texts: how to wire BC547 LED flashing circuit in EAGLE?

texts:
I'm studying electronics and I'm trying to grasp the usage of EAGLE. I got an assignment where I must first make this schematic and then wire it on a 3cm x 3cm board.
There is a condition where the LEDs and the voltage source must be arranged in a specific way.

I have no idea how I have to wire it, because if I put R3, R4, T2 and C1 on the same side with the LED2, I can't wire C1 and C2 on the opposite sides. I thought about putting the resistors in the middle but I can't wire all the components through the resistors. It just doesn't work if they have to intersect.


texts:
I have nucleo-401RE (STM32F401) board. I am trying to setup a timer (TIM4) to work above 2MHz (on bare-metal code).
Per the timer settings below I am supposed to get 10.5MHz. On scope, I am getting only 2MHz.
Am I making the correct configuration? Is there away to make it faster (I got same Hz when setting timer perload register to 3)
#include "stm32f4xx.h"
#include "dbg_pin.h"

#define DBG_PIN_HIGH(p,x)   (p->BSRR = (uint16_t)x)
#define DBG_PIN_LOW(p,x)    (p->BSRR = (uint32_t) x << 16)
#define DBG_PIN_TOGL(p,x)   ((p->ODR & x)? DBG_PIN_LOW(p,x) : DBG_PIN_HIGH(p,x))

TIM_HandleTypeDef   hTimSlice;

void SystemClock_Config(void)
{
    RCC_OscInitTypeDef RCC_OscInitStruct;
    RCC_ClkInitTypeDef RCC_ClkInitStruct;

    __HAL_RCC_PWR_CLK_ENABLE();
    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE2);

    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
    RCC_OscInitStruct.HSEState = RCC_HSE_ON;
    RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
    RCC_OscInitStruct.PLL.PLLM = 8;
    RCC_OscInitStruct.PLL.PLLN = 336;
    RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV4;
    RCC_OscInitStruct.PLL.PLLQ = 7;
    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
        return ;
    }

    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK) {
        return ;
    }
}

uint8_t timer_init()
{
    __HAL_RCC_TIM4_CLK_ENABLE();

    hTimSlice.Instance              = TIM4;
    hTimSlice.Init.Prescaler        = 0;
    hTimSlice.Init.Period           = 7;
    hTimSlice.Init.ClockDivision    = 0;
    hTimSlice.Init.CounterMode      = TIM_COUNTERMODE_UP;
    hTimSlice.Init.AutoReloadPreload= TIM_AUTORELOAD_PRELOAD_ENABLE;

    if (HAL_TIM_Base_Init(&hTimSlice) != HAL_OK){
        return 1;
    }
    HAL_NVIC_SetPriority(TIM4_IRQn, 3, 0);
    HAL_NVIC_EnableIRQ(TIM4_IRQn);
    return 0;
}

void TIM4_IRQHandler()
{
    if(__HAL_TIM_GET_FLAG(&hTimSlice, TIM_FLAG_UPDATE) != RESET) {
        if(__HAL_TIM_GET_IT_SOURCE(&hTimSlice, TIM_IT_UPDATE) !=RESET) {
            __HAL_TIM_CLEAR_IT(&hTimSlice, TIM_IT_UPDATE);
        }
    }
    DBG_PIN_TOGL(GPIOC, GPIO_PIN_8);
}

int main(void)
{
    HAL_Init();
    SystemClock_Config();

    setupDbgPin();
    timer_init();
    HAL_TIM_Base_Start_IT(&hTimSlice);

    for(;;);
}

Thanks.


texts: Is there a limit to the amount of charge that could be stored in any system as a result of the charge particles repelling each other?


texts: Is conductivity equivalent to conductance per unit length?

texts:
Conductivity is measured in units \$S/m\$. Conductance is units \$S\$, and length is units \$m\$, so conductance per length would also be \$S/m\$. Does this mean conductivity and conductance per length are equivalent? The units match, but I have some doubts.

What got me thinking about this was the typical model of characteristic impedance of a transmission line:

$$ Z_0 = \sqrt{\frac{R+j\omega L}{G+j\omega C}} $$

where \$G\$ is conductance per unit length of the dielectric. I'm unable to find actual values of \$G\$ for common coax cable, probably because \$G\$ is almost universally insignificant in this calculation, so no one bothers to provide an actual value. PET has a conductivity on the order of \$10^{-21}S/m\$; is this a valid value to use in this calculation? Or, is \$G\$ a function of both the dielectric's conductance and the cable's geometry? If geometry is relevant, how?


texts: Increase accuracy of ADC without device AGND

texts:
I am using the ADC of the PIC16F18344 —

http://www.microchip.com/wwwproducts/en/PIC16F18344

It has neither Avdd nor Agnd, but it does have selectable Vref+ and Vref- pins. If I were to stop using chip Vdd and Vss for ADC, dedicate a regulator to Avdd and Avss, run these lines to the Vref pins, and select them in the firmware, would I see accuracy benefits equivalent to a device that had dedicated analogue supply pins? I think, for this application, noise immunity is more important than absolute accuracy. There is also calibration supported, as well.

Currently the ADC is connected in simple voltage divider/"ratiometric" configuration with a rheostat:

simulate this circuit – Schematic created using CircuitLab

I am using all 10 bits of the result, although I can tolerate some error in the least-significant bits. I am using a software median filter to cancel noise and it works fairly well. The sampling rate is quite low, perhaps two or three times a second. There is a passive T filter before the ADC; the chokes are actually approximations of ferrite cores.


texts: help me pick the correct mosfets for low voltage coreless dc motors

texts:
I'm building a minidrone based on an eachine using the same components  as the original but instead controlling it with an arduino nano, a bluetooth module and a  6 axis gyroscope. I had available 2 l293d's to drive the motors but the motors barely lift the drone. I was told the problem was that l293d is terrible option for lower voltage applications and I need to use low level mosfets(low Vgs) instead(also drones don't need to reverse the voltage of the motors).I'm planning to replace the H bridges with Si2302ds mosfets and shottky diodes.

Here are the respective datasheets :

SI2302DS
https://www.vishay.com/docs/70628/70628.pdf

1N5819
https://www.diodes.com/assets/Datasheets/ds23001.pdf

and this is what I found about the motors :

1.Operating condition
Rated voltage   3.4V DC
Direction of rotation   CW and CCW
Operating voltage range DC2.0--4.5V DC
perating temperature range  -10-50°C
Motor position  all position

2.Mearsuring condition
Motor position  horizontal or vertical
Power supply    regulated DC power supply assuring unquestionable measuring
regulated DC power supply assuring unquestionable measuring 10-30°C  30-95%
If the judgment is questionable,Measurent is to be made based on JIS Standard Testing Condition(20+2°C,65+5% )
Direction of rotation   viewed from output shaft side

3.Electrical characteristics
Items   Specification   Standard value
No Load speed   67000rpm±15%    67000 rpm
No Load current 200mA max   180mA
Starting voltage    0.8V max    0.5V DC
Stall current   240mA±5%    240mA
Terminal resistance 0.9Ω ±5%    0.9Ω
Insulation resistance   10MΩ min    AT 250V DC between
motor terminal and case

I've been told that the stalling current given is wrong since a 0.9ohm motor resistance results in a 3.7 / 0.9 = ~4Amp stall current (not 240mA).

I will also power the drone with the same battery that the eachine uses:

Battery Power:3.7V 260MAH 45C

My main concern is if I'm choosing the right mosfet for this project. I'll appreciate any suggestions.


texts:
I am trying to create simple variable voltage divider circuit, with several constraints that are causing me to look for alternative solution.

Constraints:

The input voltage is 1.5 V
Maximum R1 is 5 M\$\Omega\$
Minimum R1 above 5 k\$\Omega\$
\$V_{out}(V_{R1})\$ is 0.1 mV upto 500 mV

The R1 max and min window is too small to allow for a 0.1 mV to 500 mV output.

My attempt and why I think this will not work:

To satisfy 5 k\$\Omega\$ or above resistance at output of 0.1 mV I used the equation
as below:

$$0.1mV = \frac{1.5 \times 5k}{5k + R2}$$

$$R2 = 75 M\Omega$$

$$\text{This value gives me the value of R2 and hence }R_{total}$$

To find if 75 M\$\Omega\$ total will satisfy the 5 M\$\Omega\$ max at 0.5 V I
continue from above:

$$0.5V = \frac{1.5 \times R1}{75M}$$

$$R1 = 25 M\Omega$$

$$\text{This value is way above the 5 }M\Omega \text{ limit}$$

It is clear that I can not satisfy the constraints with a voltage divider. My question is are there other solutions that may help me solve this issue?

Some background on why the constraints are there:

These constraints are due to available material and circuit requirements, i.e 5 M\$\Omega\$ limit on R1 is simply because I can't find a trim pot at any larger values. And the minimum R1 is because this circuit is simulating a electrochemical sensor that has an impedance above that value. If the voltage source has less of an impedance, the analyzer circuit will reject the source. Also the reason for using 1.5 V is because the analyzer uses 1.2 V detection signals.


texts: I just faced "UC input" while reading a Relay's catalogue. In the catalogue it has been told that the relay can have DC input,UC input and AC input. so what is UC input?  I searched for it but didn't find anything useful.


texts: Low Pass IIR filter attenuating all frequencies

texts:
I am trying to make a Low pass IIR filter in dsPIC(dsPIC33FJ12MC202) using mikroC compiler. I have generated filter coefficients using Filter Design Tool. My filter specifications are as follows:
LPF, Wp=4KHz, Ws=5KHz, Ap=0, As=60, Sampling about 20Khz

I am taking analog input from channel zero, filtering it and sending filtered value via UART. The code look something like this:

int adcValue;
char result[6];

const unsigned int BUFFER_SIZE   = 8;
const unsigned int FILTER_ORDER  = 3;

const unsigned int COEFF_B[FILTER_ORDER+1] = {0x17D9, 0x478B, 0x478B, 0x17D9};
const unsigned int COEFF_A[FILTER_ORDER+1] = {0x8000, 0xAF27, 0x383C, 0xF802};

const unsigned int SCALE_B = 1;
const unsigned int SCALE_A = 0;

unsigned int inext;
ydata unsigned int input[BUFFER_SIZE];
ydata unsigned int output[BUFFER_SIZE];

void filter(unsigned int adcValue)
{
  unsigned int CurrentValue;
  input[inext] = adcValue;

  CurrentValue = IIR_Radix( SCALE_B,
                            SCALE_A,
                            COEFF_B,        // b coefficients of the filter
                            COEFF_A,        // a coefficients of the filter
                            FILTER_ORDER+1, // Filter order + 1
                            input,          // Input buffer
                            BUFFER_SIZE,    // Input buffer length
                            output,         // Output buffer
                            inext);         // Current sample

  //CurrentValue = 2048;

  output[inext] = CurrentValue;
  inext = (inext+1) & (BUFFER_SIZE-1);    // inext = (inext + 1) mod BUFFER_SIZE;

  //Sending filtered value via UART
  WordToStr(CurrentValue, result);
  strcat(result, "\n\r");
  UART1_Write_Text(result);
}

void main()
{
   inext  = 0;                                 // Initialize buffer index
   Vector_Set(input, BUFFER_SIZE, 0);         // Clear input buffer
   Vector_Set(output, BUFFER_SIZE, 0);       // Clear output buffer

   //Using R12, R13 for Rx, Tx
   PPS_Mapping(12, _INPUT, _U1RX);
   PPS_Mapping(13, _OUTPUT, _U1TX);

   UART1_Init(115200);
   ADC1_Init();

   while(1)
   {
      adcValue = ADC1_Read(0);
      Delay_us(50);
      filter(adcValue);
   }
}

The IIR_Radix function is provided by mikroC compiler, So I am expecting below 4Khz it should give output whatever the input is and above 4KHz it should attenuates input.

Currently I am simulating circuit using Proteus and when I apply Sine Wave generator(Amplitude 5v, Freq=1000 Hz) at ADC channel I am getting output which has maximum value 95(e.g 0, 22, 69, 95, 69, 22, 0...) on Virtual Terminal. But 1000 Hz is in passband so I should get whatever the input is, like(0, 25, 499, 1023, 499, 25, 0...). So why I am getting attenuated output even for passband frequencies?

I am analyzing output on virtual terminal inside proteus simulation, see on right.


texts:
Trying to decipher the hole or shaft sizes in a stepper motor diagram.

I am using this stepper motor as an example, but the question applies to a notation in all similar types of diagrams:
https://components101.com/motors/28byj-48-stepper-motor

I am confused about how sizes (red question marks) are specified in the below diagram:

How do I read the radius or diameter of the hole shown above or the diameter of the stepper motor shaft from the above diagram?

A link to an online article explain how to read this type of sizing diagrams woyld be a great help.


texts: Active Audio Blend for Stereo Signal from single dual gang pot

texts:
This is my attempt to create a blend between 2 audio sources. The image is for one of the 2 channels.

I am concerned this will not work, however I'm struggling to decipher why.

Will this work as i am expecting. Where the pot moved to full cw will only allow the main_out_L to pass and ccw will only allow cue_out_l to pass?


texts:
The image below is an output stage I designed for research purposes on my own. It is a PI controlled DC push-pull amplifier. On the left there is a common base circuit with amplification stage (with cascode) after to generate the output stage drive. The simulation looked ok but as always simulation is never the real world. The real curcuit has some overshoot at the output when I input a step function as set voltage. However I can't get rid of it by changing the PI controller parameters. I use OPA288 as real operational amplifier. What do you guys think of that circuit. Any ideas how to get rid of the overshoot at the output?

Output voltage in time domain:


texts: As I know Bluetooth masters can be connected up to 7 slaves at once. What happens if there are 8 or 9 slaves trying to connect and send data to the master? Is there any collision algorithm like CDMA?


texts: Can I transfer data wirelessly to the inside of an aluminium can?

texts:
My problem is that I have to control (turn on and off) one LASER that is placed inside an aluminium can (not like soda can, but one 2 mm thick).

So the question is if there's any way to do that wirelessly. I've been thinking about Bluetooth and Zigbee but in my initial research I've found data may not be able to 'go through' the aluminium.

I've been thinking about IR, but it may not fit my idea because I have a camera shoting pics of the can, so the IR led may affect the images.

Any thoughts on that? Any other solution? Is there some tech that I could look for that would suit my problem?

Thanks in advance


texts: INA219 high current measurements for my autonomous boat?

texts:
I'm building an autonomous boat which will contain solar panels for its energy needs. The current prototype contains a 20W solar panel. All the electronics work great so it's time to scale up. The next prototype I'm working on will contain a 100W solar panel and the final version 200W of solar panels.
I'm currently using this INA219 power sensor:

It works great and I would like to continue to use it. However I don't think the sensor will be able to handle the increased amounts of energy I'm going to receive from the solar panels. I just tested running about 50W through the sensor (12V x 4A) for about 20 seconds and it heated up really quick.
Over on this page at Adafruit I read that their version "can measure up to ±3.2 Amps". I presume the version I have will be able to handle the same or less. Furthermore, the page at adafruit says:

Advanced hackers can remove the 0.1 ohm current sense resistor and replace it with their own to change the range (say a 0.01 ohm to measure up 32 Amps with a resolution of 8mA)

Although I wouldn't call myself an "advanced hacker" (which should be obvious from me asking this question) I guess this is what I need to do. So first things first. Is this the part that they're talking about replacing (the current sense resistor)?

So as far as I understand this R100 means it's 0.1 ohm resistance. So I need one which says R010 like for example one of these: https://www.aliexpress.com/item/32847907759.html
Would one of those be enough and can I simply replace it using my soldering iron? Do I need a certain specific size or do these always have a "standard size"? And most importantly; will changing this out with the R010 prevent the sensor from heating up like it does now? (it actually hurt my finger)
Are there other things I'm missing here? All tips are welcome!


texts: Connecting 19v 3Ah projector to 4 linked power banks

texts:
I'm trying to make my projector mobile. As per the title the power adapter gives it 19v 3Ah. Now my idea was to link 4 10Ah power banks and take the 20v down to 19v, giving it about 3 hours of mobile usage.

Questions (need those):
1. Does this work? I've got almost no experience with electronics.
2. How would I go about it?

Any tips?


texts: How bad is it to places vias under a QFN thermal pad?

texts:
I'm working on a PCB which has to be very small. There is a QFN IC which has a big thermal pad, although it doesn't really need to dissipate that much heat. So to save some space, I came up with the idea of reducing the footprint of the thermal pad so that I can place some vias and traces in there. It would be covered by solder resist so it doesn't sound unreasonable to believe that this might be okay.

However, if it were such a good idea, everyone would be doing it, and I'm wondering how bad it is. I've seen this similar question but it's not exactly the same thing.

For example:
The traces are 0.2 mm (7.87 mil) wide, the via diameter is 0.7 mm and the drill is 0.3 mm.


texts: How is the gain/phase vs frequency measured for opamps?

texts:
Opamp manufacturers post graphs like these in datasheets:

How is the data for this graph measured? Is it calculated using the mathematical model of an opamp?


texts: What is drive strength a measurement of?

texts:
In microcontrollers and the like that have programmable drive strengths for GPIOs, said drive strengths are defined in mA. For example you might have a choice of 2mA, 4mA, 6mA, 8mA, etc. My assumption, is that for each output drive strength, there is a corresponding output buffer, and that the software drive strength setting controls a mux that decides which buffer drives the pin. Is that correct?

Second question: I understand that, for example, doubling the drive strength effectively doubles the size of the output buffer (or, equivalently, halves the output impedance), but what is the drive strength actually a measure of? Say the drive strength is 4mA, what does that actually mean? My guess is that the pins Voh/Vol is not guaranteed if you draw a higher current, but I'd be curious to know how these values are characterized/chosen by the vendor.

--

I wanted to add this in response to CL. below, but I'm not sure how to add images in comments.

This is from the same datasheet he references:

Edit: jump back and forth a few times between this table, and the "typical" curves below and one gets a better feel for an interpretation of drive strength. The question however remains unanswered. Perhaps this is only something someone who writes data sheets could answer. I suppose the question could also be generalized to "how do IC companies determine their min/typ/max values?". As an example in the image above, the drive strength for "full setting" is given as 15mA, with 3V Vcc, if you want a max Vol of Vss + 0.60V. What is the process to arrive at this number? Set the pin low and force it to sink current until Vol hits 0.6V, then take the current being sunk and round down to the nearest mA? There's probably a statistical component as well to arriving at the number. I'd be surprised if they only characterize one die, probably many over all the different PVT corners.


texts: Why inductors can not be integrated into IC?

texts: If passive components like resistor and capacitor can be integrated into an IC, why not inductor?


texts: Calculating gate to source voltages in h-bridge circuit

texts:
The circuit shown above is an h-bridge circuit.  It works by letting a microcontroller send a low/high signal on R1 or R4. I've been told to determine all the Gate to source voltages for each of the four MOSFETs when R4 is getting a high signal and when R1 is getting a high signal. I started off by considering the case where R4 got a high signal and R1 low. I was able to calculate the Gate to source voltages of the two transistors Q5 and Q6, but I can't seem to calculate the gate-to-source voltages of Q3 and Q4.

So my question is how would I calculate the gate-source voltages of Q3 and Q4 when R4 receives a high signal and R1 a low signal?


texts: What is the difference between words and symbols in Qsys, how to know which one to use?

texts:
Qsys offers options to select address unit or address type. All I know is that my custom components shall write 32 or 64 bit data to a specific address and it is not byte addressable.

How do I decide which address type to use? This question comes up in Qsys custom component generation and also when instantiating an Avalon-MM BFM.

So my questions are:

What is the motivation behind have "Address units", I am confused how to decide which one to use?
Regardless of whether I select "WORDS" or "SYMBOLS", there is always a box saying "Bits per symbol" in the GUI. Why is this so?
When instantiating an Avalon-MM BFM there are options for Symbol width and Number of symbols. How do I know what to select?

Selecting over the other seems to have a big impact on the address span. But not clear how.


texts: Which capacitor to choose for ACS709 to filter 50Hz noise?

texts:
I am using the ACS709 current sensor together with an Arduino board to measure the charge/discharge current of a large battery connected to an UPS.

I noticed a strange noise pattern in my DC measurements, which seems to be 50 Hz. I guess it must be the UPSs inverter, which draws power in such a way.

My goal is to get rid of that pattern and get reading similar to what my multimeter can measure.

I have read both the documentation for ACS709 and the FAQ on their website, but being a complete newbie in electronics I have a number of questions:

I understand that I probably need to add a capacitor to the FILTER pin of ACS709, but I am not sure which capacitor should I choose.

In the FAQ they provide a formula and an example table for different capacitances, which reduce bandwidth.

What is "bandwidth" in this case? The amount of measurements per second?

I only want to measure the mean current flowing at most once per second.

Which capacitor should I choose?

--- Follow up ---

I found this equation for a low-pass RC filter:

$$
f_c = \frac{1}{2\pi RC}
$$

Solving for C gives:

$$
C = \frac{1}{2\pi Rf_c}
$$

According to the docs the ACS709 already has a built in resistor of 1700 Ohms. Choosing the frequency = 0.5 Hz gives me:C = 0.1872 mF

Is that a correct calculation? The result seems large. In the docs all examples are in the nF range.

I want to choose mono-polar electrolytic capacitors, because the ACS709 output should have polarity in only one direction. Is that the correct choice?


texts: How can I see if my filterless class-D audio amplifier is clipping or not?

texts:
So I'm using MAX98357A, which is a filterless class D audio amplifier. I'm running it using Vcc = 5 V. Looking at the page 28 of the datasheet, I see the folliwing formula for output voltage:
Output (dBV) = input (dBFS) + 2.1 dB + Gain (dB), where 0 dBFS is referenced to 0 dBV.

My Gain variable is set to 12 dB. If I set the volume of the input audio to maximum, I'd get signal with following output voltage:
Output (dbV) = 2.1 dB + 0 dBFS + 12 dB = 14.1 dBV.
 Converting this to linear units, gives me 5.06 V.

Now, I could be suffering from critical datasheet reading failure, but I couldn't find anywhere the actual limits for the output voltage compared to input voltage.

Therefore, I'd like to see somehow if my output is actually clipping or not.

Unfortunately, I'm not sure how to do this, since the amplifier relies on speakers mechanical inertia to act as a low-pass filer.


texts: Why this saw shaper circuit does not work in reality?

texts: As part of the experiment, I decided to use an optocoupler in the saw shaper circuit. Although I managed to get the effect in the simulation, the actual design does not work on a breadboard. Please advice.


texts:
I have an object that I want to know whether it is submerged into water or not for a specific period(20 seconds for example). The object will float over the water most of the time but I want to be able to know when it is submerged into water.
I don't want to detect water, I want to detect if it is submerged into water for some time...
What sensors can help me? I though to use Bluetooth: connect the object to another device that is outside the water, and as you know Bluetooth is not working underwater, so the both sides can knows that the object is now underwater and thus I can measure the period where Bluetooth was disconnected. What do you say about this way?


texts: Civil Traffic Engineers have a perpetual data gathering problem. They need intersection turning movement counts to do their studies. This has historically been a manual task. Someone sits by the intersection all day long and counts number of vehicles turning in each direction  and only recently has one company started using machine vision to automate this process (Miovision). The other method is to use License plate recognition on the 4 legs of the intersection and see which vehicles turned from where. I was wondering if there are any other ideas that can be used to count turning movements more easily. The biggest challenge is identifying vehicles accurately as they go through the intersections. Is it possible to measure the temperature or sound profile of a vehicle before it enters the intersection and after it leaves the intersection and match up these values to see which way it turned?


texts: Rotate BLDC motor with Clark and Park transform

texts:
I'm trying to rotate BLDC motor using FOC method without sensing anything from the motor. I just slowly increment angle from 0 to 2PI and then use Park-Clarke transform with Vq and Vd equal to 1.0 to get 3 phase which I then use for Space Vector modulation. The problem is that the motor doesn't rotate smoothly, here is a video of Rotating motor and here is my code for arduino platform:

#include "CDFraction.h"
#include <Arduino.h>
#include <SPI.h>
#include <limits.h>

#define CLAMP(x, a, b) ((x) < (a) ? (a) : ((x) > (b) ? (b) : (x)))

float angleIncrement = 3.141592653589793 * 0.001f;
float angle = 0;

float Vsq = 1.0;
float Vsd = 1.0;

float Va = 0;
float Vb = 0;
float Vc = 0;

int16_t Ta = 0;
int16_t Tb = 0;
int16_t Tc = 0;

SPISettings drv8305SPISettings(1000000, MSBFIRST, SPI_MODE1);
uint8_t drvSelectPin = 5;
uint8_t drvEnablePin = 4;

void setup()
{
  pinMode(3, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(drvSelectPin, OUTPUT);
  digitalWrite (drvSelectPin, HIGH);
  pinMode(drvEnablePin, OUTPUT);
  digitalWrite (drvEnablePin, LOW);

  TCCR1B &= B11111000;
  TCCR1B |= B00000001;
  TCCR2B &= B11111000;
  TCCR2B |= B00000001;

  //initialize Serial
  Serial.begin(115200);
  // initialize SPI:
  SPI.begin();

  uint16_t drvCmd = (0 << 15) | (0x7 << 11) | 0x0296;
  uint16_t drvRes = 0;

  SPI.beginTransaction(drv8305SPISettings);
  digitalWrite (drvSelectPin, LOW);
  // reading only, so data sent does not matter
  drvRes = SPI.transfer16(drvCmd);
  digitalWrite (drvSelectPin, HIGH);
  SPI.endTransaction();
  Serial.println(drvRes, BIN);

  digitalWrite (drvEnablePin, HIGH);

}

void loop()
{

  float VsqSinA = Vsq * sinf(angle);
  float VsdCosA = Vsd * cosf(angle);

  float Valpha = VsdCosA - VsqSinA;
  float Vbeta = VsdCosA + VsqSinA;

  float Valpha_temp = -0.5f * Valpha;
  float Vbeta_temp = 0.866025403784439 * Vbeta;

  Va = Valpha;
  Vb = Valpha_temp + Vbeta_temp; //-05f * alpha + sqrt(3)/2 * beta
  Vc = Valpha_temp - Vbeta_temp; //-05f * alpha - sqrt(3)/2 * beta

  float Vmax = 0;
  float Vmin = 0;

  if(Va > Vb)
  {
    Vmax = Va;
    Vmin = Vb;
  }
  else
  {
    Vmax = Vb;
    Vmin = Va;
  }

  if(Vc > Vmax)
  {
    Vmax = Vc;
  }
  else if (Vc < Vmin)
  {
    Vmin = Vc;
  }

  float Vcom = (Vmax + Vmin) * 0.5f;

  Ta = floor((Va - Vcom + 1.2246778011322)/2.4493556022644 * 12 + 0.5f);
  Tb = floor((Vb - Vcom + 1.2246778011322)/2.4493556022644 * 12 + 0.5f);
  Tc = floor((Vc - Vcom + 1.2246778011322)/2.4493556022644 * 12 + 0.5f);

  analogWrite( 3, CLAMP (Ta,  0, 255));
  analogWrite( 9, CLAMP (Tb,  0, 255));
  analogWrite(10, CLAMP (Tc,  0, 255));

//  Serial.print(Va);
//  Serial.print(" ");
//  Serial.print(Vb);
//  Serial.print(" ");
//  Serial.println(Vc);
//
//  delay(10);

  angle += angleIncrement;
  if(angle > 6.283185307179586)angle = 0;

}

What I'm doing wrong?


texts: Bluetooth class "Limited Discoverable Mode"

texts:
I have a Bluetooth-device with class 20258C. - It's a remote control. According to the Class of Device (CoD) Calculator this means the device has the following attributes:

Major Device Class: Peripheral
Limited Discoverable Mode
Audio
Pointing device
Remote control

My questions regard the "Limited Discoverable Mode".

What exactly does this mean?
How can I connect such a device to another BT-device? Is it even possible if I have no MAC-Address? I only know "Supplier ID", "Product ID" and "Bluetooth device Name"


texts: Why secondary coil in transformer have continues one direction current

texts: In primary side of transformer it change magnet north to south as ac current flow and it keep changing as ac wave passed through  coil. I do not understand why on secondary side we got a current which flow in one direction. Why not on secondary side current change its direction as magnet change in primary side.


texts: I have a problem with PCB.  When I click Design -> Update PCB Document my components are passed to PCB in a messy way. I couldn't solve this problem. Is there any way to solve this?


texts: Interfacing LM19 temperature sensor with Arduino

texts:
community! I have a problem as follows. I've been trying to interface the LM19 temperature sensor using Arduino. I made a function to read and compute the temperature from the sensor according to a formula described in its datasheet. The result was pretty good. However, when I added another function for reading ADC value from an LDR, the result of the temperature computation went crazy!!! Here's my code:

/*
 Author: M. Chenda
 Created on Tue Feb 18, 2020
*/

#define ldr 0       // assign LDR's pin to analog pin A0
#define light 8     // assign LED's pin to digital pin 8
#define lm19 2      // assign LM19's pin to analog pin A2

int ldr_val = 0;    // LDR's ADC reading variable
String state;       // string representing light's state

int lm19_val = 0;   // LM19's ADC reading variable
float Vo = 0.00;    // V output of LM19
float temp = 0.00;  // temperature variable

void setup() {
    pinMode(light, OUTPUT);
    Serial.begin(9600);
    while(!Serial) {;}  // wait for serial port connection
}

void loop() {
    lighting();
    temp_control();
    delay(500);
}

/*  LIGHT CONTROL   */
void lighting() {
    ldr_val = analogRead(ldr);  // read LDR's ADC value (brightness)
    if (ldr_val < 512) {
        digitalWrite(light, LOW);
        state = "off";
    }
    else {
        digitalWrite(light, HIGH);
        state = "on";
    }
    Serial.print("LDR's ADC:  ");
    Serial.println(ldr_val);
}

/*  VALUE MAPPING FUNCTION  */
float mapping(float x, float in_min, float in_max, float out_min, float out_max) {
    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

/*  TEMPERATURE MEASUREMENT */
void temp_control() {
    // read LM19's ADC value
    lm19_val = analogRead(lm19);
    // convert the ADC value to voltage (0 to 5V)
    Vo = mapping(lm19_val, 0, 1023, 0, 5);
    // compute temperature value in Celsius
    temp = -1481.96 + sqrt((2.1962*pow(10,6))+((1.8639-Vo)/(3.88*pow(10,-6))));
    Serial.print("      Temperature (Celsius):  ");
    Serial.println(temp);   // print the measured temperature to Serial Terminal
}

What could be the root of this problem?


texts: decoupling capacitors for DC-DC converters

texts:
I am using a DC to DC converter (Murata MEJ2S0505SC (datasheet)) (5 V to 5 V at 500 mA) for isolation purposes. Now I want to calculate the input decoupling capacitor.

Can anyone please suggest any methodology to calculate it? (Note: It is not mentioned in the data sheet.)


texts: Drift of values read by Arduino MPU6050 sensor

texts:
We are using a GY-521 Arduino MPU6050 breakout board, using Jeff Rowberg's DMP6 libaries.

However, when we read values from the sensor while it is held stationary, the values drift considerably, until they stabilize at a value after around 1 minute.

Is this expected behavior from these chips with these libraries?  We've tried with more than 4 chips, and all drift.

Notably, the chip does not drift when we use the code at the Arduino playground (http://playground.arduino.cc/Main/MPU-6050).

Rowberg's code has additional functions that we need, however.  How can we fix this?


texts: Finding the power dissipation in a wye-connection given resistors

texts:
The problem that I'm attempting to solve is the following:

Three 1000 Ω resistors are connected in Y to a 200-Vac line. The power dissipation of the Y combination would be _____W.
a. 42
b. 41
c. 40
d. 39

What I assume is that the resistors act as the impedances. So, Z_y = 1000 ohm. Now, using S = 3(I^2)Z_y leads me to 120 W. I get the current from dividing 200 and 1000. Where did I go wrong?


texts: Solving Vout for a differentiating op-amp with added resistor?

texts:
I searched through old posts and didn't find a direct answer to this - there were practical explanations but no circuit math.

I am to solve the \$V_{out}\$ value for a differentiating op-amp. I know that normally this equation is
    $$V_{out} = -R  C  \frac{dv_{in}}{dt}$$

However, the circuit I'm solving is as follows:

Would the equation for \$V_{out}\$ now just be $$V_{out} = -R_2 C\frac{dV_{in}}{dt}$$ ?

I feel like something is missing in my understanding of how to include R1.

You guys have answered a few times giving Laplace methods of solving - I understand the math behind that but it is beyond the scope of the course I am in. We have only been taught to solve using Kirchoff's laws, so if you could show me that method, it would be appreciated?

Thanks,
inkblots


texts:
Just by looking at the pictures, can anyone help me identify what kind of blanket the copper strips are glued to? The kind of material and composition.

Apparently seems to me to be a very thin glass blanket, but I'm not sure as I don't have any technical knowledge of fabrics.

I need a fabric that is electroconductive and causes the larger fabric to warm up where the blanket and the copper are glued together. This larger one is a TNT (textile non textile).


texts: CAN bus simulation (automotive purpose) - tried Arduino and SparkFun

texts:
I repair electric powered steering systems for cars, especially Fiat, Alfa, and Lancya (Delphi manufacturers), and I'm in need of making some tool to test these reparations. I mean just turning it on, for example.

I have researched during some time, and I figured I need CAN bus signals to be simulated as the eps ECU is receiving ignition packets from CAN. Here I go...

I need to know what way I could read and send CAN packets from/to the bus. I mean, what tool or anything else. I have been trying with Arduino Uno + a SparkFun CAN BUS Shield, but I don't get any results. When everything is connected, my serial console isn't sniffing any packets. I have connected all correctly, I think, and tried different bit rates, changed Arduino boards and shield, tried many different examples. I invested lots of hours with no profit... I was using SEAT Ibiza 2010 for I+D, connected CAN-H and CAN-L on the OBD port, in the CAN lines from the radio, etc...

Any idea of what could be wrong is welcome, as is a new method to make my project...

Information:

Libraries Used

UPDATE 2 (28/12/2014):
I used a multimeter because I dont have a oscilloscope. Reading the voltages are always giving me plain 2.5V on CAN-H and CAN-L, I get this readings at Arduino CAN-H CAN-L and in OBD2 Port (Pins 6 and 14)

UPDATE 3 (29/12/2014):
I'm planning to switch to some programming language with a CAN interface, any suggestions are welcome, thanks!

UPDATE 3.1 (30/12/2014):
Definitely, I'm taking another way to do this, I'm waiting Kvaser and ECOM to reply me in their support emails. That way we may know if their tools fit with my project.
I will keep you updated, thanks for all the help guys! :)


texts: Meaning of maximum load function generator can drive

texts:
For example, if a function generator has a minimum load of 1kohm and a maximum load of 50Mohm, if we connect less than 1kohm, the output amplitude will distort.

But what happens to the output waveform if we connect 60Mohm?


texts: How can I get this button to be more reliable for my arduino program?

texts:
I have been working on this program for a simple controller. I have a prototype all wired up and working however the momentary push button is not very reliable. Sometimes it reads and other times it ignors it.

Here is my code.

/*
 * Valve Purge Control/heater control
 */
#include <math.h>

int feedValve = 12;                              // feed valve is connected to pin 12
int returnValve = 11;                            // return valve is connected to pin 11
int heater = 10;                               // heater is connected to pin 10
//int loopValves = 9                             // loop valves are connected to pin 9
//int pump = 8                                   // pump is connected to pin 8
int button = 2;                                  // button is connected to pin 2

int val;                                         // variable for reading the pin status
int val2;                                        // variable for reading the delayed/debounced status
int buttonState;                                 // variable to hold the button state

int buttonMode = 0;                               // Is valve on or off?

void setup() {
  pinMode(feedValve, OUTPUT);                    // Set the Feed Valve pin as output
  pinMode(returnValve, OUTPUT);                  // Set the Return Valve pin as output
  pinMode(heater, OUTPUT);                       // Set the Heater Valve pin as output
  //pinMode(loopValves, OUTPUT);                 // Set the Loop Valves pin as output
  //pinMode(pump, OUTPUT):                       // Set Pump pin as output
  pinMode(button, INPUT);                        // Set the switch pin as input
  Serial.begin(9600);                            // Set up serial communication at 9600bps
  buttonState = digitalRead(button);             // read the initial state
}

double Thermister(int RawADC) {
  double Temp;
  Temp = log(((10240000/RawADC) - 10000));
  Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp));
  Temp = Temp - 273.15;           // Convert Kelvin to Celcius
  Temp = (Temp * 1.8) + 32.0;    // Convert to F
  return Temp;
}

void loop(){
  val = digitalRead(button);                     // read input value and store it in val
  delay(10);
  val2 = digitalRead(button);                    // read the input again to check for bounces
  if (val == val2) {                             // make sure we got 2 consistant readings!
    if (val != buttonState) {                    // the button state has changed!
      if (val == LOW) {                          // check if the button is pressed
        if (buttonMode == 0) {                   // is the button off?
           buttonMode = 1;                       // turn buttonMode to 1
          } else {
            if (buttonMode == 1){
            buttonMode = 0;                      // turn buttonMode to 0
          }
        }
      }
     buttonState = val;
    }
    if (buttonMode == 1) {
      double Temp = Thermister(analogRead(0));   // read Thermistor
      //Serial.println(Temp);
      if (Temp > 90){
        digitalWrite(feedValve, HIGH);           // turn on feed valve
        delay(5000);
        digitalWrite(returnValve, HIGH);         // turn on return valve
      }
      if (Temp < 100)digitalWrite(heater, HIGH);      // turn heater on
      else if (Temp > 105)digitalWrite(heater, LOW);  // turn heater off
    }

    if (buttonMode == 0) {
      digitalWrite(heater, LOW);                 // turn heater off
      digitalWrite(feedValve, LOW);              // turn feed valve off
      delay(5000);
      digitalWrite(returnValve, LOW);            // turn return valve off
    }
  }
}


texts: Location of input for negative feeback bandpass filter

texts:
I came across a reference design on a TI application imaged here:

It is clear to me that there is a bandpass filter on the negative loopback branch of the amplier. However, from the few electronics classes I have taken in school, typically the input is seen where the group is placed. Is there any purpose as to why?
From the figure, I deduced the transfer function as:

That is mainly just a sanity check that I can workout the transfer characteristics properly.
This is my first post so don't rip me apart (or do, if I so deserve it.)


texts: How to sense 24V AC (Thermostat) with a 5V Microcontroller

texts:
I'd like to detect thermostat events (heat, fan, ac etc) with an Arduino. I've done quite a bit of investigation but haven't found a definitive solution. Most projects I see involve controlling the thermostat however I simply want to detect on/off events.

Based on what I've gathered so far, I'd like to use an optocoupler to protect the furnace/thermostat from damage -- protecting the Arduino is important but of lesser concern. I plan to run a separate wire (cat5) from the thermostat to my project so I don't mess with the furnace wiring.

This is the optocoupler I've seen recommended http://www.digikey.com/product-detail/en/HCPL3700/HCPL3700-ND/401373 via this howto https://www.adafruit.com/blog/2012/10/04/ask-an-educator-how-can-i-measure-ac-voltage-with-my-arduino/

But where I'm confused is how to wire it altogether and what values to select for resistance.

Here's the circuit in HCPL3700 datasheet


texts:
can we set stepper motor (variable reluctance) motor to power factor 1(ideally) or close to 1 like 0.98-0.99 ?
What are the most basic techniques ?

Best regards!


texts: Why does large 12v battery deplete quicker than 3 small AAA batteries

texts:
I have an alarm in my shed.
It takes 3 x AAA batteries and lasts about 3 months.
Since it has a USB socket input, I decided I could remedy this with a larger battery and power it from here.
I bought some parts:

12v 7ah "suitable for Security Alarm & Intruder Alarm" battery
5V/4.2A USB Car Charger (With LED - maybe important)

I fully charged the battery overnight and plugged in the USB car socket and then plugged into the alarm. It all seemed to work fine.
3 weeks later, the battery is dead.
I charged the battery longer this time and tried again..
Same result.
Where has my admittedly shallow knowledge of batteries / electronics failed me?
Why do 3 tiny little AAA's last 4 times longer?


texts:
Why is it that the DC transfer characteristic isn't flattening out at -5 v, so it looks like a Z-shape? I did a DC sweep from -10 V to +10 V.

The input wave is a 2V sine wave for the graph below:


texts: USB lights up simple circuit but not coin-cell

texts:
I have 13 adafruit LED sequins in parallel hooked up to a CR2032 coin cell. This cell is also hooked up to an adafruit Gemma board (Arduino-like board using an Attiny85). Pads D0 & D1 on the Gemma each connect to a single LED sequin. D0 & D1 can do PWM, so the Gemma's program simply fades these two LEDs on and off. This is all connected using conductive steel thread.

When I use the coin cell, the 13 LEDs all light up like I would expect, but the Gemma stays dark (it has a green LED to indicate when it's powered up). When I power the Gemma via USB, it works as expected: the two LEDs connected to the PWM pads fade on and off, while the rest of the LEDs stay on.

What is the problem with my coin cell power source? Not enough voltage? Not enough current? Could I fix it by putting two of these cells together?

Note that the LED sequins each have their own 220 ohm resistor, and when "powered from 3.3V they draw about 5mA". The Gemma "draws only 9 mA while running" and has an "On-board 3.3V power regulator with 150mA output capability"


texts: Connecting signal to multiple summing amplifiers

texts:
For a normal op-amp inverting summing amplifier, each signal is tied to the negative input of the op-amp. Imagine the scenario where I have three signals. In adder 1, I want to sum A and B. In adder 2, I want to sum B and C. So I connect B to both negative inputs.

Will there be any interference between the signals? Is this going to cause any problems?

simulate this circuit – Schematic created using CircuitLab


texts: Name and reason for space between pixels on an LCD display

texts:
Hopefully this is a good place for this question... I figured it was too technical for the A/V board of StackExchange.

Question:

Simply put, a recent conversation brought up the issue of the name of and/or reason for the black space ("mesh") between the pixels on an LCD display. Both common types I have examined have this element, including twisted nematode (TN) & in-plane switching (IPS/S-IPS/a-IPS) displays.

Background:

Anyone can see the separation between pixels on most displays 10" and above today. Occasionally the dot pitch is so small that it's very difficult to see this grid/mesh, such as the 200-300ppi+ screens on new tablets (Nexus 10, Galaxy S3) or phones (i-Device Retina displays), but any modern LCD HDTV makes this easy, as the PPI is usually 40-100 at best.

I recognize that there will usually be some visible separation when only one color is fired, as this exposes the dot pitch at its worst by only lighting one color element in each pixel, but even when displaying white this effect is shown.

To illustrate the point from another perspective, another manifestation of the grid is present in projectors that use LCD displays as their source, called the "screen door effect" or "fixed-pattern noise": http://en.wikipedia.org/wiki/Screen-door_effect

Where I am so far:

I have researched much of how various types of LCDs are assembled (links below), and it appears that the cause is the electrode plane required to address and fire the pixels.

Variants and further questions:

Do all types of LCDs have this? Are there any known ways to avoid it with a certain type of display (i.e. keep the electrode element "behind" the visible layer to eliminate its visibility), including experimental/non-commercially-viable technologies?

Any explanation would great, at almost any level of technical knowledge short of a nitty-gritty explanation for SMEs only ;-). Thanks in advance!


texts:
I am making a dummy load for a 100W tube guitar amplifier. I know the basics but I'm trying to be really careful since I'm dealing with a lot of power. My dummy load is just a 100W 8Ω resistor, complete with heat sink, and I have a simple box with the circuit constructed in it and it's all working and ready to go. However, I've been nervous about what happens if the resistor fails somehow. Having that load on the output transformer is essential to keeping my amp from frying so I wondered if there was a good way to have some kind of indicator that something in the circuit has failed and the dummy load is no longer providing any load to the amplifier. Even something as simple as an LED in series would be nice, but with the high amount of wattage going through the circuit I'm not sure that there is a simple indicator bulb that would work.
Does anyone have any suggestions on what I could do?
Image from comments (SSR edit):


texts:
I have a baby monitor that accepts a 3.6v 900mA battery and is charged via USB mini.  The USB port broke off and so I was unable to charge or power the device.

The USB pins were too small to solder back on.

Instead, I removed the battery, soldered the 5v (+) USB wire to the positive pin, and the ground (-) to the negative pin.

The USB charger puts out 5v and 1A. Is this safe? The thing works fine.  What issues could it cause?

I'm not trained or educated at all in electronics.  I just like to dabble in fixing things and restoring old electrical motors.


texts:
I have the following c++ code for making a sine wave using SFML, which i got from https://github.com/SFML/SFML/wiki/Tutorial%3A-Play-Sine-Wave.
for (unsigned i = 0; i < SAMPLES ; i++) {
  raw[i] = AMPLITUDE * sin(x * TWO_PI);
  x += increment;
}

I tried to make a square and triangle wave based off this code -
//Square
    else if (wave == 1) {
        for (unsigned i = 0; i < SAMPLES; i++) {
            raw[i] = AMPLITUDE * (sin(x * TWO_PI) < 0 ? -1 : 1);
            x += increment;
        }
    }
    //Triangle
    else if (wave == 2) {
        for (unsigned i = 0; i < SAMPLES ; i++) {
            raw[i] = ((AMPLITUDE * sin(x * TWO_PI)) >= 0) ? =AMPLITUDE : -AMPLITUDE;
            x += increment;
        }
    }

They both produce some sort of weird wave when I look at it on an osciloscope. The issue isn't with the code as when I look at a square wave from youtube, a similar wave appears. This is the Image -


texts: Main switch circuit with thyristor and bridge problem

texts:
Following circuit is a 220V touch switch from this website:

http://8085projects.info/m668-based-touch-sensitive-step-dimmer-circuit.html

I'm wondering how it works because the IC take its working voltage from + and - of diode bridge but when the thyristor switching the Load, voltage through the diode bridge become about 0.9V only and this voltage is lower than standard voltage to running the IC

There are also another circuit by same concept and this time from this website:

https://www.homemade-circuits.com/220v-touch-lamp-circuit-with-delay-timer/

So my question is:

1-Dose this method works?

2-If those circuits not correct so how motion switch with only 2 wires  which available in the markets works?


texts: Instrumentation Amplifier input saturation problem

texts:
I designed and ordered some PCBs for in-amp but having a problem, I think it is input saturation. The power supply is 0V, 6V, and 12V rather than -6V, 0V, 6V but I am only interested in AC so this is the design.

Ignore the digital part at the bottom as it works fine, and the R-gain is 1M not 1k (typo). When powered on, output is stable 0V. Setting gain to min (close to 1) when I first connect one signal generator lead to one input pin, output is 0V to neg rail 60Hz square wave (hum is amplified) and connecting the one signal generator lead to other input pin output is 0V to positive rail 60Hz square wave. When I connect both signal generator leads to input pins, the output is alternating between what I would expect (amplified signal generator) and 0V at a rate of 60Hz. The op amp is TL074, resistors are 2%, caps are monolithic.

I thought there might be a ground problem, but I use battery powered scope and signal generators, and the in-amp is (of course) differential input circuit. I thought there might be a problem with the 12V, so I tried using single supply by putting two 56k resistors between 6V and 0V to make 'false ground'. I added 0.1uF decoupling caps to 6V and 'false ground'. No luck, same situation so far.

I wonder if input saturation could come from un-matched resistors (I could hand pick discrete ones)? I wonder if J-fet TL074 doesn't like 100k feedback resistors (I could lower them)? I wonder if single supply is not working (I ordered a 5.5V to +/- 12V mini supply board from China)?

(added later)

Are you suggesting additions as on this simplified schematic?

I tried connecting the signal generator at that point leaving the input caps unconnected and it didn't help. The output was the same.

(added still later)

So having a look at this less simplified schematic, the necessary modification is the addition of two R-bias, as what I believe is suggested. I had often wondered about this. My experience with in-amps is limited to study in college physics class, and this is far from that. The circuit would live in an environment where the input is a 45 ohm coil which is in close proximity to a 1000V DC circuit with a seven million watt capacity. That circuit also has a frequency modulated signal that I am interested in, about 3KHz - 9KHz of about 10 watts. The output drives a pair of 12 gauge wires that lead to the input of an AstroNova DDX100 data logger a half mile or more away. It is important that the addition of this monitor makes no interference with the other circuitry connected to the coil, thus my choice of in-amp. The only other connections are to the local power supply. So my original scheme with local +12v as V+, local +6v as V-gnd, and local 0v as V- would seem to work out OK then.

Finally there is the question of component values. Would 100K for Rbias be the highest acceptable value or is 470K or 1M possible? Can I leave out C-comp? The op amp is a TLO74 j-fet input quad device. Although I think of this as low input bias, that's not the same as 'no' input bias then. Originally I thought to use .1uf monolithic caps for the inputs and outputs, but when they asked me to pick out the parts and on Mouser I saw 10uf, I thought I would like to see that. There were no such parts around back in the 70's!


texts:
I have a few questions about gpio.

First

What if two push-pull pins with high level connected? My point of view is that there is no way for current and nothing bad will happen. And reading of pin level will give us 0.

Second

What if two input pins with pull-up connected? I think it will increase current level in line but nothing bad will happen. Reading of input will give us 1.

Third

Why should I use push-pull as output if I want to drive a line? What's wrong with switching pull-up and pull-down resistors?

And fourth

Could you give an example of pins configuration which can cause both or one of them to burn out?

Thanks.


texts: Why is the magnitude of the transfer function for my plot showing a band-pass filter, but a strange phase plot?

texts:
I am trying to plot a transfer function, and plotting the magnitude appears to show that it is a band-pass filter, which seems reasonable.

The problem is, the phase plot does not match with the magnitude plot at all. The phase plot just looks like the magnitude plot inverted. How is this possible?

I've attached my Matlab code and a figure

(the top plot is magnitude and bottom plot is phase)

Here is also my Matlab code and the function that I want to plot. My question is: what is wrong with my code, and how is this possible at all in general?

numElem = 2000;
w = linspace(1,2*pi*10^20,numElem);
wRes = 2*pi*10^9;

%%Insert wRes (resonant frequency)
for n = 1:numElem
    if w(n) > wRes
        w = [w(1:n - 1), wRes, w(n:numElem)];
        resLocation = n;
        break
    end
end

freq = w ./ (2*pi);
lambda = 299792458 ./ freq;

%Beta
B = pi/2 .* w ./wRes;
B(resLocation) = pi/2;

%Distance
d = lambda ./ 4;
Z0 = 50; %Ohms
C = 10^(-12);
L = 1/(wRes^2*C);
Zl = 1 ./ (j .* w .* C + 1 ./ (j .* w .* L));
y = 1./((Z0./Zl).^2 .* j.*sin(B .* d)/2 + exp(j .* B .* d).*(1 + Z0 ./ Zl))

Amplitude=20*log10(abs(y));
phase = angle(y)*180/pi;
subplot(211)
semilogx(w,Amplitude)
subplot(212)
semilogx(w,phase)


texts: (230v)AC-DC(12v) wall adapter flashes when connected to dc to dc buck converter

texts:
So I used a common 230vAC to 12vDc (1AMP) wall adapter with dc jack like this

and converted to 5v using a dc to dc buck converter same as based on lm2596s
But the adapter LED starts blinking (normally the LED should just light up ) even if the output is not connected to anything.
My Question: Why is it happening and what can I do to overcome this issue?
update 1: I have tried using a 12vDC 20Amps SMPS and it works well.But not with the 12VDC 1Amps adapter


texts: OP amp output not changing ( schematics )

texts:
This is a image of most of part of my circuit (555 timer IC is cut from right side)...
using the pot (RV1) , I change the non inverting input voltages of the op amps. when non inverting exceeds inverting voltages of the op amps (which is different for different op amps) is should output 5V which should take BJT at saturation. Then current will flow from pin 7 to 6 in timer IC. But as you can see from the picture, though non inverting voltage is higher then inverting voltages output op amp voltage is still low.

why this is happening ??

again if I increase non inverting voltage a little from this value, LED start to blink (555 timer start operating) but still op amp output remain low .

**why this is happening ?

what can I do to made op amp work properly ??**

thanks


texts:
I have problem with designing buck converter.

I have tried to design it by using instructions from this site:

Buck converter

And here are my parameters:

V input - 72V max

V output - 12 V
switching frequency - 100 kHz ( LTC3703)

I max -1,5 A

However, my teacher has given me a \$15 \mu\$H inductor and said that I should use that one, and that is where my problems start.

When I go to design it using formula for inductor, LIR is extremely big ( somewhere around 4-5, instead between 0.2-0.5 like proposed on web site )

This is the inductor we are using

Inductor

So can someone help me to get good LIR, or should I say that we can't use this inductor?


texts: How can an isolating tape be used as a connection to the human body?

texts:
I'm making this project: Drawdio
There are 2 connections with the human body: one via the graphite and the other with a grip made of isolating tape. I don't see how this work. This tape isolates the electric wire that is running around the pencil, so how can this serve as a connection? Or do you make a capacitor = electrical wire/isolating tape/human body that can conduct electricity?


texts: Can anyone identify this connector type?


texts: Separating an FM antenna from a topology which uses headphone ground as antenna

texts:
I have a FM radio module with Silicon Labs Si4703 integrated tuner module for Arduino. The module assumes use of headphones and use of ground wire as an antenna (advice is wire length of 1.1-1.45m). In my use case that is unpractical, because the output will be coupled with an amplifier nearby and all components will be inside an aluminum box.

I would like to decouple the antenna from the ground. In my research I found a Silicon Labs AN231 document which explains the function of the device, but nowhere could be found the information about decoupling the antenna.

This diagram on page eight seems to be very similar to the module layout:

As I am not experienced with RF, my question is, is there a simple hack that would allow me to connect an independent antenna? For example, by cutting the line from the headphones ground S1 to FMIP, connect the S1 directly to the ground and connect a dedicated antenna to the input of the LC circuit made of Lmatch and C4. Will I get a reception and do I have a need to change the value of Lmatch to get it to work?


texts: I need help with question a and b. For a i know that gain =-R2/R1 and i know you just assume a resistor values so 5kohms and 1kohms for R2 And R1 respectively. What i dont understand is why you can just ignore the R3 and R4 resistors. Never really got the whole concept of op amps. And for question b im not sure how to find R3 and R4 by using the op amp. Thanks


texts: Where is stray current coming from in uA system. BLE Nano

texts:
I am testing how low I can get the power consumption of the RedBear BLE Nano, which is a development board for the Nordic NRF51822 System on Chip that contains an ARM micrcocontroller, and BLE 4.0 mdoule.

I have produced some software that should have turned off all of the subsystems in the processor, and put the device into a sleep mode that is interrupted by a timer periodically.

This seems to work, I am powering the module form a bench supply and I have a multi-meter in series. When I have my finger touching the metal case that shields the Raytac module which is on the BLE Nano, the multimeter reads a constand 20uA, which is great. Then happily comes out of sleep mode every 10 seconds, flashes an LED and goes back to sleep, again at 20uA.

If I do not touch the metal shield, then I see this 20uA value climb to ~330uA very slowly (takes about 1-2 minutes), then descend down to ~200uA, where it seems to stabilise.

My bench supply only tells me the current draw in milliamps, so it's registering zero the whole time.

I have no idea why there is a difference when I am not touching the shielding, and whether the module is really only consuming ~20uA or closer to 200uA.

If anyone can explain which current draw is likely to be the actual one, and why there is a difference, that would be great.

Thanks


texts: Required voltage rating of PCB terminal blocks with high voltage power supply

texts:
I have designed a power supply with a 3kV output. I need connect it to external heat-sinked load. I have purchased some 15kV twisted pair cable to do this.
I am unsure the best way to bring this voltage from the board, to the load.
I have been told 600V terminal blocks will do the job.
Won't I be exceeding the voltage rating?
The voltage is floating from ground, also, so I will need two wires from the terminal block - one for VOLT+ and one for VOLT-. If using a terminal block, this means the full voltage will be imposed upon it (to my understanding.)
Is it better to just have a via, sized to the AWG of the 15kV wire, which is soldered directly into the board? Possibly then, coated with some high voltage insulation material such as silicon or what not to increase breakdown capability? Possibly I could use the PCB footprint of the terminal block, but not actually place the component at time of manufacture - instead just directly soldering the 15kV wires into the hole with HV potting applied over it.


texts: USB I2C adapter and Cognimem on Mac OS X?

texts:
I am a newbie when it comes to electronics, but because of some things I'm being exposed to at work, I've grown a bit of an interest.  I was given a Cognimem CM1K chip on a board, which is essentially a 1024-node neural network on a chip.  They have software for Java and .Net, and I'm interested in using it on Linux/Mac OS X with Python or C if possible.

I bought a USB to I2C adapter and saw on the Cognimem chip's documentation that is supports I2C.  What are some ways to get started? I was thinking just to begin by reading some basic values from the chip.

What are some things to take into consideration? How do I write code to first interact with the USB I2C adapter, then out over I2C to (in general terms) the connected device?  Thank you.


texts:
Sorry if this is too basic but I don't understand this issue.

Right now, using an MCU, I change the RGB colours of an LED strip with 3 PWM signals.
All colours works great .
The thing is, when I am trying to set the intensity of the light, I don't know how to do it.

So if, for example, I have RGB(15,170,230), then I want to slowly reduce the intensity of the light, keeping the same colour, how would I change the RGB to get that?


texts: Change only one side the roundness in SMD

texts:
I'm doing my own component in Eagle for a PCB design. This is the footprint that the manufacturer gives:

But I have a problem with the SMD roundness when I try to draw the SMD footprint at the sides. I don't know if it is possible to draw with 100% roundness at only one side of SMD foot print like in the image and leave the another side with 0% roundness.


texts:
I realise that the LPC1768's Systick is a standard accross ARM boards, while Timer0 and co, are NXP additions.

Is there any particular reason to use one over the other? Say you want to generate a periodic interrupt every was, which one would be best suited?


texts: Why is this load resistor connected this way and what could be its value?

texts:
There is a potentiometer vane and the diagram includes protection components and looks messy, I simplified it by re-drawing as below:

The circle R1, R2, R3 and the gap represents the vane's 10k potentiometer section. The datasheet says "Wiper Contact Resistance" is 400 Ohm, so I modelled it as Rwp. Rw resistances above represents the wire resistances for the red and blue wires which passes the supply current. Rs is the possible supply output resistance.

It is clear to me that Ch1 and Ch3 measures the potential difference between the point X and point Y. This is called I guess Kelvin connection. Ch2 is the poti output so the ratio Ch2/(Ch1-Ch3) can be obtained which corresponds to angle. I want to calibrate this by using an encoder versus this ratio.

The vane has a dead band. Now for the this dead zone the datasheet suggests a pull down/up resistor RL between Ch3 and Ch2 but it doesn't mention or suggest any value. My question is what could be the reason RL is tied between Ch2 and Ch3 but not between Ch2 and the ground? And what value for RL can be reasonable?


texts: ESD array power and protect from same source

texts:
I am working on incorporating ESD protection for flash circuitry on ESP32 custom PCB board, and after initial research, ordered an ESD Array (CM1293A-04SO) from digikey with datasheet here
Attached in the circuit diagram below, showing

USB Rx, Tx, and Pin 0 connecting to 3 channels of the array, and
Handmarked "Flash_3.3V" netlabel connecting to Channel 3,4 via Blue Line and connecting to IC Power Source at pin 5 via Red Line.

My questions is regarding the power line (2 options drawn in red and blue), and I am wondering if the array can simulataneously power and protect the incoming power from USB line.

I got this idea from another protection array RClamp7522T with datasheet link here. with similar electrical circuit ( but higher pricing, with lower capacitance, higher protection range for ESD, a shared zener diode, and no power source), where it shows on page 7, that IC can protect power circuit as well. Please see screenshot


texts: Which solution is right for this question? I think both of the solutions make sense

texts:
There is a multiple choice question:
 $$V_{G1}=10cos(10t+60°)$$
and

$$V_{G2}=5cos(10t)$$

The resistance of the wire is \$R=10Ω\$, which one is the power that \$G_1\$ transmits?

A. 1.25W

B. 1.5W

C. 2.5W

D. 3.25W

The answer for this question is (C)2.5W

Solution provided from the book

$$V_{G1}=10cos(10t+60°)=10∠60°$$

So the \$V_{rms}\$ of \$V_{G1}\$ is \$V^{(1)}_{rms}=\frac{10∠60°}{\sqrt{2}}=5\sqrt{2}∠60°V\$

$$V_{G2}=5cos(10t)=5∠0°$$
So the \$V_{rms}\$ of \$V_{G2}\$ is \$V^{(1)}_{rms}=\frac{5∠0°}{\sqrt{2}}=2.5\sqrt{2}∠0°V\$

Now the \$S_{12}=V^{(1)}_{rms}I^*=V^{(1)}_{rms}(\frac{V^{(1)}_{rms}-V^{(2)}_{rms}}{R∠0°})^*=5∠0°-2.5∠60°\$,so \$P_{12}=5cos0°-2.5cos60°=3.75W\$,

But there is no option that \$P_{12}=3.75W\$, so this question has a little mistake

Now my classmate said no, there is no mistake in this question. The book provided the wrong solution so the author thinks this question has a little mistake.  My classmate's solution is as below:

My classmate's solution

\$I=\frac{10-5}{10}=0.5\$,So \$P=I^2R=(0.5^2) \times 10 =2.5W\$,so the answer for this question should be (C)2.5W

The author of this book didn't design this question,and I want to ask which solution is right because I think  both of their solutions make sense.  What I don't know is which one is  correct for this question? If the answer is 2.5W,and what should we modify the question to let the answer become \$P_{12}=3.75W?\$?

my friend teaches me how to calculate this question,so my solution is the same as my classmate,but not the same as the solution from the book.Both solutions can convince me that their solution are right,however,there is only one true answer,that is why i ask here


texts:
I have been studying about time response of RC circuits. I have analyzed the below circuit.

The input signal is a pulse signal of width 1.5 sec and period 3 sec. Alternating between 0 V and 5 V.
So here is transient response i have obtained.

The first figure is voltage across the capacitor C1 and the second is the voltage across C0. Now what i understood is, when the input switches from 0 v to 5 v, the capacitors acts as a short circuit and the resistor does not have any action at this point. Hence both capacitors get charged instantly to 2.5 v as in the figure.
However once the input voltage stabilize at 5 V, the resistance comes into effect.

So my doubt is, why is the C1 capacitor discharging from 2.5 v to 0 v while c0 capacitor charges from 2.5 v to 5 v?


texts: Chaining up two solar panels of different wattage?

texts: I have a 30 watt solar panel and I'm looking to add a 80 watt solar panel to help power an 85AH battery. I know I need to connect them in parallel (positive to positive, negative to negative) but I wonder if the difference between the wattage of the two panels would cause a problem?


texts:
When making an monostable circuit with a 555 timber, the time that pin 3 is on is calculated using this:

time on = 1.1 x R1 x C1

My question is why is 1.1 included.


texts: Using transformer with secondary shorted to primary

texts: I acquired a broken piece of vintage gear in which the transformer has one primary and many secondaries.  Examining the crispy remains of the transformer, I found that one of the secondaries shorted to the primary.  All the other secondaries appear to remain isolated from everything else.  The transformer isn't easily replaced, and with all the secondaries, I'm reluctant to try to rewind it.  I'm considering adding an additional transformer to replace the one damaged secondary--my question is would I be able to safely get away with using the damaged transformer leaving the one shorted secondary out of circuit?


texts:
Background: I need a transformer that can supply 6.3V (+/-1%, as per the heater's specs) and 25 A for a heater.

As a result, I decided to hack a MOT by breaking off the bottom laminations and removing the coils.

The plan is to use a variac (0-130 VAC, 1 kW max.) that will plug into a US standard single phase outlet (110-120 VAC, 50/60 Hz). The output of the variac will lead to the primary windings of the MOT.

For reference, the MOT core has a depth of 2 inches, a width of 3.5 inches, and a height of 3 inches.

For my application, I rewound the MOT such that the primary is made up of 17 turns of 18 AWG wire insulated for 300 VAC. The secondary is comprised of a single turn of 8 AWG wire. Both the primary and the secondary take up an equal length of the MOT core.

Since the bottom of the core was broken off, it is currently a bit loose but is attached to the rest of the core via gravity.

I used a zip tie to provide a 1 cm gap between the primary and secondary windings.

Here are a few pictures of the set up for reference:

Question: Will this set up allow for me to produce a sufficient voltage (assuming I set the variac to around 107 VAC) and 25-30 A?


texts: MAX7219 Entering Test Mode and Displaying Random Characters

texts:
I'm using MAX7219 with 6 common cathode 38mm (each segment has 2 red LEDs except DP) 7-segments controlled by Arduino Mega2560. I have connected MAX7219 and the board as stated in MAX7219's datasheet (DIN to MOSI[51th pin], CLK to SCK[52th pin], LOAD to 50th I/O pin).
I'm using LedControl library as numerous sources suggested.
Arduino board is supplied by a voltage regulator(10A max) that outputs 7.5V to the board's Vin and GND pins. The connection scheme is below.
Moreover, I have a SGR 56391 Wiper motor connected to Arduino compatible relay module as shown in below. This wiper motor draws about 400mA when I don't apply any external force, and draws 2.5A when I apply external force stopping its rotation.
The relay on the relay modules are srd-05vdc-sl-c and as far as I understand, I should not supply the relay module by Arduino Mega's 5V and GND pins (I had been doing so then I supplied the relay module from the 5V 3A regulator).
I have bunch of other inputs and devices but they are practically disabled because I'm using the test code given below.
THE PROBLEM is; when I upload the code and start the system, the display starts from 000000 to 999999 because of the for loop I have written in setup(), the motor works fine but the display most of the time becomes 888888 with full brightness as soon as motor stops or starts(not while moving). Sometimes, it takes more than 1 stopping or starting of motor for the display to become 888888 with full brightness. And sometimes, the display completely goes off. The other times (rarely) I saw random segments of random digits going on or off when the motor stops or starts. I have read through the MAX7219 datasheet again and found out that there is a mode called test mode which makes all the segments and digits on (i.e. 888888) with full brightness, but I have no code associated with test mode. I have also two videos showing the problem, the links are here and here.
So, I think the data from the board to MAX7219 IC (data is transmitted from 51th[MOSI] pin of the board to DIN pin of the IC) is corrupted for some reason but I don't know why and how and what to do about it. Maybe, I should just use BTS 7960B motor driver, I don't know.
Oh, and also I have seen no problem at all when I connect a much smaller DC motor instead of the one I'm using. But I don't know what are the technical specifications of that motor, I only have seen that it has a plastic gearwheel on the back and a small circuitry with bunch of electrical components.
I have put a lot of time and effort finding out the problem and trying to find out the solution, yet I have nothing so I need help. What do you guys think?

const byte raiseBarrier = 22;
const byte lowerBarrier = 23;
const byte Max7219_CS = 50;
const byte Max7219_DIN = 51;
const byte Max7219_CLK = 52;

LedControl MAX7219 = LedControl(Max7219_DIN, Max7219_CLK, Max7219_CS, 1);

void setup() {
  pinMode(lowerBarrier, OUTPUT);
  pinMode(raiseBarrier, OUTPUT);

  digitalWrite(lowerBarrier, HIGH);
  digitalWrite(raiseBarrier, HIGH);

  MAX7219.shutdown(0, false);
  MAX7219.setScanLimit(0, 6);
  MAX7219.setIntensity(0, 10);
  MAX7219.clearDisplay(0);

  for(int i=0; i<10; i++){
    for(int j=0; j<6; j++){
      MAX7219.setDigit(0, j, i, false);
    }
    delay(250);
  }
}

void loop() {
  digitalWrite(raiseBarrier, LOW);
  delay(200);
  digitalWrite(raiseBarrier, HIGH);
  delay(1000);

  digitalWrite(lowerBarrier, LOW);
  delay(200);
  digitalWrite(lowerBarrier, HIGH);
  delay(1000);
}


texts: Logisim - wire holds value 'e' when zoomed out, but not when zoomed in

texts:
I'm trying to make a multiplier in logisim. This is a full picture of my schematic:

As you can see, there is an 'e' coming out of my 'XXXXX-XXX00' adder. But, when I look at the schematic for 'XXXXX-XXX00' adder, this is what I see:

Why am I getting 'e' outside of the adder but not inside of it? How can I get it to output the 'right' value?

Also - this one wire isn't the only place I'm getting these 'e's. Depending on the values of the 2 numbers I'm multiplying, I'll get these 'e's in all sorts of fun places.

Thanks for the help!


texts: Bluetooth or Wi-Fi or other protocol signal detector

texts:
What's the best way to have a Bluetooth/Wi-FI/other kind of protocol signal detector?

What I'm looking it's something like this:

New Bluetooth signal detected Wakes up MCU (e.g. by interrupt pin)
MCU turns ON Bluetooth transceiver
MCU uses a specific message to notify the network that he's awake

I'm not sure about the air signals that could be confused with Bluetooth, but is this possible? The ideia it's to have an embedded system turned off until someone tries to reach it (by sending a message using bluetooth or other protocol).

The problem that I think I can have with BT or Wi-Fi it's that there's a lot of messages that aren't destined for the MCU so he's going to wake up a lot without any need, so nay protocol it's welcome.


texts:
I was reading this paper "A 10 b, 20 Msample/s, 35 mW Pipeline A/D Converter" by Cho and Gray from 1995.
https://ieeexplore.ieee.org/document/364429

In it, they describe a clock multiplier circuit with two capacitors (on the charge pump principle):

My understanding of this is as follows:

During the 0 to 3.3V initial phase of the clock

C1 and C2 are completely discharged and thus appear as shorts. The inverter causes a logic high to appear at the gate of the left transistor, turning it on. Source of M1 (output) sees 3.3V
C1 is charged to 3.3V through the left transistor.
Due to C1 being at 3.3V, the right transistor now turns on and causes 3.3V to appear at the source of M1 (output)

Now from this explanation, the output node (source of M1) is at 3.3V? How does he get a square wave going from 0V to 5V?


texts: Is it safe to connect battery in series with wall adapter?

texts:
Is it safe to connect a battery in series to wall via adapter?

I have an AC adapter which gives me 10 vDC from the wall (220 volts). I've measured the adapter and it outputs 10 vDC. I have a 3 volt battery. I would like to connect in series to get 13 vDC.

Is this possible?
Is this safe? If not, what can go wrong?


texts: How to make MC34063A work as a step-up converter with 2.1V input?

texts:
According to Page 7, Table 8 in the datasheet for MC34063, the startup voltage is 2.1V typical for A series and 1.5V typical for E series.

It is also said in Note 4 that the start-up voltage is the minimum power supply voltage at which the internal oscillator begins to work.

I am trying to implement a 2-cell Ni-MH battery to 5V,100mA step up converter, where the input voltage varies from 1.8V to 3V. I know that there are more suitable ICs like this one, but I want to learn how to make MC34063 work in low voltages if it is possible.

How can I make MC34063 work as a step-up converter with 2.1V input?


texts: How to define the SPI pins in an ESP32 module?

texts:
I am working on a project where I am integrating BME688 ,CAN, LoRa, SD card, ePaper display and WiFi module. I am using the board Heltec LoRa V2. And I have found this pin diagram. What I don't understand is why did they use different pins for SPI (with LoRa) instead of the predefined ones. Based on the ESP32 data sheet the 2 SPI pins that are available are assigned to these pins:

ESP32 HSPI & VSPI

So my question is whats the benefit of changing the SPI pins (and how is that even possible)? While reading the official documentation from espressif it mentions something about GPIO matrix and IOMUX . Where it states the following

  Most peripheral signals in ESP32 can connect directly to a specific
  GPIO, which is called its IOMUX pin. When a peripheral signal is
  routed to a pin other than its IOMUX pin, ESP32 uses the less direct
  GPIO matrix to make this connection.

  If the driver is configured with all SPI signals set to their specific
  IOMUX pins (or left unconnected), it will bypass the GPIO matrix. If
  any SPI signal is configured to a pin other than its IOMUx pin, the
  driver will automatically route all the signals via the GPIO Matrix.
  The GPIO matrix samples all signals at 80MHz and sends them between
  the GPIO and the peripheral.

  When the GPIO matrix is used, signals faster than 40MHz cannot
  propagate and the setup time of MISO is more easily violated, since
  the input delay of MISO signal is increased. The maximum clock
  frequency with GPIO Matrix is 40MHz or less, whereas using all IOMUX
  pins allows 80MHz.

To me this is something new, I never heard about it. If somebody can explain whats going on and knows the reason behind this pin-choice, I would appreciate it. Additionally, can somebody help me define the pins for the free SPI (since one is being used by the LoRa module). I want to drop the oled screen that comes with the module and use an ePaper display instead.


texts: Why does the current still increase in CC mode in a power supply?

texts:
I use a power supply where the specs shown here:
http://electronics123.net/amazon/datasheet/ps613u.pdf

I want to use it as a current source but the current is not stable in cc mode. Here what I experience:

For example, I set the current limit to 0.05 ampere. The load is pure resistive. For the currents lower than 0.05 ampere,  the power supply is in cv (constant voltage mode) that is to say when I increase the voltage the current increases proportionally(since the load is a resistance and it is a DC source). So far so good. Then I expect that when I continue increasing the voltage (which increases the current as a consequence) after 0.05 amp the current must remain the same even though I try to increase the voltage more by turning the coarse. But what I see is voltage and current still slightly increase. I didn't do a similar experiment just by a variable resistor but I'm confused why the set current after a point doesn't remain constant accurately.

Recently I found the following article which might be related:
http://powersupplyblog.tm.agilent.com/2013/01/the-difference-between-constant-current.html

But the supply specs I use says it is cc not cl. Could you expound on it if you have any idea?


texts: Using three-phase transformer in reverse

texts:
I'm in the US and installing a 45 kVA 480 V/208 V transformer in reverse, to power an electric car charger that requires 480 V. The secondary of the transformer is in wye configuration and I will be connecting that to my building 208 V three-phase.
Questions:

Should I connect the neutral of the transformer to building neutral?
The transformer will be adjacent to the main breaker panel. Can I connect a grounding wire from the transformer and my downstream 480 V connector to the ground in the breaker panel, or do I need to create a local grounding using buried copper rod or similar device?
I've seen references to connecting one leg of the output 480 V (from the delta output of the transformer) to ground. Is this necessary? It intuitively doesn't seem like a safe thing to do.


texts: Stress testing a PCB’s current handling capability?

texts:
I’ve produced a simple unregulated power supply PCB, consisting of:

AC input terminals
Fuse
4 rectifier diodes
Filter/smoothing capacitors
DC output terminals

Only when the PCBs arrived did I get the sinking feeling that the traces connecting the outputs of the rectifier diodes to the rest of the board (which consists of nice chunky pours) may be too thin for the current I need to drive. Doh!

What is the best/safest way to stress test one of these boards?

I’m happy to kill one of the PCBs in the process of stress testing.

If possible, I’d also like to spare the capacitors - during testing, would it be a good idea to leave the caps off? And of course I don’t want to jeopardize the transformer (a large toroid).

My idea is to build one of the PCBs (minus the big expensive caps) connect it to some beefy dummy resistors (pulling the desired current) and then to mains. Then wait and see if anything spontaneously combusts, or if the thin traces start melting.

Update:
I’m not looking for assistance in determining the current handling ability of the trace, or for strategies to transfer heat/increase the trace width. For the sake of science, let’s assume it’s too thin. I’m looking for a general stress-test method to find the real world upper limit of what a PCB like this can safely handle.


texts: Six-step (trapezoidal) BLDC motor driving strategy

texts:
It seems that a common driving strategy for such a motor is to use the 3 half-bridge topology depicted above, and use PWM to regulate speed and/or torque.
At any given moment, two phases ("wires") of the motor are driven with PWM (or complementary PWM), and the third wire is left floating. For example, in a precise moment, mosfets 1 and 2 do complementary PWM, mosfet 4 is closed to GND (N), and all the other (3-4-5) are open (non conducting). The third wire can be, and sometimes is, used to read BEMF (velocity feedback).
What I would to know is: what happens if the third wire, normally left floating, gets tied to GND, or Udd, or modulated with a PWM?
I made some tries, but the results are unclear. My supposition was that the efficiency of the driving would decrease, because connecting the third wire to GND would consume energy shorting the BEMF to ground, and connecting the third wire to Udd would instead drive one more coil, perhaps contrasting the other two (driven) coils, or perhaps helping them...
What I have observed, and found interesting, is this: in "normal driving" (leaving the third wire open), when the speed of the motor is greater than the command (PWM) given to  it, i.e. when imposing deceleration, the power supply voltage Udd tends to rise (regenerative breaking). But in the same situation, if the third phase is connected to Udd, the rise is much more limited. This can be useful, and can be used to brake the motor without having a rise in power supply, but more gently than simply shorting its terminals.
Somebody knows what is happening? Is it possible to use the third wire, normally left floating, to achieve interesting results?


texts:
I found question OpenServo and I2C Syncronization here and I am curious what is OpenServo good for?

According to OS Tutorial, you have to remove original board from your servo and install OS board. But what is the benefit? Why should I use OS instead of original electronics in servo?


texts: What would happen if I choose a connector with current rating smaller than the actual current?

texts:
I need a butt splice connector that can handle up to 150A, which is really hard to find. What would happen if I connect it to a 12-10AWG butt splice connector?

Other type of connectors are not desirable because this is an automotive connection.


texts: Can i use a 220v power strip with usb ports on 110v?

texts:
My local power is 220v and i have a power strip that i bought locally.

I'm travelling to a country that uses 110v and i wish to bring the power strip there.

Is it safe to use my power strip there? I understand that usually those dumb power strips (those power strip that have no additional electronics inside, i.e no power indicator lights/no surge protector etc..) will have no issues.

What about my power strip with usb charging ports? is it safe to use on 110v?

The only infomation i had on the power strip in labeled on the back:

RATED PARAMETER: 2500W-10A(Max) 250V
USB OUTPUT: DC5V 3.4A(Auto) 17W
OUTPUT PORT: 3xAC | 6xUSB


texts: How to create a break away to cut the board

texts:
I am not a expert with Eagle 9.6 but I created a nice PCB. A friend of my is going to assembly the part with a pick and place machine.
He asked me to enlarge my PCB to be able to fix the board and then cut this extra PCB. Exactly as we can see in that picture

But I absolutely have no idea how to have this empty space with some small "contact" which will be break, as we can see above.
Any advise how to proceed (how to) will be greatly appreciated.


texts: Why did my fuse blow after 3+ years of no problems?

texts:
For several years, I've had a solenoid wired to the 24VDC output of a PLC (Rockewell Automation 1769-OB16).
To protect the PLC output card, a fast-acting 500mA fuse was installed between the PLC and the solenoid. The fuse has been working without any trouble for a long time.
Recently, this fuse blew. There was no change on the line, no abnormal or excessive usage of the solenoid, and nothing out of the ordinary. It just blew. I replaced the fuse with an identical one, and the solenoid works just as well as it did before the fuse blew.
I measured the current to try and find out why it blew, and found that the solenoid is actually pulling 530mA. I let the solenoid continue to pull that much for over 20 minutes, and the fuse held.
Why does the fuse not blow even though the load is pulling more than the fuse is rated for? And why would it blow only now, after more than 3 years, and not sooner?


texts:
I've been tasked with designing a circuit (actually a buck/boost converter outputting 20 Volts at up to 10 Amps) which takes "automotive voltage".  This product will be subject to some sort of official automotive certification.  Nobody at my company is currently able to tell me exactly what that means.  We're going for cost, and it needs to be integrated into our PCB, so yes I'm looking at using certain TI chips, discretes, etc.  Like a normal dc/dc supply, not a module to purchase.

Can someone give me the brief summary on what "automotive voltage" looks like?  I've been told it can go as low as 6 volts, but nothing so far in terms of spikey transients, picking up noise from other junk under the hood, etc.

In other words, what filthy input must my circuit deal with?

I'm sure I'll get a real spec eventually, but for now I'm putting together a block diagram so I'd like to get an idea of where to put in the various filters, emi junk, voltage protection, surge suppressors, etc.

Is there a 1-page AEC summary or something?


texts: How does ARM CMSIS functions access Core registers in unprivileged mode?

texts: As per my understanding the ARM M4 core registers such as NVIC registers can be accessed only when the software is in privileged mode, that means it should be running in handler mode if I am correct. I am wondering how does the CMSIS functions are able to access the core registers while running in thread mode. As per my understanding during the normal program execution time the core will be in thread mode and it should not be possible to write the core registers as it is only available in privileged mode. Please correct me if my understandings are wrong and help me to clarify this doubt.


texts:
I've got a 32 volt DC regulated bus.  I also need about 30mA at 12 volts (DC).  Is there an easy way to tap some power from the 32v bus?

My first thought was just put in a 12v linear regulator.  But those in my parts box have absolute ratings close to (or below) 32v, and I'm not one to push the envelope.

Some divider make up using hairy arsed power resistors might work, but that's not too efficient and generates HEAT.

If the solution gets complicated (e.g. build a buck down converter), I could find a 12v wall wart and tie across the mains supply to my 32v power supply.

I know about voltage multiplier circuits.  Is there a neat voltage divider trick somebody can teach a nubie?


texts: GPS Antenna | When is an Active Antenna really Necessary?

texts:
Many vendors provide positioning modules that support active antennas as well as ones that don't. I am using 4 positioning modules out of which 3 of them support active antennas and the other , CC4000 by TI , supports only passive antennas. To be honest I am testing modules for performance, in terms of TTFF for SGEE, CGEE and A-GPS.

Take a look if its necessary.

http://www.u-blox.com/en/gps-modules/pvt-modules/max-m8-series-concurrent-gnss-modules.html

https://www.linxtechnologies.com/en/products/gps-modules/fm-gps-receiver-module

http://www.ti.com/tool/cc4000gpsem

However all three claim to have almost same acquisition gains,about 143 dBi.
But let me make my question general so that it will help more people.

For all 4 positioning modules that claim to have almost same acquisition gains, how would the antenna type (active/passive) effect its performance? I mean with a passive antenna if the module can have a acquisition gain of 143dBi why bother fixing it an active antenna?

Is an active antenna necessary for applications that have really short antenna cables(about 2-3cm)?

If I have gone wrong somewhere, kindly direct me.


texts: Controling a Washing Machine AC Motor Using a Relay

texts:
I would like to control the motor of my washing machine using an Arduino.
It's an old washing machine with a mechanical controller and an AC motor connected to a 12.5 uF run/start capacitor. According to the motor specs, it operates at 230V and draws 3A (probably not the peak value, but during operation).

My thoughts:

I would like to control it using a relay with the lowest budget possible. Since it's a large inductive load I want to avoid mechanical relays, especially the cheap ones available on Aliexpress due to arcing when the connection breaks. I'm afraid such a relay would quickly start malfunctioning.

I could use something like a contactor but they are not cheap.

The SSR-40D relays look good and can also be conveniently connected directly to an arduino GPIO, but they are zero-cross relays which are not suitable for controlling large inductive loads due to large current surges. Random triggered or peak-triggered SSR relays are pretty rare and expensive, so I'd like to avoid them.
My thought was to use the zero-cross SSR, with the highest available current rating, like the SSD-100D (100 A) to control the motor.

I would just like to make sure I don't burn our house down with my DIY shenanigans. Namely, what is the peak current flowing through the high voltage side of the relay I should expect from switching on the aforementioned motor at the zero-crossing point for the given specs?


texts: ATtiny861A: ADC reference voltage should be 1 Volt under AVcc?

texts:
I just faced with that ATtiny861A datasheet forcing me to use analog reference voltage to be at least 1 Volt under analog supply voltage:

Let me doubt this datasheet statement for two reasons:

ADC should (and will as I tested) work with reverence voltage equal to Vcc (this is one of the reference options available through ADC control registers).
The same table for ATmega48A shows more reasonable ADC reference voltage range: from 1.0V to AVcc:

Actually I used to believe to the info stated into datasheet. But this time I need to call this statement to question as I NEED reference voltage to be almost 5V (or at least 4.096V which in turn also out of range).

Of course one of the possibility would be to put the schematic to the real world test. But: a) if it will work under test condition it could not work under different circumstances like high temperature or slightly lower/higher Vcc b) this will take significant time for my case.

Can anyone put some words to confirm my doubts or maybe I should contact Atmel support to clarify this point?


texts: Does anybody have any idea what this piece of equipment is?

texts:
A friend of mine picked this up at a garage sale where an elderly electrical engineer was selling a bunch of old test equipment.

It's missing a faceplate where it should name what it is, and he's googled the company name and model number, all to no avail.

Several of the engineers in my company have been by to take a look at it, and so far the consensus seems to be that it's some sort of tunable filter (it has what appears to be a large variable capacitor and large variable resistor).

I was wondering if anybody here had seen one of these before and had any idea of what it was used for, and possibly some links to relevant documentation.

UPDATE:
Added image of interior of device


texts:
I have read in Data Communications and Networking, 5th Edition, by Forouzan that the formula for calculating the bandwidth for QAM modulation is \$B=(1+d)S\$ where \$d\$ is factor that depends on filtering process and is between 0 and 1, and \$S\$ is symbol rate.

My question is why is that formula used instead of e.g. Nyquist or Shannon formula for capacity to calculate bandwidth?


texts: What are the pads without holes on perfboard for

texts:
So I bought a 10 pack of 4 x 6 cm perfboard. On two ends there is a row of pads without holes:

What are they used for?


texts: How to hook up a load cell to an Instrumentation amplifier correctly

texts:
I am trying to get load cells connected to an instrumentation amplifier. The load-cells I have are extremely similar to the ones here https://www.sparkfun.com/products/10245. They have 3 wires coming out of them. A red, white as well as black one. Now according to the schematic here which is for a single load cell , when used with a ad620, it should be hooked up like this Google Image. So my first couple of question are as follows:
-What do the red, black and white wires stand for and how do we identify the purpose of each wire
-I need to use 4 load cells instead of one. With 3 wires coming out of each load cell , I end up with a lot of wires. In what fashion should they be connected to achieve the Wheat Stone bridge?
-The wires are connected the metal with some white glue. Does this glue play a major role? Is it some special kind of glue or can I use any kind which is available?

I looked at this schematic which is an explanation about how load cells work(http://www.allaboutcircuits.com/vol_1/chpt_9/7.html) but I am still unable to figure out how to exactly make the connection. Could someone please help me out?


texts:
I having an assignment that need to design AM Transmitter using Multisim with following specification:
•   Audio input (200-14000Hz)
•   Double Sideband Full Carrier
•   RF carrier frequency of 50 MHz
•   Carrier Power  1 mW

I have totally no idea how to design a AM modulator from scratch, so i found this
video, and built this circuit and try to modify the carrier signal frequency  from 11kHz to 50Mhz it fail and didn't show any signal at the oscillator.

I know some basic concept about how AM can be achieve using transistor,but have no idea how to design it.
Is there any detail guideline i can refer or follow to design a circuit from scratch?
How do all the value of resistor is being calculated, and why is capacitor and inductor being use at the collector of the transistor.

Update: I had revise about the DC biasing of the transistor and made a update about my prototype. Here I will explain what my understanding and how I design.

First, I hope my Q-point is in the middle, so i check the datasheet of BC107B and found that Vce(sat)=200mV while Ic=100mA (there are another value Vce=70mV when Ic=10mA). Then i go though some calculation.

There are too many variable, therefore i assign some of it to simplify the calculation(Re and R1). For the tank circuit, I use frequency 50Mhz as my question RF carrier require and remain capacitor unchanged to find out the inductor value. The final circuit result is as follow.

The circuit is not working.
Please tell me if there any mistake or what i did wrong.