texts: Generate a fixed number of pulses on the STM32F4 PWM

texts:
I am trying to control a servo motor (link). It is a brushless DC motor with an interface similar to a stepper motor.

The motor rotates for a defined distance based on the number of pulses it receives from the PWM. The speed is determined by the pulse frequency of the PWM, like a stepper motor.

To control this motor I am using a microcontroller STM32F407ZET6. I can easily change the frequency and Duty Cycle of PWM, but my question is the following:

How do I generate a fixed number of pulses in the PWM? For example, I want the PWM to send 1000 pulses at a certain time with a frequency of 20kHz and a Duty Cycle of 50%. 20kHz and 50% Duty Cycle are easy to define, but I can't determine how to generate the 1000 fixed pulses.

One of the solutions I tried was to connect the PWM back to a timer in counter mode and stop the PWM when the required number of pulses has been generated. But the number of pulses is not always fixed, sometimes ranging from 998 to 1005 (for example).

Is it possible to do this without the need for feedback?


texts: Optimal design choices for mosfet driver for DC-DC step-down converter

texts:
I'm dealing with an application in which a DC-DC converter is used to transform an input voltage of 15V DC into lower voltages.
The current configuration makes use of an LM27222 with two mosfets in push-pull configuration. The output voltage is linearized into an LC filter.

Here's a picture of the general schematic used.

The LM27222 is driven by a PWM signal with a carrier frequency of 65 KHz. The mosfets used are of type FDMS86101DC. The logic level voltage is 5V.
The output current to design the system is 10A. The load is resistive.
The system works fine, but some concerns have been raised to avoid collisions between the two mosfets (both transistors ON), especially during start-up/turn-off sequence. This happened a couple of times during testing of new firmwares, but, most probably, the problem was related to the testing engineer which not so carefully "touched" the output leads generating a destructive shortcut.

According to one of the new engineers we have been working with, we should:

Substitute the LM27222 with another driver, the L6388E, which should be much more stable than the LM27222 and avoid any change of collision, even in transition sequences.
Add a diode in series with the low-side mosfet. This diode should add additional protection during transient
Add a complex filter to the Vin line. The filter should have a common-mode and a differential mode inductor, together with a large electrolytic capacitor and several small ceramic capacitors. According to the engineer this filter should limit the demand of pulsed power from the power supply, and result in a more "compliance-friendly" design to meet the EMC (electromagnetic compatibility) regulations. The Vin comes from a AC-DC desktop power adapter and he is concerned that the connection cable from the power supply to the electronic card could radiate frequencies because of the required pulsed power. Besides, since several of these power supplies got broken during tests, the engineer is also suspecting that we are throwing some important noise back into the power supply, leading to failures.

Here's a picture of the L6388E internal schematic.

I would like to ask two questions:

Is it necessary to carry out all the steps suggested by the engineer? The change of LM27222 is particularly painful and I would avoid that if it does not give clear advantages.
If we decide to keep the current configuration with the LM27222, how can we drive the LEN signal to avoid problems at start-up and turn-off of the system?


texts:
Please refer to above circuit.

I have a SIM900A module connected with the UART of a PIC. D1 toggles every second, using timer interrupt, to indicate that while loop is running satisfactorily. D2 toggles only when switch changes its state. "PORTB Interrupt on Change" is used to detect change in state of switch.

The circuit works correctly but as soon as a minute elapses and SMS is sent D2 toggles a number of times and multiple SMSs are sent instead of one indicating change in state of switch. This behavior is observed only when the switch is in closed state before sending SMS.

The problem cannot be of de-bouncing since if switch is closed initially before powering up the circuit and it remains in the same state before first minute even then the same problem is encountered.

The circuit works fine with a veroboard but started creating problems when I went to a PCB design.

What could be the possible reason and solution for this problem?

The above circuit is just part of the whole circuit.

U2 and U7 are voltage regulator but only one is used at a time. U2 is for 7805 and U7 is for LT1084. Only one of them is soldered.

RV1 and RV2 are potentiometers connected with output of two comparators of LM324(U6). RV3 is connected with LT1084 to adjust output voltage in case of using LT1084.

RSMD on the right side of board is 12mohm resistor.

U5 is MAX232.RL1 is a 5V relay and Q1 is a transistor. D2 is voltage reference for ADC while SW1 is a DIP switch to enable or disable the use of voltage reference.


texts:
I have a PIC18F26J50 and I want timer0 to output a 1Hz signal on RA6. I'm now getting ~800Hz with my current setup. Clock is 48MHz / 4 = 12MHz on RA6 (if INTOSCPLLO is enabled). Compiler is C18.

Here is my code, which is wrong obviously and I need to find out what the problem is and understand how this stuff works.

BYTE Timer0Init( WORD wTimeInterval )
{
UINT16 timerRegValue;
INT8 rc = ERROR_INVALID_COMMAND;

const UINT16 timerPeriodInSeconds = 1;
const UINT32 clockFreq = GetSystemClock();
const UINT16 prescalerValue = (256);
const UINT16 resolution = 65536;

interruptsDisableAll();

//! configure the timer 0 for 16 bit mode and preescaler of 256
T0CONbits.TMR0ON    = TMR0ON_OFF;           //! turn off
T0CONbits.T08BIT    = T08BIT_LEN_16;        //! select the 16 bit mode
T0CONbits.T0CS      = T0CS_INT;             //! internal clock
T0CONbits.T0SE      = 0;
T0CONbits.PSA       = PSA_PREESC_ASSIGN;    //! use the prescaler
T0CONbits.T0PS      = T0PS_PREESC_1_256;    //! 1/? prescaler

timerRegValue = ( clockFreq * timerPeriodInSeconds );
timerRegValue = (UINT16)( timerRegValue/(4*prescalerValue) );
timerRegValue = resolution - timerRegValue;

reloadValue_ = timerRegValue;

writeTMR0Register( timerRegValue );

INTCONbits.TMR0IF   = 0;                 //! clear the interrupt flag
INTCONbits.TMR0IE   = 1;

T0CONbits.TMR0ON = TMR0ON_ON;            //! turn on

interruptsEnableAll();

rc = ERROR_SUCCESS;

return rc;
}

I got this calculations from a formula I found on the internet. I read and re-read the datasheet and the calculations seems ok. So what is the problem anyway?

Any help is really appreciated!

Thank you.


texts: Debugging of RTC (Real Time Clock) using MPLAB ICD4 debugger

texts:
I have been searching for a process for debugging an RTC section using a debugger called MPLAB ICD4, but I didn't get an exact result from Google.
Can you please suggest me the process? And is there any process to debug the RTC with any debugger kit?


texts:
I need to analyze a schematic and I am having trouble with this part:

The thing is I don't get at all the utility of the N-channel MOSFET at the output of the op-amp. Could anyone explain the purpose of this component?

Because I think, the conversion would be done even without this transistor.


texts: I have a SEPIC supply with coupled inductors. The inductors have phase dots. What do these "phase dots" mean? Is it important to have the phase dot in the same place?


texts: Problem with 74hc595 voltage in Autodesk Circuits

texts:
I am very, very new to electronics, so please be patient with me, as I may say something silly. I also hope the question is not too wide, and would like to thank you in advance for spending your time reading it.

Anyway, here goes:

I am attempting to use a 74HC595 shift register to control a seven-segment display with Arduino using only three pins. I have used Autodesk Circuits to test the circuit before I build it. You can see the breadboard and the schematic in here, as well as the program I'm running:

Schematic

The display is common cathode.

Before I added the 100-ohm resistor to the display's common ground, the simulation would tell me that the shift register would break, as:

a) The current going through the power pins was too high (70ish mA when a max of 50 mA could be used).

b) The voltage to the DS, STCP, and SHCP pins was too high as well (5V, the max being 2.2V)

Oddly enough (to me at least! it may be obvious to someone more experienced than I) this would happen only for digits 1, 4, and 7. All others would display fine without anything blowing up.

Now, my questions are:

a) Why is it not enough to add resistors to each of the anodes?

b) Can the circuit work the same with just a large enough resistor on the common cathode?

c) Why does Autodesk Circuits say that the clock / latch pins in the shift register can only take 2.2V? The register's data sheet seems to indicate it can take up to 6V digital signal. And why would it be alright for digits 1, 4, and 7?

And finally,

Checking some diagrams online, I can see variations of essentially the same thing, such as this one (with no resistor to the common cathode), or even one in a robotics site with just two 220 ohm resistors to the two common pins only.

Are all three ways of doing it (segments only, common pins only, both) correct? How exactly do they differ?

Thanks again! And sorry for the long rant. I just began learning.


texts: How much power can a 74HC4066 switch (for LEDs)

texts:
I am using a 74HC4066 IC to switch on and off strings of LED.  If I read the documentation correctly, each 'switch' in the IC can handle 25 ma.  Is this correct?  Also, does this mean that the entire chip (with 4 switched) can handle a combined amperage of 100ma (if all 4 switches were on at once?)

If I need more than 25 ma, can I combine 2 switching units in parallel?


texts: What are the Disadvantages of unnecessary increase in PID gains?

texts: I read somewhere that if we increase the PID gains unnecessarily, it will cause more energy consumption of the controller and it will lead to noise and distortion in the practical. May someone please give me more explanation on this?? that how it lead to noise or distortion in practical??


texts: What value PTC Thermistor should I choose for over-current protection for a child's electronics kit?

texts:
What is an appropriate value for a PTC thermistor used in a 3-cell AA battery pack to provide over-current protection if the terminalsare shorted? Current draw during normal operation will be only a few hundred milliamps)

I'm looking to make something similar to this: SnapCircuits 3 battery holder so my son can experiment with connecting switches, leds, motors, etc. together without a risk of melting something.


texts: Why does more transistors = more processing power?

texts:
According to Wikipedia, processing power is strongly linked with Moore's law:

http://en.wikipedia.org/wiki/Moore's_law

  The number of transistors that can be
  placed inexpensively on an integrated
  circuit has doubled approximately
  every two years. The trend has
  continued for more than half a century
  and is not expected to stop until 2015
  or later. The capabilities of many
  digital electronic devices are
  strongly linked to Moore's law:
  processing speed, memory capacity,
  sensors and even the number and size
  of pixels in digital cameras. All
  of these are improving at (roughly)
  exponential rates as well.

As someone who has some background in computer architecture, I don't understand why throwing in more transistors in a CPU would boost a its power since ultimately, instructions are roughly read/executed sequentially. Could anyone explain which part I'm missing?


texts: How is AC travel from a central to home?

texts:
Basically, in a alternating current the electrons moves back and forth really fast. From one atome to another?

I'm wondering how the current can travel from a central to my home. I mean, for a cycle is the current can travel the whole distance then go back to the central?

There is probably a maximum distance that the AC can travel?


texts:
I'm currently learning about Field Effect Transistors in my college class. And I'm having trouble understanding how to properly read characteristics curve graphs. I'm sure it's relatively simple, but when we get asked questions like determine ID when VGS is -5 or -1.2 how would I go about determining the results?

I've searched my book and the web and I can't seem to find the formula. The examples in the book jump right to the answer without showing the method of determining the result.


texts: Solar Panel and Battery Management - 3.3V output

texts:
I'm developing a power source based on a solar panel and a battery.

Basically, during night or rainy days the power comes from the battery. At sun light the power comes from the solar panel (extra power recharge the battery).

During my search for a buck-boost converter (example TPS63024x) and a linear charger for the battery, I found bq2512x.

Looks like bq2512x has all I need (linear charger, regulated output, load switch and battery voltage monitor), but I'm a quite confusing about the circuit.

Solar panel is this one -- 5.5V - 90mA
Battery is this -- 3.7V - 1200mAh
My device is a Sensor with a Wifi transmitter. Consumes 3.3V - 15mA (200mA peak during 2 seconds, every 5 minutes)

My question is: If my understanding is correct, can someone explain to me the minimum requirements for bq2512x work as I need? Or maybe post a sample circuit with a buck-boost converter and a battery charger in a answer, so we can discuss about it.


texts:
I've trying to make a footprint for a QFN32 package using Altium compliant footprint wizard. The result looks fine :

The problem that I have  is that I can extend the length of the pads (thinking about the soldering) , even when I set a bigger value for the L in the settings , changing the length in the output  component, doesn't help! :

SO my question is there a way to do that in Altium or the only way is to it manually ?

thanks in advance !

UPDATE*
after Daniel's answer, I've managed to change the pad lenght from 0.8mm to 2mm !
the result :


texts: I²C interface between 3V/5V sensor and a 2.4V MCU

texts:
simulate this circuit – Schematic created using CircuitLab

I have an ultra low power application where the minimum VDD of my temperature sensor (ADT7420) is 2.7V, while I need to run my MCU at 2.4V. The circuit is powered from either a 3V coin cell or USB 5V [debug mode]. I have space for a single 2.4V regulator on board.

The temperature sensor interface is I2C and it also has an interrupt output that is connected to the MCU. Sensor supply min and max is 2.7V and 5.5V.

My question is:

SDA/SCL and the interrupt pins on the sensor are configured as open drain. Therefore, would I be OK if I used pull up resistors to 2.4V and connected the signals directly to the MCU? i.e., because the signals to be interfaced are open drain, I do not really need level shifters OR even current limiting resistors b/w the sensor and the MCU.


texts:
I'm trying to toggle built in LED with external interrupt instead of while loop. Probably I'm doing something wrong with EXTI functions. Can you help me to fix it?

Here is my code:

#include "stm32f4xx.h"
#include "stm32f4xx_hal.h"

void SystemClock_Config(void);

void HAL_GPIO_EXTI_Callback (uint16_t GPIO_Pin)
{
    if (GPIO_Pin == GPIO_PIN_0)
    {
HAL_NVIC_DisableIRQ(EXTI0_IRQn);
    HAL_GPIO_TogglePin(GPIOD, GPIO_PIN_12);
HAL_Delay(100);
    HAL_NVIC_EnableIRQ(EXTI0_IRQn);
  }
}

void EXTI0_IRQHandler(void)
{
  HAL_NVIC_ClearPendingIRQ(EXTI0_IRQn);
  HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_0);
  {
  /* EXTI line interrupt detected */
  if(__HAL_GPIO_EXTI_GET_IT(GPIO_PIN_0) != RESET)
  {
    __HAL_GPIO_EXTI_CLEAR_IT(GPIO_PIN_0);
    HAL_GPIO_EXTI_Callback(GPIO_PIN_0);
  }
}
}

void SysTick_Handler(void)
{
    HAL_IncTick();
}

int main(void)
{
  /* Reset of all peripherals, Initializes the Flash interface and the
Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();
  /* Initialize all configured peripherals */
        __HAL_RCC_GPIOD_CLK_ENABLE();
    __HAL_RCC_GPIOA_CLK_ENABLE();

GPIO_InitTypeDef GPIO_InitLED;
GPIO_InitLED.Pin = GPIO_PIN_12;
GPIO_InitLED.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitLED.Pull = GPIO_NOPULL;
GPIO_InitLED.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOD, &GPIO_InitLED);

GPIO_InitTypeDef GPIO_InitButton;
GPIO_InitButton.Pin = GPIO_PIN_0;
GPIO_InitButton.Mode = GPIO_MODE_IT_RISING;
GPIO_InitButton.Pull = GPIO_PULLUP;
GPIO_InitButton.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOA, &GPIO_InitButton);

HAL_NVIC_SetPriority(EXTI0_IRQn, 3, 0);
    HAL_NVIC_EnableIRQ(EXTI0_IRQn);

HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);

}

static void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_OscInitTypeDef RCC_OscInitStruct;
/* Enable HSE Oscillator and activate PLL with HSE as source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 25;
RCC_OscInitStruct.PLL.PLLN = 336;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
/* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2
clocks
dividers */
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK |
RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5); }


texts: Proteus - How to manually load the schematic's components in the PCB view?

texts:
I have been doing nasty things with my proteus, and right now, I have a schematics that's well defined, but the components are not present in the PCB layout (therefore, I can't place them, as I can't pick them in the "empty" list).

Does someone knows how to force the update the components of the PCB based on the schematics?

The other solution would be to redo everything from scratches, which don't motivates me a lot...

There should be a list of components in the field marked with the interrogation marks "?".

(For those curious, the diagram is a way to digitally control a PWM for motors with a raspberry PI ^^, )

I'll continue to search, but I already feel like having gone through every menu button...

Thank's by advance !


texts:
This is a homework question that I have stuck for a while and couldn't able to come up with the correct answer.

So here is the question,

My thoughts towards this question

When I move the  rod PQ with a constant velocity ,the area of
triangle RPQ inside the magnetic field increases .
Once the area inside the magnetic field increases E.M.F induces also
increases.
Since induce E.M.F get increased the induced current should also be
increased.

So according to my arguments  I choose the answer as the third one. But the answer in marking scheme is the first one.

What I have done wrong. Please explain this question with details.


texts:
I am using a signal generator to generate a long square pulse that is fed into a long transmission line consisting of two parallel wires. The transmission line is approximately 1km long. The near end is terminated with a 25\$\Omega\$ resistor, and the far end is unterminated. With an ADC I am sampling the incoming signal.
In the below diagram you can see the square pulse (1) I am feeding into the transmission line.
(2) shows the signal I measured with the ADC. You can see that the first plateau is at U/2. The 2nd plateau is really small and almost not there.
I would have expected a incoming signal like shown in (3). I don't understand why the plateaus shown in (2) are not at the same voltage level.

Does anyone have an idea?
In the diagram I neglected the attenuation of the cable.


texts:
I am doing a simulation on LTSpice of a three level ANPC. The ground is connected to the neutral point (i.e in the middle point of the DC input) and the gate drivers are isolated by using a DC DC converter (so the voltage is floating). The thing is that I need to gate the transistors and I have the modulation done with signals that go from 0 to 5V.

I did this signals by using BV sources connected to the common ground: one carrier that goes from 0 to 0.5, another that goes from 0.5 V to 1V and the modulating sine in the middle.

How can I impose the PWM to the input of the gate driver? How should I shift the signals to the source level of the transistors?

Thank you in advance!


texts: Not getting desired output from inverting Op Amp as adder

texts:
Here you can see for an inverting Adder Circuit of Op amp the output is 14.61V but in the second image by solving it using formula I am getting output voltage is 16V why it is happening.

Here you can see Output is 16V .Here Vi1=-7 ;vi2=5 ;vi3=-7 and feedback resistance is 10K using these values and putting it to the formula of adder circuit I got 16V but in the schematics it is showing around 14.6V i couldn't figure out what is happening here.


texts:
So here's the run down, I purchased a rework/soldering iron station off eBay years ago. Believe it's a cheap Chinese knock off labeled CE 852D+

Recently the heater element for soldering iron went bad. Bought what I thought would be an exact replacement but it was slightly longer. Original on top

Tried installing and this was the result

I tested it and it seems to work fine in terms of heating up and detecting the temp setting. I'm wondering if I alter the little indents on the bottom that seat into the soldering iron PCB so it recesses just enough to fit flush, if it would be safe to use?

I also noticed writing on the iron handle that faded and all I can make out is "907" and the last letter I think was an "A"

Also the soldering iron PCB has a "YH936B-5" marking on it

Should I be looking for a heater element for a 907A instead of the station 852D+?


texts:
I'm planning an exp-ramp generator with the following characteristics:

Implemented on the PIC16F1773, an 8-bit device with somewhat complex capture/compare/PWM hardware.
PWM module clock of 500 kHz * 32 = 16 MHz
System clock (Fosc) of 16 MHz / 2 * 4 = 32 MHz
Fixed PWM frequency of 233 Hz
Duty cycle starting at 0%, ending at 100% after 4.82 s
Approximating the exponential curve \$ y = 1 - 0.1^{t/2} \$, which has an equivalent time constant of \$ \tau \approx 0.8686 \$.

The strategy to modify the duty cycle is:

always increment the high byte of the duty cycle register PWMxDCH by 1, ignoring the low byte for simplicity
only perform a DC increment after a post-scaled counter rolls over whose input clock is the period match event of the PWM
the post-scale factor starts at 1, ends at 128, and is multiplied by 2 every ~140 PWM cycles

In a basic numerical simulation of this strategy, the approximation is quite good:

The bumps are where the post-scale factor is changed.
I have a little bit of decision paralysis around how best to implement the post-scaler. I could use a 16-bit PWM module:

interrupt on PRIF, maintain a software post-scale count variable, and on overflow of this count, increment the duty cycle. Or I could use the simpler 10-bit PWM module:

which does not support period interrupt; short the PWM output pin to the clock input pin TMRx_clk of a timer like this:

Where PRx is the post-scale value, the actual timer pre- and post-scale are not needed, and on TMR2IF, increment PWMxDCH.
I kind of prefer the secondary-timer approach because it means (1) easier external scope debugging, and (2) fewer runtime instructions required. Is there a way to make better use of the 1773's hardware to accomplish this thing?


texts: Light effiency or efficacy and watt to heat output

texts:
I am on a light forum and there are debates about watt heat output of lights.

I'm using my common sense for the debate but can't find the data online to support my ideas.

People are thinking that a 400 watt heater produces the same heat as a 30% efficient 400watt light.
And further same as 400 watt of 60% efficient lights.

Now my logic says that heat being the main by product of a heater will of course cause the 400 watt heater to produce the most heat

A light that's 60% efficient at light production like new LEDs cannot produce the same amount of heat because its byproduct is photons or light. But still produces heat as its not 100% efficient.

Can any of you geniuses explain to me smartly what heat production wold be produced from lights?

HID lighting is about 30% efficient

New led is getting to 60% and more

But people think that 400 watts translated directly to heat

update: I think I figured it out. The room is much cooler because: the 60% energy as light from LEDs is projected to concrete floor which goes for many meters outside the room and connected to the earth thus dissipating it effectively outside of my room. The remaining 40% heats the rooms air Where as a less efficient light uses 70% of its energy to heat the air and only 30% is sent to the concrete and this dissipated to earth and other rooms. Am I correct here? –


texts: I am trying to teach myself electronics, namely audio filtering, and I came across this circuit. Now with my limited knowledge the 'volume potentiometer' (that's what it is explained as) seems to be in parallel with the resistor forming the high-pass RC filter so would this mean that this circuit is wrong. I think that the output of each filter needs to be buffered and that those outputs should have the poteniometers on them? All the pots in the circuit are 10K Log's


texts: Find the maximum of three sinusoidal voltages at any point?

texts:
Given three sinusoidal input voltages, I need to design a circuit to output the highest voltage, without using opamps. I honestly have no idea where to start, so would just appreciate any hints or reading material. All I want is a pointer to the right direction.

The maximum voltage output needs to decay with a time constant of one second.

How can I go about building this circuit?


texts:
I have seen this circuit at my workplace and I'm trying to understand the working and the purpose of each component in the below schematic.
I also happen to note that this was a constant current circuit where R5 - 3ohms happens to be the load resistance, whose value can be from 3-50ohms.

simulate this circuit – Schematic created using CircuitLab
To understand about the constant current Op-amp circuit working, I read how it works. But in those circuits, the Op-amp would have a negative feedback configuration and the output of the Op-amp would drive the base of an NPN transistor which would drive a constant current connected to the emitter of the NPN transistor. The Op-amp will try to maintain the voltage between the inverting and non-inverting terminal and try to regulate the load current through the load resistor.
But in my above circuit shown above, can someone help me how, the constant current through the load resistance is achieved? I am not sure why there is a shunt regulator placed in the negative feedback path?
If possible, please also help me understand why there is a capacitor of 100nF between the inverting and non-inverting terminals of the Op-amp? I have not seen this type of a design. Would like to know the role that each component plays so that I can understand the design better.


texts: Where is the resistance in a starter motor circuit?

texts:
In a car or motorcycle, the starter motor is switched by a relay. The relay coil is switched by a key switch or small pushbutton. All of it is a 12 volt DC system.

Is it correct to think of the relay coil as having a very large resistance, and the starter motor as having very low resistance?

I'm trying to build my (so far nonexistent) electronic intuition. I know that there must be many, many more amps running through the starter motor and its large wires than through the starter button and its tiny wires. I'm struggling to understand (like deep down inside me) why the amps aren't running willy nilly through the starter button as soon as its closed, rather than through the motor which is doing a lot of work. Does the coil in the relay have a lot of resistance to lower the amperage, or is there a better way to understand what's going on?


texts:
at the moment im doing some research.
I want to create an embedded "application" with two digital cameras ( > 30fps, global shutter, >= 800x600 resolution ) on an Freescale Arm iMx. 6 Quad (i think its a good choice for later image processing).

At the moment for me it is not clear, how to synchronise these two cameras. Do i need a Framegrabber ? - which Cameras ( Ethernet , ... )

greetings


texts: Questions about a simple LED circuit using the ULN2003A

texts:
I'm a newbie, and am trying to drive several independent LEDs using a transistor array in a 5-volt CMOS circuit. Here's what I've come up with, showing only the first LED:

In the schematic, LED_ENABLE is the output of some logic IC in the circuit. I'm assuming that the LED has a voltage drop of 1.8 V and requires 20 mA of current.

Does this seem sane, or have I missed something? Specific questions:

I've tied LED_ENABLE directly to the base pin, because my understanding is that the ULN2003A's internal resistor is designed to let me do so. Is that safe to do without thinking further? It seems like the value of the resistor should need to depend on \$I_{CE}\$ and the transistor's gain, so I'm not sure how this can be one size fits all.
I chose the resistor voltage by calculating \$\frac{5 V - (0.9 V + 1.8 V)}{20 mA}=115 Ω\$ and rounding up, since the data sheet for the ULN2003A says that the collector-emitter voltage at saturation is 0.9 V for \$I_C=100 mA\$ (the lowest listed current). Is this the right calculation?
If I understand correctly, I don't need the COM pin. Is it sane to leave it floating?
And how about leaving the other base and collector pins floating? Maybe they should be tied to ground?
Anything else obvious I've missed?


texts: Different LED forward voltages depending on the order of the limiting resistor on Arduino

texts:
I'm testing the Vf of a red LED with these two simple circuits:

Circuit (A)

5V----|R|---->LED----GND

Circuit (B)

5V---->LED----|R|----GND

R=150 Ohm.

I use analog input 1 as a probe between the LED and the resistor to measure the voltage drop.

Assuming the red LED has 2V of Vf, the 150 Ohm resistor should limit the current at 20mA.

According to this, analog input should read 3V in circuit (A) and 2V in circuit (B), but that's not the case. I get 3V in circuit (A), but 4.5V in circuit (B), indicating a Vf of only 0.5V for the LED (?!).

What am I missing? Is it normal. I'ts the way I'm measuring the Vf (using analog input) what it's wrong?

Thanks!!


texts: 220V/5W means consumption of 5W at 220 volts. That implies 0.0227A current.How will this device operate at 110 volts? What will be the power consumption and how much will be the current?Sorry for bad english


texts: My project on STM32f407-Discovery. I will send a message on terminal to my board and I use this message for showing an 8-digit display. I am trying to build a look up table for the 8 digit Display. I will use it for counter but I don't know where am I starting. Can I use a switch case build for it? Please, help.


texts: How can I divide a variable voltage in half for a fan (variable load)?

texts:
I have a Peavey PV 2600 amplifier (1800W RMS) that I'm going to use in my home theater, but the 24V 80mm fan is much too loud and noisy. I want to replace it with a silent fan (Noctua NF-A8 PLX), which only come in 12V.

They Peavey outputs two voltages: 16V for normal operation, and 24V when it detects higher temperatures. There does not appear to be any in between or ramping, it's just one of the two discrete values.

I would like to keep this feature with the Noctua fan, such that at 16V the Noctua sees ~8V (pretty similar to running the Noctua at 12V with one of their 'low noise adapter' resistors), but when the amp puts out 24V the Noctua sees ~12V.

Because this will not be stuffed in a rack or driven very hard, cooling airflow isn't as critical as it would be in the amp's typical use case, and so the reduction in CFM won't be critical. However, even the Noctuas do make SOME noise at full speed (16.1 dBA), but less with their low noise adapters at ~8V (12.9 dBA), I'd only like to have the fan running at full speed when the amp needs it, not constantly.

What would the implications of calculating a single resistor value be that would be perfect for the 24V full load? I could provide the Noctua 12V, measure the current and thus derive a 'nominal' resistance while running, and add this resistor in series to drop 12V off the 24V. So if it's 40 mA, then I'd add a 300 ohm 1/2 watt or more resistor. However, at 16V, the fan now becomes less of a load, so could it potentially receive a higher voltage than it should, or such a low voltage that it stops spinning?

Most suggestions on using a 12V fan in a 24V system are to use a voltage regulator, which if I did so I would lose the two speeds and just run at a constant full power, which is undesirable to me (at least with a fixed regulator).

Could I instead do a voltage divider circuit? If so, what would the nominal resistance values be to run an x mA constant / y mA startup fan, that has somewhat varying power requirements?

If none of the above work, are there other solutions perhaps? Is there a circuit where I could use a regulator to provide exactly 1/2 Vin?
If there are no viable options without tampering with other circuits in the amplifier, are there brushless DC 24V fans that are guaranteed to be as quiet or quieter than Noctuas?

I don't think adding a second fan in the amp somewhere is too much of an option:


texts: Is it possible to use a Multimeter for detecting electric leads?

texts:
Is it possible to DIY my multimeter into a detector for active wires (charge flowing at that very moment) inside a wall?
I don't know, maybe something with a coil or metal plates?
The application would be localizing a wire in a wall so I know where not to drill into.


texts: What causes my mcu to blow up when hooking up with oscilloscope?

texts:
I was observing some timer signals yesterday, earlier in the morning I had my oscilloscope on another lab workbench where I would first make some changes, reflash the board and then take it to that workbench to observe, while providing power use a switchable microusb cord connected to a usb wall connector. Like the setup shown here :

Updates : I was probing a SMT LED.

Nothing went wrong

However, I was getting kinda lazy running back & forth so I thought maybe I could just have it connected to my PC so I can observe it right after flashing. So I hooked everything up, and then turned on the oscilloscope...and as soon as I pressed the power button, "zap" went my MCU, with a bit of smoke as well.

Setup shown here :

After some googling, I think it was maybe something to do with the scenario shown in this video (which is also the reference for my drawing), can anyone kindly help me figure out what the actual cause is? Though I have lots of spare boards, I still wanted to know how I can prevent this while also learn what had happened. Thanks in advance!


texts:
I'm dealing with a PWM generator which drives a load at 12V with pretty high currents (5-10A)
The PWM frequency is in the band of 100-200 Hz. Which is the best choice and right configuration of ferrite beads to achieve the best filtering of EMI?


texts:
I tried to make an audio amp based on LM386 but the output is noisy when the audio is playing. Here is my circuit schematic I built on a solderless protoboard:

simulate this circuit – Schematic created using CircuitLab

Power is supplied from four 1.5V batteries.
I also added 50pF between input terminals to filter-out radio noise.
When there is no sound playing, the amp is nice and quiet, but once the music starts the noise appears. There is also some reverberation when the music stops.
When the inverting input is connected to the ground the effects get even worse.
My guess is that there is a feedback loop between output and input, but I don't know why and how can be fixed. Adding coupling capacitor and/or voltage divider at non-inverting input or adding a bypass 10uF capacitor doesn't change anything.

EDIT:
According to the comments, I removed the 50pF capacitor between the inputs, connected the inverting input to the ground and added the voltage divider at the input. This made the sound much cleaner, but there was no gain. Output volume was not amplified regardless of the capacitor between pins 1 and 8.
Adding DC coupling before the potential divider makes gain work again but also makes the output really noisy.


texts:
I need some help with understanding following DC-DC converter circuit:

(Just for clarification, the three windings are on the same transformer core)

simulate this circuit – Schematic created using CircuitLab

My questions are:

How would you classify topology of this converter? Can it be called a self-oscillating flyback?
Why is secondary winding (L3) directly connected to the other windings? Is there any advantage over more common separated secondary winding?
Would you recommend to add any snubber network to protect the switching transistor againist voltage spikes?


texts: Switching a fan on/off based on an LEDs current

texts:
I have a small TV box which needs a fan because it overheats causing the cpu to throttle. I would like to have the fan turn on when the box is on, and turn off when the box is off. Unfortunately, the USB ports on the box always have power even when the box is off. The box also has no physical power switch. The only power indicator is an LED that is red when the box is off, and blue when it is on. I would like to use this LED signal to turn a small fan on and off.

The fan has a very low draw, and I will be reducing the voltage to the fan with a buck to 1.85V at which point it should draw 0.15A (It draws 0.40A @ 5V).

I have been reading about using a transistor as a switch, but most articles talk about using 5V at the base to turn the transistor on, and 0V to turn it off, while the LED on my box has much less than that. To make it more difficult, the LED never has 0V at any time on any leg. The voltages on each leg of the LED are as follows:

Leg: One Two Three

Blue: 0.60 3.26 1.90

Red:  1.97 3.26 1.39

The voltages were read using the ground of the power supply since that's what the emitter leg of a transistor would be connected to in order to switch power to the fan.

I have an S9014 NPN transistor and the specifications seem to indicate that it will turn on and off at the voltages indicated on the first leg of the LED, however I'm not certain about that. Also, many diagrams using a transistor as a switch include a resistor on the base and sometimes also on the collector of the transistor, but those diagrams are also often using 5V and not 1.97V.

Can I use the S9014 transistor with the base connected to the first leg of the LED, the emitter connected to ground, and the collector connected to a fan, with the fan connected to a 1.85V source, to switch the fan on and off? Will I have any problems with the transistor pulling too much current from the existing LED circuit? I will not be using the LED circuit to power the fan, just to signal the the transistor to turn on and off. Or am I looking in the wrong direction entirely?

Note: I need to keep all of the components being used to a minimum so they can fit inside the small TV box, so I can't use anything like an arduino, or a thermistor relay.

Note: Measuring voltage from leg 2 to legs 1 and 3 respectively, I get -2.65 and -0.15 on blue and -1.29 and -1.87 on red.


texts: Can a high voltage difference force a MOSFET open?

texts:
I'm going to assume the obvious answer is no, but I figure I should check with the experts before I go off and waste a bunch of my time.

Say you have several MOSFETS in a row controlling the flow through different components like solenoids. If they all share a ground line, and the solenoids all share the same supply line, could too high of a voltage force the MOSFET open?

simulate this circuit – Schematic created using CircuitLab


texts: Stacked PCB connections, split up current?

texts:
This may be a simple and beginner question but I am kinda lost how else I could solve my problem.
I decided to make 2 boards and stack them via a board connector. Now usually these board connector have current ratings per connection. On the bottom board I have my power regulation (24V -> 12VDC, 10A max.) that needs to get to the top board. If I now take 2x 5A connector, would that work as the current should split up equally between the pins or do I think wrong here?
Thanks.


texts: Can you use a LED driver (WS2801) for a 4-20mA control loop

texts:
I am trying to make a 4-20mA control loop on a home made sensor that will connect to a PLC. I was using Texas Instruments XTR111AIDGQR, but it is too expensive, costing $1.72. so want to try switching it out with WS2801, an LED driver that costs $0.13.

The LED driver documentation says it has a wide output current range up to 150mA, which can be adjustable to the LED current. I limited the current to 20mA using a 30ohm resistor as shown in the diagram below. I will use the TWI (Two Wire Interface) to "Dim" the 20mA current.

Will this application work? Am I not considering something that will make this not work?

WS2801 datasheet:


texts: Injecting a communication signal over DC power supply lines

texts:
I'd like to be able to daisy chain multiple devices using just the power supply wires and then inject a communications signal over the power lines to turn it into a half duplex network.

Are there any common methods of achieving this? The simpler the better and it would be great if it used the UART on the microcontroller.

Edit: There are actually two projects that I'm working on that I think would benefit from this - one is a low power sensor network. The other is a LED lighting project. In both cases the objective is to simplify wiring, but if the solution is too complex then it probably makes more sense to use three wires (pwr, gnd, comms).


texts: If a square wave has infinite bandwidth, how can we see it on an oscilloscope?

texts:
If a square wave requires infinite bandwidth how can we display it on oscilloscopes?
Link: Oscilloscope fundamentals.


texts:
I have a question regarding sending a short duration signal from  a faster clock domain to a slower clock domain. I am trying to implement a dual frame  buffer in a  dual port (dual clock) RAM. Once an entire Frame has been stored, the write clock side asserts the FrameFull register. At the end of each current display frame, the display requests a new frame,
which if available, sets the read pointer for the RAM accordingly and is also  used to deassert the FrameFull Signal so that a new frame can be loaded while this most recent one is being displayed.

The read side is operating at 50 MHz.
The write side is operating at 27 MHz.

In order to synchronize the FrameFull Signal from the write domain, I have read that its best to use a couple of synchronizing flip flops and since the FrameFull remains asserted until the buffer is switched, I think this isn't very problematic (because the FrameFull signal can't be missed).
The SwitchSuccesful signal is asserted in the read clock domain when a new Frame is requested and the FrameFull is 1, indicating buffer exchange. Now, this SwitchSuccesful needs to be sampled by the write domain so that FrameFull can be reset to 0 and can then start storing a new frame. I have thought about it and decided to use a 16-bit shift register, which, when buffers are switched, will reset to 16'hFF and then shift left with a zero being concatenated.I could then use a bitwise OR, and synchronize the result of the bitwise OR with Flip Flops in the write domain before sampling the signal. Will this be sufficient to prevent missing the SuccesfulSwitch and metastability?

CODE :

always @ (posedge read_clock)
begin
    if(SwitchRequest) begin
          case (Frame_FullSync1, Frame_Read)
          2'b00 : begin rd_ptr <= /*Some Value*/ Frame_Read <= 0; end           //Restore to Previous 0.
          2'b01 : begin rd_ptr <= /*Some Value*/ Frame_Read <= 1; end           //Restore to Previous 1.
          2'b10 : begin rd_ptr <= /*Some Value*/ Frame_Read <= 1; LE <= 1; end  //Load new ----- 0 to 1.
          2'b11 : begin rd_ptr <= /*Some Value*/ Frame_Read <= 0; LE <= 1; end  //Load new ----- 1 to 0.
          endcase
    end
    if(LE) LE <= 0;
end

always @ (posedge read_clock)  begin
    //Frame Full Synchronization from write domain to read domain
    Frame_FullSync1 <= Frame_FullSync0;
    Frame_FullSync0 <= FrameFull;
    //LE was asserted for 1 clock cycle when buffer switch was succesful
    if(LE) Sync <= 16'hFF;
    else   Sync <= Sync {Sync[15 : 1],1'b0};
end

assign SwitchSuccesful = |Sync;

always @ (posedge write_clock) begin
    //Synchronization of bitwise OR
    SwitchSuccesfulSync0 <= SwitchSuccesful;
    SwitchSuccesfulSync1 <= SwitchSuccesfulSync0;
end


texts: Help understanding the mixer of a superhetrodyne receiver

texts:
I studied all the datasheets and read a book on the basics of RF front end design. I know the receive circuit is a superhetrodyne.

I see in the datasheet the output of the mixer at pin 4 is the |f1-f2| and pin 5 is f1+f2. I understand the far left op-amp is a infinite gain 2nd order active bandpass filter. I am trying to understand what happens to the mixer outputs as they travel though the middle and left op-amp, since both mixer outputs are fed through.

Can you help me understand this circuit? The input is an 8Mhz OOK signal. The output is a 128kHz image of the input into a purpose built AFE.


texts:
I have a few basic doubts regarding this USB to UART bridge IC

My questions are just from the hardware perspective. I have little to no software knowledge. So please bear with me and help me understand your answer in simple terms.

This IC converts USB protocol to UART protocol at the available 4 output channels, right? Is there any software within the IC that will do this conversion of protocol or do we have to write separately? Like, what should a hardware person keep in mind while using the IC? Like, just connect differential lines on Input and take 4 Tx,Rx lines on the output connected appropriately to the Micro or SOC or whatever IC?
If I have one USB 2.0 running at 480Mb/s connected as the input, how is speed and addressing done for each channel? Will all output UART channels operate at the same speed? What happens if two output channels require value from USB at the same time?


texts:
I have a question about schematics on Altium. When I put a capacitor (or other component) in a diff pair line , the lane after the component loses the diff property and i have to use labels for all the slices produced by the component adition. If I use diferent labels for different names is to annoying when I have to check length matching, but if I use the same net label name then appears ghost lines on the PCB design. Is there any way to put a name for all the net without problems or using labels is the way to do that?
Thank you so much.


texts:
I am working on a simple counter that takes start, stop and increment values as decimal inputs. Here's the circuitry of the start value input of my counter:

What the whole counter does is count from whatever start value you input by whatever increment you set and should stop if the count value is over the stop value. What I'm having trouble with is getting the inputs to get read as 8-bit values by the adder. My inputs are represented by switches, each switch represents the decimal numbers 1-9. The switches are organized in 2 columns, the first column represents the MSB and the second column represents the LSB.

On the above picture, the display is currently showing 11, switch one in column 1 is switched 'on' and switch one in column 2 is switched 'on' as well. The issue I have is, when I input the data into an 8-bit adder, the outputs it as 2. The adder reads them as two separate 4bit binary numbers. I know that using a 16-bit adder would work, but is there any other way to get the 8-bit adder to read the input values as 8-bit values or do I need a 16-bit adder?


texts:
I know what battery I wish to use (3.7 V 140 mAh which I can swap for larger mAh battery)
I know what length of wire (3.5 inches or 7 inches depending on which ever would work better)
I know what temperature (110 F)
I know the the wire only needs to stay on for 10 seconds at a time
I don't know which diameter/gauge wire to use

I stuck at math and can't seem to google-fu my way into finding something that will give me the ability to calculate what nichrome wire to use. There was one site that would give let input the given parameters, but the lowest known temperature I could use was 400 F.

I need the math that let me calculate which diameter/gauge and with what resistance will give me 110 F temperature over either 3.5 or 7 inch wire using a 3.7V battery.

Please forgive any of my blaring misunderstandings or ignorances/deficiencies in formality of how to inquire this information.


texts: Is it possible to build an H-Bridge with only N-MOSFETs (and these other components)?

texts:
I am trying to design an H-bridge circuit and I am only given the following components:

Opamp
Zener Diode
Resistor
Capacitor
N-MOSFET
NPN BJT
Diode
2-input NOR
2-input NAND
Infra-red Detector
Infra-red Emitter
D flip-flop

I know that it is easy to design an H-bridge using 2 P-MOSFETs and 2 N-MOSFETs, but I am not given P-MOSFETs.

Is there an equivalent circuit for only N-MOSFETs?


texts: Electromigration, are computers nowadays less durable?

texts:
I've been reading press articles and about electromigration and how it is associated with miniaturization. I have seen old computers working for decades, and I'm wondering how bad the electromigration may be nowadays. I wonder if the miniaturization is shortening the lifespan of electronics and to what extent this is happening.

Personally I have replaced most of my computers because they broke, not because they were too old to run what I needed. I wonder if this is going to become the norm, and we should not consider technical characteristics looking ahead in time, because anyway the computer will break before it's too slow.


texts: Only allowing input after x amount of time

texts:
I've been given a problem to solve -

When the input is high (sensor), a timer should start which outputs high for 10 minutes (camera active). After 30 minutes, if the input is high, the process should being over.

I've learned about ripple counters to solve the start of the problem which is to output high for 10 minutes once the input is high

But I'm having trouble solving the other part. What I want to do is stop the input going in to the timer for 30 minutes.

The only way I can think to solve this is to break the connection between the input and the timer, and then re-connect it after 30 minutes using a switch.

Something instinctual just tells me that this is bad, and isn't the correct way.

Any help or just areas to look into would be great - Thanks


texts: What is the electrical connection of heatsink plate of PB case bridge rectifier packages?

texts:
I'm going to use two PB-case bridge rectifiers of a certain product in my circuit. I need to know the electrical connection of its heat-sink plate (i.e.; to what pin it is connected to, or if it is connected to any), so that I can decide whether I connect them to a single heat-sink or separate ones.

Datasheet of the product doesn't give any clear information about this. Is there any standard for this package type on this matter?


texts: Self-Tuning PID Controller to implement in a PLC without having the plant model?

texts:
I need to implement a self-tuning PID controller in a PLC. I know the behavior of the plant (I mean, I know that if the speed is reduced the tension gets higher and vice versa), but I do not have a mathematical model of it. Which method would you recommend?

The case is the following:

I have a system which consists of a warp beam in which a thread is wound and an AC motor to rotate the warp beam (“Process” according to the picture below). This thread should be fed at a constant tension to another machine (The whole system is a weaving machine, but I am just controlling the speed of the warp beam using a tension sensor). The motor is connected to a control motion system in which we have just to specify the speed at which the motor should rotate, so we have a PID controller to calculate the speed at which the motor should run. To measure the tension of the thread we have a tension sensor.

By the nature of the process itself, the tension on the thread has oscillations, and depends of the pattern of the woven fabric and speed. It is a “high speed” process. So we specified a target tension, which the “motor” should try to achieve, but we also specified a Max. and Min. if the tension gets out of this range the whole machine will stop.
As an example the behavior of the tension in a loom is depicted below.


texts:
There seem to be a number of different definitions of flip-flops and latches out there, some of which are contradictory.

The Computer Science text book for the course I teach is probably the most confusing (in fact I have little faith in the book because it’s just plain wrong in several places).

I am comfortable with the workings of latches (SR, gated SR, gated D), and the difference between level triggered and edge triggered devices, at least in terms of logic gates and timing diagrams.  However, I am still looking for a concise definition of a flip flop and of a latch.

This is what I believe so far:

“A flip flop is an edge triggered bi-stable device that can store 1 bit”.

“A latch is a level triggered bi-stable device that can store 1 bit.”

I’ve had a look at previous posts on this website about this and, as enlightening as they are, I am still looking for something definitive.

My current understanding, which I want to check, is in the diagrams below…

Side by side are what I understand are two implementations of a level triggered gated D latch.

Below these is a positive edge detector, at that brief moment when the NOT gate has not yet responded to the change input from low to high, namely the rising edge (red is 1 blue is 0).

In the last diagram, the edge detector has been fitted to a dated D latch and this is what makes it a flip-flop.

Is the last diagram really a flip flop, or is it still just a latch?

And why do we need the master slave version given, that this device is so much simpler?


texts:
I need to supply the galvo driver with a signal "Voltage Range ±3.0V p-p or ±10.0V p-p (Differential Input)" - that's what it says in the datasheet. I have a 0-5V single ended DAC and differential opAmp AD8132. So, I am planning to create the differential signal by the following schematic:

The output of the DAC will give me a signal ranging from 0 to 5V and I can scale it down using R26. The other pot (R25) will generate the proper voltage to offset DAC's signal to 0V DC. This way, a 0-5V wave on one input and +2.5 on the other input will give me ±2.5V between the outputs of the dual buffer U4. These signals then fed into differential opAmp U5 with G=1.

Question 1: is this the proper way to generate a differential signal? I believe that I could place a 0.1uF cap between R26 and +in of U4 and it would automatically offset it to 0V, but since a part of my signal is DC, it would compromise the signal, right?

Question 2: What should I measure on each of the differential outputs of U5 relative to ground?


texts: Where to find documentation for definitions for AVR programming in C

texts: I wonder if there is a documentation for AVR (I am using C to program) definitions like PIN5_bm or SLEEP_MODE_PWR_DOWN, or if I just have the information given in the respective header file. I tried to find this kind of information in the datasheet of the AVR chip (and elsewhere), but without success. I would like know where to look for such definitions, to find new useful ones.


texts: Is the sound of an aux-connector DAC or CODEC?

texts:
I am planning to take the audio aux signal of a raspberry pi and amplify it with a TPA2012D2 by Texas Instruments. In the datasheet there is a typical application circuit, which would match my needs (single ended input signal). Except I am not sure that the aux output is DAC or CODEC. Can someone explain to me if this would work?

I added a image of the typical application circuit below.


texts: Barkhausen condition on a Wien oscillator

texts:
Consider the Wien oscillator:

We can determinate the operational amplifier gain defined as:
$$A(s)=\frac{\bar{V_o}}{\bar{V_a}}$$
and the gain from the feedback network:
$$\beta(s)=\frac{\bar{V_a}}{\bar{V_o}}$$
where \$\bar{V_a}\$ and \$\bar{V_o}\$ are the complex amplitudes of \$v_a\$ and \$v_o\$, respectively.
For an oscillator we have the Barkhausen condition:
$$A\beta(s)=1$$
To determinate the dimension of the components from the circuit which satisfy the previous condition, we usually calculate \$A(s)\$ and \$\beta(s)\$ doing some circuit analysis and then impose \$Re\{A\beta(s)\}=1\$, \$Im\{A\beta(s)\}=0\$.

But starting from the definition of \$A\$ and \$\beta\$, we can say that:
$$A\beta(s)=\frac{\bar{V_o}}{\bar{V_a}}\frac{\bar{V_a}}{\bar{V_o}}=1$$
which already satisfies the Barkhausen condition for any dimension of the circuit components. So where is the point of finding the dimension of the components that make the circuit an oscillator, when any of them could do it?

This makes me confused...Is this thought correct?


texts:
I took apart an old printer and found two components that look like relays.

But they have no markings of any kind, save for a small sticker each that I think may be serial numbers.

They are 4335xit3 and 5345xft4.

I would love to find some data sheets to know what they can do, but I don't know how to identify them without markings.


texts: How to design an amplifier for a sensing liquid level using capacitive probes?

texts:
In this problem I have a capacitor that is submerged in a varying level of dielectric fluid. Therefore, the capacitance varies linearly with the height of the fluid. How should I design a simple op amp circuit to achieve this? I believe it should be a non-inverting amplifier circuit.

My circuit:


texts:
I have a question regarding A/C lighting for IoT just basically where to go for the information/parts I need.

I want to control the lighting in my bedroom/bathroom via IoT devices that will act as a dimmer.

I'll probably write my own small Django/Python server to control them via JSON Web API using JWT from my Raspberry Pi 3. They'll need to communicate with the light switches through some means like WiFi as the RPI3 is set up next to the TV, so I'll put whatever microcontroller board into the physical walls and route power to them (I'm not a hardware engineer so getting mains electricity behind the wall and converting it down to 5V DC is a little beyond my skillset at the moment).

In the bathroom there are 4 incandescent vanity lights, I have them controlled by manual dimmer right now. In the bedroom I have 3 incandescent lights in the ceiling fan, ceiling fan is not dimmable. The electrician who wired them did not use a neutral wire. I'd like to stay with incandescent lighting for the main lights for reasons outlined here:

https://www.scientificamerican.com/article/led-lightbulb-concerns/

I only use my Smart-Link LB130 LEDs for auxiliary lighting, they'll be using my RPI3's access point as soon as I get that set up and then controlled via Web API.

I'd prefer not to use a store bought solution for a variety of reasons.

A) Smart Hubs are ridiculously overpriced and unnecessary, and there's too much "magic" going on behind the scenes from a software perspective, not to mention highly insecure if a company produces write papers that reveal their internal radio communications protocols, which on an Insteon dimmer I bought a while back they did.

B) These lights were not wired for neutral, and most of the store bought solutions require that. It looks like there is a neutral wire behind the wall, but I'm not sure if I need to do anything more than just hook it up.

C) I'd like to create my own custom security encryption scheme and protocol for communication with the lights rather than vendor-provided, which, if my UDP-based LB130s that I reverse engineered are any indication, need a lot of improvement from a software perspective.

I'm still learning the ropes with hardware though, only have done some basic DC wiring and soldering yet.

Any ideas on how to dim A/C lighting from a microcontroller board like a TI Launchpad (I've got a MSP530F5529LP I'm playing around with, also got a Teensy I haven't touched yet) and get power to the MCU from behind the wall?


texts:
My PCB is powered from USB port and includes Recom RKZ0505D for powering dual-supply OPAMPs. Recom gives +5V and -5V outputs. So I have:

Top signal & components
Bottom signal & components
GND
3.3V
+5V
-5V

What should be the stackup of layers in a 4-layer PCB? There are about 30 ICs on the PCB. Some of them powered from 3.3V and some of them +5/-5V. If the layers used are:

Signal
3.3V
GND
Signal

Then the power lines +5/-5V will be long. How can I optimize layers and right order?


texts: LTE UE REPORTED CQI - Defined by RS-SINR or by Transport Block Mapping?

texts:
First than anything, let me assure you I am fully aware that no one REALLY knows HOW UE manufacturers specifically implement the CQI reports sent on the UL, but there should certainly be a better engineering answer to my question.

This is particularly important on today's reality where wireless operators are doing great efforts to improve the RF environment (important for high capacity venues such as Stadiums and Arenas) to provide the best customer experience (generally measure by the throughput granted to users) and throughput is directly dependent upon on LTE UE CQI reports back to the eNodeB.

Some background context.

PART 1:
Everywhere where we look we see articles like the one below. Basically, everyone states mobiles measure RS-SINR to define the CQI value to be reported back to the eNodeB. This is where the “magic” statements comes in.

http://testfirstforkevin.blogspot.com/2013/11/lte-cqi.html?m=1

PART 2:
The RS-SINR is defined by the specification(3GPP TS 36.213 V14.4.0 /2017-09) as:

  Reference signal-signal to noise and interference ratio (RS-SINR), is
  defined as the linear average over the power contribution (in [W]) of
  the resource elements carrying cell-specific reference signals divided
  by the linear average of the noise and interference power contribution
  (in [W]) over the resource elements carrying cell-specific reference
  signals within the same frequency bandwidth.  For RS-SINR
  determination, the cell-specific reference signals R0 according TS
  36.211 [3] shall be used.  The reference point for the RS-SINR shall be the antenna connector of the UE. If receiver diversity is in use by
  the UE, the reported value shall not be lower than the corresponding
  RS-SINR of any of the individual diversity branches.  If higher-layer
  signalling indicates certain subframes for performing RS-SINR
  measurements, then RS-SINR is measured in the indicated subframes.

And the specification (3GPP TS 36.214 V15.0.0 /2017-09) also defines the CQI as per the paragraphs below. Pay special attention to the BOLDED sentence.

  7.2.3 Channel Quality Indicator (CQI) definition

  The CQI indices and their interpretations are given in Table 7.2.3-1 for reporting CQI based on QPSK, 16QAM and 64QAM. The CQI indices and their
  interpretations are given in Table 7.2.3-2 for reporting CQI based on
  QPSK, 16QAM, 64QAM and 256QAM. The CQI indices and their
  interpretations are given in Table 7.2.3-3 for reporting CQI based on
  QPSK and 16QAM. For a non-BL/CE UE, based on an unrestricted
  observation interval in time unless specified otherwise in this
  Subclause, and an unrestricted observation interval in frequency, the
  UE shall derive for each CQI value reported in uplink subframe n the
  highest CQI index between 1 and 15 in Table 7.2.3-1 or Table 7.2.3-2
  which satisfies the following condition, or CQI index 0 if CQI index 1
  does not satisfy the condition:

  A single PDSCH transport block with a combination of modulation scheme and transport block size corresponding to the CQI index, and
  occupying a group of downlink physical resource blocks termed the CSI
  reference resource, could be received with a transport block error
  probability not exceeding 0.1.

The CQI definition above seems to imply that there are not RS-SINR measurements but, rather, the UE defines the CQI by looking at the transport blocks and selecting the highest CQI by a sort of reverse mapping from TBS (those that perform with a BLER < 10%) to MCS to CQI Mapping (because by knowing the TBS and MCS, it’d be relatively straightforward to make assumptions to CQI mapping).

QUESTION:
What is the actual approach given by the specification? CQI based on RS-SINR or CQI based on reverse mapping from TBS to CQI?

I hope one of you can help me on my quest!!

Thanks a lot!
Lamberto

PD: I am a newbie in the community so I could not add the tags: lte,cqi,ue to the question but these would be key tags to identify this question. If others can add it, it'd be of great help to other members.


texts: Vss and Vdd pins' position on microcontrollers

texts:
I am starting to work on some designs with MCU-based boards, or sometimes just looking at companies' products involving MCUs such as Espressif, Udoo, NXP... I have noticed a puzzling similarity between those MCUs, be it ARM Cortex, PIC or AVR family processors: the power-supply pinout.

I have looked up topics about the benefits of having  multiple Vdd and Vss pairs, but what i find disturbing is their immediate proximity, i.e. they are next to each other. While there should be little problem with reflow oven or wave soldering in assembling processes, when it comes to SMD hand soldering this gets quite tricky for assembly or repair. It is really easy to short Vdd and Vss with the latter method and unless visible or checked after assembly/repair, one might badly damage its MCU or power-supply and start the board's design anew in the worst case scenario.

Hence my question really is: are there some benefits or silicon chip design constraints to why such layout is common place on our beloved MCUs? I have little to zero knowledge about silicon chip design or manufacturing. Or is this a way to ease the placing and routing of bypass capacitors?


texts: Am I forced to use a gyro and an accelerometer, to find a relative point in space?

texts:
I am quite new into the electronic realm, so forgive my lack of proper terminology.

I am planning to build a simple device, that I will be use to manipulate a mesh on my computer. when I move the device, the mesh rotate/translate. As example, you can use one of these artist doll/mannequin used in art class, or just a hand; the concept is applicable to various uses.

For sake of clarity, let's use a human hand/glove.

So, I was looking into it, and found that I need to use a gyro (which records the rotation among the 3 axis), and an accelerometer (which would give me the variation in position, altho some says that it tells me the axis orientation relative to the ground, thanks to the gravity field).

Now, if you want to make a glove, you would end up with one gyro on the back of the hand (the hand always rotate as whole on the wrist axis), and 5 accelerometer, one per finger.

Is there another technique to have the same result, but without this waste of sensors? I've seen electric strips, which are basically variable resistors that change their value as they get curved in one direction, but the price is close to a sensor, and they offer very unstable signals, which would require a lot of compensation via software.

is there any other way, other than use a camera or the aforementioned gyro + accelerometer; to monitor the variation of position of an object? In the case of the hand, you would be interested only in variation from the starting point (say you want to make an animation of a hand that open and close), I can't really find a way to do it unless I use all these sensors.

Any help is more than welcome...I don't even know what to look for, to be honest, so I rely on your expertise. Thanks in advance.


texts:
I am looking for a way to use a MOSFET as a normally closed switch such that when a battery charger is attached it opens the switch to disconnect the battery from the rest of the circuit. I want the load to be between the MOSFET source and ground, instead of between the battery and the MOSFET drain.

EDIT: I want the load of the battery to be disconnected. Thus the battery is only connected to the charger. The battery is a single cell LiPo and the charger will be built into the board so just charging power is needed to charge the battery.


texts: So here is a MOSFET that I'm planning to use for a 10A constant current source. Look at page 3 where where they've shown how a 1 sq. in. copper pad affects the RθJA. Pins 1-3 is the source, 4 is the gate and 5-8 with the larger pad is the drain. Why are the drain pins named as DF and DS and the Source as SF and SS? Arent they the same? Also why is there a think trace on S/DS? Also is that 1 sq. in. copper pad on the bottom or the top of the PCB?


texts: How to measure small AC current using micro-controller and shunt resistor?

texts:
This must be a basic question, which I am struggling to find and understand suitable circuits to be able to read AC current using a micro-controller.

Most of the other examples are calculating DC current, while related questions such as this one, attempt to measure AC current on mains voltage which is not what I am after.

So far I have managed to calculate and measure the RMS voltage from a +-1.5 V sine wave. I am now looking to measure the current by simply using a shunt resistor in series with a larger load resistor (10 K ohm), and an op-amp, without any specifically designed IC's. Vref for my ADC is 3.3 V.

DO the circuits that measure DC current, such as the one below, still apply for AC voltage?  I cannot seem to understand this basic concept.

EDIT: Can my AC source replace the above DC supply and still get correct readings, or do I need to make changes to the circuit?

Also if the circuit above was applicable for an AC voltage source, I am thinking need to get the RMS reading at Vs. Is this correct?


texts: How to calculate voltage divider between two transistors?

texts:
I am working on a homework assignment and I don't know what it is but this problem has me stumped. Below is the subsection of the circuit we are supposed to be working with. I don't know if I put in the CMOS transistors correctly, but they are at least the N-type.

simulate this circuit – Schematic created using CircuitLab

VT,N for the transistors is 0.3V. This is the equation I tried to set up to solve this.
$$\frac{1}2\frac{(1V-\Delta V-0.3V)^2}{(1-\Delta V-0.3V)+\Delta V} = \frac{(0.8V-0.3V)^2}{(0.8V-0.3V)+\Delta V}$$

This definitely doesn't work. But I'm not sure what the correct equation should be.

Edit: I guess I'll add that this equation gave me a delta V of about 1.16V. Easy to tell that it is incorrect.

Edit2: I had a mistake in my equation I originally posted.


texts: Working principle of floating gate tunneling oxide

texts: Floating gate tunneling oxide (FLOTOX) is used in electrically alterable rom. Tunneling of charge takes place through tunneling oxide into the floating gate. What is the working principle of this? How is it designed in order to achieve write, erase and read operations?


texts: Help needed to determine inductor material/turns needed

texts:
I am trying to formulate a circuit to sense current in a standard US 120V AC power line.  I'm planning on using an inductor as a current transformer to sense current flow and allow a microcontroller to be triggered.  However, to minimize size of the transformer, I'm planning on a BJT after the CT, in the hopes that I can amplify the signal enough to avoid bulky ferrous core material found in a typical CT.  (Proposed circuit below).  In analog TVs and older radios, I recall seeing coils wound with very dense, very small wire, and it made me wonder if I could trade core material for wire.
What might make this possible is that in my application, all I am trying to do is sense current above a very small and flexbile threshold (500 mA +/- 300 mA), not to measure it, so I don't need super duper accuracy, just ability to detect current flow above that amount.  I'm planning on wrapping that inductor around one lead of a standard 16 gauge copper Romex power feed cable.
Can anyone recommend any software or good reference sites with calculations that I can use to try to predict/simulate the kinds of voltages I can expect for a given wire diameter and number of turns in that inductor?
By the way, if anyone has a better design for the circuit in general, I'd love to find other potential ways to do this.
Thanks


texts: How to create measurement points on a PCB for diagnostics?

texts: What is the best way to implement a point on a PCB, where a voltage (e. g. output of a regulator) could be measured with multimeter for the purpose of verification of the assembly or diagnostics in case of malfunction (preferably in Eagle)?


texts: Is it OK to connect ESD plug through an RCD?

texts:
I am thinking of rewiring some of my workshop with a RCD spur for my machine tools and bench and an emergency stop. I use an ESD plug to ground an antistatic mat when working on electronics on the bench.

The RCD spur will have something in the earth line to sense current - is this going to have any effect on the effectiveness of the ESD ground, or should I add another ground for ESD use?  Is having a second return path going to reduce the effectiveness of the RCD for the machine tools (not that I normally use both at the same time)?


texts: Does imposing an odd initial condition reduce spurs in MASH Delta-Sigma Modulators that has second order stages?

texts:
I've been reading about how fractional spurs can be reduced in a Digital MASH Delta Sigma Modulator (especially for application with a fractional-N PLL) by having the initial condition of the first stage be set odd (typically by just setting the LSB to 1 when the circuit is restarted).
The books/papers that come to this conclusion (Minimizing Spurious Tones in Digital Delta-Sigma Modulators by Hosseini and Kennedy and Rigorous analysis of delta-sigma modulators for fractional-N PLL frequency synthesis by Kozak and Kale) both operate on the assumption that the MASH DSM is composed entirely of first order stages (e.g. a MASH 1-1 or MASH 1-1-1); would this principle hold true for other configurations (e.g. a MASH 2-1 or MASH 2-1-1)? I haven't found any literature discussing this deterministic technique for spur reduction for other MASH configurations. If any textbooks/papers talk about it, I would very much like to know.


texts: Switching Relay with NPN and PNP transistors

texts:
I'm designing a locker system using Arduino.
Due to system requirement, two IOs will be used control the relay, and only when two IOs are ON, then the relay will be triggered.

PNP = BC807
NPN = BC817
Coil = 720 ohm, 20 mA
Diode = 1N4148

My question is will PNP be switched on/off reliably?
Any risk to consider here?

Any suggestions are welcome.


texts:
I'm trying to have a button iterate a LED strip through binary. Each press would either increment +1 or -1 depending on the button. However, My code doesn't seem to store the variable in the do-while loop. The LEDs that light up are random on each button press.

#include <avr/io.h>
#define F_CPU 16000000UL

void main(void) {
  //declare DDRx
  DDRD = 0b11111100;  //set PD2-PD7 to output
  DDRB = 0b00000011; //set PB0-PB1 to output and rest to input
  PORTB = 0b00001100; // set internal pullups in PB2 and PB3 turn PB0 and PB1 off
  PORTD = 0b00000000; //turn off PORTD
  //declare num counter
 int num = 0;

  do {

    if ((PINB & 0b0000100) == 0) { //check if PB2 is pressed
      num++;  //add 1 to n i.e. n = 1 on first loop
      PORTD &= 0b0000011; //clear bits 7 - 2
      PORTD |= (num << 2);  //shift bits

      PORTB &= 0b11111100; //clear bits 1 - 0
      PORTB |= (num >> 6);  //shit bits
    } else if ((PINB & 0b0001000) == 0) { //check if PB3 is pressed
      num--; //minus 1 to n
      PORTD &= 0b00000011; //clear bits
      PORTD |= (num << 2); //shift bits

      PORTB &= 0b11111100;
      PORTB |= (num >> 6);
    }
  } while(1);
  return 0;
}


texts: How to calibrate the vertical sensitivity of an old analog scope (Hameg HM203-6)?

texts:
I have a Hameg HM203-6 20 MHz analog 'scope I bought from a flea shop. There's about 20% mismatch of the readings of the two channels, with CH1's vertical amplification being about 20% higher than CH2 when both are at the "CAL" positions of their respective variable amplification knobs. Using a reliable 5V DC source, I've checked that CH2 shows about 5 volts exactly, whereas CH1 is close to 6 volts. On this model, the "CAL" position is at maximum CCW, and sensitivity cannot be reduced below the calibrated one.

So I assume the "calibrated position" must be recalibrated. The problem is that there's no mention on how to do this in the manual I was able to find. I see those "CH1/CH2 balance" holes on the underside of the case, but they serve a different purpose.

I'm also almost sure that the sensitivity can be calibrated through the VR703 ("Y-GAIN CH1") pot, slightly below the center in this photo.

So my questions are,

Is there anything else to it, besides the pot adjustment?
Is it a terribly bad idea to do the adjustment while the scope is naked and powered? I'm aware that exposed CRTs are lethally dangerous.


texts: Why doesn't this (adapted) circuit work with the given power voltage?

texts:
I'm helping a little friend with his first project: an electronic dice from Velleman. The circuit is here (click to enlarge):

He built it, I checked and improved it, everything was okay - except we didn't had a 2V7 zener, so we used a 3V3 on for ZD1.

We powered the device using a lab power supply at the given 9V, and it didn't work well: it showed sometimes a six (LEDs 1, 2, 3, 5, 6, 7), and sometimes a '7' (all LEDs). We had the luck that I thought the LEDs were too bright: I decreased the voltage to 6V, and then it worked...

This odd behaviour really comes from ZD1: later on, I replaced it with a 2V7 one and now everything's working fine on 9V (and 6V as well).

Can anyone explain why that is? Both ICs (4046 and 4024) are working properly on both 9V as 6V. I would expect that when you use a zener with a higher zener voltage, you'd need a higher voltage from the power supply rather than a lower.


texts:
I'm trying to figure out how to build my own PiSupply as my first electronics project. The schematics of the PiSupply are provided here as a PDF in the zip file, but I've reproduced the schematic to the best of my ability.

My questions:

Why is the normally-connected part of the SPDT switch connected to the capacitor/transistor part of the circuit at all?
Why are there two transistors in the circuit?
Why is there a resistor and ground by the SOFT_OFF?
What's going on with the relay coil being connected with a diode?

The circuit:


texts: Looking for a short range detection and identification

texts:
I am currently building a smart cat door. One of its functionalities is that it keeps the door locked until our cat comes close to it, then it unlocks the door.

I tried using RFID, the RC522 because I read that it can work fr a range of 1m.
But after testing, the max range I could get out of it was less than 10cm.

After doing some research I found out that the protocol used in the RC522 can't do more than 10cm.

Another solution I came up with was to use Bluetooth instead, but the problem with Bluetooth is that it has a long detection distance for our application (with class 2 having a range of 10m).
This will mean the door will detects the cat even if she is just setting in it's vicinity and we don't want that.

Is there any other sensor combination that can accomplish this task?

It doesn't have to be RFID or Bluetooth.
It has to detect the cat at a short range, lets say no >2 meters and no <1 meter.
It is preferable if the tag/module that goes on the cat is unpowered, or requires low power.

Thank You


texts: Efficient low-power buck (step-down) regulator IC for Li-Ion - 3.3V conversion?

texts:
It's not easy for electronics novice to find good element base, so I hope this suitable question.

Requirement: Efficiently power a lean, 3.3V-based MCU design from a Li-Ion battery. "Efficient" means no more than 20uA quiescent current, 10uA is better.
Ground current for 1mA output current <50uA.
 Maximum required output current >= 50mA.
 Having a SOT package (vs those <2x2mm SON packages) is also a plus.
 Higher frequency and smaller inductor is also good (especially if doesn't conflict with package requirement ;-) ).

Good availability and price matters too. That's definitely subjective, but providing 2-3 names is better than telling that X is the best.

Thanks!


texts:
i want to start a home automation project, so finally i choose zigbee as the communication system between the devices.
I need something easy to start, so, what do you recomend to buy? there is some nice starter or development kit, with something like RS232 or USB output, just to forget about the zigbee protocols and issues,
i need something that almost works out-of-the-box...

thanks!
Br


texts: Correct way to build a load lamp setup for circuit testing

texts:
I have a 3 way extension lead that I would like to use to stick it in the wall, put a load lamp (40W oven lamp) in series with it, and then use one of the prongs to insert my circuit under test. (the idea is that the load lamp would prevent the circuit from destroying itself in case of an issue).
(I'm in Europe where we have 230v AC, and I would like to setup a load lamp circuit to protect my circuits under tests.)
If I cut the extension cord cable , and I take the black wire out (hot), cut it and put a load lamp in between, would that be a valid circuit for a load lamp.
My apologies for the drawing, the amateurism reflects my knowledge of basic AC electrical wiring

The goal is to test a circuit that is currently causing some kind of short, and put this setup behind an isolation transformer also.
Some questions :

Is this the way to do it ?
I only have a relatively small 40 watt oven lamp ? Would that be ok ? The circuits that I would test with this are mostly switch mode power supplies
If I would short one of the prongs in the extension lead would the light simply come on and would nothing else happen ? (it is a bit counter-intuitive to short a prong like that in my head, but the way I see it the circuit would just look a standard AC light bulb circuit)
If the circuit under test is running without issues I would hardly see the bulb go on I imagine ?
I've seen videos where people put the bulb in series with the black lead, but others that put in series with the neutral / gnd lead. What is the difference ?
Does adding an isolation transformer change anything ? (the idea would be to put this on an isolation transformer instead of plugging it in the wall socket directly)


texts: Finding v0 on the right side of an op-amp?

texts:
I am trying to find \$v_0\$ in this circuit (voltage across \$R4\$):

simulate this circuit – Schematic created using CircuitLab

The issue I am having is that I would have known that the current going into the 16 ohm resistor would have been the same as the one going in the negative terminal, but that's only if they are both going into the negative terminal. I know that its 0 volts to ground on the right side. And 0 volts in between the + and -.

Can someone help me find \$v_0\$?


texts: Help needed with over discharge circuit on LifePo4 12V car battery replacement

texts:
I'm putting together a LifePo4 battery pack with the intention of replacing the 12V lead acid battery in my 4WD.
So far, what I've got is the following.
4 x 10 Ah LifePo4 batteries (38120 Headway) in series to get my 12v (12.8 is  close enough I think).
Plus 5 x 500 Farad supercaps (2.7V * 5 = 13.5V) to supply the initial starter load.
My battery pack contains 2 lots of the above to supply extra power and hopefully longevity.

What I need is some over discharge protection (and maybe overcharge?  but I dont think that should be a problem)
I'm not an electronics engineer so cant design something myself, but I was looking at something like this on ebay.
https://www.ebay.com.au/itm/3S-4S-100A-12V-w-Balance-LiFePo4-18650-Battery-BMS-Protection-Plate-Board/282814976228?ssPageName=STRK%3AMEBIDX%3AIT&var=582140823314&_trksid=p2060353.m2749.l2649
but with LifePo4 Charging specs (3.2V).

I did see this...
https://www.ebay.com.au/itm/3S-4S-100A-12V-w-Balance-LiFePo4-18650-Battery-BMS-Protection-Plate-Board/282814976228?ssPageName=STRK%3AMEBIDX%3AIT&var=582140823316&_trksid=p2060353.m2749.l2649
This seems to fit the bill better, but I'm unable to work out what to do with all the multiple input/output lines.  Can the + charge/discharge be simply joined and the same thing with the - lines?
Is there something better I can use?

Thanks in Advance

simulate this circuit – Schematic created using CircuitLab
Decided to include a very basic schematic.  What I'm really asking is;
Can anyone help me with the circuit I have just drawn as a dashed box?
I realise I may need to put a relay triggered by ignition to separate the caps from the batteries so that the caps are not constantly feeding into the charging circuit and depleting when the car is not running.  I think I may also need to put a switch on the battery to disable the charging circuit completely so that if the vehicle is left for any length of time the unit can be shut down and the charge circuitry is not still energised slowly draining the cells all the time.
My primary target vehicle is a 4WD RV used for only 1/2 the year.  I'm tired of every year replacing at least 1 of the 2 large lead acid batteries due to lack of use.  From what I understand, if I get this right, my new battery should last 10 years or more. and not suffer from lack of use.

Any help appreciated.


texts:
I have two 5-bit signals, each guaranteed to be carrying a value between 0 and 25. I would like to add them together and get another 5-bit value between 0 and 25, simply taking the sum % 26.

The best solution I have so far involves adding them together to get 6-bit sum S, then also calculating S-26 and selecting between the two based on the output of a comparator to check if S > 25. This requires quite a few parts to create (4 4bit adders, 2 4-bit comparators, 5 bit mux) and feels kinda clunky.

I know I could do it with a simple rom or micro pretty easy, but I am a bit of a masochist for designs built from 74xx and similar chips only. Is there a more elegant solution to this problem I am missing?


texts:
I have a PICkit 3 with a "PICkit 44-Pin Demo Board". To get the demo board to function I need to either disable the MCLR (#pragma config MCLRE = OFF) or put a pull up on the pin, as the PICkit leaves it floating unless in debug mode.

Is there a way of getting the PICkit to drive this pin high? Do I have a faulty PICkit (got it second hand) as I don't see anything about having to use a pull up in the demo board manual?


texts:
I made 6 different sensors , unfortunately they are separate designs, and it cots more for production as well.

I tested the prototypes and everything is working perfectly. So i dont want to change the component locations and traces.

Is there any simple way to put all those PCB files to one design as single PCB?

I tried copy and paste tools but didn't worked !


texts: Battery Reserve Capacity - how do you determine lower load capacity?

texts:
I understand that Reserve Capacity is the number of minutes a battery can deliver a useful voltage under a 25A load. I have a 2A load and I'm researching the correct battery for my application. Is it simply a matter of dividing the 25A by my actual load to determine "my" reserve capacity?

In other words, would a battery with a Reserve Capacity rating of 120 have an effective capacity of 1,500 under a 2A load?
1,500 = 120 * (25/2)


texts:
Background:

I'm working on a project that needs to accurately and quickly measure the rotational speed of the engine in my car.  It is a MK3 Ford Focus, and each spark plug has a coil-on-plug that has three wires going to it from the ECU.  They are signal, +12v, and ground.  When the ECU wants to fire one of the plugs, it sends a +12v pulse on the signal line.  The frequency of the pulse is going to be something between 0 and 100hz (ish).

Question:

What is a circuit that I can use to:

1) clean up the noise on the pulse, as it is pretty noisy.

2) Drop it to something that a) won't kill and b) can be detected by an AVR/Arduino/etc.

Is there any relatively simple way to do this?


texts: Getting Unwanted Transitional Values from Push Button Switch

texts:
When I toggle a push button switch on and off, instead of getting a pure on/off continuity levels I sometimes get "transitional" values. I need it to be purely on/off with nothing in between. What components do I need to add to the switch to make that happen?

There is +5v being applied at what is labeled "TIP".

Here is am drawing of the original circuit I am trying to replace:

Hopefully that helps explain what I am trying to do.


texts: Monitoring a fan with 2800 RPM with a Siemens 27-226 PLC

texts:
I have a fan that rotates at 2800 RPM. I need to make sure that the fan is operating. I need to monitor the fan.

It has an output that gives a signal 2 times per rotation so it's 5600 pulses which is 933 pulses per second. So I guess scan time will be a problem. So I can't use normal inputs. The machine is a Siemens S7-226. I have little experience with PLCs, however I have read the manual on the Siemens 27-2xx and it tells me that there is a high speed counter HSC0. With something like 30KHz so I guess this is what I need, right?

Also, do I just need to count up 5600 every minute to know that my fan is working, reset the counter and then count again? It seems very easy... too easy :) What am I missing?


texts: BLDC Motor Performance at high altitude?

texts:
How does a BLDC motor performance change at high altitude where the air density is really low? For example, say I have a given BLDC motor with given torque-RPM performance curves. Now, I assume these curves have been generated based on thermal limits at STP conditions. If I want to operate this motor at 50,000 feet, how would I account for the different temperature and low density on the performance curves at these conditions?

EDIT:
My (limited) understanding of how torque-RPM curves are generated comes from this datasheet: https://www.logic-control.com/datasheets/8/Catalog/Intro/011-Understanding%20Torque%20Curves.pdf

This told me that the upper bound of the continuous torque curves comes from testing to thermal limits, which led to my understanding that if the thermal environment changed, these curves themselves would change. From some of the answers, it seems like this is not the case.

With regards to the purpose of the motor, it is to drive a propeller load with a known torque and RPM demand. Thus, I was mostly curious about whether I can trust a BLDC motor's torque-RPM curve from a manufacturer, given that they probably test at STP. And if so, what corrections do I make.


texts: Where is the cold junction on the commercial thermocouples?

texts:
According to all textbooks and articles, a thermocouple must have a cold junction somewhere on the middle of it.

But none of the commercial products have a middle point or a marked spot for indicating the position of the cold junction. They are simply nothing but a long wire.

I want to place another temperature sensor near the cold junction and subtract its temperature from the measured hot junction temperature for more precise measurement. So, I need to know the location of the cold junction. How do I find it?


texts:
I'm designing a hairdryer as project for a university class, but I'm having trouble regarding the choice of the motor. I need it to have two possible speeds. My first idea was to use an AC motor and a diode as in the schematic below, when the current flows through the diode, half of the AC wave gets cut, so the motor runs at half speed. My first question is: Will it work?
I also tried to use a DC motor instead with a rectifier bridge, but using the aforementioned diode to cut the wave in half doesn't seem to change to voltage on the motor very much, how can I make it work with I choose to use a DC motor?
Thanks in advance.


texts: Learning how to choose integrated DC to DC boost converter

texts:
I am designing a microprocessor driven wristwatch with a VFD tubes 2 digits display.
These are the three major requirements:

VFDs operate at 15V
uC operates at 3V
I have to use as less space as possible

My plan is to use a 3V battery and a dc to dc step-up converter to get the 15V when I need them (that is, when I decide I want to display the time on the two VFDs). Now I have to select a suitable integrated circuit, which fits my very special needs, and this is something I've never done.
So, these are the specs I have for the booster:

Vin 3V
Vout 15V
Iout 300mA

Based on this parameters, I've identified the following component: LT3495

Do you think it would be suitable for what I need? Does a designer normally search for a new component this way, or normally are more specifications, more details needed?


texts: Safety precautions working with high voltages (Nixie Clock)

texts:
I'm building a nixie clock kit with these instructions.  I'm up to the part where I have to test (page 17) the high voltage components (the power supply is 12V 250 mA) which is up to 170 volts (page 5) and is potentially lethal.  Now I don't know if they put that disclaimer just to cover themselves or if there's really a likelihood of killing myself assembling a nixie clock kit.

I've done some electronics back in high school a few years ago but I'm no electrical engineer or electrician so I'm wondering what kind of safety precautions I should take? I don't suppose dishwashing rubber gloves suffice?


texts: Op-Amp difference amplifier low-pass filter

texts:
I have the following (summing, single supply) difference amplifier circuit:

How can I extend this circuit to a 1st or 2nd order low pass filter, with a corner frequency at about 20kHz.


texts: Requesting advice on what resistor to use with 12V LED array

texts:
I have 30 LEDs wired in parallel. At 3.4V the circuit draws 16mA. What type of resistor do I need to accommodate this voltage (12V - 3.5V) and current load (16 ma) requirement at a regulated 12V DC power supply? It's for my Jeep.

I'm sorry but the math portion of this I just can't compute.


texts:
There is a given op amp circuit with an open loop gain of 100. Rest of the parameters of the op amp is ideal.
The voltage rail of the op amp is +/- 5V.
The input wave form Vi(t) = cos(100t).

So now the question asks to find the rise time (0-100%) of Vo(t).
Can anyone please help me with this question?

So my attempt was

At t = 0 sec, my output should  be 100xcos (0) = 100V
But since my output voltage cannot go beyond +5V (Vsat), Vo = 5 V.

So I can calculate the final value, but I can’t figure out how to find the rise time. I was thinking for an ideal op amp it should be 0s. But that’s  a wild guess and I’m not really sure.


texts: How can I eliminate noise from a switched mode power supply through a laptop?

texts:
The laptop has a metal case, the charger is pulling 240v and outputting 19.5V

When my hand is in contact with the metal case there is no noise coming through the headphones.

If I draw my fingers across the metal case gently I can feel what I can only describe as a vibration.

Is there anything I can add to the case, the charger or the plug (UK 3 pin plug but the earth pin on the charger is plastic, probably because its double insulated.) to remove or reduce the noise?


texts:
Can we use zig-zag connection of transformers instead of open
delta in electrical distribution ?
If yes, then which one is the more preferable compared to other and
why ?


texts:
simulate this circuit – Schematic created using CircuitLab
Hi!
I am in need to make a high-side current monitor for detecting whether load (R1) is present or not. As currents running through my system are in range of few amps, I have tried my best with a small shunt resistor to keep voltage drop below 0.3V and used comparator in hope to get binary output.
Unfortunately the output of the system is also high in absence of load.

Could you suggest me some simple solution to this (potentially) trivial problem?


texts: What's the meaning of Electrical Inches?

texts:
I was reading a PCB design notes and guidelines from Xilinx for their 7 series FPGAs and came across this sentence:

  The capacitors should be placed as close as possible to the FPGA. Any
  placement within two electrical inches of the device’s point of load
  is acceptable.

What is the meaning of electrical inches ?


texts: RF power amplifiers and preventing damage when the antenna is disconnected

texts:
I'm looking at Wi-Fi 2.4 GHz power amplifiers and I can't find a single high power (500 mW) one including a system protecting it from damage. I can, for example, find some ~ GHz PA with protection circuits, for example from Triquint (7m9106).

I burned some PAs in some of my designs over the years but in my real world experience with electronics, I don't believe I ever damaged a device by powering it on without an antenna installed.

How are "high power" (500 mW) consumer electronics protected against users powering it on without antenna installed?

Has the power detect output pin common in most PA anything to do with it or is it just for feedback on how the PA is performing?

How do I understand from a datasheet just how likely a PA is to self destruct when operating without antenna?


texts: Why can computer circuits recognise only two states?

texts: Computers can only understand binary (that is 0s or 1s).  I want to know Is there any way that computers can understand more than 2 states.  I know that It is much harder to build components that use more than two states/levels/whatever. Of course If we have more than two states we would be able to hold more data per bit, just like our decimal number system can hold far more data in a single digit.