texts:
I want to mix up to 4 rectangle audio signals which come directly from a microcontroller's timer output pin and contain only one frequncy each. For example, if the microcontroller outputs 400Hz and 600 Hz, i want the output to contain both freqencys like they are played on individual speakers.

Afterwards, the mixed signal is amplified by a BC547, then a 2SC5449 transistor and finally played by a speaker.

The problem is that just adding the signals wouldn't apply here because the transistors just cut off everything above 1V.

So i need a mixing "function" which accepts booleans and outputs booleans. Is that possible? I tried XOR, but combining 300Hz and 400Hz sounds like a razor, which is obviously wrong.

Do you have any idea how to do this? I already have an ATtiny13, which is connected to the raw signals and the amplifier, where I XORed the signals.

The 120 ohm resistor was added later when i noticed the speaker was quite load.


texts:
I'm in a bit of a dilemma and I'm wondering if anybody here can help me.

For a display application in need to use a framebuffer which is at least 2Mbytes.This framebuffer is used to drive a 800x480 pixel TFT panel.

I wanted to use SRAM for this because I hear it is faster.

SRAM Part: IS61WV102416BLL

But i have now come across the following SDRAM IC:

SDRAM Part: IS42S16400J-7TLI

It seems to me that the SRAM has a acces time of 10ns while the SDRAM has a access time of 7ns. So, does this not mean the SDRAM is faster?

Thank you in advance!


texts: Interface with wired alarm using Arduino or similar

texts: My house is equipped with a wired alarm system that's missing the hardware controller board. Whats left is a number of sensors (NC) and the wiring to a central location. Cable lengths are anywhere from 3 to 20 meters. I would like to build a simple controller board using Arduino to read the sensor states. What would be the best approach, how would you wire the sensors to the controller board? I have tried to find the best approach online but I have seen many different solutions. I'm thinking of using a resistor in series with the sensor together with an optocoupler, feeding the sensor with 12 volt. Any ideas?


texts: Connecting two center-tap transformers for isolation transformer

texts:
I need to create an isolation transformer so I can float a Device Under Test (DUT).

The parts I have to do so are two transformers:  120V primary / 6.3V-0-6.3V secondary @ 3A.

I intend to connect the secondaries together to create an (essentially) 1:1 isolation transformer with 120V output.

My question is: do I connect the center taps?

My understanding is that with the center taps connected, the voltages reference them as neutral - essentially creating -6.3V and +6.3V  (180 degrees out of phase).

Without the center taps, 12.6V would be the voltage across the remaining two (secondary) leads - right?


texts: Unable to receive GPS data from Quectel L80 GPS module

texts:
I have a Quectel L80 GPS module with PIC24fj128ga202. I am using UART2 to get GPS data from the module and I transfer the received data to hyperterminal, using UART1. Between PIC and PC I there is an RS3232 converter. Here I did not get response data from GPSmodule in hyperterminal.

My code:

void silicon(void)
{
    OSCCON = 0x0000;
    CLKDIV   =  0x0000;
    OSCTUN = 0;
    RPINR18bits.U1RXR   = 7;
    RPOR4bits.RP8R  =   3;
    RPINR19bits.U2RXR   = 14;
    RPOR6bits.RP13R  =   5;
    ANSA = 0x0000;
    ANSB = 0x0000;
    PORTA = 0x0000;
    TRISA = 0x0000;
    PORTB = 0x0000;
    TRISB = 0xc000;
    U1MODE = 0x0000;
    U1STA = 0x0400;
    U1BRG = 25;
    U1MODEbits.UARTEN = 1;
    U2STA = 0x0400;
    U2BRG = 25;
    U2MODEbits.UARTEN = 1;
    PORTBbits.RB15=1;
    TMR1 = 0;
    while (TMR1 < DELAY)
    {

    }
    PORTBbits.RB15 =0;
    TMR1 = 0;
    while (TMR1 < DELAY)
    {

    }
}

void uartsend(char in_c)
{
    while(U1STAbits.UTXBF != 0);
    U1TXREG = in_c;
}

char uartrec()
{
    char c;
    while(U1STAbits.URXDA == 0);
    c = U1RXREG;
    return c;
}
void uartsend2(char in_c)
{
    while(U2STAbits.UTXBF != 0);
    U2TXREG = in_c;
}

char uartrec2()
{
    char c;
    while(U2STAbits.URXDA == 0);
    c = U2RXREG;
    return c;
}

int main()
{
    int i,j;
    led = 1;
    silicon();
    while(1)
    {
        uartsend(uartrec2());
        led =!led;
        for(j=0;j<250;j++)
        {
            for(i=0;i<1275;i++);
        }
    }
    return 0;
}


texts: Can anyone help me identify this transformer?

texts:
I'm trying to make a project using used part from a radio with my basic electronics knowledge.
I want to convert this AC 9.7V to a steady DC 3V using a diode bridge so I need to know what I'm working with (Amp wise) to define the diodes & capacitor I need to use.
I did'nt find anything on the net using the codes written on the transformer; all I know is that input supports 120V @ 60hz and it seems to output 9.7V.
The radio where I took the transformer from also has a backup 9V connector so could I assume that the amps is about the same as a 9V battery outputs (~450mah)?


texts: Eagle PCB : Is there a pcb equivalent to the schematic net label that I can put on my silk?

texts:
As we know the schematic editor has the ability to apply labels (of two styles) to nets that automatically update when the net name is changed.

I'm wondering if the pcb editor has an equivalent that will let me add silk text (on tPlace for example) that references the name of a net.

I know you can use codes like >NAME and >VALUE to reference the attributes of a component in a library symbol.  It seems like you can add arbitrary attributes and reference them in your footprint (see here) but I don't see a way to access the name of the net.

I guess this can be done with a ULP but I'd prefer not to resort to that.


texts: Advantages of chaining another battery to 130Ah AGM deep cycle 12V battery

texts:
I have a 130Ah AGM deep cycle 12V battery for camping connected to 2 x 100W solar panels. I have been testing the system out to see whether it will sustain what I require. I think I’ll require around 100Ah of charge per day which would approximately discharge the battery to 25% SOC.

How much charge can my solar panels theoretically replenish if I can access say 6 quality sun hours in a day?

Does the wattage of the solar panels represent the amount of charge that can be supplied to the battery per hour? If so, I imagine I could generate 1200 Watt Hours or 100 Amp Hours in a day which would be enough to replenish the amount of charge that I wish to consume. Is my math correct?

If I didn’t use more than 100Ah of charge per day, would there still be an advantage in terms of battery longevity by chaining another identical battery to my existing one to double the capacity?

If I wanted to use more than 100Ah of charge then I would require a second battery so as not to discharge the first battery to less than 25% SOC. However, would my solar panels be capable of regenerating enough charge to make adding the second battery viable? Or would there be other advantages to add the second battery in terms of operating on average at a higher SOC even if I were unable to regenerate all of the charge that I had consumed in a day?


texts: Raspberry pi3 12v led circuit - broke down pi

texts:
I wanted to use 12v led, so I tried to switching 5v(gpio pin) to 12v.

This is my 12v switching circuit.

And this circuit broke down my raspberry pi.
When I wired this circuit, they worked well. But I switched on and off several times, the transistor and raspberry pi broke down.

Why my raspberry pi and transistor died??


texts: Analog voltage level conversion (level shift)

texts:
I have a joystick that puts out analog voltage somewhere between 1.5V and 3.5V.

I want to transform this range of voltage to control a motor controller that takes analog voltage between 0V and 5V.

How do I level shift and amplify properly?


texts:
I'm aware that my phone might only demand max 1A. Let's suppose it does. Still, the following is strange to me-

How is it possible, with 2  "20 AWG" cables each capable of 2 amps, for one to give 0.4A to my phone and the other 0.7-0.9A?

I have two USB cables, from different companies. Both are 20 AWG.

I tested them with my 2A capable charger and a usb load tester showing volts and amps, that lets me adjust amps it demands, and both cables are capable of 2A.

Putting the load tester aside, using my phone instead, so I then take my 2A capable charger, USB volt meter and phone..

I plug one cable in on my phone and my USB volt amp meter  measures 0.4A

Then I change the cable.

So I plug the other cable in on my phone and the USB volt amp meter measures 0.7A

And i've tested charging my phone in two locations, (one location has one charger and usb monitor, the other location has another charger and usb volt amp monitor), so i've tested it with two different USB volt/amp meters and two different chargers. And i've seen my phone charge much faster with the one that shows 0.7A, so I believe the reading.

How is this possible.. What could it be about the cables that causes this, And what device could measure it and show it?

I've already looked when buying cables to make sure they're 20 AWG(not 28 AWG), and i've got the load tester.. i'm happy to get other devices to get to the bottom of this. What else could it be and what other devices might I need to test that that is the case?

And the cable that shows 0.4A is actually shorter than the one that shows 0.7A. So it's not a length issue.


texts:
I'd like to build an FM radio that is pre-tuned to a specific station. I could use something like the Si4703 FM tuner chip, but they're expensive and difficult to solder by hand (and require a microcontroller).

If a normal FM receiver is tuned by a variable capacitor, is there a way to calculate a fixed value for that cap so that the radio would only be tuned to one frequency?

While there are several posts asking a similar question (1, 2) none really offer an answer based in a circuit (and instead suggest hot gluing the tuner knob).


texts: how to design transmitter circuit Ma40s4s ultrasound

texts: I want to generate a pulse that have frequency 40khz and amplitude 20VPP to MA40s4s ultrasonic sensor operate. I use raspberry to generate pulse 40khz-5Vpp then using a IC CD4049BE to boost it into 20vpp as in the below figure. I have encountered the problems is that when i not insert sensor into circuit is waveform is very good but when i insert sensor, waveform is noised as in figure.Please give me how to resolve this problem.


texts: Are these ground stitching vias? If so, why are they placed in this manner?

texts:
For reference this is a cheap analog RCA capture card I got from amazon a while back. Today I broke the enclosure on accident and as a studying EE who does some PCB design, I was curious about this.
I am assuming these are GND stitching vias, but was curious why there are so many? Did they go overboard or is this crucial to have for good signal?


texts: Block current flow in one direction with FET transistors

texts:
Is it possible to block current flow in one direction like a simple diode using FET transistors to avoid the voltage drop?

simulate this circuit – Schematic created using CircuitLab

I am not talking about reverse polarity protection. With VS>0 and Vbat>0 if Vbat>VS the current flow from battery to power supply.
I want that the current only can flow from power supply to battery, so always Ich > 0.

I am reading this document from Texas Instruments: http://www.ti.com/lit/an/slva730/slva730.pdf
But I don't understand how figure 4 works. How the gates of P-channel MOSFET are driven? The FET configuration is symmetrical, how is it possible to block only the current in one direction?


texts: Power regulating on device with 1 cell Li-ion and USB

texts:
I have designed a device which is powered by USB but has a built-in battery (1 cell Li-ion with charger) for short periods wihtout USB (a day).
USB is anything near 5V and Li-ion is from 3 to 4.2V. I need 5V and 3V3, how to I regulate this?
LDO-5V can give 5V from USB, but if powered from the battery it will not give 5V, as it can only regulate voltage down. Even LDO-3v3 will not give it if the battery drops below that.
I did not find any switching regulator which will suit my needs. Do I need a step-up regulator to about 6V and then LDO 5v and LDO 3v3 from that?


texts:
I am trying to find the transfer function of a DC motor experimentally using the step response method, for that I am using the following circuit:

Hooking up to Fin a transmissive photosensor that is placed appropriately to do it's job together with a perforated disc connected straight to the motor's axle, thus generating a pulse train with a frequency proportional to the motor's speed to feed the F to V converter.
Vout is hooked up to a scope.
For the experiment I have a little switch connected to the motor's power cable, so I can start feeding a constant +15V whenever I want to, generating a step for the motor.
Now the problem is that when the experiment starts, instead of getting an exponential as the motor speeds up I get this weird kind of pulse:

Adjusting the time scale of the scope to watch this in more detail I get:

Which is really odd, since it shows an overshoot, seems to never reach stationary regime, and decays exponentially all of a sudden, which implies the speed of the motor decays to zero or near zero when I clearly see the motor never slowing down considerably!

Can anyone spot a mistake in my experiment? Is there a reason this happens?
Thanks for your help!


texts: Why does modelsim show St0, St1 & Pu0 for value of logic signal?

texts:
The design block in question is generated by Quartus, it is the shift register megafunction. When I simulate the design I find that some of the signals do not show 0 or 1, rather they show different expression for value:

Where is says Pu0, these are connected to logic 0 permanently. Where it says St0, that is driven low and where it says St1 that is driven high, but not permanently. Why do I see this instead of 0 or 1?


texts: Electronic insulation paper, home made alternatives?

texts:
I need some electric insulation paper similar to Aramid.

It's to protect lithium batteries which only operate under 200'C in a worst case scenario, and normally less than 70'C, and Aramid can handle 500'C.

Baking paper for the oven is ok at 240'C, and i figure it will be fine to fold some over and use it instead of aramid.

Do you have better suggestions of common materials that can be used for groups of lithium cells?


texts:
I am simulating the use of a tl074 quad op-amp and i have configured one of the op-amps as a non-inverting op-amp, where R1=1 Meg and R2=4 Meg and the supply voltage is 9V. Every time i put a signal in, the output is always offset negatively. Is this how the op-amp is supposed to work? or are there more components to add to get just an amplified signal rather than a negatively offset amplified signal? This is basically the configuration i used below.

simulate this circuit – Schematic created using CircuitLab

This is the signal output that i get, Green being the input. Blue being the output.

Sorry if my terminology is wrong. Ill gladly fix my terminology if it is wrong.


texts:
"In control systems, an open loop transfer function having poles in left half plane, should have positive phase margin and positive gain margin to ensure closed loop stability."

I was trying to interpret this statement. I was able to figure out why is the statement correct for gsin margin. I did so by relating root locus and Nyquist plots as follows:

For root locus with open loop poles on left half plane, we get a stable closed loop system untill the locus crosses jw axis. This may happen for larger values of gain, K. So the system is stable for smaller values of gain K. This reflects that the Nyquist plot must have smaller K, and hence would pass the negative real axis at some place greater than -1 (analogous to jw axis.) This would ensure a positive phase margin.

I made many failed attempts to prove similarly for the positive phase margin, too. But I could not figure out why the phase margin is positive for a stable closed loop system (for a open loop function with left hand poles.)

EDIT:


texts:
This circuit board is soldered at the back of a dc motor
The motor has been removed and a magnetic disc is attached to the shaft and spins over these smd components.
They seem to say A87L but I couldn’t find any info.

It has solder pads for 4 wires but there are only 3 used.

Question is: "How can I tell if the shaft is rotating with this encoder?"

I expected it had a +VCC, GND and two Outputs, but this has only three wires. I understand quadrature encoders, I can count steps up and down. But not sure how this one works.

I'd like to write an arduino like program or wire some i2c pulse counter to it.

The motor is intended to be driven by 12V DC, in both directions as it's taken from a linear actuator of the back door of a car.

The only BIAS visible in the image is connecting the isolated left pin on this side with the bias there, connecting the center pin of the left IC.

Also the component numbered 4302 makes no sense to me, unless this is a multilayered PCB (which does not seem to be) it's just there.

Thanks, and sorry for not putting the question clear.

UPDATE:
Here is what I did.
I supplied +12V to the middle pin (this will give +12V to the VCC pin according to the schematics)
Now I only had the other pin left so I connected it to the long pin of a LED, then the other pin of the led in series with GND.
LED lit up.
Now using the disc I can see how the LED lits a two distinguishable brightness levels.
Now, what would be the involved maths to calculate the required components to have a pin pull up down at 5V so I can connect it to a 5v Arduino?
I don't have oscilloscopes. Just multimeters.

Another (easier?) option I guess would be to remove the 392 Ohm resistors and wire the output of the ICs to the arduinos PIN? And power the device continuously with nothing in between? Will this work too right?

Thank you


texts: Amplify voltage controlled current source in a instrumentation amplifier

texts:
I need to apply a current in the body by two electrodes and then analyze this signal, I will receive the signal by other 2 electrodes and amplify using a instrumentation amplifier using three Op Amps (TL084CN).
But, I can not to simulate the offset by voltage controlled current source in a instrumentation amplifier.

I am using the topology described in the article "Design of an Instrumentation Amplifier - Justin Bauer", where the gain is 10.
Example:

With Vin = 500mV peak to peak, then Vout = 5V peak to peak. (Gain = 10).
Putting 5V DC on Vref, then Vout is oscillating between + 10V and 0V.
All right.

My problem is:
Using a current source (Mirrored Modified Howland Current Source (MMHCS)) where +Iout = 1mA and -Iout = -1mA.
With a initial voltage source where amplitude = 2V and the frequency = 1kHz.
I can not to simulate the offset.
Vout is always between + 10.5V and -10.5V.

I tried to apply in Vref 10V, 5V, 2V, but nothing works.
The Vout still varies from -10.5V to + 10.5V.
The Vref only distorts the voltage signal.
I want the Vout varies between (say) + 20V and 0V, it will use the AD converter Arduino Uno, that just read positive signs.
I am using Proteus 8.5.

What am I doing wrong?

Sorry my poor english, i don't speak english.

Bibliography:

http://www.egr.msu.edu/classes/ece480/capstone/spring15/group05/uploads/4/7/5/1/47515639/ece_480_app_note_justin_bauer.pdf

https://www.researchgate.net/publication/258327515_High_Accurate_Howland_Current_Source_Output_Constraints_Analysis


texts:
i have a 12v power supply and fan 5v 150mA and voltage regulator L7805 cv to reduce the voltage to 5volt  .
i need a circuit to just turn the fan on /off by switch .

can i connect the fan directly to vo & gnd from the L7805 ?


texts: Bluetooth LE with BlueGiga devboard (BLE112)

texts:
This is my first post so please forgive me for any informality but I will get straight to my point.

I am trying to send RS-232 data (8N1 asynchronous at 115,200+ baud rate) from my PIC micro via bluetooth to a smartphone. I have done this successfully with Bluetooth 2.0 but that was easy since I was able to source BT 2.0 modules with an AT command set that allowed me to configure it to whatever baudrate I wanted. Now I am transitioning to Bluetooth LE (single mode) using the Blue Giga evaluation kit and BLE-112 module. I have a general idea of how to code the BLE-112 to receive serial data using its UART but not sure how to send that data to the radio. It looks like I'll have to save the received data into a GATT file after which it will be transmitted in one of the packets? Is there any way I can just stream data like I did with BT 2.0?

Lastly, I would be streaming the data to the Bluetooth module and I know that Bluetooth 4.0 dual mode may be the better option but this single mode version is what I have to work with at the moment.


texts: Capture GPIO pin values with STMA32 and DMA

texts:
I am trying to capture all GPIO_C port pin values at a time when PA0 pin goes low. I am using STM32F091RC micro-controller. But I cant figure out why DMA1_Channel4_5_IRQHandler is never called. Any help?

My code:

#define bufferNumberOfElements 2
uint16_t buffer[bufferNumberOfElements];

void APP_Init(void)
{
  // Enable GPIOAEN, GPIOBEN, GPIOCEN, DMA1EN and TIM2EN bits in RCC
  RCC->AHBENR   |= ( RCC_AHBENR_GPIOAEN |
                 RCC_AHBENR_GPIOBEN |
                 RCC_AHBENR_GPIOCEN |
                 RCC_AHBENR_DMA1EN );
  RCC->APB1ENR  |= ( RCC_APB1ENR_TIM2EN );
  RCC->APB1ENR; // short delay might be necessary

  // Configure the GPIOC pins as input
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  GPIO_InitStruct.Pin = GPIO_IN_CS1_Pin|GPIO_IN_CS2_Pin|GPIO_IN_RD_Pin
                      |GPIO_IN_A0_Pin|GPIO_IN_D0_Pin|GPIO_IN_D1_Pin|GPIO_IN_D2_Pin
                      |GPIO_IN_D3_Pin|GPIO_IN_D4_Pin|GPIO_IN_D5_Pin|GPIO_IN_D6_Pin
                      |GPIO_IN_D7_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  // Map PA0 pin as alternate function to TIM2_CH1
  // Pin name       AF0           AF1           AF2 ...
  //      PA0         -    USART2_CTS  TIM2_CH1_ETR ...
  uint8_t AF_number = 0x2;
  GPIOA->MODER = (GPIOA->MODER & ~GPIO_MODER_MODER0) | GPIO_MODER_MODER0_1;
  GPIOA->AFR[0] = (GPIOA->AFR[0] & ~GPIO_AFRL_AFSEL0) | (AF_number << GPIO_AFRL_AFSEL0_Pos);

  // Table 31. Summary of the DMA1 requests for each channel on STM32F09x devices
  // CxS [3:0]    Channel 5
  // 0000          TIM2_CH1
  // So I will use DMA1_Channel5

  // Assign the address of the memory buffer to the CMAR register
  DMA1_Channel5->CMAR = (uint32_t)&buffer[0];

  // Assign the address of GPIOC->IDR to the CPAR register
  DMA1_Channel5->CPAR = (uint32_t)&GPIOC->IDR;

  // Put the number of elements into CNDTR
  DMA1_Channel5->CNDTR = bufferNumberOfElements;

  // Setup the DMA Channel Configuration Register (CCR) to transfer 16 bits both
  // on the memory and the peripheral side, memory increment mode, and enable the channel,
  // run capture forever in circular mode, enable half-transfer,
  // transfer-complete interrupt
  DMA1_Channel5->CCR =
    DMA_CCR_MSIZE_0 |
    DMA_CCR_PSIZE_0 |
    DMA_CCR_MINC |
    DMA_CCR_EN |
    DMA_CCR_CIRC |
    DMA_CCR_TCIE |
    DMA_CCR_HTIE;

  // Enable the DMA channel interrupt in NVIC
  HAL_NVIC_ClearPendingIRQ(DMA1_Channel4_5_IRQn);
  HAL_NVIC_SetPriority(DMA1_Channel4_5_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Channel4_5_IRQn);

  // Set filter (IC1F) bits in CCMR1 to 0b0000
  TIM2->CCMR1 &= ~TIM_CCMR1_IC1F;
  // Set trigger on the falling edge
  TIM2->CCER |= TIM_CCER_CC1P;
  // Enable channel DMA request
  TIM2->DIER |= TIM_DIER_CC1DE;
  // Enable the timer by setting TIM_CR1_CEN
  TIM2->CR1 |= TIM_CR1_CEN;

  /* Infinite loop */
  while (1)
  {
  }
}

uint16_t a;
uint16_t b;

void DMA1_Channel4_5_IRQHandler(void)
{
   a = buffer[0];
   b = buffer[1];

   //do something with data filed in a and b...
}

P.S. I have also STM32F103 if this task would be any easier on this MCU.


texts: Can't balance differential amplifier circuit

texts:
I'm trying to build a circuit which involves an  Op Amp in differential amplifier configuration.
 However I've been having difficulty balancing my output. My understanding of the differential amplifier is that if configured such that R1 = R2 = Rf = Rg then Vout should be about 0 volts except I'm always getting about 0.5-0.8 volts.

I've currently set it up so that there are 5 volts going directly into R1 and R2 with all my resistors equal to 10K ohms and still I'm getting about 0.63 volts. These are diagrams of my circuit I made:

Please also ignore the dashed lines.

This is what I was trying to build:

Edit: Original Circuit


texts:
For a project I'm trying to build a measurement tool for USB where I can measure U, I and P using the INA226 from Texas Instruments.

The shunt resistors all have a different value to measure a current from 0.200 µA to 4A.
Of course it's going to measure voltage but the INA converts it to current and later on to power.

Between the vbus and the shunt resistors I placed some Power Distribution switches so the microcontroller can chose which one would be suited from the collected measurement from the INA.

The problem is that the RDs(on) on the switch where the shunt resistor for 4A is located is almost as high as the value of the shunt resistor.

Will the INA work as configured here or do I need to place a switch so it only measures over one shunt resistor and place V+INA226 after the power distribution switch so the RDs(on) doesn't interfere in the measurement?


texts: Is it possible to implement a serial console via GDB?

texts: Is it possible to send debugging messages from MCU to PC over SWD via GDB without interrupting the running code (ie. without using breakpoints), like we could do via UART of MCU by sacrificing 2 UART pins?


texts: I am trying to use a buck regulator. Usually I make it use at its Max frequency and then just use it. But now, we want to go for Emi and emc certification. I am hence told that this switching (a few hundreds of kHz) can generate noise in the system. So what is the optimal frequency to prevent rfi or noise ?


texts:
First of all, I'm an active StackOverflow user.  This is my first time on Electrical engineering, and I HOPE this is the right place to ask this.

I just moved into a new apartment.  The breakerbox is no where to be seen sadly.  My wife to be has told me that the garage is mine to do with as I please.  So far I have placed a 46inch tv (sony bravia, older LCD, not LED), ps3, several other game systems, high powered computer, low powered HTPC, a small soundbar with sub and a couple of lamps in there.  Everything is hooked up to the one outlet that is available to my setup.  My AVR/batterybackup displays that it is receiving 121-122V.  I have no way to convert to 220 so far as I can tell, and even if I did, I doubt my apartment management would like that very much.

My AVR/Battery backup

Problem:  I currently have the tv, high powered computer (core-i5 oced to 3.8ghz, gefore 560ti448, 750W power supply, and 1 lamp on.  The AVR is reading that it is at 70% capacity. With the ps3 on, playing a netflix video, and   When I start a benchmark on the PC, it jumps to 101-105% of its capacity, and in 5 seconds, shuts itself off.  The breaker has not blown, Im sure because the AVR is absorbing the overflow and not tripping it.

Question:  Is there anyway that I could increase the ability to power my garage without major modifications?  For instance, dropping an extension cord down from the upstairs that is on another circuit is doable (fire and electrical codes not withstanding); but adding a sub-box to my breaker box is not.  Im hoping there is a better way, for instance, would piggy backing a couple of higher powered AVR/battery backup units do the trick?

Current Load information:

Computer (basic browsing)and  monitor+1 lamp: 33% - 0.173kW
Same as above with TV: 64% - 0.336kW
Same as above with PS3 - 85% 0.430kW
Computer (running benchmark)and  monitor+1 lamp: 65% - 0.362kW

Thank you all for any advice/knowledge you can impart.  And again, if this is not the correct subsite for this question, please let me know, or feel free to move it (if you are a mod)


texts:
I am working on a product that will need a unique serial number for each device.

Are there any "recommended practices" for serial number generation?

Since I never saw a device with serial number 1, 2, 3 (as they should be to be considered "serial"), I wonder what are the applications of using true serial numbering for the purpose, why the industry doesn't use it and if there is a common standard on this.


texts: How to control a lightbar with 20 individual modules?

texts:
The TL;DR version of my question is, how do you control 20 pieces of 12V/1A outputs in the most reliable, compact and cost efficient way, with something programmable?

The long version:
I got a lightbar (like the ones on top of police cars) which didn't work, turns out it was some cheap Chinese one with a crappy controller which failed, and it could only control 4 lights at a time anyway (space, and cost saving wiring), so I took it apart, threw away the electronics and now I'm rebuilding it.

The problem is, I need 20 outputs for the LED modules, around 5 inputs (more is better) for controlling and I need to store the flash patterns of the lights somewhere.

I broke the solution into 2 pieces, one is a controller, other one is the electronics for handling the current.

For the controller, my initial thought was using an Arduino Mega, which has plenty of I/O, but I had reliability problems with using it in industrial environments, and I'd prefer a 'normal' programming language over Arduino's own, other than that I couldn't find anything commercially available with this many pins. I also thought using shift registers to work around the pin number problem, but I'm worried it might be too slow for rapid flashing. Any ideas for a controller / solution?

For the electronics part, the best method I found was using 20 MOSFETs, because they can be switched quick enough, for now it seems like a good solution but if anybody has a better idea, I'm open to suggestions.

Part-wise I'm only planning on building one controlller unit (maybe two) so the plan is to do it on a solderable prototype board, designing and printing a PCB seems overly complex, but if it can be made simple, saving a few hours of soldering is always a good idea :)


texts: Why do people use a separate current limiting restore for each LED in a matrix?

texts:
This might have a really basic answer, but its been bugging me.
In a lot of circuits where you are controlling a series of leds, circuits will be draw with a separate current-limiting resistor for each led, instead of one single on the common side.

Why would you do this?

simulate this circuit – Schematic created using CircuitLab

Instead of this?

simulate this circuit


texts: Critique of my Data logger's Power circuit design

texts:
I am laying out my first full device, a fairly simple sensor-data logger, with these specs in mind:

I'm running microcontroller and sensor @ 3.3V, with load varying from 10 mA to 400 mA
device will be powered by a rechargeable Li-ion battery (4.2V maximum)
battery charged by USB (5V)
device's Power-On/Off are toggled by a pushbutton hold or upon a battery undervoltage condition (@ 3.2 V).

The below schematic shows the Power-related section of my circuit so far. Note that Microcontroller and Sensor are NOT shown here.

(EDIT: Schematic revised based on @Russell and @Madmanguruman's suggestions.)

Labels: Descriptions of a few of the labels I used in the schematic image above:

VCC: Voltage (5V) at USB power source used to charge battery
3.3V: Voltage at which Microcontroller, sensor, etc. will run
UC-PIN[1-8]: Various pins of AVR microcontroller, including ADC-capable pin
REG-ENABLE: Enable/disable Signal sent from output pin of STM6601 IC to the enable-pin of TPS63001.

Short summary of my overall approach: From the battery's supply, a buck-boost regulator provides 3.3V for the uC/sensor. This 3.3V supply is enabled/disabled (PwrON vs PwrOFF) by a specialized controller IC, which monitors for either pushbutton event or battery-undervoltage. USB power is used to charge the battery (whose voltage is measured periodically by an ADC pin on the uC). That's it.

Or more specifically, as you can see above, I am using these four components below (with their datasheet links):

MCP73871: Battery-charging IC that uses ConstantCurrent-then-ConstantVoltage approach to charge the Li-ion. I set the pins on the MCP73871 to power the charging with USB (5V) with 500 mA current.
TPS63001: Buck-boost regulator, supplied by the battery, and with a fixed output of 3.3V (Also, I have enabled "Power-save mode" on this regulator to allow higher efficiency for the smaller-load case of my device)
STM6601: Pushbutton-based ON/OFF controller IC

Initially when the STM6601 detects the pushbutton as held for a duration, then it sends out a HIGH signal, which is connected to the TPS63001, thus enabling it, and bringing the device to life.
When the STM6601 detects either that pushbutton is held again OR that the battery voltage falls below a 3.2V threshold, then the STM6601 automatically sends out a LOW, disabling the regulator.

Loadswitch (FPF1008): Controls current going from Battery V+ into a voltage divider

The divider is used to bring down the battery voltage to within the 3.3V maximum allowed on the microcontroller ADC pin.
The ADC takes battery voltage measurements periodically, which is mapped to curve of discharge level, for a rough indication to device user.

MY QUESTION: Do you have any suggestions regarding this layout and approach?

I am interested in any feedback you might have. Given my non-experience with any professional layout, I am expecting there are at least a couple of things "wrong"! Or things that could be improved upon; so I'm frankly open to any suggestions that I can learn from, small or big, even if they require me having to re-think/re-build the circuit.


texts: Ground connections and symbols in schematics: should they be separate or connected?

texts:
I'm new to this world of electronics and I'm trying to make a fuzz face pedal. I'm not comfortable with the notion and symbol of ground connections. Do I have to connect all the ground points to the negative pole or just connect them separately?

Schematics of the fuzz face pedal


texts: Does any HDMI device send commands on CEC pin

texts:
I'm using an IPTV set-top-box that is connected to my TV via HDMI cable. When I'm turn the IPTV on or off it does not affect on TV and the TV remains off or on. When I check the CEC pin by the oscilloscope it doesn't show any thing. I mean the state of pin is high (3.3V) and when I press the set-top-box remote buttons there are no pulses on the scope.

Am I testing the CEC pin right? I mean is it possible that the scope prob may affects on the bus?

Is it possible that my set-top-box do not use CEC? if yes is there any way to force the device to do that?

My main problem is that I need to use one remote control for both TV and set-top-box.

Also there are an I2C pins on HDMI, is there any packets that shows turning on or off the device? if yes maybe I can decode them by a micro-controller and command the TV to turn on and off.


texts: Regarding Power Market demand and supply

texts:
As I have read, that power supply should be equal to demand. As it can't be stored .So basically this means power is generated in real time.

Consider an area where power comes from a Substation A, which receives power generated from power plant B.Of this area suppose each device is currently switched off till now power plant B should not generate anything.

Now I switched on appliances, then at the same time power should be generated by powerplant and transmitted also in real time. So how they Know when to generate? Or correct me If I am wrong somewhere. This might seem silly but I am bit confused.


texts: Does it make sense to use MWh/h as unit of measure?

texts:
Since MW is actually the rate of energy is being used, why would we use MWh/h as in Fingrid's electricity market Load and Generation forecast page?

Wouldn't MWh/h be the same as MW???


texts:
Basically, is there any way to fully encapsulate an RFIF tag in metal and still have it working? Maybe by using the metal as part of the antenna? Low frequency RFID eg 100kHz?

Material - Platinum. Representative enclosure 40mm x 40mm x 5mm with a wall thickness of 1mm.


texts: How does a Cortex M0 perform compared to 8-bit controllers?

texts:
This document cites 60 DMIPS/mW for a Cortex M0, vs 31 DMIPS/mW for an M3. (The latter doesn't agree with the numbers in this document, which cite 1.25 DMIPS/MHz and 0.19 mW/MHz, giving 6.6 DMIPS/mW.)
Does anyone know how the M0 performance/power compares to 8/16-bit controllers like AVR, PIC and MSP430? And what's the deal with the M3 figures?


texts: Truncate and other operations on the constant in Verilog

texts:
Very simple example I am stuck with. I want design written in Verilog to return a year defined in source as 16-bit format to the outer world using two bytes.

`define MY_YEAR 16'd2017

then I need to somehow split this constant into two bytes to perform something like this

wire [7:0] w_year_byte = w_current_byte ? (`MY_YEAR >> 8) : (`MY_YEAR & 8'hff);

For me above expressions with MY_YEAR are not correct as their result is still 16-bit. And this statement does not compile at all...

I know how to do it with vectors, but have never done it before for constants; saw several answers for similar questions on the internet, but still unclear how to make things properly. May appear that my approach is totally wrong, will be extremely glad for educating me.

Update: my Verilog source is relatively big, and the main idea was to have this year definition at the very beginning of the source file, on the first line, because it will be changed frequently and I would not need to go down to find the value to change.

Reviewing Tom Carpenter's answer I realized I was making stupid mistake trying to declare parameter, local parameter or wire outside of the module (at the top of the source, before module declaration), so I follow his suggestion to have

`define MY_YEAR 16'd2017

on the first line of the source, and then somewhere after module declaration having

wire [15:0] c_MY_YEAR = `MY_YEAR;

and then using c_MY_YEAR[7:0] and c_MY_YEAR[15:8] as usual. Thanks Tom!


texts: Is the region of convergence of Laplace transforms of a right-sided signal right of the rightmost pole?

texts: I know that the ROC of a right-sided signal with a rational Laplace transform is right of the rightmost pole. Does it apply to any right-sided signal?


texts: Adding mAh when wiring battery cells in series?

texts:
When combining battery cells in series, the voltages of the cells are added to get the voltage of the final circuit.

Do the mAh add up, or stay the same?

For example, suppose you have two 3.7V cells, each with 200 mAh capacity.  When connected in series, will the resulting battery will be a 7.4V, 200mAh battery?


texts: What would cause my eReader's battery to suddenly start smoking?

texts:
I was listening to some MP3 files on my eReader while shopping at a hardware store, looking at a power generator. I previously checked the battery's percentage and it told me that it was at 80% approximately. Then, ten minutes later, it told me that it was shutting down because the battery was very low, so I was shocked to see that. My reader shut down after that, then I started feeling something warm, so I took the reader out of my pocket and noticed that the case was a little hot, so I immediately popped the lid open and shook out the battery. A strange, plastic-like smell was emanating from the battery, and I immediately dropped it. I didn't pick it up until it had cooled down.

I thought at first it was because the battery itself had shorted, but then started thinking that maybe being near the generator caused it to malfunction in some way, even though the generator was off since it was on display.

Eight hours later, I put the battery back into the reader, and it told me the battery level was approximately 54%. So, what could have been going on?

Battery specifications

Type:
Lithium polymer
Dimensions:

Length 40 mm
Width 75 mm
Height 20 mm
Capacity 1500 mAh

Source: https://tech.aph.org/bt_info.htm


texts: Bidirectional voltage and current switch using mosfets

texts:
I'm following this tutorial (spanish) which tries to create a bidirectional power switch usng mosfets based on this publication by texas instruments
The concept of the circuit looks simple enougth to me, two mosfets back to back, when mosfet 1 conducts due to Vgs, mosfet 2 is in reverse polarity so it's internal diode conducts, when you invert the voltage, it's the other way around, mosfet 1 is in reverse polarity so it's internal diode conducts, mosfet 2 conducts because of it's Vgs value.
But when I try to simulate it  it does not work, I'm still pretty new to electronics so I'm not quite sure what's going on.
What I notice is  that when the voltage source is at -5V the  switch does not conduct (and it should), this is because the MOSFET on the left has a Vgs of around 0V so yeah, that's not going to close the circuit.
The publication does advertise at page 2 that "A bidirectional powers witch(BPS)is an active switch which can support bidirectional current flow when it is in the ON condition and bidirectional voltage blocking whenit is turned OFF" and proceeds to show this circuit.
So that leaves me with  the question, am I interpreting the paper/tutorial wrong? as I understand this should work according to those sources when the polarity is inverted (that's the whole point), I guess I must have messed up the circuit somehow?
The Simulation
Circuit as shown in the paper:

Circuit as showin in the tutorial

My simulation


texts: Why need to separate the path of the current of these two signal source?

texts:
This is a differential amplifier with common-mode signal as input (figure a) :
Since equal voltages vin(CM) drive both inputs simultaneously, there is almost no current through the wire between the emitters. We will then redraw figure (a) to something like figure (b). Thenafter, we can remove the connecting wire:

So the gain of Common mode signal with single-ended output will be:
$$A_{v(CM)} =\frac{R_C} {2R_E}$$
Why don't current from both v_in went through the single R_E at the same time? Why need to separate the path of two current? It's because I see no problem squeezing the two current in a single resistor if ever they can't go past each other.


texts: Does CMOS J/K trigger need pull-up resistor

texts:
I want to use J/K trigger and I was told that usually IC outputs need pull-up resistor, but if I understand it correctly the following J/K trigger is based on CMOS: TI J/K trigger
And it seems to me that CMOS is capable of making both low and high signal, so there is no need for pull-up resistor, right?


texts: How to write on SD card smaller than sector size (512 bytes)

texts:
I am writing a library for FAT file system management on STM32 for learning purpose.
I want to use a SD/MMC card connected through SPI bus.

I do some tests with a disk image on PC (I emulate disk_read(),disk_write() with fseek(),fread(),fwrite()) to understand FAT principes.

I just finished the SD/MMC protocole implementation and realize i could not read/write block smaller than a sector (512 bytes)
For reading operation is not a problem, i can ignore unused bytes (window concept), but for writing it seems more complicated...

I heard about the principle of 'read-modify-write', so if i understand i need to read the entire sector i want to modify.
For example, if i write into a file, in worst case, i need to :

Read, modify and Write the sector in the file allocation table to update cluster indexes.
Read, modify and Write the sector in the file new allocated cluster.
Read, modify and Write the sector where the file entry reside.

So in this case, i need 3 reads and 3 writes, sounds like a waste of time, , are you confirm this ?

This also implies that in order to write i need a buffer of at least 512 bytes, are you confirm this ?

(I try to read FatFs source code but it's complicated, but it's complicated. I wonder how he manages to write with a smaller than 512 bytes buffer. Can you explain ?)

I think with a cache mecanism i can limit the number of reads (before modify-write) but this implies to increase the amount of RAM used.

Can you help me see it clearer in this 'write (read-modify-write) sector barrier' ?


texts:
Basically I have a 4 Bit Shift Register that I am trying to get to work. From my understanding when I send a pulse of 1-1 to inputs S0 and S1..it is suppose to do a parallel load.

I have ensured that the pulse coming is clocked exactly with the clock input (1hz) connected to the Shift Register. Unfortunately, every time I load 0000 inside, the value somehow erractically changes! It goes from 8-4-12-2 to 0, despite the fact that it was suppose to stay at 0!

I have no idea why this is happening please help!


texts:
I was chatting to my boss today and he said:

  My first job was electrical working in a factory for a modem company. The last model modem we made was the 1200 baud. After that they needed programmable logic and went to VLSI chips. We didn't have the scale for that and so we had to close down.

My question is: What triggered the need for VLSI chips in modems post 1200 baud?


texts: Automatic impedance matching in microwave waveguides

texts:
I am trying to building a magnetron plasma using microwave magnetron.

I now need to build magnetron to antenna link using rectangular waveguide, WR-340.

I then found out that it needs to be tuned precisely to move all power from magnetron to antenna. I also found out that waveguide can be tuned with short and two stub tuner. There are also auto tuner available that can tune waveguide automatically depending upon load, continuously.

I search over internet and found this video which explains most of the thing about what happen inside the waveguides:

http://www.youtube.com/watch?v=DovunOxlY1k

Now my questions is:

How do I measure amplitude of microwaves inside the waveguide to know the % of reflectance? Once I know it, by what amount should I change the stub height of two stub to make a match?

I am complete newbie in waves, but I am good at mechanical as well as mechatronics/automation stuffs.


texts: Gold plating versus Silver plating for electrical contacts?

texts:
I have always had it in my head that gold plated contacts were preferred.

I noticed today that the resistivity is as follows:

Silver 1.5x10-8

Gold 2.4x10-8

Is there another property that makes gold preferable to silver for use in electrical contacts?


texts: CAN communication between two ARM MCU's (LPC2129)

texts:
I am trying to communicate between two LPC2129 microcontrollers, one as transmitter and the other as receiver, using interrupts to transmit and receive the message.

The transmit and receive interrupts are occurring in simulation, but the same is not working on the MCUs. But the other interrupts, like bus error and passive error are occurring.

And if I call the receive function in this ISR the message will receive once, and after that device is going to passive mode.

Issue: Even though I have separate ISRs for transmission and reception, it's not getting executed on the MCU, BUT the other CAN interrupt's ISR is executing.

The code is as follows please help.

CAN initialization:

PINSEL1 |= (DWORD) 0x00054000;
C2MOD = 1; // Enter Reset Mode
C2GSR = 0; // Clear status register
C2BTR = 0x001C001D; // Set bit timing
C2IER = 0x000007FF;
AFMR  = 0x00000001; // Enable recieve acceptance filter
C2MOD = 0; // Enter normal operating mode

VICIntEnable |= 0x08280000; //Enable interrupts
VICVectCntl0 = 0x00000033; //Select a priority slot for a given interrupt
VICVectAddr0 = (unsigned)CAN2_ISR; //Pass the address of the IRQ

VICVectCntl1 = 0x0000003B; //Select a priority slot for a given interrupt
VICVectAddr1 = (unsigned)CAN2_Rx_ISR; //Pass the address of the IRQ

VICVectCntl2 = 0x00000035; //Select a priority slot for a given interrupt
VICVectAddr2 = (unsigned)CAN2_Tx_ISR; //Pass the address of the IRQ

AFMR = 0x00000001; //Disable the acceptance filters

Transmit function:

void Tx_Frame(unsigned int ID, unsigned long LSB_4, unsigned long MSB_4, unsigned char LEN, char RTR_FF)
{
    while ( (C2SR & 0x00000004) != 0x00000004)
        ; // Checking that the TX buffer is empty

    C2TFI1 |= (LEN << 16);    // Frame information (RTR=0, 11 bit identifier. And length is setting)
    C2TFI1 |= (RTR_FF << 30);
    C2TDA1 = LSB_4;           // Data A
    C2TDB1 = MSB_4;           // Data B
    C2TID1 = ID;              // 11 bit ID or 29 bit
    C2CMR = 0x21;             // Command: Transmit previously written message through TX buffer 1.
}

Receive function:

void Rx_Frame(void)
{
    DWORD DATA_A,DATA_B,LEN,ID;
    LEN = C2RFS;
    ID = C2RID;
    DATA_A = C2RDA;
    DATA_B = C2RDB;

    C2CMR = 0x04;  // Release receive buffer command
}


texts: Determining whether a load is reactive and its reactance type by the phasor (phase angles)

texts:
I have been given the following question:

A single-phase load is supplied by a single-phase voltage source. If the current flowing from the load to the source is 15∠-135° A and if the voltage at the load terminals is 220∠45°, V then the

load absorbs real power and delivers reactive power.
load absorbs real power and absorbs reactive power.
load delivers real power and delivers reactive power.
load delivers real power and absorbs reactive power

I have done my best and I am fully confused which one is the right answer. I think 4 might be correct because total angle is -90 degrees and current is flowing from load to source. Please give little explanation also.


texts: Operation of Induction Motors and their Back EMF

texts:
I'm trying to reconcile the physical steps that go into the operation of an AC induction motor. Looking online, I either find broad and general explanations that I already know and understand, or very specific and math heavy explanations that get a bit overly detailed.

I understand synchronous motor operation and describe it in my head like this: "From standstill, voltage is applied to the rotor. This creates a current in the rotor which generates a magnetic field which starts to turn the rotor due to attraction to the magnets of the stator. At the start, the rotor has little movement relative to the stator's field, so little back-emf is created, allowing for maximum current to flow, and so the machine has max torque at the start. As it gets up to speed, the rotor's quick movement cuts through more of the stator's flux, and generates more intense back-emf, which fights the input voltage, limiting current into the rotor, and torque drops off until some balance of speed/torque is achieved with the load.

But when I try to create the same "story" of what happens in an induction motor, I must have some fundamental misunderstanding (probably about back-emf), because I run into this: "At standstill, an AC voltage is applied to the stator windings, quickly manifesting a rotating magnetic field. This induces a voltage in the rotor coils, creating a current that manifests its own magnetic field such that the induced voltage/field opposes what created it. Now the relative motion of the rotating stator field and rotor coil would be maximum at startup, creating maximum possible back-emf.... and that's where my thinking fails. If the back-emf is biggest at the start, it'll fight the input voltage the most at the start, which will result in the least current and least torque at the start... and the thing will never get up to speed."

Obviously that's wrong, but I don't see where. In a DC motor, it makes sense easily because input voltage, back-emf, and rotation, are all in the rotor. So when the rotor speed is low, it cuts less flux, and creates low back-emf. When the rotor speed is high, it cuts more flux, and creates higher back-emf. A nice feedback loop.

But it seems reversed for the induction case the way I'm thinking of it. At a low rotor speed, the rotor would cut through more flux, because the stator field is quickly rotating around it. This would create a higher back-emf in the rotor, fighting the input voltage, limiting the input current, reducing torque, and slowing the machine or keeping it from moving.

Then at a high rotor speed, the rotor would cut through less flux, because it's catching up to the rotational speed of the stator's field. This would generate less back-emf in the rotor, which would mean the input voltage isn't being fought as much, increasing current, increasing torque, speeding the device up.

So my thinking ends up with the opposite of a self stabilizing device. If it slowed down, it'd want to keep slowing to standstill, and if it sped up, it'd want to keep speeding up...

None of that is right, so I must be messing something up about how back-emf operates in an induction motor. And I think the inverse nature of how the rotor speeding up leads to amount of flux being cut to be lower is also tripping me up...

Thank you so much for any help with a layman's quest for understanding!


texts: Can I find a file of a microchip for a 1:100000+ version on a 3D printing machine?

texts: It would be cool to replicate a semiconductor microchip on a 3D printer, i.e. a C64, an intel processor, an AMD processor. Can you think of a kind of map file format which graphs many transistors and which can sent to a voxel engine or something?


texts:
Here they define being floating as:

They mention Ungrounded = Floating.

But in another forum someone wrote:

  The signal is consider floating when it does not have the same ground
  with your device. Earth has nothing to do with it. Earth is just
  another ground.

I'm a bit confused with the meaning of floating. Is the source floating in the below system?:

If it is not floating can you give an example of a system where the source ground is floating?

EDIT:

A floating source is connected to a differential amplifier. If I add a ground where the red arrow points the simulation circuit amplifies this signal very well. But if I don't use a ground the simulation corrupts.

In real do we really need a ground at that point or is this only needed in SPICE simulation? Because if I add a ground it is not floating anymore in the diagram. This is really confusing.

EDIT 2:

Even more confusion.

I always encounter such circuit topology for differential amplifiers:

Please notice that, above the input diff signals i.e the source and the diff. amplifier again share the same ground.

But when I look at the input terminals for a voltmeter or a diff. ended data acquisition board, there is no extra ground. There are inputs for -Vin and +Vin, but not GND.

Imagine now that I have a device which has an analog ground called AGND1 and this device  has two differential outputs say 2V and -2V relative to its own AGND1. Now if I hook up its differential outputs to the voltmeter or a diff. ended DAQ board which has its own ground call it AGND2, we are facing a situation where AGND1 and AGND2 are not connected. But still these systems work as below:

As you see in a typical voltmeter or diff ended. DAQ board connection we don't connect two sytems grounds AGND1 and AGND2.

So the diff. amplifier topology I encounter uses grounds common but in real the grounds are not connected.

This is also very confusing since I dont know where my lack of knowledge comes from.


texts: What is the name of this 26 pin connector?

texts:
I am trying to reverse engineer this applied precision actuator (I'll ask different questions as I do so)

To get started I would like to know the name of the 26 pins connector! (oh and if you also know the 5 pins connector name too?)

After hours of google image search I cannot find it!


texts: LTspice error "could not open Library file" when trying to use TL431 model from TI

texts:
I downloaded the LTspice model of TL431 from the Texas Instruments website, but I am not able to simulate the circuit given below due to this error:
"could not open Library file"
https://www.ti.com/product/TL431
the second model in the Design and simulations tab
Please help


texts: Should we maintain the same impedance for the traces carrying RF signal line?

texts:
I'm designing a application circuit board which is having a power amplifier to amplify the RF signal.
Does the lines carrying the RF signal should have same impedance say 50 ohms?
Also does the signals passing through the capacitors and inductors of the matching circuit to the power amplifier should also have the same impedance?


texts:
I would like to debug my microcntroller's program via SPI connected to PC.
(Usually UART is used for debug, but I would like to debug with higher frequencies such as SPI).

Can any one recomand me on PC terminal which is capable of recieving SPI comunication.
Also recomendation on SPI to USB adapter (connected to my PC).


texts: 100k EEPROM writes "per bit" or as a whole?

texts:
As I understand it, the life of an EEPROMs is usually rated at a certain number (e.g. 100k) of writes. Is this "per byte" or writes to the EEPROM system as a whole?

E.g. If the EEPROM has 4k bytes, could I conceivably make 400 million writes if they were evenly distributed?

Specifically, I'm talking about the EEPROM in the Arduino Mega 1280/2560.

Debrief: Thank you stevenvh and Majenko for your helpful explanations. I asked because I wanted to know whether I needed to bother updating only dirty variables when saving a lot of data (a large configuration). From a wear perspective, the answer seems to be 'no': wear happens at the "bit level" and is only caused by setting bits to zero. From a speed perspective, perhaps it would make sense to minimise the size of writes, but if this is not a consideration for your application, then you needn't stress out about it.


texts: Does the N material need to be directly touching the P material?

texts:
I know a diode works like:

anode wire --[ P ][ N ]-- cathode wire

Would it also work like so?

anode wire --[ P ]-----------[ N ]-- cathode wire
                   junction
                     wire


texts: Air gap variation between metal target and planar Inductor coil changes the coil inductance and oscillating signal's frequency & amplitude?

texts:
I am working on planar coil inductive sensor.

I noticed if i change the air gap distance between the metal target and sensor coil. the Inductance of the coil changes,  frequency and voltage amplitude change in the oscillating signal(LC Tank Circuit) changes too. Some time it exceeds the working range of IC.

When the target is near to sensing coil ( Less air gap) the frequency of oscillating signal is high and voltage amplitude is low.

When the target is moved away ( More air gap) the oscillating signal's frequency is reduced and voltage amplitude is increased.

Could anyone please explain the theroy behind this occurrence in detail ?

thanks in advance


texts: AVR ATMega I/O pin overcurrent protection

texts:
I want protect I/O pin against overcurrent to make circuit more robust. Atmel's AVR040: EMC Design Considerations discusses internal overvoltage protection in General I/O Pin Protection paragraph. But I need protect case when a IC output pin is connected to a particular MCU and the MCU pin is configured unintentionally as output too because of firmware bug. And both pins are forced sometimes to opposite logic level.

Similar case when MCU pin is connected to a tactile button and pin is output at 5V.

Simple solution is adding simple serial resistor between these pins. Is it needed or MCU/IC should survive without protection?


texts: How does an LC network enable a shoot through state for an inverter

texts:
I was researching about inverters when I came across the Z source inverter. The Z source inverter is unique in a sense that it enables a shoot-through or a short circuit condition by closing any two switches of the same leg. This would not be possible in a traditional inverter as such a situation would cause the switches to get damaged. But a shoot-through state in a Z source inverter is possible due to the presence of the so called "LC" network. My question is this:

1) How does the LC network prevent any damage of the switch during the short circuit stage?(this is similar to a boost converter when the inductor charges during the 'on time' of the switch in a standard PWM. The closed switch and the inductor effectively creates a short circuit but there is no damage of the switch).

2) What is the use of connecting the capacitors in an "X" like fashion in between the inductors?


texts: So my amp worked perfectly fine in my old setup in another part of the house, but in my new setup it buzzes when I connect a cable, and with a guitar. I thought it was a grounding issue, but it didn't improve with everything plugged into a power conditioner. Also, running a extension cable from the original outlet to the new room created the same buzz as the new outlet. I tested multiple cables and nothing changed. Also, it seems to change a little based off the direction of my guitar, or cable. Any help is much appreciated!


texts:
I'm looking at a dual master spi interface, it needs to run at 20MHz which means push-pull for me.
My main concern is the output current of microprocessors, I could easily exceed the absolute maximum current rating if a software engineer decided to set one output high and the other one low on the microprocessor if they were set up as push-pull.

Open drain isn't going to work because of the 20MHz requirement and the amount of capacitance I have on my GPIO's. So my question is what circuit do I use to select between two dual masters?

simulate this circuit – Schematic created using CircuitLab


texts: Why CAN controller is causing fault codes

texts: We have been working on a PCB project that has an atMega1281 AVR, MCP2515 CAN controller and MCP2551 Transceiver. We have the boards engineered and and the code is complete on the AVR. During testing, we had great success on some vehicles but others, the device causes the CAN to go crazy and cause fault codes. On one case, the device would not let the vehicle start. The board and controller work great with a 3rd party bench simulator. My question is why on some vehicles, the CAN just goes crazy? I tend to believe its software related because it works great in some vehicles and the simulator. Has anyone experienced this and can you tell me what to look for that could be the root cause of the issue?


texts: Pinout for flat controlled impedance cable

texts:
I am confused about how to use a pre-made controlled-impedance cable like this 3M Ribbon cable. It is mentioned that the pinout to determine which are signals (S), powers(P), an ground(G) pins is programmable. Do you know how is that done? If I buy one of those cables what is the pinout? They put as example GG SS GG SS GG SS GG SS GG PP. Should I use that to be safe?
I have seen other cables where the part number determines the pinout.
I want to use it for USB 3.0, so I need 3 Pairs of signals, ground, and power. Additionally, do you know other cables with similar characteristics? Thanks


texts: PIC micro controller oscillator frequency

texts:
The internal clock (Q1–Q4) of PIC Micro controller runs at a quarter of the oscillator frequency (FOSC/4).

My question is if i divide the frequency with 4 Then the timer period of each clock pulse will increase 4 times.

However this picture is confusing. it shows after the internal circuitry divides the clock into four even quadrature clocks. the timer period of each clock (i.e Q1, Q2, Q3, and Q4) less than the main primary oscillator(that is connected to the OSC1 and OSC2 pins).
But i think time period of each clock pulse must be 4 times time period of main primary oscillator.

Can anybody explain the above??

2.What is oscillator cycle?? the frequency of oscillator cycle??

What is machine cycle ??


texts: An LM350, can I have both constant current, and specific voltage?

texts:
I have a regulator such as in this setup to provide 1.2 Amps to a load that requires constant current:

R1 is set to 1 Ohm, which nicely brings the current within range (1.25A according to a small calculator below the image), but what I do not understand is that it speaks of a 1.25V reference. Does it output 1.25V only, or does it output the input voltage (minus) voltage drop (vdrop maybe 3V) and the 1.25V is just specific to ADJ?

Can I output voltage to, say, 2V as well as 1.2A constant current with just one LM350 device?

The datasheet for the LM350 I will be using is the following:
http://www.ti.com/litv/pdf/snvs772a


texts: I have an electronic device that uses a 3.7v 1500maH LiPo battery and is encased in a poly-carbonate housing.  I understand the dangers of LiPo in general, but the battery in question is not large enough to warrant any special handling by shipping companies, so I am curious what the level of danger there is in the event that a battery were to fail.  Would this cause the types of fires and explosions we have seen with Samsung cell phone batteries, or would the risk be minimized?  I have tried to research the levels of risk based on the battery size, but have only found general information related to LiPo/.


texts: Continuity test on potential-free contacts

texts:
When testing connections on working binary potential-free device Siemens N 262E01 I have accidently put continuity test between two contacts.  I analyzed continuity test, and found its maximum values to be 1V and 400uA.  I know you don't know specific of the device, but would such voltage/current in general destroy the input or maybe even the whole device?

[BTW: continuity test beeped, if that helps answering the question.]


texts: Sniffing a proprietary data line at 47.5V

texts:
I need to sniff the physical layer of a proprietary data line with a logic analyser, but my analyser is limited to 5V input. Unfortunately the line runs at 47.5V, which would fry everything. I considered a simple voltage divider, but I'm concerned that I might pump a lot of current through it, or affect the data on the line.

Any suggestions on a way to do this? It doesn't need to be robust - it's just a one-time hack for a single purpose.

EDIT: To answer some of the questions asked: I don't know if it's 47.5V DC offset or 47.5V p-p, as I only have a single figure given to me as part of the spec. It's an old system produced by a company that no longer exists, so getting original specs and info is practically impossible. The data rate is 2Mbps, which to me implies that it shouldn't exceed 4MHz at the physical layer.


texts: Power MOSFET behaving differently at high Vds

texts:
I am trying to switch a circuit continuously by pulsing a power MOSFET(IXTN660N04T4) with a function generator. I have attached my set-up below. IXTH500N04T2 was only used for simulation. Their specs are very similar.
***Edit:

the current limiter in the circuit below is to replicate the actual power supply that I am using. It is a variable supply  max 40V or 20A at 800W.
the simulation showed similar results with and without the 1ohm test resistor I mentioned. Currently, it is used so that I can hook up the oscilloscope without causing a short. It won't be included when conducting the experiment.

Here are the current parameters for the setup:

Pulse period: 200us
Pulse width: 20 us
Pulse pk-pk: (0V-10V)
Load: 130mOhm to 500 mOhm depending on the temperature (current)

For testing the circuit, an 1ohm power resistor is attached between the source and the ground to measure the waveform using an oscilloscope.
When the power supply voltage (V1) is below 25V, the circuit behaves as expected:

resistance values throughout the circuit checked out
voltage drops through the components checked out
The waveform from the function generator and the waveform across the 1ohm resistor matched.
The current through the load was proportional to the pulse width

However, when V1 is higher than 30V(to 35V) and all other parameter remains the same, the "polarity of the pulse" seems to switch.

From the oscilloscope measurement, the switch is on when the input pulse is off.
The current decreases when the pulse width increases.

I have verified that all the parameters are within the specs sheet.
Please help!


texts: MATLAB toolbox equivalent for embedded system

texts: We have to develop control software to run in an embedded system. The prototype is made in Matlab (using neural network toolbox), and we want to port the software to C or C++. Do you know which libraries or software we could use to do this? Embedded matlab may be another option, but, from their info in the website, it seems that neural network toolbox is not supported. Any of you has worked with it before?


texts: Would a laptop charger at incorrect voltage fail to supply power?

texts:
Before I begin, I'd like to note that I am very unexperienced in the electronics field, so some things that may be obvious are completely unknown to me.

I recently was dealing with a laptop that would not charge, boot, or show any signs of life. After some discussion over the phone, I learned that the AC adapter's wire was frayed, and so I immediately ordered a new one. When it arrived, there was still no success in getting any power to the laptop. I proceeded to use a multimeter to test both AC adapters, and like I suspected, the old one was reading 0V. The new one, however, was reading only 15.3V on the multimeter. The adapter says it should be outputting at 19V (both on the adapter itself and on the box it came in). Additionally, the battery is labeled at 14.4V, if that matters at all.

So my question comes down to this: could the fact that the multimeter read 15.3V instead of 19V on the AC adapter be related to why the laptop refuses to show any signs of life? If not, I will probably have to start taking it apart until I get can at the power connector.


texts: 1PPS signal from GPS: do the electrical connections need special treatment?

texts:
I have an arduino (interrupt pin) listen to the 1PPS signal from this GPS (from the Adafruit ultimate GPS breakout).

However, sometimes it doesn't pick up the signal. Occasionally, I've been able to make it pick up a signal by fidgeting with the electrical connections, making me think a loose connection somewhere could be the problem.

The GPS is connected to the ATMEGA328P by a combination of screw terminals, male-female headers, and IC socket. I'm certain that these are fine for ordinary arduino use, but maybe the 1PPS pulse is so brief that it requires stronger connections?

Does anybody know best practices for carrying the 1PPS signal?


texts: How is the Q and Q' determined the first time in JK flip flop?

texts:
My background is in Computer Science, and this is my first time posting in electronics SE.
This is a circuit diagram of JK flip flop.

I don't understand how it works at the beginning, when the circuit is first on. In my understanding, Q and Q' does not have a value yet, then how does the circuit proceed?
I was reading from this website. I have tried three more websites, yet did not find the explanation.


texts:
Consider a one-phase transformer rated at 20 MVA, 13/2 kV and 50 Hz.
It goes through a short-circuit test with |V1|=11 kV applied on the primary side. During the test, the
primary side draws rated current and 8 MW.
Calculate cos Ф.

Hi, I have a problem that I'm not quite understanding. It's asking me to calculate the power factor, I tried a few approaches.
First by taking "P/S = cos(phi)" -> 8MW/20MVA = 0.4, which is incorrect.
Then I tried to take S/V to get the rated current; 20MVA/13kV = 1538.46 A. Then taking the rated current and multiplying it with the rated voltage of the transformer, but it ended up giving me a wrong answer as well. I do not have the right answer.
How would I go to solve this problem?


texts: How to detect which pins on a pin display are touched using capacitive sensing

texts:
I'm working on a project to apply touch sensitivity to a modified pin display. The goal is to be able to sense touch at a pin by pin level.
The current approach we're looking at is adding a PCB layer with traces and brushes on each pin, then using a bank of capacitive touch IC's. As we're looking at using a 30x30 matrix (900) pins I was worried there might be interference between the traces. I was wondering if there is a more elegant solution such as using a grid approach as detailed with a 6x6 grid (https://www.hackster.io/gatoninja236/capacitive-touch-sensing-grid-f98144).
Any advice would be really appreciated (I'm quite new to EE).
Below is an example of the type of pin display that we were looking at adding touch sensitivity too.


texts: How do I make a double dabble circuit with logic gates

texts: Im attempting to make a 8 bit binary calculator that displays on multiple seven segment displays. Can double dabble be done with logic gates. If so, how?


texts: SEM brushed DC servo has stuck brake & disassembly help

texts: 29 in/lb servo dynamics brushed DC servo motor, brake will not release when power is applied.  Motor data plate indicates 24vdc 44in/lb holding capability.  Brake terminals at the motor measure 74 Ohms and an ammeter in series reads 0.346A when 24vdc is applied.  I can override the spindle brake (without voltage applied) with torque of 39 in/lbs and that does not decrease at all with power applied and is smooth and consistent so I don't think I've dropped a magnet and it is not jammed.  This is an older servo but was working prior to being put into storage, I'm doing a CNC control retrofit.  There is almost no info on the net about disassembly of brushed DC servos other than (possibly overstated by repair facilities?) that its not possible other than by a qualified shop because of demagetization, etc.  I would just like to take the end bell off to access the brake and make sure it is not just packed with carbon dust, brake dust or delaminated/swollen brake pad material. The encoder would need to come off (easy) and there is a 7v/1000 rpm tach just under the end cover, then probably the brake, which I can't see but may be at either end of the armature. I have a complete machine shop here and have taken apart and repaired many induction and universal motors but need more information to proceed.  This motor was used vertically with pulley end down. any tips?


texts:
The cross sectional dimensions of the rectangular waveguide in the figure are
\$a=50 mm, b=25 mm\$. The waveguide consists of 3 sections filled with dielectric materials such that the relative dielectric coefficient in Sections 1 and 3 is \$\epsilon_r=16\$, while in Section 2, \$\epsilon_r=17.18\$. The lengths of Sections 2 and 3 are \$l_{\alpha}=14.6mm,l_3=12mm\$. The system is fed from the direction of waveguide 1 with a \$TE_{3,0}\$ mode. Waveguide 3 is loaded by an antenna, whose reflection coefficient, measured from waveguide 3 is \$0.167e^{-j0.947}\$ at 2.5GHz. It is assumed below that \$Z_L\$, the input impedance of the antenna, is frequency independent.
I was asked to plot the loading reflection coefficients at the end of each line, i.e., \$\Gamma_{L1},\Gamma_{L2},\Gamma_{L3}\$, in the frequency band \$2.3<f<5GHz\$.
Below is my attempt at solving this, on which I'd greatly appreciate any feedback:
\$Z^{TE}=\sqrt{\mu/\epsilon}\cdot1/\sqrt{1-(f_c/f)^2}\$,
where \$f_{c3,0}=c\cdot\sqrt{(m/a)^2+(n/b)^2}/(2\sqrt{\epsilon_r})=2.25GHz\,for\,\epsilon_r=16,\,2.17GHz\,for\,\epsilon_r=17.18\$.
Therefore,
\$Z_3^{TE}=Z_1^{TE}=30\pi/\sqrt{1-(2.25/f)^2}\$, which equals approx. \$216.22ohm\, @\, 2.5GHz\$.
\$Z_2^{TE}=120\pi/(\sqrt{17.18}\cdot\sqrt{1-(2.17/f)^2})\$
The input impedance of each section would therefore be:
\$Z_{3,in}^{TE}=Z_3^{TE}\cdot (1+\Gamma_{L3}e^{-2j \beta_3 l_3})/(1-\Gamma_{L3}e^{-2j \beta_3 l_3})\$
\$Z_{2,in}^{TE}=Z_2^{TE}\cdot (1+\Gamma_{L2}e^{-2j \beta_2 l_2})/(1-\Gamma_{L2}e^{-2j \beta_2 l_2})\$
Where,
\$\beta_3=\omega \mu/Z_3^{TE}\$
\$\beta_2=\omega \mu/Z_2^{TE}\$
Hence, \$(Z_L-Z_3^{TE})/(Z_L+Z_3^{TE})=(Z_L-216.22)/(216.22+Z_L)=0.167e^{-j0.947}\$, which yielded,
\$Z_L=302.91-j1.72\$
And,
\$\Gamma_{L3}=(Z_L-Z_3^{TE})/(Z_L+Z_3^{TE})\$
\$\Gamma_{L2}=(Z_{3,in}^{TE}-Z_2^{TE})/(Z_{3,in}^{TE}+Z_2^{TE})\$
\$\Gamma_{L1}=(Z_{2,in}^{TE}-Z_1^{TE})/(Z_{2,in}^{TE}+Z_1^{TE})\$
Does that seem correct and completes the solution or am I missing something?


texts: I am designing a bump circuit in PSPICE to determine if two voltages are equal. The schematic is shown in the figure below. The parameters are set in the subthreshold region, with a VDD of 2 volts. For the simulation, I am doing a DC sweep of V41 around 0 to 2 volts, and I hold V28 constant. The first output (shown below), the minimum bottoms out around 0.4 Volts, I then move V28 to 1.2 V with the same DC sweep and run the simulation again. I'd expect the output to have the same minimum point, instead the minimum around 1.2 Volts results in the output voltage of 0.49, which is not the desired output for the application I'm looking to use this for. The output probe is between M11 and M12. Any help understanding this result would be greatly appreciated. Thanks!


texts: Getting 4G/LTE signal through sheet metal - opening/aperture size needed?

texts:
We have a storage area, that is surrounded by corrugated sheet metal. (Appears to be galvanised steel, and probably 2-3mm thick).
Inside the sheet metal, we have a LTE/4G router, on the Telstra network.
These are the bands that Telstra uses:

2G

N/A

3G

850MHz (B5)
2100MHz* (B1)

4G

700MHz (B28)
900MHz (B8)
1800MHz (B3)
2100MHz (B1)
2600MHz (B7)

The throughput inside the storage cage is not very good - 22Mbps up, 5 Mbps down.
I assume the sheet metal surrounded the cage isn't helping.
My question is - if we created an aperture in the sheet metal - what is the minimum size of a gap that would be needed to penetrate through the sheet metal?
Using λ = C/f, I believe 2100 Mhz has a wavelength of 0.14 metres (14 cm), whilst 700 Mhz has a 0.42 metres wavelength. Does that have any bearing on the aperture (is that the right term?) size I need?
Or how do you figure it out?


texts:
I have three 24V AC lines (from a sprinkler controller) that I need to multiplex into two 12 DC lines. Here's the circuit I designed, with the AC inputs on the left, and the DC outputs on the right.
The AC inputs have a common, and the outputs have a common negative.
Each input converts AC to DC using a bridge rectifier (when active), and then uses a 7812 to reduce to 12V, which then drives a 12v relay. The purpose of the relays is to multiplex the DC outputs.
When I wire up each rectifier/7812/relay section separately, it works. However, when I use all the sections together, all the relays activate, and all the 7812s are showing 12V out.
I understand digital electronics pretty well, but analog circuits are not my strength.
I'm thinking that the commons are causing the problem, and that pull-down resistors, or diodes might solve the problem, but I'm not sure.
Any suggestions?


texts: Why is the 240VAC-12VDC giving both 12VDC and 26VAC as output?

texts: I was using this adapter to power a 12VDC LED strip and felt electric shock from the output wire. When I measured the output with a multimeter, I found both 12VDC and 26VAC on it's output. What could be the cause and can it be fixed?


texts:
I have a simple question about reflection and impedance matching.

Consider a voltage generator Vg with its output impedance Zg, and suppose it drives a load Zl. In order not to have reflection, we should have Zg = Zl. Since this is not automatically true, it is important to put an input matching network which transforms zg into an impedance equal to zl.

But this transformation will ensure that the reflection coefficient at the connection between the matching network and the load is 0. But inside the matching network there is a variation of impedance, so there may be reflection inside it. Why is this not a problem?


texts:
Are there any layout requirements/special considerations when routing traces on top and bottom layers of a double sided PCB, e.g. angle between traces, can traces pass beneath an IC, etc?

I know that ground/signal planes should have the same boundaries on top and bottom in order to avoid unwanted capacitances which may add noise. But are there similar restriction to the traces?


texts:
I recently picked up a Braum (Aldi) TV from the nature strip to play around with.
The TV seems to work perfectly fine (Channels, DVD input, sound etc) except that there's no working backlight.
I've proceeded to disassemble the TV, and found there is 9 lights x 3 strips = 27 backlights.
Each strip seems to have an identifier "94V-0 E348124". The product number for the strip: K395A0835350309686-Rev1.1 I. Looking online it seems to match a Sceptre LED backstrip.
I assume the 94V is referring to the forward voltage required to switch on the LEDS? I think the LEDs seem to be in series, so is the voltage roughly 10.5 V required per LED? (Or would it be 3.5V, assuming 3 strips?) If they are in series, if one fails they'll all fail right (hence 0% backlight)? I can see two pin contacts to test each LED which is nice.
What equipment should I use to go about testing the strips? I don't believe I have any equipment that can supply 10.5V, and haven't really done anything like this before. From looking at other  forums it seems that a common TV backlit LED runs with >3V and about 150mA. Looking for an inexpensive option.


texts: MCU - What's going to happen if I put a PWM output pin right next to a bunch of ADC input pins?

texts:
I'm currently considering a MCU-driven circuit that will do a variety of things, including drive some BLDC motors and do some analog sensing (of position sensors, temperatures and the like).

The designers of the chip I'd like to use (an STM32F4, FWIW) have deemed it appropriate to place the following two pins right next to each other:

The only possible output pin for a timer that I would like to use as a PWM output to one of the motor drivers.
ALL of the ADC inputs.

A few more tid-bits:

The PWM pin may run at very low/high duty cycles (<1% to >99%) at 20kHz
Analog signals of interest range from ~2Hz to ~200kHz, depending on sensor type.

Now, I'm going to go ahead and postulate that putting a PWM pin right next to an ADC input is bad practice, but I'm wondering:

has anyone tried this with success?
What are some potential mitigating solutions that would allow this to work?

Edit:

Here's what the MCU part looks like. I've highlighted the offending timer pin:


texts:
In OP27's datasheet, p. 14, it shows a graph when use OP27 as an 'unity-gain buffer', and give it a step input (I think it's a positive step). But it doesn't explain more about the waveform on the right.

I have two questions:

It uses the word 'drawn', does it means under a positive step input, at that time, the current will flow into the signal generator?
What happens at the points circled in red? Particularly, the point 2 and 3.


texts:
How do you indicate the width of a bus in KiCad? Is there an equivalent to the "slash accompanied by a number" symbol typically used?

For example, as used in this image:


texts:
I do have a chip where a pin can have multiple functions depending on the circumstances*.
For clearness I'd like to have multiple pins in my symbol which all map to the same physical pad.

The other way around is easy (use @: GND@1, GND@2, etc.) but when I try to map multiple pins to one pad I find Eagle 6 doesn't let me do that because "It would exceed the number of pads in my package".

*In my example a TI SSL90S901B Ethernet PHY which has bootstrap configuration input pins to configure the chip on reset (with a 2.2k pullup/pulldown) and which are used for other things during operation (eg. LEDs). But this is a common thing. An AtMega88 for example combines SPI and normal GPIO-pins.

EDIT: I tried using wires in the symbol to create fake pins. This would have the benefit of making clear these pins are the same while still allowing multiple usages. However, wires in symbols seem to be completely ornamental in Eagle :(


texts: Can I avoid tripping my breakers with an superinductor?

texts:
I was thinking about creating a circuit with a large inductor to avoid tripping my breakers when I turn on an iron.
When I use the iron, if I slowly start it with minimum heat and gradually increase it, it doesn't trip the breaker, but if I set it at medium, it breaks it. I was thinking about making an inductor circuit to avoid doing that slow increase by avoiding the spike surge. Is that doable? If so how?


texts: Circuit powered by 9V battery to output between 3.3-5V

texts:
I need to power a device (a LPWAN transmitter) at a voltage of 3.3 to 5V - it can't go below or above these voltages to avoid damaging the device - using a 9V battery. I have solved the problem of regulating down to 5V using a LM317 voltage regulator as shown in the circuit

I wanted to try using a MOSFET to cut-off below 3.5V, but I'm not sure of (1) would this circuit work as I intend and also (2) will the MOSFET drain the battery? This is important the application requires very low power/long battery life

Upon testing lab, I have found that an input of 5V to the LM317 results in 3.5V output, so am I right in thinking choosing a MOSFET with a Gate threshold voltage of 5V this circuit would work as intended?

Note: The 'Final output' with two pins is intended to be two wires, +ve and GND to go to the device that needs power via cables.

simulate this circuit – Schematic created using CircuitLab


texts: Small (max 5x5 mm) connector, panel mount, for asyncronous serial interface?

texts:
I opened a small router and hooked up 2 wires on the PCB (to catch the serial data). That works fine.

Now I'm looking for a way to make a small (tiny) connector in the enclosure, so for future use i can easy attach a connector.

My question, in the land of of a billion connectors, what would be a good small (female) connector, panel mount, max. 5x5 mm?

Many thanks.


texts:
I've got Ripple Carry adder (26bit) made from scratch.

entity Ripple_Carry26 is
port(
    A, B : in BIT_VECTOR(25 downto 0);
    Sum : out BIT_VECTOR(25 downto 0)
);
end entity;

Now I want to use it to update counter every time clock goes up. Counter is just simple register

entity Counter is
port(
    inp : in BIT_VECTOR(25 downto 0);
    clk : in BIT;
    qout : out BIT_VECTOR(25 downto 0)
);
end entity;
architecture Reg of Counter is
begin
    proc : process(clk)
    begin
        if clk'event and clk = '1' then
            qout <= inp;
        end if;
    end process;
end architecture;

If I use port map to just connect stuff, it doesn't make sense, I only want to use the adder when clock goes up, but if I use process and say something like

if clk'event and clk='1' then

I'd like to say something like "now use the adder and add 1 to it" but I'm not sure how.

(I know I'm doing it too complicated, it's all learning purposes)

Every idea helps!


texts:
I need help troubleshooting my DIY radio. I am following the schematic this link.
See pictures below for a diagram of how the components are wired and the actual wiring. The design I made is different from the schematic because I am restricted to a 3.5mm aux port.

Transistor = 2N2222A
Variable capacitor = 12 - 60 pF
Audio is connected to a 3.5mm aux port

The values I've collected through the circuit are the following

Ic = 90 mA
Ib = 0.5 mA

I've switched out every component and I still do not get any sound.


texts: Simple Buck/Boost/Other Topologies building tutorials

texts:
For educational reasons, I want to build physical DC-DC converters. I would start with simple buck or boost topology. For start, I wish to have a simple gate-drive for switches, without PWM modulation. After successful build, I would like to be able to include a simple control circuit with PWM modulation an topology I built.

Can you recommend any tutorial that would also ease components selections? Or, do you have good recommendation for gate-drivers and PWM modulation ICs that are simple enough for first-time builders? (it doesn't necessarily needs to be a buck or boost converter topology)

Thanks.


texts: Multiple PWM signals from a single audio channel

texts:
Here's my project in a nutshell:  I'm building a quadcopter and I need to control each of the four motors independently.  I'm using an iPhone as the "brain" of the quadcopter, with of all the control logic being implemented in software on the phone.

Somehow, I need to interface my iPhone with the ESCs for each of the brushless motors.  I don't have access to the Lightning port (or the money to join Apple's MFI program), so that leaves me with the headphone jack.  It would be reasonably simple to control the frequency/amplitude of the two audio channels and convert the signals to PWM, but I need to extract FOUR signals from the two channels.

My idea is this: "encode" two signals per channel by dedicating two different frequencies (say, 100Hz and 1000Hz) and modulating their amplitude in the software.  Then I need a way to split the frequencies into their own independent signals to convert to PWM, before reaching the ESCs.  What could I do to make this work?

Or, is there an easier way to accomplish what I need? I'm a Software Engineer by trade and a wanna-be EE by hobby, so my electronics experience is limited. A Fourier Transform would be the answer in the digital world, but I'm not sure how to make this work in the analog world. If somebody has a better solution, I'd love to hear it!


texts: Convert IEEE Double to Integer - Verilog

texts:
I want to convert the IEEE Double value computed in my code to Integer.

E.g. I have computed: X = 64'hxxxxxxxxxxxxxxxx; Now i want to use it as index of an array as: some_array[X];

How can I do it? Is there any IP-Core or any other third-party Core for this conversion? Or some synthesis-able method/algorithm?


texts: PS3 Sixaxis controller won't charge over USB

texts: I made a 5V charging setup and want to connect USB devices to it to charge them. Most devices work ok, but my Playstation 3 Sixaxis controllers won't charge. The voltage is ok, slightly over 5V. As prescribed by USB I short circuited both data wires to indicate to the devices that there is no data connection and they can draw high currents (1.8A). I also connected the cable's shield to the ground, which should be done on the host side. Apparently the Sixaxis controller wants to do some kind of handshaking before it wants to charge, because the only devices that will charge them are the PS3 itself and computers. I hope to hear from someone who successfully made a setup to charge the controllers. Dedicated chargers like that exist on the market.


texts: Smoothing capacitor burns out while I am trying full wave rectifier

texts:
I am new to Electronics. I am trying the Full wave rectifier.

I use a transformer and 4 1n5408 diodes (Vdrop is 1.2V) and try to get 24VDC output from 220VAC 50Hz. I measure the AC output (of the transformer) and it is 24VAC. I measure the output after these 4 diodes, it is about 23VDC.

Everything goes fine until I put the smoothing capacitor, no load yet. It is a 3300uF 25V electrolytic capacitor. When I turn on the power, the capacitor gets hot really fast, changes its shape and is going to explode.

I check the polarity, it is correct. So my question is:

Is it because my capacitor has a "too close" maximum voltage? If it is how should I choose a capacitor voltage for this circuit?
Another question though, I have seen this formula around while searching for my problem: C = I(load)/2.f.V(ripple). So if I need Vr = 2V and I(load) = 2A I need to use a 2/(2.50.2) = 0.01F = 10000uF Capacitor right?

Thank you all, really sorry for my English.


texts: Will a RCBO 4P trip in case of neutral fault/failure/interrupt/float?

texts:
We have 3 phase power supply in my home which is used to power single phase 240V 50 hz appliances with common neutral. (Diagram in the link at the bottom)

The only protection we have as of now are MCBs down each phase. But we recently faced a big problem.

Few days back, the neutral wire of the distribution line outside our home broke and fell on the ground. This happened probably due to impoper maintenance by company, summer heat and heavy load. Whatever may be the reason, this fault damaged our wasing machine, air condtioners, water filter, laptop charger and other appliences. This was a big setback for us. So, I am trying to figure out

Why this damage happened and
What can be done to prevent this in future? Are there some device which can be installed to protect the home circuit?

I researched a bit around web and it seems this problem is called neutral fault. This decreses the volatage across some loads and increases across others. High voltage can reach up to 380 to 400 V.

Solution I have found so far is to install a RCBO-4P at input from main lines. So I want to know will this solution work? Will a 4 pole residual current circuit breaker with over load protection trip, if the neutral input is disconnected?

I have tried to simulate what happened here.

Thanks a lot.

Also I found one product which match my requirement, Neutral Loss Protection Relay.
But I am doubtfull about it's current rating.

Update

Wikipedia says, "To provide some protection with an interrupted neutral, some RCDs and RCBOs are equipped with an auxiliary connection wire that must be connected to the earth busbar of the distribution board. This either enables the device to detect the missing neutral of the supply, causing the device to trip, or provides an alternative supply path for the tripping circuitry, enabling it to continue to function normally in the absence of the supply neutral."


texts:
I have several HC-SR04 modules which I wish to modify. There are two modifications in particular I want to ask about

First, I am going to use two modules in parallel to determine location as opposed to distance. I’ve seen a project where two modules are connected in parallel and triggered together. The distances returned are then used to triangulate a position. In the article, one transmitter was disabled by attaching foam in front on one transmitter.

I was able to find the article to which I’m referring.
http://forums.parallax.com/discussion/134899/triangulation-with-a-ping-array

I want to totally remove the transducer. I plan on testing whether the module without the transmitter can still detect the ping from the second module.

If not, what passive components could be used in place of the removed transducer? I’ve searched for an answer but have been unsuccessful in identifying a solution.

Secondly, I’d like to mount the second transmitter away from the module. I’d like to have the two receivers mounted about 3” apart and the transmitter to be centered between the two. This implies that the receiver will be extended by at most 1.5” from the module. Can I just wire the transducer with shirt extension wires? Should the extension be shielded? What wire gauge be used (are thinner or thicker wires better)?


texts: Driving a seven-segment LED display without interruption

texts:
Microcontroller drives 3 digits seven segment type LEDs sequentially.
while(1)
{
select left character
wait 5ms
select middle character
wait 5ms
select right character
wait 5ms
}

If I add extra 80-100ms delay in while(1), the blinking of the LEDs can be noticed by the eye or may stop momentarily.
while(1)
{
select left character
wait 5ms
select middle character
wait 5ms
select right character
wait 5ms

=> I2C read sensor(max 85ms)
//Similar operations can stop LED blinking
}

I want to read the temperature value from an SHT21 sensor and display the values on LEDs continuously. The sensor needs 85ms after write command for reading temperature value.
I2C read sensor
{
i2c_start;
i2c_write_command; //this trigger measurement
wait 85ms; //wait end of measurement

i2c_read; //Temperature value ready on chip, read it
i2c_stop;
}

I setup a timer for reading SHT21 about 1 second interval, but for the delay in the I2C transaction, I can't lock the microprocessor, so I can't use delay_ms command.
I can setup another timer which works about 85ms interval.
Maybe this will work, but the second timer may complicate the software, I am also concerned about this point.
What other approach can I use?


texts:
I am trying to read ID register of BMC150 using SPI. I am using stm32f103 microcontroller. Serial clock line is OK and the data is sent properly over MOSI of microcontroller. But no response is sent back through MISO. I have checked signals using oscilloscope. Here is a part of my C code. How can I resolve this issue? Thanks.

    while(1){
    //Activate Slave
    SPI_GPIO->BRR = SPI_PIN_SS;
    // Go to active power mode
    SPI_I2S_SendData(SPIx, 0x4B01);
    while (!(SPIx->SR & (SPI_I2S_FLAG_TXE)));
    // delay for applying setting stably
    delay_ms(1);
    // Go to normal mode
    SPI_I2S_SendData(SPIx, 0x4C00);
    while (!(SPIx->SR & (SPI_I2S_FLAG_TXE)));
    delay_ms(1);
    // read request
    SPI_I2S_SendData(SPIx, 0xC000);
    while (!(SPIx->SR & (SPI_I2S_FLAG_RXNE)));
    while (SPIx->SR & (SPI_I2S_FLAG_BSY));
    }


texts: Confusion in selecting relay while designing pcb in eagle

texts: This is the first time I am designing a PCB in Eagle. Everything is going great but the problem I am facing is selecting relay in eagle library. All the relays in eagle are actually not the size I am looking for. I am planning to use these relays but these type of relays are not available in eagle. Main point here is the shape of the relays available in eagle are of rectangular and I want to use some square one's. Can anyone help me or am I missing some library .?


texts:
I am trying to create a UART receiver in Verilog for my FPGA.  I was following this guide http://www.fpga4fun.com/SerialInterface4.html

According to it the standard practice for asynchronous communication is to oversample the signal at 16 times the BAUD rate.  This makes sense to me since I would need to do this to detect the first drop quickly and synchronize with the transmitting clock.

What I am wondering is why not just sample at the same frequency as the clock on my FPGA which is a lot fast than 16x the BAUD (my clock is 100 MHz).  Is there any harm in doing this?  I know it would probably just consume more power, but would it work or is there something I am missing?


texts:
Does somebody recognize the component labelled with "1/4"? It measures 6 mm x 2.5 mm (the white body only about 2 mm though).
It is connected between the positive pole of a 9v battery and the rest of the circuit like a fuse would be.
Is it more likely to be a traditional fuse or a PTC? What is the "1/4" label likely to mean?