texts:
This is a follow-up on a previous question that I have asked before, after making some changes as suggested through valuable inputs by other members, but with the problem persisting.

In a nutshell, the situation is as follows: I have a system that controls a lot of solenoids. Wires from the switching circuitry are rather long - between 2 to 10 meters. The heart of the system is a Microchip PIC32 microcontroller.

As stated in my previous question, the PIC undergoes intermittent resets when the solenoids are switched. This happens at random and not necessarily with a particular switching sequence.

The system consists of two PCBs - one contains all of the switching circuitry (from here on referred to as the "host" PCB), and the other (from here on referred to as the "core" PCB) contains only the PIC32 and a few other ICs (EEPROM and USB/UART bridge). The idea of having the PIC32 on a separate PCB is to make it easier to maintain the system in the event of a software bug/update, where only the small PCB containing the PIC32 can be replaced, and not the whole system (to make it a modular design).

Having said this, the core PCB is rather small - 66 x 38 mm. All of the unrouted area on this PCB is filled with a ground plane on both sides. Furthermore, there is only one single pin on this PCB that connects to the power and ground signals to the host PCB.

On the host PCB, all of the switching circuitry is optically isolated from the core PCB. There are also separate power connections between the two sides of the host PCB (thus, the two grounds are also separated). The system does make use of only one external power supply, with separate power connections for the two parts of the host PCB that are branched as close to the power supply as possible. The location where these power wires meet are thus as far away as possible from the circuitry to help prevent the inductive kickback from the solenoids coupling into the power supply for the core PCB.

This is an excerpt from the core PCB circuit showing the PIC pins in question:

This is the actual PCB layout of the circuit described above:

So far, I have taken the following steps to keep the power supply to the core PCB as clean and constant as possible and to prevent the unintentional resets:

Use Schottky diodes at the switching circuitry side of the host PCB for faster response against the inductive kickback caused by switching the solenoids.
Decoupling capacitors (C2-C7 in the above circuit) for all the power pins of the PIC on the core PCB, including at the MCLR pin.
Replacing the pull-up resistor at the MCLR pin (R1 in the above circuit) with a short circuit to force it high at all times.
Added a 1000 uF capacitor across the power supply for the FET drivers ("Local battery concept" as recommended by user analogsystemsrf in the previous question)
Placing a common-mode choke in the power supply circuit for the core PBC, as in the circuit below:

As mentioned, the resets still occur. I can only think of the following to further attempt the prevention of the resets:

Add a big capacitor (in the order of 1000 uF) across the main power and ground pins on the core PCB that come from the host PCB.
Add additional decoupling capacitors of various values to all of the power pins.
Use a completely separate power supply for the core PCB (this would be a last resort if all else fails).

Although I can perhaps just use a completely separate power supply for the core PCB, I do not want to resort to that unless I really have no other option. I am convinced that this problem can be solved by other means.

Please comment and provide some guidance on my options that I have listed here. Also, if there is anything else that anybody can recommend, that will be greatly appreciated.


texts: Do anyone know how to derive the microstrip stub equations for all four microstrip below ?


texts: Step Down Voltage Converter with Commutator motor

texts:
I got a leaf blower which I bought from Japan and intend to use it in Thailand
(220V => 100V). I found a step-down converter which can not be used on electronic stuffs.
(the blower runs on motor only so I suppose it would be fine)

The blower specs are as follows

Motor type : some kind of commutator motor
Voltage    : single-phase 100 V
Current    : 12 A
Power      : 1,100 W

the tranformer specs are

220-240VAC to 100VAC, 2.5 A Max., 50/60Hz,26-1875W

Here, I found the max current very strange.

Another device

220V±10% to 110V±10%, 10A Max. 50/60Hz, 2000W max

The problem is the current my blower need is 12A which is more than the max current specified by both devices.

Should there be any problem?
After all shouldn't the max current be calculated by max wattage divied by voltage?
Would it be okay to use any of these transformer?


texts: Controlling electric power steering using an Arduino to emulate torque sensor

texts:
I am trying to control an electric power steering rack with an Arduino.  To do this I need to "trick" the EPS module that there is torque being applied when there really isn't.

On the rack there are 4 wires coming from the torque sensors where the torsion bar is which go into the EPS module.  I cut these wires so I could splice in and play around.

I determined each wire is 5+V, T1, T2, and GND.  When I connect my own 5V and GND to the torque sensor, I am able to read T1 and T2 via the two analog-in pins on my Arduino. When no force is on the wheel, T1 reads about 2.3V and T2 reads about 2.6V.  When trying to steer left, T1 drops while T2 rises and vice-versa.

I have a shield with 4 (100k) digital potentiometers.  I figured it would be easy enough to have the Arduino "emulate" the torque sensor, so I connected the EPS module 5+V to POT1A, GND to POT1B, and T1 to POT1Wiper.  I did the same for T2 (5+V to POT2A, GND to POT2B, and T2 To POT2Wiper).

My Arduino sketch simply reads the analog pins for T1 and T2 connected to the torque sensor, scales them into a float ranging from 0.0-1.0, and then I tell each digit-pot to adjust the wiper accordingly.  What should result is the steering be close to the same as if it were directly connected to the torque sensor.

When I try applying my own 5V source to the POTs, the wiper voltage reading is correct (i.e. I tell the digi-pot to set wiper position to 128, meter reads 2.5V).  But, when connected to the EPS module, the reading is off (at 128 it reads around 4V and only changes slightly as from 0 to 256).

I then tested the EPS module wires.  Connecting my multimeter to 5+V and GND reads 5V (expected), but also reads 5+V on T1 or T2.  T1 and T2 show no voltage.

Also to note when testing voltages on T1 and T2 while the torque sensor is connected to the module like normal, the voltage readings are what I get when I power and read the torque sensor directly.

I have confirmed that the signal from the torque sensor is pure analog, no PWM or digital signals at all.

Any ideas on what the torque sensor is doing to drive the ECU properly to get this working would be much appreciated.

Thanks,
Andrew


texts: How to set up 40 hz flashing LED lights to light a room?

texts:
I am trying to figure out how to light an average size living room or bedroom with lights flashing at 40 Hz at the same time (one big light or many small ones).  I assume the range can probably be +/- 3 Hz or less but the target is 40 Hz.  This range appears to be out of the range of a common strobe...  I know there are a million answers for this problem, I figure LEDs have a natural advantage (but could be incandescent), AC or DC options will be considered, but the most user friendly options will likely win out.  I would like to set something up that even my grandmother could turn on without thinking twice.

The background information regarding why this is such a hot question on the internet can be found here: http://www.radiolab.org/story/bringing-gamma-back/

Thanks in advance!


texts:
I am trying to connect a encoder to a motor controller which runs very close to the motor that it controls (30+ amps). Due to the risk of high EMI of the motor inducing on the encoder signals, we send these signals differentially (RS485) over an SF/UTP cable. Currently, the shielding of this wire is connected directly to the ground line of the encoder. The figure below shows the current wiring:

I am not sure if this would be the proper way of wiring these signals under these circumstances. I am a bit worried that the groundloop causes ground noise and thus ruins the proper grounding that the encoder requires (it's powered by 5V and can take up to 1V of fluctuation worst-case, but better grounding is absolutely preferred). I've seen solutions where one side is connected with a cap, however this is not ideal in my case because I do not really have any room for this.

My question in a nutshell: would the groundloop in this case possibly cause issues? Note that the currents to the ground plane are limited to <250mA. Or are there other solutions that are more suitable for my case? Connecting the shielding to the frame for example.


texts: What spacing to use between microstrip trace and ground plane on same layer?

texts:
I am designing a 4 layer board (1 - signal, 2 - GND, 3 - power, 4 - signal) and I have some microstrip lines on top and bottom layers.
Should I fill the top and bottom layer with ground? What do you recommend? I intend to do so, but I don't know what clearance to keep between the microstrips and the ground planes on the same layer.


texts:
I'm getting a clearance error in Eagle, as I understanded, the error comes from the distance between two signals. As you can see in this image there is this pointy thing between pads. What is this ?

Any help would be appreciated.


texts: Reversed and Forward Biased Diodes in Parallel

texts:
simulate this circuit – Schematic created using CircuitLab
We were tasked to find the node voltage V. My analysys:

The way I approached this problem is to first make the assumptions of the state of the diodes. My guess is that D1 and D6 will be OFF while D5 will be on. My reasoning for D1 and D6 being OFF is because they have the opposite  polarity from the voltage source that are parallel with them. D5 on the other hand i think will be ON because of a positive potential difference between the anode and cathode. But i'm having trouble with the state of D2 and D3.
My guess is that given the direction current source and the fact that current moves from higher to lower potential, D2 will be ON since D2 has the +- potential.
If D2 is ON, will V just be the forward voltage of the diode? In this case, 0.7 V since these are given to be silicon diodes.


texts: Trying to understand the transient current equation on a RLC circuit

texts:
I am reading this doc

I see this magic happening on the third line of equations...

How in the name of Math, does this
\$ Ae^{st} \$
appeared there?

Magic?


texts:
Referring to question here: Click here, I'd like to use the 16 channel LED driver to run my 7-segment displays. I'm using a Spartan 6 LX9 FPGA to implement a 16-bit microprocessor that will take care of it all.

The development board I'm using is pretty barebone and has an onboard 100MHz clock, or perhaps I should say oscillator. What I was planning to do is slow it down to perhaps a few megahertz, then output it via a GPIO to the LED drivers and synchronize it that way with a separate verilog module.

My question is, do I have to take special care when trying to output a clock through a GPIO? Perhaps use a particular pin? I'm given to understand that the clock input is supposed to be through a predefined pin. The clock could be slower, as it doesn't really need to be too fast.

Here's the online user manual to the development board (pretty basic): Click here.

EDIT: More information:

I'm concerned about clock skew. The chip I'm looking at writes at every positive clock edge. What I plan to do is to divide up the clock and send it out to the chip, while the FPGA also uses the same signal to synchronize and send data to the chip serially. Timing seems to be pretty tight. A slow enough clock might be the answer though.


texts: Why do XC and XL need to roughly match in an LC tank?

texts:
In an LC tank circuit, why do XC (XC1 + XC2) and XL need to be roughly similar?

For example, in this Colpitts Oscillator taken from https://www.electronics-tutorials.ws/oscillator/colpitts.html, I calculate XC to be 703ohms and XL to be 677ohms.

Edit: I just realised that in order for a tank circuit to resonate, the reactances need to be equal at that frequency.


texts: How can I detect a safe eject of mass storage device on STM32?

texts:
I use usb module of STM32F103C8T6 to be a mass storage device, which allows user to edit some config files in the project.

I want to exit mass storage mode as soon as the user eject the disk, I tried to inquire bDeviceState but its value only changes when I replug the device(it still remains "CONFIGURED" after I safe eject the device).

I want a reliable method to detect the safe eject event from computer.Thanks.


texts:
I have always heard about EMI noises but have not really meet them or measured them.

Our system composes a MCU running at 168MHz and a 16-bit DAC which is supposed to provide high-precision voltages with very low noises. Then I observed these noises on the output of DAC. The output of the DAC are connected with the oscilloscope through a 2.54mm 2 pin header.

They are multiples of 640kHz.
The unit is dBu. When converted to V, -80dBu(the 1.2MHz peak) is around 77uVrms.

When I tried to connect the oscilloscope's both measuring probe and ground probe on the ground, very close noise patterns held. The probe we used is close to the following diagram:

The measuring probe and ground probe forms a small circle with diameter of 6cm. I suspect that the circle acting like anttena will receive the EMI noises generated by MCU.

My questions are:

Are my guesses correct? Shall I conduct more experiments to verify?
How shall I reduce the noises of the DAC output? Reducing EMI noises level or using something like a SMA connector? I wish the 640kHz noises will be as low as the noise floor shown in the diagram above.

Update
For a update, I found out the EMI noises are from SMPS circuits:

When the MCU is in halt mode, the noises disappear. So firstly I thought the MCU generates the noises.
After a second read of the datasheet of SMPS IC, it seems that the noise frequency changes as SMPS output current changes. It is the same as what I observed.
Then I add a 50Ohm resistor as the load of SMPS of 3.3V and the MCU in halt mode at the same time. The noises come out!

Now the question becomes, how to reduce the EMI noises caused by SMPS? I started by reading this from TI: Simple Success With Conducted EMI From DCDC
Converters


texts:
I would like to understand a problem which i have with a little MOSFET test with a dc motor.
My power supply drive the motor at 12V and it consume 1A.

My circuit is very basic. I have a stm32 MCU which drive a mosfet (IRLR2905ZPBF).

My motor is connected between the dc motor output and the ground. I don't need a H-Bridge.

When i increase my PWM ratio softly from 0 to 100% my dc motor works prefectly but when my motor is stopped and i put a 100% value on my pwm command, there is a big surge (i think to start the motor from stop state). So my 12V power supply is falling and i obtain a MCU reset.

I had a 100uF bulk capacitor but no better results.

Thank you very Much.

Adrien


texts:
I'm new to relays and still learning terminology. "Make before break" and "break before make" both make sense to me.

Is there such a thing, or a specific term for "break before make" relay that can delay between breaking and making connection?

I'm attempting to trigger a projector screen up/down signal using a relay, but it seems to be switching too fast. If I manually connect the wires, things seem to work (i.e. connect COMMON + DOWN, disconnect, connect COMMON + UP)


texts: Powering 5v LEDs with 6 or 12 volt batteries

texts:
I'm building an art piece that uses about 2000 RGB LEDs. They are WS 2812b LEDs, and I expect the normal draw to be around 200-300 watts. If all bulbs go full white at the same time, it could pull up to 500 watts.

I have power supplies that can handle this when I'm running off of 110v AC, but I'm trying to come up with a battery powered option.

Some concerns - the amount of light emitted will be highly variable. So I want to make sure the voltage stays within safe bounds given that reality. Also, it should be able to run for around 16 hours between chargings.

What battery configuration would you recommend for this piece?

6 volt batteries?
12 volt batteries and build a voltage regulator?

Thank you for your thoughts!


texts: In PoE: is alternative A compatible to all PDs?

texts:
I am currently designing a PoE plus device. I'm using 1G speed and currently following alternative A configuration (data pairs 1/2 and 3/6).

Question is: Can all Powered Devices (PD) support alternative A? What happens if I redesign and use alternative B instead? Can PDs still extract power from it? In other words, are PDs compatible with both alternatives A and B?

Also, if I design alternative A only, can the unused center taps be shorted so they share the same surge protection components? I know it's not recommended from a design perspective but I don't have much space on my board!


texts:
i am using CooOs with 4 tasks.the problem is that only the first task run (indefinetly).What i want to do is to toggle each task 3 seconds then switch to the other.I know that i can do that with timers or systick but i need to handle CooOs.

#include "stm32f4xx.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_tim.h"
#include "CoOS.h"

#define STACK_SIZE_TASK 100

/*---------------------------- Variable Define -------------------------------*/
OS_STK taskg_stk[STACK_SIZE_TASK];
OS_STK tasko_stk[STACK_SIZE_TASK];
OS_STK taskr_stk[STACK_SIZE_TASK];
OS_STK taskb_stk[STACK_SIZE_TASK];
void init_sys() {
SystemInit();
GPIO_InitTypeDef GPIO_InitStruct;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14
        | GPIO_Pin_15;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOD, &GPIO_InitStruct);

 }

void task_g() {
while (1) {
    GPIO_ResetBits(GPIOD, GPIO_Pin_All);
    GPIO_SetBits(GPIOD, GPIO_Pin_12);
}
}
void task_o() {
while (1) {
    GPIO_ResetBits(GPIOD, GPIO_Pin_All);
    GPIO_SetBits(GPIOD, GPIO_Pin_13);
}

}

void task_r() {
while (1) {
    GPIO_ResetBits(GPIOD, GPIO_Pin_All);
    GPIO_SetBits(GPIOD, GPIO_Pin_14);
}
 }
void task_b() {
while (1) {
    GPIO_ResetBits(GPIOD, GPIO_Pin_All);
    GPIO_SetBits(GPIOD, GPIO_Pin_15);
}
}

OS_TID g, o, r, b;

void main(void) {
    init_sys();
    CoInitOS();
//CoCreateTaskEx(task,argv,prio,stk,stkSz,timeSlice,isWaitting)
 g = CoCreateTaskEx(task_g,0,2,(int)taskg_stk,STACK_SIZE_TASK,1,0);
 o = CoCreateTaskEx(task_o,0,1,(int)tasko_stk,STACK_SIZE_TASK,3,1);
 r = CoCreateTaskEx(task_r,0,2,(int)taskr_stk,STACK_SIZE_TASK,3,1);
 b = CoCreateTaskEx(task_b,0,3,(int)taskb_stk,STACK_SIZE_TASK,3,1);
 CoStartOS();
}


texts: Transient analysis of filters inside allowed band

texts:
I understand that a zone pass filter will cut off portions of the signal in the cutoff zone, and allow or amplify the frequency parts of the signal in the allowed zone.

Now lets assume a signal that is in the allowed zone. If we exclude minor amplifications, will the signal change in time due to all the components of the filter? I mean resistors, capacitors or inductors.

So, if we have for example a sine signal in the allowed zone, will it change (excluding the amplitude due to minor amplifications)?
Or will there be some modifications? For example getting triangular a bit?

Does it make sense to try to analyze filters in the time domain? Or we just accept them as they are (black box approach) and just work with them only in the frequency domain?


texts: Admittance of the impedance of R and C in series?

texts:
I have a resistor \$R=150\$ and a capacitance \$C=\frac{1}{750\omega}\$ in series:

\$
Z=R-jX=R-j\frac{1}{\omega C}=150-j750
\$

If I take the admittance I have

\$Y=\frac{1}{Z}=\frac{1}{R-jX}=\frac{1}{3900}+j\frac{5}{3900}\$

According to my book we now have a resistor \$R=3900\$ parallell with a capacitance \$C=\frac{5}{3900\omega}\$. But why parallell now?


texts: Amplifying an audio signal with an op amp

texts:
I'm trying to build a pretty basic color organ, but i ran into a problem and I can't seem to find the solution to my specific problem.

I built this circuit (using a 3.5mm jack connected to a phone or pc as audio input) and everything worked perfectly except for the fact that I had to crank up the volume to get the leds lit (far from being bright anyway), so I thought that I could try amplifying the audio input voltage to get a better result.

I got an op-amp and tried to build a differential amplifier with a gain of 2, but it's not working at all. Where have I gone wrong?
Here is my design with the op-amp.


texts: What happens when an electric motor stalls?

texts:
Most electric motors have a “stall torque” listed and my understanding is that if you limit the output it will “stall”.  What actually happens inside the motor that causes it to stall and why does it not just provide the same amount of torque the whole time?

From Comments:

I have no idea what type of motor it is. It is the motor for my VEX Robotics team and published specs can be found at: PDF Link

Is stall torque the maximum possible torque?


texts: Wireless "Arduino" sensors - what is at least needed on circuit?

texts:
When I finished my Master Unit for Home Control, I want to attach some Wireless sensors via 433MHz Protocol. (At least 2 ones, 1 for Measuring the outdoor Temperature/Humidity with an DHT22 and Lightlevel and 1 for checking if my mailbox lid opened)

Therefor I need a 433MHz transmitter and it would be nice to be able to programm the IC in-system with another arduino or better with the Arduino USBSerial (after flashing the boot-image inside of and Arduino UNO.

The system should run (stable) on battery and send a signal every x seconds or when some external interrupts happen (like opening the lid)

What parts do I need at least? (except the microcontroller and the 433MHz transmitter) what do I need to look for in circuit design to save as much power as possible? How can I check if the battery goes low (and send an alarm signal)?


texts:
I would like to replace what I believe is a failed inductor on a monitor board.  I have searched per its marking but find nothing, SQEE13 W1.   How can I identify and find a replacement?

The board has a side marked HOT which receives 115 volts.  The component is on the side marked cold.  The bad looking solder was caused by me when removing the component.


texts:
I want to use a CMC-5042PF-AC microphone (datasheet: http://www.cui.com/product/resource/digikeypdf/cmc-5042pf-ac.pdf) to send the type of audio signal a component would expect on an RCA line (line level I am guessing). It's going to go to a wireless video/audio transmitter, which would normally except a line level signal form an audio source such as a security camera.

Here is the schematic for the mic:

I am connecting it to 5V power. From what I understand, the R1 resistor would determine the sound level, so I can play around with that to figure out what works best. But what about the capacitor? I can't find in the datasheet what kind of capacitor to use. I have seen people in other schematics use a 1uF cap. Is that what I should do? Or is there a formula I need to use to figure out the cap I need. Also, does it matter if it's a ceramic cap?

Thanks for any hints.


texts: Impedance in LTspice and current plotting

texts:
I wanted to try a test simulation on LTSpice to understand few things. I have a RLC parallel circuit and I wanted to see how the impedance varies according to each one of the components (very easy but I needed to run the simulation for visualization purposes).

To my surprise, when I plot I(V1) and I(L1)+I(R1)+I(C1) the peak of the currents at the resonance frequency are not the same, and I cannot seem to figure out why.
Any ideas?
]2
Thanks in advance :)


texts:
I have a 5V DC input. I want to convert it into 3.3V DC. I'm trying to use VBT1-S5-S3.3-SMT DC/DC converter. I'm connecting my input to second pin of the converter. But it doesn't give 3.3V DC as output. When there is no load it gives 5V DC output on it's fifth pin. When I connect it to a circuit (when there is load) it produces different outputs. I tried couple of brand new converters, but neither of them worked. Am I doing something wrong? I can't use regulator, because the load circuit must be isolated. So Is there anything I can try?

----EDIT----


texts: Piezo cantilever energy harvester: how to mesure such small power?

texts:
I am currently designing a piezo energy harvester and I would like to modify the resonating frequency to maximize the energy recovered(for exemple by changing the center of mass of the cantilever). My issue is to know how to sense the actual power drawn by the load, and as you might know it is very small with such devices. Then with a microcontroller I should be able to adjust the resonating frequency.
Thank you for your answer!


texts: Multiples of one component in a schematic

texts: In this schematic, there is a quantity of 2 MOSFETs specified. Does this simply mean that two are used with the same connections? I.e. both drains connected to VIN of the LM5088, both sources connected to SW of the LM5088 and both gates connected to HG of the LM5088?


texts:
I have an MSP430G2101 and I need to use the Watchdog to trigger an interrupt. The code I am trying to use is the following:

#include <msp430.h>
#include <stdint.h>

unsigned int cycle = 0;
unsigned int pwmred = 1;

void main(void)
{
WDTCTL = WDT_MDLY_0_5;              // WDT as interval timer (period 0,5 ms)
IE1 |= WDTIE;                       // Enable WDT interrupt

P1DIR |= BIT3 + BIT4 + BIT5;

_BIC_SR(GIE);
 while(1)
 {
 }
}

#pragma vector=WDT_VECTOR
__interrupt void watchdog_timer(void)
{
    cycle++;

     if(cycle >= pwmred) {
         P1OUT &= ~BIT3;
     }

     if (cycle >= 255)
     {
         if(pwmred > 0)
             P1OUT |= BIT3;
         cycle = 0;
     }
}

The interrupt is not triggering, I am checking using the debugger and it is also not acting as expection. I am using the latest version of code composer studio. Did I forget something important. I would expect the watchdog_timer method being called every 0.5 ms, but that is not working.


texts:
I want to send some string to PC via serial port. In cute com (software) its displaying the string but with some chars missing. Also some hex numbers are appended at the start and end of the string. What could be the problem? Can anyone please help to solve this issue. My code is here.

#include <avr/io.h>
#include <string.h>
#include <avr/interrupt.h>
#define F_CPU 16000000UL
#include <util/delay.h>
#define USART_BAUDRATE 9600    // Baud Rate value
#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)
void usart_init() {

//Enable communication in duplex mode
UCSR1A = (1 << U2X1);
UCSR1B |= (1 << RXEN1) | (1 << TXEN1);// Turn on the transmission and   reception circuitry
UCSR1C &= ~(1 << UMSEL1);
UCSR1C |= (1<<USBS1) | (1 << UCSZ10) | (1 << UCSZ11);

 UBRR1L = BAUD_PRESCALE;// Load lower 8-bits of the baud rate value into the low byte of the UBRR register
 UBRR1H = (BAUD_PRESCALE >> 8);          // Load upper 8-bits of the baud rate value..
 }

 void serial_write(unsigned char data) {

  while(!(UCSR1A & (1<<UDRE1)))
  ;
  UDR1 = data;
  _delay_ms(10);
 }

 void transmitString(unsigned char *str) {

 int i;
 for(i=0;i<strlen(str);i++) {
  serial_write(str[i]);
  _delay_ms(1);
 }
 }

 int main() {
    cli();
    usart_init();
    unsigned char buffer[20];
    strcpy(buffer, "Walk Alone");
    while(1) {
    transmitString(buffer);
    //_delay_ms(250);
  }
   return 0;
  }


texts: I swapped +5V and ground on a chip, how to know if the chip is dead?

texts:
Well, I accidentally connected ground to the +5V pin and vice-versa on a (W65C22), I don't know how to be sure that I didn't burn the chip.

One thing I was noticing is that when the cables were swapped, when I connected power not even an LED connected from 5V to ground through a resistor would turn on, so maybe the chip has some sort of security around power pins so current flows in only one direction, do chips have this kind of protection?


texts: How does the battery and power adapter interfaced in the laptop?

texts:
How is the typical laptop's battery  (multi-cell Li-Ion) and external power interfaced ? What all components go into designing that circuit ?

The required behavior is:

When power cable is connected in DC Jack, the battery starts charging and the laptop starts running on the external power.
When power cable is disconnected, laptop starts using batteries power.
Stopping the battery to charge after is has been fully charged.

I know that DC jack has a third terminal which gets disconnected from ground the power cable is plugged in, I could imagine it's use in switching between battery and power supply but How should you charge the battery ?


texts: How to find out the exact model of resistor when it's not clear?

texts:
I have 2 resistors that I can not recognize them as their color. according to the board, they are

RK-45
RK-46

honestly I'm not sure about their health, so how to test them and

how to find out the the exact model of these resistors ?

thanks in advance !


texts: I am producing a PWM pulse of say 5Mhz from one of the pin of PIC micrcontroller and I want to drive this to high speed buffer, what is the best way to transfer this RF current from the pin of uC to the pin of buffer? Do I need some kind of wave guide/microstrip or a small stranded wire would do? Can I use Litz wire for this? The distance between uC and buffer is very short.


texts: Why do EU electrical sockets/plugs have two pins for grounding?

texts: Inside a plug there is one grounding wire, while the socket has two grounding pins. I know that the wire splits into two, but why? As the wiring inside the wall is supposed to be the same between different types, I assume it is just a design decision, however does this mean that in such design I could theoretically have one broken pin for grounding and successfully ground a plugged device only by using one pin on the socket?


texts: Misunderstanding of amplifiying a current with transistor

texts:
Electrical books say that we can use transistor to amplifying current but when I simulate a circuit in proteus input current, it is smaller than emitter current but why?

This is a common collector and we expect that the current to be amplified at the emitter point.


texts: Secure a surface mount component to a plastic surface

texts:
I need to replace a broken planar circut (a Hall effect sensor) that was attached to a plastic hull of another unit (a rotor wheel assembly). And, most probably, will need to move the entire connector to a replacement assembly eventually.

The (remains of) the old circuit and its resting place look like this. The pads are thin copper. The whole depression was filled with some amber-like mass, remnants of which can be seen in the photo to the right (bonus points for any ideas what it might be).

Can someone explain how this connector was made, and how it's supposed to be worked on? For example:

If I try to just solder the new circuit in, I'm probably going to melt the underlying plastic in the process
It's unclear how whoever made this was able to place the pads by hand with such precision (the IC's size is 2x5 mm). This is clearly not any kind of printed design.

Looking around the Net found plenty of guides on soldering surface mount components, but nothing on non-PCB placement or dealing with a melty surface.

Photo from the side with all the amber-like mass removed:


texts: What is the cheapest way to email someone whenever a button is pressed or a switch is closed?

texts: I would like to be notified somewhere else on the internet every time my door opens at home. If I do this with a magnetic switch, I realize that this is an event that would probably stay under 0.3 Hz. What is the best way to do this? I was thinking arduino with an ethernet shield is a little overkill. And is there a way to make it wireless? Say with a "wireless doorbell" type circuit?


texts: Quick question: do I need a resistor for a keyboard key switch

texts:
I am building 3D printed keyboard. I am probably going to use some off-brand cherry MX switches (probably outemu switches). Since mechanical keys simply allow current when pressed in, I do not need a resistor to protect the key switch.

So my question is “do I need a resistor for a keyboard key switch?”

Edit.
So I am going to put it on a “keyboard matrix” that looks like the picture given (hopefully it was given. I don’t know how pictures work on the app)

And each output from the matrix will go into the input on an arduino.

I think I got my answer, dim. The switch itself doesn’t need a resistor. But the Arduino might. Thanks all who had input. Much appreciated


texts: MSP430 ADC least significant bits always 1

texts:
I have an MSP430F2618 with built in 12-bit ADC, but for some reason the values it returns always end with the 2 least significant bits set to 1, except when it zeroes out. In other words, the counts are always of the form 0x##3, 0x##7, 0x##B, or 0x##F. Am I missing something in my initialization that magically turns my 12bit ADC into a 10bit? Could there be some transient voltage that just happens to always saturate the sampling circuit for the least significant bits? Any suggestions?

  P6SEL |= 0x01;                            // P6.0,P6.1-ADC option select
  ADC12CTL0 = SHT0_8 + ADC12ON + MSC;       // Set sampling time, turn on ADC12 (256 ADC12CLK cycles, ADCON, Multiple sample and conversion)
  ADC12CTL1 = SHP + CONSEQ_1;                 // Use sampling timer (SAMPCON signal is sourced from the sampling timer, Sequence-of-channels conversion sequence mode)
  ADC12MCTL0 = SREF_6 + INCH_0 + EOS;             //inch (Input channel) assigns channel to this memory location, (Reference: VR+ =VeREF+ and VR- = VREF-), end of sequence
  ADC12IE = 0x01;                           // Enable interrupt
  ADC12CTL0 |= ENC;                         // Conversion enabled


texts: Capacitive voltage divider with varactor

texts: Is it possible to create a capacitive voltage divider where one of the capacitors is a varactor whose capacitance can be manipulated/varied according to a signal? A varactor is a two port device; what would the circuit look like so the voltage control signal could vary the capacitance?


texts: Connect two different sources with two Digital Ouptuts using an Adam 4055

texts:
I would like to operate an Adam 4055 module to control two different applications having their own power supply.

Adam 4055 is Digital Input/Output control module over RS-485, I use only the DO part here. Reading the doc, Adam 4055 DO are Open Collectors.

I have adapted schematic from manufacturer documentation (page 81 in search bar, P.67 within the footpage, section 3.16.1, schematic is embedded bellow) which is using a single power supply:

Provided both load loops respect manufacturer prescriptions (power, voltage, drained current), is the following schematic correct and safe (nodes are labeled as they will be connected to the module):

simulate this circuit – Schematic created using CircuitLab

In this setup I could not use pin DO.COM (I currently do not know if I must use this pin, doc is not explicit about that) because sources have different voltages. I just connect Ground (D.GND) pin to make both power supply having the same potential reference.

Is this setup correct and safe? Will it require improvement?


texts: Must both transistors in a class AB amplifier push-pull pair need to be matched?

texts: A in push pull pair the emitter of the two transistors are connected together. Therefore, what difference would it make if they are not matched vs if they are matched i.e they have same beta value.


texts: Why isn't there a voltage drop across the Main Wires?

texts:
As far as I know the power to my home is directly coming through a Step-Down transformer, so why isn't there a voltage drop and how are all the houses hooked up to the same transformer getting the same voltage?

Same is the question with Voltage Inverters which use a Step-Up Transformer. They also don't contain a "22VAC" Voltage Regulator.

If the answer is related to Amps, then how do we see the same voltage drop across a 2 Amp and 4 Amp DC Power Supply for the same load?


texts: Help With Paper Calculation for Peak Rectifier Design Problem

texts:
I am tasked with designing a circuit for the following particulars:

A peak rectifier will be used as part of a DC power supply to supply an average DC output voltage of 15V, with maximum +/- 1V ripple. The load is 150 Ohms and the rectifier is fed from a 120 V, 60 Hz source after passing through a transformer. The diodes have 0.7 V drop when conducting.

I decided to use a half-wave rectifier, and now I need the voltage seen by the circuit after it passes the transformer. Since the windings of the transformer are not specified, I thought a possible way to do this might be to use the given average load voltage, and solve for the rms value of the source seen by the circuit, since VLavg should = the average of the source - the diode drop integrated over the conduction interval.

As such, I obviously needed to find the conduction interval, but I ran into a problem: I need the rms source voltage I'm trying to find to calculate the conduction interval.

Would solving for the conduction interval in terms of the source voltage that I want be sufficient, and then integrating as I wanted to, or is there a simpler method based on the specifications that I have ignored?

EDIT: Thought I might add my circuit to date for clarity. Note that the diode is assumed to have a constant 0.7V drop.

simulate this circuit – Schematic created using CircuitLab


texts: I've got this T shaped pad that I've made with 2 fill rectangles. How do I assign a designator to it? I've tried converting to a region and couldn't figure it out that way either. I'm using AD10. Thanks.


texts: Handling brownouts during external flash writes

texts:
What techniques should be applied for writing flash in systems that have inherently unreliable power? Is there any good reading material on the subject?

If I have a microcontroller writing sensor data intermittently to external flash, and there's a brownout during one of the writes (and the whole system resets), what precautions should be taken?

I assume CRC is a must, but what else should be done?


texts: Rise time and fall time calculation of an integrated switch?

texts:
Following the analysis regarding the selection of buck converter for my application (Buck converter efficiency Vs load current:). Now I am trying to estimate the power dissipated in the integrated mosfet switch. In the datasheet LM5575, using the provided parameters how can I calculate the rise-time and fall-time of the switch.
 For the power estimation I have all the parameters ready( Ids, Vsupply, frequency) except the time parameters.


texts: Secondry side pulse by pulse current limit

texts:
Coupled inductor SEPIC converter using UC3843.

Vin nominal = 14 V
Vout max = 30 V
Iout max = 2 A

According calculations based on many resources the MOSFET's current will be

Peak =  7.62 A
RMS = 5.3 A

To achieve pulse by pulse peak current control, a shunt resistor is put on the switching MOSFET's source, and due to UC3843 Isense voltage bias of 1 V, the shunt resistor will dissipate about 7.62 W which is too much.
Of course an offset voltage can be injected over the Isense pin which will reduce the shunt resistance but also affect the stability somehow and still the power dissipation around 1.5 W.
What if, the shunt resistor put between the secondary inductor & the ground which has a peak current about 2.4 A instead of shunting the MOSFET's source which has that high current peak..
As far as I understand, the two inductors' current is proportional & synchronized.
Anybody has a deeper knowledge about such issue?


texts:
Can anyone please help me in understanding the problem. I am not able to figure what he is trying to ask.
I know one thing for sure, this problem only checks one thing that "Induction motor have high starting current"
EDIT
I am trying to attempt an explanation. Please check this
As supply is connected, high current starts flowing through G to IM which blows G.
Now, switch S is closed. Again high current starts flowing through S to IM. R gets supply across its terminals and glows continuosly.
Is this fine ??


texts: Example projects, programming and debugging tools to work with Elan EM78 series microcontrollers

texts:
I am working on several projects that involve reverse engineering of small microcontroller systems. Increasingly I am finding that these contain Elan Microelectronics Corp microcontrollers in them, most commonly the EM78 series (specifically the EM78P156K and EM78P418N). These appear to be very low cost 8-bit processors with fairly typical peripherals and OTP ROM. This wikipedia page and datasheets suggest they have some similarity with PIC processors, but it would be a stretch to call them clones based on just the information I have.

I presume that they are targeted at cheap mass-produced consumer electronics as OTP ROM makes development awkward.

I have found these in many products across a range of manufacturers now, and I am surprised at how little they are mentioned on the internet as a whole, and how poor the documentation is. EMC does not seem interested in helping those who aren't buying thousands of units.

Here is a PDF of a PowerPoint presentation that refers to the in-system-programming in a roundabout way.

As stated by m.Alin, there is a big page of supporting documentation.

However, most of these 404 for me, and if I google for other copies, they are of poor quality and very disjointed. "AN-023 On Board Program for EM78 Family's OTP" looks interesting - but if this is a google cache of it (going by filename), then it isn't.

There are references to using the UWTR and DWTR programmers. I can't find where to buy these though. There have been listings on ebay, but they are untested and infrequent.

I have just found this document ("How to Implement ICP Using ELAN EM78PXXX
General Purpose OTP MCUs") which has a couple of interesting pieces of information:

  Note: for manufacturers wanting to develop their own OTP programming
  hardware,  Elan’s OTP  programming specifications are available free
  of charge under NonDisclosure Agreement (NDA).

and

  The EM78P156 is pin and function compatible with Microchip PIC
  16C54/55/56 (see Elan application  note “Replacing Microchip’s  PIC
  16C54/55/56/57 with Elan Microelectronic’s EM78P156/P447”).

I can't find this application note unfortunately.

There are also references to a robot kit called "Cybot" and how they are PIC clones.

I have yet to get any response from their support and I have tried calling and emailing. The domain "www.elan-europe.com" mentioned on some datasheets is dead, so I am stuck with Taiwan.

So, my questions are:

How close are these to clones of PIC processors? Sounds like the EM78P156K is a direct clone - does this include ISP?
Does anyone know of any example projects, hobbyist or commercial, that are documented on the internet and use this series of processors?
Is there an open source or otherwise freely available toolchain for them?
Mention is made of in system programming in several data sheets and pages, but
I can't find any documentation. Does anyone know of any?


texts: How is Machine Learning/Artificial Intelligence used in Electrical Engineering?

texts:
So i've been trying to find out the answer to this question but i can't seem to find a specific answer with examples. by the way i have heard about "Machine Learning Processors" but i don't know what is the difference between them and ordinary Processors.

So overall i have two questions:

1- In what areas of Electrical Engineering is Machine Learning/Artificial Intelligence applied?

2- What are "Machine Learning Processors" or "AI Chips"?


texts: Will the lower frequency of 50Hz AC affect overall charging time?

texts:
I'm using a voltage converter to go from 220V to 110V to charge a small appliance. The recommended charging time is 6-8 hours. However, this is specified for US AC voltage 110V@60Hz, whereas the converter provides 110V@50Hz.
Will providing 50Hz affect overall charging time compared to 60Hz, and if so, how much?

Note: the device in question is basic handheld Stun Gun, I bought it recently, but it designed specifically for US market 110V/60Hz, European version for 220V AC is not available for this model. Therefore I use low-power(45W) AC-AC voltage converter 220V/110V to charge its internal battery. I assume this should not damage the unit. :)


texts: Understanding of Relays and associated circuitry

texts:
I needed a simple understanding of how this circuit works.

I understand everything about this circuit apart from the diode. I also know the function of the diode is to protect the transistor but from what exactly? Is it something to do with back EMF from the coil? I'm not too sure. Also I needed to confirm if the relay will function correctly with a 9V supply (regulated or unregulated). The datasheet of the relay is attached here and the part I'm going to use is '40.61' on page 20 of the datasheet.

Also any tips for making this circuit work more efficiently. Note I am going to use the relay for no more than 16A at 230VAC at 50Hz.

Thanks


texts: Voltage rating of low side resistor in voltage divider circuit

texts:
I'm building a front end for a data logging project where I need to measure the voltage of a solar PV string.  The max voltage I want to design for is 600V.

My question is: when choosing resistors R1 and R2 (see schematic below), do I need both of them to be rated for 600V?  In other words, do I design for the scenario where the connection between R2 and GND is broken, thus exposing R2 to 600V (since no current flow through R2 means that there is no voltage dropped by R1).

The problem is that the only through-hole 10k resistors I can find that meet the  voltage requirements are only accurate to within +/-5%, which makes them pretty useless for use in an ADC voltage divider.  See search results on element14.

simulate this circuit – Schematic created using CircuitLab


texts: Going 20 Volts over what a Fuse Holder is rated for

texts: I have a fuse holder that is rated for 32V DC, but I need to hook it up to some capacitors that are rated at 5 F and 50 volts. Will the fuse just blow right away even if the trip current isn't achieved, or will the fuse holder still function normally? If it will work normally, would Ohm's law apply and I just use a fuse rated lower than what I need?


texts: Using a digital signal to turn on and off a vibrating motor

texts:
I'm designing a circuit with the IOIO-OTG board and a vibrating motor. The idea would be to have a digital pin on the IOIO board control the state of the motor (either ON or OFF).

The motor operates from 2.5 to 3.8 volts and the IOIO-OTG ports provide a 3.3 or 5V digital output (up to 5V if you use a drain circuit).

My current understanding is that I should be able to do something like this:

IOIO port @3.3V -> resistor -> motor @3V -> ground on IOIO

However, from what I'm reading, I should use a transistor and have the digital pin connect to its base. I remember from my electrical engineering classes that a BJT can be used as such a switch. However, I have a few questions regarding this:

What is wrong with my original implementation above? I assume it has to do with the safety of the board.
Is the proper implementation one with a transistor?
Are there any best practices I should be observing to protect the motor and the board for my little project?


texts: I2C-ATMEGA328p as Master and 24LC256 as slave

texts:
So i am trying to establish a connection between ATMEGA328p as Master and 24LC256 EEPROM Chip using I2C protocol.

Clock is set to 100KHz
SDA and SCK lines are pulled up to Vcc using 4.7K Ohm resistors,
Start condition works fine, i get a ACK in return too,
ACK received when the right address is sent,
Fails when MSB of the address in the chip is sent!

Code:

#define FOSC         16000000UL
#define START        0x08
#define MT_SLA_ACK   0x18
#define MT_SLA_NACK  0x18
#define DEV_ADDR     0x50

typedef enum result_t{FAIL, SUCCESS}result;

void Debug_LED_ON()
{
   PORTD|=1<<PD4; //Turn on LED on PIN4 of PORTD
}

void set_clock(int freq_in_khz)
{
   TWCR = 1<<TWEN;     //Enable TWI module
   TWSR |=(1<<TWPS0); //Prescaler set to 4
   TWBR  = FOSC/freq_in_khz;
   TWBR -= 16;
   TWBR /= 8;  //2*Prescaler_value

}

void send_start()
{
   TWCR= ( (1<<TWINT) | (1<<TWEN) | (1<<TWSTA) ); //send START
   while( !(TWCR & (1<<TWINT)) ) ;                //wait for TWINT flag SET
}

void send_stop()
{
   TWCR= ( (1<<TWINT) | (1<<TWEN) | (1<<TWSTO) ); //send STOP
   //while( !(TWCR & (1<<TWINT)) ) ;                //wait for TWINT flag SET
}

result check_start_status()
{
   if ((TWSR & 0xF8) == START )
     return SUCCESS;
   else
     return FAIL;
}

void send_address(char addr_w)
{

   TWDR=addr_w; //7bit  address + W bit (write bit)
   TWCR = (1<<TWINT) | (1<<TWEN); //Clear TWINT bit to start transmission of address
   while (!(TWCR &(1<<TWINT)));  //wait for TWINT flag SET

}
result check_MT_slave_ack()
{
   if ((TWSR & 0xF8) == MT_SLA_ACK )
     return SUCCESS;
   else
     return FAIL;
}
result check_MT_slave_nack()
{
   if ((TWSR & 0xF8) == MT_SLA_NACK )
     return SUCCESS;
   else
     return FAIL;
}

void  transmit_data(char data)
{
   TWDR=data;
   TWCR = (1<<TWINT) | (1<<TWEN); //Clear TWINT bit to start transmission of Data on the bus
   while (!(TWCR &(1<<TWINT)));  //wait for TWINT flag SET

}

int main (void)
{
   DDRC=0xff;
   PORTC=0x30;   //Enable internal pullups on PORTC PINS  SDA(PC4) , SCL(PC5)
   DDRD=0xFF;   //Port D as output

   set_clock(100); //setting clock 100KHz
   send_start();

   if(check_start_status()==FAIL)
     Debug_LED_ON();

   send_address(DEV_ADDR << 1);

   if(check_MT_slave_ack()==FAIL)
    Debug_LED_ON();

   transmit_data(0x00);

   if(check_MT_slave_ack()==FAIL) //fails here!
    Debug_LED_ON();

   return 0;
}

Guess somethings wrong with the code, or the way i send the address!
A2,A1,A0 bits of 24LC256 are set to ground, therefore the device address is 0x50 << 1.

Update:

The device address is correctly sent now, now when i send the MSB of Address on the chip where i want to write data, it fails!


texts: Battery charging / discharging in a very challenging temperature environment

texts:
I'm searching for a solution to charge and discharge a battery pack. The current idea is to use 18650 cells, with 4 or 6 cells (~25-60 Wh) in series. The outside environment I'm dealing with can be between -40 and up to +55 degree C. The average temperature in the sub zero temperature window might be in the range of -15 degree C but might drop down to -40 degree in a worst case scenario. The cell manufacturer is not chosen yet, but what I've seen is that there are hardly any manufacturers, with Li-Ion cells operateable below -20 degree C due to technological limits.
The battery pack will be mounted inside a metal housing (~2-3 mm wall thickness) and in there be placed in a plastic case as well. Space inside the housing is very limited and a 6-cell series 18650 battery pack is already pushing that constraint. The battery works as a backup energy provider that may power a system up to 20 min. The battery will be used regularly but not regulary for the full 20 min - more to buffer short power losses in between. The system may consume roughly around 2-3 W. The aim is to never use the battery pack to its full potential and never use it below 50 % SoC. Most of the time the battery should topped of by a charging unit at a low charging rate (~ 0.1 C).
What I've gathered so far is that Li-Ions energy capacity will drastically drop of below zero degree celsius. Since it is not planed to use its full capacity anyways, I guess the major problem I'm facing is charging at low temperatures as this might even kill the battery. Since the battery should be always be topped off. An itendend lifespan of a battery pack should be in the range of 8 years.
I'll try to measure the temperature drop-off at the extrem temperatures inside the housing to get a feeling what I'm dealing with in detail. Additionally I think that the battery will not heat itself due to very low power consumption of the system.

Are there better battery- or energy-storage-technologies out there with an equal packaging format, energy density and cost spectrum that i might have overlooked?
Is charging Li-Ion batteries at sub zero degrees possible for the proposed 8 year battery-usage?
Would charging with the intendent low charging-rate be beneficial at low temperatures to reduce wear on the cells?
Is thermically isolating the battery-package an idea to protect it from the temperature-extremes?

Thanks in advance and best regards!


texts:
This may be a weird question but for a BJT, we have

\$I_S\$ is the reverse saturation current and \$I_C\$ is the collector current which flows through all three parts of the BJT.

Now my question is, \$I_S\$ should also flow through all three parts of the BJT, so can't we just add/subtract \$I_S\$ from \$I_C\$ via KCL? Is that where the -1 comes from?.


texts:
I need to make sure that my ATtiny does not reset unexpectedly. To do that, I am planning on connecting the RESET pin directly to VCC.

However, I have heard some places that you need a 10k resistor between VCC and the RESET pin, to prevent too much current from flowing into the RESET pin and burning the IC. I have also seen some places that you do not need a resistor between VCC and RESET, and I have also read a few places that you do not even need to connect RESET to anything, because it is pulled high internally.

I could not find any definitive answer on this, and I would like to know what the case would be for each of these condidions (directly to VCC, VCC through resistor, don't connect RESET pin at all) is.


texts: Soldering thin polyurethane covered wire

texts: Is it possible to "solder through it" or does it have to be fully stripped? The material is 0.15mm copper wire.


texts:
Consider an ideal transformer connected to a real AC voltage source (with output resistance Rg).

Now consider to apply the Thevenin theorem between the output terminals of the secondary circuit. I was told that, when we evaluate the Thevenin voltage, it is equal to Vg because:

The current in the secondary is 0 -> the current in the primary is 0 because of the transformer equation (Is = Ns/Np Ip), in which we put Ip = 0. So we get Vp = Vg and so Vthevenin= Vs = Vg.

I did not understand the physical meaning of that thing: if I have 0 current at the secondary, why should I have 0 current at the primary, which is a closed circuit? It is simply a normal circuit with an inductor.

Moreover, if it is true that Ip = 0, the transformer is off since there is not the magnetic coupling between the inductors: so how can we say that Vs = Vg?


texts: Camera - Auto Night Vision "Mode" (ON only when dark)?

texts:
I am wondering how night vision "mode" could be automatically switch on & off in commercial CCTV?
Something like this: https://www.youtube.com/watch?v=ilaXGtsx-DU
(video demonstrate CCTV product with night vision mode)
From what I knew so far, the idea of doing "night vision camera" is by removing "IR Filter" out of the camera, put some IR LED, and there you go - I've succesfully made this fun project too with my OV2640 camera module, and my hacked web cam.
However, by doing this "IR Filter" removal, it won't normally stream correct color when lights are back on (night vision are OFF)
How, then, commercial CCTV could achieve this? They seem using just 1 camera too.. or is there any way to remove "IR Filter" without the need to be physically remove it?
Haven't found any clues (or DIY tutorial) anywhere too. Any help would be appreciated!


texts: When to use multiple batteries vs a UBEC

texts:
When should you use multiple separate batteries vs a single battery with multiple UBECs?

I'm trying to design the power system for a small 2-wheeled robot. Aside from the 2 main drive motors, it also has to power an Arduino, a Raspberry Pi and a couple small servos to actuate sensors.

the motors are each rated for 6V with a peak stall current of 2.2A
the Arduino uses about 5V@100mA
the Raspberry Pi uses about 5V@700mA
the servos each use 6V and have a peak stall current of 1.2A.

So the theoretical max current draw would be 2.2*2+.1+.7+1.2*2 = 7.6A.

Originally I was planning to use three separate Lipo batteries:

one 12V using a step-down converter to power the main drive motors for 6V@4.4A peak
two 3.7V lipos each with step-up converter (rated for 5v@3A) to handle the servos and logic separately

Then I discovered UBECs, which sound too good to be true, and they seem to be both cheap (<$10) and efficient (>90%) and able to handle my exact volt/current requirements.

Should I instead use a single high-current 12V lipo with three UBECs to independently power my drive motors, sensor motors and logic? Or will this still suffer from brown-out and power irregularities if a motor draws too much current?

What am I missing?


texts: Modelling a "scope probes' acting as an antenna" phenomenon in a circuit

texts:
Here below I draw a simplistic model for stray capacitance issue in SMPSs:

Basically pF level Y capacitor across the AC line forms an RC voltage divider when measured by a voltmeter with respect to the earth. So the voltmeter will measure around 80V AC but as soon as the R1 reduced to zero Vm will approach to zero as well. And the currents are tiny. This phenomenon is sometimes called ghost-voltage.

My question is related to a similar one which happens: when we hook up scope probes to the scope and we dont measure any signal probes act as antenna and we see some hundred mV 50Hz signal. And when we touch the probe this 50Hz signal on the scope even increases a lot. Here is a related question why it is happening.

My question is not why it is happening but how can we model this as a circuit like in my SMPS leakage example. I want to see a circuit which shows this phenomena where the components should represent the scope probe, human body and the scope input impedance and maybe the earth or ground. How can it be modelled?(Simplistically)


texts: Help understanging ac signal connected to a charged capacitor (coupling capacitor)

texts:
(Assuming ideal elements) My friend is trying to convince me that the voltage across \$R_L\$ varies between 4 and 6, says the average value doesn't decrease and stays fixed at \$5V\$ forever. I'm not getting how this is possible -

simulate this circuit – Schematic created using CircuitLab

The amplitude of the input ac signal varies between -1 and 1, always less than the capacitor voltage of \$5V\$. Wouldn't the capacitor see this low voltage and start discharging ? May I ask how the 1V input ac signal can put more charge into the capacitor so that the capacitor's voltage increases, even slighlty ? Makes not much sense to me. Highly appreciate any help. Thanks!


texts:
I am prototyping the below diagram and using the following Common Mode Choke from Murata 50475C (4.7mH DCR 0.7R). When I input a signal on U1 Point B 3Mhz D = 50%, I can see AC coupled signal on U2 point A. However, when I check U2 Point B, I can also see the same signal so I am not sure where the signal is coupling from.

Also, when I use small inductance around 4.7mH I can see a Vripple at Point C around 150mV.

Can anyone explain why it is coupling on the other line? Does the CMC have something to do with it?


texts: How to choose transistor for switching bigger MOSFET

texts:
Leading on from my last question:
MOSFET choice for 12v LED Strip and 3.3v Logic
I have decided to use the IRFZ44N (despite it not being ideal for the job) for being economical the cheapest option and now need a second transistor that allows me to switch the MOSFET. The idea is the following:
Since the project already has a 12v lane in place for the RGB LED strips, I want to use another transistor in front of the MOSFET to raise the gate voltage to 12v allowing the IRFZ44N to be used for my project.

I know that I'm looking for a small transistor (nothing beefy) since all it will do is switch a MOSFET gate at 12v which is not current-intensive as far as I understand it. I want it to be fast-switching so that it does not interfere with PWM. Looking through a local supplier I found that I could get a BS170 for 10 cents. I wonder if this is a suitable transistor for switching a IRFZ44N at 12v Collector Voltage. The full plan repeated once again:

wire the BS170 to the microcontroller (3.3v on Gate), PSU (12v on Collector) and the IRFZ44N (BS170 Emitter to IRFZ44N Gate)
wire the IRFZ44N (12v on Collector, LED Strip to Emitter)

are any other components needed for this? Is the transistor a good fit? It seems to me that mostly any transistor would work as long as it is definitely conductive at 3.3v and can handle 12 Volts.

What I'm really unsure about is the amperage - how do I calculate how much current switching a MOSFET will draw? The BS170 cannot handle > 0.1A according to the datasheet (section 'transfer characteristics' for the Fairchild BS170.

Thank you for reading this - probably all too simple - question.


texts: How to limit current on parallel outputs from a power supply?

texts:
So I am trying to make a USB power dock for multiple devices. I have a 5v 20A power supply.

If I connect 10 USB ports in parallel, is there a way to cap their current to 5v 2A?
I don't want to fry my USB powered devices by plugging it to a port connected in parallel with a 5v 20A power supply... I mean, won't that damage my devices? I am not even sure here.


texts: Powering modules permanently with 3V lithium coin battery

texts:
I am going to use a MCU + bluetooth BLE module. Its VCC pins are going to connect directly to the terminals of a 3V lithium CR2032 battery, for example a standard 170mAh one. 99% of time the module will stay into deep sleep mode on which the current consumption is <= 1uA, and it will only wake from deep sleep through interrups due level change of the GPIOs. The module work as low as 1.8. The datasheet actually show 0.4uA @ deep sleep.

But there is another SOIC-8 chip on the same board, and it only works with a minimum of 2.5V. My main question is: When the 3V lithium cell reach 2.5V and the second IC start to fail, will I have used a high percentage of the load charge of the CR2032? Maybe used 80% or more of its charge capacity?

Regards.

EDIT: specs of the module.


texts: I want to understand what do they mean by ON and OFF current for a PMOS and NMOS. Is there a straight formula for it?


texts: Looking for some help with SMD Component identification N51K

texts:
I've got a faulty GTX 1070 Graphics card here with a blown SOT-23 casing IC. Looking at it you can se N51 and looking around on the board I can find another component like it with N51K.

I cannot however figure out what the component is? It looks like a transistor of sorts.

Any ideas?

EDIT:

Thanks for your help so far.

I don't know why it failed, I purchased the card on a whim in the hope I might be able to repair it. Probing around the rest of the circuit I see no reason why it shouldn't work other than this, there are no other shorts.
Please see attached for an expanded area of the circuit.
I've probed the existing N51K IC and as you look at the picture: Right pin to left 1.5v forward, centre to left 1.5v forward so it would ring true as being some kind of transistor, left pin being the gate. Does fit the theory of it being a Si2305CDS as it matches the pinout and it being PNP
The center pin on the blown IC goes to the 100ohm resistor and that goes to pin 3 on the ON 702 IC. Having done a bit of searching it seems at first look that the 702 IC is a dual N-Channel mosfet 2N7002DW however probing it doesn't fit as pin 5 probes to pin 1, so either that's a short that shouldn't happen or not the correct IC.

I'll have a further probe around and see what else I can find.


texts: How to drive a cd4051 analog mux with buttons as channel selector?

texts:
I 'd like to control an analog multiplexer cd4051 as a 8-1 switch with buttons that will act as channel selector (1-8)
I know how to do it with Arduino but is there any other way to read the state of 8 buttons and provide a 3 bit word as separate digital signals?


texts: Altium Designer - Move an object only horizontally

texts: Is there an easy method to move an object only in the horizontal direction? I know what there is the "Move Selection by X, Y, ..." command but I am looking for something that uses the cursor, since I want to be able to visualize the change in real time. For example, sometimes I need to move designators around but I still want it to be in line with other designators .


texts: Individual WS2812B circuit: Do i need a capacitor?: Power distribution?

texts:
I am currently designing a Circuit that is similar to typical WS2812B ARGB strips but seperatet into modules.
In the offical datasheet, there is no mention of using capacitors as noise protection, but in close to all similar models there is one (104, .1uF) for each lamp.
As I am not that experienced with electrical circuit, my questions are:

Is a Capacitor neccessary?
If so, what type?
Could I use one big Capacitor instead of the multiple single ones for each lamp?

.
For Power distribution, there will be 18 WS2812B Leds on each module and 6 White LEDs (datasheet)

Would it be better to run a higher Voltage line to each module and the seperate the needed Voltages of it?
Or could I connect the power of all of them in one Line?
How many modules could I connect for each Voltage Level of the Main line if I run one?

You are welcome to point out bad components or mistakes I made.
This is the current circuit:


texts: Alternating LEDs with same forward voltage

texts:
Newcomer to electronics --
I built a circuit based on the first circuit in this post https://electronics.stackexchange.com/a/162032/103970, however it only works with green (3.2 VF) and red (1.8 VF) LEDs because of the different forward voltage drops.
How can I modify this circuit to work with any color LED, ideally two of the same type?

simulate this circuit – Schematic created using CircuitLab


texts:
Have been reviewing the TI Designs – Precision: Verified Design - 1 MHz, Single-Supply, Photodiode Amplifier Reference Design.  In one of the equations (See embedded graphic below), there is a syntax that I have not seen before:

(R2||R3)

It looks like the result is close to the modulus 13700 mod 280 (result 260) but when I work backwards, I get 1/(2*pi*1/1e6 * 274.3902) == 580.028Hz so it isnt the modulus.

Does anyone know what specifically it is?


texts:
The circuit is a common source amplifier that uses the 2N3819. It is known that \$V_{DD} = 20\,V\$ and that \$R_g = 100 \,Ω\$ (the generator resistance \$V_g\$ applied in In). The entrance and exit are ports In and Out, respectively. For Q1 use the JFET parameters: \$I_{DSS}=8\,mA; V_P =-3\,V; R_0 = 30 \,k\Omega; Cgs = 5\, pF; Cgd = 2 \,pF\$. R4 is not the drawing value. \$R_4\$ is \$ 5,04\,k\Omega \$.
Calculate the polarization of the JFET, indicating the DC values of the nodal, \$V_{GS}, V_{DS}\$ and \$I_D\$ voltages.

I tried to solve it. I'd like you to confirm that it's right.

\$I_{R1}=I_{R2}\$

\$\frac{V_{DD}-V_G}{R_1}=\frac{V_G}{R_2}\Leftrightarrow\$

\$\frac{20-V_G}{120\times 10^3}=\frac{V_G}{22 \times 10^3} \Leftrightarrow\$

\$ V_G=3,10\,V\$

\$I_D=\frac{V_S}{R_5}=\frac{V_G-V_{GS}}{R_5}\$

\$I_{DS}=I_{DSS}\bigg(1-\frac{V_{GS}}{V_P}\bigg)^2=\frac{V_G-V_{GS}}{R_5}\Leftrightarrow\$

\$I_{DSS}\bigg(1-\frac{2V_{GS}}{V_P}+\frac{V_{GS}^2}{V_P^2}\bigg)=\frac{V_G}{R_5}-\frac{V_{GS}}{R_5}\Leftrightarrow\$

\$\big(I_{DSS}-\frac{V_G}{R_5}\big)+\big(\frac{1}{R_5}-\frac{-2I_{DSS}}{V_P}\big)V_{GS}+\frac{I_{DSS}}{V_P^2}V_{GS}^2=0\Leftrightarrow\$

\$\big(8\times 10^{-3}-\frac{3,10}{4,7\times 10^3}\big)+\big(\frac{1}{4,7\times 10^3}-\frac{2\times 8 \times 10^{-3}}{-3}\big)V_{GS}+\frac{8\times 10^{-3}}{(-3)^2}V_{GS}^2=0\Leftrightarrow\$

\$7,34\times 10^{-3}+5,546\times 10^{-3}V_{GS}+8,889\times 10^{-4}V_{GS}^2=0\Leftrightarrow\$

\$V_{GS}=-4,334\,V\,or\,V_{GS}=-1,905\,V\$

\$V_{GS}>V_P\Rightarrow V_{GS}=-1,905\,V\$

\$I_D=\frac{V_G-V_{GS}}{R_5}=\frac{3,10-(-1,905)}{4,7\times 10^3}=1,065\times 10^{-3}\,A\$

\$ I_D=\frac{V_S}{R_5}\Leftrightarrow V_S=1,065\times 10^{-3}\times 4,7\times 10^3=5,01\,V\$

\$V_{DS}=V_D-V_S=14,63-5,01=9,62\,V\$

\$\frac{20-V_{D}}{R_4}=\frac{V_S}{R_S}\Leftrightarrow V_D=20-1,065\times 10^{-3}\times 5040=14,63\,V\$


texts: 16x2 LCD Display Got Error Cause by External Current

texts:
As shown in the image above

the 16x2 LCD display is controlled by Arduino.
Relay and LCD both connected to +5V of Arduino

The LCD got an erroneous symbols display whenever I pug/unplug the relay to the 220Vac supply.

I guess I need to add a component in between the positive line of LCD and RELAY, but I don't know what it is. Does capacitor will help?


texts: What kind of use cases require a 2GHz, 4GHz, 6GHz, 30GHz or 100GHz oscilloscope?

texts:
I have been thinking of buying some oscilloscope for the work I do with Arduino. In my case it would be partly because of some usefulness and partly because it would give me a chance to learn an interesting tool.

But when I looked into the different models that are available I see that there are oscilloscopes with bandwidths of all the way to 100GHz (such as this LabMaster).

From the information that I have found (such as this article) I can see that, as a rule of thumb, your scope's bandwidth should be at least five times higher than the fastest digital clock rate in the system under test.

As I plan on working mostly on Arduino I would probably do fine with some scope where the bandwidth is less than 1GHz.

But I am curious on what systems would have a "clock rate" that require a higher-bandwidth oscilloscope.

Thus the question I want to ask is:

What are examples of systems that require a 2GHz, 4GHz, 6GHz, 30GHz or 100GHz oscilloscope?


texts:
I am trying to calculate the output voltage of the circuit. I know that this is a voltage follower, but I am trying to understand how it works.

simulate this circuit – Schematic created using CircuitLab

The first "golden rule" implies that

$$
V_a = V_b = V_{in}
$$

Now, the opamp has to set the output voltage to satisfy the above condition, but how do I calculate it?

I can use the second "golden rule" and assume that no current flows into the inverting input, hence there is no voltage drop across R1 and Va equals Vin. But the current does flow from input to output through R1+R2, so there will be a voltage drop across the resistors.


texts: VHDL - Does signal ever get assigned in the same clk cycle?

texts:
This is my simulation

I'm assigning different values to btnin my testbench

btn <= "1000000";
sw <= "00000001";
wait for 50*CLK_PERIOD/2;
btn <= "0101000";
sw <= "00000000";
wait for 50*CLK_PERIOD/2;

And I'm trying to check the previous state with the current state and set the interrupt

process(clk)
begin
    if clk'event and clk='1' then
        if rst = '1' then
            irq <= '0';
            irq_count <= 0;
        else
            if sw /= prev_sw_state and
                btn /= prev_btn_state and
                irq_mask(19) /= '1' then
                    irq_count <= irq_count + 1;
                    irq <= '1';
            else
                irq <= '0';
            end if;
            prev_sw_state <= sw;
            prev_btn_state <= btn;
        end if;
    end if;
end process;

The interrupt does get triggered. No problem. But the waveform doesn't look right. There should be a one clk cycle difference between prev state and current state. Am I doing something wrong?


texts: Search for the most efficient voltage regulator on low current consumption

texts:
I'm currently designing a circuit for a long term device that will consume 1-2mA at 3.3V constantly. The system is run with a default lithium polymer battery and I need to get as much time out of it as possible.
In the current state, I'm searching for the most efficient voltage regulator possible. The best one I could find was the TPS63805. It is a switching voltage regulator which means that it takes more space and costs more, which is luckily not a big problem for my project.
It seems to be that these kind of regulators are a bit more efficient on higher current consumptions. When only using 1mA, it is at about 90% efficiency, which is good but can it get better with another component or technique? (I'm already making sure to minimize the power loss through PCB design.)
Thanks for any help in advance!

PS: Sorry for any grammar or spelling mistakes, I'm not a native English speaker.


texts: How can I find the stored energy in a 2d triangle that has a different electric potential at each point?

texts:
I am writing a FEM solver for a project. I need to calculate the total energy stored in my mesh so that I can compute the capacitance of the solution.

So obviously I have to loop through all the elements and work out the stored energy in every element.

So if I have an element that consists out of three points in 2D, let's say:
X = [0 ; 1 ; 2] meters
Y = [0 ; 1 ; 0] meters
E = [0 ; 2 ; 1] volts (Potential at the point)

What would be the stored energy in that element? (assume 1m depth)

How would I work it out?

Thank you for your time guys!

EDIT: In reply to you guys. The equation for energy in an electric field is:

Energy = 0.5 * volume integral of ( D.E )

My case is 2d, so obviously that is the area integral. E and D are dependent on their X and Y position ( I have all these values already). I just don't know how to go from this triangle and electric potential, to stored energy. My integration is a bit sucky.


texts:
What is the Vadj voltage that should be considered while choosing a resistor for the LDO LDK130?
Data sheet link: LDK130 low quiescent current very low noise LDO


texts: What are MGT pins used for in fpga and what devices can they be connected to? How can I connect them on fgpa system planner?

texts: Basically, I want to know the how to connect the MGT pins of fpga to any device. And which devices can I connect it to. I am working on fpga system planner.


texts: What exactly happens to the signals hitting a common mode choke?

texts:
I'm trying to better understand the principles behind the common mode choke. I made a few drawings to clarify.

Differential Mode Signals

Differential currents (driven by differential voltages) create equal but opposite magnetic fields B in the inductor core:

These magnetic fields cancel each other out, so the net flux in the core is zero. As such, these differential currents don't "feel" any impedance.

Common Mode Signals

In contrast, common mode currents generate equal and additive magnetic fields in the core. That's why they "feel" a high impedance, and cannot get through (or getting through means they are highly attenuated).

But what exactly happens? I have several theories, which I will describe below.

Common Mode Signals - Theory 1

My first thought would be that the common mode signal hits the choke and creates a magnetic flux inside. By doing this, lots of energy is lost (hysteresis and perhaps other effects) as heat. Only a small part gets through:

What kind of common mode choke would behave in this particular way? "Burning up" the voltage spike seems a very desirable effect to me.

Common Mode Signals - Theory 2

Perhaps the voltage spike doesn't really get the chance to build up much magnetic flux in the core, or maybe the core is simply not "lossy" enough. The voltage spike bounces off the core and turns back. Only small part gets through:

Although the system on the right side of the choke is protected, the system on the left has to deal with reflected signals. Nasty things like standing waves might appear.

My questions

I've got a few questions for you:

Do you think theory 1 or theory 2 is most plausible?
Do you think certain types of common mode chokes tend to behave as described in theory 1, others like in theory 2?
Perhaps both of my theories are just plain wrong. If so, what actually does happen?

Please enlighten me.


texts: I might not be able to find an LCD with a 24 bit parallel interface, which is what my controller requires.  I have seen 18 bit parallel interfaces, though.  I assume that I could really just use the lower 6 bits of each color and not use the other two bits per color channel.  All I would have to do is make sure that my color palettes are adjusted accordingly, right?


texts:
I wonder how looks integrating code for embdedded systems. Lets suppose there are 5 programmers and everyone is doing something different. Then I am supposed to integrate the code. How do I know if it should be RTOS or not, should I be provided with some kind of API, from the programmers, that refers to theirs code ? Should the code execute sequentially or should I implement multitasking ?

There are so many things to be managed and I got no idea what to start with ? Do you know any books that would introduce me to that subject ?


texts: PIC output is high before being set high automatically

texts:
I am creating a simple pic project that uses a PIC16F877A and I have noticed something that seems odd.  Before using any code to change the state of the pins connected to port b, the port b pins are already high. Here is the code I am using in hi tech c with everything else removed to demonstrate the problem. I was wondering if it was normal for the pins to start high before being set in that state.  If that is the case I could just set PORTB to 0 at first to solve the problem, I just wanted to make sure that nothing was wrong.  This seems to be caused by the line TRISB = 0xFF but I can't understand why since that register only adjusts weather the pin is a input. If anyone requests it I can post my circuit diagram, however I was hoping to avoid having to draw schematic.

#include<htc.h>
#define _XTAL_FREQ 8000000
__CONFIG(UNPROTECT & PWRTDIS & WDTDIS & HS & LVPDIS);

int main()
{
    TRISB = 0X00;

    while(1)
    {

    }
}


texts: No response from Arducam OV5640 camera module

texts:
I am working on a project involving cameras using a Zynq FPGA on a Digilent Zybo board. I can successfully get a response from an OV7670 by configuring it via SCCB. Even without configuration the OV7670 provides a PCLK and drives the data pins as long as I provide it an appropriate XCLK signal. I have recently bought an Arducam OV5640 module. The documentation that I have read so far about this module suggests that I can still use 3.3V logic. I get no response from this module when providing a 12-25MHz XCLK signal. Can someone point me in the right direction and make me aware of what I may be doing wrong? Is it really 3.3V logic or should it be less? Is there some power-up sequence that I am not aware of that I should be doing differently than the OV7670?

Any help will be much appreciated. I am really stuck and it is well known that Omnivisions documentation is far from complete.


texts:
for my first project I decided to make a scale using a load cell, the micro load cell 3133 from Phidgets. I also used an ICL7107 as A/D converter and the op amps are LM358.

I used a differential amp to get the voltage frome the cell and then I amplify and use another op amp to make the calibration of the cell. Then I use the ICL to show the load on a 7-segment display. I'm using 1.5 V piles to get 4.5V with which I'm powering my circuit.

I'm able to get the voltage from the load cell and to amplify it but the problem is that I seem to get very annoying noise from the last op amp because the display keep switching values (about 10 or 20 mV two or three times by second). I used decoupling caps (0.1 uF) for all the amps and for the IN of the ICL as for the ICL itself.

I find it kind of weird because when I first tested it without the ICL, I was reading values with my multimeter and they were right and weren't waving. But when I connected the last op amp with the A/D, I kept getting switching values. I tried many gains (from 5 to 800) but I always get this switching effect.

You can see the circuit on the following picture.

The decoupling caps aren't there but I can assure you I put it on the board.

I changed the last op amp configuration to make a straight line configuration for the calibration and we can't see it on the picture but I was getting the flickering before I changed it.

I made some tests when all was connected to the ICL and I realized that it was the output of the last op amp which was switching. I tried different op amp but I always got the same results.

I used the same ICL for a school project (a thermometer) and the display was fine. I don't know what to do right know and if anyone got a solution or have an idea I will be very grateful.

Thanks for your help.


texts: How to power a voltage divider with 2.1V

texts:
I have a 3.3V circuit with an ADC chip that reads values between 0V and 2.1V, that means anything above 2.1V will return 2047. If I use a voltage divider with the Vcc power supply, I would lose a lot of range. What is the best solution to measure all values? Do I have to buy a 2.1V regulator? Or can I supply 2.1V with another voltage divider?

The variable resistor in that provides the voltage to measure would be a potentiometer or a light sensor (photoresistor).


texts: how to choose the right pullup resistances for i2c lines with multiple slaves

texts:
In my project I have connected multiple sensor breakout boards to a Arduino-proMIni running at 3.3V and 8Mhz as follows on a fabricated pcb but preserving the original board layouts (so that I can connect them via traces instead of loose wires)

To save power I am using the digital GPIO Pins to power all the breakout boards that are running on I2C with Vin = 3.3V.

The breakout boards for different sensors have pullup resistances for SDA/SCL lines (pulled up with Vin) and configured as follows:

When I power on the board, as long as the external eeprom is ON (but no reads or writes are happening), there is no serial output for the i2c line.

When I turn off the eeprom, the i2c line only works if all others sensors are on. Turning any one or more of the sensors off, gives no serial output for the i2c line.

After researching online I realized that we need to give a dedicated Vdd line to the pullup resistances of the SDA/SCL lines instead of the Vin lines, as turning Vin off will also pull-down the i2c lines.

So I removed the pull-up resistances on all the breakout boards and added 5k pullups to the SDA/SCL pins on the MCU with the Vdd.

Even after doing this the i2c lines only work after the external eeprom is turned off.

As For the other sensors -

The RTC now works only when all other sensors are off. Switching the
RTC on is most likely adding a lot of noise in the i2c output because
the values changes on the serial monitor change asa it is turned on
and come back to normal when turned off.
The capacitive sensor works only when the accelerometer is on.
The current odometer and the accelerometer work without any problems.

Can someone please help me figure out why all of this is happening? Can this problem be solved by merely choosing the right pull-up resistances or is it a higher order problem? Is it possible that because I am using a 30cm wire for the Accelerometer, the entire bus capacitance is increasing, adding too much noise in the system when multiple slaves run simultaneously. And hence will it help if I shift the accelerometer on the SPI protocol and decouple it from I2C?

All sensors are running at <100Khz except the eeprom which is running at 400Khz.

Update:

So I took everyones suggestion below and made 2 pcbs. In one I powered all the sensors to the Vcc line and even pulled up the i2c line on Vcc. In the other I powered all the sensors with the GPIO pins (but keeping them always on HIGH) just like before and pulled up the i2c lines with another GPIO (so that I can pull them down when all the sensors are simultaneously LOW to avoid case [4] as pointed out by @maple below). And guess what?
The GPIO powered sensors are working flawlessly while in the Vcc powered ones the i2c line i.e SDA, freezes after few seconds. This happens in the case when I am trying to communicate with the FDC1004, the adxl and ina219. RTC doesn't seems to be affected. Any clue why this could happen?


texts:
I was looking at the schematic on page 10 of this application note: http://www.ti.com/lit/an/snva557/snva557.pdf

I was looking to order parts for it but I am having trouble finding parts for Q1 and Q2. The schematic symbol is for a N-Channel Depletion Mode Single Gate MOSFET and they are labled as VN01A. I tried searching for this component, but nothing came up.

Does VN01A refer to a family of MOSFETs or is it an obsolete part? Can anyone recommend a component that works with this schematic?


texts: IR2133 Bridge driver not working as expected

texts:
I want to use the IR2133 to drive a mosfet rectifier. I have setup as in the circuit below

The probelm is (take first high side fet as example) that the signal that appears on HO1 is exactly the same as whats on VS1. The gate voltage VGS should should be VS1 + turn on voltage(30V) when the PWM signal on HIN1 is activated. The PWM has no effect on the signal whatsoever whether disconnected or not.

Do perhaps some of the other pins need to be set to enable this functionality and should this behaviour be expected in this configuration?

Edit 1:

Below is a plot of the PWM signal and the (low voltage) AC signal taken from HO1 and is the same as the input signal.

Thanks.


texts: Should startup torque be higher in value than full load torque in an induction motor?

texts:
I found out values of my 3 phase delta connected induction motor for full load torque, maximum torque and startup torque.

My maximum torque was higher than my full load torque, but the thing I'm wondering about is whether I'm right or not is that my startup torque is higher than my full load torque. Is that right, or is it supposed to be lower than full load? If it's supposed to be lower than it shows I need to look over my calculations again.

Full load torque= 25.68Nm

Max torque= 322.4Nm

Startup torque= 38.53Nm


texts: Is a human (or other) electrical signal absolutely necessary to activate a capacitive touchscreen?

texts:
I know this is the general wisdom, and that someone has asked a similar question here: How can a capacitive touch screen be triggered without human contact?

However, I didn't quite understand the conclusion that by simply grounding e.g. A carrot or stylus, or connecting them to a conductive plate, this would be enough to allow them to activate the touchscreen. Is the idea that the ground or conductive plate pick up enough electricity in the environment that they can act as a substitute for a human?

As a related note, I held a stylus through many layers of folded up, thick woollen sweater, and it was still able to activate the touchscreen. Was my body's electrical signal definitely conducted through the sweater?

Apologies if my question sounds a bit ignorant. I am not an electrician, but I understand the basics of electrical circuitry and how capacitors work. The iPhone's capacitive touchscreen nevertheless seems like a bit of a black box to me.

Thank you all. Based on your responses and my reading of the Q&A referenced by @gbarry, my understanding of this is now almost complete. There remainas these issues that I am unclear on:

It seems that it is a very common misconception, then, that it is a body's electrical signal (current) that is necessary to activate the iPhone touchscren in particular. Rather, what is sensed by the electrodes of the touchscreen circuit is either insulation or capacitive coupling, but supposedly not conductivity. Since I always considered insulation and conductivity as belonging on the same scale, could someone perhaps clear this up for me, while illuminating whether or not this is what is meant here by "capacitive coupling"?
I have understood that large surface area is often an important determinant of capacitive coupling. Is this the only reason that it is suggested the contacting body be grounded, or is it necessary for another reason, e.g., To "complete the circuit" initiated by the iPhone?

I'll gladly award the bounty to whomever can answer these questions in a way that I can understand! Thank you again.


texts:
I have a 12V 40A motor. I have a switch between the motor controller and the battery.

I want to put a pre charge resistor in the path. Like in the figure.

My questions are:

1) The pre charge resistor is connected directly to the battery, so that means the system is connected even the switch is off. How is this condition safe? How is this condition safer than having just the switch? And what should I worry about making this connection?

2) Is there in the market a switch built with this pre charge resistor? If so, what is the name of that switch?

I am thinking that I need some kind of two step switch.

EDIT 1

I will follow Whyskeyjack solution, but I have one more question:

Is it OK to have the switch in parallel?
Can the precharged switch be rated less power than the other switch?

This is the switch I got for the main path.

simulate this circuit – Schematic created using CircuitLab


texts: PCB traces: oz to mil (thickness) conversion (for stripline)

texts:
According to http://referencedesigner.com/cal/cal_02.php, the conversion between "oz" and "mil" (thickness) for a PCB trace is 1.37. Also, according to zcalc.exe (http://www.fedevel.com/welldoneblog/wp-content/uploads/2011/08/Zcalc.zip) 4.8mil correspond to 3.5 oz.

Now I get the following table from my foundry:

weight (cu)  thickness (mil)
0.25         0.30
0.375        0.45
0.5          0.6
1            1.2
2            2.4
3            3.6
4            4.8

These numbers are off by quite a bit.

How can this difference be explained?

Now I want to calculate the thicknes of my stripline (e.g. with the calculator referenced above).

But which number should I use/trust from the table for my calculations? For example, for 4oz copper ... should I use 4.8mil should I use 4x1.37=5.48mil?

(I would tend to 4.8mil because the input to the stripline equations is thickness but I do not understand the discrepancy)


texts: How can you generate a PFM signal for an LLC converter?

texts:
I am researching resonant DC/DC converters that use PFM (Pulse Frequency Modulation).
Before that, I was only familiar with PWM modulation, which I could generate at a given frequency from an Arduino or STM32.
Question: how is PFM usually generated?
Does this require separate IC's or can I implement this on Arduino / STM32?
Unfortunately StackExchange doesn't see the PFM tag.


texts: Playing back recorded movements with servos

texts:
I'm new to motors/servos so could do with a bit of advice. I'm currently working with 3 Dynamixel servos and it's cool that they can be programmed fairly easily and I can get the current position when torque is disabled. Currently I'm trying to record motions then play them back.

At the moment I have a very basic approach: I record a set of positions over time(multiple times per second) and when I 'playback' the positions, I simply pass the them as the goal positions. The problem is at the moment, with slow position increments I get jerky movement. I imagine it's because I keep setting a new goal position even though some positions are quite close. I imagine it will be more efficient to somehow split a dense list of positions into a some 'key' positions separated over a larger interval of time and only set a new goal position for those 'key' times.

Does this sound reasonable? If so, any hints to what I should into to get started? If not, what ideas are out there? How do people animating robots deal with recording movement and using it?


texts:
This is a problem that's bothering me for a while, and I'm going off accepting other people's claims rather than figuring out the first principles of circuits.

Consider this circuit right here. From my understand, when an electron/current from the 5mA source goes to the ground, it can't go to the 0.01Vo source because it would violate the circuit law of going back to a node without looping.

But from a physics standpoint, I know charge moves from high to low potential, and voltage sources need to produce some sort of electromotive force to bring a looped electron back to high potential. And in this circuit, once an electron goes to the ground, why can't it be stolen by another source and brought back to high energy? Said differently, why does current have to loop when the only thing an electron knows is to move in the direction of the direction of an electric field and not that it needs to travel to each node only once per loop?


texts: How to package a sensor watertight in a DIY environment?

texts:
I need to measure the temperature in a terrarium and use that as an input to a temperature controller. The terrarium is quite humid, e.g. above 80%. Also the packaging should have minimal thermal mass, in order not to hinder the temperature controller, causing overshoots.

The sensor is a 1-wire IC

I have solved this problem by the means of hot silicone - first I solder the 3 leads of the chip to the wire, then I pour liquid silicon until no cavities are visible.

To my surprise, this does not work. The mean time between failures is 1 month. The microcontroller just begins reading a different, fixed temperature. I have another sensor, mounted in a dry box, that I use for sanity check. Therefore, I am sure that exactly the sensor fails.

How should I handle this in a DIY environment (i.e. not industrial)? Is there a more clever approach or just a correct technique to apply glue for waterproofing individual ICs?


texts:
First of all I am a beginner in electronics / electricity. I am currently trying to connect a coffee machine to a Raspberry Pi powered relay.

No problem with that, but as I am going to put apart and rewire a coffee machine, pretty dangerous heating device after all, I wanted to fully understand its wiring diagram beforehand.

That's where I'm stuck. This is the diagram I drew of it.

I could understand that the three pin device in the middle is a rocker switch. The thing I don't get is the use of the third pin in such a device. What if there were only two pins int the switch, and the wires connected to the upper right one were just fixed together ?

Thanks in advance!


texts: Confused about the functioning of a QRE1113 reflectance sensor

texts:
First year IT student here. I've been stuck on a problem involving a QRE1113 sensor, in which we were given the schematics below:

From my understanding so far, the reflectance sensor is divided into two parts, a LED which emits IV and a phototransistor which captures it after it is reflected from the target object.
We were asked to find the resistance value of R2 in order for a V-out signal of 1.4V to correspond to a value of 0.36ma for current I2.
The answer is 10Kohms, although I'm having a hard time understanding how to get there.
Since there are two currents, this can't be a voltage divider as I initially assumed, so does that mean the circuit is in parallel?
But if so, shouldn't the voltage across R2 equal the voltage across R1 and the input voltage of 5V instead of 1.4?
I know I'm missing something fundamental here.


texts:
I've used small high speed dc motors by just wiring them to a battery and potentiometer, but i've heard a lot of talk in these forums about motor controllers and h-bridges, and I don't fully understand when they are needed.

My question is: I want to run a geared motor like one of these:

http://www.surpluscenter.com/item.asp?item=5-1571&catname=electric

http://www.hobbyengineering.com/H2013.html

Do I need a motor controller, arduino motor shield, or h-bridge to do so? Or can I just wire up a 6/12 volt power supply and use a pot to control the speed? I realize I won't be able to run it in reverse this way. Would I be able to just use a switch to reverse the polarity and run it forwards/backwards?