it's in an aircraft) will require paperwork (a far more daunting challenge than anything engineering!)

What do others do? - the aircraft is a glider, and most glider pilots use GPS to navigate.


texts: Pull-down resistors on logic gate and decoder inputs?

texts:
I'm designing a very basic circuit for testing a switch sequence. I'm using a CMOS decoder CD4028B (link to datasheet) and XOR gate (CD74HC86E - link to datasheet). Reading the switch sequence is crucial and therefore I've been thinking whether I should add pull-down resistors to all inputs of the decoder and XOR gate to prevent pin-floating and false readings? I went through the datasheet and there was no recommendation whether pull-downs should be added to prevent pin-floating. Do these logic gates usually provide internal pull-down resistors or is it necessary to add them yourself? What values are recommended? I want to draw as little current as possible. I'm sorry if this is a really basic question. We made quite a few circuits with logic gates in college but never talked about the pin-floating and current draw aspect of these circuits.

Inputs of decoder are wired to the switch that is being tested, outputs of decoder are then wired to XOR gate inputs and XOR gate outputs are then wired to BJTs to drive LEDs.

Any help would be greatly appreciated. :)

Thank you.


texts: Why is the input voltage of transistors in the CMOS circuit set to Vdd when calculating the equivalent resistance?

texts:
When deriving the equivalent resistance formula of NMOS inverter the graph which is used in derivation is  as shown:

$$R_{eq} = \frac{1}{-V_{dd}/2} \int_{V_{dd}}^{V_{dd}/2} \frac{V}{I_{Dsat}(1+\lambda V_{dd})} dx \approx \frac{3}{4}{V_{dd}}{I_{dsat}}(1-\frac{7}{9}\lambda V_{dd})$$
When calculating the equivalent resistances of NMOS and PMOS transistors in a CMOS inverter i was instructed to use this formula and for the saturated current which plays a part to take $$I_{Dsat}=\frac{B}{2}(V_{gs}-V_t)^2 = \frac{B}{2}(V_{dd}-V_t)^2$$ where B is a property of the transistor.

Why is Vdd taken as the gate-source voltage of both transistors for the saturated current if neither is in saturation at that point on the V(output)=V(V(input)) graph of CMOS inverter and why is it used in the derivation in the first place? How is it connected to the resistance which we want?

Edit: The resistance i'm asking for is the dynamic resistance of the transistor used when calculating the time-delay of the rising and falling edge of the graph. The equations of time-delay are given as:
$$tp_{HL}=0.69R_{eqn}C_l$$ where Cl is the capacitance of the inverter and tpHL is the time for output voltage to go from logical 1 to logical 0 (highest and lowest voltage). This "discharging" of the transistor is done by the NMOS transistor so Reqn is it's dynamic resistance. Similar is with Reqp (tpLH). The formulas above are connected to this Reqn and Reqp but i don't understand the way it's calculated and why it uses Vdd for both transistors when calculating the saturated current when they are not in a state of saturation at that voltage, rather NMOS is linear and PMOS is turned off.


texts:
For Inter-task communication or to share data between two tasks of RTOS, We use Queues.
But Problem with Queues is that they are slow.... They copy data in Buffer then Mutex Handling and then Data Transfer. It's irritatingly slow if you have to transfer large data.
Another problem is if same queue is accessed by Multiple tasks. Then Picture becomes like this:- First Wait to get access to The Queue then Queue internal Mutex Handling then Data Transfer.

This increases overhead on the system. What could be the Efficient replacement for Queues?

(I guess this question is Independant of RTOS we use. Most of the RTOS handle Queues in this way only)


texts:
I have two circuits connected by a shielded cabled. The cable brings 3.3V DC and LVDS communication between the circuits. The shield is being used as the sole conductor for the reference ground to the load side of the circuit.

This doesn't seem right, I know for high frequency shielding the shield should be connected to ground at both ends, but isn't that based on the thought that the ground current is to be primarily carried by a separate conductor?

Should the cable be more like:

Shield (drain)
GND
3.3V
TX_P
TX_N

instead of:

Shield (drain)
3.3V
TX_P
TX_N


texts:
I have probably a few hundred datasheets and app notes that I've collected for all sorts of parts in projects I've worked on.

Previously, I used to keep these on a basic network share sorted maybe 2-3 folders deep by rough category, but then Google Docs added a PDF reader and the ability to upload them, so I tossed them on there.  The "folders" are more abstract (a la Gmail categories), so you can put a datasheet into multiple folders (e.g. a voltage regulator also could go into LED driver folder or under the manufacturer), though this has some limitations, such as searching for text in large documents only shows the first few, and of course, dependency on an internet connection.

What other methods are there to store hundreds of datasheets/PDFs in an easily accessible manner?  Would it make any sense to use some sort of VCS?


texts:
I am reading a following Application Note about microphone amplifiers:

Here is the circuit:

At some point author says following:

  Resistor R1 and capacitor C3 form a high-pass filter. The corner frequency of this filter must be low
  enough to not attenuate low-frequency sound waves. A 5Hz corner frequency is used to calculate the
  value of C3:

How can R1 and C3 be HP filter since ac input impedance of the OPAMP circuit is impedance of C3 which is said to have high capacitance value. Even if we consider FET as a current generator in ac modus, it will see on the drain R||Zc which is LP filter.


texts: How to create a simple circuit with your body

texts:
I recently visited a museum with my son, and we both enjoyed an exhibit where there was a partially completed circuit that was completed when you touched the two end points or joined hands and each touched one of the end points.  The setup had a D battery and a small array of LEDs.  The LEDs would light up when you completed the circuit with your body.

My son asked me to make one for him at home, so I took an array of LEDs from a flashlight and soldered together a similar setup.  The problem is that it didn't work when you completed the circuit with your body (it did when you used something with less resistance, like a wrench).

What am I missing here?  I'm no electrical engineer (I'm a computer science/math geek but I do like to tinker around with electronics and I have a working knowledge of residential electrical setups), but it seems to me the issue is related to the resistance of our bodies.  If that's the case, then how could it ever work like it did in the museum with such a small power source?  How can I get my experiment working?


texts:
How can this 5V 3W power supply board be mounted and electrically connected to a custom designed PCB?

Or will it be better to get this power supply board instead due to the right angled pins which I am guessing can be soldered to the main PCB providing both mechanical and electrical connections? But I need 3W off the 5V rail, which this unit cannot seem to provide (only provides 200mA off the 5V).


texts: Are ATA and SCSI commands implemented differently from vendor to vendor?

texts: While researching the SATA and SAS interfaces, I began to wonder how certain ATA and SCSI commands/features are implemented from one vendor to another.  In other words, while the hardware interfaces are standard, is there any standard implementation used in the firmware? For example, would it be incorrect in assuming that Western Digital's implementation of native command queuing is completely different from Seagate's?


texts: distance between linear and non-linear function of op-amp system

texts:
I have a circuit which I have taken a picture of as you can see, in which i have values of
$$R1=1k\Omega,R2=10k\Omega,R3=10k\Omega.R4=10k\Omega,R5=20k\Omega$$
and sine input signal with off-set value=0, amplitude value = 0.1V and frequency=1kHz.
I have two questions about this circuit:

How can I calculate the voltage gain in this circuit with pspice? Beacuse when I calculate it myself, I get voltage gain = 20, but when I divide the Vo by Vi in pspice, it shows a very large number. So how can i calculate it with pspice?

How can I calculate the distance between linear and non-linear behavior of this circuit?


texts:
I am designing a circuit, to use an ADC(mcp3008) to read voltage, current, and temperature sensors. I have a few questons about this, as I have never done this before.

I am going to use single ended mode; Can I just plug in the sensor directly to the ADC, or does it need to go through some processing or filtering?
I need to read voltages that vary from 90-108v the maximum voltage that my board can supply the ADC for Vref is 12 Volts. How can I read this high voltage?
Are there any additional considerations that I should keep in mind to make my circuit as reliable as possible?

Thank you for your help!


texts: Stopping frequency drift NTX2B FM transmitter

texts:
I'm following the instructions here to connect an NTX2B (datasheet) to a Raspberry Pi Pico.
I have the circuit and code working correctly, however I'm having an issue with the frequency drifting.
The carrier remains stable, it is the modulating frequency that's the issue.
This frequency is determined by the voltage applied to the TXN pin on the NTX2B (VCO.) This is controlled by a voltage divider (resistors) and GPIO on the Raspberry Pi. I'm assuming thermal effects on the resistors are negligible and the Raspberry Pi GPIO voltage is stable
The circuit is currently assembled on stripboard, and solder quality is ok. No obvious shorts.
I do not currently have an antenna attached, ruling this as an issue out given the carrier is stable, and not seeing harmonics in waterfall chart.
Changing power supply has made no difference.
Anything obvious that I'm missing?


texts:
My understanding of transistor is that in it a tiny current controls a huge current.  I get that concept. If that is the case, it is not amplifying anything in my opinion. Sure it does dictate when the huge current can or can't flow but it is doesn't change the huge current in any way I think.
Is it correct to call a transistor an amplifier?
So after going through the answers and bit more reserach I think I found the answer. This is what I think is happening. In transistor, Ic is proportional to Ib (and i think this is the key). So since Ic is proportional to Ib, Ic is an ENLARGED COPY of Ib. So if Ib is our input signal, Ic becomes enlarged copy of that input signal and that is why we say it is acting as an amplifier (creating an enlarge copy of the input). Please let me know if this interpretation is correct.


texts:
I want to just get an idea about the complexity of a hobby project before getting started on it.

I want to use a sensor that outputs an analog voltage. However, I want to use an A/D convertor to convert this into a digital value and then feed this into a PC via USB. The analog voltage is between -5V to +5V.

I would really appreciate any links/guidance in what I need to read more about? I'd be happy to clarify anything?

A second question would be that if I need to provide power to the sensor, what circuitry should I be looking into?


texts: Only beta simulator and beta MPASM assembler for 16F1503

texts:
My previous question makes me wonder whether it is even possible to develop with beta simulator and beta MPASM assembler support for 16F1503 (yellow dots):

If I can't expect workign end product, how can I write code in assembly for this particular MC? Can someone explain this? Why is MICROCHIP selling MCs, if there is no support for them? Those are questions arising in my had... Is there an explanation?

I am using the latest software:

IDE:       MPLAB X IDE v1.20
Compiler:  MPASM v5.45


texts:
There is a DAQ system where one of the input is measuring pulses.
As in the figure the pulse signals are coming through a BNC cable entering into very small box called "8V clamp"
and leaving this little box with a BNC and going to one of the DAQ channels to measured.
I noticed that if the pulse amplitudes are greater than 8V this little box is stepping them all down to 8V.
But if the pulse amplitude is less than 8V pulses passes through without any change.
I think it is somehow protecting the input of DAQ kind of limiting to 8V.

My question is what can this circuitry be? A comparator or?
And it has only BNC connections which carry pulse signals.
If it has opamp in it how can it be powered since BNC only is carrying the signal and there is no other wiring to this little box?


texts: Microchip's pic-as throws syntax error on macro define

texts:
I have a file with a name like xxxx.asm
in it I have:
InitPORTA  MACRO
pic-as throws a syntax error on this line.
The code compiled fine with:
mpasmx -rdec pic-code.s
I thought *.asm files were the file type that pic-as took to mean assembly with no C contructs in them and would thus assemble them as the older assembler did.
Is there something obvious I missed?


texts:
I have built the circuit below and am trying to get the lights to go into wig wag using the relay (wig-wag is often used in emergency response vehicles with red and blue lights flashing or orange lights). I am getting my op amps to create a decent sine signal that should throw my relay on and off but it is not doing so.

I also want to implement a way to make the lights stay on at the same time and stay off using some sort of switch. I believe with the lights tied high I should be able to tie a switch to ground and use another to disconnect the switches from the relay.

"A wig-wag is a device for flashing an automobile's headlamps at a preset rate. In its traditional form a wig-wag constitutes the illuminating of the right and left headlamps alternately, with each lamp lit for around half a second at a time." source:source link


texts: is it true that if MOSFET are used in parallel, their thermal resistance (e.g. thJA) can be combined just like paralleled resistors?


texts: Parallel lipo batteries with mcp73831 charger IC

texts:
After reading this very informative blog about load sharing while charging batteries, I'm planning on using an MCP73831 in the same configuration as detailed by the blog for use in a project I'm working on.

In my project I have a space of 9.0*18*48mm to fit batteries within, but since that is an odd size and most batteries I've found on alibaba/aliexpress are very flat, I was going to solder two of these lipo batteries in parallel and stacked on top of each other to fill in the space and maximize my battery life as much as possible.

Assuming I'm using these two identical, single cell batteries and they will be joined while at the same level of charge, are there any other concerns that I should address? My assumption is that it should be fine, and I can continue to use the given circuit as shown.


texts:
After designing a board in Kicad with an SMT32L0 on it, I sent it to seeedStudio and when I received it, I noticed that some of the pads on the stm32 are missing soldermask:

I checked the gerber file for the soldermask and there is no apparent hole in the stm32 pads  :

I noticed that the pads missing the soldermask are tied together, but in two place there is also a pad that is not tied to the rest of the group that is missing soldermask which makes this impossible to solder by hand.

Upon inspection with a microscope, I noticed that the missing areas are all in the same shape which looks like this :

(blue is pads and copper and black is the cutout in the soldermask)

What happened with my pcb?

Here is the back soldermask layer with a gerber viewer :

with the back copper :


texts:
I have a 15 year old ReplayTV DVR. I got it used, I'm not sure when, but probably about a decade ago. It's turned on almost all the time, and it has a blue power LED on the front.

The LED FAQ says that many LEDs have a rated lifetime of 50,000 hours, which implies that it should only last about 5.5 years when used 24x7. Green Efficient Homes says that "an individual LED may well last 100,000 hours", so that bumps it up to 11 years.

These sites seem to be about LED light bulbs, not the individual LEDs that are used as indicators on electronic devices.

Why has this little guy been able to keep shining continuously for so long?


texts:
I have a project requiring a switch (I supply 4.8V, the switch stays off. I supply 5V, it turns on.) After some testing and asking several questions, I realized that the MOSFET I was using would not cut it. In EE.SE chat, I was informed that a comparator could solve my problems. Doing some research, I found a schematic for an OP Amp Comparator. Changing it a bit, I got this:

Assuming this works, how would I choose an OP amp to  work here? Looking on Digikey and several other online electronics stores showed me that I know next to nothing about OP amp specifications.

Generally, I want it to be fast (Using the FET for high-speed switching), and can handle 5V plus a margin (call it 6-7V?) What should I look for on a spec sheet that represents those things? Also, since there were about 10 different option tables, what would be a good, nothing fancy, set of specs to work from?


texts: Opto isolator + triac vs. solid state relay for high AMP arduino project

texts:
I building an arduino device to turn on/off a high current (~10A/120V) oven.  I was planning on using a solid state relay like this.

I keep seeing advice that talks about using an opto-isolator AND a triac for such things.  Am I misguided that a solid state relay with sufficient VOLT/AMP rating will work fine?


texts:
I am fairly new to computer architecture and having a tough time solving problems based on pipelining. I was trying to solve a problem from this pdf I found on Google
I have a doubt in part b of problem 2 where we are asked How many cycles will it take to execute on the fully bypassed MIPS processor? I have two questions: Why is there a need for a stall between lw and sw instruction and secondly, how is the final answer being calculated anyway? I don't understand the part 1 + 63 · (6 + 3) + 1 · (6 + 2) = 576 at all. Also,even if I assume the stall between lw and sw, then if next iteration of loop starts at cycles 9,18 .. and so on. This should happen 64 times and the initial one cycle from li instruction and the 3 remaining cycles for the last execution of bnez means that total cycles = 1 + 64*9 + 3 = 580, right? I got 9 cycles as shown in the timing diagram , at 9th cycle ID of bnez is going on. for the last iteration, we won't execute the branch , but we need 3 more cycles to complete the bnez instruction.
EDIT: After checking out solution to the next part of same problem, it seems that the number of cycles are actually approximated for some reason. I thought that should be done only for large number of instructions (million or above). But I am not sure if I am correct :(


texts: Are the 3 resistors in parallel or in series?

texts: Are \$R_1\$, \$R_3\$, and \$R_2\$ in series? or are \$R_1\$ and \$R_2\$ in parallel?  I'm new to all this.  Here's the circuit:


texts: Powering same LED strip from 2 drivers - diode?

texts:
So I'm looking at adding some LED mood lighting to our bedroom.
End game is to have a single LED strip controlled by 2 different switches

Currently, I have 2 switched 240V AC outlets, one either side of the bed, with each one feeding a 12v DC LED driver.
From this, I've got a short LED strip at bedside height. This works fine, as the left switch controls the left lights, and vice-versa.

I'd now like to add a strip at high-level, that is turned on when either side is switched on...
I can take a feed from both drivers to the strip, however I suspect that if I just wire the LED strip into both drivers, then if I power on one side, then the power will leach through to the other side.

What's the best way to prevent this? A quick google suggests using a Diode, however I'm struggling to pick out the best option.
Is something like a SB560 the right choice? Or should I be looking for something different?

Cheers in advance for any replies.


texts: Powering an old TI Silent 707 with a missing external AC/AC adapter

texts:
I just got my hands on a TI Silent 700 model 707, but it's missing the external power transformer. Unlike similar Silent 700 models, this features an optional battery pack which complicates things beyond my understanding.
Normally I would just look at the back to see how many volts to whack in but it looks like this thing wants AC power, which I haven't seen before at non-mains levels.

Mildly confused I looked into the datasheet to become more confused because this seems to contradict the block diagram which claims 28V:

Lucky for us, the schematics for the thing are available in the maintenance manual in this PDF on page 90 which I have reproduced here:

So, how do I power this thing? Given it accepts battery power, I'm inclined to use a 16V DC source directly into where the battery plugs are (they are readily exposed), but I'm not certain this won't cause any issues. Alternatively, assuming the 20VAC number is correct, I can purchase a mains to 20VAC wall adapter such as the WAU20-2000 from Triad Magnetics.
P.S. Does anybody know what kind of connector this is? I wasn't able to find any reference to it's type in the manual.
EDIT: After more snooping I have confirmed the AC adapter is indeed 20VAC


texts:
I want to add the component SIM968 GSM/GNSS Module to my KiCAD project. But I am not able to download any library from anywhere like I found one for the SIM908 while I was using Eagle.

Any advices as to how I could find a solution to my problem?


texts: Fully Simplifying a Boolean Expression with DeMorgan's Theorem

texts: The expression I have is \$\overline{(\bar{A}B+\bar{A}C})+(BC + \bar{B}\bar{C}) \$, and I've been asked to simplify it using DeMorgan's Theorems. I've already made a start, which was to discount the double-negation, thus giving \$(AB + A\bar{C})+(BC +\bar{B}\bar{C})\$, but find myself unsure of what further steps I could take to simplify the circuit. Can it be further simplified, or have I done all that can be done to implement the circiut more efficiently?


texts: What is the difference between these circuit?

texts:
Is there any difference between these circuit in Theory and action and Modeling?

(two capacitors are equal).


texts:
I am working with a Firgelli Linear Actuator Control board and came across an unusual component. At first I thought it was a heatsink, but there does not appear to be any component under the metal. It's very difficult to get a good image of it, but here are side and top views:

The inscribed label is:

X185F
UCK

Where the "X" could be some sort of logo (two intersecting V's, one inverted).

The three pins over it are for connecting RC servo input, and are not connected.

The lower metal tab is connected to Vcc as far as I can tell.

Edit:

The original link has broken. It appears the controller is also an Actuonix Linear Actuator Control (LAC) board.


texts:
I recently bought a PCI Ethernet Card (the computer type), I was wondering if it was possible if I could use it with my Arduino Uno.

Here is my PCI Ethernet Shield:

I have tried to find the product (it's by Inland) specification sheet, but I can't find it on Inland website Any suggestions? Thanks!


texts: Xilinx FPGA, error creating generated clock

texts:
I just got a Digilent Basys 3 board (Artix-7 FPGA) and I am trying to create a program to transmit data over the UART-USB connection.  I wrote a module but when I tried to implement it I got a timing error.  I have been using the standard 100 Mhz clock which comes with the board.  I now think I need something slower like 50 Mhz.  I don't think I can change the standard clock since that is fixed at 100 Mhz by the board so I think I need to create a generated clock.  I added the following lines to my xdc file.

set_property PACKAGE_PIN W5 [get_ports clk]
set_property IOSTANDARD LVCMOS33 [get_ports clk]
create_clock -period 10.000 -name sys_clk_pin -waveform {0.000 5.000} -add [get_ports clk]

create_generated_clock -divide_by 2 -source [get_ports clk] [get_ports clk2]

I then get the error.  Generated clock clk2 has not logical path from master clock sys_clk_pin.  Am I missing a step.  Do I need to do something more than create it in the XDC file?  Here is the header for my top level module.

module serial_emitter(
    output RsTx,
    input RsRx,
    input clk,
    input clk2,
    output [3:0] an,
    output [6:0] seg);

I want the slower clock to map to the clk2 input.


texts: How do I choose decent-quality passive component assortment kits?

texts:
I'm getting back into the electronics hobby after many years. I'm building up my workbench stock, and next on my list is passive components. I'd like to ask if anyone has suggestions for passive component assortment kits, like resistors and capacitors. The kind that come in a plastic tackle box, with hundreds or even thousands of pieces.
What should I look for in terms of quality? Certain vendors? Certain brands? With all the counterfeits, re-packaged factory rejects, and cheap garbage on the market today, I don't want to waste my money, or worse...cause myself grief with faulty components.
I could go for some premium kits from Digikey or Mouser, but I'm sure the cheaper ones from Ebay or Amazon would be fine if chosen carefully.


texts: How do I transmit an FM signal from the VGA_R port on the DE2-115?

texts:
The best reference for my question would be this youtube video: https://www.youtube.com/watch?v=4VW017qPT6Y

I'm trying to do exactly what they did with the following resources:

Matlab 2013a with HDL Coder and various other packages
The DE2-115 FPGA board
A radio

So, first I am tasked with creating an AM transmitter, then FM, but for the context of this question I will concentrate on FM.

My main concern is how to transmit a signal of 88 MHz or greater if the internal clock of the DE2-115 is 50 MHz. So, how exactly did the group at Hasselt University transmit a signal greater than 88 MHz? Or, how would you?

The FM Modulator Passband Simulink block inputs and outputs double as the data type, so, I think I need to write my own function to replace the FM Modulator Passband block. But, can I?

Thank you for any and all responses! I'll answer any questions as quickly as possible.


texts: What connector do I need to match my existing test leads?

texts:
I'm building a tester and want to use existing test leads from my multimeter which has these kinds of connectors.

The testing probes use these plugs.

What kind of connector (or is it a "plug"?) do I need to buy to accept my existing test probes?

(And just how badly am I mangling the terminology here?)


texts:
I'm just a bit confused. Consider an example where an antenna receives two signals - one with a power of -25dBm and one with a power of -47dBm and we are asked to find the total power received by the antenna

Now, if I just add -25 with -47 dBm, I get -72dBm which is a lower total power. How come?
Am I not allowed to just add these two? Intuitively, we should get a higher total power surely? Maybe something closer to 1 or 2dBm maybe but not -72dBm?


texts: Only SWDIO, SWCLK, GND three pins, how to debug

texts: I am new to microcontroller, I have a board just offer SWDIO, SWCLK, GND three pin.how to debug this board with iar through SWD


texts: convert USB to RCA phone plug in order to close a switch

texts: I would like to know if it is possible to convert a USB signal to a RCA phone plug signal in order to close a switch contact.  There are pushbutton switches that can remotely close a switch by means of a cable with a standard 3.5 mm plug on the end.  These are attached to specialized switch boxes for adaptive devices for people with disabilities.  Instead of having a physical pushbutton as the component sending the signal to the switch box, I would like to have the signal originate from a software program and be conveyed through USB or RS-232 and then be converted to the appropriate signal for closing a switch.  This is a specialized need and I am not an engineer, so it's kind of hard to explain what I am needing.  I do not really know how to look for such a solution.  I appreciate any suggestions.


texts:
I have seen that some resonant cavities are equipped with some external screws, called tuners, which can be used to vary the resonance frequency.

Can you explain me the physical reason with which to screw or unscrew the tuner influences the electromagnetic field and the resonance frequency of the guide?


texts: Designing a 3-phase pure sine inverter. Where do I start?

texts:
I'm trying to design a 3-phase pure sine inverter which will be powered by a 128 cell battery bank (3.0v-4.2v/384v-537v). Since 384v is still above the 325v peak of a 250Vrms sine wave, I figured I could build this without any transformers, just connecting an H-bridge to the battery and adjusting the SPWM to get the right output voltage (and implement a feedback system).

Now, the more I'm looking into this, the more I'm realizing that this isn't something I'll be able to do without some serious research.

I have some questions like:

How do I filter the output of the H-bridge to get a sine wave without losing power? (I'm trying to keep the efficiency as high as possible)
What's a good frequency for the SPWM? (I suppose the higher the better for smaller filter components as long as I keep an eye on the switching losses)
How do I get 3 phases and a neutral (wye) out of this? At first I thought I'd just build 3 separate, 120° shifted, inverters and connect them all to 1 point (neutral). But now that I'm thinking about it, that's probably not a great idea since they won't be electrically insulated.

If someone could answer these for me, that'd be great, but I'm also looking for some stuff to read on this, to get a better grasp on how (3-phase) inverters work before trying to design one myself.

Thanks for any help


texts: Transfer function for inverting amplifier

texts:
After reading this answer I wanted to know how the transfer function for an inverting amplifier was derived. I found this page, but it leaves me unsatisfied. Their proof is just two lines, and the opamp's amplification isn't even mentioned.
What's the proper derivation of the inverting amplifier's transfer function?


texts: Why do we not include the current source when finding the Thévenin equivalent impedance?

texts:
The problem is from Basic Engineering Circuit Analysis, by  J. David Irwin, Robert M. Nelms, chapter 9.3.

When I tried to solve this problem, I tried to find the Thévenin equivalent circuit by finding the open circuit voltage, using this diagram:

and then I tried to find the short circuit current using this diagram:

and then calculating Zth using the formula Zth = Voc / Isc

However, this gave an incorrect answer. Apparently, the correct way to find the Thévenin equivalent is by cutting off both the load, and the current source to the right, like so:

and to find the short circuit current,

and then using the formula Zth = Voc / Isc to find the correct Zl which draws maximum power.

I don't understand why finding the Thévenin equivalent with the current source attached gives an incorrect answer. Any help is very much appreciated!


texts:
Can any one help me out to design a circuit with opAmp using this transfer curve?

Here, OpAmps +V(sat) = 15v and -V(sat) = -15v


texts: How to pick the right capacitor for device with significant current peaks?

texts:
I'd like to power the GPRS modem (uBlox LEON G100) with a 4V 500mA power supply. How can I calculate the capacitor parameters so that they will provide the necessary current for TX slots?
The following image presents the current consumption during GSM frames:


texts: PIC analog to digital converter to measure more than one battery voltage (with different grounds)

texts:
I'm trying to build a circuit that can scale down several lipo batteries (5 cell) up to 22V max to be safe to either 3.3V or 5V for measuring with a PIC microcontroller using the analog to digital converter.

Now the problem is I have more than one battery for each motor and each battery is isolated from one another. There is no common ground between them.

Can someone offer some advice on how I can measure the voltage of these batteries using the PIC's ADC. Some form of voltage divider will of course be needed and suggestions on this are welcome.

My analog circuitry skills are extremely weak so please provide as much detail and or references. Any calculations would also be appreciated.

I'd like to ensure some level of filtering/isolation is present due to the LiPos obvious high current usage and noise of the motor.

PS: I know there are very cheap LED voltmeteres on ebay for this but I want to be able to send the sampled voltages back to a base in my project.


texts: Will this work? AC transformer, 15V 1ampere, center tap, voltage drop

texts: I am trying to drop the voltage of a torodial transormer to 12VAC while the configuration the same. 15-0-15 to 12-0-12.


texts: Configure microcontroller flash memory as ram?

texts: Is there anyway i can use micro-controllers flash memory as a RAM as i need 150kB of buffer but controller has 32kB of RAM and 512kB of Flash? Also can i use this ram as stack or heap?


texts: Using limit switches to reverse circuit polarity

texts:
I am designing a linear translation stage that will be driven with a DC motor. When the circuit is powered the DC motor will start turning in either direction, which will move the linear stage towards one end. At that end the stage will activate limit switch #1 and the motor will turn the opposite direction until the stage activates limit switch #2. When limit switch #2 is activated the motor will turn in the original direction and send the stage back towards limit switch #1. This process will repeat until the circuit is powered off.

Does anyone have any ideas for how to build a circuit that reverses polarity to the motor using only a momentary pulse from a limit switch? I have built this circuit:

The circuit works great for its intended purpose, but it does not work for my needs because I need to be able to use momentary switches (limit switches). The circuit shown here will stop traveling as soon as the switch is released.

I have also tried to wire the circuit above through an Arduino. I used the momentary limit switches as inputs for interrupts. I had the same issue of the motor only moving while a switch was being actively closed. Here is the sketch that I came up with:

const int interruptPin = 2;

const int interruptPin2 = 3;

const int cwPin = 10;

const int ccwPin = 11;

void setup()
{

  pinMode(cwPin, OUTPUT);

  pinMode(ccwPin, OUTPUT);

  pinMode(interruptPin, INPUT);

  pinMode(interruptPin2, INPUT);

  attachInterrupt(0, goCw, RISING);

  attachInterrupt(1, goCcw, RISING);
}

void loop()
{

digitalWrite(cwPin, HIGH);
}

void goCw()
{
 digitalWrite(cwPin, HIGH);
 digitalWrite(ccwPin, LOW);
}

void goCcw()
{
digitalWrite(cwPin, LOW);
digitalWrite(ccwPin, HIGH);
}

I would appreciate any advice that anyone has on this issue. I am open to using any method to achieve the desired outcome. I attempted to use the Arduino because I thought that it would solve my problem, but I am not against eliminating it if there is a better way.


texts: Should bias voltages still be in range without driver/output transistors?

texts:
A class AB audio amplifier has both positive and negative +/-40v rails.  There is a differential amplifier feeding a trans-impedance transistor.  The transistor is also a current source for an amplified diode.  The other end of the diode goes to the negative rail through a couple of resistors. The diode provides adjustable + /- biasing voltages for both driver transistors, around +/- .5v, respectively.

Drivers and output transistors had shorted due to accidental overload and have been removed.  Should bias voltages still be in range with these transistors out?  If not, then how can I be certain there is no problems with bias before replacing the transistors?  Are there any precautions I need to follow before powering up?

Here's a schematic that should help.  A simpler way to ask this question is: with Q806. Q807, Q809 and Q810 removed, should the bias voltages at the collector and emitter of Q804 still be around + and - .5v, respectively?

Out of curiosity I powered this up again and measured +38v on the collector of Q804 and +36.5v on its emitter. Predriver Q803 has +38.1v on both emitter and collector and +37.4v on its base. So I guess now there is either a problem with predriver Q803 and/or the differential amplifier Q801, Q802.  Anyone have anything to add?

Here is corrected schematic.

FOLLOWUP: Interestingly there is still over 35v bias.  Here are the readings:

Q801 E= -.710  B= -.127  C=37.4
Q802 E= -.710  B= -.127  C=38.2
Q803 E= 38.1   B= 37.4   C=38.0
Q804 E= 36.2   B= 36.8   C=38.0

R811,R812 junction -17.4

+40 actually is  38.2
-40 actually is -38.5

Q801. Q802 and Q803 have been replaced.  Over current protection transistors, Q805 and Q808, are still installed. Any idea why the bias is still so high?

Thanks in advance.

Thanks Dave for the explanation for the high common mode voltage and clarification between bias and common mode voltage.  I tried shorting Q804's emitter to P809 as you suggested and have 2V on Q804's collector and .125V on its emitter.  Does this seem reasonable to you?

And I tried shorting Q804's collector to P809 and got .120V on it and -1.8V on its emitter.  Does this mean I can now safely reinstall the driver and output transistors? Are there any precautions I need to follow before powering up?

Thanks Dave.  So no other steps need be taken before installing the other transistors?  I thought it might be a good idea to put a 75W lamp in series with the AC line or a 330 ohm resistor in series with each output transistor's collector in case the transistors saturate. Just want to avoid any unforseen disaster. Or don't you think any of this is necessary?


texts: How is CPM Modulation Different from PSK?

texts:
Continuous phase modulation has been described to me very similar to wikipedia's definition, which basically indicated that the CPM is different from QPSK, for example, because QPSK abruptly shifts phase on symbol transitions. But this isn't true. Every real system is bandlimited, and as such there is no such thing as an abrupt or instantaneous change. In QPSK systems, the bandwidth is limited by a nyquist filter such as a root raised cosine, to be 2*(1+ the excess bandwidth)* the symbol rate.

Per wikipedia; in CPM, "Each symbol is modulated by gradually changing the phase of the carrier from the starting value to the final value, over the symbol duration." This is exactly how PSK works.

My question is, every real system is bandlimited, which means that symbol transitions occur over a finite time period (1/2T ?), which means the instantanous phase of the waveform is continous. That said, what does Continous Phase Modulation mean to imply is done differently than in any other phase modulated waveform


texts: Drive relay with Npn transistor thanks to RTC and Rpi

texts:
It' s my first projet in electrical and I am not very sure about what I'm doing.

I Would like to drive a relay thanks to a Rpi and a RTC clock that has a alarm feature ( ds3231 with high-z/active low) ... relay that will itself drive the raspberry pi.
To sum up:

1) The RTC send a signal that turn on the Relay and thus the RPI
2) The RPi reset the RTC alarm to it previous state and configure it to
 trigger again in a determined time
3) The Rpi do what it has to do
4) The Rpi shut down and everything is back to normal
I have to keep in mind to keep the current consumption as low as possible during the "sleep" phases

So far : I intended to use NPN transistor like on my scheme.
in
1) Both the Rpi and Ds3231 are High-z so the 5v pull up and there is 5v both in the base and emmiter of the NPN =>It doesn't let the current go
2)The DS2132 become on open drain .. the npn let the current go
3) the rpi turn on and also become on open drain

EDIT : My main preoccupation is : Would this circuit work ( and if not why ? i would be happy to learn more about electronics !) I have of course to add a diode on the relay

Ps: A gpio pin is in an high impedance state when no current is applied to rpi, isn't it ?


texts: Conversion Gain Definition for DSB-SC Upconversion

texts: If I multiply a baseband signal \$A cos(C\omega t)\$ and a carrier signal \$B cos(D\omega t)\$, the result is \$\frac{AB}{2} [cos(C-D)\omega t+cos(C+D)\omega t]\$, which is a double sideband, suppressed carrier signal. My question is, how is the conversion gain defined in this situation? Would it be \$\frac{B}{2}\$ since the amplitude of each sideband is \$\frac{AB}{2}\$, or would it be \$B\$ since the total energy is spread among the two sidebands?


texts: I am currently working with TI's TPS61235.  I need to put this IC onto a custom PCB for a project, but I cannot find any libraries for PCB designing software for this VQFN-9 layout.  Is there anywhere where I can find these weird layouts to design PCBs with?


texts: Gate spike in Synchronous Boost converter

texts:
I'm trying to build a synchronous boost converter. I'm getting the following spike in the gate. Yellow is gate voltage and blue is drain to source voltage. How to get rid of this spike in the gate?
I have tried adding a capacitor to gate to source, but it slows down the mosfet switching speed and device heats up.
Is there anything I can do to reduce this spike without slowing down the mosfet switching speed?


texts: How to maintain the zero potential at the connector end?

texts:
I am developing Automated Test Equipment (ATE), from the ATE, on the output connector there will be a some potential exists.

How to maintain the zero potential at the connector end, which goes to Test Article?

Note: Before connecting to Test Article connector end potential should be zero.


texts: Can anyone help with designing a MOSFET load switch

texts:
Can anyone help me design a load switch using the Infeneon IPP120P04P4L p channel MOSFET and the necessary filter components? I would like to use the Texas Instruments ULN2803A darlington driver to drive the MOSFETs gate.
Helpful details;
Automotive application supplying fuel pump, injector and other hardware.
Expected voltage 11 to 16.
Electrical noise from alternator.
Voltage and current spikes.
I would prefer to run switch without heatsink.
Thanks.

Edit:
I would like design advice and review of this circuit redone directly from Infineon BTF5060-1TEA smart high side power switch data sheet. Has anyone ever used this device before? I intend to use a raspberry Pi 3 to command the appropriate PWM duty cycle to a fuel pump to assist in adjusting fuel pressure through this Smart switch. Fuel pump max current draw will be around 20 Amps. What frequency would you use? Any additional components you would add? Thanks

This is the diagram of the system
I’m using TXS0108EPWRG4 level converter but in this case I’m using them as buffers to protect raspberry pi. To monitor current draw and voltage I’m using INA260 power monitors.


texts: Wirelessly program AVR with Bluetooth device and can be used for data communicationtoo?

texts:
I am Embedded Software developer.
Don't have much knowledge of hardware side but am trying some hardware stuff.

Is it  possible to program AVR (ATMega328p) wirelessly using Bluetooth device (HC-05) and then use the same device for data communication?

I have tried this circuit to power ON HC-05 and HC-05 RESET(KEY) by MCU's GPIO and PIN32 of HC-05 is used to reset MCU during programming. The problem is that whenever MCU reset HC-05 also get switched OFF.

Is there any solution or any other circuit that can program AVR and also can communicate data from other Bluetooth devices?


texts:
I am trying to find a path loss model for "wireless sensor network". More specifically, I am looking for model for Cellular tower  100~1000MHz) and (60~600W) as transmitter and a small wireless sensor node as the receiver(most likely to be placed on ground level).

Then I come across on a model which is  only applicable to "

The resulting path loss model applies to base antenna heights from 10 to 80 m, base-to-terminal distances from 0.1 to 8 km, and three distinct terrain categories.
"

My question is: what is the base antenna? (Does it mean the transmitter base station antenna only or also the receiver antenna as well? Do you guys think this model will satisfy the aforemention requirement?


texts: Is it alright to connect NC (no internal connection) to the ground?

texts:
I understand "NC" means you better "leave it hangin'". However, due to the brimful nature of my boards full of components, and the Kierkegaardian genius who designed this component:
http://ww1.microchip.com/downloads/en/DeviceDoc/20002200D.pdf

that put the GND pin squarely in the middle rather on the side of the component, I now find myself in the position of having no choice but to connect a trough-hole to GND by laying tracks right through the NC pin, since under the component laid several tiny trough-holes already.

So I'm wondering is it OK for me to do that (connect NC to GND)? Since in the datasheet it specifically said:

But I'm not 100% sure?

Or I could be wrong, there shouldn't be any non-GND via under the power IC, and instead, there should be a patch of GND plane?


texts: Relate phase velocity and velocity factor (transmission medium)

texts:
I want to derive the velocity factor \$v_f\$
$$
v_f=\frac{1}{c\sqrt{L'C'}}\tag 1
$$
and this relationship with the phase velocity
\$v_p\$
$$
v_f=\frac{v_p}{c}. \tag 2
$$
\$L'\$ is the inductance per metre and \$C'\$ is the capacitance per metre.

I know the following:

The phase velocity \$v_p\$:

I guess \$\epsilon_r=\mu_r=1\$ here? So \$\epsilon=\epsilon_0\$ and \$\mu=\mu_0\$?
$$
v_p=\frac{\omega}{\beta}=\frac{1}{\sqrt{L'C'}}, \tag 3
$$
where \$\lambda=\frac{2\pi}{\beta}\$ and \$\beta=\omega\sqrt{L'C'}\$. And \$c=\frac{1}{\sqrt{\epsilon_0\mu_0}}\$, so
$$
v_p=\frac{\omega}{\frac{2\pi}{\lambda}}=\frac{\lambda}{2\pi}\omega=\lambda f =c \tag 4
$$

The velocity factor \$v_f\$:

I guess \$\epsilon_r\neq1\$, \$\mu_r\neq 1\$ here?
$$
v_p=\frac{1}{\sqrt{\epsilon\mu}}=\frac{1}{\sqrt{\epsilon_0\mu_0}}\frac{1}{\sqrt{\epsilon_r\mu_r}}=\frac{c}{\sqrt{\epsilon_r\mu_r}} \tag 5
$$

I don't know how to proceed from \$(3)-(5)\$ to find \$(1)\$ and \$(2)\$.

Thanks!


texts: need to replace my tumble dryer capacitor but most I see seem a different spec, most seem to be 8uf, am I right at saying looking at the picture it is 0.1uf? Its for a White Knight Eco43A gas tumble dryer. Really Ive been looking online but can't seem to find where I can purchase one of the same spec, sites keep showing me 8uf ones as being the compatible part, any help would be appreciated.


texts: How to read this component mechanical drawings

texts: I am adding a display to my small hobby project. And due to size and cost constraint the choice falls on Chinese QG-2864KLBLG01 OLED display. Everything about it seems to be perfect except one small detail -- I am really not sure whether I am reading their specifications correctly. The spec is available here. And the part that I am talking about is the mechanical drawing from which I am drawing a footprint. The part that I am not clear about whether pin 1 is on the left side when I look at the front side or at the back side. There is no mention of this (nor correct footprint drawing) in this specification. So I hope community can help me to figure this out -- what is the right footprint for this 1-30 (left to right) or 30-1?


texts:
Apologies if this is the wrong place.

In the UK there is a PAT test for electrical appliances to ensure it's safe to use and meets standards, and is usually a requirement from insurers.

I had to dismantle a plug today to pull it through a small gap. My manager thinks that it needs an entirely new PAT test now and I've never heard of anything like that. I haven't removed or added anything, it's the same plug just taken apart and put back together again. I didn't even disconnect the terminals.

Does anybody have any advice?


texts: How to convert any periodic signal to a square wave signal using the Schmitt Trigger?

texts:
I had to make a kind of frequency meter, and what made me stuck was the signal formatting. I couldn’t build a circuit containing the Schmitt Trigger, which will allow me to convert any periodic signal into a square wave signal afterwards. Because I will need this type of signal which will trigger a binary counter that only works if there is a square wave signal (pulses).
Here is a blueprint of this frequency meter:


texts:
I have been watching this video and when it is designing the colpitts oscillator it doesn't add a base resistor. I am thinking that is wrong because the BJT will saturate since the guy sets a base voltage 1/2VCC + VBE(0.7) to make the temperature dependent Vbe not important. So if we add a base resistor to the Collpits oscillator will that change something important (feedback fraction or the amplification of the signal ( in the  closed loop configuration ) ) .

simulate this circuit – Schematic created using CircuitLab
Why don't we add another base resistor here?

simulate this circuit


texts: How to Increase Velocity of a Servo motor, relative to resistance?

texts:
I am building a RC car which increase its speed to compensate any obstacle on its way.

A simple 4 wheel RC car, with current sensor on the two front wheels, when an obstacle is placed in front of the car, the car slows down if the obstacle is heavy and may stop if the obstacle is very heavy. my question is how can i take the input of the current sensor to increase the Motor's speed to try to compensate for the added obstacle.


texts: Wingman Wheel with different power supply?

texts:
I have an old Wingman Formula Force running on 20V / 1.5A, and I've lost my original cord/power supply.

I have 2 other supples in here, one with 12V / 2.5A
Second is 22V / 1230mA (guessing that's the same as 1.23A?)

Would it work with any of them? Is there any risk of burning the wheel?

Thanks in advance!


texts: Generic ST-Link V2 Not Resetting Target?

texts:
I bought a generic ST Link online, hooked it up to my target correctly (using SWDIO, SWCLK, GND, and RST), and tried to Target => Connect in the STM32 ST-LINK Utility, and got an error connecting (Can not connect to target). I know that this works on my target board, because with using an STM32 Discovery kit as an SWD programmer works without an issue. I've read a handful of other question on the site, and this one convinced me to trying to manually engage the reset before an operation and I have gotten a response by doing that, but it's pretty much useless if that's what's required.

So what's the deal with these programmers? Do they have crappy reset drivers or what? Feels pretty much useless to me if a manual / externally-timed reset is required. Are there known workarounds, or should I just buy Discovery boards just to use them as programmers?


texts: Altium STEP Models Aligning Underneath Board

texts: I'm trying to import a STEP model for a uFL connector and it's oddly misaligned beneath the board (see "3D uFL PCB" image attached). I've tried rotating it every which way but I cannot fathom how it wouldn't just align itself on the footprint. Photos attached. How do I get it to move up vertically onto the same top layer plane as the PCB?


texts: Creating a cosine wave of 140 MHz out of 80 MHz clock

texts:
I'm working with Virtex 5 ML507 board. I'm trying to create a cosine wave of 140 MHz out of 80 MHz clock. I'm receiving the data with a clock of 80 MHz and transmitting it with this clock (through the GTX). I want to create a cosine wave so that I can multiply the data and move the signal on the frequency level.

The thing is, I'm not sure I can create this cosine wave with this clock. I tried to create for example 40 MHz cosine wave and got only 2 points on it, for 20 MHz I got 4 points and so on, accordingly to nyquist theorem. I though of maybe of upsampling but I didn't get a chance to work with this block. I'm creating the cosine wave using CORDIC.

Any ideas?


texts: How electronic components like diodes, capacitors, resistors are added to CPU?

texts: I have been trying to understand how CPUs are manufactured with those large and complex circuits. But Making of CPU only talks about projecting transistor diagrams(May be that is the major part). Bu how additional components like diodes, capacitors etc. are added to CPU?


texts: What can be done with USB OTG ports in microcontroller.?

texts: I have PIC32 MCU. It supports USB OTG functionality. I searched a lot on google about the applications regarding OTG but didn't find many results. I was wondering if any one can explain what can be done with OTG in MCU. Can we store some data via OTG in flash drives. ?


texts: Differential analog signal conversion using Arduino Uno

texts:
I need to perform a A/D conversion for a differential signal using Arduino Uno. I have tried a software method where I connect one input to A0 and another to A1, read ADC for both channels and then subtract it in the code. But the 100 ms time to convert the analog signals is causing some errors as it is not perfectly a differential signal conversion (i.e. there is some delay between the two samples taken and hence it is not exactly differential signal).

Now I am not sure about this, but can I connect one of the analog inputs to the Arduino Uno GND pin and then perform a conversion for the other signal i.e. one input to ground of Arduino another to A0 of Arduino and then perform A/D conversion for A0. Would this be correct? Would it cause damage from a circuit perspective?


texts: Calculating electrical contact surface area

texts:
First off, I am no electrical engineer: I am a mechanical engineer. I am making a saddle (holder for the rack) for contacting to a plating rack for anodizing. We are a small plating shop and I figured I would ask to see if anybody would be willing to help me out. The rack material is made of titanium because it is light and easy for an operator to move around. The saddle can be made out of stainless steel, aluminum, or brass.

This is an image of the saddle I am thinking about making. In the two smaller holes I will be adding ball-nose spring plungers (http://www.mcmaster.com/#3408a551/=13r1zel) to create the pressure that will hopefully remove any oxidation, when the rack is pushed/slid against the teeth.

Our DC power supply has a max output of 30V at 200 amps. I need to know how much surface area of the saddle will need to be contacting the rack (not shown), in order to get good contact and not overheat the rack. I would like the operator to be able to pick it up with bare hands after 90 minutes of plating. Assuming no heat is generated from the plating process.

So how many square inches will be required to have a good contact at 30V, 200 amps without generating a significant amount of heat?

Any help would be appreciated.


texts: Can a transformer work if the core is not circular?

texts:
I am trying to build a transformer to convert 12V AC power to 5V AC. Here is what I have right now:

I haven't adjusted the coil ratio yet but I tried it just to see if there would be any output and as a matter of fact there is none. I tested the core and it's ferromagnetic, so my guesses are either it can't work because the core's center is empty (it's a pipe), or because the solenoids can't be aligned and the core has to be circular.

I would greatly appreciate if someone could explain to me what's wrong with that design and why it doesn't work (or why it should).


texts:
We are looking into setting up a very basic shielded chamber inside a small room at my company to be able to perform some basic relative radiated EMC measurements.
We will buy a somewhat cheap spectrum analyzer together with a set of near field probes and a biconical antenna, and want to have a room where we can perform measurements with as little interference as possible.
So I've been looking into doing a very cheap DIY shielded chamber inside the room, by building a wooden frame and wrapping chicken wire around the frame with thick aluminum foil to seal all joints.
The only thing I still feel unsure about is how to do the filtering for the I/O panel. What we need to get into the chamber is the following signals:

230V/50 Hz power
USB 2.0
Ethernet
Coax antenna connector for biconical antenna
Two BNC connectors for DC power supply
SMA connector for various RF stuff

So my question is how I would filter all of these signals in suitable ways? Our plan right now is to slap ferrites on all signals, but I don't think that will accomplish very much. What would be a better way?
EDIT: For anyone looking for additional answers to this question, I asked Keith Armstrong over at emcstandards.co.uk and he very kindly made this blog post about my question: https://www.emcstandards.co.uk/constructing-io-panels-for-shielded-rooms


texts: Gaussian Channel: Capacity and Explanation

texts:
Let's consider a gaussian communication channel, which is represented through this scheme:

Starting by this assumption it is possible to prove that the channel capacity is equal to

The computation of the last one is written in these slides. Now, in these slides this situation is considered:

Now I have the following questions:

1) Why is there the filter h(t)? What does it represent? Is it a physical filter that we put in the channel (and if yes, why?) or is it used to model the fact that a channel is naturally a low pass filter?

2) Why is the signal X sampled?

3) Should X be band limited or not? And why?


texts: Power and Power Loss of a DC to AC converter (Motor Driver)

texts:
I need urgent help on this matter and I really appreciate it if anyone can clear my doubts!

I have a motor driver evaluation board, namely NXP's FRDM-HB2001-EVM, which functions as a simple DC to AC converter based on the PWM input it receives. I am interested in the efficiency of this device but I need some help in properly calculating the input and output power because because PWM is involved.

My setup is as follows:

A PWM signal generated by an Arduino UNO is input into the evaluation board, FRDM-HB2001-EVM.
Input voltage of 7.2V is supplied into the FRDM-HB2001-EVM, and then input current, output voltage and output current are measure using a voltage probe and a current clamp with an oscilloscope.
The input voltage is a constant DC voltage, but the input current, output voltage and output current are 'AC' due to the effect of the PWM input, which makes the HB2001 function as a half bridge.

I would like to ask, what is the best method to accurately calculate the input power, output power, and the efficiency just by the values obtained through the oscilloscope?


texts:
This is a very basic question. I want to have a very simple BJT Signal Amplifier with variable voltage gain. Let's think about a common emitter with an emitter resistor like this:

The input signal is a sine wave and the signal amplitude is small enough to be considered as small signal (around 500mV pk-pk ) and RB,RE and RC are selected properly to work in good bias condition . According to the equation we expect the voltage gain( AV) to be approximated as AV=-RC/RE:

So I expect by turning the potentiometer, I should see different gains. This was on the paper but in reality it does not happen exactly: the gain changes well but some wave form distortion is seen in some frequencies for example in my case these distortions look like skewness to left in 2.5MHz, 7MHz ,....
 What am I missing ?


texts: Identify the tip polarity on this AC adapter without plugging it in

texts:
I have a 230V AC-DC adapter/transformer from Europe that I am trying to replace with a 120V version. I am trying to determine the tip polarity of the DC output. I cannot simply plug it in and use a multi-meter to measure the polarity because I do not have access to a 230V/50Hz source. I have several questions:

Can I plug it in to 120V anyway and just look at the polarity, even if perhaps the output voltage will be wrong?

The only symbols on the adapter are shown below. Do any of the symbols indicate tip polarity? If so, what does it indicate?

The symbol that I have highlighted with an orange arrow looks promising, but I have been unable to find something similar on the internet. The unknown symbol is an oval with a '+' sign over the letter 'S'.

Perhaps the following is true? If not, perhaps I can just assume positive tip polarity if there is no symbol at all?


texts: WS2812B with ATMega8 and light_ws2812 Libray

texts:
I have connected four WS2812B modules I got from eBay to my AtMega8 and tried to use the light_ws2812 libray to controll them.

I connected the wire used for communication to the PC5 Pin on my ATMega and wrote the following programm to controll the four LEDs.

#include <util/delay.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include "light_ws2812.h"

struct cRGB led[4];

int main(void)
{
   led[0].r=255;led[0].g=00;led[0].b=0;
   led[1].r=255;led[1].g=00;led[1].b=0;
   led[2].r=255;led[2].g=00;led[2].b=0;
   led[3].r=255;led[3].g=00;led[3].b=0;
   ws2812_setleds(led,4);

   while(1)
   {

   }
}

I followed the given Example of the Libray to write the Code. While trying to figure out the error myself and rewriting my code a little bit, I somehow managed to get the first LED to light up fully green. When I erased the complete flash memory of the ATMega the LED still stayed on.

Because of that I'm pretty sure that my problem is on the software side, but I don't know how to fix it.


texts:
I'm wondering what type of controller this is? PI right?

Looks like a PI to me. I from the s in the denominator. P from the K term.

Usually, we've been dealing with PI controller in which the I term just places a pole at origin. I'm just starting control systems and I know this may be a trivial question to everyone.


texts: What clock source is the oscillator connected at the OSC1 and OSC2 pins of a pic?

texts:
I'm connecting a Crystal SMD of 32 MHz to the OSC1 and OSC2 pins of a pic.

When doing the configurations for the pic, inside System Module on clock source i have there some options, including primary oscillator, external oscillator, and others.

I've read in some place that it is a Primary oscillator, but the logic on my mind says that it's external, which is right?

The pic in cause is PIC32MX470F512LT


texts:
I am new to electronics and have been seeing a lot of so-called "evaluation kits" for certain MCUs. For example this Atmel SAM R21 Xplained Pro kit claims to be: "a hardware platform to evaluate the ATSAMR21G18A microcontroller".
As a newcomer, I'm not entirely sure what this means, but I'm guessing that the ATSAMR21G18A is just a microchip, and not a full bore MCU. And perhaps, in order to write applications for it (that will interact with all sorts of devices and peripherals) you need a way to test the chip on a microcontroller that has memory, typical computing parts and GPIO ports on it?
So I'm guessing that the typical flow here is:

Buy one of these "evaluation kits" for your targeted microchip
Write and test your application using this kit/MCU, and hook it up to all the devices and I/O peripherals that will be there in production, and get it working correctly
Now you're ready to start figuring out what your production board (containing the targeted microchip) will look like, and you can have reasonable confidence the application will perform as expected on the production board

So first, if any of my guesses/assumptions above is incorrect (even slightly), please begin by providing some course correction for me!
Assuming I'm more or less correct here...
I assume that the reason why you wouldn't just put an evaluation kit board into production is because of cost and unnecessary waste, right? If these evaluation kits have GPIO pins/ports on them, they are too generic for you specific application at hand, and so the real difference between the evaluation board and your production board is: your production board is optimized and specific to your product and the specific application(s) running on it, yes?


texts: Why is the current limited to 20mA when there are LED but 8.04 amps without?

texts:
NOTE: I HAVE ELECTRON FLOW ON INSTEAD OF CONVENTIONAL FLOW ON PURPOSE

So I was making a circuit and it looks like this:

As you can see 8.04A are flowing. That is normal with internal resistance of the battery and the small resistance of the wire.

But when I add three LEDs:

The current is instantly 20mA, why? Shouldn't there be still 8.04A and it is burning up the LEDs, and also why is the first LED not getting burned up by the 9V going into it? I get that voltage is dropped across it. But, it doesn't just ignore the other voltage going through it, or does it? Is this a problem with the program I am using EveryCircuit or is there something I am missing?


texts: How is power divided from a wall outlet? Powering multiple motors with PSUs, extension cord

texts:
My project involves powering 7 motors from a wall outlet, using switching power supply units. I am a little over-budget on possible output power, but it is very unlikely that all motors will run max power at the same time. Below is the architecture:

EDIT - Sorry folks, typo in my "infographic". Should be 1700W from the PSUs.

My questions are below. I'm a bit of a newbie so please excuse :)

1) Can the wall outlet, plus a generic extension cord, really transmit up to ~1800W ? Like is it safe, would anything melt, etc. I've only used extension cords for small electronic devices like laptops.

2) The amperage requested by the motors may be in the 30-50 A range in total, but the wall outlet provides 15A. Just to confirm, the PSUs take care of the power conversion to the amps/volts required, right?

3) What will happen when the system requests more than 1800W ? E.g. if all motors are on and at their highest torque requirements.

4) Similar to above, but for an individual PSU with 400W. What happens if both the 288W motors are trying to request their max power, will power be split evenly at 200W per motor? What if one starts 'working hard' first (taking the max 288W), then after a few seconds the other starts requesting as much power as possible, does it get stuck with only 400-288 = 112W ?

EDIT - one more important question:

My motors are using motor drivers with adjustable current settings (so I can control max #s) and overcurrent protection. Can I leverage these current settings to operate at lower power and ensure I generally don't go over e.g. 1700W?
example product: http://www.omc-stepperonline.com/24-phase-nema-23-stepper-motor-driver-2450vdc-15a45a-256-microstep-m542t-p-293.html
(I am using Stepper Motors)

Thanks for any insights, as well feel free to suggest improvements to the setup. It's based mostly on available parts and physical space constraints, but could change. What's fixed is using the wall outlet as a source, and having those particular motors.


texts:
I'm playing around with the circuit below (it's a very slimmed down version of Figure 11.10 from High Power Audio Amplifier Construction Manual pg 348)
Can anyone explain what it is in the circuit that is causing the positive swing clipping at ~ 3V when I use a load of 4ohms.
When I use 50ohms the clipping goes away.

Many Thanks


texts:
I have a project where my power supplies are giving me a bit of a headache. I have three voltage regulators that I am trying to run from a single bench power supply. There are two 3.3V regulators, and one 12V regulator. The current draw for the 12V regulator is up to 500 mA, and each 3.3V regulator peaks at 150 mA.

When I hook up about 14V to the inputs of these regulators, the 3.3V regulators start to cook. Doing the math, that's about 1.7W of power dissipation for each of the 3.3V regulators. They're in a TO-220 package pointing straight up, and they got too hot to touch. I was able to throw a random heatsink I found on the tab and cool things down, but the top of the heatsink was about 2.5 inches high - very flimsy and cumbersome.

I really don't want to sacrifice the single power supply input, and I also really don't want to go to an on-board switching supply for either the 12V or 3.3V supplies.
What are some passive package+? solutions for dissipating up to 2.0W of heat that are physically secure and low profile (shorter than 1 inch)?

Edit:
My reasons for not wanting a switching supply are:

I don't want to deal with switching noise in the analog parts of my design
I'm less comfortable with designing a switching regulator than using a linear regulator
The PCB that I'm working on is big and expensive. I don't have the time/budget to "try out" a regulator. A linear regulator with enhanced heat dissipation seems a lot safer way to avoid making coasters than a switch mode regulator.


texts:
I've decided to take apart my old android phone, and since I've been in a great shortage of batteries for my high energy requiring protable projects, I was wondering If I colud use my phone batteries, that are quite capable in terms of Ahs.

I know the hazards of li ion batteries, and the difficulty in charging them, and I've attempted a solution by using the phone very charging circuit, or actually the pcb containing the usb port and the battery terminals.

My question is, is this safe?
I've connected the load in parallel with the battery and charging circuit, and whereas the battery should be 3.7V it remains a costant 4V, even without the charger; When I connect a motor, the voltage drops down as expected, but when the running speed is reached it's still 4 V.

I somehow managed to get the batteries to 0V, but i suspect it was some protection, but connecting the charger brings the battery to 4V immediately, whereas obviously he phone woult take hours to charge.

Also, do you think there is some cheap IC that could replace the phone pcb? I would also need to use these batteries in series or parallel, but I don't know hot to treat them tho.


texts:
Here is my task:

Find input voltage Vul and base voltage of T1, so that T1 enters full reverse active mode. Explain. Voltage base-emitter of BJT (when it conducts) is 0.7V, voltage base-emitter in saturation is 0.8V and voltage collector-emitter in saturation equals 0.1V.

For BJT to work in forward active mode, EBJ should be forward biased (Vbe = 0.7V) and CBJ should be reverse biased (Vbc < 0.4V).

For BJT to work in inverse active mode, EBJ should be reverse biased and CBJ should be forward biased. Does it mean that in this case Vbe = -0.7V and Vbc > 0.4V, for BJT on left side on image below? Does BJT in this mode behave like one on right side on same image? I know that in this mode, we have small gain Beta_reverse.


texts: what is this type of interface, located at the very edge of the PCB? What's interface standard, and what is pinout? The 5 holes in yellow circles is GND.


texts:
To this day, I feel like I don't have a good intuitive feel for how power dissipation turns into heating -- that is, if I waste 1 watt of power as heat into a device the size of a coffee mug, how hot does it get?  How about 10 watts, 100, or 1,000?

I realize quite well that material selection, air flow, surface area, et cetra make huge differences.  However, it would be nice to have some rules-of-thumb as a starting point to sanity check whether a device would be cool, warm, ridiculously hot, or an ignition hazard.

What are some of your approaches to estimate how hot your project will get without modeling or building the actual device?

EDIT:

Just to clarify, I am more interested in the steady-state temperature of the device (or at least the "touch surfaces") from continued operation; not the immediate heating effects of a momentarily on device.


texts:
According to this Quora post,

  It refers to two things: A systems bottleneck, in that the bandwidth
  between Central Processing Units and Random-Access Memory is much
  lower than the speed at which a typical CPU can process data
  internally. The 'intellectual bottleneck' in that programmers at the
  time spent a lot of time thinking about code optimisation to stop
  'lots of words' being pushed back and forth between CPU and RAM.

But according to my class lecture, it is the problem that "Generic implementation of single, common instruction and data hierarchy makes it impossible to access data and instructions at the same time. This is traditionally called von Neumann bottleneck."

Which one is correct?


texts: What component of my phone charger produces chirps and how does it do that?

texts:
My Nokia cell phone is charged with a very lightweight compact charger similar to this AC-15 (can't find the one I actually use).

While the battery is close to empty the charger works silently - just heats up a little. Then, as the battery charges it starts to produce silent yet audible chirps and the more the battery charges the more time these chirps take and less time the charger is silent - something like one chirp with duration of one second, then one second of silence. Finally as charging stops and the phone says "charging complete" the charger starts producing a continuous tone of the same frequency as those chirps. When I unplug the charger the sound fades within about two seconds.

What component of the charger circuitry produces those chirps and why and also why would chirping pattern change as battery charges?


texts: Different Vcc and input voltage into flip flop

texts:
I am building an LED matrix using flip-flops. I will have 128 rows in the matrix, so I am using 16 octal flip-flops, where all inputs to are shared and come from a microcontroller, which uses 5V logic.

I would like to supply 3.3V to the latches so I don't need to solder 128 resistors for each LED (forward voltage of my white LEDs is 3.3V). I tried doing this and the latch stopped working, producing unpredictable results. This was a bit of surprise as the flip-flop is documented to work within a range that includes these two voltages. I presumed that the flip flop didn't like two different voltages coming into it.

With my very limited electronics knowledge, I thought the following would work:

simulate this circuit – Schematic created using CircuitLab

It seems to work fine. However, I have since come across this question:

Why is it important not to exceed Vcc at the input to a logic gate?

Where it states that as long as you limit the current going in, no permanent damage will be done. So I tried removing the transistor and just placed R1 between the microcontroller and the flip-flop. It worked.

I have a feeling my circuit above either massive overkill and/or wrong in the first place. Is just using a resistor OK? Any pointers/corrections would be gratefully received.

For reference the flip flop I am using is a SN54HC574


texts: Reduction of the harmonic currents in LCC HVDC systems

texts:
Why there is a reduction of the harmonic currents in the AC side in an LCC HVDC system?
Here is represented the  AC current in yellow, in red the DC voltage and the sinusoidal waves are the AC voltages. As you can see, the AC current is not a simple step but is smoothed. Why has that behavior?


texts: Replacing a VFD (vacuum fluorescent display) with an LCD Display

texts:
I am wondering if anyone out there has tried replacing a VFD display with a modern LED or OLED display.  I would like to hack my factory car stereo (Clarion) which uses a VFD with an Arduino and an LED display.

I've already taken apart the head unit and removed the VFD.  The following inputs/outputs are silk screened on the VFD electronics:

VFD-GND
VFD+32V
F+6V
ILL+
ILL-
SYS+5V
VFD-CS
VFD-CP
VFD-DA
V/K-RESET
KEY-DI
KEY-CE
KEY-CL
KEY-DO
KEY-DI
VOL1-L
VOL2-L
TONE-SW
CD-LOAD
CD-EJECT
POWER-SW
VOL1-R
VOL2-R
U-GND

A lot of the signals are self-explanatory but the VFD ones I'm not totally familiar with.  I would like to reverse engineer the signals coming out of the radio and have the Arduino translate the signals and output them to an LED display.  I'm unsure what kind of signals the VFD uses for communication.  Anybody have a suggestion where to start?


texts:
An 8 Kbyte ROM with an active low Chip Select
input (CS') is to be used in an 8085 microprocessor based
system. The ROM should occupy the address range 1000
H to 2FFFH. The address lines are designed as A15 to A0
, where A15 is the most significant address bit. Which one
of the following logic expressions will generate the correct
CS signal for this ROM?
(A) A15 + A14 + (A13.A12+A13'.A12')
(B) A15.A14.(A13 + A12)
(C) A15' + A14'.(A13.A12' + A13'.A12)
(D) A15' + A14'+ A13.A12
(Question credit: EC-Gate 2016 SET-2)
I am trying to learn digital circuits on my own. Above is a question I am unable to solve.
According to me, the aim is to choose an option which would make the chip select signal to be 0. So both option A and B should be correct, but that is not the case. Moreover, A12 is address line for the ROM so how can we use it for CS signal.
Edit: Thanks @AJN and @Brian Drummond. I understood why option A is correct and not B but I have one more confusion, according to what I know some of the address lines coming out of the 8085 are used as address lines for the memory (ROM in this case) and others (the higher order address lines) are used as the chip select signal. My question is that when A12 is used as address lines for the ROM then can we use it for CS signal also. According to me A15, A14 and A13 should go to chip select signal and others should go to the address lines.


texts:
I have designed a circuit that can turn on and off any load connected with constant delay based on the potentiometer reading. It is based on GreatScott's design. Can anyone verify this design and point out the errors and improvements.
I'm not sure whether this design will work. So help me out!

Layout edit 2:


texts: Is there a difference between a choke, a reactor, and an inductor?

texts: I've seen all three of these terms used interchangeably. But once when I did so, I was told I was using one of the terms incorrectly. Are these terms, in fact, equivalent? Or are there differences between them?